Read Ebook: The Whence and the Whither of Man A Brief History of His Origin and Development through Conformity to Environment; Being the Morse Lectures of 1895 by Tyler John M John Mason

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We may say broadly that concerning the origin of species two theories, and only two, seem possible. The first theory is that every species is the result of an act of immediate creation. And every true species, however slightly it may differ from its nearest relative, represents such a creative act, and once created is practically unchangeable. This is the theory of immutability of species. According to the second theory all higher, probably all present existing, species are only mediately the result of a creative act. The first living germ, whenever and however created, was infused with power to give birth to higher species. Of these and their descendants some would continue to advance, others would degenerate. Each theory demands equally for its ultimate explanation a creative act; the second as much as, if not more than, the first. According to the first theory the creative power has been distributed over a series of acts, according to the second theory it has been concentrated in one primal creation. The second is the theory of the mutability of species, or, in general, of evolution, but not necessarily of Darwinism alone.

The first theory is considered by many the more attractive and hopeful. Now a theory need not be attractive, nor at first sight appear hopeful, provided only it is true. But let me call your attention to certain conclusions which, as it appears to me, are necessarily involved in it. Its central thought is the practical immutability of species. Each one of these lives its little span of time, for species are usually comparatively short-lived, grows possibly a very little better or worse, and dies. Its progress has added nothing to the total of life; its degeneration harmed no one, hardly even itself; it was doomed from the start. Progress there has been, in a sense. The Creator has placed ever higher forms on the globe. But all the progress lies in the gaps and distances between successive forms, not in any advance made, or victory won, by the species or individual. The most "aspiring ape," if ever there was such a being, remains but an ape. He must comfort himself with the thought that, while he and his descendants can never gain an inch, the gap between himself and the next higher form shall be far greater than that between himself and the lowest monkey.

And if this has been the history of thousands of other species, why should it not be true of man also? Who can wonder that many who accept this theory doubt whether the world is growing any better, or whether even man will ever be higher and better than he now is? Would it not be contrary to the whole course of past history, if you can properly call such a record a history, if he could advance at all? Now I have no wish to misrepresent this or any honestly accepted theory, but it appears to me essentially hopeless, a record not of the progress of life on the globe, but of a succession of stagnations, of deaths. I can never understand why some very good and intelligent people still think that the theory of the immediate creation of each species does more honor to the Creator and his creation than the theory of evolution. Evolution is a process, not a force. The power of the Creator is equally demanded in both cases; only it is differently distributed. And evolution is the very highest proof of the wisdom and skill of the Creator. It elevates our views of the living beings, must it not give a higher conception of Him who formed them?

The plant in its first stages shows no trace of flowers, but of leaves only. Later a branch or twig, similar in structure to all the rest, shortens. The cells and tissues which in other twigs turn into green leaves here become the petals and other organs of the rose or violet. Let us suppose for a moment that every rose and violet required a special act of immediate creation, would the springtime be as wonderful as now? Would the rose or violet be any more beautiful, or are they any less flowers because developed out of that which might have remained a common branch? The plant at least is glorified by the power to give rise to such beauty. And is not the creation of the seed of a violet or rose something infinitely grander than the decking of a flowerless plant with newly created roses? The attainment of the highest and most diversified beauty and utility with the fewest and simplest means is always the sign of what we call in man "creative" genius. Is not the same true of God? I think you all feel the force of the argument here.

There were at one time no flowering plants. The time came at last for their appearance. Which is the higher, grander mode of producing them, immediate creation of every flowering species, or development of the flower out of the green leaves of some old club moss or similar form? The latter seems to me at least by far the higher mode. And to have created a ground-pine which could give rise to a rose seems far more difficult and greater than to have created both separately. It requires more genius, so to speak. It gives us a far higher opinion of the ground-pine; does it disgrace the rose? We can look dispassionately at plants. The rose is still and always a rose, and the oak an oak, whatever its origin. And I believe that we shall all readily admit that evolution is here a theory which does the highest honor to the wisdom and power of the Creator. What if the animal kingdom is continually blossoming in ever higher forms? Does not the same reasoning hold true, only with added force? I firmly believe that we should all unhesitatingly answer, yes, could we but be assured that all men would everywhere and always believe that we, men, were the results of an immediate creative act.

