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ISLAND LIFE:

OR,

THE PHENOMENA AND CAUSES OF

tusular Saunas and Sloras,

INCLUDING A REVISION AND ATTEMPTED SOLUTION Or THE
PROBLEM OF

Geological Cltnates.

BY
ALFRED RUSSEL WALLACE,
AUTHOR OF “‘ THE MALAY ARCHIPELAGO,” ‘‘ TROPICAL NATURE,” ‘‘ THE GEOGRAPHICAL

DISTRIBUTION OF ANIMALS,” &C,

Londo :
MACIELLAN AND CoO
1880.

The Right of Translation and Reproduction is Reserved,

LONDON:
R. CLAY, SONS, AND TAYLOR,
BREAD STREET HILL.

SIR JOSEPH DALTON HOOKER,

He CO Shle wOubiy, HeRy Sis Ol. 5 OCC,
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.

me
i Bee
iN? ek

PREFACE.

THE present volume is the result of four years’ additional
thought and research on the lines laid down in my Geographical
Mstribution 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 1s 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 generally that, so far as I am able to

WaT ot PREFACE.

judge, a real advance has here been made in the mode of treating
problems in Geographical Distribution, owing to the firm estab-
lishment of a number of preliminary doctrines or “ principles,”
which in many cases lead to a far simpler and yet more com-
plete 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 correspond-
ents 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 ques-
tions 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 in-
valuable benefit of his remarks on my two chapters dealing
with the New Zealand flora.

Croypon, August, 1880.

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 ef Jays—Discontinuous generic
areas—Peculiarities of generic and family distribution—General features of over-
lapping and discontinuous areas—Restricted areas of Families—The distribution
of Orders ‘ 5 : . Pages 12—30

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 Paleearctic Region—Characteristic features of the
Palearctic 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 Geo-
graphical Divisions of the Globe . : : ; : : . Pages 31—53

x CONTENTS.

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—Disconti-
nuity of Emberiza schceniclus—The European and Japanese Jays—Supposed ex-
amples of discontinuity among North American Birds—Distribution and antiquity
of Families—Discontinuity a proof of antiyuity—Concluding Remarks

Pages 54—69

CHAPTER V.
THE POWERS OF DISPERSAL OF ANIMALS AND PLANTS.

Statement of the general question of Dispersal—The Ocean as a barrier to the dis-
persal 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 affecting their distribution . . Pages T0—80

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 formations; the Origin
of Chalk—Fresh-water and Shore-deposits as proving the permanence of Conti-
nents—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 81—102

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—Paleontological 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 : ; 3 : . Pages 103-—120

CONTENTS. XI

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—Per-
petual snow nowhere exists on lowlands—Conditions determining the presence or
absence of perpetual Snow—Efficiency of Astronomical causes in producing Glaci-
ation—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 121—162

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—EHvidences 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 Cretacious Period—Strati-
graphical evidence of long-continued mild Arctic conditions—The causes of mild
Arctic climates—Geographical conditions favouring mild northern climates in Ter-
tiary times—-The Indian Ocean as a source of heat in Tertiary times—Condi-
tion of North America during the Tertiary Period—Effect of high excentricity on
warm Polar climates—Evidences as to climate in the Secondary and Paleozoic
Epochs—Warm Arctic climates in early Secondary and Paleozoic times—Con-
clusions 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 : ; ; : ; A . Pages 163-—202

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 Harth one of exceptional stability as regards
Climate—Date- of last Glacial Epoch and its bearing on the Measurement of
Geological time—Concluding Remarks “i e : : . Pages 203—229

xii CONTENTS.

PAR Te

INSULAR FAUNAS AND FLORAS.

CHAPTER XI.
THE CLASSIFICATION OF ISLANDS.

Importance of Islands in the study of the Distribution of Organisms—Classification
of Islands with reference to Distribution—Continental Islands—Oceanic Islands
Pages 233—237

CHAPTER XII.

OCEANIC ISLANDS :—THE AZORES AND BERMUDA,

THE AZORES, OR WESTERN ISLANDS.

Position and physical features—Chief Zoological features of the Azores—Birds—
Origin of the Azorean bird-fauna—Insects of the Azores—Land-shells of the
Azores—The fiora of the Azores—The dispersal of seeds—Birds as seed-carriers
—Facilities for dispersal of Azorean plants—Important deduction from the
peculiarities of the Azorean fauna and flora. : P : . Pages 238—253

BERMUDA.

Position and physical features—The Red Clay of Bermuda—Zoology of Bermuda—
Birds of Bermuda—Comparison of the bird-faunas of Bermuda and the Azores—
Insects of Bermuda—Land Mollusea—Flora of Bermuda—Concluding remarks on
the Azores and Bermuda : : : : : ; . Pages 253—264

CHAPTER XIII
THE GALAPAGOS ISLANDS.

Position and physical features—Absence ‘of indigenous Mammalha and Amphibia—
Reptiles—Birds—Insects and Land-shells—The Keeling Islands as illustrating the
manner in which Oceanic Islands are peopled— Flora of the Galapagos—Origin of
the Flora of the Galapagos—Concluding Remarks . : . Pages 265—280

CONTENTS. xiii

CHAPTER XIV.
ST. HELENA.

Position and physical features of St. Helena—Change effected by European occupa-
tion—The Insects of St. Helena—Coleoptera—Peculiarities and origin of the
Coleoptera of St. Helena—Land-shells of St. Helena—Absence of Fresh-water
Organisms—Native vegetation of St. Helena—The relations of the St. Helena
Composite—Concluding remarks on St. Helena . : ; . Pages 281—297

CHAPTER XV.
: THE SANDWICH ISLANDS.

Position and Physical features—Zoology of the Sandwich Islands—Birds—Reptiles—
Land-shells—Insects— Vegetation of the Sandwich Islands—Peculiar features of
the Hawaiian Flora—Antiquity of the Hawaiian Fauna and Flora—Concluding
observations on the Fauna and Flora of the Sandwich Islands—General Remarks
on Oceanic Islands ‘ . : : ; : : A . Pages 298—311

CHAPTER XVI.
CONTINENTAL ISLANDS OF RECENT ORIGIN: GREAT BRITAIN.

Characteristic Features of Recent Continental Islands—Recent Physical Changes of
the British Isles—Proofs of Former Elevation—Submerged Forests—Buried River
Channels—Time of Last Union with the Continent—Why Britain is poor in
Species—Peculiar British Birds—-Fresh-water Fishes—Cause of Great Speciality
in Fishes—Peculiar British Insects—Lepidoptera confined to the British Isles—-
Peculiarities of the Isle of Man Lepidoptera—Coleoptera confined to the British
Isles—Trichoptera peculiar to the British Isles—Land and Fresh-water Shells—
Peculiarities of the British Flora --Peculiarities of the Irish Flora—Peculiar
British Mosses and Hepatice—Concluding Remarks on the Peculiarities of the
British Fauna and Flora é . : : : ‘ , . Pages 312—347

CHAPTER XVII.
BORNEO AND JAVA.

Position and physical features of Borneo—Zoological features of Borneo: Mammalia
—Birds—The affinities of the Bornean fauna—Java, its position and physical fea-
tures—General character of the fauna of Java—Differences between the fauna of
Java and that of the other Malay Islands—Special relations of the Javan fauna
to that of the Asiatic continent—Past geographical changes of Java and Borneo
—The Philippine Islands—Concluding Remarks on the Malay Islands

Pages 348—362

CHAPTER XVIII.
JAPAN AND FORMOSA.

Japan, its position and Physical features—Zoological features of J apan—Mammalia
—Birds—Birds common to Great Britain and Japan—Birds peculiar to Japan
—Japan Birds recurring in distant areas—Formosa—Physical features of For-
mosa—Animal life of Formosa—Mammalia-—Land_ birds peculiar to Formosa—
Formosan birds recurring in India or Malaya—Comparison of faunas of Hainan,
Formosa, and Japan—General Remarks on Recent Continental Islands

Pages 863—3882

XIV CONTENTS.

CHAPTER XIX.
ANCIENT CONTINENTAL ISLANDS: THE MADAGASCAR GROUP.

Remarks on Ancient Continental Islands—Physical features of Madagascar—Biolo-
gical features of Madagascar—Mammalia—Reptiles—Relation of Madagascar to
Africa—Early history of Africa and Madagascar—Anomalies of distribution and
how to explain them—The birds of Madagascar as indicating a supposed Lemu-
rian Continent— Submerged Islands between Madagascar and India—Concluding
remarks on “ Lemuria’””—The Mascarene Islands—The Comoro Islands—The Sey-
chelies Archipelago—Birds of the Seychelles—Reptiles and Amphibia—Fresh-water
Fishes—Land Shells—Mauritius, Bourbon, and Rodriguez--Birds—Extinct Birds
and their probable origin—Reptiles—Flora of Madagascar and the Mascarene
Islands—Curious relations of Mascarene plants—Endemic genera of Mauritius and
Seychelles—Fragmentary character of the Mascarene Flora—Flora of Madagascar
allied to that of South Africa—Preponderance of Ferns in the Mascarene Flora
—Concluding Remarks on the Madagascar Group ; ‘ . Pages 383—420

CHAPTER XX.
ANOMALOUS ISLANDS: CELEBES.

Anomalous relations of Celebes—Physical features of the Island—Zoological cha-
racter of the Islands around Celebes—The Malayan and Australian Banks—Zoo-
logy of Celebes: Mammalia—Probable derivation of the Mammals of Celebes—
Birds of Celebes—Bird-types peculiar to Celebes—Celebes not strictly a Conti-
nental Island—Peculiarities of the Insects of Celebes—Himalayan types of Birds
and Butterflies in Celebes—Peculiarities of shape and colour of Celebesian Butter-
flies—Concluding Remarks— Appendix on the Birds of Celebes. Pages 421—441

CHAPTER XXI.
ANOMALOUS ISLANDS: NEW ZEALAND.

Position and Physical features of New Zealand—Zoological character of New Zea-
land—Mammalia—Wingless birds living and extinct—Recent existence of the
Moa—Past changes of New Zealand deduced from its wingless Birds—Birds and
Reptiles of New Zealand—Conclusions from the peculiarities of the New Zealand
Fauna . ; : : : : : ; 5 : . . Pages 442—466

CHAPTER XXII.
THE FLORA OF NEW ZEALAND: ITS AFFINITIES AND PROBABLE ORIGIN.

Relations of the New Zealand Flora to that of Australia—General features of the
Australian Flora—The Floras of South-eastern and South-western Australia—
Geological explanation of the differences of these two floras—The origin of the
Australian element in the New Zealand Flora—Tropical character of the New
Zealand Flora explained—Species common to New Zealand and Australia mostly
temperate forms—Why easily dispersed plants have often restricted ranges—
Summary and Conclusion on the New Zealand Flora . : . Pages 457—476

CONTENTS. KY

CHAPTER XXIII.
ON THE ARCTIC ELEMENT IN SOUTH TEMPERATE FLORAS.

European species and genera of plants in the Southern Hemisphere—Aggressive power
of the Scandinavian flora—Means by which plants have migrated from north to
south—Newly moved soil as affording temporary stations to migrating plants—
Elevation and depression of the snow-line as aiding the migration of plants—
Changes of climate favourable to migration—The migration from north to south
has been long going on—Geological changes as aiding migration—Proofs of mi-
gration by way of the Andes—Proofs of migration by way of the Himalayas and
Southern Asia—Proofs of migration by way of the African highlands—Supposed
connection of South Africa and Australia—The endemic genera of plants in New
Zealand— The absence of Southern types from the Northern Hemisphere —
Concluding remarks on the New Zealand and South Temperate floras

Pages 477—498

CHAPTER XXIV.
' SUMMARY AND CONCLUSION.

The present volume is the development and application of a theory--Statement of
the Biological and Physical causes of dispersal—Investigation of the facts of dis-
persal—of the means of dispersal—of geographical changes affecting dispersal—
of climatal changes affecting dispersal—The Glacial Epoch and its causes—Alleged
ancient glacial epochs—Warm polar climates and their causes—Conclusions as to
geological climates—How far different from those of Mr. Croll—Supposed limita-
tions of geological time —Time amply sufficient both for geological and biological
development—Insular faunas and floras—The North Atlantic Islands—The Gala-
pagos—St. Helena and the Sandwich Islands—Great Britain asa recent Conti-
nental Island—Borneo and Java—Japan and Formosa—Madagascar as an ancient
Continental Island—Celebes and New Zealand as anomalous Islands—The Flora
of New Zealand and its origm—The European element in the South Temperate
Floras—Concluding Remarks . . . : a Tes . Pages 499---512

. DIAGRAM OF EXCENTRICITY AND PRECESSION .

. OUTLINE Map oF THE AZORES ...

. Map oF BERMUDA AND THE AMERICAN CoAST .... .

. Map OF THE GALAPAGOS AND ADJACENT Coasts oF SouTH AMERICA

. Map oF THE SouTH ATLANTIC, SHOWING POSITION OF ST. HELENA

. Mar oF THE SANDWICH ISLANDS ...... .

MAPS AND ILLUSTRATIONS.

. Map sHOWING THE DISTRIBUTION OF THE TRUE JAyS . . Frontispiece.
. MAP SHOWING THE ZOOLOGICAL REGIONS. Skis a. 6 a] Se ean tenes
. MAP SHOWING THE DISTRIBUTION oF PArus PALUSTRIS . . . To face
A GLACIER WITH Morarnes (From Sir C. Lyell’s Principles of Geology) .
Map oF THE ANCIENT RHONE GLAciER (From Sir C. Lyell’s Antiquity
Of DEG) tae ie as aaa) ee & 4 ep ie | -6y le | Gane s aan

DIAGRAM SHOWING THE EFFECTS OF EXCENTRICITY AND PRECESSION ON
CEIMATR foie ees

° . . . . . . ° . . .

. MAP SHOWING THE EXTENT OF THE NORTH AND SoutH Poxar Ice.

DIAGRAM SHOWING CHANGES OF EXCENTRICITY DURING THREE MILLION
WED HCL Ae a NE

SECTION OF BERMUDA AND ADJACENT SEA-BOTTOM . . .

Map -or THN GALAPAGOS “S95 J os. . 6 oe 4%.

e e ° e . . e .

Map oF THE NortTH PACIFIC, WITH ITS SUBMERGED BANKS

. MAP SHOWING THE BANK CONNECTING BRITAIN WITH THE CONTINENT .

PAGE

31
64

105

107

123
124

133

165
239
254
250
267
267
282
299
300

314

MAPS AND ILLUSTRATIONS. XVil

19. Mar oF BorNEO AND JAVA, SHOWING THE GREAT SUBMARINE BANK ie.

SEMOOUTE WASTER ASUA' our o's) (lbp ee 5 Ga nie! oo ee oe ey, 4D
BOSNIA Om JAPAN AND FORMOSA 5 2.96 of ss 3 © 6 6 « ss 6 & + 864
21. Puysicat SxetcH Map or Mapacascar (From Wature). . . . . . . 885
22. Mar oF MapAGAScAR GROUP, SHOWING DEepTHs oF SEA. .... . . 887
23. Map OF THE INDIAN OCEAN. ...... - Sha uae eee se ae OOO
24. Map oF CELEBES AND THE SURROUNDING ISLANDS... .. .. + « 428

25. Map sHOWING DEPTHS OF SEA AROUND AUSTRALIA AND New ZEALAND. 443

296. MAP SHOWING THE PROBABLE CONDITION OF AUSTRALIA DURING
THEAORETACHOUS HPOCH. «. 6 4 a) ste «ee ete ce [5,7 AGa

Naot

ISLAND LIFE.

PART, «1.

THE DISPERSAL OF ORGANISMS;

ITS PHENOMENA, LAWS, AND CAUSES.

CHAPTER I.

INTRODUCTORY.

Remarkable Contrasts in 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 distribu-
tion—Outline of the subjects to be discussed in the present volume.

WHEN an Englishman travels by the nearest sea-route from
Great Britain to Northern Japan he passes by countries very
unlike his own, both in aspect and natural productions. The
sunny isles of the Mediterranean, the sands and date-palms of
Egypt, the arid rocks of Aden, the cocoa groves of Ceylon, the
tiger-haunted jungles of Malacca and Singapore, the fertile
plains and volcanic peaks of Luzon, the forest-clad mountains
of Formosa, and the bare hills of China, pass successively in
review ; till after a circuitous voyage of thirteen thousand miles
he finds himself at Hakodadi in Japan. He is now separated
from his starting-point by the whole width of Europe and
Northern Asia, by an almost endless succession of plains and
mountains, arid deserts or icy plateaux, yet when he visits the
interior of the country he sees so many familiar natural objects
that he can hardly help fancying he is close to his home. He
finds the woods and fields tenanted by tits, hedge-sparrows,
wrens, wagtails, larks, redbreasts, thrushes, buntings, and house-
sparrows, some absolutely identical with our own feathered
friends, others so closely resembling them that it requires a
B2

4 ISLAND LIFE. [PART E

practised ornithologist to tell the difference. If he is fond of
insects he notices many butterflies and a host of beetles which,
though on close examination they are found to be distinct from
ours, are yet of the same general aspect, and seem just what
might be expected in any part of Europe. There are also of
course many birds and insects which are quite new and peculiar,
but these are by no means so numerous or conspicuous as to
remove the general impression of a wonderful resemblance
between the productions of such remote islands as Britain and
Yesso.

Now let an inhabitant of Australia sail to New Zealand, a
distance of less than thirteen hundred miles, and he will find
himself in a country whose productions are totally unlike those
of his own. Kangaroos and wombats there are none; the birds
are almost all entirely new, insects are very scarce and quite
unlike the handsome or strange Australian forms, while even
the vegetation is all changed, and no gum-tree, or wattle, or
erass-tree meets the traveller’s eye.

But there are some more striking cases even than this, of the
diversity of the productions of countries not far apart. In the
Malay Archipelago there are two islands, named Bali and
Lombok, each about as large as Corsica, and separated by a
strait only fifteen miles wide at its narrowest part. Yet these
islands differ far more from each other in their birds and quad-
rupeds than do England and Japan. ‘The birds of the one are
extremely wnlike those of the other, the difference being such
as to strike even the most ordinary observer. Bali has red and
green woodpeckers, barbets, weaver-birds, and black-and-white
magpie-robins, none of which are found in Lombok, where,
however, we find screaming cockatoos and friar-birds, and the
strange mound-building megapodes, which are all equally un-
known in Bali. Many of the kingfishers, crow-shrikes, and
other birds, though of the same general form, are of very distinct
species ;and though a considerable number of birds are the same
in both islands the difference is none the less remarkable—as
proving that mere distance is one of the least important of the
causes which have determined the likeness or unlikeness in the

animals of different countries. DSI ‘

CHAP. I.] INTRODUCTORY. 5

In the western hemisphere we find equally striking examples.
The Eastern United States possess very peculiar and interesting
plants and animals, the vegetation becoming more luxuriant as
we go south but not altering in essential character, so that when
we reach the southern extremity of Florida we still find our-
selves in the midst of oaks, sumachs, magnolias, vines, and
other characteristic forms of the temperate flora; while the
birds, insects, and land-shells are almost identical with those
found further north. But if we now cross over the narrow
strait, about fifty miles wide, which separates Florida from the
Bahama Islands, we find ourselves in a totally different country,
surrounded by a vegetation which is essentially tropical and
generally identical with that of Cuba. The change is most
striking, because there is no difference of climate, of soil,
or apparently of position, to account for it; and when we
find that the birds, the insects, and especially the land-
shells are almost all West Indian, while the North American
types of plants and animals have almost all completely
disappeared, we shall be convinced that such differences and
resemblances cannot be due to existing conditions, but must
depend upon laws and causes to which mere proximity of
position offers no clue.

Hardly less uncertain and irregular are the effects of climate.
Hot countries usually differ widely from cold ones in all their
organic forms; but the difference is by no means constant, nor
does it bear any proportion to difference of temperature.
Between frigid Canada and sub-tropical Florida there are less
marked differences in the animal productions than between
Florida and Cuba or Yucatan, so much more alike in climate and
so much nearer together. So the differences between the birds
and quadrupeds of temperate Tasmania and tropical North
Australia are slight and unimportant as compared with the
enormous differences we find when we pass from the latter
country to equally tropical Java. If we compare corresponding
portions of different continents, we find no indication that the
almost perfect similarity of climate and general conditions has
any tendency to produce similarity in the animal world. The
equatorial parts of Brazil and of the West Coast of Africa are

6 ISLAND LIFE. [PART I.

almost identical in climate and in luxuriance of vegetation, but
their animal life is totally diverse. In the former we have
tapirs, sloths, and prehensile-tailed monkeys; in the latter
elephants, antelopes, and man-like apes; while among birds,
the toucans, chatterers, and humming-birds of Brazil are re-
placed by the plantain-eaters, bee-eaters, and sun-birds of Africa,
Parts of South-temperate America, South Africa, and South
Australia, correspond closely in climate; yet the birds and
quadrupeds of these three districts are as completely unlike
each other as those of any parts of the world that can be
named.

If we visit the great islands of the globe, we find that they
present similar anomalies in their animal productions, for
while some exactly resemble the nearest continents others are
widely different. Thus the quadrupeds birds and insects of
Borneo correspond very closely to those of the Asiatic continent,
while those of Madagascar are extremely unlike African forms,
although the distance from the continent is less in the latter
case than in the former. And if we compare the three great
islands Sumatra, Borneo, and Celebes—lying as it were side by
side in the same ocean—we find that the two former, although
furthest apart, have almost identical productions, while the two
latter, though closer together, are more unlike than Britain and
Japan situated in different oceans and separated by the largest
of the great continents.

These examples will illustrate the kind of questions it is the
object of the present work to deal with. Every continent,
every country, and every island on the globe, offer similar
problems of greater or less complexity and interest, and the
time has now arrived when their solution can be attempted with
some prospect of success. Many years study of this class of
subjects has convinced me that there is no short and easy
method of dealing with them ; because they are, in their very
nature, the visible outcome and residual product of the whole
past history of the earth. If we take the organic productions
of a small island, or of any very limited tract of country such
as a moderate-sized country parish, we have, in their relations
and affinities—in the fact that they are there and others are

CHAP. I.] INTRODUCTORY. 7

not there, a problem which involves all the migrations of these
species and their ancestral forms—all the vicissitudes of climate
and all the changes of sea and land which have affected those
migrations—the whole series of actions and reactions which
have determined the preservation of some forms and the ex-
tinction of others,—in fact the whole history of the earth,
inorganic and organic, throughout a large portion of geological
time.

We shall perhaps better exhibit the scope and complexity of
the subject, and show that any intelligent study of it was
almost impossible till quite recently, if we concisely enumerate
the great mass of facts and the number of scientific theories
or principles which are necessary for its elucidation.

We require then in the first place an adequate knowledge of
the fauna and flora of the whole world, and even a detailed
knowledge of many parts of it, including the islands of more
special interest and their adjacent continents. This kind of
knowledge is of very slow growth, and is still very imperfect ;!

1 TI cannot avoid here referring to the enormous waste of labour and
money with comparatively scanty and unimportant results to natural history
of most of the great scientific voyages of the various civilized governments
during the present century. All these expeditions combined have done far
less than private collectors in making known the products of remote lands
and islands. They have brought home fragmentary collections, made in
widely scattered localities, and these have been usually described in huge
folios, whose value is often in inverse proportion to their bulk and cost.
The same species have been collected again and again, often described
‘several times over under new names, and not unfrequently stated to be
from places they never inhabited. The result of this wretched system is
that the productions of some of the most frequently visited and most in-
teresting islands on the globe are still very imperfectly known, while their
native plants and animals are being yearly exterminated, and this is the
case even with eountries under the rule or protection of European
governments. Such are the Sandwich Islands, Tahiti, the Marquesas, the
Philippine Islands, and a host of smaller ones ; while Bourbon and Mauritius,
St. Helena, and several others, have only been adequately explored after
an important portion of their productions has been destroyed by cultiva-
tion or the reckless introduction of goats and pigs. The employment in
each of our possessions, and those of other European powers, of a resident
naturalist at a very small annual expense, would have done more for
the advancement of knowledge in this direction than all the expensive
expeditions that have again and again circumnavigated the globe.

8 ISLAND LIFE. [PART I,

and in many cases it can never now be obtained owing to the
reckless destruction of forests and with them of countless species
of plants and animals. In the next place we require a true
and natural classification of animals and plants, so that we may
know their real affinities; and it is only now that this is being
generally arrived at. We further have to make use of the
theory of “descent with modification” as the only possible key
to the interpretation of the facts of distribution, and this theory
has only been generally accepted within the last twenty years.
It is evident that, so long as the belief in “special creations”
of each species prevailed, no explanation of the complex facts
of distribution could be arrived at or even conceived; for if
each species was created where it is now found no further
inquiry can take us beyond that fact, and there is an end of
the whole matter. Another important factor in our interpreta-
tion of the phenomena of distribution, is a knowledge of the
extinct forms that have inhabited each country during the
tertiary and secondary periods of geology. New facts of this
kind are daily coming to light, but except as regards Europe,
North America, and parts of India, they are extremely scanty ;
and even in the best-known countries the record itself is often
very defective and fragmentary. Yet we have already obtained
remarkable evidence of the migrations of many animals and
plants in past ages, throwing an often unexpected light on the
actual distribution of many groups.! By this means alone can
we obtain positive evidence of the past migrations of organisms ;
and when, as too frequently is the case, this is altogether
wanting, we have to trust to collateral evidence and more or
less probable hypothetical explanations. Hardly less valuable
is the evidence of stratigraphical geology; for this often shows
us what parts of a country have been submerged at certain
epochs, and thus enables us to prove that certain areas have been
long isolated and the fauna and flora allowed time for special
development. Here, too, our knowledge is exceedingly im-
pertect, though the blanks upon the geological map of the world

1 The general facts of Paleontology, as bearing on the migrations of
animal groups, are summarised in my Geographical Distribution of Animals,

Vol. I. Chapters VI., VIL, and VIII.

CHAP. J.] INTRODUCTORY. 9

are yearly diminishing in extent. Lastly, as a most valuable
supplement to geology, we require to know the exact depth
and contour of the ocean-bed, since this affords an important
clue to the former existence of now-submerged lands, uniting
islands to continents, or affording intermediate stations which
have aided the migrations of many organisms. This kind
of information has only begun to be obtained during the last
few years; and it will be seen in the latter part of this volume,
that some of the most recent deep-sea soundings have afforded
a basis for an explanation of one of the most difficult and
interesting questions in geographical biology—the origin of the
fauna and flora of New Zealand.

Such are the various classes of evidence that bear directly on
the question of the distribution of organisms; but there are
others of even a more fundamental character, and the impor-
tance of which is only now beginning to be recognised by
students of nature. These are, firstly, the wonderful alterations
cf climate which have occurred in the temperate and polar
zones, as proved by the evidences of glaciation in the one and
of luxuriant vegetation in the other; and, secondly, the theory of
the permanence of existing continents and oceans. If glacial
epochs in temperate lands and mild climates near the poles
have, as now believed by men of eminence, occurred several
times over in the past history of the earth, the effects of such
great and repeated changes, both on the migration, modification,
and extinction, of species, must have been of overwhelming
importance—of more importance perhaps than even the geo-
logical changes of sea and land. It is therefore necessary to
consider the evidence for these climatal changes; and then, by
a critical examination of their possible causes, to ascertain
whether they were isolated phenomena, were due to recurrent
cosmical actions, or were the result of a great system of terres-
trial development. The latter is the conclusion we arrive at;
and this conclusion brings with it the conviction, that in the
theory which accounts for both glacial epochs and warm polar
climates, we have the key to explain and harmonize many of
the most anomalous biological and geological phenomena, and
one which is especially valuable for the light it throws on the

10 ISLAND LIFE. [PART I.
dispersal and existing distribution of organisms. The other

important theory, or rather corollary from the preceding theory

—that of the permanence of oceans and the general stability

of continents throughout all geological time, is as yet very

imperfectly understood, and seems, in fact, to many persons in

the nature of a paradox. The evidence for it, however, appears

to me to be conclusive; and it is certainly the most fundamental

question in regard to the subject we have to deal with: since,

if we once admit that continents and oceans may have changed

places over and over again (as many writers maintain), we lose

all power of reasoning on the migrations of ancestral forms of
life, and are at the mercy of every wild theorist who chooses to

imagine the former existence of a now-submerged continent to

explain the existing distribution of a group of frogs or a genus

of beetles.

As already shown by the illustrative examples adduced in
this chapter, some of the most remarkable and interesting facts
in the distribution and affinities of organic forms are presented
by islands in relation to each other and to the surrounding
continents. The study of the productions of the Galapagos—
so peculiar, and yet so decidedly related to the American con-
tinent—appear to have had a powerful influence in determining
the direction of Mr. Darwin’s researches into the origin of
species; and every naturalist who studies them has always been
struck by the unexpected relations or singular anomalies which
are so often found to characterize the fauna and flora of islands.
Yet their full importance in connection with the history of the
earth and its inhabitants has hardly yet been recognised; and
it 1s in order to direct the attention of naturalists to this
most promising field of research, that I restrict myself in this
volume to an elucidation of some of the problems they present
to us. By far the larger part of the islands of the globe are
but portions of continents undergoing some of the various
changes to which they are ever subject; and the correlative
statement, that every part of our continents have again and
again passed through insular conditions, has not been sufficiently
considered, but is, I believe, the statement of a great and most
suggestive truth, and one which lies at the foundation of all

CHAP, 1. | INTRODUCTORY. . 11

accurate conception of the physical and organic changes which
have resulted in the present state of the earth.

The indications now given of the scope and purpose of the
present volume renders it evident that, before we can proceed
' to the discussion of the remarkable phenomena presented by
insular faunas and floras, and the complex causes which have
produced them, we must go through a series of preliminary
studies, adapted to give us a command of the more important
facts and principles on which the solution of such problems
depends. The succeeding eight chapters will therefore be
devoted to the explanation of the mode of distribution, variation,
modification, and dispersal, of species and groups, illustrated by
facts and examples; of the true nature of geological change
as affecting continents and islands; of changes of climate, their
nature, causes, and effects; of the duration of geological time
and the rate of organic development.

CHAPTER II.

THE ELEMENTARY FACTS OF DISTRIBUTION.

Importance of Locality as an essential character of Species—Areas of Dis-
tribution—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.

So long as it was believed that the several species of animals
and plants were “special creations,’ and had been formed
expressly to inhabit the countries in which they are now found,
their habitat was an ultimate fact which required no explana-
tion. It was assumed that every animal was exactly adapted
to the climate and surroundings amid which it lived, and that
the only, or, at all events, the chief reason why it did not
inhabit another country was, that the climate or general con-
ditions of that country were not suitable to it, but in what
the unsuitability consisted we could rarely hope to discover.
Hence the exact locality of any species was not thought of
much importance from a scientific point of view, and the idea
that anything could be learnt by a comparative study of
different floras and faunas never entered the minds of the
older naturalists.

But so soon as the theory of evolution came to be generally
adopted, and it was seen that each animal could only have
come into existence in some area where ancestral forms closely
allied to it already lived, a real and important relation was

cHAP. 11.] THE ELEMENTARY FACTS OF DISTRIBUTION. 13.

established between an animal and its native country, and a
new set of problems at once sprang into existence. From the
old point of view the diversities of animal life in the separate
continents, even where physical conditions were almost identical,
was the fact that excited astonishment; but seen by the light
of the evolution theory, it is the resemblances rather than the
diversities in these distant continents and islands that are most
difficult to explain. It thus comes to be admitted that a know-
ledge of the exact area occupied by a species or a group is
a real portion of its natural history, of as much importance
as its habits, its structure, or its affinities; and that we can
never arrive at any trustworthy conclusions as to how the present
state of the organic world was brought about, until we have
ascertained with some accuracy the general laws of the dis-
tribution of living things over the earth’s surface.

Areas of Distribution.—Every species of animal has a certain
area of distribution to which, as a rule, it is permanently
confined, although, no doubt, the limits of its range fluctuate
somewhat from year to year, and in some exceptional cases may
be considerably altered in a few years or centuries. Each
species is moreover usually limited to one continuous area,
over the whole of which it is more or less frequently to be met
with, but there are many partial exceptions to this rule. Some
animals are so adapted to certain kinds of country—as to forests
or marshes, mountains or deserts—that they cannot live long
elsewhere. These may be found scattered over a wide area in
suitable spots only, but can hardly on that account be said to
have several distinct areas of distribution. As an example we
may name the chamois, which lives only on high mountains,
but is found in the Pyrenees, the Alps, the Carpathians, in
some of the Greek mountams and the Caucasus. The variable
hare is another and more remarkable case, being found all over
Northern Europe and Asia beyond lat. 55°, and also in Scotland
and Ireland. In Central Europe it is unknown till we come to
the Alps, the Pyrenees, and the Caucasus, where it again appears.
This is one of the best cases known of the discontinuous dis-
tribution of a species, there being a gap of about a thousand miles
between its southern limits in Russia, and its reappearance in

14 ISLAND LIFE, [PART. I.

the Alps. There are of course numerous instances in which
species occur in two or more islands, or in an island and
continent, and are thus rendered discontinuous by the sea, but
these involve questions of changes in sea and land which we
shall have to consider further on. Other cases are believed
to exist of still wider separation of a species, as with the marsh
titmice and the reed buntings of Europe and Japan, where
similar forms are found in the extreme localities, while a distinct
variety, race, or sub-species, inhabits the intervening district.

