RECORD: Adams, L. T. 1874. Mr. Darwin and the theory of natural selection. New Englander (Issue 129, October) 33: 741-770.
REVISION HISTORY: Transcribed (single key) by AEL Data, corrections by John van Wyhe 8.2009. RN1
ARTICLE VII.—MR. DARWIN AND THE THEORY OF
1. THE GENESIS OF THE DOCTRINE.
In the year 1825 a joint arrangement was made by the British and French governments for a survey of the coasts of South America, the French taking the coast of Brazil, the British that of the southern extremity of the continent from the mouth of the river Plata to the island of Chiloe. The British expedition, consisting of the Adventure, commanded by Captain King, and the Beagle, commanded by Captain Stokes, sailed for the first time in May, 1826, and returned in October, 1830. Capt. Stokes died in Tierra del Fuego in 1828, and was ultimately succeeded by Captain, afterwards Admiral, Robert Fitzroy, who was again appointed to the Beagle, recommissioned in 1831 to continue the survey of South America, with orders to circumnavigate the globe on her return home. Capt. Fitzroy, a man of great intelligence and of scientific training, had been much impressed during the first voyage by his observations in the natural history of the continent, and before re-embarking in 1831 he wrote to the Hydrographer of the Navy, proposing that "some scientific person should be sought for who would be willing to share such accommodation as he had to offer for the sake of visiting distant countries as yet little known."† The Hydrographer approved the suggestion and wrote to Prof. Peacock of Cambridge, who again referred the matter to his colleague, the Rev. J. S. Henslow, Professor of Botany. The latter at once recommended a pupil of his own, and the result was that "Mr. Charles Darwin, grandson of Dr. Darwin the poet, a young man of promising ability, extremely fond of
* The excellent description and just criticism of the Darwinian theory, which this Article contains, give to it a special value. If, however, the author is to be understood as implying, in two or three places, a necessary incompatibility between the theory of Darwin and the doctrine of Christian Theism, his position in this particular is open to question.—Eds. New Englander.
† Narrative of the Surveying Voyages of H. M. ships Adventure and Beagle. 3 vols. London: Henry Colburn. 1839. Introd.
geology, and indeed of all branches of natural history," was attached to the expedition as Capt. Fitzroy's guest and naturalist to the Beagle, stipulating, however, that he should be at liberty to retire whenever he thought proper and to pay a fair share of the expenses of the table. The two fell into a great friendship at once, and Mr. Darwin continued to pay his mess bills regularly until the Beagle returned from her five years' voyage round the world in 1836.
Mr. Darwin at this time was a young gentleman not quite twenty-three years old, who, after a course of two years at Edinburgh and another of four at Cambridge, had just taken his degree at the latter university. The most noticeable thing about him was that he had inherited, by "reversion" as he would afterwards have called it himself, the biological tastes of his ancestor, a fantastic poet but a very able naturalist of the eighteenth century, who had actually anticipated both Lamarck and the grandson in enunciating the conception of the genesis of organic forms by adaptive modifications.* The pedigree and the penchant together won the heart of Professor Henslow, and that worthy clergyman, who, says Mr. Darwin in the preface to his Journal, "was one chief means of giving me a taste for natural history—who during my absence took charge of the collections I sent home—and by his correspondence directed my endeavors," and who, as we have seen, procured him the appointment to the expedition, must bear the responsibility of having contributed more than any other man except its author to the doctrine of Nautral Selection.
The results of the voyage are duly recorded in the Journals of Capt. Fitzroy, who aslo edited Capt. King's notes on the first voyage, and Mr. Darwin. The former has long since been forgotten, although the work of an able man and an entertaining writer. It is still worth referring to, if for nothing else, as an amusing illustration of the old formula quicquid recipitur recepitur ad modum recipientis. A man sees only what he brings the eye to see. The same phenomena which drove Mr.
* H. Spencer, Sociology. Zoonomia, vol. i, pp. 500–510, ed. 1794. Mr. Darwin alludes to his grandfather's speculations with evident satisfaction in the Historical Sketch prefixed to the 6th edition of the Origin of Species. An amusing burlesque of them will be found, of all places in the world, in Canning and Frere's "Poetry of the Anti-Jacobin."
puzzle only another illustration of the variety of the universe. Not that the puzzle was not fully recognized, but that the habit was still strong upon him of invoking creative power to account for all anomalies and surprises. Thus, remarking upon the absence of trees from the plains of Banda Oriental, which, although too far south to receive migration from the forests of Brazil, are well fitted by climate and soil to support forests of their own, he concludes that herbaceous plants instead of trees were specially created to occupy the area on its emergence from the sea. In Patagonia he found a strange bird, the Tinochorus, which almost equally partakes of the characters of the quail and the snipe, two widely contrasted birds. It is difficult to doubt that some suspicion of the possible significance of such an intermediate from must have crossed his mind, but his only comment is that, while the varied relations of the Tinochorus perplex the systematic naturalist, they may hereafter assist in revealing the grand scheme common to present and past ages on which organic beings have been created; a remark precisely in the spirit of Agassiz's Essay on Classification and a striking indication of the bent of his thinking at the time. To much the same purpose are his observations on two very singular birds which abound in Chiloe and other islands off the west coast of Patagonia. "From the great preponderance in most countries of certain kinds of birds, such as the finches, one feels surprised at meeting such peculiar forms as the commonest birds in any district. When finding, as in this case, any animal which seems to play so insignificant a part in the great scheme of nature, one is apt to wonder why a distinct species should have been created." His suggestion is "that in some other country it is perhaps an essential member of society or at some former period may have been so." Again, with reference to the slow deterioration in the types characteristic of a zoological district, as in South America, and the extermination of indigenous races by foreign races recently introduced, as in Australia, both of which facts seem to indicate an imperfect adaptation of forms as originally created to their conditions of life, his inference is that the adaptation is not alone to peculiarities of climate and country, but to other conditions also, as yet unknown; and in general that we are profoundly ignorant of the physiological relations on which the life of any species
