THE CONTROL OF SEX BY FOOD IN FIVE SPECIES 



OF ROTIFERS 



DAVID DAY WHITNEY 



Biological Laboratory, Wesleyan University, Middletown, Conn. 



SIX FIGURES 



It has been shown in the American and English rotifer, Hy- 

 datina senta, that food conditions are the controlUng factors 

 in regulating the parthenogenetic production of the two sexes. 

 When the parthenogenetic females were fed upon a diet of the 

 colorless flagellate, Polytoma, they produced female-producing 

 daughters exclusively even through a period of twenty-two months 

 and extending through many scores of generations. However, 

 when the parthenogenetic females were suddenly transferred 

 from the Polytoma diet to a diet of the green flagellate, Chlamydo- 

 monas pulvisculus, they produced in many instances as high as 

 80 per cent, or higher, of male-producing daughters within a few 

 hours. In a few selected experiments the percentage of male- 

 producing daughters reached 100 per cent when the diet of color- 

 less Polytoma was suddenly changed to a diet of the green 

 Chlamydomonas. 



. If the production of the sexes can be regulated in this rotifer 

 by the diet it is of considerable interest to know whether the 

 diet can regulate the production of the sexes in other species of 

 rotifers. Furthermore, it is quite important to determine 

 whether it was the stimulus produced by the change of food from 

 the Polytoma to the Chlamydomonas diet that caused the male- 

 producing daughters to be suddenly produced or whether it 

 was a sufficient quantity of more easily assimilated food that 

 changed the mechanism of the daughters from female to male- 

 producers, or perhaps some other factor. 



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