---------------------------------------- -------------------------- ,transcriber's note3 ,this book was published in two volumes1 of which this is the ,numbers enclosed in square brackets1 e4g4 #a1 relate to footnotes1 which have been placed at the end of the text4 ,numbers enclosed in parentheses1 e4g4 7#a71 relate to works referred to in the text and listed at the end of volume ,,ii4 ,in the text versions of these two volumes1 words in italics are enclosed in underscores1 bold words are enclosed in plus signs1 and words in ,gothic script are enclosed in equal signs4 ,curly brackets are used to represent subscripts1 e4g4 k#a4 ---------------------------------------- -------------------------- ,,the ,,history ,,of ,,creation4 ,illustration3 ,development of a ,calcareous ,sponge 7,olynthus74 ,,the ,,history ,,of ,,creation3 ,,or ,,the ,,development ,,of ,,the ,,earth ,,and ,,its ,,inhabitants ,,by ,,the ,,action ,,of ,,natural ,,causes4 ,a ,,popular ,,exposition ,,of ,,the ,,doctrine ,,of ,,evolution ,,in ,,general1 ,,and ,,of ,,that ,,of ,,darwin1 ,,goethe1 ,,and ,,lamarck ,,in ,,particular4 ,,from ,,the ,,german ,,of ,,ernst ,,haeckel1 ,,professor ,,in ,,the ,,university ,,of ,,jena4 ,,the ,,translation ,,revised ,,by ,e4 ,,ray ,,lankester1 ,m4,a41 ,,fellow ,,of ,,exeter ,,college1 ,,oxford4 ,,in ,,two ,,volumes4 ,,vol4 ,i4 ,,new ,,york3 ,d4 ,,appleton ,,and ,,company1 #a1 #c1 ,,and #e ,,bond ,,street4 #ahhj4 ,a sense sublime ,of something far more deeply interfused1 ,whose dwelling is the light of setting suns1 ,and the round ocean1 and the living air1 ,and the blue sky1 and in the mind of man2 ,a motion and a spirit that impels ,all thinking things1 all objects of all thought1 ,and rolls through all things4 ,in all things1 in all natures1 in the stars ,of azure heaven1 the unenduring clouds1 ,in flower and tree1 in every pebbly stone ,that paves the brooks1 the stationary rocks1 ,the moving waters and the invisible air4 ,,wordsworth4 ,,contents ,,of ,,vol4 ,i4 ,,chapter ,i4 ,,nature ,,and ,,importance ,,of ,,the ,,doctrine ,,of ,,filiation1 ,,or ,,descent-,,theory4 ,,page ,general ,importance and ,essential ,nature of the ,theory of ,descent as reformed by ,darwin4--,its ,special ,importance to ,biology 7,zoology and ,botany74--,its ,special ,importance to the ,history of the ,natural ,development of the ,human ,race4--,the ,theory of ,descent as the ,non-,miraculous ,history of ,creation4--,idea of ,creation4--,knowledge and ,belief4--,history of ,creation and ,history of ,development4--,the ,connection between the ,history of ,individual and ,palontological ,development4--,the ,theory of ,purposelessness1 or the ,science of ,rudimentary ,organs4--,useless and ,superfluous ,arrangements in ,organisms4--,contrast between the two entirely ,opposed ,views of ,nature3 the ,monistic 7mechanical1 causal7 and the ,dualistic 7teleological1 vital74--,proof of the former by the ,theory of ,descent4--,unity of ,organic and ,inorganic ,nature1 and the ,identity of the ,active ,causes in both4--,the ,importance of the ,theory of ,descent to the ,monistic ,conception of all ,nature #a ,,chapter ,,ii4 ,,scientific ,,justification ,,of ,,the ,,theory ,,of ,,descent4 ,,history ,,of ,,creation ,,according ,,to ,,linn,,us4 ,the ,theory of ,descent1 or ,doctrine of ,filiation1 as the ,monistic ,explanation of ,organic ,natural ,phenomena4--,its ,comparison with ,newton's ,theory of ,gravitation4--,limits of ,scientific ,explanation and of ,human ,knowledge in general4--,all ,knowledge founded originally on ,sensuous ,experience1 posteriori4--,transition of posteriori knowledge1 by inheritance1 into priori knowledge4--,contrast between the ,supernatural ,hypotheses of the ,creation according to ,linnus1 ,cuvier1 ,agassiz1 and the ,natural ,theories of ,development according to ,lamarck1 ,goethe1 and ,darwin4--,connection of the former with the ,monistic 7mechanical71 of the latter with the ,dualistic ,conception of the ,universe4--,monism and ,materialism4--,scientific and ,moral ,materialism4--,the ,history of ,creation according to ,moses4--,linnus as the ,founder of the ,systematic ,description of ,nature and ,distinction of ,species4--,linnus' ,classification and ,binary ,nomenclature4--,meaning of ,linnus' ,idea of ,species4--,his ,history of ,creation4--,linnus' view of the ,origin of ,species #bd ,,chapter ,,iii4 ,,the ,,history ,,of ,,creation ,,according ,,to ,,cuvier ,,and ,,agassiz4 ,general ,theoretical ,meaning of the ,idea of ,species4--,distinction between the ,theoretical and ,practical ,definition of the ,idea of ,species4--,cuvier's ,definition of ,species4--,merits of ,cuvier as the ,founder of ,comparative ,anatomy4--,distinction of the ,four ,principal ,forms 7types or branches7 of the ,animal ,kingdom1 by ,cuvier and ,br4--,cuvier's ,services to ,palontology4--,his ,hypothesis of the ,revolutions of our ,globe1 and the ,epochs of ,creation separated by them4--,unknown ,supernatural ,causes of the ,revolutions1 and the subsequent ,new ,creations4--,agassiz's ,teleological ,system of ,nature4--,his ,conception of the ,plan of ,creation1 and its six ,categories 7groups in classification74--,agassiz's ,views of the ,creation of ,species4--,rude ,conception of the ,creator as a man-like being in ,agassiz's ,hypothesis of ,creation4--,its internal ,inconsistency and ,contradictions with the important ,palontological ,laws discovered by ,agassiz #dg ,,chapter ,,iv4 ,,theory ,,of ,,development ,,according ,,to ,,goethe ,,and ,,oken4 ,scientific ,insufficiency of all ,conceptions of a ,creation of ,individual ,species4--,necessity of the ,counter ,theories of ,development4--,historical ,survey of the most ,important ,theories of ,development4--,aristotle4--,his ,doctrine of ,spontaneous ,generation4--,the ,meaning of ,nature-philosophy4--,goethe4--,his ,merits as a ,naturalist4--,his ,metamorphosis of ,plants4--,his ,vertebral ,theory of the ,skull4--,his ,discovery of the ,mid ,jawbone in ,man4--,goethe's ,interest in the ,dispute between ,cuvier and ,geoffroy ,st4 ,hilaire4--,goethe's ,discovery of the two ,organic ,formative ,principles1 of the ,conservative ,principle of ,specification 7by ,inheritance71 and of the ,progressive ,principle of ,transformation 7by ,adaptation74--,goethe's ,views of the ,common ,descent of all ,vertebrate ,animals1 including ,man4--,theory of ,development according to ,gottfried ,reinhold ,treviranus4--,his ,monistic ,conception of ,nature4--,oken4--,his ,nature-philosophy4--,oken's ,theory of ,protoplasm4--,oken's ,theory of ,infusoria 7,cell ,theory74--,oken's ,theory of ,development #gb ,,chapter ,v4 ,,theory ,,of ,,development ,,according ,,to ,,kant ,,and ,,lamarck4 ,kant's ,dualistic ,biology4--,his ,conception of the ,origin of ,inorganic ,nature by ,mechanical ,causes1 of ,organic ,nature by ,causes acting for a ,definite ,purpose4--,contradiction of this ,conception with his leaning towards the ,theory of ,descent4--,kant's ,genealogical ,theory of ,development4--,its ,limitation by his ,teleology4--,comparison of ,genealogical ,biology with ,comparative ,philology4--,views in favour of the ,theory of ,descent entertained by ,leopold ,buch1 ,br1 ,schleiden1 ,unger1 ,schaafhausen1 ,victor ,carus1 ,bchner4--,french ,nature-philosophy4--,lamarck's ,philosophic ,zoologique4--,lamarck's ,monistic 7mechanical7 ,system of ,nature4--,his ,views of the ,interaction of the two ,organic ,formative ,tendencies of ,inheritance and ,adaptation4--,lamarck's ,conception of ,man's ,development from ,ape-like ,mammals4--,geoffroy ,st4 ,hilaire's1 ,naudin's1 and ,lecoq's ,defence of the ,theory of ,descent4--,english ,nature-philosophy4--,views in favour of the ,theory of ,descent entertained by ,erasmus ,darwin1 ,w4 ,herbert1 ,grant1 ,freke1 ,herbert ,spencer1 ,hooker1 ,huxley4--,the ,double ,merit of ,charles ,darwin #ajj ,,chapter ,,vi4 ,,theory ,,of ,,development ,,according ,,to ,,lyell ,,and ,,darwin4 ,charles ,lyell's ,principles of ,geology4--,his ,natural ,history of the ,earth's ,development4--,origin of the ,greatest ,effects through the ,multiplication of the ,smallest ,causes4--,unlimited ,extent of ,geological ,periods4--,lyell's ,refutation of ,cuvier's ,history of ,creation4--,the ,establishment of the ,uninterrupted ,connection of ,historical ,development by ,lyell and ,darwin4--,biographical ,notice of ,charles ,darwin4--,his ,scientific ,works4--,his ,theory of ,coral ,reefs4--,development of the ,theory of ,selection4--,a ,letter of ,darwin's4--,the ,contemporaneous ,appearance of ,darwin's and ,alfred ,wallace's ,theory of ,selection4--,darwin's ,study of ,domestic ,animals and ,cultivated ,plants4--,andreas ,wagner's ,notions as to the ,special ,creation of ,cultivated ,organisms for the good of ,man4--,the ,tree of ,knowledge in ,paradise4--,comparison between ,wild and ,cultivated ,organisms4--,darwin's ,study of ,domestic ,pigeons4--,importance of ,pigeon ,breeding4--,common ,descent of all ,races of ,pigeons #abe ,,chapter ,,vii4 ,,the ,,theory ,,of ,,selection 7,,darwinism74 ,darwinism 7,theory of ,selection7 and ,lamarckism 7,theory of ,descent74--,the ,process of ,artificial ,breeding4--,selection of the ,different ,individuals for ,after-breeding4--,the ,active ,causes of ,transmutation4--,change connected with ,food and ,transmission by ,inheritance connected with ,propagation4--,mechanical ,nature of these ,two ,physiological ,functions4--,the ,process of ,natural ,breeding3 ,selection in the ,struggle for ,existence4--,malthus' ,theory of ,population4--,the ,proportion between the ,numbers of ,potential and ,actual ,individuals of every ,species of ,organisms4--,general ,struggle for ,existence1 or ,competition to attain the ,necessaries of ,life4--,transforming ,force of the ,struggle for ,existence4--,comparison of ,natural and ,artificial ,breeding4--,selection in the ,life of ,man4--,military and ,medical ,selection #adi ,,chapter ,,viii4 ,,transmission ,,by ,,inheritance ,,and ,,propagation4 ,universality of ,inheritance and ,transmission by ,inheritance4--,special ,evidences of the same4--,human ,beings with four1 six1 or seven ,fingers and ,toes4--,porcupine ,men4--,transmission of ,diseases1 especially ,diseases of the ,mind4--,original ,sin4--,hereditary ,monarchies4--,hereditary ,aristocracy4--,hereditary ,talents and ,mental ,qualities4--,material ,causes of ,transmission by ,inheritance4--,connection between ,transmission by ,inheritance and ,propagation4--,spontaneous ,generation and ,propagation4--,non-sexual or ,monogonous ,propagation4--,propagation by ,self-,division4--,monera and ,amba4--,propagation by the formation of ,buds1 by the formation of ,germ-,buds1 by the formation of ,germ-,cells4--,sexual or ,amphigonous ,propagation4--,formation of ,hermaphrodites4--,distinction of ,sexes1 or ,gonochorism4--,virginal ,breeding1 or ,parthenogenesis4--,material ,transmission of ,peculiarities of both ,parents to the ,child by ,sexual ,propagation4--,difference between ,transmission by ,inheritance in ,sexual and in ,asexual ,propagation #age ,,chapter ,,ix4 ,,laws ,,of ,,transmission ,,by ,,inheritance4 ,,adaptation ,,and ,,nutrition4 ,distinction between ,conservative and ,progressive ,transmission by ,inheritance4--,laws of ,conservative ,transmission3 ,transmission of ,inherited ,characters4--,uninterrupted or ,continuous ,transmission4--,interrupted or ,latent ,transmission4--,alternation of ,generations4--,relapse4--,degeneracy4-- ,sexual ,transmission4--,secondary ,sexual ,characters4--,mixed or ,amphigonous ,transmission4--,hybrids4--,abridged or ,simplified ,transmission4--,laws of ,progressive ,inheritance3 ,transmission of ,acquired ,characters4--,adapted or ,acquired ,transmission4--,fixed or ,established ,transmission4--,homochronous ,transmission 7,identity in ,epoch74--,homotopic ,transmission 7,identity in ,part74--,adaptation and ,mutability4--,connection between ,adaptation and ,nutrition4--,distinction between ,indirect and ,direct ,adaptation #bjc ,,chapter ,x4 ,,laws ,,of ,,adaptation4 ,laws of ,indirect or ,potential ,adaptation4--,individual ,adaptation4--,monstrous or ,sudden ,adaptation4--,sexual ,adaptation4--,laws of ,direct or ,actual ,adaptation4--,universal ,adaptation4--,cumulative ,adaptation4--,cumulative ,influence of ,external ,conditions of ,existence and ,cumulative ,counter-,influence of the ,organism4--,free ,will4--,use and ,non-use of ,organs4--,practice and ,habit4--,correlative ,adaptation4--,correlation of ,development4--,correlation of ,organs4--,explanation of ,indirect or ,potential ,adaptation by the ,correlation of the ,sexual ,organs and of the other parts of the ,body4--,divergent ,adaptation4--,unlimited or ,infinite ,adaptation #bbg ,,chapter ,,xi4 ,,natural ,,selection ,,by ,,the ,,struggle ,,for ,,existence4 ,,division ,,of ,,labour ,,and ,,progress4 ,interaction of the two ,organic ,formative ,causes1 ,inheritance and ,adaptation4--,natural and ,artificial ,selection4--,struggle for ,existence1 or ,competition for the ,necessaries of ,life4--,disproportion between the ,number of ,possible or ,potential1 and the ,number of ,real or ,actual ,individuals4--,complicated ,correlations of all ,neighbouring ,organisms4--,mode of ,action in ,natural ,selection4--,homochromic ,selection as the ,cause of ,sympathetic ,colourings4--,sexual ,selection as the ,cause of the ,secondary ,sexual ,characters4--,law of ,separation or ,division of ,labour 7,polymorphism1 ,differentiation1 ,divergence of ,characters74--,transition of ,varieties into ,species4--,idea of ,species4--,hybridism4--,law of ,progress or ,perfecting 7,progresses1 ,teleosis7 #beb ,,chapter ,,xii4 ,,laws ,,of ,,development ,,of ,,organic ,,tribes ,,and ,,of ,,individuals4 ,,phylogeny ,,and ,,ontogeny4 ,laws of the ,development of ,mankind3 ,differentiation and ,perfecting4--,mechanical ,cause of these two ,fundamental ,laws4--,progress without ,differentiation1 and ,differentiation without ,progress4--,origin of ,rudimentary ,organs by ,non-use and ,discontinuance of ,habit4--,ontogenesis1 or ,individual ,development of ,organisms4--,its ,general ,importance4--,ontogeny1 or the ,individual ,history of ,development of ,vertebrate ,animals1 including ,man4--,the ,fructification of the ,egg4--,formation of the ,three ,germ ,layers4--,history of the ,development of the ,central ,nervous ,system1 of the ,extremities1 of the ,branchial ,arches1 and of the ,tail of ,vertebrate ,animals4--,causal ,connection and ,parallelism of ,ontogenesis and ,phylogenesis1 that is1 of the ,development of ,individuals and ,tribes4--,causal ,connection of the ,parallelism of ,phylogenesis and of ,systematic ,development4--,parallelism of the three ,organic ,series of ,development #bhj ,,chapter ,,xiii4 ,,theory ,,of ,,the ,,development ,,of ,,the ,,universe ,,and ,,of ,,the ,,earth4 ,,spontaneous ,,generation4 ,,the ,,carbon ,,theory4 ,,the ,,plastid ,,theory4 ,history of the ,development of the ,earth4--,kant's ,theory of the ,development of the ,universe1 or the ,cosmological ,gas ,theory4--,development of ,suns1 ,planets1 and ,moons4--,first ,origin of ,water4--,comparison of ,organisms and ,anorgana4--,organic and ,inorganic ,substances4--,degrees of ,density1 or ,conditions of ,aggregation4--,albuminous ,combinations of ,carbon4--,organic and ,inorganic ,forms4--,crystals and ,formless ,organisms without ,organs4,stereometrical ,fundamental ,forms of ,crystals and of ,organisms4--,organic and ,inorganic ,forces4--,vital ,force4--,growth and ,adaptation in ,crystals and in ,organisms4--,formative ,tendencies of ,crystals4--,unity of ,organic and ,inorganic ,nature4--,spontaneous ,generation1 or ,archigony4--,autogony and ,plasmogony4--,origin of ,monera by ,spontaneous ,generation4--,origin of ,cells from ,monera4--,the ,cell ,theory4--,the ,plastid ,theory4--,plastids1 or ,structural-,units4--,cytods and ,cells4--,four ,different ,kinds of ,plastids #caf ,,chapter ,,xiv4 ,,migration ,,and ,,distribution ,,of ,,organisms4 ,,chorology ,,and ,,the ,,ice-,,period ,,of ,,the ,,earth4 ,chorological ,facts and ,causes4--,origin of most ,species in one ,single ,locality4--8,centres of ,creation40--,distribution by ,migration4--,active and ,passive ,migrations of ,animals and ,plants4--,means of ,transport4--,transport of ,germs by ,water and by ,wind4--,continual ,change of the ,area of ,distribution by ,elevations and ,depressions of the ,ground4--,chorological ,importance of ,geological ,processes4--,influence of the ,change of ,climate4--,ice or ,glacial ,period4--,its ,importance to ,chorology4--,importance of ,migrations for the ,origin of ,new ,species4--,isolation of ,colonists4--,wagner's ,law of ,migration4--,connection between the ,theory of ,migration and the ,theory of ,selection4--,agreement of its ,results with the ,theory of ,descent #cej ,,list ,,of ,,illustrations4 ,,plates4 ,,page ,development of a ,calcareous ,sponge 7,olynthus7 ,frontispiece ,i4--,life ,history of a ,simplest ,organism ,to face page #ahd ,,ii41 ,,iii4--,germs or ,embryos of ,four ,vertebrates 0 #cjf ,,figures4 #a4--,propagation of ,moneron #ahf #b4--,propagation of ,amba #ahh #c4--;,egg of ,mammal #ahi #d4--;,first ,development of ,mammal's ,egg #aij #e4--,the ,human ,egg ,enlarged #big #f4--;,development of ,mammal's ,egg #bii #g4--;,embryo of a ,mammal or ,bird #cjd ,,author',s ,,preface ,,to ,,the ,,english ,,edition4 ,i am desirous of prefacing the ,english edition of the 8,history of ,creation0 with a few remarks which may serve to explain the origin and object of this book4 ,in the year #ahff ,i published1 under the title 8,generelle ,morphologie10 a somewhat comprehensive work1 which constituted the first attempt to apply the general doctrine of development to the whole range of organic morphology 7,anatomy and ,biogenesis71 and thus to make use of the vast march onwards which the genius of ,charles ,darwin has effected in all biological science by his reform of the ,descent ,theory and its establishment through the doctrine of selection4 ,at the same time1 in the 8,generelle ,morphologie10 the first attempt was made to introduce the ,descent ,theory into the systematic classification of animals and plants1 and to found a 8natural system0 on the basis of genealogy2 that is1 to construct hypothetical pedigrees for the various species of organisms4 ,the 8,generelle ,morphologie0 found but few readers1 for which the voluminous and unpopular style of treatment1 and its too extensive ,greek terminology1 may be chiefly to blame4 ,but a proportionately large measure of approval has met the 8,natrliche ,schpfungsgeschichte0 in ,germany4 ,this book took its origin in the shorthand notes of a course of lectures which treated1 before a mixed audience and in a popular form1 the most important topics discussed in the 8,generelle ,morphologie40 ,the notes were subsequently revised1 and received considerable additions4 ,the book appeared first in #ahfh1 its fourth edition in #ahgc1 and has been translated into several languages4 ,i hope that it may also find sympathy in the fatherland of ,darwin1 the more so since it contains special morphological evidence in favour of many of the important doctrines with which this greatest naturalist of our century has enriched science4 ,proud as ,england may be to be called the fatherland of ,newton1 who1 with his law of gravitation1 brought inorganic nature under the dominion of natural laws of cause and effect1 yet may she with even greater pride reckon ,charles ,darwin among her sons--he who solved the yet harder problem of bringing the complicated phenomena of organic nature under the sway of the same natural laws4 ,the reproach which is now oftenest made against the ,descent ,theory is that it is not securely founded1 not sufficiently proven4 ,not only its distinct opponents maintain that there is a want of satisfactory proofs1 but even faint-hearted and wavering adherents declare that ,darwin's hypothesis is still wanting fundamental proof4 ,neither the former nor the latter estimate rightly the immeasurable weight which the great series of phenomena of comparative anatomy and ontogeny1 palontology and taxonomy1 chorology and cology1 cast into the scale in favour of the doctrine of filiation4 ,darwin's ,theory of ,selection1 which completely explains the origin of species through the combined action of ,inheritance and ,adaptation in the struggle for existence1 also appears to these persons not sufficient4 ,they demand1 over and above1 that the descent of species from common ancestral forms shall be proved in a particular case2 that1 in contradistinction to the synthetic proofs adduced for the ,descent ,theory1 the analytic proof of the genealogical continuity of the several species shall be brought forward4 ,this 8analytical solution of the problem of the origin of species0 ,i have myself endeavoured to afford in my recently published 8,monograph of the ,calcareous ,sponges40 ,for five consecutive years ,i have investigated this small but highly instructive group of animals in all its forms in the most careful manner1 and ,i venture to maintain that the monograph1 which is the result of those studies1 is the most complete and accurate morphological analysis of an entire organic group which has up to this time been made4 ,provided with the whole of the material for study as yet brought together1 and assisted by numerous contributions from all parts of the world1 ,i was able to work over the whole group of organic forms known as the ,calcareous ,sponges in that greatest possible degree of fulness which appeared indispensable for the proof of the common origin of its species4 ,this particular animal group is especially fitted for the analytical solution of the species problem1 because it presents exceedingly simple conditions of organisation1 because in it the morphological conditions possess a greatly superior1 and the physiological conditions an inferior1 import1 and because all species of ,calcispongi are remarkable for the fluidity and plasticity of their form4 ,with a view to these facts1 ,i made two journeys to the sea-coast 7#ahfi to ,norway1 #ahga to ,dalmatia71 in order to study as large a number of individuals as possible in their natural circumstances1 and to collect specimens for comparison4 ,of many species1 ,i compared several hundred individuals in the most careful way4 ,i examined with the microscope and measured in the most accurate manner the details of form of all the species4 ,as the final result of these exhaustive and almost endless examinations and measurements it appeared that 8good species10 in the ordinary dogmatic sense of the systematists1 have no existence at all among the ,calcareous ,sponges2 that the most different forms are connected one with another by numberless gradational transition forms2 and that all the different species of ,calcareous ,sponges are derived from a single exceedingly simple ancestral form1 the ,olynthus4 ,a drawing of the ,olynthus and its earliest stages of development 7observe especially the highly important ,gastrula7 is given in the frontispiece of the present edition4 ,illustrations of the various structural details which establish the derivation of all ,calcareous ,sponges from the ,olynthus1 are given in the atlas of sixty plates which accompanies my monograph of the group4 ,in the gastrula1 moreover1 is now also found the common ancestral form from which all the tribes of animals 7the lowest group1 that of the protozoa1 alone being excepted7 can without difficulty be derived4 ,it is one of the most ancient and important ancestors of the human race6 ,if we take for the limitation of genus and species an average standard1 derived from the actual practice of systematists1 and apply this to the whole of the ,calcareous ,sponges at present known1 we can distinguish about twenty-one genera1 with one hundred and eleven species 7as ,i have done in the second volume of the ,monograph74 ,i have1 however1 shown that we may draw up1 in addition to this1 another systematic arrangement 7more nearly agreeing with the arrangement of the ,calcispongi hitherto in vogue7 which gives thirty-nine genera and two hundred and eighty-nine species4 ,a systematist who gives a more limited extension to the 8ideal species0 might arrange the same series of forms in forty-three genera and three hundred and eighty-one species1 or even in one hundred and thirteen genera and five hundred and ninety species2 another systematist on the other hand1 who takes a wider limit for the 8abstract species10 would use in arranging the same series of forms only three genera1 with twenty-one species1 or might even satisfy himself with one genus and seven species4 ,the delimitation of species and genera appears to be so arbitrary a matter1 on account of endless varieties and transitional forms in this group1 that their number is entirely left to the subjective taste of the individual systematist4 ,in truth1 from the point of view of the theory of descent1 it appears altogether an unimportant question as to whether we give a wider or a narrower signification to allied groups of forms--whether we choose1 that is to say1 to call them genera or species1 varieties or sub-species4 ,the main fact remains undeniable1 viz41 the common origin of all the species from one ancestral form4 ,the many-shaped ,calcareous ,sponges furnish1 in the very remarkable conditions of their varieties of aggregation 7metrocormy71 a body of evidence in favour of this view which could hardly be more convincing4 ,not unfrequently the case occurs of several different forms growing out from a single 8stock0 or 8cormus0--forms which until now have been regarded by systematists1 not only as belonging to different species1 but even to different genera4 ,fig4 #aj in the frontispiece represents such a composite stock4 ,this solid and tangible piece of evidence in favour of the common descent of different species ought1 one would think1 to satisfy the most determined sceptic6 ,in point of fact1 ,i have a right to expect of my opponents that they shall carefully consider the 8exact empirical proof0 here brought forward for them1 as they have so eagerly demanded4 ,the opponents of the doctrine of filiation1 who have too little power of weighing evidence1 or possess too little knowledge to appreciate the overpowering weight of proof afforded by the synthetical argument 7comparative anatomy1 ontogeny1 taxonomy1 etc471 may yet be able to follow me along the path of analytical proof1 and attempt to upset the conclusion as to the common origin of all species of all ,calcareous ,sponges which ,i have given in my ,monograph4 ,i must1 however1 repeat that this conclusion is based on the most minute investigation of an extraordinarily rich mass of material1--that it is securely established by thousands of the most careful microscopical observations1 measurements1 and comparisons of every single part1 and that thousands of collected microscopic preparations render1 at any moment1 the most searching criticism of my results confirmatory of their correctness4 ,one may hope1 then1 that opponents will endeavour to confront me on the ground of this 8exact empiricism10 instead of trying to damn my 8nature-philosophical speculations40 ,one may hope that they will endeavour to bring forward some evidence to show that the latter do not follow as the legitimate consequences of the former4 ,may they1 however1 spare me the empty--though by even respectable naturalists oft-repeated--phrase1 that the monistic nature-philosophy1 as expounded in the 8,general ,morphology10 and in the 8,history of ,creation10 is wanting in actual proofs4 ,the proofs are there4 ,of course those who turn their eyes away from them will not see them4 ,precisely that 8exact0 form of analytical proof which the opponents of the descent theory demand is to be found1 by anybody who wishes to find it1 in the 8,monograph of the ,calcareous ,sponges40 ,,ernst ,,heinrich ,,haeckel4 ,jena1 ,june #bdth1 #ahgc4 ,,note4 ,feeling sure that such a book as ,professor ,haeckel's 8,schpfungsgeschichte0 would do a great deal of good1 if placed in the hands of the ,english reading public1 and of commencing students of ,natural ,history1 ,i gladly undertook to revise for the publishers the present translation1 which was made by a young lady4 ,i have not attempted to escape a difficulty by ignoring the ,german names made use of by ,professor ,haeckel for classes1 orders1 and genera1 but have adopted ,english equivalents4 ,i do not submit these names as a maturely considered ,english nomenclature1 they appear here simply as necessary parts of a close rendering of the ,german work4 ,i do1 however1 hold that some such series of ,english terms is both possible and useful1 and do not doubt--in spite of the pretended hostility of the genius of our language1 and the curious sentimental objection that ,english names are unscientific--that we shall before long make use of plain ,english in speaking of the various groups of plants and animals--much to the gain of the larger public1 and without detriment to the latinized nomenclature established for the purposes of the professional student4 ,e4 ,r4 ,l4 ,oxford1 ,october1 #ahgd4 ,,the ,,history ,,of ,,creation4 ,,chapter ,i4 ,,nature ,,and ,,importance ,,of ,,the ,,doctrine ,,of ,,filiation1 ,,or ,,descent-,,theory4 ,general ,importance and ,essential ,nature of the ,theory of ,descent as reformed by ,darwin4--,its ,special ,importance to ,biology 7,zoology and ,botany74--,its ,special ,importance to the ,history of the ,natural ,development of the ,human ,race4--,the ,theory of ,descent as the ,non-,miraculous ,history of ,creation4--,idea of ,creation4--,knowledge and ,belief4--,history of ,creation and ,history of ,development4--,the ,connection between the ,history of ,individual and ,palontological ,development4--,the ,theory of ,purposelessness1 or the ,science of ,rudimentary ,organs4--,useless and ,superfluous ,arrangements in ,organisms4--,contrast between the two entirely opposed ,views of ,nature3 the ,monistic 7mechanical1 causal7 and the ,dualistic 7teleological1 vital74--,proof of the former by the ,theory of ,descent4--,unity of ,organic and ,inorganic ,nature1 and the ,identity of the ,active ,causes in both4--,the ,importance of the ,theory of ,descent to the ,monistic ,conception of all ,nature4 ,the intellectual movement to which the impulse was given1 thirteen years ago1 by the ,english naturalist1 ,charles ,darwin1 in his celebrated work1 8,on the ,origin of ,species107#a7 has1 within this short period1 assumed dimensions which cannot but excite the most universal interest4 ,it is true the scientific theory set forth in that work1 which is commonly called briefly ,darwinism1 is only a small fragment of a far more comprehensive doctrine--a part of the universal ,theory of ,development1 which embraces in its vast range the whole domain of human knowledge4 ,but the manner in which ,darwin has firmly established the latter by the former is so convincing1 and the direction which has been given by the unavoidable conclusions of that theory to all our views of the universe1 must appear to every thinking man of such deep significance1 that its general importance cannot be over estimated4 ,there is no doubt that this immense extension of our intellectual horizon must be looked upon as by far the most important1 and rich in results1 among all the numerous and grand advances which natural science has made in our day4 ,when our century1 with justice1 is called the age of natural science1 when we look with pride upon the immensely important progress made in all its branches1 we are generally in the habit of thinking more of immediate practical results1 and less of the extension of our general knowledge of nature4 ,we call to mind the complete reform1 so infinitely rich in consequences to human intercourse1 which has been effected by the development of machinery1 by railways1 steamships1 telegraphs1 and other inventions of physics4 ,or we think of the enormous influence which chemistry has brought to bear upon medicine1 agriculture1 and upon all arts and trades4 ,but much as we may value this influence of modern science upon practical life1 still it must1 estimated from a higher and more general point of view1 stand most assuredly below the enormous influence which the theoretical progress of modern science will have on the entire range of human knowledge1 on our conception of the universe1 and on the perfecting of man's culture4 ,think of the immense revolutions in all our theoretical views which we owe to the general application of the microscope4 ,think of the cell theory1 which explains the apparent unity of the human organism as the combined result of the union of a mass of elementary vital units4 ,or consider the immense extension of our theoretical horizon which we owe to spectral analysis and to the mechanical theory of heat4 ,but among all these wonderful theoretical advances1 the theory wrought out by ,darwin occupies by far the highest rank4 ,every one of my readers has heard of the name of ,darwin4 ,but most persons have probably only an imperfect idea of the real value of his theory4 ,if a reader estimates as of equal value all that has been written upon ,darwin's memorable work since its appearance1 the value of the theory will appear very doubtful to him1 supposing that he has not been engaged in the organic natural sciences1 and has not penetrated into the inner secrets of zoology and botany4 ,the criticisms of it are so full of contradictions1 and for the most part so defective1 that we ought not to be at all astonished that even now1 after the lapse of thirteen years since the appearance of ,darwin's work1 it has not gained half that importance which is justly due to it1 and which sooner or later it certainly will attain4 ,most of the innumerable writings which have been published during these years1 both for and against ,darwinism1 are the productions of persons who are entirely wanting in the necessary amount of biological1 and especially of zoological1 knowledge4 ,although almost all of the more celebrated naturalists of the present day are adherents of the theory1 yet only a few of them have endeavoured to procure its acceptance and recognition in larger circles4 ,hence the odd contradictions and the strange opinions which may still be heard everywhere about ,darwinism4 ,this is the reason which induces me to make ,darwin's theory1 and those further doctrines which are connected with it1 the subject of these pages1 which1 ,i hope1 will be generally intelligible4 ,i hold it to be the duty of naturalists1 not merely to meditate upon improvements and discoveries in the narrow circle to which their speciality confines them1 not merely to pore over their one study with love and care1 but also to seek to make the important general results of it fruitful to the mass1 and to assist in spreading the knowledge of physical science among the people4 ,the highest triumph of the human mind1 the true knowledge of the most general laws of nature1 ought not to remain the private possession of a privileged class of savans1 but ought to become the common property of all mankind4 ,the theory which1 through ,darwin1 has been placed at the head of all our knowledge of nature1 is usually called the ,doctrine of ,filiation1 or the ,theory of ,descent4 ,others term it the ,transmutation ,theory4 ,both designations are correct4 ,for this doctrine affirms1 that all organisms 7viz41 all species of animals1 all species of plants1 which have ever existed or still exist on the earth7 are derived from one single1 or from a few simple original forms1 and that they have developed themselves from these in the natural course of a gradual change4 ,although this theory of development had already been brought forward and defended by several great naturalists1 and especially by ,lamarck and ,goethe1 in the beginning of our century1 still it was through ,darwin1 thirteen years ago1 that it received its complete demonstration and causal foundation2 and this is the reason why now it is commonly and exclusively 7though not quite correctly7 designated as ,darwin's ,theory4 ,the great and really inestimable value of the ,theory of ,descent appears in a different light1 accordingly as we merely consider its more immediate connection with organic natural science1 or its larger influence upon the whole range of man's knowledge of the universe4 ,organic natural science1 or ,biology1 which as ,zoology treats of animals1 as ,botany of plants1 is completely reformed and founded anew by the ,theory of ,descent4 ,for by this theory we are made acquainted with the active causes of organic forms1 while up to the present time ,zoology and ,botany have simply been occupied with the facts of these forms4 ,we may therefore also term the theory of descent a mechanical explanation of organic forms1 or the science of the true causes of ,organic ,nature4 ,as ,i cannot take for granted that my readers are all familiar with the terms 8organic and inorganic nature10 and as the contrast of both these natural bodies will1 in future1 occupy much of our attention1 ,i must say a few words in explanation of them4 ,we designate as ,organisms1 or ,organic bodies1 all living creatures or animated bodies2 therefore all plants and animals1 man included2 for in them we can almost always prove a combination of various parts 7instruments or organs7 which work together for the purpose of producing the phenomena of life4 ,such a combination we do not find in ,anorgana1 or inorganic natural bodies--the so-called dead or inanimate bodies1 such as minerals or stones1 water1 the atmospheric air1 etc4 ,organisms always contain albuminous combinations of carbon in a semi-fluid condition of aggregation1 which are always wanting in the ,anorgana4 ,upon this important distinction rests the division of all natural history into two great and principal parts--,biology1 or the science of ,organisms 7,zoology and ,botany71 and ,anorganology1 or the science of ,anorgana 7,mineralogy1 ,geology1 ,meteorology1 etc474 ,the great value of the ,theory of ,descent in regard to ,biology consists1 as ,i have already remarked1 in its explaining to us the origin of organic forms in a mechanical way1 and pointing out their active causes4 ,but however highly and justly this service of the ,theory of ,descent may be valued1 yet it is almost eclipsed by the immense importance which a single necessary inference from it claims for itself alone4 ,this necessary and unavoidable inference is the theory of the animal descent of the human race4 ,the determination of the position of man in nature1 and of his relations to the totality of things--this question of all questions for mankind1 as ,huxley justly calls it--is finally solved by the knowledge that man is descended from animals4 ,in consequence of ,darwin's reformed ,theory of ,descent1 we are now in a position to establish scientifically the groundwork of a non-miraculous history of the development of the human race4 ,all those who have defended ,darwin's theory1 as well as all its thoughtful opponents1 have acknowledged that1 as a matter of necessity1 it follows from his theory that the human race1 in the first place1 must be traced to ape-like mammals1 and further back to the lower vertebrate animals4 ,it is true ,darwin himself did not express at first this most important of all the inferences from his theory4 ,in his work1 8,on the ,origin of ,species10 not a word is found about the animal descent of man4 ,the courageous but cautious naturalist was at that time purposely silent on the subject1 for he anticipated that this most important of all the conclusions of the ,theory of ,descent was at the same time the greatest obstacle to its being generally accepted and acknowledged4 ,certain it is that ,darwin's book would have created1 from the beginning1 even much more opposition and offence1 if this most important inference had at once been clearly expressed4 ,it was not till twelve years later1 in his work on 8,the ,descent of ,man1 and ,selection in ,relation to ,sex10 that ,darwin openly acknowledged that far-reaching conclusion1 and expressly declared his entire agreement with those naturalists who had1 in the meantime1 themselves formed that conclusion4 ,manifestly the effect of this conclusion is immense1 and no science will be able to escape from the consequences4 ,anthropology1 or the science of man1 and consequently all philosophy1 are thereby thoroughly reformed in all their various branches4 ,it will be a later task in these pages to discuss this special point4 ,i shall not treat of the theory of the animal descent of man till ,i have spoken of ,darwin's theory1 and its general foundation and importance4 ,to express it in one word1 that most important1 but 7to most men7 at first repulsive1 conclusion is nothing more than a special deduction1 which we must draw from the general inductive law of the descent theory 7now firmly established71 according to the stern commands of inexorable logic4 ,perhaps nothing will make the full meaning of the theory of descent clearer than calling it the 8non-miraculous history of creation40 ,i have therefore chosen that name for this work4 ,it is1 however1 correct only in a certain sense1 and it must be borne in mind that1 strictly speaking1 the expression 8non-miraculous history of creation0 contains a 8contradictio in adjecto40 ,in order to understand this1 let us for a moment examine somewhat more closely what we understand by creation4 ,if we understand the creation to mean the coming into existence of a body by a creative power or force1 we may then either think of the coming into existence of its substance 7corporeal matter71 or of the coming into existence of its form 7the corporeal form74 ,creation in the former sense1 as the coming into existence of matter1 does not concern us here at all4 ,this process1 if indeed it ever took place1 is completely beyond human comprehension1 and can therefore never become a subject of scientific inquiry4 ,natural science teaches that matter is eternal and imperishable1 for experience has never shown us that even the smallest particle of matter has come into existence or passed away4 ,where a natural body seems to disappear1 as for example by burning1 decaying1 evaporation1 etc41 it merely changes its form1 its physical composition or chemical combination4 ,in like manner the coming into existence of a natural body1 for example1 of a crystal1 a fungus1 an infusorium1 depends merely upon the different particles1 which had before existed in a certain form or combination1 assuming a new form or combination in consequence of changed conditions of existence4 ,but never yet has an instance been observed of even the smallest particle of matter having vanished1 or even of an atom being added to the already existing mass4 ,hence a naturalist can no more imagine the coming into existence of matter1 than he can imagine its disappearance1 and he therefore looks upon the existing quantity of matter in the universe as a given fact4 ,if any person feels the necessity of conceiving the coming into existence of this matter as the work of a supernatural creative power1 of the creative force of something outside of matter1 we have nothing to say against it4 ,but we must remark1 that thereby not even the smallest advantage is gained for a scientific knowledge of nature4 ,such a conception of an immaterial force1 which at the first creates matter1 is an article of faith which has nothing whatever to do with human science4 ,where faith commences1 science ends4 ,both these arts of the human mind must be strictly kept apart from each other4 ,faith has its origin in the poetic imagination2 knowledge1 on the other hand1 originates in the reasoning intelligence of man4 ,science has to pluck the blessed fruits from the tree of knowledge1 unconcerned whether these conquests trench upon the poetical imaginings of faith or not4 ,if1 therefore1 science makes the 8history of creation0 its highest1 most difficult1 and most comprehensive problem1 it must accept as its idea of creation the second explanation of the word1 viz41 the coming into being of the form of natural bodies4 ,in this way geology1 which tries to investigate the origin of the inorganic surface of the earth as it now appears1 and the manifold historical changes in the form of the solid crust of the earth1 may be called the history of the creation of the earth4 ,in like manner1 the history of the development of animals and plants1 which investigates the origin of living forms1 and the manifold historical changes in animal and vegetable forms1 may be termed the history of the creation of organisms4 ,as1 however1 in the idea of creation1 although used in this sense1 the unscientific idea of a creator existing outside of matter1 and changing it1 may easily creep in1 it will perhaps be better in future to substitute for it the more accurate term1 development4 ,the great value which the ,history of ,development possesses for the scientific understanding of animal and vegetable forms1 has now been generally acknowledged for many years1 and without it it would be impossible to make any sure progress in organic morphology1 or the theory of forms4 ,but by the history of development1 only one part of this science has generally been understood1 namely1 that of organic individuals1 usually called ,embryology1 but more correctly and comprehensively1 ,ontogeny4 ,but1 besides this1 there is another history of development of organic species1 genera1 and tribes 7phyla71 which has the most important relations to the former4 ,the subject of this is furnished to us by the science of petrifactions1 or palontology1 which shows us that each tribe of animals and plants1 during different periods of the earth's history1 has been represented by a series of entirely different genera and species4 ,thus1 for example1 the tribe of vertebrated animals was represented by classes of fish1 amphibious animals1 reptiles1 birds1 and mammals1 and each of these groups1 at different periods1 by quite different kinds4 ,this palontological history of the development of organisms1 which we may term ,phylogeny1 stands in the most important and remarkable relation to the other branch of organic history of development1 ,i mean that of individuals1 or ,ontogeny4 ,on the whole1 the one runs parallel to the other4 ,in fact1 the history of individual development1 or ,ontogeny1 is a short and quick recapitulation of palontological development1 or ,phylogeny1 dependent on the laws of ,inheritance and ,adaptation4 ,as ,i shall have1 later1 to explain this most interesting and important coincidence more fully1 ,i shall not dwell further upon it here1 and merely call attention to the fact that it can only be explained and its causes understood by the ,theory of ,descent1 while without that theory it remains completely incomprehensible and inexplicable4 ,the ,theory of ,descent in the same way shows us why individual animals and plants must develop at all1 and why they do not come into life at once in a perfect and developed state4 ,no supernatural history of creation can in any way explain to us the great mystery of organic development4 ,to this most weighty question1 as well as to all other biological questions1 the ,theory of ,descent gives us perfectly satisfactory answers--and always answers which refer to purely mechanical causes1 and point to purely physico-chemical forces as the causes of phenomena which we were formerly accustomed to ascribe to the direct action of supernatural1 creative forces4 ,hence1 by our theory the mystic veil of the miraculous and supernatural1 which has hitherto been allowed to hide the complicated phenomena of this branch of natural knowledge1 is removed4 ,all the departments of ,botany and ,zoology1 and especially the most important portion of the latter1 ,anthropology1 become reasonable4 ,the dimming mirage of mythological fiction can no longer exist in the clear sunlight of scientific knowledge4 ,of special interest among general biological phenomena are those which are quite irreconcilable with the usual supposition1 that every organism is the product of a creative power1 acting for a definite object4 ,nothing in this respect caused the earlier naturalists greater difficulty than the explanation of the so-called 8rudimentary organs10--those parts in animal and vegetable bodies which really have no function1 which have no physiological importance1 and yet exist in form4 ,these parts deserve the most careful attention1 although most unscientific men know little or nothing about them4 ,almost every organism1 almost every animal and plant possesses1 besides the obviously useful arrangements of its organization1 other arrangements the purpose of which it is utterly impossible to make out4 ,examples of this are found everywhere4 ,in the embryos of many ruminating animals--among others1 in our common cattle--fore-teeth1 or incisors1 are placed in the mid-bone of the upper jaw1 which never fully develop1 and therefore serve no purpose4 ,the embryos of many whales--which afterwards possess the well-known whalebone instead of teeth--yet have before they are born1 and while they take no nourishment1 teeth in their jaws1 which set of teeth never comes into use4 ,moreover1 most of the higher animals possess muscles which are never employed2 even man has such rudimentary muscles4 ,most of us are incapable of moving our ears as we wish1 although the muscles for this movement exist1 and although individual persons who have taken the trouble to exercise these muscles do succeed in moving their ears4 ,it is still possible1 by special exercise1 by the persevering influence of the will upon the nervous system1 to reanimate the almost extinct activity in the existing but imperfect organs1 which are on the road to complete disappearance4 ,on the other hand1 we can no longer do this with another set of small rudimentary muscles1 which still exist in the cartilage of the outer ear1 but which are always perfectly inactive4 ,our long-eared ancestors of the tertiary period--apes1 semi-apes1 and pouched animals1 like most other mammals1 moved their large ear-flaps freely and actively2 their muscles were much more strongly developed and of great importance4 ,in a similar way1 many varieties of dogs and rabbits1 under the influence of civilized life1 have left off 8pricking up0 their ears1 and thereby have acquired imperfect auricular muscles and loose-hanging ears1 although their wild ancestors moved their stiff ears in many ways4 ,man has also these rudimentary organs on other parts of his body2 they are of no importance to life1 and never perform any function4 ,one of the most remarkable1 although the smallest organ of this kind1 is the little crescent-like fold1 the so-called 8plica semilunaris10 which we have in the inner corner of the eye1 near the root of the nose4 ,this insignificant fold of skin1 which is quite useless to our eye1 is the imperfect remnant of a third inner eyelid which1 besides the upper and under eyelid1 is highly developed in other mammals1 and in birds and reptiles4 ,even our very remote ancestors of the ,silurian period1 the ,primitive ,fishes1 seem to have possessed this third eyelid1 the so-called nictitating membrane4 ,for many of their nearest kin1 who still exist in our day but little changed in form1 viz41 many sharks1 possess a very strong nictitating membrane1 which they can draw right across the whole eyeball1 from the inner corner of the eye4 ,eyes which do not see form the most striking example of rudimentary organs4 ,these are found in very many animals1 which live in the dark1 as in caves or underground4 ,their eyes often exist in a well-developed condition1 but they are covered by membrane1 so that no ray of light can enter1 and they can never see4 ,such eyes1 without the function of sight1 are found in several species of moles and mice which live underground1 in serpents and lizards1 in amphibious animals 7,proteus1 ,ccilia71 and in fishes2 also in numerous invertebrate animals1 which pass their lives in the dark1 as do many beetles1 crabs1 snails1 worms1 etc4 ,an abundance of the most interesting examples of rudimentary organs is furnished by ,comparative ,osteology1 or the study of the skeletons of vertebrate animals1 one of the most attractive branches of ,comparative ,anatomy4 ,in most of the vertebrate animals we find two pairs of limbs on the body1 a pair of fore-legs and a pair of hind-legs4 ,very often1 however1 one or the other pair is imperfect2 it is seldom that both are1 as in the case of serpents and some varieties of eel-like fish4 ,but some serpents1 viz41 the giant serpents 7,boa1 ,python71 have still in the hinder portion of the body some useless little bones1 which are the remains of lost hind-legs4 ,in like manner the mammals of the whale tribe 7,cetacea71 which have only fore-legs fully developed 7breast-fins171 have further back in their body another pair of utterly superfluous bones1 which are remnants of undeveloped hind-legs4 ,the same thing occurs in many genuine fishes1 in which the hind-legs have in like manner been lost4 ,again1 in our slow-worm 7,anguis71 and in some other lizards1 no fore-legs exist1 although they have a perfect shoulder apparatus within their bodies1 which should serve as a means of affixing the legs4 ,moreover1 in various vertebrate animals1 the single bones of both pairs of legs are found in all the different stages of imperfection1 and often the degenerate bones and those muscles belonging to them are partially preserved1 without their being able in any way to perform any function4 ,the instrument is still there1 but it can no longer play4 ,moreover1 we can1 almost as generally1 find rudimentary organs in the blossoms of plants1 inasmuch as one part or another of the male organs of propagation--the stamen and anther1 or of the female organs of propagation--the style1 germ1 etc4--is more or less imperfect or abortive4 ,among these we can trace1 in various closely connected species of plants1 the organ in all stages of degeneration4 ,thus1 for example1 the great natural family of lip-blossomed plants 7,labiat71 to which the balm1 peppermint1 marjoram1 ground-ivy1 thyme1 etc41 belong1 are distinguished by the fact that their mouth-like1 two-lipped flower contains two long and two short stamens4 ,but in many exceptional plants of this family1 e4g4 in different species of sage1 and in the rosemary1 only one pair of stamens is developed2 the other pair is more or less imperfect1 or has quite disappeared4 ,sometimes stamens exist1 but without the anthers1 so that they are utterly useless4 ,less frequently the rudiment or imperfect remnant of a fifth stamen is found1 physiologically 7for the functions of life7 quite useless1 but morphologically 7for the knowledge of the form and of the natural relationship7 a most valuable organ4 ,in my 8,general ,morphology of ,organisms107#d7 in the chapter on 8,purposelessness1 or ,dysteleology10 ,i have given a great number of other examples 7,gen4 ,morph4 ii4 #bbf74 ,no biological phenomenon has perhaps ever placed zoologists or botanists in greater embarrassment than these rudimentary or abortive organs4 ,they are instruments without employment1 parts of the body which exist without performing any service--adapted for a purpose1 but without in reality fulfilling that purpose4 ,when we consider the attempts which the earlier naturalists have made in order to explain this mystery1 we can scarcely help smiling at the strange ideas to which they were led4 ,being unable to find a true explanation1 they came1 for example1 to the conclusion that the ,creator had placed these organs there 8for the sake of symmetry10 or they believed that it had appeared unwise and unsuitable to the ,creator 7seeing that their nearest kin did possess such organs7 that these organs should be completely wanting in creatures1 where they are incapable of performing a function1 and where it cannot be otherwise from the special mode of life4 ,in compensation for the non-existing function1 he had at least furnished them with the outward but empty form2 nearly in the same manner as civil officers1 in uniform1 are furnished with an innocent sword1 which is never drawn from the scabbard4 ,i scarcely believe1 however1 that any of my readers will be content with such an explanation4 ,now1 it is precisely this widely spread and mysterious phenomenon of rudimentary organs1 in regard to which all other attempts at explanation fail1 which is perfectly explained1 and indeed in the simplest and clearest way1 by ,darwin's ,theory of ,inheritance and ,adaptation4 ,we can trace the important laws of inheritance and adaptation in the domestic animals which we breed1 and the plants which we cultivate2 and a series of such laws of inheritance have already been established4 ,without going further into this at present1 ,i will only remark that some of them perfectly explain1 in a mechanical way1 the coming into existence of rudimentary organs1 so that we must look upon the appearance of such structures as an entirely natural process1 arising from the disuse of the organs4 ,by adaptation to special conditions of life1 the formerly active and really working organs have gradually ceased to be used or employed4 ,in consequence of their not being exercised they have become more and more imperfect1 but in spite of this have always been handed down from one generation to another by inheritance1 until at last they vanish partially or entirely4 ,now1 if we admit that all the vertebrate animals mentioned above are derived from one common ancestor1 possessing two seeing eyes and two well developed pairs of legs1 the different stages of suppression and degeneration of these organs are easily accounted for in such of the descendants as could no longer use them4 ,in like manner the various stages of suppression of the stamens1 originally existing to the number of five 7in the flower-bud71 among the ,labiat is explained1 if we admit that all the plants of this family sprung from one common ancestor1 provided with five stamens4 ,i have here spoken somewhat fully of the phenomena of rudimentary organs1 because they are of the utmost general importance1 and because they lead us to the great1 general1 and fundamental questions in philosophy and natural science1 for the solution of which the ,theory of ,descent has now become the indispensable guide4 ,as soon1 in fact1 as1 according to this theory1 we acknowledge the exclusive activity of physico-chemical causes in living 7organic7 bodies1 as well as in so-called inanimate 7inorganic7 nature1 we concede exclusive dominion to that view of the universe1 which we may designate as the mechanical1 and which is opposed to the teleological conception4 ,if we compare all the ideas of the universe prevalent among different nations at different times1 we can divide them all into two sharply contrasted groups--a causal or mechanical1 and a teleological or vitalistic4 ,the latter has prevailed generally in ,biology until now1 and accordingly the animal and vegetable kingdoms have been considered as the products of a creative power1 acting for a definite purpose4 ,in the contemplation of every organism the unavoidable conviction seemed to press itself upon us1 that such a wonderful machine1 so complicated an apparatus for motion as exists in the organism1 could only be produced by a power analogous to1 but infinitely more perfect than1 the power of man in the construction of his machines4 ,however sublime the former idea of a ,creator1 and his creative power1 may have been2 however much it may be attempted to divest it of all human analogy1 yet in the end this analogy still remains unavoidable and necessary in the teleological conception of nature4 ,in reality the ,creator must himself be conceived of as an organism1 that is1 as a being who1 analogous to man1 even though in an infinitely more perfect form1 reflects on his constructive power1 lays down a plan of his mechanisms1 and then1 by the application of suitable materials1 makes them answer their purpose4 ,such conceptions necessarily suffer from the fundamental error of anthropomorphism1 or man-likening4 ,in such a view1 however exalted the ,creator may be imagined1 we assign to him the human attributes of designing a plan1 and therefrom suitably constructing the organism4 ,this is1 in fact1 quite clearly expressed in that view which is most sharply opposed to ,darwin's theory1 and which has found among naturalists its most distinguished representative in ,agassiz4 ,his celebrated work1 8,an ,essay on ,classification107#e7 which is entirely opposed to ,darwin's1 and appeared almost at the same time1 has elaborated quite consistently1 and to the utmost extent1 these anthropomorphic conceptions of the ,creator4 ,i maintain with regard to the much-talked-of 8purpose in nature10 that it really has no existence but for those persons who observe phenomena in animals and plants in the most superficial manner4 ,without going more deeply into the matter1 we can see at once that the rudimentary organs are a formidable obstacle to this theory4 ,and1 indeed1 everyone who makes a really close study of the organization and mode of life of the various animals and plants1 and becomes familiar with the reciprocity or interaction of the phenomena of life1 and the so-called 8economy of nature10 must necessarily come to the conclusion that this 8purposiveness0 no more exists than the much-talked-of 8beneficence0 of the ,creator4 ,these optimistic views have1 unfortunately1 as little real foundation as the favourite phrase1 the 8moral order of the universe10 which is illustrated in an ironical way by the history of all nations4 ,the dominion of the 8moral0 popes1 and their pious inquisition1 in the medival times1 is not less significant of this than the present prevailing militarism1 with its 8moral0 apparatus of needle-guns and other refined instruments of murder4 ,if we contemplate the common life and the mutual relations between plants and animals 7man included71 we shall find everywhere1 and at all times1 the very opposite of that kindly and peaceful social life which the goodness of the ,creator ought to have prepared for his creatures--we shall rather find everywhere a pitiless1 most embittered ,struggle of ,all against ,all4 ,nowhere in nature1 no matter where we turn our eyes1 does that idyllic peace1 celebrated by the poets1 exist2 we find everywhere a struggle and a striving to annihilate neighbours and competitors4 ,passion and selfishness--conscious or unconscious--is everywhere the motive force of life4 ,the well-known words of the ,german poet-- 8,die ,welt ist vollkommen berall ,wo der ,mensch nicht hinkommt mit seiner ,qual40#a are beautiful1 but1 unfortunately1 not true4 ,man in this respect certainly forms no exception to the rest of the animal world4 ,the remarks which we shall have to make on the theory of 8,struggle for ,existence0 will sufficiently justify this assertion4 ,it is1 in fact1 ,darwin who has placed this important point1 in its high and general significance1 very clearly before our eyes1 and the chapter in his theory which he himself calls 8,struggle for ,existence0 is one of the most important parts of it4 ,whilst1 then1 we emphatically oppose the vital or teleological view of animate nature which presents animal and vegetable forms as the productions of a kind ,creator1 acting for a definite purpose1 or of a creative1 natural force acting for a definite purpose1 we must1 on the other hand1 decidedly adopt that view of the universe which is called the mechanical or causal4 ,it may also be called the monistic1 or single-principle theory1 as opposed to the twofold principle1 or dualistic theory1 which is necessarily implied in the teleological conception of the universe4 ,the mechanical view of nature has for many years been so firmly established in certain domains of natural science1 that it is here unnecessary to say much about it4 ,it no longer occurs to physicists1 chemists1 mineralogists1 or astronomers1 to seek to find in the phenomena which continually appear before them in their scientific domain the action of a ,creator acting for a definite purpose4 ,they universally1 and without hesitation1 look upon the phenomena which appear in their different departments of study as the necessary and invariable effects of physical and chemical forces which are inherent in matter4 ,thus far their view is purely materialistic1 in a certain sense of that 8word of many meanings40 ,when a physicist traces the phenomena of motion in electricity or magnetism1 the fall of a heavy body1 or the undulations in the waves of light1 he never1 in the whole course of his research1 thinks of looking for the interference of a supernatural power4 ,in this respect1 ,biology1 as the science of so-called 8animated0 natural bodies1 was formerly placed in sharp opposition to the above-mentioned inorganic natural sciences 7,anorganology74 ,it is true modern ,physiology1 the science of the phenomena of motion in animals and plants1 has completely adopted the mechanical view2 but ,morphology1 the science of the forms of animals and plants1 has not been affected at all by it4 ,morphologists1 in spite of the position of physiology1 have continued1 as before1 in opposition to the mechanical view of functions1 to look upon the forms of animals and plants as something which cannot be at all explained mechanically1 but which must owe its origin necessarily to a higher1 supernatural creative power1 acting for a definite purpose4 ,in this general view it is quite indifferent whether the creative power be worshipped as a personal god1 or whether it be termed the power of life 7vis vitalis71 or final cause 7causa finalis74 ,in any case1 to express it in one word1 its supporters have recourse to a miracle for an explanation4 ,they throw themselves into the arms of a poetic faith1 which as such can have no value in the domain of scientific knowledge4 ,all that was done before ,darwin1 to establish a natural mechanical conception of the origin of animals and plants1 has been in vain1 and until his time no theory gained a general recognition4 ,darwin's theory first succeeded in doing this1 and thus has rendered an immense service4 ,for the idea of the unity of organic and inorganic nature is now firmly established2 and that branch of natural science which had longest and most obstinately opposed mechanical conception and explanation1 viz41 the science of the structure of animate forms1 is launched on to identically the same road towards perfection as that along which all the rest of the natural sciences are travelling4 ,the unity of all natural phenomena is by ,darwin's theory finally established4 ,this unity of all nature1 the animating of all matter1 the inseparability of mental power and corporeal substance1 ,goethe has asserted in the words3 8,matter can never exist and be active without mind1 nor can mind without matter40 ,these first principles of the mechanical conception of the universe have been taught by the great monistic philosophers of all ages4 ,even ,democritus of ,abdera1 the immortal founder of the ,atomic theory1 clearly expressed them about #ejj years before ,christ2 but the great ,dominican friar1 ,giordano ,bruno1 did so even more explicitly4 ,for this he was burnt at the stake1 by the ,christian inquisition in ,rome1 on the #agth of ,feb41 #afjj1 on the same day on which1 #cf years before1 ,galileo1 his great fellow-countryman and fellow-worker1 was born4 ,such men1 who live and die for a great idea1 are usually stigmatized as 8materialists02 but their opponents1 whose arguments were torture and the stake1 are praised as 8spiritualists40 ,by the ,theory of ,descent we are for the first time enabled to conceive of the unity of nature in such a manner that a mechanico-causal explanation of even the most intricate organic phenomena1 for example1 the origin and structure of the organs of sense1 is no more difficult 7in a general way7 than is the mechanical explanation of any physical process2 as1 for example1 earthquakes1 the courses of the wind1 or the currents of the ocean4 ,we thus arrive at the extremely important conviction that all natural bodies which are known to us are equally animated1 that the distinction which has been made between animate and inanimate bodies does not exist4 ,when a stone is thrown into the air1 and falls to earth according to definite laws1 or when in a solution of salt a crystal is formed1 the phenomenon is neither more nor less a mechanical manifestation of life than the growth and flowering of plants1 than the propagation of animals or the activity of their senses1 than the perception or the formation of thought in man4 ,this final triumph of the monistic conception of nature constitutes the highest and most general merit of the ,theory of ,descent1 as reformed by ,darwin4 ,,chapter ,,ii4 ,,scientific ,,justification ,,of ,,the ,,theory ,,of ,,descent4 ,,history ,,of ,,creation ,,according ,,to ,,linn,,us4 ,the ,theory of ,descent1 or ,doctrine of ,filiation1 as the ,monistic ,explanation of ,organic ,natural ,phenomena4--,its ,comparison with ,newton's ,theory of ,gravitation4--,limits of ,scientific ,explanation and of ,human ,knowledge in general4--,all ,knowledge founded originally on ,sensuous ,experience1 a posteriori4--,transition of a posteriori knowledge1 by ,inheritance1 into a priori knowledge4--,contrast between the ,supernatural ,hypotheses of the ,creation according to ,linnus1 ,cuvier1 ,agassiz1 and the ,natural ,theories of ,development according to ,lamarck1 ,goethe1 and ,darwin4--,connection of the former with the ,monistic 7mechanical71 of the latter with the ,dualistic ,conception of the ,universe4--,monism and ,materialism4--,scientific and ,moral ,materialism4--,the ,history of ,creation according to ,moses4--,linnus as the ,founder of the ,systematic ,description of ,nature and ,distinction of ,species4--,linnus' ,classification and ,binary ,nomenclature4--,meaning of ,linnus' ,idea of ,species4--,his ,history of ,creation4--,linnus' view of the ,origin of ,species4 ,the value which every scientific theory possesses is measured by the number and importance of the objects which can be explained by it1 as well as by the simplicity and universality of the causes which are employed in it as grounds of explanation4 ,on the one hand1 the greater the number and the more important the meaning of the phenomena explained by the theory1 and the simpler1 on the other hand1 and the more general the causes which the theory assigns as explanations1 the greater is its scientific value1 the more safely we are guided by it1 and the more strongly are we bound to adopt it4 ,let us call to mind1 for example1 that theory which has ranked up to the present time as the greatest achievement of the human mind--the ,theory of ,gravitation1 which ,newton1 two hundred years ago1 established in his ,mathematical ,principles of ,natural ,philosophy4 ,here we find that the object to be explained is as large as one can well imagine4 ,he undertook to reduce the phenomena of the motion of the planets1 and the structure of the universe1 to mathematical laws4 ,as the most simple cause of these intricate phenomena of motion1 ,newton established the law of weight or attraction1 the same law which is the cause of the fall of bodies1 of adhesion1 cohesion1 and many other phenomena4 ,if we apply the same standard of valuation to ,darwin's theory1 we must arrive at the conclusion that this theory1 also1 is one of the greatest achievements of the human mind1 and that it may be placed quite on a level with ,newton's ,theory of ,gravitation4 ,perhaps this opinion will seem a little exaggerated1 or at any rate very bold1 but ,i hope in the course of this treatise to convince the reader that this estimate is not too high4 ,in the preceding chapter1 some of the most important and most general phenomena in organic nature1 which have been explained by ,darwin's theory1 have been named4 ,among them are the variations in form which accompany the individual development of organisms1 most varied and complicated phenomena1 which until now presented the greatest difficulties in the way of mechanical explanation1 that is1 in the tracing of them to active causes4 ,we have mentioned the rudimentary organs1 those exceedingly remarkable structures in animals and plants which have no object and refute every teleological explanation seeking for the final purpose of the organism4 ,a great number of other phenomena might have been mentioned1 which are no less important1 and are explained in the simplest manner by ,darwin's reformed ,theory of ,descent4 ,for the present ,i will only mention the phenomena presented to us by the geographical distribution of animals and plants on the surface of our planet1 as well as the geological distribution of the extinct and petrified organisms in the different strata of the earth's crust4 ,these important palontological and geographical phenomena1 which were formerly only known to us as facts1 are now traced to their active causes by the ,theory of ,descent4 ,the same statement applies further to all the general laws of ,comparative ,anatomy1 especially to the great law of division of labour or separation 7polymorphism1 or differentiation71 a law which determines the form or structure of human society1 as well as the organization of individual animals and plants4 ,it is this law which necessitates an ever increasing variety1 as well as a progressive development of organic forms4 ,this law of the division of labour has1 up to the present time1 been only recognized as a fact1 and it1 like the law of progressive development1 or the law of progress which we perceive active everywhere in the history of nations 7as also in that of animals and plants71 is explained by ,darwin's ,doctrine of ,descent4 ,then1 if we turn our attention to the great whole of organic nature1 if we compare all the individual groups of phenomena of this immense domain of life1 it cannot fail to appear1 in the light of the ,doctrine of ,descent1 no longer as the ingeniously designed work of a ,creator building up according to a definite purpose1 but as the necessary consequence of active causes1 which are inherent in the chemical combination of matter itself1 and in its physical properties4 ,in fact1 we can most positively assert1 and ,i shall justify this assertion in the course of these pages1 that by the ,doctrine of ,filiation1 or ,descent1 we are enabled for the first time to reduce all organic phenomena to a single law1 and to discover a single active cause for the infinitely intricate mechanism of the whole of this rich world of phenomena4 ,in this respect1 ,darwin's theory stands quite on a level with ,newton's ,theory of ,gravitation2 indeed1 it even rises higher than ,newton's theory6 ,the grounds of explanation are equally simple in the two theories4 ,in explaining this most intricate world of phenomena1 ,darwin does not make use of new or hitherto unknown properties of matter1 nor does he1 as one might suppose1 make use of discoveries of new combinations of matter or of new forces of organization2 but it is simply by extremely ingenious combination1 by the synthetic comprehension1 and by the thoughtful comparison of a number of well-known facts1 that ,darwin has solved the 8holy mystery0 of the living world of forms4 ,the consideration of the interchanging relations which exist between two general properties of organisms1 viz41 ,inheritance and ,adaptation1 is what has here been of the first importance4 ,merely by considering the relations between these two vital actions or physiological functions of organisms1 also further by considering the reciprocal interaction which all animals and plants1 living in one and the same place1 necessarily exert on one another--solely by the correct estimate of these simple facts1 and by skilfully combining them1 ,darwin has succeeded in finding the true active causes 7caus efficientes7 of the immensely intricate world of forms in organic nature4 ,in any case we are in duty bound to accept this theory till a better one be found1 which will undertake to explain the same amount of facts in an equally simple manner4 ,until now we have been in utter want of such a theory4 ,the fundamental idea that all different animal and vegetable forms must be descended from a few or even from one single1 most simple primary form1 was indeed not new4 ,this idea was long since distinctly formulated--first by the great ,lamarck1 at the beginning of our century4 ,but ,lamarck in reality only expressed the hypothesis of the ,doctrine of ,filiation1 without establishing it by an explanation of the active causes4 ,and it is just the demonstration of these causes which marks the extraordinary progress which ,darwin's theory has made beyond that of ,lamarck4 ,in the physiological properties of ,inheritance and ,adaptation of organic matter1 ,darwin discovered the true cause of the genealogical relationship of organisms4 ,it was not possible for the genius of ,lamarck in his day to command that colossal material of biological facts which has been collected by the patient zoological and botanical investigations of the last fifty years1 and which has been used by ,darwin as an overpowering apparatus of evidence4 ,darwin's theory is therefore not what his opponents frequently represent it as being--an unwarranted hypothesis taken up at random4 ,it is not for zoologists or botanists to accept or reject this as an explanatory theory1 as they please2 they are rather compelled and obliged to accept it1 according to the general principle observed in all natural sciences1 that we must accept and retain for the explanation of phenomena any theory which1 though it has only a feeble basis1 is compatible with the actual facts--until it is replaced by a better one4 ,if we do not adopt it1 we renounce a scientific explanation of phenomena1 and this is1 in fact1 the position which many biologists still maintain4 ,they look upon the whole domain of animate nature as a perfect mystery1 and upon the origin of animals and plants1 the phenomena of their development and affinities1 as quite inexplicable and miraculous2 in fact1 they will not allow that there can be a true understanding of them4 ,those opponents of ,darwin who do not exactly wish to renounce a scientific explanation are in the habit of saying1 8,darwin's theory of the common origin of the different species is only one hypothesis2 we oppose to it another1 the hypothesis that the individual animal and vegetable species have not developed one from another by descent1 but that they have come into existence independently of one another1 by a still undiscovered law of nature40 ,but as long as it is not shown how this coming into existence is to be conceived of1 and what that 8law of nature0 is--as long as not even probable grounds of explanation can be brought forward to account for the independent coming into existence of animal and vegetable species1 so long this counter-hypothesis is in fact no hypothesis1 but an empty unmeaning phrase4 ,darwin's theory ought1 moreover1 not to be called an hypothesis4 ,for a scientific hypothesis is a supposition1 postulating the existence of unknown properties or motional phenomena of natural bodies1 which properties have not as yet been observed by the experience of the senses4 ,but ,darwin's theory does not assume such unknown conditions2 it is based upon general properties of organisms that have long been recognized1 and--as has been remarked--it is the exceedingly ingenious and comprehensive combination of a number of phenomena which had hitherto stood isolated1 which gives the theory its extraordinarily great and intrinsic value4 ,by it we are for the first time in a position to demonstrate an active cause for all the known morphological phenomena in the animal and vegetable kingdoms2 and1 in fact1 this cause is always one and the same1 viz41 the alternate action of ,adaptation and ,inheritance1 therefore a physiological1 that is1 a physico-chemical or mechanical1 relationship4 ,for these reasons the acceptance of the ,doctrine of ,filiation1 as mechanically established by ,darwin1 is a binding and unavoidable necessity for the whole domain of zoology and botany4 ,as1 therefore1 in my opinion the immense importance of ,darwin's theory lies in the fact that it has mechanically explained those organic phenomena of forms which had hitherto been unexplained1 it is perhaps necessary that ,i should here say a few words about the different ideas connected with the word 8explanation40 ,it is very frequently said1 in opposition to ,darwin's theory1 that it does indeed explain those phenomena by ,inheritance and ,adaptation1 but that it does not at the same time explain those properties of organic matter1 and that therefore we do not arrive at first causes4 ,this objection is quite correct1 but it applies equally to all explanations of phenomena4 ,we nowhere arrive at a knowledge of first causes4 ,the origin of every simple salt crystal1 which we obtain by evaporating its mother liquor1 is no less mysterious to us1 as far as concerns its first cause1 and in itself no less incomprehensible than the origin of every animal which is developed out of a simple cell4 ,in explaining the most simple physical or chemical phenomena1 as the falling of a stone1 or the formation of a chemical combination1 we arrive1 by discovering and establishing the active causes--for example1 the gravitation or the chemical affinity--at other remoter phenomena1 which in themselves are mysterious4 ,this arises from the limitation or relativity of our powers of understanding4 ,we must not forget that human knowledge is absolutely limited1 and possesses only a relative extension4 ,it is1 in its essence1 limited by the very nature of our senses and of our brains4 ,all knowledge springs from sensuous perceptions4 ,in opposition to this statement1 the innate1 priori knowledge of man may be brought up2 but we can see that the so-called priori knowledge can by ,darwin's theory be proved to have been acquired posteriori1 being based on experience as its first cause4 ,knowledge which is based originally upon purely empirical observations1 and which is therefore a purely sensuous experience1 but has then been transmitted from generation to generation by inheritance1 appears in later generations as if it were independent1 innate1 and priori4 ,in our late animal ancestors1 all our so-called 8 priori knowledge0 was originally acquired posteriori1 and only gradually became priori by inheritance4 ,it is based in the first instance upon experiences1 and by the laws of ,inheritance and ,adaptation we can positively prove that knowledge priori and knowledge posteriori cannot rightly be placed in opposition1 as is usually done4 ,on the contrary1 sensuous experience is the original source of all knowledge4 ,for this reason alone1 all our knowledge is limited1 and we can never apprehend the first causes of any phenomena4 ,the force of crystallization1 the force of gravitation1 and chemical affinity remain in themselves just as incomprehensible as do ,adaptation and ,inheritance4 ,seeing that ,darwin's theory explains from a single point of view the totality of all those phenomena of which we have given a brief survey1 that it demonstrates one and the same quality of the organism as the active cause in all cases1 we must allow that it gives us for the present all that we can desire4 ,moreover1 we have good reason to hope that at some future time we shall learn to explain the first causes at which ,darwin has arrived1 namely1 the properties of ,adaptation and ,inheritance2 and that we shall succeed in discovering in the composition of albuminous matter certain molecular relations as the remoter1 simpler causes of these phenomena4 ,there is indeed no prospect of this in the immediate future1 and we content ourselves for the present with the tracing back of organic phenomena to two mysterious properties1 just as in the case of ,newton's theory we are satisfied with tracing the planetary motions to the force of gravitation1 which itself is likewise a mystery to us and not cognizable in itself4 ,before commencing our principal task1 which is the careful discussion of the ,doctrine of ,descent1 and the consequences that arise out of it1 let us take an historical retrospect of the most important and most widely spread of those views1 which before ,darwin men had elaborated concerning organic creation1 and the coming into existence of the many animal and vegetable species4 ,in doing this ,i have no intention of entertaining the reader with a statement of all the innumerable stories about the creation which have been current among the different human species1 races1 or tribes4 ,however interesting and gratifying this task would be1 from an ethnographical point of view1 as well as in a history of civilization1 it would lead us here much too far from our subject4 ,besides1 the great majority of all these legends about creation bear too