debted in a special manner to one gentleman--Mr. Theo.
D. A. Cockerell, now Curator of the Museum of the Jamaica Institute--who
supplied me with a large amount of information by searching the most recent
works in the scientific libraries, by personal inquiries among naturalists,
and also by giving me the benefit of his own copious notes and
observations. Without his assistance it would have been difficult for me to
have made the present edition so full and complete as I hope it now is. In
a work of such wide range, and dealing with so large a body of facts some
errors will doubtless be detected, though, I trust few of importance.

PARKSTONE, DORSET, _December, 1891_.

* * * * *

{ix}

PREFACE TO THE FIRST EDITION

The present volume is the result of four years' additional thought and
research on the lines laid down in my _Geographical Distribution of
Animals_, and may be considered as a popular supplement to and completion
of that work.

It is, however, at the same time a complete work in itself: and, from the
mode of treatment adopted, it will, I hope, be well calculated to bring
before the intelligent reader the wide scope and varied interest of this
branch of natural history. Although some of the earlier chapters deal with
the same questions as my former volumes, they are here treated from a
different point of view; and as the discussion of them is more elementary
and at the same time tolerably full, it is hoped that they will prove both
instructive and interesting. The plan of my larger work required that
_genera_ only should be taken account of; in the present volume I often
discuss the distribution of _species_, and this will help to render the
work more intelligible to the unscientific reader.

The full statement of the scope and object of the present essay given in
the "Introductory" chapter, together with the "Summary" of the whole work
and the general view of the more important arguments given in the
"Conclusion," render it unnecessary for me to offer any further remarks on
these points. I may, however, state {x} generally that, so far as I am able
to judge, a real advance has here been made in the mode of treating
problems in Geographical Distribution, owing to the firm establishment of a
number of preliminary doctrines or "principles," which in many cases lead
to a far simpler and yet more complete solution of such problems than have
been hitherto possible. The most