of evolution. But in this we are to be disappointed. As soon as he departed from his principles of biology, and attempted to apply those principles to the development of animal life, Treviranus became victim to those same "dreams and visions" against which he protested so strongly. He depended very largely upon the work of Buffon, and believed that modification of form was due entirely to environment. He revived the ancient doctrine of spontaneous generation of living things, or abiogenesis, stating his belief very clearly.
All of this shows that Treviranus, although an ardent believer in evolution, added very little to the idea. In his ideas of the factors of volution he did not advance beyond Buffon; in his ideas of descent he was less clear and accurate than his contemporary, Lamarck. But in his more general work, particularly in defining and organizing the science of biology, he rendered great service to future zoologists and evolutionists. And such service, slight though it was, was of value. During the early part of the nineteenth century the doctrine of evolution needed all the support that could be given it, and even a mistaken scientist was a valuable defender of a struggling cause.
Thus for more than two thousand years the theory of organic evolution had been growing. Philosophers, country doctors, poets, and naturalists had contributed their share to its volume, its character, and its support. But as yet is was little more than an idea in the rough, waiting for some one to refine it, to put
