78 GEOGRAPHICAL RANGE CHAP. 
Altogether the enormous progress in the complexity of the 
brain from the early Tertiary mammals down to the present, is 
one of the most remarkable revelations of palaeontology. It 
goes perhaps some way in explaining the remarkable diversity 
in mode of life exhibited by the mammals as compared, for 
example, with the birds, whose brains have not diverged so much 
or in so many directions from the primitive form. 
The present Distribution of the Mammalia.—In the follow- 
ing pages some of the principal facts in the geographical range 
of the orders, families, and many of the genera of Mammalia 
will be given. It has been justly observed by Mr. Sclater 
that the habitat of an animal is as much a part of its 
definition as is its structure or external form. No systematic 
account of the Mammalia would therefore be complete without 
such geographical facts. But that branch of zoology which 
is concerned with the past and present distribution of animals 
is wider in scope than this. Zoogeography deals not only 
with the actual facts in the range of animals, but with the 
inferences as to past changes in the relations of land and sea 
which the facts seem to indicate, and with speculations as to 
the place of origin of the different groups, of which more than 
hints are sometimes given by their past and present distribution. 
In addition to this, the earth can be mapped out into provinces 
and regions which are definable by their animal inhabitants. 
In the present volume, dealing only with the Mammalia, it will 
be obviously impossible to enter fully into the entire subject 
of zoogeography. All that will be attempted is a brief general 
survey of the science so far as it can be illustrated by the 
Mammalia. For fuller knowledge the reader is referred to the 
treatises mentioned below.! 
There are certain facts in the distribution of animals which 
are commonplaces of knowledge, but which may be set forth 
with definiteness. Everybody knows that an animal has a given 
range: Elephants, for example, are found in India and certain 
adjacent parts of Asia, and again in Africa; the Rhinoceroses 
have roughly the same range; the Tiger is limited to Asia; the 
1 Wallace, Zhe Geographical Distribution of Animals, 1876. Heilprin, The 
Distribution of Animals, Internat. Scientific Series, 1887. Beddard, 4A Text-book 
of Zoogeography, Cambridge Natural Science Manuals, 1895. Lydekker, Geographi- 
cal History of Mammals, Cambridge Geographical Series, 1896. W. L. and P. L. 
Sclater, The Geography of Mammals, Kegan Paul and Co. 1899. 
