1. A method for the separation of erythroblasts in quantity from normal red cells in the blood of ducks infected with malaria has been described.
2. The erythroblasts in comparison to the normal adult red cells of the duck have a larger cell volume, less hemoglobin, and show a greater discrepancy between the colorimetric hemoglobin and hemoglobin calculated from the oxygen capacity.
3. The erythroblasts in the duck use four to five times the amount of oxygen that is consumed by the adult red cells in the ducks.
4. The function and possible fates of the erythroblasts which occur in the duck during the anemia caused by malaria are discussed.