l8 MEDUSA. I. 



thin except on the adaxial side, where it is somewhat thickened (Plate II, figs. 5 and 6). The young 

 tentacle issues from the proper margin of the bell and possesses an abaxial entodermal spur-like process, 

 imbedded in the gelatinous substance on the exumbrellular side of the bell-margin (Plate II, fig. 5). 

 During the continuous growth the adaxial side of the basal part of the tentacle grows faster than the 

 outer side, and tliereby the point of issue of the tentacle is gradually removed from the bell-margin upwards 

 on the outer side of the bell; older tentacles, therefore, issue from the exumbrella at some distance 

 above the bell-margin (Plate II, figs. 6 and 8). On account of this removal the abaxial part of the 

 tentacular base, which is pushed upwards on the outer side of the umbrella, invests the spur-like 

 process, which at last entirely disappears (Plate II, fig. 6). Accordingly, a "spur" is only present on the 

 young tentacles. The fully developed tentacle turns abruptly outwards and downwards, immediately 

 after leaving the wall of the umbrella. The central canal in the tentacle has not the same width 

 everywhere, but expands and narrows at different points (Plate II, fig. 8); the greatest width is a little 

 outside the point of issue of the tentacle. The course of the canal is approximately central, except in the 

 basal part, where it passes the sharp bend very close to the adaxial side (Plate II, fig. 6). Within the 

 imbedded part of the tentacular base the canal is very narrow and opens in the circular vessel. In 

 young individuals, in which the tentacles are not so densely crowded on the bell-margin, the basal 

 bulbs are fairly broad, all the tentacles issue from the margin itself, and spurs are only just be- 

 ginning to develop. 



A small, dark, sharply defined ocellus is found on the adaxial side of the base of some of the 

 tentacles. The number of ocelli is subject to much variation; as a rule ocelli are found on every 3rd — 

 5th of the tentacles, but they may be foimd on every 2nd tentacle, rarely on two successive tentacles. 



Typical cordyli are situated between the tentacles (Plate II, figs. 5, 6, and 8). The cordyli issue 

 from the bell-margin close by the base of the velum; they are very small, hardly longer than the 

 proximal breadth of a fully-developed tentacle; they have, as a rule, a fairl)- thick distal part and a 

 very thin peduncle. In some of the cordyli the inner lumen is fairly large, in others it is very narrow or 

 nearly obliterated, being just visible as a fine streak; this variation stands in no relation to the size 

 of the cordylus. .Some of the cordyli may be mounted upon fairly large bulbi; in such cases their 

 basal part is turning inwards (adaxially). The number of cordyli is variable and may be a little larger 

 or a little smaller than the number of tentacles. This seems to depend on the stage of development 

 of the individual; in full-grown specimens the number of cordyli is, probably, always the same as the 

 number of tentacles. 



The bell-margin also bears fine cirri, which may be spirally coiled, and which are greatl)' armoured 

 with nematocysts in their distal part. According to Mayer the cirri are "usually somewhat less 

 numerous than the tentacles"; in preserved material, as a rule, only a small number of cirri are left; 

 the material, examined by me, therefore, gives no available information of their number. In badly 

 preserved specimens I have, in fact, been unable to find an\- cirri at all. 



The velum is fairly well-developed; in full-grown specimens it is about 3 mm wide. 



The colour is subject to much variation. The manubrium, the gonads, and the tentacular bulbs may 

 be reddish or greenish or nearly colourless. Most of the specimens, examined by me, are reddish, provided 

 that the colour is preserved. In an individual from the "Thor" stat. 72 (1905), the gonads are pale green. 