Extent and Limitations of Specific Areas.—Leaving for the
present these cases of want of continuity in a species, we find
the most wide difference between the extent of country occupied,
varying in fact from a few square miles to almost the entire
land surface of the globe. Among the mammalia, however,
the same species seldom inhabits both the old and new worlds,
unless they are strictly arctic animals, as the reindeer, elk, and
arctic fox, the glutton, the ermine, and some others. The
common wolf of Europe and Northern Asia is thought by
many naturalists to be identical with the variously coloured
wolves of North America extending from the Arctic Ocean to
Mexico, in which case this will have perhaps the widest range
of any species of mammal. Little doubt exists as to the iden-
tity of the brown bears and the beavers of Europe and North
America; but all these species range up to the arctic circle, and
there is no example of a mammal universally admitted to be
identical yet confined to the temperate zones of the two hemi-
spheres. Among the undisputed species of mammalia the
leopard has an enormous range, extending all over Africa and
South Asia to Borneo and the east of China, and thus having
probably the widest range of any known mammal. The winged
mammalia have not usually very wide ranges, there being only
one bat common to the Old and New Worlds. This is a British
species, Vesperugo serotinus, which is found over the larger part
of North America, Europe and Asia, as far as Pekin, and even
extends into tropical Africa, thus rivalling the leopard and the
wolf in the extent of country it occupies.

Of very restricted ranges there are many examples, but some
of these are subject to doubts as to the distinctness of the

cHaP. 1.] THE ELEMENTARY FACTS OF DISTRIBUTION. 15

species or as to its geographical limits being really known. In
Europe we have a distinct species of ibex (Capra Pyrenaica)
confined to the Pyrenean mountains, while the true marmot
is restricted to the Alpine range. More remarkable is the
Pyrenean water-mole (Mygale Pyrenaica), a curious small in-
sectivorous animal found only in a few places in the northern
valleys of the Pyrenees. In islands there are many cases of
undoubted restriction of species to a small area, but these
involve a different question from the range of species on
continents where there is no apparent obstacle to their wider
extension.

Specific range of Birds——Among birds we find instances of
much wider range of species, which is only what might be
expected considering their powers of flight; but, what is very
curious, we also find more striking (though perhaps not more
frequent) examples of extreme limitation of range among birds
than among mammals. Of the former phenomenon perhaps
the most remarkable case is that afforded by the osprey or
fishing-hawk, which ranges over the greater portion of all the
continents, as far as Brazil, South Africa, the Malay Islands, and
Tasmania. The barn-owl (Strix flammea) has nearly as wide a
range, but in this case there is more diversity of opinion as to
the specific difference of many of the forms inhabiting remote
countries, some of which seem undoubtedly to be distinct.
Among passerine birds the raven has probably the widest range,
extending from the arctic regions to Texas and New Mexico in
America, and to North India and Lake Baikal in Asia; while
the little northern willow-wren (Phylloscopus borealis) ranges
from Norway across Asia to Alaska, and southward to Ceylon,
China, Borneo, and Timor.

Of very restricted continental ranges the best examples in
Europe are, the little blue magpie (Cyanopica cookt) confined to
the central portions of the Spanish peninsula; and the Italian
sparrow found only in Italy and Corsica. In Asia, Palestine
affords some examples of birds of very restricted range—a
beautiful sun-bird (Nectarinea osea) a peculiar starling (Amy-
drus Tristramu) and some others, being almost or quite con-
fined to the warmer portions of the valley of the Jordan. In

16 ISLAND LIFE. (PART I.

the Himalayas there are numbers of birds which have very
restricted ranges, but those of the Neilgherries are perhaps
better known, several species of laughing thrushes and some
other birds being found only on the summits of these mountains.
The most wonderfully restricted ranges are, however, to be
found among the humming-birds of tropical America. The
great volcanic peaks of Chimborazo and Pichincha have each a
peculiar species of humming-bird confined to a belt just below
the limits of perpetual snow, while the extinct velcano of
Chiriqui in Veragua has a species confined to its wooded crater.
One of the most strange and beautiful of the humming-birds
(Loddigesia mirabilis) was obtained once only, more than forty
years ago, near Chachapoyas in the Andes of northern Peru ;
and though Mr. Gould has sent many drawings of the bird to
people visiting the district and has for many years offered a
high reward for a specimen, no other has ever been seen !!

The above details will sufficiently explain what is meant by
the “specific area” or range of a species. The very wide and
very narrow ranges are exceptional, the great majority of
species both of mammals and birds ranging over moderately
wide areas, which present no striking contrasts in climate and
physical conditions. Thus a large proportion of Kuropean birds
range over the whole continent in an east and west direction,
but considerable numbers are restricted either to the northern
or the southern half. In Africa some species range over all the
continent south of the desert, while large numbers are restricted
to the equatorial forests, or to the upland plains. In North
America, if we exclude the tropical and the arctic portions, a
considerable number of species range over all the temperate
parts of the continent, while still more are restricted to the
east, the centre, or the west, respectively.

Generic Areas,—Having thus obtained a tolerably clear idea
of the main facts as to the distribution of isolated species, let
us now consider those collections of closely-allied species termed
genera. What a genus is will be sufficiently understood by a
few illustrations, All the different kinds of dogs, jackals, and

1 Since these lines were written, the report comes that fresh specimens
have been found in the same locality.

oHAP. 11.] THE ELEMENTARY FACTS OF DISTRIBUTION. 17

wolves belong to the dog genus, Canis; the tiger, lion, leopard,
jaguar, and the wild cats, to the cat genus, Felis; the blackbird,
song-thrush, missel-thrush, fieldfare, and many others, to the
thrush genus, Turdus; the crow, rook, raven, and jackdaw,
to the crow genus, Corvus; but the magpie belongs to another,
though closely-allied genus, Pica, distinguished by the different
form and proportions of its wings and tail from all the species
of the crow genus. The number of species in a genus varics
greatly, from one up to several hundreds. The giraffe, the
glutton, the walrus, the bearded reedling, the secretary-bird,
and many others, have no close alles, and each forms a
genus by itself. The beaver genus, Castor, and the camel
genus, Camelus, each consist of two species. On the other
hand, the deer genus, Cervus has forty species; the mouse
and rat genus, Mus more than a hundred species; and there
is about the same number of the thrush genus; while among
the lower classes of animals genera are often very extensive,
the fine genus Papilio, or swallow-tailed butterflies, containing
-more than four hundred species; and Cicindela, which includes
our native tiger beetles, has about the same number. Many
genera of shells are very extensive, and one of them—the
genus Helix, including the commonest snails, and ranging
all over the world—is probably the most extensive in the
animal kingdom, numbering about two thousand described
species.

Separate and overlapping Areas.—The species of a genus are
distributed in two ways. Hither they occupy distinct areas
which do not touch each other and are sometimes widely
separated, or they touch and occasionally overlap each other,
each species occupying an area of its own which rarely coin-
cides exactly with that of any other species of the same genus.
In some cases, when a river, a mountain-chain, or a change of
conditions as from pasture to desert or forest, determines the
range of species, the areas of two species of the same genus
may just meet, one beginning where the other ends; but this
is comparatively rare. It occurs, however, in the Amazon
valley, where several species of monkeys, birds, and insects

come up to the south bank of the river but do not pass it,
C

18 ISLAND LIFE. [Part I.

while allied species come to the north bank, which in like
manner forms their boundary. As examples we may mention
that one of the Saki monkeys (Pithecia monachus?) comes up
to the south bank of the Upper Amazon, while immediately
we cross over to the north bank we find another species
(Pithecia rufibarbata?). Among birds we have the green
jacamar (Galbula viridis), abundant on the north bank of the
Lower Amazon, while on the south bank we have two allied
species (Galbula rufoviridis and G. cyanetcollis); and among
insects we have at Santarem, on the south bank of the Ama-
zon, the beautiful blue butterfly, Callithea sapphira, while almost
opposite to it, at Monte-alegre,an allied species, Callithea Lepriewrt
is alone found. Perhaps the most interesting and best known
case of a series of allied species, whose ranges are separate but
conterminous, is that of the beautiful South American wading
birds, called trumpeters, and forming the genus Psophia. There
are five species, all found in the Amazon valley, but each
limited to a well-marked district bounded by great rivers. On
the north bank of the Amazon there are two species, one in its
lower valley extending up to the Rio Negro, and the other in
the central part of the valley beyond that river; while to the
south of the Amazon there are three, one above the Madeira,
one below it, and a third near Para, probably separated from
the last by the Tocantins river.

Overlapping areas among the species of a genus is a more
common phenomenon, and is almost universal where these
species are numerous in the same continent. It is, however,
exceedingly irregular, so that we often find one species extend-
ing over a considerable portion of the area occupied by the
genus and including the entire areas of some of the other
species. So little has been done to work out accurately the
limits of species that it is very difficult to give examples. One
of the best is to be found in the genus Dendraca, a group of
American wood-warblers. These little birds all migrate in the
winter into the tropical regions, but in the summer they come
north, each having its particular range. Thus, D. dominica
comes as far as South Carolina, D. cwrulea to Virginia, D. dis-
color to Soutkern Maine and Canada; four other species go

onar. u.] THE ELEMENTARY FACTS OF DISTRIBUTION. ey

farther north in Canada, while five more extend to the borders
of the Arctic zone.

The species of Tits as illustrating areas of distribution.—In our
own hemisphere the overlapping of allied species may be well
illustrated by the various kinds of titmice, several of which
are among our best known English birds. The great titmouse
(Parus major) has the widest range of all, extending from the
_ Arctic circle to Algeria, Palestine, and Persia, and from Ireland
right across Siberia to the Ochotsk sea, probably following the
great northern forest belt. It does not extend into China and
Japan, where distinct species are found. Next in extent of
range is the coal tit (Parus ater), which inhabits all Europe
from the Mediterranean to about 64° N., latitude, in Asia Minor
to the Lebanon and Caucasus, and across Siberia to Amoorland.
The marsh tit (Parus palustris) inhabits temperate and south
Europe from 61° N. latitude in Norway to Poland and South-
west Russia, and in the south from Spain to Asia Minor. Closely
allied to this—of which it is probably only a variety or sub-
species—is the northern marsh tit (Parus borealis), which over-
laps the last in Norway and Sweden, and also in South Russia
and the Alps, but extends further north into Lapland and North
Russia, and thence probably in a south-easterly direction across
Central Asia to North China. Yet another closely-allied species
(Parus camischatkensis) ranges from North-eastern Russia across
Northern Siberia to Lake Baikal and to Hakodadi in Japan, thus
overlapping Parus borealis in the western portion of its area.
Our little favourite, the blue tit (Parus cwruleus) ranges over
all Europe from the Arctic circle to the Mediterranean, and on
to Asia Minor and Persia, but does not seem to pass beyond the
Ural mountains. Its lovely eastern ally the azure tit (Parus
cyaneus) overlaps the range of P. ceruleus in Western Europe as
far as St. Petersburg and Austria, rarely straggling to Den-
mark, while it stretches all across Central Asia between the
latitudes 35° and 56° N. as far as the Amoor valley. Besides
these wide-ranging species there are several others which are
more restricted. Parus tenerife, a beautiful dark blue form of
our blue tit, inhabits North-west Africa and the Canaries ; Parus
ledouct, closely allied to our coal tit, is found only in Algeria;

20 ISLAND LIFE. [PART I,

Parus lugubris, allied to the marsh tit, is confined to South-east
Kurope and Asia Minor, from Hungary and South Russia to
Palestine ;-and Parus cinctus, another allied form, is confined
to the extreme north in Lapland, Finland, and perhaps Northern
Russia and Siberia. Another beautiful little bird, the crested tit-
mouse (Parus cristatus) is sometimes placed in a separate genus.
It inhabits nearly all Central and South Europe, wherever there
are pine forests, from 64° N. latitude to Austria and North Italy,
and in the west to Spain and Gibraltar, while in the east it does
not pass the Urals and the Caucasus range. Its nearest allies
are in the high Himalayas.

These are all the European tits, but there are many others
inhabiting Asia, Africa, and North America; so that the genus
Parus has a very wide range, in Asia to Ceylon and the Malay
Islands, in Africa to the Cape, and in North America to the
highlands of Mexico.

The distribution of the Species of Jays. —Owing to the very
wide range of several of the tits, the uncertainty of the specific
distinction of others, and the difficulty in many cases of ascer-
taining their actual distribution, it has not been found prac-
ticable to illustrate this genus by means of a map. For this
purpose we have chosen the genus Garrulus or the jays, in which
the species are less numerous, the specific areas less extensive,
and the species generally better defined; while being large and
handsome birds they are sure to have been collected, or at least
noticed, wherever they occur. There are, so far as yet known,
twelve species of true jays, occupying an area extending from
Western Europe to Eastern Asia and Japan, and nowhere pass-
ing the Arctic circle to the north, or the tropic of Cancer to the
south, so that they constitute one of the most typical of the
Palearctic! genera. The following are the species, beginning
with the most westerly and proceeding towards the east. The
numbers prefixed to each species correspond to those on the
coloured map which forms the frontispiece to this volume.

1. Garrulus glandarius. —The common jay, inhabits the

1 The Palearctic region includes temperate Asia and Europe, as will be
explained in the next chapter.

cHAP, 11.] THE ELEMENTARY FACTS OF DISTRIBUTION. 21

British Isles and all Europe except the extreme north, extend-
ing also into North Africa, where it has been observed in many
parts of Algeria. It occurs near Constantinople, but apparently
not in Asia Minor, and in Russia, up to, but not beyond, the Urals.
The jays being woodland birds are not found in open plains or
barren uplands, and their distribution is hence by no means
uniform within the area they actually occupy.

2. Garrulus cervicalis.—The Algerian jay, is a very distinct
species inhabiting a limited area in North Africa, and found in
some places along with the common species.

3. Garrulus krynickt.—The black-headed jay, is closely
allied to the common species, but quite distinct, inhabiting
a comparatively small area in South-eastern Europe, and
Western Asia. |

4. Garrulus atricapillus.—The Syrian jay, is very closely allied
to the last, and inhabits an adjoining area in Syria, Palestine,
and Southern Persia.

5. Garrulus hyrcanus—The Persian jay, is a small species
allied to our jay and only known from the Elburz Mountains in
the north of Persia.

6. Garrulus brandtt.—Brandt’s jay, is a very distinct
species, having an extensive range across Asia from the Ural
Mountains to North China, Mandchuria, and the northern island
of Japan, and also crossing the Urals into Russia where it has
been found as far west as Kazan in districts where the common
jay also occurs.

7. Garrulus lanceolatus—The black-throated jay, is a very
distinct form known only from the North-western Himalayas
and Nepal, common about Simla, and extending into Cashmere
beyond the range of the next species.

8. Garrulus bispecularis—The Himalayan jay is also very
distinct, having the head coloured like the back, and not
striped as in all the western species. It inhabits the Himalayas
east of Cashmere, but is more abundant in the western than
the eastern division, though according to the Abbé David it
reaches Moupin in East Thibet.

9. Garrulus sinensis——The Chinese jay, is very closely allicd
to the Himalayan, of which it is sometimes classed as a

22 ISLAND LIBW. =. [PART I.

sub-species. It seems to be found in all the southern mountains
of China, from Foochow on the east to Sze-chuen and East Thibet
on the west, as it is recorded from Moupin by the Abbé David
as well as the Himalayan bird—-a tolerable proof that it isa
distinct form.

10. Garrulus taivanus.—The Formosan jay is a very close ally
of the preceding, confined to the island of Formosa.

11. Garrulus japonicus.—The Japanese jay is very closely
allied to our common British species, teing somewhat smaller
and less brightly coloured, and with black orbits; yet these are
the most widely separated species of the genus.

12. Garrulus lidthi—This is the handsomest of all the
jays, the head, neck, and wings being azure blue. Its locality —
was long doubtful, but it has now been ascertained to inhabit
Japan, where it is evidently very rare, its exact habitat being
still unknown.

In the accompanying map (see frontispiece) we have laid down
the distribution of each species so far as it can be ascertained
from the works of Sharpe and Dresser for Europe, Jerdon for
India, Swinhoe for China, and Messrs. Blakiston and Pryer for
Japan. There is, however, much uncertainty in many places,
and gaps have to be filled up conjecturally, while such a large
part of Asia is still very imperfectly explored, that considerable
modifications may have to be made when the country becomes
more accurately known. But though details may be modified
we can hardly suppose that the great features of the several
specific areas, or their relations to each other, will be much
affected; and these are what we have chiefly to consider as

earing on the questions here discussed.

The first thing that strikes us on looking at the map, is, the
small amount of overlapping of the several areas, and the iso-
lation of many of the species; while the next most striking
feature is the manner in which the Asiatic species almost sur-
round a vast area in which no jays are found. The only species
with large areas, are the European G. glandarius and the Asiatic
G. Brandti. The former has three species overlapping 1t—in
Algeria, in South-eastern and in North-eastern Europe respect-
ively. The Syrian jay (No. 4), is not known to occur anywhere

cHap, u.] THE ELEMENTARY FACTS OF DISTRIBUTION, 23

with the black-headed jay (No. 3), and perhaps the two areas do
not meet. The Persian jay (No. 5), is quite isolated. The Hima-
layan and Chinese jays (Nos. 7, 8, and 9) form a group which
are isolated from the rest of the genus; while the Japanese
jay (No. 11), is also completely isolated as regards the European
jays to which alone it is closely allied. These peculiarities of
distribution are no doubt in part dependent on the habits of the
jays, which live only in well-wooded districts, among deciduous
trees, and are essentially non-migratory in their habits, though
sometimes moving southwards in winter. This will explain
their absence from the vast desert area of Central Asia, but it
will not account for the gap between the North and South
Chinese species, nor for the absence of jays from the wooded
hills of Turkestan, where Mr. N. A. Severtzoff collected assid-
uously, obtaining 384 species of birds but no jay. These
peculiarities, and the fact that jays are never very abundant
anywhere, seem to indicate that the genus is now a decaying
one, and that it has at no very distant epoch occupied a larger
and more continuous area, such as that of the genus Parus at
the present day.

Discontinuous generic Areas—It is not very easy to find
good examples of genera whose species occupy two or more quite
disconnected areas, for though such cases may not be rare, we
are seldom in a position to mark out the limits of the several
species with sufficient accuracy. The best and most remarkable
case among Kuropean birds is that of the blue magpies, forming
the genus Cyanopica. One species (C. cooki) is confined (as
already stated) to the wooded and mountainous districts of Spain
and Portugal, while the only other species of the genus (C. cyanus)
is found far away in North-eastern Asia and Japan, so that the
two species are separated by about 5,000 miles of continuous
land. Another case is that of the curious little water-moles
-forming the genus Mygale, one species MZ. muscovitica, being found
only on the banks of the Volga and Don in South-eastern
Russia, while the other, M. pyrenaica, is confined to streams on
the northern side of the Pyrenees. In tropical America there
are four different kinds of bell-birds belonging to the genus
Chasmorhynchus, each of which appears to inhabit a restricted

24 ISLAND LIFE. [PART I,

area completely separated from the others. The most northerly
is C. tricarunculatus of Costa Rica and Veragua, a brown bird with
a white head and three long caruncles growing upwards at the
base of the beak. Next comes C. varegatus, in Venezuela, a
white bird with a brown head and numerous caruncles on the
throat, perhaps conterminous with the last; in Guiana, ex-
tending to near the mouth of the Rio Negro, we have C. mveus,
the bell-bird described by Waterton, which is pure white, with
a single long fleshy caruncle at the base of the beak; the last
species, C. nudicollis, inhabits South-east Brazil, and is also
white, but with black stripes over the eyes, and with a naked
throat. These birds are about the size of thrushes and are all
remarkable for their loud-ringing notes like a bell or a blow on
an anvil, as well as for their peculiar colours. They are there-
fore known to the native Indians wherever they exist, and we
ray be the more sure that they do not spread over the inter-
vening areas where they have never been found, and where the
natives know nothing of them.

A good example of isolated species of a group nearer home,
is afforded by the snow-partridges of the genus Tetraogallus.
One species inhabits the Caucasus range and nowhere else,
keeping to the higher slopes from 6,000 to 11,000 feet above the
sea, and accompaning the ibex in its wanderings, as both feed
on the same plants. Another has a wider range in Asia Minor
and Persia from the Taurus mountains to the South-east corner
of the Caspian Sea ; a third species inhabits the Western Hima-
layas, between the forests and perpetual snow, extending east-
wards to Nepal, while a fourth is found on the north side of the
mountains in Thibet, and the ranges of these two perhaps over-
lap; the last species inhabit the Altai mountains, and lke the
two first appears to be completely separated from all its allies.

There are some few still more extraordinary cases in which
the species of one genus are separated in remote continents or
islands. The most striking of these is that of the tapirs, forming
the genus Tapirus, of which there are two or three species in
South America, and one very distinct species in Malacca and
Borneo, separated by nearly half the circumference of the globe.
Another example among quadrupeds is a peculiar genus of moles

cHap, 1.] THE ELEMENTARY FACTS OF DISTRIBUTION. 25

named Urotrichus, of which one species inhabits Japan and the
other British Columbia. The cuckoo-like honey-guides, forming
the genus Indicator, are tolerably abundant in tropical Africa,
but there are two outlying species, one in the Eastern Hima-
laya mountains, the other in Borneo, both very rare, and
quite recently an allied species has been found in the Malay
peninsula. The beautiful blue and green thrush-tits forming
the genus Cochoa, have two species in the Eastern Himalayas,
while the third is confined to Java; the curious genus Eupetes,
supposed to be allied to the dippers, has two species in Sumatra,
and the other species two thousand miles distant in New Guinea ;
lastly, the lovely ground-thrushes of the genus Pitta, range
from Hindostan to Australia, while a single species, far removed
from all its near allies, inhabits West Africa.

Peculiaritres of Generic and Family Distribution.—The examples
now given sufficiently illustrate the mode in which the several
species of a genus are distributed. We have next to consider
genera as the component parts of families, and families of orders,
from the same point of view.

All the phenomena presented by the species of a genus are
reproduced by the genera of a family, and often in a more
marked degree. Owing, however, to the extreme restriction of
genera by modern naturalists, there are not many among the
higher amimals that have a world-wide distribution. Among
the mammalia there is no such thing as a truly cosmopolitan
genus. This is owing to the absence of all the higher orders
except the mice from Australia, while the genus Mus, which
occurs there, is represented by a distinct group, Hesperomys, in
America. If, however, we consider the Australian dingo asa
native animal we might class the genus Canis. as cosmopolite,
but the wild dogs of South America are now formed into
separate genera by some naturalists. Many genera, however,
range over three or more continents, as Felis (the cat genus)
absent only from Australia ; Ursus (the bear genus) absent from
Australia and tropical Africa; Cervus (the deer genus) with
nearly the same range; and Sciurus (the squirrel genus) found
in all the continents but Australia. Among birds Turdus, the
thrush, and Hirundo, the swallow genus, are the only perching

26 ISLAND LIFE. [PART I.

birds which are truly cosmopolites ; but there are many genera
of hawks, owls, wading, and swimming birds which have a
world-wide range.

As a great many genera consist of single species there is no
lack of cases of great restriction, such as the curious lemur called
the “potto” which is found only at Sierra Leone, and forms the
genus Perodicticus ; the true chinchillas found only in the Andes
of Peru and Chili south of 9° S. lat. and between 8,000 and
12,000 feet elevation ; several genera of finches each confined to
limited portions of the higher Himalayas, the blood-pheasants
(Ithaginis) found only above 10,000 feet from Nepal to East
Thibet ; the bald-headed starling of the Philippine islands, the
lyre-birds of East Australia, and a host of others.

It is among the different genera of the same family that we
meet with the most striking examples of discontinuity, although
these genera are often as unmistakably allied as are the species
of a genus; and it is these cases that furnish the most interest-
ing problems to the student of distribution. We must therefore
consider them somewhat more fully.

Among mammalia the most remarkable of these divided
families is that of the camels, of which one genus Camelus,
the true camels, comprising the camel and dromedary, is con-
fined to Asia, while the other, Auchenia, comprising the llamas
and alpacas, is found only in the high Andes and in the plains
of temperate South America. Not only are these two genera
separated by the Atlantic and by the greater part of the land of
two continents, but one is confined to the Northern and the
other to the Southern hemisphere. The next case, though not
so well known, is equally remarkable ; it is that of the Centetide,
a family of small insectivorous animals, which are wholly con-
fined to Madagascar and the large West Indian islands Cuba and
Hayti, the former containing five genera and the latter a single
genus with a species in each island. Here again we have the
whole continent of Africa as well as the Atlantic ocean separat-
ing allied genera. Two families of rat-like animals, Octodon-
tidee and Echimyide, are also divided by the Atlantic. Both are
mainly South America, but the former has two genera in North
and East Africa, and the latter also two in South and West

oHaP. 1.] THE ELEMENTARY FACTS OF DISTRIBUTION. 27

Africa. Two other families of mammalia, though confined to
the Eastern hemisphere, are yet markedly discontinuous. The
Tragulidee are small deer-like animals, known as chevrotains or
mouse-deer, abundant in India and the larger Malay islands
and forming the genus Tragulus; while another genus,
Hyomoschus, is confined to West Africa. The other family is
the Simiidz or antthropoid apes, in which we have the gorilla
and chimpanzee confined to West and Central Africa, while
the allied orangs are found only in the islands of Sumatra
and Borneo, the two groups being separated by a greater
space than the Echimyide and other rodents of Africa and
South America.

Among birds and reptiles we have several families, which,
from being found only within the tropics of Asia, Africa, and
America, have been termed tropicopolitan groups. The Mega-
leemidee or barbets are gaily coloured fruit-eating birds, almost
equally abundant in tropical Asia and Africa, but less plentiful
in America, where they probably suffer from the competition of
the larger sized toucans. The genera of each country are
distinct, but all are closely allied, the family being a very
natural one. The trogons form a family of very gorgeously
coloured and remarkable insect-eating birds very abundant in
tropical America, less so in Asia, and with a single genus of
two species in Africa.

Among reptiles we have two families of snakes—the Dendro-
phide or tree-snakes, andthe Dryiophide or green whip-snakes
—which are also found in the three tropical regions of Asia,
Africa, and America, but in these cases even some of the genera
are common to Asia and Africa, or to Africa and America. The
lizards forming the small family Lepidosternide are divided
between tropical Africa and South America, while even the
peculiarly American family of the iguanas is represented by
two genera in Madagascar. Passing on to the Amphibians the
worm-like Ceciliadz are tropicopolitan, as are also the toads of
the family Phryniscide. Insects also furnish some analogous
cases, three genera of Cicindelidee (Pogonostoma, Ctenostoma,
and Peridexia) showing a decided connection between this
family in South America and Madagascar; while the beautiful

28 ISLAND LIFE. [PART I.

genus of diurnal moths, Urania, is confined to the same
two countries. A somewhat similar but better known illus-
tration is afforded by the two genera of ostriches, one confined
to Africa and Arabia, the other to the plains of temperate South
America.

General features of Overlapping and Discontinuous Areas, —
These numerous examples of discontinuous genera and families
form an important section of the facts of animal dispersal which
any true theory must satisfactorily account for. In greater or less
prominence they are to be found all over the world, and in every
group of animals, and they grade imperceptibly into those cases
of conterminous and overlapping areas which we have seen to
prevail in most extensive groups of species, and which are
perhaps even more common in those large families which consist
of many closely allied genera. A sufficient proof of the over-
lapping of generic areas is the occurrence of a number of genera
of the same family together. Thus in France or Italy about
twenty genera of warblers (Sylviade) are found, and as each
of the thirty-three genera of this family inhabiting temperate
Europe and Asia has a different area, a great number must here
overlap. So, in most parts of Africa at least, ten or twelve
genera of antelopes may be found, and in South America a
large proportion of the genera of monkeys of the family Cebidee
occur in many districts ; and still more is this the case with the
larger bird families, such as the tanagers, the tyrant shrikes, or
the tree-creepers, so that there is in all these extensive families
no genus whose area does not overlap that of many others.
Then among the moderately extensive families we find a few
instances of one or two genera isolated from the rest, as the
spectacled bear, Tremarctos, found only in Chili, while the
remainder of the family extends from Europe and Asia over
North America to the mountains of Mexico, but no further
south; the Bovide, or hollow-horned ruminants, which have
a few isolated genera in the Rocky mountains and the islands
of Sumatra and Celebes; and from these we pass on to the
cases of wide separation already given.

Restricted Areas of Families.—As families sometimes consist
of single genera and even single species, they often present

cHAP. 1.] THE ELEMENTARY FACTS OF DISTRIBUTION, 29

examples of very restricted range; but what is perhaps more
interesting are those cases in which a family contains numerous
species and sometimes even several genera, and yet is confined
to a narrow area. Such are the golden moles (Chrysochloride)
consisting of two genera and three species, confined to extra-
tropical South Africa; the hill-tits (Liotrichide), a family of
eleven genera and thirty-five species almost wholly limited to
the Himalayas, but with a few straggling species in the Malay
countries; the Pteroptochidee, large wren-like birds, consisting
of eight genera and nineteen species, almost entirely confined
to temperate South America and the Andes; and the birds-of-
paradise, consisting of nineteen or twenty genera and about
thirty-five species, almost all inhabitants of New Guinea and
the immediately surrounding islands, while a few, doubtfully
belonging to the family, extend to Hast Australia. Among
reptiles the most striking case of restriction is that of the
rough-tailed burrowing snakes (Uropeltide), the five genera
and eighteen species being strictly confined to Ceylon and
the southern parts of the Indian Peninsula.

The Distribution of Orders —When we pass to the larger
groups, termed orders, comprising several families, we find com-
paratively few cases of restriction and many of world-wide
distribution ; and the families of which they are composed are
strictly comparable to the genera of which families are com-
posed, inasmuch as they present examples of overlapping, or
conterminous, or isolated areas, though the latter are com-
paratively rare. Among mammalia the Insectivora offer the
best example of an order, several of whose families inhabit
areas more or less isolated from the rest; while the Marsupialia
have six families in Australia, and one, the opossums, far off in
America.

Perhaps, more important is the limitation of some entire
orders to certain well-defined portions of the globe. Thus the
Proboscidea, comprising the single family and genus of the
elephants, and the Hyracoidea, that of the Hyrax or Syrian
coney, are confined to parts of Africa and Asia; the Marsupials
to Australia and America; and the Monotremata, the lowest of
all mammals—comprising the duck-billed Platypus and the

30 ISLAND LIFE. [PART I.

spiny Echidna, to Australia. Among birds the Struthiones or
ostrich tribe are almost confined to the three Southern con-
tinents, South America, Africa and Australia; and among
Amphibia the tailed Batrachia—the newts and salamanders
—are similarly restricted to the northern hemisphere.

These various facts will receive their explanation in a future
chapter.

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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
Palearctic Region—Characteristic features of the Palearctic 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.

HAVING now obtained some notion of how animals are dispersed
over the earth’s surface, whether as single species or as collected
in those groups termed genera, families, and orders, it will be
well, before proceeding further, to understand something of the
classification of the facts we have been considering, and some
of the simpler conclusions these facts lead to.

We have hitherto described the distribution of species and
groups of animals by means of the great geographical divisions
of the globe in common use; but it will have been observed
that in hardly any case do these define the limits of anything
beyond species, and very seldom, or perhaps never, even those
accurately. Thus the term “Europe” will not give, with any
approach to accuracy, the range of any one genus of mammals
or birds, and perhaps not that of half-a-dozen species. Either
they range into Siberia, or Asia Minor, or Palestine, or North
Africa; and this seems to be always the case when their area

32 ISLAND LIFE. [PART I,

of distribution occupies a large portion of Europe. There are,
indeed, a few species limited to Central or Western or Southern
Kurope, and these are almost the only cases in which we can
use the word for zoological purposes without having to add to
it some portion of another continent. Still less useful is the
term Asia for this purpose, since there is probably no single
animal or group confined to Asia which is not also more or less
nearly confined to the tropical or the temperate portion of it.
The only exception is perhaps the tiger, which may really be
called an Asiatic animal, as it occupies nearly two-thirds of the
continent; but this 1s an unique example, while the cases in
which Asiatic animals and groups are strictly limited to a
portion of Asia, or extend also into Europe or into Afriea or to
the Malay Islands, are exceedingly numerous. So, in Africa,
very few groups of animals range over the whole of it without
going beyond either into Europe or Asia Minor or Arabia,
while those which are purely African are generally confined to
the portion south of the tropic of Cancer. Australia and
America are terms which better serve the purpose of the
zoologist. The former defines the limit of many important
groups of animals; and the same may be said of the latter,
but the division into North and South America introduces
difficulties, for almost all the groups especially characteristic of
South America are found also beyond the isthmus of Panama,
in what is geographically part of the northern continent.

It being thus clear that the old and popular divisions of the
globe are very inconvenient when used to describe the range of
animals, we are naturally led to ask whether any other division
can be made which will be more useful, and will serve to group
together a considerable number of the facts we have to deal with.
Such a division was made by Mr. P. L. Sclater more than
twenty years ago, and it has, with some slight modifications,
come into pretty general use in this country, and to some extent
also on the continent; we shall therefore proceed to explain its
nature and the principles on which it is established, as it will
have to be often referred to in future chapters of this work,
and will take the place of the old geographical divisions whose
extreme inconvenience has already been pointed out. The

CHAP. u11.] ZOOLOGICAL REGIONS, — 33

primary zoological divisions of the globe are called “regions,”
and we will begin by ascertaining the limits of the region of
which our own country forms a part.

The Range of British Mammals as indicating a Zoological
Region.—We will first take our commonest wild mammalia and
see how far they extend, and especially whether they are con-
fined to Europe or range over parts of other continents :

52) 820) ur aes Europe | N. Africa | Central Asia to Amoor.
6. Stag ....:. oo aes Europe | N. Africa | Central Asia to Amoor.
@ Hiedwehog .......:. Kurope --- Central Asia to Amoor.
Se UCC) he eee eee Europe — Central Asia.

SRO GRMETOL © 2s... 05. Europe -~ Central Asia to Amoor.
ie Dormouse:........... Europe — —
11. Water-rat..... .... .. | Europe — Central Asia to Amoor.
ES UE) ON Europe — W. Siberia, Persia.