depends. In man, however, he finds an instance of notable adaptation. "Of the most destructive diseases which bear an evident relation to climate, nearly all originate in the hotter regions of the earth. As geological induction shows that the climate during the periods antecedent to the present had an extra tropical (i.e., an unusual tropical) character, so in all probability there would be an extra tendency to disease, and we can therefore see that the recent introduction of man is an adaptation to the existing conditions of the world." What Mr. Darwin's ideas were of the first condition of man is indicated in his reflections on the Fuegians, whom he carefully studied. "One's mind hurries back over past centuries and then asks, Could our progenitors have been such as these? Men whose very signs and expressions are less intelligible to us than those of the domesticated animals; men who do not possess the instincts of those animals nor yet appear to boast of human reason. I do not believe it is possible to describe or paint the difference between savage and civilized man;" a remark which may have some connection with Capt. Fitzroy's theory that man was created in perfect condition, and that savages are simply wanderers of one blood who have been variously degraded during migration from the centre of the primitive civilization. But perhaps the most interesting of all these passages occurs in the Australian notes, and is worth giving entire:
"A little time before this I had been lying on a sunny bank and was reflecting on the strange character of the animals of this country as compared with the rest of the world. An unbeliever in everything beyond his own reason might exclaim, 'Two distinct Creators must have been at work; the object, however, has been the same, and certainly the end in each case is complete." While thus thinking I observed the hollow conical pitfall of the lion-ant; first, a fly fell down the treacherous slope and immediately disappeared; then came a large but unwary ant; its struggles to escape being very violent, those curious little jets of sand, described by Kirby as being flirted by the insect's tail, were promptly directed against the expected victim. But the ant enjoyed a better fate than the fly, and excaped the fatal jaws which lay concealed at the base
of the conical hollow. There can be no doubt that this predacious larva belongs to the same genus with the European kind, though to a different species. Now what would the sceptic say to this? Would any two workmen have hit upon so beautiful, so simple, and yet so artificial a contrivance? It cannot be thought so: one Hand has surely worked throughout the universe."
This sincere and cordial use of the old-fashioned theory in the hands of the author of the Origin of Species and the Descent of Man, extremely interesting in itself, is of historical importance as a guaranty, not of Mr. Darwin's good faith, for no one ever dreamt of questioning that, but of the perfectly unpremeditated and spontaneous manner in which the theory of development through natural selection arose. During all these years he went on construing nature as the direct product of creative power and the distinct expression of creative design, unaware, so far as we can see, of the silent arrival and reception from all quarters of phenomena bearing the other way, and of the slow transformation of his own mental states under their continuous action. It is as good an example of unconscious cerebration as can be found anywhere. The old structure of thought and feeling stood erect and intact, propped up by the sheer force of habit and association, while its foundations were wearing away by imperceptible attrition and a new philosophy was rising beneath it in the dark. Yet such is the alertness and sensitiveness of the writer's intelligence and the transparency of the atmosphere in which it wrought, that any careful reader to-day can detect with precision the successive points at which the old ideas were disturbed and the impulse towards new speculations communicated; down to the very discovery, a mere trifle in itself, which concentrated the effects of all the others; the exact moment when the silent mental induction discharged itself into consciousness; as two hundred years before the vision of the universal law of gravitation flashed after the fall of an apple.
The principal facts recorded in the Journal which determined the change in Mr. Darwin's opinions are of four kinds. The first are facts, gathered indiscriminately throughout the voyage, illustrating the immense efficiency of natural means for
the dispersion of living forms, active not only in present times, but continuously through past geological ages; together with the limitations of their action by natural barriers, such as mountain ranges, seas, climate, and soil, Such facts are of course consistent with the doctrine of the origin of species by creation, but they show that in many cases the forms peculiar to any region were not specially created upon it and for it, but have arrived there by migration from other quarters; that the definite range of any given form and the geographical distribution of living beings in general are the results of secondary causes and not of supernatural adjustment. Beyond this they are of no special significance until the immutability of species is disproved, when their significance becomes great. If it is possible for a species to produce by successive modifications a new species distinct from itself, then these facts provide the natural conditions for effecting such modifications in abundance, upon the broadest scale.
The second class of facts bears directly on this question of the mutability or immutability of species. If anywhere an intermediate form or a series of such can be found filling up the gap between two distinct species of the same genus, the suspicion arises that instead of a separate creation of each of the graduated forms there has been variation out of one into the other, or descent with variation from ancestors common to all. Such suggestive forms are the Tinochorus, spoken of above, and many others. In Buenos Ayres Mr. Darwin came upon a venomous snake, the Trigonocephalus, which had already been classified by Cuvier as a subgenus of the rattlesnake, and intermediate between it and the viper. "In confirmation of this opinion I observed a fact which appears to me very curious and instructive, as showing how every character, even though it may be independent of structure, has a tendency to vary by slow degrees. The extremity of the tail of this snake is terminated by a point, which is slightly enlarged, and as the animal glided along it constantly vibrated the last inch; and this part striking against the dry grass and brushwood produced a rattling noise which could be distinctly heard at the distance of six feet. This Trigonocephalus, therefore, has in some respects the structure of Vipera with the habits of a Crotalus."
Different and more direct indications of specific origin by descent were afforded by the third class of facts, drawn from a comparison of the living with the extinct mammalia of South America. The type of both groups is the same, that is, distinctly South American, but reduced and degraded in the latest representatives. It is of course conceivable that the Creator, without abandoning his general plan, should have substituted an inferior for a superior race to meet some changed conditions of the continent; but Mr. Darwin convinced himself that in climate, soil, and configuration South America has been for ages very nearly what it is to-day. Why then should the nobler race have perished and the degraded race have succeeded? This law of succession of types was well known to Mr. Darwin, having been already observed in Australia; but, as he observes in the Origin of Species, it was not until he dug out of the cliffs of Buenos Ayres and Patagonia, with his own hands, the bones of the ancient races, that he felt its full force. "It is impossible to reflect without the deepest astonishment on the changed state of this continent. Formerly it must have swarmed with great monsters but now we find only mere pigmies compared with the antecedent races. Since their loss no very great physical changes can have taken place in the nature of the country. What then has exterminated so many living creatures?…All that at present can be said with certainty is that, as with the individual so with the species, the hour of life has run its course and is spent." How near this surprise and perplexity were to the distinct conviction that the modern races are the degraded posterity of their ancient prototypes, we know from the Origin of Species.
