HYDROIDA II 



35 



Creeping colonies with tnbular hydrothecse. The hydrotlieca stalk is irregularly, but distinctly 

 ringed or spirally coiled. The hydrothecse pass over evenly into the stalk, they are somewhat 

 expanded at the base, then tapering slightly upwards, to expand again a little towards the open- 

 ing margin, which curves somewhat outwards. The opening margin itself has four low, but distinctly 

 discernible teeth, and has four triangular opercular plates fastened between them. 



The gonothecse are unknown. 



Material: 



Greenland: Egedesminde, depth 30-50 fathoms. 



Scattered specimens of this high-arctic species have been found at West Greenland, Spitzbergen, 

 in the Murman Sea, the Barents Sea, the White Sea, the Siberian frozen Sea and the Sea of Okhotsk, 

 and must thus doubtless be referred to the circumpolar species. It belongs to the middle parts of the 

 littoral region. 



Family series Haleciina nov. 

 Family Haleciidae. 



The hydrothecse are radially symmetrical and very small, at times practically altogether dis- 

 appearing; they have as a rule a basal cavity, often marked off from the hydrotlieca itself by a dia- 

 phragm. The hydranths are large, and cannot be drawn quite into the hydrothecse. They have a 

 conical proboscis, and their gastral endoderm falls into two divisions, answering to the fore-stomach 

 and stomach of the polyp, which as a rule are separated by a limit indicated by a more or less marked 

 ring furrow round the body of the polyp. The basal part, the stomach, forms the digestive portion. 

 The polyps are radially symmetrical in structure. The colonies are stolonial or sympodial, with simple 

 or derived growth of the tips. 



Gen. Halecium Oken. 



Creeping stolonial, or upright sympodial colonies with small radially symmetrical hydrothecse 

 with basal cavitv. The diaphragm can be present or lacking. Nematotheeae and nematophores lacking. 

 The gouophores are developed in gonothecse. 



The Halecium colony, in species with polysiphonic stem, often presents a peculiar appearance, 

 differing greatly from that of other hydroid colonies, as the polysiphonic main stem, which is gener- 

 allv verv strongly developed, most frequently presents the same impression as an altogether irregularly 

 branched rhizocaulome, while the outer parts of the branches almost always exhibit regular ramifica- 

 tion. Halecium in in it turn Broch especially, seems in some respects to take up a remarkable and 

 exceptional position; according to Kramp's observations (1913 p. 5) it can at times exhibit large colon- 

 ies of composite structure with rhizocaulome-like polysiphonic main stem and main branches, while 

 otherwise, the species normally presents small, monosiphonic colonies proceeding from a network of 