1 Elia) 0) a ee | Europe | N. Africa
|

We thus see that out of thirteen of our commonest quad-
rupeds only one is confined to Europe, while seven are found
also in Northern Africa, and eleven range into Siberia, most of
them stretching quite across Asia to the valley of the Amoor
on the extreme eastern side of that continent. Two of the
above-named British species, the fox and weasel, are also in-
habitants of the New World, being as common in the northern
parts of North America as they are with us ; but with these ex-
ceptions the entire range of our commoner species is given, and
they clearly show that all Northern Asia and Northern Africa
must be added to Europe in order to form the region which they
collectively inhabit. If now we go into Central Europe and
take, for example, the quadrupeds of Germany, we shall find
that these too, although much more numerous, are confined to
the same limits, except that some of the more arctic kinds, as
already stated, extend into the colder regions of North America.

Range of Hast Asian and North African Mammals.—Let us
now pass to the other side of the great northern continent, and
examine the list of the quadrupeds of Amoorland, in the same

34 is ISLAND LIFB. [Parr 1.

latitude as Germany. We find that there are forty-four ter-
restrial species (omitting the bats, the seals, and other marine
animals), and of these no less than twenty-six are identical with
Kuropean species, and twelve or thirteen more are closely allied
representatives, leaving only five or six which are peculiarly
Asiatic. We can hardly have a more convincing proof of the
essential oneness cf the mammalia of Europe and Northern
Asia.

In Northern Africa we do not find so many European species
(though even here they are very numerous) because a con-
siderable number of West Asiatic and desert forms occur.
Having, however, shown that Europe and Western Asia have
almost identical animals, we may treat all these as really
European, and we shall then be able to compare the quadrupeds
of North Africa with those of Europe and West Asia. Taking
those of Algeria as the best known, we find that there are
thirty-three species identical with those of Europe and West
Asia, while twenty-four more, though distinct, are closely allied,
belonging to the same genera; thus making a total of fifty-
seven of European type. On the other hand, we have seven
species which are either identical with species of tropical Africa
or allied to them, and six more which are especially characteristic
of the African and Asiatic deserts which form a kind of neutral
zone between the temperate and tropical regions, If now we
consider that Algeria and the adjacent countries bordering the
Mediterranean form part of Africa, while they are separated from
Europe by a wide sea and are only connected with Asia by.a
narrow isthmus, we cannot but feel surprised at the wonderful
preponderance of the European and West Asiatic elements in
the mammalia which inhabit the district.

The Range of British Birds.—As it is very important that no
doubt should exist as to the limits of the zoological region of
which Europe forms a part, we will now examine the birds, in
order to see how far they agree in their distribution with the
mammalia. Of late years great attention has been paid to the
distribution of European and Asiatic birds, many ornithologists
having travelled in North Africa, in Palestine, in Asia Minor, in
Persia, in Siberia, in Mongolia, and in China; so that we are now

CHAP. III. ] ZOOLOGICAL REGIONS. 35
able to determine the exact ranges of many species in a manner
that would have been impossible a few years ago. These ranges
are given for all British species in the new edition of Yarrell’s
Listory of British Birds now in course of publication under the
editorship of Professor Newton, while those of all European
birds are given in still more detail in Mr. Dresser’s beautiful
work on the Birds of Europe, just completed. In order to
confine our examination within reasonable limits, and at the
same time give it the interest attaching to familiar objects, we
will take the whole series of British Passeres or perching birds
given in Professor Newton’s work (118 in number) and arrange
them in series according to the extent of their range. These
include not only the permanent residents and regular migrants
to our country, but also those which occasionally straggle here, so
that it really comprises a large proportion of all European birds.

I, British BIRDS WHICH EXTEND TO NorTH AFRICA AND CENTRAL OR
NorTH-EAST ASIA,

T, Lanius collurio...... 0.000... Red-backed Shrike (also all Africa).
DV Orolis Galoula .. 0... Golden Orio!e (also all Africa),
BD. LUTAUSEMUSICUS <i. 0ceccress Song-Thrush.
4, bey NGACUS: ys ccs os. kaas. Red-wing.
5. PE IOLETIS! Scan 528 wens Fieldfare.
6. Monticola saxatilis ......... Blue rock Thrush.
1. Ruticilla suecica .....-...... Bluethroat (also India in winter).
8. Saaicola rubicola............ Stonechat (also India in winter).
o. RP CCNONGLG oo 1. . cde0300 Wheatear (also N. America).

10. Acrocephalus arundinaceus Great Reed-Warbler.

TES YUUUG CULTUCH 0.3 6.00.00000- Lesser Whitethroat.

Wy, FArUS NUOIOM .. 0c esinie.ceee Great Titmouse.

13. Motacilla sulphurea......... Grey Wagtail (also China and Malaya).

14. P| MODY, rere sitietsien rds’ Yellow Wagtail.

PD Amis WrIvIAS oo... we ks Tree Pipit.

1Garirng (a sptloletia ...... 00.0. Water Pipit.

Wiig) oh COMPOSI IS edu Tawny Pipit.

18, Alauda arvensis ............ Skylark.

Jus) BM CRISLOUO sos cs so Bice Crested Lark.

20. Emberiza scheniclus ...... Reed Bunting.

at. 5, CUUTINCULE 62. 50s Yellow-hammer.

22. Fringilla montifringilla .... Brambling.

23. Passer montanus ........006 Tree Sparrow (also 8, Asia),

BA ie,” LOMESUICUS. ods betee House Sparrow.

25. Coccothraustes vulgaris .... Hawfinch.

26. Carduelis spinus .......0060 Siskin (also China).

2A LOLIG CUTUITOSIVE 6. e en Crossbill.

28. Sturnus vulgaris ....ccccceee Starling.

36 ISLAND LIFE. [PART I,

29. Pyrrhocorax graculus ...... Chough

30, Corvus COnone wascucn cee Crow.

B31. Hirundo rustica .........0.- Swallow (all Africa and Asia).

32. Cotyle riparia) sincere. scene Sand Martin (also India and N,. America).
II. BririsH BirDS WHICH RANGE TO CENTRAL OR NORTH-EAST ASIA.
TBE ONS CRCUOILON Wce-2-ce cscs Great Grey Shrike.

2, MEUTOUS VOUS: vc so2 sas se one White’s Thrush (also to Japan).
oe er hy CLUMOUIGTOS we cucamn: Black-throated Thrush.

4. Acrocephalus nevius ...... Grasshopper Warbler.

5. Phylloscopus superciliosus Yellow-browed Warbler.

6. Certhia familiaris ......... Tree-creeper.

1. POrus C@ruleus: v.ccscicostes Blue Titmouse.

Bio msg MOET Best eaten ts cote Coal Titmouse.

2b spt LO LUSIMIGE N.S ec seae, Marsh Titmouse.

10. Acredula caudata ......... Long-tailed Titmouse.

11. Ampelis garrulus ......... Wax-wing.

12. Anthus richards ..........+ Richard’s Pipit.

13. Alauda alpestris............ Shore Lark (also N. America).

14, Plectrophanes nivalis ...... Snow-Bunting (also N. America),

15. lapponicus Lapland Bunting.

16. Emberiza rustica ..........5. Rustic Bunting (also China).

delle si hye DUSLLLON ac oaesmeer Little Bunting.

18: Lineta nari’. vitesse soe Mealy Redpole (also N. America).

19. Pyrrhula erythrina......... Scarlet Grosbeak (also N. India, China).

20. 35. CRNCLCALOM irene Pine Grosbeak (also N. America),

Zi Loma bifasciaigia naa: Two-barred Crossbill.

D2 L-OStOF TOSCUB stn cncabuicen a Rose-coloured Starling (also India).

23. COROUS CORAL” sass steno: Raven (also N. America).

DE ECG TUSEICC Gas antes tanec: Magpie.

25. Nucifraga caryocatactes Nutcracker.

TII. BririsH BIRDS RANGING INTO N. AFRICA AND W. ASIA.

LUGS MINOT, ce atecscen ces Lesser Grey Shrike.

2. » GUriCUlatUs” 2.00: Woodchat (also Tropical Africa).

3, Muscicapa grisola .....0...00 saat wore (also E. and §.

rica).

A, 1; atricapilla ......... Pied Flycatcher (also Central Africa).
5. Turdus viscivorus ........6.+ Mistletoe-Thrush (N. India in winter).
6. weltel LOT ULOD aise), stranen teat. Blackbird.

es Boye SOOTOUOIUS J a dchccncoees Ring Ouzel.

8. Accentor modularis ........ Hedge Sparrow.

9, Hrithacus rubecula..........4. Redbreast.
10. Daultas luscinia........ccese0 Nightingale.
11. Ruticilla phenicurus ......... Redstart.
112: fiice LYS tanita Black Redstart.
13. Saateola ribetra. vi ..cc-:cec eu Whinchat.
14. Aédon galactodes ............ Rufous Warbler.
15. Acrocephalus streperus ....+ Reed Warbler.
16. a scheenobenus... Sedge Warbler.

CHAP. III. ]

Oo de

17. Melizophilus undatus
18, Sylvia rufa
19. ,, salicaria
20, 4, atricapilla
21. 4, orphea
. Phylloscopus sibilatri«
23. rs trochilus
24. 55 collybita
. Regulus cristatus +..........5.
26. » tgnicapillus

. Troglodytes parvulus
. Sitta cesia

30. » flava
. Anthus pratensis
. Alauda arborea
. Calandrella brachydactyla...
. Emberiza miliaria
35. a cirlus
36. es
. Fringilla celebs
. Coccothraustes chloris.........
. Serinus hortulanas
WACORAMCLUS CLEGOTS. .ocvrececiaeee
. Linota cannabina
. Corvus moneduld.......cscscees
43. Chelidon urbica

COCO OHO ee reer eet ror voene

ooo eooeereroovee

ACHeroecee

COCCHOE SB eer esee crore

@eeereeenreseosoe

eer eee oreerseee

ooo FP eon rnevereced

Oe Oe

eoeF PP eoeeeee

ZOOLOGICAL REGIONS.

Dartford Warbler. _
Greater Whitethroat.
Garden Warbler.
Blackeap.

Orphean Warbler.
Wood Wren.

Willow Wren.
Chiffchaff.
Golden-crested Wren.
Fire-crested Wren.
Wren.

Nuthatch.

White Wagtail (also W. Africa).
Blue-headed Wagtail.
Meadow-Pipit.
Woodlark.

Short-toed Lark.
Common Bunting.
Cirl Bunting.
Ortolan.

Chaffinch.
Greenfinch.

Serin.

Goldfinch,

Linnet.

Jackdaw.

House- Martin.

IV. British BIRDS RANGING TO NortTH AFRICA.

EVA DOLGIS 2CLETING, .....seeerresesreeseenc Icterine Warbler.
2. Acrocephalus aquaticus........0......008 Aquatic Warbler,
3. VUSCINIOIAES...-00.000.0005 Savi’s Warbler. .
Me Motaciila WUgubriss...co..dsessiats.ceeaee Pied Wagtail.

Oe UTITNIG CULOPUD siscsrseeiveie-ocvsetles Bullfinch.

6. Garrulus glandarius .......0coreccecerees Jay.

Y. British BIRDS RANGING TO West ASIA ONLY.

Black-headed Bunting,

. Muscicapa parva......

. Panurus biarmicus

. Melanocorypha sibirica White-winged Lark,
. Euspiza melanocephala

. Linota flavirostris ...... Twite.

. Corvus frugilegus vr... Rook

VI. British BIRDS CONFINED TO EUROPE.

. Cinclus aquaticus

Parus cristatus
. Anthus obscurus
, Linota rufescens
. Loxia pityopsitiacus

oc eoeeessee*® PS OOo ee FO

. Accentor collaris .........s000s-

eorese 2 PP vee
Ce ee ee
SOC oeernereeseese OFF DOO000
ee etoeee~Ba

eee POereereee0

Dipper.

Alpine Accentor., '
Crested Titmouse.
Rock Pipit.
Lesser Redpoll.
Parrot Crossbill.

Red-breasted Flycatcher (to N. W. India).
Bearded Titmouse.

38 ISLAND LIFE. [parr 1.

We find, that out of a total of 118 British Passeres there are:
32 species which range to North Africa and Central or
Kast Asia. |
25 species which range to Central or East Asia, but not
to North Africa.
43 species which range to North Africa and Western Asia.
6 species which range to North Africa, but not at all into
Asia.
6 species which range to West Asia, but not to North Africa.
6 species which do not range out of Europe.

These figures agree essentially with those furnished by the
mammalia, and complete the demonstration that all the tem-
perate portions of Asia and North Africa must be added to Europe
to form a natural zoological division of the earth. We must also
note how comparatively few of these overpass the limits thus
indicated ; only seven species extending their range occasionally
into tropical or South Africa, eight into some parts of tropical
Asia, and six into arctic or temperate North America.

Range of Hast Asian Birds.—To complete the evidence we
only require to know that the East Asiatic birds are as much
like those of Europe, as we have already shown to be the case
when we take the point of departure from our end of the
continent: This does not follow necessarily, because it is
possible that a totally distinct North Asiatic fauna might there
prevail; and, although our birds go eastward to the remotest
parts of Asia, their birds might not come westward to Kurope. ~
The birds of Eastern Siberia have been carefully studied by
Russian naturalists and afford us the means of making the
required comparison. There are 151 species belonging to the
orders Passeres and Picariz (the perching and climbing birds),
and of these no less than 77, or more than half, are absolutely
identical with European species; 63 are peculiar to North
Asia, but all except five or six of these are allied to European
forms; the remaining 11 species are migrants from South-
eastern Asia. The resemblance is therefore equally close
whichever extremity of the Euro-Asiatic continent we take
as our starting point, and is equally remarkable in birds as in
mammalia. We have now only to determine the limits of this,

CHAP. I11.| ZOOLOGICAL REGIONS. 59

our first zoological region, which has been termed the “ Pale-
arctic” by Mr. Sclater, meaning the “northern old-world”
region—a name now well known to naturalists.

The Limits of the Palearctic Region.—The boundaries of this
region, as nearly as they can be ascertained, are shown on our
general map at the beginning of this chapter, but it will be
evident on consideration, that, except in a few places, its limits
can only be approximately defined. On the north, east, and
west it extends to the ocean, and includes a number of islands
whose peculiarities will be pointed out in a subsequent chapter; —
so that the southern boundary alone remains, but as this runs
across the entire continent from the Atlantic to the Pacific
ocean, often traversing little-known regions, we may perhaps
never be able to determine it accurately, even if it admits of
such determination. In drawing the boundary line across Africa
we meet with our first difficulty. The Euro-Asiatic animals
undoubtedly extend to the northern borders of the Sahara,
while those of tropical Africa come up to its southern margin,
the desert itself forming a kind of dry sea between them. Some
of the species on either side penetrate and even cross the
desert, but it is impossible to balance these with any accuracy,
and it has therefore been thought best, as a mere matier of
convenience, to consider the geographical line of the tropic of
Cancer to form the boundary. We are thus enabled to define
the Palearctic ‘region as including all north temperate Africa ;
and,.a similar intermingling of animal types occurring in Arabia,
the same boundary line is continued to the southern shore of
the Persian Gulf. Persia and Afghanistan undoubtedly belong
to the Palearctic region, and Baluchistan should probably go
with these. The boundary in the north-western part of India
is again difficult to determine, but it cannot be far one way or
the other from the river Indus as far up as Attock, opposite the
mouth of the Cabool river. Here it will bend to the south-east,
passing a little south of Cashmeer, and along the southern
slopes of the Himalayas into East Thibet and China, at heights
varying from 9,000 to 11,000 feet according to soil, aspect,
and shelter, It may, perhaps, be defined as extending to the
upper belt of forests as far as coniferous trees prevail; but

AQ) ISLAND LIFE. [PART 1.
the temperate and tropical faunas are here so intermingled that
to draw any exact parting line is impossible. The two faunas.
are, however, very distinct. In and above the pine woods there
are abundance of warblers of northern genera, with wrens,
numerous titmice, and a great variety of buntings, grosbeaks,
bullfinches, and rosefinches, all more or less nearly allied to the
birds of Europe and Northern Asia; while a little lower down
we meet with a host of peculiar birds allied to those of tropical
Asia and the Malay Islands, but often of distinct genera. There
can be no doubt, therefore, of the existence here of a pretty
sharp line of demarcation between the temperate and tropical
faunas, though this line will be so irregular, owing to the com-
plex system of valleys and ridges, that in our present ignorance of
much of the country it cannot be marked in detail on any map.
Further east in China it is still more difficult to determine
the limits of the region, owing to the great intermixture of
migrating birds; tropical forms passing northwards in summer
as far as the Amoor river, while the northern forms visit every
part of China in winter. From what we know, however, of the
distribution of some of the more typical northern and southern
species, we are able to fix the limits of the Palearctic region
a little south of Shanghae on the coast. Several tropical genera
come as far as Ningpo or even Shanghae, but rarely beyond;
while in Formosa and Amoy tropical forms predominate. Such
decidedly northern forms as bullfinches and hawfinches are found
at Shanghae; hence we may commence the boundary line on
the coast between Shanghae and Ningpo, but inland it probably
bends a little southward, and then northward to the mountains
and valleys of West China and East Thibet in about 32° N.
latitude; where, at Moupin, a French missionary, Pere David,
made extensive collections showing this district to be at the
junction of the tropical and temperate faunas. Japan, as a
whole, is decidedly Palearctic, although its extreme southern
portion, owing to its mild insular climate and evergreen vege-
tation, gives shelter to a number of tropical forms.
Characteristic features of the Palearctic Region —Having thus
demonstrated the unity of the Palearctic region by tracing out
the distribution of a large proportion of its mammalia and birds,

CHAP. 111. ] ZOOLOGICAL REGIONS. 41
it only remains to show how far it is characterised by peculiar
groups such as genera and families, and to say a few words on
the lower forms of life which prevail in it.
_ Taking first the mammalia, we find this region is distinguished
by its possession of the entire family of Talpide or moles,
consisting of eight genera and sixteen species, all of which are con-
fined to it except one which is found in North-west America, and -
two which extend to Assam and Formosa. Among carnivorous
animals the lvnxes (nine species) and the badgers (two species)
are peculiar to it in the old world, while in the new the lynxes
are found only in the colder regions of North America. It has
six peculiar genera (with seven species) of deer; seven peculiar
genera of Bovide, chiefly antelopes; while the entire group of
goats and sheep, comprising twenty-two species, is almost confined
to it, one species only occurring in the Rocky Mountains of North
America and another in the Neilgherries of Southern India.
Among the rodents there are nine genera, with twenty-seven
species wholly confined to it, while several others, as the voles,
the dormice, and the pikas, have only a few species elsewhere.
In birds there are a large number of peculiar genera of
which we need only mention a few of the more important, as
the grasshopper-warblers (Locustella) with seven species, the
Accentors with twelve species, and about a dozen other genera
of warblers, including the robins; the bearded titmouse and
several allied genera; the long-tailed titmice forming the genus
Acredula ; the magpies, choughs, and nutcrackers; a host of
finches, among which the bullfinches (Pyrrhula) and the buntings
(Emberiza) are the most important. The true pheasants
(Phasianus) are wholly Palearctic, except one species in For-
mosa, as are several genera of wading birds. Though the
reptiles of cold countries are few as compared with those of the
tropics, the Palearctic region in its warmer portions has a
considerable number, and among these are many which are
peculiar to it. Such are two genera of snakes, seven of lizards,
eight of frogs and toads, and eight of newts and salamanders;
while of fresh-water fishes there are about twenty peculiar
genera. Among insects we may mention the elegant Apollo
butterflies of the Alps as forming a peculiar genus (Parnassius),

42 ISLAND LIFE. [PART, 1.

only found elsewhere in the Rocky Mountains of North America,
while the beautiful genus Thais of the south of Europe and
Sericinus of North China are equally remarkable. Among
other msects we can only now refer to the great family of
Carabide, or predaceous ground-beetles, which are immensely
numerous in this region, there being about fifty peculiar genera ;
‘while the large and handsome genus Carabus, with its allies
Procerus and Procrustes, containing nearly 300 species, is almost
wholly confined to this region, and would alone serve to distin-
guish it zoologically from all other parts of the globe.

Having given so full an exposition of the facts which deter-
mine the extent and boundaries of the Palzarctic region, there
is less need of entering into much detail as regards the other
regions of the Hastern Hemisphere; their boundaries being
easily defined, while their forms of animal life are well marked
and strongly contrasted.

Definition and Characteristie Groups of the Ethiopian Region.
—The Ethiopian region consists of all tropical. and south
Africa, to which is appended the large island of Madagascar and
the Mascarene Islands to the east and north of it, though these
differ materially from the continent, and will have to be dis-
cussed in a séparate chapter. For the present, then, we will
take Africa south of the tropic of Cancer, and consider how
far its animals are distinct from those of the Palearctic region.

Taking first the mammalia, we find the following remarkable
animals at once separating it from the Paleearctic and every other
region. The gorilla and chimpanzee, the baboons, numerous
lemurs, the lion, the spotted hyena, the aard-wolf and hyena-
dog, zebras, the hippopotamus, giraffe, and more than seventy
peculiar antelopes. Here we have a wonderful collection of large
and peculiar quadrupeds, but the Ethiopian region is also charac-
terised by the absence of others which are not only abundant in
the Palzearctic region but in many tropical regions aswell. The
most remarkable of these deficiencies are the bears, the deer,
and wild oxen, all of which abound in the tropical parts of Asia
while bears and deer extend into both North and South America.
Besides the large and conspicuous animals mentioned above,

CHAP. III. | ZOOLOGICAL REGIONS. 43

Africa possesses a number of completely isolated groups; such
are the potamogale, a curious otter-like water-shrew, discovered
by Du Chaillu in West Africa, so distinct as to constitute a new
family, Potamogalide; the golden moles, also forming a peculiar
family, Chrysochloride ; as do the elephant-shrews, Macrosce-
lididee ; the singular aard-varks, or earth-pigs, forming a peculiar
family of Edentata, called Orycteropodide;+while there are
numerous peculiar genera of monkeys, swine, civets, and rodents.

Among birds the most conspicuous and remarkable are, the
great-billed vulture-crows (Corvultur), the long-tailed why-
dah finches (Vidua), the curious ox-peckers (Buphaga), the
splendid metallic starlings (Lamprocolius), the handsome plan-
tain-eaters (Musophaga), the ground-hornbills (Bucorvus), the
numerous guinea-fowls belonging to four distinct genera, the
serpent-eating secretary-bird (Serpentarius), the huge boat-
billed heron (Balzeniceps), and the true ostriches. Besides
these there are three quite peculiar African families, the
Musophagidee, or plantain-eaters, including the elegant crested
touracos; the curious little finch-like colies (Coliide), and the
Irrisoridee, insect-eating birds allied to the hoopoes, but with
glossy metallic plumage, and arboreal habits.

In reptiles, fishes, insects, and land-shells, Africa is very rich,
and possesses an Immense number of peculiar forms. These are
not sufficiently known to require notice in a work of this cha-
racter, but we may mention a few as mere illustrations; the
puff-adders, the most hideous of poisonous snakes; the chame-
leons, the most remarkable of lizards; the goliath-beetles, the
largest and handsomest of the Cetonidz ; and some of the
Achatinee, which are the largest of all known land-shells.

Defimtion and Characteristic Groups of the Oriental Region,
—The Oriental region comprises all Asia south of the Pale-
arctic limits, and along with this the Malay Islands as far as
the Philippines, Borneo, and Java. It was called the Indian
region by Mr. Sclater, but this term has been objected to
because the Indo-Chinese and Malayan districts are the rich-
est and most characteristic, while the peninsula of India is
the poorest portion of it. The name “Oriental” has therefore
been adopted in my work on Zhe Geographical Distribution of

44 ISLAND LIFE [PART 1.

Animals as preferable to either Malayan or Indo-Australian,
both of which have been proposed, but are objectionable, ag
being already in use in a different sense.

The great features of the Oriental region are, the lonz-armed
apes, the orang-utans, the tiger, the sun-bears and honey-
bears, the tapir, the chevrotains or mouse-deer, and the Indian
elephant. Its most conspicuous birds are the immense number
and variety of babbling-thrushes (Timaliide), its beautiful
little hill-tits (Liotrichide), its green bulbuls (Phyllornithide),
its many varieties of the crow-family, its beautiful gapers and
pittas adorned with the most delicate colours, its great variety
of hornbills, and its magnificent Phasianidz, comprising the
‘peacocks, argus-pheasants, fire-backed pheasants, and jungle-
fowl. Many of these are, it is true, absent from the peninsula
of Hindostan, but sufficient remain there to ally it with the
other parts of the region.

Among the remarkable but less conspicuous forms of mam-
malia which are peculiar to this region are, monkeys of the
genus Presbyter, extending to every part of it; lemurs of three
peculiar genera—Nycticebus and Loris (slow lemurs) and
Tarsius (spectre lemurs) ; the flying lemur (Galeopithecus), now
classed as a peculiar family of Insectivora and found only
in the Malay Islands; the family of the Tupaias, or squirrel-
shrews, curious little arboreal Insectivora somewhat resembling
squirrels; no less than twelve peculiar genera of the civet
family, three peculiar antelopes, five species of rhinoceros, and
the round-tailed flying squirrels forming the genus Pteromys.

Of the peculiar groups of birds we can only mention a few,
The curious little tailor-birds, of the genus Orthotomus, are
found over the whole region, and almost alone serve to charac-
terise it, as do the fine laughing-thrushes, forming the genus
Garrulax; while the beautiful grass-green fruit-thrushes (Phyl-
lornis), and the brilliant little minivets (Pericrocotus), are almost
equally universal. Woodpeckers are abundant, belonging to a
dozen peculiar genera; while gaudy barbets and strange forms
of cuckoos and hornbills are also to be met with everywhere.
Among game birds, the only genus that is universally distri-
buted, and which may be said to characterise the region, is

CHAP. III.] ZOOLOGICAL REGIONS. 45

Gallus, comprising the true jungle-fowl, one of which, Gallus
bankiva, is found from the Himalayas and Central India, to
Malacca, Java, and even eastward to Timor, and is the un-
doubted origin of almost all our domestic poultry. Southern
India and Ceylon each possess distinct species of jungle-fowl,
and a third very handsome green bird (Gallus eneus) inhabits
Java.

Reptiles are as abundant as in Africa, but they present no
well-known groups which can be considered as specially cha-
racteristic. Among insects we may notice the magnificent
golden and green Papilionidz of various genera as being un-
equalled in the world; while the great Atlas moth is probably
the most gigantic of Lepidoptera, being sometimes ten inches
across the wings, which are also very broad. Among the beetles
the strange flat-bodied Malayan mormolyce is the largest of all
the Carabide, while the catoxantha is equally a giant among
the Buprestide. On the whole, the insects of this region
probably surpass those of any other part of the world, except
South America, in size, variety, and beauty.

Defimtion and Characteristic Groups of the Australian
Region—The Australian region is so well marked off from
the Oriental, as well as from all other parts of the world, by
zoological peculiarities, that we need not take up much time in
describing it, especially as some of its component islands will
come under review at a subsequent stage of our work. Its
most important portions are Australia and New Guinea, but
it also includes all the Malayan and Pacific Islands to the
east of Borneo, Java, and Bali, the Oriental region termi-
nating with the submarine bank on which those islands are
situated. The island of Celebes is included in this region
from a balance of considerations, but it almost equally well
belongs to the Oriental, and must be left out of the account
in our general sketch of the zoological features of the Austra-
lian region.

The great feature of the Australian region is the almost total
absence of all the forms of mammalia which abound in the
rest of the world, their place being supplied by a great variety
of Marsupials. In Australia and New Guinea there are no

46 ISLAND LIFE. [PART I,

Insectivora, Carnivora, nor Ungulata, while even the rodents are
only represented by a few small rats and mice. In the Pacific
Islands mammals are altogether absent (except perhaps in New
Zealand), but in the Moluccas and other islands bordering on the
Oriental region the higher mammals are represented by a few
deer, civets, and pigs, though it is doubtful whether the two
former may not have been introduced by man, as was almost
certainly the case with the semi-domesticated dingo of Australia.
These peculiarities in the mammalia are so great that every
naturalist agrees that Australia must be made a separate region,
the only difference of opinion being as to its extent, some think-
ing that New Zealand should form another separate region ; but
this question need not now delay us.

In birds Australia is by no means so isolated from the rest of
the world, as it contains great numbers of warblers, thrushes,
flycatchers, shrikes, crows, and other familiar types of the Eastern
Hemisphere; yet a considerable number of the most character-
istic Oriental families are absent. Thus there are no vultures,
woodpeckers, pheasants, bulbuls, or barbets in the Australian
region; and the absence of these is almost as marked a, feature
as that of cats, deer, or monkeys, among mammalia. The most
conspicuous and characteristic birds of the Australian region are,
the piping crows; the honey-suckers (Meliphagide), a family
quite peculiar to the region ; the lyre-birds; the great terrestrial
kingfishers (Dacelo); the great goat-suckers called more-porks
in Australia and forming the genus Podargus; the wonderful
abundance of parrots, including such remarkable forms as the
white and the black cockatoos, and the gorgeously coloured brush-
tongued lories; the almost equal abundance of fine pigeons
more gaily coloured than any others on the globe; the strange
brush-turkeys and mound-builders, the only birds that never sit
upon their eggs, but allow them to be hatched, reptile-like, by
the heat of the sand or of fermenting vegetable matter; and
lastly, the emus and cassowaries, in which the wings are far
more rudimentary than in the ostriches of Africa and South
America. New Guinea and the surrounding islands are remark-
able for their tree-kangaroos, their birds-of-paradise, their raquet-
tailed kinefishers, their great crown-pigeons, their crimson lories,

CHAB ti, | ZOOLOGICAL REGIONS. 47

and many other remarkable birds. This brief outline being
sufficient to show the distinctness and isolation of the Australian
region, we will now pass to the consideration of the Western
Hemisphere.

Definition and Characteristic Groups of the Nearctic Region. —
The Nearctic region comprises all temperate and arctic North
America, including Greenland, the only doubt being as to its
southern boundary, many northern types penetrating into the
tropical zone by means of the highlands and volcanic peaks
of Mexico and Guatemala, while a few which are characteristic
of the tropics extend northward into Texas and California.
There is, however, considerable evidence showing that on the
east coast the Rio Grande del Norte, and on the west a point
nearly opposite Cape St. Lucas, form the most natural boundary ;
but instead of being drawn straight across, the line bends to
the south-east as soon as it rises on the flanks of the table-
land, forming a deep loop which extends some distance beyond
the city of Mexico, and perhaps ought to be continued along
the higher ridges of Guatemala.

The Nearctic region is so similar to the Palearctic in position
and climate, and the two so closely approach each other at
Behring Straits, that we cannot wonder at there being a certain
amount of similarity between them—a similarity which some
naturalists have so far over-estimated as to think that the two
regions ought to be united. Let us therefore carefully examine
the special zoological features of this region, and see how far it
resembles, and how far differs from, the Palzearctic.

At first sight the mammalia of North America do not seem
to differ much from those of Europe or Northern Asia. There
are cats, lynxes, wolves and foxes, weasels, bears, elk and
deer, voles, beavers, squirrels, marmots, and hares, all very
similar to those of the Hastern Hemisphere, and several hardly
distinguishable. Even the bison or “ buffalo” of the prairies, once
so abundant and characteristic, is a close ally of the now almost
extinct “aurochs” of Lithuania. Here, then, we undoubtedly
find a very close resemblance between the two regions, and if
this were all, we should have great difficulty in separating them.
But along with these, we find another set of mammals, not

48 ISLAND LIFE. [Pani a,

quite so conspicuous but nevertheless very important. We have
first, three peculiar genera of moles, one of which, the star-
nosed mole, is a most extraordinary creature, quite unlike
anything else. Then there are three genera of the weasel
family, including the well-known skunk (Mephitis), all quite
different from Eastern forms. Then we come to a peculiar
family of carnivora, the racoons, very distinct from anything in
Europe or Asia; and in the Rocky Mountains we find the
prong-horn antelope (Antilocapra) and the mountain goat of
the trappers (Aplocerus), both peculiar genera. Coming to
the rodents we find that the mice of America differ in some
dental peculiarities from those of the rest of the world, and
thus form several distinct genera; the jumping mouse (Xapus)
is a peculiar form of the jerboa family, and then we come to the
pouched rats (Geomyide) a very curious family consisting of
four genera and nineteen species, peculiar to North America,
though not confined to the Nearctic region. The prairie dogs
(Cynomys), the tree porcupine (Hrethizon), the curious sewellel
(Haploodon), and the opossum (Didelphys) complete the list of
peculiar mammalia which distinguish the northern region of
the new world from that of the old. We must add to these
peculiarities some remarkable deficiencies. The Nearctic region
has no hedgehogs, nor wild pigs, nor dormice, and only one wild
sheep in the Rocky Mountains as against twenty species of
sheep and goats in the Palearctic region.

In birds also the similarities to our own familiar songsters
first strike us, though the differences are perhaps really greater
than in the quadrupeds. We see thrushes and wrens, tits and
finches, and what seem to be warblers and flycatchers and
starlings in abundance; but a closer examination shows the
ornithologist that what he took for the latter are really quite
distinct, and that there is not a single true flycatcher of the
family Muscicapid, or a single starling of the family Sturnidee
in the whole continent, while there are very few true warblers
(Sylviidze), their place being taken by the very distinct families
Mniotiltidze or wood-warblers, and Vireonide or greenlets. In
like manner the flycatchers of America belong to the totally
distinct family of tyrant-birds, Tyrannide, and those that look

CHAP. IU. | ZOOLOGICAL REGIONS. 49

like starlings to the hang-nests, Icteridze; and these four
peculiar families comprise more than a hundred species, and
give a special character to the ornithology of the country.
Add to these such peculiar birds as the mocking thrushes
(Mimus), the blue jays (Cyanocitta), the tanagers, the peculiar
genera of cuckoos (Coccygus and Crotophaga), the humming-
birds, the wild turkeys (Meleagris), and the turkey-buzzards
(Cathartes), and we see that if there 1s any doubt as to the
mammals of North America being sufficiently distinct to justify
the creation of a separate region, the evidence of the birds
would alone settle the question.

