Description of Characters. 



37 



DESCRIPTION, ORIGIN, AND COMPARISON OF CHARACTERS IN 



GROUP III. 



Scaly (S). 

 Description. — Scaly is a dominant, characterized by flattened, scale-like omma- 

 tidia. The eye usually has a moist appearance also. The expression of this character 

 seems to be influenced by environmental conditions. In some cultures it appears in 

 all flies heterozygous for the gene; in others many such flies have eyes normal in 

 appearance, although breeding tests show them to carry the gene. It is probable 

 that this irregularity applies even to homozygous flies, although we have not tested 

 this point thoroughly. Scaly is not lethal when homozygous and pure stock is easily 

 maintained. 



IV 



-acute (ac) 

 0- -(-Pinched (P) 



hur 



V 



0-. 



ip(hp) 



VI 



0--bent{be) 

 Net(Nt) 



57 ±-^ 



fused (fu) 

 interrupted(i) 

 Branched (B) 

 approximated (a) 

 ruffled (ru) 



Figure 8. 



Crossover maps of linkage groups IV to VI in Drosophila virilis. 



The genes are not placed on the map in group V, for 



reasons given in the text (p. 50). 



Origin. — (V 1128.) Scaly was first observed among the offspring of 3 females 

 from one stock mated to males from another stock. The mating gave S6 wild-type 

 and 23 scaly individuals, suggesting that one of the parent flies was heterozygous for 

 scaly. 



Spread (sp). 



Description. — In spread flies the wings are held out from the body at varying 

 angles, usually between 60° and 90°. Otherwise the flies appear to be normal. Their 

 viability is poor, however, making the character a difficult one to use in linkage 

 experiments. It can not be classified accurately in combination with the third- 

 chromosome character hunch, because in the latter the wings are often held out at 

 an angle also. 



