THE ORIGIN OF GYNANDROMORPHS. 



59 



nucleus contained a white miniature rudimentary cross-over X, and the 

 other nucleus a wild-t>i^e cross-over X. Each nucleus was fertilized by a 

 Y-type sperm, proof of which for the right side has been given; proof for "left 

 side is as follows: The left wing is miniature as well a* rudimentary, and since 



Text-figure 49. 



Text-figure 50. 



Text-figure 51. 



the X of the father did not carry miniature, this left side could not have 

 contained a paternal X and must therefore have contained a paternal Y 

 chromosome. 



One of the cross-over chromosomes was white as well as miniature and 

 rudimentary; but since the eye on the side with miniature was red, we may 

 suppose that all of the head came, as is very often the case, from cells from 

 one side only, namely, the right, which was here carrying red; or this cross- 

 over chromosome may have come from double crossing-over, and in this case 

 it would have carried red. 



Lejl side. 



Right side. 



W 



m 



VI 



or 



On an alternative view that both of these X's were in a single nucleus, the 

 following assumption seems necessary. An XX egg was produced by reduc- 

 tional primary non-disjunction (see Bridges, 1916), preceded by crossing-over, 

 so that one X contained white miniature rudimentary and the other was the 

 complementary X containing only wild-type genes. This XX egg wa:? then 

 fertilized by a Y sperm. 



That the individual was entirely male with no female parts can be explained 

 either by double elimination or somatic reduction at the first division of the 

 zygote; that is, one member of each pair was caught by the elimination plate, 



