Animal Geography. 
6x 
1877.] 
sub-region, since deep seas generally mark out a primary 
division in the faunae of the lands they separate— a truth 
which Mr. Wallace has enforced and utilised in his work on 
the Malay Archipelago. But the Mediterranean, though a 
very deep sea, did not always form a continuous barrier be- 
tween Europe and Africa. It was bridged over at Gibraltar, 
and again at the part between Sicily, Malta, and the African 
coast, and thus an easy communication between its northern 
and southern shores was possible. The traveller who proceeds 
from Spain or Italy, either southwards or eastwards, finds 
no very marked transition until he has reached the Niger in 
the one direction or the Indus in the other. The faunae of 
the Azores, Madeiras, and Canaries have been carefully ex- 
amined, and show unmistakable Palaeanflic affinities, having 
been derived at an early period either from South-Western 
Europe or North-Western Africa. This circumstance speaks 
against the supposition that these island-groups are the last 
remains of a former continent (Atlantis), either independent 
or connected with tropical America. In either of these 
cases their faunae would have exhibited a marked distinction 
from that of Mediterranean Europe. 
The third PalaearCtic sub-region, the Siberian, occupies 
the whole of Northern, North-Eastern, and Central Asia as 
far as the frontiers of the Oriental region. Middle and 
Northern China and the islands of Japan form the fourth 
and last sub-region. 
Each of the six great regions “ has had a history of its 
own, the main outlines of which we have been able to trace 
with tolerable certainty.” 
Tho question now arises, what are the causes of the dis- 
tribution of animals as at present existing — a distribution 
which mere differences of temperature, of moisture, and of 
the supply of food are far from fully explaining ? 
Among the agencies which have influenced the migrations 
and re-migrations of species, a prominent rank belongs to 
the Glacial epoch — perhaps we might rather say the Glacial 
epochs. It is important to note that on this subject 
Mr. Wallace accepts the views of Mr. Belt. This 
acute geologist holds that glaciation was simultaneous 
over both hemispheres, and that the amount of water 
piled up in the form of ice upon the continents so far 
lowered the depth of the ocean as to lay dry extensive 
tradts of land, now submerged to the depth of 2000 feet, 
these low-lying regions becoming the refuge for tropical 
forms of animal and vegetable life. It is scarcely necessary 
to add that this hypothesis would never have secured suf- 
