Further Data on Material Effects in Drosophila Pseudoöbscura Hybrids

Race B females of Drosophila pseudoöbscura crossed to race A males produce sterile F1 hybrid males having visibly small testes. The reciprocal cross, A ♀ X B ♂, produces in F1 sterile males that have testes of normal size. One of us(1) has shown that this difference between the reciprocal crosses is due to a maternal effect. Before fertilization, the cytoplasm of the eggs deposited by race B females is so influenced by the chromosomes present in it, that an interaction between this cytoplasm and the autosomes of race A (introduced by the spermatozoon) results in the development of small testes in males arising from such eggs.