No. 644] MUTANT CHARACTERS IN DROSOPHILA 231 



fication of rough and morula was not accurate at its first 

 appearance. 



Nicked {nk) 



Description. — Nicked is characterized bv irregular 

 notches in one or both wings (Fig. 16). The indenta- 

 tions vary in size and location, but tend to show on the 

 posterior and inner portions of the wing. In certain 

 lines, the character shows regularly, while in certain 

 other lines it overlaps normal a great deal. Flies in 

 which nicked is combined with other mutant characters 

 have rather poor viability. 



Origin. — Several individuals of both sexes were found 

 in a mass culture. 



Rosette (ro) 



Description. — ^In this mutant race, a large number of 

 characters are affected (Fig. 17). The eyes are slightly 

 roughened due to disarrangement of the facets; the 

 thoracic hairs are disarranged, looking as if they had 

 been brushed in the wrong direction; the bristles may 

 be bent; the distal tarsi of the legs may be twisted; and 

 the wings are generally held at an angle with the body, 

 and one or both may be small and circular. The rough 

 eyes and disarranged hairs are constant characters. 

 Rosette flies have very low viability and are hard to 

 breed, especially when other mutant characters are pres- 

 ent also. 



Origin. — Four rosette rough males were obtained 

 among a large number of offspring from one morula 

 male by three rough females. 



Construction of the X-Chromosome "Map" 

 With one or two exceptions the usual procedure^ has 

 been followed in constructing the chromosome "map." 

 The order of the genes was determined by means of 

 crosses involving three or more loci (Tables III-VI), and 

 that order adopted which, in the consideration of an>- 

 three points, made the double crossover class the small- 



2 See footnote, p. 213. 



