THE DARWINIAN THEORY 9 



they have arisen are very different, but there is 

 sufficient analogy to justify the inference that 

 the wild forms also, which arose without man's 

 interference and of which he has never had the 

 chance of observing the development, had a 

 similar origin, by descent with modification, 

 from older types, these again from still older, 

 and so on, further and further back into the past. 

 This line of argument is due to Darwin, who 

 first taught the world to believe in Evolution, 

 though the idea is perhaps as old as human 

 thought. Darwin used these words: "At the 

 commencement of my observations it seemed to 

 me probable that a careful study of domesti- 

 cated animals and cultivated plants would offer 

 the best chance of making out this obscure 

 problem. Nor have I been disappointed. . . . 

 I have invariably found that our knowledge, im- 

 perfect though it be, of variation under domesti- 

 cation, afforded the best and safest clue" (Origin 

 of Species, p. 3) . 



Important chapters in the Origin of Species 

 are devoted to this subject, which was worked 

 out fully in Darwin's later book on Animals and 

 Plants under Domestication. 



The Darwinian theory is not only a state- 

 ment of Evolution, it involves an explanation 

 of Evolution, and without this explanation 

 Darwin's work would not have carried convic- 



