HYDROIDA II .- 



j 



Material : 



"IngolP' St. 7, 63 13' N., 15041' W., depth 600 fathoms, 4,5 

 9, 64i8' N., 27oo' W., 295 5,8 



54, 6 3 o8' N., i 5 4 o' W., 691 3,9 



"Thor" 63 3 o' N., 2 oi 4 ' W., 80 metres - [labelled Halecmm halecinum, H. 



Beanii and H. labrosutri}. 



Greenland: Cape Tobin, depth 57 fathoms (East Greenland Expedition). 

 Iceland : Vadlavik (depth not stated) 



Vestmano, depth 3040 fathoms [labelled Halecium halecinum and H. Beanii] 

 10 miles W. of Akranes (depth not stated) [labelled Halecium Beanii]. 

 Between Iceland and The Faroe Islands, depth 192 fathoms (without further details) 

 The Faroe Islands: 6 miles N. by W. of Kalso, depth 60 fathoms 

 Stokken 2 miles in S.22E., 55 



Deep hole at north point of Nolso, depth 100 fathoms. 

 Glyversnaes near Thorshavn, on red algse. 

 Boronses 13 miles in N-75W., depth 30 fathoms. 



Halecium halecinum is generally of somewhat coarser build than Halecium Beanii, but a good 

 deal finer than Halecium scutum; it is often extremely difficult to distinguish these species one from 

 another, especially when the colonies assume an altogether irregular form, which 

 the males in particular are inclined to do. The female gonothecae in Halecium 

 halecinum will, in their normal shape, with the quite terminal lateral opening, 

 hardly be confused with normal individuals of the other species, but when, as not 

 infrequently occurs, the distal portion of the gonotheca is domed forward, so that 

 the aperture is found somewhat below the point on one side of the gonotheca, 

 the identity is by no means easy to determine. True, Halecium scutum is in 

 most instances of far coarser build than the two others, but the variation in dim- 

 ensions is within each of the three too great to permit the fixing of proper size 



Fig. XI. Halecium hak- 



limits; they would be found to overlap considerably. A useful general character ,. internode with 



for Halecium halecinum is the asymmetrical development of the basal cavity in h y drothe cae- From the 



Faroe Islands at north 



the secondary hydrotheca (fig. XI); the basal part of the adcauline wall is more point of Nolso. (x 60). 

 strongly developed, and highly curved, so that the hydrotheca axis thus diverges widely from the 

 branch. On the other hand it must be remarked that the hydrotheca aperture is perpendicular to the 

 longitudinal axis, a feature whereby the species is distinguished from Halecium Beanii. 



Halecium halecinum has an extremely wide area of distribution, and is very common right up 

 in the Mediterranean; it has also been recorded from waters south of the Equator. In the northern waters, 

 the species appears as a boreal character form, with warmer tendency (fig. XII) and is mostly met 

 with in the middle part of the littoral region; at times, however, it may penetrate right down into 

 the abyssal, as at the "Ingolf St 54, where it was taken in a depth of over 1300 metres. In purely- 

 arctic waters, it is very rare, and records of its occurrence there must be treated as doubtful, as it 



