Influence of embryonic and adult testis on the differentiation of embryonic ovary in the mouse.

The development of 11 1/2-13 1/2-day embryonic mouse ovaries subjected to the influence of adult and embryonic testes was investigated. The environment of adult testis caused severe restriction of ovarian growth, but did not produce any effects which might be considered as masculinization. The presence of embryonic testis was distinctly unfavourable to the embryonic ovary, resulting in restriction of the growth of the latter and degeneration of oocytes. Reversal of the course of differentiation of genetically female germ cells has never been observed.