ヌマガエル雄の性分化

概要

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More than 1, 500 frogs of Rana limnocharis were collected in Kumamoto district and used for a morphological study on the differentiation of their gonads. Results obtained were as follows: 1) Shortly after metamorphosis the gonads of all young frogs are of ovarian type in external appearance at least. But as they grow older, the gonads in about a half of them become testes, which are distinguishable macroscopically from the ovaries. This sex ratio is established at the end of the first year. 2) Examining the gonads microscopically at the end of metamorphosis, the gonads of the genetic males have a testicular structure, and in about a half of them the oocyte-like cells are present. 3) Although most of the oocyte-like cells degenerate during the first year, some of them remain and continue their growth in the following year. But they seldom attain about 150μ in diameter.
1951-11-15