LIFE CYCLE OF HYDATINA SENTA 



129 



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 

 filtrate of old food cultures. This one individual need scarcely 

 surprise us if we note the very high percentage of male-producers 

 in the first two generations bred in spring water. Manure solu- 

 tion does not rigidly exclude male-producers. It is important to 



TABLE 24 



Showing the number of male- and female-vroducers in the progeny of three sister 

 individuals of Hijdalina senta, one line being reared in boiled filtrate of old food 

 cultures, one in filtrate decolorized with animal charcoal, the third in spring 

 water. 



116 



159 



42.1 



21 



261 



7.4 



177 



0.5 



remember this in the consideration of other experiments where 

 various substances do not wholly prevent male-producers from 

 appearing. 



Influence of alkalinity on the percentage of male-producers 



Experiment XXIII. It was found impracticable to rear the 

 rotifers in water that was even faintly acid, so several degrees of 

 alkalinity were used. A _n solution of NaOH in distilled water 

 was kept in stock in a tightly stoppered bottle. In making up 

 this solution, no further precaution was taken to make the nor- 

 mality exact than to weigh the solid hydroxid carefully, exposed 



