20 MEDUSAE. I. 



wide, 100—140 tentacles, and, when 8 mm wide, 160—180 tentacles; in specimens of this size the ten- 

 tacles are very closely packed on the bell-margin. The number of tentacles increases tolerably pro- 

 portionally with the diameter of the individual, the average number being as follows: 



Diameter of bell n — 15 mm, 230 tentacles 



— — 16— 20 — 290 — 



— — 21—25 — 390 — 



— — 26 — 30 — 440 — 



The largest specimen examined ("Michael Sars" stat. 140 (03), east of the Orkney Islands) is 

 37 mm wide and has about 500 tentacles; but another specimen, 35 mm wide ("Thor" stat. 180(04), 

 south of Iceland) has about 620 tentacles; this is the largest number of tentacles, which I have seen 

 in tliis species. 



The number of ocelli is variable. There is an ocellus on, at least, every 5th of the tentacles. 

 Even in one and the same individual the succession of the ocelli is irregular. In a specimen from 

 Iceland ("Thor" stat. 241 (04)), about 25 mm wide, the ocelli are, on the whole, found on every second 

 tentacle; liere and there, however, two or even more successive tentacles are provided with ocelli, or 

 ocelli are wanting on two successive tentacles. From the Hebrides ("Thor" stat. 8 (08)) we possess a 

 number of young individuals, among others two specimens, 7 mm wide, with 100 — 140 tentacles; in 

 one of these specimens the ocelli are fairly regularly distributed on every 2nd tentacle, while in the 

 other .specimen ocelli are only found on every 4th to 5th of the tentacles; among two specimens, 8 mm 

 wide, one has an ocellus on every 2nd tentacle, in the other the ocelli are irregularly distributed 

 on every 2nd to every 5th of the tentacles. Specimens from the same locality, 9 and 16 mm wide, have 

 ocelli on about every 2nd tentacle. From the "Thor" stat. 11 (08), somewhat to the west of the Hebrides, we 

 possess several specimens 8—22 mm wide; in most of these specimens there is an ocellus on every 3rd — 

 5th of the tentacles, though in some specimens every 2nd tentacle bears an ocellus. In two specimens 

 from the Orkney Islands ("Thor" stat. 2(08)), 6 — 13 mm wide, the ocelli are fairly regularly distributed 

 on every 5th tentacle. Most of the specimens from Iceland have ocelli on every 3rd — 5th of the tent- 

 acles; in not a few cases, however, there is an ocellus on every 2nd tentacle; this is the case, for 

 instance, in a 12 mm wide individual and in another, 25 mm wide. — It will be seen, from the facts 

 here mentioned, that the number of ocelli stands in no ostensible relation to the size of the individual, 

 nor to the locality, in any case as far as the area here dealt with is concerned. 



Tlic question, whether the cordyli may be transformed into tentacles, has been discussed above 

 (p. 5). The number of cordyli has been used as a specific character, undoubtedly incorrectly. It is diffi- 

 cult, on ])reserved material, to state with certainty the number of cordyli, as they are very apt to drop 

 off on the preservation. With regard to the material, examined by me, the fact is, that in all full- 

 grown or nearly full-grown individuals, sufficiently well-preserved, the number of cordyli is equal to 

 the number of tentacles. Most of the small specimens are badly preserved. In a specimen, 5 mm wide, 

 from the Horns Rev, I have, in some cases, been able to find two cordyli between two successive 

 tentacles. 



With regard to the cirri, we may state as in the case of the cordyli: that they frequently dis- 



