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[Illustration: Zoogeographical Regions]
THE GEOGRAPHICAL
DISTRIBUTION OF ANIMALS
_WITH A STUDY OF THE RELATIONS OF LIVING AND EXTINCT FAUNAS AS ELUCIDATING
THE PAST CHANGES OF THE EARTH'S SURFACE._
BY ALFRED RUSSEL WALLACE,
AUTHOR OF "THE MALAY ARCHIPELAGO," ETC.
WITH MAPS AND ILLUSTRATIONS.
_IN TWO VOLUMES.--VOLUME I._
London: MACMILLAN AND CO. 1876.
[_The Right of Translation and Reproduction is Reserved._]
LONDON:
R. CLAY, SONS, AND TAYLOR, PRINTERS,
BREAD STREET HILL.
PREFACE.
The present work is an attempt to collect and summarize the existing
information on the Distribution of Land Animals; and to explain the more
remarkable and interesting of the facts, by means of established laws of
physical and organic change.
The main idea, which is here worked out in some detail for the whole earth,
was stated sixteen years ago in the concluding pages of a paper on the
"Zoological Geography of the Malay Archipelago," which appeared in the
_Journal of Proceedings of the Linnean Society_ for 1860; and again, in a
paper read before the Royal Geographical Society in 1863, it was briefly
summarized in the following passage:--
"My object has been to show the important bearing of researches into the
natural history of every part of the world, upon the study of its past
history. An accurate knowledge of any groups of birds or of insects and
of their geographical distribution, may enable us to map out the islands
and continents of a former epoch,--the amount of difference that exists
between the animals of adjacent districts being closely related to
preceding geological changes. By the collection of such minute facts,
alone, can we hope to fill up a great gap in the past history of the
earth as revealed by geology, and obtain some indications of the
existence of those ancient lands which now lie buried beneath the ocean,
and have left us nothing but these living records of their former
existence."
The detailed study of several groups of the birds and insects collected by
myself in the East, brought prominently before me some of the curious
problems of Geographical Distribution; but I should hardly have ventured to
treat the whole subject, had it not been for the kind encouragement of Mr.
Darwin and Professor Newton, who, about six years ago, both suggested that
I should undertake the task. I accordingly set to work; but soon became
discouraged by the great dearth of materials in many groups, the absence of
general systematic works, and the excessive confusion that pervaded the
classification. Neither was it easy to decide on any satisfactory method of
treating the subject. During the next two years, however, several important
catalogues and systematic treatises appeared, which induced me to resume my
work; and during the last three years it has occupied a large portion of my
time.
After much consideration, and some abortive trials, an outline plan of the
book was matured; and as this is, so far as I am aware, quite novel, it
will be well to give a few of the reasons for adopting it.
Most of the previous writings on Geographical Distribution appeared to me
to be unsatisfactory, because they drew their conclusions from a more or
less extensive _selection_ of facts; and did not clearly separate groups of
facts of unequal value, or those relating to groups of animals of unequal
rank. As an example of what is meant, I may refer to Mr. Andrew Murray's
large and valuable work on the Geographical Distribution of Mammalia, in
which an immense number of coloured maps are used to illustrate the
distribution of various groups of animals. These maps are not confined to
groups of any fixed rank, but are devoted to a selection of groups of
various grades. Some show the range of single species of a genus--as the
lion, the tiger, the puma, and a species of fox; others are devoted to
sections of genera,--as the true wolves; others to genera,--as the hyænas,
and the bears; others to portions of families,--as the flying squirrels,
and the oxen with the bisons; others to families,--as the Mustelidæ, and
the Hystricidæ; and others to groups of families or to orders,--as the
Insectivora, and the opossums with the kangaroos. But in no one grade are
all the groups treated alike. Many genera are wholly unnoticed, while
several families are only treated in combination with others, or are
represented by some of the more important genera.
In making these observations I by no means intend to criticise Mr. Murray's
book, but merely to illustrate by an example, the method which has been
hitherto employed, and which seems to me not well adapted to enable us to
establish the foundations of the science of distribution on a secure basis.
