No. 644] MUTANT CHARACTERS IN DROSOPHILA 219 



of the abdomen, which is blunted, or apparently com- 

 pressed along the anterior-posterior axis. The abdominal 

 bands are slightly irregular. 



Eeduced flies, especially females, are hard to breed in 

 pairs, although those which do produce offspring seem 

 normally fertile. 



Origin. — Many males were found among the offspring 

 from a pair mating from orange stock. The mother of 

 the culture was apparently heterozygous for the gene. 



The Scute Allelomorphic Series 

 1. Scute (sc) 



Description. — The two anterior scutellar bristles are 

 usually lacking, although occasionally only one may be 

 gone. Rarely the combination of one anterior scutellar 

 bristle and one posterior one may be found. The remain- 

 ing bristles are normal in size. The character almost 

 always manifests itself in homozygous flies. Only one 

 exception to this has been detected up to the present time. 



Origin. — .Fifteen scute males and eleven normal males 

 were obtained from a normal pair. The female offspring 

 were all normal (number not recorded). It is almost cer- 

 tain that the mother was heterozygous in this case, and 

 that the mutation occurred in a previous generation or 

 else very early in her own ontogeny. 



2. Scute-2 {sc,) 

 Description. — Scute-2, an allelomorph of scute and 

 scute-3, involves the same scutellar bristles as scute, but 

 varies toward a more extreme condition than this allelo- 

 morph. The two anterior scutellar bristles are always 

 missing, frequently one of the posterior scutellars is gone, 

 and occasionally all four are lacking. The bristles on 

 the scutellum are fine and small. In a stock homozygous 

 for reduced and scute-2, both characters are more extreme 

 than either is alone (Fig. 7). Such flies often entirely 

 lack dorso-central and scutellar bristles, and lack one or 

 more orbital bristles. 