clearly the stamp of arbitrary fiction1 and of a want of a close observance of nature1 to be of interest in a scientific treatment of the history of creation4 ,i shall therefore only select the ,mosaic history from among those that are not founded on scientific investigation1 on account of the unparalleled influence which it has gained in the western civilized world2 and then ,i shall immediately take up the scientific hypothesis about creation1 which originated with ,linnus as late as the commencement of last century4 ,all the different conceptions which man has ever formed about the coming into existence of the different animal and vegetable species may conveniently be divided into two great contrasted groups--the natural and supernatural histories of creation4 ,these two groups1 on the whole1 correspond with the two different principal forms of the human notions of the universe which we have already contrasted as the monistic and the dualistic conception of nature4 ,in the usual dualistic or teleological 7vital7 conception of the universe1 organic nature is regarded as the purposely executed production of a ,creator working according to a definite plan4 ,its adherents see in every individual species of animal and plant an 8embodied creative thought10 the material expression of a definite first cause 7causa finalis7 acting for a set purpose4 ,they must necessarily assume supernatural 7not mechanical7 processes for the origin of organisms4 ,with justice1 we may therefore designate their scheme of the world's growth as the ,supernatural ,history of ,creation4 ,among all such teleological histories of creation1 that of ,moses has gained the greatest influence1 since even so distinguished a naturalist as ,linnus has claimed admittance for it in ,natural ,science4 ,cuvier's and ,agassiz's views of creation also belong to this group1 as do in fact those of the great majority of both scientific and unscientific men4 ,on the other hand1 the theory of development carried out by ,darwin1 which we shall have to treat of here as the ,non-miraculous or ,natural ,history of ,creation1 and which has already been put forward by ,goethe and ,lamarck1 must1 if carried out logically1 lead to the monistic or mechanical 7causal7 conception of the universe4 ,in opposition to the dualistic or teleological conception of nature1 our theory considers organic1 as well as inorganic1 bodies to be the necessary products of natural forces4 ,it does not see in every individual species of animal and plant the embodied thought of a personal ,creator1 but the expression for the time being of a mechanical process of development of matter1 the expression of a necessarily active cause1 that is1 of a mechanical cause 7causa efficiens74 ,where teleological ,dualism seeks the arbitrary thoughts of a capricious ,creator in the miracles of creation1 causal ,monism finds in the process of development the necessary effects of eternal immutable laws of nature4 ,the ,monism here maintained by us is often considered identical with ,materialism4 ,now1 as ,darwinism1 and in fact the whole theory of development1 has been designated as 8materialistic10 ,i cannot avoid here at once guarding myself against this ambiguous word1 and against the malice with which1 in certain quarters1 it is employed to stigmatize our doctrine4 ,by the word 8,materialism10 two completely different things are very frequently confounded and mixed up1 which in reality have nothing whatever to do with each other1 namely1 scientific and moral materialism4 ,scientific materialism1 which is identical with our ,monism1 affirms in reality no more than that everything in the world goes on naturally--that every effect has its cause1 and every cause its effect4 ,it therefore assigns to causal law--that is1 the law of a necessary connection between cause and effect--its place over the entire series of phenomena that can be known4 ,at the same time1 scientific materialism positively rejects every belief in the miraculous1 and every conception1 in whatever form it appears1 of supernatural processes4 ,accordingly1 nowhere in the whole domain of human knowledge does it recognize real metaphysics1 but throughout only physics2 through it the inseparable connection between matter1 form1 and force becomes self evident4 ,this scientific materialism has long since been so universally acknowledged in the wide domain of inorganic science1 in ,physics and ,chemistry1 in ,mineralogy and ,geology1 that no one now doubts its sole authority4 ,but in ,biology1 or ,organic science1 the case is very different2 here its value is still continually a matter of dispute in many quarters4 ,there is1 however1 nothing else which can be set up against it1 excepting the metaphysical spectre of a vital power1 or empty theological dogma4 ,if we can prove that all nature1 so far as it can be known1 is only one1 that the same 8great1 eternal1 iron laws0 are active in the life of animals and plants1 as in the growth of crystals and in the force of steam1 we may with reason maintain the monistic or mechanical view of things throughout the domain of ,biology--in ,zoology and ,botany--whether it be stigmatized as 8materialism0 or not4 ,in such a sense all exact science1 and the law of cause and effect at its head1 is purely materialistic4 ,moral1 or ethical ,materialism1 is something quite distinct from scientific materialism1 and has nothing whatever in common with the latter4 ,this real materialism proposes no other aim to man in the course of his life than the most refined possible gratification of his senses4 ,it is based on the delusion that purely material enjoyment can alone give satisfaction to man2 but as he can find that satisfaction in no one form of sensuous pleasure1 he dashes on weariedly from one to another4 ,the profound truth that the real value of life does not lie in material enjoyment1 but in moral action--that true happiness does not depend upon external possessions1 but only in a virtuous course of life--this is unknown to ethical materialism4 ,we therefore look in vain for such materialism among naturalists and philosophers1 whose highest happiness is the intellectual enjoyment of ,nature1 and whose highest aim is the knowledge of her laws4 ,we find it in the palaces of ecclesiastical princes1 and in those hypocrites who1 under the outward mask of a pious worship of ,god1 solely aim at hierarchical tyranny over1 and material spoliation of1 their fellow-men4 ,blind to the infinite grandeur of the so-called 8raw material10 and the glorious world of phenomena arising from it--insensible to the inexhaustible charms of ,nature1 and without a knowledge of her laws--they stigmatize all natural science1 and the culture arising from it1 as sinful 8materialism10 while really it is this which they themselves exhibit in a most shocking form4 ,satisfactory proofs of this are furnished1 not only by the whole history of the ,catholic ,popes1 with their long series of crimes1 but also by the history of the morals of orthodoxy in every form of religion4 ,in order1 then1 to avoid in future the usual confusion of this utterly objectionable ,moral ,materialism with our ,scientific ,materialism1 we think it necessary to call the latter either ,monism or ,realism4 ,the principle of this ,monism is the same as what ,kant terms the 8principle of mechanism10 and of which he expressly asserts1 that without it there can be no natural science at all4 ,this principle is quite inseparable from our ,non-miraculous ,history of ,creation1 and characterizes it as opposed to the teleological belief in the miracles of a ,supernatural ,history of ,creation4 ,let us now first of all glance at the most important of all the supernatural histories of creation1 ,i mean that of ,moses1 as it has been handed down to us in the ,bible1 the ancient document of the history and laws of the ,jewish people4 ,the ,mosaic history of creation1 since in the first chapter of ,genesis it forms the introduction to the ,old ,testament1 has enjoyed1 down to the present day1 general recognition in the whole ,jewish and ,christian world of civilization4 ,its extraordinary success is explained not only by its close connection with ,jewish and ,christian doctrines1 but also by the simple and natural chain of ideas which runs through it1 and which contrasts favourably with the confused mythology of creation current among most of the other ancient nations4 ,first the ,lord ,god creates the earth as an inorganic body2 then he separates light from darkness1 then water from the dry land4 ,now the earth has become inhabitable for organisms1 and plants are first created1 animals later--and among the latter the inhabitants of the water and the air first1 afterwards the inhabitants of the dry land4 ,finally ,god creates man1 the last of all organisms1 in his own image1 and as the ruler of the earth4 ,two great and fundamental ideas1 common also to the non-miraculous theory of development1 meet us in this ,mosaic hypothesis of creation1 with surprising clearness and simplicity--the idea of separation or differentiation1 and the idea of progressive development or perfecting4 ,although ,moses looks upon the results of the great laws of organic development 7which we shall later point out as the necessary conclusions of the ,doctrine of ,descent7 as the direct actions of a constructing ,creator1 yet in his theory there lies hidden the ruling idea of a progressive development and a differentiation of the originally simple matter4 ,we can therefore bestow our just and sincere admiration on the ,jewish lawgiver's grand insight into nature1 and his simple and natural hypothesis of creation1 without discovering in it a so-called 8divine revelation40 ,that it cannot be such is clear from the fact that two great fundamental errors are asserted in it1 namely1 first1 the geocentric error that the earth is the fixed central point of the whole universe1 round which the sun1 moon1 and stars move2 and secondly1 the anthropocentric error1 that man is the premeditated aim of the creation of the earth1 for whose service alone all the rest of nature is said to have been created4 ,the former of these errors was demolished by ,copernicus' ,system of the ,universe in the beginning of the #afth century1 the latter by ,lamarck's ,doctrine of ,descent in the beginning of the #aith century4 ,although the geocentric error of the ,mosaic history was demonstrated by ,copernicus1 and thereby its authority as an absolutely perfect divine revelation was destroyed1 yet it has maintained1 down to the present day1 such influence1 that it forms in many wide circles the principle obstacle to the adoption of a natural theory of development4 ,even in our century1 many naturalists1 especially geologists1 have tried to bring the ,mosaic theory into harmony with the recent results of natural science1 and have1 for example1 interpreted ,moses' seven days of creation as seven great geological periods4 ,however1 all these ingenious attempts at interpretation have so utterly failed1 that they require no refutation here4 ,the ,bible is no scientific book1 but consists of records of the history1 the laws1 and the religion of the ,jewish people1 the high merit of which1 as a history of civilization1 is not impaired by the fact that in all scientific questions it has no commanding importance1 and is full of gross errors4 ,we may now make a great stride over more than three thousand years1 from ,moses1 who died about the year #adhj before ,christ1 to ,linnus1 who was born in the year #agjg after ,christ4 ,during this whole period no history of creation was brought forward that gained any lasting importance1 or the closer examination of which would here be of any interest4 ,indeed1 during the last fifteen hundred years1 since ,christianity gained its supremacy1 the ,mosaic history of creation1 together with the dogmas connected with it1 has become so generally predominant1 that the #aith century is the first that has dared positively to rise against it4 ,even the great ,swedish naturalist1 ,linnus1 the founder of modern natural history1 linked his ,system of ,nature most closely to the ,mosaic history of creation4 ,the extraordinary progress which ,charles ,linnus made in the so-called descriptive natural sciences1 consists1 as is well known1 in his having established a system of nomenclature of animals and plants1 which he carried out in a manner so perfectly logical and consistent1 that down to the present day it has remained in many respects the standard for all succeeding naturalists engaged in the study of the forms of animals and plants4 ,although ,linnus' system was artificial1 although in classifying animal and vegetable species he only sought and employed single parts as the foundation for his divisions1 it has1 nevertheless1 gained the greatest success2 firstly1 in consequence of its being carried out consistently1 and secondly1 by its nomenclature of natural bodies1 which has become extremely important1 and at which we must here briefly glance4 ,before ,linnus' time1 many vain attempts had been made to throw light upon the endless chaos of different animal and vegetable forms 7then known7 by adopting for them suitable names and groupings2 but ,linnus1 by a happy hit1 succeeded in accomplishing this important and difficult task1 when he established the so-called 8binary nomenclature40 ,the binary nomenclature1 or the twofold designation1 as ,linnus first established it1 is still universally applied by all zoologists and botanists1 and will1 no doubt1 maintain itself1 for a long time to come1 with undiminished authority4 ,it consists in this1 that every species of animal and plant is designated by two names1 which stand to each other in the same relation as do the christian and surnames of a man4 ,the special name which corresponds with the christian name1 and expresses the idea of 8a species10 serves as the common designation of all individual animals or plants1 which are equal in all essential matters of form1 and are only distinguished by quite subordinate features4 ,the more general name1 on the other hand1 corresponding with the surname1 and which expresses the idea of a genus1 serves for the common designation of all the most nearly similar kinds or species4 ,according to ,linnus' plan1 the more general and comprehensive generic name is written first2 the special subordinate name of the species follows it4 ,thus1 for example1 the common cat is called ,felis domestica2 the wild cat1 ,felis catus2 the panther1 ,felis pardus2 the jaguar1 ,felis onca2 the tiger1 ,felis tigris2 the lion1 ,felis leo4 ,all these six kinds of animals of prey are different species of one and the same genus--,felis4 ,or1 to add an example from the vegetable kingdom1 according to ,linnus' designation the pine is ,pinus abies2 the fir1 ,pinus picea2 the larch1 ,pinus larix2 the ,italian pine1 ,pinus pinea2 the ,siberian stone pine1 ,pinus cembra2 the knee timber1 ,pinus mughus2 the common pine1 ,pinus silvestris4 ,all these seven kinds of pines are different species of one and the same genus--,pinus4 ,perhaps this advance made by ,linnus may seem to some only of subordinate importance in the practical distinction and designation of the variously formed organisms4 ,but in reality it was of the very greatest importance1 both from a practical and theoretical point of view4 ,for now1 for the first time1 it became possible to arrange the immense mass of different organic forms according to their greater or less degree of resemblance1 and to obtain an easy survey of the general outlines of such a 8system40 ,linnus facilitated the tabulation and survey of this 8system0 of plants and animals still more by placing together the most nearly similar genera into so-called orders 7ordines72 and by uniting the most nearly similar orders into still more comprehensive main divisions or classes4 ,thus1 according to ,linnus1 each of the two organic kingdoms were broken up into a number of classes1 the vegetable kingdom into twenty-four1 and the animal kingdom into six4 ,each class again contains several orders4 ,every single order may contain a number of genera1 and1 again1 every single genus several species4 ,valuable as was ,linnus' binary nomenclature in a practical way1 in bringing about a comprehensive systematic distinction1 designation1 arrangement1 and division of the organic world of forms1 yet the incalculable theoretical influence which it gained forthwith in relation to the history of creation was no less important4 ,even now all the important fundamental questions as to the history of creation turn finally upon the decision of the very remote and unimportant question1 ,what really are kinds or species8 ,even now the idea of organic species may be termed the central point of the whole question of creation1 the disputed centre1 about the different conceptions of which ,darwinists and ,anti-,darwinists fight4 ,according to ,darwin's opinion1 and that of his adherents1 the different species of one and the same genus of animals and plants are nothing else than differently developed descendants of one and the same original primary form4 ,the different kinds of pine mentioned above would accordingly have originated from a single primval form of pine4 ,in like manner the origin of all the species of cat mentioned above would be traced to a single common form of ,felis1 the ancestor of the whole genus4 ,but further1 in accordance with the ,doctrine of ,descent1 all the different genera of one and the same order ought also to be descended from one common primary ancestor1 and so1 in like manner1 all orders of a class from a single primary form4 ,on the other hand1 according to the idea of ,darwin's opponents1 all species of animals and plants are quite independent of each other1 and only the individuals of each species have originated from a single primary form4 ,but if we ask them how they conceive these original primary forms of each species to have come into existence1 they answer with a leap into the incomprehensible1 8,they were created40 ,linnus himself defined the idea of species in this manner by saying1 8,there are as many different species as there were different forms created in the beginning by the infinite ,being40 78,species tot sunt divers1 quot diversas formas ab initio creavit infinitum ens407 ,in this respect1 therefore1 he follows most closely the ,mosaic history of creation1 which in the same way maintains that animals and plants were created 8each one after its kind40 ,linnus1 accepting this1 held that originally of each species of animals and plants either a single individual or a pair had been created2 in fact a pair1 or1 as ,moses says1 8a male and a female0 of those species which have separate sexes1 but of those species in which each individual combines both sexual organs 7hermaphrodites71 as for instance the earthworm1 the garden and vineyard snails1 as well as the great majority of plants1 a single individual4 ,linnus further follows the ,mosaic legend in regard to the flood1 by supposing that the great general flood destroyed all existing organisms1 except those few individuals of each species 7seven pairs of the birds and of clean animals1 one pair of unclean animals7 which ,noah saved in the ark1 and which were placed again on land1 on ,mount ,ararat1 after the flood had subsided4 ,he tried to explain the geographical difficulty of the living together of the most different animals and plants1 as follows3 ,mount ,ararat1 in ,armenia1 being situated in a warm climate1 and rising over #af1jjj feet in height1 combines in itself the conditions for a temporary common abode of such animals as live in different zones4 ,accordingly1 animals accustomed to the polar regions could climb up the cold mountain ridges1 those accustomed to a warm climate could go down to the foot of the mountain1 and the inhabitants of a temperate zone could remain midway up the mountain4 ,from this point it was possible for them to spread north and south over the earth4 ,it is scarcely necessary to remark that this ,linnan hypothesis of creation1 which evidently was intended to harmonize most closely with the prevailing belief in the ,bible1 requires no serious refutation4 ,when we consider ,linnus' clearness and sagacity in other matters1 we may doubt whether he believed it himself4 ,as to the simultaneous origin of all individuals of each species from one pair of ancestors respectively 7or in the case of the hermaphrodite species1 from one original hermaphrodite71 it is clearly quite untenable2 for1 apart from other reasons1 in the first days after the creation1 the few animals of prey would have sufficed to have utterly demolished all the herbivorous animals1 as the herbivorous animals must have destroyed the few individuals of the different species of plants4 ,the existence of such an equilibrium in the economy of nature as obtains at present cannot possibly be conceived1 if only one individual of each species1 or only one pair1 had originally and simultaneously been created4 ,moreover1 how little importance ,linnus himself attached to this untenable hypothesis of creation is clear1 among other things1 from the fact that he recognized ,hybridism 7crossing7 as a source of the production of new species4 ,he assumed that a great number of independent new species had originated by the interbreeding of two different species4 ,indeed1 such hybrids are not at all rare in nature1 and it is now proved that a great number of species1 for example1 of the genus ,rubus 7bramble71 mullen 7,verbascum71 willow 7,salix71 thistle 7,cirsium71 are hybrids of different species of these genera4 ,we also know of hybrids between hares and rabbits 7two species of the genus ,lepus71 further of hybrids between different species of dog 7genus ,canis71 etc41 which can be propagated as independent species4 ,it is certainly very remarkable that ,linnus asserted the physiological 7therefore mechanical7 origin of new species in this process of hybridism4 ,it clearly stands in direct opposition to the supernatural origin of the other species by creation1 which he accepted as put forward in the ,mosaic account4 ,the one set of species would therefore have originated by dualistic 7teleological7 creation1 the other by monistic 7mechanical7 development4 ,the great and well merited authority which ,linnus gained by his systematic classification and by his other services to ,biology1 was clearly the reason why his views of creation also remained1 throughout the whole of the last century1 undisputed and generally recognized4 ,if throughout systematic ,zoology and ,botany the distinctions1 classification1 and designations of species1 introduced by ,linnus1 and the dogmatic ideas connected therewith had not been maintained--more or less unaltered--we should be at a loss to understand how his idea of an independent creation of single species could have stood1 by itself down to the present day4 ,it is only owing to his great authority1 and through his attaching himself to the prevailing ,biblical belief1 that his hypothesis of creation has retained its position so long4 ,,chapter ,,iii4 ,,the ,,history ,,of ,,creation ,,according ,,to ,,cuvier ,,and ,,agassiz4 ,general ,theoretical ,meaning of the ,idea of ,species4--,distinction between the ,theoretical and ,practical ,definition of the ,idea of ,species4--,cuvier's ,definition of ,species4--,merits of ,cuvier as the ,founder of ,comparative ,anatomy4--,distinction of the ,four ,principal ,forms 7types or branches7 of the ,animal ,kingdom1 by ,cuvier and ,br4--,cuvier's ,services to ,palontology4--,his ,hypothesis of the ,revolutions of our ,globe1 and the ,epochs of ,creation separated by them4--,unknown ,supernatural ,causes of the ,revolutions1 and the subsequent ,new ,creations4--,agassiz's ,teleological ,system of ,nature4--,his ,conception of the ,plan of ,creation1 and its six ,categories 7groups in classification74--,agassiz's ,views of the ,creation of ,species4--,rude ,conception of the ,creator as a man-like being in ,agassiz's ,hypothesis of ,creation4--,its internal ,inconsistency and ,contradictions with the important ,palontological ,laws discovered by ,agassiz4 ,the real matter of dissension in the contest carried on by naturalists as to the origin of organisms1 their creation and development1 lies in the conceptions which are entertained about the nature of species4 ,naturalists either agree with ,linnus1 and look upon the different species as distinct forms of creation1 independent of one another1 or they assume with ,darwin their blood-relationship4 ,if we share ,linnus' view 7which was discussed in our last chapter71 that the different organic species came into existence independently--that they have no blood-relationship--we are forced to admit that they were created independently1 and we must either suppose that every single organic individual was a special act of creation 7to which surely no naturalist will agree71 or we must derive all individuals of every species from a single individual1 or from a single pair1 which did not arise in a natural manner1 but was called into being by command of a ,creator4 ,in so doing1 however1 we turn aside from the safe domain of a rational knowledge of nature1 and take refuge in the mythological belief in miracles4 ,if1 on the other hand1 with ,darwin1 we refer the similarity of form of the different species to real blood-relationship1 we must consider all the different species of animals and plants as the altered descendants of one or a few most simple original forms4 ,viewed in this way1 the ,natural ,system of organisms 7that is1 their tree-like and branching arrangement and division into classes1 orders1 families1 genera1 and species7 acquires the significance of a real genealogical tree1 whose root is formed by those original archaic forms which have long since disappeared4 ,but a truly natural and consistent view of organisms can assume no supernatural act of creation for even those simplest original forms1 but only a coming into existence by spontaneous generation#b 7archigony1 or generatio spontanea74 ,from ,darwin's view of the nature of species1 we arrive therefore at a natural theory of development2 but from ,linnus' conception of the idea of species1 we must assume a supernatural dogma of creation4 ,most naturalists after ,linnus1 whose great services in systematic and descriptive natural history won for him such high authority1 followed in his footsteps1 and without further inquiry into the origin of organization1 they assumed1 in the sense of ,linnus1 an independent creation of individual species1 in conformity with the ,mosaic account of creation4 ,the foundation of their conception was based upon ,linnus' words3 8,there are as many different species as there were different forms created in the beginning by the ,infinite ,being40 ,we must here remark at once1 without going further into the definition of species1 that all zoologists and botanists in their classificatory systems1 in the practical distinction and designation of species of animals and plants1 never troubled1 or even could trouble1 themselves in the slightest degree about this assumed creation of the parent forms4 ,in reference to this1 one of our first zoologists1 the ingenious ,fritz ,mller1 makes the following striking observation3 8,just as in ,christian countries there is a catechism of morals1 which every one knows by heart1 but which no one considers it his duty to follow1 or expects to see followed by others1--so zoology also has its dogmas1 which are just as generally professed as they are denied in practice40 7,fr ,darwin1 p4 #ga477af7 ,linnus' venerated dogma of species is just such an irrational dogma1 and for that very reason it is powerful4 ,although most naturalists blindly submitted to it1 yet they were1 of course1 never in a position to demonstrate the descent of individuals belonging to one species from the common1 originally created1 primitive form4 ,zoologists and botanists1 in their systems of nomenclature1 confined themselves entirely to the similarity of forms1 in order to distinguish and name the different species4 ,they placed in one species all organic individuals which were very similar1 or almost identical in form1 and which could only be distinguished from one another by very unimportant differences4 ,on the other hand1 they considered as different species those individuals which presented more essential or more striking differences in the formation of their bodies4 ,but of course this opened the flood-gates to the most arbitrary proceedings in the systematic distinctions of species4 ,for as all the individuals of one species are never completely alike in all their parts1 but as every species varies more or less1 no one could point out which degree of variation constituted a really 8good species10 or which degree indicated a 8mere variety40 ,this dogmatic conception of the idea of species1 and the arbitrary proceedings connected with it1 necessarily led to the most perplexing contradictions1 and to the most untenable suppositions4 ,this is clearly demonstrable in the case of the celebrated ,cuvier 7born in #agfi71 who next to ,linnus has exercised the greatest influence on the study of zoology4 ,in his conception and definition of the idea of species1 he agreed on the whole with ,linnus1 and shared also his belief in an independent creation of individual species4 ,cuvier considered their immutability of such importance that he was led to the foolish assertion--8,the immutability of species is a necessary condition of the existence of scientific natural history40 ,as ,linnus' definition of species did not satisfy him1 he made an attempt to give a more exact and1 for systematic practice1 a more useful definition1 in the following words3 8,all those individual animals and plants belong to one species which can be proved to be either descended from one another1 or from common ancestors1 or which are as similar to these as the latter are among themselves40 ,in dealing with this matter1 ,cuvier reasoned in the following manner3--8,in those organic individuals1 of which we know that they are descended from one and the same common form of ancestors--in which1 therefore1 their common ancestry is empirically proved--there can be no doubt that they belong to one species1 whether they differ much or little from one another1 or whether they are almost alike or very unlike4 ,moreover1 all those individuals also belong to this species which differ no more from the latter 7those proved to be derived from a common stock7 than these differ from one another40 ,in a closer examination of this definition of species given by ,cuvier1 it becomes at once evident that it is neither theoretically satisfactory nor practically applicable4 ,cuvier1 with this definition1 began to move in the same circle in which almost all subsequent definitions of species have moved1 through the assumption of their immutability4 ,considering the extraordinary authority which ,george ,cuvier has gained in the science of organic nature1 and in consequence of the almost unlimited supremacy which his views exercised in zoology1 during the first half of our century1 it seems appropriate here to examine his influence a little more closely4 ,this is all the more necessary as we have to combat1 in ,cuvier1 the most formidable opponent to the ,theory of ,descent and the monistic conception of nature4 ,one of the many and great merits of ,cuvier is that he stands forth as the founder of ,comparative ,anatomy4 ,while ,linnus established the distinction of species1 genera1 orders1 and classes mostly upon external characters1 and upon separate and easily discoverable signs in the number1 size1 place1 and form of individual organic parts of the body1 ,cuvier penetrated much more deeply into the essence of organization4 ,he demonstrated great and wide differences in the inner structure of animals1 as the real foundation of a scientific knowledge and classification of them4 ,he distinguished natural families in the classes of animals1 and established his natural system of the animal kingdom on their comparative anatomy4 ,the progress from ,linnus' artificial system to ,cuvier's natural system was exceedingly important4 ,linnus had arranged all animals in a single series1 which he divided into six classes1 two classes of ,invertebrate1 and four classes of ,vertebrate animals4 ,he distinguished these artificially1 according to the nature of their blood and heart4 ,cuvier1 on the other hand1 showed that in the animal kingdom there were four great natural divisions to be distinguished1 which he termed ,principal ,forms1 or ,general ,plans1 or ,branches of the animal kingdom 7,embranchments71 namely--#a4 ,the ,vertebrate animals 7,vertebrata72 #b4 ,the ,articulate animals 7,articulata72 #c4 ,the ,molluscous animals 7,mollusca72 and #d4 ,the ,radiate animals 7,radiata74 ,he further demonstrated that in each of these four branches a peculiar plan of structure or type was discernible1 distinguishing each branch from the three others4 ,in the ,vertebrate animals it is distinctly expressed by the form of the skeleton1 or bony framework1 as also by the structure and position of the dorsal nerve-chord1 apart from many other peculiarities4 ,the ,articulate animals are characterized by their ventral nerve-chord and their dorsal heart4 ,in ,molluscs the sack-shaped and non-articulate body is the distinguishing feature4 ,the ,radiate animals1 finally1 differ from the three other principal forms by their body being the combination of four or more main sections united in the form of radii 7antimera74 ,the distinction of these four principal forms of animals1 which has become extremely productive in the development of zoology1 is commonly ascribed entirely to ,cuvier4 ,however1 the same thought was expressed almost simultaneously1 and independently of ,cuvier1 by ,br1 one of the greatest naturalists1 and still living1 who did the most eminent service in the study of animal development4 ,br showed that in the development of animals1 also1 four different main forms 7or types7 must be distinguished47#bj7 ,these correspond with the four plans of structure in animals1 which ,cuvier distinguished on the ground of comparative anatomy4 ,thus1 for example1 the individual development of all ,vertebrate animals agrees1 from the commencement1 so much in its fundamental features that the germs or embryos of different ,vertebrate animals 7for example1 of reptiles1 birds1 and mammals7 in their earlier stages cannot be distinguished at all4 ,it is only at a late stage of development that there gradually appear the more marked differences of form which separate those different classes and orders from one another4 ,the plan of structure1 which shows itself in the individual development of ,articulate animals 7insects1 spiders1 crabs71 is from the beginning essentially the same in all ,articulate animals1 but different from that of all ,vertebrate animals4 ,the same holds good1 with certain limitations1 in ,molluscous and ,radiated animals4 ,neither ,br1 who arrived at the distinction of the four animal types or principal forms through the history of the individual development 7,embryology71 nor ,cuvier1 who arrived at the same conclusion by means of comparative anatomy1 recognized the true cause of this difference4 ,this is disclosed to us by the ,theory of ,descent4 ,the wonderful and astonishing similarity in the inner organization and in the anatomical relations of structure1 and the still more remarkable agreement in the embryonic development of all animals belonging to one and the same type 7for example1 to the branch of the ,vertebrate animals71 is explained in the simplest manner by the supposition of their common descent from a single primary original form4 ,if this view is not accepted1 then the complete agreement of the most different ,vertebrate animals1 in their inner structure and their manner of development1 remains perfectly inexplicable4 ,in fact it can only be explained by the law of inheritance4 ,next to the comparative anatomy of animals and the systematic zoology founded anew by it1 it was specially to the science of petrifactions1 or ,palontology1 that ,cuvier rendered great service4 ,we must draw special attention to this1 because these very palontological views1 and the geological ideas connected with them1 were held almost universally in the highest esteem during the first half of the present century1 and caused the greatest hindrance to the working out of a truly natural history of creation4 ,petrifactions1 the scientific study of which ,cuvier promoted at the beginning of our century in a most extensive manner1 and established quite anew for the ,vertebrate animals1 play one of the most important parts in the 8non-miraculous history of creation40 ,for these remains and impressions of extinct animals and plants1 preserved to us in a petrified condition1 are the true 8monuments of the creation10 the infallible and indisputable records which fix the correct history of organisms upon an irrefragable foundation4 ,all petrified or fossil remains and impressions tell us of the forms and structure of such animals and plants as are either the progenitors and ancestors of the present living organisms1 or they are the representatives of extinct collateral lines1 which1 together with the present living organisms1 branched off from a common stem4 ,these inestimable records of the history of creation throughout a long period played a subordinate part in science4 ,their true nature was indeed correctly understood1 even more than five hundred years before ,christ1 by the great ,greek philosopher1 ,xenophanes of ,colophon1 the same who founded the so-called ,eleatic philosophy1 and who was the first to demonstrate with convincing precision that all conceptions of personal gods result in more or less rude anthropomorphism4 ,xenophanes for the first time1 asserted that the fossil impressions of animals and plants were real remains of formerly living creatures1 and that the mountains in whose rocks they were found must at an earlier date have stood under water4 ,but although other great philosophers of antiquity1 and among them ,aristotle1 also possessed this true knowledge1 yet throughout the illiterate ,middle ,ages1 and even with some naturalists of the last century1 the idea prevailed that petrifactions were so-called freaks of nature 7lusus natur71 or products of an unknown formative power or instinct of nature 7nisus formativus1 vis plastica74 ,respecting the nature of this mysterious and mystic creative power1 the strangest ideas were formed4 ,some believed that this constructive power--the same to which they also ascribed the coming into existence of the present species of animals and plants--had made numerous attempts to create organisms of different forms1 but that these attempts had only partially succeeded1 had often failed1 and that petrifactions were nothing more than such unsuccessful attempts4 ,according to others1 petrifactions originated from the influence of the stars upon the interior of the earth4 ,others1 again1 had the still cruder notion that the ,creator had first made models 7out of mineral substances--for example1 of gypsum or clay7 of those forms of animals and plants which he afterwards executed in organic substances1 and into which he breathed his living breath2 petrifactions were accordingly such rude inorganic models4 ,even as late as the last century these crude ideas prevailed1 and it was assumed1 for example1 that there existed a special 8seminal air10 which was said to penetrate into the earth with the water1 and by fructifying the stones formed petrifactions or 8stony flesh0 7caro fossilis74 ,it took a very long time before the simple and natural view was accepted1 namely1 that petrifactions are in reality nothing but what they appear to simple observation--the indestructible remains of extinct organisms4 ,it is true the celebrated painter1 ,leonardo da ,vinci1 in the #aeth century1 ventured to assert that the mud which was constantly deposited by water was the cause of petrifactions1 as it surrounded the indestructible shells of mussels and snails which lay at the bottom of the waters1 and gradually turned them into solid stone4 ,the same idea was maintained in the #afth century by a ,parisian potter1 ,palissy by name1 who became celebrated on account of his invention of china4 ,however1 the so-called 8professional men0 were very far from paying any regard to these correct assertions of a simple and healthy human understanding2 it was not till the end of the last century that it was generally accepted1 in consequence of the foundation of the ,neptunian geology by ,werner4 ,the foundation of a more strictly scientific palontology1 however1 belongs to the beginning of our century1 when ,cuvier published his classic researches on petrified ,vertebrate animals1 and when his great opponent1 ,lamarck1 made known his remarkable investigations on fossil ,invertebrate animals1 especially on petrified snails and clams4 ,in ,cuvier's celebrated work 8,on the ,fossil ,bones0 of ,vertebrate animals--principally of mammals and reptiles--we see that he had already arrived at the knowledge of some very important and general palontological laws1 which are of great consequence to the history of creation4 ,foremost among them stands the assertion that the extinct species of animals1 whose remains we find petrified in the different strata of the earth's crust1 lying one above another1 differ all the more strikingly from the still living kindred species of animals the deeper those strata lie--in other words1 the earlier the animals lived in past ages4 ,in fact1 in every perpendicular section of the stratified crust of the earth we find that the different strata1 deposited by the water in a certain historical succession1 are characterized by different petrifactions1 and that these extinct organisms become more like those of the present day the higher the strata lie2 in other words1 the more recent the period in the earth's history in which they lived1 died1 and became encrusted by the deposited and hardened strata of mud4 ,however important this general observation of ,cuvier's was in one sense1 yet in another it became to him the source of a very serious error4 ,for as he considered the characteristic petrifactions of each individual group of strata 7which had been deposited during one main period of the earth's history7 to be entirely different from those of the strata lying above or below1 and as he erroneously believed that one and the same species of animal was never found in two succeeding groups of strata1 he arrived at the false idea1 which was accepted as a law by most subsequent naturalists1 that a series of quite distinct periods of creation had succeeded one another4 ,each period was supposed to have had its special animal and vegetable world1 each its peculiar specific ,fauna and ,flora4 ,cuvier imagined that the whole history of the earth's crust1 since the time when living creatures had first appeared on the surface1 must be divided into a number of perfectly distinct periods1 or divisions of time1 and that the individual periods must have been separated from one another by peculiar revolutions of an unknown nature 7cataclysms1 or catastrophes74 ,each revolution was followed by the utter annihilation of the till then existing animals and plants1 and after its termination a completely new creation of organic forms took place4 ,a new world of animals and plants1 absolutely and specifically distinct from those of the preceding historical periods1 was called into existence at once1 and now again peopled the globe for thousands of years1 till it again perished suddenly in the crash of a new revolution4 ,about the nature and causes of these revolutions1 ,cuvier expressly said that no idea could be formed1 and that the present active forces in nature were not sufficient for their explanation4 ,cuvier points out four active causes as the natural forces1 or mechanical agents1 at present constantly but slowly at work in changing the earth's surface3 first1 rain1 which washes down the steep mountain slopes and heaps up dbris at their foot2 secondly1 flowing waters1 which carry away this dbris and deposit it as mud in stagnant waters2 thirdly1 the sea1 whose breakers gnaw at the steep sea coasts1 and throw up 8dunes0 on the flat sea margins2 finally and fourthly1 volcanos1 which break through and heave up the strata of the earth's hardened crust1 and pile up and scatter about the products of their eruptions4 ,whilst ,cuvier recognizes the constant slow transformation of the present surface of the earth by these four mighty causes1 he asserts at the same time that they would not have sufficed to effect the revolutions of the remote ages1 and that the anatomical structure of the earth's surface cannot be explained by the necessary action of those mechanical agents3 the great and marvellous revolutions of the whole earth's surface must1 according to him1 have been rather the effects of very peculiar causes1 completely unknown to us2 the usual thread of development was broken by them1 and the course of nature altered4 ,these views ,cuvier explained in a special work 8,on the ,revolutions of the ,earth's ,surface1 and the ,changes which they have wrought in the ,animal ,world40 ,they were maintained1 and generally accepted for a long time1 and became the greatest obstacle to the development of a natural history of the creation4 ,for if such all-destructive revolutions had actually occurred1 of course a continuity of the development of species1 a connecting thread in the organic history of the earth1 could not be admitted at all1 and we should be obliged to have recourse to the action of supernatural forces2 that is1 to the interference of miracles in the natural course of things4 ,it is only through miracles that these revolutions of the earth could have been brought about1 and it is only through miracles that1 after their cessation and at the commencement of each new period1 a new animal and vegetable kingdom could have been created4 ,but science has no room for miracles1 for by miracles we understand an interference of supernatural forces in the natural course of development of matter4 ,just as the great authority which ,linnus gained by his system of distinguishing and naming organic species led his successors to a complete ossification1 as it were1 of the dogmatic idea of species and to a real abuse of the systematic distinction implied by it1 so the great services which ,cuvier had rendered to the knowledge and distinction of extinct species became the cause of a general adoption of his theory of revolutions and catastrophes1 and of the false views of creation connected therewith4 ,the consequence of this was that1 during the first half of our century1 most zoologists and botanists clung to the opinion that a series of independent periods in the organic history of the earth had existed2 that each period was distinguished by distinct and peculiar kinds of animal and vegetable species2 that these were annihilated at the termination of the period by a general revolution2 and that1 after the cessation of the latter1 a new world of different species of animals and plants was created4 ,it is true some independent thinkers1 above all the great physical philosopher1 ,lamarck1 even at an early period1 set forth a series of weighty reasons which refuted ,cuvier's theory of cataclysms1 and pointed to a perfectly continuous and uninterrupted developmental history of all the organic inhabitants of the earth through all ages4 ,they maintained that the animal and vegetable species of each period were derived from those of the preceding period1 and were only the altered descendants of the former4 ,this true conception1 however1 being opposed to ,cuvier's great authority1 was then unable to make way4 ,nay1 even after ,cuvier's theory of catastrophes had been completely cast out from the domain of geology by ,lyell's classic ,principles of ,geology1 which appeared in #ahcj1 still his idea of the specific distinctness of a series of organic creations maintained its influence1 in many ways1 in the science of ,palontology4 7,gen4 ,morph4 ii4 #cab47 ,by a curious coincidence1 thirteen years ago1 almost at the same time that ,cuvier's ,history of ,creation received its death-blow by ,darwin's book1 another celebrated naturalist made an attempt to re-establish it1 and to adopt it in the roughest manner1 as a part of a teleologico-theological system of nature4 ,this was the ,swiss geologist1 ,louis ,agassiz1 who attained a great reputation by his theory of glaciers and the ice-period1 borrowed from ,schimper and ,charpentier1 and who has been living in ,north ,america for many years4 ,he commenced in #aheh to publish a work planned on a very large scale1 which bears the title of 8,contributions to the ,natural ,history of the ,united ,states of ,north ,america40 ,the first volume of this work1 although large and costly1 owing to the patriotism of the ,americans1 had an unprecedented sale2 its title is1 8,an ,essay on ,classification407#e7 ,in this essay ,agassiz not only discusses the natural series of organisms1 and the different attempts of naturalists at classification1 but also all the general biological phenomena which have reference to it4 ,the history of the development of organisms1 both the embryonal and the palontological1 comparative anatomy1 the general economy of nature1 the geographical and topographical distribution of animals and plants--in short1 almost all the general phenomena of organic nature are discussed in ,agassiz's ,essay on ,classification1 and are explained in a sense and from a point of view which is thoroughly opposed to that of ,darwin4 ,while ,darwin's chief merit lies in the fact that he demonstrates natural causes for the coming into existence of animal and vegetable species1 and thereby establishes the mechanical or monistic view of the universe as regards this most difficult branch of the history of creation1 ,agassiz1 on the contrary1 strives to exclude every mechanical hypothesis from the subject1 and to put the supernatural interference of a personal ,creator in the place of the natural forces of matter2 consequently1 to establish a thoroughly teleological or dualistic view of the universe4 ,it will not be out of place if ,i examine a little more closely ,agassiz's biological views1 and especially his ideas of creation1 because no other work of our opponents treats the important fundamental questions with equal minuteness1 and because the utter untenableness of the dualistic conception of nature becomes very evident from the failure of this attempt4 ,the organic species1 the various conceptions of which we have above designated as the real centre of dispute in the opposed views of creation1 is looked upon by ,agassiz1 as by ,cuvier and ,linnus1 as a form unchangeable in all its essential characteristics4 ,the species may indeed change and vary within certain narrow limits2 never in essential qualities1 but only in unessential points4 ,no new species could ever proceed from the changes or varieties of a species4 ,not one of all organic species1 therefore1 is ever derived from another1 but each individual species has been separately created by ,god4 ,each individual species1 as ,agassiz expresses it1 is 8an embodied creative thought0 of ,god4 ,in direct opposition to the fact established by palontological experience1 that the duration of the individual organic species is most unequal1 and that many species continue unchanged through several successive periods of the earth's history1 while others only existed during a small portion of such a period1 ,agassiz maintains that one and the same species never occurs in two different periods1 but that each individual period is characterized by species of animals and plants which are quite peculiar1 and belong to it exclusively4 ,he further shares ,cuvier's opinion that the whole of these inhabitants were annihilated by the great and universal revolutions of the earth's surface1 which divide two successive periods1 and that after its destruction a new and specifically different assemblage of organisms was created4 ,this new creation ,agassiz supposes to have taken place in this manner3 viz41 that at each creation all the inhabitants of the earth1 in their full average number of individuals1 and in the peculiar relations corresponding to the economy of nature1 were1 as a whole1 suddenly placed upon the earth by the ,creator4 ,in saying this he puts himself in opposition to one of the most firmly established and most important laws of animal and vegetable geography--namely1 to the law that each species has a single original locality of origin1 or a so-called 8centre of creation10 from which it has gradually spread over the rest of the earth4 ,instead of this1 ,agassiz assumes each species to have been created at several points of the earth's surface1 and that in each case a large number of individuals was created4 ,the 8natural system0 of organisms1 the different groups and categories of which arranged above one another--namely1 the branches1 classes1 orders1 families1 genera1 and species--we consider1 in accordance with the ,theory of ,descent1 as different branches and twigs of the organic family-tree1 is1 according to ,agassiz1 the direct expression of the divine plan of creation1 and the naturalist1 while investigating the natural system1 repeats the creative thoughts of ,god4 ,in this ,agassiz finds the strongest proof that man is the image and child of ,god4 ,the different stages of groups or categories of the natural system correspond with the different stages of development which the divine plan of creation had attained4 ,the ,creator1 in projecting and carrying out this plan1 starting from the most general ideas of creation1 plunged more and more into specialities4 ,for instance1 when creating the animal kingdom1 ,god had in the first place four totally distinct ideas of animal bodies1 which he embodied in the different structures of the four great1 principal forms1 types1 or branches of the animal kingdom2 namely1 vertebrate animals1 articulate animals1 molluscous animals1 and radiate animals4 ,the ,creator then1 having reflected in what manner he might vary these four different plans of structure1 next created within each of the four principal forms1 several different classes--for example1 in the vertebrate animal form1 the classes of mammals1 birds1 reptiles1 amphibious animals1 and fishes4 ,then ,god further reflected upon the individual classes1 and by various modifications in the structure of each class1 he produced the individual orders4 ,by further variation in the order1 he created natural families4 ,as the ,creator further varied the peculiarities of structure of individual parts in each family1 genera arose4 ,in further meditation on his plan of creation1 he entered so much into detail that individual species came into existence1 which1 consequently1 are embodied creative thoughts of the most special kind4 ,it is only to be regretted that the ,creator expressed these most special and most deeply considered 8creative thoughts0 in so very indistinct and loose a manner1 and that he imprinted so vague a stamp upon them1 and permitted them to vary so freely that not one naturalist is able to distinguish the 8good0 from the 8bad species10 or a genuine species from varieties1 races1 etc4 7,gen4 ,morph4 ii4 #cgc47 ,we see1 then1 according to ,agassiz's conception1 that the ,creator1 in producing organic forms1 goes to work exactly as a human architect1 who has taken upon himself the task of devising and producing as many different buildings as possible1 for the most manifold purposes1 in the most different styles1 in various degrees of simplicity1 splendour1 greatness1 and perfection4 ,this architect would perhaps at first choose four different styles for all these buildings1 say the ,gothic1 ,byzantine1 ,chinese1 and ,rococo styles4 ,in each of these styles he would build a number of churches1 palaces1 garrisons1 prisons1 and dwelling-houses4 ,each of these different buildings he would execute in ruder and more perfect1 in greater and smaller1 in simpler and grander fashion1 etc4 ,however1 the human architect would perhaps1 in this respect1 be better off than the divine ,creator1 as he would have perfect liberty in the number of graduated subordinate groups4 ,the ,creator1 however1 according to ,agassiz1 can only move within six groups or categories3 the species1 genus1 family1 order1 class1 and type4 ,more than these six categories do not exist for him4 ,when we read ,agassiz's book on classification1 and see how he carries out and establishes these strange ideas1 we can scarcely understand how1 with all the appearance of scientific earnestness1 he can persevere in his idea of the divine ,creator as a man-like being 7anthropomorphism71 for by his explanation of details he produces a picture of the most absurd nonsense4 ,in the whole series of these suppositions the ,creator is nothing but an all-mighty man1 who1 plagued with ennui1 amuses himself with planning and constructing most varied toys in the shape of organic species4 ,after having diverted himself with these for thousands of years1 they become tiresome to him1 he destroys them by a general revolution of the earth's surface1 and thus throws the whole of the useless toys in heaps together2 then1 in order to while away his time with something new and better1 he calls a new and more perfect animal and vegetable world into existence4 ,but in order not to have the trouble of beginning the work of creation over again1 he keeps1 in the main1 to his original plan of creation1 and creates merely new species1 or at most only new genera1 and much more rarely new families1 new orders1 or classes4 ,he never succeeds in producing a new style or type1 and always keeps strictly within the six categories or graduated groups4 ,when1 according to ,agassiz1 the ,creator has thus amused himself for thousands of millions of years with constructing and destroying a series of different creations1 at last 7but very late7 he is struck with the happy thought of creating something like himself1 and so makes man in his own image4 ,the end of all the history of creation is thus arrived at and the series of revolutions of the earth is closed4 ,man1 the child and image of ,god1 gives him so much to do1 causes him so much pleasure and trouble1 that he is wearied no longer1 and therefore need not undertake a new creation4 ,it is clear that if1 according to ,agassiz1 we once assign to the ,creator entirely human attributes and qualities1 and regard his work of creation as entirely analogous to human creative activity1 we are necessarily obliged to admit such utterly absurd inferences as those just stated4 ,the many intrinsic contradictions and perversities in ,agassiz's view of creation--a view which necessarily led him to the most decided opposition to the ,theory of ,descent--must excite our astonishment all the more because1 in his earlier scientific works1 he had in many respects actually paved the way for ,darwin1 especially by his researches in ,palontology4 ,among the numerous investigations which created general interest in the then young science of ,palontology1 those of ,agassiz1 especially his celebrated work on 8,fossil ,fish10 rank next in importance to ,cuvier's work1 which formed the foundation of the science4 ,the petrified fish1 with which ,agassiz has made us acquainted1 have not only an extremely great importance for the understanding of all groups of ,vertebrate animals1 and their historical development1 but we have arrived through them at a sure knowledge of important general laws of development1 some of which were first discovered by ,agassiz4 ,he it was who drew special attention to the remarkable parallelism between the embryonal and the palontological development--between ontogeny and phylogeny1 which ,i have already 7p4 #aj7 claimed as one of the strongest pillars of the ,theory of ,descent4 ,no one before had so distinctly stated as ,agassiz did1 that1 of the ,vertebrate animals1 fishes alone existed1 at first1 that amphibious animals came later1 and that birds and mammals appeared only at a much later period1 further1 that among mammals1 as among fishes1 imperfect and lower orders had appeared first1 but more perfect and higher orders at a later period4 ,agassiz1 therefore1 showed that the palontological development of the whole ,vertebrate group was not only parallel with the embryonic1 but also with the systematic development1 that is1 with the graduated series which we see everywhere in the system1 ascending from the lower to the higher classes1 orders1 etc4 ,in the earth's history lower forms appeared first1 the higher forms later4 ,this important fact1 as well as the agreement of the embryonic and palontological development1 is explained quite simply and naturally by the ,doctrine of ,descent1 and without it is perfectly inexplicable4 ,this cause holds good also in the great law of progressive development1 that is1 of the historical progress of organization1 which is traceable1 broadly and as a whole1 in the historical succession of all organisms1 as well as in the special perfecting of individual parts of animal bodies4 ,thus1 for example1 the skeleton of ,vertebrate animals acquired at first slowly1 and by degrees1 that high degree of perfection which it now possesses in man and the other higher ,vertebrate animals4 ,this progress1 acknowledged in point of fact by ,agassiz1 necessarily follows from ,darwin's ,doctrine of ,descent1 which demonstrates its active causes4 ,if this doctrine is correct1 the perfecting and diversification of animal and vegetable species must of necessity have gradually increased in the course of the organic history of the earth1 and could only attain its highest perfection in most recent times4 ,the above-mentioned laws of development1 together with some other general ones1 which have been expressly admitted and justly emphasized by ,agassiz1 and some of which have first been set forth by him1 are1 as we shall see later1 only explicable by the ,theory of ,descent1 and without it remain perfectly incomprehensible4 ,the conjoint action of ,inheritance and ,adaptation1 as explained by ,darwin1 can alone be their true cause4 ,but they all stand in sharp and irreconcilable opposition to the hypothesis of creation maintained by ,agassiz1 as well as to the idea of a personal ,creator who acts for a definite purpose4 ,if we seriously wish to explain those remarkable phenomena and their inter-connection by ,agassiz's theory1 then we are necessarily driven to the curious supposition that the ,creator himself has developed1 together with the organic nature which he created and modelled4 ,we can1 in that case1 no longer rid ourselves of the idea that the ,creator himself1 like a human being1 designed1 improved1 and finally1 with many alterations1 carried out his plans4 8,man grows as higher grow his aims10 and the same supposition1 so unworthy of a ,god1 must be applied to him4 ,although1 from the reverence with which1 in every page1 ,agassiz speaks of the ,creator1 it might appear that1 on his theory1 we attain to the sublimest conception of the divine activity in nature1 yet the contrary is in truth the case4 ,the divine ,creator is degraded to the level of an idealized man1 of an organism progressing in development6 ,considering the wide popularity and great authority which ,agassiz's work has gained1 and which is perhaps justified on account of earlier scientific services rendered by the author1 ,i have thought it my duty here to show the utter untenableness of his general conceptions4 ,so far as this work pretends to be a scientific history of creation1 it is undoubtedly a complete failure4 ,but still it has great value1 being the only detailed attempt1 adorned with scientific arguments1 which an eminent naturalist of our day has made to found a teleological or dualistic history of creation4 ,the utter impossibility of such a history has thus been made obvious to every one4 ,no opponent of ,agassiz could have refuted the dualistic conception of organic nature and its origin more strikingly than he himself has done by the intrinsic contradictions which present themselves everywhere in his theory4 ,the opponents of the monistic or mechanical conception of the world have welcomed ,agassiz's work with delight1 and find in it a perfect proof of the direct creative action of a personal ,god4 ,but they overlook the fact that this personal ,creator is only an idealized organism1 endowed with human attributes4 ,this low dualistic conception of ,god corresponds with a low animal stage of development of the human organism4 ,the more developed man of the present day is capable of1 and justified in1 conceiving that infinitely nobler and sublimer idea of ,god which alone is compatible with the monistic conception of the universe1 and which recognizes ,god's spirit and power in all phenomena without exception4 ,this monistic idea of ,god1 which belongs to the future1 has already been expressed by ,giordano ,bruno in the following words3--8,a spirit exists in all things1 and no body is so small but contains a part of the divine substance within itself1 by which it is animated40 ,it is of this noble idea of ,god that ,goethe says3--8,certainly there does not exist a more beautiful worship of ,god than that which needs no image1 but which arises in our heart from converse with ,nature40 ,by it we arrive at the sublime idea of the ,unity of ,god and ,nature4 ,,chapter ,,iv4 ,,theory ,,of ,,development ,,according ,,to ,,goethe ,,and ,,oken4 ,scientific ,insufficiency of all ,conceptions of a ,creation of ,individual ,species4--,necessity of the ,counter ,theories of ,development4--,historical ,survey of the ,most ,important ,theories of ,development4--,aristotle4--,his ,doctrine of ,spontaneous ,generation4--,the ,meaning of ,natural ,philosophy4--,goethe4--,his ,merits as a ,naturalist4--,his ,metamorphosis of ,plants4--,his ,vertebral ,theory of the ,skull4--,his ,discovery of the ,mid ,jawbone in ,man4--,goethe's ,interest in the ,dispute between ,cuvier and ,geoffroy ,st4 ,hilaire4--,goethe's ,discovery of the ,two ,organic ,formative ,principles1 of the ,conservative ,principle of ,specification 7by ,inheritance71 and of the ,progressive ,principle of ,transformation 7by ,adaptation74--,goethe's ,views of the ,common ,descent of all ,vertebrate ,animals1 including ,man4--,theory of ,development according to ,gottfried ,reinhold ,treviranus4--,his ,monistic ,conception of ,nature4--,oken4--,his ,natural ,philosophy4--,oken's ,theory of ,protoplasm4--,oken's ,theory of ,infusoria 7,cell ,theory74--,oken's ,theory of ,development4 ,all the different ideas which we may form of a separate and independent origin of the individual organic species by creation lead us1 when logically carried out1 to a so-called anthropomorphism1 that is1 to imagining the ,creator as a man-like being1 as was shown in our last chapter4 ,the ,creator becomes an organism who designs a plan1 reflects upon and varies this plan1 and finally forms creatures according to this plan1 as a human architect would his building4 ,if even such eminent naturalists as ,linnus1 ,cuvier1 and ,agassiz1 the principal representatives of the dualistic hypothesis of creation1 could not arrive at a more satisfactory view1 we may take it as evidence of the insufficiency of all those conceptions which would derive the various forms of organic nature from a creation of individual species4 ,some naturalists1 indeed1 seeing the complete insufficiency of these views1 have tried to replace the idea of a personal ,creator by that of an unconsciously active and creative ,force of ,nature2 yet this expression is evidently merely an evasive phrase1 as long as it is not clearly shown what this force of nature is1 and how it works4 ,hence these attempts1 also1 have been absolute failures4 ,in fact1 whenever an independent origin of the different forms of animals and plants has been assumed1 naturalists have found themselves compelled to fall back upon so many 8acts of creation10 that is1 on supernatural interferences of the ,creator in the natural course of things1 which in all other cases goes on without interference4 ,it is true that several teleological naturalists1 feeling the scientific insufficiency of a supernatural 8creation10 have endeavoured to save the hypothesis by wishing it to be understood that creation 8is nothing else than a way of coming into being1 unknown and inconceivable to us40 ,the eminent ,fritz ,mller has cut off from this sophistic evasion every chance of escape by the following striking remark3--8,it is intended here only to express in a disguised manner the shamefaced confession1 that they neither have1 nor care to have1 any opinion about the origin of species4 ,according to this explanation of the word1 we might as well speak of the creation of cholera1 or syphilis1 of the creation of a conflagration1 or of a railway accident1 as of the creation of man40 7,jenaische ,zestscrift1 bd4 v4 p4 #bgb47 ,in the face1 then1 of these hypotheses of creation1 which are scientifically insufficient1 we are forced to seek refuge in the counter-theory of development of organisms1 if we wish to come to a rational conception of the origin of organisms4 ,we are forced and obliged to do so1 even if the theory of development only throws a glimmer of probability upon a mechanical1 natural origin of the animal and vegetable species2 but all the more if1 as we shall see1 this theory explains all facts simply and clearly1 as well as completely and comprehensively4 ,the theories of development are by no means1 as they often falsely are represented to be1 arbitrary fancies1 or wilful products of the imagination1 which only attempt approximately to explain the origin of this or that individual organism2 but they are theories founded strictly on science1 which explain in the simplest manner1 from a fixed and clear point of view1 the whole of organic natural phenomena1 and more especially the origin of organic species1 and demonstrate them to be the necessary consequences of mechanical processes in nature4 ,as ,i have already shown in the second chapter1 all these theories of development coincide naturally with that general theory of the universe which is usually designated as the uniform or monistic1 often also as the mechanical or causal1 because it only assumes mechanical causes1 or causes working by necessity 7caus efficientes71 for the explanation of natural phenomena4 ,in like manner1 on the other hand1 the supernatural hypotheses of creation which we have already discussed coincide completely with the opposite view of the universe1 which in contrast to the former is called the twofold or dualistic1 often the teleological or vital1 because it traces the organic natural phenomena to final causes1 acting and working for a definite purpose 7caus finales74 ,it is this deep and intrinsic connection of the different theories of creation with the most important questions of philosophy that incites us to their closer examination4 ,the fundamental idea1 which must necessarily lie at the bottom of all natural theories of development1 is that of a gradual development of all 7even the most perfect7 organisms out of a single1 or out of a very few1 quite simple1 and quite imperfect original beings1 which came into existence1 not by supernatural creation1 but by spontaneous generation1 or archigony1 out of inorganic matter4 ,in reality1 there are two distinct conceptions united in this fundamental idea1 but which have1 nevertheless1 a deep intrinsic connection--namely1 first1 the idea of spontaneous generation 7or archigony7 of the original primary beings2 and secondly1 the idea of the progressive development of the various species of organisms from those most simple primary beings4 ,these two important mechanical conceptions are the inseparable fundamental ideas of every theory of development1 if scientifically carried out4 ,as it maintains the derivation of the different species of animals and plants from the simplest1 common primary species1 we may term it also the ,doctrine of ,filiation1 or ,theory of ,descent2 as there is also a change of species connected with it1 it may also be termed the ,transmutation ,theory4 ,while the supernatural histories of creation must have originated thousands of years ago1 in that very remote primitive age when man1 first developing out of the monkey-state1 began for the first time to think more closely about himself1 and about the origin of the world around him1 the natural theories of development1 on the other hand1 are necessarily of much more recent origin4 ,these views are met with only among nations of a more matured civilization1 to whom1 by philosophic culture1 the necessity of a knowledge of natural causes has become apparent2 and even among these1 only individual and specially gifted natures can be expected to have recognized the origin of the world of phenomena1 as well as its course of development1 as the necessary consequences of mechanical1 naturally active causes4 ,in no nation have these preliminary conditions1 for the origin of a natural theory of development1 ever existed in so high a degree as among the ,greeks of classic antiquity4 ,but1 on the other hand1 they lacked a close acquaintance with the facts of the processes and forms of nature1 and1 consequently1 the foundation based upon experience1 for a satisfactory unravelling of the problem of development4 ,exact investigation of nature1 and the knowledge of nature founded on an experimental basis1 was of course almost unknown to antiquity1 as well as to the ,middle ,ages1 and is only an acquisition of modern times4 ,we have therefore here no special occasion to examine the natural theories of development of the various ,greek philosophers1 since they were wanting in the knowledge gained by experience1 both of organic and inorganic nature1 and since they almost always1 as the consequence1 lost themselves in airy speculations4 ,one man only must be mentioned here by way of exception1--,aristotle1 the greatest and the only truly great naturalist of antiquity and the ,middle ,ages1 one of the grandest geniuses of all time4 ,to what a degree he stands there alone1 during a period of more than two thousand years1 in the region of empirico-philosophical knowledge of nature1 and especially in his knowledge of organic nature1 is proved to us by the precious remains of his but partially surviving works4 ,in them many traces are found of a theory of natural development4 ,aristotle assumes1 as a matter of certainty1 that spontaneous generation was the natural manner in which the lower organic creatures came into existence4 ,he describes animals and plants originating from matter itself1 through its own original force2 as1 for example1 moths from wool1 fleas from putrid dung1 wood-lice from damp wood1 etc4 ,but as the distinction of organic species1 which ,linnus only arrived at two thousand years later1 was unknown to him1 he could form no ideas about their genealogical relations4 ,the fundamental notion of the theory of development1 that the different species of animals and plants have been developed from a common primary species by transformation1 could of course only be clearly asserted after the kinds of species themselves had become better known1 and after the extinct species had been carefully examined and compared with the living ones4 ,this was not done until the end of the last and the beginning of the present century4 ,it was not until the year #ahja that the great ,lamarck expressed the theory of development1 which he1 in #ahji1 further elaborated in his classical 8,philosophie ,zoologique40 ,while ,lamarck and his countryman1 ,geoffroy ,st4 ,hilaire1 in ,france1 opposed ,cuvier's views1 and maintained a natural development of organic species by transformation and descent1 ,goethe and ,oken at the same time pursued the same course in ,germany1 and helped to establish the theory of development4 ,as these naturalists are generally called nature-philosophers 7,naturphilosophen71 and as this ambiguous designation is correct in a certain sense1 it appears to me appropriate here to say a few words about the correct estimate of the 8,natur-philosophie40 ,although for many years in ,england the ideas of natural science and philosophy have been looked upon as almost equivalent1 and as every truly scientific investigator of nature is most justly called there a 8natural philosopher10 yet in ,germany for more than half a century natural science has been kept strictly distinct from philosophy1 and the union of the two into a true philosophy of nature is recognized only by the few4 ,this misapprehension is owing to the fantastic eccentricities of earlier ,german natural-philosophers1 such as ,oken1 ,schelling1 etc42 they believed that they were able to construct the laws of nature in their own heads1 without being obliged to take their stand upon the grounds of actual experience4 ,when the complete hollowness of their assumptions had been demonstrated1 naturalists1 in 8the nation of thinkers10 fell into the very opposite extreme1 believing that they would be able to reach the high aim of science1 that is1 the knowledge of truth1 by the mere experience of the senses1 and without any philosophical activity of thought4 ,from that time1 but especially since #ahcj1 most naturalists have shown a strong aversion to any general1 philosophical view of nature4 ,the real aim of natural science was now supposed to consist in the knowledge of details1 and it was believed that this would be attained in the study of biology1 when the forms and the phenomena of life1 in all individual organisms1 had become accurately known1 by the help of the finest instruments and means of observation4 ,it is true that among these strictly empirical1 or so-called exact naturalists1 there were always very many who rose above this narrow point of view1 and sought the final aim in a knowledge of the general laws of organization4 ,yet the great majority of zoologists and botanists1 during the thirty or forty years preceding ,darwin1 refused to concern themselves about such general laws2 all they admitted was1 that perhaps in the far distant future1 when the end of all empiric knowledge should have been arrived at1 when all individual animals and plants should have been thoroughly examined1 naturalists might begin to think of discovering general biological laws4 ,if we consider and compare the most important advances which the human mind has made in the knowledge of truth1 we shall soon see that it is always owing to philosophical mental operations that these advances have been made1 and that the experience of the senses which certainly and necessarily precedes these operations1 and the knowledge of details gained thereby1 only furnish the basis for those general laws4 ,experience and philosophy1 therefore1 by no means stand in such exclusive opposition to each other as most men have hitherto supposed2 they rather necessarily supplement each other4 ,the philosopher who is wanting in the firm foundation of sensuous experience1 of empirical knowledge1 is very apt to arrive at false conclusions in his general speculations1 which even a moderately informed naturalist can refute at once4 ,on the other hand1 the purely empiric naturalists1 who do not trouble themselves about the philosophical comprehension of their sensuous experiences1 and who do not strive after general knowledge1 can promote science only in a very slight degree1 and the chief value of their hard-won knowledge of details lies in the general results which more comprehensive minds will one day derive from them4 ,from a general survey of the course of biological development since ,linnus' time1 we can easily see1 as ,br has pointed out1 a continual vacillation between these two tendencies1 at one time a prevalence of the empirical--the so-called exact--and then again of the philosophical or speculative tendency4 ,thus at the end of the last century1 in opposition to ,linnus' purely empirical school1 a natural-philosophical reaction took place1 the moving spirits of which1 ,lamarck1 ,geoffroy ,st4 ,hilaire1 ,goethe1 and ,oken1 endeavoured by their mental work to introduce light and order into the chaos of the accumulated empirical raw material4 ,in opposition to the many errors and speculations of these natural philosophers1 who went too far1 ,cuvier then came forward1 introducing a second1 purely empirical period4 ,it reached its most one-sided development between the years #ahcj-ahfj1 and there now followed a second philosophical reaction1 caused by ,darwin's work4 ,thus during the last ten years1 men again have begun to endeavour to obtain a knowledge of the general laws of nature1 to which1 after all1 all detailed knowledge of experience serves only as a foundation1 and through which alone it acquires its true value4 ,it is through philosophy alone that natural knowledge becomes a true science1 that is1 a philosophy of nature4 7,gen4 ,morph4 i4 #fc-ajh47 ,jean ,lamarck and ,wolfgang ,goethe stand at the head of all the great philosophers of nature who first established a theory of organic development1 and who are the illustrious fellow-workers of ,darwin4 ,i turn first to our beloved ,goethe1 who1 among all1 stands in the closest relations to us ,germans4 ,however1 before ,i explain his special services to the theory of development1 it seems to me necessary to say a few words about his importance as a naturalist in general1 as it is commonly very little known4 ,i am sure most of my readers honour ,goethe only as a poet and a man2 only a few have any conception of the high value of his scientific works1 and of the gigantic stride with which he advanced before his own age--advanced so much that most naturalists of that time were unable to follow him4 ,in several passages of his scientific writings he bitterly complains of the narrow-mindedness of professed naturalists1 who do not know how to value his works 7who cannot see the wood for the trees71 and who cannot rouse themselves to discover the general laws of nature among the mass of details4 ,he is only too just when he utters the reproach--8,the philosophers will very soon discover that observers rarely rise to a stand-point from which they can survey so many important objects40 ,it is true1 at the same time1 that their want of appreciation was caused by the false road into which ,goethe was led in his theory of colours4 ,this theory of colours1 which he himself designates as the favourite production of his leisure1 however much that is beautiful it may contain1 is a complete failure in regard to its foundations4 ,the exact mathematical method by means of which alone it is possible1 in inorganic sciences1 but above all in physics1 to raise a structure step by step on a thoroughly firm basis1 was altogether repugnant to ,goethe4 ,in rejecting it he allowed himself not only to be very unjust towards the most eminent physicists1 but to be led into errors which have greatly injured the fame of his other valuable works4 ,it is quite different in the organic sciences1 in which we are but rarely able to proceed1 from the beginning1 upon a firm mathematical basis2 we are rather compelled1 by the infinitely difficult and intricate nature of the problem1 at the first to form inductions--that is1 we are obliged to endeavour to establish general laws by numerous individual observations1 which are not quite complete4 ,a comparison of kindred series of phenomena1 or the method of combination1 is here the most important instrument for inquiry1 and this method was applied by ,goethe with as much success as with conscious knowledge of its value1 in his works relating to the philosophy of nature4 ,the most celebrated among ,goethe's writings relating to organic nature is his ,metamorphosis of ,plants1 which appeared in #agij1 a work which distinctly shows a grasp of the fundamental idea of the theory of development1 inasmuch as ,goethe1 in it1 was labouring to point out a single organ1 by the infinitely varied development and metamorphosis of which the whole of the endless variety of forms in the world of plants might be conceived to have arisen2 this fundamental organ he found in the leaf4 ,if at that time the microscope had been generally employed1 if ,goethe had examined the structure of organisms by the means of the microscope he would have gone still further1 and would have seen that the leaf is itself a compound of individual parts of a lower order1 that is1 of cells4 ,he would then not have declared that the leaf1 but that the cell is the real fundamental organ by the multiplication1 transformation1 and combination 7synthesis7 of which1 in the first place1 the leaf is formed2 and that1 in the next place1 by transformation1 variation1 and combination of leaves there arise all the varied beauties in form and colour which we admire in the green parts1 as well as in the organs