224 THE AMERICAN NATURALIST [Vol. LVI 



Rough (r) 



Description. — Eough eye affects mainly the surface of 

 the eye (Fig. 8). When the outer portion of the eye is 

 mounted and examined under the high-power microscope 

 it is seen that the ommatidia are irregular in shape and 

 size with uneven surfaces which are more convex than 

 the normal. The normal eye has regular hexagonal 

 facets with a bristle at every alternate intersection of 

 the sides (See Carnegie Publ. 278, Plate 10, Fig. 3c for 

 the normal eye of D. melanogaster which has the same 

 arrangement). The bristles of rough eye are irregularly 

 distributed with groups collected in one place and no 

 bristles at all in another. These bristles are about one 

 and a half times the length of the normal ones. 



The roughened condition is similar to that found in 

 star eye of melanogaster (Carnegie Publ. 278, Text-fig- 

 ure 83). The eyes of willistom rough are also somewhat 

 glossy in texture, and the wing veins are slightly heavier 

 than in the normal flies. 



Origin. — Several rough males and females were found 

 in one of the bottles of a stock that had been kept in the 

 laboratory for approximately four years. It is probable 

 that the mutant gene had been present in the stock for 

 some time. 



Triple (tr) 



Description. — r Triple causes four variable wing 

 changes, one or all of which may be present in either or 

 both wings (Fig. 10). (1) The second and third veins 

 may be fused for a short distance at their origin. (2) 

 The wings, slightly tilted up at the ends, are held away 

 from the body at an angle which varies up to about 90°. 

 (3) The third veins fail to reach the distal margin of the 

 wings by amounts which vary from almost nothing to 

 one third the length of the vein. This is particularly 

 evident in the females, where a large section may be 

 missing from the central part of the third vein. (4) An 

 extra cross-vein is present between the second and third 



