The highly characteristic and instructive story of the incubation and writing of _The Origin of Species_ has been told by Darwin himself. He had been long haunted by the idea of a possible modification of species; and shortly after his return in the 'Beagle' he began to collect all facts bearing on the variation of animals and plants. His first note-book was opened in July, 1837. He read widely, conversed with breeders and gardeners, and addressed printed enquiries to such as seemed likely to give him information. He was led to the conclusion that 'selection was the keystone of man's success in making useful races of animals and plants;' but he could not understand how selection could be applied in a state of nature. The reading for amusement of Malthus on _Population_ gave him the clue. In the fierce competition for life among animals and plants, favourable variations would tend to be preserved, and unfavourable ones to be destroyed. He read Malthus in October, 1838. But, to avoid prejudice, for three years and a half, till June, 1842, he refrained from writing even the briefest sketch of his theory. In 1844 the first sketch was enlarged. In 1856 he began to write out his views on a scale much more extensive than that finally adopted; and yet, even so, it was only an abstract of the materials collected. In 1858 Mr. Wallace, then in the Malay Archipelago, sent Darwin an essay which proved to contain exactly his own theory. On the advice of Lyell and the great botanist Hooker an abstract from Darwin's manuscript was published in 1858, simultaneously with Mr. Wallace's essay. The concurrence of ideas between Mr. Wallace and himself set Darwin vigorously to work. He undertook once more to make an abstract of the manuscript begun in 1856, and in 1859 published the celebrated _Origin of Species_. The book owes much of its effect to this process of gradual expansion and gradual contraction. The reader is struck with three things in it: first, the great range, combined with sobriety, of speculation; secondly, the wonderful mastery of detail; and thirdly, the beautiful balance and proportion, the sufficiency without undue length of the arguments. Hardly any other pioneer in untravelled realms of thought has left such an impression of wholeness.[4] Neither could Darwin have done so without the long preliminary training. The _Origin_ bears on almost every page the marks that it too is a product of selection. Darwin sifts his mass of examples and chooses those best suited for his purpose. The completeness of the book moreover is largely owing to the fact, noted by Darwin himself, that for many years he had made a memorandum, at the moment, of every fact, observation or thought _opposed_ to his results; because he had found that such facts and thoughts were more apt to be forgotten than favourable ones. 'Owing to this habit,' he says, with truth, 'very few objections were raised against my views which I had not at least noticed and attempted to answer.'