LIFE CYCLE OF HYDATINA SENTA 



135 



The ammonium hydroxid, like the salts, reduced the proportion 

 of male-producers to less than half that of the line in spring water. 

 Here again it seemed unnecessary to repeat the experiment. 



Influence of beef extract on the percentage of male-producers 



The experiments with beef extract were designed chiefly to 

 test the question whether extractives, which are present in feces, 

 influence the proportion of male-producers. Liebig's extract was 

 used, because of the absence from it of certain classes of substances 

 which are present in other brands. 



TABLE 29 



Showing number of male- and female-producers in the progeny oftivo sister individuals 

 of Hydatina senta, one line being bred in dilute ammonium hydroxid, the other 

 in spring water. 



