EXPEDITION ANTARCTIQUE BELGE 



be considérée! southern, unless some reliable authority gives particulars as to its being found 

 in the southern hémisphère; so that a careful examination of the list leaves nothing to support 

 the position taken up by Pfeffer, when he says on page 471 : « Die wesentliche genetische 

 Uebereinstimmung der arktischen und antarktischen Zone findet kaum noch irgendwo im 

 Thierreich eine kraftigere Begrtindung als durch die Bryozoen. » 



In my paper on the « Bryozoa from Franz Josef Land ( r ) » I examined and reduced 

 the list of 16 species of Bryozoa, from the northern and southern hémisphères (unrecorded 

 within the tropics) as drawn up by Sir John Murray, from « Busk's Challenger Report », 

 but would add that our knowledge is very incomplète as to the tropical Bryozoa, and in consi- 

 dering the bipolar theory this want is much felt. 



Limits of the Antarctic 



Though the Arctic and Antarctic faunas are strictly those within the Arctic or Antarctic 

 circle, yet, this being an artificial division it seemed to me permissible to pass a little 

 outside the circle in the Arctic régions, so as to include everything within the air isothermal 

 of o° C, and this does not much increase the area under considération. It is certainly 

 difficult to décide what should be considered Antarctic, and if the limit of the distribution 

 of ice, as recommended by Fricker ( 2 ), is taken in the south, then the area thus included is 

 very much larger than that enclosed by the Antarctic circle ; now this limit, which has been 

 used by various authors, is not an entirely température boundary, but is largelv inrluenced 

 by currents and other causes. 



By taking the isothermal of o° C. in the Antarctic the increase of area is however 

 not very considérable ; whereas it has been seen that using the limit of the distribution of 

 ice in the south enlarges the area, thus included, very materially. Now in considering 

 geographical distribution, although température must be taken into considération it is only 

 one factor, certainly a very important one, while the question of distance is scarcely less 

 important, especially as in past âges the température may hâve been, in fact we know that 

 it has been, relatively entirely différent. Many authors hâve however written of régions, far 

 beyond the limit of ice drift, as being Antarctic, so that not only Kerguelen Island, in 

 Lat. 5o° S. (about the équivalent of Lands End and Cherbourg) are spoken of as Antarctic, 

 but also with localities still lurther north the same mistake has been made ; as for example 

 the Chatham Islands the équivalent of Genoa. Bv including localities as far away from 

 the South Pôle as the Chatham Islands, we just about double the distance apart of the 

 limits of the area, and more than double the superficial area. If the isothermal of o° C. 

 is chosen, the fauna would be comparable with the Subantarctic faunas of the south of 

 South America ; the Kerguelens ; the South Australasian ; and other southerly faunas, without 

 considering them Antarctic. 



The lavish use of the terni Antarctic was made when practically no Antarctic fauna 

 was known, whereas we are learning, that there is a rich Antarctic fauna related closely 

 to the Subantarctic, but yet differing considerably from it; so that we may find the Antarctic 



(1) Linn. Soc. Journ. Zool., vol. XXVIII, p. 4.8. 



(2) The Antarctic Régions translatée! by A. Sonnenschein, 1900. 