To do this, uniformity of treatment appeared to me essential, both as a
matter of principle, and to avoid all imputation of a partial selection of
facts, which may be made to prove anything. I determined, therefore, to
take in succession every well-established family of terrestrial
vertebrates, and to give an account of the distribution of all its
component genera, as far as materials were available. Species, as such, are
systematically disregarded,--firstly, because they are so numerous as to be
unmanageable; and, secondly, because they represent the most recent
modifications of form, due to a variety of often unknown causes, and are
therefore not so clearly connected with geographical changes as are the
natural groups of species termed genera; which may be considered to
represent the average and more permanent distribution of an organic type,
and to be more clearly influenced by the various known or inferred changes
in the organic and physical environment.
This systematic review of the distribution of families and genera, now
forms the last part of my book--Geographical Zoology; but it was nearly the
first written, and the copious materials collected for it enabled me to
determine the zoo-geographical divisions of the earth (regions and
sub-regions) to be adopted. I next drew up tables of the families and
genera found in each region and sub-region; and this afforded a basis for
the geographical treatment of the subject--Zoological Geography--the most
novel, and perhaps the most useful and generally interesting part of my
work. While this was in progress I found it necessary to make a careful
summary of the distribution of extinct Mammalia. This was a difficult task,
owing to the great uncertainty that prevails as to the affinities of many
of the fossils, and my want of practical acquaintance with Palæontology;
but having carefully examined and combined the works of the best authors, I
have given what I believe is the first connected sketch of the relation of
extinct Mammalia to the distribution of living groups, and have arrived at
some very interesting and suggestive results.
It will be observed that man is altogether omitted from the series of the
animal kingdom as here given, and some explanation of this omission may
perhaps be required. If the genus _Homo_ had been here treated like all
other genera, nothing more than the bare statement--"universally
distributed"--could have been given;--and this would inevitably have
provoked the criticism that it conveyed no information. If, on the other
hand, I had given an outline of the distribution of the _varieties_ or
_races_ of man, I should have departed from the plan of my work for no
sufficient reason. Anthropology is a science by itself; and it seems better
to omit it altogether from a zoological work, than to treat it in a
necessarily superficial manner.
The best method of illustrating a work of this kind was a matter requiring
much consideration. To have had a separate coloured or shaded map for each
family would have made the work too costly, as the terrestrial vertebrates
alone would have required more than three hundred maps. I had also doubts
about the value of this mode of illustration, as it seemed rather to
attract attention to details than to favour the development of general
views. I determined therefore to adopt a plan, suggested in conversation by
Professor Newton; and to have one general map, showing the regions and
sub-regions, which could be referred to by means of a series of numbers.
These references I give in the form of diagrammatic headings to each
family; and, when the map has become familiar, these will, I believe,
convey at a glance a body of important information.
Taking advantage of the recent extension of our knowledge of the depths of
the great oceans, I determined to give upon this map a summary of our
knowledge of the contours of the ocean bed, by means of tints of colour
increasing in intensity with the depth. Such a map, when it can be made
generally accurate, will be of the greatest service in forming an estimate
of the more probable changes of sea and land during the Tertiary period;
and it is on the effects of such changes that any satisfactory explanation
of the facts of distribution must to a great extent depend.
Other important factors in determining the actual distribution of animals
are, the zones of altitude above the sea level, and the strongly contrasted
character of the surface as regards vegetation--a primary condition for the
support of animal life. I therefore designed a series of six maps of the
regions, drawn on a uniform scale, on which the belts of altitude are shown
by contour-shading, while the forests, pastures, deserts, and perennial
snows, are exhibited by means of appropriate tints of colour.
These maps will, I trust, facilitate the study of geographical distribution
as a science, by showing, in some cases, an adequate cause in the nature of
the terrestrial surface for the actual distribution of certain groups of
animals. As it is hoped they will be constantly referred to, double folding
has been avoided, and they are consequently rather small; but Mr. Stanford,
and his able assistant in the map department, Mr. Bolton, have taken great
care in working out the details from the latest observations; and this,
combined with the clearness and the beauty of their execution, will I trust
render them both interesting and instructive.
