The development of pigment in the eye of Drosophila melanogaster and other insects has been the subject of many studies and much controversy. It has been established that the red color of eyes of wild-type D. melanogaster is due to the presence of two classes of pigments, ommochromes and pteridines (Ziegler, 1961). The relationships among the various members of each class are still obscure; the biosynthetic pathways are yet to be elucidated. No specific enzyme involved in the synthesis of any

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... mber of either group has been isolated or characterized. It has been suggested, however (Hadorn, 1955) , that these metabolic pathways may involve several organs, including the eye, but that the final deposition and conversion occur only in the eye. The recent development of a satisfactory technique for the culture of Drosophila organs (Schneider, 1964) has made possible the study of pigment development in the isolated eye and in eyes associated with selected organs. Thus it is possible to test the hypothesis that organs interact in the formation of eye pigments. MATERIALS AND METHODS Wild-type (Oregon-R) Drosophila melanogaster were used as tissue explant sources in all experiments. These were raised on the usual cornmeal-molasses-agar medium at 25 ±0-5 °C and were transferred daily to fresh food. Prepupae were removed from the bottles and placed in Petri dishes on sterile filter paper moistened with sterile saline (Waddington's modified Ringer's solution, I. Schneider, personal communication). The characteristic prepupal stage (soft and white with everted anterior spiracles) has a duration of no more than an hour; thus the development can be timed very accurately.