MIDDLE CAMBRIAN. AT 
brevity we shall term the former the principal intestine and the latter the coronal 
intestine. The central or 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 center of the gelatinous umbrella disk) lies at its aboral pole; the 
oral opening at the oral pole. The peripheral or coronal intestine (“ gaster corouaris, 
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”) lie between them. These narrow or wider fissures are the only openings by 
which the central or principal intestine communicates with the divisions of the radially 
divided coronal intestine. ' 
The central or principal intestine of the medusz is rarely perfectly simple; it is 
usually divided more or less distinctly into two or three sections or chambers, lying 
one above the other in the principal axis of the body. The lowest of these is the 
cesophagus or buccal stomach (“ gaster buccalis”), which contains the oral opening at 
the oral pole of the principal axis. The middle chamber is the principal cavity or 
central stomach (“gaster centralis”). The third or uppermost section is the peduncle 
tube or basal stomach (‘“ gaster basalis”), which ends cxeally at the aboral pole of the 
principal axis. The central stomach communicates with the basal stomach—below 
by the palatine opening (*‘ porfa palatina”); above by the pyloric opening (“porta 
pylorica”). Besides these there are usually gastral openings (‘‘ostia gastralis”), in 
the lateral walls of the stomach, by which the latter communicates with the radia, 
chambers of the coronal intestine. All three stomachs are well developed in many 
meduse of both sections (namely, Anthomedusze and Peromeduse); the uppermost 
(basal) stomach has, however, usually undergone retrograde formation. In the majority 
of medusz the buccal stomach is the longest, the central stomach the broadest of the 
three chambers, whilst the basal stomach is the smallest, or has disappeared. 
The actual and theoretical information concerning the gastrovascular 
system of this species that I have thus far secured is illustrated by text figs. 
4, 5, 6, and 7 (pp. 28, 29). The general form of fig. 4 is restored from speci- 
mens like those represented by figs. 1-4 of Pl. I; the radial canals, figs. 1, 
3, 4 of Pl. IIT; oral arms, figs. 8, 8a of Pl. II; central and buccal stomach, 
figs. 8b of Pl. Il, 1 and 4 of Pl. IIT, and 9, 10, 11 of Pl. IV. It is not pos- 
sible, owing to the condition of preservation of the inner parts of the medusz, 
to determine the shape and size of the central intestinal tube or stomach. 
That it was not simple in the typical form is fairly well shown by the 
natural section, fig. 8b of Pl. Il. In the restoration (text figs. 4 and 5) the 
central stomach may have been relatively broad in some specimens (figs. 
‘Haeckel, loc. cit., p. xlviii, par. 99. 
? Haeckel, loc. cit., p. lxxv, par. 109. 
