Darwin’s work, the _Origin of Species_, was published on November 24, 1859, after twenty-five years of study. He kept the theory of selection to himself for more than twenty years. The whole of the young generation from the beginning of the thirties, to which Haeckel belonged, grew up without any suspicion of it. Apart from the constant ill-health that hindered his work, Darwin was tortured with anxiety lest he should be treated as an imaginative _dilettante_ with his heretical ideas. In the scientific circles of the middle of the century one was apt to be disdainfully put down as a windy “natural philosopher” if one spoke of “the evolution of animal and plant species” and the like. The word had become the scarecrow of the exact, professional scientific workers; much as when commercial men exclaim, “Dear me, the man’s a poet.” Hence Darwin wanted to provide a most solid foundation of research for his work, and then to smuggle it into the house like a goblin in a jar. He took his task so seriously that, as Lyell afterwards wrote to him, he might have worked on until his hundredth year without ever being ready in the sense he wished. Chance had to intervene, and bring forward one of the younger men, who almost robbed him of the title of discoverer. Wallace arrived independently at the idea of selection, and he was within a hair’s breadth of being the first to publish it. The aged scholar at Down had to come forward. Then the great book was published, and Wallace disappeared in its shadow. In Darwin’s opinion it was only a preliminary extract, and he added many supplementary volumes as time went on. As a fact it was so severely elaborated that even the thoughtful layman, possibly with a sympathy for the idea, was almost, if not wholly, unable to digest the proofs. It had to be “translated” for the majority of Darwin’s educated countrymen. On the other hand, this mass of facts was partly strange and new to the professional biologists. What did so many of the museum-zoologists know, for instance, of the results and problems of the practical breeder? “That belongs to the province of my colleague who teaches agriculture, not to mine.” His proofs were taken indiscriminately from zoology, botany, and geology. But at that time it was woe to the man that mixed up the various branches of research. The professor of zoology could not control the botanical material, and _vice versâ_. There was, in addition, the general dislike of the natural-philosophical nucleus. It was impossible to suppose that this very individual book, transgressing every rule, should at once meet with wide encouragement, or even ordinary appreciation.