The reptiles, and some others of the lower animals, add still
more to this weight of evidence. The true rattle-snakes
are highly characteristic, and among the lizards are several
genera of the peculiar American family the Iguanide. No-
where in the world are the tailed batrachians so largely
developed as in this region, the Sirens and the Amphiumide#
forming two peculiar families, while there are nine peculiar
genera of salamanders, and two others allied respectively to
the Proteus of Europe and the Sieboldia or giant salamander
of Japan. There are about twenty-nine peculiar genera of
fresh-water fishes; while the fresh-water molluscs are more
numerous than in any other region, more than thirteen hundred
species and varieties having been described.

Combining the evidence derived from all these classes of
animals, we find the Nearctic region to be exceedingly well
characterised, and to be amply distinct from the Palarctic.
The few species that are common to the two are almost all
arctic, or, at least, northern types, and may be compared with
those desert forms which occupy the debatable ground between
the Palearctic, Ethiopian, and Oriental regions. If, however,
we compare the number of species which are common to the
Nearctic and Palearctic regions with the number common
to the western and eastern extremities of the latter region,
we shall find a wonderful difference between the two cases ;
and if we further call to mind the number of important groups
characteristic of the one region but absent from the other, we
shall be obliged to admit that the relation that undoubtedly

50 ISLAND LIFE. | [PART I.

exists between the faunas of North America and Europe is
of a very distinct nature from that which connects together
Western Europe and North-eastern Asia in the bonds of
zoological unity.

Definition and Characteristic Groups of the Neotropical Region.
—The Neotropical region requires very little definition, since it
comprises the whole of America south of the Nearctic region,
with the addition of the Antilles or West Indian Islands. Its
zoological peculiarities are almost as marked as those of
Australia, which, however, it far exceeds in the extreme richness
and variety of all its forms of life. To show how distinct it is
from all the other regions of the globe, we need only enumerate
some of the best known and more conspicuous of the animal
forms which are peculiar to it. Such are, among mammalia—
the prehensile-tailed monkeys and the marmosets, the blood-
sucking bats, the coati-mundis, the peccaries, the llamas and
alpacas, the chinchillas, the agoutis, the sloths, the armadillos,
and the ant-eaters; a series of types more varied, and more
distinct from those of the rest of the world than any other con-
tinent can boast of. Among birds we have the charming sugar-
birds, forming the family Coerebide, the immense and wonder-
fully varied group of tanagers, the exquisite little manakins,
and the gorgeously-coloured chatterers ; the host of tree-creepers
of the family Dendrocolaptide, the wonderful toucans, the puff-
birds, jacamars, todies and motmots; the marvellous assemblage
of four hundred distinct kinds of humming-birds, the gorgeous
macaws, the curassows, the trumpeters, and the sun-bitterns.
Here again there is no other continent or region that can
produce such an assemblage of remarkable and perfectly distinct
groups of birds; and no less wonderful is its richness in species,
since these fully equal, if they do not surpass, those of the two
great tropical regions of the Eastern Hemisphere (the Ethiopian
and the Oriental) combined.

As an additional indication of the distinctness and isolation of
the Neotropical region from all others, and especially from the
whole Eastern Hemisphere, we must say something of the
otherwise widely distributed groups which are absent. Among
mammalia we have first the order Insectivora, entirely absent

CHAP. III. ] ZOOLOGICAL REGIONS. 51

from South America, though a few species are found in Central
America and the West Indies; the Viverride or civet family is
wholly wanting, as are every form of sheep, oxen, or antelopes .
while the swine, the elephants, and the rhinoceroses of the old
world are represented by the diminutive peccaries and tapirs.

Among birds we have to notice the absence of tits, true
flycatchers, shrikes, sun-birds, starlings, larks (except a solitary
species in the Andes), rollers, bee-eaters, and pheasants, while
warblers are very scarce, and the almost cosmopolitan wagtails
are represented by a single species of pipit.

We must also notice the preponderance of low or archaic
types among the animals of South America. Edentates,
marsupials, and rodents form the majority of the terrestrial
mammalia; while such higher groups as the carnivora and
hoofed animals are exceedingly deficient. Among birds a
low type of Passeres, characterised by the absence of the
singing muscles, is excessively prevalent, the enormous groups
of the ant-thrushes, tyrants, tree-creepers, manakins, and

chatterers belonging to it. The Picariz (a lower group) also
prevail to a far greater extent than in any other regions, both
in variety of forms and number of species; and the chief
representatives of the gallinaceous birds—the curassows and
tinamous, are believed to be allied, the former to the brush-
turkeys of Australia, the latter (very remotely) to the ostriches,
two of the least developed types of birds.

Whether, therefore, we consider its richness in peculiar forms
of animal life, its enormous variety of species, its numerous
deficiencies as compared with other parts of the world, or the
prevalence of a low type of organisation among its higher
animals, the Neotropical region stands out as undoubtedly the
most remarkable of the great zoological divisions of the earth.

In reptiles, amphibia, fresh-water fishes, and insects, this
region is equally peculiar, but we need not refer to these here,
our only object now being to establish by a sufficient number
of well-known and easily remembered examples, the distinctness
of each region from all others, and its unity as a whole. The
former has now been sufficiently demonstrated, but it may be

well to say a few words as to the latter point.
E 2

52 ISLAND LIFE. [PART 1.

The only outlying portions of the region about which there
can be any doubt are—Central America, or that part of the
region north of the Isthmus of Panama, the Antilles or West
Indian Islands, and the temperate portion of South America
including Chili and Patagonia.

In Central America, and especially in Mexico, we have an
intermixture of South American and North American animals,
but the former undoubtedly predominate, and a large proportion
of the peculiar Neotropical groups extend as far as Costa Rica.
Kven in Guatemala and Mexico we have howling and _spider-
monkeys, coati-mundis, tapirs, and armadillos ; while chatterers,
manakins, ant-thrushes, and other peculiarly Neotropical groups
of birds are abundant. There is therefore no doubt as to Mexico
forming part of this region, although it is comparatively poor,
and exhibits the intermingling of temperate and tropical forms.

The West Indies are less clearly Neotropical, their poverty
in mammals as well as in most other groups being extreme,
while great numbers of North American birds migrate there
in winter. The resident birds, however, comprise trogons,
sugar-birds, chatterers, with many humming-birds and parrots,
representing eighteen peculiar Neotropical genera; a fact which
decides the region to which the islands belong.

South temperate America is also very poor as compared with
the tropical parts of the region, and its insects contain a con-
siderable proportion of north-temperate forms. But it contains
armadillos, cavies and opossums; and its birds are all of
American groups, though, owing to the inferior climate and
deficiency of forests, a number of the families of birds peculiar
to tropical America are wanting. Thus there are no manakins,
chatterers, toucans, trogons, or motmots; but there are abun-
dance of hang-nests, tyrant-birds, ant-thrushes, tree-creepers,
and a fair proportion of humming-birds, tanagers and parrots.
The zoology is therefore thoroughly Neotropical, although
somewhat poor; and it hasa number of peculiar forms—as the
chinchillas, alpacas, &c., which are not found in the tropical
regions except in the high Andes.

Comparison of Zoological Regions with the Geographical
Divisions of the Globe—Having now completed our survey

CHAP, 111, ] ZOOLOGICAL REGIONS, A3

of the great zoological regions of the globe, we find that they
do not differ so much from the old geographical divisions as our
first example might have led us to suppose. Europe, Asia,
Africa, Australia, North America, and South America, really
correspond, each to a zoological region, but their boundaries
require to be modified more or less considerably; and if we
remember this, and keep their extensions or limitations always
in our mind, we may use the terms “South American” or
‘North American,” as being equivalent to Neotropical and
Nearctic, without much inconvenience, while ‘“ African” and
‘Australian ’’ equally well serve to express the zoological type
of the Ethiopian and Australian regions. Europe and Asia
require more important modifications. The European fauna
does indeed well represent the Palearctic in all its main
features, and if instead of Asia we say tropical Asia we have the
Oriental region very fairly defined ; so that the relation of the
geographical and the zoological primary divisions of the earth is
sufficiently clear. In order to make these relations visible to
the eye and more easily remembered, we will put them into
a tabular form:

Regions. Geographical Equivalent,
Palearctic..... EUROPE, with north temperate Africa and Asia.
Ethiopian...... AFRICA (south of the Sahara) with Madagascar.
Oriental......... Tropica AstA, to Philippines and Java.
Australian..,.. AUSTRALIA, with Pacific Islands, Moluccas, &c.
Nearctic. ...... Norru America, to North Mexico.

Neotropical... SourH AMERICA, with tropical N. America and W. Iniies.

The following arrangement of the regions will indicate their
geographical position, and to a considerable extent their relation
to each other.

Nero Ashe Cet 1. C-—— Ae) AR Oat 1. co

ORIENTAL
ETHIOPIAN
NEO-
TROPICAL AUSTRALIAN

CHAPTER IV.

EVOLUTION 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
schceniclus—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,

In the preceding chapters we have explained the general nature
of the phenomena presented by the distribution of animals, and
have illustrated and defined the new geographical division of the
earth which is found best to agree with them. Before we go
further into the details of our subject, and especially before we
attempt to trace the causes which have brought about the exist-
ing biological relations of the islands of the globe, it is absolutely
necessary to have a clear comprehension of the collateral facts
and general principles to which we shall most frequently have
occasion to refer. These may be briefly defined as, the powers
of dispersal of animals and plants under different conditions—
geological and climatal changes—and the origin and develop-
ment of species and groups by natural selection. This last is of
the most fundamental importance, and its bearing on the dispersal
of animals has been much neglected. We therefore devote the
present chapter to its consideration.

As we have already shown in our first chapter that the distri-
bution of species, of genera, and of families, present almost

cHaP. Iv.] EVOLUTION THE KEY TO DISTRIBUTION. 55

exactly the same general phenomena in varying degrees of
complexity, and that almost all the interesting problems we
have to deal with depend upon the mode of dispersal of one
or other of these; and as, further, our knowledge of most of
these groups, in the higher animals at least, is confined to the
tertiary period of geology, it is therefore unnecessary for us to
enter into any questions involving the origin of more compre-
hensive groups, such as classes or orders. This enables us to
avoid most of the disputed questions as to the development of
animals, and to confine ourselves to those general principles
regulating the origin and development of species and genera
which were first laid down by Mr. Darwin twenty years ago,
and have now come to be adopted by naturalists as established
propositions in the theory of evolution.

The Origin of New Species.—How, then, do new species arise,
supposing the world to have been, physically, much as we now
see it; and what becomes of them after they have arisen? In
the first place we must remember that new species can only be
formed when and where there is room for them. If a continent
is fully stocked with animals, each species being so well adapted
for its mode of life that it can overcome all the dangers to
which it is exposed, and maintain on the average a tolerably
uniform population, then, so long as no change takes place, no
new species will arise. For every place or station is supposed
to be filled by creatures perfectly adapted to all surrounding
conditions, able to defend themselves from all enemies, and to
obtain food notwithstanding the rivalry of many competitors.
But such a perfect balance of organisms nowhere exists upon
the earth, and probably never has existed. The well-known
fact that some species are very common, while others are very
rare, is an almost certain proof that the one is better adapted
to its position than the other; and this belief is strengthened
when we find the individuals of one species ranging into
different climates, subsisting on different food, and competing
with different sets of animals, while the individuals of another
species will be limited to a small area beyond which they
seem unable to extend. When a change occurs, either of
climate or geography, some of the small and ill-adapted species

56 ISLAND LIFE. [PART “I,

will probably die out altogether, and thus leave room for others
to increase, or for new forms to occupy their places.

But the change will most likely affect even flourishing species
in different ways, some beneficially, others injuriously. Or,
again, it may affect a great many injuriously, to such an
extent as to require some change in their structure or habits
to enable them to get on as well as before. Now “variation”
and the “struggle for existence” come into play. All the
weaker and less perfectly organised individuals die out, while
those which vary in such a way as to bring them into more
harmony with the new conditions constantly survive. If the
change of conditions has been considerable, then, after a few
centuries, or perhaps even a few generations, one or more new
species will be almost sure to be formed.

Variation in Anvmals—To make this more intelligible to
those who have not considered the subject, and to obviate the
difficulty many feel about “ favourable variations occurring at
the right time,” it will be well to discuss this matter a little
more fully. Few persons consider how largely and universally
all animals are varying. We know, however, that in every
generation, if we could examine all the individuals of any
common species, we should find considerable differences, not
only in size and colour, but in the form and proportions of all
the parts and organs of the body. In our domesticated animals
we know this to be the case, and it is by means of the continual
selection of such slight varieties to breed from that all our ex-
tremely different domestic breeds have been produced. Think
of the difference in every limb, and every bone and muscle, and
probably in every part, internal and external of the whole body,
between a greyhound and a bull-dog! Yet, if we had the whole
series of ancestors of these two breeds before us, we should pro-
bably find that in no one generation was there a greater differ-
ence than now occurs in the same breed, or sometimes even the
same litter. It is often thought, however, that wild species do
not vary sufficiently to bring about any such change as this in
the same time; and though naturalists are we!l aware that this
is a mistake, it is only recently that they are able to adduce
positive proof of their opinion. -

cHaP, Iv.]}] EVOLUTION THE KEY TO DISTRIBUTION. 57

The Amount of Variation in North American Birds.—An
American naturalist, Mr. J. A. Allen, has made elaborate
observations and measurements of the birds of the United
States, and he finds a wonderful and altogether unsuspected
amount of variation between individuals of the same species.
They differ in the general tint, and in the markings and distri-
bution of the colours; in size and proportions ; in the length of
the wings, tail, bill, and feet ; in the length of particular feathers,
altering the shape of the wing or tail; in the length of the tarsi
and of the separate toes, and in the length, width, thickness, and
curvature of the bill. These variations are very considerable,
often reaching to one-sixth or one-seventh of the average
dimensions, and sometimes more. Thus TZurdus fuscescens
(Wilson’s thrush) varied in length of wing from 3°58 to 4°16
inches, and in the tail from 3°55 to 4°00 inches ; and in twelve
specimens, all taken in the same locality, the wing varied in length
from 14°5 to 21 per cent., and the tail from 14 to 22°5 per cent.
In Sialia sialis (the blue-bird) the middle toe varied from ‘77 to
‘91 inch, and the hind toe from ‘58 to ‘72 inch, or more than
21°5 per cent. on the mean, while the bill varied from °45 to
‘56 inch in length, and from ‘30 to °38 inch in width, or about
20 per cent. in both cases. In Dendreca coronata (the yellow-
crowned warbler) the quills vary in proportionate length, so that
the 1st, the 2nd, the 3rd, or the 4th, is sometimes longest, and
a similar variation of the wing involving a change of proportion
between two or more of the feathers is recorded in eleven species
of birds. Colour and marking vary to an equal extent; the
dark streaks on the under surface of Melospiza melodia (the
American song-sparrow) being sometimes reduced to narrow
lines, while in other specimens they are so enlarged as to cover
the greater part of the breast and sides of the body, sometimes
uniting on the middle of the breast into a nearly continuous
patch. In one of the small spotted wood-thrushes, Zwurdus
Juscescens, the colours are sometimes very pale, and the mark-
ings on the breast reduced to indistinct narrow lines, while in
other specimens the general colour is much darker, and the
breast markings dark, broad, and triangular. All the variations
here mentioned occur between adult males, so that there is no

58 ISLAND LIFE. [PART, I,

question of differences of age or sex, and the pair last referred to
were taken at the same place and on the same day.!

These interesting facts entirely support the belief in the
variability of all animals in all their parts and organs, to an ex-
tent amply sufficient for natural selection to work with. We may,
indeed, admit that these are extreme cases, and that the majority
of species do not vary half or a quarter so much as shown in the
examples quoted, and we shall still have ample variation for all
purposes of specific modification. Instead of an extreme varia-
tion in the dimensions and proportions of the various organs of
from 10 to 25 per cent. as is here proved to occur, we may as-
sume from 3 to 6 percent. as generally occurring in the majority
of species; and if we further remember that the above excessive
variations were found by comparimg a number of specimens of
each species, varying from 50 to 150 only, we may be sure that
the smaller variations we require must occur in considerable
numbers among the thousands or millions of individuals of
which all but the very rare species consist. If, therefore, we
were to divide the population of any species into three groups
of equal extent, with regard to any particular character—as
length of wing, or of toes, or thickness or curvature of bill, or
strength of markings—we should have one group in which the
mean or average character prevailed with little variation, one in
which the character was greatly, and one in which it was little,
developed. If we formed our groups, not by equal numbers,
but by equal amount of variation, we should probably find, in
accordance with the law of averages, that the central group in
which the mean characteristics prevailed was much more nume-
rous than the extremes, perhaps twice, or even three times, as
great as either of them, and forming such a series as the follow-
ing—1l10 maximum, 30 mean, 10 minimum development. In
ordinary cases we have no reason to believe that the mean cha-
racters or the amount of variation of a species changes materially
from year to year or from century to century, and we may there-

1 These facts are taken from a memoir on The Mammals and Winter
Birds of Florida, by J. A. Allen; forming Vol. II., No. 3, of the Bulletin
of the Museum of pean Vodleny at Bare College, ine ae
Massachusetts.

cHaAP. Iv.] EVOLUTION THE KEY TO DISTRIBUTION. 59

fore look upon the central group as the type of the species which
is best adapted to the conditions in which it has actually to
exist. This type will therefore always form the majority, be-
cause the struggle for existence will lead to the continual
suppression of the less perfectly adapted extremes. But some-
times a species has a wide range into countries which differ in
physical conditions, and then it often happens that one or other
of the extremes will predominate in a portion of its range.
These form local varieties, but as they occur mixed with the
other forms, they are not considered to be distinct species,
although they may differ from the other extreme form quite as
much as species often do from each other.

How new Species arise from a variable Species.—It is now
very easy to understand how, from such a variable species, one
or more new species may arise. The peculiar physical or organic
conditions that render one part of the area better adapted to an
extreme form may become intensified, and the most extreme
variations thus having the advantage, they will multiply at. the
expense of the rest. If the change of conditions spreads over
the whole area occupied by the species, this one extreme form
will replace the others; while if the area should be cut in two
by subsidence or elevation, the conditions of the two parts may
be modified in opposite directions, so as to be each adapted to
one extreme form; in which case the original type will become
extinct, being replaced by two species, each formed by a com-
bination of certain extreme characters which had before existed
in some of its varieties.

The changes of conditions which lead to such selection of
varieties are very diverse in nature, and new species may thus
be formed, diverging in many ways from the original stock.
The climate may change from moist to dry, or the reverse, or
the temperature may increase or diminish for long periods, in
either case requiring a corresponding change of constitution,
of covering, of vegetable or of insect food, to be met by the
selection of variations of colour or of swiftness, of length of
bill or of strength of claws. Again, competitors or enemies
may arrive from other regions, giving the advantage to such
varieties as can change their food, or by swifter flight or

60 ISLAND LIFE. [PART 1.

greater wariness can escape their new foes. We may thus easily
understand how a series of changes may occur at distant inter-
vals, each leading to the selection and preservation of a special
set of variations, and thus what was a single species may become
transformed into a group of allied species differing from each
other in a variety of ways, just as we find them in nature.

Among these species, however, there will be some which will
have become adapted to very local or special conditions, and
will therefore be comparatively few in number and confined
to a limited area; while others, retaining the more general
characters of the parent form, but with some important change
of structure, will be better adapted to succeed in the struggle
for existence with other animals, will spread over a wider area,
and increase so as to become common species. Sometimes these
will acquire such a perfection of organisation by successive
favourable modifications that they will be able to spread greatly
beyond the range of the parent form. They then become what
are termed dominant species, maintaining themselves in vigour
and abundance over very wide areas, displacing other species
with which they come into competition, and, under still further
changes of conditions, becoming the parents of a new set of
diverging species.

Definition and Origin of Genera—As some of the most
important and interesting phenomena of distribution relate to
genera rather than to single species, it will be well here to
explain what is meant by a genus, and how genera are supposed
to arise,

A genus is a group of allied species which differs from all
other groups in some well marked characters, usually of a
structural rather than a superficial nature. Species of one
genus usually differ from each other in size, in colour or
marking, in the proportions of the limbs or other organs, and
in the form and size of such superficial appendages as horns,
crests, manes, &c.; but they generally agree in the form and
structure of important organs, as the teeth, the bill, the feet,
and the wings. When two groups of species differ from each
other constantly in one or more of these latter particulars they
are said to belong to different genera. We have already seen

cuap. 1v.] EVOLUTION THE KEY TO DISTRIBUTION. 61

that species vary in these more important as well as in the
more superficial characters. If, then, in any part of the area
occupied by a species some change of habits becomes useful
to it, all such structural variations as facilitate the change will
be accumulated by natural selection, and when they have be-
come fixed in the proportions most beneficial to the animal, we
shall have the first species of a new genus.

A creature which has been thus modified in important
characters will be a new type, specially adapted to fill its
place in the economy of nature. It will almost certainly
have arisen from an extensive or dominant group, because
only such are sufficiently rich in individuals to afford an ample
supply of the necessary variations, and it will inherit the
vigour of constitution and adaptability to a wide range of
conditions which gave success to its ancestors. It will there-
fore have every chance in its favour in the struggle for existence ;
it may spread widely and displace many of its nearest allies,
and in doing so will itself become modified superficially and
become the parent of a number of subordinate species. It
will now have become a dominant genus, occupying an entire
continent, or perhaps even two or more continents, spreading in
every direction till it comes in contact with competing forms
better adapted to the different environments. Such a genus
may continue to exist during long geological epochs; but the
time will generally come when either physical changes, or
competing forms, or new enemies are too much for it, and it
begins to lose its supremacy. First one then another of its
component species will dwindle away and become extinct, till
at last only a few species remain. Sometimes these soon follow
the others and the whole genus dies out, as thousands of genera
have died out during the long course of the earth’s life-history ;
but it will also sometimes happen that a few species will
continue to maintain themselves in areas where they are removed
from the influences that exterminated their fellows.

Cause of the Extinction of Species—There is good reason to
believe that the most effective agent in the extinction of species
is the pressure of other species, whether as enemies or merely
as competitors. If therefore any portion of the earth is cut off

62 ISLAND LIFE. [parr 1.

from the influx of new or more highly organised animals, we may
there expect to find the remains of groups which have elsewhere
become extinct. In islands which have been long separated
from their parent continents these conditions are exactly fulfilled,
and it is in such that we find the most striking examples of the
preservation of fragments of primeval groups of animals, often
widely separated from each other, owing to their having been
preserved at remote portions of the area of the once widespread —
parental group. There are many other ways in which portions
of dying out groups may be saved. Nocturnal or subterranean
modes of life may save a species from enemies or competitors,
and many of the ancient types still existing have such habits.
The dense gloom of equatorial forests also affords means of
concealment and protection, and we sometimes find in such
localities a few remnants of low types in the midst of a general
assemblage of higher forms. Some of the most ancient types
now living inhabit: caves, like the Proteus, or bury themselves
in mud like the Lepidosiren, or in sand like the Amphioxus,
the last being the most ancient of all vertebrates; while the
Galeopithecus and Tarsius of the Malay islands and the potto
of West Africa, survive amid the higher mammalia of the
Asiatic and African continents owing to their nocturnal habits
and concealment in the densest forests.

The Rise and Decay of Species and Genera.—The preceding
sketch of the mode in which species and genera have arisen,
have come to maturity, and then decay, leads us to some very
important conclusions as to the mode of distribution of animals.
When a species or a genus is increasing and spreading, it
necessarily occupies a continuous area which gets larger and
larger till it reaches a maximum ; and we accordingly find that
almost all extensive groups are thus continuous. When decay
commences, and the group, ceasing to be in harmony with its
environment, is encroached upon by other forms, the continuity
may frequently be broken. Sometimes the outlying species
may be the first to become extinct, and the group may simply
diminish in area while keeping a compact central mass; but
more often the process of extinction will be very irregular, and
may even divide the group into two or more disconnected

CHAP, Iv.| EVOLUTION THE KEY TO DISTRIBUTION. 63

portions. This is the more likely to be the case because the
most recently formed species, probably adapted to local condi-
tions and therefore most removed from the general type of the
group, will have the best chance of surviving, and these may
exist at several isolated points of the area once occupied by the
whole group. We may thus understand how the phenomena
of discontinuous areas has come about, and we may be sure
that when allied species or varieties of the same species
are found widely separated from each other, they were once
connected by intervening forms or by each extending till it
overlapped the other’s area.

Discontinuous Specific Areas, why rare.—But although dis-
continuous generic areas, or the separation from each other of
species whose ancestors must once have occupied conterminous
or overlapping areas, is of frequent occurrence, yet undoubted
cases of discontinuous specific areas are very rare, except, as
already stated, when one portion of a species inhabits an island.
A few examples among mammalia have been referred to in our
first chapter, but it may be said that these are examples of
the very common phenomenon of a species being only found in
the station for which its organisation adapts it; so that forest
or marsh or mountain animals are of course only found where
there are forests, marshes, or mountains. This may be true,
and when the separate forests or mountains inhabited by the
same species are not far apart there is little that needs explana-
tion; but in one of the cases referred to there was a gap of a
thousand miles between two of the areas occupied by the species,
and this being too far for the animal to traverse through an
uncongenial territory, we are forced to the conclusion that it
must at some former period and under different conditions have
occupied a considerable portion of the intervening area.

Among birds such cases of specific discontinuity are very rare
and hardly ever quite satisfactory. This may be owing to birds
being more rapidly influenced by changed conditions, so that
when a species is divided the two portions almost always become
modified into varieties or distinct species; while another reason
may be that their powers of flight cause them to occupy on the
average wider and less precisely defined areas than do the species

64 ISLAND LIFE. [PART I.

of mammalia. It will be interesting therefore to examine the
few cases on record, as we shall thereby obtain additional know-
ledge of the steps and processes by which the distribution of
varieties and species has been brought about.

Discontinuaty of the Area of Parus palustris.—Mr. Seebohm,
who has travelled and collected in Europe, Siberia, and India,
and possesses extensive and accurate knowledge of Palearctic
birds, has recently called attention to the varieties and sub-
species of the marsh tit (Parus palustris), of which he has ex-
amined numerous specimens ranging from England to Japan.
The curious point is that those of Southern Europe and of
China are exactly alike, while all over Siberia a very distinct
form occurs, the sub-species P. borealis. In Japan and Kam-
schatka other varieties are found, which have been named
respectively P. japonicus and P. camschatkensis. Now it all
depends upon these forms being classed as sub-species or as
true species whether this is or is not a case of discontinuous
specific distribution. If Parus borealis is a distinct species from
Parus palustris, as it is reckoned in Gray’s Hand List of Birds,
and also in Sharpe and Dresser’s Birds of Europe, then Parus
palustris has a most remarkable discontinuous distribution, as
shown in the accompanying map, one portion of its area com-
prising Central and South Europe and Asia Minor, the other
an undefined tract in Northern China, the two portions being
thus situated in about the same latitude and having a very
similar climate, but with a distance of about 4,000 mules be-
tween them. If, however, these two forms are reckoned as
sub-species only, then the area of the species becomes con-
tinuous, while only one of its varieties or sub-species has a
discontinuous area. It is a curious fact that P. palustris and
P. borealis are found together in Southern Scandinavia and in
some parts of Central Europe, and are said to differ somewhat
in their note and their habits, as well as in colouration.

Discontinuity of Emberiza schwniclus.—The other case is that
of our reed bunting (Hmberiza schwniclus), which ranges over
almost all Europe and Western Asia as far as the Yenesai valley
and North-west India. It is then replaced by another smaller

1 See Ibis, 1879, p. 32.

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CHAP. IV.] EVOLUTION THE KEY TO DISTRIBUTION. 65

species, L. passerina, which ranges eastwards to the Lena river,
and in winter as far south as Amoy in China; but in Japan
the original species appears again, receiving a new name (£.
pyrrhulina), but Mr. Seebohm assures us that it is quite
indistinguishable from the European bird.1 Although the
distance between these two portions of the species is not so
great as in the last example, being about 2,000 miles, in other
respects the case is a most satisfactory one, because the forms
which occupy the intervening space are recognised by Mr.
Seebohm himself as undoubted species.

The European and Japanese Jays.—Another case somewhat
resembling that of the marsh tit is afforded by the HKuropean
and Japanese jays (Garrulus glandarwus and G. japonicus). Our
common jay inhabits the whole of Europe except the extreme
north, but is not known to extend anywhere into Asia, where
it is represented by several quite distinct species. (See Map,
Frontispiece.) But the great central island of Japan is in-
habited by a jay (G. japonicus) which is very like ours, and was
formerly classed as a sub-species only, in which case our jay
would be considered to have a discontinuous distribution. But
the specific distinctness of the Japanese bird is now universally
admitted, and it is certainly a very remarkable fact that among
the twelve species of jays which together range over all temperate
Europe and Asia, one which is so closely allied to our English
bird should be found at the remotest possible point from it.
Looking at the map exhibiting the distribution of the several
species, we can hardly avoid the conclusion that a bird very like
our jay once occupied the whole area of the genus, that in
various parts of Asia it became gradually modified into a variety
of distinct species in the manner already explained, a remnant
of the original type being preserved almost unchanged in
Japan, owing probably to favourable conditions of climate and
protection from competing forms.

Supposed Examples of Discontinuity among North American
Lirds—In North America the eastern and western provinces
are so different in climate and vegetation, and are besides
separated by such remarkable physical barriers—the arid

1 Ibis, 1879, p. 40.

66 | ISLAND LIFE. [parr 1.

central plains and the vast ranges of the Rocky Mountains and
Sierra Nevada, that we can hardly expect to find species whose
areas may be divided maintaining their identity. Towards the
north however the above-named barriers disappear, the forests
being almost continuous from east to west, while the mountain
range 1s broken up by passes and valleys. It thus happens
that most species of birds which inhabit both the eastern and
western coasts of the North American continent have main-
tained their continuity towards the north, while even when
differentiated into two or more allied species their areas are
often conterminous or overlapping.

Almost the only bird that seems to have a really discon-
tinuous range is the species of wren, Thryothorus bewickuw, of
which the type form ranges from the east coast to Kansas and
Minnesota, while a longer-billed variety is found in the wooded
parts of California and as far north as Puget Sound. If this
really represents the range of the species there remains a gap
of about 1,000 miles between its two disconnected areas. Other
cases are those of the greenlet, Vireosylvia gilvus, of the Hastern
States, and its variety, V. swainsonw, of the Western; and of
the purple red-finch, Carpodacus purpureus, with its variety C.
californicus ; but unfortunately the exact limits of these varieties
are in neither case known, and though each one is characteristic
of its own province, it is possible they may somewhere become
conterminous, though in the case of the red-finches this does
not seem likely to be the fact.

In a later chapter we shall have to point out some remark-
able cases of this kind where one portion of the species inhabits
an island ; but the facts now given are sufficient to prove that
the discontinuity of the area occupied by a single homogeneous
species, by two varieties of a species, by two well-marked sub-
species, and by two closely allied but distinct species, are all
different phases of one phenomenon—the decay of ill-adapted,
and their replacement by better-adapted forms, under the
pressure of a change of conditions either physical or organic.
We may now proceed with our sketch of the mode of distribution
of higher groups. |

Distribution and Antiquity of Familicsi—Just as genera are

cHApr, Iv.]| EVOLUTION THE KEY TO DISTRIBUTION. 67

groups of allied species distinguished from all other groups by
some well-marked structural characters, so famdlies are groups
of allied genera distinguished by more marked and more im-
portant characters, which are generally accompanied by a pecu-
liar outward form and style of colouration, and by distinctive
habits and mode of life. As a genus is usually more ancient
than any of the species of which it is composed, because during
its growth and development the original rudimentary species
becomes supplanted by more and more perfectly adapted forms,
so a family is usually older than its component genera, and
during the long period of its life-history may have survived
many and great terrestrial and organic changes. Many families
of the higher animals have now an almost world-wide extension,
or at least range over several continents; and it seems probable
that all families which have survived long enough to develop a
considerable variety of generic and specific forms have also at
one time or other occupied an extensive area.

Miscontinuity a proof of Antiquity—Discontinuity will there-
fore be an indication of antiquity, and the more widely the
fragments are scattered the more ancient we may usually pre-
sume the parent group to be. A striking example is furnished
by the strange reptilian fishes forming the order or sub-order
Dipnoi, which includes the Lepidosiren and its allies, Only
three or four living species are known, and these inhabit tropical
rivers situated in the remotest continents. The Lepidosiren
paradoxa is only known from the Amazon and some other South
American rivers. An allied species, Lepidosiren annectens, some-
times placed in a distinct genus, inhabits the Gambia in West
Africa, while the recent discovery in Eastern Australia of the
Ceratodus or mud-fish of Queensland, adds another form to the
same isolated group. Numerous fossil teeth, long known from
the Triassic beds of this country, and also found in Germany
and India in beds of the same age, agree so closely with those
of the living Ceratodus that both are referred to the same genus.
No more recent traces of any such animal have been discovered,
but the Carboniferous Ctenodus and the Devonian Dipterus
evidently belong to the same group, while in North America
the Devonian rocks have yielded a gigantic allied form which

F-2

68 ISLAND LIFE. [PART I,

has been named Heliodus by Professor Newberry. Thus an
enormous range in time is accompanied by a very wide and
scattered distribution of the existing species.