But why do we so strenuously object to the application to ourselves of the theory of evolution? One or two reasons are easily seen. We have all of us a great deal of innate snobbery, we would rather have been born great than to have won greatness by the most heroic struggle. But is man any less a man for having arisen from something lower, and being in a fair way to become something higher? Certainly not, unless I am less a man for having once been a baby. It is only when I am unusually cross and irritable that I object to being reminded of my infancy. But a young child does not like to be reminded of it. He is afraid that some one will take him for a baby still. And the snob is always desperately afraid that some one will fail to notice what a high-born gentleman he is.

Now man can relapse into something lower than a brute; the only genuine brute is a degenerate man. And we all recognize the strength of tendencies urging us downward. Is not this the often unrecognized kern of our eagerness for some mark or stamp that shall prove to all that we are no apes, but men? It is not the pure gold that needs the "guinea stamp." If we are men, and as we become men, we shall cease to fear the theory of evolution. Now this is not the only, or perhaps the greatest, objection which men feel or speak against the theory. But I must believe that it has more weight with us than we are willing to admit.

But some say that the theory of immediate creation and immutability of species is the more natural and has always been accepted, while the theory of evolution is new and very likely to be as short-lived as many another theory which has for a time fascinated men only to be forgotten or ridiculed.

But the idea of evolution is as old as Hindu philosophy. The old Ionic natural philosophers were all evolutionists. So Aristophanes, quoting from these or Hesiod concerning the origin of things, says: "Chaos was and Night, and Erebus black, and wide Tartarus. No earth, nor air nor sky was yet; when, in the vast bosom of Erebus winged Night brought forth first of all the egg, from which in after revolving periods sprang Eros the much desired, glittering with golden wings; and Eros again, in union with Chaos, produced the brood of the human race." Here the formative process is a birth, not a creation; it is evolution pure and simple. "According to the ancient view," says Professor Lewis, "the present world was a growth; it was born, it came from something antecedent, not merely as a cause but as its seed, embryo or principium. Plato's world was a 'zoon,' a living thing, a natural production."

Furthermore, to the ancient writers of the Bible the idea of origin by birth from some antecedent form--and this is the essential idea of evolution--was perfectly natural. They speak of the "generations of the heavens and the earth" as of the "generations" of the patriarchs. The first book of the Bible is still called Genesis, the book of births. The writer of the ninetieth Psalm says, "Before the mountains were born, or ever thou hadst brought to birth the earth and the world." And what satisfactory meaning can you give to the words, "Let the earth bring forth," and "the earth brought forth," in immediate proximity to the words, "and God made," unless while the ultimate source was God's creative power, the immediate process of formation was one of evolution.

The Bible is big and broad enough to include both ideas, the human mind is prone to overestimate the one or the other. Traces, at least, of a similar mode of thought persisted by the Greek Fathers of the Church, and disappeared, if ever, with the predominance of Latin theology. To the oriental the idea of evolution is natural. The earth is to him no inert, resistant clod; she brings forth of herself.

But our ancestors lived on a barren soil beneath a forbidding sky. They were frozen in winter and parched in summer. Nature was to them no kind foster-mother, but a cruel stepmother, training them by stern discipline to battle with her and the world. They peopled the earth with gnomes and cobolds and giants, and their nymphs were the Valkyre. Their God was Thor, of the thunderbolt and hammer, and who yet lived in continual dread of the hostile powers of Nature. A Norse prophet or prophetess standing beside Elijah at Horeb would have bowed down before the earthquake or the fire; the oriental waited for the "still small voice." And we are heirs to a Latin theology grafted on to the Thor-worship of our pagan ancestors. The idea of a Nature producing beneficently and kindly at the word of a loving God is foreign to all our inherited modes of thought. And our views of the heart of Nature are about as correct as those of our ancestors were of God. A little more of oriental tendencies of thought would harm neither our theology nor our life.

