[Ultrastructure of the blood cells present in the Y organ of Carcinus maenas L. (Crustacea, Decapoda)].

Ultrastructural characters of the hemocytes in the Y organ of Carcinus maenas lead us to assimilate these cells to the "granulocytes". In the degenerating glands, these hemocytes evolve towards a peculiar physiological state: they show a phagocytic activity which confers on them macrophagic properties.