of propagation1 or the flowers of plants4 ,goethe here showed that in order to comprehend the whole of the phenomena1 we must in the first place compare them1 and1 secondly1 search for a simple type1 a simple fundamental form1 of which all other forms are only infinite variations4 ,something similar to what he had here done for the metamorphosis of plants he then did for the ,vertebrate animals1 in his celebrated vertebral theory of the skull4 ,goethe was the first to show1 independently of ,oken1 who almost simultaneously arrived at the same thought1 that the skull of man and of all ,vertebrate animals1 in particular mammals1 is nothing more than a bony case1 formed of the same bones1--that is1 vertebr1--out of which the spine also is composed4 ,the vertebr of the skull are like those of the spine1 bony rings lying behind each other1 but in the skull are peculiarly changed and specialized 7differentiated74 ,although this idea has been strongly modified by recent discoveries1 yet in ,goethe's day it was one of the greatest advances in comparative anatomy1 and was not only one of the first advances towards the understanding of the structure of ,vertebrate animals1 but at the same time explained many individual phenomena4 ,when two parts of a body1 such as the skull and spine1 which appear at first sight so different1 were proved to be parts originally the same1 developed out of one and the same foundation1 one of the difficult problems of the philosophy of nature was solved4 ,here again we meet the notion of a single type--the conception of a single principle1 which becomes infinitely varied in the different species1 and in the parts of individual species4 ,but ,goethe did not merely endeavour to search for such far-reaching laws1 he also occupied himself most actively for a long time with numerous individual researches1 especially in comparative anatomy4 ,among these1 none is perhaps more interesting than the discovery of the mid jawbone in man4 ,as this is1 in several respects1 of importance to the theory of development1 ,i shall briefly explain it here4 ,there exist in all mammals two little bones in the upper jaw1 which meet in the centre of the face1 below the nose1 and which lie between the two halves of the real upper jawbone4 ,these two bones1 which hold the four upper cutting teeth1 are recognized without difficulty in most mammals2 in man1 however1 they were at that time unknown1 and celebrated comparative anatomists even laid great stress upon this want of a mid jawbone1 as they considered it to constitute the principal difference between men and apes--the want of a mid jawbone was1 curiously enough1 looked upon as the most human of all human characteristics4 ,but ,goethe could not accept the notion that man1 who in all other corporeal respects was clearly only a mammal of higher development1 should lack this mid jawbone4 ,by the general law of induction as to the mid jawbone he arrived at the special deductive conclusion that it must exist in man also1 and ,goethe did not rest until1 after comparing a great number of human skulls1 he really found the mid jawbone4 ,in some individuals it is preserved throughout a whole lifetime1 but usually at an early age it coalesces with the neighbouring upper jawbone1 and is therefore only to be found as an independent bone in very youthful skulls4 ,in human embryos it can now be pointed out at any moment4 ,in man1 therefore1 the mid jawbone actually exists1 and to ,goethe the honour is due of having first firmly established this fact1 so important in many respects2 and this he did while opposed by the celebrated anatomist1 ,peter ,camper1 one of the most important professional authorities4 ,the way by which ,goethe succeeded in establishing this fact is especially interesting2 it is the way by which we continually advance in biological science1 namely1 by way of induction and deduction4 ,induction is the inference of a general law from the observation of numerous individual cases2 deduction1 on the other hand1 is an inference from this general law applied to a single case which has not yet been actually observed4 ,from the collected empirical knowledge of those days1 the inductive conclusion was arrived at that all mammals had mid jawbones4 ,goethe drew from this the deductive conclusion1 that man1 whose organization was in all other respects not essentially different from mammals1 must also possess this mid jawbone2 and on close examination it was actually found4 ,the deductive conclusion was confirmed and verified by experience4 ,even these few remarks may serve to show the great value which we must ascribe to ,goethe's biological researches4 ,unfortunately most of his labours devoted to this subject are so hidden in his collected works1 and his most important observations and remarks so scattered in numerous individual treatises--devoted to other subjects--that it is difficult to find them out4 ,it also sometimes happens that an excellent1 truly scientific remark is so much interwoven with a mass of useless philosophical fancies1 that the latter greatly detract from the former4 ,nothing is perhaps more characteristic of the extraordinary interest which ,goethe took in the investigation of organic nature than the lively way in which1 even in his last years1 he followed the dispute which broke out in ,france between ,cuvier and ,geoffroy de ,st4 ,hilaire4 ,goethe1 in a special treatise which was only finished a few days before his death1 in ,march1 #ahcb1 has given an interesting description of this remarkable dispute and its general importance1 as well as an excellent sketch of the two great opponents4 ,this treatise bears the title 8,principes de ,philosophic ,zoologique par ,m4 ,geoffroy de ,saint ,hilaire02 it is ,goethe's last work1 and forms the conclusion of the collected edition of his works4 ,the dispute itself was1 in several respects1 of the highest interest4 ,it turned essentially upon the justification of the theory of development4 ,it was carried on1 moreover1 in the bosom of the ,french ,academy1 by both opponents1 with a personal vehemence almost unheard of in the dignified sessions of that learned body2 this proved that both naturalists were fighting for their most sacred and deepest convictions4 ,the conflict began on the #bbnd of ,february1 and was followed by several others2 the fiercest took place on the #aith of ,july1 #ahcj4 ,geoffroy1 as the chief of the ,french nature-philosophers1 represented the theory of natural development and the monistic conception of nature4 ,he maintained the mutability of organic species1 the common descent of the individual species from common primary forms1 and the unity of their organization--or the unity of the plan of structure1 as it was then called4 ,cuvier was the most decided opponent of these views1 and according to what we have seen1 it could not be otherwise4 ,he endeavoured to show that the nature-philosophers had no right to rear such comprehensive conclusions on the basis of the empirical knowledge then possessed1 and that the unity of organization--or plan of structure of organisms--as maintained by them1 did not exist4 ,he represented the teleological 7dualistic7 conception of nature1 and maintained that 8the immutability of species was a necessary condition for the existence of a scientific history of nature10 ,cuvier had the great advantage over his opponent1 that he was able to bring towards the proof of his assertions things obvious to the eye2 these1 however1 were only individual facts taken out of their connection with others4 ,geoffroy was not able to prove the higher and general connection of individual phenomena which he maintained1 by equally tangible details4 ,hence ,cuvier1 in the eyes of the majority1 gained the victory1 and decided the defeat of the nature-philosophy and the supremacy of the strictly empiric tendency for the next thirty years4 ,goethe of course supported ,geoffroy's views4 ,how deeply interested he was1 even in his #hast year1 in this great contest is proved by the following anecdote related by ,soret3-- 8,monday1 ,aug4 #bnd1 #ahcj4--,the news of the outbreak of the revolution of ,july arrived in ,weimar to-day1 and has caused general excitement4 ,in the course of the afternoon ,i went to ,goethe4 #8,well8' he exclaimed as ,i entered1 #8what do you think of this great event8 ,the volcano has burst forth1 all is in flames1 and there are no more negotiations behind closed doors4' #8,a dreadful affair1' ,i answered2 #8but what else could be expected under the circumstances1 and with such a ministry1 except that it would end in the expulsion of the present royal family8' #8,we do not seem to understand each other1 my dear friend1' replied ,goethe4 #8,i am not speaking of those people at all2 ,i am interested in something very different1 ,i mean the dispute between ,cuvier and ,geoffroy de ,saint ,hilaire1 which has broken out in the ,academy1 and which is of such great importance to science4' ,this remark of ,goethe's came upon me so unexpectedly1 that ,i did not know what to say1 and my thoughts for some minutes seemed to have come to a complete standstill4 #8,the affair is of the utmost importance1' he continued1 #8and you cannot form any idea of what ,i felt on receiving the news of the meeting on the #aith4 ,in ,geoffroy de ,saint ,hilaire we have now a mighty ally for a long time to come4 ,but ,i see also how great the sympathy of the ,french scientific world must be in this affair1 for1 in spite of the terrible political excitement1 the meeting on the #aith was attended by a full house4 ,the best of it is1 however1 that the synthetic treatment of nature1 introduced into ,france by ,geoffroy1 can now no longer be stopped4 ,this matter has now become public through the discussions in the ,academy1 carried on in the presence of a large audience2 it can no longer be referred to secret committees1 or be settled or suppressed behind closed doors4'0 ,in my book on 8,the ,general ,morphology of ,organisms0 ,i have placed as headings to the different books and chapters a selection of the numerous interesting and important sentences in which ,goethe clearly expresses his view of organic nature and its constant development4 ,i will here quote a passage from the poem entitled1 8,the ,metamorphosis of ,animals0 7#ahai74 8,all members develop themselves according to eternal laws1 ,and the rarest form mysteriously preserves the primitive type1 ,form therefore determines the animal's way of life1 ,and in turn the way of life powerfully reacts upon all form4 ,thus the orderly growth of form is seen to hold ,whilst yielding to change from externally acting causes40#c ,here1 clearly enough1 the contrast between two different organic constructive forms is intimated1 which are opposed to one another1 and which by their interaction determine the form of the organism2 on the one hand1 a common inner original type1 firmly maintaining itself1 constitutes the foundation of the most different forms2 on the other hand1 the externally active influence of surroundings and mode of life1 which influence the original type and transform it4 ,this contrast is still more definitely pointed out in the following passage3-- 8,an inner original community forms the foundation of all organization2 the variety of forms1 on the other hand1 arises from the necessary relations to the outer world1 and we may therefore justly assume an original difference of conditions1 together with an uninterruptedly progressive transformation1 in order to be able to comprehend the constancy as well as the variations of the phenomena of form40 ,the 8original type0 which constitutes the foundation of every organic form 8as the inner original community0 is the inner constructive force1 which receives the original direction of form-production--that is1 the tendency to give rise to a particular form--and is propagated by ,inheritance4 ,the 8uninterruptedly progressive transformation10 on the other hand1 which 8springs from the necessary relations to the outer world10 acting as an external formative force1 produces1 by ,adaptation to the surrounding conditions of life1 the 8infinite variety of forms0 7,gen4 ,morph4 i4 #aed2 ii4 #bbd74 ,the internal formative tendency of ,inheritance1 which retains the unity of the original type1 is called by ,goethe in another passage the centripetal force of the organism1 or its tendency to specification2 in contrast with this he calls the external formative tendency of ,adaptation1 which produces the variety of organic forms1 the centrifugal force of organisms1 or their tendency to variation4 ,the passage in which he clearly indicates the 8equilibrium0 of these two extremely important organic formative tendencies1 runs as follows3 8,the idea of metamorphosis resembles the vis centrifuga1 and would lose itself in the infinite1 if a counterpoise were not added to it3 ,i mean the tendency to specification1 the strong power to preserve what once has come into being1 a vis centripeta1 which in its deepest foundation cannot be affected by anything external40 ,metamorphosis1 according to ,goethe1 consists not merely1 as the word is now generally understood1 in the changes of form which the organic individual experiences during its individual development1 but1 in a wider sense1 in the transformation of organic forms in general4 ,his idea of metamorphosis is almost synonymous with the theory of development4 ,this is clear1 among other things1 from the following passage3--8,the triumph of physiological metamorphosis manifests itself where the whole separates and transforms itself into families1 the families into genera1 the genera into species1 and then again into other varieties down to the individual4 ,this operation of nature goes on ad infinitum2 she cannot rest inactive1 but neither can she keep and preserve all that she has produced4 ,from seeds there are always developed varying plants1 exhibiting the relations of their parts to one another in an altered manner40 ,goethe had1 in truth1 discovered two great mechanical forces of nature1 which are the active causes of organic formations1 his two organic formative tendencies--on the one hand the conservative1 centripetal1 and internal formative tendency of ,inheritance or specification2 and on the other hand the progressive1 centrifugal1 and external formative tendency of ,adaptation1 or metamorphosis4 ,this profound biological intuition could not but lead him naturally to the fundamental idea of the ,doctrine of ,filiation1 that is1 to the conception that the organic species resembling one another in form are actually related by blood1 and that they are descended from a common original type4 ,in regard to the most important of all animal groups1 namely that of ,vertebrate animals1 ,goethe expresses this doctrine in the following passage 7#agif73--8,thus much then we have gained1 that we may assert without hesitation that all the more perfect organic natures1 such as fishes1 amphibious animals1 birds1 mammals1 and man at the head of the last1 were all formed upon one original type1 which only varies more or less in parts which are none the less permanent1 and still daily changes and modifies its form by propagation40 ,this sentence is of interest in more than one way4 ,the theory that all 8the more perfect organic natures10 that is all ,vertebrate animals1 are descended from one common prototype1 that they have arisen from it by propagation 7,inheritance7 and transformation 7,adaptation71 may be distinctly inferred4 ,but it is especially interesting to observe that ,goethe admits no exceptional position for man1 but rather expressly includes him in the tribe of the other ,vertebrate animals4 ,the most important special inference of the ,doctrine of ,filiation1 that man is descended from other ,vertebrate animals1 may here be recognized in the germ47#c7 ,this exceedingly important fundamental idea is expressed by ,goethe still more clearly in another passage 7#ahjg71 in the following words3--8,if we consider plants and animals in their most imperfect condition1 they can scarcely be distinguished4 ,but this much we can say1 that the creatures which by degrees emerge as plants and animals out of a common phase1 where they are barely distinguishable1 arrive at perfection in two opposite directions2 so that the plant in the end reaches its highest glory in the tree1 which is immovable and stiff1 the animal in man1 who possesses the greatest elasticity and freedom40 ,this remarkable passage not only indicates most explicitly the genealogical relationship between the vegetable and animal kingdoms1 but contains the germ of the monophyletic hypothesis of descent1 the importance of which ,i shall have to explain hereafter4 7,compare ,chapter ,,xvi4 and the ,pedigree1 p4 #cih47 ,at the time when ,goethe in this way sketched the fundamental features of the ,theory of ,descent1 another ,german philosopher1 ,gottfried ,reinhold ,treviranus1 of ,bremen 7born #aggf1 died #ahcg71 was zealously engaged at the same work4 ,as ,wilhelm ,focke has recently shown1 ,treviranus1 even in the earliest of his greater works1 8,the ,biology or ,philosophy of ,animate ,nature10 which appeared at the beginning of the present century1 had already developed monistic views of the unity of nature1 and of the genealogical connection of the species of organisms1 which entirely correspond with our present view of the matter4 ,in the first three volumes of the ,biology1 which appeared successively in #ahjb1 #ahjc1 and #ahje 7therefore several years before ,oken's and ,lamarck's principal works71 we find numerous passages which are of interest in this respect4 ,i shall here quote only a few of the most important4 ,in speaking of the principal question of our theory1 the question of the origin of organic species1 ,treviranus makes the following remarks3--8,every form of life can be produced by physical forces in one of two ways3 either by coming into being out of formless matter1 or by modification of an already existing form by a continued process of shaping4 ,in the latter case the cause of this modification may lie either in the influence of a dissimilar male generative matter upon the female germ1 or in the influence of other powers which operate only after procreation4 ,in every living being there exists the capability of an endless variety of form-assumption2 each possesses the power to adapt its organization to the changes of the outer world1 and it is this power put into action by the change of the universe that has raised the simple zoophytes of the primitive world to continually higher stages of organization1 and has introduced a countless variety of species into animate nature40 ,by zoophytes1 ,treviranus here means organisms of the lowest order and of the simplest character1 namely1 those neutral primitive beings which stand midway between animals and plants1 and on the whole correspond with our protista4 8,these zoophytes10 he remarks in another passage1 8are the original forms out of which all the organisms of the higher classes have arisen by gradual development4 ,we are further of opinion that every species1 as well as every individual1 has certain periods of growth1 of bloom1 and of decay1 but that the decay of a species is degeneration1 not dissolution1 as in the case of the individual4 ,from this it appears to us to follow that it was not the great catastrophes of the earth 7as is generally supposed7 which destroyed the animals of the primitive world1 but that many survived them1 and it is more probable that they have disappeared from existing nature1 because the species to which they belonged have completed the circle of their existence1 and have become changed into other kinds40 ,when ,treviranus1 in this and other passages1 points to degeneration as the most important cause of the transformation of the animal and vegetable species1 he does not understand by it what is now commonly called degeneration4 ,with him 8degeneration0 is exactly what we now call ,adaptation or modification1 by the action of external formative forces4 ,that ,treviranus explained this trans-transformation of organic species by ,adaptation1 and its preservation by ,inheritance1 and thus the whole variety of organic forms by the interaction of ,adaptation and ,inheritance1 is clear also from several other passages4 ,how profoundly he grasped the mutual dependence of all living creatures on one another1 and in general the universal connection between cause and effect--that is1 the monistic causal connection between all members and parts of the universe--is further shown1 among others1 by the following remarks in his ,biology3--8,the living individual is dependent upon the species1 the species upon the fauna1 the fauna upon the whole of animate nature1 and the latter upon the organism of the earth4 ,the individual possesses indeed a peculiar life1 and so far forms its own world4 ,but just because its life is limited it constitutes at the same time an organ in the general organism4 ,every living body exists in consequence of the universe1 but the universe1 on the other hand1 exists in consequence of it40 ,it is self-evident that so profound and clear a thinker as ,treviranus1 in accordance with this grand mechanical conception of the universe1 could not admit for man a privileged and exceptional position in nature1 but assumed his gradual development from lower animal forms4 ,and it is equally self-evident1 on the other hand1 that he did not admit a chasm between organic and inorganic nature1 but maintained the absolute unity of the organization of the whole universe4 ,this is specially attested by the following sentence3--8,every inquiry into the influence of the whole of nature on the living world must start from the principle1 that all living forms are products of physical influences1 which are acting even now1 and are changed only in degree1 or in their direction40 ,hereby1 as ,treviranus himself says1 8,the fundamental problem of biology is solved10 and we add1 solved in a purely mechanical or monistic sense4 ,neither ,treviranus nor ,goethe is commonly considered the most eminent of the ,german nature-philosophers1 but ,lorenz ,oken1 who1 in establishing the vertebral theory of the skull1 came forward as a rival to ,goethe1 and did not entertain a very kindly feeling towards him4 ,although they lived for some time in the same neighbourhood1 yet the natures of these two men were so very different1 that they could not well be drawn towards each other4 ,oken's 8,manual of the ,philosophy of ,nature10 which may be designated as the most important production of the nature-philosophy school then existing in ,germany1 appeared in #ahji1 the same year in which ,lamarck's fundamental work1 the 8,philosophie ,zoologique10 was published4 ,as early as #ahjb1 ,oken had published an 8,outline of the ,philosophy of ,nature40 ,as we have already intimated1 in ,oken's as in ,goethe's works1 a number of valuable and profound thoughts are hidden among a mass of erroneous1 very eccentric1 and fantastic conceptions4 ,some of these ideas have only quite recently and gradually become recognized in science1 many years after they were first expressed4 ,i shall here quote only two thoughts1 which are almost prophetic1 and which at the same time stand in the closest relation to the theory of development4 ,one of the most important of ,oken's theories1 which was formerly very much decried1 and was most strongly combatted1 especially by the so-called 8exact experimentalists10 is the idea that the phenomena of life in all organisms proceed from a common chemical substance1 so to say1 from a general simple vital-substance1 which he designated by the name ,urschleim1 or original slime4 ,by it he meant1 as the name indicates1 a mucilaginous substance1 an albuminous combination1 which exists in a semi-fluid condition of aggregation1 and possesses the power1 by adaptation to different conditions of existence in the outer world and by interaction with its material1 of producing the most various forms4 ,now1 we need only change the expression 8original slime0 7,urschleim7 into ,protoplasm1 or cell-substance1 in order to arrive at one of the grandest results which we owe to microscopic investigations during the last ten years1 more especially to those of ,max ,schultze4 ,by these investigations it has been shown that in all living bodies1 without exception1 there exists a certain quantity of mucilaginous albuminous matter1 in a semi-fluid condition2 and that this nitrogen-holding carbon-compound is exclusively the original seat and agent of all the phenomena of life1 and of all production of organic forms4 ,all other substances which appear in the organism1 besides these1 are either formed by this active matter of life1 or have been introduced from without4 ,the organic egg1 the original cell out of which every animal and plant is first developed1 consists essentially only of one round little lump of such albuminous matter4 ,even the yolk of an egg is nothing but albumen1 mixed with granules of fat4 ,oken was therefore right when1 more divining than knowing1 he made the assertion--8,every organic thing has arisen out of slime1 and is nothing but slime in different forms4 ,this primitive slime originated in the sea1 from inorganic matter in the course of planetary-evolution40 ,another equally grand idea of the same philosopher is closely connected with his theory of primitive slime1 which coincides with the extremely important ,protoplasm theory4 ,for ,oken1 as early as #ahji1 asserted that the primitive slime produced in the sea by spontaneous generation1 at once assumed the form of microscopically small bladders1 which he called 8,mile10 or 8,infusoria40 8,organic nature has for its basis an infinity of such vesicles40 ,these little bladders arise from original semi-fluid globules of the primitive slime1 by the fact of their periphery becoming condensed4 ,the simplest organism1 as well as every animal and every plant of higher kind1 is nothing else than 8an accumulation 7synthesis7 of such infusorial bladders1 which by various combinations assume various forms1 and thus develop into higher organisms40 ,here again we need only translate the expression little bladder1 or infusorium1 by the word cell1 and we arrive at the ,cell theory1 one of the grandest biological theories of our century4 ,schleiden and ,schwann1 about thirty years ago1 were the first to furnish experiential proof that all organisms are either simple cells1 or accumulations 7syntheses7 of such cells1 and the more recent protoplasm theory has shown that protoplasm 7the original slime7 is the most essential 7and sometimes the only7 constituent part of the genuine cell4 ,the properties which ,oken ascribes to his ,infusoria are exactly the properties of cells1 the properties of elementary beings1 by whose accumulation1 combination1 and varying development1 the higher organisms are formed4 ,these two extremely fruitful thoughts of ,oken1 on account of the absurd form in which he expressed them1 were at first little heeded1 or entirely misunderstood1 and it was reserved for a much later era to establish them by actual observation4 ,the supposition that the individual species of plants and animals originated from common prototypes by a slow and gradual development of the higher organisms out of lower ones1 was of course most closely connected with these ideas4 ,man's descent from lower organisms was likewise asserted by ,oken--8,man has been developed1 not created40 ,although many arbitrary perversities and extravagant fancies may be found in ,oken's philosophy of nature1 they must not prevent us paying our just admiration to these grand ideas1 which were so far in advance of their age4 ,this much is clearly evident from the statements of ,goethe and ,oken which we have quoted1 and from the views of ,lamarck and ,geoffroy which have to be discussed next1 that during the first decade of our century no doctrine approached so nearly to the natural ,theory of ,descent1 newly established by ,darwin1 as the much decried 8,natur-philosophie40 ,,chapter ,v4 ,,theory ,,of ,,development ,,according ,,to ,,kant ,,and ,,lamarck4 ,kant's ,dualistic ,biology4--,his ,conception of the ,origin of ,inorganic ,nature by ,mechanical ,causes1 of ,organic ,nature by ,causes acting for a ,definite ,purpose4--,contradiction of this ,conception with his leaning towards the ,theory of ,descent4--,kant's ,genealogical ,theory of ,development4--,its ,limitation by his ,teleology4--,comparison of ,genealogical ,biology with ,comparative ,philology4--,views in favour of the ,theory of ,descent entertained by ,leopold ,buch1 ,br1 ,schleiden1 ,unger1 ,schaafhausen1 ,victor ,carus1 ,bchner4--,french ,nature-philosophy4--,lamarck's ,philosophie ,zoologique4--,lamarck's ,monistic 7mechanical7 ,system of ,nature4--,his ,views of the ,interaction of the ,two ,organic ,formative ,tendencies of ,inheritance and ,adaptation4--,lamarck's ,conception of ,man's ,development from ,ape-like ,mammals4--,geoffroy ,st4 ,hilaire's1 ,naudin's1 and ,lecoq's ,defence of the ,theory of ,descent4--,english ,nature-philosophy4--,views in favour of the ,theory of ,descent1 entertained by ,erasmus ,darwin1 ,w4 ,herbert1 ,grant1 ,freke1 ,herbert ,spencer1 ,hooker1 ,huxley4--,the ,double ,merit of ,charles ,darwin4 ,the teleological view of nature1 which explains the phenomena of the organic world by the action of a personal ,creator acting for a definite purpose1 necessarily leads1 when carried to its extreme consequences1 either to utterly untenable contradictions1 or to a twofold 7dualistic7 conception of nature1 which most directly contradicts the unity and simplicity of the supreme laws which are everywhere perceptible4 ,the philosophers who embrace teleology must necessarily assume two fundamentally different natures3 an inorganic nature1 which must be explained by causes acting mechanically 7caus efficientes71 and an organic nature1 which must be explained by causes acting for a definite purpose 7caus finales74 7,compare p4 #cd47 ,this dualism meets us in a striking manner when considering the conceptions of nature formed by ,kant1 one of the greatest ,german philosophers1 and his ideas of the coming into being of organisms4 ,a closer examination of these ideas is forced upon us here1 because in ,kant we honour one of the few philosophers who combine a solid scientific culture with an extraordinary clearness and profundity of speculation4 ,the ,knigsberg philosopher gained the highest celebrity1 not only among speculative philosophers as the founder of critical philosophy1 but acquired a brilliant name also among naturalists by his mechanical cosmogeny4 ,even in the year #agee1 in his 8,general ,history of ,nature1 and ,theory of the ,heavens107#bb7 he made the bold attempt 8to discuss the constitution and the mechanical origin of the whole universe1 according to ,newton's principles10 and to explain them mechanically by the natural course of development1 to the exclusion of all miracles4 ,this cosmogeny of ,kant1 or 8cosmological gas theory10 which we shall briefly discuss in a future chapter1 was at a later day fully established by the ,french mathematician ,laplace and the ,english astronomer ,herschel1 and enjoys at the present day almost universal recognition4 ,on account of this important work alone1 in which exact knowledge is coupled with most profound speculation1 ,kant deserves the honourable name of a natural philosopher in the best and purest sense of the word4 ,if we read ,kant's ,criticism of the ,teleological ,faculty of ,judgment1 his most important biological work1 we perceive that in contemplating organic nature he always maintains what is essentially the teleological or dualistic point of view2 whilst for inorganic nature he1 unconditionally and without reserve1 assumes the mechanical or monistic method of explanation4 ,he affirms that in the domain of inorganic nature all the phenomena can be explained by mechanical causes1 by the moving forces of matter itself1 but not so in the domain of organic nature4 ,in the whole of ,anorganology 7in ,geology and ,mineralogy1 in ,meteorology and ,astronomy1 in the physics and chemistry of inorganic natural bodies71 all phenomena are said to be explicable merely by mechanism 7causa efficiens71 without the intervention of a final purpose4 ,in the whole domain of ,biology1 on the other hand--in ,botany1 ,zoology1 and ,anthropology--mechanism is not considered sufficient to explain to us all their phenomena2 but we are supposed to be able to comprehend them only by an assumption of a final cause acting for a definite purpose 7causa finalis74 ,in several passages ,kant emphatically remarks that1 from a strictly scientific point of view1 all phenomena1 without exception1 require a mechanical interpretation1 and that mechanism alone can offer a true explanation4 ,but at the same time he thinks1 that in regard to living natural bodies1 animals and plants1 our human power of comprehension is limited1 and not sufficient for arriving at the real cause of organic processes1 especially at the origin of organic forms4 ,the right of human reason to explain all phenomena mechanically is unlimited1 he says1 but its power is limited by the fact that organic nature can be conceived only from a teleological point of view4 ,some passages are1 however1 very remarkable1 in which ,kant in a surprising manner deviates from this mode of viewing things1 and expresses1 more or less distinctly1 the fundamental idea of the ,theory of ,descent4 ,he even asserts the necessity of a genealogical conception of the series of organisms1 if we at all wish to understand it scientifically4 ,the most important and remarkable of these passages occurs in his 8,methodical ,system of the ,teleological ,faculty of ,judgment0 7 #gi71 which appeared in #agij in the 8,criticism of the ,faculty of ,judgment40 ,considering the extraordinary interest which this passage possesses1 both for forming a correct estimate of ,kant's philosophy1 as well as for the ,theory of ,descent1 ,i shall here insert it verbatim4 8,it is desirable to examine the great domain of organized nature by means of a methodical comparative anatomy1 in order to discover whether we may not find in it something resembling a system1 and that too in connection with the mode of generation1 so that we may no longer be compelled to stop short with a mere consideration of forms as they are--which gives us no insight into their generation--and need no longer give up in despair all hope of gaining a full insight into this department of nature4 ,the agreement of so many kinds of animals in a certain common plan of structure1 which seems to be visible not only in their skeletons1 but also in the arrangement of the remaining parts--so that a wonderfully simple typical form1 by the shortening and lengthening of some parts1 and by the suppression and development of others1 might be able to produce an immense variety of species--gives us a ray of hope1 though feeble1 that here perhaps some result may be obtained1 by the application of the principle of the mechanism of nature1 without which1 in fact1 no science can exist4 ,this analogy of forms 7in so far as they seem to have been produced in accordance with a common prototype1 notwithstanding their great variety7 strengthens the supposition that they have an actual blood-relationship1 due to origination from a common parent2 a supposition which is arrived at by observation of the graduated approximation of one class of animals to another1 beginning with the one in which the principle of purposiveness seems to be most conspicuous1 that is man1 and extending down to the polyps1 and from these even down to mosses and lichens1 and arriving finally at raw matter1 the lowest stage of nature observable by us4 ,from this matter and its forces the whole apparatus of ,nature seems to have descended according to mechanical laws 7such as those which she follows in the production of crystals72 yet this apparatus1 as seen in organic beings1 is so incomprehensible to us1 that we feel ourselves compelled to conceive for it a different principle4 ,but it would seem that the archologist of ,nature is at liberty to regard the great ,family of creatures 7for as a ,family we must conceive it1 if the above-mentioned continuous and connected relationship has a real foundation7 as having sprung from the immediate results of her earliest revolutions1 judging from all the laws of their mechanism known to or conjectured by him40 ,if we take this remarkable passage out of ,kant's 8,criticism of the ,teleological ,faculty of ,judgment10 and consider it by itself1 we cannot but be astonished to find how profoundly and clearly the great thinker1 even in #agij1 had recognized the inevitable necessity of the ,doctrine of ,descent1 and designated it as the only possible way of explaining organic nature by mechanical laws--that is1 by true scientific reasoning4 ,on account of this one passage taken by itself1 we might place ,kant beside ,goethe and ,lamarck1 as one of the first founders of the ,doctrine of ,descent2 and considering the high authority which ,kant's ,critical ,philosophy most justly enjoys1 this circumstance might perhaps induce many a philosopher to decide in favour of the theory4 ,but as soon as we consider this passage in connection with the other train of thoughts in the 8,criticism of the ,faculty of ,judgment10 and balance it against other directly contradictory passages1 we see clearly that ,kant1 in these and some similar 7but weaker7 sentences1 went beyond himself1 and abandoned the teleological point of view which he usually adopts in ,biology4 ,directly after the admirable passage which ,i have just quoted1 there follows a remark which completely takes off its edge4 ,after having quite correctly maintained the origin of organic forms out of raw matter by mechanical laws 7in the manner of crystallization71 as well as a gradual development of the different species by descent from one common original parent1 ,kant adds1 8,but he 7the archologist of nature1 that is the palontologist7 must for this end ascribe to the common mother an organization ordained purposely with a view to the needs of all her offspring1 otherwise the possibility of suitability of form in the products of the animal and vegetable kingdoms 7i4e4 teleological adaptation7 cannot be conceived at all40 ,this addition clearly contradicts the most important fundamental thought of the preceding passage1 viz41 that a purely mechanical explanation of organic nature becomes possible through the ,theory of ,descent4 ,and that the teleological conception of organic nature predominated with ,kant1 is shown by the heading of the remarkable #gi1 which contains the two contradictory passages cited3 8,of the ,necessary ,subordination of the ,mechanical to the ,teleological ,principle1 in the explanation of a thing as a purpose or object of ,nature40 ,he expresses himself most decidedly against the mechanical explanation of organic nature in the following passage 7 #gd73 8,it is quite certain that we cannot become sufficiently acquainted with organized creatures and their hidden potentialities by aid of purely mechanical natural principles1 much less can we explain them2 and this is so certain1 that we may boldly assert that it is absurd for man even to conceive such an idea1 or to hope that a ,newton may one day arise able to make the production of a blade of grass comprehensible1 according to natural laws ordained by no intention2 such an insight we must absolutely deny to man40 ,now1 however1 this impossible ,newton has really appeared seventy years later in ,darwin1 whose ,theory of ,selection has actually solved the problem1 the solution of which ,kant had considered absolutely inconceivable6 ,in connection with ,kant and the ,german philosophers whose theories of development have already occupied us in the preceding chapter1 it seems justifiable to consider briefly some other ,german naturalists and philosophers1 who1 in the course of our century1 have more or less distinctly resisted the prevailing teleological views of creation1 and vindicated the mechanical conception of things which is the basis of the ,doctrine of ,filiation4 ,sometimes general philosophical considerations1 sometimes special empirical observations1 were the motives which led these thinking men to form the idea that the various individual species of organisms must have originated from common primary forms4 ,among them ,i must first mention the great ,german geologist1 ,leopold ,buch4 ,important observations as to the geographical distribution of plants led him to the following remarkable assertion in his excellent 8,physical ,description of the ,canary ,islands03-- 8,the individuals of genera1 on continents1 spread and widely diffuse themselves1 and by the difference of localities1 nourishment1 and soil1 form varieties2 and being in consequence of their isolation never crossed by other varieties1 and so brought back to the main type1 they in the end become a permanent and a distinct species4 ,then1 perhaps1 in other ways1 they once more become associated with other descendants of the original form--which have likewise become new varieties--and both now appear as very distinct species1 no longer mingling with one another4 ,not so on islands4 ,being commonly confined in narrow valleys or within the limit of small zones1 individuals can reach one another and destroy every commencing production of a permanent variety4 ,much in the same way the peculiarities or faults in language1 originating with the head of some family1 become1 through the extension of the family1 indigenous throughout a whole district4 ,if the district is separated and isolated1 and if the language is not brought back to its former purity by constant connection with that spoken in neighbouring districts1 a dialect will be the result4 ,if natural obstacles1 forests1 constitution1 form of government1 unite the inhabitants of the separate district still more closely1 and separate them still more completely from their neighbours1 the dialect is fixed1 and becomes a completely distinct language40 7,uebersicht der ,flora auf den ,canarien1 ,s4 #acc47 ,we perceive that ,buch is here led to the fundamental idea of the ,theory of ,descent by the phenomena of the geography of plants1 a department of biological knowledge which in fact furnishes a mass of proofs in favour of it4 ,darwin has minutely discussed these proofs in two separate chapters of his book 7the #aath and #abth74 ,buch's remark is further of interest1 because it leads us to the exceedingly instructive comparison of the different branches of language with the species of organisms1 a comparison which is of the greatest use to ,comparative ,philology1 as well as to ,comparative ,botany and ,zoology4 ,just as1 for example1 the different dialects1 provincialisms1 branches1 and off-shoots of the ,german1 ,slavonic1 ,greco-,latin1 and ,irano-,indian parent language1 are derived from a single common ,indo-,germanic parent tongue1 and just as their differences are explained by ,adaptation1 and their common fundamental characters explained by ,inheritance1 so in like manner the different species1 genera1 families1 orders1 and classes of ,vertebrate animals are derived from a single common vertebrate form of animal4 ,here also ,adaptation is the cause of differences1 ,inheritance the cause of community of character4 ,this interesting parallelism in the divergent development of the forms of speech and the forms of organisms has been discussed in the clearest manner by one of our first comparative philologists1 the talented ,augustus ,schleicher1 whose premature death1 four years ago1 remains an irreparable loss1 not only to our ,university of ,jena1 but to the whole of monistic science47#f7 ,among other eminent ,german naturalists who have expressed their belief in the ,theory of ,descent more or less distinctly1 arriving at their conclusion in very various ways1 ,i must next mention ,carl ,ernst ,br1 the great reformer of animal embryology4 ,in a lecture delivered in #ahcd1 entitled 8,the ,most ,general ,laws of ,nature in ,all ,development10 he shows1 in the clearest way1 that only in a very childish view of nature could organic species be regarded as permanent and unchangeable types1 and that really they can be only passing series of generations1 which have developed by transformation from a common original form4 ,the same conception again received firm support from ,baer1 in #ahei1 through a consideration of the laws of the geographical distribution of organisms4 ,j4 ,m4 ,schleiden1 who founded1 thirty years ago1 in ,jena1 a new epoch in ,botany by his strictly empirico-philosophical and truly scientific method1 illustrated the philosophical significance of the conception of organic species in his incisive 8,outlines of ,scientific ,botany107#g7 and showed that it had only a subjective origin in the general law of specification4 ,the different species of plants are only the specified productions of the formative tendencies of plants1 which arise from the various combinations of the fundamental forces of organic matter4 ,the eminent botanist1 ,f4 ,unger1 of ,vienna1 was led by his profound and comprehensive investigations on extinct vegetable species1 to a palontological history of the development of the vegetable kingdom1 which distinctly asserts the principle of the ,theory of ,descent4 ,in his 8,attempt at a ,history of the ,world of ,plants0 7#aheb71 he maintains the derivation of all different species of plants from a few primary forms1 and perhaps from a single original plant1 a simple vegetable cell4 ,he shows that this view is founded on the genetic connection of all vegetable forms1 and is necessary1 not merely upon philosophical grounds1 but upon those of experience and observation47#h7 ,victor ,carus1 of ,leipzig1 in the ,introduction to his excellent 8,system of ,animal ,morphology107#i7 published in #ahec1 in which he endeavours to establish in a philosophical manner the universal constructive laws of the animal body through comparative anatomy and the history of development1 makes the following remark3--8,the organisms buried in the most ancient geological strata must be looked upon as the ancestors from whom the rich diversity of forms of the present creation have originated by continued generation1 and by accommodation to progressive and very different conditions of life40 ,in the same year 7#ahec7 ,schaaffhausen1 the anthropologist of ,bonn1 in an ,essay 8,on the ,permanence and ,transformation of ,species10 declared himself decidedly in favour of the ,theory of ,descent4 ,according to him1 the living species of animals and plants are the transformed descendants of extinct species1 from which they have arisen by gradual modification4 ,the divergence or separation of the most nearly allied species takes place by the destruction of the connecting intermediate stages4 ,schaaffhausen also maintained1 with distinctness1 the origin of the human race from animals1 and its gradual development from ape-like animals1 the most important deduction from the ,doctrine of ,filiation4 ,lastly1 we have still to mention among the ,german ,nature-philosophers the name of ,louis ,bchner1 who1 in his celebrated work1 8,force and ,matter0 7#ahee71 also independently developed the principles of the ,theory of ,descent1 taking his stand mainly on the ground of the undeniable evidences of fact which are furnished by the palontological and individual development of organisms1 as well as by their comparative anatomy and by the parallelism of these series of development4 ,bchner showed very clearly that1 even from such data alone1 the derivation of the different organic species from common primary forms followed as a necessary conclusion1 and that the origin of these original primary forms could only be conceived of as the result of a spontaneous generation4 ,we now turn from the ,german to the ,french ,nature-philosophers1 who have likewise held the ,theory of ,descent1 since the beginning of the present century4 ,at their head stands ,jean ,lamarck1 who occupies the first place next to ,darwin and ,goethe in the history of the ,doctrine of ,filiation4 ,to him will always belong the immortal glory of having for the first time worked out the ,theory of ,descent1 as an independent scientific theory of the first order1 and as the philosophical foundation of the whole science of ,biology4 ,although ,lamarck was born as early as #agdd1 he did not begin the publication of his theory until the commencement of the present century1 in #ahja1 and established it more fully only in #ahji1 in his classic 8,philosophie ,zoologique407#b7 ,this admirable work is the first connected exposition of the ,theory of ,descent carried out strictly into all its consequences4 ,by its purely mechanical method of viewing organic nature1 and the strictly philosophical proofs brought forward in it1 ,lamarck's work is raised far above the prevailing dualistic views of his time2 and with the exception of ,darwin's work1 which appeared just half a century later1 we know of none which we could in this respect place by the side of the 8,philosophie ,zoologique40 ,how far it was in advance of its time is perhaps best seen from the circumstance that it was not understood by most men1 and for fifty years was not spoken of at all4 ,cuvier1 ,lamarck's greatest opponent1 in his 8,report on the ,progress of ,natural ,sciences10 in which the most unimportant anatomical investigations are enumerated1 does not devote a single word to this work1 which forms an epoch in science4 ,goethe1 also1 who took such a lively interest in the ,french nature-philosophy and in 8the thoughts of kindred minds beyond the ,rhine10 nowhere mentions ,lamarck1 and does not seem to have known the 8,philosophie ,zoologique0 at all4 ,the great reputation which ,lamarck gained as a naturalist he does not owe to his highly important general work1 but to numerous special treatises on the lower animals1 particularly on ,molluscs1 as well as to an excellent 8,natural ,history of ,invertebrate ,animals10 which appeared1 in seven volumes1 between the years #ahae-ahbb4 ,the first volume of this celebrated work contains in the general introduction a detailed exposition of his theory of filiation4 ,i can1 perhaps1 give no better idea of the extraordinary importance of the 8,philosophie ,zoologique0 than by quoting verbatim some of the most important passages therefrom3-- 8,the systematic divisions of classes1 orders1 families1 genera1 and species1 as well as their designations1 are the arbitrary and artificial productions of man4 ,the kinds or species of organisms are of unequal age1 developed one after the other1 and show only a relative and temporary persistence2 species arise out of varieties4 ,the differences in the conditions of life have a modifying influence on the organization1 the general form1 and the parts of animals1 and so has the use or disuse of organs4 ,in the first beginning only the very simplest and lowest animals and plants came into existence2 those of a more complex organization only at a later period4 ,the course of the earth's development1 and that of its organic inhabitants1 was continuous1 not interrupted by violent revolutions4 ,life is purely a physical phenomenon4 ,all the phenomena of life depend on mechanical1 physical1 and chemical causes1 which are inherent in the nature of matter itself4 ,the simplest animals and the simplest plants1 which stand at the lowest point in the scale of organization1 have originated and still originate by spontaneous generation4 ,all animate natural bodies or organisms are subject to the same laws as inanimate natural bodies or anorgana4 ,the ideas and actions of the understanding are the motional phenomena of the central nervous system4 ,the will is in truth never free4 ,reason is only a higher degree of development and combination of judgments40 ,these are indeed astonishingly bold1 grand1 and far-reaching views1 and were expressed by ,lamarck sixty years ago2 in fact1 at a time when their establishment1 by a mass of facts1 was not nearly as possible as it is in our day4 ,indeed ,lamarck's work is really a complete and strictly monistic 7mechanical7 system of nature1 and all the important general principles of monistic ,biology are already enunciated by him3 the unity of the active causes in organic and inorganic nature2 the ultimate explanation of these causes in the chemical and physical properties of matter itself2 the absence of a special vital power1 or of an organic final cause2 the derivation of all organisms from some few1 most simple original forms1 which have come into existence by spontaneous generation out of inorganic matter2 the coherent course of the whole earth's history2 the absence of violent cataclysmic revolutions2 and in general the inconceivableness of any miracle1 of any supernatural interference1 in the natural course of the development of matter4 ,the fact that ,lamarck's wonderful intellectual feat met with scarcely any recognition1 arises partly from the immense length of the gigantic stride with which he had advanced beyond the next fifty years1 partly from its defective empirical foundation1 and from the somewhat one-sided character of some of his arguments4 ,lamarck quite correctly recognizes ,adaptation as the first mechanical cause which effects the continual transformation of organic forms1 while he traces with equal justice the similarity in form of different species1 genera1 families1 etc41 to their blood-relationship1 and thus explains it by ,inheritance4 ,adaptation1 according to him1 consists in this1 that the perpetual1 slow change of the outer world causes a corresponding change in the actions of organisms1 and thereby also causes a further change in their forms4 ,he lays the greatest stress upon the effect of habit upon the use and disuse of organs4 ,this is certainly of great importance in the transformation of organic forms1 as we shall see later4 ,however1 the way in which ,lamarck wished to explain exclusively1 or at any rate mainly1 the change of forms1 is after all in most cases not possible4 ,he says1 for example1 that the long neck of the giraffe has arisen from its constantly stretching out its neck at high trees1 and from the endeavour to pick the leaves off their branches2 as giraffes generally inhabit dry districts1 where only the foliage of trees afford them nourishment1 they were forced to this action4 ,in like manner the long tongues of wood-peckers1 humming-birds1 and ant-eaters1 are said by him to have arisen from the habit of fetching their food out of narrow1 small1 and deep crevices or channels4 ,the webs between the toes of the webbed feet in frogs and other aquatic animals have arisen solely from the constant endeavour to swim1 from striking their feet against the water1 and from the very movements of swimming4 ,inheritance fixed these habits on the descendants1 and finally1 by further elaboration1 the organs were entirely transformed4 ,however correct1 as a whole1 this fundamental thought may be1 yet ,lamarck lays the stress too exclusively on habit 7use and non-use of organs71 certainly one of the most important1 but not the only cause of the change of forms4 ,still this cannot prevent our acknowledging that ,lamarck quite correctly appreciated the mutual co-operation of the two organic formative tendencies of ,adaptation and ,inheritance4 ,what he failed to grasp is the exceedingly important principle of 8,natural ,selection in the ,struggle for ,existence10 with which ,darwin1 fifty years later1 made us acquainted4 ,it still remains to be mentioned as a special merit of ,lamarck1 that he endeavoured to prove the development of the human race from other primitive1 ape-like mammals4 ,here again it was1 above all1 to habit that he ascribed the transforming1 the ennobling influence4 ,he assumed that the lowest1 original men had originated out of men-like apes1 by the latter accustoming themselves to walk upright4 ,the raising of the body1 the constant effort to keep upright1 in the first place led to a transformation of the limbs1 to a stronger differentiation or separation of the fore and hinder extremities1 which is justly considered one of the most essential distinctions between man and the ape4 ,behind1 the calf of the leg and the flat soles of the feet were developed2 in front1 the arms and hands1 for the purpose of seizing objects4 ,the upright walk was then followed by a freer view over the surrounding objects1 and led consequently to an important progress in mental development4 ,human apes thereby soon gained a great advantage over the other apes1 and further1 over surrounding organisms in general4 ,in order to maintain the supremacy over them1 they formed themselves into companies1 and there arose1 as in the case of all animals living in company1 the desire of communicating to one another their desires and thoughts4 ,thus arose the necessity of language1 which1 consisting at first of rough and disjointed sounds1 soon became more connected1 developed1 and articulate4 ,the development of articulate speech now in turn became the strongest lever for a further progressive development of the organism1 and above all1 of the brain1 and so ape-like men became gradually and slowly transformed into real men4 ,in this way the actual descent of the lowest and rudest primitive men from the most highly developed apes was distinctly maintained by ,lamarck1 and supported by a series of the most important proofs4 ,the honour of being the chief ,french nature-philosopher is not usually assigned to ,lamarck1 but to ,etienne ,geoffroy ,st4 ,hilaire 7the elder71 born in #agga1 the same in whom ,goethe was especially interested1 and with whom we have already become acquainted as ,cuvier's most prominent opponent4 ,he developed his ideas about the transformation of organic species as far back as the end of the last century1 but published them only in the year #ahbh1 and then in the following years1 especially in #ahcj1 defended them bravely against ,cuvier4 ,geoffroy ,st4 ,hilaire in all essentials adopted ,lamarck's ,theory of ,descent1 yet he believed that the transformation of animal and vegetable species was less effected by the action of the organism itself 7by habit1 practice1 use1 or disuse of organs7 than by the 8monde ambiant10 that is1 by the continual change of the outer world1 especially of the atmosphere4 ,he conceives the organism as passive1 in regard to the vital conditions of the outer world1 while ,lamarck1 on the contrary1 regards it as active4 ,geoffroy thinks1 for example1 that birds originated from lizard-like reptiles1 simply by a diminution of the carbonic acid in the atmosphere1 in consequence of which the breathing process became more animated and energetic through the increased proportion of oxygen in the atmosphere4 ,thus there arose a higher temperature of the blood1 an increased activity of the nerves and muscles1 and the scales of the reptiles became the feathers of the birds1 etc4 ,this conception is based upon a correct thought1 but although the change of the atmosphere1 as well as the change of every other external condition of existence1 certainly effects directly or indirectly the transformation of the organism1 yet this single cause is by itself too unimportant for such effects to be ascribed to it4 ,it is even less important than practice and habit1 upon which ,lamarck lays too much stress4 ,geoffroy's chief merit consists in his having vindicated the monistic conception of nature1 the unity of organic forms1 and the deep genealogical connection of the different organic types in the face of ,cuvier's powerful influence4 ,i have already mentioned in the preceding chapter 7pp4 #hg1 #hh7 the celebrated disputes between the two great opponents in the ,academy of ,paris1 especially the fierce conflicts on the #bbnd of ,february1 and on the #aith of ,july1 in which ,goethe took so lively an interest4 ,on that occasion ,cuvier remained the acknowledged victor1 and since that time very little1 or rather nothing1 more has been done in ,france to further the development of the ,doctrine of ,filiation1 and complete the monistic theory of development4 ,this is evidently to be ascribed principally to the repressive influence exercised by ,cuvier's great authority4 ,even at the present day the majority of the ,french naturalists are the disciples and blind followers of ,cuvier4 ,in no civilized country of ,europe has ,darwin's doctrine had so little effect and been so little understood as in ,france1 so that in the further course of our examination we need not take the ,french naturalists into consideration4 ,at most1 there are two distinguished botanists1 among the recent ,french naturalists1 whom we may mention as having ventured to express themselves in favour of the mutability and transformation of species4 ,these two men are ,naudin 7#aheb7 and ,lecoq 7#ahed74 ,having discussed the early services of ,german and ,french nature-philosophy in establishing the doctrine of descent1 we turn to the third great country of ,europe1 to free ,england1 which during the last ten years has become the chief seat and starting-point for the further working out and definite establishment of the theory of development4 ,englishmen1 who now take such an active part in every great scientific progress of humanity1 and are the first to promote the eternal truths of natural science1 at the beginning of the century took but little part in the continental nature-philosophy and its most important progress1 the ,theory of ,descent4 ,almost the only earlier ,english naturalist whom we have here to mention is ,erasmus ,darwin1 the grandfather of the reformer of the ,theory of ,descent4 ,in #agie he published1 under the title of 8,zoonomia10 a scientific work in which he expresses views very similar to those of ,goethe and ,lamarck1 without1 however1 then knowing anything about these two men4 ,it is evident that the ,theory of ,descent at that time pervaded the intellectual atmosphere4 ,erasmus ,darwin lays great stress upon the transformation of animal and vegetable species by their own vital action and by their becoming accustomed to changed conditions of existence1 etc4 ,next1 ,w4 ,herbert1 in #ahbb1 expressed the opinion that species of animals and plants are nothing but varieties which have become permanent4 ,in like manner ,grant1 in ,edinburgh1 in #ahbf1 declared that new species proceed from existing species by continued transformation4 ,in #ahda ,freke maintained that all organic beings must be descended from a single primitive type4 ,in #aheb ,herbert ,spencer demonstrated minutely1 and in a very clear and philosophic manner1 the necessity of the ,doctrine of ,filiation1 and established it more firmly in his excellent 8,essays10 which appeared in #aheh1 and in his 8,principles of ,biology10 which was published at a later date4 ,he has1 at the same time1 the great merit of having applied the theory of development to psychology1 and of having shown that the emotional and intellectual faculties could only have been acquired by degrees and developed gradually4 ,lastly1 we have to mention that in #ahei ,huxley1 the first of ,english zoologists1 spoke of the ,theory of ,descent as the only hypothesis of creation reconcilable with scientific physiology4 ,the same year produced the 8,introduction to the ,flora of ,tasmania10 in which ,hooker1 the celebrated ,english botanist1 adopts the ,theory of ,descent1 supporting it with important observations of his own4 ,all the naturalists and philosophers with whom we have become acquainted in this brief historical survey1 as men adopting the ,theory of ,development1 merely arrived at the conception that all the different species of animals and plants which at any time have lived1 and still live1 upon the earth1 are the gradually changed and transformed descendants of one or some few original and very simple prototypes1 which latter arose out of inorganic matter by spontaneous generation4 ,but none of them succeeded in placing this fundamental element of the doctrine of descent in relation with some cause1 nor in satisfactorily explaining the transformation of organic species by the true demonstration of its mechanical antecedents4 ,charles ,darwin was the first who solved this most difficult problem1 and this forms the broad gulf which separates him from his predecessors4 ,the special merit of ,charles ,darwin is1 in my opinion1 twofold3 in the first place1 the doctrine of descent1 the fundamental idea of which was already clearly expressed by ,goethe and ,lamarck1 has been developed by him much more comprehensively1 has been traced much more minutely in all directions1 and carried out much more strictly and connectedly than by any of his predecessors2 and secondly1 he has established a new theory1 which reveals to us the natural causes of organic development1 the acting causes 7caus efficientes7 of organic form-production1 and of the changes and transformations of animal and vegetable species4 ,this is the theory which we call the ,theory of ,selection1 or more accurately1 the ,theory of ,natural ,selection 7selectio naturalis74 ,when we reflect that 7with the few exceptions above mentioned7 the whole science of ,biology1 before ,darwin's time1 was elaborated in accordance with the opposite views1 and that almost all zoologists and botanists regarded the absolute independence of organic species as a self-evident inference from the results of all study of forms1 we shall certainly not lightly value the twofold merit of ,darwin4 ,the false doctrine of the constancy and independent creation of individual species had gained such high authority1 was so generally recognized1 and was1 moreover1 so much favoured by delusive appearances1 accepted by superficial observation1 that1 indeed1 no small degree of courage1 strength1 and intelligence was required to rise as a reformer against its omnipotence1 and to dash to pieces the structure artificially erected upon it4 ,but1 in addition to this1 ,darwin added to ,lamarck's and ,goethe's doctrine of descent the new and highly important principle of 8natural selection40 ,we must sharply distinguish the two points--though this is usually not done--first1 ,lamarck's ,theory of ,descent1 which only asserts that all animal and vegetable species are descended from common1 most simple1 and spontaneously generated prototypes2 and secondly1 ,darwin's ,theory of ,selection1 which shows us why this progressive transformation of organic forms took place1 and what causes1 acting mechanically1 effected the uninterrupted production of new forms1 and the ever increasing variety of animals and plants4 ,darwin's immortal merit cannot be justly estimated until a later period1 when the ,theory of ,development1 after overthrowing all other theories of creation1 will be recognized as the supreme principle of explanation in ,anthropology1 and1 consequently1 in all other sciences4 ,at present1 while in the hot contest for truth the name of ,darwin is the watchword to the advocates of the natural theory of development1 his merits are inaccurately appreciated on both sides1 for some persons overestimate them as much as others underestimate them4 ,his merit is overestimated when he is regarded as the founder of the ,theory of ,descent1 or of the whole of the ,theory of ,development4 ,we have seen from the historical sketch in this and the preceding chapters1 that the ,theory of ,development1 as such1 is not new2 all philosophers who have refused to be led captive by the blind dogma of a supernatural creation1 have been compelled to assume a natural development4 ,but the ,theory of ,descent constituting the specially biological part of the universal ,theory of ,development1 had already been so clearly expressed by ,lamarck1 and carried out so fully by him to its most important consequences1 that we must honour him as the real founder of it4 ,hence it is only the ,theory of ,selection1 and not that of ,descent1 which may be called ,darwinism2 but this is in itself of so much importance1 that its value can scarcely be overestimated4 ,darwin's merit is naturally underestimated by all his opponents4 ,but it is scarcely possible in this matter to point to scientific opponents1 who are entitled by profound biological culture to pronounce an opinion4 ,for among all the works opposed to ,darwin and the ,theory of ,descent yet published1 with the exception of that of ,agassiz1 not one deserves consideration1 much less refutation2 all have so evidently been written either without thorough knowledge of biological facts1 or without a clear philosophical understanding of the question in hand4 ,we need not trouble ourselves at all about the attacks of theologians and other unscientific men1 who really know nothing whatever of nature4 ,the only eminent scientific adversary who still remains opposed to ,darwin and the whole theory of development is ,louis ,agassiz2 but the principle of his opposition in reality deserves notice only as a philosophical curiosity4 ,in a ,french translation of his 8,essay on ,classification107#e7 which we have spoken of before1 published in ,paris in #ahfi1 ,agassiz has most formally announced his opposition to ,darwinism1 which he had previously expressed in many ways4 ,to this translation he has appended a treatise of sixteen pages1 bearing the title1 8,le ,darwinisme4 ,classification de ,haeckel40 ,this curious chapter contains the most wonderful things2 as1 for example1 8,darwin's idea is a conception priori4 ,darwinism is a burlesque of facts4 ,science would renounce the claim which it has hitherto possessed to the confidence of earnest minds if such sketches were to be accepted as indications of a true progress40 ,the following passage1 however1 is the climax of this strange polemic3 8,darwinism shuts out almost the whole mass of acquired knowledge in order to retain and assimilate to itself that only which may serve its doctrine40 ,surely this is what we may call turning the whole affair topsy-turvy6 ,the biologist who knows the facts must be astounded at ,agassiz's courage in uttering such sentences--sentences without a word of truth in them1 and which he cannot himself believe6 ,the impregnable strength of the ,theory of ,descent lies just in the fact that all biological facts are explicable only through it1 and that without it they remain unintelligible miracles4 ,all our 8laborious knowledge0 in comparative anatomy and physiology--in embryology and palontology--in the doctrine of the geographical and topographical distribution of organisms1 etc41 constitutes an irrefutable testimony to the truth of the ,theory of ,descent4 ,in my ,general ,morphology1 especially in the sixth book 7in the ,general ,phylogeny71 ,i have minutely refuted ,agassiz's 8,essay on ,classification0 in all essential points4 ,the twenty-fourth chapter ,i have devoted to a very detailed and strictly scientific discussion of that section which ,agassiz himself considers the most important 7the groups or categories of systematic zoology and botany71 and have shown that this part of his work is purely chimerical1 without any trace of real foundation4 ,agassiz takes good care not to venture anywhere to touch upon my refutation1 because1 forsooth1 he is not in a position to produce anything substantial against it4 ,he fights not with arguments1 but with phrases4 ,however1 such opposition will not delay the complete victory of the ,theory of ,development1 but only accelerate it4 ,,chapter ,,vi4 ,,theory ,,of ,,development ,,according ,,to ,,lyell ,,and ,,darwin4 ,charles ,lyell's ,principles of ,geology4--,his ,natural ,history of the ,earth's ,development4--,origin of the ,greatest ,effects through the ,multiplication of the ,smallest ,causes4--,unlimited ,extent of ,geological ,periods4--,lyell's ,refutation of ,cuvier's ,history of ,creation4--,the ,establishment of the ,uninterrupted ,connection of ,historical ,development by ,lyell and ,darwin4--,biographical ,notice of ,charles ,darwin4--,his ,scientific ,works4--,his ,theory of ,coral ,reefs4--,development of the ,theory of ,selection4--,a ,letter of ,darwin's4--,the ,contemporaneous ,appearance of ,darwin's and ,alfred ,wallace's ,theory of ,selection4--,darwin's ,study of ,domestic ,animals and ,cultivated ,plants4--,andreas ,wagner's notions as to the ,special ,creation of ,cultivated ,organisms for the good of ,man4--,the ,tree of ,knowledge in ,paradise4--,comparison between ,wild and ,cultivated ,organisms4--,darwin's ,study of ,domestic ,pigeons4--,importance of ,pigeon ,breeding4--,common ,descent of all ,races of ,pigeons4 ,during the thirty years1 from #ahcj until #ahei1 when ,darwin's work appeared1 the ideas of creation introduced by ,cuvier remained predominant in the sciences of organic nature4 ,people rested satisfied with the unscientific assumption1 that in the course of the earth's history1 a series of inexplicable revolutions had periodically annihilated the whole world of animals and plants1 and that at the end of each revolution1 and the beginning of a new period1 a new enlarged1 and improved edition of the organic population had appeared4 ,although the number of these editions of creation was altogether problematical1 and in truth could not be fixed at all1 and although the numerous advances which1 during this time1 were made in all the departments of zoology and botany demonstrated more and more that ,cuvier's hypothesis was unfounded and untenable1 and that ,lamarck's natural theory of development was nearer the truth1 yet the former maintained its authority almost universally among biologists4 ,this must1 above all1 be ascribed to the veneration which ,cuvier had acquired1 and strikingly illustrates how injurious to the progress of humanity a faith in any definite authority may become4 ,authority1 as ,goethe once admirably said1 perpetuates the individual1 which as an individual should pass away1 rejects and allows to pass that which should be held fast1 and is the main obstacle to the advance of humanity4 ,it is only by having regard to the great weight of ,cuvier's authority1 and to the mighty potency of human indolence1 which is with difficulty induced to depart from the broad and comfortable way of everyday conceptions1 and to enter upon new paths not yet made easy1 that we can comprehend how it is that ,lamarck's ,theory of ,descent did not gain its due recognition until #ahei1 after ,darwin had given it a new foundation4 ,the soil had long been prepared for it by the works of ,charles ,lyell1 another ,english naturalist1 whose views are of great importance for the natural history of creation1 and must accordingly here be briefly explained4 ,in #ahcj ,charles ,lyell published1 under the title of 8,principles of ,geology10 a work in which he thoroughly reformed the science of ,geology and the history of the earth's development1 and effected this reform in a manner similar to that in which1 thirty years later1 ,darwin in his work reformed the science of ,biology4 ,lyell's great treatise1 which radically destroyed ,cuvier's hypothesis of creation1 appeared in the same year in which ,cuvier celebrated his triumph over the nature-philosophy1 and established his supremacy in the domain of morphology for the following thirty years4 ,whilst ,cuvier1 by his artificial hypothesis of creation and his theory of catastrophes connected with it1 directly obstructed the path of the theory of natural development1 and cut off all chance of a natural explanation1 ,lyell once more opened a free road1 and brought forward convincing geological evidence to show that ,cuvier's dualistic conceptions were as unfounded as they were superfluous4 ,he demonstrated that those changes of the earth's surface1 which are still taking place before our eyes1 are perfectly sufficient to explain everything we know of the development of the earth's crust in general1 and that it is superfluous and useless to seek for mysterious causes in inexplicable revolutions4 ,he showed that we need only have recourse to the hypothesis of exceedingly long periods of time in order to explain the formation of the crust of the earth in the simplest and most natural manner by means of the very same causes which are still active4 ,many geologists had previously imagined that the highest chains of mountains which rise on the surface of the earth could owe their origin only to enormous revolutions transforming a great part of the earth's surface1 especially to colossal volcanic eruptions4 ,such chains of mountains as those of the ,alps or the ,cordilleras were believed to have arisen direct from the fiery fluid of the interior of the earth1 through an enormous chasm in the broken crust4 ,lyell1 on the other hand1 showed that we can explain the formation of such enormous chains of mountains quite naturally by the same slow and imperceptible risings and depressions of the earth's surface which are still continually taking place1 and the causes of which are by no means miraculous4 ,although these depressions and risings may perhaps amount only to a few inches1 or at most a few feet1 in the course of a century2 still1 in the course of some millions of years they are perfectly sufficient to raise up the highest chains of mountains1 without the aid of mysterious and incomprehensible revolutions4 ,in like manner1 the meteorological action of the atmosphere1 the influence of rain and snow1 and1 lastly1 the breakers on the coasts1 which by themselves seem to produce an insignificant effect1 must cause the greatest changes if we only allow sufficiently long periods for their action4 ,the multiplication of the smallest causes produces the greatest effects4 ,drops of water produce a cavity in a rock4 ,i shall afterwards be obliged again to recur to the immeasurable length of geological periods which are necessary for this purpose1 for1 as we shall see1 ,darwin's theory1 as well as that of ,lyell1 renders the assumption of immense periods absolutely necessary4 ,if the earth and its organisms have actually developed in a natural way1 this slow and gradual development must certainly have taken a length of time which surpasses our powers of comprehension4 ,but as many men see in this very circumstance one of the principal difficulties in the way of those theories of development1 ,i beg leave here to remark that we have not a single rational ground for conceiving the time requisite to be limited in any way4 ,not only many ordinary persons1 but even eminent naturalists1 make it their chief objection to these theories1 that they arbitrarily claim too great a length of time3 yet the ground of objection is scarcely intelligible4 ,for it is absolutely impossible to see what can1 in any way1 limit us in assuming long periods of time4 ,we have long known1 even from the structure of the stratified crust of the earth alone1 that its origin and the formation of neptunic rocks from water must have taken1 at least1 several millions of years4 ,from a strictly philosophical point of view1 it makes no difference whether we hypothetically assume for this process ten millions or ten thousand billions of years4 ,before us and behind us lies eternity4 ,if the assumption of such enormous periods is opposed to the feelings of many1 ,i regard this simply as the consequence of false notions which are impressed upon us from our earliest youth concerning the short history of the earth1 which is said to embrace only a few thousands of years4 ,albert ,lange1 in his 8,history of ,materialism107#ab7 has convincingly shown that from a strictly philosophical point of view it is far less objectionable in a scientific hypothesis to assume periods which are too long than periods which are too short4 ,every process of development is the more intelligible the longer it is assumed to last4 ,a short and limited period is the most improbable4 ,i have no space here to enter minutely into ,lyell's great work1 and will therefore mention only its most important result1 which is1 that he completely refuted ,cuvier's history of creation with its mythical revolutions1 and established in its place the constant and slow transformation of the earth's crust by the continued action of forces1 which are still working on the earth's surface1 viz41 the movement of water and the volcanic fluid of the interior of earth4 ,lyell thus demonstrated a continuous and uninterrupted connection of the whole history of the earth1 and he proved it so irrefutably1 and established so convincingly the supremacy of the 8existing causes10 that is1 of the causes which are still active in the transformation of the earth's crust1 that ,geology in a short time completely renounced ,cuvier's hypothesis4 ,now1 it is remarkable that ,palontology1 the science of petrifactions1 so far as it was pursued by botanists and zoologists1 remained apparently unaffected by this great progress in geology4 ,biology still continued to assume repeated new creations of the whole animal and vegetable kingdoms1 at the beginning of every new period of the earth's history1 although this hypothesis of individual creations1 shoved into the world one after the other1 without the assumption of ,cuvier's cataclysms1 became pure nonsense1 and lost its foundation4 ,it is evidently perfectly absurd to assume a distinct new creation of the whole world of animals and plants at definite epochs1 without the crust of the earth itself experiencing any considerable general revolution4 ,and although this conception is most closely connected with ,cuvier's theory of catastrophes1 still it prevailed when the latter had been completely destroyed and abandoned4 ,it was reserved for the great ,english naturalist1 ,charles ,darwin1 to remove this contradiction1 and to show that the organic beings of the earth have a history as continuous and connected as the inorganic crust of the earth2 that animals and plants have arisen from one another by as gradual a transmutation as that by which the varying forms of the earth's crust1 the forms of the continents1 and of the seas surrounding and separating them1 have arisen out of earlier and quite different forms4 ,in this respect we may truly say that in the domain of ,zoology and ,botany ,darwin made the same progress as ,lyell1 his great countryman1 in the domain of ,geology4 ,both proved the uninterrupted connection of the historical development1 and demonstrated a gradual transmutation of the different conditions succeeding one another4 ,the special merit of ,darwin1 as ,i have already remarked in a preceding chapter1 is twofold4 ,in the first place1 he has treated the ,theory of ,descent1 put forth by ,lamarck and ,goethe1 in a much more comprehensive manner1 as a whole1 and carried it out in a much more connected manner1 than had been done by any one of his predecessors4 ,secondly1 he has established the causal foundation of this ,theory of ,descent by the ,theory of ,selection1 which is peculiarly his own2 that is1 he has demonstrated the acting causes of the changes which the ,theory of ,descent simply stated1 as facts4 ,the ,theory of ,descent1 introduced into ,biology in #ahji1 by ,lamarck1 asserts that all the different species of animals and plants are descended from a single or some few most simple prototypes1 produced by spontaneous generation4 ,the ,theory of ,selection1 established in #ahei by ,darwin1 shows us why this must be so2 it points out the acting causes in a manner with which ,kant would have been delighted1 and indeed1 in the domain of organic nature1 ,darwin has become the ,newton whose advent ,kant thought himself entitled prophetically to deny4 ,now1 before we approach ,darwin's theory1 it will perhaps be of interest to notice a few details as to the personal character of this great naturalist1 as to his life1 and the way in which he was led to form his doctrine4 ,charles ,robert ,darwin was born at ,shrewsbury1 on the ,severn1 on the #abth of ,february1 #ahji2 therefore1 at present he is sixty-three years old4 ,in his seventeenth year 7#ahbe7 he entered the ,university of ,edinburgh1 and two years later ,christ's ,college1 ,cambridge4 ,when scarcely twenty-two years old1 in #ahca1 he was invited to take part in a scientific expedition which was sent out by ,england1 in order to survey accurately the southernmost point of ,south ,america1 and to examine several parts of the ,south ,seas4 ,this expedition1 like many other voyages of inquiry fitted out in a praiseworthy manner by ,england1 had scientific objects1 and at the same time was intended to solve practical problems relating to navigation4 ,the vessel1 commanded by ,captain ,fitzroy1 appropriately bore the symbolic name of the ,beagle4 ,the voyage of the ,beagle1 which lasted five years1 was of the highest importance to the full development of ,darwin's genius2 for in the very first year1 when he set his foot on the soil of ,south ,america1 the outline of the doctrine of descent dawned upon him4 ,darwin himself has described this voyage in a work which is written in a very attractive style1 and the perusal of which ,i