Life Cycle of Hydatina Senta 



331 



In the first part of the experiment there is a markedly lower 

 percentage of male-producers among those reared in the drainage 

 water. In the second part, the difference is in the same direction 

 but is slight. It should be noted that a similar line in Experi- 

 ment I, derived from a sister to the parents of the two lines 

 in this experiment, and fed on the same food without drainage 

 water, yielded 60.9 per cent of male-producers from June 30 to 

 July 13, and 30.1 per cent from July 13 to July 19. That decrease 

 in the proportion of male-producers finds a parallel in the left 

 side of Table VIII, but not in the right side. 



TABLE VIII 



Showinglhe number of male- and female-producers in the progeny of two sister individuals of Hydatina senta 

 one of which was reared in dilute drainage, the other in pure spring zvater. The left side of the table is 

 the record of one continuous line, even after the conditions are reversed. 



Total. 



Dilute Drain.^ge 



Pure Water 



July 14 



15 

 16 



34 



14 



33 

 39 

 IS 

 40 



33-4 



July 14 



IS 

 16 



16 



2 



30 

 21 



IS 



23 

 42 



29 



37 



55-7 



