REPORT ON THE DEEP-SEA MEDUSAE. lxix 



central principal intestine (" gaster principalis, axogaster ") is simple and undivided, its 

 axis is at the same time the principal axis of the whole body, the umbrella cone (or 

 centre of the gelatinous umbrella disk) lies at its aboral pole, the oral opening, at the 

 oral pole. The peripheric coronal intestine ("gaster coronaris, perogaster "), on the 

 other hand, is always divided by radial septa (or cathamma), into four or more radial 

 cavities (pouches or canals). The ideal, circular or polygonal boundary line between the 

 principal intestine, and the coronal intestine is consequently defined by the proximal 

 ends of the septa or cathamma ; the gastral openings (" ostra gastralia," go) be between 

 them. These narrow or wider fissures are the only openings by which the central 

 principal intestine communicates with the divisions of the radially divided coronal 

 intestine. 



§ 100. Cathamma or fused parts. (Fusions of the two walls of the umbrella or of 

 the dorsal and ventral umbrella ; septa of the gastro vascular system). The only 

 essential difference between the more simple gastrovascular system of the polyps, and 

 the more composite system of the Medusae derived from them, consists in this, that the 

 peripheric part of the latter is divided by radial septa into a number, four at least, of 

 radial divisions (pouches or canals). These radial pouches and radial canals were 

 formerly erroneously supposed to be collective evaginations of the central gastral 

 cavity, which had grown from its margin into the solid peripheric part of the umbrella. 

 Now we know that these radial hollows have rather arisen from the fusion at definite 

 points (and first of all, at four interradial points) in the periphery of the simple gastral 

 space of its two walls (the umbral dorsal wall and the subumbral ventral wall). These 

 concrescentiae or cathammata (k) form the radial septa of the peripheric gastrovascular 

 system, between which the remains of the originally simple cavity remains open. 

 Corresponding to the origin of these septa or cathamma is a double, narrow, fused layer 

 of endoderm cells, the cathammal plates are found originally in the middle of their solid 

 gelatinous mass. 



§ 101. Cathammal plate ("lamina cathammalis," dk; endoderm lamella, gastral 

 fused plate, vascular plate). The "endoderm lamella," which on account of its origin and 

 meaning we term cathammal plate, remains intact in all Medusae in the interior of the 

 cathamma or septa, and keeps up continous connection between the hollow spaces of the 

 gastrovascular system, separated by the septa. The cathammal plate consists originally 

 of a double layer of endoderm cells (PI. XXV. figs. 8, 10) ; the outer or abaxial layer 

 (the " umbral endoderm lamella," dir) belongs to the dorsal epithelium of the coronal 

 intestine, and originally lined the concave inner surface of the notumbrella (figs. 8, 9, «</), 

 whilst the inner or axial layer (the " subumbral endoderm lamella," duf) belongs 

 genetically to the ventral epithebum of the coronal intestine, and formerly covered the 

 convex outer surface of the ccelumbrella (figs. 8, 10, zw). Sometimes (as for example, 

 very distinctly in the firm septal nodes of the Peromedusae, PI. XXV. fig. 8, 10), both 



