The story of his life at Down is almost wholly coincident with the history of the development of his views on evolution, and the growth and appearance of the successive volumes which he gave to the world. For the first four years his geological tastes continued in the ascendant. During that interval there appeared three remarkable works, his volume on Coral Islands, that on Volcanic Islands, and his Geological Observations on South America. Of these treatises that on coral reefs excited the wonder and admiration of geologists for the simplicity and grandeur of its theoretical explanations. Before it was written, the prevalent view of the origin of these insular masses of coral was that which regarded each of them as built on the summit of a volcano, the circular shape of an atoll or ring of coral being held to mark the outline of the submerged crater on which it rested. But Darwin, in showing the untenableness of this explanation, pointed out how easily the rings of coral might have arisen from the upward growth of the reef-building corals round an island slowly sinking into the sea. He was thus led to look upon the vast regions of ocean dotted with coral islands as areas of gradual subsidence, and he could adduce every stage in the process of growth, from the shore-reef just beginning, as it were, to form round the island, to the completed atoll, where the last vestige of the encircled land had disappeared under the central lagoon. More recent researches by other observers have, in the opinion of some writers, proved that the widespread submergence demanded by Darwin's theory is not required to account for the present form and distribution of coral islands. But his work will ever remain a classic in the history of geology.
After working up the geological results of the long voyage in the Beagle, he set himself with great determination to more purely zoological details. While visiting the coast of Chili, he had found a curious new cirripede, to understand the structure of which he had to examine and dissect many of the common forms. The memoir, which was originally designed to describe only his new type, gradually expanded into an elaborate monograph on the Cirrepedes (barnacles) as a Whole group. For eight years he continued this self-imposed task, getting at last so weary of it as to feel at times as if the labour had been in some sense wasted which he had spent over it, and this suspicion seems to have remained with him in maturer years. But when at last the two bulky volumes, of more than one thousand pages of text, with forty detailed plates, made their appearance, they were hailed as an admirable contribution to the knowledge of a comparatively little known department of the animal kingdom. In the interests of science, perhaps, their chief value is to be recognised not so much in their own high merit as in the practical training which their preparation gave the author in anatomical detail and classification. He spoke of it himself afterwards as a valuable discipline, and Professor Huxley truly affirms that the influence of this discipline was visible in everything which he afterwards wrote.
It was after Darwin had got rid of his herculean labours over the 'Cirripede book' that he began to settle down seriously to the great work of his life—the investigation of the origin of the species of plants and animals. One of the three volumes of the Biography is entirely devoted to tracing the growth of his views on this subject, and the preparation and reception of the great work on the Origin of Species. In no part of his task has the editor shown greater tact and skill than in this. From the earliest jottings, which show that the idea had taken hold of Darwin's mind, we are led onwards through successive journals, letters, and published works, marking as we go how steadily the idea was pursued, and how it shaped itself more and more definitely in his mind. It is impossible to condense this story within the limits of a Review article, and the condensation, even if possible, would spoil the story, which must be left as told in the author's own words. Briefly, it may be stated here that he seems to have been first led to ponder over the question of the transmutation of species by facts that had come under his notice during the South American part of the voyage in the Beagle—such as the discovery of the fossil remains of huge animals akin to, but yet very distinct from, the living armadillos of the same regions; the manner in which closely allied animals were found to replace one another, as he followed them over the continent; and the remarkable character of the flora and fauna of the Galapagos archipelago. 'It was evident,' he says, 'that such facts as these, as well as many others, could only be explained on the supposition that species gradually become modified; and the subject haunted me.' His first note-book for the accumulation of facts bearing on the question was opened in July 1837, and from that date he continued to gather them 'on a wholesale scale, more especially with respect to domesticated productions, by printed inquiries, by conversation with skilful breeders and gardeners, and by extensive reading.' He soon perceived that selection was the secret of success in the artificial production of the useful varieties of plants and animals. But how this principle, so fertile in results when employed by man, could be applied in explanation of Nature's operations, remained a mystery to him until in October 1838, when, happening to read for amusement Malthus' book On the Principle of Population, he found at last a theory with which to work. With this guiding principle he instituted a laborious investigation on the breeding of pigeons, and experiments on the flotation of eggs, the vitality of seeds, and other questions, the solution of which seemed desirable as his researches advanced. He says himself that, to avoid prejudice in favour of his own views, he refrained for some time from writing even the briefest sketch of the theory he had formed, and that it was not until June, 1842, that he allowed himself the satisfaction of writing a very brief pencil abstract in thirty-five pages, which two years afterwards he enlarged to 230 pages, and had fairly copied out. This precious manuscript was the germ of the Origin of Species.
