INFLUENCE OF ENVIRONMENT 339 



the doctrine of the inheritance of acquired 

 characters, there are many special difficulties. 

 There is no conclusive and satisfactory evi- 

 dence in favor of such inheritance. Almost all 

 the evidence adduced serves to show only that 

 characters are acquired, not that these charac- 

 ters are inherited. 



It is a matter of common observation that 

 mutilations are not inherited; wooden legs do 

 not run in families, although wooden heads do. 

 The evidence for the inheritance of peculiari- 

 ties due to excessive use or disuse is wholly in- 

 conclusive, and in general the same may be 

 said of any special character due to abnormal 

 nutrition. That unusual conditions of food, 

 temperature, moisture, etc., may affect the 

 germs of future generations so as to produce 

 general and indefinite variations is very prob- 

 able, but this is a very different thing from the 

 inheritance of acquired characters. The germ 

 cells being a part of the parental organism 

 may be modified by such changes in the en- 

 vironment as affect the body as a whole, they 

 may be well nourished or starved, they may be 

 modified by changed conditions of gravity, 