strongly recommend to the reader4 ,this book of travel1 which lies far above the usual average in interest1 not only shows in a very charming manner ,darwin's amiable character1 but we can in many ways recognize the various steps by which he arrived at his conceptions4 ,the result of the voyage was1 first1 a large scientific work1 the zoological and geological portion of which belong in a great measure to ,darwin2 and secondly1 a celebrated work by him alone on ,coral ,reefs1 which in itself would have sufficed to secure to him a lasting reputation4 ,it is well known that the islands in the ,south ,seas consist for the most part of coral reefs1 and are surrounded by them4 ,formerly no satisfactory explanation could be given of their different and remarkable forms1 and of their relation to those islands which are not formed of corals4 ,it was reserved for ,darwin to solve this difficult problem1 for together with the constructive action of the coral zoophytes1 he assumed geological risings and depressions of the bottom of the sea to account for the origin of the different forms of reefs4 ,darwin's ,theory of the ,origin of ,coral ,reefs1 like his later one as to the ,origin of ,organic ,species1 is a theory which fully explains the phenomenon1 and for this purpose assumes only the simplest natural causes1 without hypothetically supporting it with any unknown processes4 ,among the remaining works of ,darwin1 ,i must not pass over his excellent monograph on ,cirrhipedia1 a curious class of marine animals1 which in their outward appearance resemble mussels1 and were actually considered by ,cuvier as ,molluscs possessing two shells1 while in truth they belonged to the ,crustacea 7crabs74 ,the extraordinary hardships to which ,darwin had been exposed during his voyage in the ,beagle had injured his health to such a degree1 that after his return home he was obliged to withdraw from the restless turmoil of ,london life1 and since then has lived in quiet retirement on his estate at ,down1 near ,bromley1 in ,kent4 ,this seclusion from the restless activity of the great city certainly exercised a beneficial influence upon ,darwin1 and it is probable that we owe to it1 at least partially1 the formation of the ,theory of ,selection4 ,undisturbed by the various engagements which in ,london would have wasted his strength1 he was enabled to concentrate his attention upon the great problem to which his mind had been turned during his voyage in the ,beagle4 ,in order to show what kind of observations during the voyage principally gave rise to the fundamental idea of the ,theory of ,selection1 and in what manner he afterwards worked it out1 ,i shall insert here a passage from a letter which he addressed to me on the #hth of ,october1 #ahfd4 ,letter from ,charles ,darwin to ,haeckel1 #hth ,october1 #ahfd4 8,in ,south ,america three classes of facts were brought strongly before my mind4 ,firstly1 the manner in which closely allied species replace species in going southward4 ,secondly1 the close affinity of the species inhabiting the islands near ,south ,america to those proper to the continent4 ,this struck me profoundly1 especially the difference of the species in the adjoining islets in the ,galopagos ,archipelago4 ,thirdly1 the relation of the living ,edentata and ,rodentia to the extinct species4 ,i shall never forget my astonishment when ,i dug out a gigantic piece of armour like that of the living armadillo4 8,reflecting on these facts1 and collecting analogous ones1 it seemed to me probable that allied species were descended from a common parent4 ,but for some years ,i could not conceive how each form became so excellently adapted to its habits of life4 ,i then began systematically to study domestic productions1 and after a time saw clearly that man's selective power was the most important agent4 ,i was prepared1 from having studied the habits of animals1 to appreciate the struggle for existence1 and my work in geology gave me some idea of the lapse of past time4 ,therefore1 when ,i happened to read 8,malthus on ,population10 the idea of natural selection flashed on me4 ,of all the minor points1 the last which ,i appreciated was the importance and cause of the principle of divergence40 ,during the leisure and retirement in which ,darwin lived after his return1 he occupied himself1 as we see from this letter1 first and specially with the study of organisms in their cultivated state2 that is1 domestic animals and garden plants4 ,this was undoubtedly the most likely way to arrive at the ,theory of ,selection4 ,in this1 as in all his labours1 ,darwin proceeded with extreme care and accuracy4 ,with wonderful caution and self-denial1 he published nothing on this subject during a period of twenty-one years1 from #ahcg to #aheh1 not even a preliminary sketch of his theory1 which he had written as early as #ahdd4 ,he was always anxious to collect still more certain experimental proofs1 in order to be able to establish his theory in a complete form1 and on the broadest possible foundation of experience4 ,while he was thus aiming at the greatest possible perfection1 which might perhaps have led him never to publish his theory at all1 he was fortunately disturbed by a countryman of his1 who1 independently of ,darwin1 had discovered the ,theory of ,selection1 and in #aheh sent its outlines to ,darwin himself1 with the request to hand them to ,lyell for publication in some ,english journal4 ,this was ,alfred ,wallace1 one of the boldest and most distinguished scientific travellers of modern times4 ,for many years ,wallace had wandered alone in the wilds of the ,sunda ,islands1 in the dense primitive forests of the ,indian ,archipelago2 and during this close and comprehensive study of one of the richest and most interesting parts of the earth1 with its great variety of animals and plants1 he had arrived at exactly the same general views regarding the origin of organic species as ,darwin4 ,lyell and ,hooker1 both of whom had long known ,darwin's work1 now induced him to publish a short extract from his manuscripts simultaneously with the manuscript sent him by ,wallace4 ,they appeared in the ,journal of the ,linnean ,society1 ,august1 #aheh4 ,darwin's great work 8,on the ,origin of ,species10 in which the ,theory of ,selection is carried out in detail1 appeared in ,november1 #ahei4 ,darwin himself1 however1 characterizes this book 7of which a fifth edition appeared in #ahfi1 and the ,german translation by ,bronn as early as #ahfj77a7 as only a preliminary extract from a larger and more detailed work1 which is to contain a mass of facts in favour of his theory1 and comprehensive and experimental proofs4 ,the first part of the larger work promised by ,darwin appeared in #ahfh1 under the title1 8,the ,variations of ,animals and ,plants in the ,state of ,domestication10 and has been translated into ,german by ,victor ,carus47#ad7 ,it contains a rich abundance of the most valuable evidence as to the extraordinary changes of organic forms which man can produce by cultivation and artificial selection4 ,however much we are indebted to ,darwin for this abundance of convincing facts1 still we do not by any means share the opinion of those naturalists who hold that the ,theory of ,selection requires for its actual proof these further details4 ,it is our opinion that ,darwin's first work1 which appeared in #ahei1 already contains sufficient proof4 ,the unassailable strength of his theory does not lie in the immense amount of individual facts that may be adduced as proofs1 but in the harmonious connection of all the great and general phenomena of organic nature1 which agree in bearing testimony to the truth of the ,theory of ,selection4 ,darwin1 at first1 intentionally did not notice the important conclusion from his ,theory of ,descent1 namely1 the descent of the human race from other mammals4 ,it was not till this highly important conclusion had been definitely established by other naturalists as the necessary sequel of the doctrine of descent1 that ,darwin himself expressly endorsed it1 and thereby completed his system4 ,this was done in the highly interesting work1 8,the ,descent of ,man1 and ,sexual ,selection10 which appeared as late as #ahga1 and has likewise been translated into ,german by ,victor ,carus47#dh7 ,the careful study which ,darwin devoted to domestic animals and cultivated plants was of the greatest importance in establishing the ,theory of ,selection4 ,the infinitely varied changes of form which man has produced in these domesticated organisms by artificial selection are of the very highest importance for a right understanding of animal and vegetable forms2 and yet this study has1 down to the most recent times1 been most grossly neglected by zoologists and botanists4 ,without entering upon the discussion of the significance to be attached to the idea of species itself1 they have filled not only bulky volumes1 but whole libraries1 with descriptions of individual species1 and with most childish controversies as to whether these species are good1 or tolerably good1 and bad1 or tolerably bad4 ,if naturalists instead of spending their time on these useless fancies had duly studied cultivated organisms1 and had examined the transmutation of the living forms1 instead of the individual dead ones1 they would not have been led captive so long by the fetters of ,cuvier's dogma4 ,but as cultivated organisms are so extremely inconvenient to the dogmatic conception of the permanence of species1 naturalists to a great extent intentionally did not concern themselves about them1 and even celebrated naturalists have often expressed the opinion that cultivated organisms1 domesticated animals and garden plants1 are artificial productions of man1 and that their formation and transformation could not decide anything about the nature of species and about the origin of the forms of species that live in a natural state4 ,this perverse view went so far that1 for example1 ,andreas ,wagner1 a zoologist of ,munich1 quite seriously made the following ridiculous assertion3--8,animals and plants in their wild state have been called into being by the ,creator as distinctly different and unchangeable species2 but in the case of domestic animals and cultivated plants this was not necessary1 because he formed them from the beginning for the use of man4 ,the ,creator formed man out of a clod of earth1 breathed the living breath into his nostrils1 and then created for him the different useful domestic animals and garden plants1 among which he thought well to save himself the trouble of distinguishing species40 ,unfortunately1 ,andreas ,wagner does not tell us whether the ,tree of ,knowledge in ,paradise was a 8good0 wild species1 or1 as a cultivated plant1 8no species0 at all4 ,as the ,tree of ,knowledge was placed by the ,creator in the centre of ,paradise1 we might be inclined to believe that it was a highly favoured cultivated plant1 and therefore no species at all4 ,but since1 on the other hand1 the fruit of the ,tree of ,knowledge was forbidden to man1 and since many men1 as ,wagner himself clearly shows1 have never eaten of the fruit1 it was evidently not created for the use of man1 and therefore in all probability was a real species6 ,what a pity ,wagner has not given us any information about this important and difficult problem6 ,now1 however ridiculous this view may appear to us1 it is only the logical sequence of a false view 7which is widely spread7 of the special nature of cultivated organisms1 and one may occasionally hear similar objections from naturalists of great reputation4 ,i must most decidedly1 and at once1 condemn this utterly false conception4 ,it is the same perverseness which is committed by physicians who maintain that diseases are artificial productions1 and not natural phenomena4 ,it has been a work of hard labour to combat this prejudice1 and it is only in recent times that men have generally adopted the view that diseases are nothing but natural changes of the organisms1 or really natural phenomena of life1 which are produced by changed and abnormal conditions of existence4 ,disease1 therefore1 is not a life beyond ,nature's realm 7vita prter naturam71 as the early physicians used to say1 but a natural life under conditions which produce illness and threaten the body with danger4 ,just in the same manner1 cultivated organic forms are not artificial works of man1 but natural productions which have arisen under the influence of peculiar conditions of life4 ,man by his culture can never directly produce a new organic form1 but he can breed organisms under new conditions of life1 which are such as to influence and transform them4 ,all domestic animals and all garden plants are originally descended from wild species1 which have been transformed by the peculiar conditions of culture4 ,a thorough comparison of cultivated forms 7races and varieties7 with organisms not altered by cultivation 7species and varieties71 is of the utmost importance to the theory of selection4 ,what is most surprising in such a comparison is the remarkably short time in which man can produce a new form1 and the high degree in which this form1 produced by man1 can deviate from the original form4 ,while wild animals and plants1 one year after another1 appear to the zoologist and botanist approximately in the same form1 so as to have given rise to the false doctrine of the constancy of species1 domestic animals and garden plants1 on the other hand1 display the greatest changes within a few years4 ,the perfection which gardeners and farmers have attained in the art of selection now enables them1 in the space of a few years1 arbitrarily to create entirely new animal and vegetable forms4 ,for this purpose it is only necessary to keep and propagate the organism under the influence of special conditions--which are capable of producing new formations--and even at the end of a few generations new species may be obtained1 which differ from the original form in a much higher degree than so-called good species in a wild state differ from one another4 ,this fact is extremely important1 and we cannot lay sufficient stress upon it4 ,the assertion is not true that cultivated forms descended from one and the same primary form do not differ from one another as much as wild animal and vegetable species differ among themselves4 ,if we only make comparisons1 without prejudice1 we can very easily perceive that a number of races or varieties which have been derived from a single cultivated form1 within a short series of years1 differ from one another in a higher degree than so-called good species 7bon species71 or even different genera of one family1 in the wild state4 ,in order to establish this extremely important fact as firmly as possible by experiments1 ,darwin decided to make a special study of the whole extent of variation in form in a single group of domesticated animals1 and for this purpose he chose the domestic pigeons1 which are in many respects especially suited for such a study4 ,for a long time he kept on his estate all possible races and varieties of pigeons which he was able to procure1 and he was helped in this by rich contributions from all parts of the world4 ,he also joined two ,london pigeon clubs1 the members of which passionately1 and with truly artistic skill1 carry on the breeding of the different forms of pigeons4 ,lastly1 he formed connections with some of the most celebrated pigeon-fanciers2 so that he could command the richest experimental material4 ,the art of1 and fancy for1 pigeon breeding is very ancient4 ,even more than #c1jjj years before ,christ1 it was carried on by the ,egyptians4 ,the ,romans1 under the emperors1 laid out enormous sums upon the breeding of pigeons1 and kept accurate pedigrees of their descent1 just as the ,arabs keep genealogical pedigrees of their horses1 and the ,mecklenburg aristocracy of their own ancestors4 ,in ,asia1 too1 among the wealthy princes1 pigeon breeding was a very ancient fancy2 in #afjj1 the court of ,akber ,khan possessed more than #bj1jjj pigeons4 ,thus in the course of several centuries1 and in consequence of the various methods of breeding practised in the different parts of the world1 there has arisen out of one single originally tamed form1 an immense number of different races and varieties1 which in their most divergent forms are extremely different from one another1 and are often curiously characterized4 ,one of the most striking races of pigeons is the well-known fan-tailed pigeon1 which spreads its tail like the peacock1 and carries a number of 7from thirty to forty7 feathers placed in the form of radii1 while other pigeons possess much fewer tail feathers--generally twelve4 ,we may here mention that the number of feathers on the tails of birds is considered by naturalists of great value as a systematic distinction1 so that whole orders can thereby be distinguished4 ,for example1 singing birds1 almost without exception1 possess twelve tail feathers2 chirping birds 7,strisores7 ten1 etc4 ,several races of pigeons1 moreover1 are characterized by a tuft of neck feathers1 which form a kind of periwig2 others by grotesque transformation of their beaks and feet1 by peculiar and often very remarkable decorations1 as1 for example1 skinny lappets1 which develop on the head2 by a large crop1 which is formed by the gullet being strongly inclined forward1 etc4 ,remarkable1 also1 are the strange habits which many pigeons have acquired2 for example1 the turtle pigeons and the trumpeters with their musical accomplishments1 the carriers with their topographical instinct4 ,the tumblers have the strange habit of ascending into the air in great numbers1 then turning over and falling down through the air as if dead4 ,the ways and habits of these endless races of pigeons--the form1 size1 and colour of the individual parts of their bodies1 and their proportions1 differ in a most astonishing degree from one another2 in a much higher degree than is the case with the so-called good species1 or even with the perfectly distinct genera1 of wild pigeons4 ,and what is of the greatest importance1 is the fact that these differences are not confined to the external form1 but extend even to the most important internal parts2 there even occur great modifications of the skeleton and of the muscular tissues4 ,for example1 we find great differences in the number of vertebr and ribs1 in the size and shape of the gaps in the breast-bones1 in the size and shape of the merry-thought1 in the lower jaw1 in the facial bones1 etc4 ,in short1 the bony skeleton1 which morphologists consider a very permanent part of the body1 and which never varies to such an extent as the external parts--shows such great changes1 that many races of pigeons might be described as special genera1 and this would doubtless be done if all these different forms had been found in a wild and natural state4 ,how far the differences of the races of pigeons have been carried is best shown by the fact that all pigeon breeders are unanimously of opinion that each peculiar or specially marked race of pigeons must be derived from a corresponding wild original species4 ,it is true every one assumes a different number of original species4 ,yet ,darwin has most convincingly and acutely proved that all these pigeons1 without exception1 must be derived from a single wild primary species--from the blue rock-pigeon 7,columba livia74 ,in like manner1 it can be proved of most of the domestic animals and cultivated plants1 that all the different races are descendants of a single original wild species which has been brought by man into a cultivated condition4 ,an example similar to that of the domestic pigeons is furnished among mammals by our tame rabbit4 ,all zoologists1 without exception1 have long considered it proved that all its races and varieties are descended from the common wild rabbit1 that is1 from a single primary species4 ,and yet the extreme forms of these races differ to such a degree from one another1 that every zoologist1 if he met with them in a wild state1 would unhesitatingly designate them not only as an entirely distinct 8good species10 but even as species of entirely different genera of the ,leporid family4 ,not only does the colour1 length of hair1 and other qualities of the fur of the different tame races of rabbits vary exceedingly1 and form extremely broad contrasts1 but1 what is still more important1 the typical form of the skeleton and its individual parts do so also1 especially the form of the skull and the jaw 7which is of such importance in systematic arrangement72 further1 the relative proportion of the length of the ears1 legs1 etc4 ,in all these respects the races of tame rabbits avowedly differ from one another far more than all the different forms of wild rabbits and hares which are scattered over all the earth1 and are the recognized 8good species0 of the genus ,lepus4 ,and yet1 in the face of these clear facts1 the opponents of the theory of development maintain that the wild species are not descended from a common prototype1 although they at once admit it in the case of the tame races4 ,with opponents who so intentionally close their eyes against the clear light of truth1 no further dispute can be carried on4 ,while in this manner it appears certain that the domestic races of pigeons1 of tame rabbits1 of horses1 etc41 notwithstanding the remarkable difference of their varieties1 are descended in each case from but one wild1 so-called 8species02 yet1 on the other hand1 it is certainly probable that the great variety of races of some of the domestic animals1 especially dogs1 pigs1 and oxen1 must be ascribed to the existence of several wild prototypes1 which have become mixed4 ,it is1 however1 to be observed that the number of these originally wild primary species is always much smaller than that of the cultivated forms proceeding from their mingling and selection1 and naturally they were originally derived from a single primary ancestor1 common to the whole genus4 ,in no case is each separate cultivated race descended from a distinct wild species4 ,in opposition to this1 almost all farmers and gardeners maintain1 with the greatest confidence1 that each separate race bred by them must be descended from a separate wild primary species1 because they clearly perceive the differences of the races1 and attach very high importance to the inheritance of their qualities2 but they do not take into consideration the fact that these qualities have arisen only by the slow accumulation of small and scarcely observable changes4 ,in this respect it is extremely instructive to compare cultivated races with wild species4 ,many naturalists1 and especially the opponents of the ,theory of ,development1 have taken the greatest trouble to discover some morphological or physiological mark1 some characteristic property1 whereby the artificially bred and cultivated races may be clearly and thoroughly distinguished from wild species which have arisen naturally4 ,all these attempts have completely failed1 and have led only with increasing certainty to the result1 that such a distinction is altogether impossible4 ,i have minutely discussed this fact1 and illustrated it by examples in my criticism of the idea of species4 7,gen4 ,morph4 ii4 #cbc-cfd47 ,i may here briefly touch on yet another side of this question1 because not only the opponents1 but even a few of the most distinguished followers of ,darwin--for example1 ,huxley--have regarded the phenomena of bastard-breeding1 or hybridism1 as one of the weakest points of ,darwinism4 ,between cultivated races and wild species1 they say1 there exists this difference1 that the former are capable of producing fruitful bastards1 but that the latter are not4 ,two different cultivated races1 or wild varieties of one species1 are said in all cases to possess the power of producing bastards which can fruitfully mix with one another1 or with one of their parent forms1 and thus propagate themselves2 on the other hand1 two really different species1 two cultivated or wild species of one genus1 are said never to be able to produce from one another bastards which can be fruitfully crossed with one another1 or with one of their parent species4 ,as regards the first of these assertions1 it is simply refuted by the fact that there are organisms which do not mix at all with their own ancestors1 and therefore can produce no fruitful descendants4 ,thus1 for example1 our cultivated guinea-pig does not bear with its wild ,brazilian ancestor2 and again1 the domestic cat of ,paraguay1 which is descended from our ,european domestic cat1 no longer bears with the latter4 ,between different races of our domestic dogs1 for example1 between the large ,newfoundland dogs and the dwarfed lap-dogs1 breeding is impossible1 even for simple mechanical reasons4 ,a particularly interesting instance is afforded by the ,porto-,santo rabbit 7,lepus ,huxleyi74 ,in the year #adai1 a few rabbits1 born on board ship of a tame ,spanish rabbit1 were put on the island of ,porto ,santo1 near ,madeira4 ,these little animals1 there being no beasts of prey1 in a short time increased so enormously that they became a pest to the country1 and even compelled a colony to remove from the island4 ,they still inhabit the island in great numbers2 but in the course of four hundred and fifty years they have developed into a quite peculiar variety--or if you will have it1 into a 8good species0--which is distinguished by a peculiar colour1 a rat-like shape1 small size1 nocturnal life1 and extraordinary wildness4 ,the most important fact1 however1 is that this new species1 which ,i call ,lepus ,huxleyi1 no longer pairs with its ,european parent rabbit1 and no longer produces bastards with it4 ,on the other hand1 we now know of numerous examples of fruitful genuine bastards2 that is1 of mixings that have proceeded from the crossing of two entirely different species1 and yet propagate themselves with one another as well as with one of their parent species4 ,a number of such bastard species 7species ,hybrid7 have long been known to botanists2 for example1 among the genera of the thistle 7,cirsium71 the laburnum 7,cytisus71 the bramble 7,rubus71 etc4 ,among animals also they are by no means rare1 perhaps even very frequent4 ,we know of fruitful bastards which have arisen from the crossing of two different species of a genus1 as among several genera of butterflies 7,zygna1 ,saturnia71 the family of carps1 finches1 poultry1 dogs1 cats1 etc4 ,one of the most interesting is the hare-rabbit 7,lepus ,darwinii71 the bastard of our indigenous hare and rabbit1 many generations of which have been bred in ,france1 since #ahej1 for gastronomic purposes4 ,i myself possess such hybrids1 the products of pure in-breeding1 that is1 both parents of which are themselves hybrids by a hare-father and a rabbit-mother4 ,i possess them through the kindness of ,professor ,conrad1 who has repeatedly made these experiments in breeding on his estate4 ,the half-blood hybrid thus bred1 which ,i name in honour of ,darwin1 appears to propagate itself through many generations by pure in-breeding1 just as well as any genuine species4 ,although on the whole it is more like its mother 7rabbit71 still in the formation of the ears and of the hind-legs1 it possesses distinct qualities of its father 7hare74 ,its flesh has an excellent taste1 rather resembling that of a hare1 though the colour is more like that of a rabbit4 ,but the hare 7,lepus timidus7 and the rabbit 7,lepus cuniculus7 are two species of the genus ,lepus1 so different that no systematic zoologist will recognize them as varieties of one species4 ,both species1 moreover1 live in such different ways1 and in their wild state entertain so great an aversion towards one another1 that they do not pair so long as they are left free4 ,if1 however1 the newly-born young ones of both species are brought up together1 this aversion is not developed2 they pair with one another and produce the ,lepus ,darwinii4 ,another remarkable instance of the crossing of different species 7where the two species belong even to different genera67 is furnished by the fruitful hybrids of sheep and goats which have for a long time been bred in ,chili for industrial purposes4 ,on what unessential circumstances in the sexual mingling the fertility of the different species depend1 is shown by the fact that he-goats and sheep in their mingling produce fruitful hybrids1 while the ram and she-goat pair very rarely1 and then without result4 ,the phenomena of hybridism to which undue importance has been erroneously attributed are thus utterly unmeaning1 so far as the idea of species is concerned4 ,the breeding of hybrids does not enable us1 any more than other phenomena1 thoroughly to distinguish cultivated races from wild species2 and this circumstance is of the greatest importance in the ,theory of ,selection4 ,,chapter ,,vii4 ,,the ,,theory ,,of ,,selection 7,,darwinism74 ,darwinism 7,theory of ,selection7 and ,lamarckism 7,theory of ,descent74--,the ,process of ,artificial ,breeding4--,selection of the ,different ,individuals for ,after-breeding4--,the ,active ,causes of ,transmutation4--,change connected with ,food1 and ,transmission by ,inheritance connected with ,propagation4--,mechanical ,nature of these ,two ,physiological ,functions4--,the ,process of ,natural ,breeding3 ,selection in the ,struggle for ,existence4--,malthus' ,theory of ,population4--,the ,proportion between the ,numbers of ,potential and ,actual ,individuals of every ,species of ,organisms4--,general ,struggle for ,existence1 or ,competition to attain the ,necessaries of ,life4--,transforming ,force of the ,struggle for ,existence4--,comparison of ,natural and ,artificial ,breeding4--,selection in the ,life of ,man4--,military and ,medical ,selection4 ,it is1 properly speaking1 not quite correctly that the ,theory of ,development1 with which we are occupied in these pages1 is usually called ,darwinism4 ,for1 as we have seen from the historical sketch in the previous chapters1 the most important foundation of the ,theory of ,development--that is1 the ,doctrine of ,filiation1 or ,descent--had already been distinctly enunciated at the beginning of our century1 and had been definitely introduced into science by ,lamarck4 ,the portion of the ,theory of ,development which maintains the common descent of all species of animals and plants from the simplest common original forms might1 therefore1 in honour of its eminent founder1 and with full justice1 be called ,lamarckism1 if the merit of having carried out such a principle is to be linked to the name of a single distinguished naturalist4 ,on the other hand1 the ,theory of ,selection1 or breeding1 might be justly called ,darwinism1 being that portion of the ,theory of ,development which shows us in what way and why the different species of organisms have developed from those simplest primary forms4 7,gen4 ,morph4 ii4 #aff47 ,it is true we find the first trace of an idea of natural selection even forty years before the appearance of ,darwin's work4 ,for in the year #ahah there was published a paper 8,on a woman of the white race whose skin partly resembled that of a negro10 which had been read before the ,royal ,society as early as #ahac4 ,its author1 ,dr4 ,w4 ,c4 ,wells1 states that negroes and mulattoes are distinguished from the white race by their immunity from certain tropical diseases4 ,on this occasion he remarks that all animals have a tendency to change up to a certain degree1 and that farmers1 by availing themselves of this tendency1 and also by selection1 improve their domestic animals2 and then he adds1 that what is done in this latter case 8by art1 seems to be done with equal efficiency1 though more slowly1 by nature1 in the formation of varieties of mankind fitted for the country which they inhabit4 ,of the accidental varieties of man which would occur among the first few and scattered inhabitants of the middle regions of ,africa1 some one would be better fitted than the others to bear the diseases of the country4 ,this race would consequently multiply1 while the others would decrease2 not only from their inability to sustain the attacks of disease1 but from their incapacity of contending with their more vigorous neighbours4 ,the colour of this vigorous race ,i take for granted1 from what has been already said1 would be dark4 ,but the same disposition to form varieties still existing1 a darker and a darker race would in the course of time occur2 and as the darkest would be the best fitted for the climate1 this would at length become the most prevalent1 if not the only race1 in the particular country in which it had originated40 ,he then extends these same views to the white inhabitants of colder climates4 ,although ,wells clearly expresses and recognizes the principle of natural selection1 yet it is applied by him only to the very limited problem of the origin of human races1 and not at all to that of the origin of animal and vegetable species4 ,darwin's great merit in having independently developed the ,theory of ,selection1 and having brought it to complete and well merited recognition1 is as little affected by the earlier and long forgotten remark of ,wells1 as by some other fragmentary observations about natural selection made by ,patrick ,mathew1 and hidden in his book on 8,timber for ,shipbuilding1 and the ,cultivation of ,trees10 which appeared in #ahca4 ,the celebrated traveller1 ,alfred ,wallace1 who developed the ,theory of ,selection independently of ,darwin1 and had published it in #aheh1 simultaneously with ,darwin's first contribution1 likewise stands far behind his greater and elder countryman in regard to profound conception1 as well as to extended application of the theory4 ,in fact ,darwin1 by his extremely comprehensive and ingenious development of the whole doctrine1 has acquired a fair claim to see the theory connected with his own name4 ,this ,theory of ,selection1 ,darwinism in its proper sense1 to the consideration of which we now turn our attention1 rests essentially 7as has already been intimated in the last chapter7 upon the comparison of those means which man employs in the breeding of domestic animals and the cultivation of garden plants1 with those processes which in free nature1 outside the cultivated state1 lead to the coming into existence of new species and new genera4 ,we must therefore1 in order to understand the latter processes1 first turn to the artificial breeding by man1 as was1 in fact1 done by ,darwin himself4 ,we must inquire into the results to which man attains by his artificial breeding1 and what means are applied in order to obtain those results2 and we must then ask ourselves1 8,are there in nature similar forces and causes acting similarly to those resorted to by man80 ,first1 in regard to artificial breeding1 we start from the fact last discussed above1 viz41 that its products in some cases differ from one another much more than the productions of natural breeding4 ,it is a fact that races or varieties often differ from one another in a much greater degree and in much more important qualities than many so-called species1 or 8good species10--nay1 sometimes even more than so-called 8good genera0 in their natural state4 ,compare1 for example1 the different kinds of apples which the art of horticulture has derived from one and the same original apple-form1 or compare the different races of horses which their breeders have derived from one and the same original form of horse1 and it will be easily observed that the differences of the most different forms are extremely important1 and much more important than the so-called 8specific differences10 which are referred to by zoologists and botanists when comparing wild forms for the purpose of distinguishing several so-called 8good species40 ,now1 by what means does man produce this extraordinary difference or divergence of several forms which are proved to be descended from the same primary form8 ,in order to answer this question1 let us follow a gardener who desires to produce a new form of a plant1 which is distinguished by the beautiful colour of its flowers4 ,he will first of all make a selection from a great number of plants which are seedlings from one and the same parent4 ,he will pick out those plants which exhibit most distinctly the colour of flower he desires4 ,the colour of flowers is a very changeable thing4 ,plants1 for example1 which as a rule have a white flower1 frequently show deviations into the blue or red4 ,now1 supposing the gardener wishes to obtain the red colour in a plant usually producing white flowers1 he will very carefully1 from among the many different individuals which are the descendants of one and the same seed-plant1 select those which most distinctly show a reddish tint1 and sow them exclusively1 in order to produce new individuals of the same kind4 ,he would cast aside and no longer cultivate the other seedlings which show a white or less distinct red colour4 ,he will propagate exclusively the individual plants whose blossoms show the red most markedly1 and he will sow the seeds produced by these selected plants4 ,from the seedlings of this second generation1 he will again carefully select those in which the red1 which is now visible in the majority of them1 is most distinctly displayed4 ,if such a selection is carried on during a series of six or ten generations1 and if the flower which shows the deepest red is most carefully selected1 the gardener in the sixth or tenth generation will obtain the desired plants with flowers of a pure red4 ,the farmer wishing to breed a special race of animals1 for example1 a kind of sheep distinguished by particularly fine wool1 proceeds in the same manner4 ,the only process applied in the improvement of wool consists in this1 that the farmer with the greatest care and perseverance selects from a whole flock of sheep those individuals which have the finest wool4 ,these only are used in breeding1 and among the descendants of these selected sheep1 those again are chosen which have the finest wool1 etc4 ,if this careful selection is carried on through a series of generations1 the selected breeding-sheep are in the end distinguished by a wool which differs very strikingly from the wool of the original parent1 and this is exactly the advantage which the breeder desired4 ,the differences of the individuals that come into consideration in this artificial selection are very slight4 ,an ordinary unpractised man is unable to discover the exceedingly minute differences of individuals which a practised breeder perceives at the first glance4 ,the business of a breeder is not easy2 it requires an exceedingly sharp eye1 great patience1 and an extremely careful manner of treating the organisms to be bred4 ,in each individual generation1 the differences of individuals are perhaps not seen at all by the uninitiated2 but by the accumulation of these minute differences during a series of generations1 the deviation from the original form becomes in the end very great4 ,it becomes so great that the artificially produced form may in the end differ far more from the original form than do two so-called 8good species0 in their natural state4 ,the art of breeding has now made such progress1 that man can often at discretion produce certain peculiarities in cultivated species of animals and plants4 ,to practised gardeners and farmers1 you may give distinct commissions1 and say1 for example1 ,i wish to have this species of plant with this or that colour1 and with this or that shape4 ,where breeding has reached the perfection which it has attained in ,england1 gardeners and farmers are frequently able to furnish to order the desired result within a definite period1 that is1 at the end of a number of generations4 ,sir ,john ,sebright1 one of the most experienced ,english pigeon-breeders1 could assert that in three years he would produce any form of feather1 but that he required six years to obtain any desired form of the head and beak4 ,in the process of breeding the merino-sheep of ,saxony1 the animals are three times placed on a table beside one another1 and most carefully compared and studied4 ,each time only the best sheep with the finest wool are selected1 so that in the end1 out of a great multitude1 there remain only some few animals1 but their wool is exquisitely fine1 and only these last are used in breeding4 ,we see1 therefore1 that the causes through which1 in artificial breeding1 great effects are produced1 are unusually simple1 and these great effects are obtained simply by accumulating the differences which in themselves are very insignificant1 and become surprisingly increased by a continually repeated selection4 ,before we pass on to a comparison of this artificial with natural breeding1 let us see what natural qualities of the organisms are made use of by the artificial breeder or cultivator4 ,we can trace all the different qualities which here come into play to physiological fundamental qualities of the organism1 which are common to all animals and plants1 and are most closely connected with the functions of propagation and nutrition4 ,these two fundamental qualities are transmissivity1 or the capability of transmitting by inheritance1 and mutability1 or the capability of adaptation4 ,the breeder starts from the fact that all the individuals of one and the same species are different1 though in a very slight degree1 a fact which is as true of organisms in a wild as in a cultivated state4 ,if you look about you in a forest consisting of only a single species of tree1 for example of beech1 you will certainly not find in the whole forest two trees of this kind which are absolutely identical or perfectly equal in the form of their branches1 the number of their branches and leaves1 blossoms and fruits4 ,special differences occur everywhere1 just as in the case of men4 ,there are no two men who are absolutely identical1 perfectly equal in size1 in the formation of their faces1 the number of their hairs1 their temperament1 character1 etc4 ,the very same is true of individuals of all the different species of animals and plants4 ,it is true that in most organisms the differences are very trifling to the eye of the uninitiated4 ,everything here essentially depends on the exercise of the faculty of discovering these often very minute differences of form4 ,the shepherd1 for example1 knows every individual of his flock1 solely by accurately observing their features1 while the uninitiated are incapable of distinguishing at all the different individuals of one and the same flock4 ,this fact of the individual difference is the extremely important foundation on which the whole of man's power of breeding rests4 ,if individual differences did not exist everywhere1 man would not be able to produce a number of different varieties or races from one and the same original stock4 ,we must1 at the outset1 hold fast the principle that the phenomenon is quite universal2 we must necessarily assume it even where1 with the imperfect capabilities of our senses1 we are unable to discover differences4 ,among the higher plants 7the phanerogams1 or flower-plants71 where the individual stocks show such numerous differences in the number of branches or leaves1 and in the formation of the stem and branches1 we can almost always easily perceive these differences4 ,but this is not the case in the lower plants1 such as mosses1 alg1 fungi1 and in most animals1 especially the lower ones4 ,the distinction of all the individuals of one species is here1 for the most part1 extremely difficult or altogether impossible4 ,but there is no reason for ascribing individual differences only to those organisms in which we can perceive them at once4 ,we may1 on the contrary1 with full certainty assume such individuality as a universal quality of all organisms1 and we can do this all the more surely since we are able to trace the mutability of individuals to the mechanical conditions of nutrition4 ,we can show that by influencing nutrition we are able to produce striking individual differences where they would not exist if the conditions of nutrition had not been altered4 ,the many complicated conditions of nutrition are never absolutely identical in two individuals of a species4 ,now1 just as we see that the mutability or capability of adaptation has a causal connection with the general relations of nutrition in animals and plants1 so too we find the second fundamental phenomenon of life1 with which we are here concerned1 namely1 the capability of transmitting by inheritance1 to have a direct connection with the phenomenon of propagation4 ,the second thing that a farmer or gardener does in artificial breeding1 after he has selected1 and has consequently availed himself of the mutability1 is to endeavour to hold fast and develop the modified forms by ,inheritance4 ,he starts from the universal fact that children resemble their parents1 that 8the apple does not fall far from the tree40 ,this phenomenon of ,inheritance has hitherto been scientifically examined only to a very small extent1 which may partly arise from the fact that the phenomenon is of such everyday occurrence4 ,every one considers it quite natural that every species should produce its like2 that a horse should not suddenly produce a goose1 or a goose a frog4 ,we are accustomed to look upon these everyday occurrences of ,inheritance as self-evident4 ,but this phenomenon is not so simply self-evident as it appears at first sight1 and in the examination of ,inheritance the fact is very frequently overlooked that the different descendants1 derived from one and the same parents1 are in reality never quite identical1 and also never absolutely like the parents1 but are always slightly different4 ,we cannot formulate the principle of ,inheritance1 as 8,like produces like10 but we must limit the expression to 8,similar things produce similar things40 ,the gardener1 as well as the farmer1 avails himself of the fact of ,inheritance in its widest form1 and indeed with special regard to the fact that not only those qualities of organisms are transmitted by inheritance which they have inherited from their parents but those also which they themselves have acquired4 ,this is an important point upon which very much depends4 ,an organism can transmit to its descendants not only those qualities of form1 colour1 and size which it has inherited from its parents1 but it can also transmit changes of these qualities1 which it has acquired during its own life through the influence of outward circumstances1 such as climate1 nourishment1 training1 etc4 ,these are the two fundamental qualities of animals and plants of which the breeder must avail himself in order to produce new forms4 ,the theoretical principle of breeding is1 indeed1 extremely simple1 but in detail the practical application of this simple principle is difficult and immensely complicated4 ,a thoughtful breeder1 acting according to a definite plan1 must understand the art of correctly estimating1 in every case1 the general interaction between the two fundamental qualities of heirship and mutability4 ,now1 if we examine the real nature of those two important properties of life1 we find that we can trace them1 like all physiological functions1 to physical and chemical causes1 to the properties and the phenomena of motion of those substances of which the bodies of animals and plants consist4 ,as we shall hereafter have to show in the more accurate consideration of these two functions1 the transmission by ,inheritance1 if we express ourselves quite generally1 is essentially dependent upon the material continuity and partial identity of the matter in the producing and produced organism1 the parents and the child4 ,in every act of breeding a certain quantity of protoplasm or albuminous matter is transferred from the parents to the child1 and along with it there is transferred the individually peculiar molecular motion4 ,these molecular phenomena of motion in the protoplasm1 which call forth the phenomena of life1 and are their active and true cause1 differ more or less in all living individuals2 they are of infinite variety4 ,adaptation1 or transmutation is1 on the other hand1 essentially the consequence of material influences1 which the substance of the organism experiences from the material surrounding it1--in the widest sense of the word from the conditions of life4 ,the external influences of the latter are communicated to the individual parts of the body by the molecular processes of nutrition4 ,in every act of ,adaptation the individual molecular motion of the protoplasm1 peculiar to each part1 disturbs and modifies the whole individual1 or part of it1 by mechanical1 physical1 or chemical influences4 ,the innate1 inherited vital actions of the protoplasm--that is1 the molecular phenomena of motion of the smallest albuminous particles--are therefore more or less modified by it4 ,the phenomenon of ,adaptation1 or transmutation1 depends therefore upon the material influence which the organism experiences from its surroundings1 or its conditions of existence2 while the transmission by ,inheritance is due to the partial identity of the producing and produced organism4 ,these are the real1 simple1 mechanical foundations of the artificial process of breeding4 ,now ,darwin asked himself1 ,does there exist a similar process of selection in nature1 and are there forces in nature which take the place of man's activity in artificial selection8 ,is there a natural tendency among wild animals and plants which acts selectingly1 in a similar manner to the artificial selection practised by the designing will of man8 ,all here depended upon the discovery of such a relation1 and ,darwin succeeded in this so satisfactorily1 that we consider his theory of selection completely sufficient to explain1 mechanically1 the origin of the wild species of animals and plants4 ,that relation which in free nature influences the forms of animals and plants1 by selecting and transforming them1 is called by ,darwin the 8,struggle for ,existence40 ,the 8,struggle for ,existence0 has rapidly become a watchword of the day4 ,yet this designation is1 perhaps1 in many respects not very happily chosen1 and the phenomena might probably have been more accurately described as 8,competition for the ,means of ,subsistence40 ,for under the name of 8,struggle for ,life10 many relations are comprehended which properly and strictly speaking do not belong to it4 ,as we have seen from the letter inserted in the last chapter1 ,darwin arrived at the idea of the 8,struggle for ,existence0 from the study of ,malthus' book 8,on the ,conditions and the ,consequences of the ,increase of ,population40 ,it was proved in that important work1 that the number of human beings1 on the average1 increases in a geometrical progression1 while the amount of articles of food increase only in an arithmetical progression4 ,this disproportion gives rise to a number of inconveniences in the human community1 which cause among men a continual competition to obtain the necessary means of life1 which do not suffice for all4 ,darwin's theory of the struggle for life is1 to a certain extent1 a general application of ,malthus' theory of population to the whole of organic nature4 ,it starts from the consideration that the number of possible organic individuals which might arise from the germs produced1 is far greater than the number of actual individuals which1 in fact1 do simultaneously live on the earth's surface4 ,the number of possible or potential individuals is given us by the number of the eggs and organic germs produced by organisms4 ,the number of these germs1 from each of which1 under favourable circumstances1 an individual might arise1 is very much larger than the number of real or actual individuals--that is1 of those that really arise from these germs1 come into life1 and propagate themselves4 ,by far the greater number of germs perish in the earliest stage of life1 and it is only some favoured organisms which manage to develop1 and actually survive the first period of early youth1 and finally succeed in propagating themselves4 ,this important fact is easily proved by a comparison of the number of eggs in a given species with the number of individuals which exist of this species4 ,these numerical relations show the most striking contrast4 ,there are1 for example1 species of fowls which lay great numbers of eggs1 and yet are among the rarest of birds2 and the bird which is said to be the commonest 7the most widely spread7 of all1 the stormy petrel 7,procellaria glacialis71 lays only a single egg4 ,the relation is the same in other animals4 ,there are many very rare invertebrate animals1 which lay immense quantities of eggs2 and others again which produce only very few eggs1 and yet are among the commonest of animals4 ,take1 for example1 the proportion which is observed among the human tape-worms4 ,each tape-worm produces within a short period millions of eggs1 while man1 in whom these tape-worms are lodged1 forms a far smaller number of eggs1 and yet fortunately there are fewer tape-worms than human beings4 ,in like manner1 among plants there are many splendid orchids1 which produce thousands of seeds and yet are very rare1 and some kinds of asters 7,composit71 which have but few seeds1 are exceedingly common4 ,this important fact might be illustrated by an immense number of examples4 ,it is evidently1 therefore1 not the number of actually existing germs which indicates the number of individuals which afterwards come into life and maintain themselves in life2 but rather the case is this1 that the number of adult individuals is limited by other circumstances1 especially by the relations in which the organism stands to its organic and inorganic surroundings4 ,every organism1 from the commencement of its existence1 struggles with a number of hostile influences3 it struggles against animals which feed on it1 and to which it is the natural food1 against animals of prey and parasites2 it struggles against inorganic influences of the most varied kinds1 against temperature1 weather1 and other circumstances2 but it also struggles 7and this is much the most important671 above all1 against organisms most like and akin to itself4 ,every individual1 of every animal and vegetable species1 is engaged in the fiercest competition with every other individual of the same species which lives in the same place with it4 ,in the economy of nature the means of subsistence are nowhere scattered in abundance1 but are very limited1 and far from sufficient for the number of organisms which might develop from the germs produced4 ,therefore the young individuals of most species of animals and vegetables must have hard work in obtaining the means of subsistence2 this necessarily causes a competition among them in order to obtain the indispensable supplies of life4 ,this great competition for the necessaries of life goes on everywhere and at all times1 among human beings and animals as well as among plants2 in the case of the latter this circumstance1 at first sight1 is not so clearly apparent4 ,if we examine a field which is richly sown with wheat1 we can see that of the numerous young plants 7perhaps some thousands7 which shoot up on a limited space1 only a very small proportion preserve themselves in life4 ,a competition takes place for the space of ground which each plant requires for fixing its root1 a competition for sunlight and moisture4 ,and in the same manner we find that1 among all animal species1 all the individuals of one and the same species compete with one another to obtain these indispensable means of life1 or the conditions of existence in the wide sense of the word4 ,they are equally indispensable to all1 but really fall to the lot of only a few--8,many are called1 but few are chosen40 ,the fact of the great competition is quite universal4 ,you need only to cast a glance at human society1 where this competition exists everywhere1 and in all the different branches of human activity4 ,here1 too1 a struggle is brought about by the free competition of the different labourers of one and the same class4 ,here too1 as everywhere1 this competition benefits the thing1 or the work1 which is the object of competition4 ,the greater and more general the competition1 the more quickly improvements and inventions are made in the branch of labour1 and the higher is the grade of perfection of the labourers themselves4 ,the position of the different individuals in this struggle for life is evidently very unequal4 ,starting from the inequality of individuals1 which is a recognized fact1 we must in all cases necessarily suppose that all the individuals of one and the same species do not have equally favourable prospects4 ,even at the beginning they are differently placed in this competition by their different strengths and abilities1 independently of the fact that the conditions of existence are different1 and act differently at every point of the earth's surface4 ,we evidently have an infinite combination of influences1 which1 together with the original inequality of the individuals during the competition for the conditions of existence1 favour some individuals and prejudice others4 ,the favoured individuals will gain the victory over the others1 and while the latter perish more or less early1 without leaving any descendants1 the former alone will be able to survive and finally to propagate the species4 ,as1 therefore1 it is clear that in the struggle for life the favoured individuals succeed in propagating themselves1 we shall 7even as the result of this relation7 perceive in the next generation differences from the preceding one4 ,some individuals of this second generation1 though perhaps not all of them1 will1 by inheritance1 receive the individual advantage by which their parents gained the victory over their rivals4 ,but now--and this is a very important law of inheritance--if such a transmission of a favourable character is continued through a series of generations1 it is not simply transmitted in the original manner1 but it is constantly increased and strengthened1 and in a last generation it attains a strength which distinguishes this generation very essentially from the original parent4 ,let us1 for example1 examine a number of plants of one and the same species which grow together in a very dry soil4 ,as the hairs on the leaves of plants are very useful for receiving moisture from the air1 and as the hairs on the leaves are very changeable1 the individuals possessing the thickest hair on their leaves will have an advantage in this unfavourable locality where the plants have directly to struggle with the want of water1 and in addition to this have to compete with one another for the possession of what little water there may be4 ,these alone hold out1 while the others possessing less hairy leaves perish2 the more hairy ones will be propagated1 and their descendants will1 on the average1 be more distinguished by their thick and strong hairs than the individuals of the first generation4 ,if this process is continued for several generations in one and the same locality1 there will arise at last such an increase of this characteristic1 such an increase of the hairs on the surface of the leaf1 that an entirely new species seems to present itself4 ,it must here be observed1 that in consequence of the interactions of all the parts of every organism1 generally one individual part cannot be changed without at the same time producing changes in other parts4 ,if1 for instance1 in our imaginary example1 the number of the hairs on the leaves is greatly increased1 a certain amount of nourishment is thereby withdrawn from other parts2 the material which might be employed to form flowers or seeds is diminished1 and a smaller size of the flower or seed will then be the direct or indirect consequence of the struggle for life1 which in the first place only produced a change in the leaves4 ,thus the struggle for life1 in this instance1 acts as a means of selecting and transforming4 ,the struggle of the different individuals to obtain the necessary conditions of existence1 or1 taking it in its widest sense1 the inter-relations of organisms to the whole of their surroundings1 produce mutations of form such as are produced in the cultivated state by the action of man's selection4 ,this agency will perhaps appear at first sight small and insignificant1 and the reader will not be inclined to concede to the action of such relations the weight which it in reality possesses4 ,i must therefore find space in a subsequent chapter to put forward further examples of the immense and far-reaching power of transformation exhibited in natural selection4 ,for the present ,i will confine myself to simply placing side by side the two processes of artificial and natural selection1 and clearly explaining the agreement and the differences of the two4 ,both natural and artificial selection are quite simple natural1 mechanical relations of life1 which depend upon the interaction of two physiological functions1 namely1 on ,adaptation and ,inheritance1 functions which1 as such1 must again be traced to physical and chemical properties of organic matter4 ,the difference between the two forms of selection consists in this3 in artificial selection the will of man makes the selection according to a plan1 whereas in natural selection1 the struggle for life 7that universal inter-relation of organisms7 acts without a plan1 but otherwise produces quite the same result1 namely1 a selection of a particular kind of individuals for propagation4 ,the alterations produced by artificial selection are turned to the advantage of those who make the selection2 in natural selection1 on the other hand1 to the advantage of the selected organism4 ,these are the most essential differences and agreements of the two modes of selection2 it must1 however1 be further observed that there is another difference1 viz41 in the duration of time required for the two processes of selection4 ,man in his artificial selection can produce very important changes in a very short time1 while in natural selection similar results are obtained only after a much longer time4 ,this arises from the fact that man can make his selection with much greater care4 ,man is able with the greatest nicety to pick out individuals from a large number1 drop the others1 and to employ only the privileged beings for propagation1 which is not the case in natural selection4 ,in natural conditions1 besides the privileged individuals which first succeed in propagating themselves1 some few or many of the less distinguished individuals will propagate themselves by the side of the former4 ,moreover1 man can prevent the crossing of the original and the new form1 which in natural selection is often unavoidable4 ,if such a crossing1 that is1 a sexual connection1 of the new variety with the original forms takes place1 the offspring thereby produced generally returns to the original character4 ,in natural selection1 such a crossing can be avoided only when the new variety by migration separates from the original and isolates itself4 ,natural selection therefore acts much more slowly2 it requires much longer periods than the artificial process of selection4 ,but it is an essential consequence of this difference1 that the product of artificial selection disappears much more easily1 and that the new form returns rapidly to the earlier one1 which is not the case in natural selection4 ,the new species arising from natural selection maintain themselves much more permanently1 and return much less easily to the original form1 than is the case with products of artificial selection1 and accordingly maintain themselves during a much longer time than the artificial races produced by man4 ,but these are only subordinate differences1 which are explained by the different conditions of natural and artificial selection1 and in reality are connected only with differences in the duration of time4 ,the nature of the transformation and the means by which it is produced are entirely the same in both artificial and natural selection4 7,gen4 ,morph4 ii4 #bdh47 ,the thoughtless and narrow-minded opponents of ,darwin are never tired of asserting that his theory of selection is a groundless conjecture1 or at least an hypothesis which has yet to be proved4 ,that this assertion is completely unfounded1 may be perceived even from the outlines of the doctrine of selection which have just been discussed4 ,darwin assumes no kind of unknown forces of nature1 nor hypothetical conditions1 as the acting causes for the transformation of organic forms1 but solely and simply the universally recognized vital activities of all organisms1 which we term ,inheritance and ,adaptation4 ,every naturalist acquainted with physiology knows that these two phenomena are directly connected with the functions of propagation and nutrition1 and1 like all other phenomena of life1 are purely mechanical processes of nature1 that is1 they depend upon the molecular phenomena of motion in organic matter4 ,that the interaction of these two functions effect a continual1 slow transmutation of organic forms1 is a necessary result of the struggle for existence4 ,but this1 again1 is no more a hypothetical relation1 nor one requiring a proof1 than is the interaction of ,inheritance and ,adaptation4 ,the struggle for life is a mathematical necessity1 arising from the disproportion between the limited number of places in nature's household1 and the excessive number of organic germs4 ,the origin of new species is moreover greatly favoured by the active or passive migrations of animals and plants1 which takes place everywhere and at all times1 without being1 however1 entitled to rank as necessary agents in the process of natural selection4 ,the origin of new species by natural selection1 or1 what is the same thing1 by the interaction of ,inheritance and ,adaptation in the struggle for life1 is therefore a mathematical necessity of nature which needs no further proof4 ,whoever1 in spite of the present state of our knowledge1 still seeks for proofs for the ,theory of ,selection1 only shows that he either does not thoroughly understand the theory1 or is not sufficiently acquainted with the biological facts--has not the requisite amount of experimental knowledge in ,anthropology1 ,zoology1 and ,botany4 ,if1 as we maintain1 natural selection is the great active cause which has produced the whole wonderful variety of organic life on the earth1 all the interesting phenomena of human life must also be explicable from the same cause4 ,for man is after all only a most highly-developed vertebrate animal1 and all aspects of human life have their parallels1 or1 more correctly1 their lower stages of development in the animal kingdom4 ,the whole history of nations1 or what is called 8,universal ,history10 must therefore be explicable by means of 8natural selection10--must be a physico-chemical process1 depending upon the interaction of ,adaptation and ,inheritance in the struggle for life4 ,and this is actually the case4 ,we shall give further proofs of this later on4 ,it appears of interest here to remark that not only natural selection1 but also artificial selection exercises its influence in many ways in universal history4 ,a remarkable instance of artificial selection in man1 on a great scale1 is furnished by the ancient ,spartans1 among whom1 in obedience to a special law1 all newly-born children were subject to a careful examination and selection4 ,all those that were weak1 sickly1 or affected with any bodily infirmity1 were killed4 ,only the perfectly healthy and strong children were allowed to live1 and they alone afterwards propagated the race4 ,by this means1 the ,spartan race was not only continually preserved in excellent strength and vigour1 but the perfection of their bodies increased with every generation4 ,no doubt the ,spartans owed their rare degree of masculine strength and rough heroic valour 7for which they are eminent in ancient history7 in a great measure to this artificial selection4 ,many tribes also among the ,red ,indians of ,north ,america 7who at present are succumbing in the struggle for life to the superior numbers of the white intruders1 in spite of a most heroic and courageous resistance7 owe their rare degree of bodily strength and warlike bravery to a similar careful selection of the newly-born children4 ,among them1 also1 all children that are weak or affected with any infirmity are immediately killed1 and only the perfectly strong individuals remain in life1 and propagate the race4 ,that the race becomes greatly strengthened1 in the course of very many generations1 by this artificial selection cannot in itself be doubted1 and is sufficiently proved by many well known facts4 ,the opposite of this artificial selection of the wild ,redskins and the ancient ,spartans is seen in the individual selection which is universally practised in our modern military states1 for the purpose of maintaining standing armies1 and which1 under the name of military selection1 we may conveniently consider as a special form of selection4 ,unfortunately1 in our day1 militarism is more than ever prominent in our so-called 8civilization02 all the strength and all the wealth of flourishing civilized states are squandered on its development2 whereas the education of the young1 and public instruction1 which are the foundations of the true welfare of nations and the ennobling of humanity1 are neglected and mismanaged in a most pitiable manner4 ,and this is done in states which believe themselves to be the privileged leaders of the highest human intelligence1 and to stand at the head of civilization4 ,as is well known1 in order to increase the standing army as much as possible1 all healthy and strong young men are annually selected by a strict system of recruiting4 ,the stronger1 healthier1 and more spirited a youth is1 the greater is his prospect of being killed by needle-guns1 cannons1 and other similar instruments of civilization4 ,all youths that are unhealthy1 weak1 or affected with infirmities1 on the other hand1 are spared by the 8military selection10 and remain at home during the war1 marry1 and propagate themselves4 ,the more useless1 the weaker1 or infirmer the youth is1 the greater is his prospect of escaping the recruiting officer1 and of founding a family4 ,while the healthy flower of youth dies on the battle-field1 the feeble remainder enjoy the satisfaction of reproduction and of transmitting all their weaknesses and infirmities to their descendants4 ,according to the laws of transmission by inheritance1 there must necessarily follow in each succeeding generation1 not only a further extension1 but also a more deeply-seated development of weakness of body1 and what is inseparable from it1 a condition of mental weakness also4 ,this and other forms of artificial selection practised in our civilized states sufficiently explain the sad fact that1 in reality1 weakness of the body and weakness of character are on the perpetual increase among civilized nations1 and that1 together with strong1 healthy bodies1 free and independent spirits are becoming more and more scarce4 ,to the increasing enervation of modern civilized nations1 which is the necessary consequence of military selection1 there is further added another evil4 ,the progress of modern medical science1 although still little able really to cure diseases1 yet possesses and practises more than it used to do the art of prolonging life during lingering1 chronic diseases for many years4 ,such ravaging evils as consumption1 scrofula1 syphilis1 and also many forms of mental disorders1 are transmitted by inheritance to a great extent1 and transferred by sickly parents to some of their children1 or even to the whole of their descendants4 ,now1 the longer the diseased parents1 with medical assistance1 can drag on their sickly existence1 the more numerous are the descendants who will inherit incurable evils1 and the greater will be the number of individuals1 again1 in the succeeding generation1 thanks to that artificial 8medical selection10 who will be infected by their parents with lingering1 hereditary disease4 ,if any one were to venture the proposal1 after the examples of the ,spartans and ,redskins1 to kill1 immediately upon their birth1 all miserable1 crippled children to whom with certainty a sickly life could be prophesied1 instead of keeping them in life injurious to them and to the race1 our so-called 8humane civilization0 would utter a cry of indignation4 ,but the same 8humane civilization0 thinks it quite as it should be1 and accepts without a murmur1 that at the outbreak of every war 7and in the present state of civilized life1 and in the continual development of standing armies1 wars must naturally become more frequent7 hundreds and thousands of the finest men1 full of youthful vigour1 are sacrificed in the hazardous game of battles4 ,the same 8humane civilization0 at present praises the abolition of capital punishment as a 8liberal measure60 ,and yet capital punishment for incorrigible and degraded criminals is not only just1 but also a benefit to the better portion of mankind2 the same benefit is done by destroying luxuriant weeds1 for the prosperity of a well cultivated garden4 ,as by a careful rooting out of weeds1 light1 air1 and ground is gained for good and useful plants1 in like manner1 by the indiscriminate destruction of all incorrigible criminals1 not only would the struggle for life among the better portion of mankind be made easier1 but also an advantageous artificial process of selection would be set in practice1 since the possibility of transmitting their injurious qualities by inheritance would be taken from those degenerate outcasts4 ,against the injurious influence of artificial military and medical selection1 we fortunately have a salutary counterpoise1 in the invincible and much more powerful influence of natural selection1 which prevails everywhere4 ,for in the life of man1 as well as in that of animals and plants1 this influence is the most important transforming principle1 and the strongest lever for progress and amelioration4 ,the result of the struggle for life is that1 in the long run1 that which is better1 because more perfect1 conquers that which is weaker and imperfect4 ,in human life1 however1 this struggle for life will ever become more and more of an intellectual struggle1 not a struggle with weapons of murder4 ,the organ which1 above all others1 in man becomes more perfect by the ennobling influence of natural selection1 is the brain4 ,the man with the most perfect understanding1 not the man with the best revolver1 will in the long run be victorious2 he will transmit to his descendants the qualities of the brain which assisted him in the victory4 ,thus then we may justly hope1 in spite of all the efforts of retrograde forces1 that the progress of mankind towards freedom1 and thus to the utmost perfection1 will1 by the happy influence of natural selection1 become more and more certain4 ,,chapter ,,viii4 ,,transmission ,,by ,,inheritance ,,and ,,propagation4 ,universality of ,inheritance and ,transmission by ,inheritance4--,special ,evidences of the same4--,human ,beings with four1 six1 or seven ,fingers and ,toes4--,porcupine ,men4--,transmission of ,diseases1 especially ,diseases of the ,mind4--,original ,sin4--,hereditary ,monarchies4--,hereditary ,aristocracy4--,hereditary ,talents and ,mental ,qualities4--,material ,causes of ,transmission by ,inheritance4--,connection between ,transmission by ,inheritance and ,propagation4--,spontaneous ,generation and ,propagation4--,non-sexual or ,monogonous ,propagation4--,propagation by ,self-,division4--,monera and ,amb4--,propagation by the formation of ,buds1 by the formation of ,germ-,buds1 by the formation of ,germ-,cells4--,sexual or ,amphigonous ,propagation4--,formation of ,hermaphrodites4--,distinction of ,sexes1 or ,gonochorism4--,virginal ,breeding1 or ,parthenogenesis4--,material ,transmission of ,peculiarities of both ,parents to the ,child by ,sexual ,propagation4--,difference between ,transmission by ,inheritance in ,sexual and in ,asexual ,propagation4 ,the reader has1 in the last chapter1 become acquainted with natural selection according to ,darwin's theory1 as the constructive force of nature which produces the different forms of animal and vegetable species4 ,by natural selection we understand the interaction which takes place in the struggle for life between the transmission by inheritance and the mutability of organisms1 between two physiological functions which are innate in all animals and plants1 and which may be traced to other processes of life--the functions of propagation and nutrition4 ,all the different forms of organisms1 which people are usually inclined to look upon as the products of a creative power1 acting for a definite purpose1 we1 according to the ,theory of ,selection1 can conceive as the necessary productions of natural selection1 working without a purpose1--as the unconscious interaction between the two properties of ,mutability and ,hereditivity4 ,considering the importance which accordingly belongs to these vital properties of organisms1 we must examine them a little more closely1 and employ a chapter with the consideration of ,transmission by ,inheritance4 7,gen4 ,morph4 ii4 #agj-aia47 ,strictly speaking1 we must distinguish between ,hereditivity 7,transmissivity7 and ,inheritance 7,transmission74 ,hereditivity is the power of transmission1 the capability of organisms to transfer their peculiarities to their descendants by propagation4 ,transmission by ,inheritance1 or ,inheritance simply1 on the other hand1 denotes the exercise of the capability1 the actual transmission4 ,hereditivity and ,transmission by ,inheritance are such universal1 everyday phenomena1 that most people do not heed them1 and but few are inclined to reflect upon the operation and import of these phenomena of life4 ,it is generally thought quite natural and self-evident that every organism should produce its like1 and that children should more or less resemble their parents4 ,heredity is usually only taken notice of and discussed in cases relating to some special peculiarity1 which appears for the first time in a human individual without having been inherited1 and then is transmitted to his descendants4 ,it shows itself in a specially striking manner in the case of certain diseases1 and in unusual and irregular 7monstrous7 deviations from the usual formation of the body4 ,among these cases of the inheritance of monstrous deviations1 those are specially interesting which consist in an abnormal increase or decrease of the number five in the fingers or toes of man4 ,it is not unfrequently observed in families through several generations1 that individuals have six fingers on each hand1 or six toes on each foot4 ,less frequent is the number of four or seven fingers or toes4 ,the unusual formation arises at first from a single individual who1 from unknown causes1 is born with an excess of the usual number of fingers and toes1 and transmits these1 by inheritance1 to a portion of his descendants4 ,in one and the same family it has happened that1 throughout three1 four1 or more generations1 individuals have possessed six fingers and toes4 ,in a ,spanish family there were no less than forty individuals distinguished by this excess4 ,the transmission of the sixth finger or toe is not permanent or enduring in all cases1 because six-fingered people always intermarry again with those possessing five fingers4 ,if a six-fingered family were to propagate by pure in-breeding1 if six-fingered men were always to marry six-fingered women1 this characteristic would become permanent1 and a special six-fingered human race would arise4 ,but as six-fingered men usually marry five-fingered women1 and vice vers1 their descendants for the most part show a very mixed numerical relation1 and finally1 after the course of some generations1 revert again to the normal number of five4 ,thus1 for example1 among eight children of a six-fingered father and a five-fingered mother1 two children may have on both hands and feet six fingers and toes1 four children may have a mixed number1 and two children may have the usual number of five on both hands and feet4 ,in a ,spanish family1 each child except the youngest had the number six on both hands and feet2 the youngest1 only1 had the usual number on both hands and feet1 and the six-fingered father of the child refused to recognize the last one as his own4 ,the power of inheritance1 moreover1 shows itself very strikingly in the formation and colour of the human skin and hair4 ,it is well known how exactly the nature of the complexion in many families--for instance1 a peculiar soft or rough skin1 a peculiar luxuriance of the hair1 a peculiar colour and largeness of the eyes--is transmitted through many generations4 ,in like manner1 peculiar local growths or spots on the skin1 the so-called moles1 freckles1 and other accumulations of pigment which appear in certain places1 are frequently transmitted through several generations so exactly1 that in the descendants they appear on the same spots on which they existed in the parents4 ,the porcupine men of the ,lambert family1 who lived in ,london last century1 are especially celebrated4 ,edward ,lambert1 born in #agag1 was remarkable for a most unusual and monstrous formation of the skin4 ,his whole body was covered with a horny substance1 about an inch thick1 which rose in the form of numerous thorn-shaped and scale-like processes1 more than an inch long4 ,this monstrous formation of the outer skin1 or epidermis1 was transmitted by ,lambert to his sons and grandsons1 but not to his granddaughters4 ,the transmission in this instance remained in the male line1 as is often the case4 ,in like manner1 an excessive development of fat in certain parts of the body is often transmitted only in the female line4 ,i scarcely need call to mind how exactly the characteristic formation of the face is transmitted by inheritance2 sometimes it remains within the male1 sometimes within the female line2 sometimes it is blended in both4 ,the phenomena of transmission by inheritance of pathological conditions1 especially of the different forms of human diseases1 are very instructive and generally known4 ,diseases of the respiratory organs1 the glands1 and of the nervous system1 are specially liable to be transmitted by inheritance4 ,very frequently there suddenly appears in an otherwise healthy family a disease until then unknown among them2 it is produced by external causes1 by conditions of life causing disease4 ,this disease1 brought about in an individual by external cause1 is propagated and transmitted to his descendants1 and some or all of them then suffer from the same disease4 ,in case of diseases of the lungs1 for instance in consumption1 this sad transmission by inheritance is well known1 and it is the same with diseases of the liver1 with syphilis1 and diseases of the mind4 ,the latter are specially interesting4 ,just as peculiar characteristic features of man--pride1 ambition1 frivolity1 etc4--are transmitted to the descendants strictly by inheritance1 so too are the peculiar abnormal manifestations of mental activity1 which are usually called fixed ideas1 despondency1 imbecility1 and generally 8diseases of the mind40 ,this distinctly and irrefragably shows that the soul of man1 just as the soul of animals1 is a purely mechanical activity1 the sum of the molecular phenomena of motion in the particles of the brain1 and that it is transmitted by inheritance1 together with its substratum1 just as every other quality of the body is materially transmitted by propagation4 ,when this exceedingly important and undeniable fact is mentioned1 it generally causes great offence1 and yet in reality it is silently and universally acknowledged4 ,for upon what else do the ideas of 8hereditary sin10 8hereditary wisdom10 and 8hereditary aristocracy10 etc41 rest than upon the conviction that the quality of the human mind is transmitted by propagation--that is1 by a purely material process--through the body1 from the parents to the descendants8 ,the recognition of this great importance of transmission by inheritance is shown in a number of human institutions1 as for example1 among many nations in the division into castes1 such as the castes of warriors1 castes of priests1 and castes of labourers1 etc4 ,it is evident that the institution of such castes originally arose from the notion of the great importance of hereditary distinctions possessed by certain families1 which it was presumed would always be transmitted by the parents to the children4 ,the institution of an hereditary aristocracy and an hereditary monarchy is to be traced to the notion of such a transmission of special excellencies4 ,however1 it is unfortunately not only virtues1 but also vices that are transmitted and accumulated by inheritance2 and if1 in the history of the world1 we compare