With characteristic caution, however, he kept his essay in his desk, and with equally characteristic ardour, industry and patience went on with the laborious task of accumulating evidence. His friends were of course well aware of the nature of his research, and of the remarkable views to which he had been led regarding the history of species. And as these views could hardly fail in the end to become generally known, it was desirable that the first publication of them should be made by himself. This having been urged upon him by Lyell, he began early in the year 1856 to write out his views in detail on a scale three or four times as large as that on which the Origin of Species afterwards appeared. This work he continued steadily for two years, when it was interrupted (June 1858) by the arrival of a remarkable manuscript essay by Mr. A. R. Wallace, who, working in the Malay archipelago, had arrived at conclusions identical with those of Darwin himself. Darwin's generous impulse was to send this essay for publication irrespective of any claim of his own to priority: but his friends, Lyell and Sir Joseph Hooker, persuaded him to allow extracts from his early sketch of 1844, and part of a letter written to Professor Asa Gray in 1857, to be read, together with Mr. Wallace's contribution, before the Linnean Society, and to be printed in the Society's Journal. He now set to work upon that epitome of his observations and deductions which appeared in November 1859, as the immortal Origin of Species.
Those who are old enough to remember the publication of this work, cannot but marvel at the change which, since that day, not yet thirty years ago, has come alike upon the non-scientific and the scientific part of the community in their estimation of it. Professor Huxley has furnished to the Biography a graphic chapter on the reception of the book, and in his vigorous and witty style recalls the furious and fatuous objections that were urged against it. A much longer chapter will be required to describe the change which the advent of the Origin of Species has wrought in every department of science, and not of science only, but of philosophy. The principle of evolution, so early broached and so long discredited, has now at last been proclaimed and accepted as the guiding idea in the investigation of Nature.
One of the most marvellous aspects of Darwin's work was the way in which he seemed always to throw a new light upon every department of inquiry into which the course of his researches led him to look. The specialists who, in their own narrow domains, had been toiling for years, patiently gathering facts and timidly drawing inferences from them, were astonished to find that one who, to their eyes, was a kind of outsider, could point out to them the plain meaning of things which, though entirely familiar to them, they had never adequately understood. The central idea of the Origin of Species is an example of this in the biological sciences. The chapter on the imperfection of the geological record is another in the domain of geology.
After the publication of the Origin, Darwin gave to the world during a succession of years a series of volumes, in which some of his observations and conclusions were worked out in fuller detail. His books on the fertilisation of orchids, on the movements and habits of climbing plants, on the variation of animals and plants under domestication, on the effects of cross and self-fertilisation in the vegetable kingdom, on the different forms of flowers in plants of the same species, were mainly based on his own quiet work in the greenhouse and garden at Down. His volumes on the descent of man, and on the expression of the emotions in man and animals, completed his contributions to the biological argument. His last volume, published the year before his death, treated of the formation of vegetable mould, and the habits of earth-worms, and the preparation of it enabled him to renew some of the observations which had interested him in his younger days, and to revive some of the geological enthusiasm which so marked the earlier years of his life.
Such, in briefest outline, was the work accomplished by Charles Darwin. The admirable biography prepared by his son enables us to follow its progress from the beginning to the close. But higher even than the intellect which achieved the work was the moral character which shone through it all. As far as it is possible for words to convey what Darwin was to those who did not personally know him, this has been done in the Life. His son has written a touching chapter, entitled, 'Reminiscences of my Father's Everyday Life,' in which the man as he lived and worked is vividly pictured. From that sketch, and from Darwin's own letters, the reader may conceive how noble was the character of the great naturalist. His industry and patience, in spite of the daily physical suffering that marked the last forty years of his life; his utter unselfishness and tender consideration for others; his lifelong modesty that led him to see the worst of his own work and the best of that of other men; his scrupulous honour and unbending veracity; his intense desire to be accurate even in the smallest particulars, and the trouble he took to secure such accuracy; his sympathy with the struggles of younger men, and his readiness to help them; his eagerness for the establishment of truth by whomsoever discovered; his interest up to the very last in the advancement of science; his playful humour; his unfailing courtesy and gratitude for even the smallest acts of kindness—these elements of a lofty moral nature stand out conspicuously in the Biography. No one can rise from the perusal of these volumes without the conviction that, by making known to the world at large what Darwin was as a man, as well as a great original investigator, they place him on a still loftier pinnacle of greatness than that to which the voice of his contemporaries had already raised him.