Abstract
Strains of Drosophila melanogaster that carry the tumorous- head trait are characterized by amorphous growths which occur in the head region of the flies. This trait, symbolized tu-h, is extremely variable in expression with growths ranging from very small irregularities involving only a few eye facets to large tissue masses distorting most of the head (Garnder and Woolf, 1949). The abnormalities may involve one or both eyes, antennae, and areas of the face, but not the mouthparts. The phenotype results from aberrant development of the eye and antennal imaginal discs (Newby, 1949). The tumorous-head outgrowths include homoeotic changes in which parts of the head are replaced by parts of the genitalia, abdominal tergites and legs (Postlethwait, Bryant and Schubiger, 1972).