LIFE CYCLE OF HYDATINA SENTA 137 



Experiment XXVIII. Two sister females were isolated June 

 23, 1910, from one of the other experiments being performed at 

 that time. One was placed in a solution of Liebig's beef extract, 

 the other in spring water. The beef extract was dissolved in 

 spring water, and a 1 per cent solution kept in stock. This stock 

 solution was boiled once or twice a day to prevent the growth of 

 bacteria, and in the intervals was set in the cool water of a spring. 

 Loss by evaporation was restored with distilled water. The stock 

 solution was diluted with Great Bear spring water when ready to 

 be used. In the first experiment. A, table 30, a 0.03 per cent solu- 

 tion was used for the first two generations, a 0.04 per cent solu- 

 tion thereafter. In B, a female was removed from the line in 

 beef extract in A to spring water, so that here also the strength 

 of the beef extract is 0.04 per cent, the line in the extract being 

 the last part of the corresponding line in A. 



In both experiments there are considerably fewer male -pro- 

 ducers in the beef extract than in spring water. 



Experiment XXIX. The preceding experiment was repeated, 

 but this time two strengths of the extract were used, one a 0.04 

 per cent, the other a 0.05 per cent solution. Both lines are repre- 

 sented in table 31. The results of these repetitions agree closely 

 with the first experiment, even showing a smaller percentage of 

 male-producers in the stronger solution of the extract. There can 

 scarcely be any doubt that beef extract tends to reduce the pro- 

 portion of male-producers, and it seems quite possible that these 

 could even be wholly excluded by sufficiently strong solutions of 

 the extract. 



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 

 extractives 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. 



