From the beginnings of life, organisms have lived together in some
kind of grouping. Since the differentiation of plants and animals,
communities in which both occurred and interacted have undoubtedly
characterized the arrangement of living things on the face of the
earth. We know now that there are no habitats in which both
plant and animal organisms are able to live, in which both do not
occur and influence each other. In contrast, the development of the
science of ecology has been hindered in its organization and distorted
in its growth by the separate development of plant ecology on the
one hand and animal ecology on the other.

The authors were brought together in this task of attempting to
correlate the fields of plant and animal ecology by the common belief
that it would tend to advance the science of ecology in general. It
was this common interest rather than agreement in all matters which
led to the initiation of this book as a joint project several years ago.
In part, it grew out of the fact that the junior author's experience in
dealing with the marine communities of the Puget Sound region had
led to the discovery of community phenomena paralleling those found
on land and fitting the system of classification in use by the senior
author.

The phenomena under discussion naturally bring up the question
of the community processes, concepts, and nomenclature. A zoologist
may be unfamiliar with various ecological terms in use among plant
ecologists, and the reverse is also usually true. Here the writers have
not introduced all the terms which they are inclined to use in their
individual papers, designed for a more limited group of readers, but
have attempted to substitute less technical terms. Those terms ap-
plicable to communities are given to aggregations of organisms suffi-
ciently well known to enable the reader to build up a fairly clear
conception of the whole, so that the terms may be applied to the
proper grouping. For example, the term biome has been applied only
to those communities in which studies have established something of
the processes of development and the character of the final stage or

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