But the fourth class of facts seem to have had the most decisive influence, probably because they came later than most of the others, and revived the old perplexity under the most startling conditions. After spending nearly four years along the coasts of South America, the Beagle sailed from Callas in the autumn of 1835, homeward bound by the Cape of Good Hope, and on the 16th of September anchored off the southern-most of the Galapagos islands. This archipelago consists of ten or twelve islands lying under the equator, between five and six hundred miles west of the nearest point of the continent. The cons itution of the whole is volcanic, and owing to the
nature of the soil and the relatively low temperature of the surrounding sea, vegetation is confined to the summits of the ancient craters. The consequence is that the zoology of the islands is unmasked and its very peculiar character apparent at once. Mr. Darwin enumerates 2 species of mammalia, 26 of land birds, 10 of reptiles, a few aquatic birds, and a few insects. This poverty of species corresponds with inferiority of structure and appearance. With the exception of aquatic birda, which are great wanderers, the forms are highly localized, but the general type is strictly South American. In other words, the fauna of the archipelago is to the contemporary fauna of the continent what the latter is to its extinct fauna. In the one case there is persistence of type and degradation of character during geological ages; in the other across an intervening sea; the same relations manifested by succession in time and distribution in space. It is evident that Mr. Darwin's perplexity had now become a serious doubt. "I will not here attempt, he says, to come to any definite conclusions, as the species have not been accurately examined; but we may infer that with the exception of a few wanderers, the organic beings found on this archipelago are peculiar to it, and yet that their general form strongly partakes of an American character.… This similarity of type between distant islands and continents, while the species are distinct, has scarcely been sufficiently noticed. The circumstance would be explained according to the views of some authors by saying that the creative power had acted according to the same law over a wide area." The doubt was deepened by a still more startling fact which came to his knowledge on the eve of departure, and just too late for full investigation. Not only are the fauna and flora of the archipelago peculiar to it, but in some, perhaps in all cases, each island has distinct forms of its own. That is, the type is continental, the group archipelagic,and the species insular. Here again we are reminded of the saying that a man sees only what he brings the eye to see. These fine differentiations of a general form for delicate adjustment to the slight peculiarities of separate localities would have given Agassiz a fresh illustration of the consummate art of the Creator, balancing simplicity of conception by endless variety of execution, adapting a few
types of life to the differing conditions of successive ages in all parts of the world. What Mr. Darwin began to suspect was the plasticity of life and the force of circumstances; the self-adjustment in all time of the organic and inorganic worlds.
"Unfortunately I was not aware of these facts until my collection was nearly completed: it never occurred to me that the productions of islands only a few miles apart and placed under the same physical conditions would be dissimilar. I therefore did not attempt to make a series of specimens from the separate islands. It is the fate of every voyager, when he has just discovered what object in any place is more particularly worthy of his attention, to be hurried away from it."
So Mr. Darwin put his discovery into his portfolio for investigation at a later day. But practically the question was decided here. The theory of development through natural selection, which in its widest applications includes the whole evolution of the universe, is the rugged foundling of the Galapagos Archipelago.
2.THE GROWTH OF THE DOCTRINE.
The voyages of the Adventure and the Beagle had been fatal to more than one member of the expedition, and Mr. Darwin himself arrived in England in the autumn of 1836 greatly broken in health. The first years after his return were largely spent in slowly working up the general results of his explorations. His journal appeared in 1839 as the third volume of the Narrative; the Zoology of the Voyage of the Beagle, to which he contributed the introduction and the notes, in 1841; The structure and Distribution of Coral Reefs, in 1842; Geological Observations on Volcanic Islands, in 1844; Geological Observations on South America, in 1846; and the Monograph of the Cirripedia, in 1851. He published besides occasional papers in the scientific journals of the day. All these studies, however, were but the closing up of an old account. The real task of his life was the solution of the problem he had brought back with him from the Galapagos Archipelago.
"On my return home," he tells us in his introduction to the Origin of Species, "it occurred to me in 1837 that something
might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years work I allowed myself to speculate on the subject and drew up some notes." This was in 1842. In 1844 appeared the Vestiges of Creation, a work which had an immediate celebrity and which must have startled Mr. Darwin as a perilous approach to his own line of speculation. At any rate in that year he drew up a general sketch of the conclusions which seemed to him probable at the time and submitted it to Dr. Hooker, curator of the Kew Gardens, who communicated some of the conclusions to Sir Charles Lyell. Both saw the full significance of the new ideas and urged Mr. Darwin to publish without delay, but in vain, as he was always unwilling to interrupt the course of his investigations.* The slow toil of accumulation and reflection, re-enforced from this time by the immense botanical learning of Dr. Hooker, went on for fifteen years more, and to all appearance might have gone on in silence indefinitely, had not Mr. Darwin at last received a much sharper reminder than the Vestiges of Creation. In the year 1848 Mr. Alfred Russel Wallace, a young amateur naturalist, had thrown up his business in England, and gone to the valley of the Amazon, where he spent three years supporting himself by his collections in natural history. His curiosity was evidently excited by several of the phenomena of the geographical distribution of animals which had been observed by Mr. Drawin farther south,† and in 1854 he went to the Malay Archipelago, where he spent no less than eight years in a careful study of the zoology of a region upon which, more than any other on the globe, the forces of life have been concentrated, and where more obviously than anywhere else the geographical distribution and the localization of races have been determined by purely natural causes. His conclusion was precisely the one reached twenty years before in the Galapagos Archipelago, namely, that existing species have originated by descent through variation from extinct species. He drew up a state-
* Antiquity of Man, ch.xxi.
