,,the ,,story ,,of ,,evolution ,by ,joseph ,mc,cabe #aiab ,,preface ,an ingenious student of science once entertained his generation with a theory of how one might behold again all the stirring chapters that make up the story of the earth4 ,the living scene of our time is lit by the light of the sun1 and for every few rays that enter the human eye1 and convey the image of it to the human mind1 great floods of the reflected light pour out1 swiftly and indefinitely1 into space4 ,imagine1 then1 a man moving out into space more rapidly than light1 his face turned toward the earth4 ,flashing through the void at1 let us say1 a million miles a second1 he would 7if we can overlook the dispersion of the rays of light7 overtake in succession the light that fell on the ,french ,revolution1 the ,reformation1 the ,norman ,conquest1 and the faces of the ancient empires4 ,he would read1 in reverse order1 the living history of man and whatever lay before the coming of man4 ,few thought1 as they smiled over this fairy tale of science1 that some such panoramic survey of the story of the earth1 and even of the heavens1 might one day be made in a leisure hour by ordinary mortals2 that in the soil on which they trod were surer records of the past than in its doubtful literary remains1 and in the deeper rocks were records that dimly lit a vast abyss of time of which they never dreamed4 ,it is the supreme achievement of modern science to have discovered and deciphered these records4 ,the picture of the past which they afford is1 on the whole1 an outline sketch4 ,here and there the details1 the colour1 the light and shade1 may be added2 but the greater part of the canvas is left to the more skilful hand of a future generation1 and even the broad lines are at times uncertain4 ,yet each age would know how far its scientific men have advanced in constructing that picture of the growth of the heavens and the earth1 and the aim of the present volume is to give1 in clear and plain language1 as full an account of the story as the present condition of our knowledge and the limits of the volume will allow4 ,the author has been for many years interested in the evolution of things1 or the way in which suns and atoms1 fishes and flowers1 hills and elephants1 even man and his institutions1 came to be what they are4 ,lecturing and writing on one or other phase of the subject have1 moreover1 taught him a language which the inexpert seem to understand1 although he is not content merely to give a superficial description of the past inhabitants of the earth4 ,the particular features which1 it is hoped1 may give the book a distinctive place in the large literature of evolution are1 first1 that it includes the many evolutionary discoveries of the last few years1 gathers its material from the score of sciences which confine themselves to separate aspects of the universe1 and blends all these facts and discoveries in a more or less continuous chronicle of the life of the heavens and the earth4 ,then the author has endeavoured to show1 not merely how1 but why1 scene succeeds scene in the chronicle of the earth1 and life slowly climbs from level to level4 ,he has taken nature in the past as we find it to-day3 an interconnected whole1 in which the changes of land and sea1 of heat and cold1 of swamp and hill1 are faithfully reflected in the forms of its living population4 ,and1 finally1 he has written for those who are not students of science1 or whose knowledge may be confined to one branch of science1 and used a plain speech which assumes no previous knowledge on the reader's part4 ,for the rest1 it will be found that no strained effort is made to trace pedigrees of animals and plants when the material is scanty2 that1 if on account of some especial interest disputable or conjectural speculations are admitted1 they are frankly described as such2 and that the more important differences of opinion which actually divide astronomers1 geologists1 biologists1 and anthropologists are carefully taken into account and briefly explained4 ,a few ,english and ,american works are recommended for the convenience of those who would study particular chapters more closely1 but it has seemed useless1 in such a work1 to give a bibliography of the hundreds of ,english1 ,american1 ,french1 ,german1 and ,italian works which have been consulted4 ,,contents ,i4 ,,the ,,discovery ,,of ,,the ,,universe ,,ii4 ,,the ,,foundations ,,of ,,the ,,universe ,,iii4 ,,the ,,birth ,,and ,,death ,,of ,,worlds ,,iv4 ,,the ,,preparation ,,of ,,the ,,earth ,v4 ,,the ,,beginning ,,of ,,life ,,vi4 ,,the ,,infancy ,,of ,,the ,,earth ,,vii4 ,,the ,,passage ,,to ,,the ,,land ,,viii4 ,,the ,,coal-,,forest ,,ix4 ,,the ,,animals ,,of ,,the ,,coal-,,forest ,x4 ,,the ,,permian ,,revolution ,,xi4 ,,the ,,middle ,,ages ,,of ,,the ,,earth ,,xii4 ,,the ,,age ,,of ,,reptiles ,,xiii4 ,,the ,,bird ,,and ,,the ,,mammal ,,xiv4 ,,in ,,the ,,days ,,of ,,the ,,chalk ,,xv4 ,,the ,,tertiary ,,era ,,xvi4 ,,the ,,flower ,,and ,,the ,,insect ,,xvii4 ,,the ,,origin ,,of ,,our ,,mammals ,,xviii4 ,,the ,,evolution ,,of ,,man ,,xix4 ,,man ,,and ,,the ,,great ,,ice-,,age ,,xx4 ,,the ,,dawn ,,of ,,civilisation ,,xxi4 ,,evolution ,,in ,,history ,,index ,,the ,,story ,,of ,,evolution ,,chapter ,i4 ,,the ,,discovery ,,of ,,the ,,universe ,the beginning of the victorious career of modern science was very largely due to the making of two stimulating discoveries at the close of the ,middle ,ages4 ,one was the discovery of the earth3 the other the discovery of the universe4 ,men were confined1 like molluscs in their shells1 by a belief that they occupied the centre of a comparatively small disk--some ventured to say a globe--which was poised in a mysterious way in the middle of a small system of heavenly bodies4 ,the general feeling was that these heavenly bodies were lamps hung on a not too remote ceiling for the purpose of lighting their ways4 ,then certain enterprising sailors--,vasco da ,gama1 ,maghalaes1 ,columbus--brought home the news that the known world was only one side of an enormous globe1 and that there were vast lands and great peoples thousands of miles across the ocean4 ,the minds of men in ,europe had hardly strained their shells sufficiently to embrace this larger earth when the second discovery was reported4 ,the roof of the world1 with its useful little system of heavenly bodies1 began to crack and disclose a profound and mysterious universe surrounding them on every side4 ,one cannot understand the solidity of the modern doctrine of the formation of the heavens and the earth until one appreciates this revolution4 ,before the law of gravitation had been discovered it was almost impossible to regard the universe as other than a small and compact system4 ,we shall see that a few daring minds pierced the veil1 and peered out wonderingly into the real universe beyond1 but for the great mass of men it was quite impossible4 ,to them the modern idea of a universe consisting of hundreds of millions of bodies1 each weighing billions of tons1 strewn over billions of miles of space1 would have seemed the dream of a child or a savage4 ,material bodies were heavy1 and would fall down if they were not supported4 ,the universe1 they said1 was a sensible scientific structure2 things were supported in their respective places4 ,a great dome1 of some unknown but compact material1 spanned the earth1 and sustained the heavenly bodies4 ,it might rest on the distant mountains1 or be borne on the shoulders of an ,atlas2 or the whole cosmic scheme might be laid on the back of a gigantic elephant1 and--if you pressed--the elephant might stand on the hard shell of a tortoise4 ,but you were not encouraged to press4 ,the idea of the vault had come from ,babylon1 the first home of science4 ,no furnaces thickened that clear atmosphere1 and the heavy-robed priests at the summit of each of the seven-staged temples were astronomers4 ,night by night for thousands of years they watched the stars and planets tracing their undeviating paths across the sky4 ,to explain their movements the priest-astronomers invented the solid firmament4 ,beyond the known land1 encircling it1 was the sea1 and beyond the sea was a range of high mountains1 forming another girdle round the earth4 ,on these mountains the dome of the heavens rested1 much as the dome of ,st4 ,paul's rests on its lofty masonry4 ,the sun travelled across its under-surface by day1 and went back to the east during the night through a tunnel in the lower portion of the vault4 ,to the common folk the priests explained that this framework of the world was the body of an ancient and disreputable goddess4 ,the god of light had slit her in two1 as you do a dried fish1 they said1 and made the plain of the earth with one half and the blue arch of the heavens with the other4 ,so ,chaldaea lived out its #ejjj years without discovering the universe4 ,egypt adopted the idea from more scientific ,babylon4 ,amongst the fragments of its civilisation we find representations of the firmament as a goddess1 arching over the earth on her hands and feet1 condemned to that eternal posture by some victorious god4 ,the idea spread amongst the smaller nations which were lit by the civilisation of ,babylon and ,egypt4 ,some blended it with coarse old legends2 some1 like the ,persians and ,hebrews1 refined it4 ,the ,persians made fire a purer and lighter spirit1 so that the stars would need no support4 ,but everywhere the blue vault hemmed in the world and the ideas of men4 ,it was so close1 some said1 that the birds could reach it4 ,at last the genius of ,greece brooded over the whole chaos of cosmical speculations4 ,the native tradition of ,greece was a little more helpful than the ,babylonian teaching4 ,first was chaos2 then the heavier matter sank to the bottom1 forming the disk of the earth1 with the ocean poured round it1 and the less coarse matter floated as an atmosphere above it1 and the still finer matter formed an aether above the atmosphere4 ,a remarkably good guess1 in its very broad outline2 but the solid firmament still arched the earth1 and the stars were little undying fires in the vault4 ,the earth itself was small and flat4 ,it stretched 7on the modern map7 from about ,gibraltar to the ,caspian1 and from ,central ,germany--where the entrance to the lower world was located--to the ,atlas mountains4 ,but all the varied and conflicting culture of the older empires was now passing into ,greece1 lighting up in succession the civilisations of ,asia ,minor1 the ,greek islands1 and then ,athens and its sister states4 ,men began to think4 ,the first genius to have a glimpse of the truth seems to have been the grave and mystical ,pythagorus 7born about #ehb ,b4,c474 ,he taught his little school that the earth was a globe1 not a disk1 and that it turned on its axis in twenty-four hours4 ,the earth and the other planets were revolving round the central fire of the system2 but the sun was a reflection of this central fire1 not the fire itself4 ,even ,pythagoras1 moreover1 made the heavens a solid sphere revolving1 with its stars1 round the central fire2 and the truth he discovered was mingled with so much mysticism1 and confined to so small and retired a school1 that it was quickly lost again4 ,in the next generation ,anaxagoras taught that the sun was a vast globe of white-hot iron1 and that the stars were material bodies made white-hot by friction with the ether4 ,a generation later the famous ,democritus came nearer than any to the truth4 ,the universe was composed of an infinite number of indestructible particles1 called atoms1 which had gradually settled from a state of chaotic confusion to their present orderly arrangement in large masses4 ,the sun was a body of enormous size1 and the points of light in the ,milky ,way were similar suns at a tremendous distance from the earth4 ,our universe1 moreover1 was only one of an infinite number of universes1 and an eternal cycle of destruction and re-formation was running through these myriads of worlds4 ,by sheer speculation ,greece was well on the way of discovery4 ,then the mists of philosophy fell between the mind of ,greece and nature1 and the notions of ,democritus were rejected with disdain2 and then1 very speedily1 the decay of the brilliant nation put an end to its feverish search for truth4 ,greek culture passed to ,alexandria1 where it met the remains of the culture of ,egypt1 ,babylonia1 and ,persia1 and one more remarkable effort was made to penetrate the outlying universe before the night of the ,middle ,ages fell on the old world4 ,astronomy was ardently studied at ,alexandria1 and was fortunately combined with an assiduous study of mathematics4 ,aristarchus 7about #cbj-bej ,b4,c47 calculated that the sun was #hd1jjj1jjj miles away2 a vast expansion of the solar system and1 for the time1 a remarkable approach to the real figure 7#ib1jjj1jjj7 ,eratosthenes 7#bgf-aif ,b4,c47 made an extremely good calculation of the size of the earth1 though he held it to be the centre of a small universe4 ,he concluded that it was a globe measuring #bg1jjj 7instead of #bc1gjj7 miles in circumference4 ,posidonius 7#ace-ea ,b4,c47 came even nearer with a calculation that the circumference was between #be1jjj and #ai1jjj miles2 and he made a fairly correct estimate of the diameter1 and therefore distance1 of the sun4 ,hipparchus 7#aij-abj ,b4,c47 made an extremely good calculation of the distance of the moon4 ,by the brilliant work of the ,alexandrian astronomers the old world seemed to be approaching the discovery of the universe4 ,men were beginning to think in millions1 to gaze boldly into deep abysses of space1 to talk of vast fiery globes that made the earth insignificant ,but the splendid energy gradually failed1 and the long line was closed by ,ptolemaeus1 who once more put the earth in the centre of the system1 and so imposed what is called the ,ptolemaic system on ,europe4 ,the keen school-life of ,alexandria still ran on1 and there might have been a return to the saner early doctrines1 but at last ,alexandrian culture was extinguished in the blood of the aged ,hypatia1 and the night fell4 ,rome had had no genius for science2 though ,lucretius gave an immortal expression to the views of ,democritus and ,epicurus1 and such writers as ,cicero and ,pliny did great service to a later age in preserving fragments of the older discoveries4 ,the curtains were once more drawn about the earth4 ,the glimpses which adventurous ,greeks had obtained of the great outlying universe were forgotten for a thousand years4 ,the earth became again the little platform in the centre of a little world1 on which men and women played their little parts1 preening themselves on their superiority to their pagan ancestors4 ,i do not propose to tell the familiar story of the revival at any length4 ,as far as the present subject is concerned1 it was literally a ,renascence1 or re-birth1 of ,greek ideas4 ,constantinople having been taken by the ,turks 7#adec71 hundreds of ,greek scholars1 with their old literature1 sought refuge in ,europe1 and the vigorous brain of the young nations brooded over the ancient speculations1 just as the vigorous young brain of ,greece had done two thousand years before4 ,copernicus 7#adgc-aedc7 acknowledges that he found the secret of the movements of the heavenly bodies in the speculations of the old ,greek thinkers4 ,galilei 7#aefd-afdb7 enlarged the ,copernican system with the aid of the telescope2 and the telescope was an outcome of the new study of optics which had been inspired in ,roger ,bacon and other medieval scholars by the optical works1 directly founded on the ,greek1 of the ,spanish ,moors4 ,giordano ,bruno still further enlarged the system2 he pictured the universe boldly as an infinite ocean of liquid ether1 in which the stars1 with retinues of inhabited planets1 floated majestically4 ,bruno was burned at the stake 7#afjj72 but the curtains that had so long been drawn about the earth were now torn aside for ever1 and men looked inquiringly into the unfathomable depths beyond4 ,descartes 7#aeif-afej7 revived the old ,greek idea of a gradual evolution of the heavens and the earth from a primitive chaos of particles1 taught that the stars stood out at unimaginable distances in the ocean of ether1 and imagined the ether as stirring in gigantic whirlpools1 which bore cosmic bodies in their orbits as the eddy in the river causes the cork to revolve4 ,these stimulating conjectures made a deep impression on the new age4 ,a series of great astronomers had meantime been patiently and scientifically laying the foundations of our knowledge4 ,kepler 7#aega-afcj7 formulated the laws of the movement of the planets2 ,newton 7#afdb-agbg7 crowned the earlier work with his discovery of the real agency that sustains cosmic bodies in their relative positions4 ,the primitive notion of a material frame and the confining dome of the ancients were abandoned4 ,we know now that a framework of the most massive steel would be too frail to hold together even the moon and the earth4 ,it would be rent by the strain4 ,the action of gravitation is the all-sustaining power4 ,once introduce that idea1 and the great ocean of ether might stretch illimitably on every side1 and the vastest bodies might be scattered over it and traverse it in stupendous paths4 ,thus it came about that1 as the little optic tube of ,galilei slowly developed into the giant telescope of ,herschel1 and then into the powerful refracting telescopes of the ,united ,states of our time2 as the new science of photography provided observers with a new eye--a sensitive plate that will register messages1 which the human eye cannot detect1 from far-off regions2 and as a new instrument1 the spectroscope1 endowed astronomers with a power of perceiving fresh aspects of the inhabitants of space1 the horizon rolled backward1 and the mind contemplated a universe of colossal extent and power4 ,let us try to conceive this universe before we study its evolution4 ,i do not adopt any of the numerous devices that have been invented for the purpose of impressing on the imagination the large figures we must use4 ,one may doubt if any of them are effective1 and they are at least familiar4 ,our solar system--the family of sun and planets which had been sheltered under a mighty dome resting on the hill-tops--has turned out to occupy a span of space some #af1jjj1jjj1jjj miles in diameter4 ,that is a very small area in the new universe4 ,draw a circle1 #ajj billion miles in diameter1 round the sun1 and you will find that it contains only three stars besides the sun4 ,in other words1 a sphere of space measuring #cjj billion miles in circumference--we will not venture upon the number of cubic miles--contains only four stars 7the sun1 alpha ,centauri1 #ba1ahe ,lalande1 and #fa ,cygni74 ,however1 this part of space seems to be below the average in point of population1 and we must adopt a different way of estimating the magnitude of the universe from the number of its stellar citizens4 ,beyond the vast sphere of comparatively empty space immediately surrounding our sun lies the stellar universe into which our great telescopes are steadily penetrating4 ,recent astronomers give various calculations1 ranging from #bjj1jjj1jjj to #b1jjj1jjj1jjj1 of the number of stars that have yet come within our faintest knowledge4 ,let us accept the modest provisional estimate of #ejj1jjj1jjj4 ,now1 if we had reason to think that these stars were of much the same size and brilliance as our sun1 we should be able roughly to calculate their distance from their faintness4 ,we cannot do this1 as they differ considerably in size and intrinsic brilliance4 ,sirius is more than twice the size of our sun and gives out twenty times as much light4 ,canopus emits #bj1jjj times as much light as the sun1 but we cannot say1 in this case1 how much larger it is than the sun4 ,arcturus1 however1 belongs to the same class of stars as our sun1 and astronomers conclude that it must be thousands of times larger than the sun4 ,a few stars are known to be smaller than the sun4 ,some are1 intrinsically1 far more brilliant2 some far less brilliant4 ,another method has been adopted1 though this also must be regarded with great reserve4 ,the distance of the nearer stars can be positively measured1 and this has been done in a large number of cases4 ,the proportion of such cases to the whole is still very small1 but1 as far as the results go1 we find that stars of the first magnitude are1 on the average1 nearly #bjj billion miles away2 stars of the second magnitude nearly #cjj billion2 and stars of the third magnitude #dej billion4 ,if this fifty per cent increase of distance for each lower magnitude of stars were certain and constant1 the stars of the eighth magnitude would be #cjjj billion miles away1 and stars of the sixteenth magnitude would be #ajj1jjj billion miles away2 and there are still two fainter classes of stars which are registered on long-exposure photographs4 ,the mere vastness of these figures is immaterial to the astronomer1 but he warns us that the method is uncertain4 ,we may be content to conclude that the starry universe over which our great telescopes keep watch stretches for thousands1 and probably tens of thousands1 of billions of miles4 ,there are myriads of stars so remote that1 though each is a vast incandescent globe at a temperature of many thousand degrees1 and though their light is concentrated on the mirrors or in the lenses of our largest telescopes and directed upon the photographic plate at the rate of more than #hjj billion waves a second1 they take several hours to register the faintest point of light on the plate4 ,when we reflect that the universe has grown with the growth of our telescopes and the application of photography we wonder whether we may as yet see only a fraction of the real universe1 as small in comparison with the whole as the ,babylonian system was in comparison with ours4 ,we must be content to wonder4 ,some affirm that the universe is infinite2 others that it is limited4 ,we have no firm ground in science for either assertion4 ,those who claim that the system is limited point out that1 as the stars decrease in brightness1 they increase so enormously in number that the greater faintness is more than compensated1 and therefore1 if there were an infinite series of magnitudes1 the midnight sky would be a blaze of light4 ,but this theoretical reasoning does not allow for dense regions of space that may obstruct the light1 or vast regions of vacancy between vast systems of stars4 ,even apart from the evidence that dark nebulae or other special light-absorbing regions do exist1 the question is under discussion in science at the present moment whether light is not absorbed in the passage through ordinary space4 ,there is reason to think that it is4 ,let us leave precarious speculations about finiteness and infinity to philosophers1 and take the universe as we know it4 ,picture1 then1 on the more moderate estimate1 these #ejj1jjj1jjj suns scattered over tens of thousands of billions of miles4 ,whether they form one stupendous system1 and what its structure may be1 is too obscure a subject to be discussed here4 ,imagine yourself standing at a point from which you can survey the whole system and see into the depths and details of it4 ,at one point is a single star 7like our sun71 billions of miles from its nearest neighbour1 wearing out its solitary life in a portentous discharge of energy4 ,commonly the stars are in pairs1 turning round a common centre in periods that may occupy hundreds of days or hundreds of years4 ,here and there they are gathered into clusters1 sometimes to the number of thousands in a cluster1 travelling together over the desert of space1 or trailing in lines like luminous caravans4 ,all are rushing headlong at inconceivable speeds4 ,few are known to be so sluggish as to run1 like our sun1 at only #hjjj miles an hour4 ,one of the fixed stars of the ancients1 the mighty ,arcturus1 darts along at a rate of more than #bej miles a second4 ,as they rush1 their surfaces glowing at a temperature anywhere between #ajjj and #bj1jjj degrees ,c41 they shake the environing space with electric waves from every tiny particle of their body at a rate of from #djj billion to #hjj billion waves a second4 ,and somewhere round the fringe of one of the smaller suns there is a little globe1 more than a million times smaller than the solitary star it attends1 lost in the blaze of its light1 on which human beings find a home during a short and late chapter of its history4 ,look at it again from another aspect4 ,every colour of the rainbow is found in the stars4 ,emerald1 azure1 ruby1 gold1 lilac1 topaz1 fawn--they shine with wonderful and mysterious beauty4 ,but1 whether these more delicate shades be really in the stars or no1 three colours are certainly found in them4 ,the stars sink from bluish white to yellow1 and on to deep red4 ,the immortal fires of the ,greeks are dying4 ,piercing the depths with a dull red glow1 here and there1 are the dying suns2 and if you look closely you will see1 flitting like ghosts across the light of their luminous neighbours1 the gaunt frames of dead worlds4 ,here and there are vast stretches of loose cosmic dust that seems to be gathering into embryonic stars2 here and there are stars in infancy or in strenuous youth4 ,you detect all the chief phases of the making of a world in the forms and fires of these colossal aggregations of matter4 ,like the chance crowd on which you may look down in the square of a great city1 they range from the infant to the worn and sinking aged4 ,there is this difference1 however1 that the embryos of worlds sprawl1 gigantic and luminous1 across the expanse2 that the dark and mighty bodies of the dead rush1 like the rest1 at twenty or fifty miles a second2 and that at intervals some appalling blaze1 that dims even the fearful furnaces of the living1 seems to announce the resurrection of the dead4 ,and there is this further difference1 that1 strewn about the intermediate space between the gigantic spheres1 is a mass of cosmic dust--minute grains1 or large blocks1 or shoals consisting of myriads of pieces1 or immeasurable clouds of fine gas--that seems to be the rubbish left over after the making of worlds1 or the material gathering for the making of other worlds4 ,this is the universe that the nineteenth century discovered and the twentieth century is interpreting4 ,before we come to tell the fortunes of our little earth we have to see how matter is gathered into these stupendous globes of fire1 how they come sometimes to have smaller bodies circling round them on which living things may appear1 how they supply the heat and light and electricity that the living things need1 and how the story of life on a planet is but a fragment of a larger story4 ,we have to study the birth and death of worlds1 perhaps the most impressive of all the studies that modern science offers us4 ,indeed1 if we would read the whole story of evolution1 there is an earlier chapter even than this2 the latest chapter to be opened by science1 the first to be read4 ,we have to ask where the matter1 which we are going to gather into worlds1 itself came from2 to understand more clearly what is the relation to it of the forces or energies--gravitation1 electricity1 etc4--with which we glibly mould it into worlds1 or fashion it into living things2 and1 above all1 to find out its relation to this mysterious ocean of ether in which it is found4 ,less than half a century ago the making of worlds was1 in popular expositions of science1 a comparatively easy business4 ,take an indefinite number of atoms of various gases and metals1 scatter them in a fine cloud over some thousands of millions of miles of space1 let gravitation slowly compress the cloud into a globe1 its temperature rising through the compression1 let it throw off a ring of matter1 which in turn gravitation will compress into a globe1 and you have your earth circulating round the sun4 ,it is not quite so simple2 in any case1 serious men of science wanted to know how these convenient and assorted atoms happened to be there at all1 and what was the real meaning of this equally convenient gravitation4 ,there was a greater truth than he knew in the saying of an early physicist1 that the atom had the look of a manufactured article4 ,it was increasingly felt1 as the nineteenth century wore on1 that the atoms had themselves been evolved out of some simpler material1 and that ether might turn out to be the primordial chaos4 ,there were even those who felt that ether would prove to be the one source of all matter and energy4 ,and just before the century closed a light began to shine in those deeper abysses of the submaterial world1 and the foundations of the universe began to appear4 ,,chapter ,,ii4 ,,the ,,foundations ,,of ,,the ,,universe ,to the mind of the vast majority of earlier observers the phrase foundations of the universe would have suggested something enormously massive and solid4 ,from what we have already seen we are prepared1 on the contrary1 to pass from the inconceivably large to the inconceivably small4 ,our sun is1 as far as our present knowledge goes1 one of modest dimensions4 ,arcturus and ,canopus must be thousands of times larger than it4 ,yet our sun is #cbj1jjj times heavier than the earth1 and the earth weighs some #f1jjj1jjj1jjj1jjj1jjj1jjj1jjj tons4 ,but it is only in resolving these stupendous masses into their tiniest elements that we can reach the ultimate realities1 or foundations1 of the whole4 ,modern science rediscovered the atoms of ,democritus1 analysed the universe into innumerable swarms of these tiny particles1 and then showed how the infinite variety of things could be built up by their combinations4 ,for this it was necessary to suppose that the atoms were not all alike1 but belonged to a large number of different classes4 ,from twenty-six letters of the alphabet we could make millions of different words4 ,from forty or fifty different elements the chemist could construct the most varied objects in nature1 from the frame of a man to a landscape4 ,but improved methods of research led to the discovery of new elements1 and at last the chemist found that he had seventy or eighty of these ultimate realities1 each having its own very definite and very different characters4 ,as it is the experience of science to find unity underlying variety1 this was profoundly unsatisfactory1 and the search began for the great unity which underlay the atoms of matter4 ,the difficulty of the search may be illustrated by a few figures4 ,very delicate methods were invented for calculating the size of the atoms4 ,laymen are apt to smile--it is a very foolish smile--at these figures1 but it is enough to say that the independent and even more delicate methods suggested by recent progress in physics have quite confirmed them4 ,take a cubic millimetre of hydrogen4 ,as a millimetre is less than #a_/beth of an inch1 the reader must imagine a tiny bubble of gas that would fit comfortably inside the letter o as it is printed here4 ,the various refined methods of the modern physicist show that there are #dj1jjj billion molecules 7each consisting of two atoms of the gas7 in this tiny bubble4 ,it is a little universe1 repeating on an infinitesimal scale the numbers and energies of the stellar universe4 ,these molecules are not packed together1 moreover1 but are separated from each other by spaces which are enormous in proportion to the size of the atoms4 ,through these empty spaces the atoms dash at an average speed of more than a thousand miles an hour1 each passing something like #f1jjj1jjj1jjj of its neighbours in the course of every second4 ,yet this particle of gas is a thinly populated world in comparison with a particle of metal4 ,take a cubic centimetre of copper4 ,in that very small square of solid matter 7each side of the cube measuring a little more than a third of an inch7 there are about a quadrillion atoms4 ,it is these minute and elusive particles that modern physics sets out to master4 ,at first it was noticed that the atom of hydrogen was the smallest or lightest of all1 and the other atoms seemed to be multiples of it4 ,a ,russian chemist1 ,mendeleeff1 drew up a table of the elements in illustration of this1 grouping them in families1 which seemed to point to hydrogen as the common parent1 or ultimate constituent1 of each4 ,when newly discovered elements fell fairly into place in this scheme the idea was somewhat confidently advanced that the evolution of the elements was discovered4 ,thus an atom of carbon seemed to be a group of #ab atoms of hydrogen1 an atom of oxygen #af1 an atom of sulphur #cb1 an atom of copper #fd1 an atom of silver #ajh1 an atom of gold #aig1 and so on4 ,but more correct measurements showed that these figures were not quite exact1 and the fraction of inexactness killed the theory4 ,long before the end of the nineteenth century students were looking wistfully to the ether for some explanation of the mystery4 ,it was the veiled statue of ,isis in the scientific world1 and it resolutely kept its veil in spite of all progress4 ,the upper and limpid air of the ,greeks1 the cosmic ocean of ,giordano ,bruno1 was now an established reality4 ,it was the vehicle that bore the terrific streams of energy from star to planet across the immense reaches of space4 ,as the atoms of matter lay in it1 one thought of the crystal forming in its mother-lye1 or the star forming in the nebula1 and wondered whether the atom was not in some such way condensed out of the ether4 ,by the last decade of the century the theory was confidently advanced--notably by ,lorentz and ,larmor--though it was still without a positive basis4 ,how the basis was found1 in the last decade of the nineteenth century1 may be told very briefly4 ,sir ,william ,crookes had in #ahgd applied himself to the task of creating something more nearly like a vacuum than the old air-pumps afforded4 ,when he had found the means of reducing the quantity of gas in a tube until it was a million times thinner than the atmosphere1 he made the experiment of sending an electric discharge through it1 and found a very curious result4 ,from the cathode 7the negative electric point7 certain rays proceeded which caused a green fluorescence on the glass of the tube4 ,since the discharge did not consist of the atoms of the gas1 he concluded that it was a new and mysterious substance1 which he called radiant matter4 ,but no progress was made in the interpretation of this strange material4 ,the ,crookes tube became one of the toys of science--and the lamp of other investigators4 ,in #ahie ,rontgen drew closer attention to the ,crookes tube by discovering the rays which he called ,x-rays1 but which now bear his name4 ,they differ from ordinary light-waves in their length1 their irregularity1 and especially their power to pass through opaque bodies4 ,a number of distinguished physicists now took up the study of the effect of sending an electric discharge through a vacuum1 and the particles of radiant matter were soon identified4 ,sir ,j4 ,j4 ,thomson1 especially1 was brilliantly successful in his interpretation4 ,he proved that they were tiny corpuscles1 more than a thousand times smaller than the atom of hydrogen1 charged with negative electricity1 and travelling at the rate of thousands of miles a second4 ,they were the electrons in which modern physics sees the long-sought constituents of the atom4 ,no sooner had interest been thoroughly aroused than it was announced that a fresh discovery had opened a new shaft into the underworld4 ,sir ,j4 ,j4 ,thomson1 pursuing his research1 found in #ahif that compounds of uranium sent out rays that could penetrate black paper and affect the photographic plate2 though in this case the ,french physicist1 ,becquerel1 made the discovery simultaneously' and was the first to publish it4 ,an army of investigators turned into the new field1 and sought to penetrate the deep abyss that had almost suddenly disclosed itself4 ,the quickening of astronomy by ,galilei1 or of zoology by ,darwin1 was slight in comparison with the stirring of our physical world by these increasing discoveries4 ,and in #ahih ,m4 and ,mme4 ,curie made the further discovery which1 in the popular mind1 obliterated all the earlier achievements4 ,they succeeded in isolating the new element1 radium1 which exhibits the actual process of an atom parting with its minute constituents4 ,the story of radium is so recent that a few lines will suffice to recall as much as is needed for the purpose of this chapter4 ,in their study of the emanations from uranium compounds the ,curies were led to isolate the various elements of the compounds until they discovered that the discharge was predominantly due to one specific element1 radium4 ,radium is itself probably a product of the disintegration of uranium1 the heaviest of known metals1 with an atomic weight some #bdj times greater than that of hydrogen4 ,but this massive atom of uranium has a life that is computed in thousands of millions of years4 ,it is in radium and its offspring that we see most clearly the constitution of matter4 ,a gramme 7less than #ae #a_/b grains7 of radium contains--we will economise our space--#dx#aj 7superscript7#ba atoms4 ,this tiny mass is1 by its discharge1 parting with its substance at the rate of one atom per second for every #aj1jjj1jjj1jjj atoms2 in other words1 the indestructible atom has1 in this case1 a term of life not exceeding #bejj years4 ,in the discharge from the radium three elements have been distinguished4 ,the first consists of atoms of the gas helium1 which are hurled off at between #aj1jjj and #bj1jjj miles a second4 ,the third element 7in the order of classification7 consists of waves analogous to the ,rontgen rays4 ,but the second element is a stream of electrons1 which are expelled from the atom at the appalling speed of about #ajj1jjj miles a second4 ,professor ,le ,bon has calculated that it would take #cdj1jjj barrels of powder to discharge a bullet at that speed4 ,but we shall see more presently of the enormous energy displayed within the little system of the atom4 ,we may add that after its first transformation the radium passes1 much more quickly1 through a further series of changes4 ,the frontiers of the atomic systems were breaking down4 ,the next step was for students 7notably ,soddy and ,rutherford7 to find that radio-activity1 or spontaneous discharge out of the atomic systems1 was not confined to radium4 ,not only are other rare metals conspicuously active1 but it is found that such familiar surfaces as damp cellars1 rain1 snow1 etc41 emit a lesser discharge4 ,the value of the new material thus provided for the student of physics may be shown by one illustration4 ,sir ,j4 ,j4 ,thomson observes that before these recent discoveries the investigator could not detect a gas unless about a billion molecules of it were present1 and it must be remembered that the spectroscope had already gone far beyond ordinary chemical analysis in detecting the presence of substances in minute quantities4 ,since these discoveries we can recognise a single molecule1 bearing an electric charge4 ,with these extraordinary powers the physicist is able to penetrate a world that lies immeasurably below the range of the most powerful microscope1 and introduce us to systems more bewildering than those of the astronomer4 ,we pass from a portentous ,brobdingnagia to a still more portentous ,lilliputia4 ,it has been ascertained that the mass of the electron is the #a_/agjjth part of that of an atom of hydrogen1 of which1 as we saw1 billions of molecules have ample space to execute their terrific movements within the limits of the letter o4 ,it has been further shown that these electrons are identical1 from whatever source they are obtained4 ,the physicist therefore concludes--warning us that on this further point he is drawing a theoretical conclusion--that the atoms of ordinary matter are made up of electrons4 ,if that is the case1 the hydrogen atom1 the lightest of all1 must be a complex system of some #agjj electrons1 and as we ascend the scale of atomic weight the clusters grow larger and larger1 until we come to the atoms of the heavier metals with more than #bej1jjj electrons in each atom4 ,but this is not the most surprising part of the discovery4 ,tiny as the dimensions of the atom are1 they afford a vast space for the movement of these energetic little bodies4 ,the speed of the stars in their courses is slow compared with the flight of the electrons4 ,since they fly out of the system1 in the conditions we have described1 at a speed of between #ij1jjj and #ajj1jjj miles a second1 they must be revolving with terrific rapidity within it4 ,indeed1 the most extraordinary discovery of all is that of the energy imprisoned within these tiny systems1 which men have for ages regarded as dead matter4 ,sir ,j4 ,j4 ,thomson calculates that1 allowing only one electron to each atom in a gramme of hydrogen1 the tiny globule of gas will contain as much energy as would be obtained by burning thirty-five tons of coal4 ,if1 he says1 an appreciable fraction of the energy that is contained in ordinary matter were to be set free1 the earth would explode and return to its primitive nebulous condition4 ,mr4 ,fournier d',albe tells us that the force with which electrons repel each other is a quadrillion times greater than the force of gravitation that brings atoms together2 and that if two grammes of pure electrons could be placed one centimetre apart they would repel each other with a force equal to #cbj quadrillion tons4 ,the inexpert imagination reels1 but it must be remembered that the speed of the electron is a measured quantity1 and it is within the resources of science to estimate the force necessary to project it at that speed4 99 99 ,see ,sir ,j4 ,j4 ,thomson1 ,the ,corpuscular ,theory of ,matter 7#aijg7 and--for a more elementary presentment--,light ,visible and ,invisible 7#aiaa72 and ,mr4 ,fournier d',albe1 ,the ,electron ,theory 7#bnd4 ed41 #aijg74 ,such are the discoveries of the last fifteen years and a few of the mathematical deductions from them4 ,we are not yet in a position to say positively that the atoms are composed of electrons1 but it is clear that the experts are properly modest in claiming only that this is highly probable4 ,the atom seems to be a little universe in which1 in combination with positive electricity 7the nature of which is still extremely obscure71 from #agjj to #cjj1jjj electrons revolve at a speed that reaches as high as #ajj1jjj miles a second4 ,instead of being crowded together1 however1 in their minute system1 each of them has1 in proportion to its size1 as ample a space to move in as a single speck of dust would have in a moderate-sized room 7,thomson74 ,this theory not only meets all the facts that have been discovered in an industrious decade of research1 not only offers a splendid prospect of introducing unity into the eighty-one different elements of the chemist1 but it opens out a still larger prospect of bringing a common measure into the diverse forces of the universe4 ,light is already generally recognised as a rapid series of electro-magnetic waves or pulses in ether4 ,magnetism becomes intelligible as a condition of a body in which the electrons revolve round the atom in nearly the same plane4 ,the difference between positive and negative electricity is at least partly illuminated4 ,an atom will repel an atom when its equilibrium is disturbed by the approach of an additional electron2 the physicist even follows the movement of the added electron1 and describes it revolving #bbjj billion times a second round the atom1 to escape being absorbed in it4 ,the difference between good and bad conductors of electricity becomes intelligible4 ,the atoms of metals are so close together that the roaming electrons pass freely from one atom to another1 in copper1 it is calculated1 the electron combines with an atom and is liberated again a hundred million times a second4 ,even chemical action enters the sphere of explanation4 ,however these hypotheses may fare1 the electron is a fact1 and the atom is very probably a more or less stable cluster of electrons4 ,but when we go further1 and attempt to trace the evolution of the electron out of ether1 we enter a region of pure theory4 ,some of the experts conceive the electron as a minute whirlpool or vortex in the ocean of ether2 some hold that it is a centre of strain in ether2 some regard ether as a densely packed mass of infinitely small grains1 and think that the positive and negative corpuscles1 as they seem to us1 are tiny areas in which the granules are unequally distributed4 ,each theory has its difficulties4 ,we do not know the origin of the electron1 because we do not know the nature of ether4 ,to some it is an elastic solid1 quivering in waves at every movement of the particles2 to others it is a continuous fluid1 every cubic millimetre of which possesses an energy equivalent to the output of a million-horse-power station for #dj4jjj1jjj years 7,lodge72 to others it is a close-packed granular mass with a pressure of #aj1jjj tons per square centimetre4 ,we must wait4 ,it is little over ten years since the vaults were opened and physicists began to peer into the sub-material world4 ,the lower1 perhaps lowest1 depth is reserved for another generation4 ,but it may be said that the research of the last ten years has given us a glimpse of the foundations of the universe4 ,every theory of the electron assumes it to be some sort of nodule or disturbed area in the ether4 ,it is sometimes described as a particle of negative electricity and associated with a particle of positive electricity in building up the atom4 ,the phrase is misleading for those who regard electricity as a force or energy1 and it gives rise to speculation as to whether matter has not been resolved into force4 ,force or energy is not conceived by physicists as a substantial reality1 like matter1 but an abstract expression of certain relations of matter or electrons4 ,in any case1 the ether1 whether solid or fluid or granular1 remains the fundamental reality4 ,the universe does not float ,,in an ocean of ether3 it ,,is an ocean of ether4 ,but countless myriads of minute disturbances are found in this ocean1 and set it quivering with the various pulses which we classify as forces or energies4 ,these points of disturbance cluster together in systems 7atoms7 of from #ajjj to #bej1jjj members1 and the atoms are pressed together until they come in the end to form massive worlds4 ,it remains only to reduce gravitation itself1 which brings the atoms together1 to a strain or stress in ether1 and we have a superb unity4 ,that has not yet been done1 but every theory of gravitation assumes that it is a stress in the ether corresponding to the formation of the minute disturbances which we call electrons4 ,but1 it may be urged1 he who speaks of foundations speaks of a beginning of a structure2 he who speaks of evolution must have a starting-point4 ,was there a time when the ether was a smooth1 continuous fluid1 without electrons or atoms1 and did they gradually appear in it1 like crystals in the mother-lye8 ,in science we know nothing of a beginning4 ,the question of the eternity or non-eternity of matter 7or ether7 is as futile as the question about its infinity or finiteness4 ,we shall see in the next chapter that science can trace the processes of nature back for hundreds1 if not thousands1 of millions of years1 and has ground to think that the universe then presented much the same aspect as it does now1 and will in thousands of millions of years to come4 ,but if these periods were quadrillions1 instead of millions1 of years1 they would still have no relation to the idea of eternity4 ,all that we can say is that we find nothing in nature that points to a beginning or an end4 99 99 ,a theory has been advanced by some physicists that there is evidence of a beginning4 ,,within ,,our ,,experience energy is being converted into heat more abundantly than heat is being converted into other energy4 ,this would hold out a prospect of a paralysed universe1 and that stage would have been reached long ago if the system had not had a definite beginning4 ,but what knowledge have we of conversions of energy in remote regions of space1 in the depths of stars or nebulae1 or in the sub-material world of which we have just caught a glimpse8 ,roundly1 none4 ,the speculation is worthless4 ,one point only need be mentioned in conclusion4 ,do we anywhere perceive the evolution of the material elements out of electrons1 just as we perceive the devolution1 or disintegration1 of atoms into electrons8 ,there is good ground for thinking that we do4 ,the subject will be discussed more fully in the next chapter4 ,in brief1 the spectroscope1 which examines the light of distant stars and discovers what chemical elements emitted it1 finds matter1 in the hottest stars1 in an unusual condition1 and seems to show the elements successively emerging from their fierce alchemy4 ,sir ,j4 ,norman ,lockyer has for many years conducted a special investigation of the subject at the ,solar ,physics ,observatory1 and he declares that we can trace the evolution of the elements out of the fiery chaos of the young star4 ,the lightest gases emerge first1 the metals later1 and in a special form4 ,but here we pass once more from ,lilliputia to ,brobdingnagia1 and must first explain the making of the star itself4 ,,chapter ,,iii4 ,,the ,,birth ,,and ,,death ,,of ,,worlds ,the greater part of this volume will be occupied with the things that have happened on one small globe in the universe during a certain number of millions of years4 ,it cannot be denied that this has a somewhat narrow and parochial aspect4 ,the earth is1 you remember1 a million times smaller than the sun1 and the sun itself is a very modest citizen of the stellar universe4 ,our procedure is justified1 however1 both on the ground of personal interest1 and because our knowledge of the earth's story is so much more ample and confident4 ,yet we must preface the story of the earth with at least a general outline of the larger story of the universe4 ,no sensible man is humbled or dismayed by the vastness of the universe4 ,when the human mind reflects on its wonderful scientific mastery of this illimitable ocean of being1 it has no sentiment of being dwarfed or degraded4 ,it looks out with cold curiosity over the mighty scattering of worlds1 and asks how they1 including our own world1 came into being4 ,we now approach this subject with a clearer perception of the work we have to do4 ,the universe is a vast expanse of ether1 and somehow or other this ether gives rise to atoms of matter4 ,we may imagine it as a spacious chamber filled with cosmic dust2 recollecting that the chamber has no walls1 and that the dust arises in the ether itself4 ,the problem we now approach is1 in a word3 ,how are these enormous stretches of cosmic dust1 which we call matter1 swept together and compressed into suns and planets8 ,the most famous answer to this question is the nebular hypothesis4 ,let us see1 briefly1 how it came into modern science4 ,we saw that some of the ancient ,greek speculators imagined their infinite number of atoms as scattered originally1 like dust1 throughout space and gradually coming together1 as dust does1 to form worlds4 ,the way in which they brought their atoms together was wrong1 but the genius of ,democritus had provided the germ of another sound theory to the students of a more enlightened age4 ,descartes 7#aeif-afej7 recalled the idea1 and set out a theory of the evolution of stars and planets from a diffused chaos of particles4 ,he even ventured to say that the earth was at one time a small white-hot sun1 and that a solid crust had gradually formed round its molten core4 ,descartes had taken refuge in ,sweden from his persecutors1 and it is therefore not surprising that that strange genius ,swedenborg shortly afterwards developed the same idea4 ,in the middle of the eighteenth century the great ,french naturalist1 ,buffon1 followed and improved upon ,descartes and ,swedenborg4 ,from ,buffon's work it was learned by the ,german philosopher ,kant1 who published 7#agee7 a fresh theory of the concentration of scattered particles into fiery worlds4 ,then ,laplace 7#agdi-ahbg7 took up the speculation1 and gave it the form in which it practically ruled astronomy throughout the nineteenth century4 ,that is the genealogy of the famous nebular hypothesis4 ,it did not spring full-formed from the brain of either ,kant or ,laplace1 like ,athene from the brain of ,zeus4 ,laplace had one great advantage over the early speculators4 ,not only was he an able astronomer and mathematician1 but by his time it was known that nebulae1 or vast clouds of dispersed matter1 actually existed in the heavens4 ,here was a solid basis for the speculation4 ,sir ,william ,herschel1 the most assiduous explorer of the heavens1 was a contemporary of ,laplace4 ,laplace therefore took the nebula as his starting-point4 ,a quarter of an ounce of solid matter 7say1 tobacco7 will fill a vast space when it is turned into smoke1 and if it were not for the pressure of the atmosphere it would expand still more4 ,laplace imagined the billions of tons of matter which constitute our solar system similarly dispersed1 converted into a fine gas1 immeasurably thinner than the atmosphere4 ,this nebula would be gradually drawn in again by gravitation1 just as the dust falls to the floor of a room4 ,the collisions of its particles as they fell toward the centre would raise its temperature and give it a rotating movement4 ,a time would come when the centrifugal force at the outer ring of the rotating disk would equal the centripetal 7or inward7 pull of gravity1 and this ring would be detached1 still spinning round the central body4 ,the material of the ring would slowly gather1 by gravitation1 round some denser area in it2 the ring would become a sphere2 we should have the first1 and outermost1 planet circling round the sun4 ,other rings would successively be detached1 and form the rest of the planets2 and the sun is the shrunken and condensed body of the nebula4 ,so simple and beautiful a theory of the solar system could not fail to captivate astronomers1 but it is generally rejected to-day1 in the precise form which ,laplace gave it4 ,what the difficulties are which it has encountered1 and the modifications it must suffer1 we shall see later2 as well as the new theories which have largely displaced it4 ,it will be better first to survey the universe from the evolutionary point of view4 ,but ,i may observe1 in passing1 that the sceptical remarks one hears at times about scientific theories contradicting and superseding each other are frivolous4 ,one great idea pervades all the theories of the evolution of worlds1 and that idea is firmly established4 ,the stars and their planets are enormous aggregations of cosmic dust1 swept together and compressed by the action of gravitation4 ,the precise nature of this cosmic dust--whether it was gas1 meteorites and gas1 or other particles--is open to question4 ,as we saw in the first chapter1 the universe has the word evolution written1 literally1 in letters of fire across it4 ,the stars are of all ages1 from sturdy youth to decrepit age1 and even to the darkness of death4 ,we saw that this can be detected on the superficial test of colour4 ,the colours of the stars are1 it is true1 an unsafe ground to build upon4 ,the astronomer still puzzles over the gorgeous colours he finds at times1 especially in double stars3 the topaz and azure companions in beta ,cygni1 the emerald and red of alpha ,herculis1 the yellow and rose of eta ,cassiopeiae1 and so on4 ,it is at the present time under discussion in astronomy how far these colours are objective at all1 or whether1 if they are real1 they may not be due to causes other than temperature4 ,yet the significance of the three predominating colours--blue-white1 yellow1 and red--has been sustained by the spectroscope4 ,it is the series of colours through which a white-hot bar of iron passes as it cools4 ,and the spectroscope gives us good ground to conclude that the stars are cooling4 ,when a glowing gas 7not under great pressure7 is examined by the spectroscope1 it yields a few vertical lines or bars of light on a dark background2 when a glowing liquid or solid is examined1 it gives a continuous rainbow-like stretch of colour4 ,some of the nebulae give the former type of spectrum1 and are thus known to be masses of luminous gas2 many of the nebulae and the stars have the latter type of spectrum4 ,but the stretch of light in the spectrum of a star is crossed1 vertically1 by a number of dark lines1 and experiment in the laboratory has taught us how to interpret these4 ,they mean that there is some light-absorbing vapour between the source of light and the instrument4 ,in the case of the stars they indicate the presence of an atmosphere of relatively cool vapours1 and an increase in the density of that atmosphere--which is shown by a multiplication and broadening of the dark lines on the spectrum--means an increase of age1 a loss of vitality1 and ultimately death4 ,so we get the descending scale of spectra4 ,the dark lines are thinnest and least numerous in the blue stars1 more numerous in the yellow1 heavy and thick in the red4 ,as the body of the star sinks in temperature dense masses of cool vapour gather about it4 ,its light1 as we perceive it1 turns yellow1 then red4 ,the next step1 which the spectroscope cannot follow1 will be the formation of a scum on the cooling surface1 ending1 after ages of struggle1 in the imprisonment of the molten interior under a solid1 dark crust4 ,let us see how our sun illustrates this theory4 ,it is in the yellow1 or what we may call the autumnal1 stage4 ,miss ,clerke and a few others have questioned this1 but the evidence is too strong to-day4 ,the vast globe1 #hfg1jjj miles in diameter1 seems to be a mass of much the same material as the earth--about forty elements have been identified in it--but at a terrific temperature4 ,the light-giving surface is found1 on the most recent calculations1 to have a temperature of about #fgjj degrees ,c4 ,this surface is an ocean of liquid or vaporised metals1 several thousand miles in depth2 some think that the brilliant light comes chiefly from clouds of incandescent carbon4 ,overlying it is a deep layer of the vapours of the molten metals1 with a temperature of about #eejj degrees ,c42 and to this comparatively cool and light-absorbing layer we owe the black lines of the solar spectrum4 ,above it is an ocean of red-hot hydrogen1 and outside this again is an atmosphere stretching for some hundreds of thousands of miles into space4 ,the significant feature1 from our point of view1 is the sun-spot2 though the spot may be an area of millions of square miles4 ,these areas are1 of course1 dark only by comparison with the intense light of the rest of the disk4 ,the darkest part of them is #ejjj times brighter than the full moon4 ,it will be seen further1 on examining a photograph of the sun1 that a network or veining of this dark material overspreads the entire surface at all times4 ,there is still some difference of opinion as to the nature of these areas1 but the evidence of the spectroscope has convinced most astronomers that they are masses of cooler vapour lying upon1 and sinking into1 the ocean of liquid fire4 ,round their edges1 as if responding to the pressure of the more condensed mass1 gigantic spurts and mountains of the white-hot matter of the sun rush upwards at a rate of fifty or a hundred miles a second1 ,sometimes they reach a height of a hundred1 and even two hundred1 thousand miles1 driving the red-hot hydrogen before them in prodigious and fantastic flames4 ,between the black veins over the disk1 also1 there rise domes and columns of the liquid fire1 some hundreds of miles in diameter1 spreading and sinking at from five to twenty miles a second4 ,the surface of the sun--how much more the interior6--is an appalling cauldron of incandescent matter from pole to pole4 ,every yard of the surface is a hundred times as intense as the open furnace of a ,titanic4 ,from the depths and from the surface of this fiery ocean1 as1 on a small scale1 from the surface of the tropical sea1 the vapours rise high into the extensive atmosphere1 discharge some of their heat into space1 and sink back1 cooler and heavier1 upon the disk4 ,this is a star in its yellow age1 as are ,capella and ,arcturus and other stars4 ,the red stars carry the story further1 as we should expect4 ,the heavier lines in their spectrum indicate more absorption of light1 and tell us that the vapours are thickening about the globe2 while compounds like titanium oxide make their appearance1 announcing a fall of temperature4 ,below these1 again1 is a group of dark red or carbon stars1 in which the process is carried further4 ,thick1 broad1 dark lines in the red end of the spectrum announce the appearance of compounds of carbon1 and a still lower fall of temperature4 ,the veil is growing thicker2 the life is ebbing from the great frame4 ,then the star sinks below the range of visibility1 and one would think that we can follow the dying world no farther4 ,fortunately1 in the case of ,algol and some thirty or forty other stars1 an extinct sun betrays its existence by flitting across the light of a luminous sun1 and recent research has made it probable that the universe is strewn with dead worlds4 ,some of them may be still in the condition which we seem to find in ,jupiter1 hiding sullen fires under a dense shell of cloud2 some may already be covered with a crust1 like the earth4 ,there are even stars in which one is tempted to see an intermediate stage3 stars which blaze out periodically from dimness1 as if the ,cyclops were spending his last energy in spasms that burst the forming roof of his prison4 ,but these variable stars are still obscure1 and we do not need their aid4 ,the downward course of a star is fairly plain4 ,when we turn to the earlier chapters in the life of a star1 the story is less clear4 ,it is at least generally agreed that the blue-white stars exhibit an earlier and hotter stage4 ,they show comparatively little absorption1 and there is an immense preponderance of the lighter gases1 hydrogen and helium4 ,they 7,sirius1 ,vega1 etc47 are1 in fact1 known as hydrogen stars1 and their temperature is generally computed at between #bj1jjj and #cj1jjj degrees ,c4 ,a few stars1 such as ,procyon and ,canopus1 seem to indicate a stage between them and the yellow or solar type4 ,but we may avoid finer shades of opinion and disputed classes1 and be content with these clear stages4 ,we begin with stars in which only hydrogen and helium1 the lightest ,of elements1 can be traced2 and the hydrogen is in an unfamiliar form1 implying terrific temperature4 ,in the next stage we find the lines of oxygen1 nitrogen1 magnesium1 and silicon4 ,metals such as iron and copper come later1 at first in a primitive and unusual form4 ,lastly we get the compounds of titanium and carbon1 and the densely shaded spectra which tell of the thickly gathering vapours4 ,the intense cold of space is slowly prevailing in the great struggle4 ,what came before the star8 ,it is now beyond reasonable doubt that the nebula--taking the word1 for the moment1 in the general sense of a loose1 chaotic mass of material--was the first stage4 ,professor ,keeler calculated that there are at least #abj1jjj nebulae within range of our telescopes1 and the number is likely to be increased4 ,a ,german astronomer recently counted #aebh on one photographic plate4 ,many of them1 moreover1 are so vast that they must contain the material for making a great number of worlds4 ,examine a good photograph of the nebula in ,orion4 ,recollect that each one of the points of light that are dotted over the expanse is a star of a million miles or more in diameter 7taking our sun as below the average71 and that the great cloud that sprawls across space is at least #aj1jjj billion miles away2 how much more no man knows4 ,it is futile to attempt to calculate the extent of that vast stretch of luminous gas4 ,we can safely say that it is at least a million times as large as the whole area of our solar system2 but it may run to trillions or quadrillions of miles4 ,nearly a hundred other nebulae are known1 by the spectroscope1 to be clouds of luminous gas4 ,it does not follow that they are white-hot1 and that the nebula is correctly called a fire-mist4 ,electrical and other agencies may make gases luminous1 and many astronomers think that the nebulae are intensely cold4 ,however1 the majority of the nebulae that have been examined are not gaseous1 and have a very different structure from the loose and diffused clouds of gas4 ,they show two 7possibly more1 but generally two7 great spiral arms starting from the central part and winding out into space4 ,as they are flat or disk-shaped1 we see this structure plainly when they turn full face toward the earth1 as does the magnificent nebula in ,canes ,venatici4 ,in it1 and many others1 we clearly trace a condensed central mass1 with two great arms1 each apparently having smaller centres of condensation1 sprawling outward like the broken spring of a watch4 ,the same structure can be traced in the mighty nebula in ,andromeda1 which is visible to the naked eye1 and it is said that more than half the nebulae in the heavens are spiral4 ,knowing that they are masses of solid or liquid fire1 we are tempted to see in them gigantic ,catherine-wheels1 the fireworks of the gods4 ,what is their relation to the stars8 ,in the first place1 their mere existence has provided a solid basis for the nebular hypothesis1 and their spiral form irresistibly suggests that they are whirling round on their central axis and concentrating4 ,further1 we find in some of the gaseous nebulae 7,orion7 comparatively void spaces occupied by stars1 which seem to have absorbed the nebulous matter in their formation4 ,on the other hand1 we find 7in the ,pleiades7 wisps and streamers of nebulous matter clinging about great clusters of stars1 suggesting that they are material left over when these clustered worlds crystallised out of some vast nebula2 and enormous stretches of nebulous material covering regions 7as in ,perseus7 where the stars are as thick as grains of silver4 ,more important still1 we find a type of cosmic body which seems intermediate between the star and the nebula4 ,it is a more or less imperfectly condensed star1 surrounded by nebular masses4 ,but one of the most instructive links of all is that at times a nebula is formed from a star1 and a recent case of this character may be briefly described4 ,in ,february1 #aija1 a new star appeared in the constellation ,perseus4 ,knowing what a star is1 the reader will have some dim conception of the portentous blaze that lit up that remote region of space 7at least #fjj billion miles away7 when he learns that the light of this star increased #djjj-;fold in twenty-eight hours4 ,it reached a brilliance #hjjj times greater than that of the sun4 ,telescopes and spectroscopes were turned on it from all parts of the earth1 and the spectroscope showed that masses of glowing hydrogen were rushing out from it at a rate of nearly a thousand miles a second4 ,its light gradually flickered and fell1 however1 and the star sank back into insignificance4 ,but the photographic plate now revealed a new and most instructive feature4 ,before the end of the year there was a nebula1 of enormous extent1 spreading out on both sides from the centre of the eruption4 ,it was suggested at the time that the bursting of a star may merely have lit up a previously dark nebula1 but the spectroscope does not support this4 ,a dim star had dissolved1 wholly or partially1 into a nebula1 as a result of some mighty cataclysm4 ,what the nature of the catastrophe was we will inquire presently4 ,these are a few of the actual connections that we find between stars and nebulae4 ,probably1 however1 the consideration that weighs most with the astronomer is that the condensation of such a loose1 far-stretched expanse of matter affords an admirable explanation of the enormous heat of the stars4 ,until recently there was no other conceivable source that would supply the sun's tremendous outpour of energy for tens of millions of years except the compression of its substance4 ,it is true that the discovery of radio-activity has disclosed a new source of energy within the atoms themselves1 and there are scientific men1 like ,professor ,arrhenius1 who attach great importance to this source4 ,but1 although it may prolong the limited term of life which physicists formerly allotted to the sun and other stars1 it is still felt that the condensation of a nebula offers the best explanation of the origin of a sun1 and we have ample evidence for the connection4 ,we must1 therefore1 see what the nebula is1 and how it develops4 ,nebula is merely the ,latin word for cloud4 ,whatever the nature of these diffused stretches of matter may be1 then1 the name applies fitly to them1 and any theory of the development of a star from them is still a nebular hypothesis4 ,but the three theories which divide astronomers to-day differ as to the nature of the nebula4 ,the older theory1 pointing to the gaseous nebulae as the first stage1 holds that the nebula is a cloud of extremely attenuated gas4 ,the meteoritic hypothesis 7,sir ,n4 ,lockyer1 ,sir ,g4 ,darwin1 etc471 observing that space seems to swarm with meteors and that the greater part of the nebulae are not gaseous1 believes that the starting-point is a colossal swarm of meteors1 surrounded by the gases evolved and lit up by their collisions4 ,the planetesimal hypothesis1 advanced in recent years by ,professor ,moulton and ,professor ,chamberlin1 contends that the nebula is a vast cloud of liquid or solid 7but not gaseous7 particles4 ,this theory is based mainly on the dynamical difficulties of the other two1 which we will notice presently4 ,the truth often lies between conflicting theories1 or they may apply to different cases4 ,it is not improbable that this will be our experience in regard to the nature of the initial nebula4 ,the gaseous nebulae1 and the formation of such nebulae from disrupted stars1 are facts that cannot be ignored4 ,the nebulae with a continuous spectrum1 and therefore--in part1 at least--in a liquid or solid condition1 may very well be regarded as a more advanced stage of condensation of the same2 their spiral shape and conspicuous nuclei are consistent with this4 ,moreover1 a condensing swarm of meteors would1 owing to the heat evolved1 tend to pass into a gaseous condition4 ,on the tether hand1 a huge expanse of gas stretched over billions of miles of space would be a net for the wandering particles1 meteors1 and comets that roam through space4 ,if it be true1 as is calculated1 that our #bd1jjj miles of atmosphere capture a hundred million meteors a day1 what would the millions or billions of times larger net of a nebula catch1 even if the gas is so much thinner8 ,in other words1 it is not wise to draw too fine a line between a gaseous nebula and one consisting of solid particles with gas4 ,the more important question is3 ,how do astronomers conceive the condensation of this mixed mass of cosmic dust8 ,it is easy to reply that gravitation1 or the pressure of the surrounding ether1 slowly drives the particles centre-ward1 and compresses the dust into globes1 as the boy squeezes the flocculent snow into balls2 and it is not difficult for the mathematician to show that this condensation would account for the shape and temperature of the stars4 ,but we must go a little beyond this superficial statement1 and see1 to some extent1 how the deeper students work out the process4 99 99 ,see1 especially1 ,dr4 ,p4 ,lowell1 ,the ,evolution of ,worlds 7#aiji74 ,professor ,s4 ,arrhenius1 ,worlds in the ,making 7#aijh71 ,sir ,n4 ,lockyer1 ,the ,meteorite ,hypothesis 7#ahij71 ,sir ,r4 ,ball1 ,the ,earth's ,beginning 7#aiji71 ,professor ,moulton1 ,the ,astrophysical ,journal 7,october1 #aije71 and ,chamberlin and ,salisbury1 ,geology1 ,vol4 ,,ii4 7#aijc74 ,taking a broad view of the whole field1 one may say that the two chief difficulties are as follows3 ,first1 how to get the whole chaotic mass whirling round in one common direction2 secondly1 how to account for the fact that in our solar system the outermost planets and satellites do not rotate in the same direction as the rest4 ,there is a widespread idea that these difficulties have proved fatal to the old nebular hypothesis1 and there are distinguished astronomers who think so4 ,but ,sir ,r4 ,ball 7see note71 ,professor ,lowell 7see note71 ,professor ,pickering 7,annals of ,harvard ,college ,observatory1 #ec1 ,,iii71 and other high authorities deny this1 and work out the newly discovered movements on the lines of the old theory4 ,they hold that all the bodies in the solar system once turned in the same direction as ,uranus and ,neptune1 and the tidal influence of the sun has changed the rotation of most of them4 ,the planets farthest from the sun would naturally not be so much affected by it4 ,the same principle would explain the retrograde movement of the outer satellites of ,saturn and ,jupiter4 ,sir ,r4 ,ball further works out the principles on which the particles of the condensing nebula would tend to form a disk rotating on its central axis4 ,the ring-theory of ,laplace is practically abandoned4 ,the spiral nebula is evidently the standard type1 and the condensing nebula must conform to it4 ,in this we are greatly helped by the current theory of the origin of spiral nebulae4 ,we saw previously that new stars sometimes appear in the sky1 and the recent closer scrutiny of the heavens shows this occurrence to be fairly frequent4 ,it is still held by a few astronomers that such a cataclysm means that two stars collided4 ,even a partial or grazing collision between two masses1 each weighing billions of tons1 travelling 7on the average7 forty or fifty miles a second--a movement that would increase enormously as they approach each other--would certainly liquefy or vaporise their substance2 but the astronomer1 accustomed to see cosmic bodies escape each other by increasing their speed1 is generally disinclined to believe in collisions4 ,some have made the new star plunge into the heart of a dense and dark nebula2 some have imagined a shock of two gigantic swarms of meteors2 some have regarded the outflame as the effect of a prodigious explosion4 ,in one or other new star each or any of these things may have occurred1 but the most plausible and accepted theory for the new star of #aija and some others is that two stars had approached each other too closely in their wandering4 ,suppose that1 in millions of years to come1 when our sun is extinct and a firm crust surrounds the great molten ball1 some other sun approaches within a few million miles of it4 ,the two would rush past each other at a terrific speed1 but the gravitational effect of the approaching star would tear open the solid shell of the sun1 and1 in a mighty flame1 its molten and gaseous entrails would be flung out into space4 ,it has long been one of the arguments against a molten interior of the earth that the sun's gravitational influence would raise it in gigantic tides and rend the solid shell of rock4 ,it is even suspected now that our small earth is not without a tidal influence on the sun4 ,the comparatively near approach of two suns would lead to a terrific cataclysm4 ,if we accept this theory1 the origin of the spiral nebula becomes intelligible4 ,as the sun from which it is formed is already rotating on its axis1 we get a rotation of the nebula from the first4 ,the mass poured out from the body of the sun would1 even if it were only a small fraction of its mass1 suffice to make a planetary system2 all our sun's planets and their satellites taken together amount to only #a_/ajjth of the mass of the solar system4 ,we may assume1 further1 that the outpoured matter would be a mixed cloud of gases and solid and liquid particles2 and that it would stream out1 possibly in successive waves1 from more than one part of the disrupted sun1 tending to form great spiral trails round the parent mass4 ,some astronomers even suggest that1 as there are tidal waves raised by the moon at opposite points of the earth1 similar tidal outbursts would occur at opposite points on the disk of the disrupted star1 and thus give rise to the characteristic arms starting from opposite sides of the spiral nebula4 ,this is not at all clear1 as the two tidal waves of the earth are due to the fact that it has a liquid ocean rolling on1 not under1 a solid bed4 ,in any case1 we have here a good suggestion of the origin of the spiral nebula and of its further development4 ,as soon as the outbursts are over1 and the scattered particles have reached the farthest limit to which they are hurled1 the concentrating action of gravitation will slowly assert itself4 ,if we conceive this gravitational influence as the pressure of the surrounding ether we get a wider understanding of the process4 ,much of the dispersed matter may have been shot far enough into space to escape the gravitational pull of the parent mass1 and will be added to the sum of scattered cosmic dust1 meteors1 and close shoals of meteors 7comets7 wandering in space4 ,much of the rest will fall back upon the central body ,but in the great spiral arms themselves the distribution of the matter will be irregular1 and the denser areas will slowly gather in the surrounding material4 ,in the end we would thus get secondary spheres circling round a large primary4 ,this is the way in which astronomers now generally conceive the destruction and re-formation of worlds4 ,on one point the new planetesimal theory differs from the other theories4 ,it supposes that1 since the particles of the whirling nebula are all travelling in the same general direction1 they overtake each other with less violent impact than the other theories suppose1 and therefore the condensation of the material into planets would not give rise to the terrific heat which is generally assumed4 ,we will consider this in the next chapter1 when we deal with the formation of the planets4 ,as far as the central body1 the sun1 is concerned1 there can be no hesitation4 ,the #ejj1jjj1jjj incandescent suns in the heavens are eloquent proof of the appalling heat that is engendered by the collisions of the concentrating particles4 ,in general outline we now follow