THEORIES OF EVOLUTION 125 



new fields as nearly as possible like its old environ- 

 ment, but it is inconceivable that it could always 

 find exactly the same surroundings. In the latter, 

 if its powers of migration are great, the same result 

 may follow but otherwise it may be forced to avail 

 itself of other habitats in the same region. The 

 result is a variation of environmental stimuli which 

 must have an effect in the life of the organism. 

 Characters which previously served it in one way, 

 or failed to serve it to a considerable degree, may 

 take on a new importance in response to the new 

 conditions. These are the preadaptations of Cue- 

 not. What is their potency.^ May the new stimuli 

 provide for the appearance of new powers of re- 

 sponse and new development of the organs which 

 they call into use, or are they only a factor in 

 natural selection.^ 



There are valuable ideas in this material, in 

 spite of the fact that Darwinism has never been 

 free from attack. Weismann, himself an ardent 

 selectionist, admitted that the usefulness of early 

 stages in the development of organic structures 

 must be taken on faith. The weakness of the 

 selection theories in the explanation of degenera- 

 tion and overdevelopment of parts has already 

 been mentioned in connection with the theory of 

 germinal selection. More recently Cuenot ^ has 

 proposed several criticisms which seriously impugn 



® Archives de philosophie. Vol. VI, pp. 80-91, 1928. 



