1 8 A STUDY IN HEREDITY 



evolution cannot result in many directions without 

 exterminating the species, evolution during given 

 time is limited to but a few directions. We have, 

 therefore, only to note the principal causes of the 

 death-rate to discover the actual lines of evolu- 

 tion. 



The Lamarckian doctrine is very different. 

 According to it, every beneficial agency, acting on 

 a species, causes evolution ; every injurious agency 

 degeneration ; and, therefore, evolution proceeds in 

 the higher plants and animals on lines of enormous 

 complexity. Here again the Lamarckian and the 

 Neo- Darwinian doctrines are in violent contrast. 



I have said that no sane man can doubt the 

 reality of evolution. We may now go further and 

 declare that it is not possible for any sane man to 

 withhold a limited adherence to Darwin's explana- 

 tion of it. The proofs furnished by breeders are 

 too conclusive. It is quite beyond dispute that 

 offspring differ innately from their parents, that 

 these innate differences, these " variations," are 

 ransmissible to descendants, and that, if advantage 

 be taken of them by selecting for breeding purposes 

 the superior individuals, while the rest are elimin- 

 ated, evolution will result. The only point we have 

 yet to prove is that Nature like the breeder exercises 

 the necessary selection. At first sight Lamarck's 

 doctrine also seems true. Thus it appears only 



