During the year now drawing to a close not a single work which I
conceive to fall legitimately within the scope of the department of
Geography of Life has appeared in any part of the world, so far as I am
aware. It being manifestly impossible, then, to comply with the
requirement of the By-law calling for a summary of the work of the
year, I may be pardoned for digressing sufficiently to speak of what
seems to be the _function_ of this Society in its relations to biology.
The term _'Geography of Life'_ applied without limitation or
qualification to one of the five departments of the Society is not only
comprehensive, but is susceptible of different if not diverse
interpretations. Indeed, without great violence it might be construed
to comprehend nearly the whole domain of systematic botany, zoology,
and anthropology. As a matter of fact, I believe it was intended to
include everything relating directly to the distribution of life on the
earth. Thus it would naturally embrace all sources of information which
assign localities to species. Local lists and faunal publications of
every kind would fall under this head, and also the narratives of
travelers who mention the animals and plants encountered in their
journeys. In the single branch of ornithology, about fifty per cent. of
the current literature would have to be included. The most obvious
objection to this comprehensiveness of scope is the circumstance that a
mere bibliographic record of titles alone would fill a journal the size
of the NATIONAL GEOGRAPHIC MAGAZINE.
Hence it may not be amiss to attempt a preliminary reconnoissance, with
a view to what my friend Mr. Marcus Baker has recently defined as "a
Survey of Class II, for Jurisdictional purposes." Let us seek therefore
to run a boundary line about the territory we may fairly claim without
trenching on the possessions of others.
Before doing this it becomes necessary to bear in mind certain facts
and laws without a knowledge of which it is impossible to think
intelligently on the subject. It is a matter of common observation that
different groups of animals and plants inhabit different regions, even
in the same latitude; that some forms are almost world wide in
distribution; that others are restricted to very limited areas; that
the ranges of very dissimilar species are often geographically
coincident; and that, as a rule, animals inhabiting contiguous areas
are more nearly related than those inhabiting remote areas. The
recognition of these facts early led to the attempt to divide the
surface of the earth, according to its animal life, into 'faunal'
districts. By the term _fauna_ is meant the sum of the animal life of a
region.
A comparatively meagre supply of information is sufficient to indicate
the principal faunal subdivisions of a country, but for mapping the
exact boundaries of such areas a vastly greater and more precise fund
of knowledge is necessary. The way in which such maps are prepared is
by collecting all available authentic records of localities where the
particular species has been found. This is done by compiling published
records, by examining labels of specimens in various museums and
private collections, and by work in the field. The data thus brought
together are arranged on cards under authors and regions, and are
tabulated under species. The localities are then indicated by colored
spots on an outline map, the space surrounded by the spots being washed
in with a paler tint of the same color. A separate map is devoted to
each species.
Faunal maps are made by combining a large number of species maps. In
making such combinations it is found, as a rule, that a considerable
percentage of the species maps fall into certain well defined
categories whose color patches are essentially coincident. The
composite resulting from the coördination of these maps may be held to
represent the natural faunal areas of a country. Several such areas may
be characterized by the common possession of species not found
elsewhere, and may be combined to constitute a faunal province; several
provinces, a region; and several regions a realm or primary
zoö-geographical division of the earth's surface.
Having ascertained the actual extent and limitations of the natural
faunal districts, it remains to correlate the facts of distribution
with the facts of physiography.
My own convictions are that the work of this Society in Geographic
Distribution should be restricted to the generalization of results:
that we should deal with philosophic deduction rather than with
detailed observations and the tedious steps and laborious methods by
which they are made available. Our aim should be to correlate the
distribution of animals and plants with the physiographic conditions
which govern this distribution, and to formulate the laws which are
operative in bringing about the results we see. In other words, we are
to study cause and effect in the relations of physiography to biology.
The kind of works meriting discussion in the annual report of the
Vice-president of this section are such philosophic treatises as those
of Humboldt, Dana, Agassiz, DeCandolle, Engler, Darwin, Huxley,
Pelzeln, Sclater, Wallace, Baird, Verrill, Allen, Cope, and Gill. As it
is seldom that more than one or two such works appear in any single
year, there is likely to be ample opportunity for profitable
discussion.
January, 1889.