MEDUSA. I. 



103 



(the cross-arms) are seen, from the stomachal cavity, as deep, narrow grooves (Plate V, fig. 4). 

 From the distal ends of these four grooves issue the four radial canals which, from these points, run 

 upwards along the peduncle (Plate V, fig. 5). The openings of the radial canals may be completely 

 closed by contraction of the borders of the grooves, thus the lumen of the canals being separated from 

 the cavity of the stomach; in the stomach figured in Plate V, fig. 4, the openings on the left side 

 have, been closed in that manner. 



The basal part of each radial canal is a little widened and has a number of fine, transverse folds. 



The mouth-opening is wide and is provided with four large, pointed lips, complexly folded and 

 with a crenulated margin (Plate V, fig. 5). 



There are four straight radial canals and a very narrow circular vessel. The mode of attach- 

 ment of the radial canals to the subumbrella (and the stomachal peduncle) is remarkable (see Plate V, 

 fig. 10). The usu-al median streak of high entodermal cells is very narrow, but the uppermost parts of 

 the lateral entodermal layer of the canal on both sides are attached to the subumbrella, the ectoderm 

 and the mesosarc leaving the subumbrella at some distance from the median streak; thus the line of 

 attachment has secondarily become rather broad. 



The gonacls are developed upon both sides of the radial canals from the attachment to the 

 subumbrella, leaving a narrow median line free on the ventral edge. Though the line of attachment 

 to the subumbrella is straight, the lateral walls of the canals are, in the parts carrying the gonads, 

 very much folded in a fairly regular, wavy manner. The gonads extend partly over the subumbrella 

 from the base of the peduncle towards the bell-margin, reaching nearly to the circular vessel, partly 

 downwards along the peduncle, ceasing at a distance of some few millimeters above the stomach. The 

 gonads attain their highest development and are most highly folded upon the subumbrella, gradually 

 tapering during their course downwards upon the peduncle. Sections laid through different parts of 

 the gonads of one and the same specimen show, however, that the sexual products are in the same 

 state of maturity in every part. In the highly folded parts the ventral median line, free of gonads, is 

 sometimes fairly broad, sometimes very narrow, shaped like a deep furrow, and is, in such cases, hardly 

 visible, except in sections. 



The usual number of tentacles is 16. When fully expanded, the length of the tentacles is about 

 3 times the diameter of the bell. The tentacular bulbs (Plate V, figs. 6, 7, 8) are oblong, pear-shaped, 

 gradually passing into the thread-like part of the tentacles. The ectoderm of the bulb is somewhat 

 thickened, equally developed all round the bulb (Plate V, fig. 8). Proximally the abaxial side of the 

 bulb is sharply set off from the exumbrella. There is a well-developed, hollow, entodermal basal spur 

 projecting into the gelatinous substance of the exumbrella, curving outwards and upwards, its abaxial 

 side resting close to the exumbrellular epithelium, which is slightly thickened in this part (Plate V, 

 fig. 8). Above each of the tentacles there 'is a slight, rounded prominence of the exumbrella (Plate V, 

 figs. 6 and 7); this may be due to contraction owing to the preservation. The points of insertion of 

 the tentacles are usually not quite equidistant. 



Between the tentacles there is a large number of marginal warts (see Plate V, fig. 6). The base 

 of the warts is rectangular, the warts being placed closely together. In some cases they are separated 

 from each other by a sharp furrow, but sometimes they pass gradually into one another; it is difficult, 



