Gonadal Growth in Embryos of Sex reversed Mice

Gonadal volumes were measured in litters of mouse embryos, aged 15 and 16 days, which were segregating for the Sex reversed factor. The testes of XY embryos were much larger than the ovaries of female embryos and the testes of XX Sex reversed males were almost, but not quite, as large as those of XY males. One of the 13 Sex reversed embryos had ovotestes.
It is concluded that the Sex reversed factor causes an increase in the growth rate of XX gonadal rudiments and that this is a necessary prerequisite for testicular differentiation. It is further postulated that the failure of spermatogenesis seen in adult Sex reversed , XX males is a result of the suboptimal growth rate of the gonads, compared to that of normal testes seen in the embryos. The formation of ovotestes may result from a growth rate which is at a lower limit of that necessary for testicular differentiation.