The relationship between the red cell forms and surface area during thyroxine induced metamorphosis in Rana cyanophlyctis.

A study of the effect of exogenous thyroxine on the red cell form and surface area during Rana cyanophyctis metamorphosis is made. Haemoglobin presents changes in its affinity for O2 with age. A loss of 35 per cent in the mean surface is recorded on the eleventh day after thyroxine treatment. The early appearance of adult erythrocytes, compared with control is due to a change in the time scale of metamorphosis.