Life of Charles Darwin Part 2

The publication of "The Zoology of the Voyage of _The Beagle_,"

commenced in 1838, under Darwin's superintendence, gave a fuller view of the acquisitions to natural history which had been made than had previously been possible. The Treasury, acting on the representations of the presidents of the Linnean, Zoological, and Geological Societies, as well as of the naturalist himself, in 1837 made a grant of 1000 towards the expenses of publication of these memoirs. Owen's description of the fossil mammalia, completed in 1840; G. Waterhouse's of the living mammalia, in 1839; Gould's of the birds, in 1841; L. Jenyns's of the fish, in 1842; and Thomas Bell's of the reptiles, in 1843--all in quarto, with beautiful plates, were a solid testimony to a splendid success. Darwin furnished an introduction to each part, and the portions of the text referring to the habits and ranges of the living animals.

Three species of mastodon and the gigantic megatherium were the only extinct mammalia known from South America previous to Darwin's voyage.

To these were now added the _Mylodon Darwinii_, a giant sloth; the scelidotherium, a somewhat smaller form; the great camel-like, yet odd-toed, macrauchenia; and the toxodon, as large as a hippopotamus, yet having a strange resemblance to the little rodents. All these belonged to geological deposits not far anterior to the present age. The collections of living vertebrates were less profoundly interesting, but the number of new species was large; and the habits and localities being recorded by so good an observer, gave them additional value.

The fossil mammals were given by the generous traveller to the London College of Surgeons, the mammals and birds to the Zoological Society, the reptiles to the British Museum, and the fishes to the Cambridge Philosophical Society. Nor was this all. The collections of insects, sh.e.l.ls, and crustacea were described by many able specialists in scientific publications. The flowering plants were described by Hooker, and the non-flowering by Berkeley; and, altogether, no expedition ever yielded a more solid result to the scientific naturalist, while furnishing a delightful narrative to the general reader, and laying the foundation for generalisations of surpa.s.sing importance to all thinking minds.

It was evident to many geologists that the greatest value would attach to the full record of the geological observations made by the gifted young secretary of the Geological Society. A year after the publication of the Journal the first portion of these observations, dealing with coral reefs, was almost ready, but the continued ill-health of the author delayed the publication till 1842. When it appeared, under the t.i.tle of "The Structure and Distribution of Coral Reefs," its success was immediate and complete.

Ever since their first description by voyagers, marvel had been expressed at the strange and beautiful phenomena presented by coral islands. Coral, as being built up by the tireless labours of innumerable so-called "insects," or "worms," had become a.s.sociated with romantic ideas. It really consists of the internal skeletons of coral-polyps, allied to the sea anemone. Captain Basil Hall, in his "Voyage to Loo Choo," looking with the eyes of one ignorant of zoology, had credited the building of coral reefs to all kinds of creatures which lived on and near the coral after it had been made; and his erroneous views had been amplified and developed by James Montgomery, in his "Pelican Island,"

into the most fantastically incorrect description that ever versifier penned. Sad to relate, his lines were often quoted, as if correct, by scientific men in pre-Darwinian times.

Nothing gives clearer evidence of the power of mind which Darwin had already attained when voyaging round the world than the originality of his views on coral reefs. The lagoon islands, or atolls, he describes as "vast rings of coral rock, often many leagues in diameter, here and there surmounted by a low verdant island, with dazzling white sh.o.r.es, bathed on the outside by the foaming breakers of the ocean; and, on the inside, surrounding a calm expanse of water which, from reflection, is of a bright, but pale, green colour." Keeling atoll, outside which, at less than a mile and a half distance, no bottom was found with a line 7,200 feet in length, having been fully described, and an account given of all other known atoll systems, the peculiarities of the great barrier reef of North-east Australia, and that of New Caledonia, were recounted.

Off the latter, no bottom was found, at two ships' length from the reef, with a line 900 feet long. With these were linked the smaller reefs of Tahiti and others, where considerable islands are more or less completely surrounded by them. Next, the fringing or sh.o.r.e reefs, at first sight only a variety of barrier reefs, were clearly distinguished from them by the absence of an interior deep-water channel, and their not growing up from an immense, but from a moderate depth of water.

