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* * * * *
FRONTISPIECE
[Illustration]
ISLAND LIFE
OR
THE PHENOMENA AND CAUSES OF
INSULAR FAUNAS AND FLORAS
INCLUDING A REVISION AND ATTEMPTED SOLUTION OF
THE PROBLEM OF
GEOLOGICAL CLIMATES
BY
ALFRED RUSSEL WALLACE
AUTHOR OF "THE MALAY ARCHIPELAGO," "THE GEOGRAPHICAL DISTRIBUTION OF
ANIMALS,"
"DARWINISM," ETC.
_SECOND AND REVISED EDITION_
London
MACMILLAN AND CO.
AND NEW YORK
1895
_The Right of Translation and Reproduction is Reserved_
* * * * *
RICHARD CLAY AND SONS, LIMITED,
LONDON AND BUNGAY.
_First Edition printed 1880 (Med. 8vo).
Second Edition 1892 (Extra cr. 8vo). Reprinted 1895._
* * * * *
TO
SIR JOSEPH DALTON HOOKER,
K.C.S.I., C.B., F.R.S., ETC., ETC.
WHO, MORE THAN ANY OTHER WRITER,
HAS ADVANCED OUR KNOWLEDGE OF THE GEOGRAPHICAL
DISTRIBUTION OF PLANTS, AND ESPECIALLY
OF INSULAR FLORAS,
I Dedicate this Volume;
ON A KINDRED SUBJECT,
AS A TOKEN OF ADMIRATION AND REGARD.
* * * * *
{vi}
CORRECTIONS IN PRESENT ISSUE.
The first issue of this Edition being exhausted, the opportunity is taken
of making a few corrections, the most important of which are here stated:--
_Page_ 163. Statement modified as to supposed glaciation of South Africa.
_Pages_ 174 and 338. Many geologists now hold that there was no great
submergence during the glacial epoch. The passages referring to it have
therefore been re-written.
_Page_ 182. Colonel Fielden's explanation of the occurrence of large trees
on shores and in recent drift in high latitudes, is now added.
" 272. A species of Carex peculiar to Bermuda is now given.
" 356. _Geomalacus maculosus_, as a peculiar British species, is now
omitted.
Verbal alterations have also been made at pages 41, 105, 356, and 360.
* * * * *
{vii}
PREFACE TO THE SECOND EDITION
This edition has been carefully revised throughout, and owing to the great
increase to our knowledge of the Natural History of some of the islands
during the last twelve years considerable additions or alterations have
been required. The more important of these changes are the following:--
Chapter VII. The account of the migrations of animals and plants during and
since the Glacial Epoch, has been modified to accord with newer
information.
Chapters VIII and IX. The discussion of the causes of Glacial Epochs and
Mild Arctic Climates has been somewhat modified in view of the late Dr.
Croll's remarks, and the argument rendered clearer.
Chapter XIII. Several additions to the Fauna of the Galapagos have been
noted.
Chapter XV. Considerable additions have been made to this chapter embodying
the recent discoveries of birds and insects new to the Sandwich Islands,
while a much fuller account has been given of its highly peculiar and very
interesting flora.
Chapter XVI. Important additions and corrections have been made in the
lists of peculiar British animals and plants embodying the most recent
information.
Chapter XVII. Very large additions have been made to the mammalia and birds
of Borneo, and full lists of the peculiar species are given. {viii}
Chapter XVIII. A more accurate account is given of the birds of Japan.
Chapter XIX. The recent additions to the mammals and birds of Madagascar
are embodied in this chapter, and a fuller sketch is given of the rich and
peculiar flora of the island.
Chapter XXI. and XXII. Some important additions have been made to these
chapters owing to more accurate information as to the depth of the sea
around New Zealand, and to the discovery of abundant remains of fossil
plants of the tertiary and cretaceous periods both in New Zealand and
Australia.
In the body of the work I have in each case acknowledged the valuable
information given me by naturalists of eminence in their various
departments, and I return my best thanks to all who have so kindly assisted
me. I am however indebted 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 important of these doctrines are those
which establish and define--(1) The former wide extension of all groups now
discontinuous, as being a necessary result of "evolution"; (2) The
permanence of the great features of the distribution of land and water on
the earth's surface; and, (3) The nature and frequency of climatal changes
throughout geological time.
