Deternn nation of Sex, in Hydatina senta 



II 



duce about an equal number, 40 to 50 each, but the following 

 experiments will show the error of this assumption. 



1 Temperature 20° to 22'^ C. 



Experiment IV, November 5. Of 13 sister individuals kept 

 at room temperature and with the same amount of food 6 pro- 

 duced male eggs and 7 produced female eggs. The average num- 

 ber of eggs produced by each female was nearly the same. The 

 results are shown in Table V. 



2 Temperature 2^° to 2g° C. 



Experiment V, November 9. Three lots of sister-individuals 

 from three different mother-individuals were kept in an incubator 



TABLE VI 



Record of the number of eggs laid by ii sisters, of which 6 were male-laying and 5 were female-laying, 

 showing that the average number of eggs produced by the male-laying females is about two times as 

 great as the average number produced by the female-laying females. 



Temperature 24° to 2J° C. 

 II sisters 



and the number and sex character of the eggs that each produced 

 was very carefully noted. The results are shown in Tables VI, 

 VII and VIII. The records of the individuals in Tables VI and 

 VII were taken at the same temperature of 24° to 25° C. while 

 those of Table VIII were taken at a higher temperature of 26° 

 to 29° C. 



These tables show a decided change in the ratio between the 

 number of eggs produced by a male-laying female and a female- 

 laying female. As the temperature is raised the female-laying 



