224 Basis of Sex Determination 



which induces the development of eggs. The natural 

 steriHty of the neuters or workers is, therefore, to use 

 P. Marchal's expression, a case of "food castration," 

 ("castration nutriciale ") . ^ The workers originate 

 from fertilized eggs and are therefore females, but for 

 the full development of the ovaries and the other 

 sexual characters something else besides the XX 

 chromosomes is needed and this is supplied in this case 

 by the quantity or quality of the food. May we not 

 conclude that the same thing may happen generally, 

 except that these substances are formed by the body 

 under the normal conditions of nutrition through the 

 influence of constituents of the second X chromosome? 



It is known that the future queens among the bees 

 receive also a special type of food which the workers do 

 not receive. Again the idea of "food castration" of 

 the latter is suggested. 



In rotifers Whitney^ has shown that the cycle in the 

 production of males and females can be regulated by 

 the food. In some species a scanty supply of green 

 flagellates produced purely female offspring, while a 

 copious diet of the same green flagellates produced a 

 predominance of male grandchildren, sometimes as high 

 as ninety-five per cent. This was confirmed by Shull 

 and Ladoff.3 



^Thls account of Marchal's beautiful experiments is taken from 

 Caullery, M., Les Problemes de la Sexualite. Paris, 19 13. 

 'Whitney, D. D., Science, 1916, xliii., 176. 

 3 Shull, A. F., and Ladoff, S., Science, 1916, xliii., 177. 



