90 EVOLUTION 



Birds and sluggish Reptiles, we read alter- 

 natives or antitheses between activity and 

 passivity, between liberal expenditure of 

 energy and a more conservative habit of 

 storing. This primarily depends on the 

 ratio between disruptive (katabolic) processes 

 and constructive (anabolic) processes, and 

 we regard the sexes as expressions of the 

 same contrast within a given species. And 

 do not kindred yet contrasted forms, like 

 goat and sheep, wasp and bee, butterfly and 

 moth, seem as it were but the extreme ex- 

 pression of the same individual and sex 

 contrasts carried farther, upon the plane of 

 species, of genus, of order, or of class .^ 



According to this view the deep constitu- 

 tional difference between the male and the 

 female organism, which makes of the one a 

 sperm-producer and of the other an egg-pro- 

 ducer, is due to an initial difference in the 

 balance of chemical changes. The female 

 seems to be relatively the more construc- 

 tive, whence her greater capacity for organic 

 sacrifices in maternity; the male relatively 

 the more disruptive, whence his usually more 

 vivid life, his explosive energies in action. 

 In short, the sexes express a fundamental 

 difference in the rhythm of metabolism. 



This initial difference not only leads to the 

 primary functional distinction between male 