The remarkable fact was pointed out by Darwin that all coral islands are within a little more than 30 degrees of the Equator, but that, at the same time, they are absent over certain larger areas within the tropical seas. There are none on the West Coast of South America, nor on the West Coast of Africa. In this portion of his work we have another significant sentence bearing on the struggle for existence. In discussing the apparently capricious distribution of coral reefs, he remarks that "the study of the terrestrial and better-known half of the world must convince every one that no station capable of supporting life is lost--nay more, that there is a struggle for each station between the different orders of nature." He describes the large fishes and the trepangs (_holothuriae_) preying upon the coral-polyps, and shows how complex are the conditions which determine the formation of reefs on any sh.o.r.e. Perhaps no part of his work is more important than that in which he collects the evidence proving how rapidly coral ma.s.ses grow, and that they for the most part cannot flourish in a greater depth of water than fifteen fathoms.

Reasoning upon the facts observed by himself and others Darwin now proceeded to upset the received theory that atolls were based upon submarine volcanic craters, and to subst.i.tute for it the view that there has been a prolonged and gradual subsidence of the areas upon which the atolls are based, and a corresponding upward growth of the reef-building corals. Thus fringing-reefs in time become barrier-reefs; and barrier-reefs, when they encircle islands, are converted into atolls, or lagoon islands, as soon as the last pinnacle of land sinks beneath the surface of the ocean. The whole matter is summed up thus: "A magnificent and harmonious picture of the movements which the crust of the earth has within a late period undergone is presented to us. We see vast areas rising, with volcanic matter every now and then bursting forth through the vents or fissures with which they are traversed. We see other wide s.p.a.ces slowly sinking without any volcanic outbursts; and we may feel sure that this sinking must have been immense in amount as well as in area, thus to have buried over the broad face of the ocean every one of these mountains above which atolls now stand like monuments, marking the place of their former existence." "No more admirable example of scientific method was ever given to the world," says Professor A.

Geikie, "and even if he had written nothing else, this treatise alone would have placed Darwin in the very front of investigators of nature."

After thirty-two years' interval, a second edition of "Coral Reefs"

appeared, in a cheaper form, in 1874. It is rare indeed for a scientific treatise to attain at once and maintain so long a position of such undisputed authority. The eminent German naturalist, Semper, in 1863, criticised the general theory in consequence of his own careful examination of the Pelew Islands; but Darwin easily answered him by pointing to the c.u.mulative evidence in favour of his own views. The only really important work on the subject, after Darwin's, was that of Professor J. D. Dana, the eminent American naturalist and geologist, on "Corals and Coral Islands," published in 1872. Darwin, in the preface to his second edition, candidly acknowledged that he had not previously laid sufficient weight on the mean temperature of the sea in determining the distribution of coral reefs; but this did not touch his main conception. In fact, he maintained his ground undisturbed, and at the same time admired greatly Dana's book, which was the result of personal examination of more coral formations than perhaps any one man had ever studied, and which accepted Darwin's fundamental proposition, that lagoon islands or atolls and barrier-reefs have been formed during periods of subsidence.[5]

No such strikingly original theory is propounded in the second part of "The Geology of the _Beagle_" dealing chiefly with volcanic islands. St.

Jago, in the Cape de Verde Islands; Fernando Noronha, Terceira, Tahiti, Mauritius, St. Paul's, Ascension, St. Helena, and the Galapagos are in turn more or less fully described, according to the opportunities the explorer had possessed. To some extent, as in the succeeding part, Darwin adapts his views on mountain elevation too closely to those enunciated by Elie de Beaumont. The third part of the geology of the _Beagle_, ent.i.tled "Geological Observations on South America," was not published till 1846. Even this did not exhaust the contributions to geology made from the _Beagle_ voyage, for it did not include the papers on the "Connection of certain Volcanic Phenomena in South America"

(1838); on the "Distribution of Erratic Boulders" (1841); on the "Fine Dust which falls on Vessels" (1845); and on the "Geology of the Falkland Islands" (1846). A second edition of the two latter parts of "The Geology of the _Beagle_" was published in one volume in 1876.

Meanwhile, after spending a few years of his early married life in London, during which he was often in ill-health, Darwin fixed his residence in 1842 at Down House, near Beckenham, Kent. The little village of Down, three or four miles from the Orpington railway station, was near enough to London for convenient access, yet greatly secluded and thoroughly rural. The traveller's roving days were over, and his infirmity of health prevented him from undertaking very fatiguing journeys. After the cessation of his active work for the Geological Society, Darwin's chief public appearance was when he spoke at the Oxford meeting of the British a.s.sociation, in 1847, when, strange to say, Ruskin was secretary of the Geological Section.

