Development of Eye Colors in Drosophila: Time of Action of Body Fluid on Cinnabar.

HE development of vermilion eye color in mosaics of D. simulans is T not always autonomous (STURTEVANT 1932). By transplantation experiments BEADLE and EPHRUSSI (1936) have shown that the vermilion and cinnabar eye colors of D. melanogaster are not autonomous in development. Vermilion and cinnabar late larval eye discs develop the wild type pigment when transplanted to late wild type larvae. Vermilion discs also develop the wild type pigmentation when implanted in cinnabar hosts, but cinnabar discs remain cinnabar in color when developing in vermilion hosts. From this and similar data BEADLE and EPHRUSSI have postulated the presence in the wild type host of two diffusible substances (v+ and cn+ substances), the presence of only one of these (the v+ substance) in the cinnabar tissue, and the absence of both of these substances in the vermilion tissue. It is of interest to ascertain when these two genetically determined diffusible substances are present and during what period of development they operate in the determination of the ultimate eye pigment. This has been done for the v+ substance (EPHRUSSI, CLANCY, and BEADLE 1936; BEADLE, CLANCY, and EPHRUSSI 1937). They have shown by the injection of body fluid from wild type donors of various ages into apricot vermilion (w" v) hosts 60 hours after puparium formation that the v+ substance was not present in the wild type larvae 3 to 12 hours before puparium formation, but was present in the wild type from 3 to 80 hours after puparium formation. Similarly, body fluid obtained from wild type donors 60 hours after puparium formation and injected into apricot vermilion hosts of various ages effected a change in eye color in all hosts from late larvae to 64 hours old pupae, with a negative or weak effect a t 70 hours, and negative results in still older recipients. These results demonstrate the absence of the U+ substance in the wild type larval body fluid and jts presence during approximately four fifths of the prepupal and pupal periods. The data also indicate the possibility of inducing a change in eye color from vermilion toward wild type by the injection of wild type body fluid into wa v hosts at any time prior to approximately 70 hours after puparium formation. The following experiments were performed to obtain similar information regarding the cn+ substance; that is, the time during which it is present in