THE ORIGIN OF GYNANDROMORPHS. 



83 



get to the bottom of the situation in the light of more recent work, 

 for in moths it now seems probable that one Z sex chromosome 

 (the equivalent in part of one nucleus) makes a female and two a male. 

 There are, then, two kinds of ripe eggs, one with, the other without, a 

 Z, and one kind of sperm, which is Z-bearing. There are six possi- 

 bilities to be considered (see diagrams, text-figs. 66, 67, 68). 



(1) On Boveri's view (text-fig. 66, 1), if an egg with a W was the 

 kind fertilized, then one half of the maternal segmentation nucleus 

 should have no Z and would probably not develop, while the other 



Text-figure 66. 



half of the egg nucleus, that united with the sperm nucleus, should 

 have one Z and be both female and white. This explanation fails to 

 account for the male sex of the side supposed to be without a Z and for 

 the presence of zebra on that side. 



(la) On Boveri's view (text-fig. 66, la), if an egg with a Z were 

 fertilized by a sperm (bearing Z),then both the male and female sides 

 should be zebra, which is contrary to evidence. 



Text-figure 67. 



(2) On Morgan's earlier view (text-fig. 67, 2), an egg trith a W 

 fertilized by a sperm (bearing Z) should give female parts from the 

 combined nuclei which would be white. The sperm nucleus alone 

 would also give female parts which would be plain. The result is a 

 mosaic, but not a gynandromorph. 



(2a) On Morgan's view (text-fig. 67, 2a), if an egg ivith a Z had 

 been fertilized by a Z sperm, all male parts (ZZ) should be zebra. 

 The female parts would be plain, which is again contrary to fact. 



