Fluorescent granules that are stained with Nile blue sulfate are present in larval Malpighian tubules in the wild type strain of Drosophila melanogaster, Oregon-R. These granules emit a weak blue fluorescence and most of them are about 2 microns or more in diameter. The ommochrome precursor 3-hydroxy-kynurenine (3-HK) is actively transferred into the tubules of Oregon-R. Changes in the fluorescent granules in the Malpighian tubules on administration of ommochrome precursors were investigated in eye color mutants of Drosophila. The fluorescent granules in the tubules of the nonautonomous mutants v;bw and cn bw emit a strong blue fluorescence and most of them are about 1 micron or less in diameter. When v;bw and cn bw larvae were cultured on medium supplemented with kynurenine or 3-HK, respectively, the fluorescence intensity of their granules decreased, and their size increased. These additions resulted in almost equal accumulation of 3-HK to that in Oregon-R. On the other hand, no 3-HK accumulated in the tubules of larvae of the autonomous mutants bw;st, ltd bw and w, which lack the fluorescent granules. These findings indicate that the fluorescent granules are an important intracellular site for uptake or storage of ommochrome precursors in larval Malpighian tubules of Drosophila.

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Quantitative variations among strains in special cytoplasmic granules have been known in some species of insects.The mode of inheritance of such cytopla:smic granules has extensively been discussed by Caspari (1933), Cochrane (1938) and other investigators.The author (Yagi 1962b) previously demonstrated the quantitative difference among strains in the nile blue granules (N. B. G.) in fat-body cells of early prepupae of Drosophila melanogaster.And the strains studied in that investigation were classified into three types according to their relative contents of the N. B. G.; i. e., the large, intermediate and small quantity types.The present paper deals with the relative quantities of the N. B. G. in the F1 hybrids from crosses among strains belonging to different types.Special attention was paiLd to the relation between the quantity of the N. B. G. in the fat-body cells and the brown pigment in the eyes of the offspring. MATERIALS AND METHODSFive strains of D. melanogaster, Oregon-R, v (vermilion), cn (cinnabar), st (scarlet), and Muller-5, were chosen as the parental stock strains for the crossing experiments performed in the present study.According to the preliminary examination (Yagi 1962b), the wild type Oregon-R strain contained the largest quantity of the nile blue granules among all these parental stock strains and the Muller-5 strain was with the smallest quantity.The remaining three eye color mutant strains, v, cn, and st, belonged to the intermediate type.To obtain the F1 hybrids to be tested for the relative quantity of the N. B. G. in the prepupa and the eye color of the adult, various experimental crosses were made among these strains. For each experimental cross, eight to twelve virgin females were mated with an equal number of 2-day old males from another strain.The larvae were reared with a Tohoku-D4 medium (made from soybean-flour, wheat-flour, sugar, agar and water) in half pint milk-bottles at 25°C.When the larvae to be tested had grown to early prepupae, they were sexed by the size of gonads and vitally stained with 0.05 % nile blue sulfate in Ringer's solution. The quantities of the N. B. G, in the fat-body cells were measured by the grade system* as described in the previous paper (Yagi 1962b). Some of pupae saved without treating nile blue sulfate were allowed to grow into adult

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