646 VERMILION-DEFICIENCY 



females are virtually haploid for the region including the vermilion 

 locus. Linkage tests showed that the amount of crossing over in the 

 neighborhood of the deficiency was cut down by about five units. 

 Part of this may be attributed to the actual length of the "deficient" 

 region, within which it is probable that no crossing over occurs, and 

 part (probably most) to an alteration in the synaptic relations in 

 the regions immediately adjacent. In more remote regions there 

 was no disturbance or perhaps a slight rise in the frequency of cross- 

 ing over. Both the local fall and the possible rise in more distant 

 regions would seem to argue that a "pucker" at synapsis had been 

 caused by an actual shortening of the deficient chromosome. That 

 the deficient region extends to the left of the locus of vermilion was 

 indicated by a test in which it was observed that the presence of an 

 extra piece of chromosome including the loci for vermilion and sable 

 ("vermilion-sable duplication") did not neutralize the lethal action 

 of the deficiency. Haploid tests with the other recessive mutations 

 in the neighborhood of vermilion showed that the deficiency was not 

 extensive enough to include their loci. Cytological preparations 

 were made but were unsatisfactory. The stock was finally lost, ap- 

 parently as the result of injurious action upon viability, fertility, and 

 productivity by the deficiency. 



References in this paper are made to the following recessive sex -linked muta- 

 tions: "facet" eye (/o, locus 2.4), "cut" wing-shape {d, 20.0), "ocellar-bristles" 

 lacking {ob, 32.—), "vermilion" eye-color (v, 33.0), "tiny-bristles" (ib, 36.0), 

 "miniature" wing-size {m, 36.1), "sable" body-color (s, 43.0), "garnet" eye- 

 color (g, 44.4), "forked" bristles (J, 56.5). The tentative symbol for "ver- 

 milion-deficiency" is - (33. ±), for "vermilion-sable duplication" V-S (0.0), 

 and for "sable-duplication" S (0.0). The symbol -|- is read "wild-type." Sable- 

 duplication is equivalent to a wild-type allelomorph of sable situated at the ex- 

 treme left end of the X; males of the constitution S 5 are accordingly 

 wild-type in appearance. Likewise V-S duplication "covers" the recessive genes 

 vermilion and sable. 



Origin and Lethal Action of Vermilion-Deficiency. 



The recessive sex-linked mutation tiny-bristles had arisen in the 

 early work on "sable-duplication" (unpublished data). It was not 

 then convenient to give time to working out the locus of tiny-bristles 



