[The Seasonal Dynamics of Erythropoiesis in the Frog Rana Temporaria]

Studies have been made on the dynamics of erythropoietic activity of the bone marrow in mature female frogs. Evident monocyclic pattern of erythroid blood production was found, its maximum activity being closely related to seasonal changes in physiological reparation of the main bulk of functional systems of frog's organism. The data obtained indicate that the bone marrow is the main site of erythropoiesis in the frog.