the story of a star with some confidence4 ,an internal explosion1 a fatal rush into some dense nebula or swarm of meteors1 a collision with another star1 or an approach within a few million miles of another star1 scatters1 in part or whole1 the solid or liquid globe in a cloud of cosmic dust4 ,when the violent outrush is over1 the dust is gathered together once more into a star4 ,at first cold and attenuated1 its temperature rises as the particles come together1 and we have1 after a time1 an incandescent nucleus shining through a thin veil of gas--a nebulous star4 ,the temperature rises still further1 and we have the blue-hot star1 in which the elements seem to be dissociated1 and slowly re-forming as the temperature falls4 ,after1 perhaps1 hundreds of millions of years it reaches the yellow stage1 and1 if it has planets with the conditions of life1 there may be a temporary opportunity for living things to enjoy its tempered energy4 ,but the cooler vapours are gathering round it1 and at length its luminous body is wholly imprisoned4 ,it continues its terrific course through space1 until some day1 perhaps1 it again encounters the mighty cataclysm which will make it begin afresh the long and stormy chapters of its living history4 ,such is the suggestion of the modern astronomer1 and1 although we seem to find every phase of the theory embodied in the varied contents of the heavens1 we must not forget that it is only a suggestion4 ,the spectroscope and telescopic photography1 which are far more important than the visual telescope1 are comparatively recent1 and the field to be explored is enormous4 ,the mist is lifting from the cosmic landscape1 but there is still enough to blur our vision4 ,very puzzling questions remain unanswered4 ,what is the origin of the great gaseous nebulae8 ,what is the origin of the triple or quadruple star8 ,what is the meaning of stars whose light ebbs and flows in periods of from a few to several hundred days8 ,we may even point to the fact that some1 at least1 of the spiral nebulae are far too vast to be the outcome of the impact or approach of two stars4 ,we may be content to think that we have found out some truths1 by no means the whole truth1 about the evolution of worlds4 ,throughout this immeasurable ocean of ether the particles of matter are driven together and form bodies4 ,these bodies swarm throughout space1 like fish in the sea2 travelling singly 7the shooting star71 or in great close shoals 7the nucleus of a comet71 or lying scattered in vast clouds4 ,but the inexorable pressure urges them still1 until billions of tons of material are gathered together4 ,then1 either from the sheer heat of the compression1 or from the formation of large and unstable atomic systems 7radium1 etc471 or both1 the great mass becomes a cauldron of fire1 mantled in its own vapours1 and the story of a star is run4 ,it dies out in one part of space to begin afresh in another4 ,we see nothing in the nature of a beginning or an end for the totality of worlds1 the universe4 ,the life of all living things on the earth1 from the formation of the primitive microbes to the last struggles of the superman1 is a small episode of that stupendous drama1 a fraction of a single scene4 ,but our ampler knowledge of it1 and our personal interest in it1 magnify that episode1 and we turn from the cosmic picture to study the formation of the earth and the rise of its living population4 ,,chapter ,,iv4 ,,the ,,preparation ,,of ,,the ,,earth ,the story of the evolution of our solar system is1 it will now be seen1 a local instance of the great cosmic process we have studied in the last chapter4 ,we may take one of the small spiral nebulae that abound in the heavens as an illustration of the first stage4 ,if a still earlier stage is demanded1 we may suppose that some previous sun collided with1 or approached too closely1 another mighty body1 and belched out a large part of its contents in mighty volcanic outpours4 ,mathematical reasoning can show that this erupted material would gather into a spiral nebula2 but1 as mathematical calculations cannot be given here1 and are less safe than astronomical facts1 we will be content to see the early shape of our solar system in a relatively small spiral nebula1 its outermost arm stretching far beyond the present orbit of ,neptune1 and its great nucleus being our present sun in more diffused form4 ,we need not now attempt to follow the shrinking of the central part of the nebula until it becomes a rounded fiery sun4 ,that has been done in tracing the evolution of a star4 ,here we have to learn how the planets were formed from the spiral arms of the nebula4 ,the principle of their formation is already clear4 ,the same force of gravitation1 or the same pressure of the surrounding ether1 which compresses the central mass into a fiery globe1 will act upon the loose material of the arms and compress it into smaller globes4 ,but there is an interesting and acute difference of opinion amongst modern experts as to whether these smaller globes1 the early planets1 would become white-hot bodies4 ,the general opinion1 especially among astronomers1 is that the compression of the nebulous material of the arms into globes would generate enormous heat1 as in the case of the sun4 ,on that view the various planets would begin their careers as small suns1 and would pass through those stages of cooling and shrinking which we have traced in the story of the stars4 ,a glance at the photograph of one of the spiral nebulae strongly confirms this4 ,great luminous knots1 or nuclei1 are seen at intervals in the arms4 ,smaller suns seem to be forming in them1 each gathering into its body the neighbouring material of the arm1 and rising in temperature as the mass is compressed into a globe4 ,the spectroscope shows that these knots are condensing masses of white-hot liquid or solid matter4 ,it therefore seems plain that each planet will first become a liquid globe of fire1 coursing round the central sun1 and will gradually1 as its heat is dissipated and the supply begins to fail1 form a solid crust4 ,this familiar view is challenged by the new planetesimal hypothesis1 which has been adopted by many distinguished geologists 7,chamberlin1 ,gregory1 ,coleman1 etc474 ,in their view the particles in the arms of the nebula are all moving in the same direction round the sun4 ,they therefore quietly overtake the nucleus to which they are attracted1 instead of violently colliding with each other1 and much less heat is generated at the surface4 ,in that case the planets would not pass through a white-hot1 or even red-hot1 stage at all4 ,they are formed by a slow ingathering of the scattered particles1 which are called planetesimals round the larger or denser masses of stuff which were discharged by the exploding sun4 ,possibly these masses were prevented from falling back into the sun by the attraction of the colliding body1 or the body which caused the eruption4 ,they would revolve round the parent body1 and the shoals of smaller particles would gather about them by gravitation4 ,if there were any large region in the arm of the nebula which had no single massive nucleus1 the cosmic dust would gather about a number of smaller centres4 ,thus might be explained the hundreds of planetoids1 or minor planets1 which we find between ,mars and ,jupiter4 ,if these smaller bodies came within the sphere of influence of one of the larger planets1 yet were travelling quickly enough to resist its attraction1 they would be compelled to revolve round it1 and we could thus explain the ten satellites of ,saturn and the eight of ,jupiter4 ,our moon1 we shall see1 had a different origin4 ,we shall find this new hypothesis crossing the familiar lines at many points in the next few chapters4 ,we will consider those further consequences as they arise1 but may say at once that1 while the new theory has greatly helped us in tracing the formation of the planetary system1 astronomers are strongly opposed to its claim that the planets did not pass through an incandescent stage4 ,the actual features of our spiral nebulae seem clearly to exhibit that stage4 ,the shape of the planets--globular bodies1 flattened at the poles--strongly suggests that they were once liquid4 ,the condition in which we find ,saturn and ,jupiter very forcibly confirms this suggestion2 the latest study of those planets supports the current opinion that they are still red-hot1 and even seems to detect the glow of their surfaces in their mantles of cloud4 ,these points will be considered more fully presently4 ,for the moment it is enough to note that1 as far as the early stages of planetary development are concerned1 the generally accepted theory rests on a mass of positive evidence1 while the new hypothesis is purely theoretical4 ,we therefore follow the prevailing view with some confidence4 ,those of the spiral nebulae which face the earth squarely afford an excellent suggestion of the way in which planets are probably formed4 ,in some of these nebulae the arms consist of almost continuous streams of faintly luminous matter2 in others the matter is gathering about distinct centres2 in others again the nebulous matter is1 for the most part1 collected in large glowing spheres4 ,they seem to be successive stages1 and to reveal to us the origin of our planets4 ,the position of each planet in our solar system would be determined by the chance position of the denser stuff shot out by the erupting sun4 ,i have seen ,vesuvius hurl up into the sky1 amongst its blasts of gas and steam1 white-hot masses of rock weighing fifty tons4 ,in the far fiercer outburst of the erupting sun there would be at least thinner and denser masses1 and they must have been hurled so far into space that their speed in travelling round the central body1 perhaps seconded by the attraction of the second star1 overcame the gravitational pull back to the centre4 ,recollect the force which1 in the new star in ,perseus1 drove masses of hydrogen for millions of miles at a speed of a thousand miles a second4 ,these denser nuclei or masses would1 when the eruption was over1 begin to attract to themselves all the lighter nebulous material within their sphere of gravitational influence4 ,naturally1 there would at first be a vast confusion of small and large centres of condensation in the arms of the nebula1 moving in various directions1 but a kind of natural selection--and1 in this case1 survival of the biggest--would ensue4 ,the conflicting movements would be adjusted by collisions and gravitation1 the smaller bodies would be absorbed in the larger or enslaved as their satellites1 and the last state would be a family of smaller suns circling at vast distances round the parent body4 ,the planets1 moreover1 would be caused to rotate on their axes1 besides revolving round the sun1 as the particles at their inner edge 7nearer the sun7 would move at a different speed from those at the outer edge4 ,in the course of time the smaller bodies1 having less heat to lose and less 7or no7 atmosphere to check the loss1 would cool down1 and become dark solid spheres1 lit only by the central fire4 ,while the first stage of this theory of development is seen in the spiral nebula1 the later stages seem to be well exemplified in the actual condition of our planets4 ,following1 chiefly1 the latest research of ,professor ,lowell and his colleagues1 which marks a considerable advance on our previous knowledge1 we shall find it useful to glance at the sister-planets before we approach the particular story of our earth4 ,mercury1 the innermost and smallest of the planets1 measuring only some #cdjj miles in diameter1 is1 not unexpectedly1 an airless wilderness4 ,small bodies are unable to retain the gases at their surface1 on account of their feebler gravitation4 ,we find1 moreover1 that ,mercury always presents the same face to the sun1 as it turns on its axis in the same period 7eighty-eight days7 in which it makes a revolution round the sun4 ,while1 therefore1 one half of the globe is buried in eternal darkness1 the other half is eternally exposed to the direct and blistering rays of the sun1 which is only #hf1jjj1jjj miles away4 ,to ,professor ,lowell it presents the appearance of a bleached and sun-cracked desert1 or the bones of a dead world4 ,its temperature must be at least #cjj degrees ,c4 above that of the earth4 ,its features are what we should expect on the nebular hypothesis4 ,the slowness of its rotation is accounted for by the heavy tidal influence of the sun4 ,in the same way our moon has been influenced by the earth1 and our earth by the sun1 in their movement of rotation4 ,venus1 as might be expected in the case of so large a globe 7nearly as large as the earth71 has an atmosphere1 but it seems1 like ,mercury1 always to present the same face to the sun4 ,its comparative nearness to the sun 7#fg1jjj1jjj miles7 probably explains this advanced effect of tidal action4 ,the consequences that the observers deduce from the fact are interesting4 ,the sun-baked half of ,venus seems to be devoid of water or vapour1 and it is thought that all its water is gathered into a rigid ice-field on the dark side of the globe1 from which fierce hurricanes must blow incessantly4 ,it is a ,sahara1 or a desert far hotter than the ,sahara1 on one side2 an arctic region on the other4 ,it does not seem to be a world fitted for the support of any kind of life that we can imagine4 ,when we turn to the consideration of ,mars1 we enter a world of unending controversy4 ,with little more than half the diameter of the earth1 ,mars ought to be in a far more advanced stage of either life or decay1 but its condition has not yet been established4 ,some hold that it has a considerable atmosphere2 others that it is too small a globe to have retained a layer of gas4 ,professor ,poynting believes that its temperature is below the freezing-point of water all over the globe2 many others1 if not the majority of observers1 hold that the white cap we see at its poles is a mass of ice and snow1 or at least a thick coat of hoar-frost1 and that it melts at the edges as the springtime of ,mars comes round4 ,in regard to its famous canals we are no nearer agreement4 ,some maintain that the markings are not really an objective feature2 some hold that they are due to volcanic activity1 and that similar markings are found on the moon2 some believe that they are due to clouds2 while ,professor ,lowell and others stoutly adhere to the familiar view that they are artificial canals1 or the strips of vegetation along such canals4 ,the question of the actual habitation of ,mars is still open4 ,we can say only that there is strong evidence of its possession of the conditions of life in some degree1 and that living things1 even on the earth1 display a remarkable power of adaptation to widely differing conditions4 ,passing over the #gjj planetoids1 which circulate between ,mars and ,jupiter1 and for which we may account either by the absence of one large nucleus in that part of the nebulous stream or by the disturbing influence of ,jupiter1 we come to the largest planet of the system4 ,here we find a surprising confirmation of the theory of planetary development which we are following4 ,three hundred times heavier than the earth 7or more than a trillion tons in weight71 yet a thousand times less in volume than the sun1 ,jupiter ought1 if our theory is correct1 to be still red-hot4 ,all the evidence conspires to suggest that it is4 ,it has long been recognised that the shining disk of the planet is not a solid1 but a cloud1 surface4 ,this impenetrable mass of cloud or vapour is drawn out in streams or belts from side to side1 as the giant globe turns on its axis once in every ten hours4 ,we cannot say if1 or to what extent1 these clouds consist of water-vapour4 ,we can conclude only that this mantle of ,jupiter is a seething cauldron of vapours 7,lowell71 and that1 if the body beneath is solid1 it must be very hot4 ,a large red area1 at one time #cj1jjj miles long1 has more or less persisted on the surface for several decades1 and it is generally interpreted1 either as a red-hot surface1 or as a vast volcanic vent1 reflecting its glow upon the clouds4 ,indeed1 the keen ,american observers1 with their powerful telescopes1 have detected a cherry-red glow on the edges of the cloud-belts across the disk2 and more recent observation with the spectroscope seems to prove that ,jupiter emits light from its surface analogous to that of the red stars4 ,the conspicuous flattening of its poles is another feature that science would expect in a rapidly rotating liquid globe4 ,in a word1 ,jupiter seems to be in the last stage of stellar development4 ,such1 at some remote time1 was our earth2 such one day will be the sun4 ,the neighbouring planet ,saturn supports the conclusion4 ,here again we have a gigantic globe1 #bh1jjj miles in diameter1 turning on its axis in the short space of ten hours2 and here again we find the conspicuous flattening of the poles1 the trailing belts of massed vapour across the disk1 the red glow lighting the edges of the belts1 and the spectroscopic evidence of an emission of light4 ,once more it is difficult to doubt that a highly heated body is wrapped in that thick mantle of vapour4 ,with its ten moons and its marvellous ring-system--an enormous collection of fragments1 which the influence of the planet or of its nearer satellites seems to have prevented from concentrating--,saturn has always been a beautiful object to observe2 it is not less interesting in those features which we faintly detect in its disk4 ,the next planet1 ,uranus1 #cb1jjj miles in diameter1 seems to be another cloud-wrapt1 greatly heated globe1 if not1 as some think1 a sheer mass of vapours without a liquid core4 ,neptune is too dim and distant for profitable examination4 ,it may be added1 however1 that the dense masses of gas which are found to surround the outer planets seem to confirm the nebular theory1 which assumes that they were developed in the outer and lighter part of the material hurled from the sun4 ,from this encouraging survey of the sister-planets we return with more confidence to the story of the earth4 ,i will not attempt to follow an imaginative scheme in regard to its early development4 ,take four photographs--one of a spiral nebula without knots in its arms1 one of a nebula like that in ,canes ,venatici1 one of the sun1 and one of ,jupiter--and you have an excellent illustration of the chief stages in its formation4 ,in the first picture a section of the luminous arm of the nebula stretches thinly across millions of miles of space4 ,in the next stage this material is largely collected in a luminous and hazy sphere1 as we find in the nebula in ,canes ,venatici4 ,the sun serves to illustrate a further stage in the condensation of this sphere4 ,jupiter represents a later chapter1 in which the cooler vapours are wrapped close about the red-hot body of the planet4 ,that seems to have been the early story of the earth4 ,some #f1jjj1jjj1jjj billion tons of the nebulous matter were attracted to a common centre4 ,as the particles pressed centreward1 the temperature rose1 and for a time the generation of heat was greater than its dissipation4 ,whether the earth ever shone as a small white star we cannot say4 ,we must not hastily conclude that such a relatively small mass would behave like the far greater mass of a star1 but we may1 without attempting to determine its temperature1 assume that it runs an analogous course4 ,one of the many features which ,i have indicated as pointing to a former fluidity of the earth may be explained here4 ,we shall see in the course of this work that the mountain chains and other great irregularities of the earth's surface appear at a late stage in its development4 ,even as we find them to-day1 they are seen to be merely slight ridges and furrows on the face of the globe1 when we reflect on its enormous diameter1 but there is good reason to think that in the beginning the earth was much nearer to a perfectly globular form4 ,this points to a liquid or gaseous condition at one time1 and the flattening of the sphere at the poles confirms the impression4 ,we should hardly expect so perfect a rotundity in a body formed by the cool accretion of solid fragments and particles4 ,it is just what we should expect in a fluid body1 and the later irregularities of the surface are accounted for by the constant crumpling and wearing of its solid crust4 ,many would find a confirmation of this in the phenomena of volcanoes1 geysers1 and earthquakes1 and the increase of the temperature as we descend the crust4 ,but the interior condition of the earth1 and the nature of these phenomena1 are much disputed at present1 and it is better not to rely on any theory of them4 ,it is suggested that radium may be responsible for this subterraneous heat4 ,the next stage in the formation of the earth is necessarily one that we can reach only by conjecture4 ,over the globe of molten fire the vapours and gases would be suspended like a heavy canopy1 as we find in ,jupiter and ,saturn to-day4 ,when the period of maximum heat production was passed1 however1 the radiation into space would cause a lowering of the temperature1 and a scum would form on the molten surface4 ,as may be observed on the surface of any cooling vessel of fluid1 the scum would stretch and crack2 the skin would1 so to say1 prove too small for the body4 ,the molten ocean below would surge through the crust1 and bury it under floods of lava4 ,some hold that the slabs would sink in the ocean of metal1 and thus the earth would first solidify in its deeper layers4 ,there would1 in any case1 be an age-long struggle between the molten mass and the confining crust1 until at length--to employ the old ,roman conception of the activity of ,etna--the giant was imprisoned below the heavy roof of rock4 ,here again we seem to find evidence of the general correctness of the theory4 ,the objection has been raised that the geologist does not find any rocks which he can identify as portions of the primitive crust of the earth4 ,it seems to me that it would be too much to expect the survival at the surface of any part of the first scum that cooled on that fiery ocean4 ,it is more natural to suppose that millions of years of volcanic activity on a prodigious scale would characterise this early stage1 and the primitive crust would be buried in fragments1 or dissolved again1 under deep seas of lava4 ,now1 this is precisely what we find1 ,the oldest rocks known to the geologist--the ,archaean rocks--are overwhelmingly volcanic1 especially in their lower part4 ,their thickness1 as we know them1 is estimated at #ej1jjj feet2 a thickness which must represent many millions of years4 ,but we do not know how much thicker than this they may be4 ,they underlie the oldest rocks that have ever been exposed to the gaze of the geologist4 ,they include sedimentary deposits1 showing the action of water1 and even probable traces of organic remains1 but they are1 especially in their deeper and older sections1 predominantly volcanic4 ,they evince what we may call a volcanic age in the early story of the planet4 ,but before we pursue this part of the story further we must interpolate a remarkable event in the record--the birth of the moon4 ,it is now generally believed1 on a theory elaborated by ,sir ,g4 ,darwin1 that when the formation of the crust had reached a certain depth--something over thirty miles1 it is calculated--it parted with a mass of matter1 which became the moon4 ,the size of our moon1 in comparison with the earth1 is so exceptional among the satellites which attend the planets of our solar system that it is assigned an exceptional origin4 ,it is calculated that at that time the earth turned on its axis in the space of four or five hours1 instead of twenty-four4 ,we have already seen that the tidal influence of the sun has the effect of moderating the rotation of the planets4 ,now1 this very rapid rotation of a liquid mass1 with a thin crust1 would 7together with the instability occasioned by its cooling7 cause it to bulge at the equator4 ,the bulge would increase until the earth became a pear-shaped body4 ,the small end of the pear would draw further and further away from the rest--as a drop of water does on the mouth of a tap--and at last the whole mass 7some #e1jjj1jjj1jjj cubic miles of matter7 was broken off1 and began to pursue an independent orbit round the earth4 ,there are astronomers who think that other cosmic bodies1 besides our moon1 may have been formed in this way4 ,possibly it is true of some of the double stars1 but we will not return to that question4 ,the further story of the moon1 as it is known to astronomers1 may be given in a few words4 ,the rotational movement of the earth is becoming gradually slower on account of tidal influence2 our day1 in fact1 becomes an hour longer every few million years4 ,it can be shown that this had the effect of increasing the speed1 and therefore enlarging the orbit1 of the moon1 as it revolved round the earth4 ,as a result1 the moon drew further and further away from the earth until it reached its present position1 about #bdj1jjj miles away4 ,at the same time the tidal influence of the earth was lessening the rotational movement of the moon4 ,this went on until it turned on its axis in the same period in which it revolves round the earth1 and on this account it always presents the same face to the earth4 ,through what chapters of life the moon may have passed in the meantime it is impossible to say4 ,its relatively small mass may have been unable to keep the lighter gases at its surface1 or its air and water may1 as some think1 have been absorbed4 ,it is to-day practically an airless and waterless desert1 alternating between the heat of its long day and the intense cold of its long night4 ,careful observers1 such as ,professor ,pickering1 think that it may still have a shallow layer of heavy gases at its surface1 and that this may permit the growth of some stunted vegetation during the day4 ,certain changes of colour1 which are observed on its surface1 have been interpreted in that sense4 ,we can hardly conceive any other kind of life on it4 ,in the dark even the gases will freeze on its surface1 as there is no atmosphere to retain the heat4 ,indeed1 some students of the moon 7,fauth1 etc47 believe that it is an unchanging desert of ice1 bombarded by the projectiles of space4 ,an ingenious speculation as to the effect on the earth of this dislodgment of #e1jjj1jjj1jjj cubic miles of its substance is worth noting4 ,it supposes that the bed of the ,pacific ,ocean represents the enormous gap torn in its side by the delivery of the moon4 ,at each side of this chasm the two continents1 the ,old ,world and the ,new1 would be left floating on their molten ocean2 and some have even seen a confirmation of this in the lines of crustal weakness which we trace1 by volcanoes and earthquakes1 on either side of the ,pacific4 ,others1 again1 connect the shape of our great masses of land1 which generally run to a southern point1 with this early catastrophe4 ,but these interesting speculations have a very slender basis1 and we will return to the story of the development of the earth4 ,the last phase in preparation for the appearance of life would be the formation of the ocean4 ,on the lines of the generally received nebular hypothesis this can easily be imagined1 in broad outline4 ,the gases would form the outer shell of the forming planet1 since the heavier particles would travel inward4 ,in this mixed mass of gas the oxygen and hydrogen would combine1 at a fitting temperature1 and form water4 ,for ages the molten crust would hold this water suspended aloft as a surrounding shell of cloud1 but when the surface cooled to about #chj degrees ,c4 7,sollas71 the liquid would begin to pour on it4 ,a period of conflict would ensue1 the still heated crust and the frequent volcanic outpours sending the water back in hissing steam to the clouds4 ,at length1 and now more rapidly1 the temperature of the crust would sink still lower1 and a heated ocean would settle upon it1 filling the hollows of its irregular surface1 and washing the bases of its outstanding ridges4 ,from that time begins the age-long battle of the land and the water which1 we shall see1 has had a profound influence on the development of life4 ,in deference to the opinion of a number of geologists we must glance once more at the alternative view of the planetesimal school4 ,in their opinion the molecules of water were partly attracted to the surface out of the disrupted matter1 and partly collected within the porous outer layers of the globe4 ,as the latter quantity grew1 it would ooze upwards1 fill the smaller depressions in the crust1 and at length1 with the addition of the attracted water1 spread over the irregular surface4 ,there is an even more important difference of opinion in regard to the formation of the atmosphere1 but we may defer this until the question of climate interests us4 ,we have now made our globe1 and will pass on to that early chapter of its story in which living things make their appearance4 ,to some it will seem that we ought not to pass from the question of origin without a word on the subject of the age of the earth4 ,all that one can do1 however1 is to give a number of very divergent estimates4 ,physicists have tried to calculate the age of the sun from the rate of its dissipation of heat1 and have assigned1 at the most1 a hundred million years to our solar system2 but the recent discovery of a source of heat in the disintegration of such metals as radium has made their calculations useless4 ,geologists have endeavoured1 from observation of the action of geological agencies to-day1 to estimate how long it will have taken them to form the stratified crust of the earth2 but even the best estimates vary between twenty-five and a hundred million years1 and we have reason to think that the intensity of these geological agencies may have varied in different ages4 ,chemists have calculated how long it would take the ocean1 which was originally fresh water1 to take up from the rocks and rivers the salt which it contains to-day2 ,professor ,joly has on this ground assigned a hundred million years since the waters first descended upon the crust4 ,we must be content to know that the best recent estimates1 based on positive data1 vary between fifty and a hundred million years for the story which we are now about to narrate4 ,the earlier or astronomical period remains quite incalculable4 ,sir ,g4 ,darwin thinks that it was probably at least a thousand million years since the moon was separated from the earth4 ,whatever the period of time may be since some cosmic cataclysm scattered the material of our solar system in the form of a nebula1 it is only a fraction of that larger and illimitable time which the evolution of the stars dimly suggests to the scientific imagination4 ,,the ,,geological ,,series ,the scale of years adopted--#ej1jjj1jjj for the stratified rocks--is merely an intermediate between conflicting estimates4 ,,era4 ,,period4 ,,relative ,,length4 ,quaternary ,holocene #ejj1jjj years ,pleistocene ,tertiary ,pliocene #e1ejj1jjj years or ,miocene ,cenozoic ,oligocene ,eocene ,secondary ,cretaceous #g1bjj1jjj years or ,jurassic #c1fjj1jjj ,mesozoic ,triassic #b1ejj1jjj ,primary ,permian #b1hjj1jjj years or ,carboniferous #f1bjj1jjj ,palaeozoic ,devonian #h1jjj1jjj ,silurian #e1djj1jjj ,ordovician #e1djj1jjj ,cambrian #h1jjj1jjj ,archaean ,keweenawan ,unknown 7probably ,animikie at least ,huronian #ej1jjj1jjj years7 ,keewatin ,laurentian ,,chapter ,v4 ,,the ,,beginning ,,of ,,life ,there is1 perhaps1 no other chapter in the chronicle of the earth that we approach with so lively an interest as the chapter which should record the first appearance of life4 ,unfortunately1 as far as the authentic memorials of the past go1 no other chapter is so impenetrably obscure as this4 ,the reason is simple4 ,it is a familiar saying that life has written its own record1 the long-drawn record of its dynasties and its deaths1 in the rocks4 ,but there were millions of years during which life had not yet learned to write its record1 and further millions of years the record of which has been irremediably destroyed4 ,the first volume of the geological chronicle of the earth is the mass of the ,archaean 7or primitive7 rocks4 ,what the actual magnitude of that volume1 and the span of time it covers1 may be1 no geologist can say4 ,the ,archaean rocks still solidly underlie the lowest depth he has ever reached4 ,it is computed1 however1 that these rocks1 as far as they are known to us1 have a total depth of nearly ten miles1 and seem therefore to represent at least half the story of the earth from the time when it rounded into a globe1 or cooled sufficiently to endure the presence of oceans4 ,yet all that we read of the earth's story during those many millions of years could be told in a page or two4 ,that section of geology is still in its infancy1 it is true4 ,a day may come when science will decipher a long and instructive narrative in the masses of quartz and gneiss1 and the layers of various kinds1 which it calls the ,archaean rocks4 ,but we may say with confidence that it will not discover in them more than a few stray syllables of the earlier part1 and none whatever of the earliest part1 of the epic of living nature4 ,a few fossilised remains of somewhat advanced organisms1 such as shell-fish and worms1 are found in the higher and later rocks of the series1 and more of the same comparatively high types will probably appear4 ,in the earlier strata1 representing an earlier stage of life1 we find only thick seams of black shale1 limestone1 and ironstone1 in which we seem to see the ashes of primitive organisms1 cremated in the appalling fires of the volcanic age1 or crushed out of recognition by the superimposed masses4 ,even if some wizardry of science were ever to restore the forms that have been reduced to ashes in this ,archaean crematorium1 it would be found that they are more or less advanced forms1 far above the original level of life4 ,no trace will ever be found in the rocks of the first few million years in the calendar of life4 ,the word impossible or unknowable is not lightly uttered in science to-day1 but there is a very plain reason for admitting it here4 ,the earliest living things were at least as primitive of nature as the lowest animals and plants we know to-day1 and these1 up to a fair level of organisation1 are so soft of texture that1 when they die1 they leave no remains which may one day be turned into fossils4 ,some of them1 indeed1 form tiny shells of flint or lime1 or1 like the corals1 make for themselves a solid bed2 but this is a relatively late and higher stage of development4 ,many thousands of species of animals and plants lie below that level4 ,we are therefore forced to conclude1 from the aspect of living nature to-day1 that for ages the early organisms had no hard and preservable parts4 ,in thus declaring the impotence of geology1 however1 we are at the same time introducing another science1 biology1 which can throw appreciable light on the evolution of life4 ,let us first see what geology tells us about the infancy of the earth4 ,the distribution of the early rocks suggests that there was comparatively little dry land showing above the surface of the ,archaean ocean4 ,our knowledge of these rocks is not at all complete1 and we must remember that some of this primitive land may be now under the sea or buried in unsuspected regions4 ,it is significant1 however1 that1 up to the present1 exploration seems to show that in those remote ages only about one-fifth of our actual land-surface stood above the level of the waters4 ,apart from a patch of some #bj1jjj square miles of what is now ,australia1 and smaller patches in ,tasmania1 ,new ,zealand1 and ,india1 nearly the whole of this land was in the far ,north4 ,a considerable area of eastern ,canada had emerged1 with lesser islands standing out to the west and south of ,north ,america4 ,another large area lay round the basin of the ,baltic2 and as ,greenland1 the ,hebrides1 and the extreme tip of ,scotland1 belong to the same age1 it is believed that a continent1 of which they are fragments1 united ,america and ,europe across the ,north ,atlantic4 ,of the rest of what is now ,europe there were merely large islands--one on the border of ,england and ,wales1 others in ,france1 ,spain1 and ,southern ,germany4 ,asia was represented by a large area in ,china and ,siberia1 and an island or islands on the site of ,india4 ,very little of ,africa or ,south ,america existed4 ,it will be seen at a glance that the physical story of the earth from that time is a record of the emergence from the waters of larger continents and the formation of lofty chains of mountains4 ,now this world-old battle of land and sea has been waged with varying fortune from age to age1 and it has been one of the most important factors in the development of life4 ,we are just beginning to realise what a wonderful light it throws on the upward advance of animals and plants4 ,no one in the scientific world to-day questions that1 however imperfect the record may be1 there has been a continuous development of life from the lowest level to the highest4 ,but why there was advance at all1 why the primitive microbe climbs the scale of being1 during millions of years1 until it reaches the stature of humanity1 seems to many a profound mystery4 ,the solution of this mystery begins to break upon us when we contemplate1 in the geological record1 the prolonged series of changes in the face of the earth itself1 and try to realise how these changes must have impelled living things to fresh and higher adaptations to their changing surroundings4 ,imagine some early continent with its population of animals and plants4 ,each bay1 estuary1 river1 and lake1 each forest and marsh and solid plain1 has its distinctive inhabitants4 ,imagine this continent slowly sinking into the sea1 until the advancing arms of the salt water meet across it1 mingling their diverse populations in a common world1 making the fresh-water lake brackish or salt1 turning the dry land into swamp1 and flooding the forest4 ,or suppose1 on the other hand1 that the land rises1 the marsh is drained1 the genial climate succeeded by an icy cold1 the luscious vegetation destroyed1 the whole animal population compelled to change its habits and its food4 ,but this is no imaginary picture4 ,it is the actual story of the earth during millions of years1 and it is chiefly in the light of these vast and exacting changes in the environment that we are going to survey the panorama of the advance of terrestrial life4 ,for the moment it will be enough to state two leading principles4 ,the first is that there is no such thing as a law of evolution in the sense in which many people understand that phrase4 ,it is now sufficiently well known that1 when science speaks of a law1 it does not mean that there is some rule that things ,,must act in such and such a way4 ,the law is a mere general expression of the fact that they ,,do act in that way4 ,but many imagine that there is some principle within the living organism which impels it onward to a higher level of organisation4 ,that is entirely an error4 ,there is no law of progress4 ,if an animal is fitted to secure its livelihood and breed posterity in certain surroundings1 it may remain unchanged indefinitely if these surroundings do not materially change4 ,so the duckmole of ,australia and the tuatara of ,new ,zealand have retained primitive features for millions of years2 so the aboriginal ,australian and the ,fuegian have remained stagnant1 in their isolation1 for a hundred thousand years or more2 so the ,chinaman1 in his geographical isolation1 has remained unchanged for two thousand years4 ,there is no more a conservative instinct in ,chinese than there is a progressive instinct in ,europeans4 ,the difference is one of history and geography1 as we shall see4 ,to make this important principle still clearer1 let us imagine some primitive philosopher observing the advance of the tide over a level beach4 ,he must discover two things3 why the water comes onward at all1 and why it advances along those particular channels4 ,we shall see later how men of science explain or interpret the mechanism in a living thing which enables it to advance1 when it does advance4 ,for the present it is enough to say that new-born animals and plants are always tending to differ somewhat from their parents1 and we now know1 by experiment1 that when some exceptional influence is brought to bear on the parent1 the young may differ considerably from her4 ,but1 if the parents were already in harmony with their environment1 these variations on the part of the young are of no consequence4 ,let the environment alter1 however1 and some of these variations may chance to make the young better fitted than the parent was4 ,the young which happen to have the useful variation will have an advantage over their brothers or sisters1 and be more likely to survive and breed the next generation4 ,if the change in the environment 7in the food or climate1 for instance7 is prolonged and increased for hundreds of thousands of years1 we shall expect to find a corresponding change in the animals and plants4 ,we shall find such changes occurring throughout the story of the earth4 ,at one important point in the story we shall find so grave a revolution in the face of nature that twenty-nine out of every thirty species of animals and plants on the earth are annihilated4 ,less destructive and extreme changes have been taking place during nearly the whole of the period we have to cover1 entailing a more gradual alteration of the structure of animals and plants2 but we shall repeatedly find them culminating in very great changes of climate1 or of the distribution of land and water1 which have subjected the living population of the earth to the most searching tests and promoted every variation toward a more effective organisation4 99 99 ,this is a very simple expression of ,darwinism1 and will be enlarged later4 ,the reader should ignore the occasional statement of non-scientific writers that ,darwinism is dead or superseded4 ,the questions which are actually in dispute relate to the causes of the variation of the young from their parents1 the magnitude of these variations' and the transmission of changes acquired by an animal during its own life4 ,we shall see this more fully at a later stage4 ,the importance of the environment as ,i have described it1 is admitted by all schools4 ,and the second guiding principle ,i wish to lay down in advance is that these great changes in the face of the earth1 which explain the progress of organisms1 may very largely be reduced to one simple agency--the battle of the land and the sea4 ,when you gaze at some line of cliffs that is being eaten away by the waves1 or reflect on the material carried out to sea by the flooded river1 you are--paradoxical as it may seem--beholding a material process that has had a profound influence on the development of life4 ,the ,archaean continent that we described was being reduced constantly by the wash of rain1 the scouring of rivers1 and the fretting of the waves on the coast4 ,it is generally thought that these wearing agencies were more violent in early times1 but that is disputed1 and we will not build on it4 ,in any case1 in the course of time millions of tons of matter were scraped off the ,archaean continent and laid on the floor of the sea by its rivers4 ,this meant a very serious alteration of pressure or weight on the surface of the globe1 and was bound to entail a reaction or restoration of the balance4 ,the rise of the land and formation of mountains used to be ascribed mainly to the cooling and shrinking of the globe of the earth4 ,the skin 7crust71 it was thought1 would become too large for the globe as it shrank1 and would wrinkle outwards1 or pucker up into mountain-chains4 ,the position of our greater mountain-chains sprawling across half the earth 7the ,pyrenees to the ,himalaya1 and the ,rocky ,mountains to the ,andes71 seems to confirm this1 but the question of the interior of the earth is obscure and disputed1 and geologists generally conceive the rise of land and formation of mountains in a different way4 ,they are due probably to the alteration of pressure on the crust in combination with the instability of the interior4 ,the floors of the seas would sink still lower under their colossal burdens1 and this would cause some draining of the land-surface4 ,at the same time the heavy pressure below the seas and the lessening of pressure over the land would provoke a reaction4 ,enormous masses of rock would be forced toward and underneath the land-surface1 bending1 crumpling1 and upheaving it as if its crust were but a leather coat4 ,as a result1 masses of land would slowly rise above the plain1 to be shaped into hills and valleys by the hand of later time1 and fresh surfaces would be dragged out of the deep1 enlarging the fringes of the primitive continents1 to be warped and crumpled in their turn at the next era of pressure4 ,in point of geological fact1 the story of the earth has been one prolonged series of changes in the level of land and water1 and in their respective limits4 ,these changes have usually been very gradual1 but they have always entailed changes 7in climate1 etc4 7 of the greatest significance in the evolution of life4 ,what was the swampy soil of ,england in the ,carboniferous period is now sometimes thousands of feet beneath us2 and what was the floor of a deep ocean over much of ,europe and ,asia at another time is now to be found on the slopes of lofty ,alps1 or #bj1jjj feet above the sea-level in ,thibet4 ,our story of terrestrial life will be1 to a great extent1 the story of how animals and plants changed their structure in the long series of changes which this endless battle of land and sea brought over the face of the earth4 ,as we have no recognisable remains of the animals and plants of the earliest age1 we will not linger over the ,archaean rocks4 ,starting from deep and obscure masses of volcanic matter1 the geologist1 as he travels up the series of ,archaean rocks1 can trace only a dim and most unsatisfactory picture of those remote times4 ,between outpours of volcanic floods he finds1 after a time1 traces that an ocean and rivers are wearing away the land4 ,he finds seams of carbon among the rocks of the second division of the ,archaean 7the ,keewatin71 and deduces from this that a dense sea-weed population already covered the floor of the ocean4 ,in the next division 7the ,huronian7 he finds the traces of extensive ice-action strangely lying between masses of volcanic rock1 and sees that thousands of square miles of eastern ,north ,america were then covered with an ice-sheet4 ,then fresh floods of molten matter are poured out from the depths below2 then the sea floods the land for a time2 and at last it makes its final emergence as the first definitive part of the ,north ,american continent1 to enlarge1 by successive fringes1 to the continent of to-day4 99 99 ,i am quoting ,professor ,coleman's summary of ,archaean research in ,north ,america 7,address to the ,geological ,section of the ,british ,association1 #aiji74 ,europe1 as a continent1 has had more ups and downs than ,america in the course of geological time4 ,this meagre picture of the battle of land and sea1 with interludes of great volcanic activity and even of an ice age1 represents nearly all we know of the first half of the world's story from geology4 ,it is especially disappointing in regard to the living population4 ,the very few fossils we find in the upper ,archaean rocks are so similar to those we shall discuss in the next chapter that we may disregard them1 and the seams of carbon-shales1 iron-ore1 and limestone1 suggest only1 at the most1 that life was already abundant4 ,we must turn elsewhere for some information on the origin and early development of life4 ,the question of the origin of life ,i will dismiss with a brief account of the various speculations of recent students of science4 ,broadly speaking1 their views fall into three classes4 ,some think that the germs of life may have come to the earth from some other body in the universe2 some think that life was evolved out of non-living matter in the early ages of the earth1 under exceptional conditions which we do not at present know1 or can only dimly conjecture2 and some think that life is being evolved from non-life in nature to-day1 and always has been so evolving4 ,the majority of scientific men merely assume that the earliest living things were no exception to the general process of evolution1 but think that we have too little positive knowledge to speculate profitably on the manner of their origin4 ,the first view1 that the germs of life may have come to this planet on a meteoric visitor from some other world1 as a storm-driven bird may take its parasites to some distant island1 is not without adherents to-day4 ,it was put forward long ago by ,lord ,kelvin and others2 it has been revived by the distinguished ,swede1 ,professor ,svante ,arrhenius4 ,the scientific objection to it is that the more intense 7ultra-violet7 rays of the sun would frill such germs as they pass through space4 ,but a broader objection1 and one that may dispense us from dwelling on it1 is that we gain nothing by throwing our problems upon another planet4 ,we have no ground for supposing that the earth is less capable of evolving life than other planets4 ,the second view is that1 when the earth had passed through its white-hot stage1 great masses of very complex chemicals1 produced by the great heat1 were found on its surface4 ,there is one complex chemical substance in particular1 called cyanogen1 which is either an important constituent of living matter1 or closely akin to it4 ,now we need intense heat to produce this substance in the laboratory4 ,may we not suppose that masses of it were produced during the incandescence of the earth1 and that1 when the waters descended1 they passed through a series of changes which culminated in living plasm8 ,such is the cyanogen hypothesis of the origin of life1 advocated by able physiologists such as ,pfluger1 ,verworn1 and others4 ,it has the merit of suggesting a reason why life may not be evolving from non-life in nature to-day1 although it may have so evolved in the ,archaean period4 ,other students suggest other combinations of carbon-compounds and water in the early days4 ,some suggest that electric action was probably far more intense in those ages2 others think that quantities of radium may have been left at the surface4 ,but the most important of these speculations on the origin of life in early times1 and one that has the merit of not assuming any essentially different conditions then than we find now1 is contained in a recent pronouncement of one of the greatest organic chemists in ,europe1 ,professor ,armstrong4 ,he says that such great progress has been made in his science--the science of the chemical processes in living things--that their cryptic character seems to have disappeared almost suddenly4 ,on the strength of this new knowledge of living matter1 he ventures to say that a series of lucky accidents could account for the first formation of living things out of non-living matter in ,archaean times4 ,indeed1 he goes further4 ,he names certain inorganic substances1 and says that the blowing of these into pools by the wind on the primitive planet would set afoot chemical combinations which would issue in the production of living matter4 99 99 ,see his address in ,nature1 vol4 #gf1 p4 #fea4 ,for other speculations see ,verworn's ,general ,physiology1 ,butler ,burke's ,origin of ,life 7#aijf71 and ,dr4 ,bastian's ,origin of ,life 7#aiaa74 ,it is evident that the popular notion that scientific men have declared that life cannot be evolved from non-life is very far astray4 ,this blunder is usually due to a misunderstanding of the dogmatic statement which one often reads in scientific works that every living thing comes from a living thing4 ,this principle has no reference to remote ages1 when the conditions may have been different4 ,it means that to-day1 within our experience1 the living thing is always born of a living parent4 ,however1 even this is questioned by some scientific men of eminence1 and we come to the third view4 ,professor ,nageli1 a distinguished botanist1 and ,professor ,haeckel1 maintain that our experience1 as well as the range of our microscopes1 is too limited to justify the current axiom4 ,they believe that life may be evolving constantly from inorganic matter4 ,professor ,j4 ,a4 ,thomson also warns us that our experience is very limited1 and1 for all we know1 protoplasm may be forming naturally in our own time4 ,mr4 ,butler ,burke has1 under the action of radium1 caused the birth of certain minute specks which strangely imitate the behaviour of bacteria4 ,dr4 ,bastian has maintained for years that he has produced living things from non-living matter4 ,in his latest experiments1 described in the book quoted1 purely inorganic matter is used1 and it is previously subjected1 in hermetically sealed tubes1 to a heat greater than what has been found necessary to kill any germs whatever4 ,evidently the problem of the origin of life is not hopeless1 but our knowledge of the nature of living matter is still so imperfect that we may leave detailed speculation on its origin to a future generation4 ,organic chemistry is making such strides that the day may not be far distant when living matter will be made by the chemist1 and the secret of its origin revealed4 ,for the present we must be content to choose the more plausible of the best-informed speculations on the subject4 ,but while the origin of life is obscure1 the early stages of its evolution come fairly within the range of our knowledge4 ,to the inexpert it must seem strange that1 whereas we must rely on pure speculation in attempting to trace the origin of life1 we can speak with more confidence of those early developments of plants and animals which are equally buried in the mists of the ,archaean period4 ,have we not said that nothing remains of the procession of organisms during half the earth's story but a shapeless seam of carbon or limestone8 ,a simple illustration will serve to justify the procedure we are about to adopt4 ,suppose that the whole of our literary and pictorial references to earlier stages in the development of the bicycle1 the locomotive1 or the loom1 were destroyed4 ,we should still be able to retrace the phases of their evolution1 because we should discover specimens belonging to those early phases lingering in our museums1 in backward regions1 and elsewhere4 ,they might yet be useful in certain environments into which the higher machines have not penetrated4 ,in the same way1 if all the remains of prehistoric man and early civilisation were lost1 we could still fairly retrace the steps of the human race1 by gathering the lower tribes and races1 and arranging them in the order of their advancement4 ,they are so many surviving illustrations of the stages through which mankind as a whole has passed4 ,just in the same way we may marshal the countless species of animals and plants to-day in such order that they will1 in a general way1 exhibit to us the age-long procession of life4 ,from the very start of living evolution certain forms dropped out of the onward march1 and have remained1 to our great instruction1 what their ancestors were millions of years ago4 ,people create a difficulty for themselves by imagining that1 if evolution is true1 all animals must evolve4 ,a glance at our own fellows will show the error of this4 ,of one family of human beings1 as a ,french writer has said1 one only becomes a ,napoleon2 the others remain ,lucien1 ,jerome1 or ,joseph4 ,of one family of animals or trees1 some advance in one or other direction2 some remain at the original level4 ,there is no law of progress4 ,the accidents of the world and hereditary endowment impel some onward1 and do not impel others4 ,hence at nearly every great stage in the upward procession through the ages some regiment of plants or animals has dropped out1 and it represents to-day the stage of life at which it ceased to progress4 ,in other words1 when we survey the line of the hundreds of thousands of species which we find in nature to-day1 we can trace1 amid their countless variations and branches1 the line of organic evolution in the past2 just as we could1 from actual instances1 study the evolution of a ,british house1 from the prehistoric remains in ,devonshire to a mansion in ,park ,lane or a provincial castle4 ,another method of retracing the lost early chapters in the development of life is furnished by embryology4 ,the value of this method is not recognised by all embryologists1 but there are now few authorities who question the substantial correctness of it1 and we shall1 as we proceed1 see some remarkable applications of it4 ,in brief1 it is generally admitted that an animal or plant is apt to reproduce1 during its embryonic development1 some of the stages of its ancestry in past time4 ,this does not mean that a higher animal1 whose ancestors were at one time worms1 at another time fishes1 and at a later time reptiles1 will successively take the form of a little worm1 a little fish1 and a little reptile4 ,the embryonic life itself has been subject to evolution1 and this reproduction of ancestral forms has been proportionately disturbed4 ,still1 we shall find that animals will tend1 in their embryonic development1 to reproduce various structural features which can only be understood as reminiscences of ancestral organs4 ,in the lower animals the reproduction is much less disturbed than in the higher1 but even in the case of man this law is most strikingly verified4 ,we shall find it useful sometimes at least in confirming our conclusions as to the ancestry of a particular group4 ,we have1 therefore1 two important clues to the missing chapters in the story of evolution4 ,just as the scheme of the evolution of worlds is written broadly across the face of the heavens to-day1 so the scheme of the evolution of life is written on the face of living nature2 and it is written again1 in blurred and broken characters1 in the embryonic development of each individual4 ,with these aids we set out to restore the lost beginning of the epic of organic evolution4 ,,chapter ,,vi4 ,,the ,,infancy ,,of ,,the ,,earth ,the long ,archaean period1 into which half the story of the earth is so unsatisfactorily packed1 came to a close with a considerable uplift of the land4 ,we have seen that the earth at times reaches critical stages owing to the transfer of millions of tons of matter from the land to the depths of the ocean1 and the need to readjust the pressure on the crust4 ,apparently this stage is reached at the end of the ,archaean1 and a great rise of the land--probably protracted during hundreds of thousands of years--takes place4 ,the shore-bottoms round the primitive continent are raised above the water1 their rocks crumpling like plates of lead under the overpowering pressure4 ,the sea retires with its inhabitants1 mingling their various provinces1 transforming their settled homes4 ,a larger continent spans the northern ocean of the earth4 ,in the shore-waters of this early continent are myriads of living things1 representing all the great families of the animal world below the level of the fish and the insect4 ,the mud and sand in which their frames are entombed1 as they die1 will one day be the ,cambrian rocks of the geologist1 and reveal to him their forms and suggest their habits4 ,no great volcanic age will reduce them to streaks of shapeless carbon4 ,the earth now buries its dead1 and from their petrified remains we conjure up a picture of the swarming life of the ,cambrian ocean4 ,a strange1 sluggish population burrows in the mud1 crawls over the sand1 adheres to the rocks1 and swims among the thickets of sea-weed4 ,the strangest and most formidable1 though still too puny a thing to survive in a more strenuous age1 is the familiar ,trilobite of the geological museum2 a flattish animal with broad1 round head1 like a shovel1 its back covered with a three-lobed shell1 and a number of fine legs or swimmers below4 ,it burrows in the loose bottom1 or lies in it with its large compound eyes peeping out in search of prey4 ,it is the chief representative of the hard-cased group 7,crustacea7 which will later replace it with the lobster1 the shrimp1 the crab1 and the water-flea4 ,its remains form from a third to a fourth of all the buried ,cambrian skeletons4 ,with it1 swimming in the water1 are smaller members of the same family1 which come nearer to our familiar small ,crustacea4 ,shell-fish are the next most conspicuous inhabitants4 ,molluscs are already well represented1 but the more numerous are the more elementary ,brachiopods 7lampshells71 which come next to the ,trilobites in number and variety4 ,worms 7or ,annelids7 wind in and out of the mud1 leaving their tracks and tubes for later ages4 ,strange ball or cup-shaped little animals1 with a hard frame1 mounted on stony stalks and waving irregular arms to draw in the food-bearing water1 are the earliest representatives of the ,echinoderms4 ,some of these ,cystids will presently blossom into the wonderful sea-lily population of the next age1 some are already quitting their stalks1 to become the free-moving star-fish1 of which a primitive specimen has been found in the later ,cambrian4 ,large jelly-fishes 7of which casts are preserved7 swim in the water2 coral-animals lay their rocky foundations1 but do not as yet form reefs2 coarse sponges rise from the floor2 and myriads of tiny ,radiolaria and ,thalamophores1 with shells of flint and lime1 float at the surface or at various depths4 ,this slight sketch of the ,cambrian population shows us that living things had already reached a high level of development4 ,their story evidently goes back1 for millions of years1 deep into those mists of the ,archaean age which we were unable to penetrate4 ,we turn therefore to the zoologist to learn what he can tell us of the origin and family-relations of these ,cambrian animals1 and will afterwards see how they are climbing to higher levels under the eye of the geologist4 ,at the basis of the living world of to-day is a vast population of minute1 generally microscopic1 animals and plants1 which are popularly known as microbes4 ,each consists1 in scientific language1 of one cell4 ,it is now well known that the bodies of the larger animals and plants are made up of millions of these units of living matter1 or cells--the atoms of the organic world--and ,i need not enlarge on it4 ,but even a single cell lends itself to infinite variety of shape1 and we have to penetrate to the very lowest level of this luxuriant world of one-celled organisms to obtain some idea of the most primitive living things4 ,properly speaking1 there were no first living things4 ,it cannot be doubted by any student of nature that the microbe developed so gradually that it is as impossible to fix a precise term for the beginning of life as it is to say when the night ends and the day begins4 ,in the course of time little one-celled living units appeared in the waters of the earth1 whether in the shallow shore waters or on the surface of the deep is a matter of conjecture4 ,we are justified in concluding that they were at least as rudimentary in structure and life as the lowest inhabitants of nature to-day4 ,the distinction of being the lowest known living organisms should1 ,i think1 be awarded to certain one-celled vegetal organisms which are very common in nature4 ,minute simple specks of living matter1 sometimes less than the five-thousandth of an inch in diameter1 these lowly ,algae are so numerous that it is they1 in their millions1 which cover moist surfaces with the familiar greenish or bluish coat4 ,they have no visible organisation1 though1 naturally1 they must have some kind of structure below the range of the microscope4 ,their life consists in the absorption of food-particles1 at any point of their surface1 and in dividing into two living microbes1 instead of dying1 when their bulk increases4 ,a very lowly branch of the ,bacteria 7,nitrobacteria7 sometimes dispute their claim to the lowest position in the hierarchy of living nature1 but there is reason to suspect that these ,bacteria may have degenerated from a higher level4 ,here we have a convenient starting-point for the story of life1 and may now trace the general lines of upward development4 ,the first great principle to be recognised is the early division of these primitive organisms into two great classes1 the moving and the stationary4 ,the clue to this important divergence is found in diet4 ,with exceptions on both sides1 we find that the non-moving microbes generally feed on inorganic matter1 which they convert into plasm2 the moving microbes generally feed on ready-made plasm--on the living non-movers1 on each other1 or on particles of dead organic matter4 ,now1 inorganic food is generally diffused in the waters1 so that the vegetal feeders have no incentive to develop mobility4 ,on the other hand1 the power to move in search of their food1 which is not equally diffused1 becomes a most important advantage to the feeders on other organisms4 ,they therefore develop various means of locomotion4 ,some flow or roll slowly along like tiny drops of oil on an inclined surface2 others develop minute outgrowths of their substance1 like fine hairs1 which beat the water as oars do4 ,some of them have one strong oar1 like the gondolier 7but in front of the boat72 others have two or more oars2 while some have their little flanks bristling with fine lashes1 like the flanks of a ,roman galley4 ,if we imagine this simple principle at work for ages among the primitive microbes1 we understand the first great division of the living world1 into plants and animals4 ,there must have been a long series of earlier stages below the plant and animal4 ,in fact1 some writers insist that the first organisms were animal in nature1 feeding on the more elementary stages of living matter4 ,at last one type develops chlorophyll 7the green matter in leaves71 and is able to build up plasm out of inorganic matter2 another type develops mobility1 and becomes a parasite on the plant world4 ,there is no rigid distinction of the two worlds4 ,many microscopic plants move about just as animals do1 and many animals live on fixed stalks2 while many plants feed on organic matter4 ,there is so little difference of nature between the plant and the animal that the experts differ in classifying some of these minute creatures4 ,in fact1 we shall often find plants and animals crossing the line of division4 ,we shall find animals rooting themselves to the floor1 like plants1 though they will generally develop arms or streamers for bringing the food to them2 and we shall find plants becoming insect-catchers4 ,all this merely shows that the difference is a natural tendency1 which special circumstances may overrule4 ,it remains true that the great division of the organic world is due to a simple principle of development2 difference of diet leads to difference of mobility4 ,but this simple principle will have further consequences of a most important character4 ,it will lead to the development of mind in one half of living nature and leave it undeveloped in the other4 ,mind1 as we know it in the lower levels of life1 is not confined to the animal at all4 ,many even of the higher plants are very delicately sensitive to stimulation1 and at the lowest level many plants behave just like animals4 ,in other words1 this sensitiveness to stimuli1 which is the first form of mind1 is distributed according to mobility4 ,to the motionless organism it is no advantage2 to the pursuing and pursued organism it is an immense advantage1 and is one of the chief qualities for natural selection to foster4 ,for the moment1 however1 we must glance at the operation of this and other natural principles in the evolution of the one-celled animals and plants1 which we take to represent the primitive population of the earth4 ,as there are tens of thousands of different species even of microbes1 it is clear that we must deal with them in a very summary way4 ,the evolution of the plant ,i reserve for a later chapter1 and ,i must be content to suggest the development of one-celled animals on very broad lines4 ,when some of the primitive cells began to feed on each other1 and develop mobility1 it is probable that at least two distinct types were evolved1 corresponding to the two lowest animal organisms in nature to-day4 ,one of these is a very minute and very common 7in vases of decaying flowers1 for instance7 speck of plasm1 which moves about by lashing the water with a single oar 7flagellum71 or hair-like extension of its substance4 ,this type1 however1 which is known as the ,flagellate1 may be derived from the next1 which we will take as the primitive and fundamental animal type4 ,it is best seen in the common and familiar ,amoeba1 a minute sac of liquid or viscid plasm1 often not more than a hundredth of an inch in diameter4 ,as its skin is merely a finer kind of the viscous plasm1 not an impenetrable membrane1 it takes in food at any part of its surface1 makes little stomachs1 or temporary cavities1 round the food at any part of its interior1 ejects the useless matter at any point1 and thrusts out any part of its body as temporary arms or feet4 ,now it is plain that in an age of increasing microbic cannibalism the toughening of the skin would be one of the first advantages to secure survival1 and this is1 in point of fact1 almost the second leading principle in early development4 ,naturally1 as the skin becomes firmer1 the animal can no longer1 like the ,amoeba1 take food at1 or make limbs of1 any part of it4 ,there must be permanent pores in the membrane to receive food or let out rays of the living substance to act as oars or arms4 ,thus we get an immense variety amongst these ,protozoa1 as the one-celled animals are called4 ,some 7the ,flagellates7 have one or two stout oars2 some 7the ,ciliates7 have numbers of fine hairs 7or cilia74 ,some have a definite mouth-funnel1 but no stomach1 and cilia drawing the water into it4 ,some 7,vorticella1 etc471 shrinking from the open battlefield1 return to the plant-principle1 live on stalks1 and have wreaths of cilia round the open mouth drawing the water to them4 ,some 7the ,heliozoa7 remain almost motionless1 shooting out sticky rays of their matter on every side to catch the food4 ,some form tubes to live in2 some 7,coleps7 develop horny plates for armour2 and others develop projectiles to pierce their prey 7stinging threads74 ,this miniature world is full of evolutionary interest1 but it is too vast for detailed study here4 ,we will take one group1 which we know to have been already developed in the ,cambrian1 and let a study of its development stand for all4 ,in every lecture or book on the beauties of the microscope we find1 and are generally greatly puzzled by1 minute shells of remarkable grace and beauty that are formed by some of these very elementary animals ,they are the ,radiolaria 7with flinty shells1 as a rule7 and the ,thalamophora 7with chalk frames74 ,evolution furnishes a simple key to their remarkable structure4 ,as we saw1 one of the early requirements to be fostered by natural selection in the ,archaean struggle for life was a thick skin1 and the thick skin had to be porous to let the animal shoot out its viscid substance in rays and earn its living4 ,this stage above the ,amoeba is beautifully illustrated in the sun-animalcules 7,heliozoa74 ,now the lowest types of ,radiolaria are of this character4 ,they have no shell or framework at all4 ,the next stage is for the little animal to develop fine irregular threads of flint in its skin1 a much better security against the animal-eater4 ,these animalcules1 it must be recollected1 are bits of almost pure plasm1 and1 as they live in crowds1 dividing and subdividing1 but never dying1 make excellent mouthfuls for a small feeder4 ,those with the more flint in their skins were the more apt to survive and breed4 ,the threads of flint increase until they form a sort of thorn-thicket round a little social group1 or a complete lattice round an individual body4 ,next1 spikes or spines jut out from the lattice1 partly for additional protection1 partly to keep the little body afloat at the surface of the sea4 ,in this way we get a bewildering variety and increasing complexity of forms1 ascending in four divergent lines from the naked ancestral type to the extreme grace and intricacy of the ,calocyclas monumentum or the ,lychnaspis miranda4 ,these1 however1 are rare specimens in the #djjj species of ,radiolaria4 ,i have hundreds of them1 on microscopic slides1 which have no beauty and little regularity of form4 ,we see a gradual evolution1 on utilitarian principles1 as we run over the thousands of forms2 and1 when we recollect the inconceivable numbers in which these little animals have lived and struggled for life--passively--during tens of millions of years1 we are not surprised at the elaborate protective frames of the higher types4 ,the ,thalamophores1 the sister-group of one-celled animals which largely compose our chalk and much of our limestone1 are developed on the same principle4 ,the earlier forms seem to have lived in a part of the ocean where silica was scarce1 and they absorbed and built their protective frames of lime4 ,in the simpler types the frame is not unlike a wide-necked bottle1 turned upside-down4 ,in later forms it takes the shape of a spirally coiled series of chambers1 sometimes amounting to several thousand4 ,these wonderful little houses are not difficult to understand4 ,the original tiny animal covers itself with a coat of lime4 ,it feeds1 grows1 and bulges out of its chamber4 ,the new part of its flesh must have a fresh coat1 and the process goes on until scores1 or hundreds1 or even thousands1 of these tiny chambers make up the spiral shell of the morsel of living matter4 ,with this brief indication of the mechanical principles which have directed the evolution of two of the most remarkable groups of the one-celled animals we must be content1 or the dimensions of this volume will not enable us even to reach the higher and more interesting types4 ,we must advance at once to the larger animals1 whose bodies are composed of myriads of cells4 ,the social tendency which pervades the animal world1 and the evident use of that tendency1 prepare us to understand that the primitive microbes would naturally come in time to live in clusters4 ,union means effectiveness in many ways1 even when it does not mean strength4 ,we have still many loose associations of one-celled animals in nature1 illustrating the approach to a community life4 ,numbers of the ,protozoa are social2 they live either in a common jelly-like matrix1 or on a common stalk4 ,in fact1 we have a singularly instructive illustration of the process in the evolution of the sponges4 ,it is well known that the horny texture to which we commonly give the name of sponge is the former tenement and shelter of a colony of one-celled animals1 which are the real ,sponges4 ,in other groups the structure is of lime2 in others1 again1 of flinty material4 ,now1 the ,sponges1 as we have them to-day1 are so varied1 and start from so low a level1 that no other group of animals illustrates so strikingly the theory of evolution1 as ,professor ,minchin says4 ,we begin with colonies in which the individuals are 7as in ,proterospongia7 irregularly distributed in their jelly-like common bed1 each animal lashing the water1 as stalked ,flagellates do1 and bringing the food to it4 ,such a colony would be admirable food for an early carnivore1 and we soon find the protective principle making it less pleasant for the devourer4 ,the first stage may be--at least there are such ,sponges even now--that the common bed is strewn or sown with the cast shells of ,radiolaria4 ,however that may be1 the ,sponges soon begin to absorb the silica or lime of the sea-water1 and deposit it in needles or fragments in their bed4 ,the deposit goes on until at last an elaborate framework of thorny1 or limy1 or flinty material is constructed by the one-celled citizens4 ,in the higher types a system of pores or canals lets the food-bearing water pass through1 as the animals draw it in with their lashes2 in the highest types the animals come still closer together1 lining the walls of little chambers in the interior4 ,here we have a very clear evolutionary transition from the solitary microbe to a higher level1 but1 unfortunately1 it does not take us far4 ,the ,sponges are a side-issue1 or cul de sac1 from the ,protozoic world1 and do not lead on to the higher4 ,each one-celled unit remains an animal2 it is a colony of unicellulars1 not a many-celled body4 ,we may admire it as an instructive approach toward the formation of a many-celled body1 but we must look elsewhere for the true upward advance4 ,the next stage is best illustrated in certain spherical colonies of cells like the tiny green ,volvox 7now generally regarded as vegetal7 of our ponds1 or ,magosphoera4 ,here the constituent cells merge their individuality in the common action4 ,we have the first definite many-celled body4 ,it is the type to which a moving close colony of one-celled microbes would soon come4 ,the round surface is well adapted for rolling or spinning along in the water1 and1 as each little cell earns its own living1 it must be at the surface1 in contact with the water4 ,thus a hollow1 or fluid-filled1 little sphere1 like the ,volvox1 is the natural connecting-link between the microbe and the many-celled body1 and may be taken to represent the first important stage in its development4 ,the next important stage is also very clearly exhibited in nature1 and is more or less clearly reproduced in the embryonic development of all animals4 ,we may imagine that the age of microbes was succeeded by an age of these many-celled larger bodies1 and the struggle for life entered upon a new phase4 ,the great principle we have already recognised came into play once more4 ,large numbers of the many-celled bodies shrank from the field of battle1 and adopted the method of the plant4 ,they rooted themselves to the floor of the ocean1 and developed long arms or lashes for creating a whirlpool movement in the