

HEREDITY AND SEX 191 



The differences are not large and the number of observa- 

 tions are entirely too few to justify any sweeping conclu- 

 sions. Steida 1 and Berner found no relation between 

 age and the sex of offspring. The evidence of the in- 

 fluence of age on the sex of offspring is too conflicting to 

 be conclusive. 



181. Comparative vigor or sexual superiority. Vari- 

 ous authorities have attempted to explain the proportion 

 of sexes on the theory that the sex of the offspring will 

 correspond to that of the more vigorous or " superior " 

 parent. Darwin, Richarz, Hough and others regarded 

 the male as to a certain extent a superior organization, 

 and male offspring would result when the reproductive 

 functions of the mother were particularly well developed. 

 The evidence available is not sufficient to give this hypoth- 

 esis any particular importance in practical breeding. 



182. Nutrition and sex. That the nutritive condition 

 of the parents, particularly the mother, at the time of 

 fertilization and before has a preponderating influence 

 on the sex of offspring has been long believed. Yung 

 found that under certain conditions regarded as normal, 

 the proportion of sexes in tadpoles was about 57 females 

 to 100 males. By feeding the tadpoles beef, fish and 

 frog's flesh, the percentage of females enormously in- 

 creased, being in one case 92 females to 8 males. An 

 interesting case illustrating the connection of nutrition 

 and sex is found in bees. The swarm of bees is composed 

 of workers (imperfect females), drones (males) and the 

 queen (a perfect female). The drones are hatched from 

 unfertilized eggs. The queen and workers are developed 

 from fertilized eggs, but perform a very different role in 

 life. The queen becomes the mother of new generations, 



1 Ibid. 



