PRODUCTION OF MALES AND FEMALES. 45 



the percentages of male-producing females in Table III. are 

 somewhat lower than those in Table II. However, both tables 

 show that a continuous and uniform diet of Polytoma causes only 

 female-producing daughters to be produced while a sudden 

 change of the food from Polytoma to Chlamydomonas causes 

 male-producing daughters to be produced in great numbers. 



SUMMARY. 



1. A uniform diet of the colorless protozoan flagellate, Poly- 

 toma, continued for 22 months through 288 generations prac- 

 tically suppressed the production of males and caused only 

 females to be produced in the rotifer, Hydatina senta. 



2. After the adult females had been transferred from the diet 

 of Polytoma to the diet of Chlamydomonas for 12 hours they 

 produced a higher percentage of male-producing daughters than 

 they did during these 12 hours. 



3. The sudden change of food from a constant diet of Polytoma 

 to a diet of the green Chlamydomonas caused male-producing 

 daughters to be produced in the English Hydatina senta about 

 as readily as in the New Jersey Hydatina senta. 



BIOLOGICAL LABORATORY, 

 WESLEYAN UNIVERSITY, 



MlDDLETOWN, CONN. 