Whenever, therefore, we find two or more living genera be-
longing to the same family or order but not very closely allied
to each other, we may be sure that they are the remnants of a
once extensive group of genera; and if we find them now
isolated in remote parts of the globe, the natural inference is
that the family of which they are fragments once had an area
embracing the countries in which they are found. Yet this
simple and very obvious explanation has rarely been adopted
by naturalists, who have instead imagined changes of land and
sea to afford a direct passage from the one fragment to the
other. If there were no cosmopolitan or very wide-spread
families still existing, or even if such cases were rare, there
would be some justification for such a proceeding; but as about
one-fourth of the existing families of land mammalia have a
range extending to at least three or four continents, while many
which are now represented by disconnected genera are known
to have occupied intervening lands or to have had an almost
continuous distribution in tertiary times, all the presumptions
are in favour of the former continuity of the group. We have
also in many cases direct evidence that this former continuity
was effected by means of existing continents, while in no single
case has it been shown that such a continuity was impossible,
and that it either was or must have been effected by means of
continents now sunk beneath the ocean.

Concluding Remarks.—When writing on the subject of dis-
tribution it usually seems to have been forgotten that the
theory of evolution absolutely necessitates the former existence
of a whole series of extinct genera filling up the gap between
the isolated genera which in many cases now alone exist; while
it is almost an axiom of “natural selection”’ that such nume-
rous forms of one type could only have been developed in a
wide area and under varied conditions, implying a great lapse
of time. In our succeeding chapters we shall show that the
known and probable changes of sea and land, the known
changes of climate, and the actual powers of dispersal of the

cHap.Iv.}] EVOLUTION THE KEY TO DISTRIBUTION. 69

different groups of animals, were such as would have enabled
all the now disconnected groups to have once formed parts of a
continuous series. Proofs of such former continuity are con-
tinually being obtained by the discovery of allied extinct forms
in intervening lands, but the extreme imperfection of the
geological record as regards land animals renders it unlikely
that this proof will be forthcoming in the majority of cases.
The notion that if such animals ever existed their remains
would certainly be found, is a superstition which, notwith-
standing the efforts of Lyell and Darwin, still largely prevails
among naturalists; but until it is got rid of no true notions of
the former distribution of life upon the earth can be attained.

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 affecting their distribution.

In order to understand the many curious anomalies we meet
with in studying the distribution of animals and plants, and to
be able to explain how it is that some species and genera have
been able to spread widely over the globe, while others are con-
fined to one hemisphere, to one continent, or even to a single
mountain or a single island, we must make some inquiry into
the different powers of dispersal of animals and plants, into the
nature of the barriers that limit their migrations, and into the
character of the geological or climatal changes which have
favoured or checked such migrations.

The first portion of the subject—that which relates to the
various modes by which organisms can pass over wide areas of
sea and land—has been fully treated by Sir Charles Lyell, by
Mr. Darwin, and many other writers, and it will only be
necessary here to give a very brief notice of the best known
facts on the subject, which will be further referred to when we
come to discuss the particular cases that arise in regard to the
faunas and floras of remote islands. But the other side of the

CHAP. V. | DISPERSAL OF ANIMALS AND PLANTS. Gu

question of dispersal—that which depends on geological and
climatal changes—is in a far less satisfactory condition, for, though
much has been written upon it, the most contradictory opinions
still prevail, and at almost every step we find ourselves on the
battle-field of opposing schools in geological or physical science.
As, however, these questions lie at the very root of any general
solution of the problems of distribution, I have given much
time to a careful examination of the various theories that have
been advanced, and the discussions to which they have given
rise; and have arrived at some definite conclusions which I
venture to hope may serve as the foundation for a better com-
prehension of these intricate problems. The four chapters
which follow this are devoted to a full examination of these
profoundly interesting and important questions, after which we
shall enter upon our special inquiry—the nature and origin of
insular faunas and floras.

The Ocean as a Barrier to the Dispersal of Mammals—A
wide extent of ocean forms an almost absolute barrier to the-
dispersal of all land animals, and of most of those which
are aerial, since even birds cannot fly for thousands of miles
without rest and without food, unless they are aquatic birds
who can find both rest and food on the surface of the ocean.
We may be sure, therefore, that without artificial help neither
mammalia nor land birds can pass over very wide oceans. The
exact width they can pass over is not determined, but we have
a few facts to guide us. Contrary to the common notion, pigs
can swim very well, and have been known to swim over five or
six miles of sea, and the wide distzibution of pigs im the islands
of the Hastern Hemisphere may be due to this power. It is
almost certain, however, that they would never voluntarily swim
away from their native land, and if carried out to sea by a flood
they would certainly endeavour to return to the shore. We
cannot therefore believe that they would ever swim over fifty or
a hundred miles of sea, and the same may be said of all the
larger mammalia. Deer also swim well, but there is no reason
to believe that they would venture out of sight of land. With
the smaller, and especially with the arboreal, mammalia, there is
a much more effectual way of passing over the sea, by means of

72 ISLAND LIFE. [PART I.

floating trees, or those floating islands which are often formed
at the mouths of great rivers. Sir Charles Lyell describes such
floating islands which were encountered among the Moluccas, on
which trees and shrubs were growing on a stratum of soil which
even formed a white beach round the margin of each raft.
Among the Philippine Isiands similar rafts with trees growing on
them have been seen after hurricanes ; and it is easy to under-
stand how, if the sea were tolerably calm, such a raft might be
carried along by a current, aided by the wind acting on the
trees, till after a passage of several weeks it might arrive safely
on the shores of some land hundreds of miles away from its
starting-point. Such small animals as squirrels and mice might
have been carried away on the trees which formed part of such
a raft, and might thus colonise a new island; though, as it
would require a pair of the same species to be carried away
together, such accidents would no doubt be rare. Insects, how-
ever, and land-shells would almost certainly be abundant on such
a raft or island, and in this way we may account for the wide
dispersal of many species of both these groups.
Notwithstanding the occasional action of such causes, we
cannot suppose that they have been effective in the dispersal of
mammalia as a whole; and whenever we find that a considerable
number of the mammals of two countries exhibit distinct
marks of relationship, we may be sure that an actual land con-
nection, or at all events an approach to within a very few miles
of each other, has at one time existed. But a considerable
number of identical mammalian families and even genera are
actually found in all the great continents, and the present
distribution of land upon the globe renders it easy to see how
they have been able to disperse themselves so widely. All the
great land masses radiate from the arctic regions as a common
centre, the only break being at Behrings Strait, which is so
shallow that a rise of less than a thousand feet would form a
broad isthmus connecting Asia and America as far south as the
parallel of 60° N. Continuity of land therefore may be said to
exist already for all parts of the world (except Australia and a
number of large islands, which will be considered separately),
and we have thus no difficulty in the way of that former wide

CHAP, V. | DISPERSAL OF ANIMALS AND PLANTS. 73

diffusion of many groups, which we maintain to be the only
explanation of most anomalies of distribution other than such
as may be connected with unsuitability of climate.

The Dispersal of Birds—Wherever mammals can migrate
other vertebrates can generally follow with even greater facility.
Birds, having the power of flight, can pass over wide arms of
the sea, or even over extensive oceans, when these are, as in the
Pacific, studded with islands to serve as resting places. Even
the smaller land-birds are often carried by violent gales of wind
from Europe to the Azores, a distance of nearly a thousand
miles, so that it becomes comparatively easy to explain the
exceptional distribution of certain species of birds. Yet on the
whole it is remarkable how closely the majority of birds follow
the same laws of distribution as mammals, showing that they
generally require either continuous land or an island-strewn sea
as a means of dispersal to new homes.

The Dispersal of Reptiles—Reptiles appear at first sight to be
as much dependent on land for their dispersal as mammalia, but
they possess two peculiarities which favour their occasional
transmission across the sea—the one being their greater tenacity
of life, the other their oviparous mode of reproduction, A
large boa-constrictor was once floated to the island of St.
Vincent, twisted round the trunk of a cedar tree,:and was so
little injured by its voyage that it captured some sheep before
it was killed. The island is nearly two hundred miles from
Trinidad and the coast of South America, whence it almost
certainly came. Snakes are, however, comparatively scarce
on islands far from continents, but lizards are often abundant,
and though these might also travel on floating trees, it
seems more probable that there is some as yet unknown mode
by which their eggs are safely, though perhaps very rarely,
conveyed from island to island. Examples of their peculiar
distribution will be given when we treat of the fauna of some
islands in which they abound.

The Dispersal of Amphibia and Fresh-water Fishes.—
The two lower groups of vertebrates, Amphibia and fresh-
water fishes, possess special facilities for dispersal, in the fact of

1 Lyell’s Principles of Geology, II., p. 369.

74 ISLAND LIFE. [PART I.

their eggs being deposited in water, and in their aquatic or
semi-aquatic habits. They have another advantage over
reptiles in being capable of flourishing in arctic regions, and in
the power possessed by their eggs of being frozen without
injury. They have thus, no doubt, been assisted in their
dispersal by floating ice, and by that approximation of all the
continents in high northern latitudes which has been the chief
agent In producing the general uniformity in the animal pro-
ductions of the globe. Some genera of Batrachia have almost
a world-wide distribution; while the Tailed Batrachia, such as
the newts and salamanders, are almost entirely confined to the
northern hemisphere, some of the genera spreading over the
whole of the north temperate zone. Fresh-water fishes have
often a very wide range, the same species being sometimes
found in all the rivers of a continent. This is no doubt chiefly
due to the want of permanence in river basins, especially in their
lower portions, where streams belonging to distinct systems often
approach each other and may be made to change their course
from one to the other basin by very slight elevations or depres-
sions of the land. Hurricanes and water-spouts also often
carry considerable quantities of water from ponds and rivers,
and thus disperse eggs and even small fishes. As a rule, how-
ever, the same species are not often found in countries separated
by a considerable extent of sea, and in the tropics rarely the
same genera. The exceptions are in the colder regions of the
earth, where the transporting power of 1ce may have come into
play. High ranges of mountains, if continuous for long
distances, rarely have the same species of fish in the rivers on
their two sides. Where exceptions occur, it is often due to the
great antiquity of the group, which has survived so many
changes in physical geography that it has been able, step by
step, to reach countries which are separated by barriers impass-
able to more recent types. Yet another and more efficient
explanation of the distribution of this group of animals is the
fact that many families and genera inhabit both fresh and salt
water; and there is reason to believe that many of the fishes
now inhabiting the tropical rivers of both hemispheres have
arisen from allied marine forms becoming gradually modified

CHAP. V. | DISPERSAL OF ANIMALS AND PLANTS. 75

for a life in fresh water. By some of these various causes, or a
combination of them, most of the facts in the distribution of
fishes can be explained without much difficulty.

The Drspersal of Lnsects—In the enormous group of insects
the means of dispersal, among land animals reach their
maximum. Many of them have great powers of flight, and
from their extreme hghtness they can be carried immense
distances by gales of wind. Others can survive exposure to
salt water for many days, and may thus be floated long distances
by marine currents. The eggs and larve often inhabit solid
timber, or lurk under bark or in crevices of logs, and may
thus reach any countries to which such logs are floated. Another
important factor in the problem is the immense antiquity of
insects, and the long persistence of many of the best marked
types. The rich insect fauna of the Miocene period in Switzer-
land consisted largely of genera still inhabiting Europe, and
even of a considerable number identical, or almost so, with living
species. Out of 156 genera of Swiss fossil beetles no less than
114 are still living; and the general character of the species is
exactly like that of the existing fauna of the northern hemi-
sphere in a somewhat more southern latitude. There is, there-
fore, evidently no difficulty in accounting for any amount of
dispersal among insects; and it is all the more surprising that
with such powers of migration they should yet be often as
restricted in their range as the reptiles or even the mammallia.
The cause of this wonderful restriction to limited areas is,
- undoubtedly, the extreme specialisation of most insects, They
have become so exactly adapted to one set of conditions, that
when carried into a new country they cannot live. Many can
only feed in the larva state on one species of plant ; others are
bound up with certain groups of animals on whom they are
more or less parasitic. Climatal influences have a great
effect on their delicate bodies; while, however well a species
may be adapted to cope with its enemies in one locality, it may
be quite unable to guard itself against those which elsewhere
attack it. From this peculiar combination of characters 1t
happens, that among insects are to be found examples of the
widest and most erratic dispersal and also of the extremest

76 ISLAND LIFE. [PART 1.

restriction to limited areas; and it is only by bearing these
considerations in mind that we can find a satisfactory ex-
planation of the many anomalies we meet with in studying
their distribution.

The Dispersal of Land Mollusca.—The only other group
of animals we need now refer to is that of the air-breathing
mollusca, commonly called land-shells. These are almost as
ubiquitous as insects, though far less numerous ; and their wide
distribution is by no means so easy to explain. The genera
have usually a very wide, and often a cosmopolitan, range, while
the species are rather restricted, and sometimes wonderfully so.
Not only do single islands, however small, often possess peculiar
species of land-shells, but sometimes single mountains or valleys,
or even a particular mountain side, possess species or varieties
found nowhere else upon the globe. It is pretty certain that
they have no means of passing over the sea but such as are very
rare and exceptional. Some which possess an operculum, or
which close the mouth of the shell with a diaphragm of secreted
mucus, may float across narrow arms of the sea, especially
when protected in the crevices of logs of timber; while in the
young state when attached to leaves or twigs they may be
carried long distances by hurricanes.’ Owing to their exceedingly
slow motion, their powers of voluntary dispersal, even on land,
are very limited, and this will explain the extreme restriction of
their range in many cases.

Great Antiquity of Land-Shells—The clue to the almost
universal distribution of the several families and of many genera,
is to be found, however, in their immense antiquity. In the
Pliocene and Miocene formations most of the land-shells are
either identical with living species or closely allied to them,

1 Mr. Darwin found that the large Helix pomata lived after immersion
in sea-water for twenty days. It is hardly likely that this is the extreme
limit of their powers of endurance, but even this would allow of their being
floated many hundred miles at a stretch, and if we suppose the shell to be
partially protected in the crevice of a log of wood, and to be thus out of
water in calm weather, the distance might extend to a thousand miles or
more. The eggs of fresh-water mollusca are known to attach themselves
to the feet of aquatic birds, and this is supposed to account for their very
wide diffusion,

CHAP. V.] DISPERSAL OF ANIMALS AND PLANTS. 77

while even in the Eocene almost all are of living genera, and
one British Eocene fossil still lives in Texas. Strange to say,
no true land-shells have been discovered in the Secondary
formations, but they must certainly have abounded, for in the
far more ancient Palseozoic coal measures of Nova Scotia two
species belonging to the living genera Pupa and Zonites have
been found in considerable abundance.

Land-shells have therefore survived all the revolutions the
earth has undergone since Paleozoic times. They have been
able to spread slowly but surely into every land that has ever
been connected with a continent, while the rare chances of
transfer across the ocean, to which we have referred as possible,
have again and again occurred during the almost unimaginable
ages of their existence. The remotest and most solitary of the
islands of the mid-ocean have thus become stocked with them,
though the variety of species and genera bears a direct relation
to the facilities of transfer, and the shell fauna is never very
rich and varied, except in countries which have at one time or
other been united to some continental land.

Causes favouring the abundance of Land-Shells.—The abun-
dance and variety of land-shells is also, more than that of any
other class of animals, dependent on the nature of the surface
and the absence of enemies, and where these conditions are
favourable their forms are wonderfully luxuriant. The first
condition is the presence of lime in the soil, and a broken
surface of country with much rugged rock offering crevices for
concealment and hybernation. The second is a limited bird
and mammalian fauna, in which such species as are especially
shell-eaters shall be rare or absent. Both these conditions are
found in certain large islands, and pre-eminently in the Antilles,
which possess more species of land-shells than any single con-
tinent. If we take the whole globe, more species of land-shells
are found on the islands than on the continents—a state of
things to which no approach is made in any other group of
animals whatever, but which is perhaps explained by the
considerations now suggested.

The Dispersal of Plants—The ways in which plants are dis-
persed over the earth, and the special facilities they often possess

78 ISLAND LIFE. [PART I.

for migration have been pointed out by eminent botanists, and
a considerable space might be occupied in giving a summary of
what has been written on the subject. In the present work,
however, it is only in two or three chapters that I discuss the
origin of insular floras in any detail; and it will therefore be
advisable to adduce any special facts when they are required to
support the argument in particular cases. A few general
remarks only will therefore be made here.

Special adaptability of Seeds for dispersal.—Plants possess
many great advantages over animals as regards the power of
dispersal, since they are all propagated by seeds or spores, which
are hardier than the eggs of even insects, and retain their
vitality for a much longer time. Seeds may lie dormant for
many years and then vegetate, while they endure extremes of
heat, of cold, of drought, or of moisture which would almost
always be fatal to animal germs. Among the causes of the
dispersal of seeds De Candolle enumerates the wind, rivers,
ocean currents, icebergs, birds and other animals, and human
agency. Great numbers of seeds are specially adapted for
transport by one or other of these agencies. Many are very
light, and have winged appendages, pappus, or down, which
enable them to be carried enormous distances. It is true, as
De Candolle remarks, that we have no actual proofs of their
being so carried ; but this is not surprising when we consider
how small and inconspicuous most seeds are. Supposing every
year a million seeds were brought by the wind to the British
Isles from the Continent, this would be only ten to a square
mile, and the observation of a life-time might never detect
one; yet a hundredth part of this number would serve in a few
centuries to stock an island like Britain with a great variety of
continental plants.

When, however, we consider the enormous quantity of seeds
produced by plants,—that great numbers of these are more or
less adapted to be carried by the wind,—and that winds of great
violence and long duration occur in most parts of the world, we
are as sure that seeds must be carried to great distances as if
we had seen them so carried. Such storms carry leaves, hay,
dust, and many small objects to a great height im the air, while

CHAP, Y. | DISPERSAL OF ANIMALS AND PLANTS. 79

many insects have been conveyed by them for hundreds of
miles out to sea and far beyond what their unaided powers of
flight could have effected.

Birds as agents in the dispersal of Plants—Birds are un-
doubtedly important agents in the dispersal of plants over wide
spaces of ocean, either by swallowing fruits and rejecting the
seeds in a state fit for germination, or by the seeds becoming
attached to the plumage of ground-nesting birds, or to the feet
of aquatic birds embedded in small quantities of mud or earth.
Illustrations of these various modes of transport will be found
in Chapter XII. when discussing the origin of the flora of the
Azores and Bermuda.

Ocean-currents as agents im Plant-dispersal—Ocean-currents
are undoubtedly more important agents in conveying seeds
of plants than they are in the case of any other organisms,
and a considerable body of facts and experiments have been
collected proving that seeds may sometimes be carried in
this way many thousand miles and afterwards germinate.
Mr. Darwin made a series of interesting experiments on
this subject, some of which will be given in the chapter above
referred to.

Dispersal along mountain chains.—These various modes of
transport are, as will be shown when discussing special cases,
amply sufficient to account for the vegetation found on oceanic
islands, which almost always bears a close relation to that of
the nearest continent; but there are other phenomena pre-
sented by the dispersal of species and genera of plants over
very wide areas, especially when they occur in widely separated
portions of the northern and southern hemispheres, that are
not easily explained by such causes alone. It is here that
transmission along mountain chains has probably been effective;
and the exact mode in which this has occurred is discussed in
Chapter XXIII., where a considerable body of facts is given,
showing that extensive migrations may be effected by a suc-
cession of moderate steps, owing to the frequent exposure of
fresh surfaces of soil or débris on mountain sides and summits,
offering stations on which foreign plants can temporarily
establish themselves.

80 ISLAND LIFE. [PART I.

Antiquity of Plants as affecting their Disiribution—We have
already referred to the importance of great antiquity in en-

abling us to account for the wide dispersal of some genera and |

species of insects and land-shells, and recent discoveries in fossil
botany show that this cause has also had great influence in the
case of plants. Rich floras have been discovered in the Miocene,
the Eocene, and the Upper Cretaceous formations, and these
consist almost wholly of living genera, and many of them of
species very closely allied to existing forms. We have there-
fore every reason to believe that a large number of our
plant-species have survived great geological, geographical, and
climatal changes; and this fact, combined with the varied and
wonderful powers of dispersal many of them possess, renders
it far less difficult to understand the examples of wide dis-
tribution of the genera and species of plants than in the case of
similar instances among animals. ‘This subject will be further
alluded to when discussing the origin of the New Zealand flora,
in Chapter XXII.

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
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.

THE changes of land and sea which have occurred — in
particular cases will be described when we discuss the origin
and relations of the faunas of the different classes of islands,
We have here only to consider the general character and extent
of such changes, and to correct some erroneous ideas which are
prevalent on the subject. 7

Changes of Land and Sea, their nature and extent.—It is a very
common belief that geological evidence proves a complete change
of land and sea to have taken place over and over again. Every
foot of dry land has undoubtedly, at one time or other, formed
part of a sea-bottom, and we can hardly exclude the surfaces
occupied by volcanic and fresh-water deposits, since, in many
cases, if not in all, these rest upon a substratum of marine
formations. At first sight, therefore, it seems a necessary
inference that when the present continents were under water
tltere must-have been other continents situated where we now

82 ISLAND LIFE. [PART I.

find the oceans, from which the sediments came to form the
various deposits we now see. This view was held by so acute
and learned a geologist as Sir Charles Lyell, who says :—‘“‘ Con-
tinents therefore, although permanent for whole geological
epochs, shift their positions entirely in the course of ages.”!_ Mr.
T. Mellard Reade, late President of the Geological Society of
Liverpool, so recently as 1878, says :—‘“ While believing that the
ocean-depths are of enormous age, it 1s impossible to resist
other evidences that they have once been land. The very con-
tinuity of animal and vegetable life on the globe points to it.
The molluscous fauna of the eastern coast of North America is
very similar to that of Europe, and this could not have happened
without littoral continuity, yet there are depths of 1,500 fathoms
between these continents.” It is certainly strange that a
geologist should not remember the recent and long-continued
warm climates of the Arctic regions, and see that a connection
of Northern Europe by Iceland with Greenland and Labrador
over a sea far less than a thousand fathoms deep would furnish
the “littoral continuity ” required. Again, in the same pamphlet
Mr. Reade says :—“ It can be mathematically demonstrated that
the whole, or nearly the whole, of the sea-bottom has been at
one time or other dry land. If it were not so, and the oscilla-
tions of the level of the land with respect to the sea were con-
fined within limits near the present continents, the results would
have been a gradual diminution instead of development of the
calcareous rocks. To state the case in common language, the
calcareous portion of the rocks would have been washed out
during the mutations, the destruction and re-deposit of the con
tinental rocks, and eventually deposited in the depths of the
immutable sea far from land. Immense beds of limestone would
now exist at the bottom of the ocean, while the land would be
composed of sandstones and argillaceous shales. The evidence
of chemistry thus confirms the inductions drawn from the
distribution of animal life upon theglobe.”

So far from this being a “mathematical demonstration” it
appears to me to be a complete misinterpretation of the facts.

1 Principles of Geology, 11th Ed., Vol. I, p. 258.
2 On Limestone as an Index of Geological Time.

cHAP. vI.| GEOGRAPHICAL AND GEOLOGICAL CHANGES. 83

Animals did not create the lime which they secrete from the sea-
water, and therefore we have every reason to believe that the
inorganic sources which originally supplied it still keep up that
supply, though perhaps in diminished quantity. Again, the
great lime-secreters—corals—work in water of moderate depth,
that is, near land, while there is no proof whatever that there is
any considerable accumulation of limestone at the bottom of the
deep ocean. On the contrary, the fact ascertained by the
Challenger, that beyond a certain depth the “calcareous” ooze
ceases, and is replaced by red and grey clays, although the
calcareous organisms still abound in the surface waters of the
ocean, shows that the lime is dissolved again by the. excess of
carbonic acid usually found at great depths, and its accumula-
tion thus prevented. As to the increase of limestones in recent
as compared with older formations, it may be readily explained
by two considerations: in the first place, the growth and de-
velopment of the land in longer and more complex shore lines
and the increase of sedimentary over volcanic formations may
have offered more stations favourable to the growth of coral,
while the solubility of limestone in rain-water renders the
destruction of such rocks more rapid than that of sandstones
and shales, and would thus lead to their comparative abundance
in later as compared with earlier formations.

However weak we may consider the above-quoted arguments
against the permanence of oceans, the fact that these arguments
are so confidently and authoritatively put forward, renders it
advisable to show how many and what weighty considerations
can be adduced to justify the opposite belief, which is now
rapidly gaining ground among students of earth-history.

Shore Deposits and Stratified Rocks —If we go round the shores
of any of our continents we shall always find a considerable
belt of shallow water, meaning thereby water from 100 to 150
fathoms deep. The distance from the coast line at which such
depths are reached is seldom less than twenty miles, and is very
frequently more than a hundred, while in some cases such shallow
seas extend several hundred miles from existing continents. The
great depth of a thousand fathoms is often reached at thirty
miles from shore, but more frequently at about sixty or a hundred

G 2

84 ISLAND LIFE. [PART I.

miles. Round the entire African coast for example, this depth
is reached at distances varying from forty to a hundred and
fifty miles (except in the Red Sea and the Straits of Mozambique),
the average being about eighty miles. |

Now the numerous specimens of sea-bottoms collected
during the voyage of the Challenger show that true shore-
deposits—that is, materials denuded from the land and carried
down as sediment by rivers—are almost always confined within
a distance of 50 or 100 miles of the coast, the finest mud
only being sometimes carried 150 or rarely 200 miles. As the
sediment varies In coarseness and density it is evident that it
will sink to the bottom at unequal distances, the bulk of it
sinking comparatively near shore, while only the very finest and
almost impalpable mud will be carried out to the furthest limits.
Beyond these limits the only deposits (with few exceptions) are
organic, consisting of the shells of minute calcareous or siliceous
organisms with some decomposed pumice and volcanic dust which
floats out to mid-ocean. It follows, therefore, that by far the
larger part of all stratified deposits, especially those which con-
sist of sand or pebbles or any visible fragments of rock, must
have been formed within 50 or 100 miles of then existing con-
tinents, or if at a greater distance, in shallow inland seas receiving
deposits from more sides than one, or in certain exceptional areas
where deep ocean currents carry the débris of land to greater
distances.?

If we now examine the stratified rocks found in the very centre
of all our great continents, we find them to consist of sandstones,
limestones, conglomerates, or shales, which must, as we have
seen, have been deposited within a comparatively short distance
of asea-shore. Professor Archibald Geikie says :—“ Among the

1 In his Preliminary Report on Oceanic Deposit, Mr. Murray says :—‘‘ It
has been found that the deposits taking place near continents and islands
have received their chief characteristics from the presence of the débris
of adjacent lands. In some cases these deposits extend to a distance of
over 150 miles from the coast.” (Proceedings of the Royal Society,
W.ol., XXTV : p. 5192)

“The materials in suspension appear to be almost entirely deposited
within 200 miles of the land.” (Proceedings of the Royal Society of Edin-
burgh, 1876-77, p. 253.)

CHAP. vI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 85

thickest masses of sedimentary rock—those of the ancient
Paleozoic systems—no features recur more continually than the
alternations of different sediments, and the recurrence of surfaces
covered with well-preserved ripple-marks, trails and burrows of
annelides, polygonal and irregular desiccation marks, like the
cracks at the bottom of a sun-dried muddy pool. These
phenomena unequivocally point to shallow and even littoral
waters. They occur from bottom to top of formations, which
reach a thickness of several thousand feet. They can be in-
terpreted only in one way, viz., that the formations in question
began to be laid down in shallow water; that during their
formation the area of deposit gradually subsided for thousands
of feet; yet that the rate of accumulation of sediment kept
pace on the whole with this depression; and hence that the
original shallow-water character of the deposits remained, even
after the original sea-bottom had been buried under a vast mass
of sedimentary matter.” He goes onto say, that this general
statement applies to the more recent as well as to the more
ancient formations, and concludes—“ In short, the moreattentively
the stratified rocks of the earth are studied, the more striking
becomes the absence of any formations among them, which can
legitimately be considered those of a deep sea. They have all
been deposited in comparatively shallow water.”

The arrangement and succession of the stratified rocks also
indicate the mode and place of their formation. We find them
stretching across the country in one general direction, in belts
of no great width though often of immense length, just as we
should expect in shore deposits; and they often thin out and
change from coarse to fine in a definite manner, indicating the
position of the adjacent land from the débris of which they
were originally formed. Again quoting Professor Geikie :—
“The materials carried down to the sea would arrange them-
selves then as they do still, the coarser portions nearest the
shore, the finer silt and mud furthest from it. From the
earliest geological times the great area of deposit has been,
as it still is, the marginal belt of sea-floor skirting the land.

1 Geographical Evolution. (Proceedings of the Royal Geographical Societe Ys
1879, p. 426.)

86 ISLAND LIFE. [PART I.

It is there that nature has always strewn the dust of continents
to be.”

The Movements of Continents—As we find these stratified
rocks of different periods spread over almost the whole surface
of existing continents where not occupied by igneous or meta-
morphic rocks, it follows that at one period or another each
part of the continent has been under the sea, but at the same
time not far from the shore. Geologists now recognise two
kinds of movements by which the deposits so formed have been
elevated into dry land—in the one case the strata remain
almost level and undisturbed, in the other they are contorted
and crumpled, often to an enormous extent. The former often
prevails in plains and plateaus, while the latter is almost always
found in the great mountain ranges. We are thus led to picture
the land of the globe as a flexible area in a state of slow but
incessant change ; the changes consisting of low undulations
which creep over the surface so as to elevate and depress limited
portions in succession without perceptibly affecting their nearly
horizontal position, and also of intense lateral compression,
supposed to be produced by partial subsidence along certain
lines of weakness in the earth’s crust, the effect of which is to
crumple the strata and force up certain areas in great contorted
masses, which, when carved out by subaérial denudation into
peaks and valleys, constitute our great mountain systems! In
this way every part of a continent may again and again have
sunk beneath the sea, and yet as a whole may never have
ceased to exist as a continent or a vast continental archipelago.

* Professor Dana points out that the regions which, after long under-

going subsidence, and accumulating vast piles of sedimentary deposits,
have been elevated into mountain ranges, have thereby become stiff and

unyielding, and that the next depression and subsequent upheaval will be

situated on one or the other sides of it; and he shows that, in North
America, this is the case with all the mountains of the successive geological
formations. Thus, depressions and elevations of extreme slowness but
often of vast amount, have occurred successively in restricted adjacent
areas ; and the effect has been to bring each portion in succession beneath
the ocean but always bordered on one or both sides by the remainder of
the continent, from the denudation of which the deposits are formed which,
on the subsequent upheaval, become mountain ranges, (Manual of Geology,
2nd Ed., p. 751.)

cHaP. vI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 87

And, as subsidence will always be accompanied by deposition,
piles of marine strata many thousand feet thick may have been
formed in a sea which was never very deep, by means of a
slow depression either continuous or intermittent, or through
alternate subsidences and elevations, each of moderate amount.

Supposed Oceanic Formations ;—the Origin of Chalk.—There
seems very good reason to believe that few, if any, of the rocks
known to geologists correspond exactly to the deposits now
forming at the bottom of our great oceans. The white oceanic
mud, or Globigerina-ooze, found in all the great oceans at depths
varying from 250 to nearly 3,000 fathoms, and almost constantly
in depths under 2,000 fathoms, has, however, been supposed to
be an exception, and to correspond exactly to our white and
grey chalk. Hence some naturalists have maintained that
there has probably been one continuous formation of chalk in
the Atlantic from the Cretaceous epoch to the present day.
This view has been adopted chiefly on account of the similarity
of the minute organisms found to compose a considerable
portion of both deposits, more especially the pelagic Fora-
minifera, of which several species of Globigerina appear to be
identical in the chalk and the modern Atlantic mud. Other
extremely minute organisms whose nature is doubtful, called
coctoliths and discoliths, are also found in both formations,
while there is a considerable general resemblance between the
higher forms of life. Sir Wyville Thomson tells us, that—
“Sponges are abundant in both, and the recent chalk-mud
has yielded a large number of examples of the group porifera
vurea, which find their nearest representatives among the
Ventriculites of the white chalk. The echinoderm fauna of
the deeper parts of the Atlantic basin is very characteristic,
and yields an assemblage of forms which represent in a remark-
able degree the corresponding group in the white chalk. Species
of the genus Cidaris are numerous; some remarkable flexible
forms of the Diademidze seem to approach Echinothuria.”}
Now as some explanation of the origin of chalk had long been
desired by geologists, it is not surprising that the amount of
resemblance shown to exist between it and some kinds of

1 Nature, Vol. II., p. 297.

83 ISLAND LIFE. [PART I.

oceanic mud should have been at once seized upon, and the
conclusion arrived at that chalk is a deep-sea oceanic formation
exactly analogous to that which has been shown to cover large
areas of the Atlantic, Pacific, and Southern oceans.

But there are several objections to this view which seem fatal
to its acceptance. In the first place, no specimens of Globigerina-
ooze from the deep ocean-bed yet examined agree even approxi-
mately with chalk in chemical composition, only containing
from 44 to 79 per cent. of carbonate of lime, with from 5 to 11
per cent. of silica, and from 8 to 33 per cent. of alumina and
oxide of iron." Chalk, on the other hand, contains usually
from 94 to 99 per cent. of carbonate of lime, and a very minute
quantity of alumina and silica. This large proportion of car-
bonate of lime implies some other source of this mineral, and
it is probably to be found in the excessively fine mud produced
by the decomposition and denudation of coral reefs. Mr. Dana,
the geologist of the United States Exploring Expedition, found
in the elevated coral reef of Oahu, one of the Sandwich Islands,
a deposit closely resembling chalk in colour, texture, &c.; while
in several growing reefs a similar formation of modern chalk
undistinguishable from the ancient, was observed.? Sir Charles

1 Sir W. Thomson, Voyage of Challenger, Vol. T1., p. 374.
2 The following is the analysis of the chalk at Oahu:—

Carbonate, of Lime, si. <.csctennsceakocucan 92-800 per cent.
Carbonate of Maenesiag...)......¢.0.00c000-8 2°385 ss
Ailrarintina yt LIES. PASDE ke 0-250 um,
Oxide. of Romine. seit daa pci duetaands Abbie 0°543 5s
LCE. Sie Gace ies ate eene ie ecaee ra tare: 0°750 Be
Phosphoric Acid and Fluorine.............. 2°113 5
Water{ and JOgs .ocdaes uc sdteme ime on ben bas 1:148

This chalk consists simply of comminuted corals and shells of the reef.
It has been examined microscopically and found to be destitute of the
minute organisms abounding in the chalk of England. (Geology of the
United States Exploring Expedition, p. 150.)

