4 o 



HYDROIDA II 



hydrothecse are low, often hardly more than an opening in the apophyse, which is distally placed, and 

 distinctly marked. The secondary hydrothecae are likewise small, with a fairly large basal chamber, 

 which is almost always symmetrically developed. The hydrothecse have a thin, but well-developed 

 diaphragm; they expand towards the aperture, but have no outward curving margin. 



The gonothecaa are small, and attached to the apophyse at the base of the primary hydrothecae 

 The males are cylindrical to elongated oval, tapering downwards, broadly rounded distally, or cut off 

 transversely. The female gonothecae have a laterally placed opening with a pair of hydranths; the 

 opening margin has on its inner (adthecal) side a short, broadly lingueform protuberance. The gono- 

 theca openings are situated between the middle and the distal end of the gonotheca, rarely quite 

 distally. The gonotheca is often somewhat irregularly bent. 



Material : 



"Ingolf" St. 31, 6635' N., 5554' W., depth 88 fathoms 1,6 



34, 6 5 i 7 ' N, 54 i 7 ' W, 55 



Greenland: Sukkertoppen (without further details) 



Davis Strait, depth 100 fathoms (without further details) [labelled Halecium Beanii\ 

 Iceland: Vadlavik, (depth not stated) [labelled Halecium Beantt] 



Between Iceland and The Faroe Islands: 63i5' N., 935' W., depth 270 fathoms [labelled Hale- 

 cium Beanii\ 

 The Faroe Islands: Deep hole at north point of Nolso, depth 100 fathoms 



6i4o' N., y4o' W., depth 135 fathoms 

 Kara Sea: "Dijmphna" [labelled Halecium Beanii\ 



It is not without a certain doubt that we can admit Halecium scutum as a distinct species 

 and not as an arctic form of Halecium halecinum. From a geographical point of view, as also with 

 regard to most of the variational features, it stands in almost exactly the same relation to the last- 

 named species as the arctic forms of several other more or less cosmopolitan hydroids. And it is also 

 Halecium scutum which has formerly (Broch 1909 p. 144) been noted as forma gigantea of Halecium 

 halecinum. 



A comparison of the two species reveals various points of resemblance. Bonnevie's state- 

 ment (1899 p. 57) "ramification in all planes" as a characteristic feature cannot be admitted; it applies 

 as a matter of fact far more to the exceptions, the great majority of the colonies exhibiting a decided 

 main plane in which the ramification takes place. On the other hand, the short and broad internodia 

 (fig. XIV a) are typical, and differ not a little from Halecium Beanii, with which the species has espe- 

 cially been confused. The secondary hydrothecae differ normally from Halecium halecinum in having 

 a symmetrical and proportionately lower basal cavity, and from Halecium Beanii in having the plane 

 of the aperture perpendicular to the longitudinal axis. The frequent confusion of Halecium scutum 

 with Halecium Beanii is due to the great variability of the female gonothecse (figs. XIV b h) which 

 not infrequently (e /) resemble strongly those of the latter species. We should, however, note that 

 in Halecium scutum the aperture and its short neck are as a rule obliquely placed, diverging widely 

 from the line between the stalk of the gonotheca and its top; in addition, the gonotheca has an 



