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THE AMERICAN NATURALIST [Vol. L 



denly changed by the disappearance of an abundant diet or by 

 the rise or fall in the temperature male-producing females are 

 produced at once. In a few experiments very young females 

 (1-7 hours after hatching) were put from a high temperature 

 to a temperature of 9° C.-ll° C. and many of them developed • 

 into male-producers but whether this was due to the tempera- 

 ture or to some other factor was not known. 



Another fact of considerable interest was verified. It con- 

 cerned the nature of the male-producing females and the sexual 

 females (the females which produce fertilized eggs). It has 

 been observed by several investigators that if the small male eggs 

 of a male-producing female are fertilized, in a species of 

 Asplancha and Hydatina senta, they develop into the winter or 

 resting eggs. This was found to be true also in Brachionus 

 pala. 



In all the families of daughters from the various mothers it 

 was found that the male-producing daughters were among the 

 earliest ones produced of each family. This was observed in the 

 families of Hydatina senta by an earlier worker but later it was 

 found to be due entirely to the method of feeding. 



Although, as stated previously, the observations recorded in 

 this paper are from a rather small number of individuals and 

 ought to be expanded and verified, nevertheless, they show that 

 in this rotifer the production of female-producing or male-pro- 

 ducing females can be regulated by the environment and thus the 

 results are in a general accord with the observations obtained by 

 several workers with the rotifers, Asplancha, and Hydatina senta. 



D. D. Whitney 



