FOOD LEVEL IN RELATION TO RATE OF DEVELOPMENT AND EYE PIGMENTATION IN DROSOPHILA MELANOGASTER 1 G. W. BEADLE, EDWARD L. TATUM AND C. W. CLANCY (From the School of Biological Sciences, Stanford University) INTRODUCTION Beadle and Law (1938) have shown that the eye color hormones concerned in the differentiation of vermilion and cinnabar eye colors in Drosophila melanogaster are effective when administered with larval food. In attempting to develop a standardized method of feeding these hormones quantitatively, it became evident that information was needed on the relation between food-level and rate of development (see North-rop, 1917a, and Baumberger, 1919, for accounts of previous work bear-ing on this). During the course of experiments designed to give such information, Dr. Boris Ephrussi of the Institut de Biologic physico-chimique, Paris, informed us (personal communications) of feeding experiments made in his laboratory, the results of which appeared to be understandable on the assumption that food-level had an effect on pigment production in genetically vermilion brown flies. After pre-liminary experiments had given results consistent with this assumption, systematic studies, approaching the general problem in somewhat dif-ferent ways, were undertaken in the two laboratories. The paper pre-ceding this (Khouvine, Ephrussi, and Chevais, 1938) and the present report summarize these experiments. THE SEVENTY-HOUR CHANGE If larvae are removed from standard food (cornmeal-molasses-agar, seeded with an excess of fresh baker's yeast) at various stages of de-velopment, rinsed with Ringer's solution, and transferred to vials con-taining filter paper moistened with Ringer's solution, there is no further increase in size. Those removed at any time up to about 70 hours after egg-laying (at 25 C., the temperature at which all experiments were carried out) may continue to live for several days but eventually die unless given additional food. Larvae similarly removed from food shortly after 70 hours fail to increase in size but continue to differentiate 1 Work supported in part by funds granted by the Rockefeller Foundation. 447
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