Evidence for multiple sex factors in the X-chromosome of Drosophila melanogaster

The data presented here permit a decision between two alternative hypotheses regarding sex determination in Drosophila melanogaster. Bridges(1,2,3) has shown that the sex of an individual in this form is determined by a relation between the number of the X-chromosomes and that of the autosomes. From his studies of a variety of sex types (table 1), he has concluded that the X-chromosome turns the course of development toward femaleness, the autosomes toward maleness.