THE SELECTING POWER OF ENEMIES 49 



differentiation of the specific environment is 

 the only possible cause of secondary sexual 

 characters, as this volume attempts to show. 

 Although other theories, as for instance 

 Darwin's theory of Sexual Selection, attempt 

 to account for these structural differences 

 in other ways. Also, in polymorphic species, 

 the environment becomes similarly split up. 



FIG. 4. 



O. 



FIG. 5. 



It has been seen that the specific environ- 

 ment is curtailed by the limit of the ability 

 of the species to adapt itself to the diversities 

 of the factors which form its environment. 

 This property is common to all living matter, 

 and without it Life, as we know it, could not 

 exist. If living matter could not thus accom- 

 modate itself but could only occupy a homo- 



D 