† Wallace, Travels on the Amazon and Rio Negro, ch. xvi.
ment of the grounds of his belief and of the mode in which be supposed variation to have been guided, in two papers dated respectively at Sarawak in February, 1855, and Ternate in February, 1858. The latter he forwarded to Mr. Darwin, with the request that if it were found of sufficient importance it should be sent to Sir Charles Lyell. Mr. Darwin saw at once that his hand had been forced, and after consultation with Dr. Hooker and Sir Charles Lyell Mr. Wallace's paper* was sent to the Linnæan Society for publication, and on the 24th of November, 1859, appeared the first edition of the Origin of Species by Means of Natural Selection; or the Preservation of Favoured Races in the Struggle for life.
In order to understand clearly the successive stages of what has been perhaps the most formidable single-handed undertaking of our time, it will be well here to distinguish exactly what it was which Mr. Darwin began in 1837 by rejecting, and what it was he accepted instead. From the time of Aristotle the individual beings which compose the organic world have been distributed by naturalists into groups according to their resemblances to one another. This grouping, or classification, has been in large measure arbitrary, every observer selecting his own points of resemblance, so that no two systems which have been elaborated exactly coincide throughout. The nearest approach to agreement has been in distinguishing the groups which are called species. Even here there has been no real unanimity, naturalists differing not only in their enumeration of species but even fundamentally in their definitions of what a species really is. On the whole, however, in the midst of much confusion there has been a substantial consent that a species of plants or animals consists of all those individuals which are fertile when crossed with each other and whose offspring are fertile; infertile when crossed with other individuals or producing offspring which are infertile. Fertility is the character common to all members of the group; infertility, in the first crossing or in the hybrid, the sign of the natural barrier separating the group from all others outside of it. It follows that the members of any group thus strictly circumscribed are descended from common progenitors of the same
* Wallace, Contributions to the Theory of Natural Selection.
kind, and that their offspring will resemble themselves; in other words, that the species is persistent and immutable. At no point of the line has it ever by any possibility received any of the slightest admixture of foreign blood; and a fortiori, at the initial point of all it could not have been derived from any pre-existing species, for such pre-existing species was incapable of fertility beyond its own limits. Therefore, since derivation in any form is impossible, each species must have originated de novo; that is, must have been created. All the living beings of the world to-day are descended each from beings of its own kind, created from the first with perfect adaptation to their conditions of life; and the sum-total of species in any given age is precisely equal to the sum-total of species in any other age plus the species which have been created in the mean time. It is obvious that this theory is coherent and consistent throughout, the persistence of species, the immutability of species, and the origin of species by creation, all following from the fundamental assumption that a species consists of individuals fertile between themselves, immediately or remotely infertile with all individuals outside. Its weak point, if it have one, is the failure to allow for the possible effects of long continued variation begun within specific limits; an oversight due to the belief, nearly universal until lately, that the first appearance of life on the globe was a recent event.
This was the doctrine which Mr. Darwin held, down at least to 1853; which was shaken in South America and the Galapagos Islands; and distinctly rejected at least as early as 1837. Why was it rejected? Remembering the logical consistence of its parts with each other, the answer ought to be that a new group had been found endowed with all specific characters, derived from another endowed with the same characters; that is, two distinct species incapable of intercrossing, one of which was descended from the other, or both from a third pre-existing species. No such discovery was made or could have been made, as will be seen in a moment, even if the fact existed. What Mr. Darwin saw was substantially what had been seen elsewhere before without suspicion or surprise, and the effect of his discovery on his beliefs is to be accounted for by the psychological states of his own mind. He saw that the fauna of
the Galapagos Archipelago is a degraded form of the type more perfectly represented by the existing fauna of South America, and the latter of the same type magnificently developed in the extinct fauna of South America; he found here and there signs of variation away from one species in the direction of another; and all over the world a potent agency providing the conditions for variation. His decision was that the species of the islands were descended by ordinary generation from the allied but distinct species of the continent, and they again from the allied but distinct species of their geological predecessors: in general, that all species now living are descended from a smaller number of pre-existing species, mostly lost, but which had they survived would be distinct from their posterity; and ultimately, that the whole realm of organic beings throughout its history has descended from a few primordial forms, or it may be from one, about whose origin, however, he abstains from speculation. It was evident that this generalization, however satisfactory to the author, could have been satisfactory as it stood to no one else not in the same state of mind. His psychological predispositions could not have been put en evidence, and as to his facts all naturalists would have replied that they were well known before and had already been construed as the expression of a great creative law carried out over wide areas through successive ages. It was incumbent on him, therefore, for self-vindication, to go to the root of the matter; on the one hand, to break down, if he could, the immutability of species; on the other, to find some natural process by which variation has produced the adaptive structures found in plants and animals, and by which all species have been derived from primordial forms. Here it must be felt that Mr. Darwin's unpremeditation and impartiality abandon him. His first conviction had come to him unawares, it may be said in spite of himself; but once committed to it, it was necessary to find the conditions which rendered origin by descent possible; and his subsequent life-toil, in many respects as noble a devotion as has been seen in our day, has been a long endeavor to construe the phenomena of nature to fit a foregone conclusion.
The direction of his new studies is a mark, partly of the necessity of the situation, but partly also of the surpassing intelligence and originality of the man. It was unavailing to
go directly to nature for the new facts wanted by the theory, for under her air of entire candor and communicativeness nature maintains an impenetrable reserve. Her results are open to anybody, but the processes by which they are reached are too gradual and protracted for detection and measurement. There was no hope of being able to surprise her anywhere, under ordinary circumstances, in the act of elaborating a complicated structure, like the human eye or ear, out of the simple structure of some lower form; or of carrying by slow successive modifications one type of life into another. It was necessary to find her acting under conditions other than her own, in which all processes were accelerated and the intermediate stages of development left on record. With the promptitude of true genius, Mr. Darwin began his great study of the variation of plants and animals under domestication. Considering the accessibility and importance of the facts, it is remarkable that this should have been so largely an unexplored territory to science. The arts of domestication are among the earliest of man, for it is as a rude farmer and herdsman that he first passes out of barbarism; they have always been the fundamental arts of civilization; and the proportion to-day of domesticated plants and animals to those in a state of nature is very great. We must suppose that the economical importance of the subject has obscured its scientific interest, or that the artificial conditions under which the phenomena are presented tend to unfit them for scientific treatment. Mr. Darwin thought otherwise; and it may be said at once that whatever the fate of his theory, it has left behind it by far the most important addition made to biological science in our time.
