| Resumo: |
A description is given of the activity of the thyroid and of the pituitary gland during the development of the gonopodium in the viviparous Cyprinodonts Lebistes reticulatus (Peters), Xiphophorus helleri (Heckel) and Xiphophorus maculatus (Günther). During this process the thyroid gland and the glandular lobe (lobus anterior and lobus intermedius) show a gradual increase in activity. This activity was in general most pronounced in Lebistes reticulatus (Peters) and weakest in Xiphophorus maculatus (Günther). This increase in activity suggests that the developement of the gonopodium is probably regulated endocrinally. For the determination of the state of thyroid and pituitary activity use was made of the quotients d/n and D/n (Lever, 1948 and 1950; cf. Lever, Miltenburg and Van Oordt, 1949, and Stolk, 1951 c, 1956 g, 1957 b and 1958 b) and the quotients ch and cs (Stolk, 1954, 1955 a, 1956 a, 1956 c, 1956 d, 1956 e, 1956 f, 1957 a, 1958 a and 1958 b), respectively, and moreover of the nucleus size, the mitotic activity, the nucleus structure, the chondriome and the Golgi apparatus.
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