water1 and thus bringing the food into their open mouths4 ,forfeiting mobility1 they have1 like the plant1 forfeited the greater possibilities of progress1 and they remain flowering to-day on the floors of our waters1 recalling the next phase in the evolution of early life4 ,such are the hydra1 the polyp1 the coral1 and the sea-anemone4 ,it is not singular that earlier observers could not detect that they were animals1 and they were long known in science as animal-plants 7,zoophytes74 ,when we look to the common structure of these animals1 to find the ancestral type1 we must ignore the nerve and muscle-cells which they have developed in some degree4 ,fundamentally1 their body consists of a pouch1 with an open mouth1 the sides of the pouch consisting of a double layer of cells4 ,in this we have a clue to the next stage of animal development4 ,take a soft india-rubber ball to represent the first many-celled animal4 ,press in one half of the ball close upon the other1 narrow the mouth1 and you have something like the body-structure of the coral and hydra4 ,as this is the course of embryonic development1 and as it is so well retained in the lowest groups of the many-celled animals1 we take it to be the next stage4 ,the reason for it will become clear on reflection4 ,division of labour naturally takes place in a colony1 and in that way certain cells in the primitive body were confined to the work of digestion4 ,it would be an obvious advantage for these to retire into the interior1 leaving the whole external surface free for the adjustment of the animal's relations to the outer world4 ,again we must refrain from following in detail the development of this new world of life which branches off in the ,archaean ocean4 ,the evolution of the ,corals alone would be a lengthy and interesting story4 ,but a word must be said about the jelly-fish1 partly because the inexpert will be puzzled at the inclusion of so active an animal1 and partly because its story admirably illustrates the principle we are studying4 ,the ,medusa really descends from one of the plant-like animals of the early ,archaean period1 but it has abandoned the ancestral stalk1 turned upside down1 and developed muscular swimming organs4 ,its past is betrayed in its embryonic development4 ,as a rule the germ develops into a stalked polyp1 out of which the free-swimming ,medusa is formed4 ,this return to active and free life must have occurred early1 as we find casts of large ,medusae in the ,cambrian beds4 ,in complete harmony with the principle we laid down1 the jelly-fish has gained in nerve and sensitiveness in proportion to its return to an active career4 ,but this principle is best illustrated in the other branch of the early many-celled animals1 which continued to move about in search of food4 ,here1 as will be expected1 we have the main stem of the animal world1 and1 although the successive stages of development are obscure1 certain broad lines that it followed are clear and interesting4 ,it is evident that in a swarming population of such animals the most valuable qualities will be speed and perception4 ,the sluggish ,coral needs only sensitiveness enough1 and mobility enough1 to shrink behind its protecting scales at the approach of danger4 ,in the open water the most speedy and most sensitive will be apt to escape destruction1 and have the larger share in breeding the next generation4 ,imagine a selection on this principle going on for millions of years1 and the general result can be conjectured4 ,a very interesting analogy is found in the evolution of the boat4 ,from the clumsy hollowed tree of ,neolithic man natural selection1 or the need of increasing speed1 has developed the elongated1 evenly balanced modern boat1 with its distinct stem and stern4 ,so in the ,archaean ocean the struggle to overtake food1 or escape feeders1 evolved an elongated two-sided body1 with head and tail1 and with the oars 7cilia7 of the one-celled ancestor spread thickly along its flanks4 ,in other words1 a body akin to that of the lower water-worms would be the natural result2 and this is1 in point of fact1 the next stage we find in the hierarchy of living nature4 ,probably myriads of different types of this worm-like organisation were developed1 but such animals leave no trace in the rocks1 and we can only follow the development by broad analogies4 ,the lowest flat-worms of to-day may represent some of these early types1 and as we ascend the scale of what is loosely called worm organisation1 we get some instructive suggestions of the way in which the various organs develop4 ,division of labour continues among the colony of cells which make up the body1 and we get distinct nerve-cells1 muscle-cells1 and digestive cells4 ,the nerve-cells are most useful at the head of an organism which moves through the water1 just as the look-out peers from the head of the ship1 and there they develop most thickly4 ,by a fresh division of labour some of these cells become especially sensitive to light1 some to the chemical qualities of matter1 some to movements of the water2 we have the beginning of the eyes1 the nose1 and the ears1 as simple little depressions in the skin of the head1 lined with these sensitive cells4 ,a muscular gullet arises to protect the digestive tube2 a simple drainage channel for waste matter forms under the skin2 other channels permit the passage of the fluid food1 become 7in the higher worms7 muscular blood-vessels1 and begin to contract--somewhat erratically at first--and drive the blood through the system4 ,here1 perhaps1 are millions of years of development compressed into a paragraph4 ,but the purpose of this work is chiefly to describe the material record of the advance of life in the earth's strata1 and show how it is related to great geological changes4 ,we must therefore abstain from endeavouring to trace the genealogy of the innumerable types of animals which were1 until recently1 collected in zoology under the heading ,worms4 ,it is more pertinent to inquire how the higher classes of animals1 which we found in the ,cambrian seas1 can have arisen from this primitive worm-like population4 ,the struggle for life in the ,archaean ocean would become keener and more exacting with the appearance of each new and more effective type4 ,that is a familiar principle in our industrial world to-day1 and we shall find it illustrated throughout our story4 ,we therefore find the various processes of evolution1 which we have already seen1 now actively at work among the swarming ,archaean population1 and producing several very distinct types4 ,in some of these struggling organisms speed is developed1 together with offensive and defensive weapons1 and a line slowly ascends toward the fish1 which we will consider later4 ,in others defensive armour is chiefly developed1 and we get the lines of the heavy sluggish shell-fish1 the ,molluscs and ,brachiopods1 and1 by a later compromise between speed and armour1 the more active tough-coated ,arthropods4 ,in others the plant-principle reappears2 the worm-like creature retires from the free-moving life1 attaches itself to a fixed base1 and becomes the ,bryozoan or the ,echinoderm4 ,to trace the development of these types in any detail is impossible4 ,the early remains are not preserved4 ,but some clues are found in nature or in embryonic development1 and1 when the types do begin to be preserved in the rocks1 we find the process of evolution plainly at work in them4 ,we will therefore say a few words about the general evolution of each type1 and then return to the geological record in the ,cambrian rocks4 ,the starfish1 the most familiar representative of the ,echinoderms1 seems very far removed from the kind of worm-like ancestor we have been imagining1 but1 fortunately1 the very interesting story of the starfish is easily learned from the geological chronicle4 ,reflect on the flower-like expansion of its arms1 and then imagine it mounted on a stalk1 mouth side upward1 with those arms--more tapering than they now are--waving round the mouth4 ,that1 apparently1 was the past of the starfish and its cousins4 ,we shall see that the earliest ,echinoderms we know are cup-shaped structures on stalks1 with a stiff1 limy frame and 7as in all sessile animals7 a number of waving arms round the mouth4 ,in the next geological age the stalk will become a long and flexible arrangement of muscles and plates of chalk1 the cup will be more perfectly compacted of chalky plates1 and the five arms will taper and branch until they have an almost feathery appearance2 and the animal will be considered a sea-lily by the early geologist4 ,the evidence suggests that both the free-moving and the stalked ,echinoderms descend from a common stalked ,archaean ancestor4 ,some primitive animal abandoned the worm-like habit1 and attached itself1 like a polyp1 to the floor4 ,like all such sessile animals1 it developed a wreath of arms round the open mouth4 ,the sea-cucumber 7,holothurian7 seems to be a type that left the stalk1 retaining the little wreath of arms1 before the body was heavily protected and deformed4 ,in the others a strong limy skeleton was developed1 and the nerves and other organs were modified in adaptation to the bud-like or flower-like structure4 ,another branch of the family then abandoned the stalk1 and1 spreading its arms flat1 and gradually developing in them numbers of little feet 7water-tubes71 became the starfish4 ,in the living ,comatula we find a star passing through the stalked stage in its early development1 when it looks like a tiny sea-lily4 ,the sea-urchin has evolved from the star by folding the arms into a ball4 99 99 ,see the section on ,echinoderms1 by ,professor ,mac,bride1 in the ,cambridge ,natural ,history1 ,i4 ,the ,bryozoa 7sea-mats1 etc47 are another and lower branch of the primitive active organisms which have adopted a sessile life4 ,in the shell-fish1 on the other hand1 the principle of armour-plating has its greatest development4 ,it is assuredly a long and obscure way that leads from the ancestral type of animal we have been describing to the headless and shapeless mussel or oyster4 ,such a degeneration is1 however1 precisely what we should expect to find in the circumstances4 ,indeed1 the larva1 of many of the headless ,molluscs have a mouth and eyes1 and there is a very common type of larva--the trochosphere--in the ,mollusc world which approaches the earlier form of some of the higher worms4 ,the ,molluscs1 as we shall see1 provide some admirable illustrations of the process of evolution4 ,in some of the later fossilised specimens 7,planorbis1 ,paludina1 etc47 we can trace the animal as it gradually passes from one species to another4 ,the freshening of the ,caspian ,sea1 which was an outlying part of the ,mediterranean quite late in the geological record1 seems to have evolved several new genera of ,molluscs4 ,although1 therefore1 the remains are not preserved of those primitive ,molluscs in which we might see the protecting shell gradually thickening1 and deforming the worm-like body1 we are not without indications of the process4 ,two unequal branches of the early wormlike organisms shrank into strong protective shells4 ,the lower branch became the ,brachiopods2 the more advanced branch the ,molluscs4 ,in the ,mollusc world1 in turn1 there are several early types developed4 ,in the ,pelecypods 7or ,lamellibranchs--the mussel1 oyster1 etc47 the animal retires wholly within its fortress1 and degenerates4 ,the ,gastropods 7snails1 etc47 compromise1 and retain a certain amount of freedom1 so that they degenerate less4 ,the highest group1 the ,cephalopods1 keep their heads1 in the literal sense1 and we shall find them advancing from form to form until1 in the octopus of a later age1 they discard the ancestral shell1 and become the aristocrats of the ,mollusc kingdom4 ,the last and most important line that led upward from the chaos of ,archaean worms is that of the ,arthropods4 ,its early characteristic was the acquisition of a chitinous coat over the body4 ,embryonic indications show that this was at first a continuous shield1 but a type arose in which the coat broke into sections covering each segment of the body1 giving greater freedom of movement4 ,the shield1 in fact1 became a fine coat of mail4 ,the ,trilobite is an early and imperfect experiment of the class1 and the larva of the modern king-crab bears witness that it has not perished without leaving descendants4 ,how later ,crustacea increase the toughness of the coat by deposits of lime1 and lead on to the crab and lobster1 and how one early branch invades the land1 develops air-breathing apparatus1 and culminates in the spiders and insects1 will be considered later4 ,we shall see that there is most remarkable evidence connecting the highest of the ,arthropods1 the insect1 with a remote ,annelid ancestor4 ,we are thus not entirely without clues to the origin of the more advanced animals we find when the fuller geological record begins4 ,further embryological study1 and possibly the discovery of surviving primitive forms1 of which ,central ,africa may yet yield a number1 may enlarge our knowledge1 but it is likely to remain very imperfect4 ,the fossil records of the long ages during which the ,mollusc1 the ,crustacean1 and the ,echinoderm slowly assumed their characteristic forms are hopelessly lost4 ,but we are now prepared to return to the record which survives1 and we shall find the remaining story of the earth a very ample and interesting chronicle of evolution4 ,,chapter ,,vii4 ,,the ,,passage ,,to ,,the ,,land ,slender as our knowledge is of the earlier evolution of the ,invertebrate animals1 we return to our ,cambrian population with greater interest4 ,the uncouth ,trilobite and its livelier cousins1 the sluggish1 skulking ,brachiopod and ,mollusc1 the squirming ,annelids1 and the plant-like ,cystids1 ,corals1 and ,sponges are the outcome of millions of years of struggle4 ,just as men1 when their culture and their warfare advanced1 clothed themselves with armour1 and the most completely mailed survived the battle1 so1 generation after generation1 the thicker and harder-skinned animals survived in the ,archaean battlefield1 and the ,cambrian age opened upon the various fashions of armour that we there described4 ,but1 although half the story of life is over1 organisation is still imperfect and sluggish4 ,we have now to see how it advances to higher levels1 and how the drama is transferred from the ocean to a new and more stimulating environment4 ,the ,cambrian age begins with a vigorous move on the part of the land4 ,the seas roll back from the shores of the lost ,atlantis1 and vast regions are laid bare to the sun and the rains4 ,in the bays and hollows of the distant shores the animal survivors of the great upheaval adapt themselves to their fresh homes and continue the struggle4 ,but the rivers and the waves are at work once more upon the land1 and1 as the ,cambrian age proceeds1 the fringes of the continents are sheared1 and the shore-life steadily advances upon the low-lying land4 ,by the end of the ,cambrian age a very large proportion of the land is covered with a shallow sea1 in which the debris of its surface is deposited4 ,the levelling continues through the next 7,ordovician7 period4 ,before its close nearly the whole of the ,united ,states and the greater part of ,canada are under water1 and the new land that had appeared on the site of ,europe is also for the most part submerged4 ,the present ,british ,isles are almost reduced to a strip of north-eastern ,ireland1 the northern extremity of ,scotland1 and large islands in the south-west and centre of ,england4 ,we have already seen that these victories of the sea are just as stimulating1 in a different way1 to animals as the victories of the land4 ,american geologists are tracing1 in a very instructive way1 the effect on that early population of the encroachment of the sea4 ,in each arm of the sea is a distinctive fauna4 ,life is still very parochial2 the great cosmopolitans1 the fishes1 have not yet arrived4 ,as the land is revelled1 the arms of the sea approach each other1 and at last mingle their waters and their populations1 with stimulating effect4 ,provincial characters are modified1 and cosmopolitan characters increase in the great central sea of ,america4 ,the vast shallow waters provide a greatly enlarged theatre for the life of the time1 and it flourishes enormously4 ,then1 at the end of the ,ordovician1 the land begins to rise once more4 ,whether it was due to a fresh shrinking of the crust1 or to the simple process we have described1 or both1 we need not attempt to determine2 but both in ,europe and ,america there is a great emergence of land4 ,the shore-tracts and the shallow water are narrowed1 the struggle is intensified in them1 and we pass into the ,silurian age with a greatly reduced number but more advanced variety of animals4 ,in the ,silurian age the sea advances once more1 and the shore-waters expand4 ,there is another great expansive evolution of life4 ,but the ,silurian age closes with a fresh and very extensive emergence of the land1 and this time it will have the most important consequences4 ,for two new things have meantime appeared on the earth4 ,the fish has evolved in the waters1 and the plant1 at least1 has found a footing on the land4 ,these geological changes which we have summarised and which have been too little noticed until recently in evolutionary studies1 occupied #g1jjj1jjj years1 on the lowest estimate1 and probably twice that period4 ,the impatient critic of evolutionary hypotheses is apt to forget the length of these early periods4 ,we shall see that in the last two or three million years of the earth's story most extraordinary progress has been made in plant and animal development1 and can be very fairly traced4 ,how much advance should we allow for these seven or fourteen million years of swarming life and changing environments8 ,we cannot nearly cover the whole ground of paleontology for the period1 and must be content to notice some of the more interesting advances1 and then deal more fully with the evolution of the fish1 the forerunner of the great land animals4 ,the ,trilobite was the most arresting figure in the ,cambrian sea1 and its fortunes deserve a paragraph4 ,it reaches its climax in the ,ordovician sea1 and then begins to decline1 as more powerful animals come upon the scene4 ,at first 7apparently7 an eyeless organism1 it gradually develops compound eyes1 and in some species the experts have calculated that there were #ae1jjj facets to each eye4 ,as time goes on1 also1 the eye stands out from the head on a kind of stalk1 giving a wider range of vision4 ,some of the more sluggish species seem to have been able to roll themselves up1 like hedgehogs1 in their shells1 when an enemy approached4 ,but another branch of the same group 7,crustacea7 has meantime advanced1 and it gradually supersedes the dwindling ,trilobites4 ,toward the close of the ,silurian great scorpion-like ,crustaceans 7,pterygotus1 ,eurypterus1 etc47 make their appearance4 ,their development is obscure1 but it must be remembered that the rocks only give the record of shore-life1 and only a part of that is as yet opened by geology4 ,some experts think that they were developed in inland waters4 ,reaching sometimes a length of five or six feet1 with two large compound eyes and some smaller eye-spots 7ocelli71 they must have been the giants of the ,silurian ocean until the great sharks and other fishes appeared4 ,the quaint stalked ,echinoderm which also we noticed in the ,cambrian shallows has now evolved into a more handsome creature1 the sea-lily4 ,the cup-shaped body is now composed of a large number of limy plates1 clothed with flesh2 the arms are long1 tapering1 symmetrical1 and richly fringed2 the stalk advances higher and higher1 until the flower-like animal sometimes waves its feathery arms from the top of a flexible pedestal composed of millions of tiny chalk disks4 ,small forests of these sea-lilies adorn the floor of the ,silurian ocean1 and their broken and dead frames form whole beds of limestone4 ,the primitive ,cystids dwindle and die out in the presence of such powerful competitors4 ,of #bej species only a dozen linger in the ,silurian strata1 though a new and more advanced type--the ,blastoid--holds the field for a time4 ,it is the age of the ,crinoids or sea-lilies4 ,the starfish1 which has abandoned the stalk1 does not seem to prosper as yet1 and the brittle-star appears4 ,their age will come later4 ,no sea-urchins or sea-cucumbers 7which would hardly be preserved7 are found as yet4 ,it is precisely the order of appearance which our theory of their evolution demands4 ,the ,brachiopods have passed into entirely new and more advanced species in the many advances and retreats of the shores1 but the ,molluscs show more interesting progress4 ,the commanding group from the start is that of the ,molluscs which have kept their head1 the ,cephalopods1 and their large shells show a most instructive evolution4 ,the first great representative of the tribe is a straight-shelled ,cephalopod1 which becomes the tyrant and scavenger of the ,silurian ocean 7,chamberlin74 ,its tapering1 conical shell sometimes runs to a length of fifteen feet1 and a diameter of one foot4 ,it would of itself be an important evolutionary factor in the primitive seas1 and might explain more than one advance in protective armour or retreat into heavy shells4 ,as the period advances the shell begins to curve1 and at last it forms a close spiral coil4 ,this would be so great an advantage that we are not surprised to find the coiled type 7,goniatites7 gain upon and gradually replace the straight-shelled types 7,orthoceratites74 ,the ,silurian ocean swarms with these great shelled ,cephalopods1 of which the little ,nautilus is now the only survivor4 ,we will not enlarge on the ,sponges and ,corals1 which are slowly advancing toward the higher modern types4 ,two new and very powerful organisms have appeared1 and merit the closest attention4 ,one is the fish1 the remote ancestor of the birds and mammals that will one day rule the earth4 ,the other may be the ancestor of the fish itself1 or it may be one of the many abortive outcomes and unsuccessful experiments of the stirring life of the time4 ,and while these new types are themselves a result of the great and stimulating changes which we have reviewed and the incessant struggle for food and safety1 they in turn enormously quicken the pace of development4 ,the ,dreadnought appears in the primitive seas2 the effect on the fleets of the world of the evolution of our latest type of battleship gives us a faint idea of the effect1 on all the moving population1 of the coming of these monsters of the deep4 ,the age had not lacked incentives to progress2 it now obtains a more terrible and far-reaching stimulus4 ,to understand the situation let us see how the battle of land and sea had proceeded4 ,the ,devonian ,period had opened with a fresh emergence of the land1 especially in ,europe1 and great inland seas or lakes were left in the hollows4 ,the tincture of iron which gives a red colour to our characteristic ,devonian rocks1 the ,old ,red ,sandstone1 shows us that the sand was deposited in inland waters4 ,the fish had already been developed1 and the ,devonian rocks show it swarming1 in great numbers and variety1 in the enclosed seas and round the fringe of the continents4 ,the first generation was a group of strange creatures1 half fish and half ,crustacean1 which are known as the ,ostracoderms4 ,they had large armour-plated heads1 which recall the ,trilobite1 and suggest that they too burrowed in the mud of the sea or 7as many think7 of the inland lakes1 making havoc among the shell-fish1 worms1 and small ,crustacea4 ,the hind-part of their bodies was remarkably fish-like in structure4 ,but they had no backbone--though we cannot say whether they may not have had a rod of cartilage along the back--and no articulated jaws like the fish4 ,some regard them as a connecting link between the ,crustacea and the fishes1 but the general feeling is that they were an abortive development in the direction of the fish4 ,the sharks and other large fishes1 which have appeared in the ,silurian1 easily displace these clumsy and poor-mouthed competitors ,one almost thinks of the aeroplane superseding the navigable balloon4 ,of the fishes the ,arthrodirans dominated the inland seas 7apparently71 while the sharks commanded the ocean4 ,one of the ,arthrodirans1 the ,dinichthys 7terrible fish71 is the most formidable fish known to science4 ,it measured twenty feet from snout to tail4 ,its monstrous head1 three feet in width1 was heavily armoured1 and1 instead of teeth1 its great jaws1 two feet in length1 were sharpened1 and closed over the victim like a gigantic pair of clippers4 ,the strongly plated heads of these fishes were commonly a foot or two feet in width4 ,life in the waters became more exacting than ever4 ,but the ,arthrodirans were unwieldy and sluggish1 and had to give way before more progressive types4 ,the toothed shark gradually became the lord of the waters4 ,the early shark ate1 amongst other things1 quantities of ,molluscs and ,brachiopods4 ,possibly he began with ,crustacea2 in any case the practice of crunching shellfish led to a stronger and stronger development of the hard plate which lined his mouth4 ,the prickles of the plate grew larger and harder1 until--as may be seen to-day in the mouth of a young shark--the cavity was lined with teeth4 ,in the bulk of the ,devonian sharks these developed into what are significantly called pavement teeth4 ,they were solid plates of enamel1 an inch or an inch and a half in width1 with which the monster ground its enormous meals of ,molluscs1 ,crustacea1 sea-weed1 etc4 ,a new and stimulating element had come into the life of the invertebrate world4 ,other sharks snapped larger victims1 and developed the teeth on the edges of their jaws1 to the sacrifice of the others1 until we find these teeth in the course of time solid triangular masses of enamel1 four or five inches long1 with saw-like edges4 ,imagine these terrible mouths--the shears of the ,arthrodiran1 and the grindstones and terrible crescents of the giant sharks--moving speedily amongst the crowded inhabitants of the waters1 and it is easy to see what a stimulus to the attainment of speed and of protective devices was given to the whole world of the time4 ,what was the origin of the fish8 ,here we are in much the same position as we were in regard to the origin of the higher ,invertebrates4 ,once the fish plainly appears upon the scene it is found to be undergoing a process of evolution like all other animals4 ,the vast majority of our fishes have bony frames 7or are ,teleosts72 the fishes of the ,devonian age nearly all have frames of cartilage1 and we know from embryonic development that cartilage is the first stage in the formation of bone4 ,in the teeth and tails1 also1 we find a gradual evolution toward the higher types4 ,but the earlier record is1 for reasons ,i have already given1 obscure2 and as my purpose is rather to discover the agencies of evolution than to strain slender evidence in drawing up pedigrees1 ,i need only make brief reference to the state of the problem4 ,until comparatively recent times the animal world fell into two clearly distinct halves1 the ,vertebrates and the ,invertebrates4 ,there were several anatomical differences between the two provinces1 but the most conspicuous and most puzzling was the backbone4 ,nowhere in living nature or in the rocks was any intermediate type known between the backboned and the non-backboned animal4 ,in the course of the nineteenth century1 however1 several animals of an intermediate type were found4 ,the sea-squirt has in its early youth the line of cartilage through the body which1 in embryonic development1 represents the first stage of the backbone2 the lancelet and the ,appendicularia have a rod of cartilage throughout life2 the acorn-headed worm shows traces of it4 ,these are regarded as surviving specimens of various groups of animals which1 in early times1 fell between the ,invertebrate and ,vertebrate worlds1 and illustrate the transition4 ,with their aid a genealogical tree was constructed for the fish4 ,it was assumed that some ,cambrian or ,silurian ,annelid obtained this stiffening rod of cartilage4 ,the next advantage--we have seen it in many cases--was to combine flexibility with support4 ,the rod was divided into connected sections 7vertebrae71 and hardened into bone4 ,besides stiffening the body1 it provided a valuable shelter for the spinal cord1 and its upper part expanded into a box to enclose the brain4 ,the fins were formed of folds of skin which were thrown off at the sides and on the back1 as the animal wriggled through the water4 ,they were of use in swimming1 and sections of them were stiffened with rods of cartilage1 and became the pairs of fins4 ,gill slits 7as in some of the highest worms7 appeared in the throat1 the mouth was improved by the formation of jaws1 and--the worm culminated in the shark4 ,some experts think1 however1 that the fish developed directly from a ,crustacean1 and hold that the ,ostracoderms are the connecting link4 ,a close discussion of the anatomical details would be out of place here1 99 and the question remains open for the present4 ,directly or indirectly1 the fish is a descendant of some ,archaean ,annelid4 ,it is most probable that the shark was the first true fish-type4 ,there are unrecognisable fragments of fishes in the ,ordovician and ,silurian rocks1 but the first complete skeletons 7,lanarkia1 etc47 are of small shark- like creatures1 and the low organisation of the group to which the shark belongs1 the ,elasmobranchs1 makes it probable that they are the most primitive4 ,other remains 7,palaeospondylus7 show that the fish-like lampreys had already developed4 99 ,see1 especially1 ,dr4 ,gaskell's ,origin of ,vertebrates 7#aijh74 ,two groups were developed from the primitive fish1 which have great interest for us4 ,our next step1 in fact1 is to trace the passage of the fish from the water to the land1 one of the most momentous chapters in the story of life4 ,to that incident or accident of primitive life we owe our own existence and the whole development of the higher types of animals4 ,the advance of natural history in modern times has made this passage to the land easy to understand4 ,not only does every frog reenact it in the course of its development1 but we know many fishes that can live out of water4 ,there is an ,indian perch--called the climbing perch1 but it has only once been seen by a ,european to climb a tree--which crosses the fields in search of another pool1 when its own pool is evaporating4 ,an ,indian marine fish 7,periophthalmus7 remains hunting on the shore when the tide goes out4 ,more important still1 several fishes have lungs as well as gills4 ,the ,ceratodus of certain ,queensland rivers has one lung2 though1 ,i was told by the experts in ,queensland1 it is not a mud-fish1 and never lives in dry mud4 ,however1 the ,protopterus of ,africa and the ,lepidosiren of ,south ,america have two lungs1 as well as gills1 and can live either in water or1 in the dry season1 on land4 ,when the skeletons of fishes of the ,ceratodus type were discovered in the ,devonian rocks1 it was felt that we had found the fish-ancestor of the land ,vertebrates1 but a closer anatomical examination has made this doubtful4 ,the ,devonian lung-fish has characters which do not seem to lead on to the ,amphibia4 ,the same general cause probably led many groups to leave the water1 or adapt themselves to living on land as well as in water1 and the abundant ,dipoi or ,dipneusts 7double-breathers7 of the ,devonian lakes are one of the chief of these groups1 which have luckily left descendants to our time4 ,the ancestors of the ,amphibia are generally sought amongst the ,crossopterygii1 a very large group of fishes in ,devonian times1 with very few representatives to-day4 ,it is more profitable to investigate the process itself than to make a precarious search for the actual fish1 and1 fortunately1 this inquiry is more hopeful4 ,the remains that we find make it probable that the fish left the water about the beginning of the ,devonian or the end of the ,silurian4 ,now this period coincides with two circumstances which throw a complete light on the step2 one is the great rise of the land1 catching myriads of fishes in enclosed inland seas1 and the other is the appearance of formidable carnivores in the waters4 ,as the seas evaporated 99 and the great carnage proceeded1 the land1 which was already covered with plants and inhabited by insects1 offered a safe retreat for such as could adopt it4 ,emigration to the land had been going on for ages1 as we shall see4 ,curious as it must seem to the inexpert1 the fishes1 or some of them1 were better prepared than most other animals to leave the water4 ,the chief requirement was a lung1 or interior bag1 by which the air could be brought into close contact with the absorbing blood vessels4 ,such a bag1 broadly speaking1 most of the fishes possess in their floating-bladder3 a bag of gas1 by compressing or expanding which they alter their specific gravity in the water4 ,in some fishes it is double2 in some it is supplied with blood-vessels2 in some it is connected by a tube with the gullet1 and therefore with the atmosphere4 99 ,it is now usually thought that the inland seas were the theatre of the passage to land4 ,i must point out1 however1 that the wide distribution of our ,dipneusts1 in ,australia1 tropical ,africa1 and ,south ,america1 suggests that they were marine though they now live in fresh water4 ,but we shall see that a continent united the three regions at one time1 and it may afford some explanation4 ,thus we get very clear suggestions of the transition from water to land4 ,we must1 of course1 conceive it as a slow and gradual adaptation4 ,at first there may have been a rough contrivance for deriving oxygen directly and partially from the atmosphere1 as the water of the lake became impure4 ,so important an advantage would be fostered1 and1 as the inland sea became smaller1 or its population larger or fiercer1 the fishes with a sufficiently developed air-breathing apparatus passed to the land1 where1 as yet1 they would find no serious enemy4 ,the fact is beyond dispute2 the theory of how it occurred is plausible enough2 the consequences were momentous4 ,great changes were preparing on the land1 and in a comparatively short time we shall find its new inhabitant subjected to a fierce test of circumstances that will carry it to an enormously higher level than life had yet reached4 ,i have said that the fact of this transition to the land is beyond dispute4 ,the evidence is very varied1 but need not all be enlarged upon here4 ,the widespread ,dipneust fishes of the ,devonian rocks bear strong witness to it1 and the appearance of the ,amphibian immediately afterwards makes it certain4 ,the development of the frog is a reminiscence of it1 on the lines of the embryonic law which we saw earlier4 ,an animal1 in its individual development1 more or less reproduces the past phases of its ancestry4 ,so the free-swimming jelly-fish begins life as a fixed polyp2 a kind of star-fish 7,comatula7 opens its career as a stalked sea-lily2 the gorgeous dragon-fly is at first an uncouth aquatic animal1 and the ethereal butterfly a worm-like creature4 ,but the most singular and instructive of all these embryonic reminiscences of the past is found in the fact that all the higher land-animals of to-day clearly reproduce a fish-stage in their embryonic development4 ,in the third and fourth weeks of development the human embryo shows four 7closed7 slits under the head1 with corresponding arches4 ,the bird1 the dog1 the horse--all the higher land animals1 in a word1 pass through the same phase4 ,the suggestion has been made that these structures do not recall the gill-slits and gill-arches of the fish1 but are folds due to the packing of the embryo in the womb4 ,in point of fact1 they appear just at the time when the human embryo is only a fifth of an inch long1 and there is no such compression4 ,but all doubt as to their interpretation is dispelled when we remove the skin and examine the heart and blood-vessels4 ,the heart is up in the throat1 as in the fish1 and has only two chambers1 as in the fish 7not four1 as in the bird and mammal72 and the arteries rise in five pairs of arches over the swellings in the throat1 as they do in the lower fish1 but do not in the bird and mammal4 ,the arrangement is purely temporary--lasting only a couple of weeks in the human embryo--and purposeless4 ,half these arteries will disappear again4 ,they quite plainly exist to supply fine blood-vessels for breathing at the gill-clefts1 and are never used1 for the embryo does not breathe1 except through the mother4 ,they are a most instructive reminder of the ,devonian fish which quitted its element and became the ancestor of all the birds and mammals of a later age4 ,several other features of man's embryonic development--the budding of the hind limbs high up1 instead of at the base of1 the vertebral column1 the development of the ears1 the nose1 the jaws1 etc4--have the same lesson1 but the one detailed illustration will suffice4 ,the millions of years of stimulating change and struggle which we have summarised have resulted in the production of a fish which walks on four limbs 7as the ,south ,american mud-fish does to-day71 and breathes the atmosphere4 ,we have been quite unable to follow the vast changes which have meantime taken place in its organisation4 ,the eyes1 which were mere pits in the skin1 lined with pigment cells1 in the early worm1 now have a crystalline lens to concentrate the light and define objects on the nerve4 ,the ears1 which were at first similar sensitive pits in the skin1 on which lay a little stone whose movements gave the animal some sense of direction1 are now closed vesicles in the skull1 and begin to be sensitive to waves of sound4 ,the nose1 which was at first two blind1 sensitive pits in the skin of the head1 now consists of two nostrils opening into the mouth1 with an olfactory nerve spreading richly over the passages4 ,the brain1 which was a mere clump of nerve-cells connecting the rough sense-impressions1 is now a large and intricate structure1 and already exhibits a little of that important region 7the cerebrum7 in which the varied images of the outside world are combined4 ,the heart1 which was formerly was a mere swelling of a part of one of the blood-vessels1 now has two chambers4 ,we cannot pursue these detailed improvements of the mechanism1 as we might1 through the ascending types of animals4 ,enough if we see more or less clearly how the changes in the face of the earth and the rise of its successive dynasties of carnivores have stimulated living things to higher and higher levels in the primitive ocean4 ,we pass to the clearer and far more important story of life on land1 pursuing the fish through its continuous adaptations to new conditions until1 throwing out side-branches as it progresses1 it reaches the height of bird and mammal life4 ,,chapter ,,viii4 ,,the ,,coal-,,forest ,with the beginning of life on land we open a new and more important volume of the story of life1 and we may take the opportunity to make clearer certain principles or processes of development which we may seem hitherto to have taken for granted4 ,the evolutionary work is too often a mere superficial description of the strange and advancing classes of plants and animals which cross the stage of geology4 ,why they change and advance is not explained4 ,i have endeavoured to supply this explanation by putting the successive populations of the earth in their respective environments1 and showing the continuous and stimulating effect on them of changes in those environments4 ,we have thus learned to decipher some lines of the decalogue of living nature4 ,thou shalt have a thick armour1 ,thou shalt be speedy1 ,thou shalt shelter from the more powerful1 are some of the laws of primeval life4 ,the appearance of each higher and more destructive type enforces them with more severity2 and in their observance animals branch outward and upward into myriads of temporary or permanent forms4 ,but there is no consciousness of law and no idea of evading danger4 ,there is not even some mysterious instinct telling the animal1 as it used to be said1 to do certain things4 ,it is1 in fact1 not strictly accurate to say that a certain change in the environment stimulates animals to advance4 ,generally speaking1 it does not act on the advancing at all1 but on the non-advancing1 which it exterminates4 ,the procedure is simple1 tangible1 and unconscious4 ,two invading arms of the sea meet and pour together their different waters and populations4 ,the habits1 the foods1 and the enemies of many types of animals are changed2 the less fit for the new environment die first1 the more fit survive longest and breed most of the new generation4 ,it is so with men when they migrate to a more exacting environment1 whether a dangerous trade or a foreign clime4 ,again1 take the case of the introduction of a giant ,cephalopod or fish amongst a population of ,molluscs and ,crustacea4 ,the toughest1 the speediest1 the most alert1 the most retiring1 or the least conspicuous1 will be the most apt to survive and breed4 ,in hundreds or thousands of generations there will be an enormous improvement in the armour1 the speed1 the sensitiveness1 the hiding practices1 and the protective colours1 of the animals which are devoured4 ,the natural selection of the fittest really means the natural destruction of the less fit4 ,the only point assumed in this is that the young of an animal or plant tend to differ from each other and from their parents4 ,darwin was content to take this as a fact of common observation1 as it obviously is1 but later science has thrown some light on the causes of these variations4 ,in the first place1 the germs in the parent's body may themselves be subject to struggle and natural selection1 and not share equally in the food-supply4 ,then1 in the case of the higher animals 7or the majority of animals71 there is a clear source of variation in the fact that the mature germ is formed of certain elements from two different parents1 four grandparents1 and so on4 ,in the case of the lower animals the germs and larvae float independently in the water1 and are exposed to many influences4 ,modern embryologists have found1 by experiment1 that an alteration of the temperature or the chemical considerable effect on eggs and larvae4 ,some recent experiments have shown that such changes may even affect the eggs in the mother's ovary4 ,these discoveries are very important and suggestive1 because the geological changes which we are studying are especially apt to bring about changes of temperature and changes in the freshness or saltiness of water4 ,evolution is1 therefore1 not a mere description of the procession of living things2 it is to a great extent an explanation of the procession4 ,when1 however1 we come to apply these general principles to certain aspects of the advance in organisation we find fundamental differences of opinion among biologists1 which must be noted4 ,as ,sir ,e4 ,ray ,lankester recently said1 it is not at all true that ,darwinism is questioned in zoology to-day4 ,it is true only that ,darwin was not omniscient or infallible1 and some of his opinions are disputed4 ,let me introduce the subject with a particular instance of evolution1 the flat-fish4 ,this animal has been fitted to survive the terrible struggle in the seas by acquiring such a form that it can lie almost unseen upon the floor of the ocean4 ,the eye on the under side of the body would thus be useless1 but a glance at a sole or plaice in a fishmonger's shop will show that this eye has worked upward to the top of the head4 ,was the eye shifted by the effort and straining of the fish1 inherited and increased slightly in each generation8 ,is the explanation rather that those fishes in each generation survived and bred which happened from birth to have a slight variation in that direction1 though they did not inherit the effect of the parent's effort to strain the eye8 ,or ought we to regard this change of structure as brought about by a few abrupt and considerable variations on the part of the young8 ,there you have the three great schools which divide modern evolutionists3 ,lamarckism1 ,weismannism1 and ,mendelism 7or ,mutationism74 ,all are ,darwinians4 ,no one doubts that the flat-fish was evolved from an ordinary fish--the flat-fish is an ordinary fish in its youth--or that natural selection 7enemies7 killed off the old and transitional types and overlooked 7and so favoured7 the new4 ,it will be seen that the language used in this volume is not the particular language of any one of these schools4 ,this is partly because ,i wish to leave seriously controverted questions open1 and partly from a feeling of compromise1 which ,i may explain4 99 99 ,of recent years another compromise has been proposed between the ,lamarckians and ,weismannists4 ,it would say that the efforts of the parent and their effect on the position of the eye--in our case--are not inherited1 but might be of use in sheltering an embryonic variation in the direction of a displaced eye4 ,first1 the plain issue between the ,mendelians and the other two schools--whether the passage from species to species is brought about by a series of small variations during a long period or by a few large variations 7or mutations7 in a short period--is open to an obvious compromise4 ,it is quite possible that both views are correct1 in different cases1 and quite impossible to find the proportion of each class of cases4 ,we shall see later that in certain instances where the conditions of preservation were good we can sometimes trace a perfectly gradual advance from species to species4 ,several shellfish have been traced in this way1 and a sea-urchin in the chalk has been followed1 quite gradually1 from one end of a genus to the other4 ,it is significant that the advance of research is multiplying these cases4 ,there is no reason why we may not assume most of the changes of species we have yet seen to have occurred in this way4 ,in fact1 in some of the lower branches of the animal world 7,radiolaria1 ,sponges1 etc47 there is often no sharp division of species at all1 but a gradual series of living varieties4 ,on the other hand we know many instances of very considerable sudden changes4 ,the cases quoted by ,mendelists generally belong to the plant world1 but instances are not unknown in the animal world4 ,a shrimp 7,artemia7 was made to undergo considerable modification1 by altering the proportion of salt in the water in which it was kept4 ,butterflies have been made to produce young quite different from their normal young by subjecting them to abnormal temperature1 electric currents1 and so on2 and1 as ,i said1 the most remarkable effects have been produced on eggs and embryos by altering the chemical and physical conditions4 ,rats--,i was informed by the engineer in charge of the refrigerating room on an ,australian liner--very quickly became adapted to the freezing temperature by developing long hair4 ,all that we have seen of the past changes in the environment of animals makes it probable that these larger variations often occur4 ,i would conclude1 therefore1 that evolution has proceeded continuously 7though by no means universally7 through the ages1 but there were at times periods of more acute change with correspondingly larger changes in the animal and plant worlds4 ,in regard to the issue between the ,lamarckians and ,weismannists--whether changes acquired by the parent are inherited by the young--recent experiments again suggest something of a compromise4 ,weismann says that the body of the parent is but the case containing the germ-plasm1 so that all modifications of the living parent body perish with it1 and do not affect the germ1 which builds the next generation4 ,certainly1 when we reflect that the #gj1jjj ova in the human mother's ovary seem to have been all formed in the first year of her life1 it is difficult to see how modifications of her muscles or nerves can affect them4 ,thus we cannot hope to learn anything1 either way1 by cutting off the tails of cows1 and experiments of that kind4 ,but it is acknowledged that certain diseases in the blood1 which nourishes the germs1 may affect them1 and recent experimenters have found that they can reach and affect the germs in the body by other agencies1 and so produce inherited modifications in the parent4 99 ,if this claim is sustained and enlarged1 it may be concluded that the greater changes of environment which we find in the geological chronicle may have had a considerable influence of this kind4 99 ,see a paper read by ,professor ,bourne to the ,zoological ,section of the ,british ,association1 #aiaj4 ,it must be understood that when ,i speak of ,weismannism ,i do not refer to this whole theory of heredity1 which1 he acknowledges1 has few supporters4 ,the ,lamarckian view is represented in ,britain by ,sir ,w4 ,turner and ,professor ,darwin4 ,in other countries it has a larger proportion of distinguished supporters4 ,on the whole subject see ,professor ,j4 ,a4 ,thomson's ,heredity 7#aiji71 ,dewar and ,finn's ,making of ,species 7#aiji--;a ,mendelian work71 and1 for essays by the leaders of each school1 ,darwinism and ,modern ,science 7#aiji74 ,the general issue1 however1 must remain open4 ,the ,lamarckian and ,weismannist theories are rival interpretations of past events1 and we shall not find it necessary to press either4 ,when the fish comes to live on land1 for instance1 it develops a bony limb out of its fin4 ,the ,lamarckian says that the throwing of the weight of the body on the main stem of the fin strengthens it1 as practice strengthens the boxer's arm1 and the effect is inherited and increased in each generation1 until at last the useless paddle of the fin dies away and the main stem has become a stout1 bony column4 ,weismann says that the individual modification1 by use in walking1 is not inherited1 but those young are favoured which have at birth a variation in the strength of the stem of the fin4 ,as each of these interpretations is1 and must remain1 purely theoretical1 we will be content to tell the facts in such cases4 ,but these brief remarks will enable the reader to understand in what precise sense the facts we record are open to controversy4 ,let us return to the chronicle of the earth4 ,we had reached the ,devonian age1 when large continents1 with great inland seas1 existed in ,north ,america1 north-west ,europe1 and north ,asia1 probably connected by a continent across the ,north ,atlantic and the ,arctic region4 ,south ,america and ,south ,africa were emerging1 and a continent was preparing to stretch from ,brazil1 through ,south ,africa and the ,antarctic1 to ,australia and ,india4 ,the expanse of land was1 with many oscillations1 gaining on the water1 and there was much emigration to it from the over-populated seas4 ,when the fish went on land in the ,devonian1 it must have found a diet 7insects1 etc47 there1 and the insects must have been preceded by a plant population4 ,we have first1 therefore1 to consider the evolution of the plant1 and see how it increases in form and number until it covers the earth with the luxuriant forests of the ,carboniferous period4 ,the plant world1 we saw1 starts1 like the animal world1 with a great kingdom of one-celled microscopic representatives1 and the same principles of development1 to a great extent1 shape it into a large variety of forms4 ,armour-plating has a widespread influence among them4 ,the graceful ,diatom is a morsel of plasm enclosed in a flinty box1 often with a very pretty arrangement of the pores and markings4 ,the ,desmid has a coat of cellulose1 and a less graceful coat of cellulose encloses the ,peridinean4 ,many of these minute plants develop locomotion and a degree of sensitiveness 7,diatoms1 ,peridinea1 ,euglena1 etc474 ,some 7,bacteria7 adopt animal diet1 and rise in power of movement and sensitiveness until it is impossible to make any satisfactory distinction between them and animals4 ,then the social principle enters4 ,first we have loose associations of one-celled plants in a common bed1 then closer clusters or many-celled bodies4 ,in some cases 7,volvox7 the cluster1 or the compound plant1 is round and moves briskly in the water1 closely resembling an animal4 ,in most cases1 the cells are connected in chains1 and we begin to see the vague outline of the larger plant4 ,when we had reached this stage in the development of animal life1 we found great difficulty in imagining how the chief lines of the higher ,invertebrates took their rise from the ,archaean chaos of early many-celled forms4 ,we have an even greater difficulty here1 as plant remains are not preserved at all until the ,devonian period4 ,we can only conclude1 from the later facts1 that these primitive many-celled plants branched out in several different directions4 ,one section 7at a quite unknown date7 adopted an organic diet1 and became the ,fungi2 and a later co-operation1 or life-partnership1 between a ,fungus and a one-celled ,alga led to the ,lichens4 ,others remained at the ,alga-level1 and grew in great thickets along the sea bottoms1 no doubt rivalling or surpassing the giant sea-weeds1 sometimes #djj feet long1 off the ,american coast to-day4 ,other lines which start from the level of the primitive many-celled ,algae develop into the ,mosses 7,bryophyta71 ,ferns 7,pteridophyta71 ,horsetails 7,equisetalia71 and ,club-mosses 7,lycopodiales74 ,the mosses1 the lowest group1 are not preserved in the rocks2 from the other three classes will come the great forests of the ,carboniferous period4 ,the early record of plant-life is so poor that it is useless to speculate when the plant first left the water4 ,we have somewhat obscure and disputed traces of ferns in the ,ordovician1 and1 as they and the ,horsetails and ,club-mosses are well developed in the ,devonian1 we may assume that some of the sea-weeds had become adapted to life on land1 and evolved into the early forms of the ferns1 at least in the ,cambrian period4 ,from that time they begin to weave a mantle of sombre green over the exposed land1 and to play a most important part in the economy of nature4 ,we saw that at the beginning of the ,devonian there was a considerable rise of the land both in ,america and ,europe1 but especially in ,europe4 ,a distant spectator at that time would have observed the rise of a chain of mountains in ,scotland and a general emergence of land north-western ,europe4 ,a continent stretched from ,ireland to ,scandinavia and ,north ,russia1 while most of the rest of ,europe1 except large areas of ,russia1 ,france1 ,germany1 and ,turkey1 was under the sea4 ,where we now find our ,alps and ,pyrenees towering up to the snow-line there were then level stretches of ocean4 ,even the north-western continent was scooped into great inland seas or lagoons1 which stretched from ,ireland to ,scandinavia1 and1 as we saw1 fostered the development of the fishes4 ,as the ,devonian period progressed the sea gained on the land1 and must have restricted the growth of vegetation1 but as the lake deposits now preserve the remains of the plants which grow down to their shores1 or are washed into them1 we are enabled to restore the complexion of the landscape4 ,ferns1 generally of a primitive and generalised character1 abound1 and include the ferns such as we find in warm countries to-day4 ,horsetails and ,club-mosses already grow into forest-trees4 ,there are even seed-bearing ferns1 which give promise of the higher plants to come1 but as yet nothing approaching our flower and fruit-bearing trees has appeared4 ,there is as yet no certain indication of the presence of ,conifers4 ,it is a sombre and monotonous vegetation1 unlike any to be found in any climate to-day4 ,we will look more closely into its nature presently4 ,first let us see how these primitive types of plants come to form the immense forests which are recorded in our coal-beds4 ,dr4 ,russel ,wallace has lately represented these forests1 which have1 we shall see1 had a most important influence on the development of life1 as somewhat mysterious in their origin4 ,if1 however1 we again consult the geologist as to the changes which were taking place in the distribution of land and water1 we find a quite natural explanation4 ,indeed1 there are now distinguished geologists 7e4g4 ,professor ,chamberlin7 who doubt if the ,coal-forests were so exceptionally luxuriant as is generally believed4 ,they think that the vegetation may not have been more dense than in some other ages1 but that there may have been exceptionally good conditions for preserving the dead trees4 ,we shall see that there were2 but1 on the whole1 it seems probable that during some hundreds of thousands of years remarkably dense forests covered enormous stretches of the earth's surface1 from the ,arctic to the ,antarctic4 ,the ,devonian period had opened with a rise of the land1 but the sea eat steadily into it once more1 and1 with some inconsiderable oscillations of the land1 regained its territory4 ,the latter part of the ,devonian and earlier part of the ,carboniferous were remarkable for their great expanses of shallow water and low-lying land4 ,except the recent chain of hills in ,scotland we know of no mountains4 ,professor ,chamberlin calculates that #bj1jjj1jjj1 or #cj1jjj1jjj square miles of the present continental surface of ,europe and ,america were covered with a shallow sea4 ,in the deeper and clearer of these waters the earliest ,carboniferous rocks1 of limestone1 were deposited4 ,the millstone grit1 which succeeds the limestone1 indicates shallower water1 which is being rapidly filled up with the debris of the land4 ,in a word1 all the indications suggest the early and middle ,carboniferous as an age of vast swamps1 of enormous stretches of land just above or below the sea-level1 and changing repeatedly from one to the other4 ,further1 the climate was at the time--we will consider the general question of climate later--moist and warm all over the earth1 on account of the great proportion of sea-surface and the absence of high land 7not to speak of more disputable causes74 ,these were ideal conditions for the primitive vegetation1 and it spread over the swamps with great vigour4 ,to say that the ,coal-forests were masses of ,ferns1 ,horsetails1 and ,club-mosses is a lifeless and misleading expression4 ,the ,club-mosses1 or ,lycopodiales1 were massive trees1 rising sometimes to a height of #abj feet1 and probably averaging about fifty feet in height and one or two feet in diameter4 ,the largest and most abundant of them1 the ,sigillaria1 sent up a scarred and fluted trunk to a height of seventy or a hundred feet1 without a branch1 and was crowned with a bunch of its long1 tapering leaves4 ,the ,lepidodendron1 its fellow monarch of the forest1 branched at the summit1 and terminated in clusters of its stiff1 needle-like leaves1 six' or seven inches long1 like enormous exaggerations of the little cones at the ends of our ,club-mosses to-day4 ,the ,horsetails1 which linger in their dwarfed descendants by our streams to-day1 and at their exceptional best 7in a part of ,south ,america7 form slender stems about thirty feet high1 were then forest-trees1 four to six feet in circumference and sometimes ninety feet in height4 ,these ,calamites probably rose in dense thickets from the borders of the lakes1 their stumpy leaves spreading in whorls at every joint in their hollow stems4 ,another extinct tree1 the ,cordaites1 rivalled the ,horsetails and ,club-mosses in height1 and its showers of long and extraordinary leaves1 six feet long and six inches in width1 pointed to the higher plant world that was to come4 ,between these gaunt towering trunks the graceful tree-ferns spread their canopies at heights of twenty1 forty1 and even sixty feet from the ground1 and at the base was a dense undergrowth of ferns and fern-like seed-plants4 ,mosses may have carpeted the moist ground1 but nothing in the nature of grass or flowers had yet appeared4 ,imagine this dense assemblage of dull1 flowerless trees pervaded by a hot1 dank atmosphere1 with no change of seasons1 with no movement but the flying of large and primitive insects among the trees and the stirring of the ferns below by some passing giant salamander1 with no song of bird and no single streak of white or red or blue drawn across the changeless sombre green1 and you have some idea of the character of the forests that are compressed into our seams of coal4 ,imagine these forests spread from ,spitzbergen to ,australia and even1 according to the south polar expeditions1 to the ,antarctic1 and from the ,united ,states to ,europe1 to ,siberia1 and to ,china1 and prolonged during some hundreds of thousands of years1 and you begin to realise that the ,carboniferous period prepared the land for the coming dynasties of animals4 ,let some vast and terrible devastation fall upon this luxuriant world1 entombing the great multitude of its imperfect forms and selecting the higher types for freer life1 and the earth will pass into a new age4 ,but before we describe the animal inhabitants of these forests1 the part that the forests play in the story of life1 and the great cataclysm which selects the higher types from the myriads of forms which the warm womb of the earth has poured out1 we must at least glance at the evolutionary position of the ,carboniferous plants themselves4 ,do they point downward to lower forms1 and upward to higher forms1 as the theory of evolution requires8 ,a close inquiry into this would lead us deep into the problems of the modern botanist1 but we may borrow from him a few of the results of the great labour he has expended on the subject within the last decade4 ,just as the animal world is primarily divided into ,invertebrates and ,vertebrates1 the plant world is primarily divided into a lower kingdom of spore-bearing plants 7the ,cryptogams7 and an upper kingdom of seed-bearing plants 7the ,phanerogams74 ,again1 just as the first half of the earth's story is the age of ,invertebrate animals1 so it is the age of ,cryptogamous plants4 ,so far evolution was always justified in the plant record4 ,but there is a third parallel1 of much greater interest4 ,we saw that at one time the evolutionist was puzzled by the clean division of animals into ,invertebrate and ,vertebrate1 and the sudden appearance of the backbone in the chronicle3 he was just as much puzzled by the sharp division of our plants into ,cryptogams and ,phanerogams1 and the sudden appearance of the latter on the earth during the ,coal-forest period4 ,and the issue has been a fresh and recent triumph for evolution4 ,plants are so well preserved in the coal that many years of microscopic study of the remains1 and patient putting-together of the crushed and scattered fragments1 have shown the ,carboniferous plants in quite a new light4 ,instead of the ,coal-forest being a vast assemblage of ,cryptogams1 upon which the higher type of the ,phanerogam is going suddenly to descend from the clouds1 it is1 to a very great extent1 a world of plants that are struggling upward1 along many paths1 to the higher level4 ,the characters of the ,cryptogam and ,phanerogam are so mixed up in it that1 although the special lines of development are difficult to trace1 it is one massive testimony to the evolution of the higher from the lower4 ,the reproductive bodies of the great ,lepidodendra are sometimes more like seeds than spores1 while both the wood and the leaves of the ,sigillaria have features which properly belong to the ,phanerogam4 ,in another group 7called the ,sphenophyllales7 the characters of these giant ,club-mosses are blended with the characters of the giant ,horsetails1 and there is ground to think that the three groups have descended from an earlier common ancestor4 ,further1 it is now believed that a large part of what were believed to be ,conifers1 suddenly entering from the unknown1 are not ,conifers at all1 but ,cordaites4 ,the ,cordaites is a very remarkable combination of features that are otherwise scattered among the ,cryptogams1 ,cycads1 and ,conifers4 ,on the other hand1 a very large part of what the geologist had hitherto called ,ferns have turned out to be seed-bearing plants1 half ,cycad and half ,fern4 ,numbers of specimens of this interesting group--the ,cycadofilices 7cycad-ferns7 or ,pteridosperms 7seed-ferns7--have been beautifully restored by our botanists4 99 ,they have afforded a new and very plausible ancestor for the higher trees which come on the scene toward the close of the ,coal-forests1 while their fern-like characters dispose botanists to think that they and the ,ferns may be traced to a common ancestor4 ,this earlier stage is lost in those primitive ages from which not a single leaf has survived in the rocks4 ,we can only say that it is probable that the ,mosses1 ,ferns1 ,lycopods1 etc41 arose independently from the primitive level4 ,but the higher and more important development is now much clearer4 ,the ,coal-forest is not simply a kingdom of ,cryptogams4 ,it is a world of aspiring and mingled types4 ,let it be subjected to some searching test1 some tremendous spell of adversity1 and we shall understand the emergence of the higher types out of the luxuriant profusion and confusion of forms4 99 ,see1 especially1 ,d4 ,h4 ,scott1 ,studies of ,fossil ,botany 7#bnd ed41 #aijh71 and ,the ,evolution of ,plants 7#aiaj--small popular manual74 ,,chapter ,,ix4 ,,the ,,animals ,,of ,,the ,,coal-,,forest ,we have next to see that when this period of searching adversity comes--as it will in the next chapter--the animal world also offers a luxuriant variety of forms from which the higher types may be selected4 ,this1 it need hardly be said1 is just what we find in the geological record4 ,the fruitful1 steaming1 rich-laden earth now offered tens of millions of square miles of pasture to vegetal feeders2 the waters1 on the other hand1 teemed with gigantic sharks1 huge ,cephalopods1 large scorpion-like and lobster-like animals1 and shoals of armour-plated1 hard-toothed fishes4 ,successive swarms of vegetarians--,worms1 ,molluscs1 etc4--followed the plant on to the land2 and swarms of carnivores followed the vegetarians1 and assumed strange1 new forms in adaptation to land-life4 ,the migration had probably proceeded throughout the ,devonian period1 especially from the calmer shores of the inland seas4 ,by the middle of the ,coal-forest period there was a very large and varied animal population on the land4 ,like the plants1 moreover1 these animals were of an intermediate and advancing nature4 ,no bird or butterfly yet flits from tree to tree2 no mammal rears its young in the shelter of the ferns4 ,but among the swarming population are many types that show a beginning of higher organisation1 and there is a rich and varied material provided for the coming selection4 ,the monarch of the ,carboniferous forest is the ,amphibian4 ,in that age of spreading swamps and dim1 watery woodlands1 the stupid and sluggish ,amphibian finds his golden age1 and1 except perhaps the scorpion1 there is no other land animal competent to dispute his rule4 ,even the scorpion1 moreover1 would not find the ,carboniferous ,amphibian very vulnerable4 ,we must not think of the smooth-skinned frogs and toads and innocent newts which to-day represent the fallen race of the ,amphibia4 ,they were then heavily armoured1 powerfully armed1 and sometimes as large as alligators or young crocodiles4 ,it is a characteristic of advancing life that a new type of organism has its period of triumph1 grows to enormous proportions1 and spreads into many different types1 until the next higher stage of life is reached1 and it is dethroned by the new-comers4 ,the first indication--apart from certain disputed impressions in the ,devonian--of the land-vertebrate is the footprint of an ,amphibian on an early ,carboniferous mud-flat4 ,hardened by the sun1 and then covered with a fresh deposit when it sank beneath the waters1 it remains to-day to witness the arrival of the five-toed quadruped who was to rule the earth4 ,as the period proceeds1 remains are found in great abundance1 and we see that there must have been a vast and varied population of the ,amphibia on the shores of the ,carboniferous lagoons and swamps4 ,there were at least twenty genera of them living in what is now the island of ,britain1 and was then part of the ,british-,scandinavian continent4 ,some of them were short and stumpy creatures1 a few inches long1 with weak limbs and short tails1 and broad1 crescent-shaped heads1 their bodies clothed in the fine scaly armour of their fish-ancestor 7the ,branchiosaurs74 ,some 7the ,aistopods7 were long1 snake-like creatures1 with shrunken limbs and bodies drawn out until1 in some cases1 the backbone had #aej vertebrae4 ,they seem to have taken to the thickets1 in the growing competition1 as the serpents did later1 and lost the use of their limbs1 which would be merely an encumbrance in winding among the roots and branches4 ,some 7the ,microsaurs7 were agile little salamander-like organisms1 with strong1 bony frames and relatively long and useful legs2 they look as if they may even have climbed the trees in pursuit of snails and insects4 ,a fourth and more formidable sub-order1 the ,labyrinthodonts--which take their name from the labyrinthine folds of the enamel in their strong teeth--were commonly several feet in length4 ,some of them attained a length of seven or eight feet1 and had plates of bone over their heads and bellies1 while the jaws in their enormous heads were loaded with their strong1 labyrinthine teeth4 ,life on land was becoming as eventful and stimulating as life in the waters4 ,the general characteristic of these early ,amphibia is that they very clearly retain the marks of their fish ancestry4 ,all of them have tails2 all of them have either scales or 7like many of the fishes7 plates of bone protecting the body4 ,in some of the younger specimens the gills can still be clearly traced1 but no doubt they were mainly lung-animals4 ,we have seen how the fish obtained its lungs1 and need add only that this change in the method of obtaining oxygen for the blood involved certain further changes of a very important nature4 ,following the fossil record1 we do not observe the changes which are taking place in the soft internal organs1 but we must not lose sight of them4 ,the heart1 for instance1 which began as a simple muscular expansion or distension of one of the blood-vessels of some primitive worm1 then doubled and became a two-chambered pump in the fish1 now develops a partition in the auricle 7upper chamber71 so that the aerated blood is to some extent separated from the venous blood4 ,this approach toward the warm-blooded type begins in the mud-fish1 and is connected with the development of the lungs4 ,corresponding changes take place in the arteries1 and we shall find that this change in structure is of very great importance in the evolution of the higher types of land-life4 ,the heart of the higher land-animals1 we may add1 passes through these stages in its embryonic development4 ,externally the chief change in the ,amphibian is the appearance of definite legs4 ,the broad paddle of the fin is now useless1 and its main stem is converted into a jointed1 bony limb1 with a five-toed foot1 spreading into a paddle1 at the end4 ,but the legs are still feeble1 sprawling supports1 letting the heavy body down almost to the ground4 ,the ,amphibian is an imperfect1 but necessary1 stage in evolution4 ,it is an improvement on the ,dipneust fish1 which now begins to dwindle very considerably in the geological record1 but it is itself doomed to give way speedily before one of its more advanced descendants1 the ,reptile4 ,probably the giant salamander of modern ,japan affords the best suggestion of the large and primitive salamanders of the ,coal-forest1 while the ,caecilia--snake-like ,amphibia with scaly skins1 which live underground in ,south ,america--may not impossibly be degenerate survivors of the curious ,aistopods4 ,our modern tailless ,amphibia1 frogs and toads1 appear much later in the story of the earth1 but they are not without interest here on account of the remarkable capacity which they show to adapt themselves to different surroundings4 ,there are frogs1 like the tree-frog of ,martinique1 and others in regions where water is scarce1 which never pass through the tadpole stage2 or1 to be quite accurate1 they lose the gills and tail in the egg1 as higher land-animals do4 ,on the other hand1 there is a modern ,amphibian1 the axolotl of ,mexico1 which retains the gills throughout life1 and never lives on land4 ,dr4 ,gadow has shown that the lake in which it lives is so rich in food that it has little inducement to leave it for the land4 ,transferred to a different environment1 it may pass to the land1 and lose its gills4 ,these adaptations help us to understand the rich variety of ,amphibian forms that appeared in the changing conditions of the ,carboniferous world4 ,when we think of the diet of the ,amphibia we are reminded of the other prominent representatives of land life at the time4 ,snails1 spiders1 and myriapods crept over the ground or along the stalks of the trees1 and a vast population of insects filled the air4 ,we find a few stray wings in the ,silurian1 and a large number of wings and fragments in the ,devonian1 but it is in the ,coal-forest that we find the first great expansion of insect life1 with a considerable development of myriapods1 spiders1 and scorpions4 ,food was enormously abundant1 and the insect at least had no rival in the air1 for neither bird nor flying reptile had yet appeared4 ,hence we find the same generous growth as amongst the ,amphibia4 ,large primitive may-flies had wings four or five inches long2 great locust-like creatures had fat bodies sometimes twenty inches in length1 and soared on wings of remarkable breadth1 or crawled on their six long1 sprawling legs4 ,more than a thousand species of insects1 and nearly a hundred species of spiders and fifty of myriapods1 are found in the remains of the ,coal-forests4 ,from the evolutionary point of view these new classes are as obscure in their origin1 yet as manifestly undergoing evolution when they do fully appear1 as the earlier classes we have considered4 ,all are of a primitive and generalised character2 that is to say1 characters which are to-day distributed among widely different groups were then concentrated and mingled in one common ancestor1 out of which the later groups will develop4 ,all belong to the lowest orders of their class4 ,no ,hymenopters 7ants1 bees1 and wasps7 or ,coleopters 7beetles7 are found in the ,coal-forest2 and it will be many millions of years before the graceful butterfly enlivens the landscapes of the earth4 ,the early insects nearly all belong to the lower orders of the ,orthopters 7cockroaches1 crickets1 locusts1 etc47 and ,neuropters 7dragon-flies1 may-flies1 etc474 ,a few traces of ,hemipters 7now mainly represented by the degenerate bugs7 are found1 but nine-tenths of the ,carboniferous insects belong to the lowest orders of their class1 the ,orthopters and ,neuropters4 ,in fact1 they are such primitive and generalised insects1 and so frequently mingle the characteristics of the two orders1 that one of the highest authorities1 ,scudder1 groups them in a special and extinct order1 the ,palmodictyoptera2 though this view is not now generally adopted4 ,we shall find the higher orders of insects making their appearance in succession as the story proceeds4 ,thus far1 then1 the insects of the ,coal-forest are in entire harmony with the principle of evolution1 but when we try to trace their origin and earlier relations our task is beset with difficulties4 ,it goes without saying that such delicate frames as those of the earlier insects had very little chance of being preserved in the rocks until the special conditions of the forest-age set in4 ,we are1 therefore1 quite prepared to hear that the geologist cannot give us the slenderest information4 ,he finds the wing of what he calls the primitive bug 7,protocimex71 an ,hemipterous insect1 in the later ,ordovician1 and the wing of a primitive cockroach 7,palaeoblattina7 in the ,silurian4 ,from these we can merely conclude that insects were already numerous and varied4 ,but we have already1 in similar difficulties1 received assistance from the science of zoology1 and we now obtain from that science a most important clue to the evolution of the insect4 ,in ,south ,america1 ,south ,africa1 and ,australasia1 which were at one time connected by a great southern continent1 we find a little caterpillar-like creature which the zoologist regards with profound interest4 ,it is so curious that he has been obliged to create a special class for it alone--a distinction which will be appreciated when ,i mention that the neighbouring class of the insects contains more than a quarter of a million living species4 ,this valuable little animal1 with its tiny head1 round1 elongated body1 and many pairs of caterpillar-like legs1 was until a few decades ago regarded as an ,annelid 7like the earth-worm74 ,it has1 in point of fact1 the peculiar kidney-structures 7nephridia7 and other features of the ,annelid1 but a closer study discovered in it a character that separated it far from any worm-group4 ,it was found to breathe the air by means of tracheae 7little tubes running inward from the surface of the body71 as the myriapods1 spiders1 and insects do4 ,it was1 in other words1 a kind of half-way animal between the ,arthropods and the ,annelids 7,cambridge ,natural ,history1 iv1 p4 #e71 a surviving kink in the lost chain of the ancestry of the insect4 ,through millions of years it has preserved a primitive frame that really belongs to the ,cambrian1 if not an earlier1 age4 ,it is one of the most instructive living fossils in the museum of nature4 ,peripatus1 as the little animal is called1 points very clearly to an ,annelid ancestor of all the ,tracheates 7the myriapods1 spiders1 and insects71 or all the animals that breathe by means of trachere4 ,to understand its significance we must glance once more at an early chapter in the story of life4 ,we saw that a vast and varied wormlike population must have filled the ,archaean