The epithelium of the roof of the stomach is not specially differentiated and apparently has little or no part in digestion. The epithelium of the floor, on the other hand, is composed chiefly of very high and thickly crowded columnar cells which are usually described as coarsely granular, but under high powers appear to be filled with vacuoles surrounded by a network of cell substance. Thickly interspersed among these columnar cells are goblet cells filled with mucus. The floor is thrown into numerous wrinkles by ridges in the supporting gelatine resulting in increase of digestive surface. The four perradial grooves of the proboscis are continued in the perradii along the floor of the stomach as four fairly deep furrows, which lead directly to the gastric ostia and stomach pockets--structures to be described presently. These furrows are lined with crowded columnar cells, smaller and denser than the other cells of the digestive epithelium, containing no granules and but little beside the relatively large, compact, deeply staining nuclei. The furrows probably represent special ciliated courses. 7. _Phacelli._ Lying in the four interradial corners of the stomach are the four phacelli or tufts of gastral filaments to the number of thirty or thirty-five in each tuft. The filaments are attached to a single stalk, like the fringe of an epaulette or the hairs of a coarse brush. The stalk bearing the filaments is an outgrowth of the lower wall of the stomach just at the point where it fuses with the upper. The phacelli are therefore structures of the subumbrella, proof of which will be found under the special topic of the vascular lamellæ. The stalk, an indication of which appears in _sph_. Fig. 6 (the section being a little below the axis of the stalk, which lies horizontally), consists of a firm core of gelatine covered with the high columnar epithelium of the floor of the stomach. The filaments themselves are slender processes repeating the structure of the stalk and having a central axis of gelatine for support covered with glandular epithelium, which in the case of the filaments bears numerous nettle cells. These processes are extremely contractile, and in the living animal show a continuous, slow, squirming movement like a mass of worms. The section just referred to (Fig. 6) shows diagrammatically three of these filaments (_fph_) cut across in each quadrant. 8. _Peripheral Part of the Gastro-vascular System._ The proboscis and stomach proper comprise the central part of the gastro-vascular system. In direct communication with the central is a peripheral part composed of pouches or pockets lying in the vertical sides of the cube-shaped bell, just as the central stomach lies in its roof. The peripheral part may be subdivided for convenience of description into the stomach pockets, the marginal pockets, and the canals of the tentacles and sensory clubs.