[Comparative analysis of the seasonal changes in hematopoietic processes in the spleen and peripheral blood of the common frog. I. The erythroid series].

To determine the rate of erythrocyte maturation, changes in the number of different erythroblast types in the frog peripheral blood were studied. In the blood flow, erythroblasts were found to develop in summer as an independent, partly synchronized cell population. The most advanced erythroid cells capable of DNA synthesis (the acidophilic erythroblasts) were estimated using thymidine autoradiography. These cells entered the mitosis 1-2 days after DNA synthesis. The time of erythrocyte maturation, following the last S-phase, was 9-12 days. The functioning of the peripheral blood as a locus of erythropoiesis is suggested to be an adaptation associated with the seasonal periodicity of haemopoiesis.