ANTHOMKDrs.K Hul ( ;\I NVI I.I.I A . 



Each cluster of tentacles arises from a large bulbous swelling upon the bell-margin. There 

 are 10 to 15 tentacles in each cluster. The tentacles are highh contractile and are normally 

 about two-thirds as long as the bell-diameter. There is a single, very dark-brown ocellus 

 within the ectoderm ot the inner (velar) side of the base of each tentacle. The velum is well 

 developed. There are 4 straight, narrow radial-canals, which arise from the 4 radial corners 

 of the stomach. The stomach is wide and quadratic in cross-section and flask-shaped in 

 longitudinal outline. It is mounted upon a 4-sided peduncle which is about half as long as 

 the stomach itselt. There are 4 radially situated, oral tentacles, each of which branches dichot- 

 omously about 5 times. 1 he mouth is situated at the extremity of a short, simple tube and 

 the lips are not prominent. The mature genital products are situated within the ectoderm 

 of the 4 interradial sides of the stomach. There are thus 4 intei radial gonads, above the zone 

 of the oral tentacles. Ibis species is thus separated from It. li,ll,i by having 4 interradial 

 instead ot 8 adradial gonads. In the temale, according to Hartlaub, l8i;~, the large eggs 

 may be seen lying within the ectoderm close to the supporting lamella. As thev gmw larger 

 they approach the surface, and finally become inclosed in epithelial, nematocyst-bearing 

 capsules, derived from the ectoderm cells of the stomach-wall. These capsules finally protrude 

 from the sides ot the manubrium, but each one remains attached to it by a narrow stalk. In 

 this situation the egg develops into a planula which finally breaks through the walls ot the 



capsule and escapes into the water. Hartlaub 

 showed that although the large eggs were found 

 in the ectoderm they were derived from the entoderm 

 of the young medusa. In the young and immature 

 medusa the supporting lamella does not completely 

 separate the ectoderm from the entoderm, and the 

 egg-cells then migrate from the entoderm into the 



DO o 



ectoderm (see Hartlaub, 180,-, pp. 400, 4-01.* The 

 sperm originates in the ectoderm and there develops 

 without migration. 



The entoderm of the manubrium and tentacle- 

 bulbs is rosin-yellow or reddish-brown, and tin- 

 gelatinous substance of the bell often has a decided 

 yellowish tinge. 



HyJirinl mi,/ \riung medusa. 'I he hydroid is 

 usually found attached to rocks, and lives in the 

 purest sea-water. It grows in clusters, not more than 

 50 mm. high. The stems give rise to pnmaiy and 

 secondary branches, which arise somewhat irregu- 

 larly, though more or less alternately and spirally. The base ot every branch is ringed with from 

 510 10 annotations. The chitinous sheath which incloses the stem thins out as it passes on to 

 the polypites and disappears entirely below the circlet of tentacles. Each polypite has from I 5 

 to 20 long, slender tentacles which arise from a single circlet near the distal end ot the polypite. 

 Each tentacle is ringed at regular intervals by clusters ot nematocv st-cells. The medusa- 

 buds arise singly and somewhat irregularly from the sides of the stem, near the proximal 

 bases of the polypites. Each medusa-bud is inclosed in a thin capsule toimed from the 

 chitinous ectosarc of the stem. When set tree the young medusa usually has X marginal 

 tentacles, 2 at the base of each radial tube. The young tentacles are each provided with a 

 centripetal, ectodermal ocellus. The manubrium is short and tubular and tlu-ie are 4 short, 

 knob-shaped, unbranched, oral tentacles. 



In common with other Arctic medusa? this species appears upon the southern coast of 

 New England early in April and soon disappears. It is found throughout the summer, 

 however, north of Cape Cod, and mature individuals are occasionally taken at Eastport, 

 Maine, in August. This species has been found by Eevinsen, 181;^. off the west coast of 

 Greenland, and according to Birula, i8g6, it is the most abundant medusa in the White Sea 

 in July. Hartlaub, 1807, found it at Helgoland, and I.inko, 10.04, found it in Barents Sea, 



* It is interesting to observe that other species of the Bougainvillidi, such as ('\i.ri , .I|*M rrt.iin the emhrvos within the ectin- 

 ilerm of the manubrium until the planula tji;r. Tins was first observe, I bv Mrr.-si hmvskv, iX?.j, an, I has since been con- 

 firmed by N. Wagner, 18X5, ami by Hartlaub, 1897. 



Fit;. 87. Bougainvillia su6ffrc///<v7*, after I.. 



in Mem. Amer, AcaJ. Arts anil Sci 

 iSatf. Si;le \ii-w uf tnetlusa. 



