PENNATULIDA. 89 



temperatures. The climatic influence of the submarine barriers reaches, however, to the upper layers 

 of water also; these are considerably colder on the north than on the south side. The influence on 

 the currents is briefly thus: the warm body of water of the Atlantic streams north-east towards 

 Iceland and the ridges; here it is turned off in such a way, that it bends towards the west at the 

 ridge of the Denmark Straits, and then streams south alongside the south-going East-Greenland 

 Polar Current, forming the principal part of the Irminger Current; here accordingly, it returns to 

 the Atlantic; at the ridge between Iceland and the Faeroes the warm body of water is turned east- 

 ward and led towards Norway, where it streams northward. This water is only cooled far to the 

 north, then sinks to the bottom, and is led southward in the Arctic basin as cold water towards the 

 north side of the ridges without being able to pass these to any considerable degree. 



From this it follows that the deep-sea animals which rise so much above the bottom as to live 

 in this Atlantic water (which may be thought to apply among others to the larvae of bottom animals), 

 are partly retained in the Atlantic, and may partly wander towards Norway; here some of them may 

 take root, as the conditions to a depth of ca. 300 fathoms agree with those of corresponding depths 

 south of the ridges; and this holds good far north of the Polar Circle. Thus, the Atlantic fauna 

 reigns not only south of the mentioned boundary of the cold region, but also east of this region along 

 the whole Scandinavian peninsula. It is quite wrong to regard some deep-sea animals as arctic 

 forms, because they were first known from high northern latitudes at Norway; like several southern 

 animals from the same regions they belong really to a widely spread Atlantic fauna. A great number, 

 at least, of the animals found at the Scandinavian peninsula even to the North Cape, are also found 

 along the Atlantic side of southern Europe; some of them even pass into the Mediterranean; several 

 occur at the Azores, and still more on the east side of North America (at latitudes corresponding to 

 southern, and partly to Central Europe) ; and now the Ingolf Expedition has been able to show further 

 that some follow the warm layer of water far up on the west of Greenland. 



When we now turn to the Pennatulids, we find that of the 21 species enumerated here, no 

 less than 20 have been found in the Atlantic territory; only one, Umbellula encrinus, is an exclusively 

 Arctic species. But among the species from the Atlantic region there are two which may occur 

 beyond the boundary towards the cold region, viz. Virgularia cladiscus and Kophobelemnon steltiferum. 

 With regard to the latter, however, it has only been found in single instances and only in the narrow 

 branch sent off from the cold deep waters towards the Wy ville Thomson ridge in the Faeroe Channel ; 

 this species has otherwise the widest possible distribution inside the warm area. Virgularia cladiscus, 

 certainly, has been found more frequently and in several places inside the cold area, but always near 

 to the boundary towards the warm area; both these species must assuredly be regarded as Atlantic 

 species endowed with more than common hardiness with regard to temperature. 



The preponderance in richness of forms shown by the Atlantic territory in respect to Penna- 

 tulids, is a general feature; the cold territory of the depths of the North Atlantic is upon the whole 

 poor; but to be sure, the contrast is not so large in all groups as in this. 



The common characteristic of the fauna of the Atlantic territory with regard to the northern 

 Pennatulids will be seen plainly from the table below. 



The Ingolf-Expedition. V. i. 12 



