4 Darwin, and after Darwin. 



less and walks more than the wild duck, and its limb bones 

 have become diminished and increased in a corresponding 

 manner in comparison with those of the wild duck. A horse is 

 trained to certain paces, and the colt inherits similar consensual 

 movements. The domesticated rabbit becomes tame from 

 close confinement ; the dog, intelligent from associating with 

 man ; the retriever is taught to fetch and carry ; and these 

 mental endowments and bodily powers are all inherited. 

 Nothing in the whole circuit of physiology is more wonderful. 

 How can the use or disuse of a particular limb or of the brain 

 affect a small aggregate of reproductive cells, seated in a distant 

 part of the body, in such a manner that the being developed 

 from these cells inherits the characters of either one or both 

 parents .? . . . In the chapters devoted to inheritance, it was 

 shown that a multitude of newly acquired characters, whether 

 injurious or beneficial, whether of the lowest or highest vital 

 importance, are often faithfully transmitted '." 



" When discussing special cases, Mr. Mivart passes over the 

 effects of the increased use and disuse of parts, which I have 

 always maintained to be highly important, and have treated in 

 my 'Variation under Domestication' at greater length than, 

 as I believe, any other writer '." 



So much for the matured opinion of Darwin touching 

 the vaUdity of the theory of use-inheritance. Turning 

 now to his opinion on the question whether or not 

 there are yet any further factors concerned in the 

 process of organic evolution, I think it will be sufficient 

 to quote a single passage from the Origin of Species. 

 The first paragraph of the " Conclusion " is devoted 

 to a rhumi of his views upon this matter, and con- 

 sists of the following most emphatic words. 



" I have now recapitulated the facts and considerations which 



have thoroughly convinced me that species have bfeen modified 



during a long course of descent. This has been effected chiefly 



through the natural selection of numerous successive, slight 



' Variation &c. ii. p. 367. ' Origin of Species, p. 176. 