What, then, is the biblical idea of Nature? God speaks to the earth, in the first chapter of Genesis, and the earth responds by "giving birth" to mountains and living beings. It is evidently no mere lifeless, inert clod, but pulsating with life and responsive to the divine commands. While yet a chaos it had been brooded over by the Divine Spirit. It is like the great "wheels within wheels," with rings full of eyes round about, which Ezekiel saw in his vision by the river Chebar. "When the living creatures went, the wheels went by them; and when the living creatures were lifted up from the earth, the wheels were lifted up. Whithersoever the spirit was to go, they went, thither was their spirit to go; and the wheels were lifted up over against them: for the spirit of the living creatures was in the wheels." And above the living creatures was the firmament and the throne of God. So Nature may be material, but it is material interpenetrated by the divine; if you call it a fabric, the woof may be material but the warp is God. This view contains all the truth of materialism and pantheism, and vastly more than they, and it avoids their errors and omissions.

To the old metaphysical hypothesis of evolution Mr. Darwin gave a scientific basis. It had always been admitted that species were capable of slight variation and that this divergence might become hereditary and thus perhaps give rise to a variety of the parent species. But it was denied that the variation could go on increasing indefinitely, it seemed soon to reach a limit and stop. Early in the present century Lamarck had attempted to prove that by the use and disuse of organs through a series of generations a great divergence might arise resulting in new species. But the theory was crude, capable at best of but limited application, and fell before the arguments and authority of Cuvier. The times were not ripe for such a theory. Some fifty years later, Mr. Darwin called attention to the struggle for existence as a means of aggregating these slight modifications in a divergence sufficient to produce new species, genera, or families. His argument may be very briefly stated as follows:

And yet even they give but a faint idea of the reproductive powers of plants and animals. The female fish produces often many thousands, sometimes hundreds of thousands of eggs. Insects generally from a hundred to a thousand. Even birds, slowly as they increase, produce in a lifetime probably at least from twelve to twenty eggs. Now let us suppose that all these eggs developed, and all the birds lived out their normal period of life, and reproduced at the same rate. After not many centuries there would not be standing room on the globe for the descendants of a single pair.

Again, of the one hundred eggs of an insect let us suppose that only sixty develop into the first larval, caterpillar, stage. Of these sixty, the number of members of the species remaining constant, only two will survive. The other fifty-eight die--of starvation, parasites, or other enemies, or from inclement weather. Now which two of all shall survive? Those naturally best able to escape their enemies or to resist unfavorable influences; in a word, those best suited to their conditions, or, to use Mr. Darwin's words, "conformed to their environment."

Now if any individual has varied so as to possess some peculiarity which enables it even in slight degree to better escape its enemies or to resist unfavorable conditions, those of its descendants who inherit most markedly this peculiar quality or variation will be the most likely to escape, those without it to perish. If a form varies unfavorably, becomes for instance more conspicuous to its enemies, it will almost certainly perish. Thus favorable variations tend to increase and become more marked from generation to generation.

Now it has always been known that breeders could produce a race of markedly peculiar form or characteristics by selecting the individuals possessing this quality in the highest degree and breeding only from these. The breeder depends upon heredity, variation, and his selection of the individuals from which to breed. Similarly in nature new species have arisen through heredity, variation, and a selection according to the laws of nature of those varying in conformity with their environment. And this Mr. Darwin called natural, in contrast with the breeder's artificial, "selection," arising from the "struggle for existence," and resulting in what Mr. Spencer has called the "survival of the fittest."

Let us take a single illustration. Many of the species of beetles on oceanic islands have very rudimentary wings, or none at all, and yet their nearest relatives are winged forms on some neighboring continent. Mr. Darwin would explain the origin of these evidently distinct wingless species as follows: They are descended from winged ancestors blown or otherwise transported thither from the neighboring continent. But beetles are slow and clumsy fliers, and on these wind-swept islands those which flew most would be blown out to sea and drowned. Those which flew the least, and these would include the individuals with more poorly developed wings, would survive. There would thus be a survival in every generation of a larger proportion of those having the poorest wings, and destruction of those whose wings were strong, or whose habits most active. We have here a natural selection which must in time produce a species with rudimentary or aborted wings, just as surely as a human breeder, by artificial selection can produce such an animal as a pug or a poodle. These, like sin, are a human device; nature should not be held responsible for them.