In order to make the book more intelligible to those readers who have no
special knowledge of systematic zoology, and to whom most of the names with
which its pages are often crowded must necessarily be unmeaning, I give a
series of twenty plates, each one illustrating at once the physical aspect
and the special zoological character of some well-marked division of a
region. Great care has been taken to associate in the pictures, such
species only as do actually occur together in nature; so that each plate
represents a scene which is, at all events, not an impossible one. The
species figured all belong to groups which are either peculiar to, or very
characteristic of, the region whose zoology they illustrate; and it is
hoped that these pictures will of themselves serve to convey a notion of
the varied types of the higher animals in their true geographical
relations. The artist, Mr. J. B. Zwecker, to whose talent as a zoological
draughtsman and great knowledge both of animal and vegetable forms we are
indebted for this set of drawings, died a few weeks after he had put the
final touches to the proofs. He is known to many readers by his vigorous
illustrations of the works of Sir Samuel Baker, Livingstone, and many other
travellers,--but these, his last series of plates, were, at my special
request, executed with a care, delicacy, and artistic finish, which his
other designs seldom exhibit. It must, however, be remembered, that the
figures of animals here given are not intended to show specific or generic
characters for the information of the scientific zoologist, but merely to
give as accurate an idea as possible, of some of the more remarkable and
more restricted types of beast and bird, amid the characteristic scenery of
their native country;--and in carrying out this object there are probably
few artists who would have succeeded better than Mr. Zwecker has done.
The general arrangement of the separate parts of which the work is
composed, has been, to some extent, determined by the illustrations and
maps, which all more immediately belong to Part III. It was at first
intended to place this part last, but as this arrangement would have
brought all the illustrations into the second volume, its place was
changed,--perhaps in other respects for the better, as it naturally follows
Part II. Yet for persons not well acquainted with zoology, it will perhaps
be advisable to read the more important articles of Part IV. (and
especially the observations at the end of each order) after Part II., thus
making Part III. the conclusion of the work.
Part IV. is, in fact, a book of reference, in which the distribution of all
the families and most of the genera of the higher animals, is given in
systematic order. Part III. is treated somewhat more popularly; and,
although it is necessarily crowded with scientific names (without which the
inferences and conclusions would have nothing solid to rest on), these may
be omitted by the non-scientific reader, or merely noted as a certain
number or proportion of peculiar generic types. Many English equivalents to
family and generic names are, however, given; and, assisted by these, it is
believed that any reader capable of understanding Lyell's "Principles," or
Darwin's "Origin," will have no difficulty in following the main arguments
and appreciating the chief conclusions arrived at in the present work.
To those who are more interested in facts than in theories, the book will
serve as a kind of dictionary of the geography and affinities of animals.
By means of the copious Index, the native country, the systematic position,
and the numerical extent of every important and well established genus of
land-animal may be at once discovered;--information now scattered through
hundreds of volumes.
In the difficult matters of synonymy, and the orthography of generic names,
I have been guided rather by general utility than by any fixed rules. When
I have taken a whole family group from a modern author of repute, I have
generally followed his nomenclature throughout. In other cases, I use the
names which are to be found in a majority of modern authors, rather than
follow the strict rule of priority in adopting some newly discovered
appellation of early date. In orthography I have adopted all such modern
emendations as seem coming into general use, and which do not lead to
inconvenience; but where the alteration is such as to completely change the
pronunciation and appearance of a well-known word, I have not adopted it. I
have also thought it best to preserve the initial letter of well-known and
old-established names, for convenience of reference to the Indices of
established works. As an example I may refer to _Enicurus_,--a name which
has been in use nearly half a century, and which is to be found under the
letter _E_, in Jerdon's Birds of India, Blyth's Catalogue, Bonaparte's
Conspectus, and the Proceedings of the Zoological Society of London down to
1865. Classicists now write _Henicurus_ as the correct form; but this seems
to me one of those cases in which orthographical accuracy should give way
to priority, and still more to convenience.
In combining and arranging so much detail from such varied sources, many
errors and omissions must doubtless have occurred. Owing to my residence at
a distance from the scientific libraries of the metropolis, I was placed at
a great disadvantage; and I could hardly have completed the work at all,
had I not been permitted to have a large number of volumes at once, from
the library of the Zoological Society of London, and to keep them for
months together;--a privilege for which I return my best thanks to Mr.