ocean1 and that all the higher lines of animal development start from one or other point in this broad kingdom4 ,the ,annelids1 in which the body consists of a long series of connected rings or segments1 as in the earth-worm1 are one of the highest groups of these worm-like creatures1 and some branch of them developed a pair of feet 7as in the caterpillar7 on each segment of the body and a tough1 chitinous coat4 ,thus arose the early ,arthropods1 on tough-coated1 jointed1 articulated animals4 ,some of these remained in the water1 breathing by means of gills1 and became the ,crustacea4 ,some1 however1 migrated to the land and developed what we may almost call lungs--little tubes entering the body at the skin and branching internally1 to bring the air into contact with the blood1 the tracheae4 ,in ,peripatus we have a strange survivor of these primitive ,annelid-,tracheates of many million years ago4 ,the simple nature of its breathing apparatus suggests that the trachere were developed out of glands in the skin2 just as the fish1 when it came on land1 probably developed lungs from its swimming bladders4 ,the primitive ,tracheates1 delivered from the increasing carnivores of the waters1 grew into a large and varied family1 as all such new types do in favourable surroundings4 ,from them in the course of time were evolved the three great classes of the ,myriapods 7millipedes and centipedes71 the ,arachnids 7scorpions1 spiders1 and mites71 and the ,insects4 ,i will not enter into the much-disputed and ,obscure question of their nearer relationship4 ,some derive the ,insects from the ,myriapods1 some the ,myriapods from the ,insects1 and some think they evolved independently2 while the rise of the spiders and scorpions is even more obscure4 ,but how can we see any trace of an ,annelid ancestor in the vastly different frames of these animals which are said to descend from it8 ,it is not so difficult as it seems to be at first sight4 ,in the ,myriapod we still have the elongated body and successive pairs of legs4 ,in the ,arachnid the legs are reduced in number and lengthened1 while the various segments of the body are fused in two distinct body-halves1 the thorax and the abdomen4 ,in the ,insect we have a similar concentration of the primitive long body4 ,the abdomen is composed of a large number 7usually nine or ten7 of segments which have lost their legs and fused together4 ,in the thorax three segments are still distinctly traceable1 with three pairs of legs--now long jointed limbs--as in the caterpillar ancestor2 in the ,carboniferous insect these three joints in the thorax are particularly clear4 ,in the head four or five segments are fused together4 ,their limbs have been modified into the jaws or other mouth-appendages1 and their separate nerve-centres have combined to form the large ring of nerve-matter round the gullet which represents the brain of the insect4 ,how1 then1 do we account for the wings of the insect8 ,here we can offer nothing more than speculation1 but the speculation is not without interest4 ,it may be laid down in principle that the flying animal begins as a leaping animal4 ,the flying fish may serve to suggest an early stage in the development of wings2 it is a leaping fish1 its extended fins merely buoying it1 like the surfaces of an aeroplane1 and so prolonging its leap away from its pursuer4 ,but the great difficulty is to imagine any part of the smooth-coated primitive insect1 apart from the limbs 7and the wings of the insect are not developed from legs1 like those of the bird71 which might have even an initial usefulness in buoying the body as it leaped4 ,it has been suggested1 therefore1 that the primitive insect returned to the water1 as the whale and seal did in the struggle for life of a later period4 ,the fact that the mayfly and dragon-fly spend their youth in the water is thought to confirm this4 ,returning to the water1 the primitive insects would develop gills1 like the ,crustacea4 ,after a time the stress of life in the water drove them back to the land1 and the gills became useless4 ,but the folds or scales of the tough coat1 which had covered the gills1 would remain as projecting planes1 and are thought to have been the rudiment from which a long period of selection evolved the huge wings of the early dragon-flies and mayflies4 ,it is generally believed that the wingless order of insects 7,aptera7 have not lost1 but had never developed1 wings1 and that the insects with only one or two pairs all descend from an ancestor with three pairs4 ,the early date of their origin1 the delicacy of their structure1 and the peculiar form which their larval development has generally assumed1 combine to obscure the evolution of the insect1 and we must be content for the present with these general indications4 ,the vast unexplored regions of ,africa1 ,south ,america1 and ,central ,australia1 may yet yield further clues1 and the riddle of insect-metamorphosis may some day betray the secrets which it must hold4 ,for the moment the ,carboniferous insects interest us as a rich material for the operation of a coming natural selection4 ,on them1 as on all other ,carboniferous life1 a great trial is about to fall4 ,a very small proportion of them will survive that trial1 and they trill be the better organised to maintain themselves and rear their young in the new earth4 ,the remaining land-life of the ,coal-forest is confined to worm-like organisms whose remains are not preserved1 and land-snails which do not call for further discussion4 ,we may1 in conclusion1 glance at the progress of life in the waters4 ,apart from the appearance of the great fishes and ,crustacea1 the ,carboniferous period was one of great stimulation to aquatic life4 ,constant changes were taking place in the level and the distribution of land and water4 ,the aspect of our coal seams to-day1 alternating between thick layers of sand and mud1 shows a remarkable oscillation of the land4 ,many recent authorities have questioned whether the trees grew on the sites where we find them to-day1 and were not rather washed down into the lagoons and shallow waters from higher ground4 ,in that case we could not too readily imagine the forest-clad region sinking below the waves1 being buried under the deposits of the rivers1 and then emerging1 thousands of years later1 to receive once more the thick mantle of sombre vegetation4 ,probably there was less rising and falling of the crust than earlier geologists imagined4 ,but1 as one of the most recent and most critical authorities1 ,professor ,chamberlin1 observes1 the comparative purity of the coal1 the fairly uniform thickness of the seams1 the bed of clay representing soil at their base1 the frequency with which the stumps are still found growing upright 7as in the remarkable exposed ,coal-forest surface in ,glasgow1 at the present ground-level71 99 the perfectly preserved fronds and the general mixture of flora1 make it highly probable that the coal-seam generally marks the actual site of a ,coal-forest1 and there were considerable vicissitudes in the distribution of land and water4 ,great areas of land repeatedly passed beneath the waters1 instead of a re-elevation of the land1 however1 we may suppose that the shallow water was gradually filled with silt and debris from the land1 and a fresh forest grew over it4 99 ,the civic authorities of ,glasgow have wisely exposed and protected this instructive piece of ,coal-forest in one of their parks4 ,i noticed1 however that in the admirable printed information they supply to the public1 they describe the trees as at least several hundred thousand years old4 ,there is no authority in the world who would grant less than ten million years since the ,coal-forest period4 ,these changes are reflected in the progress of marine life1 though their influence is probably less than that of the great carnivorous monsters which now fill the waters4 ,the heavy ,arthrodirans languish and disappear4 ,the pavement-toothed sharks1 which at first represent three-fourths of the ,elasmobranchs1 dwindle in turn1 and in the formidable spines which develop on them we may see evidence of the great struggle with the sharp-toothed sharks which are displacing them4 ,the ,ostracoderms die out in the presence of these competitors4 ,the smaller fishes 7generally ,crossopterygii7 seem to live mainly in the inland and shore waters1 and advance steadily toward the modern types1 but none of our modern bony fishes have yet appeared4 ,more evident still is the effect of the new conditions upon the ,crustacea4 ,the ,trilobite1 once the master of the seas1 slowly yields to the stronger competitors1 and the latter part of the ,carboniferous period sees the last genus of ,trilobites finally extinguished4 ,the ,eurypterids 7large scorpion-like ,crustacea1 several feet long7 suffer equally1 and are represented by a few lingering species4 ,the stress favours the development of new and more highly organised ,crustacea4 ,one is the ,limulus or king-crab1 which seems to be a descendant1 or near relative1 of the ,trilobite1 and has survived until modern times4 ,others announce the coming of the long-tailed ,crustacea1 of the lobster and shrimp type4 ,they had primitive representatives in the earlier periods1 but seem to have been overshadowed by the ,trilobites and ,eurypterids4 ,as these in turn are crushed1 the more highly organised ,malacostraca take the lead1 and primitive specimens of the shrimp and lobster make their appearance4 ,the ,echinoderms are still mainly represented by the sea-lilies4 ,the rocks which are composed of their remains show that vast areas of the sea-floor must have been covered with groves of sea-lilies1 bending on their long1 flexible stalks and waving their great flower-like arms in the water to attract food4 ,with them there is now a new experiment in the stalked ,echinoderm1 the ,blastoid1 an armless type2 but it seems to have been a failure4 ,sea-urchins are now found in the deposits1 and1 although their remains are not common1 we may conclude that the star-fishes were scattered over the floor of the sea4 ,for the rest we need only observe that progress and rich diversity of forms characterise the other groups of animals4 ,the ,corals now form great reefs1 and the finer ,corals are gaining upon the coarser4 ,the ,foraminifers 7the chalk-shelled1 one-celled animals7 begin to form thick rocks with their dead skeletons2 the ,radiolaria 7the flinty-shelled microbes7 are so abundant that more than twenty genera of them have been distinguished in ,cornwall and ,devonshire4 ,the ,brachiopods and ,molluscs still abound1 but the ,molluscs begin to outnumber the lower type of shell-fish4 ,in the ,cephalopods we find an increasing complication of the structure of the great spiral-shelled types4 ,such is the life of the ,carboniferous period4 ,the world rejoices in a tropical luxuriance4 ,semi-tropical vegetation is found in ,spitzbergen and the ,antarctic1 as well as in ,north ,europe1 ,asia1 and ,america1 and in ,australasia2 corals and sea-lilies flourish at any part of the earth's surface4 ,warm1 dank1 low-lying lands1 bathed by warm oceans and steeped in their vapours1 are the picture suggested--as we shall see more closely--to the minds of all geologists4 ,in those happy conditions the primitive life of the earth erupts into an abundance and variety that are fitly illustrated in the well-preserved vegetation of the forest4 ,and when the earth has at length flooded its surface with this seething tide of life2 when the air is filled with a thousand species of insects1 and the forest-floor feels the heavy tread of the giant salamander and the light feet of spiders1 scorpions1 centipedes1 and snails1 and the lagoons and shores teem with animals1 the ,golden ,age begins to close1 and all the semi-tropical luxuriance is banished4 ,a great doom is pronounced on the swarming life of the ,coal-forest period1 and from every hundred species of its animals and plants only two or three will survive the searching test4 ,,chapter ,x4 ,,the ,,permian ,,revolution ,in an earlier chapter it was stated that the story of life is a story of gradual and continuous advance1 with occasional periods of more rapid progress4 ,hitherto it has been1 in these pages1 a slow and even advance from one geological age to another1 one level of organisation to another4 ,this1 it is true1 must not be taken too literally4 ,many a period of rapid change is probably contained1 and blurred out of recognition1 in that long chronicle of geological events4 ,when a region sinks slowly below the waves1 no matter how insensible the subsidence may be1 there will often come a time of sudden and vast inundations1 as the higher ridges of the coast just dip below the water-level and the lower interior is flooded4 ,when two invading arms of the sea meet at last in the interior of the sinking continent1 or when a land-barrier that has for millions of years separated two seas and their populations is obliterated1 we have a similar occurrence of sudden and far-reaching change4 ,the whole story of the earth is punctuated with small cataclysms4 ,but we now come to a change so penetrating1 so widespread1 and so calamitous that1 in spite of its slowness1 we may venture to call it a revolution4 ,indeed1 we may say of the remaining story of the earth that it is characterised by three such revolutions1 separated by millions of years1 which are very largely responsible for the appearance of higher types of life4 ,the facts are very well illustrated by an analogy drawn from the recent and familiar history of ,europe4 ,the socio-political conditions of ,europe in the eighteenth century1 which were still tainted with feudalism1 were changed into the socio-political conditions of the modern world1 partly by a slow and continuous evolution1 but much more by three revolutionary movements4 ,first there was the great upheaval at the end of the eighteenth century1 the tremors of which were felt in the life of every country in ,europe4 ,then1 although1 as ,freeman says1 no part of ,europe ever returned entirely to its former condition1 there was a profound and almost universal reaction4 ,in the 'thirties and 'forties1 differing in different countries1 a second revolutionary disturbance shook ,europe4 ,the reaction after this upheaval was far less severe1 and the conditions were permanently changed to a great extent1 but a third revolutionary movement followed in the next generation1 and from that time the evolution of socio-political conditions has proceeded more evenly4 ,the story of life on the earth since the ,coal-forest period is similarly quickened by three revolutions4 ,the first1 at the close of the ,carboniferous period1 is the subject of this chapter4 ,it is the most drastic and devastating of the three1 but its effect1 at least on the animal world1 will be materially checked by a profound and protracted reaction4 ,at the end of the ,chalk period1 some millions of years later1 there will be a second revolution1 and it will have a far more enduring and conspicuous result1 though it seem less drastic at the time4 ,yet there will be something of a reaction after a time1 and at length a third revolution will inaugurate the age of man4 ,if it is clearly understood that instead of a century we are contemplating a period of at least ten million years1 and instead of a decade of revolution we have a change spread over a hundred thousand years or more1 this analogy will serve to convey a most important truth4 ,the revolutionary agency that broke into the comparatively even chronicle of life near the close of the ,carboniferous period1 dethroned its older types of organisms1 and ushered new types to the lordship of the earth1 was cold4 ,the reader will begin to understand why ,i dwelt on the aspect of the ,coal-forest and its surrounding waters4 ,there was1 then1 a warm1 moist earth from pole to pole1 not even temporarily chilled and stiffened by a few months of winter1 and life spread luxuriantly in the perpetual semi-tropical summer4 ,then a spell of cold so severe and protracted grips the earth that glaciers glitter on the flanks of ,indian and ,australian hills1 and fields of ice spread over what are now semitropical regions4 ,in some degree the cold penetrates the whole earth4 ,the rich forests shrink slowly into thin tracts of scrubby1 poverty-stricken vegetation4 ,the loss of food and the bleak and exacting conditions of the new earth annihilate thousands of species of the older organisms1 and the more progressive types are moulded into fitness for the new environment4 ,it is a colossal application of natural selection1 and amongst its results are some of great moment4 ,in various recent works one reads that earlier geologists1 led astray by the nebular theory of the earth's origin1 probably erred very materially in regard to the climate of primordial times1 and that climate has varied less than used to be supposed4 ,it must not be thought that1 in speaking of a ,permian revolution1 ,i am ignoring or defying this view of many distinguished geologists4 ,i am taking careful account of it4 ,there is no dispute1 however1 about the fact that the ,permian age witnessed an immense carnage of ,carboniferous organisms1 and a very considerable modification of those organisms which survived the catastrophe1 and that the great agency in this annihilation and transformation was cold4 ,to prevent misunderstanding1 nevertheless1 it will be useful to explain the controversy about the climate of the earth in past ages which divides modern geologists4 ,the root of the difference of opinion and the character of the conflicting parties have already been indicated4 ,it is a protest of the ,planetesimalists against the older1 and still general1 view of the origin of the earth4 ,as we saw1 that view implies that1 as the heavier elements penetrated centreward in the condensing nebula1 the gases were left as a surrounding shell of atmosphere4 ,it was a mixed mass of gases1 chiefly oxygen1 hydrogen1 nitrogen1 and carbon-dioxide 7popularly known as carbonic acid gas74 ,when the water-vapour settled as ocean on the crust1 the atmosphere remained a very dense mixture of oxygen1 nitrogen1 and carbon-dioxide--to neglect the minor gases4 ,this heavy proportion of carbon-dioxide would cause the atmosphere to act as a glass-house over the surface of the earth1 as it does still to some extent4 ,experiment has shown that an atmosphere containing much vapour and carbon-dioxide lets the heat-rays pass through when they are accompanied by strong light1 but checks them when they are separated from the light4 ,in other words1 the primitive atmosphere would allow the heat of the sun to penetrate it1 and then1 as the ground absorbed the light1 would retain a large proportion of the heat4 ,hence the semi-tropical nature of the primitive earth1 the moisture1 the dense clouds and constant rains that are usually ascribed to it4 ,this condition lasted until the rocks and the forests of the ,carboniferous age absorbed enormous quantities of carbon-dioxide1 cleared the atmosphere1 and prepared an age of chill and dryness such as we find in the ,permian4 ,but the planetesimal hypothesis has no room for this enormous percentage of carbon-dioxide in the primitive atmosphere4 ,hinc illoe lachrymoe3 in plain ,english1 hence the acute quarrel about primitive climate1 and the close scanning of the geological chronicle for indications that the earth was not moist and warm until the end of the ,carboniferous period4 ,once more ,i do not wish to enfeeble the general soundness of this account of the evolution of life by relying on any controverted theory1 and we shall find it possible to avoid taking sides4 ,i have not referred to the climate of the earth in earlier ages1 except to mention that there are traces of a local ice-age about the middle of the ,archaean and the beginning of the ,cambrian4 ,as these are many millions of years removed from each other and from the ,carboniferous1 it is possible that they represent earlier periods more or less corresponding to the ,permian4 ,but the early chronicle is so compressed and so imperfectly studied as yet that it is premature to discuss the point4 ,it is1 moreover1 unnecessary because we know of no life on land in those remote periods1 and it is only in connection with life on land that we are interested in changes of climate here4 ,in other words1 as far as the present study is concerned1 we need only regard the climate of the ,devonian and ,carboniferous periods4 ,as to this there is no dispute2 nor1 in fact1 about the climate from the ,cambrian to the ,permian4 ,as the new school is most brilliantly represented by ,professor ,chamberlin1 99 it will be enough to quote him4 ,he says of the ,cambrian that1 apart from the glacial indications in its early part1 the testimony of the fossils1 wherever gathered1 implies nearly uniform climatic conditions444 throughout all the earth wherever records of the ,cambrian period are preserved 7ii1 #bgc74 ,of the ,ordovician he says3 ,all that is known of the life of this era would seem to indicate that the climate was much more uniform than now throughout the areas where the strata of the period are known 7ii1 #cdb74 ,in the ,silurian we have much to suggest uniformity of climate--in fact1 we have just the same evidence for it--and in the ,devonian1 when land-plants abound and afford better evidence1 we find the same climatic equality of living things in the most different latitudes4 ,finally1 most of the data at hand indicate that the climate of the ,lower ,carboniferous was essentially uniform1 and on the whole both genial and moist 7ii1 #eah74 ,the data1 we may recall1 are in this case enormously abundant1 and indicate the climate of the earth from the ,arctic regions to the ,antarctic4 ,another recent and critical geologist1 ,professor ,walther 7,geschichte der ,erde und des ,lebens1 #aijh71 admits that the coal-vegetation shows a uniformly warm climate from ,spitzbergen to ,africa4 ,mr4 ,drew 7,the ,romance of ,modern ,geology1 #aiji7 says that nearly all over the globe the climate was the same--hot1 close1 moist1 muggy 7p4 #bai74 99 ,an apology is due here in some measure4 ,the work which ,i quote as of ,professor ,chamberlin 7,geology1 #aijc7 is really by two authors1 ,professors ,chamberlin and ,salisbury4 ,i merely quote ,professor ,chamberlin for shortness1 and because the particular ideas ,i refer to are expounded by him in separate papers4 ,the work is the finest manual in modern geological literature4 ,i have used it much1 in conjunction with the latest editions of ,geikie1 ,le ,conte1 and ,lupparent1 and such recent manuals as ,walther1 ,de ,launay1 ,suess1 etc41 and the geological magazines4 ,the exception which ,professor ,chamberlin has in mind when he says most of the data is that we find deposits of salt and gypsum in the ,silurian and ,lower ,carboniferous1 and these seem to point to the evaporation of lakes in a dry climate4 ,he admits that these indicate1 at the most1 local areas or periods of dryness in an overwhelmingly moist and warm earth4 ,it is thus not disputed that the climate of the earth was1 during a period of at least fifteen million years 7from the ,cambrian to the ,carboniferous71 singularly uniform1 genial1 and moist4 ,during that vast period there is no evidence whatever that the earth was divided into climatic zones1 or that the year was divided into seasons4 ,to such an earth was the prolific life of the ,coal-forest adapted4 ,it is1 further1 not questioned that the temperature of the earth fell in the latter part of the ,carboniferous age1 and that the cold reached its climax in the ,permian4 ,as we turn over the pages of the geological chronicle1 an extraordinary change comes over the vegetation of the earth4 ,the great ,lepidodendra gradually disappear before the close of the ,permian period2 the ,sigillariae dwindle into a meagre and expiring race2 the giant ,horsetails 7,calamites7 shrink1 and betray the adverse conditions in their thin1 impoverished leaves4 ,new1 stunted1 hardy trees make their appearance3 the ,walchia1 a tree something like the low ,araucarian conifers in the texture of its wood1 and the ,voltzia1 the reputed ancestor of the cypresses4 ,their narrow1 stunted leaves suggest to the imagination the struggle of a handful of pines on a bleak hill-side4 ,the rich fern-population is laid waste4 ,the seed-ferns die out1 and a new and hardy type of fern1 with compact leaves1 the ,glossopteris1 spreads victoriously over the globe2 from ,australia it travels northward to ,russia1 which it reaches in the early ,permian1 and westward1 across the southern continent1 to ,south ,america4 ,a profoundly destructive influence has fallen on the earth1 and converted its rich green forests1 in which the mighty ,club-mosses had reared their crowns above a sea of waving ferns1 into severe and poverty-stricken deserts4 ,no botanist hesitates to say that it is the coming of a cold1 dry climate that has thus changed the face of the earth4 ,the geologist finds more direct evidence4 ,in the ,werribee ,gorge in ,victoria ,i have seen the marks which ,australian geologists have discovered of the ice-age which put an end to their ,coal-forests4 ,from ,tasmania to ,queensland they find traces of the rivers and fields of ice which mark the close of the ,carboniferous and beginning of the ,permian on the southern continent4 ,in ,south ,africa similar indications are found from the ,cape to the ,transvaal4 ,stranger still1 the geologists of ,india have discovered extensive areas of glaciation1 belonging to this period1 running down into the actual tropics4 ,and the strangest feature of all is that the glaciers of ,india and ,australia flowed1 not from the temperate zones toward the tropics1 but in the opposite direction4 ,two great zones of ice-covered land lay north and south of the equator4 ,the total area was probably greater than the enormous area covered with ice in ,europe and ,america during the familiar ice-age of the latest geological period4 ,thus the central idea of this chapter1 the destructive inroad of a colder climate upon the genial ,carboniferous world1 is an accepted fact4 ,critical geologists may suggest that the temperature of the ,coal-forest has been exaggerated1 and the temperature of the ,permian put too low4 ,we are not concerned with the dispute4 ,whatever the exact change of temperature was1 in degrees of the thermometer1 it was admittedly sufficient to transform the face of the earth1 and bring a mantle of ice over millions of square miles of our tropical and subtropical regions4 ,it remains for us to inquire into the causes of this transformation4 ,it at once occurs to us that these facts seem to confirm the prevalent idea1 that the ,coal-forests stripped the air of its carbon-dioxide until the earth shivered in an atmosphere thinner than that of to-day4 ,on reflection1 however1 it will be seen that1 if this were all that happened1 we might indeed expect to find enormous ice-fields extending from the poles--which we do not find--but not glaciation in the tropics4 ,others may think of astronomical theories1 and imagine a shrinking or clouding of the sun1 or a change in the direction of the earth's axis4 ,but these astronomical theories are now little favoured1 either by astronomers or geologists4 ,professor ,lowell bluntly calls them astrocomic theories4 ,geologists think them superfluous4 ,there is another set of facts to be considered in connection with the ,permian cold4 ,as we have seen several times1 there are periods when1 either owing to the shrinking of the earth or the overloading of the sea-bottoms1 or a combination of the two1 the land regains its lost territory and emerges from the ocean4 ,mountain chains rise2 new continental surfaces are exposed to the sun and rain4 ,one of the greatest of these upheavals of the land occurs in the latter half of the ,carboniferous and the ,permian4 ,in the middle of the ,carboniferous1 when ,europe is predominantly a flat1 low-lying land1 largely submerged1 a chain of mountains begins to rise across its central part4 ,from ,brittany to the east of ,saxony the great ridge runs1 and by the end of the ,carboniferous it becomes a chain of lofty mountains 7of which fragments remain in the ,vosges1 ,black ,forest1 and ,hartz mountains71 dragging ,central ,europe high above the water1 and throwing the sea back upon ,russia to the north and the ,mediterranean region to the south4 ,then the chain of the ,ural ,mountains begins to rise on the ,russian frontier4 ,by the beginning of the ,permian ,europe was higher above the water than it had ever yet been2 there was only a sea in ,russia and a southern sea with narrow arms trailing to the northwest4 ,the continent of ,north ,america also had meantime emerged4 ,the rise of the ,appalachia and ,ouachita mountains completes the emergence of the eastern continent1 and throws the sea to the west4 ,the ,asiatic continent also is greatly enlarged1 and in the southern hemisphere there is a further rise1 culminating in the ,permian1 of the continent 7,gondwana ,land7 which united ,south ,america1 ,south ,africa1 the ,antarctic land1 ,australia and ,new ,zealand1 with an arm to ,india4 ,in a word1 we have here a physical revolution in the face of the earth4 ,the changes were generally gradual1 though they seem in some places to have been rapid and abrupt 7,chamberlin72 but in summary they amounted to a vast revolution in the environment of animals and plants4 ,the low-lying1 swampy1 half-submerged continents reared themselves upward from the sea-level1 shook the marshes and lagoons from their face1 and drained the vast areas that had fostered the growth of the ,coal-forests4 ,it is calculated 7,chamberlin7 that the shallow seas which had covered twenty or thirty million square miles of our continental surfaces in the early ,carboniferous were reduced to about five million square miles in the ,permian4 ,geologists believe1 in fact1 that the area of exposed land was probably greater than it is now4 ,this lifting and draining of so much land would of itself have a profound influence on life-conditions1 and then we must take account of its indirect influence4 ,the moisture of the earlier period was probably due in the main to the large proportion of sea-surface and the absence of high land to condense it4 ,in both respects there is profound alteration1 and the atmosphere must have become very much drier4 ,as this vapour had been one of the atmosphere's chief elements for retaining heat at the surface of the earth1 the change will involve a great lowering of temperature4 ,the slanting of the raised land would aid this1 as1 in speeding the rivers1 it would promote the circulation of water4 ,another effect would be to increase the circulation of the atmosphere4 ,the higher and colder lands would create currents of air that had not been formed before4 ,lastly1 the ocean currents would be profoundly modified2 but the effect of this is obscure1 and may be disregarded for the moment4 ,here1 therefore1 we have a massive series of causes and effects1 all connected with the great emergence of the land1 which throw a broad light on the change in the face of the earth4 ,we must add the lessening of the carbon dioxide in the atmosphere4 ,quite apart from theories of the early atmosphere1 this process must have had a great influence1 and it is included by ,professor ,chamberlin among the causes of the world-wide change4 ,the rocks and forests of the ,carboniferous period are calculated to have absorbed two hundred times as much carbon as there is in the whole of our atmosphere to-day4 ,where the carbon came from we may leave open4 ,the ,planetesimalists look for its origin mainly in volcanic eruptions1 but1 though there was much volcanic activity in the later ,carboniferous and the ,permian1 there is little trace of it before the ,coal-forests 7after the ,cambrian74 ,however that may be1 there was a considerable lessening of the carbon-dioxide of the atmosphere1 and this in turn had most important effects4 ,first1 the removal of so much carbon-dioxide and vapour would be a very effective reason for a general fall in the temperature of the earth4 ,the heat received from the sun could now radiate more freely into space4 ,secondly1 it has been shown by experiment that a richness in carbon-dioxide favours ,cryptogamous plants 7though it is injurious to higher plants71 and a reduction of it would therefore be hurtful to the ,cryptogams of the ,coal-forest4 ,one may almost put it that1 in their greed1 they exhausted their store4 ,thirdly1 it meant a great purification of the atmosphere1 and thus a most important preparation of the earth for higher land animals and plants4 ,the reader will begin to think that we have sufficiently explained the ,permian revolution4 ,far from it4 ,some of its problems are as yet insoluble4 ,we have given no explanation at all why the ice-sheets1 which we would in a general way be prepared to expect1 appear in ,india and ,australia1 instead of farther north and south4 ,professor ,chamberlin1 in a profound study of the period 7appendix to vol4 ii1 ,geology71 suggests that the new land from ,new ,zealand to ,antarctica may have diverted the currents 7sea and air7 up the ,indian ,ocean1 and caused a low atmospheric pressure1 much precipitation of moisture1 and perpetual canopies of clouds to shield the ice from the sun4 ,since the outer polar regions themselves had been semi-tropical up to that time1 it is very difficult to see how this will account for a freezing temperature in such latitudes as ,australia and ,india4 ,there does not seem to have been any ice at the ,poles up to that time1 or for ages afterwards1 so that currents from the polar regions would be very different from what they are today4 ,if1 on the other hand1 we may suppose that the rise of ,gondwana ,land 7from ,brazil to ,india7 was attended by the formation of high mountains in those latitudes1 we have the basis1 at least1 of a more plausible explanation4 ,professor ,chamberlin rejects this supposition on the ground that the traces of ice-action are at or near the sea-level1 since we find with them beds containing marine fossils4 ,but this only shows1 at the most1 that the terminations of the glaciers reached the sea4 ,we know nothing of the height of the land from which they started4 ,for our main purpose1 however1 it is fortunately not necessary to clear up these mysteries4 ,it is enough for us that the ,carboniferous land rises high above the surface of the ocean over the earth generally4 ,the shallow seas are drained off its surface2 its swamps and lagoons generally disappear2 its waters run in falling rivers to the ocean4 ,the dense1 moist1 warm atmosphere that had so long enveloped it is changed into a thinner mantle of gas1 through which1 night by night1 the sun-soaked ground can discharge its heat into space4 ,cold winds blow over it from the new mountains2 probably vast regions of it are swept by icy blasts from the glaciated lands4 ,as these conditions advance in the ,permian period1 the forests wither and shrink4 ,of the extraordinarily mixed vegetation which we found in the ,coal-forests some few types are fitted to meet the severe conditions4 ,the seed-bearing trees1 the thin1 needle-leafed trees1 the trees with stronger texture of the wood1 are slowly singled out by the deepening cold4 ,the golden age of ,cryptogams is over4 ,the age of the ,cycad and the ,conifers is opening4 ,survivors of the old order linger in the warmer valleys1 as one may see to-day tree-ferns lingering in nooks of southern regions while an ,antarctic wind is whistling on the hills above them2 but over the broad earth the luscious pasturage of the ,coal-forest has changed into what is comparatively a cold desert4 ,we must not1 of course1 imagine too abrupt a change4 ,the earth had been by no means all swamp in the ,carboniferous age4 ,the new types were even then developing in the cooler and drier localities4 ,but their hour has come1 and there is great devastation among the lower plant population of the earth4 ,it follows at once that there would be1 on land1 an equal devastation and a similar selection in the animal world4 ,the vegetarians suffered an appalling reduction of their food2 the carnivores would dwindle in the same proportion4 ,both types1 again1 would suffer from the enormous changes in their physical surroundings4 ,vast stretches of marsh1 with teeming populations1 were drained1 and turned into firm1 arid plains or bleak hill-sides4 ,the area of the ,amphibia1 for instance1 was no less reduced than their food4 ,the cold1 in turn1 would exercise a most formidable selection4 ,before the ,permian period there was not on the whole earth an animal with a warm-blooded 7four-chambered7 heart or a warm coat of fur or feathers2 nor was there a single animal that gave any further care to the eggs it discharged1 and left to the natural warmth of the earth to develop4 ,the extermination of species in the egg alone must have been enormous4 ,it is impossible to convey any just impression of the carnage which this ,permian revolution wrought among the population of the earth4 ,we can but estimate how many species of animals and plants were exterminated1 and the reader must dimly imagine the myriads of living things that are comprised in each species4 ,an earlier ,american geologist1 ,professor ,le ,conte1 said that not a single ,carboniferous species crossed the line of the ,permian revolution4 ,this has proved to be an exaggeration1 but ,professor ,chamberlin seems to fall into an exaggeration on the other side when he says that #cjj out of #aj1jjj species survived4 ,there are only about #cjj species of animals and plants known in the whole of the ,permian rocks 7,geikie71 and most of these are new4 ,for instance1 of the enormous plant-population of the ,coal-forests1 comprising many thousands of species1 only fifty species survived unchanged in the ,permian4 ,we may say that1 as far as our knowledge goes1 of every thirty species of animals and plants in the ,carboniferous period1 twenty-eight were blotted out of the calendar of life for ever2 one survived by undergoing such modifications that it became a new species1 and one was found fit to endure the new conditions for a time4 ,we must leave it to the imagination to appreciate the total devastation of individuals entailed in this appalling application of what we call natural selection4 ,but what higher types of life issued from the womb of nature after so long and painful a travail8 ,the annihilation of the unfit is the seamy side1 though the most real side1 of natural selection4 ,we ignore it1 or extenuate it1 and turn rather to consider the advances in organisation by which the survivors were enabled to outlive the great chill and impoverishment4 ,unfortunately1 if the ,permian period is an age of death1 it is not an age of burials4 ,the fossil population of its cemeteries is very scanty4 ,not only is the living population enormously reduced1 but the areas that were accustomed to entomb and preserve organisms--the lake and shore deposits--are also greatly reduced4 ,the frames of animals and plants now rot on the dry ground on which they live4 ,even in the seas1 where life must have been much reduced by the general disturbance of conditions1 the record is poor4 ,molluscs and ,brachiopods and small fishes fill the list1 but are of little instructiveness for us1 except that they show a general advance of species4 ,among the ,cephalopods1 it is true1 we find a notable arrival4 ,on the one hand1 a single small straight-shelled ,cephalopod lingers for a time with the ancestral form2 on the other hand1 a new and formidable competitor appears among the coiled-shell ,cephalopods4 ,it is the first appearance of the famous ,ammonite1 but we may defer the description of it until we come to the great age of ,ammonites4 ,of the insects and their fortunes in the great famine we have no direct knowledge2 no insect remains have yet been found in ,permian rocks4 ,we shall1 however1 find them much advanced in the next period1 and must conclude that the selection acted very effectively among their thousand ,carboniferous species4 ,the most interesting outcome of the new conditions is the rise and spread of the reptiles4 ,no other sign of the times indicates so clearly the dawn of a new era as the appearance of these primitive1 clumsy reptiles1 which now begin to oust the ,amphibia4 ,the long reign of aquatic life is over2 the ensign of progress passes to the land animals4 ,the half-terrestrial1 half-aquatic ,amphibian deserts the water entirely 7in one or more of its branches71 and a new and fateful dynasty is founded4 ,although many of the reptiles will return to the water1 when the land sinks once more1 the type of the terrestrial quadruped is now fully evolved1 and from its early reptilian form will emerge the lords of the air and the lords of the land1 the birds and the mammals4 ,to the uninformed it may seem that no very great advance is made when the reptile is evolved from the ,amphibian4 ,in reality the change implies a profound modification of the frame and life of the vertebrate4 ,partly1 we may suppose1 on account of the purification of the air1 partly on account of the decrease in water surface1 the gills are now entirely discarded4 ,the young reptile loses them during its embryonic life--as man and all the mammals and birds do to-day--and issues from the egg a purely lung-breathing creature4 ,a richer blood now courses through the arteries1 nourishing the brain and nerves as well as the muscles4 ,the superfluous tissue of the gill-structures is used in the improvement of the ear and mouth-parts2 a process that had begun in the ,amphibian4 ,the body is raised up higher from the ground1 on firmer limbs2 the ribs and the shoulder and pelvic bones--the saddles by which the weight of the body is adjusted between the limbs and the backbone--are strengthened and improved4 ,finally1 two important organs for the protection and nurture of the embryo 7the amnion and the allantois7 make their appearance for the first time in the reptile4 ,in grade of organisation the reptile is really nearer to the bird than it is to the salamander4 ,yet these ,permian reptiles are so generalised in character and so primitive in structure that they point back unmistakably to an ,amphibian ancestry4 ,the actual line of descent is obscure4 ,when the reptiles first appear in the rocks1 they are already divided into widely different groups1 and must have been evolved some time before4 ,probably they started from some group or groups of the ,amphibia in the later ,carboniferous1 when1 as we saw1 the land began to rise considerably4 ,we have not yet recovered1 and may never recover1 the region where the early forms lived1 and therefore cannot trace the development in detail4 ,the fossil archives1 we cannot repeat too often1 are not a continuous1 but a fragmentary1 record of the story of life4 ,the task of the evolutionist may be compared to the work of tracing the footsteps of a straying animal across the country4 ,here and there its traces will be amply registered on patches of softer ground1 but for the most part they will be entirely lost on the firmer ground4 ,so it is with the fossil record of life4 ,only in certain special conditions are the passing forms buried and preserved4 ,in this case we can say only that the ,permian reptiles fall into two great groups1 and that one of these shows affinities to the small salamander-like ,amphibia of the ,coal-forest 7the ,microsaurs71 while the other has affinities to the ,labyrinthodonts4 ,a closer examination of these early reptiles may be postponed until we come to speak of the age of reptiles4 ,we shall see that it is probable that an even higher type of animal1 the mammal1 was born in the throes of the ,permian revolution4 ,but enough has been said in vindication of the phrase which stands at the head of this chapter2 and to show how the great ,primary age of terrestrial life came to a close4 ,with its new inhabitants the earth enters upon a fresh phase1 and thousands of its earlier animals and plants are sealed in their primordial tombs1 to await the day when man will break the seals and put flesh once more on the petrified bones4 ,,chapter ,,xi4 ,,the ,,middle ,,ages ,,of ,,the ,,earth ,the story of the earth from the beginning of the ,cambrian period to the present day was long ago divided by geologists into four great eras4 ,the periods we have already covered--the ,cambrian1 ,ordovician1 ,silurian1 ,devonian1 ,carboniferous1 and ,permian--form the ,primary or ,palaeozoic ,era1 to which the earlier ,archaean rocks were prefixed as a barren and less interesting introduction4 ,the stretch of time on which we now enter1 at the close of the ,permian1 is the ,secondary or ,mesozoic ,era4 ,it will be closed by a fresh upheaval of the earth and disturbance of life-conditions in the ,chalk period1 and followed by a ,tertiary ,era1 in which the earth will approach its modern aspect4 ,at its close there will be another series of upheavals1 culminating in a great ,ice-age1 and the remaining stretch of the earth's story1 in which we live1 will form the ,quaternary ,era4 ,in point of duration these four eras differ enormously from each other4 ,if the first be conceived as comprising sixteen million years--a very moderate estimate--the second will be found to cover less than eight million years1 the third less than three million years1 and the fourth1 the ,age of ,man1 much less than one million years2 while the ,archaean ,age was probably as long as all these put together4 ,but the division is rather based on certain gaps1 or unconformities1 in the geological record2 and1 although the breaches are now partially filled1 we saw that they correspond to certain profound and revolutionary disturbances in the face of the earth4 ,we retain them1 therefore1 as convenient and logical divisions of the biological as well as the geological chronicle1 and1 instead of passing from one geological period to another1 we may1 for the rest of the story1 take these three eras as wholes1 and devote a few chapters to the chief advances made by living things in each era4 ,the ,mesozoic ,era will be a protracted reaction between two revolutions3 a period of low-lying land1 great sea-invasions1 and genial climate1 between two upheavals of the earth4 ,the ,tertiary ,era will represent a less sharply defined depression1 with genial climate and luxuriant life1 between two such upheavals4 ,the ,mesozaic 7middle life7 ,era may very fitly be described as the ,middle ,ages of life on the earth4 ,it by no means occupies a central position in the chronicle of life from the point of view of time or antiquity1 just as the ,middle ,ages of ,europe are by no means the centre of the chronicle of mankind1 but its types of animals and plants are singularly transitional between the extinct ancient and the actual modern types4 ,life has been lifted to a higher level by the ,permian revolution4 ,then1 for some millions of years1 the sterner process of selection relaxes1 the warm bosom of the earth swarms again with a teeming and varied population1 and a rich material is provided for the next great application of drastic selective agencies4 ,to a poet it might seem that nature indulges each succeeding and imperfect type of living thing with a golden age before it is dismissed to make place for the higher4 ,the ,mesozoic opens in the middle of the great revolution described in the last chapter4 ,its first section1 the ,triassic period1 is at first a mere continuation of the ,permian4 ,a few hundred species of animals and hardy plants are scattered over a relatively bleak and inhospitable globe4 ,then the land begins to sink once more4 ,the seas spread in great arms over the revelled continents1 the plant world rejoices in the increasing warmth and moisture1 and the animals increase in number and variety4 ,we pass into the ,jurassic period under conditions of great geniality4 ,warm seas are found as far north and south as our present polar regions1 and the low-lying fertile lands are covered again with rich1 if less gigantic1 forests1 in which hordes of stupendous animals find ample nourishment4 ,the mammal and the bird are already on the stage1 but their warm coats and warm blood offer no advantage in that perennial summer1 and they await in obscurity the end of the golden age of the reptiles4 ,at the end of the ,jurassic the land begins to rise once more4 ,the warm1 shallow seas drain off into the deep oceans1 and the moist1 swampy lands are dried4 ,the emergence continues throughout the ,cretaceous 7,chalk7 period4 ,chains of vast mountains rise slowly into the air in many parts of the earth1 and a new and comparatively rapid change in the vegetation--comparable to that at the close of the ,carboniferous--announces the second great revolution4 ,the ,mesozoic closes with the dismissal of the great reptiles and the plants on which they fed1 and the earth is prepared for its new monarchs1 the flowering plants1 the birds1 and the mammals4 ,how far this repeated levelling of the land after its repeated upheavals is due to a real sinking of the crust we cannot as yet determine4 ,the geologist of our time is disposed to restrict these mysterious rises and falls of the crust as much as possible4 ,a much more obvious and intelligible agency has to be considered4 ,the vast upheaval of nearly all parts of the land during the ,permian period would naturally lead to a far more vigorous scouring of its surface by the rains and rivers4 ,the higher the land1 the more effectively it would be worn down4 ,the cooler summits would condense the moisture1 and the rains would sweep more energetically down the slopes of the elevated continents4 ,there would thus be a natural process of levelling as long as the land stood out high above the water-line1 but it seems probable that there was also a real sinking of the crust4 ,such subsidences have been known within historic times4 ,by the end of the ,triassic--a period of at least two million years--the sea had reconquered a vast proportion of the territory wrested from it in the ,permian revolution4 ,most of ,europe1 west of a line drawn from the tip of ,norway to the ,black ,sea1 was under water--generally open sea in the south and centre1 and inland seas or lagoons in the west4 ,the invasion of the sea continued1 and reached its climax1 in the ,jurassic period4 ,the greater part of ,europe was converted into an archipelago4 ,a small continent stood out in the ,baltic region4 ,large areas remained above the sea-level in ,austria1 ,germany1 and ,france4 ,ireland1 ,wales1 and much of ,scotland were intact1 and it is probable that a land bridge still connected the west of ,europe with the east of ,america4 ,europe generally was a large cluster of islands and ridges1 of various sizes1 in a semi-tropical sea4 ,southern ,asia was similarly revelled1 and it is probable that the seas stretched1 with little interruption1 from the west of ,europe to the ,pacific4 ,the southern continent had deep wedges of the sea driven into it4 ,india1 ,new ,zealand1 and ,australia were successively detached from it1 and by the end of the ,mesozoic it was much as we find it to-day4 ,the ,arctic continent 7north of ,europe7 was flooded1 and there was a great interior sea in the western part of the ,north ,american continent4 ,this summary account of the levelling process which went on during the ,triassic and ,jurassic will prepare us to expect a return of warm climate and luxurious life1 and this the record abundantly evinces4 ,the enormous expansion of the sea--a great authority1 ,neumayr1 believes that it was the greatest extension of the sea that is known in geology--and lowering of the land would of itself tend to produce this condition1 and it may be that the very considerable volcanic activity1 of which we find evidence in the ,permian and ,triassic1 had discharged great volumes of carbon-dioxide into the atmosphere4 ,whatever the causes were1 the earth has returned to paradisiacal conditions4 ,the vast ice-fields have gone1 the scanty and scrubby vegetation is replaced by luscious forests of cycads1 conifers1 and ferns1 and warmth-loving animals penetrate to what are now the ,arctic and ,antarctic regions4 ,greenland and ,spitzbergen are fragments of a continent that then bore a luxuriant growth of ferns and cycads1 and housed large reptiles that could not now live thousands of miles south of it4 ,england1 and a large part of ,europe1 was a tranquil blue coral-ocean1 the fringes of its islands girt with reefs such as we find now only three thousand miles further south1 with vast shoals of ,ammonites1 sometimes of gigantic size1 preying upon its living population or evading its monstrous sharks2 while the sunlit lands were covered with graceful1 palmlike cycads and early yews and pines and cypresses1 and quaint forms of reptiles throve on the warm earth or in the ample swamps1 or rushed on outstretched wings through the purer air4 ,it was an evergreen world1 a world1 apparently1 of perpetual summer4 ,no trace is found until the next period of an alternation of summer and winter--no trees that shed their leaves annually1 or show annual rings of growth in the wood--and there is little trace of zones of climate as yet4 ,it is true that the sensitive ,ammonites differ in the northern and the southern latitudes1 but1 as ,professor ,chamberlin says1 it is not clear that the difference points to a diversity of climate4 ,we may conclude that the absence of corals higher than the north of ,england implies a more temperate climate further north1 but what ,sir ,a4 ,geikie calls 7with slight exaggeration7 the almost tropical aspect of ,greenland warns us to be cautious4 ,the climate of the mid-,jurassic was very much warmer and more uniform than the climate of the earth to-day4 ,it was an age of great vital expansion4 ,and into this luxuriant world we shall presently find a fresh period of elevation1 disturbance1 and cold breaking with momentous evolutionary results4 ,meantime1 we may take a closer look at these interesting inhabitants of the ,middle ,ages of the earth1 before they pass away or are driven1 in shrunken regiments1 into the shelter of the narrowing tropics4 ,the principal change in the aspect of the earth1 as the cold1 arid plains and slopes of the ,triassic slowly yield the moist and warm ow-lying lands of the ,jurassic1 to consists in the character of the vegetation4 ,it is wholly intermediate in its forms between that of the primitive forests and that of the modern world4 ,the great ,cryptogams of the ,carboniferous world--the giant ,club-mosses and their kindred--have been slain by the long period of cold and drought4 ,smaller ,horsetails 7sometimes of a great size1 but generally of the modern type7 and ,club-mosses remain1 but are not a conspicuous feature in the landscape4 ,on the other hand1 there is as yet--apart from the ,conifers--no trace of the familiar trees and flowers and grasses of the later world4 ,the vast majority of the plants are of the cycad type4 ,these--now confined to tropical and subtropical regions--with the surviving ferns1 the new ,conifers1 and certain trees of the ginkgo type1 form the characteristic ,mesozoic vegetation4 ,a few words in the language of the modern botanist will show how this vegetation harmonises with the story of evolution4 ,plants are broadly divided into the lower kingdom of the ,cryptogams 7spore-bearing7 and the upper kingdom of the ,phanerogams 7seed-bearing74 ,as we saw1 the ,primary ,era was predominantly the age of ,cryptogams2 the later periods witness the rise and supremacy of the ,phanerogams4 ,but these in turn are broadly divided into a less advanced group1 the ,gymnosperms1 and a more advanced group1 the ,angiosperms or flowering plants4 ,and1 just as the ,primary ,era is the age of ,cryptogams1 the ,secondary is the age of ,gymnosperms1 and the ,tertiary 7and present7 is the age of ,angiosperms4 ,of about #ahj1jjj species of plants in nature to-day more than #ajj1jjj are ,angiosperms2 yet up to the end of the ,jurassic not a single true ,angiosperm is found in the geological record4 ,this is a broad manifestation of evolution1 but it is not quite an accurate statement1 and its inexactness still more strongly confirms the theory of evolution4 ,though the ,primary ,era was predominantly the age of ,cryptogams1 we saw that a very large number of seed-bearing plants1 with very mixed characters1 appeared before its close4 ,it thus prepares the way for the cycads and conifers and ginkgoes of the ,mesozoic1 which we may conceive as evolved from one or other branch of the mixed ,carboniferous vegetation4 ,we next find that the ,mesozoic is by no means purely an age of ,gymnosperms4 ,i do not mean merely that the ,angiosperms appear in force before its close1 and were probably evolved much earlier4 ,the fact is that the ,gymnosperms of the ,mesozoic are often of a curiously mixed character1 and well illustrate the transition to the ,angiosperms1 though they may not be their actual ancestors4 ,this will be clearer if we glance in succession at the various types of plant which adorned and enriched the ,jurassic world4 ,the ,european or ,american landscape--indeed1 the aspect of the earth generally1 for there are no pronounced zones of climate--is still utterly different from any that we know to-day4 ,no grass carpets the plains2 none of the flowers or trees with which we are familiar1 except conifers1 are found in any region4 ,ferns grow in great abundance1 and have now reached many of the forms with which we are acquainted4 ,thickets of bracken spread over the plains2 clumps of ,royal ferns and ,hartstongues spring up in moister parts4 ,the trees are conifers1 cycads1 and trees akin to the ginkgo1 or ,maidenhair ,tree1 of modern ,japan4 ,cypresses1 yews1 firs1 and araucarias 7the ,monkey ,puzzle group7 grow everywhere1 though the species are more primitive than those of today4 ,the broad1 fan-like leaves and plum-like fruit of the ginkgoales1 of which the temple-gardens of ,japan have religiously preserved a solitary descendant1 are found in the most distant regions4 ,but the most frequent and characteristic tree of the ,jurassic landscape is the cycad4 ,the cycads--the botanist would say ,cycadophyta or ,cycadales1 to mark them off from the cycads of modern times--formed a third of the whole ,jurassic vegetation1 while to-day they number only about a hundred species in #ahj1jjj1 and are confined to warm latitudes4 ,all over the earth1 from the ,arctic to the ,antarctic1 their palm-like foliage showered from the top of their generally short stems in the ,jurassic4 ,but the most interesting point about them is that a very large branch of them 7the ,bennettiteae7 went far beyond the modern ,gymnosperm in their flowers and fruit1 and approached the ,angiosperms4 ,their fructifications rivalled the largest flowers of the present day in structure and modelling 7,scott71 and possibly already gave spots of sober colour to the monotonous primitive landscape4 ,on the other hand1 they approached the ferns so much more closely than modern cycads do that it is often impossible to say whether ,jurassic remains must be classed as ferns or cycads4 ,we have here1 therefore1 a most interesting evolutionary group4 ,the botanist finds even more difficulty than the zoologist in drawing up the pedigrees of his plants1 but the general features of the larger groups which he finds in succession in the chronicle of the earth point very decisively to evolution4 ,the seed-bearing ferns of the ,coal-forest point upward to the later stage1 and downward to a common origin with the ordinary spore-bearing ferns4 ,some of them are altogether of a cycadean type 7,scott7 in respect of the seed4 ,on the other hand1 the ,bennettiteae of the ,jurassic have the mixed characters of ferns1 cycads1 and flowering plants1 and thus1 in their turn1 point downward to a lower ancestry and upward to the next great stage in plant-development4 ,it is not suggested that the seed-ferns we know evolved into the cycads we know1 and these in turn into our flowering plants4 ,it is enough for the student of evolution to see in them so many stages in the evolution of plants up to the ,angiosperm level4 ,the gaps between the various groups are less rigid than scientific men used to think4 ,taller than the cycads1 firmer in the structure of the wood1 and destined to survive in thousands of species when the cycads would be reduced to a hundred1 were the pines and yews and other conifers of the ,jurassic landscape4 ,we saw them first appearing1 in the stunted ,walchias and ,voltzias1 during the severe conditions of the ,permian period4 ,like the birds and mammals they await the coming of a fresh period of cold to give them a decided superiority over the cycads4 ,botanists look for their ancestors in some form related to the ,cordaites of the ,coal-forest4 ,the ginkgo trees seem to be even more closely related to the ,cordaites1 and evolved from an early and generalised branch of that group4 ,the ,cordaites1 we may recall1 more or less united in one tree the characters of the conifer 7in their wood7 and the cycad 7in their fruit74 ,so much for the evolutionary aspect of the ,jurassic vegetation in itself4 ,slender as the connecting links are1 it points clearly enough to a selection of higher types during the ,permian revolution from the varied mass of the ,carboniferous flora1 and it offers in turn a singularly varied and rich group from which a fresh selection may choose yet higher types4 ,we turn now to consider the animal population which1 directly or indirectly1 fed upon it1 and grew with its growth4 ,to the reptiles1 the birds1 and the mammals1 we must devote special chapters4 ,here we may briefly survey the less conspicuous animals of the ,mesozoic ,epoch4 ,the insects would be one of the chief classes to benefit by the renewed luxuriance of the vegetation4 ,the ,hymenopters 7butterflies7 have not yet appeared4 ,they will1 naturally1 come with the flowers in the next great phase of organic life4 ,but all the other orders of insects are represented1 and many of our modern genera are fully evolved4 ,the giant insects of the ,coal-forest1 with their mixed patriarchal features1 have given place to more definite types4 ,swarms of dragon-flies1 may-flies1 termites 7with wings71 crickets1 and cockroaches1 may be gathered from the preserved remains4 ,the beetles 7,coleopters7 have come on the scene in the ,triassic1 and prospered exceedingly4 ,in some strata three-fourths of the insects are beetles1 and as we find that many of them are wood-eaters1 we are not surprised4 ,flies 7,dipters7 and ants 7,hymenopters7 also are found1 and1 although it is useless to expect to find the intermediate forms of such frail creatures1 the record is of some evolutionary interest4 ,the ants are all winged4 ,apparently there is as yet none of the remarkable division of labour which we find in the ants to-day1 and we may trust that some later period of change may throw light on its origin4 ,just as the growth of the forests--for the ,mesozoic vegetation has formed immense coal-beds in many parts of the world1 even in ,yorkshire and ,scotland--explains this great development of the insects1 they would in their turn supply a rich diet to the smaller land animals and flying animals of the time4 ,we shall see this presently4 ,let us first glance at the advances among the inhabitants of the seas4 ,the most important and stimulating event in the seas is the arrival of the ,ammonite4 ,one branch of the early shell-fish1 it will be remembered1 retained the head of its naked ancestor1 and lived at the open mouth of its shell1 thus giving birth to the ,cephalopods4 ,the first form was a long1 straight1 tapering shell1 sometimes several feet long4 ,in the course of time new forms with curved shells appeared1 and began to displace the straight-shelled4 ,then ,cephalopods with close-coiled shells1 like the nautilus1 came1 and--such a shell being an obvious advantage--displaced the curved shells4 ,in the ,permian1 we saw1 a new and more advanced type of the coiled-shell animal1 the ,ammonite1 made its appearance1 and in the ,triassic and ,jurassic it becomes the ogre or tyrant of the invertebrate world4 ,sometimes an inch or less in diameter1 it often attained a width of three feet or more across the shell1 at the aperture of which would be a monstrous and voracious mouth4 ,the ,ammonites are not merely interesting as extinct monsters of the earth's ,middle ,ages1 and stimulating terrors of the deep to the animals on which they fed4 ,they have an especial interest for the evolutionist4 ,the successive chambers which the animal adds1 as it grows1 to the habitation of its youth1 leave the earlier chambers intact4 ,by removing them in succession in the adult form we find an illustration of the evolution of the elaborate shell of the ,jurassic ,ammonite4 ,it is an admirable testimony to the validity of the embryonic law we have often quoted--that the young animal is apt to reproduce the past stages of its ancestry--that the order of the building of the shell in the late ,ammonite corresponds to the order we trace in its development in the geological chronicle4 ,about a thousand species of ,ammonites were developed in the ,mesozoic1 and none survived the ,mesozoic4 ,like the ,trilobites of the ,primary ,era1 like the contemporary great reptiles on land1 the ,ammonites were an abortive growth1 enjoying their hour of supremacy until sterner conditions bade them depart4 ,the pretty nautilus is the only survivor to-day of the vast ,mesozoic population of coiled-shell ,cephalopods4 ,a rival to the ,ammonite appeared in the ,triassic seas1 a formidable forerunner of the cuttle-fish type of ,cephalopod4 ,the animal now boldly discards the protecting and confining shell1 or spreads over the outside of it1 and becomes a shell-fish with the shell inside4 ,the octopus of our own time has advanced still further1 and become the most powerful of the invertebrates4 ,the ,belemnite1 as the ,mesozoic cuttle-fish is called1 attained so large a size that the internal bone1 or pen 7the part generally preserved71 is sometimes two feet in length4 ,the ink-bags of the ,belemnite also are sometimes preserved1 and we see how it could balk a pursuer by darkening the waters4 ,it was a compensating advantage for the loss of the shell4 ,in all the other classes of aquatic animals we find corresponding advances4 ,in the remaining ,molluscs the higher or more effective types are displacing the older4 ,it is interesting to note that the oyster is fully developed1 and has a very large kindred1 in the ,mesozoic seas4 ,among the ,brachiopods the higher sloping-shoulder type displaces the square-shoulder shells4 ,in the ,crustacea the ,trilobites and ,eurypterids have entirely disappeared2 prawns and lobsters abound1 and the earliest crab makes its appearance in the ,english ,jurassic rocks4 ,this sudden arrival of a short-tailed ,crustacean surprises us less when we learn that the crab has a long tail in its embryonic form1 but the actual line of its descent is not clear4 ,among the ,echinoderms we find that the ,cystids and ,blastoids have gone1 and the sea-lilies reach their climax in beauty and organisation1 to dwindle and almost disappear in the last part of the ,mesozoic4 ,one ,jurassic sea-lily was found to have #fjj1jjj distinct ossicles in its petrified frame4 ,the free-moving ,echinoderms are now in the ascendant1 the sea-urchins being especially abundant4 ,the ,corals are1 as we saw1 extremely abundant1 and a higher type 7the ,hexacoralla7 is superseding the earlier and lower 7,tetracoralla74 ,finally1 we find a continuous and conspicuous advance among the fishes4 ,at the close of the ,triassic and during the ,jurassic they seem to undergo profound and comparatively rapid changes4 ,the reason will1 perhaps1 be apparent in the next chapter1 when we describe the gigantic reptiles which feed on them in the lakes and shore-waters4 ,a greater terror than the shark had appeared in their environment4 ,the ,ganoids and ,dipneusts dwindle1 and give birth to their few modern representatives4 ,the sharks with crushing teeth diminish in number1 and the sharp-toothed modern shark attains the supremacy in its class1 and evolves into forms far more terrible than any that we know to-day4 ,skates and rays of a more or less modern type1 and ancestral gar-pikes and sturgeons1 enter the arena4 ,but the most interesting new departure is the first appearance1 in the ,jurassic1 of bony-framed fishes 7,teleosts74 ,their superiority in organisation soon makes itself felt1 and they enter upon the rapid evolution which will1 by the next period1 give them the first place in the fish world4 ,over the whole ,mesozoic world1 therefore1 we find advance and the promise of greater advance4 ,the ,permian stress has selected the fittest types to survive from the older order2 the ,jurassic luxuriance is permitting a fresh and varied expansion of life1 in preparation for the next great annihilation of the less fit and selection of the more fit4 ,life pauses before another leap4 ,the ,mesozoic earth--to apply to it the phrase which a geologist has given to its opening phase--welcomes the coming and speeds the parting guest4 ,in the depths of the ocean a new movement is preparing1 but we have yet to study the highest forms of ,mesozoic life before we come to the ,cretaceous disturbances4 ,,chapter ,,xii4 ,,the ,,age ,,of ,,reptiles ,from one point of view the advance of life on the earth seems to proceed not with the even flow of a river1 but in the successive waves of an oncoming tide4 ,it is true that we have detected a continuous advance behind all these rising and receding waves1 yet their occurrence is a fact of some interest1 and not a little speculation has been expended on it4 ,when the great procession of life first emerges out of the darkness of ,archaean times1 it deploys into a spreading world of strange ,crustaceans1 and we have the ,age of ,trilobites4 ,later there is the ,age of ,fishes1 then of ,cryptogams and ,amphibia1 and then of ,cycads and ,reptiles1 and there will afterwards be an ,age of ,birds and ,mammals1 and finally an ,age of ,man4 ,but there is no ground for mystic speculation on this circumstance of a group of organisms fording the earth for a few million years1 and then perishing or dwindling into insignificance4 ,we shall see that a very plain and substantial process put an end to the ,age of the ,cycads1 ,ammonites1 and ,reptiles1 and we have seen how the earlier dynasties ended4 ,the phrase1 however1 the ,age of ,reptiles1 is a fitting and true description of the greater part of the ,mesozoic ,era1 which lies1 like a fertile valley1 between the ,permian and the ,chalk upheavals4 ,from the bleak heights of the ,permian period1 or--more probably--from its more sheltered regions1 in which they have lingered with the ferns and cycads1 the reptiles spread out over the earth1 as the summer of the ,triassic period advances4 ,in the full warmth and luxuriance of the ,jurassic they become the most singular and powerful army that ever trod the earth4 ,they include small lizard-like creatures and monsters more than a hundred feet in length4 ,they swim like whales in the shallow seas2 they shrink into the shell of the giant turtle2 they rear themselves on towering hind limbs1 like colossal kangaroos2 they even rise into the air1 and fill it with the dragons of the fairy tale4 ,they spread over the whole earth from ,australia to the ,arctic circle4 ,then the earth seems to grow impatient of their dominance1 and they shrink towards the south1 and struggle in a diminished territory4 ,the colossal monsters and the formidable dragons go the way of all primitive life1 and a ragged regiment of crocodiles1 turtles1 and serpents in the tropics1 with a swarm of smaller creatures in the fringes of the warm zone1 is all that remains1 by the ,tertiary ,era1 of the world-conquering army of the ,mesozoic reptiles4 ,they had appeared1 as we said1 in the ,permian period4 ,probably they had been developed during the later ,carboniferous1 since we find them already branched into three orders1 with many sub-orders1 in the ,permian4 ,the stimulating and selecting disturbances which culminated in the ,permian revolution had begun in the ,carboniferous4 ,their origin is not clear1 as the intermediate forms between them and the amphibia are not found4 ,this is not surprising1 if we may suppose that some of the amphibia had1 in the growing struggle1 pushed inland1 or that1 as the land rose and the waters were drained in certain regions1 they had gradually adopted a purely terrestrial life1 as some of the frogs have since done4 ,in the absence of water their frames would not be preserved and fossilised4 ,we can1 therefore1 understand the gap in the record between the amphibia and the reptiles4 ,from their structure we gather that they sprang from at least two different branches of the amphibia4 ,their remains fall into two great groups1 which are known as the ,diapsid and the ,synapsid reptiles4 ,the former seem to be more closely related to the ,microsauria1 or small salamander-like amphibia of the ,coal-forest2 the latter are nearer to the ,labyrinthodonts4 ,it is not suggested that these were their actual ancestors1 but that they came from the same early amphibian root4 ,we find both these groups1 in patriarchal forms1 in ,europe1 ,north ,america1 and ,south ,africa during the ,permian period4 ,they are usually moderate in size1 but in places they seem to have found good conditions and prospered4 ,a few years ago a ,permian bed in ,russia yielded a most interesting series of remains of ,synapsid reptiles4 ,some of them were large vegetarian animals1 more than twelve feet in length2 others were carnivores with very powerful heads and teeth as formidable as those of the tiger4 ,another branch of the same order lived on the southern continent1 ,gondwana ,land1 and has left numerous remains in ,south ,africa4 ,we shall see that they are connected by many authorities with the origin of the mammals4 99 ,the other branch1 the ,diapsids1 are represented to-day by the curiously primitive lizard of ,new ,zealand1 the tuatara 7,sphenodon1 or ,hatteria71 of which ,i have seen specimens1 nearly two feet in length1 that one did not care to approach too closely4 ,the ,diapsids are chiefly interesting1 however1 as the reputed ancestors of the colossal reptiles of the ,jurassic age and the birds4 99 ,these ,synapsid reptiles are more commonly known as ,pareiasauria or ,theromorpha4 ,the purified air of the ,permian world favoured the reptiles' being lung-breathers1 but the cold would check their expansion for a time4 ,the reptile1 it is important to remember' usually leaves its eggs to be hatched by the natural warmth of the ground4 ,but as the cold of the ,permian yielded to a genial climate and rich vegetation in the course of the ,triassic1 the reptiles entered upon their memorable development4 ,the amphibia were now definitely ousted from their position of dominance4 ,the increase of the waters had at first favoured them1 and we find more than twenty genera1 and some very large individuals1 of the amphibia in the ,triassic4 ,one of them1 the ,mastodonsaurus1 had a head three feet long and two feet wide4 ,but the spread of the reptiles checked them1 and they shrank rapidly into the poor and defenceless tribe which we find them in nature to-day4 ,to follow the prolific expansion of the reptiles in the semi-tropical conditions of the ,jurassic age is a task that even the highest authorities approach with great diffidence4 ,science is not yet wholly agreed in the classification of the vast numbers of remains which the ,mesozoic rocks have yielded1 and the affinities of the various groups are very uncertain4 ,we cannot be content1 however1 merely to throw on the screen1 as it were1 a few of the more quaint and monstrous types out of the teeming ,mesozoic population1 and describe their proportions and peculiarities4 ,they fall into natural and intelligible groups or orders1 and their features are closely related to the differing regions of the ,jurassic world4 ,while1 therefore1 we must abstain from drawing up settled genealogical trees1 we may1 as we review in succession the monsters of the land1 the waters1 and the air1 glance at the most recent and substantial conjectures of scientific men as to their origin and connections4 ,the ,deinosaurs 7or terrible reptiles71 the monarchs of the land and the swamps1 are the central and outstanding family of the ,mesozoic reptiles4 ,as the name implies1 this group includes most of the colossal animals1 such as the ,diplodocus1 which the illustrated magazine has made familiar to most people4 ,fortunately the assiduous research of ,american geologists and their great skill and patience in restoring the dead forms enable us to form a very fair picture of this family of medieval giants and its remarkable ramifications4 99 99 ,see1 besides the usual authorities1 a valuable paper by ,dr4 ,r4 ,s4 ,lull1 ,dinosaurian ,distribution 7#aiaj74 ,the ,diapsid reptiles of the ,permian had evolved a group with horny1 parrot-like beaks1 the ,rhyncocephalia 7or beak-headed reptiles71 of which the tuatara of ,new ,zealand is a lingering representative4 ,new ,zealand seems to have been cut off from the southern continent at the close of the ,permian or beginning of the ,triassic1 and so preserved for us that very interesting relic of ,permian life4 ,from some primitive level of this group1 it is generally believed1 the great ,deinosaurs arose4 ,two different orders seem to have arisen independently1 or diverged rapidly from each other1 in different parts of the world4 ,one group seems to have evolved on the lost ,atlantis1 the land between ,western ,europe and ,america1 whence they spread westward to ,america1 eastward over ,europe1 and southward to the continent which still united ,africa and ,australia4 ,we find their remains in all these regions4 ,another stock is believed to have arisen in ,america4 ,both these groups seem to have been more or less biped1 rearing themselves on large and powerful hind limbs1 and 7in some cases1 at least7 probably using their small front limbs to hold or grasp their food4 ,the first group was carnivorous1 the second herbivorous2 and1 as the reptiles of the first group had four or five toes on each foot1 they are known as the ,theropods 7or beast-footed 71 while those of the second order1 which had three toes1 are called the ,ornithopods 7or bird-footed74 ,each of them