At Down then, situated some 400 feet above the sea level on a plateau of chalk, interrupted by wavy hollows with beech woods on the slopes, about forty years of Darwin's life were pa.s.sed. Down House, one of the square red brick mansions of the last century, to which have been since added a gable-fronted wing on one side and a more squarely-built wing and pillared portico on the other, is shut in and almost hidden from the roadway by a high wall and belt of trees. On the south side a walled garden opens into a quiet meadow, bounded by underwood, through which is seen a delightful view of the narrow valley beyond, towards Westerham.

One of the most admirable chapters of the well-known "Manual of Scientific Enquiry," published in 1849, for the use of the navy and travellers generally, and edited by Sir John Herschel, was Darwin's, on Geology. The explorer is here taught to make the most of his opportunities upon the soundest principles. The habits which the author had himself formed are inculcated upon the observer--copious collecting, accurate recording, much thinking. Nothing is omitted. Number-labels which can be read upside down must have a stop to indicate the right way up; every specimen should be ticketed on the day of collection; diagrams of all kinds should be made, as nearly as possible, to scale. "Acquire the habit of always seeking an explanation of every geological point met with." "No one can expect to solve the many difficulties which will be encountered, and which for a long time will remain to perplex geologists; _but a ray of light will occasionally be his reward, and the reward is ample_." Truly an ample reward awaited the observer who could thus speak of the value of "a ray of light;" he certainly did, to use the concluding words of the essay, "enjoy the high satisfaction of contributing to the perfection of the history of this wonderful world."

Meanwhile Darwin had been carrying on a great research on the very peculiar order of crustacea, termed Cirripedia, better known as barnacles and acorn sh.e.l.ls. He had originally only intended to describe a single abnormal member of the group, from South America, but was led, for the sake of comparison, to examine the internal parts of as many as possible. The British Museum collection was freely opened to him, and as the importance of studying the anatomy of many specimens became evident, the splendid collections of Messrs. Stutchbury, c.u.ming, and others were placed at his disposal, and he was permitted to open and to dissect unique specimens of great value. In fact, almost every naturalist of note who had any knowledge of the subject freely aided him, and the result was a masterly series of finely ill.u.s.trated volumes; two on the living Cirripedia, issued by the Ray Society in 1851 and 1854; and two on the fossil Cirripedia of Great Britain, by the Palaeontographical Society, published in the same years. There is evidence in these volumes that careful observations on the growth of these creatures had been made as far back as the visit to the Galapagos Islands in 1835. In many respects these works are as masterly as any the author ever wrote. Considering the previous obscurity of the subject, the difficulties attending the research, the almost entire lack at that time of any general microscopical knowledge of tissues, and especially of those of embryos, Darwin's success is marvellous. The details are too technical for statement here, but any one with a zoological training, who studies the strange complication of the reproductive systems, and the remarkable transformations which the young undergo, as told in these volumes, will appreciate more than ever the breadth and the solidity of the basis of patiently acquired knowledge which Charles Darwin had acc.u.mulated while his "Origin of Species" was taking shape.

At the anniversary meeting of the Royal Society in November, 1853, a royal medal was presented to the author of "Coral Reefs" and the "Memoir on the Cirripedia," the president, the Earl of Rosse, eulogizing the former as one of the most important contributions to modern geology, and the latter as containing new facts and conclusions of first-rate interest. Finally, this chapter of Darwin's life may be closed with the tardy award of the Wollaston medal to him by the Geological Society, in February, 1859, when Professor John Phillips spoke of him as combining the rarest acquirements as a naturalist, with the qualifications of a first-cla.s.s geologist, and as having by his admirable monograph on the fossil Cirripedia added much to a reputation already raised to the highest rank.

Yet even such a reputation could not secure fair treatment and impartial judgment for the coming book, the subject of which might be supposed to require supreme gifts of the very kind Darwin possessed.

