64 THE SURVIVAL OF THE UNLIKE. [ll. 



orif;iiiating in the body of the organism cannot be trans- 

 mitted. The exact means or machinery through which 

 he supposes heredity to act is rather more an embryo - 

 logical matter than a philosophical one. We are partic- 

 ularly concerned in its results, which are the distinguish- 

 ing marks of Neo - Darwinism — that variation is of sex- 

 ual or internal origin, and that acquired characters are 

 not hereditary. 



In opposition to this body of belief, which has been 

 upheld, particularly in England, with much aggressive- 

 ness, is Neo-Lamarckism, which is a compound of both 

 Lamarckism and Darwinism, and which has an especially 

 strong following in North America. The particular 

 aanons of this philosophy are the belief that external 

 causes, or the environment, are directly responsible for 

 much variation, and that acquired characters are often 

 hereditary. Other features of it, held in varying degrees 

 by different persons, are the belief in the transforming 

 effects of use and disuse, and in natural selection. 



The one great schism between the Neo -Darwinians 

 and the Neo-Lamarckians is the controversy over the 

 hereditability of acquired characters, and just at present 

 this question has come so strongly to the fore that other 

 differences in the two hypotheses have been obscured. 

 It is worthy of remark that Darwinism and Neo-La- 

 marckism see first the facts or phenomena and then try 

 to explain then; while Neo-Darwinism or Weismannism 

 assumes first a hypothesis and then tries to prove it. I 

 think that any one will be struck with this difference of 

 attitude, if he read Darwin's chapter upon pangenesis, 

 and then read Weismann's essay upon heredity. The 

 Neo -Darwinians are loud in demand of facts or proofs 

 that acquired characters are hereditary, and they attempt 