Sclater the Secretary, and to the Council.
Should my book meet with the approval of working naturalists, I venture to
appeal to them, to assist me in rendering any future editions more
complete, by sending me (to the care of my publishers) notes of any
important omissions, or corrections of any misstatements of fact; as well
as copies of any of their papers or essays, and especially of any lists,
catalogues, and monographs, containing information on the classification or
distribution of living or extinct animals.
To the many friends who have given me information or assistance I beg to
tender my sincere thanks. Especially am I indebted to Professor Newton, who
not only read through much of my rough MSS., but was so good as to make
numerous corrections and critical notes. These were of great value to me,
as they often contained or suggested important additional matter, or
pointed out systematic and orthographical inaccuracies.
Professor Flower was so good as to read over my chapters on extinct
animals, and to point out several errors into which I had fallen.
Dr. Günther gave me much valuable information on the classification of
reptiles, marking on my lists the best established and most natural genera,
and referring me to reliable sources of information.
I am also greatly indebted to the following gentlemen for detailed
information on special subjects:--
To Sir Victor Brooke, for a MS. arrangement of the genera of Bovidæ, with
the details of their distribution:
To Mr. Dresser, for lists of the characteristic birds of Northern and
Arctic Europe:
To Dr. Hooker, for information on the colours and odours of New Zealand
plants:
To Mr. Kirby, for a list of the butterflies of Chili:
To Professor Mivart, for a classification of the Batrachia, and an early
proof of his article on "Apes" in the Encyclopedia Britannica:
To Mr. Salvin, for correcting my list of the birds of the Galapagos, and
for other assistance:
To Mr. Sharpe, for MS. lists of the birds of Madagascar and the Cape Verd
Islands:
To Canon Tristram, for a detailed arrangement of the difficult family of
the warblers,--Sylviidæ:
To Viscount Walden, for notes on the systematic arrangement of the
Pycnonotidæ and Timaliidæ, and for an early proof of his list of the birds
of the Philippine Islands.
I also have to thank many naturalists, both in this country and abroad, who
have sent me copies of their papers; and I trust they will continue to
favour me in the same manner.
An author may easily be mistaken in estimating his own work. I am well
aware that this first outline of a great subject is, in parts, very meagre
and sketchy; and, though perhaps overburthened with some kinds of detail,
yet leaves many points most inadequately treated. It is therefore with some
hesitation that I venture to express the hope that I have made some
approach to the standard of excellence I have aimed at;--which was, that my
book should bear a similar relation to the eleventh and twelfth chapters of
the "Origin of Species," as Mr. Darwin's "Animals and Plants under
Domestication" does to the first chapter of that work. Should it be judged
worthy of such a rank, my long, and often wearisome labours, will be well
repaid.
MARCH, 1876.
CONTENTS OF THE FIRST VOLUME.
PART I.
THE PRINCIPLES AND GENERAL PHENOMENA OF DISTRIBUTION.
CHAPTER I.
INTRODUCTORY.
CHAPTER II.
THE MEANS OF DISPERSAL AND THE MIGRATIONS OF ANIMALS.
Means of Dispersal of Mammalia (p. 10)--Climate as a Limit to the Range
of Mammals (p. 11)--Valleys and Rivers as Barriers to Mammals (p. 12)--
Arms of the Sea as Barriers to Mammals (p. 13)--Ice-floes and drift-wood
as aiding the Dispersal of Mammals (p. 14)--Means of Dispersal of Birds
(p. 15)--Dispersal of Birds by Winds (p. 16)--Barriers to the Dispersal
of Birds (p. 17)--The Phenomena of Migration (p. 18)--Migrations of Birds
(p. 19)--General remarks on Migration (p. 25)--Means of Dispersal of
Reptiles and Amphibia (p. 28)--Means of Dispersal of Fishes (p. 29)--
Means of Dispersal of Mollusca (p. 30)--Means of Dispersal of Insects and
the Barriers which limit their Range (p. 32) 10-34
CHAPTER III.
DISTRIBUTION AS AFFECTED BY THE CONDITIONS AND CHANGES OF THE EARTH'S
SURFACE.