then gave birth to an order of quadrupeds4 ,in the spreading waters and rich swamps of the later ,triassic some of the ,theropods were attracted to return to an amphibious life1 and became the vast1 sprawling1 ponderous ,sauropods1 the giants in a world of giants4 ,on the other hand1 a branch of the vegetarian ,ornithopods developed heavy armour1 for defence against the carnivores1 and became1 under the burden of its weight1 the quadrupedal and monstrous ,stegosauria and ,ceratopsia4 ,taking this instructive general view of the spread of the ,deinosaurs as the best interpretation of the material we have1 we may now glance at each of the orders in succession4 ,the ,theropods varied considerably in size and agility4 ,the ,compsognathus was a small1 active1 rabbit-like creature1 standing about two feet high on its hind limbs1 while the ,megalosaurs stretched to a length of thirty feet1 and had huge jaws armed with rows of formidable teeth4 ,the ,ceratosaur1 a seventeen-foot-long reptile1 had hollow bones1 and we find this combination of lightness and strength in several members of the group4 ,in many respects the group points more or less significantly toward the birds4 ,the brain is relatively large1 the neck long1 and the fore limbs might be used for grasping1 but had apparently ceased to serve as legs4 ,many of the ,theropods were evidently leaping reptiles1 like colossal kangaroos1 twenty or more feet in length when they were erect4 ,it is the general belief that the bird began its career as a leaping reptile1 and the feathers1 or expanded scales1 on the front limbs helped at first to increase the leap4 ,some recent authorities hold1 however1 that the ancestor of the bird was an arboreal reptile4 ,to the order of the ,sauropods belong most of the monsters whose discovery has attracted general attention in recent years4 ,feeding on vegetal matter in the luscious swamps1 and having their vast bulk lightened by their aquatic life1 they soon attained the most formidable proportions4 ,the admirer of the enormous skeleton of ,diplodocus 7which ran to eighty feet7 in the ,british ,museum must wonder how even such massive limbs could sustain the mountain of flesh that must have covered those bones4 ,it probably did not walk so firmly as the skeleton suggests1 but sprawled in the swamps or swam like a hippopotamus4 ,but the ,diplodocus is neither the largest nor heaviest of its family4 ,the ,brontosaur1 though only sixty feet long1 probably weighed twenty tons4 ,we have its footprints in the rocks to-day1 each impression measuring about a square yard4 ,generally1 it is the huge thigh-bones of these monsters that have survived1 and give us an idea of their size4 ,the largest living elephant has a femur scarcely four feet long1 but the femur of the ,atlantosaur measures more than seventy inches1 and the femur of the ,brachiosaur more than eighty4 ,many of these ,deinosaurs must have measured more than a hundred feet from the tip of the snout to the end of the tail1 and stood about thirty feet high from the ground4 ,the ,european ,sauropods did not1 apparently1 reach the size of their ,american cousins--so early did the inferiority of ,europe begin--but our ,ceteosaur seems to have been about fifty feet long and ten feet in height4 ,its thigh-bone was sixty-four inches long and twenty-seven inches in circumference at the shaft4 ,and in this order of reptiles1 it must be remembered1 the bones are solid4 ,to complete the picture of the ,sauropods1 we must add that the whole class is characterised by the extraordinary smallness of the brain4 ,the twenty-ton ,brontosaur had a brain no larger than that of a new-born human infant4 ,quite commonly the brain of one of these enormous animals is no larger than a man's fist4 ,it is true that1 as far as the muscular and sexual labour was concerned1 the brain was supplemented by a great enlargement of the spinal cord in the sacral region 7at the top of the thighs74 ,this inferior brain was from ten to twenty times as large as the brain in the skull4 ,it would1 however1 be fully occupied with the movement of the monstrous limbs and tail1 and the sex-life1 and does not add in the least to the mental power of the ,sauropods4 ,they were stupid1 sluggish1 unwieldy creatures1 swollen parasites upon a luxuriant vegetation1 and we shall easily understand their disappearance at the end of the ,mesozoic ,era1 when the age of brawn will yield to an age of brain4 ,the next order of the ,deinosaurs is that of the biped vegetarians1 the ,ornithopods1 which gradually became heavily armoured and quadrupedal4 ,the familiar ,iguanodon is the chief representative of this order in ,europe4 ,walking on its three-toed hind limbs1 its head would be fourteen or fifteen feet from the ground4 ,the front part of its jaws was toothless and covered with horn4 ,it had1 in fact1 a kind of beak1 and it also approached the primitive bird in the structure of its pelvis and in having five toes on its small front limbs4 ,some of the ,ornithopods1 such as the ,laosaur1 were small 7three or four feet in height7 and active1 but many of the ,american specimens attained a great size4 ,the ,camptosaur1 which was closely related to the ,iguanodon in structure1 was thirty feet from the snout to the end of the tail1 and the head probably stood eighteen feet from the ground4 ,one of the last great representatives of the group in ,america1 the ,trachodon1 about thirty feet in length1 had a most extraordinary head4 ,it was about three and a half feet in length1 and had no less than #bjjj teeth lining the mouth cavity4 ,it is conjectured that it fed on vegetation containing a large proportion of silica4 ,in the course of the ,jurassic1 as we saw1 a branch of these biped1 bird-footed vegetarians developed heavy armour1 and returned to the quadrupedal habit4 ,we find them both in ,europe and ,america1 and must suppose that the highway across the ,north ,atlantic still existed4 ,the ,stegosaur is one of the most singular and most familiar representatives of the group in the ,jurassic4 ,it ran to a length of thirty feet1 and had a row of bony plates1 from two to three feet in height1 standing up vertically along the ridge of its back1 while its tail was armed with formidable spikes4 ,the ,scleidosaur1 an earlier and smaller 7twelve-foot7 specimen1 also had spines and bony plates to protect it4 ,the ,polacanthus and ,ankylosaur developed a most effective armour-plating over the rear4 ,as we regard their powerful armour1 we seem to see the fierce-toothed ,theropods springing from the rear upon the poor-mouthed vegetarians4 ,the carnivores selected the vegetarians1 and fitted them to survive4 ,before the end of the ,mesozoic1 in fact1 the ,ornithopods became aggressive as well as armoured4 ,the ,triceratops had not only an enormous skull with a great ridged collar round the neck1 but a sharp beak1 a stout horn on the nose1 and two large and sharp horns on the top of the head4 ,we will see something later of the development of horns4 ,the skulls of members of the ,ceratops family sometimes measured eight feet from the snout to the ridge of the collar4 ,they were1 however1 sluggish and stupid monsters1 with smaller brains even than the ,sauropods4 ,such1 in broad outline1 was the singular and powerful family of the ,mesozoic ,deinosaurs4 ,further geological research in all parts of the world will1 no doubt1 increase our knowledge of them1 until we can fully understand them as a great family throwing out special branches to meet the different conditions of the crowded ,jurassic age4 ,even now they afford a most interesting page in the story of evolution1 and their total disappearance from the face of the earth in the next geological period will not be unintelligible4 ,we turn from them to the remaining orders of the ,jurassic reptiles4 ,in the popular mind1 perhaps1 the ,ichthyosaur and ,plesiosaur are the typical representatives of that extinct race4 ,the two animals1 however1 belong to very different branches of the reptile world1 and are by no means the most formidable of the ,mesozoic reptiles4 ,many orders of the land reptiles sent a branch into the waters in an age which1 we saw1 was predominantly one of water-surface4 ,the ,ichthyosauria 7fish-reptiles7 and ,thalattosauria 7sea-reptiles7 invaded the waters at their first expansion in the later ,triassic4 ,the latter groups soon became extinct1 but the former continued for some millions of years1 and became remarkably adapted to marine life1 like the whale at a later period4 ,the ,ichthyosaur of the ,jurassic is a remarkably fish-like animal4 ,its long tapering frame--sometimes forty feet in length1 but generally less than half that length--ends in a dip of the vertebral column and an expansion of the flesh into a strong tail-fin4 ,the terminal bones of the limbs depart more and more from the quadruped type1 until at last they are merely rows of circular bony plates embedded in the broad paddle into which the limb has been converted4 ,the head is drawn out1 sometimes to a length of five feet1 and the long narrow jaws are set with two formidable rows of teeth2 one specimen has about two hundred teeth4 ,in some genera the teeth degenerate in the course of time1 but this merely indicates a change of diet4 ,one fossilised ,ichthyosaur of the weaker-toothed variety has been found with the remains of two hundred ,belemnites in its stomach4 ,it is a flash of light on the fierce struggle and carnage which some recent writers have vainly striven to attenuate4 ,the eyes1 again1 which may in the larger animals be fifteen inches in diameter1 are protected by a circle of radiating bony plates4 ,in fine1 the discovery of young developed skeletons inside the adult frames has taught us that the ,ichthgosaur had become viviparous1 like the mammal4 ,cutting its last connection with the land1 on which it originated it ceased to lay eggs1 and developed the young within its body4 ,the ,ichthyosaur came of the reptile group which we have called the ,diapsids4 ,the ,plesiosaur seems to belong to the ,synapsid branch4 ,in the earlier ,mesozoic we find partially aquatic representatives of the line1 like the ,nothosaur1 and in the later ,plesiosaur the adaptation to a marine life is complete4 ,the skin has lost its scales1 and the front limbs are developed into powerful paddles1 sometimes six feet in length4 ,the neck is drawn out until1 in some specimens1 it is found to consist of seventy-six vertebrae3 the longest neck in the animal world4 ,it is now doubted1 however1 if the neck was very flexible1 and1 as the jaws were imperfectly joined1 the common picture of the ,plesiosaur darting its snake-like neck in all directions to seize its prey is probably wrong4 ,it seems to have lived on small food1 and been itself a rich diet to the larger carnivores4 ,we find it in all the seas of the ,mesozoic world1 varying in length from six to forty feet1 but it is one of the sluggish and unwieldy forms that are destined to perish in the coming crisis4 ,the last1 and perhaps the most interesting1 of the doomed monsters of the ,mesozoic was the ,pterosaur1 or flying reptile4 ,it is not surprising that in the fierce struggle which is reflected in the arms and armour of the great reptiles1 a branch of the family escaped into the upper region4 ,we have seen that there were leaping reptiles with hollow bones1 and although the intermediate forms are missing1 there is little doubt that the ,pterosaur developed from one or more of these leaping ,deinosaurs4 ,as it is at first small1 when it appears in the early ,jurassic--it is disputed in the late ,triassic--it probably came from a small and agile ,deinosaur1 hunted by the carnivores1 which relied on its leaping powers for escape4 ,a flapperlike broadening of the fore limbs would help to lengthen the leap1 and we must suppose that this membrane increased until the animal could sail through the air1 like the flying-fish1 and eventually sustain its weight in the air4 ,the wing is1 of course1 not a feathery frame1 as in the bird1 but a special skin spreading between the fore limb and the side of the body4 ,in the bat this skin is supported by four elongated fingers of the hand1 but in the ,pterosaur the fifth 7or fourth7 finger alone--which is enormously elongated and strengthened--forms its outer frame4 ,it is as if1 in flying experiments1 a man were to have a web of silk stretching from his arm and an extension of his little finger to the side of his body4 ,from the small early specimens in the early ,jurassic the flying reptiles grow larger and larger until the time of their extinction in the stresses of the ,chalk upheaval4 ,small ,pterosaurs continue throughout the period1 but from these bat-like creatures we rise until we come to such dragons as the ,american ,pteranodon1 with a stretch of twenty-two feet between its extended wings and jaws about four feet long4 ,there were long-tailed ,pterosaurs 7,ramphorhyncus71 sometimes with a rudder-like expansion of the end of the tail1 and short-tailed ,pterosaurs 7,pterodactyl71 with compact bodies and keeled breasts1 like the bird4 ,in the earlier part of the period they all have the heavy jaws and numerous teeth of the reptile1 with four or five well-developed fingers on the front limbs4 ,in the course of time they lose the teeth--an advantage in the distribution of the weight of the body while flying--and develop horny beaks4 ,in the gradual shaping of the breast-bone and head1 also1 they illustrate the evolution of the bird-form4 ,but the birds were meantime developing from a quite different stock1 and would replace the ,pterosaurs at the first change in the environment4 ,there is ground for thinking that these flying reptiles were warm-blooded like the birds4 ,their hollow bones seem to point to the effective breathing of a warm-blooded animal1 and the great vitality they would need in flying points toward the same conclusion4 ,their brain1 too1 approached that of the bird1 and was much superior to that of the other reptiles4 ,but they had no warm coats to retain their heat1 no clavicle to give strength to the wing machinery1 and1 especially in the later period1 they became very weak in the hind limbs 7and therefore weak or slow in starting their flight74 ,the coming selection will therefore dismiss them from the scene1 with the ,deinosaurs and ,ammonites1 and retain the better organised bird as the lord of the air4 ,there remain one or two groups of the ,mesozoic reptiles which are still represented in nature4 ,the turtle-group 7,chelonia7 makes its appearance in the ,triassic and thrives in the ,jurassic4 ,its members are extinct and primitive forms of the thick-shelled reptiles1 but true turtles1 both of marine and fresh water1 abound before the close of the ,mesozoic4 ,the sea-turtles attain an enormous size4 ,archelon1 one of the primitive types1 measured about twelve feet across the shell4 ,another was thirteen feet long and fifteen feet from one outstretched flipper to the other4 ,in the ,chalk period they form more than a third of the reptile remains in some regions4 ,they are extremely interesting in that they show1 to some extent1 the evolution of their characteristic shell4 ,in some of the larger specimens the ribs have not yet entirely coalesced4 ,the ,crocodilians also appear in the later ,triassic1 abound in the ,jurassic1 and give way before the later types1 the true ,crocodiles1 in the ,cretaceous4 ,they were marine animals with naked skin1 a head and neck something like that of the ,ichthyosaur1 and paddles like those of the ,plesiosaur4 ,their back limbs1 however1 were not much changed after their adaptation to life in the sea1 and it is concluded that they visited the land to lay their eggs4 ,the ,teleosaur was a formidable narrow-spouted reptile1 somewhat resembling the crocodiles of the ,ganges in the external form of the jaws4 ,the modern crocodiles1 which replaced this ancient race of sea-crocodiles1 have a great advantage over them in the fact that their nostrils open into the mouth in its lower depths4 ,they can therefore close their teeth on their prey under water and breathe through the nose4 ,snakes are not found until the close of the ,mesozoic1 and do not figure in its characteristic reptile population4 ,we will consider them later4 ,but there was a large group of reptiles in the later ,mesozoic seas which more or less correspond to the legendary idea of a sea-serpent4 ,these ,dolichosaurs 7long reptiles7 appear at the beginning of the ,chalk period1 and develop into a group1 the ,mososaurians1 which must have added considerably to the terrors of the shore-waters4 ,their slender scale-covered bodies were commonly twenty to thirty feet in length4 ,the supreme representative of the order1 the ,mososaur1 of which about forty species are known1 was sometimes seventy-five feet long4 ,it had two pairs of paddles--so that the name of sea-serpent is very imperfectly applicable--and four rows of formidable teeth on the roof of its mouth4 ,like the ,deinosaurs and ,pterosaurs1 the order was doomed to be entirely extinguished after a brief supremacy in its environment4 ,from this short and summary catalogue the reader will be able to form some conception of the living inhabitants of the ,mesozoic world4 ,it is assuredly the ,age of ,reptiles4 ,worms1 snails1 and spiders were1 we may assume1 abundant enough1 and a great variety of insects flitted from tree to tree or sheltered in the fern brakes4 ,but the characteristic life1 in water and on land1 was the vast and diversified family of the reptiles4 ,in the western and the eastern continent1 and along the narrowing bridge that still united them1 in the northern hemisphere and the southern1 and along every ridge of land that connected them1 these sluggish but formidable monsters filled the stage4 ,every conceivable device in the way of arms and armour1 brute strength and means of escape1 seemed to be adopted in their development1 as if they were the final and indestructible outcome of the life-principle4 ,and within a single geological period the overwhelming majority of them1 especially the larger and more formidable of them1 were ruthlessly slain1 leaving not a single descendant on the earth4 ,let us see what types of animals were thus preferred to them in the next great application of selective processes4 ,,chapter ,,xiii4 ,,the ,,bird ,,and ,,the ,,mammal ,in one of his finest stories1 ,sur ,la ,pierre ,blanche1 ,anatole ,france has imagined a group of ,roman patricians discussing the future of their ,empire4 ,the ,christians1 who are about to rise to power on their ruin1 they dismiss with amiable indifference as one of the little passing eccentricities of the religious life of their time4 ,they have not the dimmest prevision1 even as the dream of a possibility1 that in a century or two the ,empire of ,rome will lie in the dust1 and the cross will tower above all its cities from ,york to ,jerusalem4 ,if we might for a moment endow the animals of the ,mesozoic world with ,a,esopian wisdom1 we could imagine some such discussion taking place between a group of ,deinosaur patricians4 ,they would reflect with pride on the unshakable empire of the reptiles1 and perhaps glance with disdain at two types of animals which hid in the recesses or fled to the hills of the ,jurassic world4 ,and before another era of the earth's story opened1 the reptile race would be dethroned1 and these hunted and despised and feeble eccentricities of ,mesozoic life would become the masters of the globe4 ,these two types of organisms were the bird and the mammal4 ,both existed in the ,jurassic1 and the mammals at least had many representatives in the ,triassic4 ,in other words1 they existed1 with all their higher organisation1 during several million years without attaining power4 ,the mammals remained1 during at least #c1jjj1jjj years1 a small and obscure caste1 immensely overshadowed by the small-brained reptiles4 ,the birds1 while making more progress1 apparently1 than the mammals1 were far outnumbered by the flying reptiles until the last part of the ,mesozoic4 ,then there was another momentous turn of the wheel of fate1 and they emerged from their obscurity to assume the lordship of the globe4 ,in earlier years1 when some serious hesitation was felt by many to accept the new doctrine of evolution1 a grave difficulty was found in the circumstance that new types--not merely new species and new genera1 but new orders and even sub-classes--appeared in the geological record quite suddenly4 ,was it not a singular coincidence that in ,,all cases the intermediate organisms between one type and another should have wholly escaped preservation8 ,the difficulty was generally due to an imperfect acquaintance with the conditions of the problem4 ,the fossil population of a period is only that fraction of its living population which happened to be buried in a certain kind of deposit under water of a certain depth4 ,we shall read later of insects being preserved in resin 7amber71 and we have animals 7and even bacteria7 preserved in trees from the ,coal-forests4 ,generally speaking1 however1 the earth has buried only a very minute fraction of its land-population4 ,moreover1 only a fraction of the earth's cemeteries have yet been opened4 ,when we further reflect that the new type of organism1 when it first appears1 is a small and local group1 we see what the chances are of our finding specimens of it in a few scattered pages of a very fragmentary record of the earth's life4 ,we shall see that we have discovered only about ten skeletons or fragments of skeletons of the men who lived on the earth before the ,neolithic period2 a stretch of some hundreds of thousands of years1 recorded in the upper strata of the earth4 ,whatever serious difficulty there ever was in this scantiness of intermediate types is amply met by the fact that every fresh decade of search in the geological tombs brings some to light4 ,we have seen many instances of this--the seed-bearing ferns and flower-bearing cycads1 for example1 found in the last decade--and will see others4 ,but one of the most remarkable cases of the kind now claims our attention4 ,the bird was probably evolved in the late ,triassic or early ,jurassic4 ,it appears in abundance1 divided into several genera1 in the ,chalk period4 ,luckily1 two bird-skeletons have been found in the intermediate period1 the ,jurassic1 and they are of the intermediate type1 between the reptile and the bird1 which the theory of evolution would suggest4 ,but for the fortunate accident of these two birds being embedded in an ancient ,bavarian mud-layer1 which happened to be opened1 for commercial purposes1 in the second half of the nineteenth century1 critics of evolution--if there still were any in the world of science--might be repeating to-day that the transition from the reptile to the bird was unthinkable in theory and unproven in fact4 ,the features of the ,archaeopteryx 7primitive bird7 have been described so often1 and such excellent pictorial restorations of its appearance may now be seen1 that we may deal with it briefly4 ,we have in it a most instructive combination of the characters of the bird and the reptile4 ,the feathers alone1 the imprint of which is excellently preserved in the fine limestone1 would indicate its bird nature1 but other anatomical distinctions are clearly seen in it4 ,there is1 says ,dr4 ,woodward1 a typical bird's 'merrythought' between the wings1 and the hind leg is exactly that of a perching bird4 ,in other words1 it has the shoulder-girdle and four-toed foot1 as well as the feathers1 of a bird4 ,on the other hand1 it has a long tail 7instead of a terminal tuft of feathers as in the bird7 consisting of twenty-one vertebrae1 with the feathers springing in pairs from either side2 it has biconcave vertebrae1 like the fishes1 amphibia1 and reptiles2 it has teeth in its jaws2 and it has three complete fingers1 free and clawed1 on its front limbs4 ,as in the living ,peripatus1 therefore1 we have here a very valuable connecting link between two very different types of organisms4 ,it is clear that one of the smaller reptiles--the ,archaeopteryx is between a pigeon and a crow in size--of the ,triassic period was the ancestor of the birds4 ,its most conspicuous distinction was that it developed a coat of feathers4 ,a more important difference between the bird and the reptile is that the heart of the bird is completely divided into four chambers1 but1 as we saw1 this probably occurred also in the other flying reptiles4 ,it may be said to be almost a condition of the greater energy of a flying animal4 ,when the heart has four complete chambers1 the carbonised blood from the tissues of the body can be conveyed direct to the lungs for purification1 and the aerated blood taken direct to the tissues1 without any mingling of the two4 ,in the mud-fish and amphibian1 we saw1 the heart has two chambers 7auricles7 above1 but one 7ventricle7 below1 in which the pure and impure blood mingle4 ,in the reptiles a partition begins to form in the lower chamber4 ,in the turtle it is so nearly complete that the venous and the arterial blood are fairly separated2 in the crocodile it is quite complete1 though the arteries are imperfectly arranged4 ,thus the four-chambered heart of the bird and mammal is not a sudden and inexplicable development4 ,its advantage is enormous in a cold climate4 ,the purer supply of blood increases the combustion in the tissues1 and the animal maintains its temperature and vitality when the surrounding air falls in temperature4 ,it ceases to be cold-blooded4 ,but the bird secures a further advantage1 and here it outstrips the flying reptile4 ,the naked skin of the ,pterosaur would allow the heat to escape so freely when the atmosphere cooled that a great strain would be laid on its vitality4 ,a man lessens the demand on his vitality in cold regions by wearing clothing4 ,the bird somehow obtained clothing1 in the shape of a coat of feathers1 and had more vitality to spare for life-purposes in a falling temperature4 ,the reptile is strictly limited to one region1 the bird can pass from region to region as food becomes scarce4 ,the question of the origin of the feathers can be discussed only from the speculative point of view1 as they are fully developed in the ,archaeopteryx1 and there is no approach toward them in any other living or fossil organism4 ,but a long discussion of the problem has convinced scientific men that the feathers are evolved from the scales of the reptile ancestor4 ,the analogy between the shedding of the coat in a snake and the moulting of a bird is not uninstructive4 ,in both cases the outer skin or epidermis is shedding an old growth1 to be replaced by a new one4 ,the covering or horny part of the scale and the feather are alike growths from the epidermis1 and the initial stages of the growth have certain analogies4 ,but beyond this general conviction that the feather is a development of the scale1 we cannot proceed with any confidence4 ,nor need we linger in attempting to trace the gradual modification of the skeleton1 owing to the material change in habits4 ,the horny beak and the reduction of the toes are features we have already encountered in the reptile1 and the modification of the pelvis1 breast-bone1 and clavicle are a natural outcome of flight4 ,in the ,chalk period we find a large number of bird remains1 of about thirty different species1 and in some respects they resume the story of the evolution of the bird4 ,they are widely removed from our modern types of birds1 and still have teeth in the jaws4 ,they are of two leading types1 of which the ,ichthyornis and ,hesperornis are the standard specimens4 ,the ,ichthyornis was a small1 tern-like bird with the power of flight strongly developed1 as we may gather from the frame of its wings and the keel-shaped structure of its breast-bone4 ,its legs and feet were small and slender1 and its long1 slender jaws had about twenty teeth on each side at the bottom4 ,no modern bird has teeth2 though the fact that in some modern species we find the teeth appearing in a rudimentary form is another illustration of the law that animals tend to reproduce ancestral features in their development4 ,a more reptilian character in the ,ichthyornis group is the fact that1 unlike any modern bird1 but like their reptile ancestors1 they had biconcave vertebrae4 ,the brain was relatively poor4 ,we are still dealing with a type intermediate in some respects between the reptile and the modern bird4 ,the gannets1 cormorants1 and pelicans are believed to descend from some branch of this group4 ,the other group of ,cretaceous birds1 of the ,hesperornis type1 show an actual degeneration of the power of flight through adaptation to an environment in which it was not needed1 as happened1 later1 in the kiwi of ,new ,zealand1 and is happening in the case of the barn-yard fowl4 ,these birds had become divers4 ,their wings had shrunk into an abortive bone1 while their powerful legs had been peculiarly fitted for diving4 ,they stood out at right angles to the body1 and seem to have developed paddles4 ,the whole frame suggests that the bird could neither walk nor fly1 but was an excellent diver and swimmer4 ,not infrequently as large as an ostrich 7five to six feet high71 with teeth set in grooves in its jaws1 and the jaws themselves joined as in the snake1 with a great capacity of bolting its prey1 the ,hesperornis would become an important element in the life of the fishes4 ,the wing-fingers have gone1 and the tail is much shortened1 but the grooved teeth and loosely jointed jaws still point back to a reptilian ancestry4 ,these are the only remains of bird-life that we find in the ,mesozoic rocks4 ,admirably as they illustrate the evolution of the bird from the reptile1 they seem to represent a relatively poor development and spread of one of the most advanced organisms of the time4 ,it must be understood that1 as we shall see1 the latter part of the ,chalk period does not belong to the depression1 the age of genial climate1 which ,i call the ,middle ,ages of the earth1 but to the revolutionary period which closes it4 ,we may say that the bird1 for all its advances in organisation1 remains obscure and unprosperous as long as the ,age of ,reptiles lasts4 ,it awaits the next massive uplift of the land and lowering of temperature4 ,in an earlier chapter ,i hinted that the bird and the mammal may have been the supreme outcomes of the series of disturbances which closed the ,primary ,epoch and devastated its primitive population4 ,as far as the bird is concerned1 this may be doubted on the ground that it first appears in the upper or later ,jurassic1 and is even then still largely reptilian in character4 ,we must remember1 however1 that the elevation of the land and the cold climate lasted until the second part of the ,triassic1 and it is generally agreed that the bird may have been evolved in the ,triassic4 ,its slow progress after that date is not difficult to understand4 ,the advantage of a four-chambered heart and warm coat would be greatly reduced when the climate became warmer4 ,the stimulus to advance would relax4 ,the change from a coat of scales to a coat of feathers obviously means adaptation to a low temperature1 and there is nothing to prevent us from locating it in the ,triassic1 and indeed no later known period of cold in which to place it4 ,it is much clearer that the mammals were a product of the ,permian revolution4 ,they not only abound throughout the ,jurassic1 in which they are distributed in more than thirty genera1 but they may be traced into the ,triassic itself4 ,both in ,north ,america and ,europe we find the teeth and fragments of the jaws of small animals which are generally recognised as mammals4 ,we cannot1 of course1 from a few bones deduce that there already1 in the ,triassic1 existed an animal with a fully developed coat of fur and an apparatus1 however crude1 in the breast for suckling the young4 ,but these bones so closely resemble the bones of the lowest mammals of to-day that this seems highly probable4 ,in the latter part of the long period of cold it seems that some reptile exchanged its scales for tufts of hair1 developed a four-chambered heart1 and began the practice of nourishing the young from its own blood which would give the mammals so great an ascendancy in a colder world4 ,nor can we complain of any lack of evidence connecting the mammal with a reptile ancestor4 ,the earliest remains we find are of such a nature that the highest authorities are still at variance as to whether they should be classed as reptilian or mammalian4 ,a skull and a fore limb from the ,triassic of ,south ,africa 7,tritylodon and ,theriodesmus7 are in this predicament4 ,it will be remembered that we divided the primitive reptiles of the ,permian period into two great groups1 the ,diapsids and ,synapsids 7or ,theromorphs74 ,the former group have spread into the great reptiles of the ,jurassic2 the latter have remained in comparative obscurity4 ,one branch of these ,theromorph reptiles approach the mammals so closely in the formation of the teeth that they have received the name of the ,theriodonts1 or beast-toothed reptiles4 ,their teeth are1 like those of the mammals1 divided into incisors1 canines 7sometimes several inches long71 and molars2 and the molars have in some cases developed cusps or tubercles4 ,as the earlier remains of mammals which we find are generally teeth and jaws1 the resemblance of the two groups leads to some confusion in classifying them1 but from our point of view it is not unwelcome4 ,it narrows the supposed gulf between the reptile and the mammal1 and suggests very forcibly the particular branch of the reptiles to which we may look for the ancestry of the mammals4 ,we cannot say that these ,theriodont reptiles were the ancestors of the mammals4 ,but we may conclude with some confidence that they bring us near to the point of origin1 and probably had at least a common ancestor with the mammals4 ,the distribution of the ,theriodonts suggests a further idea of interest in regard to the origin of the mammals4 ,it would be improper to press this view in the present state of our knowledge1 yet it offers a plausible theory of the origin of the mammals4 ,the ,theriodonts seem to have been generally confined to the southern continent1 ,gondwana ,land 7,brazil to ,australia71 of which an area survives in ,south ,africa4 ,it is there also that we find the early disputed remains of mammals4 ,now we saw that1 during the ,permian1 ,gondwana ,land was heavily coated with ice1 and it seems natural to suppose that the severe cold which the glacial fields would give to the whole southern continent was the great agency in the evolution of the highest type of the animal world4 ,from this southern land the new-born mammals spread northward and eastward with great rapidity4 ,fitted as they were to withstand the rigorous conditions which held the reptiles and amphibia in check1 they seemed destined to attain at once the domination of the earth4 ,then1 as we saw1 the land was revelled once more until its surface broke into a fresh semi-tropical luxuriance1 and the ,deinosaurs advanced to their triumph4 ,the mammals shrank into a meagre and insignificant population1 a scattered tribe of small insect-eating animals1 awaiting a fresh refrigeration of the globe4 ,the remains of these interesting early mammals1 restricted1 as they generally are1 to jaws and teeth and a few other bones that cannot in themselves be too confidently distinguished from those of certain reptiles1 may seem insufficient to enable us to form a picture of their living forms4 ,in this1 however1 we receive a singular and fortunate assistance4 ,some of them are found living in nature to-day1 and their distinctly reptilian features would1 even if no fossil remains were in existence1 convince us of the evolution of the mammals4 ,the southern continent on which we suppose the mammals to have originated had its eastern termination in ,australia4 ,new ,zealand seems to have been detached early in the ,mesozoic1 and was never reached by the mammals4 ,tasmania was still part of the ,australian continent4 ,to this extreme east of the southern continent the early mammals spread1 and then1 during either the ,jurassic or the ,cretaceous1 the sea completed its inroad1 and severed ,australia permanently from the rest of the earth4 ,the obvious result of this was to shelter the primitive life of ,australia from invasion by higher types1 especially from the great carnivorous mammals which would presently develop4 ,australia became1 in other words1 a protected area1 in which primitive types of life were preserved from destruction1 and were at the same time sheltered from those stimulating agencies which compelled the rest of the world to advance4 ,advance ,australia is the fitting motto of the present human inhabitants of that promising country2 but the standard of progress has been set up in a land which had remained during millions of years the ,chinese ,empire of the living world4 ,australia is a fragment of the ,middle ,ages of the earth1 a province fenced round by nature at least three million years ago and preserving1 amongst its many invaluable types of life1 representatives of that primitive mammal population which we are seeking to understand4 ,it is now well known that the ,duckbill or ,platypus 7,ornithorhyncus7 and the ,spiny ,anteater 7,echidna7 of ,australia and ,tasmania--with one representative of the latter in ,new ,guinea1 which seems to have been still connected--are semi-reptilian survivors of the first animals to suckle their young4 ,like the reptiles they lay tough-coated eggs and have a single outlet for the excreta1 and they have a reptilian arrangement of the bones of the shoulder-girdle2 like the mammals1 they have a coat of hair and a four-chambered heart1 and they suckle the young4 ,even in their mammalian features they are1 as the careful research of ,australian zoologists has shown1 of a transitional type4 ,they are warm-blooded1 but their temperature is much lower than that of other mammals1 and varies appreciably with the temperature of their surroundings4 99 ,their apparatus for suckling the young is primitive4 ,there are no teats1 and the milk is forced by the mother through simple channels upon the breast1 from which it is licked by the young4 ,the ,anteater develops her eggs in a pouch4 ,they illustrate a very early stage in the development of a mammal from a reptile2 and one is almost tempted to see in their timorous burrowing habits a reminiscence of the impotence of the early mammals after their premature appearance in the ,triassic4 99 ,see ,lucas and ,le ,soulf's ,animals of ,australia1 #aiji4 ,the next level of mammal life1 the highest level that it attains in ,australia 7apart from recent invasions71 is the ,marsupial4 ,the pouched animals 7kangaroo1 wallaby1 etc47 are the princes of pre-human life in ,australia1 and represent the highest point that life had reached when that continent was cut off from the rest of the world4 ,a few words on the real significance of the pouch1 from which they derive their name1 will suffice to explain their position in the story of evolution4 ,among the reptiles the task of the mother ends1 as a rule1 with the laying of the egg4 ,one or two modern reptiles hatch the eggs1 or show some concern for them1 but the characteristic of the reptile is to discharge its eggs upon the warm earth and trouble no further about its young4 ,it is a reminiscence of the warm primitive earth4 ,the bird and mammal1 born of the cooling of the earth1 exhibit the beginning of that link between mother and offspring which will prove so important an element in the higher and later life of the globe4 ,the bird assists the development of the eggs with the heat of her own body1 and feeds the young4 ,the mammal develops the young within the body1 and then feeds them at the breast4 ,but there is a gradual advance in this process4 ,the ,duckbill lays its eggs just like the reptile1 but provides a warm nest for them at the bottom of its burrow4 ,the ,anteater develops a temporary pouch in its body1 when it lays an egg1 and hatches the egg in it4 ,the ,marsupial retains the egg in its womb until the young is advanced in development1 then transfers the young to the pouch1 and forces milk into its mouth from its breasts4 ,the real reason for this is that the ,marsupial falls far short of the higher mammals in the structure of the womb1 and cannot fully develop its young therein4 ,it has no placenta1 or arrangement by which the blood-vessels of the mother are brought into connection with the blood-vessels of the foetus1 in order to supply it with food until it is fully developed4 ,the ,marsupial1 in fact1 only rises above the reptile in hatching the egg within its own body1 and then suckling the young at the breast4 ,these primitive mammals help us to reconstruct the mammal life of the ,mesozoic ,epoch4 ,the bones that we have are variously described in geological manuals as the remains of ,monotremes1 ,marsupials1 and ,insectivores4 ,many of them1 if not most1 were no doubt insect-eating animals1 but there is no ground for supposing that what are technically known as ,insectivores 7moles and shrews7 existed in the ,mesozoic4 ,on the other hand1 the lower jaw of the ,marsupial is characterised by a peculiar hooklike process1 and this is commonly found in ,mesozoic jaws4 ,this circumstance1 and the witness of ,australia1 permit us1 perhaps1 to regard the ,jurassic mammals as predominantly marsupial4 ,it is more difficult to identify ,monotreme remains1 but the fact that ,monotremes have survived to this day in ,australia1 and the resemblance of some of the ,mesozoic teeth to those found for a time in the young ,duckbill justify us in assuming that a part of the ,mesozoic mammals correspond to the modern ,monotremes4 ,not single specimen of any higher1 or placental1 mammal has yet been found in the whole ,mesozoic ,era4 ,we must1 however1 beware of simply transferring to the ,mesozoic world the kinds of ,monotremes and ,marsupials which we know in nature to-day4 ,in some of the excellent restorations of ,mesozoic life which are found in recent illustrated literature the early mammal is represented with an external appearance like that of the ,duckbill4 ,this is an error1 as the ,duckbill has been greatly modified in its extremities and mouth-parts by its aquatic and burrowing habits4 ,as we have no complete skeletons of these early mammals we must abstain from picturing their external appearance4 ,it is enough that the living ,monotreme and ,marsupial so finely illustrate the transition from a reptilian to a mammalian form4 ,there may have been types more primitive than the ,duckbill1 and others between the ,duckbill and the ,marsupial4 ,it seems clear1 at least1 that two main branches1 the ,monotremes and ,marsupials1 arose from the primitive mammalian root4 ,whether either of these became in turn the parent of the higher mammals we will inquire later4 ,we must first consider the fresh series of terrestrial disturbances which1 like some gigantic sieve1 weeded out the grosser types of organisms1 and cleared the earth for a rapid and remarkable expansion of these primitive birds and mammals4 ,we have attended only to a few prominent characters in tracing the line of evolution1 but it will be understood that an advance in many organs of the body is implied in these changes4 ,in the lower mammals the diaphragm1 or complete partition between the organs of the breast and those of the abdomen1 is developed4 ,it is not a sudden and mysterious growth1 and its development in the embryo to-day corresponds to the suggestion of its development which the zoologist gathers from the animal series4 ,the ear also is now fully developed4 ,how far the fish has a sense of hearing is not yet fully determined1 but the amphibian certainly has an organ for the perception of waves of sound4 ,parts of the discarded gill-arches are gradually transformed into the three bones of the mammal's internal ear2 just as other parts are converted into mouth cartilages1 and as--it is believed--one of the gill clefts is converted into the ,eustachian tube4 ,in the ,monotreme and ,marsupial the ear-hole begins to be covered with a shell of cartilage2 we have the beginning of the external ear4 ,the jaws1 which are first developed in the fish1 now articulate more perfectly with the skull4 ,fat-glands appear in the skin1 and it is probably from a group of these that the milk-glands are developed4 ,the origin of the hairs is somewhat obscure4 ,they are not thought to be1 like the bird's feathers1 modifications of the reptile's scales1 but to have been evolved from other structures in the skin1 possibly under the protection of the scales4 ,my purpose is1 however1 rather to indicate the general causes of the onward advance of life than to study organs in detail--a vast subject--or construct pedigrees4 ,we therefore pass on to consider the next great stride that is taken by the advancing life of the earth4 ,millions of years of genial climate and rich vegetation have filled the earth with a prolific and enormously varied population4 ,over this population the hand of natural selection is outstretched1 as it were1 and we are about to witness another gigantic removal of older types of life and promotion of those which contain the germs of further advance4 ,as we have already explained1 natural selection is by no means inactive during these intervening periods of warmth4 ,we have seen the ammonites and reptiles1 and even the birds and mammals1 evolve into hundreds of species during the ,jurassic period4 ,the constant evolution of more effective types of carnivores and their spread into new regions1 the continuous changes in the distribution of land and water1 the struggle for food in a growing population1 and a dozen other causes1 are ever at work4 ,but the great and comprehensive changes in the face of the earth which close the eras of the geologist seem to give a deeper and quicker stimulus to its population and result in periods of especially rapid evolution4 ,such a change now closes the ,mesozoic ,era1 and inaugurates the age of flowering plants1 of birds1 and of mammals4 ,,chapter ,,xiv4 ,,in ,,the ,,days ,,of ,,the ,,chalk ,in accordance with the view of the later story of the earth which was expressed on an earlier page1 we now come to the second of the three great revolutions which have quickened the pulse of life on the earth4 ,many men of science resent the use of the word revolution1 and it is not without some danger4 ,it was once thought that the earth was really shaken at times by vast and sudden cataclysms1 which destroyed its entire living population1 so that new kingdoms of plants and animals had to be created4 ,but we have interpreted the word revolution in a very different sense4 ,the series of changes and disturbances to which we give the name extended over a period of hundreds of thousands of years1 and they were themselves1 in some sense1 the creators of new types of organisms4 ,yet they are periods that stand out peculiarly in the comparatively even chronicle of the earth4 ,the ,permian period transformed the face of the earth2 it lifted the low-lying land into a massive relief1 drew mantles of ice over millions of miles of its surface1 set volcanoes belching out fire and fumes in many parts1 stripped it of its great forests1 and slew the overwhelming majority of its animals4 ,on the scale of geological time it may be called a revolution4 ,it must be confessed that the series of disturbances which close the ,secondary and inaugurate the ,tertiary ,era cannot so conveniently be summed up in a single formula4 ,they begin long before the end of the ,mesozoic1 and they continue far into the ,tertiary1 with intervals of ease and tranquillity4 ,there seems to have been no culminating point in the series when the uplifted earth shivered in a mantle of ice and snow4 ,yet ,i propose to retain for this period--beginning early in the ,cretaceous 7,chalk7 period and extending into the ,tertiary--the name of the ,cretaceous ,revolution4 ,i drew a fanciful parallel between the three revolutions which have quickened the earth since the sluggish days of the ,coal-forest and the three revolutionary movements which have changed the life of modern ,europe4 ,it will be remembered that1 whereas the first of these ,european revolutions was a sharp and massive upheaval1 the second consisted in a more scattered and irregular series of disturbances1 spread over the fourth and fifth decades of the nineteenth century2 but they amounted1 in effect1 to a revolution4 ,so it is with the ,cretaceous ,revolution4 ,in effect it corresponds very closely to the ,permian ,revolution4 ,on the physical side it includes a very considerable rise of the land over the greater part of the globe1 and the formation of lofty chains of mountains2 on the botanical side it means the reduction of the rich ,mesozoic flora to a relatively insignificant population1 and the appearance and triumphant spread of the flowering plants1 on the zoological side it witnesses the complete extinction of the ,ammonites1 ,deinosaurs1 and ,pterosaurs1 an immense reduction of the reptile world generally1 and a victorious expansion of the higher insects1 birds1 and mammals2 on the climatic side it provides the first definite evidence of cold zones of the earth and cold seasons of the year1 and seems to represent a long1 if irregular1 period of comparative cold4 ,except1 to some extent1 the last of these points1 there is no difference of opinion1 and therefore1 from the evolutionary point of view1 the ,cretaceous period merits the title of a revolution4 ,all these things were done before the ,tertiary period opened4 ,let us first consider the fundamental and physical aspect of this revolution1 the upheaval of the land4 ,it began about the close of the ,jurassic period4 ,western and ,central ,europe emerged considerably from the warm ,jurassic sea1 which lay on it and had converted it into an archipelago4 ,in ,north-western ,america also there was an emergence of large areas of land1 and the ,sierra and ,cascade ranges of mountains were formed about the same time4 ,for reasons which will appear later we must note carefully this rise of land at the very beginning of the ,cretaceous period4 ,however1 the sea recovered its lost territory1 or compensation for it1 and the middle of the ,cretaceous period witnessed a very considerable extension of the waters over ,america1 ,europe1 and southern ,asia4 ,the thick familiar beds of chalk1 which stretch irregularly from ,ireland to the ,crimea1 and from the south of ,sweden to the south of ,france1 plainly tell of an overlying sea4 ,as is well known1 the chalk consists mainly of the shells or outer frames of minute one-celled creatures 7,thalamophores7 which float in the ocean1 and form a deep ooze at its bottom with their discarded skeletons4 ,what depth this ocean must have been is disputed1 and hardly concerns us4 ,it is clear that it must have taken an enormous period for microscopic shells to form the thick masses of chalk which cover so much of southern and eastern ,england4 ,on the lowest estimates the ,cretaceous period1 which includes the deposit of other strata besides chalk1 lasted about three million years4 ,and as people like to have some idea of the time since these things happened1 ,i may add that1 on the lowest estimate 7which most geologists would at least double71 it is about three million years since the last stretches of the chalk-ocean disappeared from the surface of ,europe4 ,but while our chalk cliffs conjure up a vision of ,england lying deep--at least twenty or thirty fathoms deep--below a warm ocean1 in which gigantic ,ammonites and ,belemnites and sharks ply their deadly trade1 they also remind us of the last phase of the remarkable life of the earth's ,middle ,ages4 ,in the latter part of the ,cretaceous the land rises4 ,the chalk ocean of ,europe is gradually reduced to a series of inland seas1 separated by masses and ridges of land1 and finally to a series of lakes of brackish water4 ,the masses of the ,pyrenees and ,alps begin to rise2 though it will not be until a much later date that they reach anything like their present elevation4 ,in ,america the change is even greater4 ,a vast ridge rises along the whole western front of the continent1 lifting and draining it1 from ,alaska to ,cape ,horn4 ,it is the beginning of the ,rocky ,mountains and the ,andes4 ,even during the ,cretaceous period there had been rich forests of ,mesozoic vegetation covering about a hundred thousand square miles in the ,rocky ,mountains region4 ,europe and ,america now begin to show their modern contours4 ,it is important to notice that this great uprise of the land and the series of disturbances it entails differ from those which we summed up in the phrase ,permian ,revolution4 ,the differences may help us to understand some of the changes in the living population4 ,the chief difference is that the disturbances are more local1 and not nearly simultaneous4 ,there is a considerable emergence of land at the end of the ,jurassic1 then a fresh expansion of the sea1 then a great rise of mountains at the end of the ,cretaceous1 and so on4 ,we shall find our great mountain-masses 7the ,pyrenees1 ,alps1 ,himalaya1 etc47 rising at intervals throughout the whole of the ,tertiary ,era4 ,however1 it suffices for the moment to observe that in the latter part of the ,mesozoic and early part of the ,tertiary there were considerable upheavals of the land in various regions1 and that the ,mesozoic ,era closed with a very much larger proportion of dry land1 and a much higher relief of the land1 than there had been during the ,jurassic period4 ,the series of disturbances was1 says ,professor ,chamberlin1 greater than any that had occurred since the close of the ,palaeozoic4 ,from the previous effect of the ,permian upheaval1 and from the fact that the living population is now similarly annihilated or reduced1 we should at once expect to find a fresh change in the climate of the earth4 ,here1 however1 our procedure is not so easy4 ,in the ,permian age we had solid proof in the shape of vast glaciated regions4 ,it is claimed by continental geologists that certain early ,tertiary beds in ,bavaria actually prove a similar1 but smaller1 glaciation in ,europe1 but this is disputed4 ,other beds may yet be found1 but we saw that there was not a general upheaval1 as there had been in the ,permian1 and it is quite possible that there were few or no ice-fields4 ,we do not1 in fact1 know the causes of the ,permian icefields4 ,we are thrown upon the plant and animal remains1 and seem to be in some danger of inferring a cold climate from the organic remains1 and then explaining the new types of organisms by the cold climate4 ,this1 of course1 we shall not do4 ,the difficulty is made greater by the extreme disinclination of many recent geologists1 and some recent botanists who have too easily followed the geologists1 to admit a plain climatic interpretation of the facts4 ,let us first see what the facts are4 ,in the latter part of the ,jurassic we find three different zones of ,ammonites3 one in the latitude of the ,mediterranean1 one in the latitude of ,central ,europe1 and one further north4 ,most geologists conclude that these differences indicate zones of climate 7not hitherto indicated71 but it cannot be proved1 and we may leave the matter open4 ,at the same time the warm-loving corals disappear from ,europe1 with occasional advances4 ,it is said that they are driven out by the disturbance of the waters1 and1 although this would hardly explain why they did not spread again in the tranquil chalk-ocean1 we may again leave the point open4 ,in the early part of the ,cretaceous1 however1 the ,angiosperms 7flowering plants7 suddenly break into the chronicle of the earth1 and spread with great rapidity4 ,they appear abruptly in the east of the ,north ,american continent1 in the region of ,virginia and ,maryland4 ,they are small in stature and primitive in structure4 ,some are of generalised forms that are now unknown2 some have leaves approaching those of the oak1 willow1 elm1 maple1 and walnut2 some may be definitely described as fig1 sassafras1 aralia1 myrica1 etc4 ,eastern ,america1 it may be recalled1 is much higher than western until the close of the ,cretaceous period4 ,the ,angiosperms do not spread much westward2 they appear next in ,greenland1 and1 before the middle of the ,cretaceous1 in ,portugal4 ,they have travelled over the ,north ,atlantic continent1 or what remains of it4 ,the process seems very rapid as we write it1 but it must be remembered that the first half of the ,cretaceous period means a million or a million and a half years4 ,the cycads1 and even the conifers1 shrink before the higher type of tree4 ,the landscape1 in ,europe and ,america1 begins to wear a modern aspect4 ,long before the end of the ,cretaceous most of the modern genera of ,angiosperm trees have developed4 ,to the fig and sassafras are now added the birch1 beech1 oak1 poplar1 walnut1 willow1 ivy1 mulberry1 holly1 laurel1 myrtle1 maple1 oleander1 magnolia1 plane1 bread-fruit1 and sweet-gum4 ,most of the ,american trees of to-day are known4 ,the sequoias 7the giant ,californian trees7 still represent the conifers in great abundance1 with the eucalyptus and other plants that are now found only much further south4 ,the ginkgoes struggle on for a time4 ,the cycads dwindle enormously4 ,of #gjj specimens in one early ,cretaceous deposit only #if are ,angiosperms2 of #dfj species in a later deposit about #djj are ,angiosperms4 ,they oust the cycads in ,europe and ,america1 as the cycads and conifers had ousted the ,cryptogams4 ,the change in the face of the earth would be remarkable4 ,instead of the groves of palm-like cycads1 with their large and flower-like fructifications1 above which the pines and firs and cypresses reared their sombre forms1 there were now forests of delicate-leaved maples1 beeches1 and oaks1 bearing nutritious fruit for the coming race of animals4 ,grasses also and palms begin in the ,cretaceous2 though the grasses would at first be coarse and isolated tufts4 ,even flowers1 of the lily family 7apparently71 are still detected in the crushed and petrified remains4 ,we will give some consideration later to the evolution of the ,angiosperms4 ,for the moment it is chiefly important to notice a feature of them to which the botanist pays less attention4 ,in his technical view the ,angiosperm is distinguished by the structure of its reproductive apparatus1 its flowers1 and some recent botanists wonder whether the key to this expansion of the flowering plants may not be found in a development of the insect world and of its relation to vegetation4 ,in point of fact1 we have no geological indication of any great development of the insects until the ,tertiary ,era1 when we shall find them deploying into a vast army and producing their highest types4 ,in any case1 such a view leaves wholly unexplained the feature of the ,angiosperms which chiefly concerns us4 ,this is that most of them shed the whole of their leaves periodically1 as the winter approaches4 ,no such trees had yet been known on the earth4 ,all trees hitherto had been evergreen1 and we need a specific and adequate explanation why the earth is now covered1 in the northern region1 with forests of trees which show naked boughs and branches during a part of the year4 ,the majority of palaeontologists conclude at once1 and quite confidently1 from this rise and spread of the deciduous trees1 that a winter season has at length set in on the earth1 and that this new type of vegetation appears in response to an appreciable lowering of the climate4 ,the facts1 however1 are somewhat complex1 and we must proceed with caution4 ,it would seem that any general lowering of the temperature of the earth ought to betray itself first in ,greenland1 but the flora of ,greenland remains far warmer1 so to say1 than the flora of ,central ,europe is to-day4 ,even toward the close of the ,cretaceous its plants are much the same as those of ,america or of ,central ,europe4 ,its fossil remains of that time include forty species of ferns1 as well as cycads1 ginkgoes1 figs1 bamboos1 and magnolias4 ,sir ,a4 ,geikie ventures to say that it must then have enjoyed a climate like that of the ,cape or of ,australia to-day4 ,professor ,chamberlin finds its flora like that of warm temperate regions1 and says that plants which then flourished in latitude #gb degrees are not now found above latitude #cj degrees4 ,there are1 however1 various reasons to believe that it is unsafe to draw deductions from the climate of ,greenland4 ,there is1 it is true1 some exaggeration in the statement that its climate was equivalent to that of ,central ,europe4 ,the palms which flourished in ,central ,europe did not reach ,greenland1 and there are differences in the northern ,molluscs and ,echinoderms which--like the absence of corals above the north of ,england--point to a diversity of temperature4 ,but we have no right to expect that there would be the same difference in temperature between ,greenland and ,central ,europe as we find to-day4 ,if the warm current which is now diverted to ,europe across the ,atlantic--the ,gulf ,stream--had then continued up the coast of ,america1 and flowed along the coast of the land that united ,america and ,europe1 the climatic conditions would be very different from what they are4 ,there is a more substantial reason4 ,we saw that during the ,mesozoic the ,arctic continent was very largely submerged1 and1 while ,europe and ,america rise again at the end of the ,cretaceous1 we find no rise of the land further north4 ,a difference of elevation would1 in such a world1 make a great difference in temperature and moisture4 ,let us examine the animal record1 however1 before we come to any conclusion4 ,the chronicle of the later ,cretaceous is a story of devastation4 ,the reduction of the cyeads is insignificant beside the reduction or annihilation of the great animals of the ,mesozoic world4 ,the skeletons of the ,deinosaurs become fewer and fewer as we ascend the upper ,cretaceous strata4 ,in the uppermost layer 7,laramie7 we find traces of a last curious expansion--the group of horned reptiles1 of the ,triceratops type1 which we described as the last of the great reptiles4 ,the ,ichthyosaurs and ,plesiosaurs vanish from the waters4 ,the sea-serpents 7,mososaurs7 pass away without a survivor4 ,the flying dragons1 large and small1 become entirely extinct4 ,only crocodiles1 lizards1 turtle1 and snakes cross the threshold of the ,tertiary ,era4 ,in one single region of ,america 7,puerco beds7 some of the great reptiles seem to be making a last stand against the advancing enemy in the dawn of the ,tertiary ,era1 but the exact date of the beds is disputed1 and in any case their fight is soon over4 ,something has slain the most formidable race that the earth had yet known1 in spite of its marvellous adaptation to different environments in its innumerable branches4 ,we turn to the seas1 and find an equal carnage among some of its most advanced inhabitants4 ,the great cuttlefish-like ,belemnites and the whole race of the ,ammonites1 large and small1 are banished from the earth4 ,the fall of the ,ammonites is particularly interesting1 and has inspired much more or less fantastic speculation4 ,the shells begin to assume such strange forms that observers speak occasionally of the convulsions or death-contortions of the expiring race4 ,some of the coiled shells take on a spiral form1 like that of a snail's shell4 ,some uncoil the shell1 and seem to be returning toward the primitive type4 ,a rich eccentricity of frills and ornamentation is found more or less throughout the whole race4 ,but every device--if we may so regard these changes--is useless1 and the devastating agency of the ,cretaceous1 whatever it was1 removes the ,ammonites and ,belemnites from the scene4 ,the ,mollusc world1 like the world of plants and of reptiles1 approaches its modern aspect4 ,in the fish world1 too1 there is an effective selection in the course of the ,cretaceous4 ,all the fishes of modern times1 except the large family of the sharks1 rays1 skates1 and dog-fishes 7,elasmobranchs71 the sturgeon and chimaera1 the mud-fishes1 and a very few other types1 are ,teleosts1 or bony-framed fishes--the others having cartilaginous frames4 ,none of the ,teleosts had appeared until the end of the ,jurassic4 ,they now1 like the flowering plants on land1 not only herald the new age1 but rapidly oust the other fishes1 except the unconquerable shark4 ,they gradually approach the familiar types of ,teleosts1 so that we may say that before the end of the ,cretaceous the waters swarmed with primitive and patriarchal cod1 salmon1 herring1 perch1 pike1 bream1 eels1 and other fishes4 ,some of them grew to an enormous size4 ,the ,portheus1 an ,american pike1 seems to have been about eight feet long2 and the activity of an eight-foot pike may be left to the angler's imagination4 ,all1 however1 are1 as evolution demands1 of a generalised and unfamiliar type3 the material out of which our fishes will be evolved4 ,of the insects we have very little trace in the ,cretaceous4 ,we shall find them developing with great richness in the following period1 but1 imperfect as the record is1 we may venture to say that they were checked in the ,cretaceous4 ,there were good conditions for preserving them1 but few are preserved4 ,and of the other groups of invertebrates we need only say that they show a steady advance toward modern types4 ,the sea-lily fills the rocks no longer2 the sea-urchin is very abundant4 ,the ,molluscs gain on the more lowly organised ,brachiopods4 ,to complete the picture we must add that higher types probably arose in the later ,cretaceous which do not appear in the records4 ,this is particularly true of the birds and mammals4 ,we find them spreading so early in the ,tertiary that we must put back the beginning of the expansion to the ,cretaceous4 ,as yet1 however1 the only mammal remains we find are such jaws and teeth of primitive mammals as we have already described4 ,the birds we described 7after the ,archaeopteryx7 also belong to the ,cretaceous1 and they form another of the doomed races4 ,probably the modern birds were already developing among the new vegetation on the higher ground4 ,these are the facts of ,cretaceous life1 as far as the record has yielded them1 and it remains for us to understand them4 ,clearly there has been a great selective process analogous to1 if not equal to1 the winnowing process at the end of the ,palaeozoic4 ,as there has been a similar1 if less considerable1 upheaval of the land1 we are at once tempted to think that the great selective agency was a lowering of the temperature4 ,when we further find that the most important change in the animal world is the destruction of the cold-blooded reptiles1 which have no concern for the young1 and the luxuriant spread of the warm-blooded animals1 which do care for their young1 the idea is greatly confirmed4 ,when we add that the powerful ,molluscs which are slain1 while the humbler ,molluscs survive1 are those which--to judge from the nautilus and octopus--love warm seas1 the impression is further confirmed4 ,and when we finally reflect that the most distinctive phenomenon of the period is the rapid spread of deciduous trees1 it would seem that there is only one possible interpretation of the ,cretaceous ,revolution4 ,this interpretation--that cold was the selecting agency--is a familiar idea in geological literature1 but1 as ,i said1 there are recent writers who profess reserve in regard to it1 and it is proper to glance at1 or at least look for1 the alternatives4 ,before doing so let us be quite clear that here we have nothing to do with theories of the origin of the earth4 ,the ,permian cold--which1 however1 is universally admitted--is more or less entangled in that controversy2 the ,cretaceous cold has no connection with it4 ,whatever excess of carbon-dioxide there may have been in the early atmosphere was cleared by the ,coal-forests4 ,we must set aside all these theories in explaining the present facts4 ,it is also useful to note that the fact that there have been great changes in the climate of the earth in past time is beyond dispute4 ,there is no denying the fact that the climate of the earth was warm from the ,arctic to the ,antarctic in the ,devonian and ,carboniferous periods3 that it fell considerably in the ,permian3 that it again became at least warm temperate 7,chamberlin7 from the ,arctic to the ,antarctic in the ,jurassic1 and again in the ,eocene3 that some millions of square miles of ,europe and ,north ,america were covered with ice and snow in the ,pleistocene1 so that the reindeer wandered where palms had previously flourished and the vine flourishes to-day2 and that the pronounced zones of climate which we find today have no counterpart in any earlier age4 ,in view of these great and admitted fluctuations of the earth's temperature one does not see any reason for hesitating to admit a fall of temperature in the ,cretaceous1 if the facts point to it4 ,on the other hand1 the alternative suggestions are not very convincing4 ,we have noticed one of these suggestions in connection with the origin of the ,angiosperms4 ,it hints that this may be related to developments of the insect world4 ,most probably the development of the characteristic flowers of the ,angiosperms is connected with an increasing relation to insects1 but what we want to understand especially is the deciduous character of their leaves4 ,many of the ,angiosperms are evergreen1 so that it cannot be said that the one change entailed the other4 ,in fact1 a careful study of the leaves preserved in the rocks seems to show the deciduous ,angiosperms gaining on the evergreens at the end of the ,cretaceous4 ,the most natural1 it not the only1 interpretation of this is that the temperature is falling4 ,deciduous trees shed their leaves so as to check their transpiration when a season comes on in which they cannot absorb the normal amount of moisture4 ,this may occur either at the on-coming of a hot1 dry season or of a cold season 7in which the roots absorb less74 ,everything suggests that the deciduous tree evolved to meet an increase of cold1 not of heat4 ,another suggestion is that animals and plants were not climatically differentiated until the ,cretaceous period2 that is to say1 that they were adapted to all climates before that time1 and then began to be sensitive to differences of climate1 and live in different latitudes4 ,but how and why they should suddenly become differentiated in this way is so mysterious that one prefers to think that1 as the animal remains also suggest1 there were no appreciable zones of climate until the ,cretaceous4 ,the magnolia1 for instance1 flourished in ,greenland in the early ,tertiary1 and has to live very far south of it to-day4 ,it is much simpler to assume that ,greenland changed--as a vast amount of evidence indicates--than that the magnolia changed4 ,finally1 to explain the disappearance of the ,mesozoic reptiles without a fall in temperature1 it is suggested that they were exterminated by the advancing mammals4 ,it is assumed that the spreading world of the ,angiospermous plants somewhere met the spread of the advancing mammals1 and opened out a rich new granary to them4 ,this led to so powerful a development of the mammals that they succeeded in overthrowing the reptiles4 ,there are several serious difficulties in the way of this theory4 ,the first and most decisive is that the great reptiles have practically disappeared before the mammals come on the scene4 ,only in one series of beds 7,puerco7 in ,america1 representing an early period of the ,tertiary ,era1 do we find any association of their remains2 and even there it is not clear that they were contemporary4 ,over the earth generally the geological record shows the great reptiles dying from some invisible scourge long before any mammal capable of doing them any harm appears2 even if we suppose that the mammal mainly attacked the eggs and the young4 ,we may very well believe that more powerful mammals than the primitive ,mesozoic specimens were already developed in some part of the earth--say1 ,africa--and that the rise of the land gave them a bridge across the ,mediterranean to ,europe4 ,probably this happened2 but the important point is that the reptiles were already almost extinct4 ,the difficulty is even greater when we reflect that it is precisely the most powerful reptiles 7,deinosaurs7 and least accessible reptiles 7,pterosaurs1 ,ichthyosaurs1 etc47 which disappear1 while the smaller land and water reptiles survive and retreat southward--where the mammals are just as numerous4 ,that assuredly is not the effect of an invasion of carnivores1 even if we could overlook the absence of such carnivores from the record until after the extinction of the reptiles in most places4 ,i have entered somewhat fully into this point1 partly because of its great interest1 but partly lest it be thought that ,i am merely reproducing a tradition of geological literature without giving due attention to the criticisms of recent writers4 ,the plain and common interpretation of the ,cretaceous revolution--that a fall in temperature was its chief devastating agency--is the only one that brings harmony into all the facts4 ,the one comprehensive enemy of that vast reptile population was cold4 ,it was fatal to the adult because he had a three-chambered heart and no warm coat2 it was fatal to the ,mesozoic vegetation on which1 directly or indirectly1 he fed2 it was fatal to his eggs and young because the mother did not brood over the one or care for the other4 ,it was fatal to the ,pterosaurs1 even if they were warm-blooded1 because they had no warm coats and did not 7presumably7 hatch their eggs2 and it was equally fatal to the viviparous ,ichthyosaurs4 ,it is the one common fate that could slay all classes4 ,when we find that the surviving reptiles retreat southward1 only lingering in ,europe during the renewed warmth of the ,eocene and ,miocene periods1 this interpretation is sufficiently confirmed4 ,and when we recollect that these things coincide with the extinction of the ,ammonites and ,belemnites1 and the driving of their descendants further south1 as well as the rise and triumph of deciduous trees1 it is difficult to see any ground for hesitating4 ,but we need not1 and must not1 imagine a period of cold as severe1 prolonged1 and general as that of the ,permian period4 ,the warmth of the ,jurassic period is generally attributed to the low relief of the land1 and the very large proportion of water-surface4 ,the effect of this would be to increase the moisture in the atmosphere4 ,whether this was assisted by any abnormal proportion of carbon-dioxide1 as in the ,carboniferous1 we cannot confidently say4 ,professor ,chamberlin observes that1 since the absorbing rock-surface was greatly reduced in the ,jurassic1 the carbon-dioxide would tend to accumulate in its atmosphere1 and help to explain the high temperature4 ,but the great spread of vegetation and the rise of land in the later ,jurassic and the ,cretaceous would reduce this density of the atmosphere1 and help to lower the temperature4 ,it is clear that the cold would at first be local4 ,in fact1 it must be carefully realised that1 when we speak of the ,jurassic period as a time of uniform warmth1 we mean uniform at the same altitude4 ,everybody knows the effect of rising from the warm1 moist sea-level to the top of even a small inland elevation4 ,there would be such cooler regions throughout the ,jurassic1 and we saw that there were considerable upheavals of land towards its close4 ,to these elevated lands we may look for the development of the ,angiosperms1 the birds1 and the mammals4 ,when the more massive rise of land came at the end of the ,cretaceous1 the temperature would fall over larger areas1 and connecting ridges would be established between one area and another4 ,the ,mesozoic plants and animals would succumb to this advancing cold4 ,what precise degree of cold was necessary to kill the reptiles and ,cephalopods1 yet allow certain of the more delicate flowering plants to live1 is yet to be determined4 ,the vast majority of the new plants1 with their winter sleep1 would thrive in the cooler air1 and1 occupying the ground of the retreating cycads and ginkgoes would prepare a rich harvest for the coming birds and mammals4 ,,chapter ,,xv4 ,,the ,,tertiary ,,era ,we have already traversed nearly nine-tenths of the story of terrestrial life1 without counting the long and obscure ,archaean period1 and still find ourselves in a strange and unfamiliar earth4 ,with the close of the ,chalk period1 however1 we take a long stride in the direction of the modern world4 ,the ,tertiary ,era will1 in the main1 prove a fresh period of genial warmth and fertile low-lying regions4 ,during its course our deciduous trees and grasses will mingle with the palms and pines over the land1 our flowers will begin to brighten the landscape1 and the forms of our familiar birds and mammals1 even the form of man1 will be discernible in the crowds of animals4 ,at its close another mighty period of selection will clear the stage for its modern actors4 ,a curious reflection is prompted in connection with this division of the earth's story into periods of relative prosperity and quiescence1 separated by periods of disturbance4 ,there was--on the most modest estimate--a stretch of some fifteen million years between the ,cambrian and the ,permian upheavals4 ,on the same chronological scale the interval between the ,permian and ,cretaceous revolutions was only about seven million years1 and the ,tertiary ,era will comprise only about three million years4 ,one wonders if the ,fourth 7,quaternary7 ,era in which we live will be similarly shortened4 ,further1 whereas the earth returned after each of the earlier upheavals to what seems to have been its primitive condition of equable and warm climate1 it has now entirely departed from that condition1 and exhibits very different zones of climate and a succession of seasons in the year4 ,one wonders what the climate of the earth will become long before the expiration of those ten million years which are usually assigned as the minimum period during which the globe will remain habitable4 ,it is premature to glance at the future1 when we are still some millions of years from the present1 but it will be useful to look more closely at