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CHAELES ZELENY AND E. W. MATTOON 



with those of the later emerging ones. The averages for the 

 two are approximately equal. 



A sample of five hundred individuals, 250 males and 250 

 females, taken from the general population of the mutant showed 

 a range of variation in the number of facets from 45 to 182 with 



Fig, 1 A. Noraial full eye of Drosophila. 

 the faceted regions. 



B. 'Bar' eye. The dark areas are 



Facet number 16-30 31-45 46-60 61-75 76-90 91-105106-120121-135136-150151-165166-180181-195196-210 

 Frequency _fl 2 18 56 113 164 73 30 24 17 3 1 



Fig. 2 Variation of facet number in the unselected population of the 'bar' 

 eye mutant of Drosophila ampelophila. Five hundred individuals are repre- 

 sented, two hundred and fifty males and two liundred and fifty females reduced 

 to the male level. 



a mean of 98.03 ± 0.73 and a standard deviation of ± 24.30. 

 The variation curve is shown in figure 2. The average for ten 

 individuals of the normal wild race was 701.1 facets. 



Unselected stock was carried as a control through the period 

 of the experiment. There was practically no change in the 



