214 



CHARLES ZELENY 



siderable number were tested and were shown not to differ from 

 wild full. Several of them serve as the starting-points of the 

 full stocks listed in table 1 as derived from bar. 



One of the most striking results is the uniformity in rate of 

 mutation among the different kinds of bar stocks. There is no 

 essential difference in this respect between unselected bar, high 

 bar or low bar, or bar derived from ultra-bar (table 3). The 

 only exception is emarginate eye (fig. 1, E, and table 2). The 

 two emarginate stocks give only one mutant in 9544 individuals, 

 giving a coefficient of 0.00010, though the number of observations 

 is too small to give this value any special significance. 

 Emarginate is a very high bar resembling in character a full 



TABLE 3 



Effect of origin and of selection for high and low facet number upon the rate of muta- 

 tion in bar stocks 



ORIGIN or STOCKS 



Unselected 



High selection 



Low selection 



Bar from ultra-bar 



NUMBER 

 OF INDI- 

 VIDUALS 



11,760 

 22,125 

 21,510 

 13,109 



Number of 

 mutations 



14 

 15 

 10 



Coefficient 



of 

 mutability 



0.00068 

 0.00063 

 0.00069 

 0.00076 



TO ULTRA-BAR 



Number of 

 mutations 



Coefficient 



0.00000 

 0.00009 

 0.00005 

 0.00000 



with a notch in one side. It has been shown to be due to 

 accessory factors which are not sex-linked. A female heterozy- 

 gous for the bar factor but retaining both emarginate factors is 

 full-eye in appearance so that there is no possibility of mistaking 

 a mutation of a bar factor to full. There does not seem to be any 

 valid reason for expecting the presence of the emarginate factors 

 in the autosomes or other factors present in the emarginate 

 stock to influence the rate of mutation in the bar gene which is 

 located in the sex chromosome. Until a larger number of in- 

 dividuals has been observed the low apparent rate of mutation 

 in this stock may be ascribed to random sampling. 



In the discussion of the mutations from bar special attention 

 is called to the behavior of individuals undergoing selection for 

 high or for low facet number, because it has frequently been stated 