Land and Water (p. 35)--Continental Areas (p. 36)--Recent Changes in the
Continental Areas (p. 38)--The Glacial Epoch as affecting the
Distribution of Animals (p. 40)--Changes of Vegetation as affecting the
Distribution of Animals (p. 43)--Organic Changes as affecting
Distribution (p. 44) 35-49
CHAPTER IV.
ON ZOOLOGICAL REGIONS.
Principles upon which Zoological Regions should be formed (p. 53)--Which
class of Animals is of most importance in determining Zoological Regions
(p. 56)--Various Zoological Regions proposed since 1857 (p. 58)--
Discussion of proposed Regions (p. 61)--Reasons for adopting the Six
Regions first proposed by Mr. Sclater (p. 63)--Objections to the system
of Circumpolar Zones (p. 67)--Does the Arctic Fauna characterise an
independent Region (p. 68)--Palæarctic Region (p. 71)--Ethiopian Region
(p. 73)--Oriental Region (p. 75)--Australian Region (p. 77)--Neotropical
Region (p. 78)--Nearctic Region (p. 79)--Observations on the series of
Sub-regions (p. 80) 50-82
CHAPTER V.
CLASSIFICATION AS AFFECTING THE STUDY OF GEOGRAPHICAL DISTRIBUTION.
Classification of the Mammalia (p. 85)--Classification of Birds (p. 92)--
Classification of Reptiles (p. 98)--Classification of Amphibia (p. 100)--
Classification of Fishes (p. 101)--Classification of Insects (p. 102)--
Classification of Mollusca (p. 104) 83-104
PART II.
ON THE DISTRIBUTION OF EXTINCT ANIMALS.
CHAPTER VI.
THE EXTINCT MAMMALIA OF THE OLD WORLD.
Historic and Post-pliocene Period (p. 110)--Pliocene Period (p. 112)--
General Conclusions as to the Pliocene and Post-pliocene Faunas of Europe
(p. 113)--Miocene Period (p. 114)--Extinct Animals of Greece (p. 115)--
Miocene Fauna of Central and Western Europe (p. 117)--Upper Miocene
Deposits of India (p. 121)--General Observations on the Miocene Faunas of
Europe and Asia (p. 123)--Eocene Period (p. 124)--General Considerations
on the Extinct Mammalian Fauna of Europe (p. 126) 107-128
CHAPTER VII.
EXTINCT MAMMALIA OF THE NEW WORLD.
North America--Post-pliocene Period (p. 129)--Remarks on the Post-
pliocene Fauna of North America (p. 130)--Tertiary Period (p. 132)--
Primates (p. 132)--Insectivora (p. 133)--Carnivora (p. 134)--Ungulata
(p. 135)--Proboscidea (p. 138)--Tillodontia (p. 139)--Rodentia (p. 140)--
General Relations of the Extinct Tertiary Mammalia of North America and
Europe (p. 140)--South America (p. 143)--Fauna of the Brazilian Caves
(p. 143)--Pliocene Period of Temperate South America (p. 146)--Pliocene
Mammalia of the Antilles (p. 148)--Eocene Fauna of South America (p. 148)
--General Remarks on the Extinct Mammalian Fauna of the Old and New
Worlds (p. 148)--The Birth-place and Migrations of some Mammalian
Families and Genera (p. 153) 129-156
CHAPTER VIII.
VARIOUS EXTINCT ANIMALS;--AND ON THE ANTIQUITY OF THE GENERA OF
INSECTS AND LAND-MOLLUSCA.
Extinct Mammalia of Australia (p. 157)--Mammalian Remains of the
Secondary Formations (p. 159)--Extinct Birds (p. 160)--Palæarctic Region
and North India (p. 161)--North America (p. 163)--South America,
Madagascar, New Zealand (p. 164)--Extinct Tertiary Reptiles (p. 165)--
Antiquity of the Genera of Insects (p. 166)--Antiquity of the Genera of
Land and Fresh-water Shells (p. 168) 157-170
PART III.
ZOOLOGICAL GEOGRAPHY: A REVIEW OF THE CHIEF FORMS OF LIFE
IN THE SEVERAL REGIONS AND SUB-REGIONS, WITH THE INDICATIONS
THEY AFFORD OF GEOGRAPHICAL MUTATIONS.