58 DISTRIBUTION OF ANIMALS. [PART I, 
maintained. For they will find, that a careful consideration of 
the exceptional means of dispersal and conditions of existence of 
each group, will explain most of the divergences from the normal 
distribution of higher animals. 
We shall thus be led to an intelligent comprehension of the 
phenomena of distribution in all groups, which would not be 
the case if every specialist formed regions for his own particular 
study. In many cases we should find that no satisfactory 
division of the earth could be made to correspond with the dis- 
tribution even of an entire class; but we should have the cole- 
opterist and the lepidopterist each with his own Geography. Aud 
even this would probably not suffice, for it is very doubtful if 
the detailed distribution of the Longicornes, so closely dependent 
on woody vegetation, could be made to agree with that of the 
Staphylinide or the Carabidze which abound in many of the 
most barren regions, or with that of the Scarabeide, largely de- 
pendent on the presence of herbivorous mammalia. And when 
each of these enquirers had settled a division of the earth into 
“regions ” which exhibited with tolerable accuracy the pheno- 
mena of distribution of his own group, we should have gained 
nothing whatever but a very complex mode of exhibiting 
the bare facts of distribution. We should then have to begin 
to work out the causes of the divergence of one group from 
another in this respect ; but as each worker would refer to his 
own set of regions as the type, the whole subject would become 
involved in inextricable confusion. These considerations seem 
to make it imperative that one set of “regions” should be 
established as typical for’ Zoology; and it is hoped the reasons 
here advanced will satisfy most naturalists that these regions 
can be best determined, in the first place, by a study of the dis- 
tribution of the mammalia, supplemented in doubtful cases by 
that of the other vertebrates. We will now proceed to a discus- 
sion of what these regions are. 
Various Zoological Regions proposed since 1857.—It has already 
been pointed out that a very large number of birds are limited 
by the same kind of barriers as mammalia; it will therefore 
not be surprising that a system of regions formed to suit the 
