330 



Aaron Franklin Shall 



TABLE VII 



Showing the number of male- and female-producers in the progeny of two individuals of H ydatina senta re~ 

 lated to each other as fourth cousins, both lines being partially starved, one on new food, the other on old 

 food cultures. 



Influence of Substances in Water on Percentage of Male-producers 



Experiment VII. On June 29 samples of water were taken 

 from the drainage ditch in Grantwood, N. J., where two weeks 

 earlier rotifers and an abundance of green flagellates had been 

 found. At this date, however, no rotifers nor flagellates could be 

 discovered; almost all life, except mosquito larvae, was wanting. 

 The water was somewhat cloudy, as if with soap solution. This 

 water may or may not have contained approximately the same 

 substances as two weeks before. Two parallel lines of rotifers, 

 derived from sister females, were fed on the same food and other 

 conditions were kept the same, except that about eight drops of 

 this drainage was added to each dish in one series, an equal 

 amount of spring water to the other. After nine generations, the 

 conditions were reversed; the line previously reared in dilute drain- 

 age was kept in pure spring water, and that previously raised in 

 pure water was then given the usual amount oi drainage. Table 

 VIII shows the details of the experiment. 