the different individuals of the different dynasties1 we shall everywhere find a great number of proofs of the transmission of qualities by inheritance1 but fewer of transmissions of virtues than of vices4 ,look only1 for example1 at the ,roman emperors1 at the ,julii and the ,claudii1 or at the ,bourbons in ,france1 ,spain1 and ,italy6 ,in fact1 scarcely anywhere could we find such a number of striking examples of the remarkable transmission of bodily and mental features by inheritance1 as in the history of the reigning houses in hereditary monarchies4 ,this is specially true in regard to the diseases of the mind previously mentioned4 ,it is in reigning families that mental disorders are hereditary in an unusual degree4 ,thus ,esquirol1 distinguished for his knowledge of mental diseases1 proved that the number of insane individuals in the reigning houses was1 in proportion to the number among the ordinary population1 as #fj to #a2 that is1 that disorders of the brain occur #fj times more frequently in the privileged families of the ruling houses than among ordinary people4 ,if equally accurate statistics were made of the hereditary nobility1 the result would probably be that here also we should find an incomparably larger contingent of mental diseases than among the common1 ignoble portion of mankind4 ,this phenomenon can scarcely astonish us if we consider what injury these privileged castes inflict upon themselves by their unnatural1 one-sided education1 and by their artificial separation from the rest of mankind4 ,by this means many dark sides of human nature are specially developed and1 as it were1 artificially bred1 and1 according to the laws of transmission by inheritance1 are propagated through series of generations with ever-increasing force and dominance4 ,it is sufficiently obvious from the history of nations how in successive generations of many dynasties1 for example1 of the princes of ,saxon ,thuringia and of the ,medici1 the noble solicitude for the most perfect human accomplishments in science and art were retained and transmitted from father to son2 and how1 on the other hand1 in many other dynasties1 for centuries a special partiality for the profession of war1 for the oppression of human freedom1 and for other rude acts of violence1 have been hereditary4 ,in like manner talents for special mental activities are transmitted in many families for generations1 as1 for instance1 talent for mathematics1 poetry1 music1 sculpture1 the investigation of nature1 philosophy1 etc4 ,in the family of ,bach there have been no less than twenty-two eminent musicians4 ,of course the transmission of such peculiarities of mind depends upon the material process of reproduction1 as does the transmission of mental qualities in general4 ,in this case again1 the vital phenomenon1 the manifestation of force 7as everywhere in nature71 is directly connected with definite relations in the admixture of the material components of the organism4 ,it is this definite proportion and molecular motion of matter which is transmitted by generation4 ,now1 before we examine the numerous1 and in some cases most interesting and important1 laws of transmission by inheritance1 let us make ourselves acquainted with the actual nature of the process4 ,the phenomena of transmission by inheritance are generally looked upon as something quite mysterious1 as peculiar processes which cannot be fathomed by natural science1 and the causes and actual nature of which cannot be understood4 ,it is precisely in such a case that people very generally assume supernatural influences4 ,but even in the present state of our physiology it can be proved with complete certainty that all the phenomena of inheritance are entirely natural processes1 that they are produced by mechanical causes1 and that they depend on the material phenomena of motion in the bodies of organisms1 which we may consider as a part of the phenomena of propagation4 ,all the phenomena of ,heredity and the laws of ,transmission by ,inheritance can be traced to the material process of ,propagation4 ,every organism1 every living individual1 owes its existence either to an act of unparental or ,spontaneous ,generation 7,generatio ,spontanea1 ,archigonia71 or to an act of ,parental ,generation or ,propagation 7,generatio ,parentalis1 ,tocogonia74 ,in a future chapter we shall have to consider ,spontaneous ,generation1 or ,archigony4 ,at present we must occupy ourselves with ,propagation1 or ,tocogony1 a closer examination of which is of the utmost importance for understanding transmission by inheritance4 ,most of my readers probably only know those phenomena of ,propagation which are seen universally in the higher plants and animals1 the processes of ,sexual ,propagation1 or ,amphigony4 ,the processes of ,non-sexual ,propagation1 or ,monogony1 are much less generally known4 ,the latter1 however1 are far more suited to throw light upon the nature of transmission by inheritance in connection with propagation4 ,for this reason1 we shall first consider only the phenomena of non-sexual or monogonic propagation 7,monogonia74 ,this appears in a variety of different forms1 as for example1 self-division1 formation of buds1 the formation of germ-cells or spores 7,gen4 ,morph4 ii4 #cf-eh74 ,it will be most instructive1 first1 to examine the propagation of the simplest organisms known to us1 which we shall have to return to later1 when considering the question of spontaneous generation4 ,these very simplest of all organisms yet known1 and which1 at the same time1 are the simplest imaginable organisms1 are the ,monera living in water2 they are very small living corpuscles1 which1 strictly speaking1 do not at all deserve the name of organism4 ,for the designation 8organism10 applied to living creatures1 rests upon the idea that every living natural body is composed of organs1 of various parts1 which fit into one another and work together 7as do the different parts of an artificial machine71 in order to produce the action of the whole4 ,during late years we have become acquainted with ,monera1 organisms which are1 in fact1 not composed of any organs at all1 but consist entirely of shapeless1 simple1 homogeneous matter4 ,the entire body of one of these ,monera1 during life1 is nothing more than a shapeless1 mobile1 little lump of mucus or slime1 consisting of an albuminous combination of carbon4 ,simpler or more imperfect organisms we cannot possibly conceive4 ,the first complete observations on the natural history of a ,moneron 7,protogenes primordialis7 were made by me at ,nice1 in #ahfd4 ,other very remarkable ,monera ,i examined later 7#ahff7 in ,lanzarote1 one of the ,canary ,islands1 and in #ahfg in the ,straits of ,gibraltar4 ,the complete history of one of these ,monera1 the orange-red ,protomyxa aurantiaca1 is represented in ,plate ,i1 and its explanation is given in the ,appendix4 ,i have found some curious ,monera also in the ,north ,sea1 off the ,norwegian coast1 near ,bergen4 ,cienkowski has described 7#ahfe7 an interesting ,moneron from fresh waters1 under the name of ,vampyrella4 ,but perhaps the most remarkable of all ,monera was discovered by ,huxley1 the celebrated ,english zoologist1 and called ,bathybius ,hckelii4 8,bathybius0 means1 living in the deep4 ,this wonderful organism lives in immense depths of the ocean1 which are over #ab1jjj--;indeed1 in some parts #bd1jjj feet below the surface1 and which have become known to us within the last ten years1 through the laborious investigations made by the ,english4 ,there1 among the numerous ,polythalamia and ,radiolaria which inhabit the fine calcareous mud of these abysses1 the ,bathybius is found in great quantities1 sometimes in the shape of roundish1 formless lumps of mucus1 sometimes in the form of a network of mucus1 covering fragments of stone and other objects4 ,small particles of chalk are frequently embedded in these mucous gelatinous masses1 and are1 perhaps1 products of their secretion4 ,the entire body of this remarkable ,bathybius consists solely of shapeless plasma1 or protoplasm1 as in the case of the other ,monera--that is1 it consists of the same albuminous combination of carbon1 which in infinite modifications is found in all organisms1 as the essential and never-failing seat of the phenomena of life4 ,i have given a detailed description and drawing of the ,bathybius and other ,monera in my 8,monographie der ,moneren10 #ahgj17ae7 from which the drawing in ,fig4 #i is taken4 ,illustration3 ,life history of a simplest organism4 ,pl4 ,i4 ,e4 ,haeckel del4 ,prototmyxa aurantiaca4 ,lagesse sc4 ,in a state of rest most ,monera appear as small globules of mucus or slime1 invisible1 or nearly so1 to the naked eye2 they are at most as large as a pin's head4 ,when the ,moneron moves itself1 there are formed on the upper surface of the little mucous globule1 shapeless1 fingerlike processes1 or very fine radiated threads2 these are the so-called false feet1 or pseudopodia4 ,the false feet are simple1 direct continuations of the shapeless albuminous mass1 of which the whole body consists4 ,we are unable to perceive different parts in it1 and we can give a direct proof of the absolute simplicity of the semi-fluid mass of albumen1 for with the aid of the microscope we can follow the ,moneron as it takes in nourishment4 ,when small particles suited for its nourishment--for instance1 small particles of decayed organic bodies or microscopic plants and infusoria--accidentally come into contact with the ,moneron1 they remain hanging to the sticky semi-fluid globule of mucus1 and here create an irritation1 which is followed by a strong afflux of the mucous substance1 and1 in consequence1 they become finally completely inclosed by it1 or are drawn into the body of the ,moneron by displacement of the several albuminous particles1 and are there digested1 being absorbed by simple diffusion 7endosmosis74 ,illustration3 ,,fig4 #a4--,propagation of the simplest organism1 a ,moneron1 by self-division4 ,a4 ,the entire ,moneron1 a ,protamba4 ,b4 ,it falls into two halves by a contraction in the middle4 ,c4 ,each of the two halves has separated from the other1 and now represents an independent individual4 ,just as simple as the process of nutrition is the propagation of these primitive creatures1 which in reality we can neither call animals nor plants4 ,all ,monera propagate themselves only in an asexual manner by monogony2 and in the simplest case1 by that kind of monogony which we place at the head of the different forms of propagation1 that is1 by self-division4 ,when such a little globule1 for example a ,protamba or a ,protogenes1 has attained a certain size by the assimilation of foreign albuminous matter1 it falls into two pieces2 a pinching in takes place1 contracting the middle of the globule on all sides1 and finally leads to the separation of the two halves 7compare ,fig4 #a74 ,each half then becomes rounded off1 and now appears as an independent individual1 which commences anew the simple course of the vital phenomena of nutrition and propagation4 ,in other ,monera 7,vampyrella71 the body in the process of propagation does not fall into two1 but into four equal pieces1 and in others1 again 7,protomonas1 ,protomyxa1 ,myxastrum71 at once into a number of small globules of mucus1 each of which again1 by simple growth1 becomes like the parent body4 ,here it is evident that the process of propagation is nothing but a growth of the organism beyond its own individual limit of size4 ,the simple method of propagation of the ,moneron by self-division is1 in reality1 the most universal and most widely spread of all the different modes of propagation2 for by the same simple process of division1 cells also propagate themselves4 ,cells are those simple organic individuals1 a large number of which constitute the bodies of most organisms1 the human body not excepted4 ,with the exception of the organisms of the lowest order1 which have not even the perfect form of a cell 7,monera71 or during life only represent a single cell 7many ,protista and single-celled plants71 the body of every organic individual is composed of a great number of cells4 ,every organic cell is to a certain degree an independent organism1 a so-called 8elementary organism10 or an 8individual of the first order40 ,every higher organism is1 in a measure1 a society or a state of such variously shaped elementary individuals1 variously developed by division of labour47#ci7 ,originally every organic cell is only a single globule of mucus1 like a ,moneron1 but differing from it in the fact that the homogeneous albuminous substance has separated itself into two different parts1 a firmer albuminous body1 the cell-kernel 7nucleus71 and an external1 softer albuminous body1 the cell-substance or body 7protoplasma74 ,besides this1 many cells later on form a third 7frequently absent7 distinct part1 inasmuch as they cover themselves with a capsule1 by exuding an outer pellicle or cell-membrane 7membrana74 ,all other forms of cells1 besides these1 are of subordinate importance1 and are of no further interest to us here4 ,every organism composed of many cells was originally a single cell1 and it becomes many-celled owing to the fact that the original cell propagates itself by self-division1 and that the new individual cells originating in this manner remain together1 and by division of labour form a community or a state4 ,the forms and vital phenomena of all many-celled organisms are merely the effect or the expression of all the forms and vital phenomena of all the individual cells of which they are composed4 ,the egg1 from which most animals and plants are developed1 is a simple cell4 ,illustration3 ,,fig4 #b4--,propagation of a single-celled organism1 ,amba sphrococcus1 by self-division4 ,a4 ,the enclosed ,amba1 a simple globular cell consisting of a lump of protoplasm 7c71 which contains a kernel 7b7 and a kernel speck 7a71 and is surrounded by a cell-membrane or capsule4 ,b4 ,the free ,amba1 which has burst and left the cyst or cell-membrane4 ,c4 ,it begins to divide by its kernel forming two kernels1 and by the cell-substance between the two becoming contracted4 ,d4 ,the division is completed by the cell-substance likewise falling into two halves 7,da and ,db74 ,the single-celled organisms1 that is1 those which during life retain the form of a single cell1 for example the ,amb1 as a rule propagate themselves in the simplest way by self-division4 ,this process differs from the previously described self-division of the ,moneron only in the fact that at the commencement the firmer cell-kernel 7nucleus7 falls into two halves1 by a pinching in at its middle4 ,the two young kernels separate from each other and act now as two distinct centres of attraction upon the surrounding softer albuminous matter1 that is1 the cell-substance 7protoplasma74 ,by this process finally the latter also divides into two halves1 and there now exist two new cells1 which are like the mother cell4 ,if the cell was surrounded by a membrane1 this either does not divide at all1 as in the case of egg-cleavage 7,fig4 #c1 #d71 or it passively follows the active pinching in of the protoplasm2 or1 lastly1 every new cell exudes a new membrane for itself4 ,illustration3 ,,fig4 #c4--;,egg of a mammal 7a simple cell74 a4 ,the small kernel speck or nucleolus 7the so-called germ-spot of the egg74 b4 ,kernel or nucleus 7the so-called germ-bladder of the egg74 c4 ,cell-substance or protoplasm 7the so-called yolk of the egg74 d4 ,cell-capsule or membrane 7membrane of the yolk7 of the egg2 called in mammals1 on account of its transparency1 ,membrana pellucida4 ,the non-independent cells which remain united in communities or states1 and thus constitute the body of higher organisms1 are propagated in the same manner as are independent single-celled organisms1 for example1 ,amba 7,fig4 #b74 ,just as in that case1 the cell with which most animals and plants commence their individual existence1 namely1 the egg1 multiplies itself by simple division4 ,when an animal1 for instance a mammal 7,fig4 #c1 #d71 develops out of an egg1 this process of development always begins by the simple egg-cell 7,fig4 #c7 forming an accumulation of cells 7,fig4 #d7 by continued self-division4 ,the outer covering1 or cell membrane1 of the globular egg remains undivided4 ,first1 the cell-kernel of the egg 7the so-called germinal vesicle7 divides itself into two kernels1 then follows the cell-substance 7the yolk of the egg7 7,fig4 #d ,a74 ,in like manner1 the two cells1 by continued self-division1 separate into four 7,fig4 #d ,b71 these into eight 7,fig4 #d ,c71 into sixteen1 thirty-two1 etc41 and finally there is produced a globular mass of very numerous little cells 7,fig4 #d ,d74 ,these now1 by further increase and heterogeneous development 7division of labour71 gradually build up the compound many-celled organism4 ,every one of us1 at the commencement of our individual development1 has undergone the very same process as that represented in ,fig4 #d4 ,the egg of a mammal--represented in ,fig4 #c1 and its development in ,fig4 #d--might as well be that of a man1 as of an ape1 dog1 horse1 or any other placental mammal4 ,illustration3 ,,fig4 #d4--;,first commencement of the development of a mammal's egg1 the so-called 8cleavage of the egg0 7propagation of the egg-cell by repeated self-division74 ,a4 ,the egg1 by the formation of the first furrow1 falls into two cells4 ,b4 ,these separate by division into four cells4 ,c4 ,the latter have divided into eight cells4 ,d4 ,by repeated division a globular accumulation of numerous cells has arisen4 ,now1 when one examines this simplest form of propagation1 this self-division1 it surely cannot be considered wonderful that the products of the division of the original organism should possess the same qualities as the parental individual4 ,for they are parts or halves of the parental organism1 and the matter or substance in both halves is the same1 and as both the young individuals have received an equal amount and the same quality of matter from the parent individual1 one can but consider it natural that the vital phenomena1 the physiological qualities should be the same in both children4 ,in fact1 in regard to their form and substance1 as well as to their vital phenomena1 the two produced cells can in no respect be distinguished from one another1 or from the mother cell4 ,they have inherited from her the same nature4 ,but this same simple propagation by self-division is not only confined to simple cells--it is the same also in the higher many-celled organisms2 for example1 in the coral zoophytes4 ,many of them which exhibit a high complexity of composition and organization1 nevertheless1 propagate themselves by simple division4 ,in this case the whole organism1 with all its organs1 falls into two equal halves as soon as by growth it has attained a certain size4 ,each half again develops itself1 by growth1 into a complete individual4 ,here1 again1 it is surely self-evident that the two products of division will share the qualities of the parental organism1 as they themselves are in fact halves of that parent4 ,next to propagation by division we come to propagation by the formation of buds4 ,this kind of monogony is exceedingly widely spread4 ,it occurs both in the case of simple cells 7though not frequently7 and in the higher organisms composed of many cells4 ,the formation of buds is universal in the vegetable kingdom1 less frequent in the animal kingdom4 ,however1 here also it occurs in the tribe of ,plant-like ,animals1 especially among the ,coral ,zoophytes1 and among the greater portion of the ,hydroid ,polyps very frequently1 further also among some worms 7,planarian ,worms1 ,ring-,worms1 ,moss ,animals1 ,tunicates74 ,most branching animal-trees or colonies1 which are exceedingly like branching plants1 arise like those plants1 by the formation of buds4 ,propagation by the formation of buds 7,gemmatio7 is essentially distinguished from propagation by division1 in the fact that the two organisms thus produced by budding are not of equal age1 and therefore at first are not of equal value1 as they are in the case of division4 ,in division we cannot clearly distinguish either of the two newly produced individuals as the parental1 that is as the producer1 because1 in fact1 both have an equal share in the composition of the original parental individual4 ,if1 on the other hand1 an organism sends out a bud1 then the latter is the child of the former4 ,the two individuals are of unequal size and of unequal form4 ,if1 for instance1 a cell propagates itself by the formation of buds1 we do not see the cell fall into two equal halves1 but there appears at one point of it a protuberance1 which becomes larger and larger1 more or less separates itself from the parental cell1 and then grows independently4 ,in like manner we observe in the budding of a plant or animal1 that a small local growth arises on a part of the mature individual1 which growth becomes larger and larger1 and likewise more or less separates itself from the parental organism by an independence in its growth4 ,the bud1 after it has attained a certain size1 may either completely separate itself from the parental individual1 or it may remain connected with it and form a stock or colony1 whilst at the same time its life may be quite independent of that of its parent4 ,while the growth which starts the propagation1 in the case of self-division1 is a total one affecting the whole body1 it is in the formation of buds only partial1 affecting merely a portion of the parental organism4 ,but here1 also1 the bud--the newly-produced individual which remains so long most directly connected with the parental organism1 and which proceeds from it--retains the essential qualities and the original tendency of development of its parent4 ,a third mode of non-sexual propagation1 that of the formation of germ-buds 7,polysporogonia71 is intimately connected with the formation of buds4 ,in the case of the lower1 imperfect organisms1 among animals1 especially in the case of the ,plant-like animals and ,worms1 we very frequently find that in the interior of an individual composed of many cells1 a small group of cells separates itself from those surrounding it1 and that this small isolated group gradually develops itself into an individual1 which1 becomes like the parent1 and sooner or later comes out of it4 ,thus1 for example1 in the body of the ,fluke-worms 7,trematodes7 there often arise numerous little bodies consisting of many cells1 that is germ-buds1 or polyspores1 which1 at an early stage separate themselves completely from the parent body1 and leave it when they have attained a certain stage of development4 ,the formation of germ-buds is evidently but little different from real budding4 ,but1 on the other hand1 it is connected with a fourth kind of non-sexual propagation1 which almost forms a transition to sexual reproduction1 namely1 the formation of germ-cells 7,monosporogonia71 which is often briefly called formation of spores 7sporogonia74 ,in this case it is no longer a group of cells1 but a single cell1 which separates itself from the surrounding cells in the interior of the producing organism1 and which only becomes further developed after it has come out of its parent4 ,after this germ-cell1 or monospore 7or1 briefly1 spore71 has left the parental individual1 it multiplies by division1 and thus forms a many-celled organism1 which by growth and gradual development attains the hereditary qualities of the parental organism4 ,this occurs very generally among lower plants 7,cryptogama74 ,although the formation of germ-cells very much resembles the formation of germ buds1 it evidently and very essentially differs from the latter1 and also from the other forms of non-sexual propagation which have previously been mentioned1 by the fact that only a very small portion of the producing organism takes part in the propagation and1 accordingly1 in the transmission by inheritance4 ,in the case of self-division1 where the whole organism falls into two halves1 in the formation of buds1 where a considerable portion of the whole body1 already more or less developed1 separates from the producing individual1 we easily understand that the forms and vital phenomena should be the same in the producing and produced organism4 ,it is much more difficult to understand in the formation of germ-buds1 and more difficult still in the formation of germ-cells1 how this very small1 quite undeveloped portion of the body1 this group of cells1 or this single cell1 not only directly takes with it certain parental qualities into its independent existence1 but also after its separation from the parental individual develops into a many-celled body1 and in this repeats the forms and vital phenomena of the original producing organism4 ,this last form of monogonic propagation--that of the germ cells1 or spore-formation--leads us directly to a form of propagation which is the most difficult of all to explain1 namely1 sexual propagation4 ,sexual or amphigonic propagation 7,amphigonia7 is the usual method of propagation among all higher animals and plants4 ,it is evident that it has only developed1 at a very late period of the earth's history1 from non-sexual propagation1 and apparently in the first instance from the method of propagation by germ-cells4 ,in the earliest periods of the organic history of the earth1 all organisms propagated themselves in a non-sexual manner1 as numerous lower organisms still do1 especially all those which are at the lowest stage of organization1 and which1 strictly speaking1 can be considered neither as animals nor as plants1 and which therefore1 as primary creatures1 or ,protista1 are best excluded from both the animal and vegetable kingdoms4 ,in the case of the higher animals and plants1 the increase of individuals1 as a rule1 is at present brought about in the majority of cases by sexual propagation4 ,in all the chief forms of non-sexual propagation mentioned above--in fission1 in the formation of buds1 germ buds1 and germ cells--the separated cell or group of cells was able by itself to develop into a new individual1 but in the case of sexual propagation the cell must first be fructified by another generative substance4 ,the fructifying male sperm must first mix with the female germ-cell 7the egg7 before the latter can develop into a new individual4 ,these two different generative substances1 the male sperm and the female egg1 are either produced by one and the same individual hermaphrodite 7,hermaphroditismus71 or by two different individuals 7sexual separation1 ,gonochorismus7 7,gen4 ,morph4 ii4 #eh1 #ei74 ,the simpler and more ancient form of sexual propagation is through double-sexed individuals 7,hermaphroditismus74 ,it occurs in the great majority of plants1 but only in a minority of animals1 for example1 in the garden snails1 leeches1 earth-worms1 and many other worms4 ,every single individual among hermaphrodites produces within itself materials of both sexes--eggs and sperm4 ,in most of the higher plants every blossom contains both the male organ 7stamens and anther7 and the female organs 7style and germ74 ,every garden snail produces in one part of its sexual gland eggs1 and in another part sperm4 ,many hermaphrodites can fructify themselves2 in others1 however1 copulation and reciprocal fructification of both hermaphrodites is necessary for causing the development of the eggs4 ,this latter case is evidently a transition to sexual separation4 ,sexual separation 7,gonochorismus17 which characterizes the more complicated of the two kinds of sexual reproduction1 has evidently been developed from the condition of hermaphroditism at a late period of the organic history of the world4 ,it is at present the universal method of propagation of the higher animals1 and occurs1 on the other hand1 only in the minority of plants 7for example1 in many aquatic plants1 e4g4 ,hydrocharis1 ,vallisneria2 and in trees1 e4g4 ,willows1 ,poplars74 ,every organic individual1 as a non-hermaphrodite 7,gonochoristus71 produces within itself only one of two generative substances1 either the male or the female4 ,the female individuals1 both in animals and plants1 produce eggs or egg-cells4 ,the eggs of plants in the case of flowering plants 7,phanerogama71 are commonly called 8embryo sacs02 in the case of flowerless plants 7,cryptogama71 8fruit spores40 ,in animals1 the male individual secretes the fructifying sperm 7sperma72 in plants1 the corpuscles1 which correspond to the sperm4 ,in the ,phanerogama1 these are the pollen grains1 or flower-dust2 in the ,cryptogama1 a sperm1 which1 like that of most animals1 consists of floating vibratile cells actively moving in a fluid--the zoosperms1 spermatozoa1 or sperm-cells4 ,the so-called virginal reproduction 7,parthenogenesis7 offers an interesting form of transition from sexual reproduction to the non-sexual formation of germ-cells 7which most resembles it72 it has been demonstrated to occur in many cases among ,insects1 especially by ,siebold's excellent investigations4 ,in this case germ-cells1 which otherwise appear and are formed exactly like egg-cells1 become capable of developing themselves into new individuals without requiring the fructifying seed4 ,the most remarkable and most instructive of the different partheno-genetic phenomena are furnished by those cases in which the same germ-cells1 according as they are fructified or not1 produce different kinds of individuals4 ,among our common honey bees1 a male individual 7a drone7 arises out of the eggs of the queen1 if the egg has not been fructified2 a female 7a queen1 or working bee71 if the egg has been fructified4 ,it is evident from this1 that in reality there exists no wide chasm between sexual and non-sexual reproduction1 but that both modes of reproduction are directly connected4 ,the parthenogenesis of ,insects must probably be regarded as a relapse from the sexual mode of propagation 7possessed by the original parents of the insects7 to the earlier condition of non-sexual propagation4 7,gen4 ,morph4 ii4 #hf47 ,in any case1 however1 sexual reproduction1 both in plants and animals1 which seems such a wonderful process1 has only arisen at a later date out of the more ancient process of non-sexual reproduction4 ,in both cases heredity is a necessary part of the phenomenon4 ,in all the different modes of propagation the essential point of the process is invariably a detachment of a portion of the parental organism possessing the capability of leading an individual1 independent existence4 ,we may1 therefore1 in all cases expect1 priori1 that the produced individuals--which are1 in fact1 as is commonly said1 8the flesh and blood0 of the parents--will receive the vital characteristics and qualities of form which the parental individuals possess4 ,it is simply a larger or smaller quantity of the parental material1 in fact of its albuminous protoplasm1 or cell-substance1 which passes to the produced individual4 ,but together with the material1 its vital properties--that is1 the molecular motions of the plasma--are transmitted1 which then manifest themselves in its form4 ,inheritance by sexual breeding loses very much of the mysterious and wonderful character which it at first sight possesses for the uninitiated1 if we consider the above-mentioned series of the different modes of propagation1 and their connection one with another4 ,it at first appears exceedingly wonderful that in the sexual propagation of man1 and of all higher animals1 the small egg1 the minute cell1 often invisible to the naked eye1 is able to transfer to the produced organism all the qualities of the maternal organism1 and1 no less mysterious1 that at the same time the essential qualities of the paternal organism are transferred to the offspring by means of the male sperm1 which fructifies the egg-cell by means of a viscid substance in which minute thread-like cells or zoosperms move about4 ,but as soon as we compare the connected stages of the different kinds of propagation1 in which the produced organism separates itself more and more as a distinct growth from the parental individual1 and more or less early enters upon its independent career2 as soon as we consider1 at the same time1 that the growth and development of every higher organism only depends upon the increase of the cells composing it--that is1 upon their simple propagation by division--it becomes quite evident that all these remarkable processes belong to one series4 ,the life of every organic individual is nothing but a connected chain of very complicated material phenomena of motion4 ,these motions must be considered as changes in the position and combination of the molecules1 that is1 of the smallest particles of animated matter 7of atoms placed together in the most varied manner74 ,the specific1 definite tendency of these orderly1 continuous1 and inherent motions of life depends1 in every organism1 upon the chemical mingling of the albuminous generative matter to which it owes its origin4 ,in man1 as in the case of the higher animals which propagate themselves in a sexual manner1 the individual vital motion commences at the moment in which the egg-cell is fructified by the spermatic filaments of the seed1 in which process both generative substances actually mix2 and here the tendency of the vital motion is determined by the specific1 or more accurately1 by the individual nature of the sperm as well as of the egg4 ,there can be no doubt as to the purely mechanical material nature of this process4 ,but here we stand full of wonder and astonishment before the infinite and inconceivable delicacy of this albuminous matter4 ,we are amazed at the undeniable fact that the simple egg-cell of the maternal organism1 and a single paternal sperm-thread1 transfer the molecular individual vital motion of these two individuals to the child so accurately1 that afterwards the minutest bodily and mental peculiarities of both parents reappear in it4 ,here we stand before a mechanical phenomenon of nature of which ,virchow1 whose genius founded the 8cellular pathology10 says with full justice3 8,if the naturalist cared to follow the custom of historians and preachers1 and to clothe phenomena1 which are in their way unique1 with the hollow pomp of ponderous and sounding words1 this would be the opportunity for him2 for we have now approached one of those great mysteries of animal nature1 which encircle the region of animal life as opposed to all the rest of the world of phenomena4 ,the question of the formation of cells1 the question of the excitation of a continuous and equable motion1 and1 finally1 the questions of the independence of the nervous system and of the soul--these are the great problems on which the human mind can measure its strength40 ,to comprehend the relation of the male and female to the egg-cell is almost as much as to solve all those mysteries4 ,the origin and development of the egg-cell in the mother's body1 the transmission of the bodily and mental peculiarities of the father to it by his seed1 touch upon all the questions which the human mind has ever raised about man's existence4 ,and1 we add1 these most important questions are solved1 by means of the ,theory of ,descent1 in a purely mechanical and purely monistic sense6 ,there can then be no further doubt that1 in the sexual propagation of man and all higher organisms1 inheritance1 which is a purely mechanical process1 is directly dependent upon the material continuity of the producing and produced organism1 just as is the case in the simplest non-sexual propagation of the lower organisms4 ,however1 ,i must at once take this opportunity of drawing attention to an important difference which inheritance presents in sexual and non-sexual propagation4 ,it is a fact long since acknowledged1 that the individual peculiarities of the producing organism are much more accurately transmitted to the produced organism by non-sexual than by sexual propagation4 ,gardeners have for a long time made use of this fact in many ways4 ,when1 for instance1 a single individual of a species of tree with stiff1 upright branches accidentally produces down-hanging branches1 a gardener1 as a rule1 cannot transmit this peculiarity by sexual1 but only by non-sexual propagation4 ,the twigs cut off such a weeping tree and planted as cuttings or slips1 afterwards produce trees having likewise hanging branches1 as1 for example1 the weeping willows and beeches4 ,seedlings1 on the other hand1 which have been reared out of the seed of such a weeping tree1 generally have the original stiff and upright form of branches possessed by their ancestors4 ,the same may be observed in a very striking manner in the so-called 8copper-coloured trees10 that is1 varieties of trees which are characterized by a red or reddish brown colour of the leaves4 ,off-shoots from such copper-coloured trees 7for example1 the copper beech71 which have been propagated by cuttings in a non-sexual manner1 show the peculiar colour and nature of the leaves which distinguished the parental individual1 while others reared from seeds of such a copper-coloured tree return to the green-coloured condition of leaf4 ,this difference in inheritance will seem very natural when we consider that the material connection between the producing and produced individuals is much closer and lasts much longer in non-sexual than in sexual propagation4 ,the special tendency of the molecular motion of life can therefore fix itself much longer and more thoroughly in the filial organism1 and be more strictly transmitted by non-sexual than by sexual propagation4 ,all these phenomena1 considered in connection1 clearly prove that the transmission of bodily and mental peculiarities is a purely material and mechanical process4 ,by propagation a greater or lesser quantity of albuminous particles1 and together with them the individual form of motion inherent in these molecules of protoplasm1 are transmitted from the parental organism to the offspring4 ,as this form of motion remains continuous1 the more delicate peculiarities inherent in the parental organism must sooner or later reappear in the filial organism4 ,,chapter ,,ix4 ,,laws ,,of ,,transmission ,,by ,,inheritance4 ,,adaptation ,,and ,,nutrition4 ,distinction between ,conservative and ,progressive ,transmission by ,inheritance4--,laws of ,conservative ,transmission3 ,transmission of ,inherited ,characters4--,uninterrupted or ,continuous ,transmission4--,interrupted or ,latent ,transmission4--,alternation of ,generations4--,relapse4--,degeneracy4-- ,sexual ,transmission4--,secondary ,sexual ,characters4--,mixed or ,amphigonous ,transmission4--,hybrids4--,abridged or ,simplified ,transmission4--,laws of ,progressive ,inheritance3 ,transmission of ,acquired ,characters4--,adapted or ,acquired ,transmission4--,fixed or ,established ,transmission4--,homochronous ,transmission 7,identity in ,epoch74--,homotopic ,transmission 7,identity in ,part74--,adaptation and ,mutability4--,connection between ,adaptation and ,nutrition4--,distinction between ,indirect and ,direct ,adaptation4 ,in the last chapter we considered ,transmission by ,inheritance1 one of the two universal vital activities of organisms1 ,adaptation and ,inheritance1 which by their interaction produce the different species of organisms1 and we have endeavoured to trace this very mysterious vital activity to a more general physiological function of organisms1 namely1 to ,propagation4 ,this latter in its turn1 like other vital phenomena of animals and plants1 depends on physical and chemical relations4 ,it is true they appear at times exceedingly complicated1 but can nevertheless in reality be traced to simple mechanical causes--that is1 to the relations of attraction and repulsion in the particles or molecules--in fact1 to the motional phenomena of matter4 ,now1 before we turn our attention to the second function1 the phenomenon of ,adaptation or ,mutability1 which counteracts the ,transmission by ,inheritance1 it seems appropriate first to cast one more glance at the various manifestations of ,heredity1 which we may perhaps even now denominate the 8laws of transmission by inheritance40 ,unfortunately1 up to the present time very little has been done for this most important subject1 either in zoology or in botany1 and almost all we know of the different laws of inheritance is confined to the experiences of gardeners and farmers4 ,it is not therefore to be wondered at1 that on the whole these exceedingly interesting and important phenomena have not been investigated with desirable scientific accuracy1 or reduced to the form of scientific laws4 ,accordingly1 what ,i shall relate of the different laws of transmission are only some preliminary fragments taken out of the infinitely rich store which lies open to our inquiry4 ,we may first divide all the different phenomena of inheritance into two groups1 which we may distinguish as the transmission of inherited characters1 and the transmission of acquired characters2 and we may call the former the conservative transmission1 and the latter the progressive transmission by inheritance4 ,this distinction depends upon the exceedingly important fact that the individuals of every species of animals and plants can transmit to their descendants1 not only those qualities which they themselves have inherited from their ancestors1 but also the peculiar1 individual qualities which they have acquired during their own life4 ,the latter are transmitted by progressive1 the former by conservative inheritance4 ,we have now first to examine the phenomena of conservative inheritance1 that is1 the transmission of such qualities as the organism has already received from its parents or ancestors4 7,gen4 ,morph4 ii4 #ahj47 ,among the phenomena of conservative inheritance we are first struck by that which is its most general law1 and which we may term the law of uninterrupted or continuous transmission4 ,it is so universal among the higher animals and plants1 that the uninitiated might overestimate its action and consider it as the only normal law of transmission by inheritance4 ,this law simply consists in the fact that among most species of animals and plants1 every generation is1 on the whole1 like the preceding--that the parents are as like the grandparents as they are like the children4 8,like produces like10 as is commonly said1 but more accurately 8similar things produce similar things40 ,for1 in reality1 the descendants of every organism are never absolutely equal in all points1 but only similar in a greater or less degree4 ,this law is so generally known1 that ,i need not give any examples of it4 ,the law of interrupted or latent transmission by inheritance1 which might also be termed alternating transmission1 is in a measure opposed to the preceding law4 ,this important law appears principally active among many lower animals and plants1 and manifests itself in contrast to the former in the fact that the offspring are not like their parents1 but very dissimilar1 and that only the third or a later generation becomes similar to the first4 ,the grandchildren are like the grandparents1 but quite unlike the parents4 ,this is a remarkable phenomenon1 and1 as is well known1 occurs also very frequently1 though in a less degree1 in human families4 ,every one of my readers doubtless knows some members of a family who1 in this or that peculiarity1 much more resemble the grandfather or grandmother than the father or mother4 ,sometimes it lies in bodily peculiarities1 for example1 features of face1 colour of hair1 size of body--sometimes in mental qualities1 for example1 temperament1 energy1 understanding--which are transmitted in this manner4 ,this fact may be observed in domestic animals as well as in the case of man4 ,among the domestic animals most liable to vary--as the dog1 horse1 and ox--breeders very frequently find that the product by breeding resembles the grandparents far more than it does its own parental organism4 ,if we express this general law and the succession of generations by the letters of the alphabet1 then ,a ,c ,e1 whilst ,b ,d ,f1 and so on4 ,this very remarkable fact appears in a more striking way in the lower animals and plants than in the higher1 and especially in the well-known phenomenon of alternation of generations 7metagenesis74 ,here we very frequently find--for example1 among the ,planarian worms1 sea-squirts or ,tunicates1 ,zoophytes1 and also among ferns and mosses--that the organic individual in the first place produces1 by propagation1 a form completely different from the parental form1 and that only the descendants of this generation1 again1 become like the first4 ,this regular change of generation was discovered by the poet ,chamisso1 on his voyage round the world in #ahai1 among the ,salp1 cylindrical tunicates1 transparent like glass1 which float on the surface of the sea4 ,here the larger generation1 the individuals of which live isolated and possess an eye of the form of a horse-shoe1 produce in a non-sexual manner 7by the formation of buds7 a completely different and smaller generation4 ,the individuals of this second smaller generation live united in chains and possess a cone-shaped eye4 ,every individual of such a chain produces1 in a sexual manner 7hermaphrodite7 again1 a non-sexual solitary form of the first and larger generation4 ,among the ,salp1 therefore1 it is always the first1 third1 and fifth generation1 and in like manner the second1 fourth1 and sixth generations1 that are entirely like one another4 ,however1 it is not always only one1 but in other cases a number of generations1 which are thus leapt over2 so that the first generation resembles the fourth and seventh1 the second resembles the fifth and eighth1 the third resembles the sixth and ninth1 and so on4 ,three different generations alternate with one another2 for example1 among the neat little sea-buoys 7,doliolum71 small tunicates closely related to the ,salp4 ,in this case it is ,a ,d ,g1 further1 ,b ,e ,h1 and ,c ,f ,i4 ,among the plant-lice 7,aphides71 each sexual generation is followed by a succession of from eight to ten or twelve non-sexual generations1 which are like one another1 but differ from the sexual generations4 ,then1 again1 a sexual generation reappears like the one long before vanished4 ,if we further follow this remarkable law of latent or interrupted inheritance1 and take into consideration all the phenomena appertaining to it1 we may comprise under it also the well-known phenomena of reversion4 ,by the term 8reversion0 or 8atavism0 we understand the remarkable fact known to all breeders of animals1 that occasionally single and individual animals assume a form which has not existed for many generations1 but belongs to a generation which has long since disappeared4 ,one of the most remarkable instances of this kind is the fact that in some horses there sometimes appear singular dark stripes1 similar to those of the zebra1 quagga1 and other wild species of ,african horses4 ,domestic horses of the most different races and of all colours sometimes show such dark stripes2 for example1 a stripe along the back1 a stripe across the shoulders1 and the like4 ,the sudden appearance of these stripes can only be explained by the supposition that it is the effect of a latent transmission1 a relapse into the ancient original form1 which has long since vanished1 and was once common to all species of horses2 the original form1 undoubtedly1 was originally striped like the zebras1 quaggas1 etc4 ,in like manner1 certain qualities in other domestic animals sometimes appear quite suddenly1 which once marked their wild ancestors1 now long since extinct4 ,in plants1 also1 such a relapse can be observed very frequently4 ,all my readers probably know the wild yellow toad-flax 7,linaria vulgaris71 a plant very common in our fields and hedges4 ,its dragon-mouthed yellow flower contains two long and two short stamens4 ,but sometimes there appears a single blossom 7,peloria7 which is funnel-shaped1 and quite regularly composed of five individual and equal sections1 with five corresponding stamens4 ,this ,peloria can only be explained as a relapse into the long since extinct and very ancient common form of all those plants which1 like the toad-flax1 possess dragon-mouthed1 two-lipped flowers1 with two long and two short stamens4 ,the original form1 like the ,peloria1 possessed a regular five-spurred blossom1 with five equal stamens1 which only later and by degrees have become unequal 7compare p4 #ag74 ,all such relapses are to be brought under the law of interrupted or latent transmission1 although the number of intervening generations may be enormous4 ,when cultivated plants or domestic animals become wild1 when they are withdrawn from the conditions of cultivated life1 they experience changes which appear not only as adaptations to their new mode of life1 but partially also as relapses into the ancient original form out of which the cultivated forms have been developed4 ,thus the different kinds of cabbage1 which are exceedingly different in form1 may be led back to the original form1 by allowing them to grow wild4 ,in like manner1 dogs1 horses1 heifers1 etc41 when growing wild1 often revert more or less to a long extinct generation4 ,an immensely long succession of generations may pass away before this power of latent transmission becomes extinguished4 ,a third law of conservative transmission may be called the law of sexual transmission1 according to which each sex transmits to the descendants of the same sex peculiarities which are not inherited by the descendants of the other sex4 ,the so-called secondary sexual characters1 which in many respects are of extraordinary interest1 everywhere furnish numerous examples of this law4 ,subordinate or secondary sexual characters are those peculiarities of one of the two sexes which are not directly connected with the sexual organs themselves2 such characters1 which exclusively belong to the male sex1 are1 for example1 the antlers of the stag1 the mane of the lion1 and the spur of the cock4 ,the human beard1 an ornament commonly denied to the female sex1 belongs to the same class4 ,similar characteristics by which the female sex is alone distinguished are1 for example1 the developed breasts1 with the lactatory glands of female mammals and the pouch of the female opossum4 ,the bodily size1 also1 and complexion1 differs in female animals of many species from that of the male4 ,all these secondary sexual qualities1 like the sexual organs themselves1 are transmitted by the male organism only to the male1 not to the female1 and vice vers4 ,contrary facts are rare exceptions to the rule4 ,a fourth law of transmission1 which has here to be mentioned1 in a certain sense contradicts the last1 and limits it1 viz41 the law of mixed or mutual 7amphigonous7 transmission4 ,this law tells us that every organic individual produced in a sexual way receives qualities from both parents1 from the father as well as from the mother4 ,this fact1 that personal qualities of each of the two sexes are transmitted to both male and female descendants1 is very important1 ,goethe mentions it of himself1 in the beautiful lines-- 8,von ,vater hab ich die ,statur1 des ,lebens ernstes ,fhren ,von ,mtterchen die ,frohnatur und ,lust zu fabuliren40 8,from my father ,i have my stature and the serious tenour of my life1 ,from my mother a joyous nature and a turn for poetizing40 ,this phenomenon1 ,i suppose1 is so well-known to all1 that ,i need not here enter upon it4 ,it is according to the different portions of their character which father and mother transmit to their children1 that the individual differences among brothers and sisters are chiefly determined4 ,the very important and interesting phenomenon of hybridism also belongs to this law of mixed or amphigonous transmission4 ,it alone1 when rightly estimated1 is quite sufficient to refute the prevailing dogma of the constancy of species4 ,plants1 as well as animals1 belonging to quite different species1 may sexually mingle with one another and produce descendants which in many cases can again propagate themselves1 and that indeed either 7more frequently7 by mingling with one of the two parental species1 or 7more rarely7 by pure in-breeding1 hybrid mixing with hybrid4 ,the latter is well established1 for example1 in the hybrids of hares and rabbits 7,lepus ,darwinii1 p4 #adg74 ,the hybrids of a horse and a donkey1 two different species of the same genus 7,equus71 are well known4 ,these hybrids differ according as the father or the mother belongs to the one or the other species--the horse or the donkey4 ,the mule produced by a mare and a he-donkey has qualities quite different from those of the jinny 7,hinnus71 the hybrid of a horse and she-donkey4 ,in both cases the hybrid produced by the crossing of two different species is a mixed form1 which receives qualities from both parents2 but the qualities of the hybrid are different1 according to the form of the crossing4 ,in like manner1 mulattoes produced by a ,european and a negress show a different mixture of characters from the hybrids produced by a negro with a ,european female4 ,in these phenomena of hybrid-breeding1 as well as in the other laws of transmission previously mentioned1 we are as yet unable to show the acting causes in detail2 but no naturalist doubts the fact that the causes are in all cases purely mechanical and dependent upon the nature of organic matter itself4 ,if we possessed more delicate means of investigation than our rude organs of sense and auxilliary instruments1 we should be able to discover those causes1 and to trace them to the chemical and physical properties of matter4 ,among the phenomena of conservative transmission1 we must now mention1 as the fifth law1 the law of abridged or simplified transmission4 ,this law is very important in regard to embryology or ontogeny1 that is in regard to the history of the development of organic individuals4 ,ontogeny1 or the history of the development of individuals1 as ,i have already mentioned in the first chapter 7p4 #aj71 and as ,i subsequently shall explain more minutely1 is nothing but a short and quick repetition of ,phylogeny dependent on the laws of transmission and adaptation--that is1 a repetition of the palontological history of development of the whole organic tribe1 or phylum1 to which the organism belongs4 ,if1 for example1 we follow the individual development of a man1 an ape1 or any other higher mammal within the maternal body from the egg1 we find that the ftus or embryo arising out of the egg passes through a series of very different forms1 which on the whole agrees with1 or at least runs parallel to1 a series of forms which is presented to us by the historical chain of ancestors of the higher mammals4 ,among these ancestors we may mention certain fishes1 amphibians1 marsupials1 etc4 ,but the parallelism or agreement of these two series of development is never quite complete2 on the contrary1 in ontogeny there are always gaps and leaps which indicate the omission of certain stages belonging to the phylogeny4 ,fritz ,mller1 in his excellent work1 8,fr ,darwin107#af7 has clearly shown in the case of the ,crustacea1 or crabs1 that 8the historical record preserved in the individual history of development is gradually obscured1 in proportion as development takes a more and more direct route from the egg to the complete animal40 ,this process of obscuring and shortening is determined by the law of abridged transmission1 and ,i mention it here specially because it is of great importance for the understanding of embryology1 and because it explains the fact1 at first so strange1 that the whole series of forms which our ancestors have passed through in their gradual development are no longer visible in the series of forms of our own individual development from the egg4 ,opposed to the laws of the conservative transmission1 hitherto discussed1 are the phenomena of the transmission of the second series1 that is1 the laws of progressive transmission by inheritance4 ,as already mentioned1 they depend upon the fact that the organism transmits to its descendants not only those qualities which it has inherited from its own ancestors1 but also a number of those individual qualities which it has acquired during its own lifetime4 ,adaptation is here seen to be connected with transmission by inheritance 7,gen4 ,morph4 ii4 #ahf74 ,at the head of these important phenomena of progressive transmission1 we may mention the law of adapted or acquired transmission4 ,in reality it asserts nothing more than what ,i have said above1 that in certain circumstances the organism is capable of transmitting to its descendants all the qualities which it has acquired during its own life by adaptation4 ,this phenomenon1 of course1 shows itself most distinctly when the newly acquired peculiarity produces any considerable change in the inherited form4 ,this is the case in the examples ,i mentioned in the preceding chapter as to transmission in general1 in the case of the men with six fingers and toes1 the porcupine men1 copper beeches1 weeping willows1 etc4 ,the transmission of acquired diseases1 such as consumption1 madness1 and albinism1 likewise form very striking examples4 ,albinoes are those individuals who are distinguished by the absence of colouring matter1 or pigments1 in the skin4 ,they are of frequent occurrence among men1 animals1 and plants4 ,in the case of animals of a definite dark colour1 individuals are not unfrequently born which are entirely without colour1 and in animals possessing eyes1 this absence of pigment extends even to the eyes1 so that the iris of the eye1 which is commonly of a bright or intense colour1 is colourless1 but appears red1 on account of the blood-vessels being seen through it4 ,among many animals1 such as rabbits and mice1 albinoes with white fur and red eyes are so much liked that they are propagated in great numbers as a special race4 ,this would be impossible were it not for the law of the transmission of adaptations4 ,which of the changes acquired by an organism are transmitted to its descendants1 and which are not1 cannot be determined priori1 and we are unfortunately not acquainted with the definite conditions under which the transmission takes place4 ,we only know in a general way that certain acquired qualities are much more easily transmitted than others1 for example1 more easily than the mutilations caused by accidents4 ,these latter are generally not transmitted by inheritance1 otherwise the descendants of men who have lost their arms or legs would be born without the corresponding arm or leg2 but here1 also1 exceptions occur1 and a race of dogs without tails has been produced by consistently cutting off the tails of both sexes of the dog during several generations4 ,a few years ago a case occurred on an estate near ,jena1 in which by a careless slamming of a stable door the tail of a bull was wrenched off1 and the calves begotten by this bull were all born without a tail4 ,this is certainly an exception2 but it is very important to note the fact1 that under certain unknown conditions such violent changes are transmitted in the same manner as many diseases4 ,in very many cases the change which is transmitted and preserved by adapted transmission is constitutional or inborn1 as in the case of albinism mentioned before4 ,the change then depends upon that form of adaptation which we call the indirect or potential4 ,a very striking instance is furnished by the hornless cattle of ,paraguay1 in ,south ,america4 ,a special race of oxen is there bred which is entirely without horns4 ,it is descended from a single bull1 which was born in #aggj of an ordinary pair of parents1 and the absence of horns was the result of some unknown cause4 ,all the descendants of this bull produced with a horned cow were entirely without horns4 ,this quality was found advantageous1 and by propagating the hornless cattle among one another1 a hornless race was obtained1 which at present has almost entirely supplanted the horned cattle in ,paraguay4 ,the case of the otter-sheep of ,north ,america forms a similar example4 ,in the year #agia a farmer1 by name ,seth ,wright1 lived in ,massachusetts1 in ,north ,america2 in his normally formed flock of sheep a lamb was suddenly born with a surprisingly long body and very short and crooked legs4 ,it was therefore unable to take any great leaps1 and especially unable to leap across a hedge into a neighbour's garden--a quality which seemed advantageous to the owner1 as the territories were divided by hedges4 ,it therefore occurred to him to transmit this quality to other sheep1 and by crossing this ram with normally shaped ewes1 he produced a whole race of sheep1 all of which had the qualities of the father1 short and crooked legs and a long body4 ,none of them could leap across the hedges1 and they therefore were much liked and propagated in ,massachusetts4 ,a second law1 which likewise belongs to the series of progressive transmissions1 may be called the law of established or habitual transmission4 ,it manifests itself in this1 that qualities acquired by an organism during its individual life are the more certainly transmitted to its descendants the longer the causes of that change have been in action1 and that this change becomes the more certainly the property of all subsequent generations the longer the cause of change acts upon these latter also4 ,the quality newly acquired by adaptation or mutation must be established or constituted to a certain degree before we can calculate with any probability that it will be transmitted at all to the descendants4 ,in this respect transmission resembles adaptation4 ,the longer a newly acquired quality has been transmitted by inheritance1 the more certainly will it be preserved in future generations4 ,if1 therefore1 for example1 a gardener by methodical treatment has produced a new kind of apple1 he may calculate with the greater certainty upon preserving the desired peculiarity of this sort the longer he has transmitted the same by inheritance4 ,the same is clearly shown in the transmission of diseases4 ,the longer consumption or madness has been hereditary in a family the deeper is the root of the evil1 and the more probable it is that all succeeding generations will suffer from it4 ,we may conclude the consideration of the phenomena of inheritance with the two very important laws of homotopic and contemporaneous transmission by inheritance4 ,we understand by them the fact that changes acquired by an organism during its life1 and transmitted to its descendants1 appear in the same part of the body in which the parental organism was first affected by them1 and that they also appear in the offspring at the same age as that at which they did so in the parent4 ,the law of contemporaneous or homochronous transmission1 which ,darwin calls the law of 8transmission in corresponding periods of life10 can be shown very clearly in the transmission of diseases1 especially of such as are recognized as very destructive1 on account of their hereditary character4 ,they generally appear in the organism of the child at the time corresponding with that in which the parental organism contracted the disease4 ,hereditary diseases of the lungs1 liver1 teeth1 brain1 skin1 etc41 usually appear in the descendants at the same period1 or a little earlier than they showed themselves in the parental organism1 or were contracted by it4 ,the calf gets its horns at the same period of life as its parents did4 ,in like manner the young stag receives its antlers at the same period of life in which they appeared in its father or grandfather4 ,in every one of the different sorts of vine the grapes ripen at the same time as they did in the case of their progenitors4 ,it is well known that the time of ripening varies greatly in the different sorts2 but as all are descended from a single species1 this variation has been acquired by the progenitors of the several sorts1 and has then been transmitted by inheritance4 ,the law of homotopic transmission1 which is most closely connected with the last mentioned law1 and which might be called the law of transmission in corresponding parts of the body1 may also be very distinctly recognized in pathological cases of inheritance4 ,large moles1 for example1 or accumulations of pigment in several parts of the skin1 tumours also1 often appear during many generations1 not only at the same period of life1 but also in the same part of the skin4 ,excessive development of fat in certain parts of the body is likewise transmitted by inheritance4 ,above all1 it is to be noted that numerous examples of this1 as well as of the preceding law1 may be found everywhere in the study of embryology4 ,both the law of homochronous and homotopic transmission are fundamental laws of embryology1 or ontogeny4 ,for these laws explain the remarkable fact that the different successive forms of individual development in all generations of one and the same species always appear in the same order of succession1 and that the variations of the body always take place in the same parts4 ,this apparently simple and self-evident phenomenon is nevertheless exceedingly wonderful and curious2 we cannot explain its real causes1 but may confidently assert that they are due to the direct transmission of the organic matter from the parental organism to that of the offspring1 as we have seen above in the case of the process of transmission in general1 by a consideration of the details of the various modes of reproduction4 ,having thus1 then1 considered the most important laws of ,inheritance1 we now turn to the second series of phenomena bearing on natural selection1 viz41 to those of ,adaptation or ,variation4 ,these phenomena1 taken as a whole1 stand in a certain opposition to the phenomena of ,inheritance1 and the difficulty which arises in examining them consists mainly in the two sets of phenomena being so completely intercrossed and interwoven4 ,we are but seldom able to say with certainty--of the variations of form which occur before our eyes--how much is owing to ,inheritance1 and how much to ,adaptation4 ,all characters of form1 by which organisms are distinguished1 are caused either by ,inheritance or by ,adaptation2 but as both functions are continually interacting with each other1 it is extremely difficult for the systematic inquirer to recognize the share belonging to each of the two functions in the special structure of individual forms4 ,this is1 at present1 all the more difficult1 because we are as yet scarcely aware of the immense importance of this fact1 and because most naturalists have neglected the theory of ,adaptation1 as well as that of ,inheritance4 ,the laws of ,inheritance1 which we have just discussed1 as well as the laws of ,adaptation1 which we shall consider directly1 in reality form only a small portion of the phenomena existing in this domain1 but which have not as yet been investigated2 and since every one of these laws can interact with every other1 it is clear that there is an infinite complication of physiological actions1 which are at work in the construction of organisms4 ,but now1 as to the phenomenon of variation or adaptation in general1 we must1 as in the case of inheritance1 view it as a quite universal1 physiological fundamental quality of all organisms1 without exception--as a manifestation of life which cannot be separated from the idea of organism4 ,strictly speaking1 we must here also1 as in the case of inheritance1 distinguish between ,adaptation itself and ,adaptability4 ,by ,adaptation 7,adaptio71 or ,variation 7,variatio71 we understand the fact that the organism1 in consequence of influences of the surrounding outer world1 assumes certain new peculiarities in its vital activity1 composition1 and form which it has not inherited from its parents2 these acquired individual qualities are opposed to those which have been inherited1 or1 in other words1 those which have been transmitted to it from its parents or ancestors4 ,on the other hand1 we call ,adaptability 7,adaptabilitas71 or ,variability 7,variabilitas71 the capability inherent in all organisms to acquire such new qualities under the influence of the outer world4 7,gen4 ,morph4 ii4 #aia47 ,the undeniable fact of organic adaptation or variation is universally known1 and can be observed at every moment in thousands of phenomena surrounding us4 ,but just because the phenomena of variation by external influences appear so self-evident1 they have hitherto undergone scarcely any accurate scientific investigation4 ,to them belong all the phenomena which we look upon as the results of contracting and giving up habits1 of practice and giving up practices1 or as the results of training1 of education1 of acclimatization1 of gymnastics1 etc4 ,many permanent variations brought about by causes producing disease1 that is to say1 many diseases1 are nothing but dangerous adaptations of the organism to injurious conditions of life4 ,in the case of cultivated plants and domestic animals1 variation is so striking and powerful that the breeder of animals and the gardener found their whole mode of proceeding upon it1 or rather upon the interaction between these phenomena and those of ,inheritance4 ,it is also well known to every one that animals and plants1 in their wild state1 are subject to variation4 ,every systematic treatise on a group of animals or plants1 if it were to be quite complete and exhaustive1 ought to mention in every individual species the number of variations which differ more or less from the prevailing or typical form of the species4 ,indeed1 in every careful systematic special treatise one finds1 in the case of most species1 mention of a number of such variations1 which are described sometimes as individual deviations1 and sometimes as so-called races1 varieties1 degenerate species1 or subordinate species1 and which often differ exceedingly from the original species1 solely in consequence of the adaptation of the organism to the external conditions of life4 ,if we now endeavour to fathom the general causes of these phenomena of ,adaptation1 we arrive at the conclusion that in reality they are as simple as the causes of the phenomena of ,inheritance4 ,we have shown that the nature of the process of propagation furnishes the real explanation of the facts of ,transmission by ,inheritance1 that is1 the transmission of parental matter to the body of the offspring2 and in like manner we can show that the physiological function of nutrition1 or change of substance1 affords a general explanation of ,adaptation or ,variation4 ,when ,i here point to 8nutrition0 as the fundamental cause of variation and adaptation1 ,i take this word in its widest sense1 and ,i understand by it the whole of the material changes which the organism undergoes in all its parts through the influences of the surrounding outer world4 ,nutrition thus comprises not only the reception of actual nutritive substances and the influence of different kinds of food1 but also1 for example1 the action upon the organism of water and of the atmosphere1 the influence of sunlight1 of temperature1 and of all those meteorological phenomena which are implied in the term 8climate40 ,the indirect and direct influence of the nature of the soil and of the dwelling-place also belong to it2 and further1 the extremely important and varied influence which is exercised upon every animal and every plant by the surrounding organisms1 friends and neighbours1 enemies and robbers1 parasites1 etc4 ,all these and many other very important influences1 all of which more or less modify the organism in its material composition1 must be taken into consideration in studying the change of substance which goes on in living things4 ,adaptation1 accordingly1 is the consequence of all those material variations which are produced in the change of substance of the organism by the external conditions of existence1 or by the influences of the surrounding external world4 ,how very much every organism is dependent upon the whole of its external surroundings1 and changed by their alteration1 is1 in a general way1 well known to every one4 ,only think how much the human power of action is dependent upon the temperature of the air1 or how much the disposition of our minds depends upon the colour of the sky4 ,accordingly as the sky is cloudless and sunny1 or covered with large heavy clouds1 our state of mind is cheerful or dull4 ,how differently do we feel and think in a forest during a stormy winter night and during a bright summer day6 ,all the different moods of our soul depend upon purely material changes of our brain1 upon movements of molecular plasma1 which are started through the medium of the senses by the different influences of light1 warmth1 moisture1 etc4 8,we are a plaything to every pressure of the air40 ,no less important and deeply influential are the effects produced upon our mind and body by the different quality and quantity of food4 ,our mental activity1 the activity of our understanding and of our imagination1 is quite different accordingly as we have taken tea or coffee1 wine or beer1 before or during our work4 ,our moods1 wishes1 and feelings are quite different when we are hungry and when we are satisfied4 ,the national character of ,englishmen and ,gauchos1 in ,south ,america1 who live principally on meat and food rich in nitrogen1 is wholly different from that of the ,irish1 feeding on potatoes1 and that of the ,chinese1 living on rice1 both of whom take food deficient in nitrogen4 ,the latter also form much more fat than the former4 ,here1 as everywhere1 the variations of the mind go hand in hand with the corresponding transformations of the body2 both are produced by purely material causes4 ,but all other organisms1 in the same way as man1 are varied and changed by the different influences of nutrition4 ,it is well known that we can change in an arbitrary way the form1 size1 colour1 etc41 of our cultivated plants and domestic animals1 by change of food2 that1 for example1 we can take from or give to a plant definite qualities1 accordingly as we expose it to a greater or less degree of sunlight and moisture4 ,as these phenomena are generally widely known1 and as we shall proceed presently to the consideration of the different laws of adaptation1 we will not dwell here any longer on the general facts of variation4 ,as the different laws of transmission may be naturally divided into the two series of conservative and progressive transmission1 so we may also distinguish between two series of the laws of adaptation1 first1 the series of laws of indirect1 and secondly1 the series of laws of direct adaptation4 ,the latter may also be called the laws of actual1 and the former the laws of potential1 adaptation4 ,the first series1 comprising the phenomena of indirect 7potential7 adaptation1 has1 on the whole1 hitherto been little attended to1 and ,darwin has the merit of having directed special attention to this series of changes4 ,it is somewhat difficult to place this subject clearly before the reader2 ,i will endeavour to make it clear hereafter by examples4 ,speaking quite generally1 indirect or potential adaptation consists in the fact that certain changes in the organism1 effected by the influence of nutrition 7in its widest sense7 and of the external conditions of existence in general1 show themselves not in the individual form of the respective organism1 but in that of its descendants4 ,thus1 especially in organisms propagating themselves in a sexual way1 the reproductive system1 or sexual apparatus1 is often influenced by external causes 7which little affect the rest of the organism71 to such a degree that its descendants show a complete alteration of form4 ,this can be seen very strikingly in artificially produced monstrosities4 ,monstrosities can be produced by subjecting the parental organism to certain extraordinary conditions of life1 and1 curiously enough1 such an extraordinary condition of life does not produce a change of the organism itself1 but a change in its descendants4 ,this cannot be called transmission by inheritance1 because it is not a quality existing in the parental organism that is transmitted by inheritance4 ,it is1 on the contrary1 a change affecting the parental organism1 but not perceptible in it1 that appears in the peculiar formation of its descendants4 ,it is only the impulse to this new formation which is transmitted in propagation through the egg of the mother or the sperm of the father4 ,the new formation exists in the parental organism only as a possibility 7potential72 in the descendants it becomes a reality 7actual74 ,as this very important and very general phenomenon had hitherto been entirely neglected1 people were inclined to consider all the visible variations and transformations of organic forms as phenomena of adaptation of the second series1 that is1 as phenomena of direct or actual adaptation4 ,the essence of this latter kind of adaptation consists in the fact that the change affecting the organism 7through nutrition1 etc47 shows itself immediately by some transformation1 and does not only make itself apparent in the descendants4 ,to this class belong all the well-known phenomena in which we can directly trace the transforming influence of climate1 food1 education1 training1 etc41 in their effects upon the individual itself4 ,we have seen how the two series of phenomena of progressive and conservative transmission1 in spite of their difference in principle1 in many ways interfere with and modify each other1 and in many ways co-operate with and cross each other4 ,the same is the case1 in a still higher degree1 in the two series of phenomena of indirect and direct adaptation1 which are opposed to each other and yet closely connected4 ,some naturalists1 especially ,darwin and ,carl ,vogt1 ascribe to the indirect or potential adaptation by far the more important and almost exclusive influence4 ,but the majority of naturalists have hitherto been inclined to take the opposite view1 and to attribute the principal influence to direct or actual adaptation4 ,i consider this controversy1 in the mean while1 as almost useless4 ,it is but seldom that we are in a condition1 in any individual case of variation1 to judge how much of it belongs to direct and how much to indirect adaptation4 ,we are1 on the whole1 still too little acquainted with these exceedingly important and intricate relations1 and can only assert1 in a general way1 that the transformation of organic forms is to be ascribed either to direct adaptation alone1 or to indirect adaptation alone1 or lastly1 to the co-operation of both direct and indirect adaptation4 ,,chapter ,x4 ,,laws ,,of ,,adaptation4 ,laws of ,indirect or ,potential ,adaptation4--,individual ,adaptation4--,monstrous or ,sudden ,adaptation4--,sexual ,adaptation4--,laws of ,direct or ,actual ,adaptation4--,universal ,adaptation4--,cumulative ,adaptation4--,cumulative ,influence of ,external ,conditions of ,existence and ,cumulative ,counter-,influence of the ,organism4--,free ,will4--,use and ,non-use of ,organs4--,practice and ,habit4--,correlative ,adaptation4--,correlation of ,development4--,correlation of ,organs4--,explanation of ,indirect or ,potential ,adaptation by the ,correlation of the ,sexual ,organs and of the other parts of the ,body4--,divergent ,adaptation4--,unlimited or ,infinite ,adaptation4 ,in the last chapter we reduced into two groups the phenomena of ,adaptation or ,variation1 which1 in connection and interaction with the phenomena of ,heredity1 produce all the endless variety of forms in animals and plants--first1 the group of indirect or potential1 and secondly1 the group of direct or actual ,adaptation4 ,we shall occupy ourselves with a closer examination of the different laws which we can discover in these two groups of the phenomena of variation4 ,let us first take into consideration the remarkable and very important1 although hitherto much neglected1 phenomena of indirect variation4 ,indirect or potential adaptation manifests itself1 it will be remembered1 in the striking and exceedingly important fact that organic individuals experience transformations and assume forms in consequence of changes of nutrition which have not operated on them themselves1 but upon their parental organism4 ,the transforming influence of the external conditions of existence1 of climate1 of nutrition1 etc41 shows its effects here not directly in the transformation of the organism itself1 but indirectly in that of its descendants4 7,gen4 ,morph4 ii4 #bjb47 ,as the principal and most universal of the laws of indirect variation must be mentioned the law of individual adaptation1 or the important proposition that all organic individuals from the commencement of their individual existence are unequal1 although often very much alike4 ,as a proof of this proposition1 ,i may at once point to the fact1 that in the human race in general all brothers and sisters1 all children of the same parents1 are unequal from their birth4 ,no one will venture to assert that two children at their birth are perfectly alike2 that the size of the individual parts of their bodies1 the number of hairs on their heads1 the number of cells composing their outer skins or epidermis1 the number of blood-cells are the same in both children1 or that both children have come into the world with the same abilities or talents4 ,but what more specially proves this law of individual difference1 is the fact that in the case of those animals which produce several young ones at a time1--for instance1 dogs and cats1--all the young of each birth differ from one another more or less strikingly in size and colour of the individual parts of the body1 or in strength1 etc4 ,now this law is universal4 ,all organic individuals from their beginning are distinguished by certain1 though often extremely minute1 differences1 and the cause of these individual differences1 though in detail usually utterly unknown to us1 depends partly or entirely on certain influences which the organs of propagation in the parental organism have undergone4 ,a second law of indirect adaptation1 which we shall call the law of monstrous or sudden adaptation1 is of less importance and less general than the law of individual adaptation4 ,here the divergences of the child-organism from the parental form are so striking that1 as a rule1 we may designate them as monstrosities4 ,in many cases they are produced1 as has been proved by experiments1 by the parental organism having been subject to a certain treatment1 and placed under peculiar conditions of nutrition2 for example1 when air and light are withdrawn from it1 or when other influences powerfully acting upon its nutrition are changed in a certain way4 ,the new condition of existence causes a strong and striking modification of form1 not directly of the organism itself1 but only of that of its descendants4 ,the mode of this influence in detail we cannot discover1 and we can only in a very general way detect a causal connection between the abnormal formation of the child and a certain change in the conditions of existence of its parents exerting a special influence upon the organs of propagation in the latter4 ,the previously mentioned phenomenon of albinism probably belongs to this group of abnormal or sudden variations1 also the individual cases of human beings with six fingers and toes1 the case of the hornless cattle1 as well as those of sheep and goats with four or six horns4 ,the abnormal deviation in all these cases probably owes its origin to a cause which at first only affected the reproductive system of the parental organism1 the egg of the mother or the sperm of the father4 ,a third curious manifestation of indirect adaptation may be termed the law of sexual adaptation4 ,under this name we indicate the remarkable fact that certain influences1 which act upon the male organs of propagation only1 affect the structure of the male descendants1 and in like manner other influences1 which act upon the female organs of propagation only1 manifest their effect only in the change of structure of the female descendants4 ,this remarkable phenomenon is still very obscure1 and has not as yet been investigated1 but is probably of great importance in regard to the origin of 8secondary sexual characteristics10 to which we have already made allusion4 ,all the phenomena of sexual1 monstrous1 and individual adaptation1 which we may comprise under the name of the laws of indirect or potential adaptation1 are as yet very little known to us in their real nature and in their deeper causal connection4 ,only this much we can at present maintain with certainty1 that numerous and important transformations in organic forms owe their existence to this process4 ,many and striking variations of form solely depend on causes which at first only affect the nutrition of the parental organism1 and specially its organs of propagation4 ,evidently the relations in which