INTRODUCTION 23 



identical with one of a previous generation, it will 

 be identical with its ancestor only if it encounters 

 an identical environment. If the environment 

 undergoes fluctuation, the individuals of succes- 

 sive generations will differ. But since we have 

 never been able to witness such a change, the ques- 

 tion still confronts us : can such variable responses 

 bring about a change in the mass of individuals 

 which constitute a species, beyond the initial range 

 of variation? Logically, since the species is the 

 sum of all its individuals, this must depend upon 

 the ability of individual heritages to pass beyond 

 the bounds of previous possibilities. What occurs 

 in the individual belongs to the species, regardless 

 of whether it belongs to all other individuals or not. 



In view of these indubitable facts it is not strange 

 that the acquisition by species of the adaptations 

 which appear in individuals in response to the 

 environment was long taken for granted. The idea 

 is exceedingly plausible. Nevertheless the investi- 

 gations of biologists have continued negative. We 

 still do not know with absolute certainty what is 

 the relation of individual adaptations to the char- 

 acters of species. 



In pursuing an inquiry into this subject, it is 

 possible to find some precedent for a method of 

 treatment. The sources of the antagonistic points 

 of view are generally regarded as Lamarck's and 

 Darwin's theories of evolutionary method, the one 



