Influence of heterospecific testis graft on the gonadal sex differentiation of female bird embryos.

Testes from duck and chick embryos grafted, respectively, to chick and duck genetically female host embryos modifies their gonadal differentiation. It results in masculinization developing, in some cases as far as testis formation. This demonstrates 'in vivo' that the testis inductor(s) secreted by the grafted testis is (are) interspecific. Duck gonads are more sensitive than chick gonads. Such grafts also cause the regression of Müllerian ducts. Comparison of the effects on ducts and gonads reinforces the view that both could depend on the same substance, i.e., anti-Müllerian hormone.