HYDROIDA II 



J3 1 



Jan Mayen, depth 50 — 60 fathoms (East-Greenland Expedition). 

 Iceland: Mouth of Berufjord, depth 41—54 fathoms. 

 Kara Sea, "Dijmphna". 



Sertularia Fabricii is very closely related to Sertularia < upressina, but differs primarily in its 

 dextrorse stem. Moreover, its hydrothecae are as a rule more deeply imbedded than in the latter 

 species (fig. LXIX). Levinsen (1893 p. 48) calls attention to a peculiarity in the species, to wit, that 

 the basal branches throw off their extreme parts, leaving only the proximal internodium ; this appears 

 to be a characteristic feature in the species, the explanation of which cannot be arrived at from our 

 present knowledge of its biology; it gives the species a highly remarkable appearance. Another char- 



._ _ 1000 m. 



2 00 m. 600 m. 



Fig. LXX. Finds of Sertularia Fabricii in the Northern Atlantic. 



acter which has been emphasised is less reliable; according to Levinsen, the upright direction of 

 the branches is 45 with the longitudinal axis of the stem; but the colonies from Jan Mayen and 

 from the "Ingolf" St. 2 had branches standing out almost perpendicularly from the stem, and farther 

 out even turning downwards; in these colonies also, the tendency to unilateral arrangement of the 

 hydrothecae is remarkably slight; despite this, and despite the fact that they are of finer build than 

 those from Greenland, they cannot be regarded as types of a distinct species. 



It is interesting to note how exactly the hydrothecae in Sertularia Fabricii follow the same 

 rules in their variation as in Sertularia cuprcssina. On the proximal part of the branches, the hydro- 

 thecae are far more deeply imbedded than at the extremities (fig. EXIX). The gonothecae, on the 

 other hand, evince a much slighter variational tendency in the present specimens, which rather give 