This absence of Globigerine is a local phenomenon. They are quite
absent in the Arafura Sea, and no Globigerina-ooze was found in any of
the enclosed seas of the Pacific, but with these exceptions the Globigerine
“are really found all over the bottom of the ocean.” (Murray on Oceanic
Deposits—Proceedings of Royal Society, Vol. XXIV., p. 523.)

The above analysis shows a far closer resemblance to chalk than that
of the Globigerina-ooze of the Atlantic, four specimens of which given by

CHAP, VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 89

Lyell well remarks that the pure calcareous mud produced by
the decomposition of the shelly coverings of mollusca and
zoophytes would be much hghter than argillaceous or arena-
ceous mud, and being thus transported to greater distances
would be completely separated from all impurities.

Now the Globigerinze have been shown by the Challenger
explorations to abound in all moderately warm seas; living
both at the surface, at various depths in the water, and at the
bottom. It was long thought that they were surface-dwellers
only, and that their dead tests sank to the bottom, producing
the Globigerina-ooze in those areas where other deposits
were absent or scanty. But the examination of the whole
of the dredgings and surface-gatherings of the Challenger by

Sir W. Thomson (Voyage of the Challenger. Vol. Il. Appendix, pp. 374-
376, Nos. 9, 10, 11 and 12) from the mid-Atlantic, show the following
proportions :—

Carbonate of Lime....,...0...s.3. 43°93 to 79-17 per cent.
Carbonate of Magnesia.......... LAO Ost 1 y2 58s) th
Alumna and Oxide of Iron..... 6:00? to, 32°98 -- ;,
MC ee a Sein seed eac dn oakcatiise ses 460 to 11:23

In addition to the above there is a quantity of insoluble residue consist-
ing of small particles of sanidine, augite, hornblende, and magnetite,
supposed to be the product of volcanic dust or ashes carried either in
the air or by ocean currents. This volcanic matter amounts to from 4°60
to 8°33 per cent. of the Globigerina-ooze of the mid-Atlantic, where it
seems to be always present ; and the small proportion of similar matter
in true chalk is another proof that its origin is different, and that it was
deposited far more rapidly than the oceanic ooze.

The following analysis of chalk by Mr. D. Forbes will show the difference
between the two formations :—

Grey Chalk, White Chalk,

: Folkestone, Shoreham.
Warkonate of Himes .s 0% ls.c.cieecee es 94:09 98°40
Carbonate of Magnesia............ ... 0-31 0:08
Alumina and Phosphoric Acid... a trace 0-42
Chloride Or MOGIUM. .o.ccce cess coset ce 1:29 —
Tmsolble éO11S. bic: veces ceetvae cece ses 361 1:10

(From Quarterly Journal of the Geological Society, Vol. XX VII.)

The large proportion of carbonate of lime, and the very small quantity
of silica, alumina, and insoluble débris, at once distinguish true chalk from
the Globigerina-ooze of the deep ocean bed.

90 . ISLAND LIFE. [PART I.

Mr. H. B. Brady has led him to a different conclusion; for he
finds numerous forms at the bottom quite distinct from those
which inhabit the surface, while, when the same species live
both at surface and bottom, the latter are always larger and
have thicker and stronger cell-walls. This view is also sup-
ported by the fact that in many stations not far from our own
shores Globigerine are abundant in bottom dredgings, but are
never found on the surface in the towing-nets.!_ These organisms
then exist almost universally where the waters are pure and are
not too cold, and they would naturally abound most where the
diffusion of carbonate of lime both in suspension and solution
afforded them an abundant supply of material for their shelly
coverings. Dr. Wallich believes that they flourish best where
the warm waters of the Gulf Stream bring organic matter from
which they derive nutriment, since they are wholly wanting
in the course of the Arctic current between Greenland and
Labrador. Dr. Carpenter also assures us that they are rigorously
limited to warm areas.

Now with regard to the depth at which our chalk was formed,
we have evidence of several distinct kinds to show that it was
not profoundly oceanic. Mr. J. Murray, in the Report already
referred to, says: “The Globigerina-oozes which we get in
shallow water resemble the chalk much more than those in
deeper water, say over 1,000 fathoms.” ? This is important and
weighty evidence, and it is supported in a striking manner by
the nature of the molluscan fauna of the chalk. Mr. Gwyn
Jeffries, one of our greatest authorities on shells, who has
himself dredged largely both in deep and shallow water and
who has no theory to support, has carefully examined this
question. Taking the whole series of genera which are found
in the Chalk formation, seventy-one in number, he declares
that they are all comparatively shallow-water forms, many
living at depths not exceeding 40 to 50 fathoms, while some
are confined to still shallower waters. Even more important
is the fact that the genera especially characteristic of the deep

1 Notes on Reticularian Rhizopoda ; in Microscopical Journal, Vol. X1X.,

New Series, p. 84.
2 Proceedings of the Royal Society, Vol. XXIV. p. 532.

cHAP. v1.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 91

Atlantic ooze—Leda, Verticordia, Nezra, and the Bulla family
—are either very rare or entirely wanting in the ancient
Cretaceous deposits.!

Let us now see how the various facts already adduced will
enable us to explain the peculiar characteristics of the chalk
formation. Sir Charles Lyell tells us that “pure chalk, of
nearly uniform aspect and composition, is met with in a north-
west and south-east direction, from the north of Ireland to the
Crimea, a distance of about 1,140 geographical miles; and in
an opposite direction it extends from the south of Sweden to
the south of Bordeaux, a distance of about 840 geographical
miles.” This marks the extreme limits within which true chalk
is found, though it 1s by no means continuous. It probably
implies, however, the existence across Central Europe of a sea
somewhat larger than the Mediterranean. It may have been
much larger, because this pure chalk formation would only be
formed at a considerable distance from land, or in areas where
there was no other shore deposit. This sea was probably
bounded on the north by the old Scandinavian highlands, ex-
tending to Northern Germany and North-western Russia, where
Paleozoic and ancient Secondary rocks have a wide extension,
though now partially concealed by late Tertiary deposits; while
on the south it appears to have been limited by land extend-
ing through Austria, South Germany, and the south of France,
as shown in the map of Central Europe during the Cretaceous
period in Professor Heer’s Primeval World of Switzerland, p.175.
To the north the sea may have had an outlet to the Arctic Ocean
between the Ural range and Finland. South of the Alps there
was probably another sea, which may have communicated with
the northern one just described, and there was also a narrow
strait across Switzerland, north of the Alps, but, as might be
expected, in this only marls, clays, sandstones, and limestones
were deposited instead of true chalk. It is also a suggestive
fact that both above and below the true chalk, in almost all the
countries where it occurs, are extensive deposits of marls, clays,

1 See Presidential Address in Sect. D. of British Association at Plymouth,
1877.

92 ISLAND LIFE. [part 1,

and even pure sands and sandstones, characterised by the same
general types of fossil remains as the chalk itself. These beds
imply the vicinity of land, and this is even more clearly proved
by the occurrence, both in the Upper and Lower Cretaceous, of
deposits containing the remains of land-plants in abundance,
indicating a rich and varied flora.

Now all these facts are totally opposed to the idea of any-
thing like oceanic conditions having prevailed in Europe during
the Cretaceous period ; but it is quite consistent with the ex-
istence of a great Mediterranean sea of considerable depth in
its central portions, and occupying, either at one or successive
periods, the whole area of the Cretaceous formation. We may
also note that the Maestricht beds in Belgium and the Faxoe
chalk in Denmark are both highly coralline, the latter being,
in fact, as completely composed of corals as a modern coral-
reef; so that we have here a clear indication of the source
whence the white calcareous mud was derived which forms
the basis of chalk. If we suppose that during this period the
comparatively shallow sea-bottom between Scandinavia and
Greenland was elevated, forming a land connection between
these countries, the result would be that a large portion of the
Gulf Stream would be diverted into the inland European sea,
and would bring with it that abundance of Globigerine, and
other Foraminifera, which form such an important constituent
of chalk. This sea was probably bordered with islands and
coral-reefs, and if no very large rivers flowed into it we should
have all the conditions for the production of the true chalk, as
well as the other members of the Cretaceous formation. The
products of the denudation of its shores and islands would form
the various sandstones, marls, and clays, which would be de-
posited almost wholly within a few miles of its coasts; while
the great central sea, perhaps at no time more than a few
thousand feet deep, would receive only the impalpable mud of
the coral-reefs and the constantly falling tests of Forami-
nifera. ‘These would imbed and preserve for us the numerous
echinoderms, sponges, and mollusca, which lived upon the
bottom, the fishes and turtles which swam in its waters,
and sometimes the winged reptiles that flew overhead, The

CHAP, vI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES, 93

abundance of ammonites, and other cephalopods, in the chalk,
is another indication that the water in which they lived was not
very deep, since Dr. 8. P. Woodward thinks that these organ-
isms were limited to a depth of about thirty fathoms.

The best example of the modern formation of chalk is
perhaps to be found on the coasts of sub-tropical North
America, as described in the following passage :—

“The observations of Pourtales show that the steep banks of
Bahama are covered with soft white hme mud. The lme-
bottom, which consists almost entirely of Polythalamia, covers
in greater depths the entire channel of Florida. This formation
extends without interruption over the whole bed of the Gulf-
stream in the Gulf of Mexico, and is continued along the
Atlantic coast of America. The commonest genera met with
in this deposit are Globigerina, Rotalia cultrata, in large num-
bers, several Textilariz, Marginuline, &c. Beside these, small
free corals, Alcyonide, Ophiure, Mollusca, Crustacea, small
fishes, &c., are found living in these depths. The whole sea-
bottom appears to be covered with a vast deposit of white
chalk still in formation,” |

There is yet another consideration which seems to have been
altogether overlooked by those who suppose that a deep and
open island-studded ocean occupied the place of Europe in Cre-
taceous times. No fact is more certain than the considerable
break, indicative of a great lapse of time, intervening between
the Cretaceous and Tertiary formations. A few deposits of
intermediate age have indeed been found, but these have been
generally allocated either with the Chalk or the Eocene, leaving
the gap almost as pronounced as before. Now, what does this
gap mean? It implies that when the deposition of the various
Cretaceous beds of Europe came to an end they were raised
above the sea-level and subject to extensive denudation, and
that for a long but unknown period no extensive portion of
what is now European land was below the sea-level. It was
only when this period terminated that large areas in
several parts of Europe became submerged and received the
earliest Tertiary deposits known as Eocene. If, therefore,

* Geological Magazine, 1871, p. 426.

94 ISLAND LIFE. [PART 1.

Europe at the close of the Cretaceous period was generally
identical with what it is now, and perhaps even more extensive,
it is absurd to suppose that it was all, or nearly all, under water
during that period ; or in fact that any part of it was submerged,
except those areas on which we actually find Cretaceous deposits,
or where we have good reason to believe they have existed.

The several considerations now adduced are, I think, suffi-
cient to show that the view put forth by some naturalists (and
which has met with a somewhat hasty acceptance by geologists)
that our white chalk is an oceanic formation strictly comparable
with that now forming at depths of a thousand fathoms and
upwards in the centre of the Atlantic, gives a totally erroneous
idea of the actual condition of Europe during that period. In-
stead of being a wide ocean, with a few scattered islands,
comparable to some parts of the Pacific, it formed as truly a
portion of the great northern continent as it does now, although
the inland seas of that epoch may have been more extensive and
more numerous than they are at the present day.1

Fresh-water and Shore Deposits as proving the Permanence of
Continents.—The view here maintained, that all known marine
deposits have been formed near the coasts of continents and
islands, and that our actual continents have been in continuous
existence under variously modified forms during the whole period
of known geological history, is further supported by another and

1 In his lecture on Geographical Evolution (which was published after
the greater part of this chapter had been written) Professor Geikie expresses
views in complete accordance with those here advocated. He says:—‘‘ The
next long era, the Cretaceous, was more remarkable for slow accumulation
of rock under the sea than for the formation of new land. During that
time the Atlantic sent its waters across the whole of Europe and into Asia.
But they were probably nowhere more than a few hundred feet deep over
the site of our continent, even at their deepest part. Upon their bottom
there gathered a vast mass of calcareous mud, composed in great part of
foraminifera, corals, echinoderms, and molluscs. Our English chalk, which
ranges across the north of France, Belgium, Denmark, and the north of
Germany, represents a portion of the deposits of that sea-floor.” The
weighty authority of the Director of the Geological Survey of Scotland
may perhaps cause some geologists to modify their views as to the deep-
sea origin of chalk, who would have treated any arguments advanced by
myself as not worthy of consideration.

CHAP. v1.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 95

totally distinct series of facts. In almost every period of geology,
and in all the continents which have been well examined, there
are found lacustrine, estuarine, or shore deposits, containing the
remains of land animals or plants, thus demonstrating the con-
tinuous existence of extensive land areas on or adjoining the
sites of our present continents. Beginning with the Miocene,
or Middle Tertiary period, we have such deposits with remains
of land-animals, or plants, in Devonshire and Scotland, in
France, Switzerland, Germany, Croatia, Vienna, Greece, North
India, Central India, Burmah, North America, both east and
west of the Rocky Mountains, Greenland, and other parts of
the Arctic regions. In the older Eocene period similar forma-
tions are widely spread in the south of England, in France, and
to an enormous extent on the central plateau of North America ;
while in the eastern states, from Maryland to Alabama, there
are extensive marine deposits of the same age, which, from the
abundance of fossil remains of a large cetacean (Zeuglodon),
must have been formed in shallow gulfs or estuaries where
these huge animals were stranded. Going back to the Creta-
ceous formation we have the same indications of persisting lands
in the rich plant-beds of Aix-la-Chapelle, and a few other locali-
ties on the continent, as well as in coniferous fruits from the
Gault of Folkestone; while in North America cretaceous plant-
beds occur in New Jersey, Alabama, Kansas, the sources of the
Missouri, the Rocky Mountains from New Mexico to the Arctic
Ocean, Alaska (British Columbia), California, and in Greenland
and Spitzbergen ; while birds and land reptiles are found in
the Cretaceous deposits of Colorado and other western districts.
Fresh-water deposits of this age are also found on the coast
of Brazil. In the lower part of this formation we have the
fresh-water Wealden deposits of England, extending into France,
Hanover, and Westphalia. In the older Oolite or Jurassic
formation we have abundant proofs of continental conditions in
the fresh-water and “dirt’”-beds of the Purbecks, in the south
of England, with plants, insects and mammals; the Bavarian
lithographic stone, with fossil birds and insects; the earlier
“forest marble” of Wiltshire, with ripple-marks, wood, and
broken shells, indicative of an extensive beach; the Stones-

96 ISLAND LIFE. [PART I.

field slate, with plants, insects, and marsupials; and the Oolitic
coal of Yorkshire and Sutherlandshire. Beds of the same age
occur in the Rocky Mountains of North America, containing
abundance of Dinosaurians and other reptiles, among which is
the Atlantosaurus, the largest land-animal ever known to have
existed. Professor O. C. Marsh describes it as having been
between fifty and sixty feet long, and when standing erect at
least thirty feet high! Such monsters could hardly have been
developed except in an extensive land area. A small mammal,
Dryolestes, has been discovered in the same deposits. A rich
Jurassic flora has also been found in Hast Siberia and the
Amur valley. The older Triassic deposits are very extensively
developed in America, and both in the Connecticut valley and
the Rocky Mountains show tracks or remains of land reptiles,
amphibians and mammalia, while coalfields of the same age in
Virginia and Carolina produce abundance of plants. Here too
are found the ancient mammal, Microlestes, of Wurtemberg, with
the ferns, conifers, and Labyrinthodonts of the Bunter Sand-
stone in Germany; while the beds of rock-salt in this forma-
tion, both in England and in many parts of the continent,
could only have been formed in inland seas or lakes, and thus
equally demonstrate continental conditions.

We now pass into the oldest or Palseozoic formations, but
find no diminution in the proofs of continental conditions. The
Permian formation has a rich flora often producing coal in
England, France, Saxony, Thuringia, Silesia, and Hastern Russia.
Coalfields of the same age occur in Ohio in North America.
In the still more ancient Carboniferous formation we find the
most remarkable proofs of the existence of our present continents
at that remote epoch, in the wonderful extension of coal beds in
all the known continents. We find them in Ireland, England,
and Scotland; in France, Spain, Belgium, Saxony, Prussia,
Bohemia, Hungary, Sweden, Spitzbergen, Siberia, Russia,
Greece, Turkey, and Persia; in many parts of continental
India, extensively in China, and in Australia, Tasmania and

1 Introduction and Succession of Vertebrate Life in America, by Professor

O. C. Marsh. Reprinted from the Popular Science Monthly, March, April,
1878.

——

CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 97

New Zealand. In North America there are immense coal
fields in Nova Scotia and New Brunswick, from Pennsylvania
southward to Alabama, in Indiana and I]linois, and in Missouri ;
and there is also a true coal formation in South Brazil. This
wonderfully wide distribution of coal, implying, as it does, a
rich vegetation and extensive land areas, carries back the proof
of the persistence and general identity of our continents to a
period so remote that none of the higher animal types had
probably been developed. . But we can go even further back
than this, to the preceding Devonian formation, which was
almost certainly an inland deposit often containing remains
of fresh-water shells, plants, and even Insects; while Professor
Ramsay believes that he has found “sun-cracks and_ rain-
pittings” in the Longmynd beds of the still earlier Cambrian
formation. If now, in addition to the body of evidence here
adduced, we take into consideration the fresh-water deposits
that still remain to be discovered, and those extensive areas
where they have been destroyed by denudation or remain
deeply covered up by later marine or volcanic formations, we
cannot but be struck by the abounding proofs of the permanence
of the great features of land and sea as they now exist; and we
shall see how utterly gratuitous, and how entirely opposed to all
the evidence at our command, are the hypothetical continents
bridging over the deep oceans, by the help of which it is so
often attempted to cut the Gordian knot presented by some
anomalous fact in geographical distribution.

Oceanic Islands as Indications of the Permanence of Continents
and Oceans—Coming to the question from the other side,
Mr. Darwin has adduced an argument of considerable weight
in favour of the permanence of the great oceans. He says
(Origin of Species, 6th Hd. p. 288): ‘‘ Looking to existing oceans,
which are thrice as extensive as the land, we see them studded
with many islands; but hardly one truly oceanic island (with
the exception of New Zealand, if this can be called a truly
oceanic island) is as yet known to afforl even a fragment of
any Paleeozoic or Secondary formation. Hence we may perhaps
infer that during the Paleozoic and Secondary periods neither

1 Physical Geography and Geology of Great Britain, 5th Ed. p. 61,
H

98 ISLAND LIFE. [PART 1.

continents nor continental islands existed where our oceans
now extend; for had they existed, Palzozoic and Secondary
formations would in all probability have been accumulated
from sediment derived from their wear and tear; and these
would have been at least partially upheaved by the oscillations
of level, which must have intervened during these enormously
long periods. If then we may infer anything from these facts,
we may infer that, where our oceans now extend, oceans have
extended from the remotest period of which we have any
record; and, on the other hand, that where continents now |
exist, large tracts of land have existed, subjected no doubt to
ereat oscillations of level, since the Cambrian period.” This
argument standing by itself has not received the attention it
deserves, but coming in support of the long series of facts of
an altogether distinct nature, going to show the permanence of
continents, the cumulative effect of the whole must, I think,
be admitted to be irresistible,’

1 Of late it has been the custom to quote the so-called “ridge” down
the centre of the Atlantic as indicating an extensive ancient land. Even
Professor Judd adopts this view, for he speaks of the great belt of Tertiary
volcanoes ‘‘ which extended through Greenland, Iceland, the Faroe Islands,
the Hebrides, Ireland, Central France, the Iberian Peninsula, the Azores,
Madeira, Canaries, Cape de Verde Islands, Ascension, St. Helena, and
Tristan d' Acunha,and which constituted as shown by the recent soundings
of H.M 8. Challenger a mountain-range, comparable in its extent, elevation,
and volcanic character with the Andes of South America’? (Geological
Mag. 1874, p. 71). On examining the diagram of the Atlantic Ocean in
the Challenger Reports, No. 7, a considerable part of this ridge is found
to be more than 1,900 fathoms deep, while the portion called the “Connecting
hidge” seems to be due in part to the deposits carried out by the River
Amazon. In the neighbourhood of the Azores, St. Paul’s Rocks, Ascension,
and Tristan d’Acunha are considerable areas varying from 1,200 to 1,500
fathoms deep, while the rest of the ridge is usually 1,800 or 1,900 fathoms,
The shallower water is no doubt due to volcanic upheaval and the accumu-
lation of volcanic ejections, and there may be many other deeply submerged
old volcanoes on the ridge; but that it ever formed a chain of mountains
‘‘comparable in elevation with the Andes,” there seems not a particle of
evidence to prove. It is however probable that this ridge indicates the
former existence of some considerable Atlantic islands, which will serve
to explain the presence of a few identical genera, and even species of
plants and insects in Africa and South America, while the main body
of the fauna and flora of these two continents remains radically distinct.

cHAP, VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 29

General Stability of Continents with Constant Change of Form.
—It will be observed that the very same evidence which has been
adduced to prove the general stability and permanence of our
continental areas also goes to prove that they have been sub-
jected to wonderful and repeated changes in detail. Every
square mile of their surface has been again and again under
water, sometimes a few hundred feet deep, sometimes perhaps
several thousands. Lakes and inland seas have been formed,
have been filled up with sediment, and been subsequently raised
into hills or even mountains. Arms of the sea have existed
crossing the continents in various directions, and thus completely
isolating the divided portions for varying intervals, Seas have
been changed into deserts and deserts into seas. Volcanoes
have grown into mountains, have been degraded and sunk
beneath the ocean, have been covered with sedimentary
deposits, and again raised up into mountain ranges; while
other mountains have been formed by the upraised coral reefs
of inland seas. The mountains of one period have disappeared
by denudation or subsidence, while the mountains of the suc-
ceeding period have been rising from beneath the waves. The
valleys, the ravines, and the mountain peaks, have been carved
out and filled up again; and all the vegetable forms which
clothe the earth and furnish food for the various classes of
animals have been completely changed again and again.

Liffect of Continental Changes on the Distribution of Ammals.—
tis impossible to exaggerate, or even adequately to conceive,
the effect of these endless mutations on the animal world.
Slowly but surely the whole population of living things must
have been driven backward and forward from east to west, or
from north to south, from one side of a continent or a hemi-
sphere to the other. Owing to the remarkable continuity of
all the land masses, animals and plants must have often been
compelled to migrate into other continents, where in the
struggle for existence under new conditions many would
succumb; while such as were able to survive would consti-
tute those wide-spread groups whose distribution often puzzles
us. Owing to the repeated isolation of portions of continents
for long periods, special forms of life would have time to be

18h

100 ISLAND LIFE. [Parr 1.

developed, which, when again brought into competition with
the fauna from which they had been separated, would cause
fresh struggles of ever increasing complexity, and thus lead to
the development and preservation of every weapon, every habit,
and every instinct, which could in any way cuonduce to the
safety and preservation of the several species.

Changed Distribution proved by the Katinct Animals of Different
epochs.—We thus find that, while the morganic world has been
in a state of continual though very gradual change, the species
of the organic world have also been slowly changing in form and
in the localities they inhabit; and the records of these changes
and these migrations are everywhere to be found, in the “actual
distribution of the species no less than in the fossil remains
which are preserved in the rocks. Everywhere the animals
which have most recently become extinct resemble more or less
closely those which now live in the same country; and where
there are exceptions to the rule, we can generally trace them to
some changed conditions which have led to the extinction of
certain types. But when we go a little further back, to the late
or middle Tertiary deposits, we almost always find, along with
forms which might have been the ancestors of some now living,
others which are only now found in remote regions and often in
distinct continents—clear indications of those extensive migra-
tions which have ever been going on. Every large island
contains in its animal inhabitants a record of the period when
it was last separated from the adjacent continent, while some
portions of existing continents still show by the comparative
poverty and speciality of their animals that at no distant epoch
they were cut off by arms of the sea and formed islands. If
the geclogical record were more perfect, or even if we had as
good a knowledge of that record in all parts of the world as we
have in Europe and North America, we could arrive at much
more accurate results than we are able to do with our present
very imperfect knowledge of extinct forms of life; but even
with our present scanty information we are able to throw much
light upon the past history of our globe and its inhabitants, and
can sketch out with confidence many of the changes they must
have undergone.

cmap. vi.] GEOGRAPHICAL AND GEOLOGICAL CHANGES, 101

Summary of Hvidence for the General Permanence of Continents
and Oceans.—As this question of the permanence of our
continents lies at the root of all our inquiries into the past
changes of the earth and its inhabitants, and as it is at present
completely ignored by many writers, and even by naturalists of
eminence, it will be well to summarise the various kinds of
evidence which go to establish it! We know as a fact that all
sedimentary deposits have been formed under water, but we
also know that they were largely formed in lakes or inland
seas, or near the coasts of continents or great islands, and that
deposits uniform in character and more than 150 or 200 miles
wide were rarely, if ever, formed at the same time. The further
we go from the land the less rapidly deposition takes place,
hence the great bulk of all the strata must have been formed
near land. Some deposits are, it is true, continually forming in
the midst of the great oceans, but these are chiefly organic and
increase very slowly, and there is no proof that any part of the
series of known geological formations exactly resembles them.
Chalk, which is still believed to be such a deposit by many
naturalists, has been shown, by its contained fossils, to be a

1 In a review of Mr. Reade’s Chemical Denudation and Geological Time
in Nature (Oct. 2nd, 1879) the writer remarks as follows:—“ One of the
funny notions of some scientific thinkers meets with no favour from Mr,
Reade, whose geological knowledge is practical as well as theoretical, They
consider that because the older rocks contain nothing like the present red
clays, &c., of the ocean floor, that the oceans have always been in their
present positions, Mr, Reade points out that the first proposition is not
yet proved, and the distribution of animals and plants and the fact that
the bulk of the strata on land are of marine origin are opposed to the hypo-
thesis.” We must leave it to our readers to decide whether the “notion”
developed in this chapter is “ funny,” or whether such hasty and superficial
arguments as those here quoted from a “practical geologist” have any
value as against the different classes of facts, all pointing to an opposite
conclusion, which have now been briefly laid before them, supported as
they are by the expressed opinion of so weighty an authority as Professor
Archibald Geikie, who, in the lecture already quoted says:—‘ From all
this evidence we may legitimately conclude that the present land of the
globe, though formed in great measure of marine formations, has never
Jain under the deep sea; but that its site must always have been near
land. Even its thick marine limestones are the deposits of comparatively
shallow water.”

102 | ISLAND LIFE. [PART I.

comparatively shallow water formation—that is, one formed at a
depth measured by hundreds rather than by thousands of
fathoms. The nature of the formations composing all our
continents also proves the continuity of those continents. Every-
where we find clearly marked shore and estuarine deposits,
showing that every part of the existing land has in turn been
on the sea-shore; and we also find in all periods lacustrine for-
mations of considerable extent with remains of plants and land
animals, proving the existence of continents or extensive lands,
in which such lakes or estuaries could be formed. These lacus-
trine deposits can be traced back through every period, from the
newer Tertiary to the Devonian and Cambrian, and in every
continent which has been geologically explored; and thus com-
plete the proof that our continents have been in existence under
ever changing forms throughout the whole of that enormous
lapse of time.

On the side of the oceans we have also a great weight of
evidence in favour of their permanence and stability. In addi-
tion to their enormous depths and great extent, and the circum-
stance that the deposits now forming in them are distinct from
anything found upon the land-surface, we have the extraordinary
fact that the countless islands scattered over their whole area
(with one or two exceptions only) never contain any Palzeozoic
or Secondary rocks-—that is, have not preserved any fragments
of the supposed ancient continents, nor of the deposits which
must have resulted from their denudation during the whole
period of their existence! The exceptions are New Zealand
and the Seychelles Islands, both situated near to continents,
leaving almost the whole of the vast areas of the Atlantic,
Pacific, Indian, and Southern oceans, without a solitary relic of

the great islands or continents supposed to have sunk beneath
their waves,

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
—Paleontological 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.

WE have now to consider another set of physical revolutions
which have profoundly affected the whole organic world.
Besides the wonderful geological changes to which, as we have
seen, all continents have been exposed, and which must, with
extreme slowness, have brought about the greater features of
the dispersal of animals and plants throughout the world, there
have been also a long succession of climatal changes, which,
though very slow and gradual when measured by centuries, may
have sometimes been rapid as compared with the slow march of
geological mutations.

These climatal changes may be divided into two classes, which
have been thought to be the opposite phases of the same great
phenomenon—cold or even glacial epochs in the Temperate zones
on the one hand, and mild or even warm periods extending into
the Arctic regions on the cther. The evidence for both these
changes baving occurred is conclusive; and as they must be
taken account of whenever we endeavour to explain the past

104 ISLAND LIFE. [PART T.

migrations and actual distribution of the animal world, a brief
outline of the more important facts and of the conclusions they
lead to must be here given.

Proofs of the Recent Occurrence of a Glacial Epoch.—The
phenomena that prove the recent occurrence of glacial epochs in
the temperate regions are exceedingly varied, and extend over
very wide areas. It will be well therefore to state, first, what
those facts are as exhibited in our own country, referring
afterwards to similar phenomena in other parts of the world.

Perhaps the most striking of all the evidences of glaciation
are the grooved, scratched, or striated rocks. These occur
_ abundantly in Scotland, Cumberland, and North Wales, and no
rational explanation of them has ever been given except that
they were formed by glaciers. In many valleys, as, for instance,
that of Llanberris in North Wales, hundreds of examples may
be seen, consisting of deep grooves several inches wide, smaller
furrows, and striz of extreme fineness wherever the rock is of
sufficiently close and hard texture to receive such marks. These
grooves or scratches are often many yards long, they are found
in the bed of the valley as well as high up on its sides, and they
are almost all without exception in one general direction—that
of the valley itself, even though the particular surface they are
upon slopes in another direction. When the native covering of
turf is cleared away from the rock the grooves and striz are often
found in great perfection, and there is reason to believe that
such markings cover, or have once covered, a large part of the
surface. Accompanying these markings we find another, hardly
less curious phenomenon, the rounding off or planing down of
the hardest rocks to a smooth undulating surface. Hard erys-
talline schists with their strata nearly vertical, and which one
would expect to find exposing jagged edges, are found ground
off to a perfectly smooth but never to a flat surface. These
rounded surfaces are found not only on single rocks but over
whole valleys and mountain sides, and form what are termed
roches noutonnées, from their often having the appearance at a
distance of sheep lying down.

Now these two phenomena are actually produced by existing
glaciers, while there is no other known or even conceivable cause

CHAP. VI. | THE GLACIAL EPOCH. 105

that could have produced them. Whenever the Swiss glaciers
retreat a little, as they sometimes do, the rocks in the bed of the
valley they have passed over are found to be rounded, grooved,
and striated just as are those of Wales and Scotland. The two
sets of phenomena are so exactly identical that no one who has
ever compared them can doubt that they are due to the same
causes. But we have further and even more convincing evi-
dence. Glaciers produce many other effects besides these two,
and whatever effects they produce in Switzerland, in Norway, or
in Greenland, we find examples of similar effects having been
produced in our own country. The most striking of these are
moraines and travelled blocks.

Re
oe

A GLACIER WITH MORAINES,

Moraines.—Almost every existing glacier carries down with it
great masses of rock, stones, and éarth, which fall on its surface
from the precipices and mountain slopes which hem it in, or the

106 ISLAND LIFE. [PART I,

rocky peaks which rise above it. As the glacier slowly moves
downward, this débris forms long lines on each side, or on the
centre whenever two glacier-streams unite, and is deposited at
its termination in a huge mound called the terminal moraine.
The decrease of a glacier may often be traced by successive old
moraines across the valley up which it has retreated. When
once seen and examined, these moraines can always be distin-
guished almost at a glance. Their position is most remarkable,
having no apparent natural relation to the form of the valley or
the surrounding slopes, so that they look like huge earthworks
formed by man for purposes of defence. Their composition is
equally peculiar, consisting of a mixture of earth and rocks of
all sizes, usually without any arrangement, the rocks often
being huge angular masses just as they had fallen from the sur-
rounding precipices. Some of these rock masses often rest on the
very top of the moraine in positions where no other natural
force but that of ice could have placed them. Exactly similar
mounds are found in the valleys of North Wales and Scotland,
and always where the other evidences of ice-action occur
abundantly.