the sexual organs stand to other parts of the body are of the greatest importance4 ,we shall have more to say of these presently1 when we speak of the law of correlative adaptation4 ,how powerfully the variations in the conditions of life and nutrition affect the propagation of organisms is rendered obvious by the remarkable fact that numerous wild animals which we keep in our zoological gardens1 and exotic plants which are grown in our botanical gardens1 are no longer able to reproduce themselves4 ,this is the case1 for example1 with most birds of prey1 parrots1 and monkeys4 ,the elephant1 also1 and the animals of prey of the bear genus1 in captivity hardly ever produce young ones4 ,in like manner many plants in a cultivated state become sterile4 ,the two sexes may indeed unite1 but no fructification1 or no development of the fructified germ1 takes place4 ,from this it follows with certainty that the changed mode of nutrition in the cultivated state is able completely to destroy the capability of reproduction1 and therefore to exercise the greatest influence upon the sexual organs4 ,in like manner other adaptations or variations of nutrition in the parental organism may cause1 not indeed a complete want of descendants1 but still important changes in their form4 ,much better known than the phenomena of indirect or potential adaptation are those of direct or actual adaptation1 to the consideration of which we now turn our attention4 ,to them belong all those changes of organisms which are generally considered to be the results of practice1 habit1 training1 education1 etc42 also those changes of organic forms which are effected directly by the influence of nutrition1 of climate1 and other external conditions of existence4 ,as has already been remarked in direct or actual adaptation1 the transforming influence of the external cause affects the form of the organism itself1 and does not only manifest itself in that of the descendants4 7,gen4 ,morph4 ii4 #bjg47 ,we may place the law of universal adaptation at the head of the different laws of direct or actual adaptation1 because it is the chief and most comprehensive among them4 ,it may be briefly explained in the following proposition3 8,all organic individuals become unequal to one another in the course of their life by adaptation to different conditions of life1 although the individuals of one and the same species remain mostly very much alike40 ,a certain inequality of organic individuals1 as we have seen1 was already to be assumed in virtue of the law of individual 7indirect7 adaptation4 ,but1 beyond this1 the original inequality of individuals is afterwards increased by the fact that every individual1 during its own independent life1 subjects and adapts itself to its own peculiar conditions of existence4 ,all different individuals of every species1 however like they may be in their first stages of life1 become in the further course of their existence less like to one another4 ,they deviate from one another in more or less important peculiarities1 and this is a natural consequence of the different conditions under which the individuals live4 ,there are no two single individuals of any species which can complete their life under exactly the same external circumstances4 ,the vital conditions of nutrition1 of moisture1 air1 light2 further1 the vital conditions of society1 the inter-relations with surrounding individuals of the same or other species1 are different in every individual being2 and this difference first affects the functions1 and later changes the form of every individual organism4 ,if the children of a human family show1 even at the beginning1 certain individual inequalities which we may consider as the consequence of individual 7indirect7 adaptation1 they will appear still more different at a later period of life1 when each child has passed through different experiences1 and has adapted itself to different conditions of life4 ,the original difference of the individual processes of development1 evidently becomes greater the longer the life lasts and the more various the external conditions which influence the separate individuals4 ,this may be demonstrated in the simplest manner in man1 as well as in domestic animals and cultivated plants1 in which the vital conditions may be arbitrarily modified4 ,two brothers1 of whom one is brought up as a workman and the other as a priest1 develop quite differently in body as well as in mind2 in like manner1 two dogs of one and the same birth1 of which one is trained as a sporting dog and the other chained up as a watch dog4 ,the same observation may also readily be made as to organic individuals in a natural state4 ,if1 for instance1 one carefully compares all the trees in a fir or beech forest1 which consists of trees of a single species1 one finds that among all the hundreds or thousands of trees1 there are not two individual trees completely agreeing in size of trunk and other parts1 in the number of branches1 leaves1 etc4 ,everywhere we find individual inequalities which1 in part at least1 are merely the consequences of the different conditions of life under which the trees have developed4 ,it is true we can never say with certainty how much of this dissimilarity in all the individuals of every species may have originally been caused by indirect individual adaptation1 and how much of it acquired under the influence of direct or universal adaptation4 ,a second series of phenomena of direct adaptation1 which we may comprise under the law of cumulative adaptation1 is no less important and general than universal adaptation4 ,under this name ,i include a great number of very important phenomena1 which are usually divided into two quite distinct groups4 ,naturalists1 as a rule1 have distinguished1 first1 those variations of organisms which are produced directly by the permanent influence of external conditions 7by the constant action of nutrition1 of climate1 of surroundings1 etc471 and secondly1 those variations which arise from habit and practice1 from accustoming themselves to definite conditions of life1 and from the use and non-use of organs4 ,the latter influences have been set forth especially by ,lamarck as important causes of the change of organic forms1 while the former have for a very long time been recognized as such more generally4 ,the sharp distinction usually made between these two groups of cumulative adaptation1 and which even ,darwin still maintains1 disappears as soon as we reflect more accurately and deeply upon the real nature and causal foundation of these two1 apparently very different1 series of adaptations4 ,we then arrive at the conviction that in both cases there are always two different active causes to be dealt with3 on the one hand the external influence or action of adaptative conditions of life1 and on the other hand the internal reaction of the organism which subjects and adapts itself to that condition of life4 ,if cumulative adaptation is considered from the first point of view alone1 and the transforming actions of the permanent external conditions of life are traced to those conditions solely1 then the principal stress is laid unduly upon the external factor1 and the necessary internal reaction of the organism is not taken into proper consideration4 ,if1 on the other hand1 cumulative adaptation is unjustly regarded solely in relation to its second factor1 and the transforming action of the organism itself1 its reaction against the external influences1 its change by practice1 habit1 use1 or non-use of organs1 is put into the foreground1 then we forget that this reaction is first called into play by the action of external conditions of existence4 ,hence it seems that the distinction made between these two groups lies only in the different manner of viewing them1 and ,i believe that they can1 with full justice1 be considered as one4 ,the most essential fact in these phenomena of cumulative adaptation is that the change of the organism which manifests itself first in the functions1 and at a later period in the form1 is the result either of long enduring1 or of often repeated1 influences of an external cause4 ,the smallest cause1 by cumulation of its action1 can attain the greatest results4 ,there are innumerable examples of this kind of direct adaptation4 ,in whatever direction we may examine the life of animals and plants1 we discover on all hands evident and undeniable changes of this kind4 ,let me first mention some of those phenomena of adaptation occasioned directly by nutrition itself4 ,every one knows that the domestic animals which are bred for certain purposes can be variously modified1 according to the different quantity and quality of the food given to them4 ,if a farmer in breeding sheep wishes to produce fine wool1 he gives them different food from what he would give if he wished to obtain good flesh or an abundance of fat4 ,choice race and carriage horses receive better food than dray and cart horses4 ,even the bodily form of man--for example1 the amount of fat--is quite different according to his nutrition4 ,food containing much nitrogen produces little fat1 that containing little nitrogen produces a great deal of fat4 ,people who1 by means of ,banting's system1 at present so popular1 wish to become thin eat only meat and eggs--no bread1 no potatoes4 ,the important variations that can be produced among cultivated plants1 solely by changing the quantity and quality of nourishment1 are well known4 ,the same plant acquires an altogether different appearance1 according as it is placed in a dry and warm place1 exposed to the sunlight or placed in a cool damp spot in the shade4 ,many plants1 if transferred to the sea shore1 get in a short space of time thick1 fleshy leaves1 and the same plants placed in a particularly dry and hot locality get thin hairy leaves4 ,all these variations arise directly from the cumulative influence of changed nutrition4 ,but it is not only the quantity and quality of the articles of nutrition which affect and powerfully change and transform the organism1 but it is affected also by all the other external conditions of existence1 above all by its nearest organic surroundings1 the society of friendly or hostile organisms4 ,one and the same kind of tree develops itself quite differently in an open locality1 where it is free on all sides1 and in a forest where it must adapt itself to its surroundings1 where it is pressed on all sides by its nearest neighbours1 and is forced to shoot upwards4 ,in the former case1 the branches of the tree spread widely out2 in the latter1 the trunk extends upwards1 and the top of the tree remains small and contracted4 ,how powerfully all these circumstances1 and how powerfully the hostile or friendly influence of surrounding organisms1 of parasites1 etc41 affect every animal and every plant1 is so well known1 that it appears superfluous to quote further examples4 ,the change of form1 or transformation which is thereby effected1 is never solely the direct result of the external influence1 but must always be traced to the corresponding reaction1 and to the activity of the organism itself1 which consists in contracting a habit1 or practice1 and in the use or non-use of organs4 ,the fact that these latter phenomena1 as a rule1 have been considered distinct from the former1 is owing first to the one-sided manner of viewing them already mentioned1 and secondly to the wrong notion which has been formed as to the nature and the influence of the activity of the will in animals4 ,the activity of the will1 which is the organ of habit1 of practice1 of the use or non-use of organs among animals1 is1 like every other activity of the animal soul1 dependent upon material processes in the central nervous system1 upon peculiar motions which emanate from the albuminous matter of the ganglion cells1 and the nervous fibres connected with them4 ,the will1 as well as the other mental activities1 in higher animals1 in this respect is different from that of men only in quantity1 not in quality4 ,the will of the animal1 as well as that of man1 is never free4 ,the widely spread dogma of the freedom of the will is1 from a scientific point of view1 altogether untenable4 ,every physiologist who scientifically investigates the activity of the will in man and animals1 must of necessity arrive at the conviction that in reality the will is never free1 but is always determined by external or internal influences4 ,these influences are for the most part ideas which have been either formed by ,adaptation or by ,inheritance1 and are traceable to one or other of these two physiological functions4 ,as soon as we strictly examine the action of our own will1 without the traditional prejudice about its freedom1 we perceive that every apparently free action of the will is the result of previous ideas1 which are based on notions inherited or otherwise acquired1 and are therefore1 in the end1 dependent on the laws of ,adaptation and ,inheritance4 ,the same also applies to the action of the will in all animals4 ,as soon as their will is considered in connection with their mode of life1 in its relation to the changes which the mode of life is subject to from external conditions1 we are at once convinced that no other view is possible4 ,hence the changes of the will which follow the changes of nutrition1 and which1 in the form of practice1 habit1 etc41 produce variations in structure1 must be reckoned among the other material processes of cumulative adaptation4 ,whilst an animal's will is adapting itself to changed conditions of existence by the acquisition of new habits1 practices1 etc41 it not unfrequently effects the most remarkable transformations of the organic form4 ,numerous instances of this may be found everywhere in animal life4 ,thus1 for example1 many organs in domestic animals are suppressed1 when in consequence of a changed mode of life they cease to act4 ,ducks and fowls in a wild state fly exceedingly well1 but lose this facility more or less in a cultivated state4 ,they accustom themselves to use their legs more than their wings1 and in consequence the muscles and skeleton used in flying are essentially changed in their development and form4 ,darwin has proved this by a very careful comparative measurement and weighing of the respective parts of the skeleton in the different races of domestic ducks1 which are all descended from the wild duck 7,anas boschas74 ,the bones of the wings in tame ducks are weaker1 the bones of the legs1 on the other hand1 are more strongly developed than in wild ducks4 ,in ostriches and other running birds which have become completely unaccustomed to fly1 the consequence is that their wings are entirely crippled and degenerate into mere 8rudimentary organs0 7p4 #ab74 ,in many domestic animals1 especially in many races of dogs and rabbits1 we find that in the cultivated state they have acquired pendulous ears4 ,this is simply a consequence of a diminished use of the auricular muscles4 ,in a wild state these animals have to exert their ears very much in order to discover an approaching foe1 and this is accompanied by a strong development of the muscular apparatus1 which keeps the outer ears in an upright position1 and by which they can turn them in all directions4 ,in a domestic state the same animals no longer require to listen so attentively1 they prick up or turn their ears only a little2 the auricular muscles cease to be used1 gradually become weakened1 and the ears hang down flabbily1 or become rudimentary4 ,as in these cases the function1 and consequently the form also1 of the organ becomes degenerated through disuse1 so1 on the other hand1 it becomes more developed by greater use4 ,this is particularly striking if we compare the brain1 and the mental activity belonging to it1 in wild animals and those domestic animals which are descended from them4 ,the dog and horse1 which are so vastly improved by cultivation1 show an extraordinary degree of mental development1 in comparison with their wild original ancestors1 and evidently the change in the bulk of the brain1 which is connected with it1 is mainly determined by persistent exercise4 ,it is also well known how quickly and powerfully muscles grow and change their form by continual practice4 ,compare1 for example1 the arms and legs of a trained gymnast with those of an immovable book-worm4 ,how powerfully external influences affect the habits of animals and their mode of life1 and in this way still further change their forms1 is very strikingly shown in many cases among amphibious animals and reptiles4 ,our commonest indigenous snake1 the ringed snake1 lays eggs which require three weeks' time to develop4 ,but when it is kept in captivity1 and no sand is strewn in the cage1 it does not lay its eggs1 but retains them until the young ones are developed4 ,the difference between animals producing living offspring and those laying eggs is here effaced simply by the change of the ground upon which the animal lives4 ,the water-salamanders1 or tritons1 which have been artificially made to retain their original gills1 are extremely interesting in this respect4 ,the tritons are amphibious animals1 nearly akin to frogs1 and possess1 like the latter1 in their youth external organs of respiration--gills--with which they1 while living in water1 breathe the air dissolved in the water4 ,at a later date a metamorphosis takes place in tritons1 as in frogs4 ,they leave the water1 lose their gills1 and accustom themselves to breathe with their lungs4 ,but if they are prevented from doing this by being kept shut up in a tank1 they do not lose their gills4 ,the gills remain1 and the water salamander continues through life in that low stage of development1 beyond which its lower relations1 the gilled salamanders1 or ,sozobranchiata1 never pass4 ,the gilled salamander attains its full size1 its sexual development1 and reproduces itself without losing its gills4 ,great interest was caused a short time ago1 among zoologists1 by the axolotel 7,siredon pisciformis71 a gilled salamander from ,mexico1 nearly related to the triton2 it had already been known for a long time1 and been bred on a large scale in the zoological garden in ,paris4 ,this animal possesses external gills1 like the young salamander1 but retains them all its life1 like all other ,sozobranchiata4 ,this gilled salamander generally remains in the water1 with its aquatic organs of respiration1 and also propagates itself there4 ,but in the ,paris garden1 unexpectedly from among hundreds of these animals1 a small number crept out of the water on to the dry land1 lost their gills1 and changed themselves into gill-less salamanders1 which are not to be distinguished from a ,north-,american genus of tritons 7,amblystoma71 and breathe only through lungs4 ,in this exceedingly curious case we can directly follow the great stride from water-breathing to air-breathing animals1 a stride which can indeed be observed every spring in the individual history of development of frogs and salamanders4 ,just as every separate frog and every separate salamander transforms itself from an amphibious animal breathing through gills1 at a later period into one breathing through lungs1 so the whole group of frogs and salamanders have arisen from animals breathing through gills1 and akin to the ,siredon4 ,the ,sozobranchiata have remained up to the present day in that low stage of development4 ,ontogeny here explains phylogeny2 the history of the development of individuals explains that of the whole group 7p4 #aj74 ,to the law of accumulative adaptation there closely follows a third law of direct or actual adaptation1 the law of correlative adaptation4 ,according to this important law1 actual adaptation not only changes those parts of the organism which are directly affected by its influence1 but other parts also not directly affected by it4 ,this is the consequence of organic solidarity1 and especially of the unity of the nutrition existing among all the parts of every organism4 ,if1 for example1 the hairiness of the leaves increases in a plant by its being transferred to a dry locality1 then this change reacts upon the nutrition of other parts1 and it may result in a shortening of the parts of the stalk1 and produce a more contracted form of the whole plant4 ,in some races of pigs and dogs--for example1 in the ,turkish dog--which by adaptation to a warmer climate have more or less lost their hair1 the teeth also have degenerated4 ,whales and ,endentata 7armadillos71 which by their curious skin-covering are removed from the other mammals1 also show the greatest deviations in the formation of their teeth4 ,further1 those races of domestic animals 7oxen and pigs7 which have acquired short legs have1 as a rule1 also a short and compact head4 ,among other examples1 the races of pigeons which have the longest legs are also characterized by the longest beaks4 ,the same correlation between the length of the legs and beaks is universal in the order of stilted-birds 7,grallatores71 in storks1 cranes1 snipe1 etc4 ,the correlations which thus exist between different parts of the organism are most remarkable1 but their real cause is unknown to us4 ,in general1 we can of course say1 the changes of nutrition affecting an individual part must necessarily react on the other parts1 because the nutrition of every organism is a connected1 centralized activity4 ,but why just this or that part should exhibit this or that particular correlation is in most cases quite unknown to us4 ,we know a great number of such correlations in nutrition2 they are especially seen in those changes of animals and plants which give rise to an absence of pigment 7noticed previously7--in albinoes4 ,the want of the usual colouring matter goes hand in hand with certain changes in the formation of other parts2 for example1 of the muscular and osseous system1 consequently of organic systems which are not at all ultimately connected with the system of the outer skin4 ,very frequently albinoes are more feebly developed1 and consequently the whole structure of the body is more delicate and weak than in coloured animals of the same species4 ,the organs of the senses and nervous system are in like manner curiously affected when there is this want of pigment4 ,white cats with blue eyes are nearly always deaf4 ,white horses are distinguished from coloured horses by their special liability to form sarkomatous tumours4 ,in man1 also1 the degree of the development of pigment in the outer skin greatly influences the susceptibility of the organism for certain diseases2 so that1 for instance1 ,europeans with a dark complexion1 black hair1 and brown eyes become more easily acclimatized to tropical countries1 and are less subject to the diseases there prevalent 7inflammation of the liver1 yellow fever1 etc47 than ,europeans of white complexion1 fair hair1 and blue eyes4 7,compare above1 p4 #aej47 ,among these correlations in the formation of different organs1 those are specially remarkable which exist between the sexual organs and other parts of the body4 ,no change of any part reacts so powerfully upon the other parts of the body as a certain treatment of the sexual organs4 ,farmers who wish to obtain an abundant formation of fat in pigs1 sheep1 etc41 remove the sexual organs by cutting them out 7castration71 and this is indeed done to animals of both sexes4 ,the result is an excessive development of fat4 ,the same is done to the singers in certain religious corporations4 ,these unfortunates are castrated in early youth1 in order that they may retain their high boyish voices4 ,in consequence of this mutilation of the genitals1 the larynx remains in its youthful stage of development4 ,the muscular tissues of the body remain at the same time weakly developed1 while below the skin an abundance of fat accumulates4 ,but this mutilation also powerfully reacts upon the development of the nervous system1 the energy of the will1 etc41 and it is well known that human castrates1 or eunuchs1 as well as castrated animals1 are utterly deficient in the special psychical character which distinguishes the male sex4 ,man is a man1 both in body and soul1 solely through his male generative glands4 ,these most important and influential correlations between the sexual organs and the other parts of the body1 especially the brain1 are found equally in both sexes4 ,this might be expected even priori1 because in most animals the two kinds of organs develop themselves from the same foundation1 and at the beginning are not different4 ,in man1 as in the rest of the vertebrate animals1 the male and female organs in the original state of the germ are entirely the same1 and the differences of the two sexes only gradually arise in the course of embryonic development 7in man1 in the ninth week of embryonic life71 by one and the same gland developing in the female as the ovary1 and in the male as the testicle4 ,every change of the female ovary1 therefore1 has a no less important reaction upon the whole female organism than every change of the testicle has upon the male organism4 ,virchow has expressed the importance of this correlation in his admirable essay on 8,das ,weib und die ,zelle0 78,woman and the ,cell071 in the following words3--8,woman is woman only by her sexual glands2 all the peculiarities of her body and mind1 of her nutrition and her nervous activity1 the sweet delicacy and roundness of her limbs1 the peculiar formation of the pelvis1 the development of the breasts1 the continuance of the high voice1 that beautiful ornament of hair on her head1 with the scarcely perceptible soft down on the rest of the skin--then again1 the depth of feeling1 the truth of her direct perceptions1 her gentleness1 devotion1 and fidelity--in short1 all the feminine qualities which we admire and honour in a true woman are but a dependence of the ovary4 ,take this ovary away1 and the man-woman stands before us--a loathly abortion40 ,the same close correlation between the sexual organs and the other parts of the body occurs among plants as generally as among animals4 ,if one wishes to obtain an abundance of fruit from a garden plant1 the growth of the leaves is curtailed by cutting off some of them4 ,if1 on the other hand1 an ornamental plant with a luxuriance of large and beautiful leaves is desired1 then the development of the blossoms and fruit is prevented by cutting off the flower buds4 ,in both cases one system of organs develops at the cost of the others4 ,thus1 also1 most variations in the formation of leaves in wild plants result in corresponding transformations of the generative parts or blossoms4 ,the great importance of this 8compensation of development10 of this 8correlation of parts10 has been already set forth by ,goethe1 by ,geoffroy ,st4 ,hilaire1 and other nature-philosophers4 ,it rests mainly upon the fact that direct or actual adaptation cannot produce an important change in a single part of the body1 without at the same time affecting the whole organism4 ,the correlative adaptation between the reproductive organs and the other parts of the body deserves a very special consideration1 because it is1 above all others1 likely to throw light upon the obscure and mysterious phenomena of indirect or potential adaptation1 which have already been considered4 ,for just as every change of the sexual organs powerfully reacts upon the rest of the body1 so on the other hand every important change in another part of the body must necessarily more or less react on the sexual organs4 ,this reaction1 however1 will only become perceptible in the formation of the offspring which arise out of the changed generative parts4 ,it is1 in fact1 precisely those remarkable and imperceptible changes of the genital system 7in themselves utterly insignificant changes7--changes of the eggs and the sperm--brought about by such correlations1 which have the greatest influence upon the formation of the offspring1 and all the phenomena of indirect or potential adaptation previously mentioned may in the end be traced to correlative adaptation4 ,a further series of remarkable examples of correlative adaptation is furnished by the different animals and plants which become degenerated through parasitic life or parasitism4 ,no other change in the mode of life so much affects the shapes of organisms as the adoption of a parasitical life4 ,plants thereby lose their green leaves2 as1 for instance1 our native parasitical plants1 ,orobanche1 ,lathra1 ,monotropa4 ,animals which originally have lived freely and independently1 but afterwards adopt a parasitical mode of life on other animals or plants1 in the first place cease to use their organs of motion and their organs of sense4 ,the loss of this activity is succeeded by the loss of the organs themselves1 and thus we find1 for example1 many crabs1 or crustacea1 which in their youth possess a tolerably high degree of organization1 viz41 legs1 antenn1 and eyes1 in old age completely degenerate1 living as parasites1 without eyes1 without apparatus of motion1 and without antenn4 ,the lively1 active form of youth1 has become a shapeless1 motionless lump4 ,only the most necessary organs of nutrition and propagation retain their activity2 all the rest of the body has degenerated4 ,evidently these complete transformations are1 to a large extent1 the direct consequences of cumulative adaption1 of the non-use and defective exercise of the organs1 but a great portion of them must certainly be attributed also to correlative adaptation4 7,compare ,plate ,x4 and ,,xi47 ,a seventh law of adaptation1 the fourth in the group of direct adaptation1 is the law of divergent adaptation4 ,by this law we indicate the fact that parts originally formed alike have developed in different ways under the influence of external conditions4 ,this law of adaptation is extremely important for the explanation of the phenomenon of division of labour1 or polymorphism4 ,we can see this very easily in our own selves2 for instance1 in the activity of our two hands4 ,we usually accustom our right hand to quite different work from that which we give our left1 and in consequence of the different occupation there arises a different formation of the two hands4 ,the right hand1 which we use much more than the left1 shows a stronger development of the nerves1 muscles1 and bones4 ,the same applies to the whole arm4 ,in most human beings the bones and flesh of the right arm are1 in consequence of their being more employed1 stronger and heavier than those of the left arm4 ,now1 as the special use of the right arm has been adopted and transmitted by inheritance for thousands of years among ,europeans1 the stronger shape and size of the right arm have already become hereditary4 ,p4 ,harting1 an excellent ,dutch naturalist1 has shown by measuring and weighing newly-born children1 that even in them the right arm is more developed than the left4 ,according to the same law of divergent adaptation1 both eyes also frequently develop differently4 ,if1 for example1 a naturalist accustoms himself always to use one eye for the microscope 7it is better to use the left71 then that eye will acquire a power different from that of the other1 and this division of labour is of great advantage4 ,the one eye will become more short-sighted1 and better suited for seeing things near at hand2 the other eye becomes1 on the contrary1 more long-sighted1 more acute for looking at an object in the distance4 ,if1 on the other hand1 the naturalist alternately uses both eyes for the microscope1 he will not acquire the short-sightedness of the one eye and the compensatory degree of long-sight in the other1 which is attained by a wise distribution of these different functions of sight between the two eyes4 ,here then again the function1 that is the activity1 of originally equally-formed organs can become divergent by habit2 the function reacts again upon the form of the organ1 and thus we find1 after a long duration of such an influence1 a change in the more delicate parts and the relative growth of the divergent organs1 which in the end becomes apparent even in their coarser outlines4 ,divergent adaptation can very easily be perceived among plants1 especially in creepers4 ,branches of one and the same creeping plant1 which originally were formed alike1 acquire a completely different form and extent1 a completely different degree of curvature and diameter of spiral winding1 according as they twine themselves round a thinner or a thicker bar4 ,the divergent change of form of parts originally identical in form1 which tending in different directions develop themselves under different external conditions1 can be distinctly demonstrated in many other examples4 ,as this divergent adaptation interacts with progressive inheritance1 it becomes the cause of a division of labour among the different organs4 ,an eighth and last law of adaptation we may call the law of unlimited or infinite adaptation4 ,by it we simply mean to express that we know of no limit to the variation of organic forms occasioned by the external conditions of existence4 ,we can assert of no single part of an organism1 that it is no longer variable1 or that if it were subjected to new external conditions it would not be changed by them4 ,it has never yet been proved by experience that there is a limit to variation4 ,if1 for example1 an organ degenerates from non-use1 this degeneration ends finally in a complete disappearance of the organ1 as is the case with the eyes of many animals4 ,on the other hand1 we are able1 by continual practice1 habit1 and the ever-increasing use of an organ1 to bring it to a degree of perfection which we should at the beginning have considered to be impossible4 ,if we compare the uncivilized savages with civilized nations1 we find among the former a development of the organs of sense--sight1 smell1 and hearing--such as civilized nations can hardly conceive of4 ,on the other hand1 the brain1 that is mental activity1 among more civilized nations is developed to a degree of which the wild savages have no idea4 ,there appears indeed to be a limit given to the adaptability of every organism1 by the 8type0 of its tribe or phylum2 that is1 by the essential fundamental qualities of this tribe1 which have been inherited from a common ancestor1 and transmitted by conservative inheritance to all its descendants4 ,thus1 for example1 no vertebrate animal can acquire the ventral nerve-chord of articulate animals1 instead of the characteristic spinal marrow of the vertebrate animals4 ,however1 within this hereditary primary form1 within this inalienable type1 the degree of adaptability is unlimited4 ,the elasticity and fluidity of the organic form manifests itself1 within the type1 freely in all directions1 and to an unlimited extent4 ,but there are some animals1 as1 for example1 the parasitically degenerate crabs and worms1 which seem to pass even the limit of type1 and have forfeited all the essential characteristics of their tribe by an astonishing degree of degeneration4 ,as to the adaptability of man1 it is1 as in all other animals1 also unlimited1 and since it is manifested in him above all other animals1 in the modifications of the brain1 there can be absolutely no limit to the knowledge which man in a further progress of mental cultivation may not be able to exceed4 ,the human mind1 according to the law of unlimited adaptation1 enjoys an infinite perspective of becoming ever more and more perfect4 ,these remarks are sufficient to show the extent of the phenomena of ,adaptation1 and the great importance to be attached to them4 ,the laws of ,adaptation1 or the facts of ,variation caused by the influence of external conditions1 are just as important as the laws of ,inheritance4 ,all phenomena of ,adaptation1 in the end1 can be traced to conditions of nutrition of the organism1 in the same way as the phenomena of ,inheritance are referable to conditions of reproduction2 but the latter1 as well as the former1 may further be traced to chemical and physical1 that is to mechanical1 causes4 ,according to ,darwin's ,theory of ,selection the new forms of organisms1 the transformations which artificial selection produces in the state of cultivation1 and which natural selection produces in the state of nature1 arise solely by the interaction of such causes4 ,,chapter ,,xi4 ,,natural ,,selection ,,by ,,the ,,struggle ,,for ,,existence4 ,,division ,,of ,,labour ,,and ,,progress4 ,interaction of the ,two ,organic ,formative ,causes1 ,inheritance and ,adaptation4--,natural and ,artificial ,selection4--,struggle for ,existence1 or ,competition for the ,necessaries of ,life4--,disproportion between the ,number of ,possible or ,potential1 and the ,number of ,real or ,actual ,individuals4--,complicated ,correlations of all ,neighbouring ,organisms4--,mode of ,action in ,natural ,selection4--,homochromic ,selection as the ,cause of ,sympathetic ,colourings4--,sexual ,selection as the ,cause of the ,secondary ,sexual ,characters4--,law of ,separation or ,division of ,labour 7,polymorphism1 ,differentiation1 ,divergence of ,characters74--,transition of ,varieties into ,species4--,idea of ,species4--,hybridism4--,law of ,progress or ,perfectioning 7,progressus1 ,teleosis74 ,in order to arrive at a right understanding of ,darwinism1 it is1 above all1 necessary that the two organic functions of ,inheritance and ,adaptation1 which we spoke of in our last chapter1 should be more closely examined4 ,if we do not1 on the one hand1 examine the purely mechanical nature of these two physiological activities1 and the various action of their different laws1 and if1 on the other hand1 we do not consider how complicated the interaction of these different laws of ,inheritance and ,adaptation must be1 we shall not be able to understand how these two functions1 by themselves1 have been able to produce all the variety of animal and vegetable forms1 which1 in fact1 they have4 ,we have1 at least1 hitherto been unable to discover any other formative causes besides these two1 and if we rightly understand the necessary and infinitely complicated interaction of ,inheritance and ,adaptation1 we do not require to look for other unknown causes for the change of organic forms4 ,these two fundamental causes are1 as far as we can see1 completely sufficient4 ,even long before ,darwin had published his ,theory of ,selection1 some naturalists1 and especially ,goethe1 had assumed the interaction of two distinct formative tendencies--a conservative or preserving1 and a progressive or changing formative tendency--as the causes of the variety of organic forms4 ,the former was called by ,goethe the centripetal or specifying tendency1 the latter the centrifugal tendency1 or the tendency to metamorphosis 7p4 #hi74 ,these two tendencies completely correspond with the two processes of ,inheritance and ,adaptation4 ,inheritance is the centripetal or internal formative tendency which strives to keep the organic form in its species1 to form the descendants like the parents1 and always to produce identical things from generation to generation4 ,adaptation1 on the other hand1 which counteracts inheritance1 is the centrifugal or external formative tendency1 which constantly strives to change the organic forms through the influence of the varying agencies of the outer world1 to create new forms out of those existing1 and entirely to destroy the constancy or permanency of species4 ,accordingly as ,inheritance or ,adaptation predominates in the struggle1 the specific form either remains constant or changes into a new species4 ,the degree of constancy of form in the different species of animals and plants1 which obtains at any moment1 is simply the necessary result of the momentary predominance which either of these two formative powers 7or physiological activities7 has acquired over the other4 ,if we now return to the consideration of the process of selection or choice1 the outlines of which we have already examined1 we shall be in a position to see clearly and distinctly that both artificial and natural selection rest solely upon the interaction of these two formative tendencies4 ,if we carefully watch the proceedings of an artificial selector--a farmer or a gardener--we find that only these two constructive forces are used by him for the production of new forms4 ,the whole art of artificial selection rests solely upon a thoughtful and wise application of the laws of ,inheritance and ,adaptation1 and upon their being applied and regulated in an artistic and systematic manner4 ,here the will of man constitutes the selecting force4 ,the case of natural selection is quite similar1 for it also employs merely these two organic constructive forces1 these ingrained physiological properties of ,adaptation and ,heredity1 in order to produce the different species4 ,but the selecting principle or force1 which in artificial selection is represented by the conscious will of man acting for a definite purpose1 consists in natural selection of the unconscious struggle for existence acting without a definite plan4 ,what we mean by 8struggle for existence0 has already been explained in the seventh chapter4 ,it is the recognition of this exceedingly important identity which constitutes one of the greatest of ,darwin's merits4 ,but as this relation is very frequently imperfectly or falsely understood1 it is necessary to examine it now more closely1 and to illustrate by a few examples the operation of the struggle for life1 and the operation of natural selection by means of the struggle for life 7,gen4 ,morph4 ii4 #bca74 ,when considering the struggle for life1 we started from the fact that the number of germs which all animals and plants produce is infinitely greater than the number of individuals which actually come to life and remain alive for a longer or shorter time4 ,most organisms produce during life thousands or millions of germs1 from each of which1 under favourable circumstances1 a new individual might arise4 ,in most animals and plants these germs are eggs1 that is cells1 which for their development require sexual fructification4 ,but among the ,protista1 the lowest organisms1 which are neither animals nor plants1 and which propagate themselves only in a non-sexual manner1 the germ-cells1 or spores1 require no fructification4 ,now1 in all cases the number of unsexual1 as well as of sexual germs1 is out of all proportion to the number of actually living individuals of every species4 ,taken as a whole1 the number of living animals and plants on our earth remains always about the same4 ,the number of places in the economy of nature is limited1 and in most parts of the earth's surface these places are always approximately occupied4 ,certainly there occur everywhere and in every year fluctuations in the absolute and in the relative number of individuals of all species4 ,however1 taken as a whole1 these fluctuations are of little importance1 and it is broadly the fact that the total number of all individuals remains1 on an average1 almost constant4 ,there is a constant fluctuation1 which depends on the fact that in one year or another one or other series of animals and plants predominates1 and that every year the struggle for life somewhat alters their relations4 ,every single species of animals and plants would have densely peopled the whole earth's surface in a short time1 if it had not had to struggle against a number of enemies and hostile influences4 ,even ,linnus calculated that if an annual plant only produced two seeds 7and there is not one which produces so few71 it would have yielded in twenty years a million of individuals4 ,darwin has calculated of elephants1 which of all animals seem the slowest to increase1 that in seven hundred and fifty years the descendants of a single pair would amount to nineteen millions of individuals2 this is supposing that every elephant1 during its period of fertility 7from the #cjth to the #ijth year71 produced only three pairs of young ones1 and survived itself to its hundredth year4 ,in like manner the increase of the number of human beings--if calculated on the average proportion of births to population1 and no hindrances to the natural increase stood in the way--would be such as to double the total in twenty-five years4 ,in every century the total number of men would have increased sixteen-fold2 whereas we know that the total number of human beings increases but slowly1 and that the increase of population is very different in different countries4 ,while ,european tribes spread over the whole globe1 other tribes or species of men every year draw nearer to their complete extinction4 ,this is the case especially with the redskins of ,america1 and with the copper-coloured natives of ,australia4 ,even if these races were to propagate more abundantly than the white ,europeans1 yet they would sooner or later succumb to the latter in the struggle for life4 ,but of all human individuals1 as of all other organisms1 by far the majority perish at the earliest period of their lives4 ,of the immense quantity of germs which every species produce1 only very few actually succeed in developing1 and of these few it is again only a very small portion which attain to the age in which they can reproduce themselves 7compare p4 #afa74 ,from the disproportion between the immense excess of organic germs and the small number of chosen individuals which are actually able to continue in existence beside one another1 there follows of necessity that universal struggle for life1 that constant fight for existence1 that perpetual competition for the necessaries of life1 of which ,i gave a sketch in my seventh chapter4 ,it is this struggle for life which brings natural selection into play1 which in its turn is made use of by the interaction of the phenomena of ,inheritance and ,adaptation as a sifting agency1 and which thus causes a continual change in all organic forms4 ,in this struggle for acquiring the necessary conditions of existence1 those individuals will always overpower their rivals who possess any individual privilege1 any advantageous quality1 of which their fellow competitors are destitute4 ,it is true we are able only in the fewest cases 7in those animals and plants best known to us7 to form an approximate conception of the infinitely complicated interaction of the numerous circumstances1 all of which here come into combination4 ,only think how infinitely varied and complicated are the relations of every single human being to the rest of mankind1 and in general1 to the whole of the surrounding outer world4 ,but similar relations prevail also among all animals and plants which live together in one place4 ,all influence one another actively or passively4 ,every animal and every plant struggles directly with a number of enemies1 beasts of prey1 parasitic animals1 etc4 ,plants standing together struggle with one another for the space of ground requisite for their roots1 for the necessary amount of light1 air1 moisture1 etc4 ,in like-manner1 animals living together struggle with one another for their food1 dwelling-place1 etc4 ,in this most active and complicated struggle1 any personal superiority1 however small1 any individual advantage1 may possibly decide the issue in favour of the one possessing it4 ,this privileged individual remains the victor in the struggle1 and propagates itself1 while its fellow-competitors perish before they succeed in propagating themselves4 ,the personal advantage which gave it the victory is transmitted by inheritance to its descendants1 and by a further development may become so strongly marked as to cause us to consider the later generations as a new species4 ,the infinitely complicated correlations which exist between the organisms of every district1 and which must be looked upon as the real conditions of the struggle for life1 are mostly unknown to us1 and are very difficult to discover4 ,we have hitherto been able to trace them only to a certain point in individual cases1 as in the example given by ,darwin of the relations between cats and red clover in ,england4 ,the red clover 7,trifolium pratense71 which in ,england is among the best fodder for cattle1 requires the visit of humming-bees in order to attain the formation of seeds4 ,these insects1 while sucking the honey from the bottom of the flower1 bring the pollen in contact with the stigma1 and thus cause the fructification of the flower1 which never takes place without it4 ,darwin has shown by experiments1 that red clover which is not visited by humming-bees does not yield a single seed4 ,the number of bees is determined by the number of their enemies1 the most destructive of which are the field-mice4 ,the more the field-mice predominate1 the less the clover is fructified4 ,the number of field-mice1 again1 is dependent upon the number of their enemies1 principally cats4 ,hence in the neighbourhood of villages and towns1 where many cats are kept1 there are plenty of bees4 ,a great number of cats1 therefore1 is evidently of great advantage for the fructification of clover4 ,this example may be followed still further1 as has been done by ,carl ,vogt1 if we consider that cattle which feed on red clover are one of the most important foundations of the wealth of ,england4 ,englishmen preserve their bodily and mental powers chiefly by making excellent meat--roast beef and beefsteak--their principal food4 ,the ,english owe the superiority of their brains and minds over those of other nations in a great measure to their excellent meat4 ,but this is clearly indirectly dependent upon the cats1 which pursue the mice4 ,we may1 with ,huxley1 even trace the chain of causes to those old maids who cherish and keep cats1 and1 consequently1 are of the greatest importance to the fructification of the clover and to the prosperity of ,england4 ,from this example we can see that the further it is traced the wider is the circle of action and of correlation4 ,we can with certainty maintain that there exist a great number of such correlations in every plant and in every animal1 only we are not always able to point out and survey their concatenation as in the last instance4 ,another remarkable example of important correlations is the following1 given by ,darwin4 ,in ,paraguay1 there are no wild oxen and horses1 as in the neighbouring parts of ,south ,america1 both north and south of ,paraguay4 ,this surprising circumstance is explained simply by the fact that in that country a kind of small fly is very frequent1 and is in the habit of laying its eggs in the navel of newly-born calves and foals4 ,the newly-born animals die in consequence of this attack1 and the small deadly fly is therefore the cause of oxen and horses never becoming wild in that district4 ,supposing that this fly were destroyed by some insect-eating bird1 then these large mammals would grow wild in ,paraguay1 as well as in the neighbouring parts of ,south ,america2 and as they would eat a quantity of certain species of plants1 the whole flora1 and1 consequently again1 the whole fauna of the country would become changed4 ,it is hardly necessary to state1 that at the same time the whole economy1 and consequently the character1 of the human population would alter4 ,thus the prosperity1 nay1 even the existence of whole populations can be indirectly determined by a single small animal or vegetable form in itself extremely insignificant4 ,there are small coral islands whose human inhabitants live almost entirely upon the fruit of a species of palm4 ,the fructification of this palm is principally effected by insects1 which carry the pollen from the male to the female palm trees4 ,the existence of these useful insects is endangered by insect-eating birds1 which in their turn are pursued by birds of prey4 ,the birds of prey1 however1 often succumb to the attack of a small parasitical mite1 which develops itself in millions in their feathers4 ,this small1 dangerous parasite1 again1 may be killed by parasitical moulds4 ,moulds1 birds of prey1 and insects would in this case favour the prosperity of the palm1 and consequently of man2 birds1 mites1 and insect-eating birds would1 on the other hand1 endanger it4 ,interesting examples in relation to the change of correlations in the struggle for life are furnished also by those isolated oceanic islands1 uninhabited by man1 on which at different times goats and pigs have been placed by navigators4 ,these animals become wild1 and having no enemies1 they increase in number so excessively1 that the rest of the animal and vegetable population suffer in consequence1 and the island finally may become almost a waste1 because there is insufficient food for the large mammals which increase too numerously4 ,in some cases on an island thus overrun with goats and pigs1 other navigators have let loose a couple of dogs1 who enjoyed this superabundance of food1 and they again increased so numerously1 and made such havoc among the herds1 that after several years the dogs themselves lacked food1 and they also almost died out4 ,the equilibrium of species continually changes in this manner in nature's economy1 accordingly as one or another species increases at the expense of the rest4 ,in most cases the relations of different species of animals and plants to one another are much too complicated for us to be able to follow them1 and ,i leave it to the reader to picture to himself what an infinitely complicated machinery is at work in every part of the world in consequence of this struggle4 ,the impulses which started the struggle1 and which altered and modified it in different places1 are in the end seen to be the impulses of self-preservation--in fact1 the instinct leading individuals to preserve themselves 7the instinct of obtaining food71 and the instinct leading them to preserve the species 7instinct of propagation74 ,it is these two fundamental instincts of organic self-preservation of which ,schiller1 the idealist 7not ,goethe1 the realist67 says3 8,meanwhile1 until philosophy ,sustains the structure of the world1 ,her workings will be carried on ,by hunger and by love40#d ,it is these two powerful fundamental instincts which1 by their varying activity1 produce such extraordinary differences in species through the struggle for life4 ,they are the foundations of the phenomena of ,inheritance and ,adaptation4 ,we have1 in fact1 traced all phenomena of ,inheritance to propagation1 all phenomena of ,adaptation to nutrition1 as the two wider classes of material phenomena to which they belong4 ,the struggle for life in natural selection acts with as much selective power as does the will of man in artificial selection4 ,the latter1 however1 acts according to a plan and consciously1 the former without a plan and unconsciously4 ,this important difference between artificial and natural selection deserves especial consideration4 ,for we learn by it to understand how arrangements serving a purpose can be produced by mechanical causes acting without an object1 as well as by causes acting for an object4 ,the products of natural selection are arranged even more for a purpose than the artificial products of man1 and yet they owe their existence not to a creative power acting for a definite purpose1 but to a mechanical relation acting unconsciously and without a plan4 ,if we had not thoroughly considered the interaction of ,inheritance and ,adaptation under the influence of the struggle for life1 we should not at first be inclined to expect such results from this natural process of selection as are1 in fact1 furnished by it4 ,it may therefore be appropriate here to mention a few especially striking examples of the activity of natural selection4 ,let us first take ,darwin's homochromic selection of animals1 or the so-called 8sympathetic selection of colours10 into consideration4 ,earlier naturalists have remarked that numerous animals are of nearly the same colour as their dwelling-place1 or the surroundings in which they permanently live4 ,thus1 for example1 plant-lice and many other insects living on leaves are of a green colour4 ,the inhabitants of the deserts1 the jerboa1 or leaping mice1 foxes of the desert1 gazelles1 lions1 etc41 are mostly of a yellow or yellowish-brown colour1 like the sand of the desert4 ,the polar animals1 which live on the ice and snow1 are white or grey1 like ice and snow4 ,many of these animals change their colour in summer and winter4 ,in summer1 when the snow partly vanishes1 the fur of these polar creatures becomes brownish-grey or blackish1 like the naked earth1 while in winter it again becomes white4 ,butterflies and insects which hover round the gay and bright flowers are like them in colour4 ,now1 ,darwin explains this surprising circumstance quite simply by the fact that such colours as agree with the colour of the habitation are of the greatest use to the animals concerned4 ,if these animals are animals of prey1 they will be able to approach the object of their pursuit more safely and with less likelihood of observation1 and1 in like manner1 those animals which are pursued will be able to escape more easily1 if their colour is as little different as possible from that of their surroundings4 ,if therefore originally an animal species varied so as to present cases of all colours1 those individuals whose colour most resembled the surroundings must have been most favoured in the struggle for life4 ,they remained more unobserved1 maintained and propagated themselves1 while those individuals or varieties differently coloured died out4 ,i have tried to explain1 by the same sympathetic selection of colour1 the wonderful fact that the majority of pelagic animals--that is1 of those which live on the surface of the open sea--are bluish1 or completely colourless and transparent1 like glass and water itself4 ,such colourless1 glassy animals are met with in the most different classes4 ,to them belong1 among fish1 the ,helmicthyid1 through whose crystalline bodies the words of a book can be read2 among the molluscs1 the finned snails 7,heteropods7 and sea-butterflies1 or whales-food 7,pteropods72 among worms1 the ,salp1 ,alciope1 and ,sagitta2 further1 a great number of pelagic crabs 7,crustacea71 and the greater part of the ,medus ,umbrella-jellies1 7,discomedus72 ,comb-jellies1 7,ctenophora74 ,all of these pelagic animals1 which float on the surface of the ocean1 are transparent and colourless1 like glass and like the water itself1 while their nearest kin live at the bottom of the ocean1 and are coloured and opaque like the inhabitants of the land4 ,this remarkable fact1 like the sympathetic colouring of the inhabitants of the earth1 can be explained by natural selection4 ,among the ancestors of the pelagic glass-like animals which showed a different degree of colourlessness and transparency1 those that were the most colourless and transparent must have been most favoured in the active struggle for life which takes place on the surface of the ocean4 ,they were enabled to approach their prey the most easily unobserved1 and were themselves least observed by their enemies4 ,hence they could preserve and propagate themselves more easily than their more coloured and opaque relatives2 and finally1 by accumulative adaptation and transmission by inheritance1 through natural selection1 in the course of many generations their bodies would attain that degree of crystal-like transparency and colourlessness which we at present admire in them4 7,gen4 ,morph4 ii4 #bdb47 ,no less interesting and instructive than homochromic selection is that species of natural selection which ,darwin calls 8sexual selection10 which explains the origin of the so-called 8secondary sexual characters40 ,we have already mentioned these subordinate sexual characteristics1 so instructive in many respects4 ,they comprise those peculiarities of animals and plants which belong only to one of the two sexes1 and which do not stand in any direct relation to the act of propagation itself 7compare above1 p4 #bdd74 ,such secondary sexual characters occur in great variety among animals4 ,we all know how striking is the difference of the two sexes in size and colour in many birds and butterflies4 ,the male sex is generally the larger and more beautiful4 ,it often possesses special decorations or weapons2 as for example1 the spur and comb of the cock1 the antlers of the stag and deer1 etc4 ,all these peculiarities of the two sexes have nothing directly to do with propagation itself1 which is effected by the 8primary sexual characters10 or actual sexual organs4 ,now1 the origin of these remarkable 8secondary sexual characters0 is explained by ,darwin simply by a choice or selection which takes place in the propagation of animals4 ,in most animals the number of individuals of both sexes is unequal2 either the number of the female or the number of the male individuals is greater1 and1 as a rule1 when the season of propagation approaches1 a struggle takes place between the rivals for the possession of the animals of the other sex4 ,it is well known with what vigour and vehemence this struggle is fought out among the higher animals--among mammals and birds--especially among those of polygamous habits4 ,among gallinaceous birds1 where for one cock there are several hens1 a severe struggle takes place between the competing cocks for as large a harem as possible4 ,the same is the case with many ruminating animals4 ,among stags and deer1 for instance1 at the period of rut1 deadly struggles take place between the males for the possession of the females4 ,the secondary sexual character which here distinguishes the males--the antlers of stags and deer--not possessed by the female1 is1 according to ,darwin1 the consequence of that struggle4 ,here the motive and cause determining the struggle is not1 as in the case of the struggle for individual existence1 self-preservation1 but the preservation of the species--propagation4 ,there are numerous passive weapons of defence1 as well as active weapons for attack4 ,the lion's mane1 not possessed by the female1 is evidently such a weapon of defence2 it is an excellent means of protection against the bites which the male lions try to inflict on each other's necks when fighting for the females2 consequently those males with the strongest manes have the greatest advantage in the sexual struggle4 ,the dewlap of the ox and the comb of the cock are similar defensive weapons4 ,active weapons of attack1 on the other hand1 are the antlers of the stag1 the tusks of the boar1 the spur of the cock1 and the hugely developed pair of jaws in the male stag-beetle2 all are instruments employed by the males in the struggle for the females1 for annihilating or chasing away their rivals4 ,in the cases just mentioned1 it is the bodily 8struggle to the death0 which determines the origin of the secondary sexual characters4 ,but1 besides these mortal struggles1 there are other important competitions in sexual selection1 which no less influence the structure of the rivals4 ,these consist principally in the fact that the courting sex tries to please the other by external finery1 by beauty of form1 or by a melodious voice4 ,darwin thinks that the beautiful voices of singing birds have principally originated in this way4 ,many male birds carry on a regular musical contest when they contend for the possession of the females4 ,it is known of several singing birds1 that in the breeding season the males assemble in numbers round the females1 and let their songs resound before them1 and that then the females choose the singers who best please them for their mates4 ,among other songsters1 individual males pour out their songs in the loneliness of the forest in order to attract the females1 and the latter follow the most attractive calls4 ,a similar musical contest1 though certainly less melodious1 takes place among crickets and grasshoppers4 ,the male cricket has on its belly two instruments like drums1 and produces with these the sharp chirping notes which the ancient ,greeks curiously enough thought beautiful music4 ,male grasshoppers1 partly by using their hind-legs like the bow of a violin against their wing coverings1 and partly by rubbing their wing coverings together1 bring out tones which are1 indeed1 not melodious to us1 but which please the female grasshoppers so much that they choose the male who fiddles the best4 ,among other insects and birds it is not song or1 in fact1 any musical accomplishment1 but finery or beauty of the one sex which attracts the other4 ,thus we find that1 among most gallinaceous birds1 the cocks are distinguished by combs on their heads1 or by a beautiful tail1 which they can spread out like a fan2 as for example1 in the case of the peacock and turkey-cock4 ,the magnificent tail of the bird of paradise is also an exclusive ornament of the male sex4 ,in like manner1 among very many other birds and very many insects1 principally among butterflies1 the males are distinguished from the females by special colours or other decorations4 ,these are evidently the results of sexual selection4 ,as the females do not possess these attractions and decorations1 we must come to the conclusion that they have been acquired by degrees by the males in the competition for the females1 which takes its origin in the selective discrimination of the females4 ,we may easily picture to ourselves1 in detail1 the application of this interesting conclusion to the human community4 ,here1 also1 the same causes have evidently influenced the development of the secondary sexual characters4 ,the characteristics distinguishing the man1 as well as those distinguishing the woman1 owe their origin1 certainly for the most part1 to the sexual selection of the other sex4 ,in antiquity and in the ,middle ,ages1 especially in the romantic age of chivalry1 it was the bodily struggles to the death--the tournaments and duels--which determined the choice of the bride2 the strongest carried home the bride4 ,in more recent times1 however1 in our so-called 8polished0 or 8highly civilized0 society1 competing rivals prefer to contend indirectly by means of musical accomplishments1 instrumental performances and song1 by bodily charms1 natural beauty1 or artificial decoration4 ,but by far the most important of these different forms of sexual selection in man is that form which is the most exalted1 namely1 psychical selection1 in which the mental excellencies of the one sex influence and determine the choice of the other4 ,the most highly intellectually developed types of men have1 throughout generations1 when choosing a partner in life1 been guided by her excellencies of soul1 and have thus transmitted these qualities to their posterity1 and they have in this way1 more than by any other thing1 helped to create the deep chasm which at present separates civilized men from the rudest savages1 and from our common animal ancestors4 ,in fact1 both the part played by the prevalence of a higher standard of sexual selection1 and the part played by the due division of labour between the two sexes1 is exceedingly important1 and ,i believe that here we must seek for the most powerful causes which have determined the origin and the historical development of the races of man4 7,gen4 ,morph4 ii4 #bdg47 ,as ,darwin1 in his exceedingly interesting work1 published in #ahga1 on 8,the ,origin of ,man and ,sexual ,selection107#dh7 has discussed this subject in the most masterly manner1 and has illustrated it by most remarkable examples1 ,i refer for further detail to that work4 ,but now let us look again at two extremely important organic laws which can be explained by the theory of selection1 as necessary consequences of natural selection in the struggle for existence4 ,i mean the law of division of labour1 or differentiation1 and the law of progress1 or perfecting4 ,when the phenomena due to these two laws first became known1 through observation of the historical development1 the individual development1 and the comparative anatomy of animals and plants1 naturalists were inclined to trace them to a direct creative influence4 ,it was supposed to be part of the plan of the ,creator1 acting for a definite purpose1 in the course of time to develop the forms of animals and plants more and more variously1 and to bring them more and more to a state of perfection4 ,we shall evidently make a great advance in the knowledge of nature if we reject this teleological and anthropomorphic conception1 and if we can prove the two laws of ,division of ,labour and ,perfecting to be the necessary consequences of natural selection in the struggle for life4 ,the first great law which follows directly and of necessity from natural selection1 is that of separation1 or differentiation1 which is frequently called division of labour1 or polymorphism1 and which ,darwin speaks of as divergence of character4 7,gen4 ,morph4 ii4 #bdi47 ,we understand by it the general tendency of all organic individuals to develop themselves more and more diversely1 and to deviate from the common primary type4 ,the cause of this general inclination towards differentiation and the formation of heterogeneous forms from homogeneous beginnings is1 according to ,darwin1 simply to be traced to the circumstance that the struggle for life between every two organisms rages all the more fiercely the nearer the relation in which they stand to one another1 or the more nearly alike they are4 ,this is an exceedingly important1 and in reality an exceedingly simple relation1 but it is usually not duly considered4 ,it must be obvious to every one1 that in a field of a certain size1 beside the corn-plants which have been sown1 a great number of weeds can exist1 and1 moreover1 in places which could not have been occupied by corn-plants4 ,the more dry and sterile places of the ground1 in which no corn-plant would thrive1 may still furnish sustenance to weeds of different kinds2 and such species and individuals of weeds will more readily be able to exist in such conditions1 in proportion as they are suited to adapt themselves to the different parts of the ground4 ,it is the same with animals4 ,it is evident that a much greater number of animal individuals can live together in one and the same limited district1 if they are of various and different natures1 than if they are all alike4 ,there are trees 7for example1 the oak7 on which a couple of hundred of different species of insects live together4 ,some feed on the fruits of the tree1 others on the leaves1 others again on the bark1 the root1 etc4 ,it would be quite impossible for an equal number of individuals to live on this tree if all were of one species2 if1 for example1 all fed on the bark1 or only upon the leaves4 ,exactly the same is the case in human society4 ,in one and the same small town1 only a certain number of workmen can exist1 even when they follow different occupations4 ,the division of labour1 which is of the greatest use to the whole community1 as well as to the individual workman1 is a direct consequence of the struggle for life1 of natural selection2 for this struggle can be sustained more easily the more the activities1 and hence1 also1 the forms of the different individuals deviate from one another4 ,the different function naturally produces its reaction in changing the form1 and the physiological division of labour necessarily determines the morphological differentiation1 that is1 the 8divergence of character407#cg7 ,now1 ,i beg the reader again to remember that all species of animals and plants are variable1 and possess the capability of adapting themselves to different places or to local relations4 ,the varieties or races of each species1 according to the laws of adaptation1 deviate all the more from the original primary species1 the greater the difference of the new conditions to which they adapt themselves4 ,if we imagine these varieties--which have proceeded from a common primary form--to be disposed in the shape of a branching1 radiating bunch1 then those varieties will be best able to exist side by side and propagate which are most distant from one another1 which stand at the ends of the series1 or at the opposite sides of the bunch4 ,those forms1 on the other hand1 occupying a middle position--presenting a state of transition--have the most difficult position in the struggle for life4 ,the necessaries of life differ most in the two extremes1 in the varieties most distant from one another1 and consequently these will get into the least serious conflict with one another in the general struggle for life4 ,but the intermediate forms1 which have deviated less from the original primary form1 require nearly the same necessaries of life as the original form1 and therefore1 in competing for them1 they will have to struggle most with1 and be most seriously threatened by1 its members4 ,consequently1 when numerous varieties of a species live side by side on the same spot of the earth1 the extremes1 or those forms deviating most from one another1 can much more easily continue to exist beside one another than the intermediate forms which have to struggle with each of the different extremes4 ,the intermediate forms will not be able to resist1 for any length of time1 the hostile influences which the extreme forms victoriously overcome4 ,these alone maintain and propagate themselves1 and at length cease to be any longer connected with the original primary species through intermediate forms of transition4 ,thus arise 8good species0 out of varieties4 ,thus1 then1 the struggle for life necessarily favours the general divergence of organic forms1 that is1 the constant tendency of organisms to form new species4 ,this fact does not rest upon any mystic quality1 or upon an unknown formative tendency1 but upon the interaction of ,inheritance and ,adaptation in the struggle for life4 ,as the intermediate forms1 that is1 the individuals in a state of transition1 of the varieties of every species die out and become extinct1 the process of divergence constantly goes further1 and from the extremes forms develop which we distinguish as new species4 ,although all naturalists have been obliged to acknowledge the variability and mutability of all species of animals and plants1 yet most of them have hitherto denied that the modification or transformation of the organic form surpasses the original limit of the characters of the species4 ,our opponents cling to the proposition--8,however far a species may exhibit deviations from its usual form in a collection of varieties1 yet the varieties of it are never so distinct from one another as two really good species40 ,this assertion1 which ,darwin's opponents usually place at the head of their arguments1 is utterly untenable and unfounded4 ,this will become quite clear as soon as we critically compare the various attempts to define the idea of species4 ,no naturalist can answer the question as to what is in reality a 8genuine or good species0 78bona species072 yet every systematic naturalist uses this expression every day1 and whole libraries have been written on the question as to whether this or that observed form is a species or a variety1 whether it is a really good or a bad species4 ,the most general answer to this question used to be the following3 8,to one species belong all those individuals which agree in all essential characteristics4 ,essential characteristics of species are those which remain permanent or constant1 and never become modified or vary40 ,but as soon as a case occurred in which the characteristic--which had hitherto been considered essential--did become modified1 then it was said1 8,this characteristic is not essential to the species1 for essential characteristics never vary40 ,those who argued thus evidently moved in a circle1 and the navet with which this circular method of defining species is laid down in thousands of books as an unassailable truth1 and is still constantly repeated1 is truly astonishing4 ,all other attempts which have been made to arrive at a definite and logical determination of the idea of organic 8species0 have1 like the last1 been utterly futile1 and led to no results4 ,considering the nature of the case1 it cannot be otherwise4 ,the idea of species is just as truly a relative one and not absolute1 as is the idea of variety1 genus1 family1 order1 class1 etc4 ,i have proved this in detail in the criticism of the idea of species in my 8,general ,morphology0 7,gen4 ,morph4 ii4 #cbc-cfd74 ,i will waste no more time on this unsatisfactory discussion1 and now only add a few words about the relation of species to hybridism4 ,formerly it was regarded as a dogma1 that two good species could never produce hybrids which could reproduce themselves as such4 ,those who thus dogmatized almost always appealed to the hybrids of a horse and donkey1 the mule and the hinny1 which1 truly enough1 are seldom able to reproduce themselves4 ,but the truth is that such unfruitful hybrids are rare examples1 and in the majority of cases hybrids of two totally different species are fruitful and able to reproduce themselves4 ,they can almost always fruitfully mix with one or other of the parent species1 and sometimes also among themselves2 and in this way completely new forms can originate according to the laws of 8mixed transmission by inheritance40 ,thus1 in fact1 hybridism is a source of the origin of new species1 distinct from the source we have hitherto considered--natural selection4 ,i have already spoken occasionally of these hybrid species 7species hybrid71 especially of the hare-rabbit 7,lepus ,darwinii71 which has arisen from the crossing of a male hare and a female rabbit2 the goat-sheep 7,capra ovina71 which has arisen from the pairing of a he-goat and ewe2 also the different species of thistles 7,cirsium71 brambles 7,rubus71 etc4 ,it is possible that many wild species have originated in this way1 as even ,linnus assumed4 ,at all events1 these hybrid species1 which can maintain and propagate themselves as well as pure species1 prove that hybridism cannot serve in any way to give an absolute definition to the idea of species4 ,i have already mentioned 7p4 #dg7 that the many vain attempts to define the idea of species theoretically have nothing whatever to do with the practical distinction of species4 ,the extensive practical application of the idea of species1 as it is carried out in systematic zoology and botany1 is very instructive as furnishing an example of human folly4 ,hitherto1 by far the majority of zoologists and botanists1 in distinguishing and describing the different forms of animals and plants1 have endeavoured1 above all things1 to distinguish accurately kindred forms as so many 8good species40 ,however1 it has been found scarcely possible1 in any group1 to make an accurate and consistent distinction of such 8genuine or good species40 ,there are no two zoologists1 no two botanists1 who agree in all cases as to which of the nearly related forms of a genus are good species1 and which are not4 ,all authors have different views about them4 ,in the genus ,hieracium1 for example1 one of the commonest genera of ,european plants1 no less than #cjj species have been distinguished in ,germany alone4 ,the botanist ,fries1 however1 only admits #ajf1 ,koch only #eb1 as 8good species10 and others accept scarcely #bj4 ,the differences in the species of brambles 7,rubus7 are equally great4 ,where one botanist makes more than a hundred species1 a second admits only about one half of that number1 a third only five or six1 or even fewer species4 ,the birds of ,germany have long been very accurately known4 ,bechstein1 in his careful 8,natural ,history of ,german ,birds10 has distinguished #cfg species1 ,l4 ,reichenbach #cgi1 ,meyer and ,wolff #djf1 and ,brehm1 a clergyman learned in ornithology1 distinguishes even more than #ijj different species4 ,thus we see that here1 and1 in fact1 in every other domain of systematic zoology and botany1 the most arbitrary proceedings prevail1 and1 from the nature of the case1 must prevail4 ,for it is quite impossible accurately to distinguish varieties and races from so-called 8good species40 ,varieties are commencing species4 ,the variability or adaptability of species1 under the influence of the struggle for life1 necessitates the continual and progressive separation or differentiation of varieties1 and the perpetual delimitation of new forms4 ,whenever these are maintained throughout a number of generations by inheritance1 whilst the intermediate forms die out1 they form independent 8new species40 ,the origin of new species by division of labour1 or separation1 divergence1 or differentiation of varieties1 is therefore a necessary consequence of natural selection47#cg7 ,the same kind of interest attaches to a second great law which we deduce from natural selection1 and which is1 indeed1 closely connected with the law of ,divergence1 but in no way identical with it2 namely1 the law of ,progress 7progressus71 or ,perfecting 7teleosis74 7,gen4 ,morph4 ii4 #beg47 ,this great and important law1 like the law of differentiation1 had long been empirically established by palontological experience1 before ,darwin's ,theory of ,selection gave us the key to the explanation of its cause4 ,the most distinguished palontologists have pointed out the law of progress as the most general result of their investigations of fossil organisms4 ,this has been specially done by ,bronn1 whose investigations on the laws of construction7#ah7 and the laws of the development7#ai7 of organisms1 although little heeded1 are excellent1 and deserve most careful consideration4 ,the general results of the law of differentiation and the law of progress1 at which ,bronn arrived by a purely mechanical hypothesis1 and by exceedingly accurate1 laborious1 and careful investigations1 are brilliant confirmations of the truth of these two great laws which we deduce as necessary inferences from the theory of selection4 ,the law of progress or of perfecting establishes the exceedingly important fact1 on the ground of palontological experience1 that in successive periods of this earth's history1 a continual increase in the perfection of organic formations has taken place4 ,since that inconceivably remote period in which life on our planet began with the spontaneous generation of ,monera1 organisms of all groups1 both collectively as well as individually1 have continually become more perfectly and highly developed4 ,the steadily increasing variety of living forms has always been accompanied by progress in organization4 ,the lower the strata of the earth in which the remains of extinct animals and plants lie buried1 that is1 the older the strata are1 the more simple and imperfect are the forms which they contain4 ,this applies to organisms collectively1 as well as to every single large or small group of them1 setting aside1 of course1 those exceptions which are due to the process of degeneration1 which we shall discuss hereafter4 ,as a confirmation of this law ,i shall mention only the most important of all animal groups1 the tribe of vertebrate animals4 ,the oldest fossil remains of vertebrate animals known to us belong to the lowest class1 that of ,fishes4 ,upon these there followed later more perfect ,amphibious animals1 then ,reptiles1 and lastly1 at a much later period1 the most highly organized classes of vertebrate animals1 ,birds and ,mammals4 ,of the latter only the lowest and most imperfect forms1 without placenta1 appeared at first1 such as are the pouched animals 7,marsupials71 and afterwards1 at a much later period1 the more perfect mammals1 with placenta4 ,of these1 also1 at first only the lower kinds appeared1 the higher forms later2 and not until the late tertiary period did man gradually develop out of these last4 ,if we follow the historical development of the vegetable kingdom we shall find the same law operative there4 ,of plants there existed at first only the lowest and most imperfect classes1 the ,alg or tangles4 ,later there followed the group of ,ferns or ,filicin 7ferns1 pole-reeds1 scale-plants1 etc474 ,but as yet there existed no flowering plants1 or ,phanerogama4 ,these originated later with the ,gymnosperms 7firs and cycads71 whose whole structure stands far below that of the other flowering plants 7,angiosperms71 and forms the transition from the group of fern-like plants to the ,angiosperms4 ,these latter developed at a still later date1 and among them there were at first only flowering plants without corolla 7,monocotyledons and ,monochlamyds72 only later were there flowering plants with a corolla 7,dichlamyds74 ,finally1 again1 among these the lower polypetalous plants preceded the higher gamopetalous plants4 ,the whole series thus constitutes an irrefutable proof of the great law of progressive development4 ,now1 if we ask what is the cause of this fact1 we again1 just as in the case of differentiation1 come back to natural selection in the struggle for life4 ,if once more we consider the whole process of natural selection1 how it operates through the complicated interaction of the different laws of ,inheritance and ,adaptation1 we shall recognize not only divergence of character1 but also the perfecting of