CHANGE IN THE BAR GENE OF DROSOPHILA 



309 



As discussed in a separate paper, the value of a factor or com- 

 bination of factors affecting facet number is put on the basis of 

 10 per cent units. An arbitrary point, the mean facet value in 

 the unselected stock, is taken as the point of reference, and dis- 

 tribution classes are so arranged that the facet range of each 

 class is 10 per cent of the mean facet value of that class. In 

 this scheme any facet value may be represented as being a de- 

 parture plus or minus a certain number of 10 per cent units from 

 the point of reference. The method is based on the view that 



TABLE 7 

 Dominance values in ultra-bar, bar, and full eye 



FEMALES 



Ultra-bar stock 



Full stock 



Heterozygotes 



Low selected bar (F24 



Full stock 



Heterozygotes 



Ultra-bar stock 



Low selected bar (F2) 

 Heterozygotes 



CATALOG 

 NUMBERS 



158^99 

 345 

 357 



391.2 

 345 



769 



158-499 



144-145 



742 



INDIVID- 

 UALS 



1590 

 10 

 54 



129 

 10 

 19 



1590 

 179 



87 



MEAN 

 FACET 

 VALUES 



21.96 

 810.6 

 36.54 



35.1 

 810.6 

 399.9 



21.96 



61.8 



25.7 



FACTORIAL 

 UNITS 



-9.79 



-f-26.67 

 -4.26 



-4.45 

 +26.67 

 +19.44 



-9.79 

 +0.74 

 -7.95 



FACTORIAL 

 UNITS 

 FROM 

 HETERO- 

 ZYGOTES 



-5.53 

 +30.93 



+23.89 

 -7.23 



-1.84 

 +8.69 



DOMI- 

 NANCE IN 

 PER 



CENTS 



84.8 

 15.2 



23.2 

 76.8 



82.6 

 17.4 



change in facet number is not a matter of accretion, but that the 

 whole facet-producing mass is involved. According to this view, 

 the factorial value of the difference between a 50-facet and a 

 55-facet individual is the same as that of the difference between 

 a 500- and a 550-facet individual. In other words, an environ- 

 mental or germinal change in what would otherwise have been 

 a 500-facet stock and which produces instead 550 facets would, 

 if acting upon a 50-facet stock, produce 55 facets and not 100 

 facets. The ordinary tabulations of variation in which classes 

 have equal character values over the whole range of variation 

 do not give equal factorial values. 