the facts which inspire this reflection4 ,from what we have seen1 and shall further see1 it is clear that1 in spite of all the recent controversy about climate among our geologists1 there has undeniably been a progressive refrigeration of the globe4 ,every geologist1 indeed1 admits oscillations of climate1 as ,professor ,chamberlin puts it4 ,but amidst all these oscillations we trace a steady lowering of the temperature4 ,unless we put a strained and somewhat arbitrary interpretation on the facts of the geological record1 earlier ages knew nothing of our division of the year into pronounced seasons and of the globe into very different climatic zones4 ,it might plausibly be suggested that we are still living in the last days of the ,ice-,age1 and that the earth may be slowly returning to a warmer condition4 ,shackleton1 it might be observed1 found that there has been a considerable shrinkage of the south polar ice within the period of exploration4 ,but we shall find that a difference of climate1 as compared with earlier ages1 was already evident in the middle of the ,tertiary ,era1 and it is far more noticeable to-day4 ,we do not know the causes of this climatic evolution--the point will be considered more closely in connection with the last ,ice-,age--but we see that it throws a flood of light on the evolution of organisms4 ,it is one of the chief incarnations of natural selection4 ,changes in the distribution of land and water and in the nature of the land-surface1 the coming of powerful carnivores1 and other agencies which we have seen1 have had their share in the onward impulsion of life1 but the most drastic agency seems to have been the supervention of cold4 ,the higher types of both animals and plants appear plainly in response to a lowering of temperature4 ,this is the chief advantage of studying the story of evolution in strict connection with the geological record4 ,we shall find that the record will continue to throw light on our path to the end1 but1 as we are now about to approach the most important era of evolution1 and as we have now seen so much of the concrete story of evolution1 it will be interesting to examine briefly some other ways of conceiving that story4 ,we need not return to the consideration of the leading schools of evolution1 as described in a former chapter4 ,nothing that we have seen will enable us to choose between the ,lamarckian and the ,weismannist hypothesis2 and ,i doubt if anything we are yet to see will prove more decisive4 ,the dispute is somewhat academic1 and not vital to a conception of evolution4 ,we shall1 for instance1 presently follow the evolution of the horse1 and see four of its toes shrink and disappear1 while the fifth toe is enormously strengthened4 ,in the facts themselves there is nothing whatever to decide whether this evolution took place on the lines suggested by ,weismann1 or on the lines suggested by ,lamarck and accepted by ,darwin4 ,it will be enough for us merely to establish the fact that the one-toed horse is an evolved descendant of a primitive five-toed mammal1 through the adaptation of its foot to running on firm ground1 its teeth and neck to feeding on grasses1 and so on4 ,on the other hand1 the facts we have already seen seem to justify the attitude of compromise ,i adopted in regard to the ,mutationist theory4 ,it would be an advantage in many ways if we could believe that new species arose by sudden and large variations 7mutations7 of the young from the parental type4 ,in the case of many organs and habits it is extremely difficult to see how a gradual development1 by a slow accentuation of small variations1 is possible4 ,when we further find that experimenters on living species can bring about such mutations1 and when we reflect that there must have been acute disturbances in the surroundings of animals and plants sometimes1 we are disposed to think that many a new species may have arisen in this way4 ,on the other hand1 while the palaeontological record can never prove that a species arose by mutations1 it does sometimes show that species arise by very gradual modification4 ,the ,chalk period1 which we have just traversed1 affords a very clear instance4 ,one of our chief investigators of the ,english ,chalk1 ,dr4 ,rowe1 paid particular attention to the sea-urchins it contains1 as they serve well to identify different levels of chalk4 ,he discovered1 not merely that they vary from level to level1 but that in at least one genus 7,micraster7 he could trace the organism very gradually passing from one species to another1 without any leap or abruptness4 ,it is certainly significant that we find such cases as this precisely where the conditions of preservation are exceptionally good4 ,we must conclude that species arise1 probably1 both by mutations and small variations1 and that it is impossible to say which class of species has been the more numerous4 ,there remain one or two conceptions of evolution which we have not hitherto noticed1 as it was advisable to see the facts first4 ,one of these is the view--chiefly represented in this country by ,professor ,henslow--that natural selection has had no part in the creation of species2 that the only two factors are the environment and the organism which responds to its changes4 ,this is true enough in the sense that1 as we saw1 natural selection is not an action of nature on the fit1 but on the unfit or less fit4 ,but this does not in the least lessen the importance of natural selection4 ,if there were not in nature this body of destructive agencies1 to which we apply the name natural selection1 there would be little--we cannot say no--evolution4 ,but the rising carnivores1 the falls of temperature1 etc41 that we have studied1 have had so real1 if indirect1 an influence on the development of life that we need not dwell on this4 ,another school1 or several schools1 while admitting the action of natural selection1 maintain that earlier evolutionists have made nature much too red in tooth and claw4 ,dr4 ,russel ,wallace from one motive1 and ,prince ,krapotkin from another1 have insisted that the triumphs of war have been exaggerated1 and the triumphs of peace1 or of social co-operation1 far too little appreciated4 ,it will be found that such writers usually base their theory on life as we find it in nature to-day1 where the social principle is highly developed in many groups of animals4 ,this is most misleading1 since social co-operation among animals1 as an instrument of progress1 is 7geologically speaking7 quite a recent phenomenon4 ,nearly every group of animals in which it is found belongs1 to put it moderately1 to the last tenth of the story of life1 and in some of the chief instances the animals have only gradually developed social life4 99 ,the first nine-tenths of the chronicle of evolution contain no indication of social life1 except--curiously enough--in such groups as the ,sponges1 ,corals1 and ,bryozoa1 which are amongst the least progressive in nature4 ,we have seen plainly that during the overwhelmingly greater part of the story of life the predominant agencies of evolution were struggle against adverse conditions and devouring carnivores2 and we shall find them the predominant agencies throughout the ,tertiary ,era4 99 ,thus the social nature of man is sometimes quoted as one of the chief causes of his development4 ,it is true that it has much to do with his later development1 but we shall see that the statement that man was from the start a social being is not at all warranted by the facts4 ,on the other hand1 it may be pointed out that the ants and termites had appeared in the ,mesozoic4 ,we shall see some evidence that the remarkable division of labour which now characterises their life did not begin until a much later period1 so that we have no evidence of social life in the early stages4 ,yet we must protest against the exaggerated estimate of the conscious pain which so many read into these millions of years of struggle4 ,probably there was no consciousness at all during the greater part of the time4 ,the wriggling of the worm on which you have accidentally trodden is no proof whatever that you have caused conscious pain4 ,the nervous system of an animal has been so evolved as to respond with great disturbance of its tissue to any dangerous or injurious assault4 ,it is the selection of a certain means of self-preservation4 ,but at what level of life the animal becomes conscious of this disturbance1 and feels pain1 it is very difficult to determine4 ,the subject is too vast to be opened here4 ,in a special investigation of it4 99 ,i concluded that there is no proof of the presence of any degree of consciousness in the invertebrate world even in the higher insects2 that there is probably only a dull1 blurred1 imperfect consciousness below the level of the higher mammals and birds2 and that even the consciousness of an ape is something very different from what educated ,europeans1 on the ground of their own experience1 call consciousness4 ,it is too often forgotten that pain is in proportion to consciousness4 ,we must beware of such fallacies as transferring our experience of pain to a ,mesozoic reptile1 with an ounce or two of cerebrum to twenty tons of muscle and bone4 99 ,the ,evolution of ,mind 7,black71 #aiaa4 ,one other view of evolution1 which we find in some recent and reputable works 7such as ,professor ,geddes and ,thomson's ,evolution1 #aiaa71 calls for consideration4 ,in the ordinary ,darwinian view the variations of the young from their parents are indefinite1 and spread in all directions4 ,they may continue to occur for ages without any of them proving an advantage to their possessors4 ,then the environment may change1 and a certain variation may prove an advantage1 and be continuously and increasingly selected4 ,thus these indefinite variations may be so controlled by the environment during millions of years that the fish at last becomes an elephant or a man4 ,the alternative view1 urged by a few writers1 is that the variations were definitely directed4 ,the phrase seems merely to complicate the story of evolution with a fresh and superfluous mystery4 ,the nature and precise action of this definite direction within the organism are quite unintelligible1 and the facts seem explainable just as well--or not less imperfectly--without as with this mystic agency4 ,radiolaria1 ,sponges1 ,corals1 ,sharks1 ,mudfishes1 ,duckbills1 etc41 do not change 7except within the limits of their family7 during millions of years1 because they keep to an environment to which they are fitted4 ,on the other hand1 certain fishes1 reptiles1 etc41 remain in a changing environment1 and they must change with it4 ,the process has its obscurities1 but we make them darker1 it seems to me1 with these semi-metaphysical phrases4 ,it has seemed advisable to take this further glance at the general principles and current theories of evolution before we extend our own procedure into the ,tertiary ,era4 ,the highest types of animals and plants are now about to appear on the stage of the earth2 the theatre itself is about to take on a modern complexion4 ,the ,middle ,ages are over2 the new age is breaking upon the planet4 ,we will1 as before1 first survey the ,tertiary ,era as a whole1 with the momentous changes it introduces1 and then examine1 in separate chapters1 the more important phases of its life4 ,it opens1 like the preceding and the following era1 with the area of land large and its relief pronounced4 ,this is the outcome of the ,cretaceous revolution4 ,southern ,europe and ,southern ,asia have risen1 and shaken the last masses of the ,chalk ocean from their faces2 the whole western fringe of ,america has similarly emerged from the sea that had flooded it4 ,in many parts1 as in ,england 7at that time a part of the ,continent71 there is so great a gap between the latest ,cretaceous and the earliest ,tertiary strata that these newly elevated lands must evidently have stood out of the waters for a prolonged period4 ,on their cooler plains the tragedy of the extinction of the great reptiles comes to an end4 ,the cyeads and ginkgoes have shrunk into thin survivors of the luxuriant ,mesozoic groves4 ,the oak and beech and other deciduous trees spread slowly over the successive lands1 amid the glare and thunder of the numerous volcanoes which the disturbance of the crust has brought into play4 ,new forms of birds fly from tree to tree1 or linger by the waters2 and strange patriarchal types of mammals begin to move among the bones of the stricken reptiles4 ,but the seas and the rains and rivers are acting with renewed vigour on the elevated lands1 and the ,eocene period closes in a fresh age of levelling4 ,let us put the work of a million years or so in a sentence4 ,the southern sea1 which has been confined almost to the limits of our ,mediterranean by the ,cretaceous upheaval1 gradually enlarges once more4 ,it floods the north-west of ,africa almost as far as the equator2 it covers most of ,italy1 ,turkey1 ,austria1 and ,southern ,russia2 it spreads over ,asia ,minor1 ,persia1 and ,southern ,asia1 until it joins the ,pacific2 and it sends a long arm across the ,franco-,british region1 and up the great valley which is now the ,german ,ocean4 ,from earlier chapters we now expect to find a warmer climate1 and the record gives abundant proof of it4 ,to this period belongs the ,london ,clay1 in whose thick and--to the unskilled eye--insignificant bed the geologist reads the remarkable story of what ,london was two or three million years ago4 ,it tells us that a sea1 some #ejj or #fjj feet deep1 then lay over that part of ,england1 and fragments of the life of the period are preserved in its deposit4 ,the sea lay at the mouth of a sub-tropical river on whose banks grew palms1 figs1 ginkgoes1 eucalyptuses1 almonds1 and magnolias1 with the more familiar oaks and pines and laurels4 ,sword-fishes and monstrous sharks lived in the sea4 ,large turtles and crocodiles and enormous sea-serpents lingered in this last spell of warmth that ,central ,europe would experience4 ,a primitive whale appeared in the seas1 and strange large tapir-like mammals--remote ancestors of our horses and more familiar beasts--wandered heavily on the land4 ,gigantic primitive birds1 sometimes ten feet high1 waded by the shore4 ,deposits of the period at ,bournemouth and in the ,isle of ,wight tell the same story of a land that bore figs1 vines1 palms1 araucarias1 and aralias1 and waters that sheltered turtles and crocodiles4 ,the ,parisian region presented the same features4 ,in fact1 one of the most characteristic traces of the southern sea which then stretched from ,england to ,africa in the south and ,india in the east indicates a warm climate4 ,it will be remembered that the ,cretaceous ocean over ,southern ,europe had swarmed with the animalcules whose dead skeletons largely compose our chalk-beds4 ,in the new southern ocean another branch of these ,thalamophores1 the ,nummulites1 spreads with such portentous abundance that its shells--sometimes alone1 generally with other material--make beds of solid limestone several thousand feet in thickness4 ,the pyramids are built of this nummulitic limestone4 ,the one-celled animal in its shell is1 however1 no longer a microscopic grain4 ,it sometimes forms wonderful shells1 an inch or more in diameter1 in which as many as a thousand chambers succeed each other1 in spiral order1 from the centre4 ,the beds containing it are found from the ,pyrenees to ,japan4 ,that this vast warm ocean1 stretching southward over a large part of what is now the ,sahara1 should give a semitropical aspect even to ,central ,europe and ,asia is not surprising4 ,but this genial climate was still very general over the earth4 ,evergreens which now need the warmth of ,italy or the ,riviera then flourished in ,lapland and ,spitzbergen4 ,the flora of ,greenland--a flora that includes magnolias1 figs1 and bamboos--shows us that its temperature in the ,eocene period must have been about #cj degrees higher than it is to-day4 99 ,the temperature of the cool ,tyrol of modern ,europe is calculated to have then been between #gd and #ha degrees ,f4 ,palms1 cactuses1 aloes1 gum-trees1 cinnamon trees1 etc41 flourished in the latitude of ,northern ,france4 ,the forests that covered parts of ,switzerland which are now buried in snow during a great part of the year were like the forests one finds in parts of ,india and ,australia to-day4 ,the climate of ,north ,america1 and of the land which still connected it with ,europe1 was correspondingly genial4 99 ,the great authority on ,arctic geology1 ,heer1 who makes this calculation1 puts this flora in the ,miocene4 ,it is now usually considered that these warmer plants belong to the earlier part of the ,tertiary era4 ,this indulgent period 7the ,oligocene1 or later part of the ,eocene71 scattering a rich and nutritious vegetation with great profusion over the land1 led to a notable expansion of animal life4 ,insects1 birds1 and mammals spread into vast and varied groups in every land4 ,had any of the great ,mesozoic reptiles survived1 the warmer age might have enabled them to dispute the sovereignty of the advancing mammals4 ,but nothing more formidable than the turtle1 the snake1 and the crocodile 7confined to the waters7 had crossed the threshold of the ,tertiary ,era1 and the mammals and birds had the full advantage of the new golden age4 ,the fruits of the new trees1 the grasses which now covered the plains1 and the insects which multiplied with the flowers afforded a magnificent diet4 ,the herbivorous mammals became a populous world1 branching into numerous different types according to their different environments4 ,the horse1 the elephant1 the camel1 the pig1 the deer1 the rhinoceros gradually emerge out of the chaos of evolving forms4 ,behind them1 hastening the course of their evolution1 improving their speed1 arms1 and armour1 is the inevitable carnivore4 ,he1 too1 in the abundance of food1 grows into a vast population1 and branches out toward familiar types4 ,we will devote a chapter presently to this remarkable phase of the story of evolution4 ,but the golden age closes1 as all golden ages had done before it1 and for the same reason4 ,the land begins to rise1 and cast the warm shallow seas from its face4 ,the expansion of life has been more rapid and remarkable than it had ever been before1 in corresponding periods of abundant food and easy conditions2 the contraction comes more quickly than it had ever done before4 ,mountain masses begin to rise in nearly all parts of the world4 ,the advance is slow and not continuous1 but as time goes on the ,atlas1 ,alps1 ,pyrenees1 ,apennines1 ,caucasus1 ,himalaya1 ,rocky ,mountains1 and ,andes rise higher and higher4 ,when the geologist looks to-day for the floor of the ,eocene ocean1 which he recognises by the shells of the ,nummulites1 he finds it #aj1jjj feet above the sea-level in the ,alps1 #af1jjj feet above the sea-level in the ,himalaya1 and #bj1jjj feet above the sea-level in ,thibet4 ,one need not ask why the regions of ,london and ,paris fostered palms and magnolias and turtles in ,tertiary times1 and shudder in their dreary winter to-day4 ,the ,tertiary ,era is divided by geologists into four periods3 the ,eocene1 ,oligocene1 ,miocene1 and ,pliocene4 ,cene is our barbaric way of expressing the ,greek word for new1 and the classification is meant to mark the increase of new 7or modern and actual7 types of life in the course of the ,tertiary ,era4 ,many geologists1 however1 distrust the classification1 and are disposed to divide the ,tertiary into two periods4 ,from our point of view1 at least1 it is advisable to do this4 ,the first and longer half of the ,tertiary is the period in which the temperature rises until ,central ,europe enjoys the climate of ,south ,africa2 the second half is the period in which the land gradually rises1 and the temperature falls1 until glaciers and sheets of ice cover regions where the palm and fig had flourished4 ,the rise of the land had begun in the first half of the ,tertiary1 but had been suspended4 ,the ,pyrenees and ,apennines had begun to rise at the end of the ,eocene1 straining the crust until it spluttered with volcanoes1 casting the nummulitic sea off large areas of ,southern ,europe4 ,the ,nummulites become smaller and less abundant4 ,there is also some upheaval in ,north ,america1 and a bridge of land begins to connect the north and south1 and permit an effective mingling of their populations4 ,but the advance is1 as ,i said1 suspended1 and the ,oligocene period maintains the golden age4 ,with the ,miocene period the land resumes its rise4 ,a chill is felt along the ,american coast1 showing a fall in the temperature of the ,atlantic4 ,in ,europe there is a similar chill1 and a more obvious reason for it4 ,there is an ascending movement of the whole series of mountains from ,morocco and the ,pyrenees1 through the ,alps1 the ,caucasus1 and the ,carpathians1 to ,india and ,china4 ,large lakes still lie over ,western ,europe1 but nearly the whole of it emerges from the ocean4 ,the ,mediterranean still sends an arm up ,france1 and with another arm encircles the ,alpine mass2 but the upheaval continues1 and the great nummulitic sea is reduced to a series of extensive lakes1 cut off both from the ,atlantic and ,pacific4 ,the climate of ,southern ,europe is probably still as genial as that of the ,canaries to-day4 ,palms still linger in the landscape in reduced numbers4 ,the last part of the ,tertiary1 the ,pliocene1 opens with a slight return of the sea4 ,the upheaval is once more suspended1 and the waters are eating into the land4 ,there is some foundering of land at the south-western tip of ,europe2 the ,straits of ,gibraltar begin to connect the ,mediterranean with the ,atlantic1 and the ,balearic ,islands1 ,corsica1 and ,sardinia remain as the mountain summits of a submerged land4 ,then the upheaval is resumed1 in nearly every part of the earth4 ,nearly every great mountain chain that the geologist has studied shared in this remarkable movement at the end of the ,tertiary ,era4 ,the ,pyrenees1 ,alps1 ,himalaya1 etc41 made their last ascent1 and attained their present elevation4 ,and as the land rose1 the aspect of ,europe and ,america slowly altered4 ,the palms1 figs1 bamboos1 and magnolias disappeared2 the turtles1 crocodiles1 flamingoes1 and hippopotamuses retreated toward the equator4 ,the snow began to gather thick on the rising heights2 then the glaciers began to glitter on their flanks4 ,as the cold increased1 the rivers of ice which flowed down the hills of ,switzerland1 ,spain1 ,scotland1 or ,scandinavia advanced farther and farther over the plains4 ,the regions of green vegetation shrank before the oncoming ice1 the animals retreated south1 or developed ,arctic features4 ,europe and ,america were ushering in the great ,ice-,age1 which was to bury five or six million square miles of their territory under a thick mantle of ice4 ,such is the general outline of the story of the ,tertiary ,era4 ,we approach the study of its types of life and their remarkable development more intelligently when we have first given careful attention to this extraordinary series of physical changes4 ,short as the ,era is1 compared with its predecessors1 it is even more eventful and stimulating than they1 and closes with what ,professor ,chamberlin calls the greatest deformative movements in post-,cambrian history4 ,in the main it has1 from the evolutionary point of view1 the same significant character as the two preceding eras4 ,its middle portion is an age of expansion1 indulgence1 exuberance1 in which myriads of varied forms are thrown upon the scene1 its later part is an age of contraction1 of annihilation1 of drastic test1 in which the more effectively organised will be chosen from the myriads of types4 ,once more nature has engendered a vast brood1 and is about to select some of her offspring to people the modern world4 ,among the types selected will be ,man4 ,,chapter ,,xvi4 ,,the ,,flower ,,and ,,the ,,insect ,,as we approach the last part of the geological record we must neglect the lower types of life1 which have hitherto occupied so much of our attention1 so that we may inquire more fully into the origin and fortunes of the higher forms which now fill the stage4 ,it may be noted1 in general terms1 that they shared the opulence of the mid-,tertiary period1 produced some gigantic specimens of their respective families1 and evolved into the genera1 and often the species1 which we find living to-day4 ,a few illustrations will suffice to give some idea of the later development of the lower invertebrates and vertebrates4 ,monstrous oysters bear witness to the prosperity of that ancient and interesting family of the ,molluscs4 ,in some species the shells were commonly ten inches long2 the double shell of one of these ,tertiary bivalves has been found which measured thirteen inches in length1 eight in width1 and six in thickness4 ,in the higher branch of the ,mollusc world the naked ,cephalopods 7cuttle-fish1 etc47 predominate over the nautiloids--the shrunken survivors of the great coiled-shell race4 ,among the sharks1 the modern ,squalodonts entirely displace the older types1 and grow to an enormous size4 ,some of the teeth we find in ,tertiary deposits are more than six inches long and six inches broad at the base4 ,this is three times the size of the teeth of the largest living shark1 and it is therefore believed that the extinct possessor of these formidable teeth 7,carcharodon megalodon7 must have been much more than fifty1 and was possibly a hundred1 feet in length4 ,he flourished in the waters of both ,europe and ,america during the halcyon days of the ,tertiary ,era4 ,among the bony fishes1 all our modern and familiar types appear4 ,the amphibia and reptiles also pass into their modern types1 after a period of generous expansion4 ,primitive frogs and toads make their first appearance in the ,tertiary1 and the remains are found in ,european beds of four-foot-long salamanders4 ,more than fifty species of ,tertiary turtles are known1 and many of them were of enormous size4 ,one carapace that has been found in a ,tertiary bed measures twelve feet in length1 eight feet in width1 and seven feet in height to the top of the back4 ,the living turtle must have been nearly twenty feet long4 ,marine reptiles1 of a snake-like structure1 ran to fifteen feet in length4 ,crocodiles and alligators swarmed in the rivers of ,europe until the chilly ,pliocene bade them depart to ,africa4 ,in a word1 it was the seven years of plenty for the whole living world1 and the expansive development gave birth to the modern types1 which were to be selected from the crowd in the subsequent seven years of famine4 ,we must be content to follow the evolution of the higher types of organisms4 ,i will therefore first describe the advance of the ,tertiary vegetation1 the luxuriance of which was the first condition of the great expansion of animal life2 then we will glance at the grand army of the insects which followed the development of the flowers1 and at the accompanying expansion and ramification of the birds4 ,the long and interesting story of the mammals must be told in a separate chapter1 and a further chapter must be devoted to the appearance of the human species4 ,we saw that the ,angiosperms1 or flowering plants1 appeared at the beginning of the ,cretaceous period1 and were richly developed before the ,tertiary ,era opened4 ,we saw also that their precise origin is unknown4 ,they suddenly invade a part of ,north ,america where there were conditions for preserving some traces of them1 but we have as yet no remains of their early forms or clue to their place of development4 ,we may conjecture that their ancestors had been living in some elevated inland region during the warmth of the ,jurassic period4 ,as it is now known that many of the cycad-like ,mesozoic plants bore flowers--as the modern botanist scarcely hesitates to call them--the gap between the ,gymnosperms and ,angiosperms is very much lessened4 ,there are1 however1 structural differences which forbid us to regard any of these flowering cycads1 which we have yet found1 as the ancestors of the ,angiosperms4 ,the most reasonable view seems to be that a small and local branch of these primitive flowering plants was evolved1 like the rest1 in the stress of the ,permian-,triassic cold2 that1 instead of descending to the warm moist levels with the rest at the end of the ,triassic1 and developing the definite characters of the cycad1 it remained on the higher and cooler land2 and that the rise of land at the end of the ,jurassic period stimulated the development of its ,angiosperm features1 enlarged the area in which it was especially fitted to thrive1 and so permitted it to spread and suddenly break into the geological record as a fully developed ,angiosperm4 ,as the cycads shrank in the ,cretaceous period1 the ,angiosperms deployed with great rapidity1 and1 spreading at various levels and in different kinds of soils and climates1 branched into hundreds of different types4 ,we saw that the oak1 beech1 elm1 maple1 palm1 grass1 etc41 were well developed before the end of the ,cretaceous period4 ,the botanist divides the ,angiosperms into two leading groups1 the ,monocotyledons 7palms1 grasses1 lilies1 orchises1 irises1 etc47 and ,dicotyledons 7the vast majority71 and it is now generally believed that the former were developed from an early and primitive branch of the latter4 ,but it is impossible to retrace the lines of development of the innumerable types of ,angiosperms4 ,the geologist has mainly to rely on a few stray leaves that were swept into the lakes and preserved in the mud1 and the evidence they afford is far too slender for the construction of genealogical trees4 ,the student of living plants can go a little further in discovering relationships1 and1 when we find him tracing such apparently remote plants as the apple and the strawberry to a common ancestor with the rose1 we foresee interesting possibilities on the botanical side4 ,but the evolution of the ,angiosperms is a recent and immature study1 and we will be content with a few reflections on the struggle of the various types of trees in the changing conditions of the ,tertiary1 the development of the grasses1 and the evolution of the flower4 ,in other words1 we will be content to ask how the modern landscape obtained its general vegetal features4 ,broadly speaking1 the vegetation of the first part of the ,tertiary ,era was a mixture of sub-tropical and temperate forms1 a confused mass of ,ferns1 ,conifers1 ,ginkgoales1 ,monocotyledons1 and ,dicotyledons4 ,here is a casual list of plants that then grew in the latitude of ,london and ,paris3 the palm1 magnolia1 myrtle1 ,banksia1 vine1 fig1 aralea1 sequoia1 eucalyptus1 cinnamon tree1 cactus1 agave1 tulip tree1 apple1 plum1 bamboo1 almond1 plane1 maple1 willow1 oak1 evergreen oak1 laurel1 beech1 cedar1 etc4 ,the landscape must have been extraordinarily varied and beautiful and rich4 ,to one botanist it suggests ,malaysia1 to another ,india1 to another ,australia4 ,it is really the last gathering of the plants1 before the great dispersion4 ,then the cold creeps slowly down from the ,arctic regions1 and begins to reduce the variety4 ,we can clearly trace its gradual advance4 ,in the ,carboniferous and ,jurassic the vegetation of the ,arctic regions had been the same as that of ,england2 in the ,eocene palms can flourish in ,england1 but not further north2 in the ,pliocene the palms and bamboos and semi-tropical species are driven out of ,europe2 in the ,pleistocene the ice-sheet advances to the valleys of the ,thames and the ,danube 7and proportionately in the ,united ,states71 every warmth-loving species is annihilated1 and our grasses1 oaks1 beeches1 elms1 apples1 plums1 etc41 linger on the green southern fringe of the ,continent1 and in a few uncovered regions1 ready to spread north once more as the ice creeps back towards the ,alps or the ,arctic circle4 ,thus1 in few words1 did ,europe and ,north ,america come to have the vegetation we find in them to-day4 ,the next broad characteristic of our landscape is the spreading carpet of grass4 ,the interest of the evolution of the grasses will be seen later1 when we shall find the evolution of the horse1 for instance1 following very closely upon it4 ,so striking1 indeed1 is the connection between the advance of the grasses and the advance of the mammals that ,dr4 ,russel ,wallace has recently claimed 7,the ,world of ,life1 #aiaj7 that there is a clear purposive arrangement in the whole chain of developments which leads to the appearance of the grasses4 ,he says that the very puzzling facts of the immense reptilian development in the ,mesozoic can only be understood on the supposition that they were evolved to keep down the coarser vegetation1 to supply animal food for the larger ,carnivora1 and thus give time for higher forms to obtain a secure foothold and a sufficient amount of varied form and structure 7p4 #bhd74 ,every insistence on the close connection of the different strands in the web of life is welcome1 but ,dr4 ,wallace does not seem to have learned the facts accurately4 ,there is nothing puzzling about the ,mesozoic reptilian development2 the depression of the land1 the moist warmth1 and the luscious vegetation of the later ,triassic and the ,jurassic amply explain it4 ,again1 the only carnivores to whom they seem to have supplied food were reptiles of their own race4 ,nor can the feeding of the herbivorous reptiles be connected with the rise of the ,angiosperms4 ,we do not find the flowering plants developing anywhere in those vast regions where the great reptiles abounded2 they invade them from some single unknown region1 and mingle with the pines and ginkgoes1 while the cyeads alone are destroyed4 ,the grasses1 in particular1 do not appear until the ,cretaceous1 and do not show much development until the mid-,tertiary2 and their development seems to be chiefly connected with physical conditions4 ,the meandering rivers and broad lakes of the mid-,tertiary would have their fringes of grass and sedge1 and1 as the lakes dried up in the vicissitudes of climate1 large areas of grass would be left on their sites4 ,to these primitive prairies the mammal 7not reptile7 herbivores would be attracted1 with important results4 ,the consequences to the animals we will consider presently4 ,the effect on the grasses may be well understood on the lines so usefully indicated in ,dr4 ,wallace's book4 ,the incessant cropping1 age after age1 would check the growth of the larger and coarser grasses give opportunity to the smaller and finer1 and lead in time to the development of the grassy plains of the modern world4 ,thus one more familiar feature was added to the landscape in the ,tertiary ,era4 ,as this fresh green carpet spread over the formerly naked plains1 it began to be enriched with our coloured flowers4 ,there were large flowers1 we saw1 on some of the ,mesozoic cycads1 but their sober yellows and greens--to judge from their descendants--would do little to brighten the landscape4 ,it is in the course of the ,tertiary ,era that the mantle of green begins to be embroidered with the brilliant hues of our flowers4 ,grant ,allen put forward in #ahhb 7,the ,colours of ,flowers7 an interesting theory of the appearance of the colours of flowers1 and it is regarded as probable4 ,he observed that most of the simplest flowers are yellow2 the more advanced flowers of simple families1 and the simpler flowers of slightly advanced families1 are generally white or pink2 the most advanced flowers of all families1 and almost all the flowers of the more advanced families1 are red1 purple1 or blue2 and the most advanced flowers of the most advanced families are always either blue or variegated4 ,professor ,henslow adds a number of equally significant facts with the same tendency1 so that we have strong reason to conceive the floral world as passing through successive phases of colour in the ,tertiary ,era4 ,at first it would be a world of yellows and greens1 like that of the ,mesozoic vegetation1 but brighter4 ,in time splashes of red and white would lie on the face of the landscape2 and later would come the purples1 the rich blues1 and the variegated colours of the more advanced flowers4 ,why the colours came at all is a question closely connected with the general story of the evolution of the flower1 at which we must glance4 ,the essential characteristic of the flower1 in the botanist's judgment1 is the central green organ which you find--say1 in a lily--standing out in the middle of the floral structure1 with a number of yellow-coated rods round it4 ,the yellow rods bear the male germinal elements 7pollen72 the central pistil encloses the ovules1 or female elements4 ,angiosperm means covered-seed plant1 and its characteristic is this protection of the ovules within a special chamber1 to which the pollen alone may penetrate4 ,round these essential organs are the coloured petals of the corolla 7the chief part of the flower to the unscientific mind7 and the sepals1 often also coloured1 of the calyx4 ,there is no doubt that all these parts arose from modifications of the leaves or stems of the primitive plant2 though whether the bright leaves of the corolla are directly derived from ordinary leaves1 or are enlarged and flattened stamens1 has been disputed4 ,and to the question why these bright petals1 whose colour and variety of form lend such charm to the world of flowers1 have been developed at all1 most botanists will give a prompt and very interesting reply4 ,as both male and female elements are usually in one flower1 it may fertilise itself1 the pollen falling directly on the pistil4 ,but fertilisation is more sure and effective if the pollen comes from a different individual--if there is cross fertilisation4 ,this may be accomplished by the simple agency of the wind blowing the pollen broadcast1 but it is done much better by insects1 which brush against the stamens1 and carry grains of the pollen to the next flower they visit4 ,we have here a very fertile line of development among the primitive flowers4 ,the insects begin to visit them1 for their pollen or juices1 and cross-fertilise them4 ,if this is an advantage1 attractiveness to insects will become so important a feature that natural selection will develop it more and more4 ,in plain ,english1 what is meant is that those flowers which are more attractive to insects will be the most surely fertilised and breed most1 and the prolonged application of this principle during hundreds of thousands of years will issue in the immense variety of our flowers4 ,they will be enriched with little stores of honey and nectar2 not so mysterious an advantage1 when we reflect on the concentration of the juices in the neighbourhood of the seed4 ,then they must advertise their stores1 and the strong perfumes and bright colours begin to develop1 and ensure posterity to their possessors4 ,the shape of the corolla will be altered in hundreds of ways1 to accommodate and attract the useful visitor and shut out the mere robber4 ,these utilities1 together with the various modifying agencies of different environments1 are generally believed to have led to the bewildering variety and great beauty of our floral world4 ,it is proper to add that this view has been sharply challenged by a number of recent writers4 ,it is questioned if colours and scents do attract insects2 though several recent series of experiments seem to show that bees are certainly attracted by colours4 ,it is questioned if cross-fertilisation has really the importance ascribed to it since the days of ,darwin4 ,some of these writers believe that the colours and the peculiar shape which the petals take in some flowers 7orchises1 for instance7 have been evolved to deter browsing animals from eating them4 ,the theory is thus only a different application of natural selection2 ,professor ,henslow1 on the other hand1 stands alone in denying the selection1 and believing that the insects directly developed the scents1 honeys1 colours1 and shapes by mechanical irritation4 ,the great majority of botanists adhere to the older view1 and see in the wonderful ,tertiary expansion of the flowers a manifold adaptation to the insect friends and insect foes which then became very abundant and varied4 ,resisting the temptation to glance at the marvellous adaptations which we find to-day in our plant world--the insect-eating plants1 the climbers1 the parasites1 the sensitive plants1 the water-storing plants in dry regions1 and so on--we must turn to the consideration of the insects themselves4 ,we have already studied the evolution of the insect in general1 and seen its earlier forms4 ,the ,tertiary ,era not only witnessed a great deployment of the insects1 but was singularly rich in means of preserving them4 ,the fly in amber has ceased to be a puzzle even to the inexpert4 ,amber is the resin that exuded from pine-like trees1 especially in the ,baltic region1 in the ,eocene and ,oligocene periods4 ,insects stuck in the resin1 and were buried under fresh layers of it1 and we find them embalmed in it as we pick up the resin on the shores of the ,baltic to-day4 ,the ,tertiary lakes were also important cemeteries of insects4 ,a great bed at ,florissart1 in ,colorado1 is described by one of the ,american experts who examined it as a ,tertiary ,pompeii4 ,it has yielded specimens of about a thousand species of ,tertiary insects4 ,near the large ancient lake1 of which it marks the site1 was a volcano1 and the fine ash yielded from the cone seems to have buried myriads of insects in the water4 ,at ,oeningen a similar lake-deposit has1 although only a few feet thick1 yielded #ijj species of insects4 ,yet these rich and numerous finds throw little light on the evolution of the insect1 except in the general sense that they show species and even genera quite different from those of to-day4 ,no new families of insects have appeared since the ,eocene1 and the ancient types had by that time disappeared4 ,since the ,eocene1 however1 the species have been almost entirely changed1 so that the insect record1 from its commencement in the ,primary ,era1 has the stamp of evolution on every page of it4 ,unfortunately1 insects1 especially the higher and later insects1 are such frail structures that they are only preserved in very rare conditions4 ,the most important event of the insect-world in the ,tertiary is the arrival of the butterflies1 which then appear for the first time4 ,we may assume that they spread with great rapidity and abundance in the rich floral world of the mid-,jurassic4 ,more than #ac1jjj species of ,lepidoptera are known to-day1 and there are probably twice that number yet to be classified by the entomologist4 ,but so far the ,tertiary deposits have yielded only the fragmentary remains of about twenty individual butterflies4 ,the evolutionary study of the insects is1 therefore1 not so much concerned with the various modifications of the three pairs of jaws1 inherited from the primitive ,tracheate1 and the wings1 which have given us our vast variety of species4 ,it is directed rather to the more interesting questions of what are called the instincts of the insects1 the remarkable metamorphosis by which the young of the higher orders attain the adult form1 and the extraordinary colouring and marking of bees1 wasps1 and butterflies4 ,even these questions1 however1 are so large that only a few words can be said here on the tendencies of recent research4 ,in regard to the psychic powers of insects it may be said1 in the first place1 that it is seriously disputed among the modern authorities whether even the highest insects 7the ant1 bee1 and wasp7 have any degree whatever of the intelligence which an earlier generation generously bestowed on them4 ,wasmann and ,bethe1 two of the leading authorities on ants1 take the negative view2 ,forel claims that they show occasional traces of intelligence4 ,it is at all events clear that the enormous majority of1 if not all1 their activities--and especially those activities of the ant and the bee which chiefly impress the imagination--are not intelligent1 but instinctive actions4 ,and the second point to be noted is that the word instinct1 in the old sense of some innate power or faculty directing the life of an animal1 has been struck out of the modern scientific dictionary4 ,the ant or bee inherits a certain mechanism of nerves and muscles which will1 in certain circumstances1 act in the way we call instinctive4 ,the problem is to find how this mechanism and its remarkable actions were slowly evolved4 ,in view of the innumerable and infinitely varied forms of instinct in the insect world we must restrict ourselves to a single illustration--say1 the social life of the ants and the bees4 ,we are not without indications of the gradual development of this social life4 ,in the case of the ant we find that the ,tertiary specimens--and about a hundred species are found in ,switzerland alone1 whereas there are only fifty species in the whole of ,europe to-day--all have wings and are1 apparently1 of the two sexes1 not neutral4 ,this seems to indicate that even in the mid-,tertiary some millions of years after the first appearance of the ant1 the social life which we admire in the ants today had not yet been developed4 ,the ,tertiary bees1 on the other hand1 are said to show some traces of the division of labour 7and modification of structure7 which make the bees so interesting2 but in this case the living bees1 rising from a solitary life through increasing stages of social co-operation1 give us some idea of the gradual development of this remarkable citizenship4 ,it seems to me that the great selective agency which has brought about these1 and many other remarkable activities of the insects 7such as the storing of food with their eggs by wasps71 was probably the occurrence of periods of cold1 and especially the beginning of a winter season in the ,cretaceous or ,tertiary age4 ,in the periods of luxuriant life 7the ,carboniferous1 the ,jurassic1 or the ,oligocene71 when insects swarmed and varied in every direction1 some would vary in the direction of a more effective placing of the eggs2 and the supervening period of cold and scarcity would favour them4 ,when a regular winter season set in1 this tendency would be enormously increased4 ,it is a parallel case to the evolution of the birds and mammals from the reptiles4 ,those that varied most in the direction of care for the egg and the young would have the largest share in the next generation4 ,when we further reflect that since the ,tertiary the insect world has passed through the drastic disturbance of the climate in the great ,ice-,age1 we seem to have an illuminating clue to one of the most remarkable features of higher insect life4 ,the origin of the colour marks' and patterns on so many of the higher insects1 with which we may join the origin of the stick-insects1 leaf-insects1 etc41 is a subject of lively controversy in science to-day4 ,the protective value of the appearance of insects which look almost exactly like dried twigs or decaying leaves1 and of an arrangement of the colours of the wings of butterflies which makes them almost invisible when at rest1 is so obvious that natural selection was confidently invoked to explain them4 ,in other cases certain colours or marks seemed to have a value as warning colours1 advertising the nauseousness of their possessors to the bird1 which had learned to recognise them2 in other cases these colours and marks seemed to be borrowed by palatable species1 whose unconscious mimicry led to their survival2 in other cases1 again1 the patterns and spots were regarded as recognition marks1 by which the male could find his mate4 ,science is just now passing through a phase of acute criticism--as the reader will have realised by this time--and many of the positions confidently adopted in the earlier constructive stage are challenged4 ,this applies to the protective colours1 warning colours1 mimicry1 etc41 of insects4 ,probably some of the affirmations of the older generation of evolutionists were too rigid and extensive2 and probably the denials of the new generation are equally exaggerated4 ,when all sound criticism has been met1 there remains a vast amount of protective colouring1 shaping1 and marking in the insect world of which natural selection gives us the one plausible explanation4 ,but the doctrine of natural selection does not mean that every feature of an animal shall have a certain utility4 ,it will destroy animals with injurious variations and favour animals with useful variations2 but there may be a large amount of variation1 especially in colour1 to which it is quite indifferent4 ,in this way much colour-marking may develop1 either from ordinary embryonic variations or 7as experiment on butterflies shows7 from the direct influence of surroundings which has no vital significance4 ,in this way1 too1 small variations of no selective value may gradually increase until they chance to have a value to the animal4 99 99 ,for a strong statement of the new critical position see ,dewar and ,finn's ,making of ,species1 #aiji1 ch4 vi4 ,the origin of the metamorphosis1 or pupa-stage1 of the higher insects1 with all its wonderful protective devices1 is so obscure and controverted that we must pass over it4 ,some authorities think that the sleep-stage has been evolved for the protection of the helpless transforming insect2 some believe that it occurs because movement would be injurious to the insect in that stage2 some say that the muscular system is actually dissolved in its connections2 and some recent experts suggest that it is a reminiscence of the fact that the ancestors of the metamorphosing insects were addicted to internal parasitism in their youth4 ,it is one of the problems of the future4 ,at present we have no fossil pupa-remains 7though we have one caterpillar7 to guide us4 ,we must leave these fascinating but difficult problems of insect life1 and glance at the evolution of the birds4 ,to the student of nature whose interest is confined to one branch of science the record of life is a mysterious ,succession of waves4 ,a comprehensive view of nature1 living and non-living1 past and present1 discovers scores of illuminating connections1 and even sees at times the inevitable sequence of events4 ,thus if the rise of the ,angiospermous vegetation on the ruins of the ,mesozoic world is understood in the light of geological and climatic changes1 and the consequent deploying of the insects1 especially the suctorial insects1 is a natural result1 the simultaneous triumph of the birds is not unintelligible4 ,the grains and fruits of the ,angiosperms and the vast swarms of insects provided immense stores of food2 the annihilation of the ,pterosaurs left a whole stratum of the earth free for their occupation4 ,we saw that a primitive bird1 with very striking reptilian features1 was found in the ,jurassic rocks1 suggesting very clearly the evolution of the bird from the reptile in the cold of the ,permian or ,triassic period4 ,in the ,cretaceous we found the birds distributed in a number of genera1 but of two leading types4 ,the ,ichthyornis type was a tern-like flying bird1 with socketed teeth and biconcave vertebrae like the reptile1 but otherwise fully evolved into a bird4 ,its line is believed to survive in the gannets1 cormorants1 pelicans1 and frigate-birds of to-day4 ,the less numerous ,hesperornis group were large and powerful divers4 ,then there is a blank in the record1 representing the ,cretaceous upheaval1 and it unfortunately conceals the first great ramification of the bird world4 ,when the light falls again on the ,eocene period we find great numbers of our familiar types quite developed4 ,primitive types of gulls1 herons1 pelicans1 quails1 ibises1 flamingoes1 albatrosses1 buzzards1 hornbills1 falcons1 eagles1 owls1 plovers1 and woodcocks are found in the ,eocene beds2 the ,oligocene beds add parrots1 trogons1 cranes1 marabouts1 secretary-birds1 grouse1 swallows1 and woodpeckers4 ,we cannot suppose that every type has been preserved1 but we see that our bird-world was virtually created in the early part of the ,tertiary ,era4 ,with these more or less familiar types were large ostrich-like survivors of the older order4 ,in the bed of the sea which covered the site of ,london in the ,eocene are found the remains of a toothed bird 7,odontopteryx71 though the teeth are merely sharp outgrowths of the edge of the bill4 ,another bird of the same period and region 7,gastornis7 stood about ten feet high1 and must have looked something like a wading ostrich4 ,other large waders1 even more ostrich-like in structure1 lived in ,north ,america2 and in ,patagonia the remains have been found of a massive bird1 about eight feet high1 with a head larger than that of any living animal except the elephant1 rhinoceros1 and hippopotamus 7,chamberlin74 ,the absence of early ,eocene remains prevents us from tracing the lines of our vast and varied bird-kingdom to their ,mesozoic beginnings4 ,and when we appeal to the zoologist to supply the missing links of relationship1 by a comparison of the structures of living birds1 we receive only uncertain and very general suggestions4 99 ,he tells us that the ostrich-group 7especially the emus and cassowaries7 are one of the most primitive stocks of the bird world1 and that the ancient ,dinornis group and the recently extinct moas seem to be offshoots of that stock4 ,the remaining many thousand species of ,carinate birds 7or flying birds with a keel carina-shaped breast-bone for the attachment of the flying muscles7 are then gathered into two great branches1 which are traceable to a common stock 7,pycraft71 and branch in their turn along the later lines of development4 ,one of these lines--the pelicans1 cormorants1 etc4--seems to be a continuation of the ,ichthyornis type of the ,cretaceous1 with the ,odontopteryx as an ,eocene offshoot2 the divers1 penguins1 grebes1 and petrels represent another ancient stock1 which may be related to the ,hesperornis group of the ,cretaceous4 ,dr4 ,chalmers ,mitchell thinks that the screamers of ,south ,america are the nearest representatives of the common ancestor of the keel-breasted birds4 ,but even to give the broader divisions of the #ai1jjj species of living birds would be of little interest to the general reader4 99 ,the best treatment of the subject will be found in ,w4 ,p4 ,pycraft's ,history of ,birds1 #aiaj4 ,the special problems of bird-evolution are as numerous and unsettled as those of the insects4 ,there is the same dispute as to protective colours and recognition marks1 the same uncertainty as to the origin of such instinctive practices as migration and nesting4 ,the general feeling is that the annual migration had its origin in the overcrowding of the regions in which birds could live all the year round4 ,they therefore pushed northward in the spring and remained north until the winter impoverishment drove them south again4 ,on this view each group would be returning to its ancestral home1 led by the older birds1 in the great migration flights4 ,the curious paths they follow are believed by some authorities to mark the original lines of their spread1 preserved from generation to generation through the annual lead of the older birds4 ,if we recollect the ,ice-,age which drove the vast majority of the birds south at the end of the ,tertiary1 and imagine them later following the northward retreat of the ice1 from their narrowed and overcrowded southern territory1 we may not be far from the secret of the annual migration4 ,a more important controversy is conducted in regard to the gorgeous plumage and other decorations and weapons of the male birds4 ,darwin1 as is known1 advanced a theory of sexual selection to explain these4 ,the male peacock1 to take a concrete instance1 would have developed its beautiful tail because1 through tens of thousands of generations1 the female selected the more finely tailed male among the various suitors4 ,dr4 ,wallace and other authorities always disputed this aesthetic sentiment and choice on the part of the female4 ,the general opinion today is that ,darwin's theory could not be sustained in the range and precise sense he gave to it4 ,some kind of display by the male in the breeding season would be an advantage1 but to suppose that the females of any species of birds or mammals had the definite and uniform taste necessary for the creation of male characters by sexual selection is more than difficult4 ,they seem to be connected in origin rather with the higher vitality of the male1 but the lines on which they were selected are not yet understood4 ,this general sketch of the enrichment of the earth with flowering plants1 insects1 and birds in the ,tertiary ,era is all that the limits of the present work permit us to give4 ,it is an age of exuberant life and abundant food2 the teeming populations overflow their primitive boundaries1 and1 in adapting themselves to every form of diet1 every phase of environment1 and every device of capture or escape1 the spreading organisms are moulded into tens of thousands of species4 ,we shall see this more clearly in the evolution of the mammals4 ,what we chiefly learn from the present chapter is the vital interconnection of the various parts of nature4 ,geological changes favour the spread of a certain type of vegetation4 ,insects are attracted to its nutritious seed-organs1 and an age of this form of parasitism leads to a signal modification of the jaws of the insects themselves and to the lavish variety and brilliance of the flowers4 ,birds are attracted to the nutritious matter enclosing the seeds1 and1 as it is an advantage to the plant that its seeds be scattered beyond the already populated area1 by passing through the alimentary canal of the bird1 and being discharged with its excrements1 a fresh line of evolution leads to the appearance of the large and coloured fruits4 ,the birds1 again1 turn upon the swarming insects1 and the steady selection they exercise leads to the zigzag flight and the protective colour of the butterfly1 the concealment of the grub and the pupa1 the marking of the caterpillar1 and so on4 ,we can understand the living nature of to-day as the outcome of that teeming1 striving1 changing world of the ,tertiary ,era1 just as it in turn was the natural outcome of the ages that had gone before4 ,,chapter ,,xvii4 ,,the ,,origin ,,of ,,our ,,mammals ,in our study of the evolution of the plant1 the insect1 and the bird we were seriously thwarted by the circumstance that their frames1 somewhat frail in themselves1 were rarely likely to be entombed in good conditions for preservation4 ,earlier critics of evolution used1 when they were imperfectly acquainted with the conditions of fossilisation1 to insinuate that this fragmentary nature of the geological record was a very convenient refuge for the evolutionist who was pressed for positive evidence4 ,the complaint is no longer found in any serious work4 ,where we find excellent conditions for preservation1 and animals suitable for preservation living in the midst of them1 the record is quite satisfactory4 ,we saw how the chalk has yielded remains of sea-urchins in the actual and gradual process of evolution4 ,tertiary beds which represent the muddy bottoms of tranquil lakes are sometimes equally instructive in their fossils1 especially of shell-fish4 ,the ,paludina of a certain ,slavonian lake-deposit is a classical example4 ,it changes so greatly in the successive levels of the deposit that1 if the intermediate forms were not preserved1 we should divide it into several different species4 ,the ,planorbis is another well-known example4 ,in this case we have a species evolving along several distinct lines into forms which differ remarkably from each other4 ,the ,tertiary mammals1 living generally on the land and only coming by accident into deposits suitable for preservation1 cannot be expected to reveal anything like this sensible advance from form to form4 ,they were1 however1 so numerous in the mid-,tertiary1 and their bones are so well calculated to survive when they do fall into suitable conditions1 that we can follow their development much more easily than that of the birds4 ,we find a number of strange patriarchal beasts entering the scene in the early ,eocene1 and spreading into a great variety of forms in the genial conditions of the ,oligocene and ,miocene4 ,as some of these forms advance1 we begin to descry in them the features1 remote and shadowy at first1 of the horse1 the deer1 the elephant1 the whale1 the tiger1 and our other familiar mammals4 ,in some instances we can trace the evolution with a wonderful fullness1 considering the remoteness of the period and the conditions of preservation4 ,then1 one by one1 the abortive1 the inelastic1 the ill-fitted types are destroyed by changing conditions or powerful carnivores1 and the field is left to the mammals which filled it when man in turn began his destructive career4 ,the first point of interest is the origin of these ,tertiary mammals4 ,their distinctive advantage over the mammals of the ,mesozoic ,era was-the possession by the mother of a placenta 7the after-birth of the higher mammals71 or structure in the womb by which the blood-vessels of the mother are brought into such association with those of the foetus that her blood passes into its arteries1 and it is fully developed within the warm shelter of her womb4 ,the mammals of the ,mesozoic had been small and primitive animals1 rarely larger than a rat1 and never rising above the marsupial stage in organisation4 ,they not only continued to exist1 and give rise to their modern representatives 7the opossum1 etc47 during the ,tertiary ,era1 but they shared the general prosperity4 ,in ,australia1 where they were protected from the higher carnivorous mammals1 they gave rise to huge elephant-like wombats 7,diprotodon71 with skulls two or three feet in length4 ,over the earth generally1 however1 they were superseded by the placental mammals1 which suddenly break into the geological record in the early ,tertiary1 and spread with great vigour and rapidity over the four continents4 ,were they a progressive offshoot from the ,mesozoic ,marsupials1 or ,monotremes1 or do they represent a separate stock from the primitive half-reptile and half-mammal family8 ,the point is disputed2 nor does the scantiness of the record permit us to tell the place of their origin4 ,the placental structure would be so great an advantage in a cold and unfavourable environment that some writers look to the northern land1 connecting ,europe and ,america1 for their development4 ,we saw1 however1 that this northern region was singularly warm until long after the spread of the mammals4 ,other experts1 impressed by the parallel development of the mammals and the flowering plants1 look to the elevated parts of eastern ,north ,america4 ,such evidence as there is seems rather to suggest that ,south ,africa was the cradle of the placental mammals4 ,we shall find that many of our mammals originated in ,africa2 there1 too1 is found to-day the most primitive representative of the ,tertiary mammals1 the hyrax2 and there we find in especial abundance the remains of the mammal-like reptiles 7,theromorphs7 which are regarded as their progenitors4 ,further search in the unexplored geological treasures and dense forests of ,africa is needed4 ,we may provisionally conceive the placental mammals as a group of the ,south ,african early mammals which developed a fortunate variation in womb-structure during the severe conditions of the early ,mesozoic4 ,in this new structure they would have no preponderant advantage as long as the genial ,jurassic age favoured the great reptiles1 and they may have remained as small and insignificant as the ,marsupials4 ,but with the fresh upheaval and climatic disturbance at the end of the ,jurassic1 and during the ,cretaceous1 they spread northward1 and replaced the dying reptiles1 as the ,angiosperms replaced the dying cycads4 ,when they met the spread of the ,angiosperm vegetation they would receive another great stimulus to development4 ,they appear in ,europe and ,north ,america in the earliest ,cretaceous4 ,the rise of the land had connected many hitherto isolated regions1 and they seem to have poured over every bridge into all parts of the four continents4 ,the obscurity of their origin is richly compensated by their intense evolutionary interest from the moment they enter the geological record4 ,we have seen this in the case of every important group of plants and animals1 and can easily understand it4 ,the ancestral group was small and local2 the descendants are widely spread4 ,while1 therefore1 we discover remains of the later phases of development in our casual cuttings and quarries1 the ancestral tomb may remain for ages in some unexplored province of the geological world4 ,if this region is1 as we suspect1 in ,africa1 our failure to discover it as yet is all the more intelligible4 ,but these mammals of the early ,tertiary are still of such a patriarchal or ancestral character that the student of evolution can dispense with their earlier phase4 ,they combine in their primitive frames1 in an elementary way1 the features which we now find distributed in widely removed groups of their descendants4 ,most of them fall into two large orders3 the ,condylarthra1 the ancestral herbivores from which we shall find our horses1 oxen1 deer1 elephants1 and hogs gradually issuing1 and the ,creodonta1 the patriarchal carnivores1 which will give birth to our lions and tigers1 wolves and foxes1 and their various cousins4 ,as yet even the two general types of herbivore and carnivore are so imperfectly separated that it is not always possible to distinguish between them4 ,nearly all of them have the five-toed foot of the reptile ancestor2 and the flat nails on their toes are the common material out of which the hoof of the ungulate and the claw of the carnivore will be presently fashioned4 ,nearly all have forty-four simply constructed teeth1 from which will be evolved the grinders and tusks of the elephant or the canines of the tiger4 ,they answer in every respect to the theory that some primitive local group was the common source of all our great mammals4 ,with them are ancestral forms of ,edentates 7sloths1 etc47 and ,insectivores 7moles1 etc471 side-branches developing according to their special habits2 and before the end of the ,eocene we find primitive ,rodents 7squirrels1 etc47 and ,cheiroptera 7bats74 ,from the description of the ,tertiary world which we have seen in the last chapter we understand the rapid evolution of the herbivorous ,condylarthra4 ,the rich vegetation which spreads over the northern continents1 to which they have penetrated1 gives them an enormous vitality and fecundity1 and they break into groups1 as they increase in number1 adapted to the different conditions of forest1 marsh1 or grass-covered plain4 ,some of them1 swelling lazily on the abundant food1 and secure for a time in their strength1 become the ,deinosaurs of their age1 mere feeding and breeding machines4 ,they are massive1 sluggish1 small-brained animals1 their strong stumpy limbs terminating in broad five-toed feet4 ,coryphodon1 sometimes as large as an ox1 is a typical representative4 ,it is a type fitted only for prosperous days1 and these ,amblypoda1 as they are called1 will disappear as soon as the great carnivores are developed4 ,another doomed race1 or abortive experiment of early mammal life1 were the remarkable ,deinocerata 7terrible-horned mammals74 ,they sometimes measured thirteen feet in length1 but had little use for brain in the conditions in which they were developed4 ,the brain of the ,deinoceras was only one-eighth the size of the brain of a rhinoceros of the same bulk2 and the rhinoceros is a poor-brained representative of the modern mammals4 ,to meet the growing perils of their race they seem to have developed three pairs of horns on their long1 flat skulls1 as we find on them three pairs of protuberances4 ,a late specimen of the group1 ,tinoceras1 had a head four feet in length1 armed with these six horns1 and its canine teeth were developed into tusks sometimes seven or eight inches in length4 ,they suggest a race of powerful but clumsy and grotesque monsters1 making a last stand1 and developing such means of protection as their inelastic nature permitted4 ,but the horns seem to have proved a futile protection against the advancing carnivores1 and the race was extinguished4 ,the horns may1 of course1 have been mainly developed by1 or for1 the mutual butting of the males4 ,the extinction of these races will remind many readers of a theory on which it is advisable to say a word4 ,it will be remembered that the last of the ,deinosaurs and the ,ammonites also exhibited some remarkable developments in their last days4 ,these facts have suggested to some writers the idea that expiring races pass through a death-agony1 and seem to die a natural death of old age like individuals4 ,the ,trilobites are quoted as another instance2 and some ingenious writers add the supposed eccentricities of the ,roman ,empire in its senile decay and a number of other equally unsubstantial illustrations4 ,there is not the least ground for this fantastic speculation4 ,the destruction of these doomed races is as clearly traceable to external causes as is the destruction of the ,roman ,empire2 nor1 in fact1 did the ,roman ,empire develop any such eccentricities as are imagined in this superficial theory4 ,what seem to our eye the eccentricities and convulsions of the ,ceratopsia and ,deinocerata are much more likely to be defensive developments against a growing peril1 but they were as futile against the new carnivores as were the assegais of the ,zulus against the ,european4 ,on the other hand1 the eccentricities of many of the later ,trilobites--the ,,latest ,trilobites1 it may be noted1 were chaste and sober specimens of their race1 like the last ,roman patricians--and of the ,ammonites may very well have been caused by physical and chemical changes in the sea-water4 ,we know from experiment that such changes have a disturbing influence1 especially on the development of eggs and larvae2 and we know from the geological record that such changes occurred in the periods when the ,trilobites and ,ammonites perished4 ,in fine1 the vast majority of extinct races passed through no convulsions whatever4 ,we may conclude that races do not die2 they are killed4 ,the extinction of these races of the early ,condylarthra1 and the survival of those races whose descendants share the earth with us to-day1 are quite intelligible4 ,the hand of natural selection lay heavy on the ,tertiary herbivores4 ,apart from overpopulation1 forcing groups to adapt themselves to different regions and diets1 and apart from the geological disturbances and climatic changes which occurred in nearly every period1 the shadow of the advancing carnivores was upon them4 ,primitive but formidable tigers1 wolves1 and hyenas were multiplying1 and a great selective struggle set in4 ,some groups shrank from the battle by burrowing underground like the rabbit2 some1 like the squirrel or the ape1 took refuge in the trees2 some1 like the whale and seal1 returned to the water2 some shrank into armour1 like the armadillo1 or behind fences of spines1 like the hedgehog2 some1 like the bat1 escaped into the air4 ,social life also was probably developed at this time1 and the great herds had their sentinels and leaders4 ,but the most useful qualities of the large vegetarians1 which lived on grass and leaf1 were acuteness of perception to see the danger1 and speed of limb to escape it4 ,in other words1 increase of brain and sense-power and increase of speed were the primary requisites4 ,the clumsy early ,condylarthra failed to meet the tests1 and perished2 the other branches of the race were more plastic1 and1 under the pressure of a formidable enemy1 were gradually moulded into the horse1 the deer1 the ox1 the antelope1 and the elephant4 ,we can follow the evolution of our mammals of this branch most easily by studying the modification of the feet and limbs4 ,in a running attitude--the experiment may be tried--the weight of the body is shifted from the flat sole of the foot1 and thrown upon the toes1 especially the central toes4 ,this indicates the line of development of the ,ungulates 7hoofed animals7 in the struggle of the ,tertiary ,era4 ,in the early ,eocene we find the ,condylarthra 7such as ,phenacodus7 with flat five-toed feet1 and such a mixed combination of characters that they might serve very well for the ancestors of all the later ,ungulata 7,woodward74 ,we then presently find this generalised ,ungulate branching into three types1 one of which seems to be a patriarchal tapir1 the second is regarded as a very remote ancestor of the horse1 and the third foreshadows the rhinoceros4 ,the feet have now only three or four toes2 one or two of the side-toes have disappeared4 ,this evolution1 however1 follows two distinct lines4 ,in one group of these primitive ,ungulates the main axis of the limb1 or the stress of the weight1 passes through the middle toe4 ,this group becomes the ,perissodactyla 7odd-toed ,ungulates7 of the zoologist1 throwing out side-branches in the tapir and the rhinoceros1 and culminating in the one-toed horse4 ,in the other line1 the ,artiodactyla 7the even-toed or cloven-hoofed ,ungulates71 the main axis or stress passes between the third and fourth toes1 and the group branches into our deer1 oxen1 sheep1 pigs1 camels1 giraffes1 and hippopotamuses4 ,the elephant has developed along a separate and very distinctive line1 as we shall see1 and the hyrax is a primitive survivor of the ancestral group4 ,thus the evolutionist is able to trace a very natural order in the immense variety of our ,ungulates4 ,he can follow them in theory as they slowly evolve from their primitive ,eocene ancestor according to their various habits and environments2 he has a very rich collection of fossil remains illustrating the stages of their development2 and in the hyrax 7or coney7 he has one more of those living fossils1 or primitive survivors1 which still fairly preserve the ancestral form4 ,the hyrax has four toes on the front foot and three on the hind foot1 and the feet are flat4 ,its front teeth resemble those of a rodent1 and its molars those of the rhinoceros4 ,in many respects it is a most primitive and generalised little animal1 preserving the ancestral form more or less faithfully since ,tertiary days in the shelter of the ,african ,continent4 ,the rest of the ,ungulates continued to develop through the ,tertiary1 and fortunately we are enabled to follow the development of two of the most interesting of them1 the horse and the elephant1 in considerable detail4 ,as ,i said above1 the primitive ,ungulate soon branches into three types which dimly foreshadow the tapir1 the horse1 and the rhinoceros1 the three forms of the ,perissodactyl4 ,the second of these types is the ,hyracotherium4 ,it has no distinct equine features1 and is known only from the skull1 but the authorities regard it as the progenitor 7or representative of the progenitors7 of the horse-types4 ,in size it must have been something like the rabbit or the hyrax4 ,still early in the ,eocene1 however1 we find the remains of a small animal 7,eohippus71 about the size of a fox1 which is described as undoubtedly horse-like4 ,it had only three toes on its hind feet1 and four on its front feet2 though it had also a splint-bone1 representing the shrunken and discarded fifth toe1 on its fore feet4 ,another form of the same period 7,protorohippus7 shows the central of the three toes on the hind foot much enlarged1 and the lateral toes shrinking4 ,the teeth1 and the bones and joints of the limbs1 are also developing in the direction of the horse4 ,in the succeeding geological period1 the ,oligocene1 we find several horse-types in which the adaptation of the limbs to running on the firm grassy plains and of the teeth to eating the grass continues4 ,mesohippus has lost the fourth toe of the fore foot1 which is now reduced to a splintbone1 and the lateral toes of its hind foot are shrinking4 ,in the ,miocene period there is a great development of the horse-like mammals4 ,we have the remains of more than forty species1 some continuing the main line of development on the firm and growing prairies of the ,miocene1 some branching into the softer meadows or the forests1 and giving rise to types which will not outlive the ,tertiary4 ,they have three toes on each foot1 and have generally lost even the rudimentary trace of the fourth toe4 ,in most of them1 moreover1 the lateral toes--except in the marsh-dwelling species1 with spreading feet--scarcely touch the ground1 while the central toe is developing a strong hoof4 ,the leg-bones are longer1 and have a new type of joint2 the muscles are concentrated near the body4 ,the front teeth are now chopping incisors1 and the grinding teeth approach those of the modern horse in the distribution of the enamel1 dentine1 and cement4 ,they are now about the size of a donkey1 and must have had a distinctly horsy appearance1 with their long necks and heads and tapering limbs4 ,one of them1 ,merychippus1 was probably in the direct line of the evolution of the horse4 ,from ,hipparion some of the authorities believe that the zebras may have been developed4 ,miohippus1 ,protohippus1 and ,hypohippus1 varying in size from that of a sheep to that of a donkey1 are other branches of this spreading family4 ,in the ,pliocene period the evolution of the main stem culminates in the appearance of the horse1 and the collateral branches are destroyed4 ,pliohippus is a further intermediate form4 ,it has only one toe on each foot1 with two large splint bones1 but its hoof is less round than that of the horse1 and it differs in the shape of the skull and the length of the teeth4 ,the true horse 7,equus7 at length appears1 in ,europe and ,america1 before the close of the ,tertiary period4 ,as is well known1 it still has the rudimentary traces of its second and fourth toes in the shape of splint bones1 and these bones are not only more definitely toe-shaped in the foal before birth1 but are occasionally developed and give us a three-toed horse4 ,from these successive remains we can confidently picture the evolution1 during two or three million years1 of one of our most familiar mammals4 ,it must not1 of course1 be supposed that these fossil remains all represent