484 WATASE. [Vol. VI . 



ture was maintained between 26° C. and 28° C. The five females 

 were kept till death, and in their lifetime they laid 104 eggs, of 

 which 97 per cent, were males and only 3 per cent, were females. 

 He took another set of five young females, and kept them in a 

 refrigerator where the temperature was between 14° C. and 

 15° C. They laid 260 eggs during their lifetime, of which 95 

 per cent, were females and only 5 per cent, were males. 



In his second experiment, he took five young females, and 

 kept them in the temperature between 14° C. and 15° C. They 

 laid no eggs, of which '/6 per cent, gave rise to females 

 and 24 per cent, to males. He then transferred the same five 

 females into the humid chamber, with the temperature 26°- 

 28° C. They produced, up to the time of their death, 118 eggs, 

 of which 81 per cent, gave rise to males and 19 per cent, to 

 females. 



In his third experiment, Maupas took six young females, and 

 these when kept in the lower temperature (14°-! 5° C.) laid 34 

 eggs, of which 88 per cent, were females and 12 per cent, were 

 males. When the same female parents were placed under the 

 influence of the higher temperature (26°-28° C), they laid 44 

 eggs, of which 95 per cent, were males and 5 per cent, were 

 females. Maupas exposed the same females alternately to the 

 higher and the lower temperature, and in one instance fully 

 100 per cent, of the eggs produced in the higher temperature 

 turned out to be males. In the last four days of their exist- 

 ence they were placed in the cold chamber again, when they 

 produced 50 eggs, of which 83 per cent, were females and 

 17 per cent, were males. 



In short, when the young females of Hydatina were placed 

 under the influence of the lower temperature, only 5-24 per 

 cent, of eggs laid gave rise to males, while 76-95 per cent, of 

 the eggs gave rise to females ; when, however, they were placed 

 under the influence of the higher temperature, 81-100 per cent, 

 of the eggs were males and 0-19 per cent, were females. 



These observations of Maupas are most conclusive in show- 

 ing that external influence does actually determine the sex of 

 the offspring. The works of Mrs. Mary Treat, ^ on Lepidoptera, 



1 ]Mrs. Mary Treat, Controlling Sex in Butterflies, American Naturalist, Vol. 7, 

 1873- 



