24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



plant supplies to the blood of the mutant host the necessary precursor 

 substance in the presence of which the pigment synthesis can be com- 

 pleted. Injection of the pure precursor, in this case kynurenine, also 

 restores pigment formation. The genetic evidence, however, suggests 

 that there are after 3-hydroxykynurenine two further steps before the 

 final pigment is formed. The corresponding intermediate compounds 

 are not known and they are apparently also not diffusible. 



Since most of the experiments involving the transplantation tech- 

 nique as a tool for the analysis of eye-color development in flies were 

 performed on Drosophila, it was of interest to know whether the same 

 metabolic pattern also holds for other Diptera. The occurrence of two 

 eye-color mutants, one in our Musca domestica and the other in our 

 Phormia regina culture, provided the experimental material for such a 

 comparison. The eye color of these two mutants is a yellowish green, 

 strikingly distinct from the reddish-brown eye color of the wild-type 

 flies. It was soon established that the development of the brown pig- 

 ment in the green-eyed mutant depended on a diffusible intermediate, 

 for the eyes of both green mutants on transplantation into a normal 

 wild-type host developed an eye coloration that approximated the color 

 of the wild-type host. It was also found that other wild-type genera 

 elicited the diffusible precursors needed for the development of pig- 

 ment in the eyes of the green mutants. All the experimental evidence 

 reported in this paper, based on transplantation of organs between 

 different genera, on injections of pure pigment precursors, and on ob- 

 servations of testis pigmentation suggests that the biosynthesis of the 

 brown pigment in Musca and Phormia is very similar to that found 

 in Drosophila and other insects. 



MATERIAL AND METHODS 



The experimental material used for these investigations includes the 

 following Diptera: Musca domestica (Linn.), Musca domestica mu- 

 tant green, Phormia regina (Meigen), Phormia regina mutant green, 

 Callitroga macellaria (Fahv.), Fucellia maritima (Haliday), Cynomya 

 cadaverina (Fabr.), and Sarcophaga bullata (Parker). The majority 

 of the experiments were performed on Musca domestica and Phormia 

 regina and their two green-eyed mutants. The eye color of these two 

 mutants is very similar: it is a yellowish green. The eye of the 

 Phormia mutant is perhaps a little more yellow. Both mutant stocks, 

 if raised on meat, produce in mass culture flies with remarkably uni- 

 form eye color. 



Last-stage larvae, shortly before puparium formation, were used 