ancestors of the horse4 ,in some cases they may very well do so2 in others1 as we saw1 they represent sidebranches of the family which have become extinct4 ,but even such successive forms as the ,eohippus1 ,mesohippus1 ,miohippus1 and ,pliohippus must not be arranged in a direct line as the pedigree of the horse4 ,the family became most extensive in the ,miocene1 and we must regard the casual fossil specimens we have discovered as illustrations of the various phases in the development of the horse from the primitive ,ungulate4 ,when we recollect what we saw in an earlier chapter about the evolution of grassy plains and the successive rises of the land during the ,tertiary period1 and when we reflect on the simultaneous advance of the carnivores1 we can without difficulty realise this evolution of our familiar companion from a hyrax-like little animal of two million years ago4 ,we have not in many cases so rich a collection of intermediate forms as in the case of the horse1 but our fossil mammals are numerous enough to suggest a similar development of all the mammals of to-day4 ,the primitive family which gave birth to the horse also gave us1 as we saw1 the tapir and the rhinoceros4 ,we find ancestral tapirs in ,europe and ,america during the ,tertiary period1 but the later cold has driven them to the warm swamps of ,brazil and ,malaysia4 ,the rhinoceros has had a long and interesting history4 ,from the primitive ,hyrochinus of the ,eocene1 in which it is dimly foreshadowed1 we pass to a large and varied family in the later periods4 ,in the ,oligocene it spreads into three great branches1 adapted1 respectively1 to life on the elevated lands1 the lowlands1 and the water4 ,the upland type 7,hyracodon7 was a light-limbed running animal1 well illustrating the close relation to the horse4 ,the aquatic representative 7,metamynodon7 was a stumpy and bulky animal4 ,the intermediate lowland type was probably the ancestor of the modern animal4 ,all three forms were yet hornless4 ,in the ,miocene the lowland type 7,leptaceratherium1 ,aceratherium1 etc47 develops vigorously1 while the other branches die4 ,the ,european types now have two horns1 and in one of the ,american species 7,diceratherium7 we see a commencement of the horny growths from the skull4 ,we shall see later that the rhinoceros continued in ,europe even during the severe conditions of the glacial period1 in a branch that developed a woolly coat4 ,there were also in the early ,tertiary several sidebranches of the horse-tapir-rhinoceros family4 ,the ,palaeotheres were more or less between the horse and the tapir in structure2 the ,anoplotheres between the tapir and the ruminant4 ,a third doomed branch1 the ,titanotheres1 flourished vigorously for a time1 and begot some strange and monstrous forms 7,brontops1 ,titanops1 etc474 ,in the larger specimens the body was about fourteen feet long1 and stood ten feet from the ground4 ,the long1 low skull had a pair of horns over the snout4 ,they perished like the equally powerful but equally sluggish and stupid ,deinocerata4 ,the ,tertiary was an age of brain rather than of brawn4 ,as compared with their early ,tertiary representatives' some of our modern mammals have increased seven or eight-fold in brain-capacity4 ,while the horses and tapirs and rhinoceroses were being gradually evolved from the primitive types1 the ,artiodactyl branch of the ,ungulates--the pigs1 deer1 oxen1 etc4--were also developing4 ,we must dismiss them briefly4 ,we saw that the primitive herbivores divided early in the ,eocene into the odd-toed and even-toed varieties2 the name refers1 it will be remembered1 not to the number of toes1 but to the axis of stress4 ,the ,artiodactyl group must have quickly branched in turn1 as we find very primitive hogs and camels before the end of the ,eocene4 ,the first hog-like creature 7,homacodon7 was much smaller than the hog of to-day1 and had strong canine teeth1 but in the ,oligocene the family gave rise to a large and numerous race1 the ,elotheres4 ,these giant-pigs1 as they have been called1 with two toes on each foot1 flourished vigorously for a time in ,europe and ,america1 but were extinguished in the ,miocene1 when the true pigs made their appearance4 ,another doomed race of the time is represented by the ,hyopotamus1 an animal between the pig and the hippopotamus2 and the ,oreodontids1 between the hog and the deer1 were another unsuccessful branch of the early race4 ,the hippopotamus itself was widespread in ,europe1 and a familiar form in the rivers of ,britain1 in the latter part of the ,tertiary4 ,the camel seems to be traceable to a group of primitive ,north ,american ,ungulates 7,paebrotherium1 etc47 in the later ,eocene period4 ,the ,paebrotherium1 a small animal about two feet long1 is followed by ,pliauchenia1 which points toward the llamas and vicunas1 and ,procamelus1 which clearly foreshadows the true camel4 ,in the ,pliocene the one branch went southward1 to develop into the llamas and vicunas1 and the other branch crossed to ,asia1 to develop into the camels4 ,since that time they have had no descendants in ,north ,america4 ,the primitive giraffe appears suddenly in the later ,tertiary deposits of ,europe and ,asia4 ,the evidence points to an invasion from ,africa1 and1 as the region of development is unknown and unexplored1 the evolution of the giraffe remains a matter of speculation4 ,chevrotains flourished in ,europe and ,north ,america in the ,oligocene1 and are still very primitive in structure1 combining features of the hog and the ruminants4 ,primitive deer and oxen begin in the ,miocene1 and seem to have an earlier representative in certain ,american animals 7,protoceras71 of which the male has a pair of blunt outgrowths between the ears4 ,the first true deer are hornless 7like the primitive muskdeer of ,asia to-day71 but by the middle of the ,miocene the males have small two-pronged antlers1 and as the period proceeds three or four more prongs are added4 ,it is some confirmation of the evolutionary embryonic law that we find the antlers developing in this way in the individual stag to-day4 ,a very curious race of ruminants in the later ,tertiary was a large antelope 7,sivatherium7 with four horns4 ,it had not only the dimensions1 but apparently some of the characters1 of an elephant4 ,the elephant itself1 the last type of the ,ungulates1 has a clearer line of developments4 ,a chance discovery of fossils in the ,fayum district in ,egypt led ,dr4 ,c4 ,w4 ,andrews to make a special exploration1 and on the remains which he found he has constructed a remarkable story of the evolution of the elephant4 99 ,it is clear that the elephant was developed in ,africa1 and a sufficiently complete series of remains has been found to give a good idea of the origin of its most distinctive features4 ,in the ,eocene period there lived in the ,egyptian region an animal1 something like the tapir in size and appearance1 which had its second incisors developed into small tusks and--to judge from the nasal opening in the skull--a somewhat prolonged snout4 ,this animal 7,moeritherium7 only differed from the ordinary primitive ,ungulate in these incipient elephantine features4 ,in the later ,eocene a larger and more advanced animal1 the ,palaeomastodon1 makes its appearance4 ,its tusks are larger 7five or six inches long71 its molars more elephantine1 the air-cells at the back of the head more developed4 ,it would look like a small elephant1 except that it had a long snout1 instead of a flexible trunk1 and a projecting lower jaw on which the snout rested4 99,see this short account1 ,guide to the ,elephants in the ,british ,museum1 #aijh4 ,up to the beginning of the ,miocene1 ,africa was1 as we saw1 cut off from ,europe and ,asia by the sea which stretched from ,spain to ,india4 ,then the land rose1 and the elephant passed by the new tracts into the north4 ,its next representative1 ,tetrabelodon1 is found in ,asia and ,europe1 as well as ,north ,africa4 ,the frame is as large as that of a medium-sized elephant1 and the increase of the air-cells at the back of the skull shows that an increased weight has to be sustained by the muscles of the neck4 ,the nostrils are shifted further back4 ,the tusks are from twenty to thirty inches long1 and round1 and only differ from those of the elephant in curving slightly downward1 ,the chin projects as far as the tusks4 ,the neck is shorter and thicker1 and1 as the animal increases in height1 we can understand that the long snout--possibly prehensile at its lower end--is necessary for the animal to reach the ground4 ,but the snout still lies on the projecting lower jaw1 and is not a trunk4 ,passing over the many collateral branches1 which diverge in various directions1 we next kind that the chin is shortening 7in ,tetrabelodon longirostris71 and1 through a long series of discovered intermediate forms1 we trace the evolution of the elephant from the mastodon4 ,the long supporting skin disappears1 and the enormous snout becomes a flexible trunk4 ,southern ,asia seems to have been the province of this final transformation1 and we have remains of some of these primitive elephants with tusks nine and a half feet long4 ,a later species1 which wandered over ,central and ,southern ,europe before the close of the ,tertiary1 stood fifteen feet high at the shoulder1 while the mammoth1 which superseded it in the days of early man1 had at times tusks more than ten feet in length4 ,it is interesting to reflect that this light on the evolution of one of our most specialised mammals is due to the chance opening of the soil in an obscure ,african region4 ,it suggests to us that as geological exploration is extended1 many similar discoveries may be made4 ,the slenderness of the geological record is a defect that the future may considerably modify4 ,from this summary review of the evolution of the ,ungulates we must now pass to an even briefer account of the evolution of the ,carnivores4 ,the evidence is less abundant1 but the characters of the ,carnivores consist so obviously of adaptations to their habits and diet that we have little difficulty in imagining their evolution4 ,their early ,eocene ancestors1 the ,creodonts1 gave rise in the ,eocene to forms which we may regard as the forerunners of the cat-family and dog-family1 to which most of our familiar ,carnivores belong4 ,patriofelis1 the patriarchal cat1 about five or six feet in length 7without the tail71 curiously combines the features of the cat and the seal-family4 ,cyonodon has a wolf-like appearance1 and ,amphicyon rather suggests the fox4 ,primitive weasels1 civets1 and hyaenas appear also in the ,eocene4 ,the various branches of the ,carnivore family are already roughly represented1 but it is an age of close relationships and generalised characters4 ,in the ,miocene we find the various groups diverging still further from each other and from the extinct stocks4 ,definite wolves and foxes abound in ,america1 and the bear1 civet1 and hyaena are represented in ,europe1 together with vague otter-like forms4 ,the dog-family seems to have developed chiefly in ,north ,america4 ,as in the case of the ,ungulates1 we find many strange side-branches which flourished for a time1 but are unknown to-day4 ,machoerodus1 usually known as the sabre-toothed tiger1 though not a tiger1 was one of the most formidable of these transitory races4 ,its upper canine teeth 7the sabres7 were several inches in length1 and it had enormously distensible jaws to make them effective4 ,the great development of such animals1 with large numbers of hyaenas1 civets1 wolves1 bears1 and other ,carnivores1 in the middle and later ,tertiary was probably the most effective agency in the evolution of the horse and deer and the extinction of the more sluggish races4 ,the aquatic branch of the ,carnivores 7seals1 walruses1 etc47 is little represented in the ,tertiary record4 ,we saw1 however1 that the most primitive representatives of the elephant-stock had also some characters of the seal1 and it is thought that the two had a common origin4 ,the ,moeritherium was a marsh-animal1 and may very well have been cousin to the branch of the family which pushed on to the seas1 and developed its fore limbs into paddles4 ,the ,rodents are represented in primitive form early in the ,eocene period4 ,the teeth are just beginning to show the characteristic modification for gnawing4 ,a large branch of the family1 the ,tillodonts1 attained some importance a little later4 ,they are described as combining the head and claws of a bear with the teeth of a rodent and the general characters of an ungulate4 ,in the ,oligocene we find primitive squirrels1 beavers1 rabbits1 and mice4 ,the ,insectivores also developed some of the present types at an early date1 and have since proved so unprogressive that some regard them as the stock from which all the placental mammals have arisen4 ,the ,cetacea 7whales1 porpoises1 etc47 are already represented in the ,eocene by a primitive whale-like animal 7,zeuglodon7 of unknown origin4 ,some specimens of it are seventy feet in length4 ,it has large teeth1 sometimes six inches long1 and is clearly a terrestrial mammal that has returned to the waters4 ,some forms even of the modern whale develop rudimentary teeth1 and in all forms the bony structure of the fore limbs and degenerate relic of a pelvis and back limbs plainly tell of the terrestrial origin4 ,dolphins appear in the ,miocene4 ,finally1 the ,edentates 7sloths1 anteaters1 and armadilloes7 are represented in a very primitive form in the early ,eocene4 ,they are then barely distinguishable from the ,condylarthra and ,creodonta1 and seem only recently to have issued from a common ancestor with those groups4 ,in the course of the ,tertiary we find them--especially in ,south ,america1 which was cut off from the ,north and its invading ,carnivores during the ,eocene and ,miocene--developed into large sloths1 armadilloes1 and anteaters4 ,the reconnection with ,north ,america in the ,pliocene allowed the northern animals to descend1 but gigantic sloths 7,megatherium7 and armadilloes 7,glyptodon7 flourished long afterwards in ,south ,america4 ,the ,megatherium attained a length of eighteen feet in one specimen discovered1 and the ,glyptodon often had a dorsal shield 7like that of the armadillo7 from six to eight feet long1 and1 in addition1 a stoutly armoured tail several feet long4 ,the richness and rapidity of the mammalian development in the ,tertiary1 of which this condensed survey will convey some impression1 make it impossible to do more here than glance over the vast field and indicate the better-known connections4 ,it will be seen that evolution not only introduces a lucid order and arrangement into our thousands of species of living and fossil mammals1 but throws an admirable light on the higher animal world of our time4 ,the various orders into which the zoologist puts our mammals are seen to be the branches of a living tree1 approaching more and more closely to each other in early ,tertiary times1 in spite of the imperfectness of the geological record4 ,we at last trace these diverging lines to a few very primitive1 generalised1 patriarchal groups1 which in turn approach each other very closely in structure1 and plainly suggest a common ,cretaceous ancestor4 ,whether that common ancestor was an ,edentate1 an ,insectivore1 or ,creodont1 or something more primitive than them all1 is disputed4 ,but the divergence of nearly all the lines of our mammal world from those patriarchal types is admirably clear4 ,in the mutual struggle of carnivore and herbivore1 in adaptation to a hundred different environments 7the water1 the land1 and the air1 the tree1 the open plain1 the underground1 the marsh1 etc47 and forms of diet1 we find the descendants of these patriarchal animals gradually developing their distinctive characters4 ,then we find the destructive agencies of living and inorganic nature blotting out type after type1 and the living things that spread over the land in the later ,tertiary are found to be broadly identical with the living things of to-day4 ,the last great selection1 the northern ,ice-,age1 will give the last touches of modernisation4 ,,chapter ,,xviii4 ,,the ,,evolution ,,of ,,man ,we have reserved for a closer inquiry that order of the placental mammals to which we ourselves belong1 and on which zoologists have bestowed the very proper and distinguishing name of the ,primates4 ,since the days of ,darwin there has been some tendency to resent the term lower animals1 which man applies to his poorer relations4 ,but1 though there is no such thing as an absolute standard by which we may judge the higher or lower status of animals or plants1 the extraordinary power which man has by his brain development attained over both animate and inanimate nature fully justifies the phrase4 ,the ,primate order is1 therefore1 of supreme interest as the family that gave birth to man1 and it is important to discover the agencies which impelled some primitive member of it to enter upon the path which led to this summit of organic nature4 ,the order includes the femurs1 a large and primitive family with ape-like features--the ,germans call them half-apes--the monkeys1 the man-like apes1 and man4 ,this classification according to structure corresponds with the successive appearance of the various families in the geological record4 ,the femurs appear in the ,eocene2 the monkeys1 and afterwards the apes1 in the ,miocene1 the first semi-human forms in the ,pleistocene1 though they must have been developed before this4 ,it is hardly necessary to say that science does not regard man as a descendant of the known anthropoid apes1 or these as descended from the monkeys4 ,they are successive types or phases of development1 diverging early from each other4 ,just as the succeeding horse-types of the record are not necessarily related to each other in a direct line1 yet illustrate the evolution of a type which culminates in the horse1 so the spreading and branching members of the ,primate group illustrate the evolution of a type of organism which culminates in man4 ,the particular relationship of the various families1 living and dead1 will need careful study4 ,that there is a general blood-relationship1 and that man is much more closely related to the anthropoid apes than to any of the lower ,primates1 is no longer a matter of controversy4 ,in ,rudolph ,virchow there died1 a few years ago1 the last authoritative man of science to express any doubt about it4 ,there are1 however1 non-scientific writers who1 by repeating the ambiguous phrase that it is only a theory1 convey the impression to inexpert readers that it is still more or less an open question4 ,we will therefore indicate a few of the lines of evidence which have overcome the last hesitations of scientific men1 and closed the discussion as to the fact4 ,the very close analogy of structure between man and the ape at once suggests that they had a common ancestor4 ,there are cases in which two widely removed animals may develop a similar organ independently1 but there is assuredly no possibility of their being alike in all organs1 unless by common inheritance4 ,yet the essential identity of structure in man and the ape is only confirmed by every advance of science1 and would of itself prove the common parentage4 ,such minor differences as there are between man and the higher ape--in the development of the cerebrum1 the number of the teeth or ribs1 the distribution of the hair1 and so on--are quite explicable when we reflect that the two groups must have diverged from each other more than a million years ago4 ,examining the structure of man more closely1 we find this strong suggestion of relationship greatly confirmed4 ,it is now well known that the human body contains a number of vestigial organs--organs of no actual use1 and only intelligible as vestiges of organs that were once useful4 ,whatever view we take of the origin of man1 each organ in his frame must have a meaning2 and1 as these organs are vestigial and useless even in the lowest tribes of men1 who represent primitive man1 they must be vestiges of organs that were of use in a remote pre-human ancestor4 ,the one fact that the ape has the same vestigial organs as man would1 on a scientific standard of evidence1 prove the common descent of the two4 ,but these interesting organs themselves point back far earlier than a mixed ape-human ancestor in many cases4 ,the shell of cartilage which covers the entrance to the ear--the gristly appendage which is popularly called the ear--is one of the clearest and most easily recognised of these organs4 ,the ear of a horse or a cat is an upright mobile shell for catching the waves of sound4 ,the human ear has the appearance of being the shrunken relic of such an organ1 and1 when we remove the skin1 and find seven generally useless muscles attached to it1 obviously intended to pull the shell in all directions 7as in the horse71 there can be no doubt that the external ear is a discarded organ1 a useless legacy from an earlier ancestor4 ,in cases where it has been cut off it was found that the sense of hearing was scarcely1 if at all1 affected4 ,now we know that it is similarly useless in all tribes of men1 and must therefore come from a pre-human ancestor4 ,it is also vestigial in the higher apes1 and it is only when we descend to the lower monkeys and femurs that we see it approaching its primitive useful form4 ,one may almost say that it is a reminiscence of the far-off period when1 probably in the early ,tertiary1 the ancestors of the ,primates took to the trees4 ,the animals living on the plain needed acute senses to detect the approach of their prey or their enemies2 the tree-dweller found less demand on his sense of hearing1 the speaking-trumpet was discarded1 and the development of the internal ear proceeded on the higher line of the perception of musical sounds4 ,we might take a very large number of parts of the actual human body1 and discover that they are similar historical or archaeological monuments surviving in a modern system1 but we have space only for a few of the more conspicuous4 ,the hair on the body is a vestigial organ1 of actual use to no race of men1 an evident relic of the thick warm coat of an earlier ancestor4 ,it in turn recalls the dwellers in the primeval forest4 ,in most cases--not all1 because the wearing of clothes for ages has modified this feature--it will be found that the hairs on the arm tend upward from the wrist to the elbow1 and downward from the shoulder to the elbow4 ,this very peculiar feature becomes intelligible when we find that some of the apes also have it1 and that it has a certain use in their case4 ,they put their hands over their heads as they sit in the trees during ram1 and in that position the sloping hair acts somewhat like the thatched roof of a cottage4 ,again1 it will be found that in the natural position of standing we are not perfectly flat-footed1 but tend to press much more on the outer than on the inner edge of the foot4 ,this tendency1 surviving after ages of living on the level ground1 is a lingering effect of the far-off arboreal days4 ,a more curious reminiscence is seen in the fact that the very young infant1 flabby and powerless as it is in most of its muscles1 is so strong in the muscles of the hand and arm that it can hang on to a stick by its hands1 and sustain the whole weight of its body1 for several minutes4 ,finally1 our vestigial tail--for we have a tail comparable to that of the higher apes--must be mentioned4 ,in embryonic development the tail is much longer than the legs1 and some children are born with a real tail1 which they move as the puppy does1 according to their emotional condition4 ,other features of the body point back to an even earlier stage4 ,the vermiform appendage--in which some recent medical writers have vainly endeavoured to find a utility--is the shrunken remainder of a large and normal intestine of a remote ancestor4 ,this interpretation of it would stand even if it were found to have a certain use in the human body4 ,vestigial organs are sometimes pressed into a secondary use when their original function has been lost4 ,the danger of this appendage in the human body to-day is due to the fact that it is a blind alley leading off the alimentary canal1 and has a very narrow opening4 ,in the ape the opening is larger1 and1 significantly enough1 it is still larger in the human foetus4 ,when we examine some of the lower mammals we discover the meaning of it4 ,it is in them an additional storage chamber in the alimentary system4 ,it is believed that a change to a more digestible diet has made this additional chamber superfluous in the ,primates1 and the system is slowly suppressing it4 ,other reminiscences of this earlier phase are found in the many vestigial muscles which are found in the body to-day4 ,the head of the quadruped hangs forward1 and is held by powerful muscles and ligaments in the neck4 ,we still have the shrunken remainder of this arrangement4 ,other vestigial muscles are found in the forehead1 the scalp1 the nose--many people can twitch the nostrils and the scalp--and under the skin in many parts of the body4 ,these are enfeebled remnants of the muscular coat by which the quadruped twitches its skin1 and drives insects away4 ,a less obvious feature is found by the anatomist in certain blood-vessels of the trunk4 ,as the blood flows vertically in a biped and horizontally in a quadruped1 the arrangement of the valves in the blood-vessels should be different in the two cases2 but it is the same in us as in the quadruped4 ,another trace of the quadruped ancestor is found in the baby4 ,it walks on all fours so long1 not merely from weakness of the limbs1 but because it has the spine of a quadruped4 ,a much more interesting fact1 but one less easy to interpret1 is that the human male has1 like the male ape1 organs for suckling the young4 ,that there are real milk-glands1 usually vestigial1 underneath the teats in the breast of the boy or the man is proved by the many known cases in which men have suckled the young4 ,several friends of the present writer have seen this done in ,india and ,ceylon by male wet-nurses4 ,as there is no tribe of men or species of ape in which the male suckles the young normally1 we seem to be thrown back once more upon an earlier ancestor4 ,the difficulty is that we know of no mammal of which both parents suckle the young1 and some authorities think that the breasts have been transferred to the male by a kind of embryonic muddle4 ,that is difficult to believe1 as no other feature has ever been similarly transferred to the opposite sex4 ,in any case the male breasts are vestigial organs4 ,another peculiarity of the mammary system is that sometimes three1 four1 or five pairs of breasts appear in a woman 7and several have been known even in a man74 ,this is1 apparently1 an occasional reminiscence of an early mammal ancestor which had large litters of young and several pairs of breasts4 ,but there are features of the human body which recall an ancestor even earlier than the quadruped4 ,the most conspicuous of these is the little fleshy pad at the inner corner of each eye4 ,it is a common feature in mammals1 and is always useless4 ,when1 however1 we look lower down in the animal scale we find that fishes and reptiles 7and birds7 have a third eyelid1 which is drawn across the eye from this corner4 ,there is little room to doubt that the little fleshy vestige in the mammal's eye is the shrunken remainder of the lateral eyelid of a remote fish-ancestor4 ,a similar reminiscence is found in the pineal body1 a small and useless object1 about the size and shape of a hazel-nut1 in the centre of the brain4 ,when we examine the reptile we find a third eye in the top of the head4 ,the skin has closed over it1 but the skull is still1 in many cases1 perforated as it is for the eyes in front4 ,i have seen it standing out like a ball on the head of a dead crocodile1 and in the living tuatara--the very primitive ,new ,zealand lizard--it still has a retina and optic nerve4 ,as the only animal in nature to-day with an eye in this position 7the ,pyrosome1 a little marine animal of the sea-squirt family7 is not in the line of reptile and mammal ancestry1 it is difficult to locate the third eye definitely4 ,but when we find the skin closing over it in the amphibian and reptile1 then the bone1 and then see it gradually atrophying and being buried under the growing brain1 we must refer it to some early fish-ancestor4 ,this ancestor1 we may recall1 is also reflected for a time in the gill-slits and arches1 with their corresponding fish-like heart and blood-vessels1 during man's embryonic development1 as we saw in a former chapter4 ,these are only a few of the more conspicuous instances of vestigial structures in man4 ,metchnikoff describes about a hundred of them4 ,even if there were no remains of primitive man pointing in the direction of a common ancestry with the ape1 no lower types of men in existence with the same tendency1 no apes found in nature to-day with a structure so strikingly similar to that of man1 and no fossil records telling of the divergence of forms from primitive groups in past time1 we should be forced to postulate the evolution of man in order to explain his actual features4 ,the vestigial structures must be interpreted as we interpret the buttons on the back of a man's coat4 ,they are useless reminiscences of an age in which they were useful4 ,when their witness to the past is supported by so many converging lines of evidence it becomes irresistible4 ,i will add only one further testimony which has been brought into court in recent years4 ,the blood consists of cells1 or minute disk-shaped corpuscles1 floating in a watery fluid1 or serum4 ,it was found a few years ago1 in the course of certain experiments in mixing the blood of animals1 that the serum of one animal's blood sometimes destroyed the cells of the other animal's blood1 and at other times did not4 ,when the experiments were multiplied1 it was found that the amount of destructive action exercised by one specimen of blood upon another depended on the nearness or remoteness of relationship between the animals4 ,if the two are closely related1 there is no disturbance when their blood is mixed2 when they are not closely related1 the serum of one destroys the cells of the other1 and the intensity of the action is in proportion to their remoteness from each other4 ,another and more elaborate form of the experiment was devised1 and the law was confirmed4 ,on both tests it was found by experiment that the blood of man and of the anthropoid ape behaved in such a way as to prove that they were closely related4 ,the blood of the monkey showed a less close relationship--a little more remote in the ,new ,world than in the ,old ,world monkeys2 and the blood of the femur showed a faint and distant relationship4 ,the ,,fact of the evolution of man and the apes from a common ancestor is1 therefore1 outside the range of controversy in science2 we are concerned only to retrace the stages of that evolution1 and the agencies which controlled it4 ,here1 unfortunately1 the geological record gives us little aid4 ,tree-dwelling animals are amongst the least likely to be buried in deposits which may preserve their bones for ages4 ,the distribution of femur and ape remains shows that the order of the ,primates has been widespread and numerous since the middle of the ,tertiary ,era1 yet singularly few remains of the various families have been preserved4 ,hence the origin of the ,primates is obscure4 ,they are first foreshadowed in certain femur-like forms of the ,eocene period1 which are said in some cases 7,adapis7 to combine the characters of pachyderms and femurs1 and in others 7,anaptomorphus7 to unite the features of ,insectivores and femurs4 ,perhaps the more common opinion is that they were evolved from a branch of the ,insectivores1 but the evidence is too slender to justify an opinion4 ,it was an age when the primitive placental mammals were just beginning to diverge from each other1 and had still many features in common4 ,for the present all we can say is that in the earliest spread of the patriarchal mammal race one branch adopted arboreal life1 and evolved in the direction of the femurs and the apes4 ,the generally arboreal character of the ,primates justifies this conclusion4 ,in the ,miocene period we find a great expansion of the monkeys4 ,these in turn enter the scene quite suddenly1 and the authorities are reduced to uncertain and contradictory conjectures as to their origin4 ,some think that they develop not from the femurs1 but along an independent line from the ,insectivores1 or other ancestors of the ,primates4 ,we will not linger over these early monkeys1 nor engage upon the hopeless task of tracing their gradual ramification into the numerous families of the present age4 ,it is clear only that they soon divided into two main streams1 one of which spread into the monkeys of ,america and the other into the monkeys of the ,old ,world4 ,there are important anatomical differences between the two4 ,the monkeys remained in ,central and ,southern ,europe until near the end of the ,tertiary4 ,gradually we perceive that the advancing cold is driving them further south1 and the monkeys of ,gibraltar to-day are the diminished remnant of the great family that had previously wandered as far as ,britain and ,france4 ,a third wave1 also spreading in the ,miocene1 equally obscure in its connection with the preceding1 introduces the man-like apes to the geologist4 ,primitive gibbons 7,pliopithecus and ,pliobylobates71 primitive chimpanzees 7,palaeopithecus71 and other early anthropoid apes 7,oreopithecus1 ,dryopithecus1 etc471 lived in the trees of ,southern ,europe in the second part of the ,tertiary ,era4 ,they are clearly disconnected individuals of a large and flourishing family1 but from the half-dozen specimens we have yet discovered no conclusion can be drawn1 except that the family is already branching into the types of anthropoid apes which are familiar to us4 ,of man himself we have no certain and indisputable trace in the ,tertiary ,era4 ,some remains found in ,java of an ape-man 7,pithecanthropus71 which we will study later1 are now generally believed1 after a special investigation on the spot1 to belong to the ,pleistocene period4 ,yet no authority on the subject doubts that the human species was evolved in the ,tertiary ,era1 and very many1 if not most1 of the authorities believe that we have definite proof of his presence4 ,the early story of mankind is gathered1 not so much from the few fragments of human remains we have1 but from the stone implements which were shaped by his primitive intelligence and remain1 almost imperishable1 in the soil over which he wandered4 ,the more primitive man was1 the more ambiguous would be the traces of his shaping of these stone implements1 and the earliest specimens are bound to be a matter of controversy4 ,it is claimed by many distinguished authorities that flints slightly touched by the hand of man1 or at least used as implements by man1 are found in abundance in ,england1 ,france1 and ,germany1 and belong to the ,pliocene period4 ,continental authorities even refer some of them to the ,miocene and the last part of the ,oligocene4 ,the question whether an implement-using animal1 which nearly all would agree to regard as in some degree human1 wandered over what is now the ,south of ,england 7,kent1 ,essex1 ,dorsetshire1 etc47 as many hundred thousand years ago as this claim would imply1 is certainly one of great interest4 ,but there would be little use in discussing here the question of the ,eoliths1 as these disputed implements are called4 ,a very keen controversy is still being conducted in regard to them1 and some of the highest authorities in ,england1 ,france1 and ,germany deny that they show any trace of human workmanship or usage4 ,although they have the support of such high authorities as ,sir ,j4 ,prestwich1 ,sir ,e4 ,ray ,lankester1 ,lord ,avebury1 ,dr4 ,keane1 ,dr4 ,blackmore1 ,professor ,schwartz1 etc41 they are one of those controverted testimonies on which it would be ill-advised to rely in such a work as this4 ,we must say1 then1 that we have no undisputed traces of man in the ,tertiary ,era4 ,the ,tertiary implements which have been at various times claimed in ,france1 ,italy1 and ,portugal are equally disputed2 the remains which were some years ago claimed as ,tertiary in the ,united ,states are generally disallowed2 and the recent claims from ,south ,america are under discussion4 ,yet it is the general feeling of anthropologists that man was evolved in the ,tertiary ,era4 ,on the one hand1 the anthropoid apes were highly developed by the ,miocene period1 and it would be almost incredible that the future human stock should linger hundreds of thousands of years behind them4 ,on the other hand1 when we find the first traces of man in the ,pleistocene1 this development has already proceeded so far that its earlier phase evidently goes back into the ,tertiary4 ,let us pass beyond the ,tertiary ,era for a moment1 and examine the earliest and most primitive remains we have of human or semi-human beings4 ,the first appearance of man in the chronicle of terrestrial life is a matter of great importance and interest4 ,even the least scientific of readers stands1 so to say1 on tiptoe to catch a first glimpse of the earliest known representative of our race1 and half a century of discussion of evolution has engendered a very wide interest in the early history of man4 99 99 ,a personal experience may not be without interest in this connection4 ,among the many inquiries directed to me in regard to evolution ,i received1 in one month1 a letter from a negro in ,british ,guiana and an extremely sensible query from an inmate of an ,english asylum for the insane6 ,the problem that beset the latter of the two was whether the ,lemuranda preceded the ,lemurogona in ,eocene times4 ,he had found a contradiction in the statements of two scientific writers4 ,fortunately1 although these patriarchal bones are very scanty--two teeth1 a thigh-bone1 and the skull-cap--we are now in a position to form some idea of the nature of their living owner4 ,they have been subjected to so searching a scrutiny and discussion since they were found in ,java in #ahia and #ahib that there is now a general agreement as to their nature4 ,at first some of the experts thought that they were the remains of an abnormally low man1 and others that they belonged to an abnormally high ape4 ,the majority held from the start that they belonged to a member of a race almost midway between the highest family of apes and the lowest known tribe of men1 and therefore fully merited the name of ,ape-,man 7,pithecanthropus74 ,this is now the general view of anthropologists4 ,the ,ape-,man of ,java was in every respect entitled to that name4 ,the teeth suggest a lower part of the face in which the teeth and lips projected more than in the most ape-like types of ,central ,africa4 ,the skull-cap has very heavy ridges over the eyes and a low receding forehead1 far less human than in any previously known prehistoric skull4 ,the thigh-bone is very much heavier than any known human femur of the same length1 and so appreciably curved that the owner was evidently in a condition of transition from the semi-quadrupedal crouch of the ape to the erect attitude of man4 ,the ,ape-,man1 in other words1 was a heavy1 squat1 powerful1 bestial-looking animal2 of small stature1 but above the pygmy standard2 erect in posture1 but with clear traces of the proneness of his ancestor2 far removed from the highest ape in brainpower1 but almost equally far removed from the lowest savage that is known to us4 ,we shall see later that there is some recent criticism1 by weighty authorities1 of the earlier statements in regard to the brain of primitive man4 ,this does not apply to the ,ape-,man of ,java4 ,the average cranial capacity 7the amount of brain-matter the skull may contain7 of the chimpanzees1 the highest apes1 is about #fjj cubic centimetres4 ,the average cranial capacity of the lowest races of men1 of moderate stature1 is about #abjj4 ,and the cranial capacity of ,ape-,man was about #ijj ,it is immaterial whether or no these bones belong to the same individual4 ,if they do not1 we have remains of two or three individuals of the same intermediate species4 ,nor does it matter whether or no this early race is a direct ancestor of the later races of men1 or an extinct offshoot from the advancing human stock4 ,it is1 in either case1 an illustration of the intermediate phase between the ape and man ,the more important tasks are to trace the relationship of this early human stock to the apes1 and to discover the causes of its superior evolution4 ,the first question has a predominantly technical interest1 and the authorities are not agreed in replying to it4 ,we saw that1 on the blood-test1 man showed a very close relationship to the anthropoid apes1 a less close affinity to the ,old ,world monkeys1 a more remote affinity to the ,american monkeys1 and a very faint and distant affinity to the femurs4 ,a comparison of their structures suggests the same conclusion4 ,it is1 therefore1 generally believed that the anthropoid apes and man had a common ancestor in the early ,miocene or ,oligocene1 that this group was closely related to the ancestral group of the ,old ,world monkeys1 and that all originally sprang from a primitive and generalised femur-group4 ,in other words1 a branch of the earliest femur-like forms diverges1 before the specific femur-characters are fixed1 in the direction of the monkey2 in this still vague and patriarchal group a branch diverges1 before the monkey-features are fixed1 in the direction of the anthropoids2 and this group in turn spreads into a number of types1 some of which are the extinct apes of the ,miocene1 four become the gorilla1 chimpanzee1 orang1 and gibbon of to-day1 and one is the group that will become man4 ,to put it still more precisely1 if we found a whole series of remains of man's ancestors during the ,tertiary1 we should probably class them1 broadly1 as femur-remains in the ,eocene1 monkey-remains in the ,oligocene1 and ape-remains in the ,miocene4 ,in that sense only man descends from a monkey4 ,the far more important question is3 ,how did this one particular group of anthropoid animals of the ,miocene come to surpass all its cousins1 and all the rest of the mammals1 in brain-development8 ,let us first rid the question of its supposed elements of mystery and make of it a simple problem4 ,some imagine that a sudden and mysterious rise in intelligence lifted the progenitor of man above its fellows4 ,the facts very quickly dispel this illusion4 ,we may at least assume that the ancestor of man was on a level with the anthropoid ape in the ,miocene period1 and we know from their skulls that the apes were as advanced then as they are now4 ,but from the early ,miocene to the ,pleistocene is a stretch of about a million years on the very lowest estimate4 ,in other words1 man occupied about a million years in travelling from the level of the chimpanzee to a level below that of the crudest savage ever discovered4 ,if we set aside the ,java man1 as a possible survivor of an earlier phase1 we should still have to say that1 much more than a million years after his departure from the chimpanzee level1 man had merely advanced far enough to chip stone implements2 because we find no other trace whatever of intelligence than this until near the close of the ,palaeolithic period4 ,if there is any mystery1 it is in the slowness of man's development4 ,let us further recollect that it is a common occurrence in the calendar of life for a particular organ to be especially developed in one member of a particular group more than in the others4 ,the trunk of the elephant1 the neck of the giraffe1 the limbs of the horse or deer1 the canines of the satire-toothed tiger1 the wings of the bat1 the colouring of the tiger1 the horns of the deer1 are so many examples in the mammal world alone4 ,the brain is a useful organ like any other1 and it is easy to conceive that the circumstances of one group may select it just as the environment of another group may lead to the selection of speed1 weapons1 or colouring4 ,in fact1 as we saw1 there was so great and general an evolution of brain in the ,tertiary ,era that our modern mammals quite commonly have many times the brain of their ,tertiary ancestors4 ,can we suggest any reasons why brain should be especially developed in the apes1 and more particularly still in the ancestors of man8 ,the ,primate group generally is a race of tree-climbers4 ,the appearance of fruit on early ,tertiary trees and the multiplication of carnivores explain this4 ,the ,primate is1 except in a few robust cases1 a particularly defenceless animal4 ,when its earliest ancestors came in contact with fruit and nut-bearing trees1 they developed climbing power and other means of defence and offense were sacrificed4 ,keenness of scent and range of hearing would now be of less moment1 but sight would be stimulated1 especially when soft-footed climbing carnivores came on the scene4 ,there is1 however1 a much deeper significance in the adoption of climbing1 and we must borrow a page from the modern physiology of the brain to understand it4 ,the stress laid in the modern education of young children on the use of the hands is not merely due to a feeling that they should handle objects as well as read about them4 ,it is partly due to the belief of many distinguished physiologists that the training of the hands has a direct stimulating effect on the thought-centres in the brain4 ,the centre in the cerebrum which controls the use of the hands is on the fringe of the region which seems to be concerned in mental operations4 ,for reasons which will appear presently1 we may add that the centres for controlling the muscles of the face and head are in the same region4 ,any finer training or the use of the hands will develop the centre for the fore limbs1 and1 on the principles1 may react on the more important region of the cortex4 ,hence in turning the fore foot into a hand1 for climbing and grasping purposes1 the primitive ,primate entered upon the path of brain-development4 ,even the earliest ,primates show large brains in comparison with the small brains of their contemporaries4 ,it is a familiar fact in the animal world that when a certain group enters upon a particular path of evolution1 some members of the group advance only a little way along it1 some go farther1 and some outstrip all the others4 ,the development of social life among the bees will illustrate this4 ,hence we need not be puzzled by the fact that the lemurs have remained at one mental level1 the monkeys at another1 and the apes at a third4 ,it is the common experience of life2 and it is especially clear among the various races of men4 ,a group becomes fitted to its environment1 and1 as long as its surroundings do not change1 it does not advance4 ,a related group1 in a different environment1 receives a particular stimulation1 and advances4 ,if1 moreover1 a group remains unstimulated for ages1 it may become so rigid in its type that it loses the capacity to advance4 ,it is generally believed that the lowest races of men1 and even some of the higher races like the ,australian aboriginals1 are in this condition4 ,we may expect this unteachability in a far more stubborn degree in the anthropoid apes1 which have been adapted to an unchanging environment for a million years4 ,all that we need further suppose is--and it is one of the commonest episodes in terrestrial life--that one branch of the ,miocene anthropoids1 which were spread over a large part of the earth1 received some stimulus to change which its cousins did not experience4 ,it is sometimes suggested that social life was the great advantage which led to the superior development of mind in man4 ,but such evidence as there is would lead us to suppose that primitive man was solitary1 not social4 ,the anthropoid apes are not social1 but live in families1 and are very unprogressive4 ,on the other hand1 the earliest remains of prehistoric man give no indication of social life4 ,fire-places1 workshops1 caves1 etc41 enter the story in a later phase4 ,some authorities on prehistoric man hold very strongly that during the greater part of the ,old ,stone ,age 7two-thirds1 at least1 of the human period7 man wandered only in the company of his mate and children4 99 99 ,the point will be more fully discussed later4 ,this account of prehistoric life is well seen in ,mortillet's ,prehistorique 7#aijj74 ,the lowest races also have no tribal life1 and ,professor ,westermarck is of opinion that early man was not social4 ,we seem to have the most plausible explanation of the divergence of man from his anthropoid cousins in the fact that he left the trees of his and their ancestors4 ,this theory has the advantage of being a fact--for the ,ape-,man race of ,java has already left the trees--and providing a strong ground for brain-advance4 ,a dozen reasons might be imagined for his quitting the trees--migration1 for instance1 to a region in which food was more abundant1 and carnivores less formidable1 on the ground-level--but we will be content with the fact that he did4 ,such a change would lead to a more consistent adoption of the upright attitude1 which is partly found in the anthropoid apes1 especially the gibbons4 ,the fore limb would be no longer a support of the body2 the hand would be used more for grasping2 and the hand-centre in the brain would be proportionately stimulated4 ,the adoption of the erect attitude would further lead to a special development of the muscles of the head and face1 the centre for which is in the same important region in the cortex4 ,there would also be a direct stimulation of the brain1 as1 having neither weapons nor speed1 the animal would rely all the more on sight and mind4 ,if we further suppose that this primitive being extended the range of his hunting1 from insects and small or dead birds to small land-animals1 the stimulation would be all the greater4 ,in a word1 the very fact of a change from the trees to the ground suggests a line of brain-development which may plausibly be conceived1 in the course of a million years1 to evolve an ,ape-,man out of a man-like ape4 ,and we are not introducing any imaginary factor in this view of human origins4 ,the problem of the evolution of man is often approached in a frame of mind not far removed from that of the educated1 but inexpert1 ,european who stands before the lowly figure of the chimpanzee1 and wonders by what miracle the gulf between it and himself was bridged4 ,that is to lay a superfluous strain on the imagination4 ,the proper term of comparison is the lowest type of human being known to us1 since the higher types of living men have confessedly evolved from the lower4 ,but even the lowest type of existing or recent savage is not the lowest level of humanity4 ,whether or no the ,tasmanian or the ,yahgan is a primitive remnant of the ,old ,stone ,age1 we have a far lower depth in the ,java race4 ,what we have first to do is to explain the advance to that level1 in the course of many hundreds of thousands of years3 a period fully a hundred times as long as the whole history of civilisation4 ,time itself is no factor in evolution1 but in this case it is a significant condition4 ,it means that1 on this view of the evolution of man1 we are merely assuming that an advance in brain-development took place between the ,miocene and the ,pleistocene1 not similar to1 but immeasurably less than1 the advance which we know to have been made in the last fifty thousand years4 ,in point of fact1 the most mysterious feature of the evolution of man was its slowness4 ,we shall see that1 to meet the facts1 we must suppose man to have made little or no progress during most of this vast period1 and then to have received some new stimulation to develop4 ,what it was we have now to inquire4 ,,chapter ,,xix4 ,,man ,,and ,,the ,,great ,,ice-,,age ,in discussing the development of plants and animals during the ,tertiary ,era we have already perceived the shadow of the approaching ,ice-,age4 ,we found that in the course of the ,tertiary the types which were more sensitive to cold gradually receded southward1 and before its close ,europe1 ,asia1 and ,north ,america presented a distinctly temperate aspect4 ,this is but the penumbra of the eclipse4 ,when we pass the limits of the ,tertiary ,era1 and enter the ,quaternary1 the refrigeration steadily proceeds1 and1 from temperate1 the aspect of much of ,europe and ,north ,america becomes arctic4 ,from six to eight million square miles of the northern hemisphere are buried under fields of snow and ice1 and even in the southern regions smaller glacial sheets spread from the foot of the higher ranges of mountains4 ,it is unnecessary to-day to explain at any length the evidences by which geologists trace this enormous glaciation of the northern hemisphere4 ,there are a few works still in circulation in which popular writers1 relying on the obstinacy of a few older geologists1 speak lightly of the nightmare of the ,ice-,age4 ,but the age has gone by in which it could seriously be suggested that the boulders strewn along the east of ,scotland--fragments of rock whose home we must seek in ,scandinavia--were brought by the vikings as ballast for their ships4 ,even the more serious controversy1 whether the scratches and the boulders which we find on the face of ,northern ,europe and ,america were due to floating or land ice1 is virtually settled4 ,several decades of research have detected the unmistakable signs of glacial action over this vast area of the northern hemisphere4 ,most of ,europe north of the ,thames and the ,danube1 nearly all ,canada and a very large part of the ,united ,states1 and a somewhat less expanse of ,northern ,asia1 bear to this day the deep scars of the thick1 moving ice-sheets4 ,exposed rock-surfaces are ground and scratched1 beds of pebbles are twisted and contorted hollows are scooped out1 and moraines--the rubbish-heaps of the glaciers--are found on every side4 ,there is now not the least doubt that1 where the great ,deinosaurs had floundered in semi-tropical swamps1 where the figs and magnolias had later flourished1 where the most industrious and prosperous hives of men are found to-day1 there was1 in the ,pleistocene period1 a country to which no parallel can be found outside the polar circles to-day4 ,the great revolution begins with the gathering of snows on the mountains4 ,the ,alps and ,pyrenees had now1 we saw1 reached their full stature1 and the gathering snows on their summits began to glide down toward the plains in rivers of ice4 ,the ,apennines 7and even the mountains of ,corsica71 the ,balkans1 ,carpathians1 ,caucasus1 and ,ural ,mountains1 shone in similar mantles of ice and snow4 ,the mountains of ,wales1 the north of ,england1 ,scotland1 and ,scandinavia had even heavier burdens1 and1 as the period advanced1 their sluggish streams of ice poured slowly over the plains4 ,the trees struggled against the increasing cold in the narrowing tracts of green2 the animals died1 migrated to the south1 or put on arctic coats4 ,at length the ice-sheets of ,scandinavia met the spreading sheets from ,scotland and ,wales1 and crept over ,russia and ,germany1 and an almost continuous mantle1 from which only a few large areas of arctic vegetation peeped out1 was thrown over the greater part of ,europe4 ,ten thousand feet thick where it left the hills of ,norway and ,sweden1 several thousand feet thick even in ,scotland1 the ice-sheet that resulted from the fusion of the glaciers gradually thinned as it went south1 and ended in an irregular fringe across ,central ,europe4 ,the continent at that time stretched westward beyond the ,hebrides and some two hundred miles beyond ,ireland4 ,the ice-front followed this curve1 casting icebergs into the ,atlantic1 then probably advanced up what is now the ,bristol ,channel1 and ran across ,england and ,europe1 in a broken line1 from ,bristol to ,poland4 ,south of this line there were smaller ice-fields round the higher mountains1 north of it almost the whole country presented the appearance that we find in ,greenland to-day4 ,in ,north ,america the glaciation was even more extensive4 ,about four million square miles of the present temperate zone were buried under ice and snow4 ,from ,greenland1 ,labrador1 and the higher ,canadian mountains the glaciers poured south1 until1 in the east1 the mass of ice penetrated as far as the valley of the ,mississippi4 ,the great lakes of ,north ,america are permanent memorials of its ,ice-,age1 and over more than half the country we trace the imprint and the relics of the sheet4 ,south ,america1 ,australia1 ,tasmania1 and ,new ,zealand had their glaciated areas4 ,north ,asia was largely glaciated1 but the range of the ice-sheet is not yet determined in that continent4 ,this summary statement will convey some idea of the extraordinary phase through which the earth passed in the early part of the present geological era4 ,but it must be added that a singular circumstance prolonged the glacial regime in the northern hemisphere4 ,modern geologists speak rather of a series of successive ice-sheets than of one definite ,ice-,age4 ,some1 indeed1 speak of a series of ,ice-,ages1 but we need not discuss the verbal question4 ,it is now beyond question that the ice-sheet advanced and retreated several times during the ,glacial ,epoch4 ,the ,american and some ,english geologists distinguished six ice-sheets1 with five intermediate periods of more temperate climate4 ,the ,german and many ,english and ,french geologists distinguish four sheets and three interglacial epochs4 ,the exact number does not concern us1 but the repeated spread of the ice is a point of some importance4 ,the various sheets differed considerably in extent4 ,the wide range of the ice which ,i have described represents the greatest extension of the glaciation1 and probably corresponds to the second or third of the six advances in ,dr4 ,geikie's 7and the ,american7 classification4 ,before we consider the biological effect of this great of refrigeration of the globe1 we must endeavour to understand the occurrence itself4 ,here we enter a world of controversy1 but a few suggestions at least may be gathered from the large literature of the subject1 which dispel much of the mystery of the ,great ,ice-,age4 ,it was at one time customary to look out beyond the earth itself for the ultimate causes of this glaciation4 ,imagine the sheet of ice1 which now spreads widely round the ,north ,pole1 shifted to another position on the surface of the planet1 and you have a simple explanation of the occurrence4 ,in other words1 if we suppose that the axis of the earth does not consistently point in one direction--that the great ball does not always present the same average angle in relation to the sun--the poles will not always be where they are at present1 and the ,pleistocene ,ice-,age may represent a time when the north pole was in the latitude of ,north ,europe and ,north ,america4 ,this opinion had to be abandoned4 ,we have no trace whatever of such a constant shifting of the polar regions as it supposes1 and1 especially1 we have no trace that the warm zone correspondingly shifted in the ,pleistocene4 ,a much more elaborate theory was advanced by ,dr4 ,croll1 and is still entertained by many4 ,the path of the earth round the sun is not circular1 but elliptical1 and there are times when the gravitational pull of the other planets increases the eccentricity of the orbit4 ,it was assumed that there are periods of great length1 separated from each other by still longer periods1 when this eccentricity of the orbit is greatly exaggerated4 ,the effect would be to prolong the winter and shorten the summer of each hemisphere in turn4 ,the total amount of heat received would not alter1 but there would be a long winter with less heat per hour1 and a short summer with more heat4 ,the short summer would not suffice to melt the enormous winter accumulations of ice and snow1 and an ice-age would result4 ,to this theory1 again1 it is objected that we do not find the regular succession of ice-ages in the story of the earth which the theory demands1 and that there is no evidence of an alternation of the ice between the northern and southern hemispheres4 ,more recent writers have appealed to the sun itself1 and supposed that some prolonged veiling of its photosphere greatly reduced the amount of heat emitted by it4 ,more recently still it has been suggested that an accumulation of cosmic or meteoric dust in our atmosphere1 or between us and the sun1 had1 for a prolonged period1 the effect of a colossal fire-screen4 ,neither of these suppositions would explain the localisation of the ice4 ,in any case we need not have recourse to purely speculative accidents in the world beyond until it is clear that there were no changes in the earth itself which afford some explanation4 ,this is by no means clear4 ,some writers appeal to changes in the ocean currents4 ,it is certain that a change in the course of the cold and warm currents of the ocean to-day might cause very extensive changes of climate1 but there seems to be some confusion of ideas in suggesting that this might have had an equal1 or even greater1 influence in former times4 ,our ocean currents differ so much in temperature because the earth is now divided into very pronounced zones of climate4 ,these zones did not exist before the ,pliocene period1 and it is not at all clear that any redistribution of currents in earlier times could have had such remarkable consequences4 ,the same difficulty applies to wind-currents4 ,on the other hand1 we have already1 in discussing the ,permian glaciation1 discovered two agencies which are very effective in lowering the temperature of the earth4 ,one is the rise of the land2 the other is the thinning of the atmosphere4 ,these are closely related agencies1 and we found them acting in conjunction to bring about the ,permian ,ice-,age4 ,do we find them at work in the ,pleistocene8 ,it is not disputed that there was a very considerable upheaval of the land1 especially in ,europe and ,north ,america1 at the end of the ,tertiary ,era4 ,every mountain chain advanced1 and our ,alps1 ,pyrenees1 ,himalaya1 etc41 attained1 for the first time1 their present1 or an even greater elevation4 ,the most critical geologists admit that ,europe1 as a whole1 rose #djjj feet above its earlier level4 ,such an elevation would be bound to involve a great lowering of the temperature4 ,the geniality of the ,oligocene period was due1 like that of the earlier warm periods1 to the low-lying land and very extensive water-surface4 ,these conditions were revolutionised before the end of the ,tertiary4 ,great mountains towered into the snow-line1 and vast areas were elevated which had formerly been sea or swamp4 ,this rise of the land involved a great decrease in the proportion of moisture in the atmosphere4 ,the sea surface was enormously lessened1 and the mountains would now condense the moisture into snow or cloud to a vastly greater extent than had ever been known before ,there would also be a more active circulation of the atmosphere1 the moist warm winds rushing upward towards the colder elevations and parting with their vapour4 ,as the proportion of moisture in the atmosphere lessened the surface-heat would escape more freely into space1 the general temperature would fall1 and the evaporation--or production of moisture would be checked1 while the condensation would continue4 ,the prolonging of such conditions during a geological period can be understood to have caused the accumulation of fields of snow and ice in the higher regions4 ,it seems further probable that these conditions would lead to a very considerable formation of fog and cloud1 and under this protecting canopy the glaciers would creep further down toward the plains4 ,we have then to consider the possibility of a reduction of the quantity of carbon-dioxide in the atmosphere ,the inexpert reader probably has a very exaggerated idea of the fall in temperature that would be required to give ,europe an ,ice-,age4 ,if our average temperature fell about #e-h degrees ,c4 below the average temperature of our time it would suffice2 and it is further calculated that if the quantity of carbon-dioxide in our atmosphere were reduced by half1 we should have this required fall in temperature4 ,so great a reduction would not be necessary in view of the other refrigerating agencies4 ,now it is quite certain that the proportion of carbon-dioxide was greatly reduced in the ,pleistocene4 ,the forests of the ,tertiary ,era would steadily reduce it1 but the extensive upheaval of the land at its close would be even more important4 ,the newly exposed surfaces would absorb great quantities of carbon4 ,the ocean1 also1 as it became colder1 would absorb larger and larger quantities of carbon-dioxide4 ,thus the ,pleistocene atmosphere1 gradually relieved of its vapours and carbon-dioxide1 would no longer retain the heat at the surface4 ,we may add that the growth of reflective surfaces--ice1 snow1 cloud1 etc4--would further lessen the amount of heat received from the sun4 ,here1 then1 we have a series of closely related causes and effects which would go far toward explaining1 if they do not wholly suffice to explain1 the general fall of the earth's temperature4 ,the basic cause is the upheaval of the land--a fact which is beyond controversy1 the other agencies are very plain and recognisable consequences of the upheaval4 ,there are1 however1 many geologists who do not think this explanation adequate4 ,it is pointed out1 in the first place1 that the glaciation seems to have come long after the elevation4 ,the difficulty does not seem to be insurmountable4 ,the reduction of the atmospheric vapour would be a gradual process1 beginning with the later part of the elevation and culminating long afterwards4 ,the reduction of the carbon-dioxide would be even more gradual4 ,it is impossible to say how long it would take these processes to reach a very effective stage1 but it is equally impossible to show that the interval between the upheaval and the glaciation is greater than the theory demands4 ,it is also said that we cannot on these principles understand the repeated advance and retreat of the ice-sheet4 ,this objection1 again1 seems to fail4 ,it is an established fact that the land sank very considerably during the ,ice-,age1 and has risen again since the ice disappeared4 ,we find that the crust in places sank so low that an arctic ocean bathed the slopes of some of the ,welsh mountains2 and ,american geologists say that their land has risen in places from #bjjj to #cjjj feet 7,chamberlin7 since the burden of ice was lifted from it4 ,here we have the possibility of an explanation of the advances and retreats of the glaciers4 ,the refrigerating agencies would proceed until an enormous burden of ice was laid on the land of the northern hemisphere4 ,the land apparently sank under the burden1 the ice and snow melted at the lower level and there was a temperate interglacial period4 ,but the land1 relieved of its burden1 rose once more1 the exposed surface absorbed further quantities of carbon1 and a fresh period of refrigeration opened4 ,this oscillation might continue until the two sets of opposing forces were adjusted1 and the crust reached a condition of comparative stability4 ,finally1 and this is the more serious difficulty1 it is said that we cannot in this way explain the localisation of the glacial sheets4 ,why should ,europe and ,north ,america in particular suffer so markedly from a general thinning of the atmosphere8 ,the simplest answer is to suggest that they especially shared the rise of the land4 ,geology is not in a position either to prove or disprove this1 and it remains only a speculative interpretation of the fact ,we know at least that there was a great uprise of land in ,europe and ,north ,america in the ,pliocene and ,pleistocene and may leave the precise determination of the point to a later age4 ,at the same time other local causes are not excluded4 ,there may have been a large extension of the area of atmospheric depression which we have in the region of ,greenland to-day4 ,when we turn to the question of chronology we have the same acute difference of opinion as we have found in regard to all questions of geological time4 ,it used to be urged1 on astronomical grounds1 that the ,ice-,age began about #bdj1jjj years ago1 and ended about #fj1jjj years ago1 but the astronomical theory is1 as ,i said1 generally abandoned4 ,geologists1 on the other hand1 find it difficult to give even approximate figures4 ,reviewing the various methods of calculation1 ,professor ,chamberlin concludes that the time of the first spread of the ice-sheet is quite unknown1 the second and greatest extension of the glaciation may have been between #cjj1jjj and a million years ago1 and the last ice-extension from #bj1jjj to #fj1jjj years ago2 but he himself attaches very little value to the figures4 ,the chief ice-age was some hundreds of thousands of years ago1 that is all we can say with any confidence4 ,in dismissing the question of climate1 however1 we should note that a very serious problem remains unsolved4 ,as far as present evidence goes we seem to be free to hold that the ice-ages which have at long intervals invaded the chronicle of the earth were due to rises of the land4 ,upheaval is the one constant and clearly recognisable feature associated with1 or preceding1 ice-ages4 ,we saw this in the case of the ,cambrian1 ,permian1 ,eocene1 and ,pleistocene periods of cold1 and may add that there are traces of a rise of mountains before the glaciation of which we find traces in the middle of the ,archaean ,era4 ,there are problems still to be solved in connection with each of these very important ages1 but in the rise of the land and consequent thinning of the atmosphere we seem to have a general clue to their occurrence4 ,apart from these special periods of cold1 however1 we have seen that there has been1 in recent geological times1 a progressive cooling of the earth1 which we have not explained4 ,winter seems now to be a permanent feature of the earth's life1 and polar caps are another recent1 and apparently permanent1 acquisition4 ,i find no plausible reason assigned for this4 ,the suggestion that the disk of the sun is appreciably smaller since ,tertiary days is absurd2 and the idea that the earth has only recently ceased to allow its internal heat to leak through the crust is hardly more plausible4 ,the cause remains to be discovered4 ,we turn now to consider the effect of the great ,ice-,age1 and the relation of man to it4 ,the ,permian revolution1 to which the ,pleistocene ,ice-,age comes nearest in importance1 wrought such devastation that the overwhelming majority of living things perished4 ,do we find a similar destruction of life1 and selection of higher types1 after the ,pleistocene perturbation8 ,in particular1 had it any appreciable effect upon the human species8 ,a full description of the effect of the great ,ice-,age would occupy a volume4 ,the modern landscape in ,europe and ,north ,america was very largely carved and modelled by the ice-sheet and the floods that ensued upon its melting4 ,hills were rounded1 valleys carved1 lakes formed1 gravels and soils distributed1 as we find them to-day4 ,in its vegetal aspect1 also1 as we saw1 the modern landscape was determined by the ,pleistocene revolution4 ,a great scythe slowly passed over the land4 ,when the ice and snow had ended1 and the trees and flowers1 crowded in the southern area1 slowly spread once more over the virgin soil1 it was only the temperate species that could pass the zone guarded by the ,alps and the ,pyrenees4 ,on the ,alps themselves the ,pleistocene population still lingers1 their successful adaptation to the cold now preventing them from descending to the plains4 ,the animal world in turn was winnowed by the ,pleistocene episode4 ,the hippopotamus1 crocodile1 turtle1 flamingo1 and other warm-loving animals were banished to the warm zone4 ,the mammoth and the rhinoceros met the cold by developing woolly coats1 but the disappearance of the ice1 which had tempted them to this departure1 seems to have ended their fitness4 ,other animals which became adapted to the cold--arctic bears1 foxes1 seals1 etc4--have retreated north with the ice1 as the sheet melted4 ,for hundreds of thousands of years ,europe and ,north ,america1 with their alternating glacial and interglacial periods1 witnessed extraordinary changes and minglings of their animal population4 ,at one time the reindeer1 the mammoth1 and the glutton penetrate down to the ,mediterranean1 in the next phase the elephant and hippopotamus again advance nearly to ,central ,europe4 ,it is impossible here to attempt to unravel these successive changes and migrations4 ,great numbers of species were destroyed1 and at length1 when the climatic condition of the earth reached a state of comparative stability1 the surviving animals settled in the geographical regions in which we find them to-day4 ,the only question into which we may enter with any fullness is that of the relation of human development to this grave perturbation of the condition of the globe4 ,the problem is sometimes wrongly conceived4 ,the chief point to be determined is not whether man did or did not precede the ,ice-,age4 ,as it is the general belief that he was evolved in the ,tertiary1 it is clear that he existed in some part of the earth before the ,ice-,age4 ,whether he had already penetrated as far north as ,britain and ,belgium is an interesting point1 but not one of great importance4 ,we may1 therefore1 refrain from discussing at any length those disputed crude stone implements 7,eoliths7 which1 in the opinion of many1 prove his presence in northern regions before the close of the ,tertiary4 ,we may also now disregard the remains of the ,java ,ape-,man4 ,there are authorities1 such as ,deniker1 who hold that even the latest research shows these remains to be ,pliocene1 but it is disputed4 ,the ,java race may be a surviving remnant of an earlier phase of human evolution4 ,the most interesting subject for inquiry is the fortune of our human and prehuman forerunners during the ,pliocene and ,pleistocene periods4 ,it may seem that if we set aside the disputable evidence of the ,eoliths and the ,java remains we can say nothing whatever on this subject4 ,in reality a fact of very great interest can be established4 ,it can be shown that the progress made during this enormous lapse of time--at least a million years--was remarkably slow4 ,instead of supposing that some extraordinary evolution took place in that conveniently obscure past1 to which we can find no parallel within known times1 it is precisely the reverse4 ,the advance that has taken place within the historical period is far greater1 comparatively to the span of time1 than that which took place in the past4 ,to make this interesting fact clearer we must attempt to measure the progress made in the ,pliocene and ,pleistocene4 ,we may assume that the precursor of man had arrived at the anthropoid-ape level by the middle of the ,miocene period4 ,he is not at all likely to have been behind the anthropoid apes1 and we saw that they were well developed in the mid-,tertiary4 ,now we have a good knowledge of man as he was in the later stage of the ,ice-,age--at least a million years later--and may thus institute a useful comparison and form some idea of the advance made4 ,in the later stages of the ,pleistocene a race of men lived in ,europe of whom we have a number of skulls and skeletons1 besides vast numbers of stone implements4 ,it is usually known as the ,neanderthal race1 as the first skeleton was found1 in #ahef1 at ,neanderthal1 near ,dusseldorf4 ,further skeletons were found at ,spy1 in ,belgium1 and ,krapina1 in ,croatia4 ,a skull formerly found at ,gibraltar is now assigned to the same race4 ,in the last five years a jaw of the same 7or an earlier7 age has been found at ,mauer1 near ,heidelberg1 and several skeletons have been found in ,france 7,la ,vezere and ,chapelle-aux-,saints74 ,from these1 and a few earlier fragments1 we have a confident knowledge of the features of this early human race4 ,the highest appreciation of the ,neanderthal man--a somewhat flattering appreciation1 as we shall see--is that he had reached the level of the ,australian black of to-day4 ,the massive frontal ridges over his eyes1 the very low1 retreating forehead1 the throwing of the mass of the brain toward the back of the head1 the outthrust of the teeth and jaws1 and the complete absence 7in some cases7 or very slight development of the chin1 combine to give the head what the leading authorities call a bestial or simian aspect4 ,the frame is heavy1 powerful1 and of moderate height 7usually from two to four inches over five feet74 ,the thigh-bones are much more curved than in modern man4 ,we cannot enter here into finer anatomical details1 but all the features are consistent and indicate a stage in the evolution from ape-man to savage man4 ,one point only calls for closer inquiry4 ,until a year or two ago it was customary to state that in cranial capacity also--that is to say1 in the volume of brain-matter that the skull might contain--the ,neanderthal race was intermediate between the ,ape-,man and modern man4 ,we saw above that the cranial capacity of the highest ape is about #fjj cubic centimetres1 and that of the ,ape-,man 7variously given as #hej and #iej7 is about #ijj4 ,it was then added that the capacity of the ,neanderthal race was about #abjj1 and that of civilised man 7on the average7 #afjj4 ,this seemed to be an effective and convincing indication of evolution1 but recent writers have seriously criticised it4 ,sir ,edwin ,ray ,lankester1 ,professor ,sollas1 and ,dr4 ,keith have claimed in recent publications that the brain of ,neanderthal man was as large as1 if not larger than1 that of modern man4 99 ,professor ,sollas even observes that the brain increases in volume as we go backward4 ,this is1 apparently1 so serious a reversal of the familiar statement in regard to the evolution of man that we must consider it carefully4 99,see especially an address by ,professor ,sollas in the ,quarterly ,journal of the ,geological ,society1 ,vol4 ,,lxvi4 7#aiaj74 ,largeness of brain in an