sical and organic changes which have resulted in the present state
of the earth.

The indications now given of the scope and purpose of the present volume
renders it evident that, before we can proceed to the discussion of the
remarkable phenomena presented by insular faunas and floras, and the
complex causes which have produced them, we must go through a series of
preliminary studies, adapted to give us a command of the more important
facts and principles on which the solution of such problems depends. The
succeeding eight chapters will therefore be devoted to the explanation of
the mode of distribution, variation, modification, and dispersal, of
species and groups, illustrated by facts and examples; of the true nature
of geological change as affecting continents and islands; of changes of
climate, their nature, causes, and effects; of the duration of geological
time and the rate of organic development.

* * * * *

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CHAPTER II

THE ELEMENTARY FACTS OF DISTRIBUTION

Importance of Locality as an essential character of Species--Areas of
Distribution--Extent and Limitations of Specific Areas--Specific range
of Birds--Generic Areas--Separate and overlapping areas--The species of
Tits as illustrating Areas of Distribution--The distribution of the
species of Jays--Discontinuous generic areas--Peculiarities of generic
and family distribution--General features of overlapping and
discontinuous areas--Restricted areas of Families--The distribution of
Orders.

So long as it was believed that the several species of animals and plants
were "special creations," and had been formed expressly to inhabit the
countries in which they are now found, their habitat was an ultimate fact
which required no explanation. It was assumed that every animal was
_exactly_ adapted to the climate and surroundings amid which it lived, and
that the only, or, at all events, the chief reason why it did not inhabit
another country was, that the climate or general conditions of that country
were not suitable to it, but in what the unsuitability consisted we could
rarely hope to discover. Hence the exact locality of any species was not
thought of much importance from a scientific point of view, and the idea
that anything could be learnt by a comparative study of different floras
and faunas never entered the minds of the older naturalists.

But so soon as the theory of evolution