4IO Experimental Zoology 



view, they will be maternal. At present we lack the data to 

 decide between these alternatives. 



In other groups of- animals, gynandromorphous forms are 

 great rarities. Weber described a finch that had feathers Hke 

 the female on the left side and Hke the male on the right. There 

 was also an ovary on the left side and a testis on the right. Un- 

 til we know more of the conditions that determine the sex of 

 birds, it is useless to speculate about this case. 



The Sex oj Multiple Embryos 



Another group of facts discovered in other hymenoptera seems 

 to show that the sex of the embryo is already determined in the 

 egg. The chalcid fly (Ageniaspis fuscicollis) lays its eggs in the 

 egg of a moth. Both eggs develop, the latter into a caterpillar 

 and the former into its parasite. The parasite develops in a 

 most remarkable manner. Marchal (1904) found that from a 

 single egg a chain of embryos develops, and these embryos are 

 all of one sex. Bugnion had already (1891) observed that the 

 individuals that emerge from a single caterpillar are generally of 

 one sex, and both authors have interpreted the result to mean that 

 if the egg has been fertihzed, a chain of female individuals is 

 formed ; but if the egg is not fertihzed, males are produced. More 

 recently Silvestri has studied the early development of another 

 insect (Litomastix truncatellus), and finds, in fact, evidence 

 showing that the eggs mayor may not be fertihzed, and that it con- 

 tinues to develop in either case. Silvestri finds that a single egg 

 may produce a thousand sexual individuals, and also several hun- 

 dred sexless larvae that lack the circulatory and respiratory system. 

 The details of the early development of these forms are remark- 

 able, but cannot be considered at present. The point of espe- 

 cial importance is the conclusion that the sex of the embryo 

 must be determined at an early stage, and is not later altered, 

 since all the sexual embryos of a chain are of the same sex. 



It is true that there may sometimes emerge from a caterpillar 

 both males and females, but this is supposed to be due to two eggs 

 — one fertihzed, the other not — having been laid in the same egg 



