164 



THE SECOND-CHROMOSOME GROUP 



equally well by jaunty or by black, but black continues to be chosen, 

 because of its greater prestige, because black already exists in many use- 

 ful combinations and multiple stocks, while jaunty is not combined with 

 other useful characters, and because black has at present less masking 

 effect than jaunty. The wing-mutations of the second chromosome are 

 rekitively numerous and tend to mask each other's effects. Generally, 

 therefore, two wing-characters are not used simultaneoulsy, and the 

 choice falls on the one having the locus best adapted for the particular 

 experiment. If jaunty were in the neighborhood of streak or in any of 

 the long empty regions of the second chromosome it would be consid- 

 ered a mutation of first rank. 



CURVED (c). 



(Text-figure 75.) 



DISCOVERY AND STOCK. 



A third mutation in the rudimentary stock, curved wings, was found 

 by Bridges December 24, 1911 (notebook A, p. 43). This mutation 

 appeared in both males and females and both as rudimentary and as 

 not-rudimentary individuals (fig. 75), from which facts it was concluded 

 that the mutation was probably not sex-linked. The not-rudimentary 

 curved males and females were mated together and produced in the 

 next generation a stock about 80 per cent of which was curved; the 

 20 per cent of not-curved flies was the result of non- virgin mothers. 



Virgin not-rudimentary curved females were mated in pairs to 

 similar males, and all of these pairs produced pure stock of curved. 

 Furthermore, about half of the pairs gave no rudimentary sons, and 

 these cultures, known to be entirely free from rudimentary, were used 

 as the permanent stock of the mutation. 



DESCRIPTION OF CURVED. 



The most characteristic feature of the mutation '' curved " is perhaps 

 the thin texture of the wing and its accompanjdng slight but charac- 

 teri'stic crinkhness like waxed paper. More striking than the texture, 

 though perhaps a result of it, is the strong downward curve of the wing. 

 The curved wings are generally held out at a wide angle (60°) from 

 the body and are elevated (30° to 60°). The pose and curvature of 

 the wings are quite bird-like, and the first name of the mutation was 

 "gull." The divergence of the wings, as in all other mutants possess- 

 ing such a characteristic, is the first index of the mutation to catch the 

 eye when the flies are drawn out in a windrow for separations. In a 

 few of the flies both the elevation and the divergence of the wings are 

 sHght, and in these cases the curvature and the texture of the wings 

 are used as indexes. In spite of the thin texture of the wing and the 



