130 



A. FRANKLIN SHULL 



to the air. A /^ solution of HCl was made up by titration against 

 the NaOH solution immediately after the latter was prepared, 

 and was kept in stock. Three grades of alkalinity were used 

 in the experiment, the solutions being prepared as follows : Great 

 Bear spring water, which is itself alkaline, was used unaltered in 

 one line; for the second line, the /o NaOH solution was diluted to 

 ten times its volume with Great Bear water; for the third line, the 

 /s HCl solution was diluted to forty times its volume with Great 

 Bear water. The alkalinity of the Great Bear water was not 



TABLE 25 



Showing number of male- arid female-producers in the progeny of three sister indi- 

 viduals of Hydatina senta, one line being bred in Great Bear spring water, one in 

 water less alkaline, and the third in water more alkaline, than Great Bear water. 



accurately determined, but was less than /g, so that addition of 

 /o NaOH increased its alkalinity ; neither was the alkalinity of the 

 diluted solutions known. As it was necessary to expose the NaOH 

 solution to the air while it was being used, the dilute solution was 

 made up daily. The data from this experiment are given in table 

 25, where the alkalinity increases from left to right. 



From this experiment it would seem that the greater the alka- 

 linity the fewer the male-producers, but the differences are too 

 small to draw a safe conclusion from one experiment. 



