igii] 



A. Franklin Shull 



TABLE 14. 



y 



191 



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

 sister individuals of Hydatina senta, one line being reared in spring water, the 

 other two in creatin Solutions of different strengths. 



Proportion of male-producers In Hydatina. The conclusions 

 reached may be summarized as follows : 



An extract of horse-manure may wholly prevent male-producers 

 from appearing. Boiling such a manure extract does not diminish 

 its effect, neither does drying and redissolving it. 



The substance in manure extract which prevents male-producers 

 from appearing is apparently insoluble in ether and absolute 

 alcohol. 



The brown colored substance of manure extracts probably does 

 not affect the proportion of male-producers. 



The degree of alkalinity, when comparatively small, seems to 

 have a determining influence; but the differences obtained were 

 slight and the results were not uniform. 



Urea tends to reduce the proportion of male-producers. Other 

 substances having the same effect are ammonium hydroxid and 

 three ammonium salts : the chlorid, the carbonate, and the nitrate. 



Beef extract and creatin Solutions greatly reduce the proportion 

 of male-producers. 



*Remainder of family not recorded. 