I have now only to thank the many friends and correspondents who have given
me information or advice. Besides those whose assistance is acknowledged in
the body of the work, I am especially indebted to four gentlemen who have
been kind enough to read over the proofs of chapters dealing with questions
on which they have special knowledge, giving me the benefit of valuable
emendations and suggestions. Mr. Edward R. Alston has looked over those
parts of the earlier chapters which relate to the mammals of Europe and the
North Temperate zone; Mr. S. B. J. Skertchley, of the Geological Survey,
has read the chapters which discuss the glacial epoch and other geological
questions; Professor A. Newton has looked over the passages referring to
the birds of the Madagascar group; while Sir Joseph D. Hooker has given me
the invaluable benefit of his remarks on my two chapters dealing with the
New Zealand flora.
CROYDON, _August, 1880_.
* * * * *
{xi}
CONTENTS
PART I
THE DISPERSAL OF ORGANISMS; ITS PHENOMENA, LAWS, AND CAUSES
CHAPTER I
INTRODUCTORY
Remarkable Contrasts in the Distribution of Animals--Britain and
Japan--Australia and New Zealand--Bali and Lombok--Florida and Bahama
Islands--Brazil and Africa--Borneo, Madagascar, and Celebes--Problems in
Distribution to be found in every Country--Can be Solved only by the
Combination of many distinct lines of inquiry, Biological and
Physical--Islands offer the best Subjects for the Study of
Distribution--Outline of the Subjects to be discussed in the Present
Volume.
_Pages_ 3-11
CHAPTER II
THE ELEMENTARY FACTS OF DISTRIBUTION.
Importance of Locality as an Essential Character of Species--Areas of
Distribution--Extent and Limitations of Specific Areas--Specific Range of
Birds--Generic Areas--Separate and Overlapping Areas--The Species of Tits
as illustrating Areas of Distribution--The Distribution of the Species of
Jays--Discontinuous Generic Areas--Peculiarities of Generic and Family
Distribution--General Features of Overlapping and Discontinuous
Areas--Restricted Areas of Families--The Distribution of Orders
_Pages_ 12-30
{xii}
CHAPTER III
CLASSIFICATION OF THE FACTS OF DISTRIBUTION.--ZOOLOGICAL REGIONS
The Geographical Divisions of the Globe do not Correspond to Zoological
Divisions--The Range of British Mammals as Indicating a Zoological
Region--Range of East Asian and North African Mammals--The Range of British
Birds--Range of East Asian Birds--The Limits of the Palaearctic
Region--Characteristic Features of the Palaearctic Region--Definition and
Characteristic Groups of the Ethiopian Region--Of the Oriental Region--Of
the Australian Region--Of the Nearctic Region--Of the Neotropical
Region--Comparison of Zoological Regions with the Geographical Divisions of
the Globe
_Pages_ 31-54
CHAPTER IV
EVOLUTION AS THE KEY TO DISTRIBUTION
Importance of the Doctrine of Evolution--The Origin of New
Species--Variation in Animals--The amount of Variation in North American
Birds--How New Species Arise from a Variable Species--Definition and Origin
of Genera--Cause of the Extinction of Species--The Rise and Decay of
Species and Genera--Discontinuous Specific Areas, why Rare--Discontinuity
of the Area of Parus Palustris--Discontinuity of Emberiza Schoeniclus--The
European and Japanese Jays--Supposed examples of Discontinuity among North
American Birds--Distribution and Antiquity of Families--Discontinuity a
Proof of Antiquity--Concluding remarks
_Pages_ 55-71
CHAPTER V
THE POWERS OF DISPERSAL OF ANIMALS AND PLANTS
Statement of the General Question of Dispersal--The Ocean as a Barrier to
the Dispersal of Mammals--The Dispersal of Birds--The Dispersal of
Reptiles--The Dispersal of Insects--The Dispersal of Land Mollusca--Great
Antiquity of Land-shells--Causes Favouring the Abundance of
Land-shells--The Dispersal of Plants--Special Adaptability of Seeds for
Dispersal--Birds as Agents in the Dispersal of Seeds--Ocean Currents as
Agents in Plant Dispersal--Dispersal along Mountain Chains--Antiquity of
Plants as Effecting their Distribution
_Pages_ 72-82
CHAPTER VI
GEOGRAPHICAL AND GEOLOGICAL CHANGES: THE PERMANENCE OF CONTINENTS
Changes of Land and Sea, their Nature and Extent--Shore-Deposits and
Stratified Rocks--The Movements of Continents--Supposed Oceanic {xiii}
Formations; the Origin of Chalk--Fresh-water and Shore-deposits as Proving
the Permanence of Continents--Oceanic Islands as Indications of the
Permanence of Continents and Oceans--General Stability of Continents with
Constant Change of Form--Effect of Continental Changes on the Distribution
of Animals--Changed Distribution Proved by the Extinct Animals of Different
Epochs--Summary of Evidence for the General Permanence of Continents and
Oceans.
