SEXUAL VARIATION 107 



thereof. Whilst among tadpoles left to themselves, 

 the females are in a slight majority, the proportion 

 increases from 54 to 78 per cent, when the 

 tadpoles are fed with beef, to 8 1 per cent, when fed 

 with fish, and, when fed with frog-flesh, to 92 per cent. 1 

 Thus food, and the nature of food, has much to do in 

 the determination of sex. The same is the case with 

 bees, where the production of queens, workers, and 

 drones is in great part a matter of nutrition. A 

 worker-larva may be reared into a queen, if royal food 

 is provided. Other facts show similarly that external 

 influence must be at work to operate in the deter- 

 mination of sex. Fisch has noted the sex of 66,327 

 plants of hemp, and he finds there are 154 female 

 against 100 male plants. Among other plants, such 

 as Spinacia oleracea and Ruinex acetosella, the 

 proportions vary much, as in some cases the one sex, 

 in others the other, is predominant. In the human 

 species males are constantly in slight excess over 

 females 105 against 100. The same condition 

 obtains among oxen, sheep, hogs, and domestic 

 birds. But in the case of the latter, the constancy 

 is less, and during some particular years there is 

 a very large number of individuals of one sex 

 against a small number of the other. There 



1 See Yung, Propos Scientijiques, 1890, Reinwald, Paris, quoted in 

 Evolution of Sex, P. Geddes and J. A. Thomson, Lond. , 1889. 



