Lamarckism

Charles Darwin made use of Lamarck's thesis of the "transmission of acquired traits" as a factor giving rise to evolution. (See Lamarck, Jean B.)

Gordon Rattray Taylor, a researcher and proponent of evolution, described Lamarckism in his book The Great Evolution Mystery, and explained why Darwin was so heavily influenced by it: 

Lamarckism is known as the inheritance of acquired characteristics . . . Darwin himself, as a matter of fact, was inclined to believe that such inheritance occurred and cited the reported case of a man who had lost his fingers and bred sons without fingers . . . [Darwin] had not, he said, gained a single idea from Lamarck. This was doubly ironical, for Darwin repeatedly toyed with the idea of the inheritance of acquired characteristics and, if it is so dreadful, it is Darwin who should be denigrated rather than Lamarck. . . In the 1859 edition of his work, Darwin refers to ‘changes of external conditions' causing variation but subsequently these conditions are described as directing variation and cooperating with natural selection in directing it. . . Every year he attributed more and more to the agency of use or disuse. . . By 1868, when he published Varieties of Animals and Plants under Domestication,he gave a whole series of examples of supposed Lamarckian inheritance: such as a man losing part of his little finger and all his sons being born with deformed little fingers and boys born with foreskins much reduced in length as a result of generations of circumcision.15

15. Gordon Rattray Taylor, The Great Evolution Mystery, London: Abacus, 1984, pp. 36-41.