FOOTNOTES:

[5: Mr. John Murray's views, derived from the experience acquired in the voyage of the _Challenger_, and published in 1880, tend to modify Darwin's conclusions to some extent. Mr. Murray says that it is now shown that many submarine mountains exist, which are usually volcanic, and which, being built upon by various forms of sh.e.l.l-bearing animals, could be raised to such a level that ordinary corals could build upon them. He concludes that probably all atolls are seated on submarine volcanoes, and thus it is not necessary to suppose such extensive and long-continued subsidences as Darwin suggested. This view is also in harmony with Dana's views of the great antiquity and permanence of the great ocean basin. See "The Structure and Origin of Reefs and Islands." By John Murray; Proc. Roy. Soc., Edin., x. 505-18 (abstract); also _Nature_, xxii. 351-5.]

CHAPTER IV.

If no other record of Darwin's twenty-two years (1837-59) of life and thought after his return to England remained than the papers and books he published during that period, we should find enough to place him on a level with the most gifted biologists and geologists of his age. But all that time he was occupied with thoughts, researches, and experiments, of which the world at large perceived no fruits. Few persons suspected that a tremendous revolution in scientific thought was in preparation at the quiet country home at Down. New species of animals and plants were being described by naturalists at an alarming rate. The bulk of knowledge of specific characters and the necessity of specialisation bade fair to make every species-monger a dry and narrow pedant; and the pedants quarrelled about the characters and limits of their species.

In the later years of this period some rays of improvement shone out. To end the reign of Owen's misleading types and imaginary archetypes, there arose a wielder of two potent words, "morphology" and "biology," the sciences of form and of life, who showed that differences of adult form grew out of likeness and simplicity in the young; and that the life of plants and animals was one science, their study one discipline. What Huxley had begun to proclaim from the housetop, Darwin was meditating in secret; and much more. Let us see how he states the case in the famous modest opening of the "Origin of Species" (1859): "When on board H.M.S.

_Beagle_, as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent.

These facts seemed to me to throw some light on the origin of species--that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home, it occurred to me, in 1837, that something might perhaps be made out on this question by patiently acc.u.mulating 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 short notes; these I enlarged in 1844 into a sketch of the conclusions, which then seemed to me probable: from that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details, as I give them to show that I have not been hasty in coming to a decision." We learn also, independently, from the "Expression of the Emotions" (p. 19), that Darwin as early as 1838 was inclined to believe in the principle of evolution, or the derivation of species from other and lower forms.

It is somewhat difficult to decide precisely what Darwin owed to his predecessors who believed in the mutability of species and doubted their separate creation; this is partly owing to his exceeding modesty. He was over-ready to acknowledge the value to himself of other people's ideas, and he under-estimated the strength of the illumination which his own mind threw upon those ideas, transforming them from guesses into probable hypotheses, confirming them by his vast and varied knowledge, and building a superstructure where they had laid but an uncertain foundation. The question was in the air; guessing replies of great interest were made by a few who doubted the received belief; but they were not satisfying answers and they did not effect a revolution. Goethe in Germany, Erasmus Darwin in England,[6] and Geoffroy Saint Hilaire in France, came independently to similar conclusions as to the mutability of species; and Lamarck followed with several well-known works in 1801-15, in which he upholds the doctrine that all species, including man, are descended from other species. As Darwin says, Lamarck first did the eminent service of arousing attention to the probability of all change in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition. He saw the difficulty of distinguishing between species and varieties, the almost perfect gradation of form in some groups, and the great similarity of domestic breeds of animals to such species. He believed that some degree of change was produced by the physical conditions of life, the intercrossing of species, and by habits causing increased use or disuse of parts. Indeed he thought very many remarkable adaptations, such as that of the neck of the giraffe for browsing on trees, were the effect of habit. But he attributed, perhaps, more to a law of progressive development impressed on all forms of life, which thus would all in time gradually cease to be lowly, their place being taken by new forms continually or "spontaneously" generated.

It does not appear that Lamarck would by any means have sufficed to convince Darwin, judging from his references to him in his Journal and the "Origin." Here is the pa.s.sage in which in the second edition of his Journal he refers to the blindness of the Brazilian Tucutuco, or Ctenomys, a rodent or gnawing mammal with the habits of a mole: "Considering the strictly subterranean habits of the Tucutuco, the blindness, though so common, cannot be a very serious evil; yet it appears strange that any animal should possess an organ frequently subject to be injured. Lamarck would have been delighted with this fact had he known it when speculating (probably with more truth than usual with him) on the gradually _acquired_ blindness of the Aspalax, a gnawer living underground, and of the Proteus, a reptile living in dark caverns filled with water, in both of which animals the eye is in an almost rudimentary state, and is covered with a tendinous membrane and skin....

