THE THEORY 11 



3. Individuals differ widely in structure : 

 male from female, young from old. 



4. Correlation of these three facts : unequal 

 value with difference of structure, and both 

 with the formation of societies. 



Sequence of argument : 



1. Natural Selection must appreciate differ- 

 ences in structure ; 



2. Natural Selection must treat associations 

 as units ; 



3. And bring about diversity of structure 

 in them ; 



4. Which structures control Natural Selec- 

 tion, so that less valuable individuals are more 

 liable to be destroyed than more valuable. 



Thus when male is found to be different 

 from female it is necessary to inquire whether 

 the difference be due to (1) a character of 

 the individual which fits a monosexual en- 

 vironment, or (2) a character of the pair, also 

 of cause an environmental character, that 

 controls Natural Selection. And so with all 

 structures occurring in sociable animals and 

 confined to particular individuals. 



Thus it is as a working hypothesis that this 

 new theory is brought forward, in the hope 

 that it may possibly explain the origin and 

 use of some polymorphisms. 



