HYDROIDA II 



15 



same. Such "species" will on further investigation often be found to represent regular groups of vari- 

 ants. And this is precisely the case here. In Lafoea fruticosa, the transition forms are not infrequent 

 in boreal waters, and it may often appear doubtful where the limits should be drawn. It is perfectly 

 admissible, in the case of Lafoea fruticosa, to distinguish between a forma gemiina as opposed to forma 

 grandis, the first-named comprising that group of variants hitherto indicated as Lafoea fruticosa, and 

 the latter embracing the species Lafoea grandis and Lafoea symmetrica. The two forms also make 

 typical geographical groups. 



Forma genuina, which must be regarded as the mother form, is of very wide distribution; it 

 is encountered together with the following form (text fig. Ill) in the arctic region, and alone in boreal 

 and southern waters, both in the Atlantic and the Pacific, where it has been met with so far down 

 as Hawaii. Intermediate forms are, as mentioned, frequently found in boreal and arctic waters, more 

 particularly in the transition zones between the two. 



Forma grandis is of strictly arctic occurrence, and must here be regarded as a typical character 

 form. Billard's record (1907 p. 176) of a find at Cape Spartel must, from the measurements and 

 figures given, be due to incorrect diagnosis. 



Gen. Toichopoma Levinsen. 



The colonies are creeping, or form upright, irregularly branched rhizocaulomes, with stalked, 

 cylindrical hydrothecae. The hydrothecse lack the diaphragm, but have a primitive closing apparatus; 

 the distal integral part of one side of the hydrotheca wall can be closed down over the aperture. 



Toichopoma obliquum (Hincks) Levinsen. 

 1874 Calycella obliqua, Hincks, On deep-water Hydroida from Iceland, p. 149, pi. 6, figs. 4—5. 

 1893 Toichopoma obliquum, Levinsen, Meduser, Ctenophorer og Hydroider, p. 178. 



191 1 — Kramp, Report on the Hydroids, p. 374, pi. XX, fig. 4, pi. XXIII, figs. 5 — 8, 



pi. XXIV, fig. 1. 



The colonies are creeping, or form upright irregularly branched rhizocaulomes. The hydrothecae 

 have a, short stalk with a varying number of spiral windings; the)- are cylindrical, curved, with an 

 adcauline convexity, as a rule somewhat expanded near the base, and slightly broader again near the 

 aperture, which in open hydrothecae is somewhat asymmetrical; the hydrotheca passes gradually over 

 into the stalk. The abcauline distal part of the aperture is thin, and can be closed in towards the 

 opposite wall over the contracted polyp. 



The gonothecae are closely packed in a (hermaphroditic?) coppinia on stem or branches; the 

 single gonothecse are pentagonal or hexagonal, with a short, narrow cylindrical neck. Between the 

 gonothecae are inserted long, highly curved tubes, forming a close network over the coppinia. 

 Material : 



Greenland : Jakobshavn (no details noted) 

 Egedesminde ( - — — ) 



Toichopoma obliquam is a high arctic species, recorded both from West and East Greenland, 

 as well as from Spitzbergen and the Murman Sea. 



