MALE-PRODUCTION IN HYDATINA 



153 



hours had already hatched. These females were transferred 

 to spring water at that time; in table 20 they are recorded as 

 'older daughters.' On the following day all the remaining eggs 



TABLE 20 



The parents were reared in strong manure solution, but in one-half of the experi- 

 ment this solution was saturated with an atmosphere 40 per cent of which was 

 oxygen. All offspring were reared in spring water. The oxygen approximately 

 doubled the proportion of male-prodUcers 