In the Tucutuco, which, I believe, never comes to the surface of the ground, the eye is rather larger (than in the mole), but often rendered blind and useless, though without apparently causing any inconvenience to the animal: no doubt Lamarck would have said that the Tucutuco is now pa.s.sing into the state of the Aspalax and Proteus." Many years afterwards in the "Origin of Species" Darwin referred to the "erroneous views and grounds of opinion of Lamarck."

No doubt some impulse to Darwin's views in this direction would be due to his intercourse with Dr. Grant at Edinburgh, whose celebrated paper on the fresh-water sponge concludes with a declaration of his belief that species are descended from other species, and that they become improved in the course of modification. But previous to the occurrences of his voyage, we can find no stronger influence tending to make Darwin an evolutionist, than Lyell's "Principles of Geology," which, by showing constant and gradual change as the law of the world's history now as in past periods, gave emphasis and point to all observations of change and succession in the living world. Indeed, in June, 1836, before Darwin's voyage was over, Lyell writes to Sir John Herschel: "In regard to the origination of new species, I am very glad to find that you think it probable that it may be carried on through the intervention of intermediate causes. I left this rather to be inferred, not thinking it worth while to offend a certain cla.s.s of persons by embodying in words what would only be a speculation. But the German critics have attacked me vigorously, saying, that by the impugning of the doctrine of spontaneous generation, and subst.i.tuting nothing in its place, I have left them nothing but the direct and miraculous intervention of the First Cause, as often as a new species is introduced, and hence I have overthrown my own doctrine of revolutions carried on by a regular system of secondary causes.... When I first came to the notion, which I never saw expressed elsewhere, though I have no doubt it had all been thought out before, of a succession of extinction of species, and creation of new ones going on perpetually now, and through an indefinite period of the past, and to continue for ages to come, all in accommodation to the changes which must continue in the inanimate and habitable earth, the idea struck me as the grandest which I had ever conceived, so far as regards the attributes of the Presiding Mind."

In a succeeding paragraph, Lyell very remarkably foreshadows Darwin's "natural selection" and "struggle for existence." He speaks of a species being rendered more prolific in order to perpetuate its existence; "but this would perhaps make it press too hard upon other species at other times. Now if it be an insect it may be made in one of its transformations to resemble a dead stick, or a leaf, or a lichen, or a stone, so as to be somewhat less easily found by its enemies; or if this would make it too strong, an occasional variety of the species may have this advantage conferred on it; or if this would be still too much, one s.e.x of a certain variety. _Probably there is scarcely a dash of colour on the wing or body of which the choice would be quite arbitrary, or which might not affect its duration for thousands of years._" The significance of the last sentence is immense, and when we reflect that this bold but cautious thinker was in constant intercourse with Darwin, we can readily comprehend why the second edition of the Journal was so enthusiastically dedicated to Lyell. On page 481 of the "Origin of Species," Darwin acknowledges that the belief that species were immutable productions was almost unavoidable, as long as the history of the world was thought to be of short duration: which affords another proof how profoundly Lyell's views on the long duration of the past history of the globe, and its modification by the slow operation of existing causes, influenced Darwin, and led him to comprehend how species might be modified.

We see Darwin, then, possessed of the idea that species are mutable, informed as to past and recent changes in the animal, plant, and physical world, seeking for causes which should suffice to produce modification of species by a continuous law. The next step in his progress was attention to domestic animals and cultivated plants. As he wrote in 1864 to Haeckel, one of his most brilliant followers: "In South America three cla.s.ses of facts were brought strongly before my mind.

Firstly, the manner in which closely-allied species replace species in going southward. Secondly, the close affinity of the species inhabiting the islands near South America to those proper to the continent. This struck me profoundly, especially the difference of the species in the adjoining islets in the Galapagos Archipelago. Thirdly, the relation of the living Edentata and Rodentia to the extinct species. I shall never forget my astonishment when I dug out a gigantic piece of armour like that of the living armadillo.

