sex-linked mutant deep orange (dor) of Drosophila melanogaster is T z o n s i b l e for a peculiar type of female sterility: mutant females produce no progeny when crossed to mutant males but yield some offspring (heterozygous daughters) when mated to wild-type males (MERRELL 1947). The effects of this mutant on embryonic development have been extensively studied by COUNCE (1956a) and more rece...