The first and most obvious effect of domestication is an increased sensitiveness and variability in the organisms subjected to it. Domestication means restraint, confinement, protection, high feeding, stimulation, and often entire change of domicile. Under these potent influences any race taken by man from nature after a few generations begins to show extreme instability, a tendency to the abundant production of new characters. Among other notable changes effected is a partial elimination of sterility; for there is reason to believe that many species which are incapable of interbreeding when wild are perfectly
fertile together when domesticated. Yet this apparently unregulated and indefinite variation acting through long ages has not resulted in a confusion of organic forms, but, on the contrary, in forms almost as systematically allied and as easily classified as natural forms. Thus we have at one end of the line the scanty collection of plants and animals won from the wilderness by the first human societies, with the subsequent additions made to them; at the other the multitude of well discriminated forms in man's possession to-day; and the historical certainty that the latter have descended from the former.
What is the power which has thus regulated variability and directed descent? Partly, no doubt, it is the long-continued action of fixed conditions of life; partly also the action of other known and unknown forces. But principally it is beyond any question the power of man over his dependents. The various domesticated breeds have been made what they are simply by the process of breeding. Variability has been kept in order in the long run because out of the aggregate of variations presented to him man has selected each new one useful or pleasing to himself and has perpetuated it by availing himself of the law of heredity, according to which any character, as soon as it appears, tends to transmission and increment from generation to generation. In this way, by selecting for breeding individuals which show any desirable character, and by continuing to breed from their selected offspring, he has produced out of the merest germs and hints the most elaborate structures and adaptations; and new groups of beings which, so far as organization, habits, and appearance are concerned, must be classed not only as distinct species, but in many cases as distinct species of different genera. In short, like the magician mimicking Moses, he has done over again everything that nature has done—with one momentous exception; he has never yet derived from one species a new one infertile when crossed with the parent form, or two new species infertile when crossed with each other. All the so-called varieties, species, and genera of domesticated beings which are known to be descended from common progenitors, however widely they differ in other characters, are persistently fertile with each other.
This is one side of the art of selection. On the other hand, man has neglected or destroyed all variations injurious, useless, or uninteresting, and such variations have in consequence tended to extinction. In this way many intermediate forms have perished, and the whole result of the three processes of extinction, survival, and divergence of character is the present systematic distribution of domesticated plants and animals.
With this clue in his hand Mr. Darwin went back to the labyrinth of nature. Given at the beginning, let us say by creation, a few primordial forms of life, and at the end the numerous highly differentiated groups of living beings existing to-day; is there any conceivable process analogous to man's selection by which the latter may have been derived from the former; and if so has nature provided the conditions for its action?
In the first place, the sensitiveness of organization so conspicuous in domesticated animals and plants and the extraordinary amount of variation they undergo, are not originated by domestication itself. Artificial conditions of life have simply intensified a character common to all living beings. Organized material itself, in its lowest and simplest states, is at once discriminated from inorganic matter by great instability; and all the way up the ascending scale of organization to the most complex and highly specialized structures, where stability would be found if anywhere, the same phenomena recur. No child exactly resembles it parents; no individual at two successive periods exactly resembles itself. Changes are ceaselessly induced in each cell or atom of organized matter, in each organ or set of organs, in the whole structure and character of the individual, in all groups of individuals throughout the world of living beings. These changes are less accentuated and rapid than changes under domestication, because, in the absence of artificial conditions, disturbance has been less powerful and profound. But change there is universal throughout the world and continuous through time. Its causes are obscure, for they belong to the inner mystery of life, and all we can say is that there is something in the nature of organized matter which renders it sensitive after its own fashion to the influences
of the surrounding world; but its effects are obvious, and if in nature there is anything resembling man's art of selection it provides the first condition for its action.
In the second place, these variations, however they may be induced and wherever they occur, tend to be inherited. There are, doubtless, limits to the tendency, so that many of them go as they come; not being transmitted, they disappear; but the exceptions do not disprove the rule. The most striking fulfillment of the great law of heredity is the persistence of slight modifications from generation to generation.
If now we inquire, as before, what is the power which has regulated variability and guided descent; which, on the one hand, has withheld this universal movement away from fixed forms, this ceaseless production of minute, indefinite, and characterless variations from ending in confusion worse confounded; which, on the other, has determined development along certain lines into a well-defined and orderly whole: the old answer at once would be, the Creator had done it by fixing the type of the species in the beginning, and by confining all change within specific limits, so that the multiplication of new forms results only in a wider harmony than before. When the spirit of rationalism, which began by rejecting the miracles of Scripture and the Church, ended in the domain of biological science by rejecting the more stupendous miracles of creation, other answers had to be found. Geoffroy St. Hilaire looked for the controlling power in the "monde ambiant," the combined action of the forces of the surrounding world on organisms, gradually modifying them to suit the situations in which they are found. Goethe nearly at the same time came to the same conclusion. To the action of external conditions Lamarck added the force of habit, or of use and disuse of particular parts, while beneath both he recognized an innate tendency in living matter towards progressive development. With the exception of the last, the efficiency of all these influences and others of the kind besides has been acknowledged by Mr. Darwin from the first. But many of them, or all together, are clearly inadequate, whether qualitatively or quantitatively, to account for the phenomena, which imply on the very face of them the action of some one universal and persistent power as discriminating, rigorous, and efficient as providence itself.
