THEORY OF SEX-DIMORPHISM 79 



Another physiological theory was put for- 

 ward by the authors in 1889 in The Evolution 

 of Sex, where it was maintained that the deep 

 constitutional difference between the male 

 and the female organism, which makes of the 

 one a sperm-producer and of the other an 

 egg-producer, is due to an initial difference 

 in the balance or rhythm of chemical changes. 

 That is to say, the two sexes differ funda- 

 mentally in the life-ratio of anabolic to 

 katabolic changes. In the female, the balance 

 of income and outlay, of constructive to 

 disruptive changes, is the more favourable 

 one ; the anabolic process tends to have 

 relative preponderance, and this profit may 

 be devoted to growth, and towards offspring, 

 in producing which she hence can afford to 

 bear the larger share. In short, the life-ratio 



of anabolic to katabolic changes, -, in the 



K 



female is normally greater than the corre- 

 sponding life-ratio, , in the male of the same 



K. 



species. Now it would be crude to suppose 

 that structures like yolk-glands or milk-glands 

 are the direct outcome of the relatively greater 

 anabolism of the female. Nor can greater 

 exuberance of integumentary structures and 

 more abundance of pigmentation in them 

 be regarded as the necessary outcome of the 

 relatively katabolic male constitution. But 

 it may be that masculine and feminine 

 secondary sex-characters are on the whole 

 congruent with the kind of constitution which 

 implies maleness and femaleness respectively. 

 Whether a character in the germinal inherit- 



