I9II] 



A. Franklin Shull 



183 



known, however, for the food cultures were of varying alkalinity; 

 and, because the protozoa in them were not always equally abun- 

 dant, a variable quantity of the cultures was necessarily used. 

 Before adding food to the dishes, the three Solutions used were 

 respectively n/200 NaOH, neutral (distilled water), and M/300 

 HCl. After adding food, the acid Solution was practically neutral 

 or faintly alkaline, while the alkalinity of the other two Solutions 



TABLE 6. 



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

 sister individuals of Hydatina senta, one line being bred in Great Bear spring 

 water, a second in water less alkaline, and the third in zvater more alkaline, than 

 Great Bear water. 



was slightly altered. In Table 7 the columns are designated accord- 

 ing to the acidity or alkalinity of the Solutions before adding food 

 but it should be remembered that an actually acid Solution was 

 never used. 



While the highest percentage of male-producers is found as 

 before in the lowest degree of alkalinity, there is not the regulär 

 decrease in the proportion of male-producers with increase of alka- 

 linity, such as was seen in the preceding experiment. As it would 

 not be practicable to rear the rotifers in much more alkaline water, 

 all that we may safely conclude is that if alkalinity influences the 

 Proportion of male-producers it does so to only a small extent. 



