Additional growth--a link between mammalian testes, avian ovaries, gonadal asymmetry in hermaphrodites and the expression of H-Y antigen.

In human hermaphrodites, testes are preferentially situated on the right and ovaries on the left side. This asymmetry can be related to the results of measurements on the growth of fetal gonads. Testes exceed ovaries in weight, protein and DNA contents in fetuses of the same crown-rump length, and in both sexes, right gonads exceed left gonads in the same criteria. These findings, support the hypothesis that in mammals, a basic growth rate will convert the bipotential gonadal rudiment into an ovary while an increased growth rate is required for testicular development. Relative growth rates of chick embryo gonads are largely, although not entirely, the opposite of those in mammals: during the major period of gonadal differentiation, the ovary exceeds the testes in growth. The expression of H-Y antigen in birds and mammals seems to correspond to the presence of the faster growing gonad. These data do not support the hypothesis that H-Y antigen is the primary determiner of sex but a secondary involvement is likely.