Hilaire came quite independently to the conclusion that species were not permanent, and each offered some explanation of the process of change. Following them came Lamarck, a leader of the French anti-creationists, who published, between the years of 1800 and 1815, a series of books, whose great thesis was that every living thing, including man himself, was descended from some earlier, and in most cases simpler living thing. These books attracted much attention, especially because of the opposition which they aroused, and undoubtedly did much to prepare continental Europe for the coming of evolution.
Inasmuch as Lamarck was the foremost evolutionist to precede Darwin, it is worth while to know what influence he may have exerted, and what his ideas were. In the first place, he saw clearly that species were not distinct units, as the earlier naturalist has supposed. Instead, they were more or less artificial definitions, applied to animals and plants that constantly varied, and among which there often was almost perfect graduation from one group to another. In addition, Lamarck saw that the domesticated species were not constant, and could be changed at will, even though they maintained fairly uniform distinctions. In explaining changes in form, color, and so on, he supposed that there was a very close correlation between the characters of a plant or animal and the conditions of its life, the circumstances of crossing with other species, and by habits causing an increase or decrease of certain parts—all underlain by a universal tendency for perfection. According to Lamarck, the giraffe has
