It will be seen that although Darwin had in all probability thought out all his important theoretical conclusions before 1869, when he reached the 'fatal age,' yet, owing to various delays, the books, in which he embodied his views, had not all appeared till more than four years later.
Lyell, who was a convinced evolutionist before the publication of the Principles of Geology, as is shown by his letters,—and the fact is strongly insisted on both by Huxley and Haeckel[141],—was slow in coming into complete agreement with Darwin concerning the theory of Natural Selection. While he followed his friend's investigations with the deepest interest, his less sanguine nature led him often to despair of the possibility of solving 'the mystery of mysteries.' As Darwin wrote only a year before his own death, Lyell 'would advance all possible objections to my suggestions, and even after these were exhausted would long remain dubious[142].' It is evident from the correspondence that Darwin was at times tempted to become impatient with the friend, for whose advocacy of his views he so deeply longed. Fourteen years after the publication of the Origin of Species, however, Lyell, in his Antiquity of Man, gave in his adhesion to Darwin's theory but, even then, not in the unqualified manner that the latter desired. Yet I have reason to know that some years before his death, Lyell was able to assure his friend of his complete agreement, and Darwin, six years after the loss of his friend, wrote, 'His candour was highly remarkable. He exhibited this by becoming a convert to the Descent theory, though he had gained much fame by opposing Lamarck's views, and this after he had grown old.' Darwin adds that Lyell, referring to the 'fatal age' of sixty, said 'he hoped that now he might be allowed to live[143]!'
When I first came into personal relations with Darwin, after the death of Lyell in 1875, he was in the habit of deprecating any idea of his writing on theoretical questions. He used to talk of 'playing with plants and such things,' and undoubtedly derived the greatest pleasure from his ingenious experimental researches. The result of this 'play' in which Darwin took such delight is seen in his books on the Power of Movement in Plants and Insectivorous Plants; full of the records of ingenious experiments and patient observation.
It was a great relief to Darwin that his friend Wallace was able in 1871 to undertake the preparation of a work on The Geographical Distribution of Animals, for, on many points, the views held by Wallace on this subject were more in accordance with Darwin's own, than were those of Lyell and Hooker. Nevertheless, on all questions connected with the geographical distribution of plants, and the causes by which they were brought about, Darwin always expressed the fullest confidence in Hooker's judgment, and the greatest satisfaction with his results.
With regard to another great division of his work, that dealing with the imperfection, but yet great value, of the geological record, Darwin was always anxious, when I met him, to learn of any new discoveries. But he felt that he had done all that was possible in his outline of the subject in the Origin, and that he must leave to palaeontologists all over the world the filling in of these outlines. So great was the delight with which he used to hear of new discoveries in palaeontology, that I often recall our conversations in these later days, when so many interesting forms of extinct animal and vegetable life—veritable 'missing links'—are being discovered in all parts of the globe, and wish that he could have known of them. They are indeed 'Facts for Darwin.'
Very happy indeed was Charles Darwin in the last years of his useful life, in returning to his oldest 'love'—geology. In studying the action of earthworms he found a geological study in which his rare powers of ingenious experimentation could be employed with profit. His earliest published memoir had dealt with the question, and for more than forty years with dogged perseverance, he had laboured at it from time to time. It was delightful to watch his pleasure as he examined what was going on in the flower-pots full of mould in his study, and when his book was published and favourably received, he rejoiced in it as 'the child of his old age[144].'
Charles Darwin's death took place rather more than twenty-two years after the publication of the Origin of Species. Before he passed away, he had the satisfaction of knowing that the doctrine of evolution had come to be—mainly through his own great efforts—the accepted creed of all naturalists and that even for the world at large it had lost its imaginary terrors. As Huxley wrote a few days after our sad loss, 'None have fought better, and none have been more fortunate, than Charles Darwin. He found a great truth trodden underfoot, reviled by bigots, and ridiculed by all the world; he lived long enough to see it, chiefly by his own efforts, irrefragably established in science, inseparably incorporated with the common thoughts of men, and only hated and feared by those who would revile, but dare not. What shall a man desire more than this[145]?'
More than a quarter of a century has passed since these words were written. How during that period the influence of Darwin's writings on human thought has grown, in an accelerated ratio, will be seen by anyone who will turn the pages of the memorial volume—Darwin and Modern Science—published fifty years after the Origin of Species. Therein, not only zoologists, botanists and geologists, but physicists, chemists, anthropologists, psychologists, sociologists, philologists, historians—and even politicians and theologians—are found testifying to the important part which Darwin's great work has played, in revolutionising ideas and moulding thought in connexion with all branches of knowledge and speculation.