structure to be the direct and necessary result of it4 ,we can trace the same thing in the history of the human race4 ,here1 too1 it is natural and necessary that the progressive division of labour constantly furthers mankind1 and urges every individual branch of human activity into new discoveries and improvements4 ,this progress itself universally depends on differentiation1 and is consequently1 like it1 a direct result of natural selection in the struggle for life4 ,,chapter ,,xii4 ,,laws ,,of ,,development ,,of ,,organic ,,tribes ,,and ,,of ,,individuals4 ,,phylogeny ,,and ,,ontogeny4 ,laws of the ,development of ,mankind3 ,differentiation and ,perfecting4--,mechanical ,cause of these two ,fundamental ,laws4--,progress without ,differentiation1 and ,differentiation without ,progress4--,origin of ,rudimentary ,organs by ,non-use and ,discontinuance of ,habit4--,ontogenesis1 or ,individual ,development of ,organisms4--,its ,general ,importance4--,ontogeny1 or the ,individual ,history of ,development of ,vertebrate ,animals1 including ,man4--,the ,fructification of the ,egg4--,formation of the three ,germ ,layers4--,history of the ,development of the ,central ,nervous ,system1 of the ,extremities1 of the ,branchial ,arches1 and of the ,tail of ,vertebrate ,animals4--,causal ,connection and ,parallelism of ,ontogenesis and ,phylogenesis1 that is of the ,development of ,individuals and ,tribes4--,causal ,connection of the ,parallelism of ,phylogenesis and of ,systematic ,development4--,parallelism of the three ,organic ,series of ,development4 ,if man wishes to understand his position in nature1 and to comprehend as natural facts his relations to the phenomena of the world cognisable by him1 it is absolutely necessary that he should compare human with extra-human phenomena1 and1 above all1 with animal phenomena4 ,we have already seen that the exceedingly important physiological laws of ,inheritance and ,adaptation apply to the human organism in the same manner as to the animal and vegetable kingdoms1 and in both cases interact with one another4 ,consequently1 natural selection in the struggle for life acts so as to transform human society1 just as it modifies animals and plants1 and in both cases constantly produces new forms4 ,the comparison of the phenomena of human and animal transformation is especially interesting in connection with the laws of divergence and progress1 the two fundamental laws which1 at the end of the last chapter1 we proved to be direct and necessary consequences of natural selection in the struggle for life4 ,a comparative survey of the history of nations1 or what is called 8universal history10 will readily yield to us1 as the first and most general result1 evidence of a continually increasing variety of human activities1 both in the life of individuals and in that of families and states4 ,this differentiation or separation1 this constantly increasing divergence of human character and the form of human life1 is caused by the ever advancing and more complete division of labour among individuals4 ,while the most ancient and lowest stages of human civilization show us throughout the same rude and simple conditions1 we see in every succeeding period of history1 among different nations1 a greater variety of customs1 practices1 and institutions4 ,the increasing division of labour necessitates an increasing variety of forms corresponding to it4 ,this is expressed even in the formation of the human face4 ,among the lowest tribes of nations1 most of the individuals resemble one another so much that ,european travellers often cannot distinguish them at all4 ,with increasing civilization the physiognomy of individuals becomes differentiated1 and finally1 among the most highly civilized nations1 the ,english and ,germans1 the divergence in the characters of the face is so great that we very rarely mistake one face for another4 ,the second great fundamental law which is obvious in the history of nations is the great law of progress or perfecting4 ,taken as a whole1 the history of man is the history of his progressive development4 ,it is true that everywhere and at all times we may notice individual retrogressions1 or observe that crooked roads towards progress have been taken1 which lead only towards one-sided and external perfecting1 and thus deviate more and more from the higher goal of internal and enduring perfecting4 ,however1 on the whole1 the movement of development of all mankind is and remains a progressive one1 inasmuch as man continually removes himself further from his ape-like ancestors1 and continually approaches nearer to his own ideal4 ,now1 if we wish to know what causes actually determine these two great laws of development in man1 namely1 the law of divergence and the law of progress1 we must compare them with the corresponding laws of development in animals1 and on a close examination we shall inevitably come to the conclusion that the phenomena1 as well as their causes1 are exactly the same in the two cases4 ,the course of development in man1 just as in that of animals1 being directed by the two fundamental laws of differentiation and perfecting1 is determined solely by purely mechanical causes1 and is solely the necessary consequence of natural selection in the struggle for life4 ,perhaps in the preceding discussion the question has presented itself to some--8,are not these two laws identical8 ,is not progress in all cases necessarily connected with divergence80 ,this question has often been answered in the affirmative1 and ,carl ,ernst ,br1 for example1 one of the greatest investigators in the domain of the history of development1 has set forth the following proposition as one of the principal laws in the ontogenesis of the animal body3--8,the degree of development 7or perfecting7 depends on the stage of separation 7or differentiation7 of the parts407#bj7 ,correct as this proposition may be on the whole1 yet it is not universally true4 ,in many individual cases it can be proved that divergence and progress by no means always coincide4 ,every progress is not a differentiation1 and every differentiation is not a progress4 ,naturalists1 guided by purely anatomical considerations1 had already set forth the law relating to progress in organization1 that the perfecting of an organism certainly depends1 for the most part1 upon the division of labour among the individual organs and parts of the body1 but that there are also other organic transformations which determine a progress in organization4 ,one1 in particular1 which has been generally recognized1 is the numerical diminution of identical parts4 ,if1 for example1 we compare the lower articulated animals of the crustacean group1 which possess numerous pairs of legs1 with spiders which never have more than four pairs of legs1 and with insects which always possess only three pairs of legs1 we find this law1 for which a great number of examples could be adduced1 confirmed4 ,the numerical diminution of pairs of legs is a progress in the organization of articulated animals4 ,in like manner the numerical diminution of corresponding vertebral joints in the trunk of vertebrate animals is a progress in their organization4 ,fishes and amphibious animals with a very large number of identical vertebral joints are1 for this very reason1 less perfect and lower than birds and mammals1 in which the vertebral joints1 as a whole1 are not only very much more differentiated1 but in which the number of corresponding vertebr is also much smaller4 ,further1 according to the same law of numerical diminution1 flowers with numerous stamens are more imperfect than the flowers of kindred plants with a smaller number of stamens1 etc4 ,if therefore originally a great number of homogeneous parts exist in an organic body1 and if1 in the course of very many generations1 this number be gradually decreased1 this transformation will be an example of perfecting4 ,another law of progress1 which is quite independent of differentiation1 nay1 even appears to a certain extent opposed to it1 is the law of centralization4 ,in general the whole organism is the more perfect the more it is organized as a unit1 the more the parts are subordinate to the whole1 and the more the functions and their organs are centralized4 ,thus1 for example1 the system of blood-vessels is most perfect where a centralized heart exists4 ,in like manner1 the dense mass of marrow which forms the spinal cord of vertebrate animals1 and the ventral cord of the higher articulated animals1 is more perfect than the decentralized chain of ganglia of the lower articulated animals1 and the scattered system of ganglia in the molluscs4 ,considering the difficulty of explaining these complicated laws of progress in detail1 ,i cannot here enter upon a closer discussion of them1 and must refer to ,bronn's excellent 8,morphologischen ,studien10 and to my 8,general ,morphology0 7,gen4 ,morph4 i4 #cgj1 #eej2 ii4 #beg-bff74 ,just as we have become acquainted with phenomena of progress1 quite independent of divergence1 so we shall1 on the other hand1 very often meet with divergencies which are not perfecting1 but which are rather the contrary1 that is retrogressions or degenerations4 ,it is easy to see that the changes which every species of animal and plant experiences cannot always be improvements4 ,but rather many phenomena of differentiation1 which are of direct advantage to the organism itself1 are yet1 in a wider sense1 detrimental1 inasmuch as they lessen its general capabilities4 ,frequently a relapse to simpler conditions of life takes place1 and by adaptation to them a divergence in a retrograde direction4 ,if1 for instance1 organisms which have hitherto lived independently accustom themselves to a parasitical life1 they thereby degenerate or retrograde4 ,such animals1 which hitherto had possessed a well-developed nervous system and quick organs of sense1 as well as the power of moving freely1 lose these when they accustom themselves to a parasitical mode of life2 they consequently retrograde more or less4 ,there the differentiation viewed by itself is a degeneration1 although it is advantageous to the parasitical organism4 ,in the struggle for life such an animal1 which has accustomed itself to live at the expense of others1 by retaining its eyes and apparatus of motion1 which are of no more use to it1 would only expend so much material uselessly2 and when it loses these organs1 then a great quantity of nourishment which was employed for the maintenance of these parts1 benefits other parts4 ,in the struggle for life between the different parasites1 therefore1 those which make least pretensions will have advantage over the others1 and this favours their degeneration4 ,just as this is found to be the case with the whole organism1 so it is also with the parts of the body of an individual organism4 ,a differentiation of parts1 which leads to a partial degeneration1 and finally even to the loss of individual organs1 is1 when looked at by itself1 a degeneration1 but yet may be advantageous to the organism in the struggle for life4 ,it is easier to fight when useless baggage is thrown aside4 ,hence we meet everywhere1 in the more highly-developed animal and vegetable bodies1 processes of divergence1 the essence of which is that they cause the degeneration1 and finally the loss1 of particular parts4 ,and at this point the most important and instructive of all the series of phenomena bearing upon the history of organisms presents itself to us1 namely1 that of rudimentary or degenerate organs4 ,it will be remembered that even in my first chapter ,i considered this exceedingly remarkable series of phenomena1 from a theoretical point of view1 as one of the most important and most striking proofs of the truth of the doctrine of descent4 ,we designated as rudimentary organs those parts of the body which are arranged for a definite purpose and yet are without function4 ,let me remind the reader of the eyes of those animals which live in the dark in caves and underground1 and which consequently never can use them4 ,in these animals we find real eyes hidden under the skin1 frequently developed exactly as are the eyes of animals which really see2 and yet these eyes never perform any function1 indeed cannot1 simply for the reason that they are covered by an opaque membrane1 and consequently no ray of light falls upon them 7compare above1 p4 #ac74 ,in the ancestors of these animals1 which lived in open daylight1 the eyes were well developed1 covered by a transparent horny capsule 7cornea71 and actually served the purpose of seeing4 ,but as the animals gradually accustomed themselves to an underground mode of life1 and withdrew from the daylight and no longer used their eyes1 these became degenerated4 ,very clear examples of rudimentary organs1 moreover1 are the wings of animals which cannot fly2 for example1 the wings of the running birds1 like the ostrich1 emeu1 cassowary1 etc41 the legs of which have become exceedingly developed4 ,these birds having lost the habit of flying1 have consequently lost the use of their wings2 however1 the wings are still there1 although in a crippled form4 ,we very frequently find such crippled wings in the class of insects1 most members of which can fly4 ,from reasons derived from comparative anatomy and other circumstances1 we can with certainty draw the inference that all insects now living 7all dragon-flies1 grasshoppers1 beetles1 bees1 bugs1 flies1 butterflies1 etc47 have originated from a single common parental form1 from a primary insect which possessed two well-developed pairs of wings1 and three pairs of legs4 ,yet there are very many insects in which either one or both pairs of wings have become more or less degenerated1 and many in which they have even completely disappeared4 ,for example1 in the whole order of flies1 or ,diptera1 the hinder pair of wings--in the bee-parasites1 or ,strepsiptera1 on the other hand1 the fore pair of wings--have become degenerated or entirely disappeared4 ,moreover1 in every order of insects we find individual genera1 or species1 in which the wings have more or less degenerated or disappeared4 ,the latter is the case especially in parasites4 ,the females have frequently no wings1 whereas the males have2 for instance1 in the case of glow-worms 7,lampyris71 ,strepsiptera1 etc4 ,this partial or complete degeneration of the wings of insects has evidently arisen from natural selection in the struggle for life4 ,for we find insects without wings living under circumstances where flying would be useless1 or even decidedly injurious to them4 ,if1 for example1 insects living on islands fly about much1 it may easily happen that when flying they are blown into the sea by the wind1 and if 7as is always the case7 the power of flying is differently developed in different individuals1 then those which fly badly have an advantage over those which fly well2 they are less easily blown into the sea1 and remain longer in life than the individuals of the same species which fly well4 ,in the course of many generations1 by the action of natural selection1 this circumstance must necessarily lead to a complete suppression of the wings4 ,if this conclusion had been arrived at on purely theoretical grounds1 we might be pleased to find its truth established by facts4 ,for upon isolated islands the proportion of wingless insects to those possessing wings is surprisingly large1 much larger than among the insects inhabiting continents4 ,thus1 for example1 according to ,wollaston1 of the #eej species of beetles which inhabit the island of ,madeira1 #bbj are wingless1 or possess such imperfect wings that they can no longer fly2 and of the #bi genera which belong to that island exclusively1 no less than #bc contain such species only4 ,it is evident that this remarkable circumstance does not need to be explained by the special wisdom of the ,creator1 but is sufficiently accounted for by natural selection1 because in this case the hereditary disuse of the wings1 the discontinuance of flying in the presence of dangerous winds1 has been very advantageous in the struggle for life4 ,in other wingless insects the want of wings has been advantageous for other reasons4 ,viewed by itself1 the loss of wings is a degeneration1 but in these special conditions of life it is advantageous to the organism in the struggle for life4 ,among other rudimentary organs ,i may here1 by way of example1 further mention the lungs of serpents and serpent-like lizards4 ,all vertebrate animals possessing lungs1 such as amphibious animals1 reptiles1 birds1 and mammals1 have a pair of lungs1 a right and a left one4 ,but in cases where the body is exceedingly thin and elongated1 as in serpents and serpent-like lizards1 there is no room for the one lung by the side of the other1 and it is an evident advantage to the mechanism of respiration if only one lung is developed4 ,a single large lung here accomplishes more than two small ones side by side would do2 and consequently1 in these animals1 we invariably find only the right or only the left lung fully developed4 ,the other is completely aborted1 although existing as a useless rudiment4 ,in like manner1 in all birds the right ovary is aborted and without function2 only the left one is developed1 and yields all the eggs4 ,i mentioned in the first chapter that man also possesses such useless and superfluous rudimentary organs1 and ,i specified as such the muscles which move the ears4 ,another of them is the rudiment of the tail which man possesses in his #c--e tail vertebr1 and which1 in the human embryo1 stands out prominently during the first two months of its development 7compare ,plates ,,ii4 and ,,iii474 ,it afterwards becomes completely hidden4 ,the rudimentary little tail of man is an irrefutable proof of the fact that he is descended from tailed ancestors4 ,in woman the tail is generally by one vertebra longer than in man4 ,there still exist rudimentary muscles in the human tail which formerly moved it4 ,another case of human rudimentary organs1 only belonging to the male1 and which obtains in like manner in all male mammals1 is furnished by the mammary glands on the breast1 which1 as a rule1 are active only in the female sex4 ,however1 cases of different mammals are known1 especially of men1 sheep1 and goats1 in which the mammary glands were fully developed in the male sex1 and yielded milk as food for their offspring4 ,i have already mentioned before 7p4 #ab7 that the rudimentary auricular muscles in man can still be employed to move their ears1 by some persons who have perseveringly practised them4 ,in fact1 rudimentary organs are frequently very differently developed in different individuals of the same species2 in some they are tolerably large1 in others very small4 ,this circumstance is very important for their explanation1 as is also the other circumstance that generally in embryos1 or in a very early period of life1 they are much larger and stronger in proportion to the rest of the body than they are in fully developed and fully grown organisms4 ,this can1 in particular1 be easily pointed out in the rudimentary sexual organs of plants 7stamens and pistil71 which ,i have already mentioned4 ,they are proportionately much larger in the young flower-bud than in the mature flower4 ,i have remarked 7p4 #ae7 that rudimentary or suppressed organs were the strongest supports of the monistic or mechanical conception of the universe4 ,if its opponents1 the dualists and teleologists1 understood the immense significance of rudimentary organs1 it would put them into a state of despair4 ,their ludicrous attempts to explain that rudimentary organs were given to organisms by the ,creator 8for the sake of symmetry10 or 8as a formal provision10 or 8in consideration of his general plan of creation10 sufficiently prove the utter impotence of their perverse conception of the universe4 ,i must here repeat that1 even if we knew absolutely nothing of the other phenomena of development1 we should be obliged to believe in the truth of the ,theory of ,descent1 solely on the ground of the existence of rudimentary organs4 ,not one of its opponents has been able to throw even a feeble glimmer of an acceptable explanation upon these exceedingly remarkable and important phenomena4 ,there is scarcely any highly developed animal or vegetable form which has not some rudimentary organs1 and in most cases it can be shown that they are the products of natural selection1 and that they have become suppressed by disuse4 ,it is the reverse of the process of formation in which new organs arise from adaptation to certain conditions of life1 and by the use of parts as yet incompletely developed4 ,it is true our opponents usually maintain that the origin of altogether new parts is completely inexplicable by the ,theory of ,descent4 ,however1 ,i distinctly assert that to those who possess a knowledge of comparative anatomy and physiology this matter does not present the slightest difficulty4 ,every one who is familiar with comparative anatomy and the history of development will find as little difficulty about the origin of completely new organs as about the utter disappearance of rudimentary organs4 ,the disappearance of the latter1 viewed by itself1 is the converse of the origin of the former4 ,both processes are particular phenomena of differentiation1 which1 like all others1 can be explained quite simply and mechanically by the action of natural selection in the struggle for life4 ,the infinitely important study of rudimentary organs and their origin1 the comparison of their palontological and embryological development1 now naturally leads us to the consideration of one of the most important and instructive of all biological phenomena1 namely1 the parallelism which the phenomena of progress and divergence present to us in three different series4 ,when1 in the last chapter1 we spoke of perfecting and division of labour1 we understood by those words progress and separation1 and those changes effected by them1 which in the long and slow course of the earth's history have led to a continual variation of the flora and fauna1 to the origin of new and to the disappearance of ancient species of animals and plants4 ,now1 if we follow the origin1 the development1 and the life of every single organic individual1 we meet with exactly the same phenomena of progress and differentiation4 ,the individual development1 or the ontogenesis of every single organism1 from the egg to the complete form is nothing but a growth attended by a series of diverging and progressive changes4 ,this applies equally to animals1 plants1 and protista4 ,if1 for example1 we consider the ontogeny of any mammal1 of man1 of an ape1 or of a pouched animal1 or if we follow the individual development of any other vertebrate animal of another class1 we everywhere find essentially the same phenomena4 ,every one of these animals develops itself originally out of a single cell1 the egg4 ,this cell increases by self-division1 and forms a number of cells1 and by the growth of this accumulation of cells1 by the divergent development of originally identical cells1 by the division of labour among them1 and by their perfecting1 there arises the perfect organism1 the complicated composition of which excites our admiration4 ,it seems to me here indispensable to draw attention more closely to those infinitely important and interesting processes which accompany ontogenesis1 or the individual development of organisms1 and especially to that of vertebrate animals1 man included4 ,i wish especially to recommend these exceedingly remarkable and instructive phenomena to the reader's most careful consideration1 first1 because they are among the strongest supports of the ,theory of ,descent1 and secondly1 because1 considering their immense general importance1 they have hitherto been properly considered only by a few privileged persons4 ,we cannot indeed but be astonished when we consider the deep ignorance which still prevails1 in the widest circles1 about the facts of the individual development of man and organisms in general4 ,these facts1 the universal importance of which cannot be estimated too highly1 were established1 in their most important outlines1 even more than a hundred years ago1 in #agei1 by the great ,german naturalist ,caspar ,friedriech ,wolff1 in his classical 8,theoria ,generationis40 ,but1 just as ,lamarck's ,theory of ,descent1 founded in #ahji1 lay dormant for half a century1 and was only awakened to new and imperishable life in #ahei1 by ,darwin1 in like manner ,wolff's ,theory of ,epigenesis remained unknown for nearly half a century2 and it was only after ,oken1 in #ahjf had published his history of the development of the intestinal tube1 and after ,meckel1 in #ahab1 had translated ,wolff's work 7written in ,latin7 on the same subject into ,german1 that ,wolff's theory of epigenesis became more generally known1 and formed the foundation of all subsequent investigations of the history of individual development4 ,the study of ontogenesis now received a great stimulus1 and soon there appeared the classical investigations of the two friends1 ,christian ,pander 7#ahag7 and ,carl ,ernst ,br 7#ahai74 ,br1 in his remarkable 8,entwickelungsgeschichte der ,thiere107#bj7 worked out the ontogeny of vertebrate animals in all its important facts4 ,he carried out a series of such excellent observations1 and illustrated them by such profound philosophical reflections1 that his work became the foundation for a thorough understanding of this important group of animals1 to which1 of course1 man also belongs4 ,the facts of embryology alone would be sufficient to solve the question of man's position in nature1 which is the highest of all problems4 ,look attentively at and compare the eight figures which are represented on the adjoining ,plates ,,ii4 and ,,iii41 and it will be seen that the philosophical importance of embryology cannot be too highly estimated4 ,we may well ask1 ,what do our so-called 8educated0 circles1 who think so much of the high civilization of the #aith century1 know of these most important biological facts1 of these indispensable foundations for understanding their own organism8 ,how much do our speculative philosophers and theologians know about them1 who fancy they can arrive at an understanding of the human organism by mere guesswork or divine inspiration8 ,what indeed do the majority of naturalists1 not excepting the majority of the so-called 8zoologists0 7including the entomologists671 know about them8 ,the answer to this question tells much to the shame of the persons above indicated1 and we must confess1 willingly or unwillingly1 that these invaluable facts of human ontogeny are1 even at the present day1 utterly unknown to most people1 or are in no way valued as they deserve to be4 ,it is in the face of such a condition of things as this that we see clearly upon what a wrong and one-sided road the much vaunted culture of the #aith century still moves4 ,ignorance and superstition are the foundations upon which most men construct their conception of their own organism and its relation to the totality of things2 and these palpable facts of the history of development1 which might throw the light of truth upon them1 are ignored4 ,it is true these facts are not calculated to excite approval among those who assume a thorough difference between man and the rest of nature1 and who will not acknowledge the animal origin of the human race4 ,that origin must be a very unpleasant truth to members of the ruling and privileged castes in those nations among which there exists an hereditary division of social classes1 in consequence of false ideas about the laws of inheritance4 ,it is well known that1 even in our day1 in many civilized countries the idea of hereditary grades of rank goes so far1 that1 for example1 the aristocracy imagine themselves to be of a nature totally different from that of ordinary citizens1 and nobles who commit a disgraceful offence are punished by being expelled from the caste of nobles1 and thrust down among the pariahs of 8vulgar citizens40 ,what are these nobles to think of the noble blood which flows in their privileged veins1 when they learn that all human embryos1 those of nobles as well as commoners1 during the first two months of development1 are scarcely distinguishable from the tailed embryos of dogs and other mammals8 ,as the object of these pages is solely to further the general knowledge of natural truths1 and to spread1 in wider circles1 a natural conception of the relations of man to the rest of nature1 ,i shall be justified if ,i do not pay any regard to the widely-spread prejudice in favour of an exceptional and privileged position for man in creation1 and simply give here the embryological facts from which the reader will be able to draw conclusions affirming the groundlessness of those prejudices4 ,i wish all the more to entreat him to reflect carefully upon these facts of ontogeny1 as it is my firm conviction that a general knowledge of them can only promote the intellectual advance1 and thereby the mental perfecting1 of the human race4 ,amidst all the infinitely rich and interesting material which lies before us in the ontogeny of vertebrate animals1 that is1 in the history of their individual development1 ,i shall here confine myself to showing some of those facts which are of the greatest importance to the ,theory of ,descent in general1 as well as in its special application to man4 ,man is at the beginning of his individual existence a simple egg1 a single little cell1 just the same as every animal organism which originates by sexual generation4 ,the human egg is essentially the same as that of all other mammals1 and cannot be distinguished from the egg of the higher mammals4 ,the egg represented in ,fig4 #e might be that of a man or an ape as well as of a dog1 a horse1 or any other mammal4 ,not only the form and structure1 but even the size of the egg in most mammals is the same as in man1 namely1 about the #abjth part of an inch in diameter1 so that the egg under favorable circumstances1 with the naked eye1 can just be perceived as a small speck4 ,the differences which really exist between the eggs of different mammals and that of man do not consist in the form1 but in the chemical mixture1 in the molecular composition of the albuminous combination of carbon1 of which the egg essentially consists4 ,these minute individual differences of all eggs1 which depend upon indirect or potential adaptation 7and especially upon the law of individual adaptation71 are indeed not directly perceptible to the exceedingly imperfect senses of man1 but are cognisable through indirect means1 as the primary causes of the difference of all individuals4 ,illustration3 ,,fig4 #e4--,the human egg a hundred times enlarged4 a4 ,the kernel speck1 or nucleolus 7the so-called germinal spot of the egg74 b4 ,kernel1 or nucleus 7the so-called germinal vesicle of the egg74 c4 ,cell-substance1 or protoplasm 7so-called yolk of the egg74 d4 ,cell-membrane 7the yolk-membrane of the egg2 in mammals1 on account of its transparency1 called zona pellucida74 ,the eggs of other mammals are of the same form4 ,the human egg is1 like that of all other mammals1 a small globular bladder1 which contains all the constituent parts of a simple organic cell 7,fig4 #e74 ,the most essential parts of it are the mucous cell-substance1 or the protoplasma 7c71 which in an egg is called the 8yolk10 and the cell-kernel1 or nucleus 7b71 surrounded by it1 which is here called by the special name of the 8germinal vesicle40 ,the latter is a delicate1 clear1 glassy globule of albumen1 of about #a-fjjth part of an inch in diameter1 and surrounds1 a still smaller1 sharply-marked1 rounded granule 7a71 the kernel-speck1 or the nucleolus of the cell 7in the egg it is called the 8germinal spot074 ,the outside of the globular egg-cell of a mammal is surrounded by a thick pellucid membrane1 the cell-membrane or yolk-membrane1 which here bears the special name of zona pellucida 7d74 ,the eggs of many lower animals 7for example of many ,medus7 differ from this in being naked cells1 as the outer covering1 or cell-membrane1 is wanting4 ,as soon as the egg 7ovulum7 of the mammal has attained its full maturity1 it leaves the ovary of the female1 in which it originates1 and passes into the oviduct1 and through this narrow passage into the wider pouch or womb 7uterus74 ,if1 meanwhile1 the egg is fructified by the male seed 7sperm71 it develops itself in this pouch into an embryo1 and does not leave it until perfectly developed and capable of coming into the world at birth as a young mammal4 ,the variations of form and transformations which the fructified egg must go through within the uterus before it assumes the form of the mammal are exceedingly remarkable1 and proceed from the beginning in man1 in precisely the same way as in the other mammals4 ,at first the fructified egg of the mammal acts as a single-celled organism1 which is about to propagate independently and increase itself2 for example1 an ,amba 7compare ,fig4 #b1 p4 #ahh74 ,in point of fact the simple egg-cell becomes two1 by the process of cell-division which ,i have previously described4 ,there arise from the single germinal spot 7the small kernel-speck of the original simple egg-cell7 two new kernel-specks1 and then in like manner1 out of the germinal vesicle 7the nucleus71 two new cell-kernels4 ,then1 and not until then1 does the globular protoplasma first separate itself by an equatorial furrow into two halves1 in such a manner that each half encloses one of the two kernels1 together with its kernel-speck4 ,thus the simple egg-cell1 within the original cellular membrane1 has become two naked cells1 each possessing its own kernel 7,fig4 #f74 ,illustration3 ,,fig4 #f4--;,first commencement of the development of a mammal's egg1 the so-called 8yolk-cleavage0 7propagation of the egg-cell by repeated self-division74 ,a4 ,the egg1 by the formation of the first furrow1 falls into two cells4 ,b4 ,these by division fall into four cells4 ,c4 ,these latter have fallen into eight cells4 ,d4 ,by continued division a globular mass of numerous cells has arisen4 ,the same process of cell-division now repeats itself several times in succession4 ,in this way1 from two cells 7,fig4 #f ,a7 there arise four 7,fig4 #f ,b72 from four1 eight 7,fig4 #f ,c72 from eight1 sixteen2 from these1 thirty-two1 etc4 ,each time the division of the kernel-speck precedes that of the kernel2 this1 again1 precedes that of the cell-substance1 or protoplasma4 ,as the division of the latter always commences with the formation of a superficial annular furrow1 or cleft1 the whole process is usually called the furrowing of the egg1 or yolk-cleavage1 and the products of it1 that is1 the cells arising from the continued halving1 are called the cleavage spheres4 ,however1 the whole process is nothing more than a simple1 oft-repeated division of cells1 and the products of it are actual1 naked cells4 ,finally1 through the continued division or 8furrowing0 of the mammal's egg there arises a mulberry-shaped ball1 which is composed of a great number of small spheres1 naked cells1 containing kernels 7,fig4 #f ,d74 ,these cells are the materials out of which the body of the young mammal is constructed4 ,every one of us has once been such a simple mulberry-shaped ball1 composed only of small equi-formal cells4 ,the further development of the globular lump of cells1 which now represents the young body of the mammal1 consists first in its changing into a globular bladder1 as fluid accumulates within it4 ,this bladder is called the germ-bladder 7vesicula blastodermica74 ,its wall is at first composed of merely equi-formal cells4 ,but soon1 at one point on the wall1 arises a disc-shaped thickening1 as the cells here increase rapidly1 and this thickening is now the foundation of the actual body of the germ or embryo1 while the other parts of the germ-bladder serve only for its nutrition4 ,the thickened disc1 or foundation of the embryo1 soon assumes an oblong1 and then a fiddle-shaped form1 in consequence of its right and left walls becoming convex 7,fig4 #g1 p4 #cjd74 ,at this stage of development in the first form of their germ or embryo1 not only all mammals1 including man1 but even all vertebrate animals in general--birds1 reptiles1 amphibious animals1 and fishes--can either not be distinguished from one another at all1 or only by very unessential differences1 such as the arrangement of the egg-coverings4 ,in all the whole body consists of nothing but a quite simple1 oblong1 oval1 or violin-shaped thin disc1 which is composed of three closely connected membranes or plates1 lying one above another4 ,each of the three plates or layers of the germ consists simply of cells all exactly like one another2 but each layer has a different function in the building up of the vertebrate animal body4 ,out of the upper or outer germ-layer arises solely the outer skin 7epidermis71 together with the central parts of the nervous system 7spinal marrow and brain72 out of the lower or inner layer arises only the inner delicate skin 7epithelium7 which lines the whole intestinal tube from the mouth to the anus1 together with all the glands connected with it 7lung1 liver1 salivary glands1 etc472 out of the middle germ-layer lying between the two others arise all the other organs1 muscles1 bones1 blood-vessels4 ,now1 the processes by which the various and exceedingly complicated parts of the fully-formed body of vertebrate animals arise out of such simple material--out of the three germ-layers composed only of cells--are1 in the first place1 the repeated division1 and consequently the increase of cells2 in the second place1 the division of labour or differentiation of these cells2 and thirdly1 the union of the variously developed or differentiated cells1 for the formation of the different organs4 ,thus arises the gradual progress or perfecting which can be traced step by step in the development of the embryonic body4 ,the simple embryonic cells1 which are to constitute the body of the vertebrate animal1 stand in the same relation to each other as citizens who wish to found a state4 ,some take to one occupation1 others to another1 and work together for the good of the whole4 ,by this division of labour1 or differentiation1 and the perfecting 7the organic progress7 which is connected with it1 it becomes possible for the whole state to accomplish undertakings which would have been impossible to the single individual4 ,the whole body of the vertebrate animal1 like every other many-celled organism1 is a republican state of cells1 and consequently it can accomplish organic functions which the individual cell1 as a solitary individual 7for example1 an ,amba1 or a single-celled plant71 could never perform4 ,no sensible person supposes that carefully devised institutions1 which have been established for the good of the whole1 as well as for the individual1 in every human state1 are the results of the action of a personal and supernatural ,creator1 acting for a definite purpose4 ,on the contrary1 every one knows that these useful institutions of organization in the state are the consequences of the co-operation of the individual citizens and their common government1 as well as of adaptation to the conditions of existence of the outer world4 ,just in the same way we must judge of the many-celled organism4 ,in it also all the useful arrangements are solely the natural and necessary result of the co-operation1 differentiation1 and perfecting of the individual citizens--the cells--and by no means the artificial arrangements of a ,creator acting for a definite purpose4 ,if we rightly consider this comparison1 and pursue it further1 we can distinctly see the perversity of that dualistic conception of nature which discovers the action of a creative plan of construction in the various adaptations of the organization of living things4 ,let us pursue the individual development of the vertebrate animal body a few stages further1 and see what is next done by the citizens of this embryonic organism4 ,in the central line of the violin-shaped disc1 which is composed of the three cellular germ-layers1 there arises a straight delicate furrow1 the so-called 8primitive streak10 by which the violin-shaped body is divided into two equal lateral halves--a right and a left part or 8antimer40 ,on both sides of that streak or furrow1 the upper or external germ-layer rises in the form of a longitudinal fold1 and both folds then grow together over the furrow in the central line1 and thus form a cylindrical tube4 ,this tube is called the marrow-tube1 or medullary canal1 because it is the foundation of the central nervous system1 the spinal marrow 7medulla spinalis74 ,at first it is pointed both in front and behind1 and it remains so for life in the lowest vertebrate animal1 the brainless1 skull-less ,lancelet 7,amphioxus74 ,but in all other vertebrate animals1 which we distinguish from the latter as skulled animals1 or ,craniota1 a difference between the fore and hinder end of the marrow tube soon becomes visible1 the fore end becoming dilated1 and changing into a roundish bladder1 the foundation of the brain4 ,in all ,craniota1 that is1 in all vertebrate animals possessing skull and brain1 the brain1 which is at first only the bladder-shaped dilatation of the anterior end of the spinal marrow1 divides into five bladders lying one behind the other1 four superficial1 transverse in-nippings being formed4 ,these five brain-bladders1 out of which afterwards arise all the different parts of the intricately constructed brain1 can be seen in their original condition in the embryo represented in ,fig4 #g4 ,it is just the same whether we examine the embryo of a dog1 a fowl1 a lizard1 or any other higher vertebrate animal4 ,for the embryos of the different skulled animals 7at least the three higher classes of them1 the reptiles1 birds and mammals7 cannot be in any way distinguished at the stage represented in ,fig4 #g4 ,the whole form of the body is as yet exceedingly simple1 being merely a thin1 leaf-like disc4 ,face1 legs1 intestines1 etc41 are as yet completely wanting4 ,but the five bladders are already quite distinct from one another4 ,illustration3 ,,fig4 #g4--;,embryo of a mammal or bird1 in which the five brain-bladders have just commenced to develop4 v4 ,fore brain4 z4 ,twixt brain4 m4 ,mid brain4 h4 ,hind brain4 n4 ,after brain4 p4 ,spinal-marrow4 a4 ,eye-bladders4 w4 ,primitive vertebr4 d4 ,spinal-axis or notochord4 ,the first bladder1 the fore brain 7a71 is in so far the most important that it principally forms the hemispheres of the so-called larger brain 7cerebrum71 that part which is the seat of the higher mental activities4 ,the more these activities are developed in the series of vertebrate animals1 the more do the two lateral halves of the fore brain1 or the hemispheres1 grow at the expense of the other bladders1 and overlap them in front and from above4 ,in man1 where they are most strongly developed1 agreeing with his higher mental activity1 they eventually almost entirely cover the other parts from above 7compare ,plates ,,ii4 and ,,iii47 ,the second bladder1 the twixt brain 7z71 forms that portion of the brain which is called the centre of sight1 and stands in the closest relation to the eyes 7a71 which grow right and left out of the fore brain in the shape of two bladders1 and later lie at the bottom of the twixt brain4 ,the third bladder1 the mid brain 7m71 for the most part vanishes in the formation of the so-called four bulbs1 a bossy portion of the brain1 which is strongly developed in reptiles and birds 7,fig4 ,e1 ,f1 ,plate ,,ii471 whereas in mammals it recedes much more 7,fig4 ,g1 ,h1 ,plate ,,iii474 ,the fourth bladder1 the hind brain 7h71 forms the so-called little hemispheres1 together with the middle part of the small brain 7cerebellum71 a part of the brain as to the function of which the most contradictory conjectures are entertained1 but which seems principally to regulate the co-ordination of movements4 ,lastly1 the fifth bladder1 the after brain 7n71 develops into that very important part of the central nervous system which is called the prolonged marrow 7medulla oblongata74 ,it is the central organ of the respiratory movements1 and of other important functions1 and an injury to it immediately causes death1 whereas the large hemispheres of the fore brain 7or the organ of the 8soul10 in a restricted sense7 can be removed bit by bit1 and even completely destroyed1 without causing the death of the vertebrate animal--only its higher mental activities disappearing in consequence4 ,these five brain bladders1 in all vertebrate animals which possess a brain at all1 are originally arranged in the same manner and develop gradually in the different groups so differently1 that it is afterwards very difficult to recognize the corresponding parts in the fully-developed brains4 ,in the early stage of development which is represented in ,fig4 #g1 it seems as yet quite impossible to distinguish the embryos of the different mammals1 birds1 and reptiles1 from one another4 ,but if we compare the much more developed embryos on ,plates ,,ii4 and ,,iii4 with one another1 we can clearly see an inequality in their development1 and especially it will be perceived that the brain of the two mammals 7,g and ,h7 already strongly differ from that of birds 7,f7 and of reptiles 7,e74 ,in the two latter the mid brain predominates1 but in the former the fore brain4 ,even at this stage the brain of the bird 7,f7 is scarcely distinguishable from that of the tortoise 7,e71 and in like manner the brain of the dog 7,g7 is as yet almost the same as that of man 7,h74 ,if1 on the other hand1 we compare the brains of these four vertebrate animals in a fully developed condition1 we find them so very different in all anatomical particulars1 that we cannot doubt for a moment as to which animal each brain belongs4 ,i have here explained the original equality1 the gradual commencement1 and the ever increasing separation or differentiation of the embryos in the different vertebrate animals1 taking the brain as a special example1 just because this organ of the soul's activity is of special interest4 ,but ,i might as well have discussed in its stead the heart1 or the liver1 or the limbs1 in short1 any other part of the body1 since the same wonder of creation is here ever repeated1 namely1 this1 that all parts are originally the same in the different vertebrate animals1 and that the variations by which the different classes1 orders1 families1 genera1 etc41 differ and deviate from one another1 are only gradually developed4 ,there are certainly few parts of the body which are so differently constructed as the limbs or extremities of the vertebrate animals4 ,now1 ,i wish the reader to compare in ,fig4 ,a-,h on ,plates ,,ii4 and ,,iii41 the four extremities 7bv7 of the embryos with one another1 and he will scarcely be able to perceive any important differences between the human arm 7,h bv71 the wing of a bird 7,f bv71 the slim foreleg of a dog 7,g bv71 and the plump foreleg of the tortoise 7,e bv74 ,in comparing the hinder extremities 7bh7 in these figures he will find it equally difficult to distinguish the leg of a man 7,h bh71 of a bird 7,f bh71 the hind-leg of a dog 7,g bh71 and that of a tortoise 7,e bh74 ,the fore as well as the hinder extremities are as yet short1 broad lumps1 at the ends of which the foundations of the five toes are placed1 connected as yet by a membrane4 ,at a still earlier stage 7,fig4 ,a-,d7 the five toes are not marked out at all1 and it is quite impossible to distinguish even the fore and hinder extremities from one another4 ,the latter1 as well as the former1 are nothing but simple roundish processes1 which have grown out of the side of the trunk4 ,at the very early stage represented in ,fig4 #g they are completely wanting1 and the whole embryo is a simple trunk without a trace of limbs4 ,illustration3 ,pl4 ,,ii4 ,germs or ,embryos of four ,vertebrates4 v4 ,fore-brain4 z4 ,twixt-brain4 m4 ,mid-brain4 h4 ,hind-brain4 n4 ,after-brain4 w4 ,spine4 r4 ,spinal-cord4 ,illustration3 ,pl4 ,,iii4 ,germs or ,embryos of four ,vertebrates4 na4 ,nose4 a4 ,eyes4 o4 ,ear4 k#a k#b k#c4 ,gill-arches4 s4 ,tail4 bv4 ,fore-leg4 bh4 ,hind-leg4 ,i wish especially to draw attention in ,plates ,,ii4 and ,,iii41 which represents embryos in early stages of development 7,fig4 ,a-,d7--and in which we are not able to recognize a trace of the full-grown animal--to an exceedingly important formation1 which originally is common to all vertebrate animals1 but which at a later period is transformed into the most different organs4 ,every one surely knows the gill-arches of fish1 those arched bones which lie behind one another1 to the number of three or four1 on each side of the neck1 and which support the gills1 the respiratory organs of the fish 7double rows of red leaves1 which are popularly called 8fishes' ears407 ,now1 these gill-arches originally exist exactly the same in man 7,d71 in dogs 7,c71 in fowls 7,b71 and in tortoises 7,a71 as well as in all other vertebrate animals4 7,in ,fig4 ,a-,d the three gill-arches of the right side of the neck are marked k#a k#b k#c74 ,now1 it is only in fishes that these remain in their original form1 and develop into respiratory organs4 ,in the other vertebrate animals they are partly employed in the formation of the face 7especially the jaw apparatus71 and partly in the formation of the organ of hearing4 ,finally1 when comparing the embryos on ,plates ,,ii4 and ,,iii41 we must not fail to give attention again to the human tail 7s71 an organ which1 in the original condition1 man shares with all other vertebrate animals4 ,the discovery of tailed men was long anxiously expected by many monistic philosophers1 in order to establish a closer relationship between man and the other mammals4 ,and in like manner their dualistic opponents often maintained with pride that the complete want of a tail formed one of the most important bodily distinctions between men and animals1 though they did not bear in mind the many tailless animals which really exist4 ,now1 man in the first months of development possesses a real tail as well as his nearest kindred1 the tailless apes 7orang-outang1 chimpanzee1 gorilla71 and vertebrate animals in general4 ,but whereas1 in most of them--for example1 the dog 7,c1 ,g7--in the course of development it always grows longer1 in man 7,fig4 ,d1 ,h7 and in tailless mammals1 at a certain period of development1 it degenerates and finally completely disappears4 ,however1 even in fully developed men1 the remnant of the tail is seen in the three1 four1 or five tail vertebr 7vertebr coccyge7 as an aborted or rudimentary organ1 which forms the hinder or lower end of the vertebral column 7p4 #bhi74 ,most persons even now refuse to acknowledge the most important deduction of the ,theory of ,descent1 that is1 the palontological development of man from ape-like1 and through them from still lower1 mammals1 and consider such a transformation of organic form as impossible4 ,but1 ,i ask1 are the phenomena of the individual development of man1 the fundamental features of which ,i have here given1 in any way less wonderful8 ,is it not in the highest degree remarkable that all vertebrate animals of the most different classes--fishes1 amphibious animals1 reptiles1 birds1 and mammals--in the first periods of their embryonic development cannot be distinguished at all1 and even much later1 at a time when reptiles and birds are already distinctly different from mammals1 that the dog and the man are almost identical8 ,verily1 if we compare those two series of development with one another1 and ask ourselves which of the two is the more wonderful1 it must be confessed that ontogeny1 or the short and quick history of development of the individual1 is much more mysterious than phylogeny1 or the long and slow history of development of the tribe4 ,for one and the same grand change of form is accomplished by the latter in the course of many thousands of years1 and by the former in the course of a few months4 ,evidently this most rapid and astonishing transformation of the individual in ontogenesis1 which we can actually point out at any moment by direct observation1 is in itself much more wonderful and astonishing than the corresponding1 but much slower and gradual transformation which the long chain of ancestors of the same individual has gone through in phylogenesis4 ,the two series of organic development1 the ontogenesis of the individual and the phylogenesis of the tribe to which it belongs1 stand in the closest causal connection with each other4 ,i have endeavoured1 in the second volume of the 8,general ,morphology107#d7 to establish this theory in detail1 as ,i consider it exceedingly important4 ,as ,i have there shown1 ontogenesis1 or the development of the individual1 is a short and quick repetition 7recapitulation7 of phylogenesis1 or the development of the tribe to which it belongs1 determined by the laws of inheritance and adaptation2 by tribe ,i mean the ancestors which form the chain of progenitors of the individual concerned4 7,gen4 ,morph4 ii4 #aaj-adg1 #cga47 ,in this intimate connection of ontogeny and phylogeny1 ,i see one of the most important and irrefutable proofs of the ,theory of ,descent4 ,no one can explain these phenomena unless he has recourse to the laws of ,inheritance and ,adaptation2 by these alone are they explicable4 ,these laws1 which we have previously explained1 are the laws of abbreviated1 of homochronic1 and of homotopic inheritance1 and here deserve renewed consideration4 ,as so high and complicated an organism as that of man1 or the organism of every other mammal1 rises upwards from a simple cellular state1 and as it progresses in its differentiation and perfecting it passes through the same series of transformations which its animal progenitors have passed through1 during immense spaces of time1 inconceivable ages ago4 ,i have already pointed out this extremely important parallelism of the development of individuals and tribes 7p4 #aj74 ,certain very early and low stages in the development of man1 and the other vertebrate animals in general1 correspond completely in many points of structure with conditions which last for life in the lower fishes4 ,the next phase which follows upon this presents us with a change of the fish-like being into a kind of amphibious animal4 ,at a later period the mammal1 with its special characteristics1 develops out of the amphibian1 and we can clearly see1 in the successive stages of its later development1 a series of steps of progressive transformation which evidently correspond with the differences of different mammalian orders and families4 ,now1 it is precisely in the same succession that we also see the ancestors of man1 and of the higher mammals1 appear one after the other in the earth's history2 first fishes1 then amphibians1 later the lower1 and at last the higher mammals4 ,here1 therefore1 the embryonic development of the individual is completely parallel to the palontological development of the whole tribe to which it belongs1 and this exceedingly interesting and important phenomenon can be explained only by the interaction of the laws of ,inheritance and ,adaptation4 ,the example last mentioned1 of the parallelism of the palontological and of the individual developmental series1 now directs our attention to a third developmental series1 which stands in the closest relations to these two1 and which likewise runs1 on the whole1 parallel to them4 ,i mean that series of development of forms which constitutes the object of investigation in comparative anatomy1 and which ,i will briefly call the systematic developmental series of species4 ,by this we understand the chain of the different1 but related and connected forms1 which exist side by side at any one period of the earth's history2 as for example1 at the present moment4 ,while comparative anatomy compares the different forms of fully-developed organisms with one another1 it endeavours to discover the common prototypes which underlie1 as it were1 the manifold forms of kindred genera1 classes1 etc41 and which are more or less concealed by their particular differentiation4 ,it endeavours to make out the series of progressive steps which are indicated in the different degrees of perfection of the divergent branches of the tribe4 ,to make use again of the same particular instance1 comparative anatomy shows us how the individual organs and systems of organs in the tribe of vertebrate animals--in the different classes1 families1 and species of it--have unequally developed1 differentiated1 and perfected themselves4 ,it shows us how far the succession of classes of vertebrate animals1 from the ,fishes upwards1 through the ,amphibia to the ,mammals1 and here again1 from the lower to the higher orders of ,mammals1 forms a progressive series or ladder4 ,this attempt to establish a connected anatomical developmental series we may discover in the works of the great comparative anatomists of all ages--in the works of ,goethe1 ,meckel1 ,cuvier1 ,johannes ,mller1 ,gegenbaur1 and ,huxley4 ,the developmental series of mature forms1 which comparative anatomy points out in the different diverging and ascending steps of the organic system1 and which we call the systematic developmental series1 is parallel to the palontological developmental series1 because it deals with the result of palontological development1 and it is parallel to the individual developmental series1 because this is parallel to the palontological series4 ,if two parallels are parallel to a third1 they must be parallel to one another4 ,the varied differentiation1 and the unequal degree of perfecting which comparative anatomy points out in the developmental series of the ,system1 is chiefly determined by the ever increasing variety of conditions of existence to which the different groups adapt themselves in the struggle for life1 and by the different degrees of rapidity and completeness with which this adaptation has been effected4 ,conservative groups which have retained their inherited peculiarities most tenaciously remain1 in consequence1 at the lowest and rudest stage of development4 ,those groups progressing most rapidly and variously1 and which have adapted themselves to changed conditions of existence most readily have attained the highest degree of perfection4 ,the further the organic world developed in the course of the earth's history1 the greater must the gap between the lower conservative and the higher progressive groups have become1 as in fact may be seen too in the history of nations4 ,in this way also is explained the historical fact1 that the most perfect animal and vegetable groups have developed themselves in a comparatively short time to a considerable height1 while the lowest or most conservative groups have remained stationary throughout all ages in their original simple stage1 or have progressed1 but very slowly and gradually4 ,the series of man's progenitors clearly shows this state of things4 ,the sharks of the present day are still very like the primary fish1 which are among the most ancient vertebrate progenitors of man1 and the lowest amphibians of the present day 7the gilled salamanders and salamanders7 are very like the amphibians which first developed themselves out of fishes4 ,so1 too1 the later ancestors of man1 the ,monotremata and ,marsupials1 the most ancient mammals1 are at the same time the most imperfect animals of the class which still exist4 ,the laws of inheritance and adaptation known to us are completely sufficient to explain this exceedingly important and interesting phenomenon1 which may be briefly designated as the parallelism of individual1 of palontological1 and of systematic development4 ,no opponent of the ,theory of ,descent has been able to give an explanation of this extremely wonderful fact1 whereas it is perfectly explained1 according to the ,theory of ,descent1 by the laws of ,inheritance and ,adaptation4 ,if we examine this parallelism of the three organic series of development more accurately1 we have to add the following special qualifications4 ,ontogeny1 or the history of the individual development of every organism 7embryology and metamorphology71 presents us with a simple unbranching or graduated chain of forms2 and so it is with that portion of phylogeny which comprises the palontological history of development of the direct ancestors only of an individual organism4 ,but the whole of phylogeny--which meets us in the natural system of every organic tribe or phylum1 and which is concerned with the investigation of the palontological development of all the branches of this tribe--forms a branching or tree-shaped developmental series1 a veritable pedigree4 ,if we examine and compare the branches of this pedigree1 and place them together according to the degree of their differentiation and perfection1 we obtain the tree-shaped1 branching1 systematic developmental series of comparative anatomy4 ,strictly speaking1 therefore1 the latter is parallel to the whole of phylogeny1 and consequently is only partially parallel to ontogeny2 for ontogeny itself is parallel only to a portion of phylogeny4 ,all the phenomena of organic development above discussed1 especially the threefold genealogical parallelism1 and the laws of differentiation and progress1 which are evident in each of these three series of organic development1 and1 further1 the whole history of rudimentary organs1 are exceedingly important proofs of the truth of the ,theory of ,descent4 ,for by it alone can they be explained1 whereas its opponents cannot even offer a shadow of an explanation of them4 ,without the ,doctrine of ,filiation1 the fact of organic development in general cannot be understood4 ,we should therefore1 for this reason alone1 be forced to accept ,lamarck's ,theory of ,descent1 even if we did not possess ,darwin's ,theory of ,selection4 ,,chapter ,,xiii4 ,,theory ,,of ,,the ,,development ,,of ,,the ,,universe ,,and ,,of ,,the ,,earth4 ,,spontaneous ,,generation4 ,,the ,,carbon ,,theory4 ,,the ,,plastid ,,theory4 ,history of the ,development of the ,earth4--,kant's ,theory of the ,development of the ,universe1 or the ,cosmological ,gas ,theory4--,development of ,suns1 ,planets1 and ,moons4--,first ,origin of ,water4--,comparison of ,organisms and ,anorgana4--,organic and ,inorganic ,substances4--,degrees of ,density1 or ,conditions of ,aggregation4--,albuminous ,combinations of ,carbon4--,organic and ,inorganic ,forms4--,crystals and ,formless ,organisms without ,organs4--,stereometrical ,fundamental ,forms of ,crystals and of ,organisms4--,organic and ,inorganic ,forces4--,vital ,force4--,growth and ,adaptation in ,crystals and in ,organisms4--,formative ,tendencies of ,crystals4--,unity of ,organic and ,inorganic ,nature4--,spontaneous ,generation1 or ,archigony4--,autogony and ,plasmogony4--,origin of ,monera by ,spontaneous ,generation4--,origin of ,cells from ,monera4--,the ,cell ,theory4--,the ,plastid ,theory4--,plastids1 or ,structural ,units4--,cytods and ,cells4--,four ,different ,kinds of ,plastids4 ,in our considerations hitherto we have endeavoured to answer the question1 8,by what causes have new species of animals and plants arisen out of existing species80 ,we have answered this question according to ,darwin's theory1 that natural selection in the struggle for existence--that is1 the interaction of the laws of ,inheritance and ,adaptation--is completely sufficient for producing mechanically the endless variety of the different animals and plants1 which have the appearance of being organized according to a plan for a definite purpose4 ,meanwhile the question must have already repeatedly presented itself to the reader1 how did the first organisms1 or that one original and primval organism arise1 from which we derive all the others8 ,this question ,lamarck7#b7 answered by the hypothesis of spontaneous generation1 or archigony4 ,but ,darwin passes over and avoids this subject1 as he expressly remarks that he has 8nothing to do with the origin of the soul1 nor with that of life itself40 ,at the conclusion of his work he expresses himself more distinctly in the following words3--8,i imagine that probably all organic beings which ever lived on this earth descended from some primitive form1 which was first called into life by the ,creator40 ,moreover1 ,darwin1 for the consolation of those who see in the ,theory of ,descent the destruction of the whole 8moral order of the universe10 appeals to the celebrated author and divine who wrote to him1 that 8he has gradually learnt to see that it is just as noble a conception of the ,deity to believe that he created a few original forms capable of self-development into other and needful forms1 as to believe that he required a fresh act of creation to supply the voids caused by the action of his laws40 ,those to whom the belief in a supernatural creation is an emotional necessity may rest satisfied with this conception4 ,they may reconcile that belief with the ,theory of ,descent2 for in the creation of a single original organism possessing the capability to develop all others out of itself by inheritance and adaptation1 they can really find much more cause for admiring the power and wisdom of the ,creator than in the independent creation of different species4 ,if1 taking this point of view1 we were to explain the origin of the first terrestrial organisms1 from which all the others are descended1 as due to the action of a personal ,creator acting according to a definite plan1 we should of course have to renounce all scientific knowledge of the process1 and pass from the domain of true science to the completely distinct domain of poetical faith4 ,by assuming a supernatural act of creation we should be taking a leap into the inconceivable4 ,before we decide upon this latter step1 and thereby renounce all pretension to a scientific knowledge of the process1 we are at all events in duty bound to endeavour to examine it in the light of a mechanical hypothesis4 ,we must at least examine whether this process is really so wonderful1 and whether we cannot form a tenable conception of a completely non-miraculous origin of the first primary organism4 ,we might then be able entirely to reject miracle in creation4 ,it will be necessary for this purpose1 first of all1 to go back further into the past1 and to examine the history of the creation of the earth4 ,going back still further1 we shall find it necessary to consider the history of the creation of the whole universe in its most general outlines4 ,all my readers undoubtedly know that from the structure of the earth1 as it is at present known to us1 the notion has been derived1 and as yet has not been refuted1 that its interior is in a fiery fluid condition1 and that the firm crust1 composed of different strata1 on the surface of which organisms are living1 forms only a very thin pellicle or shell round the fiery fluid centre4 ,we have arrived at this idea by different confirmatory experiments and reasonings4 ,in the first place1 the observation that the temperature of the earth's crust continually increases towards the centre is in favour of this supposition4 ,the deeper we descend1 the greater the warmth of the ground1 and in such proportion1 that with every #ajj feet the temperature increases about one degree4 ,at a depth of six miles1 therefore1 a heat of #aejj would be attained1 sufficient to keep most of the firm substances of our earth's crust in a molten1 fiery1 fluid state4 ,this depth1 however1 is only the #bhfth part of the whole diameter of the earth 7#agag miles74 ,we further know that springs which rise out of a considerable depth possess a very high temperature1 and sometimes even throw water up to the surface in a boiling state4 ,lastly1 very important proofs are furnished by volcanic phenomena1 the eruption of fiery fluid masses of stone bursting through certain parts of the earth's crust4 ,all these phenomena lead us with great certainty to the important assumption that the firm crust of the earth forms only quite a small fraction1 not nearly the one-thousandth part of the whole diameter of the terrestrial globe1 and that the rest is still for the most part in a molten or fiery fluid state4 ,now if1 starting with this assumption1 we reflect on the ancient history of the development of the globe1 we are logically carried back a step further1 namely1 to the assumption that at an earlier date the whole earth was a fiery fluid body1 and that the formation of a thin1 stiffened crust on the surface was only a later process4 ,only gradually1 by radiating its intrinsic heat into the cold space of the universe1 has the surface of the glowing ball become condensed into a thin crust4 ,that the temperature of the earth in remote times was much higher than it is now1 is proved by many phenomena4 ,among other things1 this is rendered probable by the equal distribution of organisms in remote times of the earth's history4 ,while at present1 as is well known1 the different populations of animals and plants correspond to the different zones of the earth and their appropriate temperature1 in earlier times this was distinctly not the case4 ,we see from the distribution of fossils in the remoter ages1 that it was only at a very late date1 in fact1 at a comparatively recent period of the organic history of the earth 7at the beginning of the so-called cnolithic or tertiary period71 that a separation of zones and of the corresponding organic populations occurred4 ,during the immensely long primary and secondary periods1 tropical plants1 which require a very high degree of temperature1 lived not only in the present torrid zone1 under the equator1 but also in the present temperate and frigid zones4 ,many other phenomena also demonstrate a gradual decrease of the temperature of the globe as a whole1 and especially a late and gradual cooling of the earth's crust about the poles4 ,bronn1 in his excellent 8,investigations of the ,laws of ,development of the ,organic ,world10 has collected numerous geological and palontological proofs of this fact4 ,these phenomena and the mathematico-astronomical knowledge of the structure of the universe justify the theory that1 inconceivable ages ago1 long before the first existence of organisms1 the whole earth was a fiery fluid globe4 ,now1 this theory corresponds with the grand theory of the origin of the universe1 and especially of our planetary system1 which1 on the ground of mathematical and astronomical facts1 was put forward in #agee by our critical philosopher ,kant17#bb7 and was later more thoroughly established by the celebrated mathematicians1 ,laplace and ,herschel4 ,this cosmogeny1 or theory of the development of the universe1 is now almost universally acknowledged2 it has not been replaced by a better one1 and mathematicians1 astronomers1 and geologists have continually1 by various arguments1 strengthened its position4 ,kant's cosmogeny maintains that the whole universe1 inconceivable ages ago1 consisted of a gaseous chaos4 ,all the substances which are found at present separated on the earth1 and other bodies of the universe1 in different conditions of density--in the solid1 semi-fluid1 liquid1 and elastic fluid or gaseous states of aggregation--originally constituted together one single homogeneous mass1 equally filling up the space of the universe1 which1 in consequence of an extremely high degree of temperature1 was in an exceedingly thin gaseous or nebulous state4 ,the millions of bodies in the universe which at present form the different solar systems did not then exist4 ,they originated only in consequence of a universal rotatory movement1 or rotation1 during which a number of masses acquired greater density than the remaining gaseous mass1 and then acted upon the latter as central points of attraction4 ,thus arose a separation of the chaotic primary nebula1 or gaseous universe1 into a number of rotating nebulous spheres1 which became more and more condensed4 ,our solar system was such a gigantic gaseous or nebulous ball1 all the particles of which revolved round a common central point1 the solar nucleus4 ,the nebulous ball itself1 like all the rest1 in consequence of its rotatory movement1 assumed a spheroidal or a flattened globular form4 ,while the centripetal force attracted the rotating particles nearer and nearer to the firm central point of the nebulous ball1 and thus condensed the latter more and more1 the centrifugal force1 on the other hand1 always tended to separate the peripheral particles further and further from it1 and to hurl them off4 ,on the equatorial sides of the ball1 which was flattened at both poles1 this centrifugal force was strongest1 and as soon as1 by increase of density1 it attained predominance over the centripetal force1 a circular nebulous ring separated itself from the rotating ball4 ,this nebulous ring marked the course of future planets4 ,the nebulous mass of the ring gradually condensed1 and became a planet1 which revolved round its own axis1 and at the same time rotated round the central body4 ,in precisely the same manner1 from the equator of the planetary mass1 as soon as the centrifugal force gained predominance over the centripetal force1 new nebulous rings were ejected1 which moved round the planets as the latter moved round the sun4 ,these nebulous rings1 too1 became condensed into rotating balls4 ,thus arose the moons1 only one of which moves round our earth1 whilst four move round ,jupiter1 and six round ,uranus4 ,the ring of ,saturn still shows us a moon in its early stage of development4 ,as by increasing refrigeration these simple processes of condensation and expulsion repeated themselves over and over again1 there arose the different solar systems1 the planets rotating round their central suns1 and the satellites or moons moving round their planets4 ,the original gaseous condition of the rotating bodies of the universe gradually changed1 by increasing refrigeration and condensation1 into the fiery fluid or molten state of aggregation4 ,by the process of condensation1 a great quantity of heat was emitted1 and the rotating suns1 planets1 and moons1 soon changed into glowing balls of fire1 like gigantic drops of melted metal1 which emitted light and heat4 ,by loss of heat1 the melted mass on the surface of the fiery fluid ball became further condensed1 and thus arose a thin1 firm crust1 which enclosed a fiery fluid nucleus4 ,in all essential respects our mother earth probably did not differ from the other bodies of the universe4 ,in view of the object of these pages1 it will not be of especial interest to follow in detail the history of the natural creation of the universe1 with its different solar and planetary systems1 and to establish it mathematically by the different astronomical and geological proofs4 ,the outlines of it1 which ,i have just mentioned1 must be sufficient here1 and for further details ,i refer to ,kant's#e 8,general ,history of ,nature and ,theory of the ,heavens407#bb7 ,i will only add that this wonderful theory1 which might be called the cosmological gas theory1 harmonizes with all the general series of phenomena at present known to us1 and stands in no irreconcilable contradiction to any one of them4 ,moreover1 it is purely mechanical or monistic1 makes use exclusively of the inherent forces of eternal matter1 and entirely excludes every supernatural process1 every prearranged and conscious action of a personal ,creator4 ,kant's ,cosmological ,gas ,theory consequently occupies a similar supreme position in ,anorganology1 especially in ,geology1 and forms the crown of our knowledge in that department1 in the same way as ,lamarck's ,theory of ,descent does in ,biology1 and especially in ,anthropology4 ,both rest exclusively upon mechanical or unconscious causes 7caus efficientes71 in no case upon prearranged or conscious causes 7caus finales74 7,compare above1 p4 #ajj-ajf47 ,both therefore fulfil all the demands of a scientific theory1 and consequently will remain generally acknowledged until they are replaced by better ones4 ,i will1 however1 not deny that ,kant's grand cosmogeny has some weak points1 which prevent our placing the same unconditional confidence in it as in ,lamarck's ,theory of ,descent4 ,the notion of an original gaseous chaos filling the whole universe presents great difficulties of various kinds4 ,a great and unsolved difficulty lies in the fact that the ,cosmological ,gas ,theory furnishes no starting-point at all in explanation of the first impulse which caused the rotary motion in the gas-filled universe4 ,in seeking for such an impulse1 we are involuntarily led to the mistaken questioning about a 8first beginning40 ,we can as little imagine a first beginning of the eternal phenomena of the motion of the universe as of its final end4 ,the universe is unlimited and immeasurable in both space and time4 ,it is eternal1 and it is infinite4 ,nor can we imagine a beginning or end to the uninterrupted and eternal motion in which all particles of the universe are always engaged4 ,the great laws of the conservation of force7#ch7 and the conservation of matter1 the foundations of our whole conception of nature1 admit of no other supposition4 ,the universe1 as far as it is cognisable to human capability1 appears as a connected chain of material phenomena of motion1 necessitating a continual change of forms4 ,every form1 as the temporary result of a multiplicity of phenomena of motion1 is as such perishable1 and of limited duration4 ,but1 in the continual change of forms1 matter and the motion inseparable from it remain eternal and indestructible4 ,now1 although ,kant's ,cosmological ,gas ,theory is not able to explain the development of motion in the whole universe in a satisfactory manner1 beyond that gaseous state of chaos1 and although many other weighty considerations may be brought forward against it1 especially by chemistry and geology1 yet we must on the whole acknowledge its great merit1 inasmuch as it explains in an excellent manner1 by due consideration of development1 the whole structure of all that is accessible to our observation1 that is1 the anatomy of the solar systems1 and especially of our planetary system4 ,it may be that this development was altogether different from what ,kant supposes1 and our earth may have arisen by the aggregation of numberless small meteorides1 scattered in space1 or in any other manner1 but hitherto no one has as yet been able to establish any other theory of development1 or to offer one in the place of ,kant's cosmogeny4 ,after this general glance at the monistic cosmogeny1 or the non-miraculous history of the development of the universe1 let us now return to a minute fraction of it1 to our mother earth1 which we left as a ball flattened at both poles and in a fiery fluid state1 its surface having condensed by becoming cooled into a very thin firm crust4 ,the crust1 on first cooling1 must have covered the whole surface of the terrestrial sphere as a continuous smooth and thin shell4 ,but soon it must have become uneven and hummocky2 for1 since during the continued cooling1 the fiery fluid nucleus became more and more condensed and contracted1 and consequently the diameter of the earth diminished1 the thin cold crust1 which could not closely follow the softer nuclear mass1 must have fallen in1 in many places4 ,an empty space would have arisen between the two1 had not the pressure of the outer atmosphere forced down the fragile crust towards the interior1 breaking it in so doing4 ,other unevennesses probably arose from the fact that1 in different parts1 the cooled crust during the process of refrigeration contracted also itself1 and thus became fissured with cracks and rents4 ,the fiery fluid nucleus flowed up to the external surface through these cracks1 and again became cooled and stiff4 ,thus1 even at an early period there arose many elevations and depressions1 which were the first foundations of mountains and valleys4 ,after the temperature of the cooled terrestrial ball had fallen to a certain degree1 a very important new process was effected1 namely1 the first origin of water4 ,water had until then existed only in the form of steam in the atmosphere surrounding the globe4 ,the water could evidently not condense into a state of fluid drops until the temperature of the atmosphere had considerably decreased4 ,now1 then1 there began a further transformation of the earth's crust by the force of water4 ,it continually fell in the form of rain1 and in that form washed down the elevations of the earth's crust1 filling the depressions with the mud carried along1 and1 by depositing it in layers1 it caused the extremely important neptunic transformations of the earth's crust1 which have continued since then uninterruptedly1 and which in our next chapter we shall examine a little more closely4 ,it was not till the earth's crust had so far cooled that the water had condensed into a fluid form1 it was not till the hitherto dry crust of the earth had for the first time become covered with liquid water1 that the origin of the first organisms could take place4 ,for all animals and all plants--in fact1 all organisms--consist in great measure of fluid water1 which combines in a peculiar manner with other substances1 and brings them into a semi-fluid state of aggregation4 ,we can therefore1 from these general outlines of the inorganic history of the earth's crust1 deduce the important fact1 that at a certain definite time life had its beginning on earth1 and that terrestrial organisms did not exist from eternity1 but at a certain period came into existence for the first time4 ,now1 how are we to conceive of this origin of the first organisms8 ,this is the point at which most naturalists1 even at the present day1 are inclined to give up the attempt at natural explanation1 and take refuge in the miracle of an inconceivable creation4 ,in doing so1 as has already been remarked1 they quit the domain of scientific knowledge1 and renounce all further insight into the eternal laws which have determined nature's history4 ,but before despondingly taking such a step1 and before we despair of the possibility of any knowledge of this important process1 we may at least make an attempt to understand it4 ,let us see if in reality the origin of a first organism out of inorganic matter1 the origin of a living body out of lifeless matter1 is so utterly inconceivable and beyond all experience4 ,in one word1 let us examine the question of spontaneous generation1 or archigony4 ,in so doing1 it is above all things necessary to form a clear idea of the principal properties of the two chief groups of natural bodies1 the so-called inanimate or inorganic1 and the animate or organic bodies1 and then establish what is common to1 and what are the differences between1 the two groups4 ,it is desirable to go somewhat carefully into the comparison of organisms and anorgana1 since it is commonly very much neglected1 although it is necessary for a right understanding of nature from the monistic point of view4 ,it will be most advantageous here to look separately at the three fundamental properties of every natural body2 these are matter1 form1 and force4 ,let us begin with matter4 7,gen4 ,morph4 iii47 ,by chemistry we have succeeded in analysing all bodies known to us into a small number of elements or simple substances1 which cannot be further divided1 for example1 carbon1 oxygen1 nitrogen1 sulphur1 and the different metals3 potassium1 sodium1 iron1 gold1 etc4 ,at present we know about seventy such elements or simple substances4 ,the majority of them are unimportant and rare2 the minority only are widely distributed1 and compose not only most of the anorgana1 but also all organisms4 ,if we compare those elements which constitute the body of organisms with those which are met with in anorgana1 we have first to note the highly important fact that in animal and vegetable bodies no element occurs but what can be found outside of them in inanimate nature4 ,there are no special organic elements or simple organic substances4 ,the chemical and physical differences existing between organisms and anorgana1 consequently1 do not lie in their material foundation2 they do not arise from the different nature of the elements composing them1 but from the different manner in which the latter are united by chemical combination4 ,this different manner of combination gives rise to certain physical peculiarities1 especially in density of substance1 which at first sight seems to constitute a deep chasm between the two groups of bodies4 ,inorganic or inanimate natural bodies1 such as crystals and the amorphous rocks1 are in a state of density which we call the firm or solid state1 and which we oppose to the liquid state of water and to the gaseous state of air4 ,it is familiar to every one that these three different degrees of density1 or states of aggregation of anorgana1 are by no means