CHANGE IN THE BAR GENE OF DROSOPHTLA 313 



T)/TT 



or ultra bar females and or heterozygous females with 



ultra-bar and full-eye factors. If crossing over occurs there 



TJ/ TJ 



should be in addition to the above or bar males, 



X X 



B 



— X- 



u 



■X- 



or full males with an U accessory factor, or hetero- 



X X 



B' U 

 zygous females with bar and ultra-bar factors and 



X X 



B' U 



or heterozygous females with ultra-bar and full factors plus an 

 U accessory factor. 



As bar males are readily distinguishable from ultra-bars, the 

 test of the hypothesis is the presence or absence of bar males in 

 Fo. The other differences indicated by the formulae can prob- 

 ably not be detected with certainty as the effect of an accessory 

 U factor upon full is unknown, the heterozygote between bar 

 and ultra-bar is so close to pure ultra-bar that it cannot be dis- 

 tinguished with certainty and the effect of an extra accessory U 

 upon the heterozygote between ultra-bar and full is unknown. 



Full females crossed with ultra-bar males give in Fi heterozyg- 

 ous females and full males. The expected F2 males are the same 

 as those in the reciprocal cross. If there is no crossing over, the 



B'TT 

 expected females are or heterozygotes with low facet num- 



X 



bers and ZIZZZ or full females. If crossing over occurs there 



B' 



are to be expected in addition to the above or heterozy- 

 gotes with high facet number and or full females with a U 



X 



accessory factor. 



The heterozygotes between ultra-bar and full are so much 

 lower than those between bar and full that the two can be easily 

 differentiated. The facet values of the other differences are 

 unknown. 



