FACTORS OF EVOLUTION 229 



" We may rest assured that the execution of experi- 

 ments will cause a great number of questions to arise, 

 of which we can at present have no idea. This is one 

 of the great advantages of experiment. If we do not 

 always find what we are seeking after, while starting 

 from hypotheses which the facts do not support, we 

 often find what we were not looking for, and light is 

 thus cast on regions which till then seemed buried in 

 complete darkness." 



This I consider as exactly true, and many unexpect- 

 ed questions will certainly turn up of which we have 

 no idea, while answers to others may also be found. 

 But, if it is impossible to state exactly what will be 

 done, we may at least gather some idea of the principal 

 methods and hints of experimental transformism. 



The methods first. 



What can the methods of experimental trans- 

 formism be ? The only answer to this question is 

 based on the consideration of what the Factors of 

 Evolution are or are supposed to be. At the present 

 moment five are usually recognised. 1 I quote from 

 Le Contc's able paper of recent date : 



" First. Presence of a changing environment affect- 

 ing functions, and functions affecting structure, and the 

 changed structure and function inherited and integ- 

 rated through successive generations indefinitely. 



1 Cf. Herbert Spencer's Factors of Organic Evolution, and Le Conte's 

 The Factors of Evolution in The Monist, April, 1891. 



