14 



Linkage Group I. 



II. LINKAGE GROUP I. SEX-LINKED CHARACTERS. 



The sex-linked group consists of 18 characters. These are listed 

 in table 1 in chronological order. The first 10 have been described 

 previously (Nos. 1 to 4, Metz, 1916c?; Nos. 5 to 8, Metz, 1918; No. 9, 

 Metz, 19206; No. 10, Weinstein, 1920). In the accompanying 

 descriptions the order of treatment is not chronological, but conforms 

 to the order of the genes on the chromosome map. Under each 

 heading is given a description of the character, an account of its 

 origin, and a comparison with similar characters in other species where 

 such are known. 



DESCRIPTION, ORIGIN AND COMPARISON OF 

 SEX-LINKED CHARACTERS. 



Sepia (se). (Plate 1, Figure 6.) 



Description. — The only visible effect of sepia is on the eyes, which are deep opaque 

 brown, almost lacking in red. The character is readily recognized in both young and 

 old flies, but is most striking in young ones. 



Origin. — (L404) 8 sepia males were obtained from a mating of 2 heterozygous 

 pinched females with one mosaic (or deformed) male. (The male may have been a 

 true mosaic or merely deformed by injury. Its left wing was short and the scutellar 

 bristles on the left side were forked. Evidently its germ-cells were not affected, 

 however, for the character did not appear again in its descendants.) 



Comparison. — Sepia bears a general resemblance to various dark eye-colors in 

 other species (e. g., prune, ruby, purple in Drosophila melanogaster, and prune and 

 plum in D. simulans), and also to magenta and garnet in D. virilis. The flat or 

 opaque nature of the color, with a minimum of red in its composition, particularly 

 suggests "prune" in melanogaster and simulans. 



