ipll] 



A. Franklin Skull 



i8i 



stibstances to some extent. But if the colored substance is wholly 

 responsible for the non-occurrence of male-producers in a manure 

 Solution, such a decolorized Solution should yield the same Propor- 

 tion of male-producers as pure water. Whether it does or not may 

 be Seen from Table 5. The experiment was performed in May, 

 19 10, with rotifers descended from a winter egg collected in Grant- 

 wood, N. J., in April, and kept in an ice-chest for a month. 



Even the decolorized filtrate greatly reduces the proportion of 

 male-producers, though not as much as the merely boiled filtrate 



TABLE 5. 



Shoziring the nnmber of male- and fcmale-producers in the progeny of three 

 sister individuals of Hydatina senta, one line being reared in boiled filtrate of old 

 food cultures, a second in filtrate decolorized with animal charcoal, the third in 

 spring water. 



Whether the 7 per cent. difference between the decolorized filtrate 

 and the boiled filtrate is due to total removal of the colored sub- 

 stance or to partial removal of some other substances, can not 

 be decided from this experiment alone. That the latter is the 

 case, at least in part, will appear later, when it is shown that cer- 

 tain other substances which are presumably present in the manure, 

 and which were probably carried down mechanically by the char- 

 coal, do reduce the percentage of male-producers. This does not 

 show, however, that the colored substance may not also have the 

 same effect to a slight extent. 



The one male-producer in the first generation bred in the boiled 

 filtrate is the only one I have ever obtained in undiluted filtrates 



