ing upon each species its immutable characters."
As early as 1755, however, Buffon found that his studies in comparative anatomy placed many difficulties in the way of these "simple but beautiful laws" and "immutable characters." He calls attention to the fact that the pig is plainly the "compound of other animals," possessing many parts for which it has no use, and concludes that "Nature is far from subjecting herself to final causes in the formation of her creatures," and that by continually searching for such causes men "deprive philosophy of its true character, and misrepresent its object, which consists in the knowledge of the 'how' of things." In 1761 he acknowledged a belief in the frequent modification of species, but believed that some animals were much more subject to variation than others. He understood the struggle for existence, with its consequent elimination of the species least capable of living under unfavorable circumstances, and stated it very clearly.
One of the most interesting portions of Buffon's evolutionary philosophy was his belief that external conditions could directly modify the structure of animals and plants, and that these modifications were hereditary. This was, in essence, the theory of transmission of acquired characters—a theory which was to be greatly elaborated by one of Buffon's successors, and which was to cause trouble among evolutionists for many decades. Buffon applied it particularly to the animals of the western hem-
