i84 



Life Cycle of Hydatina Scnfa 



[Dec. 



TABLE 7. 



Showing the nuniber of male- and female-producers in the progeny of three 

 sister individuals of Hydatina senta, one line being reared in n/200 NaOH, a 

 second in distilled water and one in n/300 HCl (tut see text). 



4. Influenae of urea on the percentage of male-producers. 



Experiment 25. One line of rotifers was bred in a w/400 Solu- 

 tion of urea, a control line derived from a sister individual was 

 reared in spring water. The experiment was performed twice, 

 A and B, in Table 8. In A, the parents of both lines had been in 

 spring water before the beginning of the experiment; in B, both 

 had been in urea. This experiment seems to indicate that urea 

 in the water tends to reduce the proportion of male-producers. 



5. Influenae of ammonium Compounds on the percentage of 

 male-producers. Experiment 26. Ammonium salts. Four 

 sister individuals became the parents of the four lines in this experi- 

 ment, which was performed in June, 19 10. One line was reared in 

 spring water, the others in ammonium salts of the following 

 strengths: 7/7/500 NH4CI, w/500 NH4NO3, and ammonium car- 

 bonate i gram to 7500 c.c. of the Solution. The carbonate was not 

 computed in terms of molecular Solution, because the c.p. salt was 

 not used. The substance taken was probably what is known as the 

 sesquicarbonate, a mixture of the bicarbonate and the carbamate. 

 Table 9 gives the details of each line. 



All of these ammonium salts reduced the proportion of male- 

 producers, two of them to one-half the proportion obtained in 

 spring water, the other to one-third. The consistent results from 



