14 JOHNS HOPKINS UNIVEESITY MORPHOLOGICAL MONOGRAPHS. 



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 there- 

 fore structures of the subumbrella, proof of which will be found under 

 the special topic of the vascular lamellae. 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. 



(a) Stomach Pockets. These are four broad, thin pouches lying 

 between the exumbrella and the subumbrella in the four perradii (e. g. 



