Life Cycle of Hydatina Senta 



319 



TABLE I Continued 



EXPERIMENTS 



Normal Course of Parthenogenetic Series 



Experiment I. A stock of rotifers had been brought into the 

 laboratory about the middle of May and there multiphed rapidly. 

 After being kept in a dish for about four days, the rotifers were 

 nearly all dead, but many winter eggs had been laid. The culture 

 was then placed in a refrigerator at a temperature, of 10° to 14° C. 

 until June 26, excepting three days from June 16 to 19. On June 

 26 it was brought to room temperature, and on June 27 a young 

 female was isolated from it. From this female was bred a series 

 of 81 generations under what seemed to be the best obtainable 

 conditions. The first member of each family became, when 

 possible, the parent of the next generation. Usually only one 

 family was reared in each generation. 



The purpose of this experiment was to ascertain the nature of 

 the fluctuations in percentage of male-producers, which might 

 occur without intentional alteration of the conditions by the 

 experimenter. The results are shown in Table I. 



