114 DOCTRINE OF EVOLUTION 



to environmental influences and before it begins to 

 use its various organs. For example, it is a matter of 

 common observation that a child with light hair and 

 blue eyes may have dark-eyed and brown-haired 

 parents. The fact of difference is a phenomenon of 

 variation ; the causes for this fact cannot be found 

 in any other category than that comprising the 

 hereditary and congenital influences of parent upon 

 offspring. How the effect is produced by such causes 

 is less important in the present connection than the 

 natural fact of congenital variation. Science, however, 

 has learned much about the causes in question, as we 

 shall see at a later point. 



Thus the first step which is necessary for an 

 evolution and transformation of organic mechanisms 

 proves to be entirely natural when we give only 

 passing attention to certain obvious phenomena of 

 life. The fact of "becoming different" cannot be 

 questioned without indicting our powers of observa- 

 tion, and we must believe in it on account of its 

 reality, even though the ultimate analysis of the way 

 variations of different kinds are produced remains for 

 the future. 



Having learned that animals are able to change in 

 various ways, the next question is whether variations 

 can be transmitted to future generations through the 

 operation of secondary factors. Long ago Buffon 

 held that the direct effects of the environment are im- 

 mediately heritable, although the mode of this in- 

 heritance was not described; it was simply assumed 

 and taken for granted. Thus the darker color of the 

 skin of tropical human races would be viewed by Buffon 



