THE EFFECT OF SELECTION UPON THE 'BAR EYE' 

 MUTANT OF DROSOPHILAi 



CHARLES ZELENY and E. W. MATTOON 



FIVE FIGURES 



The selection experiment described in the present paper was 

 made with a view to testing the germinal uniformity as regards 

 the distinguishing characteristic in a recent mutant, the 'bar 

 eye' race of Drosophila. In this race the ommatidia are reduced 

 in number and the facets are restricted to a vertical band or 

 'bar' as shown in figure 1. The characteristic appeared in a 

 single male during 1913 (Tice, '14)^ and the whole 'bar eye' 

 stock is descended from this individual. The race has under- 

 gone no apparent change during the two years of its existence. 

 Our material was obtained in January 1914 through the kind- 

 ness of Prof. T. H. Morgan. 



There is a pronounced sexual dimorphism in the number of 



facets, the males averaging 98.03 and the females 65.06. In 



every case in the present paper the female number is transformed 



98 03 

 to the male basis by multiplying it by nr\n = 1-51. 



There is often a slight difference between the number of facets 

 in the right and that in the left eye. For one hundred indi- 

 viduals the average difference was 0.245 per cent in favor of the 

 left eye. This difference is obviously not significant. The right 

 eye only is given in the present records. 



The number of facets seems not to vary with the length of 

 the period of development. In five broods counts were made 

 of the facets of the earlier emerging individuals and compared 



1 Contribution from the Zoological Laboratory of the University of Illinois 

 No. 50. 



^ Tice, S. A. 1914. A new sex-linked character in Drosophila. Biological 

 Bulletin, vol. 26, pp. 221 to 230. 



515 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 19. NO. 4 



