That these "pinks" were really products of the cross is proven by the result of crossing one of them to one of her eosin vermilion brothers, for she showed herself to be heterozygous for eosin, vermilion, and sable.
"Sex-linked Inheritance in Drosophila"
Thomas Hunt Morgan Calvin B. Bridges
Although the mother was fertilized by a normal male, every daughter is heterozygous for one or the other of the lethal factors.
"Sex-linked Inheritance in Drosophila"
Thomas Hunt Morgan Calvin B. Bridges
The normal male is heterozygous for this normal factor.
"Hormones and Heredity"
J. T. Cunningham