But you may urge that the variation which would take place in a single generation would be, as a rule, too slight to be of any practical value to the animal, and could not be fostered by natural selection until greatly enhanced by some other means. Let us think a moment. If ten ordinary men run in a foot-race, the two foremost may lead by several feet. But if the number of runners be continually increased the finish will be ever closer until finally but an atom more wind or muscle or pluck would make all the difference between winning and losing the prize.

Similarly the million or more young of any species of insect in a given area may be said to run a race of which the prize is life, and the losing of which means literally death. The competition is inconceivably severe. How indefinitely slight will be the difference between the poorest of the 2,000 or 20,000 survivors and the best of the more than 900,000 which perish. The very slightest favorable variation may make all the difference between life and sure death. And yet these indefinitely slight variations continued and aggregated through ages would foot up an immense total divergence. The chalk cliffs of England have been built up of microscopic shells.

I have tried to give you very briefly a sketch of the essential points of Mr. Darwin's theory of evolution. But you should all read that marvel of patience, industry, clear insight, close reasoning, and grand honesty, the "Origin of Species." I have no time to give the arguments in its favor or to attempt to meet the objections which may arise in your minds. I ask you to believe only this much; that the theory is accepted with practical unanimity by scientific men because it, and it alone, furnishes an explanation for the facts which they discover in their daily work. And this is the strongest proof of the truth of any accepted theory.

Inasmuch as it is accepted by all scientists and largely by the public, it is certainly worth your while to know whether it has any bearing on the great moral and religious questions which you are considering. And in these lectures I shall take for granted, what some scientists still doubt, that man also is a product of evolution. For the weight of evidence in favor of this view is constantly increasing, and seems already to strongly preponderate. Also I wish in these lectures to grant all that the most ardent evolutionist can possibly claim. Not that I would lower man's position, but I have a continually increasing respect for the so-called "lower animals."

Now if the theory of evolution be true, and really only on this condition, life has had a history; and human history began ages before man's actual appearance on the globe, just as American history began to be fashioned by Anglo-Saxons, Danes, and Normans before they set foot even in England. We study history mainly to deduce its laws; and that knowing them we may from the past forecast the future, prepare for its emergencies, and avoid or wisely meet, its dangers. And we rely on these laws of history because they are the embodiment of ages of human experience.

Whatever be our system of philosophy we all practically rely on past experience and observation. Fire burns and water drowns. This we know, and this knowledge governs our daily lives, whatever be our theories, or even our ignorance, of the laws of heat and respiration. Now human history is the embodiment of the experience of the race; and we study it in the full confidence that, if we can deduce its laws, we can rely on racial experience certainly as safely as on that of the individual. Furthermore, if we can discover certain great movements or currents of human action or progress moving steadily on through past centuries, we have full confidence that these movements will continue in the future. The study of history should make us seers.

But the line of human progress is like a mountain road, veering and twisting, and often appearing to turn back upon itself, and having many by-roads, which lead us astray. If we know but a few miles of it we cannot tell whether it leads north or south or due west. But if from any mountain-top we can gain a clear bird's-eye view of its whole course, we easily distinguish the main road, its turns become quite insignificant, we see that it leads as directly as any engineering skill could locate it through the mountains to the fertile plains and rich harvests beyond.

Now our knowledge of the history of man covers so brief a period that we can scarcely more than hazard a guess as to the trend of human progress. Many of the most promising social movements are like by-roads which, at first less steep and difficult, end sooner or later against impassable obstacles. And even if there be a main line of march, advance seems to alternate with retreat, progress with retrogression. To illustrate further, the great waves rush onward only to fall back again, and we can hardly tell whether the tide is flowing or ebbing.

Yet already certain tendencies appear fairly clear. Governments tend to become democratic, if we define democracy as "any form of government in which the will of the people finds sovereign expression." The tendency of society seems to be toward furnishing all its members equality of opportunity to make the most of their natural endowments. But if we are convinced that these statements express even vaguely the tendency of human development in all its past history, we are confident that these tendencies will continue in the future for a period somewhat proportional to their time of growth in the past. If we are wise, we try to make our own lives and actions, and those of our fellows, conform to and advance them. Otherwise our lives will be thrown away.

