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PREFACE
IN the present volume I have attempted to summarise and
complete my half- century of thought and work on the
Darwinian theory of evolution. In several directions I
have extended the scope and application of the theory, and
have shown that it is capable of explaining many of the
phenomena of living things hitherto thought to be beyond
its range.
Among these are the detailed distribution of plants and
animals, which I have discussed at some length. It occupies
about one-fourth of the volume (Chapters II. to VI.), and
brings out certain facts and conclusions which I believe will
be of interest to all plant-lovers, and also be not without a
certain value to botanists.
Next in importance are three chapters (X., XI., and XII.)
devoted to a general review of the Geological Record and a
discussion of the various problems arising out of it. Some
of the conclusions to which this examination leads us are, I
believe, both important and of much general interest.
In Chapter VIII. I have endeavoured to show natural
selection actually at work in continually perfecting that
wonderful co-adaptation of the most diverse forms of life
which pervades all nature. Some little-known aspects of
bird-migration are here discussed, and proof is given of the
enormous importance of mosquitoes for the very existence
of a considerable proportion of our birds, including most of
our most favoured pets and songsters. This chapter will, I
think, have a special interest for every bird-lover.
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