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



XVII.) as a shorter or longer quadrilateral canal which traverses the apical process or 

 peduncle of the umbrella, and terminates csecally at its aboral end. The four interradial 

 tamiola (ft) divide the peduncle canal into four perradial semicanals (peduncular grooves 

 or niches of the basal stomach, "semicanales basales," gn., PL XVI. fig. 13). In some 

 Lucernaridse these become four separate peduncular canals (" canales basales "), as the 

 four interradial tamiola met in the axis of the stomach where they are fused into a central 

 column (" columella "). In the Peromedusse, the basal stomach is always highly 

 developed, is sharply defined from the central stomach by the pyloric ring (which 

 corresponds to the upper margin of the " coronal sinus "), and is divided by the projecting 

 tseniola into four niches or semicanals. The division into four of the conical basal 

 stomach is more strikingly defined if the four tamiola are transformed into hollow cones 

 by the subumbral funnel cavities, which in Periphylla penetrate to the point of the cone 

 (PI. XXI. figs. 12-18, ib.). In the Cubomedusse the basal stomach is sometimes fused 

 with the central stomach, sometimes separated from it by a pyloric stricture, in which 

 case it forms a very flat, low, quadrate cavity ; its four interradial angles are sometimes 

 extended into four low, triangular pyloric pouches (" bursse pyloricse, by), which are 

 separated from the central stomach by four projecting pyloric valves (System, p. 430). 



§ 121. The two principal forms of the coronal intestine (" gaster coronaris," 

 " perogaster "). Under the term "coronal intestine," we include the whole peripheric 

 gastrovascular system of the Medusas, which surrounds the central principal intestine 

 like a garland, and only communicates with it by the gastral openings. Although it 

 has essentially the same formation in both sections of the class, we may assume that it 

 has been developed independently in both sections. The fusion of the two walls of the 

 peripheric gastral space, by which the radial chambers of the coronal intestine originate, 

 shows an essential difference in the two sections. In the Craspedotse, which are descended 

 from Hydropolyps (without tseniola), the concave inner surface of the not-umbrella 

 or dorsal umbrella, is fused almost throughout its entire extent with the convex outer 

 surface of the ccelumbrella or ventral umbrella, in such way that the catliamma originally 

 represent four broad plates, between which only four narrow radial canals remain over; 

 these are connected in a supplementary manner by a secondary coronal canal. In the 

 Acraspedse, on the other hand, which are descended from the Scyphopolyps (with the 

 four characteristic tamiola), these gastral ridges are the starting-point of the concresence; 

 at four interradial points the dorsal point of the four tamiola (on the notumbrella) is 

 fused with their ventral part (on the ccelumbrella) in such a way that the cathamma 

 originally represent four small nodes or narrow ridges, between which the four broad 

 radial pouches remain free ; these communicate at the peripheric umbrella margin below 

 the four nodes, by a primary coronal canal, the distal remains of the simple gastral space. 

 Although these two essentially different principal forms of the coronal intestine in the 

 two sections probably express a comprehensive primary difference in its conformation, 