But if the theory of evolution be true, human history is only the last page of the one history of all life. If we are to gain any adequate, true, extensive view of human progress, we must read more than this. We must take into account the history of man when he was not yet man. And if we believe in the future continuance of tendencies of a few centuries' growth, we shall rest assured of the permanence of tendencies which have grown and strengthened through the ages.

Our confidence in the results of historical study is therefore proportioned to the extent and thoroughness of the experience which they record, and to the time during which these laws can be proven to have held good. If I can make it even fairly probable that these laws, on obedience to which human progress and success seem to depend, are merely quoted from a grander code applicable to all life in all times, your confidence in them will be even greater. I trust I can prove to you that the animal kingdom has not drifted aimlessly at the mercy of every wind and tide and current of circumstance. I hope to show that along one line it has from the beginning through the ages held a steady course straight onward, and that deviation from this course has always led to failure or degeneration. From so vast a history we may hope to deduce some of the great laws of true success in life. Furthermore, if along this central line, at the head of which man stands, there always has been progress, we cannot doubt that future progress will be as certain, and perhaps far more rapid. In all the struggle of life we shall have the sure hope of success and victory; if not for ourselves still for those who shall come after us. "We are saved by hope." And we may be confident that this hope will never make us ashamed.

Finally, even from our present knowledge of the past progress of life we shall hope to catch hints at least that man's only path to his destined goal is the straight and narrow road pointed out in the Bible. If in this we are even fairly successful we shall find a relation and bond between the Bible and Science worthy of all consideration. And this is the only agreement which can ever satisfy us.

If I wished to bring before you a view of the development of man, I should best choose individuals or families from various periods of human history from the earliest times down to the present. I should try to tell you how they looked and lived. But if anyone should attempt to condense into three lectures such a history of even one line of the human race, you would probably think him insane. Even if he succeeded in giving a fairly clear view of the different stages, the successive stages would be so remote from one another, such vast changes would necessarily remain unnoticed or unexplained that you would hardly believe that they could have any genetic relation or belong to one developmental series.

But the history which I must attempt to condense for you is measured by ages, and the successive terms of the series will be indefinitely more remote from each other than the life and thoughts of Lincoln or Washington from those of our most primitive Aryan ancestor or of the rudest savage of the Stone Age. The series must appear exceedingly disconnected. Systems of organs will apparently spring suddenly into existence, and we shall have no time to trace their origin or earlier development. Even if we had an abundance of time many gaps would still remain; for the forms, which according to our theory must have occupied their place, have long since disappeared and left no trace nor sign. We have generally no conception at all of the amount of extermination and degeneration which have taken place in past ages.

I grant frankly that I do not believe that the forms which I have selected represent exactly the ancestors of man. They have all been more or less modified. I claim only that in the balance and relative development of their organic systems--muscular, digestive, nervous, etc.--they give us a very fair idea of what our ancestor at each stage must have been. But it is on this balance and relative development of the different systems, that is, whether an animal is more reproductive, digestive, or nervous, that my argument will in the main be based.

But if the older ancestors have so generally disappeared, and their surviving relatives have been so greatly modified, how can we make even a shrewd guess at the ancestry of higher forms? The genealogy of the animal kingdom has been really the study of centuries, although the earlier zo?logists did not know that this was to be the result of their labors. The first work of the naturalist was necessarily to classify the plants and animals which he found, and catalogue and tabulate them so that they might be easily recognized, and that later discovered forms might readily find a place in the system. Hypotheses and theories were looked upon with suspicion. "Even Linnaeus," says Romanes, "was express in his limitations of true scientific work in natural history to the collecting and arranging of species of plants and animals." The question, "What is it?" came first; then, "How did it come to be what it is?" We are just awakening to the question, "Why this progressive system of forms, and what does it all mean?"

Let us experiment a little in forming our own classification of a few vertebrates. We see a bat flying through the air. We mistake it for a bird. But a glance at it shows that it is a mammal. It is covered with hair. It has fore and hind legs. Its wings are membranes stretched between the fingers and along the sides of the body. It has teeth. It suckles its young. In all these respects it differs from birds. It differs from mammals only in its wings. But we remember that flying squirrels have a membrane stretching along the sides of the body and serving as a parachute, though not as wings. We naturally consider the wings as a sort of after-thought superinduced on the mammalian structure. We do not hesitate to call it a mammal.

