An Hereditary Tumor in the Fruit Fly, Drosophila

Abstract

In the fruit-fly Drosophila melanogaster ( ampelophila ) there have been found by various workers certain factors called “lethals,” the observed effect of which is to kill the fly at some pre-adult stage. There was, however, little direct evidence to show how these factors produced their lethal effect until the discovery by C. B. Bridges of a lethal, lethal 7, which causes the development of one or several black granules within the body of the larvae (Bridges, Genetics , Jan., 1916). Bridges observed that in the cultures of lethal 7, about a quarter of the larvae showed these intense black “spots” and further that these larvae behaved very differently from normal larvae, frequently crawling out of the food and wandering about upon the walls of the culture bottle. These black-spotted larvae died in great numbers either upon the walls of the culture bottle or in the food. From the definite mode of occurrence of these black-spotted larvae throughout many and varied experiments made to test the mode of inheritance and the location of the: factor involved in lethal 7, he concluded that these black-granuled larvae were the males having the lethal 7 factor, and that their death was probably connected with the development of the black bodies. The lethal 7 stock was turned over to the author to find out (1) the nature of the black body found in the larvae that die; (2) whether it is in itself the cause of death or only a by-product of the condition of the larvae; (3) whether by removal of the black body the life of the larva would be prolonged; (4) whether the transfer of the black body to normal larvae would cause their death; (5) the effects of x -rays upon the black body; (6) in what tissues the black body develops.