CH. XXI] AND THE MUTATION THEORY 227 



later periods during the wandering of the new forms, when un- 

 expectedly they arrive in environments specially fitted for them. 



The usual phrase, that species are adapted to their environ- 

 ment, should therefore be read inversely, stating that most 

 species are now found to live under conditions fit for them. The 

 adaptation is not on the side of the species, but on that of the 

 environment. In a popular way we could say that in the long 

 run species choose their best environment. Favourable local 

 conditions induce a rapid multiplication, whereas elsewhere the 

 forms remain rare, or are seen to disappear slowly. 



The general belief in adaptation as one of the chief causes of 

 the evolution of specific characters is thus directly contradicted 

 by the statistical studies of Willis, which are independent of all 

 personal appreciation or estimation of a supposed value. This 

 result must be considered as the one great proof, which the 

 mutation theory still wanted for its acceptance in the field of 

 systematic zoology and botany. 



15—2 