His first hint here came from a work, nearly obsolete not so many years ago, but now returning to celebrity on the flood tide of Darwinism, the Essay of Malthus on the Principles of Population. It is certain that all living beings multiply in a geometrical progression, with a varying ratio which, however, is high in the slowest breeders. The successive additions of each generation to the numbers of any race would suffice, if unchecked, to stock the whole world in a few centuries, or even in many cases in a few years. In point of fact, however, the number of any race is as nearly as possible a fixed quantity, the limit of population having been reached early in its history, and practically never varying afterwards. It follows, therefore, that enormous destruction is going on throughout the living world; that of all the individuals born at any given time only a few survive, the remainder perishing from exposure, lack of food, the attacks of enemies, or other of the natural checks upon population. From birth life is a struggle for existence, with the odds heavily against the struggler. What determines the issue? In many cases the merest accident will determine it, but in general we may be sure that the favored individuals will be the superior individuals; the survivors will be precisely the "fittest" for survival; those which in structure, constitution, or appearance, have any advantage over their competitors. Since all the new born of any race are of necessity closely alike, superiority will be determined, not by great differences, but by small ones. Any variation, no matter how slight, which is favorable to the possessor by increasing its strength or endurance, by aiding it in the search for food, concealment, or shelter, will increase its chances of escape and longevity. Thus out of the whole number of new births a few will be selected for survival and the vast remainder for extinction, and the discrimination between the two by the forces of nature will be as searching and rigorous as man's selection among domesticated beings, and will be determined by analagous causes, namely, the presence or absence of useful variations. Such variations, furthermore, will be likely to descend by inheritance from parent to offspring, who again may add useful variations of their own; and so on in series, with a continuous, increasing tendency to differentiation and
advancement of organization; until a new variety is produced, which on the one hand will be able to beat competing varieties in the struggle for existence, and on the other to live under new conditions, to seize upon a new district from which its progenitors were excluded; the whole process ending at last in a new species incapable of crossing with the parent form, or with any of the other allied species descended from it.
Such is the process of Natural Selection, or as Mr. Herbert Spencer calls it, dropping the metaphor, of survival of the fittest, which together with the auxiliary process of sexual selection and coöperating with the minor laws of variation, has presided, if not over the origin, at least over the entire development of life upon the globe. The whole system in nature and the whole expression of the system in science, or classification, are purely genealogical from first to last. We have but to assume the then well ascertained facts of the variability of living beings, inheritance, and reproduction in geometrical ratio, and everything follows in intelligible sequence. The first individual germ or cell of organized matter varying for any reason, in any degree, however slight, in a manner profitable to itself, will be more likely to survive than others not varying at all, or not varying usefully; and surviving, will be likely to transmit the beneficial variation to its offspring. Departure from the primitive forms sets in in every direction, never to cease, until in their remote posterity we reach through cycles of deterioration and extermination, of improvement, survival, and divergence of character, a world of diversified beings ranging from the lowest plant to the highest animal, fitted with wonderful adaptations to their conditions of life, and grouped together in orderly distribution of varieties, species, genera, families, orders, classes, and branches.
Not only so. We have but to carry the analogy across the barrier between animate and inanimate matter to account for the evolution of the entire universe from the homogeneity of primitive being; a generalization, as it stands, as impressive as any devised by the wit of man.
3. THE DIFFICULTIES AND LIMITATIONS OF THE THEORY.
The first edition of the Origin of Species appeared in 1859 as an abstract of a larger work, which would require many years to complete. The sixth and last edition (1872) repeats the same announcement. The Variation of Animals and Plants under Domestication was published in 1868; also a first installment of works which have never appeared. Beside these we have the essay on the Fertilization of Orchids (1862); the Descent of Man and Selection in relation to Sex (1871); and the Expression of the Emotions in Man and Animals (1872).
If anyone will take the trouble, not a light one by any means, to follow the first draft of the new theory step by step through the storm of subsequent controversy, he will leave his studies convinced, if not of the durability of the theory, at least of the constancy of the author. No other speculation so daring and revolutionary has over been produced with more foresight and precaution, or maintained with more candor and conscientiousness. Mr. Darwin has been accused more than once in high quarters of treating his friends with exceptional tenderness and of ignoring all the more formidable of his adversaries; the simple fact being that the difficulties in his way have been as carefully considered and as powerfully stated by himself as by any other man. The larger part of them are already anticipated and fully discussed in the first edition of the Origin of Species. Others that have arisen since have been met either by a frank change of front or by an extension of his original lines. Of the former there are only two or three instances to be found. In reply to several criticisms and more particularly to an Article in the North British Review for 1867, he at once admitted that he had overrated the importance of natural selection by attributing to it effects undoubtedly due to other laws of variation. The best example of the latter will be found in the reply to Mr. St. George Mivart's Genesis of Species, published in 1872, an attack so formidable that it drew from Mr. Darwin's serenity, for the first time in the controversy, a flash of temper—and, perhaps, the most powerful rejoinder of recent polemics.* But for the most part the Dar-
* Origin of Species, 6th ed., ch. vii.
winian doctrine stands to-day where it stood in 1859. Natural selection has been withdrawn to admit a somewhat larger action of mere spontaneous variability, of the conditions of life, of habit or the use and disuse of parts, and of sexual selection in the discrimination of races. It has been extended to take in the origin and descent of man, and is still maintained to the full as the great law which has presided over the whole development of the living world.
Setting aside the entire teleological argument, with which, whether logically or not, no evolutionist now concerns himself, the acknowledged difficulties of the theory are all reducible to three classes. The first are certain postulates or implications necessarily involved which seem to be incredible. Natural selection is simply an accumulation of such minute successive variations as are useful to organisms and the neglect or rejection of those which are useless or hurtful. The incipient stages, of useful structures, including every organ by which any living being communicates with the surrounding world, must have consisted of some slight modification of previous structure. How could such slight modifications have been useful to the organism in any way; much more how could they have been useful in the direction of the remote perfected organ? And if not useful they could not have been naturally selected. The difficulty is vastly increased when we reflect that many individuals must have begun to vary in the same manner at the same time, for in the deadly struggle for existence going on everywhere a slight useful variation in one individual would soon disappear among its competitors. This indeed is an objection so serious that Mr. Darwin, as has been said, at once admitted a far larger action of the conditions of life to account for simultaneous variations of the same kind. But even then, unless we suppose that the whole species began to vary at once, how are we to account for the persistence of a new, slightly discriminated variety side by side with the parent and other competing forms? And when this competition is escaped, there are later transitional states in which persistence is equally inconceivable. According to the necessary lines of descent many species now living under one set of conditions must formerly have lived under widely different ones. How could
any of them survive the stage between the two? the transition, for example, from an aquatic to a terrestrial life? In any event, all these processes are incalculably slow, and the sum-total of them must far more than exhaust the whole time allowed either by astronomy or geology.