"Having reflected much on the foregoing facts, it seemed to me probable that allied species were descended from a common ancestor. But during several years I could not conceive how each form could have been modified so as to become admirably adapted to its place in nature. I began, therefore, to study domesticated animals and cultivated plants,[7] and after a time perceived that man's power of selecting and breeding from certain individuals was the most powerful of all means in the production of new races. Having attended to the habits of animals, and their relations to the surrounding conditions, I was able to realise the severe struggle for existence to which all organisms are subjected; and my geological observations had allowed me to appreciate, to a certain extent, the duration of past geological periods. With my mind thus prepared, I fortunately happened to read Malthus's 'Essay on Population;' and the idea of natural selection through the struggle for existence at once occurred to me. Of all the subordinate points in the theory, the last which I understood was the cause of the tendency in the descendants from a common progenitor to diverge in character."[8]

Malthus taught the inevitable tendency of all animal life to increase beyond the means of subsistence, and expounded the checks which begin to act when population increases too rapidly. But his book had lain unfruitful to naturalists since 1798, until Darwin read it, and with his special knowledge evolved from it the brilliant idea of the preservation of better-equipped races in the struggle for life, or, as Herbert Spencer put it, the survival of the fittest. At one bound the gloomy revelations of misery which the "Essay on Population" contained, were exchanged for the bright view of perpetual progress and improvement as being necessitated and brought about by the very struggle which ensued upon the natural increase of animal and plant life. Instead of struggle and pain, producing starvation and extinction merely, struggle and pain were seen as the conditions of development and improvement; the death of the lower, the life of the higher.

It is less profitable here to attempt to sketch the history of ideas of evolution in general, because that history as now revealed by research, and as detailed by many writers, was not the path along which Darwin travelled. Indeed, many of these ideas were not disinterred, and certainly were not brought to Darwin's notice till after the publication of the "Origin of Species." True he read Robert Chambers's "Vestiges of Creation," which, with its "powerful and brilliant style," although displaying in its earlier editions "little accurate knowledge and a great want of scientific caution," Darwin acknowledges to have done excellent service in calling attention to the subject, in removing prejudice, and in preparing the ground for the reception of a.n.a.logous views. Herbert Spencer, in his Essay on the Development Hypothesis, first published in _The Leader_ in March, 1852, and republished in his "Essays" (first series, 1858), argued that species have been modified owing to change of circ.u.mstances, basing his argument upon the a.n.a.logy of domestic animals and plants, the changes which the embryos of many species undergo, and the difficulty of distinguishing species and varieties.

But we need not here dwell on the works of these thinkers, important as they are to the general history of evolutionary thought, because Darwin's speculations had taken form long before, and he could be but slightly indebted to them. Far in advance of them he was at work collecting and testing the facts which alone could win general support for his views, and experimenting incessantly with the same object in view. Lyell and Hooker were in his confidence, and in Lyell's letters we meet with references such as the following, dated November 13, 1854: "You probably know about this (the remarkable orchid, Catasetum), which will figure in C. Darwin's book on 'Species,' with many other 'ugly facts,' as Hooker, clinging like me to the orthodox faith, calls these and other abnormal vagaries," showing at the same time how completely Darwin was the leader, while his friends, advanced as they were, hung back. Again (Lyell to Hooker, July 25, 1856): "Whether Darwin persuades you and me to renounce our faith in species (when geological epochs are considered) or not, I foresee that many will go over to the indefinite modifiability doctrine."

Further light is thrown on the progress of ideas on species by Sir Joseph Hooker's admirably written Introductory Essay to the "Flora Novae Zelandiae," dated November, 1853, in which he discusses among other questions, "The Limits of Species; their Dispersion and Variation."

While still adhering on the whole to the origin of species from single parents, or from one pair, and the permanence of specific characters, he insists that species vary more, and are more widely distributed, than is generally admitted, and that their distribution has been brought about by natural causes. In this essay he makes the following statements: "Mr.

Darwin not only directed my earliest studies in the subjects of the distribution and variation of species, but has discussed with me all the arguments, and drawn my attention to many of the facts which I have endeavoured to ill.u.s.trate in this essay. I know of no other way in which I can acknowledge the extent of my obligation to him, than by adding that I should never have taken up the subject in its present form but for the advantages I have derived from his friendship and encouragement."

