190 



Life Cycle of Hydatina Senta 



[Dec. 



some of the eggs laid in the creatin Solution did not hatch in the 

 usual short time reqnired in spring water. In such cases the creatin 



TABLE 13. 



Showing the number of male- and female-producers in the progeny of three 

 sister individuals of Hydatina senta, one line being bred in spring water, the other 

 two in creatin Solutions of different strengths. 



was diluted after the death of the parent, and many of the eggs 

 then hatched. Table 14 presents the details of the experiments. 

 In both of these tables the same result appears, that is, a lower 

 percentage of male-producers in the creatin Solution than in spring 

 water, and a lower percentage in the stronger Solution than in the 

 weaker. The differences are as great as were those of the beef 

 extract, and are too marked to leave any doubt regarding the influ- 

 ence of creatin. 



III. SUMMARY AND CONCLUSIONS 



From the results of the foregoing experiments it seems clear that 

 certain chemical Compounds in the water may greatly modify the 



*Remainder of family not recorded. 