_Pages_ 83-105
CHAPTER VII
CHANGES OF CLIMATE WHICH HAVE INFLUENCED THE DISPERSAL OF ORGANISMS: THE
GLACIAL EPOCH
Proofs of the Recent Occurrence of a Glacial Epoch--Moraines--Travelled
Blocks--Glacial Deposits of Scotland: the "Till"--Inferences from the
Glacial Phenomena of Scotland--Glacial Phenomena of North America--Effects
of the Glacial Epoch on Animal Life--Warm and Cold
Periods--Palaeontological Evidence of Alternate Cold and Warm
Periods--Evidence of Interglacial Warm Periods on the Continent and in
North America--Migrations and Extinctions of Organisms Caused by the
Glacial Epoch
_Pages_ 106-124
CHAPTER VIII
THE CAUSES OF GLACIAL EPOCHS
Various Suggested Causes--Astronomical Causes of Changes of
Climate--Difference of Temperature Caused by Varying Distances of the
Sun--Properties of Air and Water, Snow and Ice, in Relation to
Climate--Effects of Snow on Climate--High Land and Great Moisture Essential
to the Initiation of a Glacial Epoch--Perpetual Snow nowhere Exists on
Lowlands--Conditions Determining the Presence or Absence of Perpetual
Snow--Efficiency of Astronomical causes in Producing Glaciation--Action of
Meteorological Causes in Intensifying Glaciation--Summary of Causes of
Glaciation--Effect of Clouds and Fog in Cutting off the Sun's Heat--South
Temperate America as Illustrating the Influence of Astronomical Causes on
Climate--Geographical Changes how far a Cause of Glaciation--Land Acting as
a Barrier to Ocean-currents--The Theory of Interglacial Periods and their
Probable Character--Probable Effect of Winter in _aphelion_ on the Climate
of Britain--The Essential Principle of Climatal Change Restated--Probable
Date of the Last Glacial Epoch--Changes of the Sea-level Dependent on
Glaciation--The Planet Mars as Bearing on the Theory of Excentricity as a
Cause of Glacial Epochs
_Pages_ 125-168
{xiv}
CHAPTER IX
ANCIENT GLACIAL EPOCHS, AND MILD CLIMATES IN THE ARCTIC REGIONS
Mr. Croll's Views on Ancient Glacial Epochs--Effects of Denudation in
Destroying the Evidence of Remote Glacial Epochs--Rise of Sea-level
Connected with Glacial Epochs a Cause of Further Denudation--What Evidence
of Early Glacial Epochs may be Expected--Evidences of Ice-action During the
Tertiary Period--The Weight of the Negative Evidence--Temperate Climates in
the Arctic Regions--The Miocene Arctic Flora--Mild Arctic Climates of the
Cretaceous Period--Stratigraphical Evidence of Long-continued Mild Arctic
Conditions--The Causes of Mild Arctic Climates--Geographical Conditions
Favouring Mild Northern Climates in Tertiary Times--The Indian Ocean as a
Source of Heat in Tertiary Times--Condition of North America During the
Tertiary Period--Effect of High Excentricity on Warm Polar
Climates--Evidences as to Climate in the Secondary and Palaeozoic
Epochs--Warm Arctic Climates in Early Secondary and Palaeozoic
Times--Conclusions as to the Climates of Secondary and Tertiary
Periods--General View of Geological Climates as Dependent on the Physical
Features of the Earth's Surface--Estimate of the Comparative Effects of
Geographical and Physical Causes in Producing Changes of Climate.
_Pages_ 169-209
CHAPTER X
THE EARTH'S AGE, AND THE RATE OF DEVELOPMENT OF ANIMALS AND PLANTS
Various Estimates of Geological Time--Denudation and Deposition of Strata
as a Measure of Time--How to Estimate the Thickness of the Sedimentary
Rocks--How to Estimate the Average Rate of Deposition of the Sedimentary
Rocks--The Rate of Geological Change Probably Greater in very Remote
Times--Value of the Preceding Estimate of Geological Time--Organic
Modification Dependent on Change of Conditions--Geographical Mutations as a
Motive Power in Bringing about Organic Changes--Climatal Revolutions as an
Agent in Producing Organic Changes--Present Condition of the Earth One of
Exceptional Stability as Regards Climate--Date of Last Glacial Epoch and
its Bearing on the Measurement of Geological Time--Concluding Remarks
_Pages_ 210-237
{xv}
PART II
INSULAR FAUNAS AND FLORAS