16 ON THE GEOGRAPHY OF ANIMALS. 
turalist more especially, to be borne in mind than this. 
What beings can be more dissimilar than an African 
negro and a Greek Caucasian? Yet who has ventured 
to pronounce in what regions the Ethiopian form ac- 
tually blends into that of the Caucasian ? or this, again, 
into the Mongolian? Such are the difficulties that 
will for ever baffle all attempts at unexceptionable 
definition, or every effort to define the precise limits of 
natural groups or zoological regions. Nature, in fact, 
seems to abhor those arbitrary rules, with which man 
has invested her operations ; and which, for centuries, 
have shackled the progress of zoological knowledge. 
(21.) In attempting, therefore, to give a more accu- 
rate definition to the foregoing divisions, we are com- 
pelled to fill up the outline, at the best with diffidence, 
and, in some cases, by conjecture. The following, how- 
ever, may be regarded as some approximation to the 
truth. 1. The European or Caucasian range includes 
the whole of Europe, properly so called, with part of 
Asia Minor, and the shores of the Mediterranean: in 
Northern Africa the zoological peculiarities of this re- 
gion begin to disappear ; they are lost to the eastward 
of the Caucasian mountains, and are blended with those 
of Asia and America to the north. 2. The Asiatic range : 
comprehending the whole of Asia east of the Ural 
mountains, a natural and well-defined barrier between 
the two continents. The chief seat of this zoological re- 
gion is probably in central Asia; its western confines 
blend into the European towards Persia, and disappear 
on the west of the Caucasian chain ; it is united to the 
African range among the provinces of Asia Minor ; and 
is again connected with Europe, and also with America, 
by the arctic regions of the three continents ; finally, its 
most southern limits are marked by the islands of Java 
and Sumatra, where the zoological character of the Aus- 
tralian region begins to be apparent. 3. The American 
range. United to Europe and Asia at its northern limits, 
this region or province comprehends the whole of the 
New World; but into which it blends at the other ex- 
