On the Inheritance and Expression of a Mottledeyed Mutant in Drosophila Melanogaster.

OTTLED-EYED flies have been reported on various occasions by M numerous investigators. The following paper presents further data on the inheritance and expression of a mottled-eyed mutant of Drosophila melanogaster. The mutant first appeared in a progeny of flies which had been subjected to supersonic vibrations in an experiment conducted by HERSH, KARRER and LOOMIS (1930), in an attempt to induce mutation. In this experiment there appeared five mottled-eyed males in the progeny of 26,135 flies, resulting from matings of treated cut forked Bar males with virgin double-yellow females with attached X chromosomes. This fact suggested sex linkage. The mottled males were bred to the double-yellow sisters and the flies in the F1 were normal in each case. Upon allowing the F1 to interbreed some mottled flies of both sexes appeared in the Fz. The character was then carried along with a greater or smaller number occurring in each generation. The mutant was later crossed with a vermilion stock by DR. W. P. SPENCER thus producing a stock of vermilion mottled-eyed flies. Such was the nature of the stock at the beginning of this investigation. The mutant shows a pronounced dark mottling of the eyes and was illustrated by SURRARRER (1935). These illustrations show variations from almost complete dark pigmentation to nearly entire removal. At temperatures of 25°C and above complete removal of the dark pigmentation results. Not only is there variation in the magnitude of the effect, but also a considerable variation in the compactness of the darkened area. Because of this variability and frequent lack of the character expression under ordinary culture conditions, it was necessary to find control methods for production. The author found (1935) that the character was expressed at temperatures of 2ooC or below. It was further found that the temperature-effective period was in the pupa stage and that the percentage of the area of the eye affected was inversely proportional to the developmental temperature. If the main problem of genetics and development is the determination