LAMARCK 



the most distinguished botanists and pahieontologists 

 of his time; he had been professor of invertebrate 

 zoology in Paris for many years, and had, in fact, 

 created the science of those lower forms of animals 

 which are especially valuable to the theory of evo- 

 lution. And finally, he draws on this immense and 

 varied store of information to confirm his theory of 

 evolution. Surely there are few cases of more perfect 

 induction. 



If we turn to the development of Darwin's theory 

 we shall encounter an unusually clear example of de- 

 duction. As a youth of twenty-three years, Darwin, 

 who was practically untrained as a biologist or ge- 

 ologist, takes his trip on the Beagle. During the five 

 years of this voyage he collects specimens of the rocks 

 and the fauna and flora of southern lands and waters. 

 He reads Lyell's geology with great care and becomes 

 a convert to this uniformitarian doctrine; he also 

 notes the biological and geological relations between 

 the continent of South America and the islands of the 

 Pacific Ocean and is struck with the changes which 

 the habitat produces on both flora and fauna. He un- 

 doubtedly loses his faith in special creation and 

 adopts a tentative belief in variation, in accordance 

 with the ideas of Lyell. After his return, he quickly 

 becomes a convinced evolutionist. At the age of twen- 

 ty-eight he opens his first note-book on variation 

 caused by natural selection. After many efforts to 

 find a cause for evolution, he suddenly obtains his 



C 167 1 



