MALE-PRODUCTION IN HYDATINA 



135 



In the single line here recorded the first generation was reared in spring water {from 

 a parent reared in -^^jj calcium chloride); the second generation was reared in a 

 calcium chloride solution {from a parent reared of course in spring water). Most 

 of the male-producers are daughters of parents reared in calcium chloride 



Experiment 7. Calcium chloride and a New Jersey line of rotifers. 

 The effect of continuous rearing in calcium chloride of two concentra- 

 tions was tested in a line of rotifers from New Jersey, to check the 

 results in the three preceding experiments, in all of which the Nebrasla 

 line was used. The method of conducting the experiment was the 

 same, except that different concentrations were used, but, as may be 

 seen from table 7, the results were different. There is a reduction 

 in the number of male-producers in calcium chloride in this line. 



We are unable to explain the difTerence between the Nebraska 

 and the New Jersey line in this respect, though inherited physio- 

 logical differences of other kinds are well known. The constancy 

 of the results obtained with calcium chloride in the Nebraska 

 line, even if the differences produced were small, lead us to 

 attribute these effects with some confidence to the action of 

 the calcium chloride. 



Experiment 8. Magnesium chloride. The physiological effect of 

 magnesium upon other organisms is in some ways in strong contrast 

 to the effect of calcium. We hoped to find this difference extended 

 to their effect upon the life cycle of Hydatina. A ^^^ solution of 

 magnesium chloride was used for one hne, spring water in another 