Travelled Blocks.—The phenomenon of traveled or perched
blocks is also a common one inall glacier countries, marking out
very clearly the former extent of the ice. When a glacier fills
a lateral valley, its foot will sometimes cross over the main
valley and abut against its opposite slope, and it will deposit
there some portion of its terminal moraine. But in these cir-
cumstances the end of the glacier not being confined laterally will
spread out, and the moraine matter will be distributed over a
large surface, so that the only well-marked token of its presence
will be the larger masses of rock that may have been brought
down. Such blocks are found abundantly in many of the
districts of our own country where other marks of glaciation
exist, and they often rest on ridges or hillocks over which the
ice has passed, these elevations consisting sometimes of loose
material and sometimes of rock different from that of which the
blocks are composed. These are called travelled blocks, and can
almost always be traced to their source in one of the higher
valleys from which the glacier descended. Some of the most

—

CHAP. VII. ] THE GLACIAL EPOCH. 107

remarkable examples of such travelled blocks are to be found on
the southern slopes of the Jura. These consist of enormous
angular blocks of granite, gneiss, and other crystalline rocks,
quite foreign to the Jura mountains, but exactly agreeing with
those of the Alpine range fifty miles away across the great
central valley of Switzerland. One of the largest of these blocks

SS Ly Ay
ST IN SIN NSS ss aN Hy
Tle es

x 8 . % :

RS
ao if Hy

‘ne

07
?
“ YEE ht ®
: aie
ebig it PRAY
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MAP SHOWING THE COURSE OF THE ANCIENT GLACIER OF THE RHONE, AND THE DISTRIBUTION
OF ERRATIC BLOCKS ON THE JURA,

is forty feet diameter, and is situated 900 feet above the level of
the Lake of Neufchatel. These blocks have been proved by
Swiss geologists to have been brought by the ancient glacier of
the Rhone which was fed by the whole Alpine range from Mont
Blanc to the Furka Pass. This glacier must have been many
thousand feet thick at the mouth of the Rhone valley near the

108 ISLAND LIFE. [PART 1.

head of the Lake of Geneva, since it spread over the whole of
the great valley of Switzerland, extending from Geneva to
Neufchatel, Berne, and Soleure, and even on the flanks of the
Jura, reached a maximum height of 2,015 feet above the valley.
The numerous blocks scattered over the Jura for a distance of
about a hundred miles vary considerably in the material of
which they are composed, but they are found to be each trace-
able to a part of the Alps corresponding to their position, on
the theory that they have been brought by a glacier spreading
out from the Rhone valley. Thus, all the blocks situated to the
east of a central point G (see map) can be traced to the eastern
side of the Rhone valley (Jed), while those found towards
Geneva have all come from the west side (ph). It is also very
suggestive that the highest blocks on the Jura at G have come
from the eastern shoulder of Mont Blanc in the direct line
h BF G. Here the glacier would naturally preserve its
greatest thickness, while as it spread out eastward and westward
it would become thinner. We accordingly find that the
travelled blocks on either side of the central point become lower
and lower, till near Soleure and Geneva they are not more than
500 feet above the valley. The evidence is altogether so con-
clusive that, after personal examination of the district in com-
pany with eminent Swiss geologists, Sir Charles Lyell gave up
the view he had first adopted—that the blocks had been car-
ried by ice during a period of submergence—as altogether
untenable.?

The phenomena now described demonstrate a change of
climate sufficient to cover all our higher mountains with
perpetual snow, and fill the adjacent valleys with huge glaciers
at least as extensive as those now found in Switzerland. But
there are other phenomena, best developed in the northern part
of our islands, which show that even this state of things was
but the concluding phase of the glacial period, which, during
its maximum development, must have reduced the northern
half of our island to a condition only to be paralleled now in
Greenland and the Antarctic regions. As few persons besides
professed geologists are acquainted with the weight of evidence

1 Antiquity of Man, 4th Kd. pp. 340-348.

CHAP. VII.] THE GLACIAL EPOCH. 109

for this statement, and as it is most important for our purpose
to understand the amount of the climatal changes the northern
hemisphere has undergone, I will endeavour to make the
evidence intelligible, referring my readers for full details to
Dr. James Geikie’s descriptions and illustrations.?

Glacial Deposits of Scotland: the ‘ Till.”—Over almost all
the lowlands and in most of the highland valleys of Scotland

there are immense superficial deposits of clay, sand, gravel,
or drift, which can be traced more or less directly to glacial
action. Some of these are moraine matter, others are lacus-
trine deposits, while others again have been formed or modified
by the sea during periods of submergence. But below them
all, and often resting directly on the rock-surface, there are
extensive layers of avery tough clayey deposit known as “ till.”
The till is very fine in texture, very tenacious, and often of a
rock-like hardness. It is always full of stones, all of which are
of rude form, but with the angles rubbed off, and almost always
covered with scratches and striz often crossing each other in
various directions. Sometimes the stones are so numerous that
there seems to be only just enough clay to unite them into a
solid mass, and they are of all sizes, from mere grit up to rocks
many feet in diameter. The “ till” is found chiefly in the low-
lying districts, where it covers extensive areas sometimes to a
depth of a hundred feet; while in the highlands it occurs in
much smaller patches, but in some of the broader valleys forms
terraces which have been cut through by the streams. Occa-
sionally it is found as high as two thousand feet above the sea,
in hollows or hill-sides, where it seems to have been protected
from denudation.

The “till” is totally unstratified, and the rock-surfaces on
which it almost always rests are invariably worn smooth, and
much grooved and striated when the rock is hard; but when
it is soft or jointed, it frequently shows a greatly broken surface.
Its colour and texture, and the nature of the stones it contains,
all correspond to the character of the rock of the district where
it occurs, so that it is clearly a local formation. It is often

1 The Great Ice Age and its Relation to the Antiquity of Man. By James
Geikie, F.R.S. (Isbister and Co., 1874.)

110 ISLAND LIFE, [PART I,
found underneath moraines, drift, and other late glacial deposits,
but never overlies them (except in special cases to be hereafter
referred to), so that it is certainly an earlier deposit.

Throughout Scotland, where “till” is found, the glacial strie,
perched blocks, roches moutonnées, and other marks of glacial
action, occur very high up the mountains to at least 3,000 and
often even to 3,500 feet above the sea, while all lower hills and
mountains are rounded and grooved on their very summits;
and these grooves always radiate outwards from the highest
peaks and ridges towards the valleys or the sea.

Inferences from the Glacial Phenomena of Scotland.— Now all
these phenomena taken together render it certain that the
whole of Scotland was once buried in a vast sea of ice, out of
which only the highest mountains raised their summits. There
is absolutely no escape from this conclusion ; for the facts which
lead to it are not local— found only in one spot or one valley—but
general throughout the entire length and breadth of Scotland ;
and are besides supported by such a mass of detailed corrobo-
rative evidence as to amount to absolute demonstration. The
weight of this vast ice-sheet, at least three thousand feet in
maximum thickness, and continually moving seaward with a
slow grinding motion like that of all existing glaciers, must have
ground down the whole surface of the country, especially all the
prominences, leaving the rounded rocks as well as the grooves
and striee we still see marking the direction of its motion. All
the loose stones and rock-masses which lay on the surface woud be
pressed into the ice; the harder blocks would serve as scratching
and grinding tools, and would thus themselves become rounded,
scratched, and striated as we see them, while all the softer masses
would be ground up into impalpable mud along with the
material planed off the rocky projections of the country, leaving
them in the condition of roches moutonnées.

The peculiar characters of the “till,” its fineness and tena-
city, correspond closely with the fine matter which now issues
from under all glaciers, making the streams milky white,
yellow, or brown, according to the nature of the rock, The
sediment from such water is a fine unctuous sticky deposit,
only needing pressure to form it into a tenacious clay; and

CHAP. VIL | THE GLACIAL EPOCH. it

when ‘ till” is exposed to the action of water, it dissolves into a
similar soft sticky unctuous mud. The present glaciers of the
Alps, being confined to valleys which carry off a large quantity of
drainage water, lose this mud perhaps as rapidly as it is formed ;
but when the ice covered the whole country, there was com-
paratively little drainage water, and thus the mud and _ stones
collected in vast compact masses in all the hollows, and espe-
cially in the lower flat valleys, so that, when the ice retreated,
the whole country was more or less covered with it. It was
then, no doubt, rapidly denuded by rain and rivers, but, as we
have seen, great quantities remain to the present day to tell the
tale of its wonderful formation.1 There is good evidence that,

1 This view of the formation of “till” is that adopted by Dr. Geikie,
and upheld by almost all the Scotch, Swiss, and Scandinavian geologists.
The objection however is made by many eminent English geologists,
including Mr. Searles V. Wood, Jun., that mud ground off the rocks
cannot remain beneath the ice, forming sheets of great thickness, be-
cause the glacier cannot at the same time grind down solid rock and
yet pass over the surface of soft mud and loose stones, But this
difficulty will disappear if we consider the numerous fluctuations in the
glacier with increasing size, and the additions it must have been con-
stantly receiving as the ice from one valley after another joined together,
and at last produced an ice-sheet covering the whole country. The
grinding power is the motion and pressure of the ice, and the pressure
will depend on its thickness. Now the points of maximum thickness
must have often changed their positions, and the result would be that the
matter ground out in one place would be forced into another place where
the pressure was less. If there were no lateral escape for the mud, it
would necessarily support the ice over it just as a water-bed supports the
person lying on it; and when there was little drainage water, aud the ice
extended, say, twenty miles in every direction froma given part of a valley
where the ice was of less than the average thickness, the mud would ne-
cessarily accumulate at this part simply because there was no escape for
it. Whenever the pressure all round any area was greater than the pressure
on that area, the débris of the surrounding parts would be forced into it,
and would even raise up the ice to give itroom, This is a necessary
result of hydrostatic pressure. During this process the superfluous water
would no doubt escape through fissures or pores of the ice, and would
leave the mud and stones in that excessively compressed and tenacious
condition in which the “till” is found. The unequal thickness and
pressure of the ice above referred to would be a necessary consequence
of the inequalities in the valleys, now narrowing into gorges, now opening
out into wide plains, and again narrowed lower down; and it is just in

112 ISLAND LIFE. [PART 1.

when the ice was at its maximum, it extended not only over the
land, but far out to sea, covering all the Scottish islands, and
stretching in one connected sheet to Ireland and Wales, where
all the evidences of glaciation are as well marked as in Scotland,
though the ice did not of course attain quite so great a thickness.!

It is evident that the change of climate requisite to produce
such marvellous effects in the British Isles could not have been
local, and we accordingly find strikingly similar proofs that —
Scandinavia and all northern Europe have also been covered
with a huge ice-sheet ; while we have already seen that a similar
gigantic glacier buried the Alps, carrying granitic blocks to the
Jura, where it deposited them at a height of 3,450 feet above
the sea; while to the south, in the plains of Italy, the terminal
moraines left by the retreating glaciers have formed extensive
hills, those of Ivrea, the work of the great glacier from the
Val d’ Aosta being fifteen miles across, and from 700 to 1,500
feet high.

Glacial Phenomena in North America.—In North America
the marks of glaciation are even more extensive and striking

these openings in the valleys that the ‘‘ till” is said to be found, and also in
the lowlands where an ice-sheet must have extended for many miles in
every direction. In these lowland valleys the “till” is both thickest and
most wide-spread, and this is what we might expect. At first, when the
elaciers from the mountains pushed out into these valleys, they would
grind out the surface beneath them into hollows, and the drainage-water
would carry away the débris. But when they spread all over the surface
from sea to sea, and there was little or no drainage water compared to the
enormous area covered with ice, the great bulk of the débris must gather
under the ice wherever the pressure was least, and the ice would
necessarily rise as it accumulated. Some of the mud would no doubt be
forced out along lines of least resistance to the sea, but the friction of the
stone-charged “ till”’ would be so enormous that it would be impossible for
any large part of it to be disposed of in this way.

1 That the ice-sheet was continuous from Scotland to Ireland is proved
by the glacial phenomena in the Isle of Man, where “ till” similar to that in
Scotland abounds, and rocks are found in it which must have come from
Cumberland and Scotland, as well as from the north of Ireland. This
would show that glaciers from each of these districts reached the Isle
of Man, where they met and flowed southwards down the Irish Sea. Ice-
marks are traced over the tops of the mountains which are nearly 2,000 feet
high. (See A Sketch of the Geology of the Isle of Man, by John Horne,
¥.G.8. Trans. of the Edin. Geol. Soc. Vol. II. pt. 3, 1874.)

CHAP, VII.] THE GLACIAL EPOCH.. 113

than in Europe, stretching over the whole of Canada and to the
south of the great lakes as far as latitude 39°. There is, in all
these countries, a wide-spread deposit like the “till” of Scotland,
produced by the grinding of the great ice-sheet when it was at its
maximum thickness ; and also extensive beds of moraine-matter,
true moraines, and travelled blocks, left by the glaciers as they
retreated towards the mountains and finally withdrew into the
upland valleys. There are, also, both in Britain, Scandinavia,
and North America, proofs of the submersion of the land
beneath the sea to a depth of upwards of a thousand feet; but
this is a subject we need not here enter upon, as our special
object is to show the reality and amount of that wonderful and
comparatively recent change of climate termed the glacial epoch.
Many persons, even among scientific men, who have not given
much attention to the question, look upon the whole subject of
the glacial epoch as a geological theory made to explain certain
phenomena which are otherwise a puzzle; and they would not
be much surprised if they were some day told that it was all a
delusion, and that Mr. So-and-so had explained the whole thing
in a much more simple way. It is to prevent my readers being
imposed upon by any such statements or doubts, that I have
given this very brief and imperfect outline of the nature, extent,
and completeness of the evidence on which the existence of the
glacial epoch depends. There is perhaps no great conclusion in
any science which rests upon a surer foundation than this; and
if we are to be guided by our reason at all in deducing the un-
known from the known, the past from the present, we cannot
refuse our assent to the reality of the glacial epoch of the
northern hemisphere in all its more important features, .
Effects of the Glacial Epoch on Animal Life: Warm and Cold
Periods.—lIt is hardly necessary to point out what an important
effect this great climatal cycle must have had upon all living
things. When an icy mantle crept gradually over much of the
northern hemisphere till large portions of Europe and North
America were reduced to the condition of Greenland now, the
greater part of the animal life must have been driven south-
ward, causing a struggle for existence which must have led to

the extermination of many forms, and the migration of others
I

1i4 ISLAND LIFE, [PART I.

into new areas, But these effects must have been greatly
multiplied and intensified if, as there is very good reason to
believe, the glacial epoch itself—or at least the earlier and later
phases of it—consisted of two or more alternations of warm and
cold periods.

The evidence that such was the case is very remarkable. The
“till,” as we have seen, could only have been formed when the
country was entirely buried under a large ice-sheet of enormous
thickness, and when it must therefore have been, in all the parts
so covered, almost entirely destitute of animal and vegetable
life. But in several places in Scotland fine layers of sand and
gravel with beds of peaty matter, have been found resting on
“till” and again covered by “ till.” Sometimes these intercalated
beds are very thin, but in other cases they are twenty or thirty
feet thick, and in them have been found remains of the extinct
ox, the Irish elk, the horse, reindeer and mammoth. Here we
have evidence of two distinct periods of intense cold, and an
intervening milder period sufficiently prolonged for the country
to become covered with vegetation and stocked with animal
life. In some districts borings have proved the existence of no
less than four distinct formations of “till” separated from each
other by beds of sand from two to twenty feet in thickness.?
Facts of a similar nature have been observed in other parts of
our islands. In the east of England, Mr. Skertchly (of the
Geological Survey) enumerates four distinct boulder clays with
intervening deposits of gravels and sands.2_ Mr. Searles V.
Wood, Jun., classes the most recent (Hessle) boulder clay as
“post-glacial,” but he admits an intervening warmer period,
characterised by southern forms of mollusca and insects, after
which glacial conditions again prevailed with northern types of
mollusca.? Elsewhere he says: “ Looking at the presence of
such fluviatile mollusca as Cyrena fluminalis and Unio littoralis
and of such mammalia as the hippopotamus and other great

1 The Great Ice Age, p. 177.

2 These are named, in descending order, Hessle Boulder Clay, Purple -

Boulder Clay, Chalky Boulder Clay, and Lower Boulder Clay—below which
is the Norwich Crag.

3 “On the Climate of the Post-Glacial Period.” Geological Magazine,
1872, p. 158, 160,

CHAP, VII.] THE GLACIAL EPOCH. 115

pachyderms, and of such a littoral Lusitanian fauna as that of
the Selsea bed where it is mixed up with the remains of some
of those pachyderms, as well as of some other features, it has
seemed to me that the climate of the earlier part of the post-
glacial period in England was possibly even warmer than our
present climate; and that it was succeeded by a refrigeration
sufficiently severe to cause ice to form all round our coasts, and
glaciers to accumulate in the valleys of the mountain districts ;
and that this increased severity of climate was preceded, and
partially accompanied, by a limited submergence, which no-
where apparently exceeded 300 feet, and reached that amount
only in the northern counties of England.”! This decided
admission of an alternation of warm and cold climates since the
height of the glacial epoch by so cautious a geologist as Mr,
Wood is very important, as is his statement of an accompanying
depression of the land, accompanying the increased cold, because
many geologists maintain that a greater elevation of the land is
the true and sufficient explanation of glacial periods.

Further evidence of this alternation is found both in the
Isle of Man and in Ireland, where two distinct boulder clays
have been described with intervening beds of gravels and sands.

Paleontological evidence of alternate Cold and Warm periods.—
Especially suggestive of a period warmer than the present, im-
mediately following glacial conditions, is the occurrence of the
hippopotamus in caves, brick-earths, and gravels of paleeolithic
age. Entire skeletons of this animal have been found at Leeds
in a bed of dark blue clay overlaid by gravel. Further north, at
Kirkdale cave, in N. Lat. 54°15’, remains of the hippopotamus
occur abundantly along with those of the ox, elephant, horse,
and other quadrupeds, and with countless remains of the
hysenas which devoured them; while it has also been found
in cave deposits in Glamorganshire, at Durdham Down, near
Bristol, and in the post-Pliocene drifts of Dorsetshire. It is im-
portant to note that where it is associated with other mammals
in caves—which are hyzna-dens, and not mere receptacles of
water-carried remains—these always imply a mild climate, the
elephant and rhinoceros found with it being species character-

1 Gevlogical Magazine, 1876, p. 36.
2

116 ISLAND LIFE. [PART I.

istic of temperate latitudes (Hlephas antiquus and Rhinoceros
hemitechus). But when it occurs in gravels or in water-borne
cave-deposits it 1s sometimes associated with the mammoth, the
woolly rhinoceros and the reindeer, animals which, as certainly,
imply a cold or even arctic climate. This difference is intelligible
if we consider that the hyena which carried the bones of all
these animals into the caves, is itself indicative of a mild
climate, and that there is nothing to cause the remains of
animals of successive epochs to be intermingled in such caves,
In the gravels however it is very different. During the warm
periods the rivers would be inhabited by hippopotami, and the
adjacent plains by elephants and horses, and their remains
would be occasionally imbedded in deposits formed during
floods. But when the cold period came on and these had
passed southward, the same river banks would be grazed by
mammoths and reindeer whose remains would sometimes inter-
mingle with those of the animals which preceded them. It is
to be noted, also, that in many of these river-deposits there
are proofs of violent floods causing much re-arrangement of
materials, so that the remains of the two periods would be thus
still further intermingled.!

The fact of the hippopotamus having lived at 54° N. Lat. in
England, quite close to the time of the glacial epoch, is absolutely
inconsistent with a mere gradual amelioration of climate from
that time till the present day. The immense quantity of vege-
table food which this creature requires, implies a mild and
uniform climate with hardly any severe winter ; and no theory
that has yet been suggested renders this possible except that of
alternate cold and warm periods during the glacial epoch itself.
In order that the hippopotamus could have reached Yorkshire
and retired again as the climate changed, we may suppose it to
have been a permanent inhabitant of the lower Rhone, between
which river and the Rhine there is an easy communication by
means of the Doubs and the Ill, some of whose tributaries
approach within a mile or two of each other about fifteen miles
south-west of Mulhausen. Thence the passage would be easy

1 A. Tylor, on “Quaternary Gravels.” Quarterly Journal of Geological
Society of London, 1869, pp. 83-95 (woodcuts).

CHAP. VIL] THE GLACIAL EPOCH, ely

down the Rhine into the great river which then flowed up the
bed of the North Sea, and thence up the Humber and Ouse
into Yorkshire. By this route there would be only one
watershed to cross, and this might probably have been marshy ;
but we may also suppose the animals to have ascended the
Bristo! Channel after passing round a long extent of French and
English coast (which would then have consisted of vast plains
stretching far beyond the Scilly Isles), in which case they would
find an equally easy passage over a low watershed from the
valley of the Avon to that of the Trent and Yorkshire Ouse.
A consideration of the long and circuitous journey required on
any hypothesis, will at once convince us that it could never
have been made (as some have supposed) annually, during the
short hot summer of the glacial period itself; whereas the
interglacial warm periods lasting several thousand years would
allow for the animals’ gradual migration into all suitable river-
valleys. Thus, the very existence of the hippopotamus in
Yorkshire as well as in the south of England, in close associa-
tion with glacial conditions, must be held to be a strong
corroborative argument in favour of the reality of an inter-
glacial warm period.

Evidence of interglacial warm periods on the Continent and im
North America.—Besides the evidence already adduced from our
own islands, many similar facts have been noted in other
countries. In Switzerland two glacial periods are distinctly
recognised, between which was a warm period when vegetation
was so luxuriant as to form beds of lignite sufficiently thick to
be worked for coal. The plants found in these deposits are
similar to those now inhabiting Switzerland—pines, oaks,
birches, larch, etc., but numerous animal remains are also found
showing that the country was then inhabited by an elephant
(Elephas antiquus), a rhinoceros (Rhinoceros etruscus), the urus
(Bos primigenius), the red deer, (Cervus elephas) and the cave-
bear, (Ursus spelwus); and there were also abundance of
insects.’

In Sweden also there are two “ tills,’ the lower one having
been in places partly broken up and denuded before the upper

1 Heer’s Primeval World of Switzerland. Vol. II., pp. 148-168.

118 ISLAND LIFE. [PART. I.

one was deposited, but no interglacial deposits have yet been
found. In North America more complete evidence has been
obtained. On the shores of Lake Ontario sections are exposed
showing three separate beds of “till” with intervening stratified
deposits, the lower one of which has yielded many plant
remains and fresh-water organisms. These deposits are seen to
extend continuously for more than nine miles, and the fossil-~
iferous interglacial beds attain a thickness of 140 feet. Similar
beds have been discovered near Cleveland, Ohio, consisting, first
of “till” at the lake-level, secondly of about 48 feet of sand
and loam, and thirdly of unstratified “till” full of striated
stones—six feet thick. On the other side of the continent, in
British Columbia, Mr. G. M. Dawson, geologist to the North
American Boundary Commission, has discovered similar
evidence of two glaciations divided from each other by a
warm period.

This remarkable series of observations, spread over so wide
an area, seems to afford ample proof that the glacial epoch did
not consist merely of one process of change, from a temperate
to a cold and arctic climate, which, having reached a maximum,

then passed slowly and completely away; but that there were

certainly two, and probably several more alternations of arctic
and temperate climates.

It is evident however, that if there have been, not two only,
but a series of such alternations of climate, we could not
possibly expect to find more than the most slender indications
of them, because each succeeding ice-sheet would necessarily
grind down or otherwise destroy much of the superficial deposits
left by its predecessors, while the torrents that must always
have accompanied the melting of these huge masses of ice
would wash away even such fragments as might have escaped
the ice itself. It is a fortunate thing therefore, that we should
find any fragments of these interglacial deposits containing
animal and vegetable remains; and just as we should expect,
the evidence they afford seems to show that the later phase of
the cold period was less severe than the earlier. Of such
deposits as were formed on land during the coming on of the

1 Dr. James Geikie in Geological Magazine, 1878, p. 77.

CHAP, VII.] THE GLACIAL EPOCH. Hg

glacial epoch when it was continually increasing in severity
hardly a trace has been preserved, because each succeeding ex-
tension of the ice being greater and thicker than the last, de-
stroyed what had gone before it till the maximum was reached.

Migrations and Extinction of Organisms caused by the Glacial
Epoch.—Our last glacial epoch was accompanied by at least two
considerable submergences and elevations of the land, and there
is some reason to think, as we have already explained, that
the two classes of phenomena are connected as cause and effect.
We can easily see how such repeated submergences and eleva-
tions would increase and aggravate the migrations and extinc-
tions that a glacial epoch is calculated to produce. We can
therefore hardly fail to be right in attributing the wonderful
changes in animal and vegetable life that have occurred in
Europe and N. America between the Miocene Period and the
present day, in part at least, to the two or more cold epochs
that have probably intervened. These changes consist, first, in
the extinction of a whole host of the higher animal forms, and
secondly, in a complete change of types due to extinction and
emigration, leading to a much greater difference between the
vegetable and animal forms of the eastern and western hemis-
phere than before existed. Many large and powerful mammalia
lived in ourown country in Pliocene times and apparently survived
apart of the glacial epoch; but when it finally passed away
they too had disappeared, some having become altogether
extinct while others continued to exist in more southern lands.
Among the first class are the sabre-toothed tiger, the extinct
Siberian camel (Merycotherium), three species of elephant, two
of rhinoceros, a hippopotamus, two bears, five species of deer, and
the gigantic beaver; among the latter are the hyzena, bear, and
lion, which are considered to be only varieties of those which
once inhabited Britain. Down to Pliocene times the flora of
Europe was very similar to that which now prevails in Eastern
Asia and Eastern North America. Hundreds of species of
trees and shrubs of peculiar genera which still flourish in those
countries are now completely wanting in Europe, and we have
good reason to believe that these were exterminated during the
glacial period, being cut off from a southern migration, first by

120 ISLAND LIFE. [PART I,

the Alps, and then by the Mediterranean ; whereas in eastern
America and Asia the mountain chains run in a north and
south direction, and there is nothing to prevent the flora from

having been preserved by a southward migration into a milder
region.

Our next two chapters will be devoted to a discussion of the
causes which brought about the glacial epoch, and that still
more extraordinary climatic phenomenon—the mild climate and
luxuriant vegetation of the Arctic zone. If my readers will
follow me with the care and attention so difficult and interest-
ing a problem requires and deserves, they will find that I have
grappled with all the facts which have to be accounted for, and
offered what I believe is the first complete and sufficient ex-
planation of them. The important influence of climatal changes
on the dispersal of animals and plants isa sufficient justification
for introducing such a discussion into the present volume.

CHAPTER VIITL
THE CAUSES OF GLACIAL EPOCHS.

Various suggested causes—Astronomical causes of changes of Climate—
Difference of Temperature caused by varying distance 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—HEfficiency 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.

No less than seven different causes have been at various times
advanced to account for the glacial epoch and other changes of
climate which the geological record proves to have taken place.
These, as enumerated by Mr. Searles V. Wood, Jun., are as
follows :—

1. A decrease in the original heat of our planet.

2, Changes in the obliquity of the ecliptic.

3. The combined effect of the precession of the equinoxes
and of the excentricity of the earth’s orbit.

122 ISLAND LIFE. (PART I.

4. Changes in the distribution of land and water.

5. Changes in the position of the earth’s axis of rotation.

6. A variation in the amount of heat radiated by the sun.

7. A variation in the temperature of space.

Of the above, causes (1) and (2) are undoubted fealiviane but
it is now generally admitted that they are utterly inadequate
to produce the observed effects. Causes (5) (6) and (7) are
all purely hypothetical, for though such changes may have
occurred there is no evidence that they have occurred during
geological time; and it is besides certain that they would not,
either singly or combined, be adequate to explain the whole of
the phenomena. There remain causes (3) and (4), which have
the advantage of being demonstrated facts, and which are uni-
versally admitted to be capable of producing some effect of the
nature required, the only question being whether, either alone
or in combination, they are adequate to produce all the observed
effects. It is therefore to these two causes that we shall confine
our inquiry, taking first those astronomical causes whose complex
and wide reaching effects have been so admirably explained and
discussed by Dr. Croll in numerous papers and in his work—
‘Climate and Time in their Geological Relations.”

Astronomical Causes of Changes of Climate.—The earth moves
in an elliptical orbit round the sun, which is situated in one of
the foci of the ellipse, so that the distance of the sun from us
varies during the year to a considerable amount. Strange to
" say we are now three millions of miles nearer to the sun in
winter than in summer, while the reverse is the case in the
southern hemisphere; and this must have some effect in making
our northern winters less severe than those of the south temperate
zone. But the earth moves more rapidly in that part of its
orbit which is nearer to the sun, so that our winter is not only
milder, but several days shorter, than that of the southern
hemisphere. The distribution of land and sea and other local
causes prevent us from making any accurate estimate of the
effects due to these differences ; but there can be no doubt that
if our winter were now as long as our summer, and we were also
three million miles further from the sun at the former period, a
very decided difference of climate would result—our winter

GHAP, VIII. ] THE CAUSES OF GLACIAL EPOCHS. 123

would be colder and longer, our summer hotter and shorter.
Now there is a combination of astronomical revolutions (the
precession of the equinoxes and the motion of the aphelion)
which actually brings this change about every 10,500 years, so
that after this interval the condition of the two hemispheres is
reversed as regards nearness to the sun in summer, and com-
parative duration of summer and winter; and this change has
been going on throughout all geological periods. (See Diagram.)
The influence of the present phase of precession is perhaps
seen in the great extension of the antarctic ice-fields, and the
existence of glaciers at the sea-level in the southern hemisphere,
in latitudes corresponding to that of England; but it is not
supposed that similar effects would be produced with us at the

N.HEMISPHERE WINTER IN APHELION S .HEMISPHERE WINTER IN APHELION

GLACIAL EPOCH IN GLACIAL EPOCH IN
N.HEMISPHERE S.HEMISPHERE

DIAGRAM SHOWING THE ALTERED POSITION OF THE POLES AT INTERVALS OF 10,500 YEARS

PRODUCED BY THE PRECESSION OF THE EQUINOXES AND THE MOTION OF THE APHELION ;
AND ITS EFFECT ON CLIMATE DURING A PERIOD OF HIGH EXCENTRICITY,

last cold period, 10,500 years ago, because we are exceptionally
favoured, by the Gulf stream warming the whole North Atlantic
ocean and by the prevalence of westerly winds which convey
that warmth to our shores; and also by the comparatively small
quantity of high land around the North Pole which does not
encourage great accumulations of ice. But the amount of
excentricity itself varies very largely, though very slowly,
and it is now nearly at a minimum. It also varies very
irregularly ; but its amount has been calculated for several
million years back. Fifty thousand years ago it was rather
less than it is now, but it then increased, and when we come
to a hundred thousand years ago there is a difference of

124 ISLAND LIFE, [PART I,

eight and a half millions of miles between our distance from the
sun in aphelion and perehelion (as the most distant and nearest
points of the earth’s orbit are termed). Ata hundred and fifty
thousand years back it had decreased somewhat—to six millions
of miles; but then it increased again, till at two hundred
thousand years ago it was ten anda quarter, and at two hundred
and ten thousand years ten and a half millions of miles. By
reference to the accompanying diagram, which ineludes the

last great period of excentricity, we find, that for the immense

period of a hundred and sixty thousand years (commencing

PROBABLE DURATION OF THE GLACIAL EPOCH),
:

ee)
ae a oe es Ge oe

ine
Whit

THOUSAND YEARS ACO FROM
A.D.1800.

DIAGRAM OF EXCENTRICITY AND PRECESSION.
The dark and light bands mark the phases of precession, the dark showing short mild winters,
and the light long cold winters, the contrast being greater as the excentricity is higher.

The horizontal dotted line marks the present excentricity. The figures show the maxima
and minima of excentricity during the last 300,000 years from Dr. Croll’s Tables.

about eighty thousand years ago) the excentricity was very
great, reaching a maximum of three and a half times its
present amount at almost the remotest part of this period, at
which time the length of summer in one hemisphere and of
winter in the other would be nearly twenty-eight days in excess.
Now, during all this time, our position would change, as above
described (and as indicated on the diagram), every ten thousand
five hundred years; so that we should have alternate periods
of very long and cold winters with short hot summers, and short
mild winters with long cool summers. In order to understand
the important effects which this would produce we must ascertain

CHAP. VIII.] THE CAUSES OF GLACIAL EPOCHS. 125

two things—first, what actual difference of temperature would
be caused by varying distances of the sun, and, secondly, what
are the properties of snow and ice in regard to climate.
Difference of Temperature caused by varying distances of the Sun.
—QOn this subject comparatively few persons have correct ideas
owing to the unscientific manner in which we reckon heat by our
thermometers. Our zero is thirty-two degrees below the freezing
point of water, or, in the centigrade thermometer, the freezing
point itself, both of which are equally misleading when applied
to cosmical problems. If we say that the mean temperature of
a place is 50° F. or 10° C., these figures tell us nothing of how
much the sun warms that place, because if the sun were with-
drawn the temperature would fall far below either of the zero
points. In the last Arctic Expedition a temperature of —74°
F. was registered, or 106° below the freezing point of water ;
and as at the same time the earth, at a depth of two feet, was
only—13° F. and the sea water + 28° F., we may be sure that
even this intense cold was not near the possible minimum
temperature. By various calculations and experiments which
cannot be entered upon here, it has been determined that the
temperature of space, independent of solar (but not of stellar)
influence, is about —259° F., and physicists almost universally
adopt this quantity in all estimates of cosmical temperature.
It follows, that if the mean temperature of the earth’s surface
at any time is 50° F. it is really warmed by the sun to an amount
measured by 50 + 239 = 289° F., which is hence termed its
absolute temperature. Now during the time of the glacial
epoch the greatest distance of the sun in winter was 973
millions of miles, whereas it is now, in winter, only 91 millions
of miles. But the quantity of heat received from the sun is
inversely as the square of the distance, so that it would then be
in the proportion of 8,281 to 9,506 now, or nearly one eighth
less than its present amount. The mean temperature of Eng-
land in January is about 39° F., which equals 278° F. of absolute
temperature. But the above named fraction of 278° is 36°,
representing the amount which must be deducted to obtain the
January temperature during the glacial epoch, which will there-
fore be 3° F. Our actual temperature at that time might,

126 ISLAND LIFE, [PART I.

however, have been very different from this, because the
temperature of a place does not depend so much on the amount
of heat it receives directly from the sun, as on the amount
brought to it or carried away from it by warm or cold winds.
We often have it bitterly cold in the middle of May when we
are receiving as much sun heat as many parts of the tropics,
but we get cold winds from the iceberg-laden North Atlantic,
and this partially neutralises the effect of the sun. So we often
have it very mild in December if south-westerly winds bring
us warm moist air from the Gulf-stream. But though the above
method does not give correct results for any one time or place,
it 1s more nearly correct for very large areas, because all the
sensible surface-heat which produces climates comes from the
sun, and its proportionate amount may be very nearly calculated
in the manner above described. We may therefore say, generally,
that during our northern winter, at the time of the glacial epoch,
the northern hemisphere was receiving so much less heat from
the sun as to lower its surface temperature on an average about
35° F., while during the height of summer of the same period
it would be receiving so much more heat as would suffice to
raise its mean temperature about 60° F. above what it 1s now.
The winter, however, would be long and the summer short, the
difference being twenty-six days.

