ROUGHOID, A MUTANT LOCATED TO THE LEFT OF 



SEPIA IN THE THIRD CHROMOSOME OF 



DROSOPHILA MELANOGASTER. 



LEONELL C. STRONG, 

 COLUMBIA UNIVERSITY. 



ORIGIN OF THE CHARACTER, ROUGHOID (RU). 



In March, 1919, Dr. A. H. Sturtevant handed over to me a 

 culture of Drosophila melanogasler, containing a new mutant, 

 named by him "roughoid," owing to its similarity with the old 

 character "rough." 



In December, 1918, he had collected a single pair of wild 

 flies near Columbia, S. C. The F 2 generation from these was 

 found, two months later (February 14, 1919), to contain many 

 roughoids (culture 5570 A.H.S.). Hence one of the wild flies 

 must have been heterozygous for the mutant gene. The point 

 of special interest in connection with roughoid is that its locus 

 is to the left of that of sepia and therefore establishes a new 

 left end of the map of the third chromosome. 



DESCRIPTION OF THE ROUGHOID CHARACTER. 



This gene produces somatic effects mainly upon the size and 

 texture of the normal eye; (a) it materially decreases both 

 the length and width of the eye as well as making it more convex; 

 (6) the ommatidia lose their hexagonal shape, and become 

 crowded together irregularly; (c) due to this irregularity, the 

 hairs project in all directions from the surface; (d) the hairs are 

 somewhat thickened and strikingly longer than in the normal 

 eye. These effects are very constant in appearance and have 

 proven to be favorable for purposes of classification. Associated 

 with these effects there are found sometimes, (e) several black 

 ommatidia distributed over the surface of the eye, but more 

 commonly in the posterior ventral region. They tend to darken 

 the normal red eye color. They are more than likely a part of 

 the roughoid character since I have never seen this effect in any 



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