Appropriately enough, it was through Lyell and Hooker that the new theory was introduced to the public, and it was owing to them that Darwin did not obliterate his own claims to priority, and give them over to Alfred Russel Wallace, who had independently come to similar conclusions. The letter, dated June 30, 1858, in which the announcement was conveyed to the Linnean Society, deserves quotation, as being the authoritative and accurate record of the circ.u.mstances which launched the "Origin of Species" upon the world:

"The accompanying papers, which we have the honour of communicating to the Linnean Society, and which all relate to the same subject, viz., 'The Laws which affect the Production of Varieties, Races, and Species,' contain the results of the investigations of two indefatigable naturalists, Mr. Charles Darwin and Mr. Alfred Wallace.

"These gentlemen having, independently and unknown to one another, conceived the same very ingenious theory to account for the appearance and perpetuation of varieties and of specific forms on our planet, may both fairly claim the merit of being original thinkers in this important line of inquiry; but neither of them having published his views, though Mr. Darwin has been repeatedly urged by us to do so, and both authors having now unreservedly placed their papers in our hands, we think it would best promote the interests of science that a selection from them should be laid before the Linnean Society.

"Taken in the order of their dates, they consist of--

"1. Extracts from a MS. work on species, by Mr. Darwin, which was sketched in 1839, and copied in 1844, when the copy was read by Dr.

Hooker, and its contents afterwards communicated to Sir Charles Lyell. The first part is devoted to 'The Variation of Organic Beings under Domestication and in their Natural State'; and the second chapter of that part, from which we propose to read to the Society the extracts referred to, is headed, 'On the Variation of Organic Beings in a State of Nature; on the Natural Means of Selection; on the Comparison of Domestic Races and true Species.'

"2. An abstract of a private letter addressed to Professor Asa Gray, of Boston, U.S., in October, 1857, by Mr. Darwin, in which he repeats his views, and which shows that these remained unaltered from 1839 to 1857.

"3. An essay by Mr. Wallace, ent.i.tled 'On the Tendency of Varieties to depart indefinitely from the Original Type.' This was written at Ternate in February, 1858, for the perusal of his friend and correspondent, Mr. Darwin, and sent to him with the expressed wish that it should be forwarded to Sir Charles Lyell, if Mr. Darwin thought it sufficiently novel and interesting. So highly did Mr.

Darwin appreciate the value of the views therein set forth, that he proposed, in a letter to Sir Charles Lyell, to obtain Mr. Wallace's consent to allow the essay to be published as soon as possible. Of this step we highly approved, provided Mr. Darwin did not withhold from the public, as he was strongly inclined to do (in favour of Mr. Wallace) the memoir which he had himself written on the same subject, and which, as before stated, one of us had perused in 1844, and the contents of which we had both of us been privy to for many years. On representing this to Mr. Darwin, he gave us permission to make what use we thought proper of his memoir, &c.; and in adopting our present course, of presenting it to the Linnean Society, we have explained to him that we are not solely considering the relative claims to priority of himself and his friend, but the interests of science generally; for we feel it to be desirable that views founded on a wide deduction from facts, and matured by years of reflection, should const.i.tute at once a goal from which others may start, and that, while the scientific world is waiting for the appearance of Mr. Darwin's complete work, some of the leading results of his labours, as well as those of his able correspondent, should together be laid before the public."

In these papers, read on July 1, 1858, Darwin's share amounts to little more than six pages, yet within this s.p.a.ce he describes the geometrical rate of increase of animals, the checks that occur, the effects of changed conditions, the natural selection of the better equipped forms resulting from the struggle for existence, and the influence of s.e.xual selection. Wallace insists on essentially the same view, which he calls that of progression and continued divergence. "This progression, by minute steps, in various directions, but always checked and balanced by the necessary conditions, subject to which alone existence can be preserved, may, it is believed, be followed out so as to agree with all the phenomena presented by organised beings, their extinction and succession in past ages, and all the extraordinary modifications of form, instinct, and habits which they exhibit." Those who read Wallace's original essay can best appreciate the extraordinary simplicity and n.o.bility of character which inclined the elder naturalist, who had so long held the same views, to step aside in favour of the younger man, who from different researches was led to such similar conclusions. It may here be added that Hooker, in the Introductory Essay to the "Flora Tasmaniae," dated November 4, 1859, before the publication of the "Origin of Species," but after seeing much of it in ma.n.u.script, accepted and advocated the view that species are derivative and mutable, and developed it as regards the geographical distribution of plants.

FOOTNOTES:

[6: It is worth while to reproduce here a few sentences from Erasmus Darwin's "Zoonomia," showing how acutely he guessed in the direction of evolution.