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Morphology of Cell Types from the Gastric Epithelium of Ciona Intestinalis

The stomach is the principal region of extracellular digestion in the alimentary tract of Ciona intestinalis (L.) (Yonge, 1925; Morton, 1960). The region is oval and has a lining epithelium thrown into 30 or 40 longitudinal ridges. Previous authors have described the following cell types in this gastric epithelium: a mucous cell (Roule, 1884; van Weel, 1940); an un-differentiated cell (Yonge, 1925; Millar, 1953; Fouque, 1954); an absorptive cell (Yonge, 1925; Berrill, 1929; van Weel, 1940; Morton, 1960); a storage cell (Yonge, 1925; van Weel, 1940) and several different secretory cells (Roule, 1884; Yonge, 1925; Berrill, 1929; van Weel, 1940; Millar, 1953; Fouque, 1954; Morton, 1960). The present paper reports a re-investigation of the gastric epithelium by histochemical methods and by electron microscopy, and a comparison of the observations with those of previous authors. The fine structure of the gastric cells is compared with that of cell types in the ‘liver’ of Pyuridae (Degail & Lévi, 1964) and in the alimentary tract of other animals.