In Different Species. 59 



In most cases there is a moderate range of variability in the character, 

 so the description is made to represent the average condition as 

 nearly as possible. 



D. melanogaster: forked, (forked-2), forked-3, (forked-4), forked-5. 



singed, singed-2. 

 D. wiUisloni: forked-l, (forked-2). 



stubby. 

 D. virilis: forked. 



singed. 

 D. obscura: singed. 



(stubby) . 

 D. simulans: forked. 

 D. funebris: forked. 



Drosophila melanogasteh. 



Forked. — Effect moderate to extreme. Bristles shortened, t^visted, sharply forked; 

 not depressed. Hairs somewhat stubby, not depressed or curled. Both sexes fertile. 

 Eggs normal. Heterozygous females apparently normal. 



Forked-2. — (From Mohr, 1922.) Effect slight, variable, more pronounced in 

 females than in males. Bristles long, not crinkled or t'v^asted; one or more usually 

 forked at tip. Head bristles rarely affected. Presumably hairs and bristles not 

 depressed; females fertile; eggs normal. (These features not mentioned in descrip- 

 tion.) 



Forked-3. — Effect slight. Bristles mostly not forked, but only stubby; not de- 

 pressed; few bristles forked at tip, or bent sharplj^ back, hook-shaped; bristles not 

 wavy. Hairs on thorax, abdomen, legs, and wings normal or nearly so; bristles 

 bordering segments of abdomen curled slightly. Hairs on arista apparently normal. 

 Both sex3s fertile; eggs normal. Heterozygous females not examined. 



Forked-4.— (From Mohr, 1922.) Effect strikingly like that of singed. Differs 

 only slightly. Bristles and hairs all over the body affected; bristles curled as in 

 singed. "The bristles are slightly thicker in forked-4 than in singed flies, small 

 bifurcations of the bristles are somewhat more frequent in the former, and the altera- 

 tion of the small hairs all over the body seems to be slightly less pronounced in 

 forked-4 than in singed individuals." Females fertile, eggs presumably normal. 

 Heterozygous females not examined. 



Forked-5. — Effect extreme. Bristles heavy, depressed, greatly twisted, knotted 

 and forked, projections sharp, hairs on head, thorax, abdomen and legs depressed 

 and often curled; hairs on costa hea\'>', stand out at a greater angle than usual. 

 Hairs on arista practically normal. (See also under singed.) Both sexes fertile; 

 eggs normal. Heterozygous females not examined. It is possible that forked-5 

 and forked-4 are identical. 



Singed. — Effect extreme, but not as extreme as forked-5. Very much like forked-5 

 in most respects. Bristles longer and more slender, but twisted and forked in much 

 the same manner. Hairs on entire fly essentially the same as in forked-5. Females 

 sterile. Eggs abnormal, short filaments (Mohr, 1922). Double recessive singed-forked 

 indistinguishable from singed (Mohr, 1922). Double recessive singed-forked-4 in- 

 distinguishable from singed or from forked-4 (Mohr, 1922). Heterozygous females 

 not examined. 



Singed-2. — Effect slight to moderate, much less extreme than singed. Bristles 

 wavy, somewhat depressed, a few slightly forked at the tip. Hairs on thorax de- 

 pressed, those on abdomen, legs and wings practically normal. Arista practically 

 normal. Females fertile; eggs normal. (This is not singed-2 of Mohr, 1922, which 

 was indistinguishable from singed.) Heterozj'gous females not examined. 



