HEREDITY AND SEX 



Nevertheless an argtunent for the artificial con- 

 trol of sex based on such evidence is from time 

 to time brought forward, as, for example, a 

 few years since by Schenk. The latest advocate 

 of sex-control by artificial means is an Italian, 

 Russo (1909). He claims in the case of rabbits 

 that by feeding the mother on lecithin or by 

 injections of lecithin, the proportion of female 

 births may be increased. His evidence in sup- 

 port of this claim is, however, wholly inade- 

 quate, and two independent repetitions of his 

 experiments, made by Basile in Italy and by 

 Punnett in England, have given entirely nega- 

 tive results. 



An alternative hypothesis concerning the de- 

 termination of sex has been steadily gaining 

 ground during the last ten years, that sex has 

 its beginning in gametic differentiation and is 

 finally determined beyond recall in the ferti- 

 lized egg by the nature of the uniting gametes. 

 Instructive in this connection is a study of 

 parthenogenesis, — reproduction by unfertilized 

 eggs. But before entering upon this, it may 

 be well to review briefly the changes which 

 regularly take place in the egg which is to be 



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