Report on the Hydroids. 



377 



"Die Zweigspitze dieser Art [G. immersa] zeigt einen regelmässigen 

 parallelen Zuwachs sämtlicher Tuben, so dass sie im Gegensatz zu 

 der vorhergehenden Art ein regelmässig abgerundetes Ansehen bekommt 

 (Taf. III, Fig. 6)"); — but this does not always hold good. On the 

 other hand, the form of the hydrothecae seems to be characteristic. 

 In G. abietina they are strongly bent, cut off square at the end and 

 with a slightly everted rim. In G. immersa the rim of the aperture 

 is not everted, and the hydrothecae are less bent, obliquely cut off 

 at the end in such a manner, that the plane of the aperture is 

 parallel with the direction of the branches (Text-fig. 6), 

 which in G. abietina is attained by the greater curvature. 

 When a hydrotheca of G. immersa grows further out than 

 usual, the plane of the aperture will form a small angle 

 with the direction of the branches, the aperture thus 

 facing somewhat downwards (text-fig. 6). — It may be 

 mentioned further, that G. immersa is smaller and more 

 slender than G. abietina, and that the free end of the 

 hydrotheca is usually shorter; in the specimens to hand 

 the branches are always constricted proximally. — In his 

 original description (45) Nutting says : "The distal ends 

 of the hydrothecæ are abruptly bent outward, so that 

 the round, even aperture is vertical", and he figures a 

 piece of a branch to illustrate this. As mentioned аЬолт, 

 the vertical position of the aperture is attained in the 

 specimens of the Danmark Expedition not only by the 

 bending but also by the aperture being cut oil" obliquely. 

 — In spite of these ditTerences from the descriptions and 

 figures of Nutting and Broch, there is no doubt that 

 the specimens of the Danmark Expedition really belong to the 

 species G. immersa Nutting, as they agree in all other respects with 

 Nutting's clear and detailed description. Further, they agree with 

 Jaderholm's descriptions and figures (33) and (34); though in Jäder- 

 holm's specimens the branches are not always constricted proximall3\ 



The colonies from St. (58 a occur on a large colony of Halecium 

 muricatnm. 



Hab.: St. 68 a, 71a. 



Depth: 30— 60 m . 



Geographical distribution: Arctic: circumpolar. — Northern 

 Pacific, America. 



Fam. Campaimlinidae. 

 Investigations on the structure and development of the 



о p e r с u 1 u m. 



The family Campannlinidae may be characterized as Thecaphora 

 conica, the hydrothecae of which, at least in their distal part, are 



Text-fig. 6. 



