76 THE VOYAGE OF H.M.S. CHALLENGER. 



(fe), and form the lateral boundary margin of a gastral opening (go). The four gastral 

 openings or perradial clefts of the central stomach (" ostia gastralia," go), are four wide, long 

 cleft openings, by which the central stomach communicates in its whole length with the 

 coronal sinus, and whose middle line corresponds to the four perradial borders of the obelisk 

 or, what is the same thing, to the ideal boundary line, at which each of the two obelisk 

 plates touch. The gastral openings have a narrow lanceolate shape, and are broadest in the 

 middle (6-8 mm.) and 36-40 mm. long (figs. 8, go; 12, go). The upper or aboral pointed 

 end of each gastral opening touches the perradial point of the pyloric stricture (gy) ; on 

 the other hand, the lower or oral end touches the perradial point of the palatine opening 

 (gp), and is intersected here in the form of a peculiar groove, the palatine groove already 

 described, which is embedded in the firm palatine nodes. The border of gastral filaments 

 (fg) ends somewhat above the palatine groove. 



The pylorus, or pyloric opening, is the name which I have given to the quadrate 

 opening, by which the central stomach communicates with the basal stomach (" pylorus, 

 porta pylorica," gy ; figs. 8, 12, 13 ; gy, fig. 15). The four perradial angles of this quad- 

 rate form the aboral end of the four gastral ostia (go). The four interradial lateral fines 

 of the quadrate, 3 cm. in length, form the upper (aboral) boundary lines of the obelisk 

 plates, in which they touch the axial walls of the basal funnel cavities. As each of the 

 two adjacent basal funnels touch each other by their lower ends at the pyloric opening, two 

 gastral filaments (fig. 15, b) are placed in each corner of the pyloric quadrate. It is 

 only in the four pyloric corners (fig. 15, gy) that the wall of the pyloric opening touches 

 the gelatinous wall of the umbrella (ug), from which it is otherwise completely separated 

 by the four interradial subumbral funnel cavities (ii). 



The basal stomach (" gaster basalis," peduncle stomach, gb ; PL XX. fig. 8 ; PL XXI. 

 fig. 14) forms the upper or aboral third of the axial principal intestine, and has the 

 form of a regular hollow cone, whose base is the pylorus, and whose point is the cone of 

 the umbrella. As, however, it encloses the four interradial conical funnel cavities, it really 

 has the geometrical fundamental form of a quadrilateral regular pyramid. This is 4 cm. 

 high, whilst the length of its edges amounts to 5 cm. and the lateral length of its quad- 

 rate base to 3 cm. The point of the pyramid is prolonged into a narrow caecal tube, 

 which traverses the aboral cone of the gelatinous umbrella, and whose point nearly 

 touches the external surface of the latter. This canal of the umbrella peduncle- (fig. 8, cb) 

 is here closed caacally, and does not open by an aj>erture into the upper surface, as 

 appears at first sight. The cavity of the narrow spindle-shaped peduncle canal is fined with 

 dark-brown pigment, and therefore stands out conspicuously in the clear gelatinous mass 

 (fig. 1, in the point above). As the four interradial conical subumbral funnel cavities (ib) 

 already described traverse the whole length of the basal stomach and meet above in its 

 point, the periphery of its conical hollow space is divided into four perradial grooves, the 

 basal pouches, or niches of the basal stomach (" bursas basales," gn). They are 