peculiar to the different elements1 but are the results of a certain degree of temperature4 ,every inorganic solid body1 by increase of temperature1 can be reduced to the liquid or melted state1 and1 by further heat1 to the gaseous or elastic state4 ,in the same way most gaseous bodies1 by a proper decrease of temperature can first be converted into a liquid state1 and further1 into a solid state of density4 ,in opposition to these three states of density of anorgana1 the living body of all organisms--animals as well as plants--is in an altogether peculiar fourth state of aggregation4 ,it is neither solid like stone1 nor liquid like water1 but presents rather a medium between these two states1 which may therefore be designated as the firm-fluid or swollen state of aggregation 7viscid74 ,in all living bodies1 without exception1 there is a certain quantity of water combined in a peculiar way with solid matter1 and owing to this characteristic combination of water with solid matter we have that soft state of aggregation1 neither solid nor liquid1 which is of great importance in the mechanical explanation of the phenomena of life4 ,its cause lies essentially in the physical and chemical properties of a simple1 indivisible1 elementary substance1 namely1 carbon 7,gen4 ,morph4 i4 #abb-acj74 ,of all elements1 carbon is to us by far the most important and interesting1 because this simple substance plays the largest part in all animal and vegetable bodies known to us4 ,it is that element which1 by its peculiar tendency to form complicated combinations with the other elements1 produces the greatest variety of chemical compounds1 and among them the forms and living substance of animal and vegetable bodies4 ,carbon is especially distinguished by the fact that it can unite with the other elements in infinitely manifold relations of number and weight4 ,by the combination of carbon with three other elements1 with oxygen1 hydrogen1 and nitrogen 7to which generally sulphur1 and frequently1 also1 phosphorus is added71 there arise those exceedingly important compounds which we have become acquainted with as the first and most indispensable substratum of all vital phenomena1 the albuminous combinations1 or albuminous bodies 7protean matter74 ,we have before this 7p4 #ahe7 become acquainted with the simplest of all species of organisms in the ,monera1 whose entire bodies when completely developed consist of nothing but a semi-fluid albuminous lump2 they are organisms which are of the utmost importance for the theory of the first origin of life4 ,but most other organisms1 also1 at a certain period of their existence--at least1 in the first period of their life--in the shape of egg-cells or germ-cells1 are essentially nothing but simple little lumps of such albuminous formative matter1 known as plasma1 or protoplasma4 ,they then differ from the ,monera only by the fact that in the interior of the albuminous corpuscle the cell-kernel1 or nucleus1 has separated itself from the surrounding cell-substance 7protoplasma74 ,as we have already pointed out1 the cells1 with their simple attributes1 are so many citizens1 who by co-operation and differentiation build up the body of even the most perfect organism2 this being1 as it were1 a cell republic 7p4 #cja74 ,the fully developed form and the vital phenomena of such an organism are determined solely by the activities of these small albuminous corpuscles4 ,it may be considered as one of the greatest triumphs of recent biology1 especially of the theory of tissues1 that we are now able to trace the wonder of the phenomena of life to these substances1 and that we can demonstrate the infinitely manifold and complicated physical and chemical properties of the albuminous bodies to be the real cause of organic or vital phenomena4 ,all the different forms of organisms are simply and directly the result of the combination of the different forms of cells4 ,the infinitely manifold varieties of form1 size1 and combination of the cells have arisen only gradually by the division of labour1 and by the gradual adaptation of the simple homogeneous lumps of plasma1 which originally were the only constituents of the cell-mass4 ,from this it follows of necessity that the fundamental phenomena of life--nutrition and generation--in their highest manifestations1 as well as in their simplest expressions1 must also be traced to the material nature of that albuminous formative substance4 ,the other vital activities are gradually evolved from these two4 ,thus1 then1 the general explanation of life is now no more difficult to us than the explanation of the physical properties of inorganic bodies4 ,all vital phenomena and formative processes of organisms are as directly dependent upon the chemical composition and the physical forces of organic matter as the vital phenomena of inorganic crystals--that is1 the process of their growth and their specific formation--are the direct results of their chemical composition and of their physical condition4 ,the ultimate causes1 it is true1 remain in both cases concealed from us4 ,when gold and copper crystallize in a cubical1 bismuth and antimony in a hexagonal1 iodine and sulphur in a rhombic form of crystal1 the occurrence is in reality neither more nor less mysterious to us than is every elementary process of organic formation1 every self-formation of the organic cell4 ,in this respect we can no longer draw a fundamental distinction between organisms and anorgana1 a distinction of which1 formerly1 naturalists were generally convinced4 ,let us secondly examine the agreements and differences which are presented to us in the formation of organic and inorganic natural bodies 7,gen4 ,morph4 i4 #acj74 ,formerly the simple structure of the latter and the composite structure of the former were looked upon as the principal distinction4 ,the body of all organisms was supposed to consist of dissimilar or heterogeneous parts1 of instruments or organs which worked together for the purposes of life4 ,on the other hand1 the most perfect anorgana1 that is to say1 crystals1 were supposed to consist entirely of continuous or homogeneous matter4 ,this distinction appears very essential4 ,but it loses all importance through the fact that in late years we have become acquainted with the exceedingly remarkable and important ,monera47#ae7 7,compare above1 p4 #ahe47 ,the whole body of these most simple of all organisms--a semi-fluid1 formless1 and simple lump of albumen--consists1 in fact1 of only a single chemical combination1 and is as perfectly simple in its structure as any crystal1 which consists of a single inorganic combination1 for example1 of a metallic salt or of a silicate of the earths and alkalies4 ,as naturalists believed in differences in the inner structure or composition1 so they supposed themselves able to find complete differences in the external forms of organisms and anorgana1 especially in the mathematically determinable crystalline forms of the latter4 ,certainly crystallization is pre-eminently a quality of the so-called anorgana4 ,crystals are limited by plane surfaces1 which meet in straight lines and at certain measurable angles4 ,animal and vegetable forms1 on the contrary1 seem at first sight to admit of no such geometrical determination4 ,they are for the most part limited by curved surfaces and crooked lines1 which meet at variable angles4 ,but in recent times we have become acquainted1 among ,radiolaria7#bc7 and among many other ,protista1 with a large number of lower organisms1 whose body1 in the same way as crystals1 may be traced to a mathematically determinable fundamental form1 and whose form in its whole1 as well as in its parts1 is bounded by definite geometrically determinable planes and angles4 ,in my general doctrine of ,fundamental ,forms1 or ,promorphology1 ,i have given detailed proofs of this1 and at the same time established a general system of forms1 the ideal stereometrical type-forms1 which explain the real forms of inorganic crystals1 as well as of organic individuals 7,gen4 ,morph4 i4 #cge-egd74 ,moreover1 there are also perfectly amorphous organisms1 like the ,monera1 ,amba1 etc41 which change their forms every moment1 and in which we are as little able to point out a definite fundamental form as in the case of the shapeless or amorphous anorgana1 such as non-crystallized stones1 deposits1 etc4 ,we are consequently unable to find any essential difference in the external forms or the inner structure of anorgana and organisms4 ,thirdly1 let us turn to the forces or the phenomena of motion of these two different groups of bodies 7,gen4 ,morph4 i4 #adj74 ,here we meet with the greatest difficulties4 ,the vital phenomena1 known as a rule only in the highly developed organisms1 in the more perfect animals and plants1 seem there so mysterious1 so wonderful1 so peculiar1 that most persons are decidedly of opinion that in inorganic nature there occurs nothing at all similar1 or in the least degree comparable to them4 ,organisms are for this very reason called animate1 and the anorgana1 inanimate natural bodies4 ,hence1 even so late as the commencement of the present century1 the science which investigates the phenomena of life1 namely physiology1 retained the erroneous idea that the physical and chemical properties of matter were not sufficient for explaining these phenomena4 ,in our own day1 especially during the last ten years1 this idea may be regarded as having been completely refuted4 ,in physiology1 at least1 it has now no place4 ,it now never occurs to a physiologist to consider any of the vital phenomena as the result of a mysterious vital force1 of an active power working for a definite purpose1 standing outside of matter1 and1 so to speak1 taking only the physico-chemical forces into its service4 ,modern physiology has arrived at the strictly monistic conviction that all of the vital phenomena1 and1 above all1 the two fundamental phenomena of nutrition and propagation are purely physico-chemical processes1 and directly dependent on the material nature of the organism1 just as all the physical and chemical qualities of every crystal are determined solely by its material composition4 ,now1 as the elementary substance which determines the peculiar material composition of organisms is carbon1 we must ultimately reduce all vital phenomena1 and1 above all1 the two fundamental phenomena of nutrition and propagation to the properties of the carbon4 ,the peculiar-chemico-physical properties1 and especially the semi-fluid state of aggregation1 and the easy decomposibility of the exceedingly composite albuminous combinations of carbon1 are the mechanical causes of those peculiar phenomena of motion which distinguish organisms from anorgana1 and which in a narrow sense are usually called 8life40 ,in order to understand this 8carbon theory10 which ,i have established in detail in the second book of my ,general ,morphology1 it is necessary1 above all things1 closely to examine those phenomena of motion which are common to both groups of natural bodies4 ,first among them is the process of growth4 ,if we cause any inorganic solution of salt slowly to evaporate1 crystals are formed in it1 which slowly increase in size during the continued evaporation of the water4 ,this process of growth arises from the fact that new particles continually pass over from the fluid state of aggregation into the solid1 and1 according to certain laws1 deposit themselves upon the firm kernel of the crystal already formed4 ,from such an apposition of particles arise the mathematically definite crystalline shapes4 ,in like manner the growth of organisms takes place by the accession of new particles4 ,the only difference is that in the growth of organisms1 in consequence of their semi-fluid state of aggregation1 the newly-added particles penetrate into the interior of the organism 7inter-susception71 whereas anorgana receive homogeneous matter from without only by apposition or an addition of new particles to the surface4 ,this important difference of growth by inter-susception and by apposition is obviously only the necessary and direct result of the different conditions of density or state of aggregation in organisms and anorgana4 ,unfortunately ,i cannot here follow in detail the various exceedingly interesting parallels and analogies which occur between the formation of the most perfect anorgana1 the crystals1 and the formation of the simplest organisms1 the ,monera and their next kindred forms4 ,for this ,i must refer to a minute comparison of organisms and anorgana1 which ,i have carried out in the fifth chapter of my ,general ,morphology 7,gen4 ,morph4 i4 #aaa-afj74 ,i have there shown in detail that there exist no complete differences between organic and inorganic natural bodies1 neither in respect to form and structure1 nor in respect to matter and force2 and that the actually existing differences are dependent upon the peculiar nature of the carbon2 and that there exists no insurmountable chasm between organic and inorganic nature4 ,we can perceive this most important fact very clearly if we examine and compare the origin of the forms in crystals and in the simplest organic individuals4 ,in the formation of crystal individuals1 two different counteracting formative tendencies come into operation4 ,the inner constructive force1 or the inner formative tendency1 which corresponds to the ,heredity of organisms1 in the case of the crystal is the direct result of its material constitution or of its chemical composition4 ,the form of the crystal1 so far as it is determined by this inner original formative tendency1 is the result of the specific and definite way in which the smallest particles of the crystallizing matter unite together in different directions according to law4 ,that independent inner formative force1 which is directly inherent in the matter itself1 is directly counteracted by a second formative force4 ,the external constructive force1 or the external formative tendency1 may be called ,adaptation in crystals as well as in organisms4 ,every crystal individual during its formation1 like every organic individual1 must submit and adapt itself to the surrounding influences and conditions of existence of the outer world4 ,in fact1 the form and size of every crystal is dependent upon its whole surroundings1 for example1 upon the vessel in which the crystallization takes place1 upon the temperature and the pressure of the air under which the crystal is formed1 upon the presence or absence of heterogeneous bodies1 etc4 ,consequently1 the form of every single crystal1 like the form of every single organism1 is the result of the interaction of two opposing factors--the inner formative tendency1 which is determined by the chemical constitution of the matter itself1 and of the external formative tendency1 which is dependent upon the influence of surrounding matter4 ,both these constructive forces interact similarly also in the organism1 and1 just as in the crystal1 are of a purely mechanical nature and directly inherent in the substance of the body4 ,if we designate the growth and the formation of organisms as a process of life1 we may with equal reason apply the same term to the developing crystal4 ,the teleological conception of nature1 which looks upon organisms as machines of creation arranged for a definite purpose1 must logically acknowledge the same also in regard to the forms of crystals4 ,the differences which exist between the simplest organic individuals and inorganic crystals are determined by the solid state of aggregation of the latter1 and by the semi-fluid state of the former4 ,beyond that the causes producing form are exactly the same in both4 ,this conviction forces itself upon us most clearly1 if we compare the exceedingly remarkable phenomena of growth1 adaptation1 and the 8correlation of parts0 of developing crystals with the corresponding phenomena of the origin of the simplest organic individuals 7,monera and cells74 ,the analogy between the two is so great that1 in reality1 no accurate boundary can be drawn4 ,in my ,general ,morphology ,i have quoted in support of this a number of striking facts 7,gen4 ,morph4 i4 #adf1 #aef1 #aeh47 ,if we vividly picture to ourselves this 8unity of organic and inorganic nature0 this essential agreement of organisms and anorgana in matter1 form1 and force1 and if we bear in mind that we are not able to establish any one fundamental distinction between these two groups of bodies 7as was formerly generally assumed71 then the question of spontaneous generation will lose a great deal of the difficulty which at first seems to surround it4 ,then the development of the first organism out of inorganic matter will appear a much more easily conceivable and intelligible process than has hitherto been the case1 whilst an artificial absolute barrier between organic or animate1 and inorganic or inanimate nature was maintained4 ,in the question of spontaneous generation1 or archigony1 which we can now answer more definitely1 it must be borne in mind that by this conception we understand generally the non-parental generation of an organic individual1 the origin of an organism independent of a parental or producing organism4 ,it is in this sense that on a former occasion 7p4 #ahc7 ,i mentioned spontaneous generation 7archigony7 as opposed to parental generation or propagation 7tocogony74 ,in the latter case the organic individual arises by a greater or less portion of an already existing organism separating itself and growing independently4 7,gen4 ,morph4 ii4 #cb47 ,in spontaneous generation1 which is often also called original generation 7generatio spontanea1 quivoca1 primaria etc471 we must first distinguish two essentially different kinds1 namely1 autogeny and plasmogeny4 ,by autogeny we understand the origin of a most simple organic individual in an inorganic formative fluid1 that is1 in a fluid which contains the fundamental substances for the composition of the organism dissolved in simple and loose combinations 7for example1 carbonic acid1 ammonia1 binary salts1 etc474 ,on the other hand1 we call spontaneous generation plasmogeny when the organism arises in an organic formative fluid1 that is1 in a fluid which contains those requisite fundamental substances dissolved in the form of complicated and fluid combinations of carbon 7for example1 albumen1 fat1 hydrate of carbon1 etc474 7,gen4 ,morph4 i4 #agd1 ii4 #cc47 ,neither the process of autogeny1 nor that of plasmogeny1 has yet been directly observed with perfect certainty4 ,in early1 and also in more recent times1 numerous and interesting experiments have been made as to the possibility or reality of spontaneous generation4 ,almost all these experiments refer not to autogeny1 but to plasmogeny1 to the origin of an organism out of already formed organic matter4 ,it is evident1 however1 that this latter process is only of subordinate interest for our history of creation4 ,it is much more important for us to solve the question1 8,is there such a thing as autogeny8 ,is it possible that an organism can arise1 not out of pre-existing organic1 but out of purely inorganic1 matter80 ,hence we can quietly lay aside all the numerous experiments which refer only to plasmogeny1 which have been carried on very zealously during the last ten years1 and which for the most part have had a negative result4 ,for even supposing that the reality of plasmogeny were strictly proved1 still autogeny would not be explained by it4 ,the experiments on autogeny have likewise as yet furnished no certain and positive result4 ,yet we must at the outset most distinctly protest against the notion that these experiments have proved the impossibility of spontaneous generation in general4 ,most naturalists who have endeavoured to decide this question experimentally1 and who1 after having employed all possible precautionary measures1 under well-ascertained conditions1 have seen no organisms come into being1 have straightway made the assertion1 on the ground of these negative results3 8,that it is altogether impossible for organisms to come into existence by themselves without parental generation40 ,this hasty and inconsiderate assertion they have supported by the negative results of their experiments1 which1 after all1 could prove nothing except that1 under these or those highly artificial circumstances created by the experimenters themselves1 no organism was developed4 ,from these experiments1 which have been for the most part made under the most unnatural conditions1 and in a highly artificial manner1 we can by no means draw the conclusion that spontaneous generation in general is impossible4 ,the impossibility of such a process can1 in fact1 never be proved4 ,for how can we know that in remote primval times there did not exist conditions quite different from those at present obtaining1 and which may have rendered spontaneous generation possible8 ,indeed1 we can even positively and with full assurance maintain that the general conditions of life in primval times must have been entirely different from those of the present time4 ,think only of the fact that the enormous masses of carbon which we now find deposited in the primary coal mountains were first reduced to a solid form by the action of vegetable life1 and are the compressed and condensed remains of innumerable vegetable substances1 which have accumulated in the course of many millions of years4 ,but at the time when1 after the origin of water in a liquid state on the cooled crust of the earth1 organisms were first formed by spontaneous generation1 those immeasurable quantities of carbon existed in a totally different form1 probably for the most part dispersed in the atmosphere in the shape of carbonic acid4 ,the whole composition of the atmosphere was therefore extremely different from the present4 ,further1 as may be inferred upon chemical1 physical1 and geological grounds1 the density and the electrical conditions of the atmosphere were quite different4 ,in like manner the chemical and physical nature of the primval ocean1 which then continuously covered the whole surface of the earth as an uninterrupted watery sheet1 was quite peculiar4 ,the temperature1 the density1 the amount of salt1 etc41 must have been very different from those of the present ocean4 ,in any case1 therefore1 even if we do not know anything more about it1 there remains to us the supposition1 which can at least not be disputed1 that at that time1 under conditions quite different from those of to-day1 a spontaneous generation1 which now is perhaps no longer possible1 may have taken place4 ,but it is necessary to add here that1 by the recent progress of chemistry and physiology1 the mysterious and miraculous character which at first seems to belong to this much disputed and yet inevitable process of spontaneous generation1 has been to a great extent1 or almost entirely1 destroyed4 ,not fifty years ago1 all chemists maintained that we were unable to produce artificially in our laboratories any complicated combination of carbon1 or so-called 8organic combination40 ,the mystic 8vital force0 alone was supposed to be able to produce these combinations4 ,when1 therefore1 in #ahbh1 ,whler1 in ,gttingen1 for the first time refuted this dogma1 and exhibited pure 8organic0 urea1 obtained in an artificial manner from a purely inorganic body 7cyanate of ammonium71 it caused the greatest surprise and astonishment4 ,in more recent times1 by the progress of synthetic chemistry1 we have succeeded in producing in our laboratories a great variety of similar 8organic0 combinations of carbon1 by purely artificial means--for example alcohol1 acetic acid1 formic acid4 ,indeed1 many exceedingly complicated combinations of carbon are now artificially produced1 so that there is every likelihood1 sooner or later1 of our producing artificially the most complicated1 and at the same time the most important of all1 namely1 the albuminous combinations1 or plasma-bodies4 ,by the consideration of this probability1 the deep chasm which was formerly and generally believed to exist between organic and inorganic bodies is almost or entirely removed1 and the way is paved for the conception of spontaneous generation4 ,of still greater1 nay1 the very greatest importance to the hypothesis of spontaneous generation are1 finally1 the exceedingly remarkable ,monera1 those creatures which we have already so frequently mentioned1 and which are not only the simplest of all observed organisms1 but even the simplest of all imaginable organisms4 ,i have already described these wonderful 8organisms without organs10 when examining the simplest phenomena of propagation and inheritance4 ,we already know seven different genera of these ,monera1 some of which live in fresh water1 others in the sea 7compare above1 p4 #ahd2 also ,plate ,i4 and its explanation in the ,appendix74 ,in a perfectly developed and freely motile state1 they one and all present us with nothing but a simple little lump of an albuminous combination of carbon4 ,the individual genera and species differ only a little in the manner of propagation and development1 and in the way of taking nourishment4 ,through the discovery of these organisms1 which are of the utmost importance1 the supposition of a spontaneous generation loses most of its difficulties4 ,for as all trace of organization--all distinction of heterogeneous parts--is still wanting in them1 and as all the vital phenomena are performed by one and the same homogeneous and formless matter1 we can easily imagine their origin by spontaneous generation4 ,if this happens through plasmogeny1 and if plasma capable of life already exists1 it then only needs to individualize itself in the same way as the mother liquor of crystals individualizes itself in crystallization4 ,if1 on the other hand1 the spontaneous generation of the ,monera takes place by true autogeny1 then it is further requisite that that plasma capable of life1 that primval mucus1 should be formed out of simpler combinations of carbon4 ,as we are now able artificially to produce1 in our laboratories1 combinations of carbon similar to this in the complexity of their constitution1 there is absolutely no reason for supposing that there are not conditions in free nature also1 in which such combinations could take place4 ,formerly1 when the doctrine of spontaneous generation was advocated1 it failed at once to obtain adherents on account of the composite structure of the simplest organisms then known4 ,it is only since we have discovered the exceedingly important ,monera1 only since we have become acquainted in them with organisms not in any way built up of distinct organs1 but which consist solely of a single chemical combination1 and yet grow1 nourish1 and propagate themselves1 that this great difficulty has been removed1 and the hypothesis of spontaneous generation has gained a degree of probability which entitles it to fill up the gap existing between ,kant's cosmogony and ,lamarck's ,theory of ,descent4 ,even among the ,monera at present known there is a species which probably1 even now1 always comes into existence by spontaneous generation4 ,this is the wonderful ,bathybius ,hckelii1 discovered and described by ,huxley4 ,as ,i have already mentioned 7p4 #ahd71 this ,moneron is found in the greatest depths of the sea1 at a depth of between #ab1jjj and #bd1jjj feet1 where it covers the ground partly as retiform threads and plaits of plasma1 partly in the form of larger or smaller irregular lumps of the same material4#f ,only such homogeneous organisms as are yet not differentiated1 and are similar to inorganic crystals in being homogeneously composed of one single substance1 could arise by spontaneous generation1 and could become the primval parents of all other organisms4 ,in their further development we have pointed out that the most important process is the formation of a kernel or nucleus in the simple little lump of albumen4 ,we can conceive this to take place in a purely physical manner1 by the condensation of the innermost central part of the albumen4 ,the more solid central mass1 which at first gradually shaded off into the peripheral plasma1 becomes sharply separated from it1 and thus forms an independent1 round1 albuminous corpuscle1 the kernel2 and by this process the ,moneron becomes a cell4 ,now1 it must have become evident from our previous chapters1 that the further development of all other organisms out of such a cell presents no difficulty1 for every animal and every plant1 in the beginning of its individual life1 is a simple cell4 ,man1 as well as every other animal1 is at first nothing but a simple egg-cell1 a single lump of mucus1 containing a kernel 7p4 #big1 ,fig4 #e74 ,in the same way as the kernel of the organic cell arose in the interior or central mass of the originally homogeneous lump of plasma1 by separation1 so1 too1 the first cell-membrane was formed on its surface4 ,this simple1 but most important process1 as has already been remarked1 can likewise be explained in a purely physical manner1 either as a chemical deposit1 or as a physical condensation in the uppermost stratum of the mass1 or as a secretion4 ,one of the first processes of adaptation effected by the ,moneron originating by spontaneous generation must have been the condensation of an external crust1 which as a protecting covering shut in the softer interior from the hostile influences of the outer world4 ,as soon as1 by condensation of the homogeneous ,moneron1 a cell-kernel arose in the interior and a membrane arose on the surface1 all the fundamental parts of the unit were furnished1 out of which1 by infinitely manifold repetition and combination1 as attested by actual observation1 the body of higher organisms is constructed4 ,as has already been mentioned1 our whole understanding of an organism rests upon the cell theory established thirty years ago by ,schleiden and ,schwann4 ,according to it1 every organism is either a simple cell or a cell-community1 a republic of closely connected cells4 ,all the forms and vital phenomena of every organism are the collective result of the forms and vital phenomena of all the single cells of which it is composed4 ,by the recent progress of the cell theory it has become necessary to give the elementary organisms1 that is1 the 8organic0 individuals of the first order1 which are usually designated as cells1 the more general and more suitable name of form-units1 or plastids4 ,among these form-units we distinguish two main groups1 namely1 the cytods and the genuine cells4 ,the cytods are1 like the ,monera1 pieces of plasma without a kernel 7p4 #ahf1 ,fig4 #a74 ,cells1 on the other hand1 are pieces of plasma containing a kernel or nucleus 7p4 #ahh1 ,fig4 #b74 ,each of these two main groups of plastids is again divided into two subordinate groups1 according as they possess or do not possess an external covering 7skin1 shell1 or membrane74 ,we may accordingly distinguish the following four grades or species of plastids1 namely3 #a4 ,simple cytods 7p4 #ahf1 ,fig4 #a ,a72 #b4 ,encased cytods2 #c4 ,simple cells 7p4 #ahh1 ,fig4 #b ,b72 #d4 ,encased cells 7p4 #ahh1 ,fig4 #b ,a74 7,gen4 ,morph4 i4 #bfi-bhi47 ,concerning the relation of these four forms of plastids to spontaneous generation1 the following is the most probable3--#a4 ,the simple cytods 7,gymnocytoda71 naked particles of plasma without kernel1 like the still living ,monera1 are the only plastids which directly come into existence by spontaneous generation4 #b4 ,the enclosed cytods 7,lepocytoda71 particles of plasma without kernel1 which are surrounded by a covering 7membrane or shell71 arose out of the simple cytods either by the condensation of the outer layers of plasma or by the secretion of a covering4 #c4 ,the simple cells 7,gymnocyta71 or naked cells1 particles of plasma with kernel1 but without covering1 arose out of the simple cytods by the condensation of the innermost particles of plasma into a kernel1 or nucleus1 by differentiation of a central kernel and peripheral cell-substance4 #d4 ,the enclosed cells 7,lepocyta71 or testaceous cells1 particles of plasma with kernel and an outer covering 7membrane or shell71 arose either out of the enclosed cytods by the formation of a kernel1 or out of the simple cells by the formation of a membrane4 ,all the other forms of form-units1 or plastids1 met with1 besides these1 have only subsequently arisen out of these four fundamental forms by natural selection1 by descent with adaptation1 by differentiation and transformation4 ,by this theory of plastids1 by deducing all the different forms of plastids1 and hence1 also1 all organisms composed of them1 from the ,monera1 we obtain a simple and natural connection in the whole series of the development of nature4 ,the origin of the first ,monera by spontaneous generation appears to us as a simple and necessary event in the process of the development of the earth4 ,we admit that this process1 as long as it is not directly observed or repeated by experiment1 remains a pure hypothesis4 ,but ,i must again say that this hypothesis is indispensable for the consistent completion of the non-miraculous history of creation1 that it has absolutely nothing forced or miraculous about it1 and that certainly it can never be positively refuted4 ,it must be taken into consideration that the process of spontaneous generation1 even if it still took place daily and hourly1 would in any case be exceedingly difficult to observe and establish with absolute certainty as such4 ,with regard to the ,monera1 we find ourselves placed before the following alternative3 either they are actually directly derived from pre-existing1 or 8created10 most ancient ,monera1 and in this case they would have had to propagate themselves unchanged for many millions of years1 and to have maintained their original form of simple particles of plasma2 or1 the present ,monera have originated much later in the course of the organic history of the earth1 by repeated acts of spontaneous generation1 and in this case spontaneous generation may take place now as well as then4 ,the latter supposition has evidently much more probability on its side than the former4 ,if we do not accept the hypothesis of spontaneous generation1 then at this one point of the history of development we must have recourse to the miracle of a supernatural creation4 ,the ,creator must have created the first organism1 or a few first organisms1 from which all others are derived1 and as such he must have created the simplest ,monera1 or primval cytods1 and given them the capability of developing further in a mechanical way4 ,i leave it to each one of my readers to choose between this idea and the hypothesis of spontaneous generation4 ,to me the idea that the ,creator should have in this one point arbitrarily interfered with the regular process of development of matter1 which in all other cases proceeds entirely without his interposition1 seems to be just as unsatisfactory to a believing mind as to a scientific intellect4 ,if1 on the other hand1 we assume the hypothesis of spontaneous generation for the origin of the first organisms1 which in consequence of reasons mentioned above1 and especially in consequence of the discovery of the ,monera1 has lost its former difficulty1 then we arrive at the establishment of an uninterrupted natural connection between the development of the earth and the organisms produced on it1 and1 in this last remaining lurking-place of obscurity1 we can proclaim the unity of all ,nature1 and the unity of her laws of ,development 7,gen4 ,morph4 i4 #afd74 ,,chapter ,,xiv4 ,,migration ,,and ,,distribution ,,of ,,organisms4 ,,chorology ,,and ,,the ,,ice-,,period ,,of ,,the ,,earth4 ,chorological ,facts and ,causes4--,origin of most ,species in one ,single ,locality3 8,centres of ,creation40--,distribution by ,migration4--,active and ,passive ,migrations of ,animals and ,plants4--,means of ,transport4--,transport of ,germs by ,water and by ,wind4--,continual ,change of the ,area of ,distribution by ,elevations and ,depressions of the ,ground4--,chorological ,importance of ,geological ,processes4--,influence of the ,change of ,climate4--,ice or ,glacial ,period4--,its ,importance to ,chorology4--,importance of ,migrations for the ,origin of ,new ,species4--,isolation of ,colonists4--,wagner's ,law of ,migration4--,connection between the ,theory of ,migration and the ,theory of ,selection4--,agreement of its ,results with the ,theory of ,descent4 ,as ,i have repeatedly said1 but cannot too much emphasize1 the actual value and invincible strength of the ,theory of ,descent does not lie in its explaining this or that single phenomenon1 but in the fact that it explains all biological phenomena1 that it makes all botanical and zoological series of phenomena intelligible in their relations to one another4 ,hence every thoughtful investigator is the more firmly and deeply convinced of its truth the more he advances from single biological observations to a general view of the whole domain of animal and vegetable life4 ,let us now1 starting from this comprehensive point of view1 survey a biological domain1 the varied and complicated phenomena of which may be explained with remarkable simplicity and clearness by the theory of selection4 ,i mean ,chorology1 or the theory of the local distribution of organisms over the surface of the earth4 ,by this ,i do not only mean the geographical distribution of animal and vegetable species over the different parts and provinces of the earth1 over continents and islands1 seas1 and rivers2 but also their topographical distribution in a vertical direction1 their ascending to the heights of mountains1 and their descending into the depths of the ocean4 7,gen4 ,morph4 ii4 #bhf47 ,the strange chorological series of phenomena which show the horizontal distribution of organisms over parts of the earth1 and their vertical distribution in heights and depths1 have long since excited general interest4 ,in recent times ,alexander ,humboldt7#ci7 and ,frederick ,schouw have especially discussed the geography of plants1 and ,berghaus and ,schmarda the geography of animals1 on a large scale4 ,but although these and several other naturalists have in many ways increased our knowledge of the distribution of animal and vegetable forms1 and laid open to us a new domain of science1 full of wonderful and interesting phenomena1 yet ,chorology as a whole remained1 as far as their labours were concerned1 only a desultory knowledge of a mass of individual facts4 ,it could not be called a science as long as the causes for the explanation of these facts were wanting4 ,these causes were first disclosed by the theory of selection and its doctrine of the migrations of animal and vegetable species1 and it is only since the works of ,darwin and ,wallace that we have been able to speak of an independent science of ,chorology4 ,if all the phenomena of the geographical and topographical distribution of organisms are examined by themselves1 without considering the gradual development of species1 and if at the same time1 following the customary superstition1 the individual species of animals and plants are considered as forms independently created and independent of one another1 then there remains nothing for us to do but to gaze at those phenomena as a confused collection of incomprehensible and inexplicable miracles4 ,but as soon as we leave this low stand-point1 and rise to the height of the theory of development1 by means of the supposition of a blood-relationship between the different species1 then all at once a clear light falls upon this strange series of miracles1 and we see that all chorological facts can be understood quite simply and clearly by the supposition of a common descent of the species1 and their passive and active migrations4 ,the most important principle from which we must start in chorology1 and of the truth of which we are convinced by due examination of the theory of selection1 is that1 as a rule1 every animal and vegetable species has arisen only once in the course of time and only in one place on the earth--its so-called 8centre of creation0--by natural selection4 ,i share this opinion of ,darwin's unconditionally1 in respect to the great majority of higher and perfect organisms1 and in respect to most animals and plants in which the division of labour1 or differentiation of the cells and organs of which they are composed1 has attained a certain stage4 ,for it is quite incredible1 or could at best only be an exceedingly rare accident1 that all the manifold and complicated circumstances--all the different conditions of the struggle for life1 which influence the origin of a new species by natural selection--should have worked together in exactly the same agreement and combination more than once in the earth's history1 or should have been active at the same time at several different points of the earth's surface4 ,on the other hand1 ,i consider it to be very probable that certain exceedingly imperfect organisms of the simplest structure1 forms of species of an exceedingly indifferent nature1 as1 for example1 many single-celled ,protista1 but especially the ,monera1 the simplest of them all1 should have several times or simultaneously arisen in their specific form in several parts of the earth4 ,for the few and very simple conditions by which their specific form was changed in the struggle for life may surely have often been repeated1 in the course of time1 independently in different parts of the earth4 ,further1 those higher specific forms also1 which have not arisen by natural selection1 but by hybridism 7the previously-mentioned hybrid species1 pp4 #adg and #bge71 may have repeatedly arisen anew in different localities4 ,as1 however1 this proportionately small number of organisms does not especially interest us here1 we may1 in respect of chorology1 leave them alone1 and need only take into consideration the distribution of the great majority of animal and vegetable species in regard to which the single origin of every species in a single locality1 in its so-called 8central point of creation10 can be considered as tolerably certain4 ,every animal and vegetable species from the beginning of its existence has possessed the tendency to spread beyond the limited locality of its origin1 beyond the boundary of its 8centre of creation10 or1 in other words1 beyond its primval home1 or its natal place4 ,this is a necessary consequence of the relations of population and over-population 7pp4 #afa and #bef74 ,the more an animal or vegetable species increases1 the less is its limited natal place sufficient for its sustenance1 and the fiercer the struggle for life2 the more rapid the over-population of the natal spot1 the more it leads to emigration4 ,these migrations are common to all organisms1 and are the real cause of the wide distribution of the different species of organisms over the earth's surface4 ,just as men leave over-crowded states1 so all animals and plants migrate from their over-crowded primval homes4 ,many distinguished naturalists1 especially ,lyell7#aa7 and ,schleiden1 have before this repeatedly drawn attention to the great importance of these very interesting migrations of organisms4 ,the means of transport by which they are effected are extremely varied4 ,darwin has discussed these most excellently in the eleventh and twelfth chapters of his work1 which are exclusively devoted to 8geographical distribution40 ,the means of transport are partly active1 partly passive2 that is to say1 the organism effects its migration partly by free locomotion due to its own activity1 and partly by the movements of other natural bodies in which it has no active share4 ,it is self-evident that active migrations play the chief part in animals able to move freely4 ,the more freely an animal's organization permits it to all move in directions1 the more easily the animal species can migrate1 and the more rapidly it will spread over the earth4 ,flying animals are of course most favoured in this respect1 among vertebrate animals especially birds1 and among articulated animals1 insects4 ,these two classes1 as soon as they came into existence1 can have more easily spread over the whole earth than any other animal1 and this fact partly explains the extraordinary uniformity of structure which characterizes these two great classes of animals4 ,for1 although they contain an exceedingly large number of different species1 and although the insect class alone is said to possess more different species than all other classes of animals together1 yet all the innumerable species of insects1 and in like manner1 also1 the different species of birds1 agree most strikingly in all essential peculiarities of their organization4 ,hence1 in the class of insects1 as well as in that of birds1 we can distinguish only a very small number of large natural groups or orders1 and these few orders differ but very little from one another in their internal structure4 ,the orders of birds with their numerous species are not nearly as distinct from one another as the orders of the mammalian class1 containing much fewer species2 and the orders of insects1 which are extremely rich in genera and species1 resemble one another much more closely in their internal structure than do the much smaller orders of the crab class4 ,the general parallelism between birds and insects is also very interesting in relation to systematic zoology2 and the great importance of their richness in forms1 for scientific morphology1 lies in the fact that they show us how1 within the narrowest anatomical sphere1 and without profound changes of the essential internal organization1 the greatest variety in external bodily forms can be attained4 ,the reason of this is evidently their flying mode of life and their free locomotion4 ,in consequence of this birds1 as well as insects1 have spread very rapidly over the whole surface of the earth1 have settled in all possible localities inaccessible to other animals1 and variously modified their specific form by superficial adaptation to particular local relations4 ,next to the flying animals1 those animals1 of course1 have spread most quickly and furthest which were next best able to migrate1 that is1 the best runners among the inhabitants of the land1 and the best swimmers among the inhabitants of the water4 ,however1 the power of such active migrations is not confined to those animals which throughout life enjoy free locomotion4 ,for the fixed animals also1 such as corals1 tubicolous worms1 sea-squirts1 lily encrinites1 sea-acorns1 barnacles1 and many other lower animals which adhere to seaweeds1 stones1 etc41 enjoy1 at least at an early period of life1 free locomotion4 ,they all migrate before they adhere to anything4 ,their first free locomotive condition of early life is generally that of a 8ciliated0 larva1 a roundish1 cellular corpuscle1 which1 by means of a garb of movable 8flimmer-hairs10 7,latin1 8cilia07 swarms about in the water and bears the name of ,planula4 ,but the power of free locomotion1 and hence1 also1 of active migration1 is not confined to animals alone1 but many plants likewise enjoy it4 ,many lower aquatic plants1 especially the class of the ,tangles 7,alg71 swim about freely in the water in early life1 like the lower animals just mentioned1 by means of a vibratile hairy coat1 a vibrating whip1 or a covering of tremulous fringes1 and only at a later period adhere to objects4 ,even in the case of many higher plants1 which we designate as creepers and climbing plants1 we may speak of active migration4 ,their elongated stalks and perennial roots creep or climb during their long process of growth to new positions1 and by means of their widespread branches they acquire new habitations1 to which they attach themselves by buds1 and bring forth new colonies of individuals of their species4 ,influential as these active migrations of most animals and many plants are1 yet alone they would by no means be sufficient to explain the chorology of organisms4 ,passive migrations have ever been by far the more important1 and of far greater influence1 in the case of most plants and in that of many animals4 ,such passive changes of locality are produced by extremely numerous causes4 ,air and water in their eternal motion1 wind and waves with their manifold currents1 play the chief part4 ,the wind in all places and at all times raises light organisms1 small animals and plants1 but especially their young germs1 animal eggs and plant seeds1 and carries them far over land and seas4 ,where they fall into the water they are seized by currents or waves and carried to other places4 ,it is well known1 from numerous examples1 how far in many cases trunks of trees1 hard shelled fruits1 and other not readily perishable portions of plants are carried away from their original home by the course of rivers and by the currents of the sea4 ,trunks of palm trees from the ,west ,indies are brought by the ,gulf ,stream to the ,british and ,norwegian coasts4 ,all large rivers bring down driftwood from the mountains1 and frequently alpine plants are carried from their home at the source of the river into the plains1 and even further1 down to the sea4 ,frequently numerous inhabitants live between the roots of the plants thus carried down1 and between the branches of the trees thus washed away there are various inhabitants which have to take part in the passive migration4 ,the bark of the tree is covered with mosses1 lichens1 and parasitic insects4 ,other insects1 spiders1 etc41 even small reptiles and mammals1 are hidden within the hollow trunk or cling to the branches4 ,in the earth adhering to the fibres of the roots1 in the dust lying in the cracks of the bark1 there are innumerable germs of smaller animals and plants4 ,now1 if the trunk thus washed away lands safely on a foreign shore or on a distant island1 the guests who had to take part in the involuntary voyage can leave their boat and settle in the new country4 ,a very remarkable kind of water-transport is formed by the floating icebergs which annually become loosened from the eternal ice of the ,polar ,sea4 ,although these cold regions are thinly peopled1 yet many of their inhabitants1 who were accidentally upon an iceberg while it was becoming loosened1 are carried away with it by the currents1 and landed on warmer shores4 ,in this manner1 by means of loosened blocks of ice from the northern ,polar ,sea1 often whole populations of small animals and plants have been carried to the northern shores of ,europe and ,america4 ,nay1 even polar foxes and polar bears have been carried in this way to ,iceland and to the ,british ,isles4 ,transport by air is no less important than transport by water in this matter of passive migration4 ,the dust covering our streets and roofs1 the earth lying on dry fields and dried-up pools1 the light moist soil of forests1 in short1 the whole surface of the globe contains millions of small organisms and their germs4 ,many of these small animals and plants can without injury become completely dried up1 and awake again to life as soon as they are moistened4 ,every gust of wind raises up with the dust innumerable little creatures of this kind1 and often carries them away to other places miles off4 ,but even larger organisms1 and especially their germs1 may often make distant passive journeys through the air4 ,the seeds of many plants are provided with light feathery processes1 which act as parachutes and facilitate their flight in the air1 and prevent their falling4 ,spiders make journeys of many miles through the air on their fine filaments1 their so-called gossamer threads4 ,young frogs are frequently raised by whirlwinds into the air by thousands1 and fall down in a distant part as a 8shower of frogs40 ,storms may carry birds and insects across half the earth's circumference4 ,they drop in the ,united ,states1 having risen in ,england4 ,starting from ,california1 they only come to rest in ,china4 ,but1 again1 many other organisms may make the journey from one continent to another together with the birds and insects4 ,of course all parasites1 the number of which is legion1 fleas1 lice1 mites1 moulds1 etc41 migrate with the organisms upon which they live4 ,in the earth which often remains sticking to the claws of birds there are also small animals and plants or their germs4 ,thus the voluntary or involuntary migration of a single larger organism may carry a whole small flora and fauna from one part of the earth to another4 ,besides the means of transport here mentioned1 there are many others which explain the distribution of animal and vegetable species over the large tracts of the earth's surface1 and especially the general distribution of the so-called cosmopolitan species4 ,but these alone would not nearly be sufficient to explain all chorological facts4 ,how is it1 for example1 that many inhabitants of fresh water live in various rivers or lakes far away and quite apart from one another8 ,how is it that many inhabitants of mountains1 which cannot exist in plains1 are found upon entirely separated and far distant chains of mountains8 ,it is difficult to believe1 and in many cases quite inconceivable1 that these inhabitants of fresh water should have in any way1 actively or passively1 migrated over the land lying between the lakes1 or that the inhabitants of mountains in any way1 actively or passively1 crossed the plains lying between their mountain homes4 ,but here geology comes to our help1 as a mighty ally1 and completely solves these difficult problems for us4 ,the history of the earth's development shows us that the distribution of land and water on its surface is ever and continually changing4 ,in consequence of geological changes of the earth's crust1 elevations and depressions of the ground take place everywhere1 sometimes more strongly marked in one place1 sometimes in another4 ,even if they happen so slowly that in the course of centuries the seashore rises or sinks only a few inches1 or even only a few lines1 still they nevertheless effect great results in the course of long periods of time4 ,and long--immeasurably long--periods of time have not been wanting in the earth's history4 ,during the course of many millions of years1 ever since organic life existed on the earth1 land and water have perpetually struggled for supremacy4 ,continents and islands have sunk into the sea1 and new ones have arisen out of its bosom4 ,lakes and seas have slowly been raised and dried up1 and new water basins have arisen by the sinking of the ground4 ,peninsulas have become islands by the narrow neck of land which connected them with the mainland sinking into the water4 ,the islands of an archipelago have become the peaks of a continuous chain of mountains by the whole floor of their sea being considerably raised4 ,thus the ,mediterranean at one time was an inland sea1 when1 in the place of the ,straits of ,gibraltar1 an isthmus connected ,africa with ,spain4 ,england1 even during the more recent history of the earth1 when man already existed1 has repeatedly been connected with the ,european continent and been repeatedly separated from it4 ,nay1 even ,europe and ,north ,america have been directly connected4 ,the ,south ,sea at one time formed a large ,pacific ,continent1 and the numerous little islands which now lie scattered in it were simply the highest peaks of the mountains covering that continent4 ,the ,indian ,ocean formed a continent which extended from the ,sunda ,islands along the southern coast of ,asia to the east coast of ,africa4 ,this large continent of former times ,sclater1 an ,englishman1 has called ,lemuria1 from the monkey-like animals which inhabited it1 and it is at the same time of great importance from being the probable cradle of the human race1 which in all likelihood here first developed out of anthropoid apes4 ,the important proof which ,alfred ,wallace has furnished17#cf7 by the help of chorological facts1 that the present ,malayan ,archipelago consists in reality of two completely different divisions1 is particularly interesting4 ,the western division1 the ,indo-,malayan ,archipelago1 comprising the large islands of ,borneo1 ,java1 and ,sumatra1 was formerly connected by ,malacca with the ,asiatic continent1 and probably also with the ,lemurian continent just mentioned4 ,the eastern division1 on the other hand1 the ,austro-,malayan ,archipelago1 comprising ,celebes1 the ,moluccas1 ,new ,guinea1 ,solomon's ,islands1 etc41 was formerly directly connected with ,australia4 ,both divisions were formerly two continents separated by a strait1 but they have now for the most part sunk below the level of the sea4 ,wallace1 solely on the ground of his accurate chorological observations1 has been able in the most acute manner to determine the position of this former strait1 the south end of which passes between ,balij and ,lombok4 ,thus1 ever since liquid water existed on the earth1 the boundaries of water and land have eternally changed1 and we may assert that the outlines of continents and islands have never remained for an hour1 nay1 even for a minute1 exactly the same4 ,for the waves eternally and perpetually break on the edge of the coast1 and whatever the land in these places loses in extent1 it gains in other places by the accumulation of mud1 which condenses into solid stone and again rises above the level of the sea as new land4 ,nothing can be more erroneous than the idea of a firm and unchangeable outline of our continents1 such as is impressed upon us in early youth by defective lessons on geography1 which are devoid of a geological basis4 ,i need hardly draw attention to the fact that these geological changes of the earth's surface have ever been exceedingly important to the migrations of organisms1 and consequently to their ,chorology4 ,from them we learn to understand how it is that the same or nearly related species of animals and plants can occur on different islands1 although they could not have passed through the water separating them1 and how other species living in fresh water can inhabit different enclosed water-basins1 although they could not have crossed the land lying between them4 ,these islands were formerly mountain peaks of a connected continent1 and these lakes were once directly connected with one another4 ,the former were separated by geological depressions1 the latter by elevations4 ,now1 if we further consider how often and how unequally these alternating elevations and depressions occur on the different parts of the earth1 and how1 in consequence of this1 the boundaries of the geographical tracts of distribution of species become changed1 and if we further consider in what exceedingly various ways the active and passive migrations of organisms must have been influenced by them1 then we shall be in a position to completely understand the great variety of the picture which is at present offered to us by the distribution of animal and vegetable species4 ,there is yet another important circumstance to be mentioned here1 which is likewise of great importance for a complete explanation of this varied geographical picture1 and which throws light upon many very obscure facts1 which1 without its help1 we should not be able to comprehend4 ,i mean the gradual change of climate which has taken place during the long course of the organic history of the earth4 ,as we saw in our last chapter1 at the beginning of organic life on the earth a much higher and more equal temperature must have generally prevailed than at present4 ,the differences of zones1 which in our time are so very striking1 did not exist at all in those times4 ,it is probable that for many millions of years but one climate prevailed over the whole earth1 which very closely resembled1 or even surpassed1 the hottest tropical climate of the present day4 ,the highest north which man has yet reached was then covered with palms and other tropical plants1 the fossil remains of which are still found there4 ,the temperature of this climate at a later period gradually decreased2 but still the poles remained so warm that the whole surface of the earth could be inhabited by organisms4 ,it was only at a comparatively very recent period of the earth's history1 namely1 at the beginning of the tertiary period1 that there occurred1 as it seems1 the first perceptible cooling of the earth's crust at the poles1 and through this the first differentiation or separation of the different zones of temperature or climatic zones4 ,but the slow and gradual decrease of temperature continued to extend more and more within the tertiary period1 until at last1 at both poles of the earth1 the first permanent ice caps were formed4 ,i need scarcely point out in detail how very much this change of climate must have affected the geographical distribution of organisms1 and the origin of numerous new species4 ,the animal and vegetable species1 which1 down to the tertiary period1 had found an agreeable tropical climate all over the earth1 even as far as the poles1 were now forced either to adapt themselves to the intruding cold1 or to flee from it4 ,those species which adapted and accustomed themselves to the decreasing temperature became new species simply by this very acclimatization1 under the influence of natural selection4 ,the other species1 which fled from the cold1 had to emigrate and seek a milder climate in lower latitudes4 ,the tracts of distribution which had hitherto existed must by this have been vastly changed4 ,however1 during the last great period of the earth's history1 during the quaternary period 7or diluvial period7 succeeding the tertiary one1 the decrease of the heat of the earth from the poles did not by any means remain stationary4 ,the temperature fell lower and lower1 nay1 even far below the present degree4 ,northern and ,central ,asia1 ,europe1 and ,north ,america from the north pole1 were covered to a great extent by a connected sheet of ice1 which in our part of the earth seems to have reached the ,alps4 ,in a similar manner the cold also advancing from the south pole covered a large portion of the southern hemisphere1 which is now free from it1 with a rigid sheet of ice4 ,thus1 between these vast lifeless ice continents there remained only a narrow zone to which the life of the organic world had to withdraw4 ,this period1 during which man1 or at least the human ape1 already existed1 and which forms the first period of the so-called diluvial epoch1 is now universally known as the ice or glacial period4 ,the ingenious ,carl ,schimper is the first naturalist who clearly conceived the idea of the ice period1 and proved the great extent of the former glaciation of ,central ,europe by the help of the so-called boulders1 or erratic blocks of stone1 as also by the 8glacier tables40 ,louis ,agassiz1 stimulated by him1 and considerably supported by the independent investigations of the eminent geologist ,charpentier1 afterwards undertook the task of carrying out the theory of the ice period4 ,in ,england1 the geologist ,forbes distinguished himself in this matter1 and also was the first to apply it to the theory of migrations and the geographical distribution of species dependent upon migration4 ,agassiz1 however1 afterwards injured the theory by his one-sided exaggeration1 inasmuch as1 from his partiality to ,cuvier's theory of cataclysms1 he endeavoured to attribute the destruction of the whole animate creation then existing1 to the sudden coming on of the cold of the ice period and the 8revolution0 connected with it4 ,it is unnecessary here to enter into detail as to the ice period itself1 and into investigations about its limits1 and ,i may omit this all the more reasonably since the whole of our recent geological literature is full of it4 ,it will be found discussed in detail in the works of ,cotta17#ca7 ,lyell17#cj7 ,vogt17#bg7 ,zittel17#cb7 etc4 ,its great importance to us here is that it helps us to explain the most difficult chorological problems1 as ,darwin has correctly perceived4 ,for there can be no doubt that this glaciation of the present temperate zones must have exercised an exceedingly important influence on the geographical and topographical distribution of organisms1 and that it must have entirely changed it4 ,while the cold slowly advanced from the poles towards the equator1 and covered land and sea with a connected sheet of ice1 it must of course have driven the whole living world before it4 ,animals and plants had to migrate if they wished to escape being frozen4 ,but as at that time the temperate and tropical zones were probably no less densely peopled with animals and plants than at present1 there must have arisen a fearful struggle for life between the latter and the intruders coming from the poles4 ,during this struggle1 which certainly lasted many thousands of years1 many species must have perished and many become modified and been transformed into new species4 ,the hitherto existing tracts of distribution of species must have become completely changed1 and the struggle have been continued1 nay1 indeed1 must have broken out anew and been carried on in new forms1 when the ice period had reached and gone beyond its furthest point1 and when in the post-glacial period the temperature again increased1 and organisms began to migrate back again towards the poles4 ,in any case this great change of climate1 whether a greater or less importance be ascribed to it1 is one of those occurrences in the history of the earth which have most powerfully influenced the distribution of organic forms4 ,but more especially one important and difficult chorological circumstance is explained by it in the simplest manner1 namely1 the specific agreement of many of our ,alpine inhabitants with some of those living in polar regions4 ,there is a great number of remarkable animal and vegetable forms which are common to these two far distant parts of the earth1 and which are found nowhere in the wide plains lying between them4 ,their migration from the polar lands to the ,alpine heights1 or vice versa1 would be inconceivable under the present climatic circumstances1 or could be assumed at least only in a few rare instances4 ,but such a migration could take place1 nay1 was obliged to take place1 during the gradual advance and retreat of the ice-sheet4 ,as the glaciation encroached from ,northern ,europe towards our ,alpine chains1 the polar inhabitants retreating before it--gentian1 saxifrage1 polar foxes1 and polar hares--must have peopled ,germany1 in fact all ,central ,europe4 ,when the temperature again increased1 only a portion of these ,arctic inhabitants returned with the retreating ice to the ,arctic zones4 ,another portion of them climbed up the mountains of the ,alpine chain instead1 and there found the cold climate suited to them4 ,the problem is thus solved in a most simple manner4 ,we have hitherto principally considered the theory of the migrations of organisms in so far as it explains the radiation of every animal and vegetable species from a single primval home1 from a 8central point of creation10 and the dispersion of these species over a greater or less portion of the earth's surface4 ,but these migrations are also of great importance to the theory of development1 because we can perceive in them a very important means for the origin of new species4 ,when animals and plants migrate they meet in their new home1 in the same way as do human emigrants1 with conditions which are more or less different from those which they have inherited throughout generations1 and to which they have been accustomed4 ,the emigrants must either submit and adapt themselves to these new conditions of life or they perish4 ,by adaptation their peculiar specific character becomes the more changed the greater the difference between the new and the old home4 ,the new climate1 the new food1 but above all1 new neighbours in the forms of other animals and plants1 influence and tend to modify the inherited character of the immigrant species1 and if it is not hardy enough to resist the influences1 then sooner or later a new species must arise out of it4 ,in most cases this transformation of an immigrant species takes place so quickly under the influence of the altered struggle for life1 that even after a few generations a new species arises from it4 ,migration has an especial influence in this way on all organisms with separate sexes4 ,for in them the origin of new species by natural selection is always rendered difficult1 or delayed1 by the fact that the modified descendants occasionally again mix sexually with the unchanged original form1 and thus by crossing return to the first form4 ,but if such varieties have migrated1 if great distances or barriers to migration--seas1 mountains1 etc4--have separated them from the old home1 then the danger of a mingling with the primary form is prevented1 and the isolation of the emigrant form1 which becomes a new species by adaptation1 prevents its breeding with the old stock1 and hence prevents its return in this way to the original form4 ,the importance of migration for the isolation of newly-originating species and the prevention of a speedy return to the primary form has been especially pointed out by the philosophic traveller1 ,moritz ,wagner1 of ,munich4 ,in a special treatise on 8,darwin's ,theory and the ,law of the ,migration of ,organisms107#dj7 ,wagner gives from his own rich experience a great number of striking examples which confirm the theory of migration set forth by ,darwin in the eleventh and twelfth chapters of his book1 where he especially discusses the effect of the complete isolation of emigrant organisms in the origin of new species4 ,wagner sets forth the simple causes which have 8locally bounded the form and founded its typical difference10 in the following three propositions3--#a4 ,the greater the total amount of change in the hitherto existing conditions of life which the emigrating individuals find on entering a new territory1 the more intensely must the innate variability of every organism manifest itself4 #b4 ,the less this increased individual variability of organisms is disturbed in the peaceful process of reproduction by the mingling of numerous subsequent immigrants of the same species1 the more frequently will nature succeed1 by intensification and transmission of the new characteristics1 in forming a new variety or race1 that is1 a commencing species4 #c4 ,the more advantageous the changes experienced by the individual organs are to the variety1 the more readily will it be able to adapt itself to the surrounding conditions2 and the longer the undisturbed breeding of a commencing variety of colonists in a new territory continues without its mingling with subsequent immigrants of the same species1 the oftener a new species will arise out of the variety4 ,every one will agree with these three propositions of ,moritz ,wagner's4 ,but we must consider his view1 that the migration and the subsequent isolation of the emigrant individuals is a necessary condition for the origin of new species1 to be completely erroneous4 ,wagner says1 8without a long-enduring separation of colonists from their former species1 the formation of a new race cannot succeed--selection1 in fact1 cannot take place4 ,unlimited crossing1 unhindered sexual mingling of all individuals of a species will always produce uniformity1 and drive varieties1 whose characteristics have not been fixed throughout a series of generations1 back to the primary form40 ,this sentence1 in which ,wagner himself comprises the main result of his investigations1 he would be able to defend only if all organisms were of separate sexes1 if every origin of new individuals were possible only by the mingling of male and female individuals4 ,but this is by no means the case4 ,curiously enough1 ,wagner says nothing of the numerous hermaphrodites which1 possessing both the sexual organs1 are capable of self-fructification1 and likewise nothing of the countless organisms which are not sexually differentiated4 ,now1 from the earliest times of the organic history of the earth1 there have existed thousands of organic species 7thousands of which still exist7 in which no difference of sex whatever exists1 and1 in fact1 in which no sexual propagation takes place1 and which exclusively reproduce themselves in a non-sexual manner by division1 budding1 formation of spores1 etc4 ,all the great mass of ,protista1 the ,monera1 ,amb1 ,myxomycetes1 ,rhizopoda1 etc41 in short1 all the lower organisms which we shall have to enumerate in the domain of ,protista1 standing midway between the animal and vegetable kingdoms1 propagate themselves exclusively in a non-sexual manner4 ,and this domain comprises a class of organisms which is one of the richest in forms1 nay1 even in a certain respect the richest of all in forms1 as all possible geometrical fundamental forms are represented in it4 ,i allude to the wonderful class of the ,rhizopoda1 or ,ray-streamers1 to which the lime-shelled ,acyttaria and the flint-shelled ,radiolaria belong4 7,compare chapter xvi47 ,it is self-evident1 therefore1 that ,wagner's theory is quite inapplicable to all these non-sexual organisms4 ,moreover1 the same applies to all those hermaphrodites in which every individual possesses both male and female organs and is capable of self-fructification4 ,this is the case1 for instance1 in the ,flat-worms1 flukes1 and tape-worms1 further in the important ,sack-worms 7,tunicates71 the invertebrate relatives of the vertebrate animals1 and in very many other organisms of different groups4 ,many of these species have arisen by natural selection1 without a 8crossing0 of the originating species with its primary form having been possible4 ,as ,i have already shown in the eighth chapter1 the origin of the two sexes1 and consequently sexual propagation in general1 must be considered as a process which began only in later periods of the organic history of the earth1 being the result of differentiation or division of labour4 ,the most ancient terrestrial organisms can have propagated themselves only in the simplest non-sexual manner4 ,even now all ,protista1 as well as all the countless forms of cells1 which constitute the body of higher organisms1 multiply themselves only by non-sexual generation4 ,and yet there arise here 8new species0 by differentiation in consequence of natural selection4 ,but even if we were to take into consideration the animal and vegetable species with separate sexes1 in this case too we should have to oppose ,wagner's chief proposition1 that 8the migration of organisms and their formation of colonies is the necessary condition of natural selection40 ,august ,weismann1 in his treatise on the 8,influence of ,isolation upon the ,formation of ,species107#bd7 has already sufficiently refuted that proposition1 and has shown that even in one and the same district one bi-sexual species may divide itself into several species by natural selection4 ,in relation to this question1 ,i must again call to mind the great influence which division of labour1 or differentiation1 possesses1 being one of the necessary results of natural selection4 ,all the different kinds of cells constituting the body of the higher organisms1 the nerve cells1 muscle cells1 gland cells1 etc41 all these 8good species10 these 8bon species0 of elementary organisms1 have arisen solely by division of labour1 in consequence of natural selection1 although they not only never were locally isolated1 but ever since their origin have always existed in the closest local relations one with another4 ,now1 the same reasoning that applies to these elementary organisms1 or 8individuals of the first order10 applies also to the many-celled organisms of a higher order which only at a later date have arisen as 8good species0 from among their fellows4 ,we are therefore of the same opinion as ,darwin and ,wallace1 that the migration of organisms and their isolation in their new home is a very advantageous condition for the origin of new species2 but we cannot admit1 as ,wagner asserts1 that it is a necessary condition1 and that without it no species can arise4 ,wagner sets up this opinion1 8that migration is a necessary condition for natural selection10 as a special 8law of migration02 but we consider it sufficiently refuted by the above-mentioned facts4 ,we have1 moreover1 already pointed out that in reality the origin of new species by natural selection is a mathematical and logical necessity which1 without anything else1 follows from the simple combination of three great facts4 ,these three fundamental facts are--the ,struggle for ,life1 the ,adaptability1 and the ,hereditivity of organisms4 ,we cannot here enter into detail concerning the numerous interesting phenomena furnished by the geographical and topographical distribution of organic species1 which are all wonderfully explained by the theory of selection and migration4 ,for these ,i refer to the writings of ,darwin17#a7 ,wallace17#cf7 and ,moritz ,wagner17#dj7 in which the important doctrine of the limits of distribution--seas1 rivers1 and mountains--is excellently discussed and illustrated by numerous examples4 ,only three other phenomena must be mentioned here on account of their special importance4 ,first1 the close relation of forms1 that is1 the striking 8family likeness0 existing between the characteristic local forms of every part of the globe1 and their extinct fossil ancestors in the same part of the globe2 secondly1 the no less striking 8family likeness0 between the inhabitants of island groups and those of the neighbouring continent from which the islands were peopled2 lastly and thirdly1 the peculiar character presented in general by the flora and fauna of islands taken as a whole4 ,all these chorological facts given by ,darwin1 ,wallace1 and ,wagner--especially the remarkable phenomena of the limited local fauna and flora1 the relations of insular to continental inhabitants1 the wide distribution of the so-called 8cosmopolitan species10 the close relationship of the local species of the present day with the extinct species of the same limited territory1 the demonstrable radiation of every species from a single central point of creation--all these1 and all other phenomena furnished to us by the geographical and the topographical distribution of organisms1 are explained in a simple and thorough manner by the theory of selection and migration1 while without it they are simply incomprehensible4 ,consequently1 in the whole of this series of phenomena we find a new and weighty proof of the truth of the ,theory of ,descent4 #a ,the world is perfect save where ,man ,comes in with his strife4 #b ,archebiosis 7,bastian71 ,abiogenesis 7,huxley74 #c ,alle ,glieder bilden sich aus nach ew'gen ,gesetzen1 ,und die seltenste ,form bewahrt im ,geheimniss das ,urbild4 ,also bestimmt die ,gestalt die ,lebensweise des ,thieres4 ,und die ,weise zu leben1 sie wirkt auf alle ,gestalten ,mchtig zurck4 ,so zeiget sich fest die geordnete ,bildung1 ,welche zum ,wechsel sich neigt durch usserlich wirkende ,wesen4 #d 8,einstweilen bis den ,bau der ,welt ,philosophie zusammenhlt1 ,erhlt sich ihr ,getriebe ,durch ,hunger und durch ,liebe40 #e 8,allgemeine ,naturgeschichte und ,theorie des ,himmels40 #f ,we must wait for fuller information on the subject of ,bathybius1 at the hands of the naturalists of the ,challenger expedition1 before accepting it finally as a distinct organism4--,editor4 ,,end ,,of ,,vol4 ,i4 ,,works ,,of ,,professor ,,ernst ,,haeckel4 ,,freedom ,,in ,,science ,,and ,,teaching4 ,from the ,german of ,,ernst ,,haeckel4 ,with a ,prefatory ,note by ,t4 ,h4 ,huxley1 ,f4,r4,s4 #a vol41 #abmo4 ,,the ,,evolution ,,of ,,man4 ,a ,popular ,exposition of the ,principal ,points of ,human ,ontogeny and ,phylogeny4 ,from the ,german of ,,ernst ,,haeckel1 ,professor in the ,university of ,jena1 author of 8,the ,history of ,creation10 etc4 ,with numerous ,illustrations4 ,in two vols41 #abmo4 ,cloth4 ,price1 #e4jj4 ,from the ,london ,saturday ,review4 8,in this excellent translation of ,professor ,haeckel's work1 the ,english reader has access to the latest doctrines of the ,continental school of evolution1 in its application to the history or man4 ,it is in ,germany1 beyond any other ,european country1 that the impulse given by ,darwin twenty years ago to the theory of evolution has influenced the whole tenor of philosophical opinion4 ,there may be1 and are1 differences in the degree to which the doctrine may be held capable of extension into the domain of mind and morals2 but there is no denying1 in scientific circles at least1 that as regards the physical history of organic nature much has been done toward making good a continuous scheme of being40 ,,the ,,history ,,of ,,creation2 or1 the ,development of the ,earth and its ,inhabitants by the ,action of ,natural ,causes4 ,a ,popular ,exposition of the ,doctrine of ,evolution in general1 and of that of ,darwin1 ,goethe1 and ,lamarck in particular4 ,from the ,german of ,ernst ,haeckel1 ,professor in the ,university of ,jena4 ,the translation revised by ,professor ,e4 ,ray ,lankester1 ,m4,a41 ,f4,r4,s41 ,fellow of ,exeter ,college1 ,oxford4 ,illustrated with ,lithographic ,plates4 ,in #b vols41 #abmo4 ,cloth1 #e4jj4 ,,works ,,of ,,thomas ,h4 ,,huxley1 ,,ll4,d41 ,f4,r4,s4 ,,man',s ,,place ,,in ,,nature4 #a vol41 #abmo4 ,cloth1 #a4be4 ,,on ,,the ,,origin ,,of ,,species4 #a vol41 #abmo4 ,cloth1 #a4jj4 ,,more ,,criticisms ,,on ,,darwin1 ,,and ,,administrative ,,nihilism4 #a vol41 #abmo4 ,limp cloth1 #ej cents4 ,a ,,manual ,,of ,,the ,,anatomy ,,of ,,vertebrated ,,animals4 ,illustrated4 #a vol41 #abmo4 ,cloth1 #b4ej4 ,a ,,manual ,,of ,,the ,,anatomy ,,of ,,invertebrated ,,animals4 #b4ej4 ,,laysermons1 ,,addresses1 ,,and ,,reviews4 #a vol41 #abmo4 ,cloth1 #a4ge4 ,,critiques ,,and ,,addresses4 #abmo4 ,cloth1 #a4ej4 ,,american ,,addresses2 with a ,lecture on the ,study of ,biology4 #abmo4 ,cloth1 #a4be4 ,,physiography3 an ,introduction to the ,study of ,nature4 ,with ,illustrations and ,colored ,plates4 #abmo4 ,cloth1 #b4ej4 ,,elements ,,of ,,physiology ,,and ,,hygiene4 ,by ,t4 ,h4 ,huxley and ,w4 ,j4 ,youmans4 #a vol41 #abmo4 #a4ej4 ,d4 ,,appleton ,,co41 ,,publishers1 #a1 #c1 #e ,,bond ,,street1 ,n4 ,y4 ,,eminent ,,modern ,,scientists4 ,,herbert ,,spencer',s ,,works4 #ad vols41 #abmo4 ,cloth1 #be4be4 ,,first ,,principles4 #b #jj ,,principles ,,of ,,biology4 #b vols4 #d #jj ,,principles ,,of ,,psychology4 #b vols4 #d #jj ,,principles ,,of ,,sociology4 ,vol4 ,i4 ,parts ,i41 ,,ii41 and ,,iii4 #b #jj ,,ceremonial ,,institutions4 ,being ,part ,,iv4 of the ,principles of ,sociology4 #a #be ,,data ,,of ,,ethics4 #a #be ,,study ,,of ,,sociology4 7,international ,scientific ,series7 #a #ej ,,education4 #a #be ,,discussions ,,in ,,science1 ,,philosophy1 ,,and ,,morals4 #b #jj ,,universal ,,progress4 #b #jj ,,essays3 ,,moral1 ,,political1 ,,and ,,sthetic4 #b #jj ,,social ,,statics4 #b #jj ,,philosophy ,,of ,,style4 #abmo4 ,flexible cloth1 #ej cents4 ,,descriptive ,,sociology4 ,to ,subscribers1 for the whole work1 per part1 #c4ej2 single part #d4jj4 ,published in folio1 with ,tables4 ,six ,parts now ready1 namely3 #a4 ,english2 #b4 ,ancient ,americans2 #c4 ,negritto and ,malayo-,polynesian ,races2 #d4 ,african ,races2 #e4 ,asiatic ,races2 #f4 ,north and ,south ,american ,races4 ,,charles ,,darwin',s ,,works4 #aa vols41 #abmo4 ,cloth1 #bd4jj4 ,,origin ,,of ,,species4 #b #jj ,,descent ,,of ,,man4 #c #jj ,,journal ,,of ,,researches4 #b #jj ,,emotional ,,expression4 #c #ej ,,animals ,,and ,,plants ,,under ,,domestication4 #b vols4 #e #jj ,,insectivorous ,,plants4 #b #jj ,,climbing ,,plants4 #a #be ,,orchids ,,fertilized ,,by ,,insects4 #a #ge ,,fertilization ,,in ,,the ,,vegetable ,,kingdom4 #b #jj ,,forms ,,of ,,flowers4 #a #ej ,,thomas ,h4 ,,huxley',s ,,works4 #aa vols41 #abmo4 ,cloth1 #ah4jj4 ,,man',s ,,place ,,in ,,nature4 #a #be ,,on ,,the ,,origin ,,of ,,species4 #a #jj ,,more ,,criticisms ,,on ,,darwin1 ,,and ,,administrative ,,nihilism4 #ej ,a ,,manual ,,of ,,the ,,anatomy ,,of ,,vertebrated ,,animals4 ,illus'd4 #b #ej ,a ,,manual ,,of ,,the ,,anatomy ,,of ,,invertebrated ,,animals4 ,illus'd4 #b #ej ,,lay ,,sermons1 ,,addresses1 ,,and ,,reviews4 #a #ge ,,critiques ,,and ,,addresses4 #a #ej ,,american ,,addresses4 #a #be ,,physiography4 #b #ej ,,elements ,,of ,,physiology ,,and ,,hygiene4 ,by ,t4 ,h4 ,huxley and ,w4 ,j4 ,youmans4 #a #ej ,,the ,,crayfish3 ,an ,introduction to ,zology4 7,international ,scientific ,series74 #a #ge ,,john ,,tyndall',s ,,works4 #aj vols41 #abmo4 ,cloth1 #ai4ge4 ,,heat ,,as ,a ,,mode ,,of ,,motion4 #b #jj ,,on ,,sound4 #b #jj ,,fragments ,,of ,,science4 #b #ej ,,light ,,and ,,electricity4 #a #be ,,lessons ,,in ,,electricity4 #a #jj ,,hours ,,of ,,exercise ,,in ,,the ,,alps4 #b #jj ,,faraday ,,as ,a ,,discoverer4 #a #jj ,,on ,,forms ,,of ,,water4 #a #ej ,,radiant ,,heat4 #e #jj ,,six ,,lectures ,,on ,,light4 #a #ej ,,banquet ,,at ,,delmonico',s1 paper1 #ej cents2 ,,belfast ,,address1 paper1 #ej cents4 ,d4 ,,appleton ,,co41 ,,publishers1 #a1 #c1 #e ,,bond ,,street1 ,,new ,,york4