THE DETERMINATION OF SEX 631 



the ovum is large, well supplied with nourishment, and not 

 given to activity ; while the sperm plasm, spermatozoon, or 

 pollen grain, is small, and poor in food material, but character- 

 ized by great activity. 



Aside from this, males and females differ far less than is 

 popularly supposed. The artificial conventionalities and the es- 

 tablished divisions of labor exaggerate differences of sex in man, 

 and over-enthusiastic writers have formed out of these exaggera- 

 tions conclusions as far-reaching as they are grotesque. 



Sex differences are few and slight, and mostly connected with 

 the serious business of reproduction. We need not, therefore, 

 in seeking causes for their determination, look for such as strike 

 at the very foundation of racial characters. Sex is something 

 superimposed upon all other considerations not a fundamental 

 division halving the population into one section that may, and 

 another that may not, enter into the full possession of all the 

 endowments of the race. 



SECTION II INFLUENCE OF NUTRITION 



In tadpoles. According to Pfliiger, 1 three forms develop : 

 (a) distinct males, (b] distinct females, and (c) hermaphrodites. 

 In the last case the male organs " develop round primitive 

 ovaries, and if the tadpoles are to become males the inclosed 

 female organs are absorbed." 



According to Young, 2 sex in tadpoles remains a long time 

 indeterminate, and during this time the amount of food exerts 

 a controlling influence upon the sex. He had three broods of 

 tadpoles. 



Brood i, under natural conditions, developed 54 per cent 

 females, but when fed freely with beef it developed females in 

 the proportion of 78 per cent; the proportion of females from 

 brood 2 was increased by a generous diet of fish, from 61 per 

 cent to 8 1 per cent ; and in the same way a diet of frogs' flesh 

 raised the proportion in brood 3 from 56 per cent when "left 

 alone " to 92 per cent when fed, all of which looks as though 

 nutrition has some influence upon sex in frogs at least. 



1 Geddes and Thomson, The Evolution of Sex, p. 45. 2 Ibid. 