In the second place, there are certain facts wanting in nature which are required by the theory. Thus there are organs of general utility which have been granted to one animal or plant only and denied to many others in equal need of them and equally capable of receiving them; and characters found nowhere which, if utility to the organism alone is considered, ought to occur. Again, the necessary result of long-continued divergence of character would seem to be an indefinite multiplication of specific forms. Species no doubt are numerous and are not always easily distinguished, but the confusion is in our ignorance and not in nature itself. Lastly, between two distinct allied species there must at some time have existed many intermediate forms, some of which, at least, ought to have survived. Yet they cannot be found in the world to-day, and what is more, they cannot be found in the geological record of past ages.
In the third place, there are certain facts in nature which cannot be accounted for by natural selection. How is it that an universal process of improvement and divergence of character has after all left behind it unchanged so vast a portion of living beings? Below the tribes of relatively high organization there is a populous world of plants and animals which show hardly any organization at all, and, we have reason to believe, are now what they were ages ago at the very dawn of life. Their progenitors have been the common progenitors of all. Why have the one been taken and the other left? Furthermore, the first appearance in the geological record of beings of a higher order is very abrupt. Already in the earliest fossiliferous strata we find, not single individuals alone, but allied groups of at least three of the four great types of the animal kingdom. We are compelled to infer either instantaneous creation, or sudden development, or an enormous lapse of time between the first appearance of life on the globe and its first appearance in the record. Not only so, but the record is similarly interrupted
all the way down, so that natural selection must have got over its heaviest work in cras entirely unrepresented. Or, taking the world as it stands to-day, we are confronted everywhere with phenomena whose origin does not seem to be in the least provided for by allowing unlimited time to natural selection. Such are the organs of great complexity and perfection in the higher races, on the one hand, and useless or unimportant organs, on the other; the occurrence of similar organs in widely contrasted races; the instincts and motions of animals; the reason, the conscience, and the self-consciousness of man; and the geographical distribution of living beings over the globe.
All these, or many of them, as Mr. Darwin remarks in his candid way, are difficulties grave enough to stagger and confound any man. He has met them with inexhaustible learning and ingenuity, either by producing the very facts, or facts of the very order, disputed; or by suggesting conditions under which the presence or absence of certain facts may be accounted for consistently with his theory; or by frankly turning the objection out of court on the plea of insufficient evidence; as in his argument that the testimony of geology is admissible because the record is imperfect. Every thinker will have his own opinion of the adequacy of the defence, but supposing it to have been perfectly successful there still remains the earliest difficulty of all, the old fact, or dogma, of the immutability of species, affirmed as it seems to be by the phenomena of hybridism and confirmed by the suspicious absence of immediate forms. This has been the Hougoumont of the fight from the very first, and nobody has been better aware of it than Mr. Darwin, for the effect of it is to break down the analogy between domesticated and natural races, on which he relies. He has planted his heaviest batteries and marshalled his strongest squadrons around this one obstacle, and so far there can be no doubt that he has failed to carry it. His argument, briefly stated, is that the alleged fact, while it exists, is relative and not absolute, for there are all degrees of infertility between distinct species, ranging from perfect sterility very nearly, if not quite up to, perfect fecundity; that the infertility of the first cross and that of the hybrid are two very different things: that there is a closely corresponding series of phe-
nomena in the crossing of varieties, which therefore may be considered incipient species; and finally that the character, whatever else may be said of it, is not a supernatural endowment of species to preserve their distinctness, but a result of secondary causes, probably of the long-continued action of fixed conditions of life on the reproductive system. Meanwhile the fact remains, and obviously is to be got rid of only in one way, namely, by producing an actual case of two distinct species infertile when crossed, one of which has been derived from the other, or both from a common parent form; which has never yet been done. Mr. St. George Mivart, it is to be feared, has been overthrown like Blucher at Ligny, but so far the obstinate sterility of the mule is very nearly—where it was.
The commanding importance of this point is likely to be still more evident in the sequel, for it suggests an ulterior question which has not been very prominent in the discussion hitherto. Are the ambiguous phenomena of variation the only phenomena involved? Admitting, as we must, the incessant changes which all organisms have undergone and are undergoing to-day; admitting, as we may, that some such law as that of natural selection has controled and directed them; still we are entitled to ask, is this the whole of the matter and is there nothing beyond? In this continual changefulness is there nothing unchanging? Are there no phenomena anterior to variability, persistent in the midst of it, and so not to be accounted for by any of its laws?
Now there is at least one such fixed and constant factor involved which natural selection, so far from accounting for, is obliged to assume as the condition of its own efficiency; namely, the law of inheritance, the absolutely universal fact that like produces like, that each being gives birth, directly as in sexual generation, indirectly as in alternate generation, to new beings resembling itself. In the very beginning of life, before natural selection began to act, as the indispensable preliminary to its action, all organisms whatsoever were already endowed with this function, and from that day to this every child born into the world has inherited the nature of its parents. Not only so, but to increase the mystery, there is a latent tendency to inherit, through parents and grandparents, the lost
characters of remote ancestors. This is a fact so obtrusive and significant that Mr. Darwin himself has attempted an explanation of it in what he has called the "provisional hypothesis of Pangenesis. Starting from the admitted fact that the cells or units of organized bodies propagate themselves by self-division, he assumes, first, that such cells are continually throwing off minute particles, which circulate freely through the system, each again multiplying by self-divison, and subsequently developing new cells like those from which they were derived: secondly, that these freely circulating particles, or "gemmules," have elective affinities for each other, leading in the one direction to the continued growth and repair of the substances of the body, in the other to their aggregation into the buds of plants or the ovules of animals. Every bud, or seed, or ovule, is thus made up of particles derived from all the cells of all parts of the parent body in all stages of growth, each with its own tendency to development and union with other particles, and the result is similarity of structure, constitution, and character between parent and offspring. The objection to this hypothesis is not that it is false, for the probabilities are that in some form it is true; but that it leaves the original mystery more complex and impenetrable than ever. How came the cells to be endowed at the outset with these astounding functions of proliferation, discriminating union with each other, and aggregation either into new tissue or into the germ of a new being? How have the additional affidities and discriminations involved in every fresh advancement of organization been acquired?*
Again, as natural selection is obliged to assume the law of inheritance as a previous fact, so is sexual selection obliged to assume the distinction of the sexes. This, it may be objected, is not an universal fact like the other, for there are low forms of life in which reproduction is asexual. But Mr. Darwin himself has shown that the structure of every organism whatsoever appears to be especially adapted for the concurrence, at least occasionally, of two individuals. The distinction, therefore, is essential; and at any rate it appears whenever we reach organ-
* The Evolutionists themselves are rather shy of Pangenesla. See the "Genesis of Species" and Dr. Bastian's "Beginnings of Life" ch. xiv.
