306 H. H, Howorth— Circumpolar Lands. 
and important to consider under what conditions such a result 
would be forthcoming. 
The fauna of the polar lands is so uniform in all longitudes that 
they constitute one of the best-defined zoological provinces; a 
province to which the name Circumpolar or Panarctic has been 
given. So far as our evidence goes, the solidarity and identity of 
forms which now mark the circumpolar lands was shared in the 
Mammoth age by a considerable zone south of this area, a zone now 
constituting the greater part of the Palearctic and Nearctic provinces 
of Mr. Sclater. If we are to judge by the remains which we can 
examine of the Mammoth and its contemporaries the Musk Sheep, 
the Bison, the Horse, the Elk, the Red Deer, the Reindeer, ete., etc., 
from the Old and the New World, there were not in the Mammoth 
age the distinctions which now mark off the mammals of North 
America from those of Northern Asia, and the panarctic and nearctic 
regions were then condensed into a fairly homogeneous zoological 
province. 
This means of course that there must have existed in the Mam- 
moth age a bridge over which the mammals at least could travel 
between the Old and the New World and vice versdé. Such a bridge 
would enable the animals to intermingle, and prevent isolation, which 
is the recognized causa causans of divergence of forms. If this be 
granted, and I cannot see how it can be contested, we have next to 
discover where this bridge was situated. In my work on the Mam- 
moth J have followed in the footsteps of Mr. A. Murray, and en- 
larged his reasons for believing that it is quite impossible to suppose 
that this intermigration took place across the ice of Bering’s Straits. 
Tn addition to the arguments there adduced, I would remark that if 
Bering’s Straits were frozen over, it could only be under climatic 
conditions, when the Mammoth and its companions would find it 
impossible to exist on the land on either side of that water-way ; 
and if we postulate (as the facts compel us to do) a comparatively 
mild winter climate in the Tchukchi peninsula and Alaska when 
the Mammoth lived, then we cannot also postulate that Bering’s 
Straits were at the same time closed by thick ice such as would 
alone afford a highway for the animals to travel over. The notion 
that the intermigration took place over the ice of Bering’s Straits is 
in fact an immature and very superficial one. 
Putting aside a highway of ice across Bering’s Straits, we are 
bound to postulate a land communication between Asia and America 
at this period, and the question is, where this bridge was planted. 
It is quite clear that, wherever placed, it must have connected the 
Mammoth area on the one continent with the Mammoth area on the 
other, and since, the Mammoth, so far as we know, did not live in 
Japan, but was there replaced by another species of Hlephant, this 
communication must have been north of Japan. Inasmuch as neither 
the Tichorhine Rhinoceros, nor the Hyena, nor the Great Ox (Bos 
primigenius), Whose remains are all found along the latitude of 
Central Siberia (the Rhinoceros occurring as far north as the river 
Wilui), have ever been found in America, and, so far as we know, 
