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



principal parts, the central principal intestine and the peripheric coronal intestine. The 

 central part or the axial principal intestine (" gaster principalis ") communicates with the 

 peripheric coronal intestine by the four perradial openings (" ostia gastralia"), and is 

 divided into three different sections, the basal, the central, and the oral stomach. The 

 aboral basal stomach or peduncle canal (" gaster basalis,"</6), which may also be called the 

 " apical canal," is a narrow, almost cylindrical, hollow space occupying the entire cone of 

 the umbrella, in whose point it ends csecally above, whilst below it opens by the pylorus 

 (gy) into the central stomach. Four longitudinal gelatinous selvages, the important 

 interradial tamiola, project from the inner surface into its hollow space, and, as in 

 the closely-allied Lucernaridaa, traverse the entire length of the hollow basal umbrella 

 peduncle (figs. 2, 3, 8, ft). The peripheric part of the basal stomach is thus divided into 

 four perradial grooves (figs. 3, 8, gb). 



The central stomach (" gaster centralis," gc) has, on the whole, a spheroidal or almost 

 quadrangularly pyramidal form, which, however, is complicated by the four interradial 

 exodermal funnel cavities (ii) sinking down into it from above. The distal processes of 

 the four tseniola, each of which bears two rows of gastral filaments (ft) inside in the central 

 stomach, run as projecting selvages on the endodermal gastral surface of the funnel 

 cavities. The central stomach opens above by the " porta pylorica " (gy) into the basal 

 stomach, below in the centre by the "porta palatina" (gp) into the oral stomach, and round 

 by the four cleft-shaped gastral openings into the coronal intestine. The gastral open- 

 ings (fig. 6, go) are narrow, almost horizontal clefts, divided from one another by the 

 four interradial septal nodes ("nodi cathammales," kn), these important points of fusion 

 at which the umbral and the subumbral wall of the gastral space have grown together. 

 That this is really a fused plate is plain from the fact that an endodermal layer of 

 epithelium — " endodermal lamella " or cathammal plate — runs in the middle through the 

 cartilaginous-like gelatinous mass of the septal node. 



The oral stomach or oesophagus ("proboscis," go) is formed of a quadrangularly 

 prismatic tube, nearly equal in length to the breadth of the umbrella (figs. 1, 2, at). It is 

 four times as long as broad, and has four projecting perradial angles which run into the 

 four mesenteries above, whilst the external surface is depressed like a groove between 

 them (fig. 6, a). The oral opening is surrounded by an undulating oral margin 

 crowded with thread cells, and runs out into four short perradial lobes (fig. 4 in the 

 middle). 



The peripheric coronal intestine (" gaster coronaris "), which in most Acraspedae is 

 divided into from four to sixteen radial pouches or canals, forms a simple wide coronal 

 sinus (" sinus coronaris," cs) in Tesserantha as in Periphylla. It occupies the whole space 

 between the septal nodes and the umbrella margin (figs. 2, 3, 5, cs). The broad gastral 

 openings only may, therefore, be considered as homologous with the four radial pouches 

 (6p) ; in fact, the four short septal nodes which divide the gastral openings correspond 



