We are only at the beginning of trying to find out what matings produce the best offspring.
"The Book of Life: Vol. I Mind and Body; Vol. II Love and Society"
Upton Sinclair
Since both females and males of chrome were on hand, it should have been an easy matter to continue the stock, but many matings failed, and it was necessary to resort to breeding in heterozygous form.
"Sex-linked Inheritance in Drosophila"
Thomas Hunt Morgan Calvin B. Bridges
Do not be in any hurry to mate them, as their first eggs are usually bad and they sometimes will break their matings when taken out too young.
"Raising P.V. Squabs for Profit"
John S. Trecartin