U Mohr. 



Table 5. Pi. wild-type Qo X eosiii veiniiliou forked^ oo: B.C., 

 Fl wild-type c v eosin vermilion forked* rf o"- 



ill this paper is recorded another allelomorph of the same gene, Dr. 

 Bridges has obtained still another (forked^). The one here described 

 being number four in the series of forked allelomorphs was accordingly 

 called forked*. In addition Bridges has found on two occasions forked 

 characters not distinguishable somatically from the original type of 

 forked and occupying the same locus. 



Description of forked*. 



A comparison of Fig. 1 with Fig. 3 demonstrates the striking 

 resemblance between the forked* and the singed characters. As in 

 singed individuals not only the bristles but also the small hairs all over 

 the body are affected, in contrast to the condition in ordinary forked 

 flies. The forked* bristles are curled in contrast to the ordinary forked 

 ones which are crinkled, bent at sharp angles and frequently bifurcated. 



Examination with Mgher magnification reveals very slight diffe- 

 rences between the forked* and the singed character but they are not 

 distinct enough so as to make possible a reliable separation between 

 the two. The bristles are slightly thicker in forked* than in singed 

 flies, small bifurcations of the bristles are somewhat more frequent in 

 the former, and the alteration of the small hairs all over the body 

 seems to be slightly less pronounced in forked* than in singed individuals. 

 Thus, the two somewhat larger hairs on the marginal vein just before 

 the apex of the first vein are often unaffected in forked^ flies, while 

 they are constantly affected in singed indi\dduals. 



However, these somatic differences are very minute, so the two 

 characters furnish a very striking case of mimic mutations. In spite 

 of the fact that each of the two genes, both sex-linked recessives, pro- 

 duces such a very particular alteration as the general hair and bristle 



