Rat megacaryocytes in the thrombocytogenic stage were studied in fetal liver and adult bone
marrow. Megacaryocytes are spherical or ovoid cells during differentiation. Prior to the
liberation of platelets in the thrombocytogenic stage, the cells become highly irregular in
outline owing to the formation of cytoplasmic extensions protruding between neighbouring
parenchymal cells or into sinusoids between sinusoidal lining cells. Pieces of cytoplasm of
varying sizes are released from the cytoplasmic extensions; the pieces subsequently …