NEW DATA. 



77 



the smaller, giving a blotched appearance to the eye. The short hairs 

 between the facets point in all directions instead of radially, as in the 

 normal eye. The irregular reflection breaks up the dark fleck which is 

 characteristic of the normal eye. The shape of the eye differs some- 

 what from the normal; it is more convex, smaller, and is encircled by 

 a narrow rim destitute of ommatidia. 



Facet arose in a back-cross to test the independence of speck (second 

 chromosome) and maroon (third chromosome). One of the cultures 

 produced, among the first males to hatch, some males which showed the 

 facet disarrangement. None of the females showed this character. 

 The complete output was that typical of a female heterozygous for a 

 recessive sex-linked character: not-facet 9 9 (2), 112; not-facet c? cf 

 (i), 57; facet rfcF (i), 51. 



Of the three characters which were shown by the F 2 males, one, facet, 

 is sex-linked, another, speck, is in the second chromosome, and maroon 

 is in the third chromosome. All eight F 2 classes are therefore expected 

 to be equal in size, and each pair of characters should show free assort- 

 ment, that is, 50 per cent. The assortment value for facet speck is 48, 

 for speck maroon 52, and for facet maroon 48, as calculated from the 

 F 2 males of table 58. 



TABLE 58. PI speck maroon d" X wild 99. B.C. F\ wild-type 9 X speck 



maroon cf. 



LINKAGE OF FACET, VERMILION, AND SABLE. 



In order to determine the location of facet in the first chromosome, 

 one of the facet males which appeared in culture 66 was crossed out to 

 vermilion sable females. Three of the wild-type daughters were back- 

 crossed to vermilion sable males. The females of the next generation 

 should give data upon the linkage of vermilion and sable, while the 

 males should show the linkage of all three gens, facet, vermilion, and 

 sable. The offspring of these three females are classified in table 59. 



The cross-over fraction for vermilion sable as calculated from the 

 females is yW- The cross-over value corresponding to this fraction is 

 10 units, which was the value found in the more extensive experiments 

 given in the section on sable. 



It will be noticed that the results in the males of culture 150 are 

 markedly different from those of the other two pairs. While the sable 

 males are fully represented, their opposite classes, the gray males, are 