The whale makes us more trouble; it certainly looks remarkably like a fish. But the fin of its tail is horizontal, not vertical. Its front flippers differ altogether from the corresponding fins of fish; their bones are the same as those occurring in the forelegs of mammals, only shorter and more crowded together. Later we find that it has lungs, and a heart with four chambers instead of only two, as in fish. The vertebrae of its backbone are not biconcave, but flat in front and behind. And, finally, we discover that it suckles its young. It, too, is in all its deep-seated characteristics a mammal. It is fish-like only in characteristics which it might easily have acquired in adaptation to its aquatic life. And there are other aquatic mammals, like the seals, in which these characteristics are much less marked. Their adaptation has evidently not gone so far.

Now the first attempts resulted in artificial classifications, much like our grouping of bats with birds and whales with fish. All animals, like coral animals and starfishes, whose similar parts were arranged in lines radiating from a centre, were united as radiates, however much they might differ in internal structure and grade of organization. But this radiate structure proved again to be largely a matter of adaptation.

Practically all animals having a heavy calcareous shell were grouped with the snails and oysters as mollusks. But the barnacle did not fit well with other mollusks. Its shell was entirely different. It had several pairs of legs; and no mollusk has legs. The barnacle is evidently a sessile crab or better crustacean. Its molluscan characteristics were only skin-deep, evidently an adaptation to a mode of life like that of mollusks. The old artificial systems were based too much on merely external characteristics, the results of adaptation. When the internal anatomy had been thoroughly studied their groups had to be rearranged.

Reptiles and amphibia were at first united in one class because of their resemblance in external form. Our common salamanders look so much like lizards that they generally pass by this name. But the young salamander, like all amphibia, breathes by gills, its skeleton differs greatly from, and is far weaker than, that of the lizard, and there are important differences in the circulatory and other systems. Moreover, practically all amphibia differ from all reptiles in these respects. Evidently the fact that the alligator and many snakes and turtles live almost entirely in the water, is no better reason for classifying these with amphibia than to call a whale a fish, and not a mammal, because of its form and aquatic life.

When the comparative anatomy of fish, amphibia, and reptiles had been carefully studied it was evident that the amphibia stood far nearer the fish in general structure, while the higher reptiles closely approached birds. Then it was noticed that our common fish formed a fairly well-defined group, but that the ganoids, including the sturgeons, gar-pikes, and some others, had at least traces of amphibian characteristics. Such generalized forms, with the characteristics of the class less sharply marked, were usually by common consent placed at the bottom of the class. And this suited well their general structure, while in particular characteristics they were often more highly organized than higher groups of the same class.

The palaeontologist found that the oldest fossil forms belonged to these generalized groups, and that more highly specialized forms--that is, those in which the special class distinctions were more sharply and universally marked--were of later geological origin. Thus the oldest fish were most like our present ganoids and sharks, though differing much from both. Our common teleost fish, like perch and cod, appeared much later. The oldest bird, the archaeopteryx, had a long tail like that of a lizard, and teeth; and thus stood in many respects almost midway between birds and reptiles. And most of the earliest forms were "comprehensive," uniting the characteristics of two or more later groups. Thus as the classification became more natural, based on a careful comparison of the whole anatomy of the animals, its order was found to coincide in general with that of geological succession.

Then the zo?logist began to ask and investigate how the animal grew in the egg and attained its definite form. And this study of embryology brought to light many new and interesting facts. Agassiz especially emphasized and maintained the universality of the fact that there was a remarkable parallelism between embryos of later forms and adults of old or fossil groups. The embryos of higher forms, he said, pass through and beyond certain stages of structure, which are permanent in lower and older members of the same group.

You remember that the fin on the tail of a fish is as a rule bilobed. Now the backbone of a perch or cod ends at a point in the end of the tail opposite the angle between the two lobes, without extending out into either of them. In the shark it extends almost to the end of the upper lobe. Now we have seen that sharks and ganoids are older than cod. In the embryo of the cod or perch the backbone has, at an early stage, the same position as in the shark or ganoid; only at a later stage does it attain its definite position.

