NON-CRISS-CROSS INHERITANCE. 269 



chromosomes were transmitted together to the next generation, 

 producing (wherever they occurred) females, because there were 

 always two of them. No male offspring could be yellow, because 

 no single yellow chromosome was transmitted (see Fig. 2). The 

 sons must receive their X-chromosome from their father. The 

 mosaic, as already stated, was not virgin ; her brothers were all 

 forked and some of them were bar, so that the two forked bar sons 

 were in all probability offspring of a first mating and the other 

 sons were offspring of the black male. 



Three of the F t females were mated to three brothers, but no 

 one of the pairs produced offspring; neither did a mass culture of 

 F x males and females, nor did three F x males outcrossed to yellow- 

 white females have any offspring. On the other hand, ~F l females 

 outbred were fertile, and the sons of these were also fertile. The 

 sterility of the F x males was expected if the X-chromosomes of 

 the mosaic parent remained together, as the analysis shows, for 

 then she should have produced two kinds of eggs (cf. Fig. 2), one 

 kind with the double X and one kind with no X-chromosome. 

 The XX-eggs fertilized by X-sperm would have produced XX X 

 females (triploid-X females which would die) ; the XX-eggs, fer- 

 tilized by Y-sperm, would have produced XX Y females, the yel- 

 low daughters. The no-X or O-eggs, if fertilized by X-sperm, 

 would have produced XO males, in appearance like the father, but 

 sterile because lacking a Y-chromosome, and the O-eggs fertilized 

 by Y-sperm would have produced YO males which would have 

 died. Half the F l males and half the F females presumably died 

 and the sex-ratio remained I : I. The actual numbers were 43 

 females to 59 males. The daughters were all yellow, but differed 

 from their yellow mother in having, besides the " yellow-bearing " 

 double chromosome, a Y-chromosome from their father; their sons 

 therefore received from them a Y-chromosome and were fertile, 

 and the surviving half, receiving their X-chromosome from the 

 father, resembled him. Such patroclinous sons were produced by 

 mating F l yellow daughters to wild type, to yellow white, to Xple, 

 and to yellow broad, eosin, ruby males. The ratio of females to 

 males in 8 cultures was 435 : 437, as would be expected again in 

 this generation, since out of the four classes one class of females 

 (XX X) would die, one class (XX Y) would survive, one class of 



