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Show 1903.] MEDUSAE F R O M BRITISH COLUMBIA A N D ALASKA. 181 same depth as the oral peduncle, being very wide at the top, almost half the diameter of the bell. Mouth much lobed, the lobes being narrow, pointed, and finely toothed. There are half as many lobes as there are radial canals. There are about a hundred radial canals; these run from the peripheral canal inwards and upwards to the highest point of the stomach. Each radial canal is covered on its outer surface by a ridge of glandular cells. Sometimes these are continued over the stomach and oral peduncle down to the lobes of the mouth, giving an appearance similar to that presented by the ovaries of Orchistoma. The two kinds of umbrellar papilla? are present. Colour.-Organs and bell-margin white, with a very slight trace of blue in the larger tentacles. Habitat.-Victoria Harbour, Esquimalt Harbour, collected by Shearer; Pleasant Beach, collected by Kincaid. Discussion.-On first examination this Medusa was taken to be Orchistoma. That it is an undoubted ^Equorid is borne out by the presence of marginal vesicles, of which there are one or two between successive tentacles, the absence of eye-spots, and the presence of excretory papilla? under the velum. The papilla? which are in the same row as the tentacle-bulbs are young tentacles. Brandt describes (6) bodies on the inner side of the bell-margin which Haeckel is probably right in considering to be excretory papilla?. Brandt speaks of them as follows (p. 361):-"An der innern Seite der Basis des Saumes findet sich eine Anzahl kleiner, tassenformiger, an Gestalt der Cupula einer Eichel nicht unahnlicher Korperchen." No mention is made as to their relation with the circular canal, and Brandt thinks they are the rudiments of a third row of tentacles. Evidently Mertens did not observe whether they were inside the velum, and perhaps his remarks refer to the young tentacle-buds we have described above in M victoria, and not to the true excretory papilla? under the velum. Some slight confusion has arisen over the position of these papilla?. Haeckel (18) and Hertwig (21) describe umbrellar papilla?, which are outside the velum (centrifugal), which are, according to them, blind tentacle-bases, or spurs, possessing no openings. Distinct from these are the subumbrellar papilla?, inside (centripetal) to the velum, arranged one opposite each marginal tentacle-spur on the outside ; they are connected by an opening at their apex with the circular canal of the bell-margin, and have been interpreted as excretory in nature. Haeckel (18) expressly states (p. 119) that they are inside the velum, and thus in the subumbrellar cavity; yet in pi. xi. fig. 13 of the same work he shows them as if they were in the same row with the tentacles on the external surface of the bell-edge, and thus outside the velum; from his figure it is impossible to make out their true position under the velum*. Mayer (28) has described centrifugal excretory papilla? on the * Since the above was written, it has been found that Clans (10, p. 13) makes practically the same comment, although his figures 29 and 30 are not clear. |
