HEEEDITY AND SEX 



it is highly improbable that the breeder will 

 ever be able to control sex. Male and female 

 zygotes should forever continue to be produced 

 in approximate equality, and consistent inequal- 

 ity of male and female births could result only 

 from greater mortality on the part of one sort 

 of zygote than of the other. Only in partheno- 

 genesis can man at will control sex, and until 

 he can produce artificial parthenogenesis in the 

 higher animals, he can scarcely hope to con- 

 trol sex in such animals. 



Negative as are the results of our study of sex- 

 control, they are perhaps not wholly without 

 practical value. It is something to know our 

 limitations. We may thus save time from 

 useless attempts at controlling what is uncon- 

 trollable and devote it to more profitable em- 

 ployments. 



BIBLIOGRAPHY 



Bateson, W. 



1909. (See Bibliography to Chapter IV.) 



Castle, W. E. 



1909. "A Mendelian View of Sex-heredity." Science, 

 N. S., vol. 29, pp. 395^00. 



Cu^NOT, L. 



1900. "Sur la determination du s6xe chez les animaux." 

 Bull. Sci. de la France et de la Belgique. 



13 181 



