The first case of a melanotic lethal in Drosophila melanogaster was reported by Bridges in 1916. He described the appearance of black masses in the larvae and demonstrated that this hereditary abnormality was caused by a sex-linked factor. Stark ('18) made a histological study of this abnormality and called the black masses "tumors" since they represented cellular overgrowths. She assumed that the 1 (1) 7 tumors were malignant because the larvae developing these black masses always died. Later several other tumorous strains were found which were not lethal, and Russell ('40) implanted tumors from the supposedly malignant strain and tumors from non-malignant strains into normal hosts. She reported that all of the tumors were benign, and the death of 1(1)7 larvae was caused by an abnormality of the gut rather than the presence of tumors.
Oftedal ('53) examined 6 tumorous stocks and concluded that tumors in Drosophila result from the aggregation of blood cells without any atypical cell proliferation. The common feature of all the tumorous stocks was the presence of spindle shaped blood cells. The encapsulation of various Supported by an institutional grant-in-aid from the American Cancer Society, administered by the Yale University Committee on Atypical Growth.