REPORT ON THE DEEP-SEA MEDUSAE. 97 



fibrillar cords (an upper and an under) lying on it with the peculiar nerve epithelium lying 

 above them. Extensive plexuses of fibrillse with large multipolar and spindle-shaped 

 ganglion cells run out thence and spread chiefly on the subumbrella. The finer 

 structure of the nervous system and the organs of sense have been recently described in 

 detail by Claus in Charybdea marsupialis (1879, loc. cit.). His endeavour to compare the 

 condition of this structure of the Cubomedusae with that of the Craspedota, is, however, 

 untenable, as the two have arisen independently of one another, and are, therefore, not 

 homologous. The nerve ring of the Cubomedusae also corresponds only to the lower 

 (suburethral) nerve ring of the Craspedotse, whilst the upper (exumbral) ring of the former 

 is entirely wanting. On the other hand, the central nervous system of the Peromedusae 

 is probably essentially closely allied to that of the Cubomedusse. 



The gastrovascular system (figs. 1-10) resembles that of the Stauromedusse in 

 the simplicity of its formation (Tesserantha, PI. XV. ; Lucernaria, Pis. XVI., XVII. ). The 

 principal stomach or axial intestine is connected by four horizontal perradial gastral 

 openings with four wide quadrangular radial pouches, which are divided in their entire 

 length by four narrow interradial septal selvages, and communicate by a narrow circular 

 canal at the distal end of the selvages. The axial principal intestine, or the stomach in 

 the wider sense (" gaster principalis "), really consists in most Cubomedusae of the same 

 three sections as in the Stauromedusee and Peromedusaa, viz. , an aboral basal stomach, a 

 middle central stomach, and an oral buccal stomach ; the pyloric opening (" pylorus/' 

 gy) also forms in this case the boundary between the basal and the central stomach 

 and the palatine opening (" palatum," gp), that between the central and the buccal 

 stomach. In Charybdea, however, as in many other Charybdeidae, the pyloric open- 

 ing is very wide and the pyloric stricture very slightly developed, so that, taken together, 

 the basal and the central stomach seem to form a single, simple, somewhat flat, quadratic 

 chamber. 



The buccal stomach or oesophagus (" gaster buccalis," go) — the " oral funnel " of Fritz 

 Muller, " oral peduncle " of Claus — is comparatively small in our species, and forms a flat 

 quadrate pyramid. Its truncated point is formed by the narrow palatine opening (fig. 9, 

 gp), its angles by the four perradial strong oral ribs, thickened selvages of the gelatinous 

 plate, which gives consistence to the whole stomach. The oral ends of these buccal ribs 

 project considerably at the quadrate oral opening, and cause the formation of the four 

 lanceolate or oval " oral lobes." A deep perradial groove runs on the axial endodermal 

 surface of these frilled triangular oral lobes ; it bends with a sharp turn towards the out- 

 side at the palatine opening, and runs, enclosed in the mesogonial fold, on the inner sur- 

 face of the subumbral wall of the central stomach as far as the middle line of the radial 

 pouch (figs. 4, 6, gs). The thickened oral rib itself, which at the same time forms the 

 midrib of the leaf-shaped many-folded oral lobe, runs at the palate immediately into the 

 low mesogonial fold. The folded oral tubes, which were strongly contracted in our 



(ZOOL. CHALL. EXP. PART XII. 1881.) M 13 



