REPORT ON CEPHALODISCTJS DODECALOPHUS. 17 



(Esophagus. — The firm and finely glandular oesophageal region (PI. III. fig. 3, a little 

 behind ce), which is characterised by the paucity of its folds, is comparatively short, for it 

 merges into the gastric chamber a little behind the termination of the buccal shield 

 (PI. III. fig. 3). 



Stomach. — The stomach forms a large cavity, which in some instances fills the whole 

 of the body-space, with the exception of the dorsal area occupied by the intestine. In 

 certain longitudinal sections the oesophagus forms a comparatively limited tube, while the 

 stomach fills the entire body-cavity (PI. III. fig. 3), liut dorso-ventral flattening of the 

 former may have occurred in such cases. The wall of this region is also somewhat thick, 

 and when fully formed, is distinguished from the oesophageal region by its more numerous 

 and often symmetrical folds, and sometimes by a differentiation into three pseudo-strata, 

 viz., a deeply stained, granular, epithelial, superficial layer marked by close parallel striae, 

 a pale intermediate region with granular glands, and externally another deeply stained 

 stratum of granular glands. It is not implied that there is separation in continuity 

 between the three regions indicated, but rather that either from preparation or otherwise 

 such a condition appears in the stomach. The colour of this region in life is probably as 

 characteristic as in Rhabdopleura, where it is yellowish, but this feature cannot be 

 made out in the spirit-specimens, for all are bleached. In the preparations it not 

 unfrequently happens that rupture of the alimentary wall occurs along the middle region, 

 so that the complexity of the folds in the body-cavity is increased. Externally the 

 whole organ is surrounded by a firm basement-layer continued from the oesophageal 

 region, and from its elasticity this probably subserves certain of the functions of a more 

 elaborate contractile apparatus, for muscular fibres have not been clearly determined. 

 The chamber narrows posteriorly towards the pedicle, and terminates in the intestine, 

 the glandular wall, however, undergoing no change of note. 



In Rhabdopleura, Sars ^ mentions that the stomach has tolerably thin walls, but in 

 all probability he speaks comparatively, as from the nature of the glandular tissue such 

 organs have proportionally thick walls. 



Intestine. — As in Rhahdopleura, the stomach terminates at the posterior end of the 

 body-cavity at the base of the pedicle by a wide aperture in the intestine. In favourable 

 sections (PL III. fig. 3) the intestine is observed to leave the ventral side of the fundus 

 of the stomach, and passing under it, curve forwards along the dorsal wall. The glandular 

 lining of the ventral wall of the stomach passes evenly into the intestine and gradually 

 diminishes in thickness, whereas the lining of the posterior wall shows a characteristic 

 bend at the pylorus, and again a fold in the anterior wall of the intestine behind the 

 fundus (PI. III. fig. 3, near vtd). This peculiar fold in the wall of the canal probably 

 indicates a tendency to the formation of a second or pyloric stomach, as in 

 Phoronis, and is therefore of considerable morphological significance. The intestine 



' Op. cit., p. 5. 

 ^OOIi. CHALL, EXP. — PART LXII. — 1887.) Qqq 3 



