A SOMATIC MUTATION IN DHÜSOPIIII.A M1;|,AN{)<;ASTEH 



147 



singed. Tlic same was Iruo of tlie. l)ristlos and liairs on the dorsal 

 part of tlie right half of the tliorax, while the rest of the thorax had 

 normal bristles. Thus, the right sterno-pleiirals were \vild-typc in 

 contrast to all the other thoracical macrochaetae, (Fig. 2 and 3). The 

 i)order line between the two zones followed on the ventral side of the 

 thorax the median j)lane strictly. 



The entire lell lialf of Uie abdomen had singed hairs and bristles 

 in contrast to the normal ones of the right half. The border line 

 between the singed and the non-singed part here followed strictly 

 the median plane, and could be controlled, on the dorsal side by the 

 shape of the hairs and bristles on the dorso-lateral plates, on the 

 ventral sid(> by llie shape of the hairs on the ventral plates, which 



The mosaic as seen from the left side. 



had singed hairs on the left and wild-type hairs on the right side. 

 The hairs and bristles on the genital arch and the anal plates were 

 singed on the left side, wild-type on the right. 



The hairs on the alula and on the costa of the left wing were 

 singed, in contrast to the corresponding wild-type ones on the right 

 wing. The difference is most easily detected by comparing on both sides 

 the form of the larger pair of bristle-like hairs just before the apex of the 

 first vein. The bristles on the coxae as well as those on the femur and 

 near the apex of the tibia were on the left legs typically singed, while 

 the corresponding ones on the right legs were of the wild type. 



Summing up, we find accordingly that the entire left half of the 

 individual, except for the head, is singed. The border line separating 