So Agassiz says the young lepidosteus , long after it is hatched, exhibits in the form of its tail characters thus far known only among the fossil fishes of the Devonian period. The embryology of turtles throws light upon the fossil chelonians. It is already known that the embryonic changes of frogs and toads coincide with what is known of their succession in past ages. The characteristics of extinct genera of mammals exhibit everywhere indications that their living representatives in early life resemble them more than they do their own parents. A minute comparison of a young elephant with any mastodon will show this most fully, not only in the peculiarities of their teeth, but even in the proportion of their limbs, their toes, etc. It may therefore be considered as a general fact that the phases of development of all living animals correspond to the order of succession of their extinct representatives in past geological times. The above statements are quoted almost word for word from Professor Agassiz's "Essay on Classification." The larvae of barnacles and other more degraded parasitic crustacea are almost exactly like those of Crustacea in general. The embryos of birds have a long tail containing almost or quite as many vertebrae as that of archaeopteryx. But most of these never reach their full development but are absorbed into the pelvis, or into the "ploughshare" bone supporting the tail feathers. Thus older forms may be said to have retained throughout life a condition only embryonic in their higher relatives. And the natural classification gave the order not only of geological succession but also of stages of embryonic development. Thus the system of classification improved continually, although more and more intermediate forms, like archaeopteryx, were discovered, and certain aberrant groups could find no permanent resting-place.

But why should the generalized comprehensive forms stand at the bottom rather than the top of the systematic arrangement of their classes? Why should the system of classification coincide with the order of geologic occurrence, and this with the series of embryonic stages? Above all, why should the embryos of bird and perch form their tails by such a roundabout method? Why should the embryo of the bird have the tail of a lizard? No one could give any satisfactory explanation, although the facts were undoubted.

Mr. Darwin's theory was the one impulse needed to crystallize these disconnected facts into one comprehensible whole. The connecting link was everywhere common descent, difference was due to the continual variation and divergence of their ancestors. The classification, which all were seeking, was really the ancestral tree of the animal kingdom. Forms more generalized should be placed lower down on the ancestral tree, and must have had an earlier geological occurrence because they represented more nearly the ancestors of the higher. But this explains also the facts of embryonic development.

According to Mr. Darwin's theory all the species of higher animals have developed from unicellular ancestors. It had long been known that all higher forms start in life as single cells, egg and spermatozoon. And these, fused in the process of fertilization, form still a single cell. And when this single cell proceeds through successive embryonic stages to develop into an adult individual it naturally, through force of hereditary habit, so to speak, treads the same path which its ancestors followed from the unicellular condition to their present point of development. Thus higher forms should be expected to show traces of their early ancestry in their embryonic life. Older and lower adult forms should represent persistent embryonic stages of higher. It could not well be otherwise.

But the path which the embryo has to follow from the egg to the adult form is continually lengthening as life advances ever higher. From egg to sponge is, comparatively speaking, but a step; it is a long march from the egg to the earthworm; and the vertebrate embryo makes a vast journey. But embryonic life is and must remain short. Hence in higher forms the ancestral stages will often be slurred over and very incompletely represented. And the embryo may, and often does, shorten the path by "short-cuts" impossible to its original ancestor. Still it will in general hold true, and may be recognized as a law of vast importance, that any individual during his embryonic life repeats very briefly the different stages through which his ancestors have passed in their development since the beginning of life. Or, briefly stated, ontogenesis, or the embryonic development of the individual, is a brief recapitulation of phylogenesis, or the ancestral development of the phylum or group.

This law is even more strikingly illustrated in the embryonic development of the vertebral column and skull, if we had time to trace their development. And the development of the excretory system points to an ancestor far more primitive than even the fish. Our embryonic development is one of the very strongest evidences of our lowly origin.

Thus we have three sources of information for the study of animal genealogy. First, the comparative anatomy of all the different groups of animals; second, their comparative embryology; and third, their palaeontological history. Each source has its difficulties or defects. But taken all together they give us a genealogical tree which is in the main points correct, though here and there very defective and doubtful in detail. The points in which we are left most in doubt in regard to each ancestor are its modes of life and locomotion, and body form. But these may temporarily vary considerably without affecting to any great extent the general plan of structure and the line of development of the most important deep-seated organs.

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