Bd. V: 6) THE FISHES OF THE SWEDISH SOUTH POLAR EXPEDITION. 3 



tried to apply these principles, because I think that the systematical knowledge is 

 best served in this way. Unfortunately there remains nevertheless some uncertainty 

 concerning which characteristics may be regarded as being of specific or only of 

 subspecific value and in some cases this must be almost a matter of personal taste 

 or conviction. But even with this weakness the use of a ternary nomenclature, 

 when needed, appears to be better than an indiscriminate "splitting" or "lumping". 

 It is better than the "splitting", because it permits a subordination of unequal notions 

 which with this latter method is impossible when only specific names are used, so 

 that two or more forms, which are nearly related and perhaps only varieties (geo- 

 graphical or not) of one and the same, must appear to stand quite as much apart 

 from each other as in reality sharph' defined and isolated species do. The "lump- 

 ing" is still more apt to bring confusion in the system, when it tends to throw- 

 together two or more forms which have only superficial likeness and perhaps in 

 reality are only distantly or not at all related. For the study of zoogeography the 

 recognition of subspecies is a great help, because it, at once, viz. already in the names, 

 gives information as well about which forms belong together, as about which, through 

 isolation or other causes, have become difterentiated from a common type, thus as 

 well about major as minor zoogeographical districts. 



When the present author promised (p. 2) to describe in a separate chapter 

 the fishes collected by this Expedition in the true Antarctic Region it is evident 

 that he understands with the "Antarctic Region" something else than Dr. L. Doi.LO, 

 who in his learned treatise on the fishes of the Expedition of "Belgica" * appears 

 to count to this region only the interior of the Antarctic Polar Circle although he 

 admits himself that this only is a provisorical arrangement. I cannot agree with 

 Dr. DoLLO in circumscribing the Antarctic Region, taken in a biological sense, in 

 such a purely mathematical wa\'. The life-zones do not and cannot coincide with 

 the mathematical divisions of the earth, because the physical conditions, on which 

 the former are utterly dependent, do not directl}' and only in a remote degree cor- 

 respond with the mathematical divisions. A glance at a map, on which the isotherms 

 have been laid out, suffices to show this. The experience from the Arctic Region 

 proves also in the most eminent manner that the Arctic Circle has nothing to do 

 with the Arctic life-zone which for instance, on the european side, is pushed back 

 far above the Polar Circle, but, on the american side, extends far to the south of 

 the same, a fact so well known by all biologists that it need no further explication. 

 It is also known that the climatological conditions, which cause this, in their turn 

 are due to the great sea currents which on the eastern side of the Atlantic move 

 great masses of warm sea water towards the north and on the western side in a 



* Résultats du Voyage du S. V. Belgica. Rapports Scientifiques. Zoologie. Poissons par L. Dollo. 

 Anvers 1904. 



