DARWINIAN ORGANIC EVOLUTION. 73 



The differences among animals of admit- 

 tedly the same race. 



The known effects of (a) selective breed- 

 ing, (b) the use or disuse of parts, and 

 (c) the direct action of external condi- 

 tions of existence. 



We propose first to define what we mean 

 by a " race," and then to examine in detail 

 the real meaning and significance of the 

 phenomena to which Darwin appeals, and 

 also the value of the arguments based on his 

 interpretation of these phenomena. 



