SPECIAL CASES OF SEX-INHERITANCE 221 



as a rule in the hollow stems of plants, each egg in a 

 separate compartment. In some of the compartments 

 she stores away much more food than in others. From 

 these compartments large females hatch. From com- 

 partments where less food is stored the smaller males 

 are produced. It may seem that the amount of food 

 stored up determines the sex of the bee. To test this 

 Fabre took out the excess of food from the large 

 compartments. The wasp that emerged, although 

 small for want of food, was in every case a female. 

 Fabre enlarged the smaller compartments and added 

 food. The wasp that came out was a male, larger 

 than the normal male. 



It is evident that food does not determine the sex, 

 but the mother wasp must fertilize the eggs that she 

 lays in chambers where she has stored up more food, 

 and not fertilize those eggs that she deposits in com- 

 partments where she has accumulated less food. 



(2) A curious sex ratio appeared in one race of fruit 

 flies. Some of the females persisted in producing twice 

 as many females as males. This was first discovered 

 by Miss Rawls. In order to study what was taking 

 place, I bred one of these females that had red eyes to 

 a white-eyed male of another stock. All the offspring 

 had red eyes, as was to be expected. I then bred these 

 daughters individually to white-eyed males again 

 (Fig. 106). Half of the daughters gave a normal 

 ratio ; the other half gave the following ratio : 



