20S MKIK'S-K OF THE WORLD. 



There is a circlet of 10 to 12 short, stout tentacles, the bases of which are connected by a web. 

 At the end of six months the hydroid colonies were about 8 mm. in height. 



In the youngest medusa observed the bell is about twice as high as broad and the bell- 

 walls are thin and flexible. There are 2 well-developed, diametrically opposite tentacles and 

 2 small, undeveloped tentacle-bulbs. There are 4 straight, radial tubes. The manubrium is 

 very small and there are 4 simple lips. 



When the medusa is 1.5 mm. in diameter (plate 23, fig. 4) the bell has become relatively 

 flatter and broader. There are now 8 tentacles, 4 long radial and 4 short interradial ones. 

 There are, as yet, but 4 radial tubes and 4 lips. The bell-walls are still thin. 



When the medusa is about 4 mm. in diameter (plate 24, fig. 5), the bell has become 

 pvriform in shape and the gelatinous substance has greatly increased in thickness. There 

 are }2 tentacles in several stages of development. There are 8 radial-tubes, 4 of which are 

 broad, and 4 very narrow and almost thread-like. The 4 thread-like tubes are new and arise 

 from the periphery of the stomach and extend down toward the circular vessel. The manu- 

 brium is shallow and there are 8 simple lips. The gonads begin at this stage upon the 4 broad 

 radial-canals. The other 4 radial-canals acquire them later. The gonads first appear near the 

 periphery of the stomach and extend down the radial-canals until they reach the circular tube. 



This medusa is common on the New England coast, north of Cape Cod, during May and 

 early ] une. It has not been taken south of Cape Cod. It is exceedingly abundant on the sur- 

 face in Salem Harbor, Massachusetts, early in the summer, but disappears about the middle 

 of July. The medusa is very constant to its type, individuals having more or less than 8 

 radial-canals being exceedingly rare. Lmko finds it to be rare off the Murman coast, Northern 

 Russia, near Norway. 



Mehcertum oi'torostntiint ( = 0ceania octocostnta Sars) of the northern Atlantic coasts of 

 Europe is closely allied to, if not identical with, our American medusa. 



Melicertum octocostatum Haeckel. 



Oimntti tjilfjcottatti, SARS, 1831;, Beskriv og Jagttag, p. 24, plate 4, fig. 9 -</. 



\tfliif>ntm campanulalum, EHRENBERG, 1837, Abhandl. d. k. Akad. Wissen. zu Berlin (1835), pp. 190, 255, taf. 8, fign. 5-7- 



Thaumantias mtlltri, LANDSBOROUGH, 1847, Arran, a poem, p. 265. 



Stomobrachium octocostatum, FORBES, 1848, British Naked-eyed Medusae, p. 30, plate 4, fig. I . ROMANES, 1876, Journal Linnean 



SMC. London, vol. 12, p. 526. 



Mclicfrtum octocostalurri, Mcltctrtidium oclofottatutn, HAK.CIO.L, 1879, Syst. der Medusen, p. 138. 

 Mi-la frlnlium octocostatum, HARTLAUB, 1894, Wissen. Meeresuntersuch. Kornm. Meere Kiel, Helgoland, Neue Folge, Bd. i, p. 



192. BROWNE, 1905 Proc. Roy. Soc. Edinburgh, vol. 25, p. 762. BEDOT, 1905, Revue Suisse de Zool., tome 13, p. 138 



(literature 1835-50). 



Bell somewhat conical to pyntorm, with thick, solid apex and thinner sides. About I I 

 to 13 mm. high and 10 to 1 1 mm. wide. There are about 64 large, alternating with 64 small, 

 tentacles having laterally compressed basal bulbs and no ocelli. No clubs or cirri. Velum 

 narrow. There are 3 to 5 fine, longitudinal lines of nematocyst ( :) cells upon the subumbrella, 

 extending from stomach to margin between each successive pair of radial-canals. These lines 

 occasionally branch or anastomose. In large medusae these lines are usually confined to parts 

 near the margin, extending upward for a short distance only. Such lines have never been 

 observed in the American M. campanula. 



The stomach is octagonal, prismatic, one-fourth as long as the depth of the bell-cavity. 

 It has 8 slightly crinkled lips. A short, broad peduncle is sometimes present. The 8 radial- 

 canals are broad and straight, and the sinuous linear gonads extend along their outer two- 

 thirds, reaching the bell-margin. 



Color of gonads, stomach, and basal bulbs of large tentacles, yellow to yellowish-brown. 



Found ofF the northern Atlantic coasts of Europe, Norway, Helgoland, Scotland. The 

 best modern descriptions are given by Browne and Hartlaub. 



This medusa appears to differ from the American M . campanula Agassiz in having fine 

 radiating lines of nematocysts over its subumbrella. The gonads appear to be more re- 

 stricted in their position upon the radial-canals, and the tentacles to be more markedly of two 

 sr/.es in the European form. Nevertheless the two "species" are evidently closely related and 

 may eventually prove to be identical. This is rendered probable on account of the Arctic 

 range of M . anufiuuula Agassiz. 



