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



sixteen radial coronal pouches, always forms the principal component part of the coronal 

 intestine in the Ephyroniae, whilst in the Tesseroniae it has retreated completely against 

 the inner quadrilocular pouch corona. Important differences, are, however, connected with 

 the further organisation of the two sub-sections. It is therefore practical to consider the 

 radial pouches of the Tesseroniae and Ephyroniae separately. 



§ 128. The four perradial pouches of the Tesseroniae. In all the three orders of the 

 Tesseroniae, the Stauromedusae, Peromedusae, and Cubomedusae, the four primary perradial 

 pouches (bj)) form, from their circumference and extent, by far the most important part 

 of the coronal intestine, whilst, on the other hand, the marginal pouch corona has retired 

 against its periphery (System, pp. 363-449, taf. xxi.-xxvi.). As in all Tesseroniae, 

 the umbrella is highly vaulted, and its fundamental form represents a high quadrate 

 pyramid (usually truncated above), the four broad pouches occupy its four lateral 

 surfaces, whilst the intermediate four interradial septa correspond to the four angles of 

 the regular pyramid. Each quadrangular pouch communicates at the upper or proximal 

 margin by a fissure-shaped gastral ostium (go) with the central stomach, at the lower or 

 distal margin by two or more fissures with the marginal pouches ; its two lateral 

 margins are formed by the septa or cathamma, and their ideal (interradial) prolonga- 

 tions. All the four perradial pouches communicate below the four cathamma, by four 

 interradial fissures, which taken together represent an ideal primary coronal canal, 

 the coronal sinus ("sinus coronaris," § 134). Of the two flat, quadrangular walls 

 of each perradial pouch, the outer (abaxial) is formed by the inner (concave) endodermal 

 surface of the notumbrella, whilst the inner (axial) is formed by the endodermal surface of 

 the coelumbrella. Whilst all Tesseroniae agree without exception in these essential 

 general conditions of structure, many important modifications are found in detail which 

 are referable on the one hand to the different extent of the cathamma, and on the other 

 to the different position of the gastral ostia. In one portion of the Stauromedusae, and 

 in all Peromedusse, the gastral ostia form narrow longitudinal fissures of the central 

 stomach, standing more or less vertically, whilst in another portion of the Stauroniedusae, 

 and in all Cubomedusae, they form broad transverse fissures, standing more or less 

 horizontally ; the special anatomical relation of the proximal part of the pouch to the 

 central stomach, therefore, differs considerably. As regards the four interradial septa of 

 the four pouches or the four primary cathamma, in one portion of the Stauromedusae 

 (Tesseridae), and in all Peromedusse, they form small, but very firm nodes, as hard as 

 cartilage (" nodi cathammales," PI. XV. figs. 2-6, hi; Pis. XX. -XXIV., hn) ; whilst in 

 the other portion of the Stauromedusae (Lucernaridae), and in all Cubomedusae, they form 

 long, narrow ridges (" limites cathammales," Pis. XVI., XVIL, hs). The Peromedusae are, 

 moreover, distinguished from all other Tesseroniae by the union of the four perradial 

 pouches above the four septal nodes, into a powerful upper coronal sinus, which 

 encircles the central stomach, and reaches with its upper (closed) margin up to the 

 pyloric ring (Periphyllidte, Pis. XX., XXL, co" ; comp. § 134). 



