550 



D. D. WHITNEY 



when the diet of their mothers was changed from Polytoma 

 to Dunahella. In the general control experiments in which a 

 continuous diet of Polytoma was maintained 177 mothers 

 produced 2500 daughters, of which 2+ per cent were male- 

 producing daughters. 



The highest percentage of male-producing daughters which 

 was produced by a change of the diet in the experiments in tables 

 1 to 3 is 83 + but as high a percentage as 87 + was produced in 

 the experiment in table 4. 



If twenty-five of the best experiments in tables 1 to 3 are 

 selected and the percentage computed for the male-producing 

 daughters, it is seen that a change of diet from the Polytoma to 



TABLE 1 



Shouittg that adult female-producing females of various ages, selected at random 

 from a rotifer culture reared on a Polytoma diet through several generations, can 

 he forced to produce a high percentage of male-producing daughters by being trans- 

 ferred from a Polytoma diet to a Dunaliella diet 



