176 



Life Cycle of Hydatina Senta 



[Dec. 



chemical dififerences in the food cultiires from which the rotifers 

 were fed. The food used in my experiments consisted of various 

 organisms reared in an infusion of fresh horse manure, about one 



TABLE I. 



Showiug the nmnber of male- and fcmale-producers in the progeny of five 

 sister individuals of Hydatina senta., one line heing reared in spring zvater, the 

 others in various concentrations of the filtrate from old food cultures. Male- 

 producers are indicated by c?$, female-prodncers by ??. 



volume of manure to three volumes of water, It was conceivable 

 that the manure Solution itself might alter the cycle of the rotifers. 

 Experiment 9. The influence of substances found in the food 

 cultures, as distinguished from the flagellate used as food, was 

 tested as f ollows : An old manure culture, which had been made up 

 with spring water, and which had been rejected about ten days 

 before, was filtered through a Berkefeld filter. The filtrate was 

 examined with a microscope and found to be free from protozoa. 

 Rotifers were reared in various concentrations of this filtrate, one- 

 fourth, one-half, three-fourths, and undiluted, as well as in pure 

 spring water. The five lines were derived from sisters, and were 

 fed equal quantities of food from the same fresh cultures. The 



