STORAGE CELLS OF MUSSEL, Mytilus galloprovincialis: HISTOCHEMICDAELM ONSTRATION OF GLYCOGEN. - This study deals with the demonstration and localization of glycogen in the storage cells (vesicular cells, VC and adipogranular cells, ADG) of the mussel. Mantle portions of mussel, Mytilus galloprovincialis (Lmk.) were directly processed in the cryomicrotome; other portions were immersed in different fixatives and embedded in paraffin. The glycogen contained in the vesicular cells (hydrosoluble) remains present in samples non included in paraffin. Two types of glycogen could be detected in the adipogranular cells, the conservation of which depends on the composition of the fixatives.