5° 



HYDROIDA II 



of the actual conditions; a point which has likewise been demonstrated by Kramp. Stechow's 

 drawings in the mentioned work are sadly schematic, and thus afford but poor support. 



Halecium tenellum belongs to. the littoral region, and appears to occur but rarely deeper down 

 in northern waters. From records in the literature, the species is altogether cosmopolitan, penetrating 

 far into the Arctic waters, albeit it must here evidently have been frequently confused with the related 

 Halecium minutum. Despite the fact that it is cosmopolitan, its occurrence in the boreal waters (fig. 

 XXI) is remarkably scattered, and apparently irregular. It is probably considerably more common than 

 appears from the chart, but occurs often in insignificant little colonies which may easily escape notice. 



Halecium minutum Broch. 

 1903 Halecium minutum, Broch, Die von . . . "Michael Sars" . . . gesammelten Hydroiden, p. 4, Taf. I, 



figs. 1—4. 



Colonies upright, generally with small, monosiphonic hydrocaulus, with regular, zigzag shaped 

 sympodial growth; these small colonies arise as a rule from creeping stolons, but at times the stolons 

 may collect together into well developed, branched and polysiphonic rhizocaulome-like formations, 

 from which small branches with sympodial ramification proceed. New branchlets arise from under the 

 base of the primary hydrothecae, normally only one branch at the hydrotheca. The renewal of the 

 hydrothecae is lively, and gives rise to pseudohydrocauli, which may more rarely serve as the base 

 for secondary sympodial formations. The hydrothecae are fairly large, expanding considerably upwards 

 from the slightly developed diaphragm, and have as a rule a highly curved margin ; the stalks of the 

 secondary hydrothecse are ringed; the branches have distinct rings under the uppermost hydrothecae, 

 rarely elsewhere. 



The gonothecae arise from the creeping stolons or from the tubes of the polysiphonic parts of 

 the colony. The females are very large, up to 3 mm. long, broad oval to round, and may not infre- 

 quently even be broader than long; they are highly flattened, with spines along the edge, especially in 

 the distal part. The male gonothecae are smaller, elliptical, and smooth; they may also proceed from 

 beneath the base of the primary hydrothecae. 



Material: 



"Thor" 66°ic/ N. 23°i4' W.; depth 115 -120 metres 

 Greenland: Egedesminde (without further details) 

 Iceland: 9 miles N.74°E. of Hornet, depth 38 fathoms 



Vadlavik, — 80 — [labelled Halecium lenellum\ 



Djupivogr 8 — | 



64°i7' N., i4°44' W. — 75 metres | — | 



Skagi — 40 — 



Hvalfjord — 46 — | — Schneidrri\ 



Skjalfandi Bay — 28 fathoms. 



Kramp's studies (1913 p. 5) of Halecium minutum are highly interesting. He has succeeded 

 in finding fertile female colonies, the identitv of which is thus placed beyond doubt, but where the 



