The megaloblast is an abnormal immature red cell precursor and is the equivalent of the normoblast in normal red cell production. (The general term 'erythroblast' covers both normoblasts and megaloblasts). The megaloblast is characterized by (a) its larger size and (b) the fine reticular nuclear structure in comparison with the nuclear structure of a normoblast at the same stage of cytoplamic haemoglobinization.