ization of any complexity, after which it is the law alike of all plants and all animals. Of course, inasmuch as important ends are gained by the concourse of the sexes, it is conceivable that sex has arisen, like other useful characters, through natural selection. But the strong presumption is that we have here a constant, universal fact anterior to and independent of all ordinary variation.
What, once more, are we to say of the division of living beings into the two kingdoms of plants and animals? It is certain, if anything is, that this is a chasm traversing the whole organic world from top to bottom and from first to last. Biologists have thrown a vast deal of dust into our eyes of late by the affirmation that the lowest forms of life are indistinguishable in character, which is true; and by the inference that being indistinguishable they are one, which is false. An animal of any grade is an animal and not a plant, because it possesses the faculty of voluntary motion. It is what it is, and not something else by virtue of will. A being may easily be found so low in organization and so obscure in character that no human senses or scientific tests can say whether it is one thing or the other; but this we can always say, that it either is capable of voluntary motion or is not. If it is, it is an animal; if it is not, it is a plant. It must be one and it can't be both. The distinction is primordial, persistent, and absolute; a third of the great constants anterior to and independent of all ordinary variation.
One is tempted to add, although the fact is less available for argument, that as the animal is distinguished from the vegetable world by the faculty of will, so is man from all other animals by the faculty of self-consciousness. It will at once be replied that self-consciousness is a late development and not a primitive fact, for we cannot imagine an unborn child or an undeveloped germ as conscious of itself. But we may at least avail ourselves of the analogy of Pangenesis to affirm that a character inseparable from human nature sooner or later, exists in some obscure form, some determining predisposition or condition, at the very root and beginning of human life; and the first predisposition is as unaccountable as the ultimate fact.
It is impossible to reflect upon these and other great uniformities of the living world without the suspicion that Darwinism is an incomplete induction; that back of the phenomena it deals with there resides in organic beings some power which is the principal factor involved, which has controlled all the secondary causes and laws of variability and has probably originated variation itself. This after all is the weak point of the new philosophy, that it refuses to offer any explanation of the fundamental fact of organic variability. Mr. Darwin has ingeniously cut off all discussion in this direction by insisting that whatever may have been the obscure causes of variation they have had no relation to the structure which natural selection has built up out of them. "If an architect," he says, "were to rear an edifice without the use of uncut stone by selecting from the fragments at the base of precipice wedgedformed stones for his arches, elongated stones for his lintels, and flat stones for his roof, we should regard his as the paramount power. Such fragments bear to the edifice built the same relation as the fluctuating variations of each organic being bear to the structures ultimately acquired by its modified descendants? Definite causes no doubt have given to each fragment its shape, but they have acted without reference to the edifice into which it has been built. But what shall we say of edifice and architect if at the base of his precipice he finds not merely a heap of uncut stones, but foundations and arches, framework and outlines already erected and waiting for him? And this is what natural selection finds, a power anterior and superior to its own, which not only provides its building material, but prescribes the limits and the character of its work. Moreover, the illustration breaks down at the essential point of all, for in reality the fitness of the uncut stones for the use of the architect has no true analogy with the fitness of organic variations for the use of natural selection. We may be sure that no atom of organized material has been put into a contrivance like the human eye for any other cause than its adaptation to the one specific purpose of vision. We may dissect the most complete structure into its simplest elements, and we get at the very last, in each constituent particle, not a fluctuating, characterless variation, but perfect fitness for an end;
a relation not to be accounted for or disposed of by any theory of subsequent aggregation and co-ordination. It is here again as with the theory of Pangenesis; we are no better off at the end of our analysis than we were at the beginning. The original mystery of the complex organ has simply retreated behind the ultimate atom as dark and unfathomable as ever.
It is, therefore, precisely within the region which Mr. Darwin has closed to us as both impenetrable and irrelevant that the whole controversy lies in its last analysis, and whither it must be carried sooner or later as to a court of last resort. Why is organic material variable at all and how does it vary? The most obvious answer is that it varies according to the action of external conditions, the incident forces of the universe around it. But all those forces act too upon inorganic matter. Does the one respond to the action as the other does or differently? We know that it responds differently. The moment we pass from an inorganic molecule to an organized germ we get a new, dissimilar reply to the appeal of the surrounding universe; we have now the responsive phenomena of vitality. There is therefore something within the nature of organic material itself which determines its behaviour under the action of incident forces; a power, or necessity, or tendency, whatever we choose to call it, which adapts variation to organization and conducts it along particular lines in definite directions; producing at once, or sooner or later, the facts of heredity, the discrimination of plants and animals, the discrimination of the sexes, it may be the immutability of species, the spiritual nature of man, the innermost individuality of each living being and of every group of such. We may allow to natural selection the largest latitude it can maintain: here at least, it would seem, is an ultimate verity which does not crumble under its analysis or fit into its synthesis; which therefore compels us to supplement its action by the larger generalizations of some comprehensive theory of evolution: or that, failing to revert to the ancient postulate of some power, other and higher than the forces and properties of matter, which is the principal factor in the product of the universe.
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