186 



HEREDITY AND SEX 



crop of male eggs that develop into males without 

 being fertilized at all. 



There are several facts of unusual interest in the 



HYDAT/MA SEMTA 



Male 



FIG. 95. Life cycle of Hydatina senta. 



life history of hydatina, but we have occasion to consider 

 only one of them. It has been claimed in this case 

 also that external conditions determine the production 

 of males. A more striking example of the erroneous- 