individual is no indication of intelligence1 and smallness of brain no proof of low mentality4 ,some of the greatest thinkers1 such as ,aristotle and ,leibnitz1 had abnormally small heads4 ,further1 the size of the brain is of no significance whatever except in strict relation to the size and weight of the body4 ,woman has five or six ounces less brain-matter than man1 but in proportion to her average size and the weight of the vital tissue of her body 7excluding fat7 she has as respectable a brain as man4 ,when1 however1 these allowances have been made1 it has usually been considered that the average brain of a race is in proportion to its average intelligence4 ,this is not strictly true4 ,the rabbit has a larger proportion of brain to body than the elephant or horse1 and the canary a larger proportion than the chimpanzee4 ,professor ,sollas says that the average cranial capacity of the ,eskimo is #aedf cubic centimetres1 or nearly that assigned to the average ,parisian4 ,clearly the question is very complex1 and some of these recent authorities conclude that the cranial capacity1 or volume of the brain1 has no relation to intelligence1 and therefore the size of the ,neanderthal skull neither confirms nor disturbs the theory of evolution4 ,the wise man will suspend his judgment until the whole question has been fully reconsidered4 ,but ,i would point out that some of the recent criticisms are exaggerated4 ,the ,gibraltar skull is estimated by ,professor ,sollas himself to have a capacity of about #abfj2 and his conclusion that it is an abnormal or feminine skull rests on no positive grounds4 ,the ,chapelle-aux-,saints skull ,,alone is proved to have the high capacity of #afbj2 and it is as yet not much more than a supposition that the earlier skulls had been wrongly measured4 ,but1 further1 the great ,french authority1 ,m4 ,boule1 who measured the capacity of the ,chapelle-aux ,saints skull1 observes 99 that the anomaly disappears on careful study4 ,he assures us that a modern skull of the same dimensions would have a capacity of #ahjj-aijj cubic centimetres1 and warns us that we must take into account the robustness of the body of primitive man4 ,he concludes that the real volume of the ,neanderthal brain 7in this highest known specimen7 is slight in comparison with the volume of the brain lodged in the large heads of to-day1 and that the bestial or ape-like characters of the race are not neutralised by this gross measurement4 99,see his article in ,anthropologie1 ,vol4 ,,xx4 7#aiji71 p4 #beg4 ,as ,professor ,sollas mainly relies on ,boule1 it is important to see that there is a very great difference between the two4 ,we must therefore hesitate to accept the statement that primitive man had as large a brain1 if not a larger brain1 than a modern race4 ,the basis is slender1 and the proportion of brain to body-tissue has not been taken into account4 ,on the other hand1 the remains of this early race are1 ,professor ,sollas says1 obviously more brutal than existing men in all the other ascertainable characters by which they differ from them4 ,nor are we confined to precarious measurements of skulls4 ,we have the remains of the culture of this early race1 and in them we have a surer trace of its mental development4 ,here again we must proceed with caution1 and set aside confused and exaggerated statements4 ,some refer us to the artistic work of primitive man4 ,we will consider his drawings and carvings presently1 but they belong to a later race1 not the ,neanderthal race4 ,some lay stress on the fact1 apparently indicated in one or two cases out of a dozen1 that primitive man buried his dead4 ,professor ,sollas says that it indicates that even ,neanderthal man had reached a comparatively high stage in the evolution of religious ideas 2 but the ,australians bury their dead1 and the highest authorities are not agreed whether they have any idea whatever of a supreme being or of morality4 ,we must also disallow appeals to the use of fire1 the taming of animals1 pottery1 or clothing4 ,none of these things are clearly found in conjunction with the ,neanderthal race4 ,the only certain relic of ,neanderthal culture is the implement which the primitive savage fashioned1 by chipping or pressure1 of flint or other hard stone4 ,the fineness of some of these implements is no indication of great intelligence4 ,the ,neanderthal man inherited a stone culture which was already of great antiquity4 ,at least one1 if not two or three1 prolonged phases of the ,old ,stone ,age were already over when he appeared4 ,on the most modest estimate men had by that time been chipping flints for several hundred thousand years1 and it is no argument of general intelligence that some skill in the one industry of the age had been developed4 ,the true measure of ,neanderthal man's capacity is that1 a million years or so after passing the anthropoid-age level1 he chipped his stones more finely and gave them a better edge and contour4 ,there is no evidence that he as yet hefted them4 ,it is flattering to him to compare him with the ,australian aboriginal4 ,the native art1 the shields and spears and boomerangs1 and the elaborate tribal and matrimonial arrangements of the ,australian black are not known to have had any counterpart in his life4 ,it would therefore seem that the precursors of man made singularly little1 if any1 progress during the vast span of time between the ,miocene and the ,ice-,age1 and that then something occurred which quickened the face of human evolution4 ,from the ,neanderthal level man will advance to the height of modern civilisation in about one-tenth the time that it took him to advance from the level of the higher ape to that of the lowest savage4 ,something has broken into the long lethargy of his primitive career1 and set him upon a progressive path4 ,let us see if a careful review of the stages of his culture confirms the natural supposition that this something was the fall in the earth's temperature1 and how it may have affected him4 ,,chapter ,,xx4 ,,the ,,dawn ,,of ,,civilisation ,the story of man before the discovery of metal and the attainment of civilisation is notoriously divided into a ,palaeolithic 7,old ,stone7 ,age1 and a ,neolithic 7,new ,stone7 ,age4 ,each of these ages is now subdivided into stages1 which we will review in succession4 ,but it is important to conceive the whole story of man in more correct proportion than this familiar division suggests4 ,the historical or civilised period is now computed at about ten thousand years4 ,the ,neolithic ,age1 which preceded civilisation1 is usually believed to be about four or five times as long1 though estimates of its duration vary from about twenty to a hundred thousand years4 ,the ,palaeolithic ,age in turn is regarded as at least three or four times as long as the ,neolithic2 estimates of time vary from a hundred to five hundred thousand years4 ,and before this there is the vast stretch of time in which the ape slowly became a primitive human4 ,this long1 early period is1 as we saw1 still wrapped in mist and controversy4 ,a few bones tell of a race living1 in semi-human shape1 in the region of the ,indian ,ocean2 a few crude stones are held by many to indicate that a more advanced1 but very lowly race1 wandered over the south of ,europe and north of ,africa before the ,ice-,age set in4 ,the starting-point or cradle of the race is not known4 ,the old idea of seeking the patriarchal home on the plains to the north of ,india is abandoned1 and there is some tendency to locate it in the land which has partly survived in the islands of the ,indian ,ocean4 ,the finding of early remains in ,java is not enough to justify that conclusion1 but it obtains a certain probability when we notice the geographical distribution of the ,primates4 ,the femurs and the apes are found to-day in ,africa and ,asia alone2 the monkeys have spread eastward to ,america and westward to ,europe and ,africa2 the human race has spread north-eastward into ,asia and ,america1 northwestward into ,europe1 westward into ,africa1 and southward to ,australia and the islands4 ,this distribution suggests a centre in the ,indian ,ocean1 where there was much more land in the ,tertiary ,era than there is now4 ,we await further exploration in that region and ,africa4 ,there is nothing improbable in the supposition that man wandered into ,europe in the ,tertiary1 and has left in the ,eoliths the memorials of his lowly condition4 ,the anthropoid apes certainly reached ,france4 ,however that may be1 the ,ice-,age would restrict all the ,primates to the south4 ,it will be seen1 on a glance at the map1 that a line of ice-clad mountains would set a stern barrier to man's advance in the early ,pleistocene1 from the ,pyrenees to the ,himalaya1 if not to the ,pacific4 ,he therefore spread westward and southward4 ,one branch wandered into ,australia1 and was afterwards pressed by more advanced invaders 7the present blacks of ,australia7 into ,tasmania1 which seems to have been still connected by land4 ,another branch1 or branches1 spread into ,africa1 to be driven southward1 or into the central forests1 by later and better equipped invaders4 ,they survive1 little changed 7except by recent contact with ,europeans71 in the ,bushmen and in large populations of ,central ,africa which are below the level of tribal organisation4 ,others remained in the islands1 and we seem to have remnants of them in the ,kalangs1 ,veddahs1 etc4 ,but these islands have been repeatedly overrun by higher races1 and the primitive life has been modified4 ,comparing the most isolated of these relics of early humanity1 we obtain many suggestions about the life of that remote age4 ,the aboriginal ,tasmanians1 who died out about forty years ago1 were of great evolutionary interest4 ,it is sometimes said that man is distinguished from all other animals by the possession of abstract ideas1 but the very imperfect speech of the ,tasmanians expressed no abstract ideas4 ,their mind seems to have been in an intermediate stage of development4 ,they never made fire1 and1 like the other surviving fragments of early humanity1 they had no tribal organisation1 and no ideas of religion or morality4 ,the first effect of the ,ice-,age on this primitive humanity would be to lead to a beginning of the development of racial characters4 ,the pigment under the skin of the negro is a protection against the actinic rays of the tropical sun2 the white man1 with his fair hair and eyes1 is a bleached product of the northern regions2 and the yellow or brown skin seems to be the outcome of living in dry regions with great extremes of temperature4 ,as the northern hemisphere divided into climatic zones these physical characters were bound to develop4 ,the men who went southward developed1 especially when fully exposed to the sun on open plains1 the layer of black pigment which marks the negroid type4 ,there is good reason1 as we shall see to think that man did not yet wear clothing1 though he had a fairly conspicuous1 if dwindling1 coat of hair4 ,on the other hand the men who lingered further north1 in ,south-western ,asia and ,north ,africa1 would lose what pigment they had1 and develop the lighter characters of the northerner4 ,it has been noticed that even a year in the arctic circle has a tendency to make the eyes of explorers light blue4 ,we may look for the genesis of the vigorous1 light-complexioned races along the fringe of the great ice-sheet4 ,it must be remembered that when the limit of the ice-sheet was in ,central ,germany and ,belgium1 the climate even of ,north ,africa would be very much more temperate than it is to-day4 ,as the ice-sheet melted1 the men who were adapted to living in the temperate zone to the south of it penetrated into ,europe1 and the long story of the ,old ,stone ,age opened4 ,it must not1 of course1 be supposed that this stage of human culture only began with the invasion of ,europe4 ,men would bring their rough art of fashioning implements with them1 but the southern regions are too little explored to inform us of the earlier stage4 ,but as man enters ,europe he begins to drop his flints on a soil that we have constant occasion to probe--although the floor on which he trod is now sometimes forty or fifty feet below the surface--and we obtain a surer glimpse of the fortunes of our race4 ,most ,european geologists count four distinct extensions of the ice-sheet1 with three interglacial periods4 ,it is now generally believed that man came north in the third interglacial period2 though some high authorities think that he came in the second4 ,as far as ,england is concerned1 it has been determined1 under the auspices of the ,british ,association1 that our oldest implements 7apart from the ,eoliths7 are later than the great ice-sheet1 but there is some evidence that they precede the last extension of the ice4 ,two stages are distinguished in this first part of the ,palaeolithic ,age--the ,acheulean and ,chellean--but it will suffice for our purpose to take the two together as the earlier and longer section of the ,old ,stone ,age4 ,it was a time of temperate1 if not genial1 climate4 ,the elephant 7an extinct type71 the rhinoceros1 the hippopotamus1 the hyaena1 and many other forms of animal life that have since retired southward1 were neighbours of the first human inhabitant of ,europe4 ,unfortunately1 we have only one bone of this primitive race1 the jaw found at ,mauer in #aijg1 but its massive size and chinless contour suggest a being midway between the ,java man and the ,neanderthal race4 ,his culture confirms the supposition4 ,there is at this stage no clear trace of fire1 clothing1 arrows1 hefted weapons1 spears1 or social life4 ,as the implements are generally found on old river-banks or the open soil1 not in caves1 we seem to see a squat and powerful race wandering1 homeless and unclad1 by the streams and broad1 marshy rivers of the time4 ,the ,thames and the ,seine had not yet scooped out the valleys on the slopes of which ,london and ,paris are built4 ,this period seems1 from the vast number of stone implements referred to it1 to have lasted a considerable time4 ,there is a risk in venturing to give figures1 but it may be said that few authorities would estimate it at less than a hundred thousand years4 ,man still advanced with very slow and uncertain steps1 his whole progress in that vast period being measured by the invention of one or two new forms of stone implements and a little more skill in chipping them4 ,at its close a great chill comes over ,europe--the last ice-sheet is1 it seems1 spreading southward--and we enter the ,mousterian period and encounter the ,neanderthal race which we described in the preceding chapter4 ,it must be borne in mind that the whole culture of primitive times is crushed into a few feet of earth4 ,the anthropologist is therefore quite unable to show us the real succession of human stages1 and has to be content with a division of the whole long and gradual evolution into a few well-marked phases4 ,these phases1 however1 shade into each other1 and are merely convenient measurements of a continuous story4 ,the ,chellean man has slowly advanced to a high level4 ,there is no sudden incoming of a higher culture or higher type of man4 ,the most impressive relics of the ,mousterian period1 which represent its later epoch1 are merely finely chipped implements4 ,there is no art as yet1 no pottery1 and no agriculture2 and there is no clear trace of the use of fire or clothing1 though we should be disposed to put these inventions in the chilly and damp ,mousterian period4 ,there is therefore no ground for resenting the description1 the primeval savage1 which has been applied to early man4 ,the human race is already old1 yet1 as we saw1 it is hardly up to the level of the ,australian black4 ,the skeleton found at ,chapelle-aux-,saints is regarded as the highest known type of the race1 yet the greatest authority on it1 ,m4 ,boule1 says emphatically3 ,in no actual race do we find the characters of inferiority--that is to say1 the ape-like features--which we find in the ,chapelle-aux-,saints head4 ,the largeness of the head is in proportion to the robust frame1 but in its specifically human part--the front--it is very low and bestial2 while the heavy ridges over the large eyes1 the large flat stumpy nose1 the thick bulge of the lips and teeth1 and the almost chinless jaw1 show that the traces of his ancestry cling close to man after some hundreds of thousands of years of development4 ,the cold increases as we pass to the last part of the ,old ,stone ,age1 the ,solutrean and ,magdalenian periods2 and nothing is clearer than that the pace of development increases at the same time4 ,short as the period is1 in comparison with the preceding1 it witnesses a far greater advance than had been made in all the rest of the ,old ,stone ,age4 ,beyond a doubt men now live in caves1 in large social groups1 make clothing from the skins of animals1 have the use of fire1 and greatly improve the quality of their stone axes1 scrapers1 knives1 and lance-heads4 ,there is at last some promise of the civilisation that is coming4 ,in the soil of the caverns in which man lived1 especially in ,southern ,france and the ,pyrenean region1 we find the debris of a much larger and fuller life4 ,even the fine bone needles with which primitive man sewed his skin garments1 probably with sinews for thread1 survive in scores4 ,in other places we find the ashes of the fires round which he squatted1 often associated with the bones of the wild horses1 deer1 etc41 on which he lived4 ,but the most remarkable indication of progress in the cave-man is his artistic skill4 ,exaggerated conclusions are sometimes drawn from the statuettes1 carvings1 and drawings which we find among the remains of ,magdalenian life4 ,most of them are crude1 and have the limitations of a rustic or a child artist4 ,there is no perspective1 no grouping4 ,animals are jumbled together1 and often left unfinished because the available space was not measured4 ,there are1 however1 some drawings--cut on bone or horn or stone with a flint implement--which evince great skill in line-drawing and1 in a few cases1 in composition4 ,some of the caves also are more or less frescoed2 the outlines of animals1 sometimes of life-size and in great numbers1 are cut in the wall1 and often filled in with pigment4 ,this skill does not imply any greater general intelligence than the rest of the culture exhibits4 ,it implies persistent and traditional concentration upon the new artistic life4 ,the men who drew the reindeer of ,thayngen and carved the remarkable statuettes of women in ivory or stone1 were ignorant of the simplest rudiments of pottery or agriculture1 which many savage tribes possess4 ,some writers compare them with the ,eskimo of to-day1 and even suggest that the ,eskimo are the survivors of the race1 retreating northward with the last ice-sheet1 and possibly egged onward by a superior race from the south4 ,it is1 perhaps1 not a very extravagant claim that some hundreds of thousands of years of development--we are now only a few tens of thousands of years from the dawn of civilisation--had lifted man to the level of the ,eskimo1 yet one must hesitate to admit the comparison4 ,lord ,avebury reproduces an ,eskimo drawing1 or picture-message1 in his ,prehistoric ,times1 to which it would be difficult to find a parallel in ,magdalenian remains4 ,i do not mean that the art is superior1 but the complex life represented on the picture-message1 and the intelligence with which it is represented1 are beyond anything that we know of ,palaeolithic man4 ,i may add that nearly all the drawings and statues of men and women which the ,palaeolithic artist has left us are marked by the intense sexual exaggeration--the obscenity1 in modern phraseology--which we are apt to find in coarse savages4 ,three races are traced in this period4 ,one1 identified by skeletons found at ,mentone and by certain statuettes1 was negroid in character4 ,probably there was an occasional immigration from ,africa4 ,another race 7,cro-,magnon7 was very tall1 and seems to represent an invasion from some other part of the earth toward the close of the ,old ,stone ,age4 ,the third race1 which is compared to the ,eskimo1 and had a stature of about five feet1 seem to be the real continuers of the ,palaeolithic man of ,europe4 ,curiously enough1 we have less authentic remains of this race than of its predecessor1 and can only say that1 as we should expect1 the ape-like features--the low forehead1 the heavy frontal ridges1 the bulging teeth1 etc4--are moderating4 ,the needles we have found--round1 polished1 and pierced splinters of bone1 sometimes nearly as fine as a bodkin--show indisputably that man then had clothing1 but it is curious that the artist nearly always draws him nude4 ,there is also generally a series of marks round the contour of the body to indicate that he had a conspicuous coat of hair4 ,unfortunately1 the faces of the men are merely a few unsatisfactory gashes in the bone or horn1 and do not picture this interesting race to us4 ,the various statuettes of women generally suggest a type akin to the wife of the ,bushman4 ,we have1 in fine1 a race of hunters1 with fine stone knives and javelins4 ,toward the close of the period we find a single representation of an arrow1 which was probably just coming into use1 but it is not generally known in the ,old ,stone ,age4 ,one of the drawings seems to represent a kind of bridle on a horse1 but we need more evidence than this to convince us that the horse was already tamed1 nor is there any reason to suppose that the dog or reindeer had been tamed1 or that the ground was tilled even in the most rudimentary way4 ,artistic skill1 the use of clothing and fire1 and a finer feeling in the shaping of weapons and implements1 are the highest certain indications of the progress made by the end of the ,old ,stone ,age4 ,but there was probably an advance made which we do not find recorded1 or only equivocally recorded1 in the memorials of the age4 ,speech was probably the greatest invention of ,magdalenian man4 ,it has been pointed out that the spine in the lower jaw1 to which the tongue-muscle is attached1 is so poorly developed in ,palaeolithic man that we may infer from it the absence of articulate speech4 ,the deduction has been criticised1 but a comparison of the ,palaeolithic jaw with that of the ape on one hand and modern man on the other gives weight to it4 ,whatever may have been earlier man's power of expression1 the closer social life of the ,magdalenian period would lead to a great development of it4 ,some writers go so far as to suggest that certain obscure marks painted on pebbles or drawn on the cavern-walls by men at the close of the ,palaeolithic ,age may represent a beginning of written language1 or numbers1 or conventional signs4 ,the interpretation of these is obscure and doubtful4 ,it is not until ages afterwards that we find the first clear traces of written language1 and then they take the form of pictographs 7like the ,egyptian hieroglyphics or the earliest ,chinese characters74 ,we cannot doubt1 however1 that articulate speech would be rapidly evolved in the social life of the later ,magdalenian period1 and the importance of this acquisition can hardly be exaggerated4 ,imagine even a modern community without the device of articulate language4 ,a very large proportion of the community1 who are now maintained at a certain level by the thought of others1 communicated to them by speech1 would sink below the civilised standard1 and the transmission and improvement of ideas would be paralysed4 ,it would not be paradoxical to regard the social life and developing speech of ,magdalenian man as the chief cause of the rapid advance toward civilisation which will follow in the next period4 ,and it is not without interest to notice that a fall in the temperature of the earth is the immediate cause of this social life4 ,the building of homes of any kind seems to be unknown to ,magdalenian man4 ,the artist would have left us some sketchy representation of it if there had been anything in the nature of a tent in his surroundings4 ,the rock-shelter and the cave are the homes which men seek from the advancing cold4 ,as these are relatively few in number1 fixed in locality1 and often of large dimensions1 the individualism of the earlier times is replaced by collective life4 ,sociologists still dispute whether the clan arose by the cohesion of families or the family arose within the clan4 ,such evidence as is afforded by prehistoric remains is entirely in favour of the opinion of ,professor ,westermarck1 that the family preceded the larger group4 ,families of common descent would now cling together and occupy a common cavern1 and1 when the men gathered at night with the women for the roasting and eating of the horse or deer they had hunted1 and the work of the artist and the woman was considered1 the uncouth muttering and gesticulating was slowly forged into the great instrument of articulate speech4 ,the first condition of more rapid progress was instinctively gained4 ,our story of life has so often turned on this periodical lowering of the climate of the earth that it is interesting to find this last and most important advance so closely associated with it that we are forced once more to regard it as the effective cause4 ,the same may be said of another fundamental advance of the men of the later ,palaeolithic age1 the discovery of the art of making fire4 ,it coincides with the oncoming of the cold1 either in the ,mousterian or the ,magdalenian4 ,it was more probably a chance discovery than an invention4 ,savages so commonly make fire by friction--rubbing sticks1 drills1 etc4--that one is naturally tempted to regard this as the primitive method4 ,i doubt if this was the case4 ,when1 in ,neolithic times1 men commonly bury the dead1 and put some of their personal property in the grave with them1 the fire-kindling apparatus we find is a flint and a piece of iron pyrites4 ,palaeolithic man made his implements of any kind of hard and heavy stone1 and it is probable that he occasionally selected iron ore for the purpose4 ,an attempt to chip it with flint would cause sparks that might fall on inflammable material1 and set it alight4 ,little intelligence would be needed to turn this discovery to account4 ,apart from these conjectures as to particular features in the life of prehistoric man1 it will be seen that we have now a broad and firm conception of its evolution4 ,from the ape-level man very slowly mounts to the stage of human savagery4 ,during long ages he seems to have made almost no progress4 ,there is nothing intrinsically progressive in his nature4 ,let a group of men be isolated at any stage of human evolution1 and placed in an unchanging environment1 and they will remain stationary for an indefinite period4 ,when ,europeans began to traverse the globe in the last few centuries1 they picked up here and there little groups of men who had1 in their isolation1 remained just where their fathers had been when they quitted the main road of advance in the earlier stages of the ,old ,stone ,age4 ,the evolution of man is guided by the same laws as the evolution of any other species4 ,thus we can understand the long period of stagnation1 or of incalculably slow advance4 ,thus1 too1 we can understand why1 at length1 the pace of man toward his unconscious goal is quickened4 ,he is an inhabitant of the northern hemisphere1 and the northern hemisphere is shaken by the last of the great geological revolutions4 ,from its first stress emerges the primeval savage of the early part of the ,old ,stone ,age1 still bearing the deep imprint of his origin1 surpassing his fellow-animals only in the use of crude stone implements4 ,then the stress of conditions relaxes--the great ice-sheet disappears--and again during a vast period he makes very little progress4 ,the stress returns4 ,the genial country is stripped and impoverished1 and the reindeer and mammoth spread to the south of ,europe4 ,but once more the adversity has its use1 and man1 stimulated in his hunt for food1 invigorated by the cold1 driven into social life1 advances to the culmination of the ,old ,stone ,age4 ,we are still very far from civilisation1 but the few tens of thousands of years that separate ,magdalenian man from it will be traversed with relative speed--though1 we should always remember1 with a speed far less than the pace at which man is advancing to-day4 ,a new principle now enters into play3 a specifically human law of evolution is formulated4 ,it has no element of mysticism1 and is merely an expression of the fact that the previous general agencies of development have created in man an intelligence of a higher grade than that of any other animal4 ,in his larger and more plastic brain the impressions received from the outer world are blended in ideas1 and in his articulate speech he has a unique means of entering the idea-world of his fellows4 ,the new principle of evolution1 which arises from this superiority1 is that man's chief stimulus to advance will now come from his cultural rather than his physical environment4 ,physical surroundings will continue to affect him4 ,one race will outstrip another because of its advantage in soil1 climate1 or geographical position4 ,but the chief key to the remaining and more important progress of mankind1 which we are about to review1 is the stimulating contact of the differing cultures of different races4 ,this will be seen best in the history of civilisation1 but the principle may be recognised in the ,new ,stone ,age which leads from primeval savagery to civilisation1 or1 to be more accurate and just1 to the beginning of the historical period4 ,it used to be thought that there was a mysterious blank or gulf between the ,old and the ,new ,stone ,age4 ,the ,palaeolithic culture seemed to come to an abrupt close1 and the ,neolithic culture was sharply distinguished from it4 ,it was suspected that some great catastrophe had destroyed the ,palaeolithic race in ,europe1 and a new race entered as the adverse conditions were removed4 ,this was especially held to be the case in ,england4 ,the old ,palaeolithic race had never reached ,ireland1 which seems to have been cut oft from the ,continent during the ,ice-,age1 and most of the authorities still believe--in spite of some recent claims--that it never reached ,scotland4 ,england itself was well populated1 and the remains found in the caves of ,derbyshire show that even the artist--or his art--had reached that district4 ,this ,palaeolithic race seemed to come to a mysterious end1 and ,europe was then invaded by the higher ,neolithic race4 ,england was probably detached from the ,continent about the end of the ,magdalenian period4 ,it was thought that some great devastation--the last ice-sheet1 a submersion of the land1 or a plague--then set in1 and men were unable to retreat south4 ,it is now claimed by many authorities that there are traces of a ,middle ,stone 7,mesolithic7 period even in ,england1 and nearly all the authorities admit that such a transitional stage can be identified in the ,pyrenean region4 ,this region had been the great centre of the ,magdalenian culture4 ,its large frescoed caverns exhibit the culmination of the ,old ,stone life1 and afford many connecting links with the new4 ,it is1 however1 a clearly established and outstanding fact that the characteristic art of ,magdalenian man comes to an abrupt and complete close1 and it does not seem possible to explain this without supposing that the old race was destroyed or displaced4 ,if we could accept the view that it was the ,eskimo-like race of the ,palaeolithic that cultivated this art1 and that they retreated north with the reindeer and the ice1 and survive in our ,eskimo1 we should have a plausible explanation4 ,in point of fact1 we find no trace whatever of this slow migration from the south of ,europe to the north4 ,the more probable supposition is that a new race1 with more finished stone implements1 entered ,europe1 imposed its culture upon the older race1 and gradually exterminated or replaced it4 ,we may leave it open whether a part of the old race retreated to the north1 and became the ,eskimo4 ,whence came the new race and its culture8 ,it will be seen on reflection that we have so far been studying the evolution of man in ,europe only1 because there alone are his remains known with any fullness4 ,but the important region which stretches from ,morocco to ,persia must have been an equally1 if not more1 important theatre of development4 ,while ,europe was shivering in the last stage of the ,ice-,age1 and the mammoth and reindeer browsed in the snows down to the south of ,france1 this region would enjoy an excellent climate and a productive soil4 ,we may confidently assume that there was a large and stirring population of human beings on it during the ,magdalenian cold4 ,we may1 with many of the authorities1 look to this temperate and fertile region for the slight advance made by early ,neolithic man beyond his predecessor4 ,as the cold relaxed1 and the southern fringe of dreary steppe w as converted once more into genial country1 the race would push north4 ,there is evidence that there were still land bridges across the ,mediterranean4 ,from ,spain and the south of ,france this early ,neolithic race rapidly spread over ,europe4 ,it must not be supposed that the ,new ,stone ,age at first goes much beyond the ,old in culture4 ,works on prehistoric man are apt to give as features of ,neolithic man all that we know him to have done or discovered during the whole of the ,new ,stone ,age4 ,we read that he not only gave a finer finish to1 and sometimes polished1 his stone weapons1 but built houses1 put imposing monuments over his dead1 and had agriculture1 tame cattle1 pottery1 and weaving4 ,this is misleading1 as the more advanced of these accomplishments appear only late in the ,new ,stone ,age4 ,the only difference we find at first is that the stone axes1 etc41 are more finely chipped or flaked1 and are frequently polished by rubbing on stone moulds4 ,there is no sudden leap in culture or intelligence in the story of man4 ,it would be supremely interesting to trace the evolution of human industries and ideas during the few tens of thousands of years of the ,new ,stone ,age4 ,during that time moral and religious ideas are largely developed1 political or social forms are elaborated1 and the arts of civilised man have their first rude inauguration4 ,the foundations of civilisation are laid4 ,unfortunately1 precisely because the period is relatively so short and the advance so rapid1 its remains are crushed and mingled in a thin seam of the geological chronicle1 and we cannot restore the gradual course of its development with any confidence4 ,estimates of its duration vary from #bj1jjj to #gj1jjj years2 though ,sir ,w4 ,turner has recently concluded1 from an examination of marks on ,scottish monuments1 that ,neolithic man probably came on foot from ,scandinavia to ,scotland1 and most geologists would admit that it must be at least a hundred thousand years since one could cross from ,norway to ,scotland on foot4 ,as usual1 we must leave open the question of chronology1 and be content with a modest provisional estimate of #dj1jjj or #ej1jjj years4 ,we dimly perceive the gradual advance of human culture in this important period4 ,during the ,old ,stone ,age man had made more progress than he had made in the preceding million years2 during the ,new ,stone ,age--at least one-fourth as long as the ,old--he made even greater progress2 and1 we may add1 in the historical period1 which is one-fourth the length of the ,neolithic ,age1 he will make greater progress still4 ,the pace of advance naturally increases as intelligence grows1 but that is not the whole explanation4 ,the spread of the race1 the gathering of its members into tribes1 and the increasing enterprise of men in hunting and migration1 lead to incessant contacts of different cultures and a progressive stimulation4 ,at first ,neolithic man is content with finer weapons4 ,his stone axe is so finely shaped and polished that it sometimes looks like forged or moulded metal4 ,he also drills a clean hole through it--possibly by means of a stick working in wet sand--and gives it a long wooden handle4 ,he digs in the earth for finer flints1 and in some of his ancient shafts 7,grimes1 ,graves and ,cissbury7 we find picks of reindeer horn and hollowed blocks of chalk in which he probably burned fat for illumination underground4 ,but in the later part of the ,neolithic--to which much of this finer work also may belong--we find him building huts1 rearing large stone monuments1 having tame dogs and pigs and oxen1 growing corn and barley1 and weaving primitive fabrics4 ,he lives in large and strong villages1 round which we must imagine his primitive cornfields growing and his cattle grazing1 and in which there must have been some political organisation under chiefs4 ,when we wish to trace the beginning of these inventions we have the same difficulty that we experienced in tracing the first stages of new animal types4 ,the beginning takes place in some restricted region1 and our casual scratching of the crust of the earth or the soil may not touch it for ages1 if it has survived at all4 ,but for our literature and illustrations a future generation would be equally puzzled to know how we got the idea of the aeroplane or the electric light4 ,in some cases we can make a good guess at the origin of ,neolithic man's institutions4 ,let us take pottery4 ,palaeolithic man cooked his joint of horse or reindeer1 and1 no doubt1 scorched it4 ,suppose that some ,palaeolithic ,soyer had conceived the idea of protecting the joint1 and preserving its juices1 by daubing it with a coat of clay4 ,he would accidentally make a clay vessel4 ,this is ,mr4 ,clodd's ingenious theory of the origin of pottery4 ,the development of agriculture is not very puzzling4 ,the seed of corn would easily be discovered to have a food-value1 and the discovery of the growth of the plant from the seed would not require a very high intelligence4 ,some ants1 we may recall1 have their fungus-beds4 ,it would be added by many that the ant gives us another parallel in its keeping of droves of aphides1 which it milks4 ,but it is now doubted if the ant deliberately cultivates the aphides with this aim4 ,early weaving might arise from the plaiting of grasses4 ,if wild flax were used1 it might be noticed that part of it remained strong when the rest decayed1 and so the threads might be selected and woven4 ,the building of houses1 after living for ages in stone caverns1 would not be a very profound invention4 ,the early houses were--as may be gathered from the many remains in ,devonshire and ,cornwall--mere rings of heaped stones1 over which1 most probably1 was put a roof of branches or reeds1 plastered with mud4 ,they belong to the last part of the ,new ,stone ,age4 ,in other places1 chiefly ,switzerland1 ,neolithic man lived in wooden huts built on piles in the shallow shores of lakes4 ,it is an evidence that life on land is becoming as stimulating as we find it in the age of ,deinosaurs or early mammals4 ,these pile-villages of ,switzerland lasted until the historical period1 and the numerous remains in the mud of the lake show the gradual passage into the age of metal4 ,before the metal age opened1 however1 there seem to have been fresh invasions of ,europe and changes of its culture4 ,the movements of the various early races of men are very obscure1 and it would be useless to give here even an outline of the controversy4 ,anthropologists have generally taken the relative length and width of the skull as a standard feature of a race1 and distinguished long-headed 7dolichocephalic71 short-headed 7brachycephalic71 and middle-headed 7mesaticephalic7 races4 ,even on this test the most divergent conclusions were reached in regard to early races1 and now the test itself is seriously disputed4 ,some authorities believe that there is no unchanging type of skull in a particular race1 but that1 for instance1 a long-headed race may become short-headed by going to live in an elevated region4 ,it may be said1 in a few words1 that it is generally believed that two races invaded ,europe and displaced the first ,neolithic race4 ,the race which chiefly settled in the ,swiss region is generally believed to have come from ,asia1 and advanced across ,europe by way of the valley of the ,danube4 ,the native home of the wheat and barley and millet1 which1 as we know1 the lake-dwellers cultivated1 is said to be ,asia4 ,on the other hand1 the ,neolithic men who have left stone monuments on our soil are said to be a different race1 coming1 by way of ,north ,africa1 from ,asia1 and advancing along the west of ,europe to ,scandinavia4 ,a map of the earth1 on which the distribution of these stone monuments--all probably connected with the burial of the dead--is indicated1 suggests such a line of advance from ,india1 with a slighter branch eastward4 ,but the whole question of these invasions is disputed1 and there are many who regard the various branches of the population of ,europe as sections of one race which spread upward from the shores of the ,mediterranean4 ,it is clear at least that there were great movements of population1 much mingling of types and commercial interchange of products1 so that we have the constant conditions of advance4 ,a last invasion seems to have taken place some two or three thousand years before the ,christian era1 when the ,aryans overspread ,europe4 ,after all the controversy about the ,aryans it seems clear that a powerful race1 representing the ancestors of most of the actual peoples of ,europe and speaking the dialects which have been modified into the related languages of the ,greeks1 ,romans1 ,germans1 ,celts1 ,lithuanians1 etc41 imposed its speech on nearly the whole of the continent4 ,only in the ,basques and ,picts do we seem to find some remnants of the earlier non-,aryan tongues4 ,but whether these ,aryans really came from ,asia1 as it used to be thought1 or developed in the east of ,europe1 is uncertain4 ,we seem justified in thinking that a very robust race had been growing in numbers and power during the ,neolithic ,age1 somewhere in the region of ,south-east ,europe and ,southwest ,asia1 and that a few thousand years before the ,christian ,era one branch of it descended upon ,india1 another upon the ,persian region1 and another overspread ,europe4 ,we will return to the point later4 ,instead of being the bearers of a higher civilisation1 these primitive ,aryans seem to have been lower in culture than the peoples on whom they fell4 ,the ,neolithic ,age had meantime passed into the ,age of ,metal4 ,copper was probably the first metal to be used4 ,it is easily worked1 and is found in nature4 ,but the few copper implements we possess do not suggest a ,copper ,age of any length or extent4 ,it was soon found1 apparently1 that an admixture of tin hardened the copper1 and the ,bronze ,age followed4 ,the use of bronze was known in ,egypt about #dhjj ,b4,c4 7,flinders ,petrie71 but little used until about #bjjj ,b4,c4 ,by that time 7or a few centuries later7 it had spread as far as ,scandinavia and ,britain4 ,the region of invention is not known1 but we have large numbers of beautiful specimens of bronze work--including brooches and hair-pins--in all parts of ,europe4 ,finally1 about the thirteenth century ,b4,c41 we find the first traces of the use of iron4 ,the first great centre for the making of iron weapons seems to have been ,hallstatt1 in the ,austrian ,alps1 whence it spread slowly over ,europe1 reaching ,scandinavia and ,britain between #ejj and #cjj ,b4,c4 ,but the story of man had long before this entered the historical period1 to which we now turn4 ,,chapter ,,xxi4 ,,evolution ,,in ,,history ,in the preceding chapters ,i have endeavoured to show how1 without invoking any definitely directed variations1 which we seem to have little chance of understanding1 we may obtain a broad conception of the way in which the earth and its living inhabitants came to be what they are4 ,no one is more conscious than the writer that this account is extremely imperfect4 ,the limits of the volume have permitted me to use only a part of the material which modern science affords1 but if the whole of our discoveries were described the sketch would still remain very imperfect4 ,the evolutionary conception of the world is itself undergoing evolution in the mind of man4 ,age by age the bits of fresh discovery are fitted into the great mosaic4 ,large areas are still left for the scientific artist of the future to fill4 ,yet even in its imperfect state the evolutionary picture of the world is most illuminating4 ,the questions that have been on the lips of thoughtful men since they first looked out with adult eyes on the panorama of nature are partly answered4 ,whence and ,why are no longer sheer riddles of the sphinx4 ,it remains to be seen if evolutionary principles will throw at least an equal light on the progress of humanity in the historical period4 ,here again the questions1 ,whence and ,why1 have been asked in vain for countless ages4 ,if man is a progressive animal1 why has the progress been confined to some of the race8 ,if humanity shared at first a common patrimony1 why have the savages remained savages1 and the barbarians barbaric8 ,why has progress been incarnated so exceptionally in the white section of the race1 the ,europeans8 ,we approach these questions more confidently after surveying the story of terrestrial life in the light of evolutionary principles4 ,since the days of the primeval microbe it has happened that a few were chosen and many were left behind4 ,there was no progressive element in the advancing few that was not shared by the stagnant many4 ,the difference lay in the environment4 ,let us see if this principle applies to the history of civilisation4 ,in the last chapter ,i observed that1 with the rise of human intelligence1 the cultural environment becomes more important than the physical4 ,since human progress is a progress in ideas and the emotions which accompany them1 this may seem to be a truism4 ,in point of fact it is assailed by more than one recent historical writer4 ,the scepticism is partly due to a misunderstanding4 ,no one but a fanatical adherent of extreme theories of heredity will deny that the physical surroundings of a race continue to be of great importance4 ,the progress of a particular people may often be traced in part to its physical environment2 especially to changes of environment1 by migration1 for instance4 ,further1 it is not for a moment suggested that a race never evolves its own culture1 but has always to receive it from another4 ,if we said that1 we should be ultimately driven to recognise culture1 like the early ,chinese1 as a gift of the gods4 ,what is meant is that the chief key to the progress of certain peoples1 the arrest of progress in others1 and the entire absence of progress in others1 is the study of their relations with1 or isolation from1 other peoples4 ,they make progress chiefly according to the amount of stimulation they get by contact with a diverse culture4 ,let us see if this furnishes a broad explanation of the position of the various peoples of the world4 ,the ,ethnologist tells us that the lowest peoples of the earth are the ,yahgans of ,tierra del ,fuego1 the ,hottentots1 a number of little-understood peoples in ,central ,africa1 the wild ,veddahs of ,ceylon1 the 7extinct7 ,tasmanians1 the ,aetas in the interior of the ,philippines1 and certain fragments of peoples on islands of the ,indian ,ocean4 ,there is not the least trace of a common element in the environment of these peoples to explain why they have remained at the level of primitive humanity4 ,many of them lived in the most promising and resourceful surroundings4 ,what is common to them all is their isolation from the paths of later humanity4 ,they represent the first wave of human distribution1 pressed to the tips of continents or on islands by later waves1 and isolated4 ,the position of the ,veddahs is1 to some extent1 an exception2 and it is interesting to find that the latest ,german students of that curious people think that they have been classed too low by earlier investigators4 ,we cannot run over all the peoples of the earth in this way1 but will briefly glance at the lower races of the various continents4 ,a branch of the second phase of developing humanity1 the negroid stock1 spread eastward over the ,asiatic islands and ,australia1 and westward into ,africa4 ,the extreme wing of this army1 the ,australian blacks1 too clearly illustrates the principle to need further reference4 ,it has retained for ages the culture of the middle ,palaeolithic4 ,the negritos who penetrated to the ,philippines are another extreme instance of isolation4 ,the ,melanesians of the islands of the ,indian and ,pacific ,ocean are less low1 because those islands have been slowly crossed by a much higher race1 the ,polynesians4 ,the ,maoris of ,new ,zealand1 the ,tongans1 ,hawaians1 etc41 are people of our own 7,caucasic7 stock1 probably diverging to the south-east while our branch of the stock pressed westward4 ,this not only explains the higher condition of the ,maoris1 etc41 but also shows why they have not advanced like their ,european cousins4 ,their environment is one of the finest in the world1 but--it lies far away from the highways of culture4 ,in much the same way can we interpret the swarming peoples of ,africa4 ,the more primitive peoples which arrived first1 and were driven south or into the central forests by the later and better equipped invaders from the central zone1 have remained the more primitive4 ,the more northern peoples1 on the fringe of1 or liable to invasion from1 the central zone1 have made more advance1 and have occasionally set up rudimentary civilisations4 ,but the movements from the north to the south in early historical times are too obscure to enable us to trace the action of the principle more clearly4 ,the peoples of the ,mediterranean fringe of ,africa1 living in the central zone of stimulation1 have proved very progressive4 ,under the ,romans ,north ,africa was at least as civilised as ,britain1 and an equally wise and humane ,european policy might lead to their revival to-day4 ,when we turn to ,asia we encounter a mass of little-understood peoples and a few civilisations with obscure histories1 but we have a fairly clear application of the principle4 ,the northern1 more isolated peoples1 are the more primitive2 the north-eastern1 whose isolation is accentuated by a severe environment1 are most primitive of all4 ,the ,eskimo1 whether they are the survivors of the ,magdalenian race or a regiment thrown off the ,asiatic army as it entered ,america1 remain at the primitive level4 ,the ,american peoples in turn accord with this view4 ,those which penetrate furthest south remain stagnant or deteriorate2 those which remain in the far north remain below the level of civilisation1 because the land-bridge to ,asia breaks down2 but those which settle in ,central ,america evolve a civilisation4 ,a large zone1 from ,mexico to ,peru1 was overspread by this civilisation1 and it was advancing steadily when ,european invaders destroyed it1 and reduced the civilised ,peruvians to the ,quichas of to-day4 ,there remain the civilisations of ,asia1 and here we have a new and interesting aspect of the question4 ,how did these civilisations develop in ,asia1 and how is it that they have remained stagnant for ages1 while ,europe advanced8 ,the origin of the ,asiatic civilisations is obscure4 ,the common idea of their vast antiquity has no serious ground4 ,the civilisation of ,japan cannot be traced back beyond about the eighth century ,b4,c4 ,even then the population was probably a mixed flotsam from neighbouring lands--,ainus1 ,koreans1 ,chinese1 and ,malays4 ,what was the character of the primitive civilisation resulting from the mixture of these different cultures we do not know4 ,but the chief elements of ,japanese civilisation came later from ,china4 ,japan had no written language of any kind until it received one from ,china about the sixth century of the ,christian ,era4 ,the civilisation of ,china itself goes back at least to about #bcjj ,b4,c41 but we cannot carry it further back with any confidence4 ,the authorities1 endeavouring to pick their steps carefully among old ,chinese legends1 are now generally agreed that the primitive ,chinese were a nomadic tribe which slowly wandered across ,asia from about the shores of the ,caspian ,sea4 ,in other words1 they started from a region close to the cradle of western civilisation4 ,some students1 in fact1 make them akin to the ,akkadians1 who founded civilisation in ,mesopotamia4 ,at all events1 they seem to have conveyed a higher culture to the isolated inhabitants of ,western ,asia1 and a long era of progress followed their settlement in a new environment4 ,for more than two thousand years1 however1 they have been enclosed in their walls and mountains and seas1 while the nations of the remote west clashed unceasingly against each other4 ,we need no other explanation of their stagnation4 ,to speak of the unprogressiveness of the ,chinese is pure mysticism4 ,the next generation will see4 ,the civilisation of ,india is also far later than the civilisation of the west1 and seems to be more clearly due to borrowing from the west4 ,the primitive peoples who live on the hills about ,india1 or in the jungles1 are fragments1 apparently1 of the ,stone ,age inhabitants of ,india1 or their descendants4 ,their culture may have degenerated under the adverse conditions of dislodgement from their home1 but we may fairly conclude that it was never high4 ,on these primitive inhabitants of the plains of ,india there fell1 somewhere about or before #ajjj ,b4,c41 the ,asiatic branch of the ,aryan race4 ,a very recent discovery 7#aijh7 has strongly confirmed and illumined this view of the origin of ,indian civilisation4 ,explorers in the ruins of the ancient capital of the ,hittite ,empire 7in ,north ,syria and ,cappadocia7 found certain treaties which had been concluded1 about #acjj ,b4,c41 between the ,hittites and the king of the ,aryans4 ,the names of the deities which are mentioned in the treaties seem to show that the ,persian and ,indian branches of the ,aryan race were not yet separated1 but formed a united kingdom on the banks of the ,euphrates4 ,they seem to have come from ,bactria 7and possibly beyond71 and introduced the horse 7hitherto unknown to the ,babylonians7 about #ahjj ,b4,c4 ,it is surmised by the experts that the ,indian and ,persian branches separated soon after #acjj ,b4,c41 possibly on account of religious quarrels1 and the ,sanscrit-speaking branch1 with its ,vedic hymns and its ,hinduism1 wandered eastward and northward until it discovered and took possession of the ,indian peninsula4 ,the long isolation of ,india1 since the cessation of its commerce with ,rome until modern times1 explains the later stagnation of its civilisation4 ,thus the supposed non-progressiveness of the east1 after once establishing civilisation1 turns out to be a question of geography and history4 ,we have now to see if the same intelligible principles will throw light on the progressiveness of the western branch of the ,aryan race1 and on the course of western civilisation generally4 99 99 ,in speaking of ,europeans as ,aryans ,i am1 of course1 allowing for an absorption of the conquered non-,aryans4 ,a ,european nation is no more ,aryan1 in strict truth1 than the ,english are ,anglo-,saxon4 ,the first two centres of civilisation are found in the valley of the ,nile and the valley of the ,tigris and ,euphrates2 the civilisations of ,egypt and ,babylon1 the oldest in the world4 ,there is1 however1 a good deal of evidence by which we may bring these civilisations nearer to each other in their earliest stages1 so that we must not confidently speak of two quite independent civilisations4 ,the civilisation which developed on the ,euphrates is found first at ,susa1 on the hills overlooking the plains of ,mesopotamia1 about #fjjj ,b4,c4 ,a people akin to the ,turkish or ,chinese lives among the hills1 and makes the vague advance from higher ,neolithic culture to primitive civilisation4 ,about the same time the historical or dynastic civilisation begins in ,egypt1 and some high authorities1 such as ,mr4 ,flinders ,petrie1 believe that the evidence suggests that the founders of this dynastic civilisation came from the mountainous region between ,egypt and the ,red ,sea4 ,from the northern part of the same region1 we saw1 the ancestors of the ,chinese set out across ,asia4 ,we have here a very suggestive set of facts in connection with early civilisation4 ,the ,syro-,arabian region seems to have been a thickly populated centre of advancing tribes1 which would be in striking accord with the view of progress that ,i am following4 ,but we need not press the disputed and obscure theory of the origin of the historic ,egyptians4 ,the remains are said to show that the lower valley of the ,nile1 which must have been but recently formed by the river's annual deposit of mud1 was a theatre of contending tribes from about #hjjj to #fjjj ,b4,c4 ,the fertile lands that had thus been provided attracted tribes from east1 west1 and south1 and there is a great confusion of primitive cultures on its soil4 ,it is not certain that the race which eventually conquered and founded the historical dynasties came from the mountainous lands to the east4 ,it is enough for us to know that the whole region fermented with jostling peoples4 ,why it did so the previous chapters will explain4 ,it is the temperate zone into which men had been pressed by the northern ice-sheet1 and from ,egypt to the ,indian ,ocean it remained a fertile breeding-ground of nations4 ,these early civilisations are merely the highest point of ,neolithic culture4 ,the ,egyptian remains show a very gradual development of pottery1 ornamentation1 etc41 into which copper articles are introduced in time4 ,the dawn of civilisation is as gradual as the dawn of the day4 ,the whole gamut of culture--,eolithic1 ,palaeolithic1 ,neolithic1 and civilised--is struck in the successive layers of ,egyptian remains4 ,but to give even a summary of its historical development is neither necessary nor possible here4 ,the maintenance of its progress is as intelligible as its initial advance4 ,unlike ,china1 it lay in the main region of human development1 and we find that even before #fjjj ,b4,c4 it developed a system of shipping and commerce which kept it in touch with other peoples over the entire region1 and helped to promote development both in them and itself4 ,equally intelligible is the development of civilisation in ,mesopotamia4 ,the long and fertile valley which lies between the mountainous region and the southern desert is1 like the valley of the ,nile1 a quite recent formation4 ,the rivers have gradually formed it with their deposit in the course of the last ten thousand years4 ,as this rich soil became covered with vegetation1 it attracted the mountaineers from the north4 ,as ,i said1 the earliest centre of the civilisation which was to culminate in ,babylon and ,nineveh is traced at ,susa1 on the hills to the north1 about #fjjj ,b4,c4 ,the ,akkadians 7highlanders7 or ,sumerians1 the ,turanian people who established this civilisation1 descended upon the rivers1 and1 about #ejjj ,b4,c41 set up the early cities of ,mesopotamia4 ,as in the case of ,egypt1 again1 more tribes were attracted to the fertile region1 and by about #djjj ,b4,c4 we find that ,semitic tribes from the north have superseded the ,sumerians1 and taken over their civilisation4 ,in these ancient civilisations1 developing in touch with each other1 and surrounded by great numbers of peoples at the high ,neolithic level from which they had themselves started1 culture advanced rapidly4 ,not only science1 art1 literature1 commerce1 law1 and social forms were developed1 but moral idealism reached a height that compares well even with that of modern times4 ,the recovery in our time of the actual remains of ,egypt and ,babylon has corrected much of the libellous legend1 which found its way into ,greek and ,european literature1 concerning those ancient civilisations4 ,but1 as culture advances1 human development becomes so complex that we must refrain from attempting to pursue1 even in summary1 its many outgrowths4 ,the evolution of morality1 of art1 of religion1 of polity1 and of literature would each require a whole volume for satisfactory treatment4 ,all that we can do here is to show how the modern world and its progressive culture are related to these ancient empires4 ,the aphorism that all light comes from the east may at times be pressed too literally4 ,to suggest that western peoples have done no more than receive and develop the culture of the older east would be at once unscientific and unhistorical4 ,by the close of the ,neolithic age a great number of peoples had reached the threshold of civilisation1 and it would be extremely improbable that in only two parts of the world the conditions would be found of further progress4 ,that the culture of these older empires has enriched ,europe and had a great share in its civilisation1 is one of the most obvious of historical truths4 ,but we must not seek to confine the action of later peoples to a mere borrowing of arts or institutions4 ,yet some recent historical writers1 in their eagerness to set up indigenous civilisations apart from those of ,egypt and ,mesopotamia1 pass to the opposite extreme4 ,we are prepared to find civilisation developing wherever the situation of a people exposes it to sufficient stimulation1 and we do find advance made among many peoples apart from contact with the great southern empires4 ,it is uncertain whether the use of bronze is due first to the southern nations or to some ,european people1 but the invention of iron weapons is most probably due to ,european initiative4 ,again1 it is now not believed that the alphabets of ,europe are derived from the hieroglyphics of ,egypt1 though it is an open question whether they were not derived1 through ,phoenicia1 from certain signs which we find on ancient ,egyptian pottery4 ,if we take first a broad view of the later course of civilisation we see at a glance the general relation of east and west4 ,some difficulty would arise1 if we pressed1 as to the exact stage in which a nation may be said to become civilised1 but we may follow the general usage of archaeologists and historians4 ,they tell us1 then1 that civilisation first appears in ,egypt about #hjjj ,b4,c4 7settled civilisation about #fjjj ,b4,c471 and in the ,mesopotamian region about #fjjj ,b4,c4 ,we next find ,neolithic culture passing into what may be called civilisation in ,crete and the neighbouring islands some time between #djjj and #cjjj ,b4,c41 or two thousand years after the development of ,egyptian commerce in that region4 ,we cannot say whether this civilisation in the ,a,egean sea preceded others which we afterwards find on the ,asiatic mainland4 ,the beginning of the ,hittite ,empire in ,asia ,minor1 and of ,phoenician culture1 is as yet unknown4 ,but we can say that there was as yet no civilisation in ,europe4 ,it is not until after #afjj that civilisation is established in ,greece 7,mycenae and ,tiryns7 as an offshoot of ,a,egean culture4 ,later still it appears among the ,etruscans of ,italy--to which1 as we know1 both ,egyptian and ,a,egean vessels sailed4 ,in other words1 the course of civilisation is very plainly from east to west4 ,but we must be careful not to imagine that this represents a mere transplantation of southern culture on a rude northern stock4 ,the whole region to the east of the ,mediterranean was just as fitted to develop a civilisation as the valley of the ,nile4 ,it swarmed with peoples having the latest ,neolithic culture1 and1 as they advanced1 and developed navigation1 the territory of many of them became the high road of more advanced peoples4 ,a glance at the map will show that the easiest line of expansion for a growing people was westward4 ,the ocean lay to the right of the ,babylonians1 and the country north and south was not inviting4 ,the calmer ,mediterranean with its fertile shores was the appointed field of expansion4 ,the land route from ,egypt lay1 not to the dreary west in ,africa1 but along the eastern shore of the ,mediterranean1 through ,syria and ,asia ,minor4 ,the land route from ,babylon lay across northern ,syria and ,asia ,minor4 ,the sea route had ,crete for its first and most conspicuous station4 ,hence the gradual appearance of civilisation in ,phoenicia1 ,cappadocia1 ,lydia1 and the ,greek islands is a normal and natural outcome of the geographical conditions4 ,but we must dismiss the later ,asiatic civilisations1 whose remains are fast coming to light1 very briefly4 ,phoenicia probably had less part in the general advance than was formerly supposed4 ,now that we have discovered a powerful civilisation in the ,greek islands themselves1 we see that it would keep ,tyre and ,sidon in check until it fell into decay about #ajjj ,b4,c4 ,after that date1 for a few centuries1 ,phoenicia had a great influence on the development of ,europe4 ,the ,hittites1 on the other hand1 are as yet imperfectly known4 ,their main region was ,cappadocia1 where1 at least as far back as #aejj ,b4,c41 they developed so characteristic a civilisation1 that its documents or inscriptions are almost undecipherable4 ,they at one time overran the whole of ,asia ,minor4 ,other peoples such as the ,elamites1 represent similar offshoots of the fermenting culture of the region4 ,the ,hebrews were probably a small and unimportant group1 settled close round ,jerusalem1 until a few centuries before the ,christian ,era4 ,they then assimilated the culture of the more powerful nations which crossed and recrossed their territory4 ,the ,persians were1 as we saw1 a branch of the ,aryan family which slowly advanced between #aejj and #gjj ,b4,c41 and then inherited the empire of dying ,babylon4 ,the most interesting1 and one of the most recently discovered1 of these older civilisations1 was the ,a,egean4 ,its chief centre was ,crete1 but it spread over many of the neighbouring islands4 ,its art and its script are so distinctive that we must recognise it as a native development1 not a transplantation of ,egyptian culture4 ,its ruins show it gradually emerging from the ,neolithic stage about #djjj ,b4,c41 when ,egyptian commerce was well developed in its seas4 ,somewhere about #bejj ,b4,c4 the whole of the islands seem to have been brought under the ,cretan monarchy1 and the concentration of wealth and power led to a remarkable artistic development1 on native lines4 ,we find in ,crete the remains of splendid palaces1 with advanced sanitary systems and a great luxuriance of ornamentation4 ,it was this civilisation which founded the centre at ,mycenae1 on the ,greek mainland1 about the middle of the second millennium ,b4,c4 ,but our inquiry into the origin of ,european civilisation does not demand any extensive description of the ,a,egean culture and its ,mycenaean offshoot4 ,it was utterly destroyed between #aejj and #ajjj ,b4,c41 and this was probably done by the ,aryan ancestors of the later ,greeks or ,hellenes4 ,about the time when one branch of the ,aryans was descending upon ,india and another preparing to rival decaying ,babylonia1 the third branch overran ,europe4 ,it seems to have been a branch of these that swept down the ,greek peninsula1 and crossed the sea to sack and destroy the centres of ,a,egean culture4 ,another branch poured down the ,italian peninsula2 another settled in the region of the ,baltic1 and would prove the source of the ,germanic nations2 another1 the ,celtic1 advanced to the west of ,europe4 ,the mingling of this semi-barbaric population with the earlier inhabitants provided the material of the nations of modern ,europe4 ,our last page in the story of the earth must be a short account of its civilisation4 ,the first branch to become civilised1 and to carry culture to a greater height than the older nations had ever done1 was the ,hellenes4 ,there is no need for us to speculate on the genius of the ,hellenes1 or even to enlarge on the natural advantages of the lower part of the peninsula which they occupied4 ,a glance at the map will explain why ,european civilisation began in ,greece4 ,the ,hellenes had penetrated the region in which there was constant contact with all the varied cultures of the older world4 ,although they destroyed the ,a,egean culture1 they could not live amidst its ruins without receiving some influence4 ,then the traders of ,phoenicia1 triumphing in the fall of their ,a,egean rivals1 brought the great pacific cultural influence of commerce to bear on them4 ,after some hundreds of years of internal trouble1 barbaric quarrels1 and fresh arrivals from the north1 ,greece began to wear an aspect of civilisation4 ,many of the ,greeks passed to ,asia ,minor1 as they increased1 and1 freed from the despotism of tradition1 in living contact with the luxury and culture of ,persia1 which had advanced as far as ,europe1 they evolved the fine civilisation of the ,greek colonies1 and reacted on the motherland4 ,finally1 there came the heroic struggle against the ,persian invaders1 and from the ashes of their early civilisation arose the marble city which will never die in the memory of ,europe4 ,the ,romans had meantime been advancing4 ,we may neglect the older ,italian culture1 as it had far less to do with the making of ,italy and ,europe than the influence of the east4 ,by about #ejj ,b4,c4 ,rome was a small kingdom with a primitive civilisation1 busy in subduing the neighbouring tribes who threatened its security1 and unconsciously gathering the seeds of culture which some of them contained4 ,by about #cjj ,b4,c4 the vigour of the ,romans had united all the tribes of ,italy in a powerful republic1 and wealth began to accumulate at ,rome4 ,not far to the east was the glittering civilisation of ,greece2 to the south was ,carthage1 a busy centre of commerce1 navigation1 and art2 and from the ,mediterranean came processions of ships bringing stimulating fragments and stories of the hoary culture of the east4 ,within another two hundred years ,rome annihilated ,carthage1 paralysed and overran ,greece1 and sent its legions over the ,asiatic provinces of the older empires4 ,by the beginning of the ,christian ,era all that remained of the culture of the old world was gathered in ,rome4 ,all the philosophies of ,greece1 all the religions of ,persia and ,judea and ,egypt1 all the luxuries and vices of the east1 found a home in it4 ,every stream of culture that had started from the later and higher ,neolithic age had ended in ,rome4 ,and in the meantime ,rome had begun to disseminate its heritage over ,europe4 ,its legions poured over ,spain and ,gaul and ,germany and ,britain4 ,its administrators and judges and teachers followed the eagles1 and set up schools and law-courts and theatres and baths and temples4 ,it flung broad roads to the north of ,britain and the banks of the ,rhine and ,danube4 ,under the shelter of the ,roman ,peace the peoples of ,europe could spare men from the plough and the sword for the cultivation of art and letters4 ,the civilisations of ,britain1 ,france1 ,germany1 ,spain1 ,north ,africa1 and ,italy were ushered into the calendar of mankind1 and were ready to bear the burden when the mighty city on the ,tiber let the sceptre fall from its enfeebled hands4 ,rome fell4 ,the more accurate historians of our time correct the old legend of death from senile decay or from the effect of dissipation4 ,races of men1 like races of animals1 do not die2 they are killed4 ,the physical deterioration of the citizens of ,rome was a small matter in its fall4 ,fiscal and imperial blunders loosed the frame of its empire4 ,the resources were still there1 but there was none to organise and unify them4 ,the imperial system--or chaos--ruined ,rome4 ,and just when the demoralisation was greatest1 and the ,teutonic tribes at the frontiers were most numerous and powerful1 an accident shook the system4 ,a fierce and numerous people from ,asia1 the ,huns1 wandered into ,europe1 threw themselves on the ,teutonic tribes1 and precipitated these tribes upon the ,empire4 ,a ,diocletian might still have saved the ,empire1 but there was none to guide it4 ,the northern barbarians trod its civilisation underfoot1 and ,europe passed into the ,dark ,ages4 ,one more application of the evolutionary principle1 and we close the story4 ,the barbarians--the ,goths and ,vandals and their ,germanic cousins--were barbaric only in comparison with the art and letters of ,rome4 ,they had law1 polity1 and ideals4 ,european civilisation owes elements to them1 as well as to ,rome4 ,to say simply that the barbarians destroyed the institutions of ,rome is no adequate explanation of the ,dark ,ages4 ,let us see rather how the ,dark ,ages were enlightened4 ,it is now fully recognised that the reawakening of ,europe in the twelfth and thirteenth centuries was very largely due to a fresh culture-contact with the older civilisations4 ,the ,arabs had1 on becoming civilised1 learned from the ,nestorians1 who had been driven out of the ,greek world for their heresies1 the ancient culture of ,greece4 ,they enshrined it in a brilliant civilisation which it inspired them to establish4 ,by the ninth century this civilisation was exhibited in ,spain by its ,moorish conquerors1 and1 as its splendour increased1 it attracted the attention of ,europe4 ,some ,christian scholars visited ,spain1 as time went on1 but the ,jews were the great intermediaries in disseminating its culture in ,europe4 ,there is now no question about the fact that the rebirth of positive learning1 especially of science1 in ,europe was very largely due to the literature of the ,moors1 and their luxury and splendour gave an impulse to ,european art4 ,europe entered upon the remarkable intellectual period known as ,scholasticism4 ,besides this stimulus1 it must be remembered1 the scholars of ,europe had at least a certain number of old ,latin writers whose works had survived the general wreck of culture4 ,in the fifteenth century the awakening of ,europe was completed4 ,the ,turks took ,constantinople1 and drove large numbers of ,greek scholars to ,italy4 ,out of this catastrophe issued the great ,renaissance1 or rebirth1 of art1 science1 and letters in ,italy1 and then in ,france1 ,germany1 and ,england4 ,in the new intellectual ferment there appeared the great artists1 great thinkers and inventors1 and great navigators who led the race to fresh heights4 ,the invention of printing alone would almost have changed the face of ,europe4 ,but it was accompanied by a hundred other inventions and discoveries1 by great liberating and stimulating movements like the ,reformation1 by the growth of free and wealthy cities1 and by the extension of peace over larger areas1 and the concentration of wealth and encouragement of art which the growth and settlement of the chief ,european powers involved4 ,europe entered upon the phase of evolution which we call modern times4 9999999999 ,the future of humanity cannot be seen even darkly1 as in a glass4 ,no forecast that aspires beyond the immediate future is worth considering seriously4 ,if it be a forecast of material progress1 it is rendered worthless by the obvious consideration that if we knew what the future will do1 we would do it ourselves4 ,if it is a forecast of intellectual and social evolution1 it is inevitably coloured by the intellectual or social convictions of the prophet4 ,i therefore abstain wholly from carrying the story of evolution beyond realities4 ,but ,i would add two general considerations which may enable a reflective reader to answer certain questions that will arise in his mind at the close of this survey of the story of evolution4 ,are we evolving to-day8 ,is man the last word of evolution8 ,these are amongst the commonest questions put to me4 ,whether man is or is not the last word of evolution is merely a verbal quibble4 ,now that language is invented1 and things have names1 one may say that the name man will cling to the highest and most progressive animal on earth1 no matter how much he may rise above the man of to-day4 ,but if the question is whether he ,,will rise far above the civilisation of to-day1 we can1 in my opinion1 give a confident answer4 ,there is no law of evolution1 but there is a fact of evolution4 ,ten million years ago the highest animal on the earth was a reptile1 or1 at the most1 a low1 rat-like marsupial4 ,the authorities tell us that1 unless some cosmic accident intervene1 the earth will remain habitable by man for at least ten million years4 ,it is safe to conclude that the man of that remote age will be lifted above the man of to-day as much as we transcend the reptile in intelligence and emotion4 ,it is most probable that this is a quite inadequate expression of the future advance4 ,we are not only evolving1 but evolving more rapidly than living thing ever did before4 ,the pace increases every century4 ,a calm and critical review of our development inspires a conviction that a few centuries will bring about the realisation of the highest dream that ever haunted the mind of the prophet4 ,what splendours lie beyond that1 the most soaring imagination cannot have the dimmest perception4 ,and the last word must meet an anxiety that arises out of this very confidence4 ,darwin was right4 ,it is--not exclusively1 but mainly--the struggle for life that has begotten higher types4 ,must every step of future progress be won by fresh and sustained struggle8 ,at least we may say that the notion that progress in the future depends1 as in the past1 upon the pitting of flesh against flesh1 and tooth against tooth1 is a deplorable illusion4 ,such physical struggle is indeed necessary to evolve and maintain a type fit for the struggle4 ,but a new thing has come into the story of the earth--wisdom and fine emotion4 ,the processes which begot animal types in the past may be superseded2 perhaps must be superseded4 ,the battle of the future lies between wit and wit1 art and art1 generosity and generosity2 and a great struggle and rivalry may proceed that will carry the distinctive powers of man to undreamed-of heights1 yet be wholly innocent of the passion-lit1 blood-stained conflict that has hitherto been the instrument of progress4