380 ^Experimental Zoology 



ments. Cuenot concludes, therefore, that sex is not determined 

 by external conditions, but is predetermined in the egg. 



The question turns, therefore, on what condition determines 

 the sex of the egg. Can the nutrition of the parents during the 

 larval stages affect the proportion of male and female eggs? 

 Cuenot carried out some experiments to test this possibiHty. 



Experiment I. Larvae of CalUphora vomitoria, that had been 

 poorly nourished from the time of hatching, produced 12 males 

 and 5 females that were not more than half the normal size. 

 The flies were inclosed in a cage and fed on sugar and meat. 

 They laid 20 lots of eggs. The larvae that hatched were fed 

 and produced 359 females and 353 males. No influence due 

 to the starved condition of their parents was observed. 



Experiment II. Adult flies of CaUiphora vomitoria that had 

 hibernated in the laboratory all winter without food were cap- 

 tured in March and April. They were fed on sugar and meat, 

 and then laid 7 lots of eggs. The larvae were well fed and 

 produced 306 females and 308 males. This result also shows 

 that the condition of the parents is without effect on the sex of 

 the offspring. 



Pictet has recorded the proportion of males and females that 

 appear when the food of caterpillars is different from the normal. 

 The general effects of the change of diet was in some cases to give 

 insufficient nourishment, in other cases more nourishment than 

 supplied by the normal food. The results seem to show that 

 when the food is insufficient the proportion of males is greater. 

 Thus Ocneria dispar fed on walnut leaves gave in the first genera- 

 tion 54 males to 46 females, and in the second generation 65 

 males to 35 females. When the first generation was fed on wal- 

 nut leaves and the second on oak leaves (the normal food), 

 there were 61 males to 39 females. When the first generation 

 was fed on walnut, the second on oak, and the third on walnut 

 again, there were 65 males to 35 females. 



Esparcette and dandylion furnish an ample supply of nour- 

 ishment; the former gave in the first generation 51 males to 49 

 females, and the latter 52 males to 48 females. 



