Development of Eye Colors in Drosophila: Production and Release of cn Substance by the Eyes of Different Eye Color Mutants.

H E evidence given in previous papers by the authors has led to the T hypothesis that individuals with the mutant eye color vermilion are deficient in two diffusible substances. These have been designated v+ and cn+ substances. It has been shown also that either one or both of these substances are necessary for the development of any one of several other mutant eye colors. The method of establishing the latter fact was to transplant eye anlagen from larvae homozygous for vermilion and for the mutant gene in question (vvxx) into wild type larvae. Such implants developed the color characteristic of the mutant x (that is, ++xx) and not that of the combination vvxx. A genetically vermilion eye-implant was thus modified by the host into a nonvermilion phenotype. The phenotype x thus depends upon v+ or cn+ substance or both. These are supplied by the wild type host, but not by the genetically vermilion donor. This is not true of the vermilion-like eye color mutants (cardinal, cinnabar and scarlet) ; here we have no evidence that the double recessives with vermilion are phenotypically different from vermilion. Eye disks of the mutants bordeaux ( b o ) , clot (c l ) , Henna-recessive (Hn') , mahogany (mah), purpleoid ( p d ) , prune-a (pn2), purple ( p r ) , raspberry-a (vas2), sepia ( se) , sepiaoid ( sed) , and safranin-a ( s j2 ) grown in vermilion hosts give rise to eyes more or less intermediate in color between their own control implants and control implants of the double recessives with vermilion. It was concluded (EPHRUSSI and BEADLE 1937") that, in these mutants, the eye itself is incapable of producing sufficient v+ or cn+ substance, or both, to give the characteristic pigmentation of the mutant.l Since we know that a vermilion host is deficient in both v+ and cn+ substances, the above experiments do not distinguish between production of the two different substances by the implant. By growing eye-implants in cinnabar hosts, which are deficient in cn+ substance but not in v+ substance, it should be possible to make this distinction; this is the primary purpose of the work reported in this paper. In studies of the release of diffusible substances by eye-implants, it has