igii] 



A. Franklin Shull 



189 



TABLE 12. 



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

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

 two in Solutions of beef extract of different strengths. 



male-producers, and it seems quite possible that these could even 

 be wholly excluded by sufficiently strong Solutions of the extract. 



7. Influence of creatin on the percentage of male-producers. 

 The positive results from the beef extract in the experiments of 

 the preceding section suggested, among other things, that extrac- 

 tives may alter the proportion of male-producers. One of the 

 commoner extractives, creatin, was selected to put this matter to 

 the test. The creatin used in these experiments was not pure, but 

 contained an admixture of Creatinin. 



Experiment 30. From three sister females, three lines were 

 reared, starting on July 18, 1910. One line was reared in a 0.02 

 per Cent. Solution of the crude creatin in Great Bear spring water, 

 one in a 0.025 per cent. Solution, the third in spring water alone. 

 Table 13 shows the three pure lines in detail. 



Experiment 31. This is a repetition of Experiment 30, but 

 with weaker Solutions of creatin in both parts, a o.oi per cent. and a 

 0.015 PS'* cent. Solution being used. In both of these experiments 



