PRIMITIVE ERYTHROPOIETIC SERIES IN CHICK EMBRYO, STUDIED WITH ELECTRON MICROSCOPE

The ultrastructural aspects of the chick embryo primitive erythrocytic cell series are described. There are two points of particular interest: the appearance of ferritin in erythroblast cytoplasm in 20 somite stage embryos and the behaviour of ribosomes during the red cell maturation period, both with regard to their progressive diminution and how they are grouped in polyribosomes. Ribosomes are still present in primitive series erythrocytes, although fewer than in the immature cells, and they are mainly in group form. A morphological comparison of the primitive red series erythrocytes with those of the definitive red series has also been made. Copyright © 1969 Wiley‐Liss, Inc.