We have here certainly a superabundant amount of cold in
winter to produce a glacial period,' especially as this cold would

1 In a letter to Nature of October 30th, 1879, the Rev. O. Fisher calls
attention to a result arrived at by Pouillet, that the temperature which the
surface of the ground would assume if the sun were extinguished would
be —128° F. instead of —239°F. If this corrected amount were used in
our calculations, the January temperature of England during the glacial
epoch would come out 17° F.,and this Mr. Fisher thinks not low enough to
cause any extreme difference from the present climate. In this opinion,
however, I cannot agree with him. On the contrary, it would, I think, be
a relief to the theory were the amounts of decrease of temperature in
winter and increase in summer rendered more moderate, since according
to the usual calculation (which I have adopted) the differences are un-
necessarily great. I cannot therefore think that this modification of the
temperatures, should it be ultimately proved to be correct (which is
altogether denied by Dr. Croll), would be any serious objection to the

CHAP. VIII. | THE CAUSES OF GLACIAL EPOCHS. 127

be long continued; but at the same time we should have almost
tropical heat in summer, although that season would be some-
what shorter. How then, it may be asked, could such a climate
have the effect supposed? Would not the snow that fell in
winter be all melted by the excessively hot summer? In order
to answer this question we must take account of certain
properties of water and air, snow and ice, to which due weight
has not been given by writers on this subject.

Properties of Air and Water, Snow and Ice, in relation to
Climate-—The great aerial ocean which surrounds us has the
wonderful property of allowing the heat-rays from the sun to
pass through it without its being warmed by them; but when
the earth is heated the air gets warmed by contact with it, and
also to a considerable extent by the heat radiated from the
warm earth, because, although pure dry air allows such dark
heat-rays to pass freely, yet the aqueous vapour and carbonic
acid in the air intercept and absorb them. But the air thus
warmed by the earth is in continual motion owing to
changes of density. It rises up and flows off, while cooler air
supplies its place; and thus heat can never accumulate in the
atmosphere beyond a very moderate degree, the excessive sun-
heat of the tropics being much of it carried away to the upper
atmosphere and radiated into space. Water also is very mobile;
and although it receives and stores up a great deal of heat, it
is for ever dispersing it over the earth. The rain which brings
down a certain portion of heat from the atmosphere, and which
often absorbs heat from the earth on which it falls, flows away
in streams to the ocean; while the ocean itself, constantly im-
pelled by the winds, forms great currents, which carry off the

adoption of Dr. Croll’s theory of the Astronomical and Physical causes of
the Glacial Epoch.

The reason of the increase of summer heat being 60° while the decrease
of winter cold is only 35°, is because our summer is now below and our
winter above the average. A large part of the 60° increase of temperature
would no doubt be used up in evaporating water, so that there would be a
much less increase of sensible heat ; while only a portion of the 35°
lowering of temperature in winter would be actually produced owing to
equalising effect of winds and currents, and the storing up of heat by
the earth and ocean.

128 ISLAND LIFE. [PART 1,

surplus heated water of the tropics to the temperate and even
to the polar regions, while colder water flows from the poles to
ameliorate the heat of the tropics. An immense quantity of
sun-heat is also used up in evaporating water, and the vapour
thus produced is conveyed by the aerial currents to distant
countries, where, on being condensed into rain, it gives up much
of this heat to the earth and atmosphere.

The power of water in carrying away heat is well exhibited
by the fact of the abnormally high temperature of arid deserts
and of very dry countries generally ; while the still more power-
ful influence of moving air may be appreciated, by considering
the effects of even our northern sun in heating a tightly-closed
glass house to far above the temperature produced by the
vertical sun of the equator where the free air and abundance of
moisture exert their beneficial influence. Were it not for the
large proportion of the sun’s heat carried away by air and
water the tropics would become uninhabitable furnaces—as
would indeed any part of the earth where the sun shone brightly
throughout a summer's day.

We see, therefore, that the excess of heat derived from the sun
at any place cannot be stored up to an important amount owing
to the wonderful dispersing agency of air and water; and
though some heat does penetrate the ground and is stored up
there, this is so little in proportion to the whole amount received,
and the larger part of it is so soon given out from the surface
layers, that any surplus heat that may be thus preserved during
one summer rarely or never remains in sufficient quantity to
affect the temperature of the succeeding summer, so that there
is no such thing as an accumulation of earth-heat from year to
year. But, though heat cannot, cold can be stored up to an
almost unlimited amount, owing to the peculiar property water
possesses of becoming solid at a moderately low temperature ;
and as this is a subject of the very greatest importance to our
inquiry—the whole question of the possibility of glacial epochs
and warm periods depending on it—we must consider it in
some detail.

Effects of Snow on Cluinate-—Let us then examine the very
different effects produced by water falling as a liquid in the

CHAP, VIII. | *THE CAUSES OF GLACIAL EPOCHS. 129

form of rain, or as a solid in the form of snow, although the two
may not differ from each other more than two or three degrees
in temperature. The rain, however much of it may fall, runs off
rapidly into streams and rivers, and soon reaches the ocean. If
cold it cools the air and the earth somewhat while passing
through or over them, but produces no permanent effect on
temperature, because a few hours of sunshine restore to the air
or the surface-soil all the heat they had lost. But if snow
falls for a long time, the effect, as we all know, is very different,
because it has no mobility. It remains where it fell and becomes
compacted into a mass, and it then keeps the earth below it and
the air above, at or near the freezing-point till it is all melted.
If the quantity is great it may take days or weeks to melt; .and
if snow continues falling it goes on accumulating all over the
surface of a country (which water cannot do), and may thus
form such a mass that the warmth of the whole succeeding
summer may not be able to melt it. it then produces perpetual
snow, such as we find above a certain altitude on all the great
mountains of the globe; and when this takes place cold is
rendered permanent, no amount of sun-heat warming the air or
the earth much above the freezing-point. This is illustrated by
the often-quoted fact that at 80° N. Lat., Captain Scoresby had
the pitch melted on one side of his ship by the heat of the sun,
while water was freezing on the other side owing to the coldness
of the air.

The quantity of heat required to melt ice or snow is very
great, as we all know by experience of the long time masses of
snow will remain unmelted even in warm weather. We shall
however be better able to appreciate the great effect this has
upon climate, by a few figures showing what this amount really
is. In order to melt one cubic foot of ice, as much heat is
required as would heat a cubic foot of water from the freezing-
point to 176° F., or two cubic feet to 88° F. To melt a layer of
ice a foot thick will therefore use up as much heat as would
raise a layer of water two feet thick to the temperature of
88° F.; and the effect becomes still more easily understood if
we estimate it as applied to air, for to melt a layer of ice only
14 inches thick would require as much heat as would raise a

130 ISLAND LIFE. [PART I.

stratum of air 800 feet thick from the freezing point to the
tropical heat of 88° F.! | We thus obtain a good idea, both of
the wonderful power of snow and ice in keeping down tempera-
ture, and also of the reason why it requires so long a time
to melt away, and is able to go on accumulating to such an
extent as to become permanent. These properties would, how-
ever, be of no avail if it were liquid, like water; hence it is
the state of solidity and almost complete immobility of ice
that enables it to produce by its accumulation such extra-
ordinary effects in physical geography and in climate, as we
see in the glaciers of Switzerland and the ice-capped interior
of Greenland.

High Land and great Moisture essential to the initiation of a
Glacial epoch._—Another point of great importance in connection
with this subject, is the fact, that this permanent storing up of
cold depends entirely on the annual amount of snow-fall in pro-
portion to that of the sun and air-heat, and not on the actual
cold of winter, or even on the average cold of the year. A
place may be intensely cold in winter and may have a short
arctic summer, yet, if so little snow falls that it is quickly melted
by the returning sun, there is nothing to prevent the summer
being hot and the earth producing a luxuriant vegetation. As
an example of this we have great forests in the extreme north
of Asia and America where the winters are colder and the
summers shorter than in Greenland in Lat. 62° N., or than in
Heard Island and South Georgia, both in Lat. 53° S. in the
Southern Ocean, and almost wholly covered with perpetual snow
and ice. At the “Jardin” on the Mount Blanc range, above
the line of perpetual snow, a thermometer in an exposed situa-
tion marked —6° F, as the lowest winter temperature: while in
many parts of Siberia mercury freezes several weeks in winter,
showing a temperature below —40° F.; yet here the summers
are hot, all the snow disappears, and there is a luxuriant vege-
tation. Even in the very highest latitudes reached by our last
Arctic Expedition there is very little perpetual snow or ice, for
Captain Nares tells us that north of Haye’s Sound, in Lat. 79°
N., the mountains were remarkably free from ice-cap, while
extensive tracts of land were free from snow during summer,

CHAP. VIII. | THE CAUSES OF GLACIAL EPOCHS. 131

and covered with a rich vegetation with abundance of bright
flowers. The reason of this is evidently the scanty snow-fall,
which rendered it sometimes difficult to obtain enough to form
shelter-banks around the ships; and this was north of 80° N.
Lat., where the sun was absent for 142 days.

Perpetual Snow nowhere exists on Lowlands.—It is a very
remarkable and most suggestive fact, that nowhere in the world
at the present time are there any extensive lowlands covered
with perpetual snow. The Tundras of Siberia and the barren
grounds of N. America are all clothed with some kind of summer
' vegetation ;1 and it is only where there are lofty mountains or
plateaus—as in Greenland, Spitzbergen, and Grinnell’s Land—
that glaciers, accompanied by perpetual snow, cover the country,
and descend in places to the level of the sea. In the Antarctic
regions there are extensive highlands and lofty mountains, and
these are everywhere exposed to the influence of moist sea-air ;
and it is here, accordingly, that we find the nearest approach to
a true ice-cap covering the whole circumference of the Antarctic
continent, and forming a girdle of ice-cliffs which almost every-
where descend to the sea. Such Antarctic islands as South
Georgia, South Shetland, and Heard Island, are often said to
have perpetual snow at sea-level; but they are all very moun-
tainous, and send down glaciers into the sea, and as they are
exposed to moist sea-air on every side, the precipitation, almost
all of which takes the form of snow even in summer, is of
course unusually large.

That high land in an area of great precipitation is the neces-
sary condition of glaciation, is well shown by the general state
of the two polar areas at the present time. The northern part of
the north temperate zone 1s almost all land, mostly low but with

1 In an account of Prof. Nordenskjold’s recent expedition round the
northern coast of Asia, given in Nature, November 20th, 1879, we have
the following passage, fully supporting the statement in the text. « “ Along
the whole coast, from the White Sea to Behring’s Straits, no glacier was
seen. During autumn the Siberian coast is nearly free of ice and snow.
There are no mountains covered all the year round with snow, although
some of them rise to a height of more than 2,000 feet.” It must be
remembered that the north coast of Eastern Siberia is in the area of
supposed greatest winter cold on the globe.

Kee

132 ISLAND LIFE. | [PART 1.

elevated borders; while the polar area is, with the exception of
Greenland and a few other considerable islands, almost all water.
In the southern hemisphere the temperate zone is almost all
water, while the polar area is almost all land, or is at least inclosed
by a ring of high and mountainous land. The result is that in
the north the polar area is free from any accumulation of per-
manent ice (except on the highlands of Greenland and Grin-
nell’s Land), while in the south a complete barrier of ice of
enormous thickness appears to surround the pole. Dr. Croll
shows, from the measured height of numerous Antarctic ice-
bergs (often miles in length) that the ice-sheet from which they
are the broken outer fragments must be from a mile to a mile
and a half in thickness. As this is the thickness of the outer
edge of the ice it must be far thicker inland; and we thus find
that the Antarctic continent is at this very time suffering glacia-
tion to quite as great an extent as we have reason to believe
occurred in the same latitudes of the northern hemisphere
during the last glacial epoch.

The accompanying diagrams show the comparative state of
the two polar areas both as regards the distribution of land and
sea, and the extent of the ice-sheet and floating icebergs. - The
much greater quantity of ice at the south pole is undoubtedly
due to the presence of a large extent of high land, which acts as
a condenser, and an unbroken surrounding ocean, which affords
a constant supply of vapour; and the effect is intensified by
winter being there in aphelion, and thus several days longer
than with us, while the whole southern hemisphere is at that
time farther from the sun, and therefore receives less heat.

We see, however, that with less favourable conditions for the
production and accumulation of ice, Greenland is glaciated
down to Lat. 61°. What, then, would be the effect if the
Antarctic continent, instead of being confined almost wholly
within the south polar circle, were to extend in one or two
ereat mountainous promontories far into the temperate zone?
The comparatively small Heard Island in 8. Lat. 53° is even
now glaciated down to the sea. What would be its condition

1 “On the Glacial Epoch,” by James Croll. Geol. Mag. July, August,
1874.

CHAP. VIIL.]

THE CAUSES OF GLACIAL EPOCHS.

133

NORTH POLAR REGIONS.

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Diagram of the approximate extent of Permanent and Floating Ice arcund the North and the South Poles. “(Utter Petermann.)

134 ISLAND LIFE. | [Parr 1.

were it a northerly extension of a lofty Antarctic continent ?
We may be quite sure that glaciation would then be far more
severe, and that an ice-sheet corresponding to that of Greenland
might extend to beyond the parallel of 50° 8. Lat. Even
this is probably too low an estimate, for on the west coast of
New Zealand in 8. Lat. 43° 35’ a glacier even now descends to
within 705 feet of the sea-level; and if those islands were
the northern extension of an Antarctic continent, we may

be pretty sure that they would be nearly in the ice-covered

condition of Greenland, although situated in the latitude of
Marseilles.

Conditions determining the presence or absence of perpetual
Snow.—lIt is clear, then, that the vicinity of a sea or ocean to
supply moisture, together with high land to serve as a con-
denser of that moisture into snow, are the prime essentials of
a great accumulation of ice; and it is fully in accordance with
this view that we find the most undoubted signs of extensive
glaciation in the west of Europe and the east of North America,
both washed by the Atlantic and both having abundance of high
land to condense the moisture which it supplies. Without these
conditions cold alone, however great, can produce no glacial
epoch. This is strikingly shown by the fact, that in the very
coldest portions of the two northern continents—Eastern Siberia
and the north-western shores of Hudson’s Bay—there is no per-
ennial covering of snow or ice whatever. No less remarkable
is the coincidence of the districts of greatest glaciation with
those of greatest rainfall at the present time. Looking at a
rain-map of the British Isles, we see that the greatest area of
excessive rainfall is the Highlands of Scotland, then follows
the west of Ireland, Wales, and the north of England; and
these were glaciated pretty nearly in proportion to the area of
country over which there is an abundant supply of moisture.
So in Europe, the Alps and the Scandinavian mountains have
excessive rainfall, and have been areas of excessive glaciation,
while the Ural and Caucasian mountains, with less rain, never
seem to have been proportionally glaciated. In North America
the eastern coast has an abundant rainfall, and New England

CHAP, VIIi.] THE CAUSES OF GLACIAL EPOCHS. 135

with North-eastern Canada seems to have been the source of
much of the glaciation of that continent.

The reason why no accumulation of snow or ice ever takes
place on Arctic lowlands is explained by the observations of
Lieut. Payer of the Austrian Polar Expedition, who found that
during the short Arctic summer of the highest latitudes the ice-
fields diminished four feet in thickness under the influence of the
sun and wind. To replace this would require a precipitation of
snow equivalent to about 45 inches of rain, an amount which
rarely occurs in lowlands out of the tropics. In Siberia, within
and near the Arctic circle, about six feet of snow covers the
country all the winter and spring, and is not sensibly diminished
by the powerful sun so long as northerly winds keep the air
below the freezing-point and occasional snow-storms occur. But
early in June the wind usually changes to southerly, probably the
south-western anti-trades overcoming the northern inflow; and
under its influence the snow all disappears in a few days and the
vegetable kingdom bursts into full luxuriance. This is very
important as showing the impotence of mere sun-heat to get rid
of a thick mass of snow so long as the air remains cold, while
currents of warm air are in the highest degree effective. If,
however, they are not of sufficiently high temperature or do not
last long enough to melt the snow, they are likely to increase it,

1 “The general absence of recent marks of glacial action in Eastern
Europe is well known; and the series of changes which have been so well
traced and described by Prof. Szabé as occurring in those districts seems to
leave no room for those periodical extensions of ‘ice-caps’ with which
some authors in this country have amused themselves and their readers.
Mr. Campbell, whose ability to recognise the physical evidence of glaciers
will scarcely be questioned, finds quite the same absence of the proof of
extensive ice-action in North America, westward of the meridian of
Chicago.” (Prof. J. W. Judd in Geol. Mag. 1876, p. 535.)

The same author notes the diminution of marks of ice-action on going
eastward in the Alps; and the Altai Mountains far in Central Asia show
no signs of having been largely glaciated. West of the Rocky Mountains,
however, in the Sierra Nevada and the coast ranges further north, signs
of extensive old glaciers again appear; all which phenomena are strikingly
in accordance with the theory here advocated, of the absolute dependence
of glaciation on abundant rainfall and elevated snow-condensers and
accumulators,

136 ISLAND LIFE. [PART I,

from the quantity of moisture they bring with them which will
be condensed into snow by coming into contact with the frozen
surface. We may therefore expect the transition from perpetual
snow to a luxuriant arctic vegetation to-be very abrupt, depend-
ing as it must on.a few degrees more or less in the summer
temperature of the air; and this is quite in accordance with the
fact of corn ripening by the sides of alpine glaciers.

Lifficiency of Astronomical Causes in producing Glaciation.—
Having now collected a sufficient body of facts, let us endeavour
to ascertain what would be the state to which the northern
hemisphere would be reduced by a high degree of excentricity
and a winter in aphelion. When the glacial epoch is supposed
to have been at its maximum, about 210,000 years ago, the

excentricity was more than three times as great as it 1s now,

and, according to Dr. Croll’s calculations, the mid-winter tem-
perature of the northern hemisphere would have been lowered
36° F., while the winter half of the year would have been
twenty-six days longer than the summer half. This would
bring the January mean temperature of England and Scotland
almost down to zero or about 30° F. of frost, a winter climate
corresponding to that of Labrador, or the coast of Greenland on
the Arctic circle. But we must remember that the summer
would be just as much hotter than it is now, and the problem
to be solved is, whether the snow that fell in winter would
accumulate to such an extent that it would not be melted in
summer, and so go on increasing year by year till it covered the
whole of Scotland, Ireland, and Wales, and much of England.
Dr. Croll and. Dr. Geikie answer without hesitation that it
would. Sir Charles Lyell maintained that it would only do so
when geographical conditions were favourable; while the late
Mr. Belt has argued, that excentricity alone would not produce
the effect unless aided by increased obliquity of the ecliptic,
which, by extending the width of the polar regions, would
increase the duration and severity of the winter to such an
extent that snow and ice would be formed in the Arctic and
Antarctic regions at the same time whether the winter were in
perihelion or aphelion.

The problem we have now to solve is a very difficult one,

CHAP. VIII. ] THE CAUSES OF GLACIAL EPOCHS. 137

because we have no case at all parallel to it from which we can
draw direct conclusions. It is, however, clear from the various
considerations we have already adduced, that the increased
cold of winter when the excentricity was great and the sun in
aphelion during that season, would not of itself produce a glacial
epoch unless the amount of vapour supplied for condensation
was also exceptionally great. The greatest quantity of snow
falls in the Arctic regions in summer and autumn, and with us
the greatest quantity of rain falls in the autumnal months. It
seems probable, then, that in all northern lands glaciation would
commence when autumn occurred in aphelwon, All the rain
which falls on our mountains at that season would then fall as
snow, and, being further increased by the snow of winter, would
form accumulations which the summer might not be able to
melt. As time went on, and the aphelion.occurred in winter,
the perennial snow on the mountains would have accumulated
to such an extent as to chill the spring and summer vapours, so
that they too would fall as snow, and thus increase the amount
of deposition ; but it is probable that this would never in our
latitudes have been sufficient to produce glaciation, were it not
for a series of climatal reactions which tend still further to
increase the production of snow.

Action of Meteorological Causes in intensifying Glaciation, —The
trade-winds owe their existence to the great difference between
the temperature of the equator and the poles, which causes a
constant flow of air towards the equator. The strength of this
flow depends on the difference of temperature and. the extent
of the cooled and heated masses of air, and this effect is now
greatest between: the south pole and the equator, owing to the
much greater accumulation of ice in the Antarctic regions. The
consequence is, that the south-east trades are stronger than the
north-east, the neutral zone or belt of calms between them not
being on the equator but several degrees to the north of it.
But just in proportion to the strength of the trade-winds is the
strength of the anti-trades, that is, the upper return current
which carries the warm moisture-laden air of the tropics to-
wards the poles, descending in the temperate zone as west and
south-west winds. These are now strongest in the southern

138 ISLAND LIFE. 5 [PART I.

hemisphere, and, passing everywhere over a wide ocean, they
supply the moisture necessary to produce the enormous quantity
of snow which falls in the Antarctic area. During the period we
are now discussing, however, this state of things would have
been partially reversed. The south polar area, having its
winter in perihelion, would probably have had less ice, while
the north-temperate and Arctic regions would have been largely
ice-clad ; and the north-east trades would therefore be stronger
than they are now. The south-westerly anti-trades would also
be stronger in the same proportion, and would bring with them
a greatly increased quantity of moisture, which is the prime
necessity to produce a condition of glaciation.

But this is only one-half of the effect that would be produced,
for the increased force of the trades sets up another action which
still further helps on the accumulation of snow and ice. It is
now generally admitted that we owe much of our mild climate
and our comparative freedom from snow to the influence of the
Gulf Stream, which also ameliorates the climate of Scandinavia
and Spitzbergen, as shown by the remarkable northward cur-
vature of the isothermal lines, so that Drontheim in N, Lat. 62°
has the same mean temperature as Halifax (Nova Scotia) in
N. Lat, 45°. The quantity of heat now brought into the North
Atlantic by the Gulf Stream depends mainly on the superior
strength of the south-east trades. When the north-east trades
were the more powerful, the Gulf Stream would certainly be of
much less magnitude and velocity; while it is possible, as Dr.
Croll thinks, that a large portion of it might be diverted south- —
ward owing to the peculiar form of the east coast of South
America, and so go to swell the Brazilian current and ameliorate
the climate of the southern hemisphere.

That effects of this nature would follow from any increase of
the Arctic, and decrease of the Antarctic ice, may be considered
certain; and Dr. Croll has clearly shown that in this case cause
and effect act and react on each other in a remarkable way,
The increase of snow and ice in the northern hemisphere is the
cause of an increased supply of moisture being brought by the
more powerful anti-trades, and this greater supply of moisture
leads to an extension of the ice, which reacts in still further

CHAP, VIII. ] THE CAUSES OF GLACIAL EPOCHS. 139

increasing the supply of moisture. The same increase of snow
and ice, by causing the north-east to be stronger than the south-
east trade-winds, diminishes the force of the Gulf Stream, and
this diminution lowers the temperature of the North Atlantic
both in summer and winter, and thus helps on still further the
formation and perpetuation of the icy mantle. It must also be
remembered that these agencies are at the same time acting in
a reverse way in the southern hemisphere, diminishing the
supply of the moisture carried by the anti-trades, and increasing
the temperature by means of more powerful southward ocean-
currents ;—and all this again reacts on the northern hemisphere,
increasing yet further the supply of moisture by the more
powerful south-westerly winds, while still further lowering the
temperature by the southward diversion of the Gulf Stream.

Summary of principal Causes of Glaciation.—I have now suf-
ficiently answered the question, why the short hot summer would
not melt the snow which accumulated during the long cold
winter (produced by high excentricity and winter in aphelion),
although the annual amount of heat received from the sun was
exactly the same as it is now, and equal in the two hemispheres.
It may be well, before going further, briefly to summarise the
essential causes of this apparent paradox. These are—primarily,
the fact that solar heat cannot be stored up owing to its being
continually carried away by air and water, while cold can be so
stored up owing to the comparative immobility of snow and
ice; and, in the second place, because the two great heat-
distributing agencies, the winds and the ocean currents, are so
affected by an increase of the snow and ice towards one pole
and its diminution towards the other, as to help on the process
when it has once begun, and by their action and reaction pro-
duce a maximum of effect which, without their aid, would be
altogether unattainable.

But even this does not exhaust the causes at work, all tending
in one direction. Snow and ice reflect heat to a much greater
degree than do land or water. The heat, therefore, of the short
summer would have far less effect than is due to its calculated
amount in melting the snow, because so much of it would be
lost by reflection. A portion of the reflected heat would no

140 ISLAND LIFE, [PART 1.

doubt warm the vapour in the atmosphere, but this heat would
be carried off to other parts of the earth, while a considerable
portion of the whole would be lost in space. It must also be
remembered that an enormous quantity of heat is used up in
melting snow and ice, without raising its temperature; each
cubic foot of ice requiring as much heat to melt it as would
raise nearly six cubic feet of water 30° F. It has, however,
been argued that because when water is frozen it evolves just
as much heat as it requires to melt it again, there is no loss of
heat on the whole; and as this is adduced as a valid argument
over and over again in every criticism of Dr. Cro!l’s theory, it
may be well to consider it a little more closely. In the act
of freezing no doubt water gives up some of its heat to the
surrounding air; but that air stil remains below the freezing
point or freezing would not take place. The heat liberated by
freezing is, therefore, what may be termed low-grade heat—
heat incapable of melting snow or ice; while the heat absorbed
while ice or snow is melting is high-grade heat, such as is
capable of melting snow and supporting vegetable growth.
Moreover, the low-grade heat liberated in the formation of
snow is usually liberated high wp im the atmosphere, where it
may be carried off by winds to more southern latitudes, while
the heat absorbed in melting the surface of snow and ice is
absorbed close to the earth and is thus prevented from warming
the lower atmosphere, which is in contact with vegetation.
The two phenomena, therefore, by no means counterbalance or
counteract each other, as it is so constantly and superficially
asserted that they do.

Effect of Clouds and Fog in cutting off the Sun’s heat.—Another
very important cause of diminution of heat during summer in
a glaciated country would be the intervention of clouds and
fogs, which would reflect or absorb a large proportion of the
sun-heat and prevent it reaching the surface of the earth ; and
such a cloudy atmosphere would be a necessary result of large
areas of high land covered with snow and ice. That such a
prevalence of fogs and cloud is an actual fact in all ice-clad
countries has been shown by Dr, Croll most conclusively, and
he has further shown that the existence of perpetual snow often

CHAP, VII. | THE CAUSES OF GLACIAL EPOCHS. 141

depends upon it. South Georgia in the latitude of Yorkshire
is almost, and Sandwich Land in the latitude of the north of
Scotland, is entirely covered with perpetual snow; yet in their
summer the sun is three million miles nearer the earth than it
is in our summer, and the heat actually received from the sun
must be sufficient to raise the temperature 20° F. higher than
in the same latitudes in the northern hemisphere, were the con-
ditions equal—instead of which their summer temperature is
probably full 20° lower. The chief cause of this can only be
that the heat of the sun does not reach the surface of the earth ;
and that this is the fact 1s testified by all Antarctic voyagers.
Darwin notes the cloudy sky and constant moisture of the
southern part of Chile, and in his remarks on the climate and
productions of the Antarctic islands he says: “In the Southern
Ocean the winter is not so excessively cold, but the summer is
far less hot (than in the north), for the clouded sky seldom allows
the sun to warm the ocean, itself a bad absorbent of heat; and
hence the mean temperature of the year, which regulates the
zone of perpetually congealed under soil, is low.” Sir James
Ross, Lieutenant Wilkes, and other Antarctic voyagers speak
of the snow-storms, the absence of sunshine, and the freezing
temperature in the height of summer; and Dr. Croll shows
that this is a constant phenomenon accompanying the presence
of large masses of ice in every part of the world.?

In reply to the objections of a recent critic Dr. Croll has
given a new proof of this important fact by comparing the
known amount of snow-fall with the equally well-known melting
power of direct sun-heat in different latitudes. He says: “The
annual precipitation on Greenland in the form of snow and rain,
according to Dr. Rink, amounts to only twelve inches, and two
inches of this he considers is never melted, but is carried away
in the form of icebergs. The quantity of heat received at the
equator from sunrise to sunset, if none were cut off by the
atmosphere, would melt 34 inches of ice, or 100 feet in a year.
The quantity received between latitude 60° and 80°, which is
1 For numerous details and ilustrations see the paper—“*On Ocean

Currents in relation to the Physical Theory of Secular Changes of Climate ”
—in the Philosophical Magazine, 1870.

142 ISLAND LIFE. [PART 1.

that of Greenland, is, according to Meech, one-half that received
at the equator. The heat received by Greenland from the sun,
if none were cut off by the atmosphere, would therefore melt
fifty feet of ice per annum, or fifty times the amount of snow
which falls on that continent. What then cuts off the ninety-
eight per cent of the sun’s heat?” The only possible answer
is, that it is the clonds and fog during a great part of the
summer, and reflection from the surface of ‘the snow and ice
when these are absent.

South Temperate America as illustrating the unfluence of Astro-
nomical Causes on Climate.—Those persons who still doubt the
effect of winter in aphelion with a high degree of excentricity
in producing glaciation, should consider how the condition of
south temperate America at the present day is explicable if
they reject this agency. The line of perpetual snow in the
Southern Andes is so low as 6,000 feet in the same latitude as
the Pyrenees ; in the latitude of the Swiss Alps mountains only
6,200 feet high produce immense glaciers which descend to the
sea-level; while in the latitude of Cumberland mountains only
from 3,000 to 4,000 feet high have every valley filled with
streams of ice descending to the sea-coast and giving off
abundance of huge icebergs. Here we have exactly the con- -
dition of things to which England and Western Europe were
subjected during the latter portion of the glacial epoch, when
every valley in Wales, Cumberland, and Scotland had its glacier;
and to what can this state of things be imputed if not to the
fact that there is now a moderate amount of excentricity,
and the winter of the southern hemisphere is in aphelion ?
The mere geographical position of the southern extremity of
America does not seem especially favourable to the production
of such a state of glaciation. The land narrows from the tropics
southwards and terminates altogether in about the latitude of
Edinburgh; the mountains are of moderate height; while during
summer the sun is three millions of miles nearer, and the heat
received from it is equivalent to a rise of 20° F. as compared
with the same season in the northern hemisphere. The only

1 See Darwin’s Naturalist’s Voyage Round the World, 2nd Edition, pp.
244-251,

Cray, 5.111. | THE CAUSES OF GLACIAL EPOCHS, 145

important differences are: the open southern ocean, the longer
and colder winter, and the general low temperature caused by
the south polar ice. But the great accumulation of south polar
ice is itself due to the great extent of high land within the
Antarctic circle acted upon by the long cold winter and furnished
with moisture by the surrounding wide ocean. These conditions
of high land and open ocean we know did not prevail to so
great an extent in the northern hemisphere during the glacial
epoch, as they do in the southern hemisphere at the present
time ; but the other acting cause—the long cold winter—existed
in a far higher degree, owing to the excentricity being about
three times as much as it is now. It is, so far as we know or
are justified in believing, the only efficient cause of glaciation
which was undoubtedly much more powerful at that time ; and
we are therefore compelled to accept it as the most probable
cause of the much greater glaciation which then prevailed.
Geographical changes, how far a Cause of Glacvation—Messrs.
Croll and Geikie have both objected to the views of Sir Charles
Lyell as to the preponderating influence of the distribution of
land and sea.on climate; and they maintain that if the land
were accumulated almost wholly in the equatorial regions, the
temperature of the earth’s surface as a whole would be lowered,
not raised, as Sir Charles Lyell maintained. The reason given
is, that the land being heated heats the air, which rises and thus
gives off much of the heat to space, while the same area covered
with water would retain more of the heat, and by means of
currents carry it to other parts of the earth’s surface. But
although the mean temperature of the whole earth might be
somewhat lowered by such a disposition of the land, there can
be little doubt that it would render all extremes of temperature
impossible, and that even during a period of high excentricity
there would be no glacial epochs, and perhaps no such thing as
ice anywhere produced, This would result from there being no
land near the poles to retain snow, while the constant inter-
change of water by means of currents between the polar and
tropical regions would most likely prevent ice from ever forming
in the sea. On the other hand, were all the land accumulated in
the polar and temperate regions there can be little doubt that a

144 ISLAND LIFE. [PART I.

state of almost perpetual glaciation of much of the land would
result, notwithstanding that the whole earth should theoretically
be at a somewhat higher temperature. Two main causes would
bring about this glaciation. A very large area of elevated land
in high latitudes would act as a powerful condenser of the
enormous quantity of vapour produced by the whole of the
equatorial and much of the temperate regions being areas of
evaporation, and thus a greater accumulation of snow and ice
would take place around both poles than would be possible
under any other conditions. In the second place there would
be little or no check to this accumulation of ice, because, owing
to the quantity of land around the polar areas, warm oceanic
currents could not reach them, while the warm winds would
necessarily bring so much moisture that they would help on
instead of checking the process of ice-accumulation. If we
suppose the continents to be of the same total area and to have
the same extent and altitude of mountain ranges as the present
ones, these mountains must necessarily offer an almost continu-
ous barrier to the vapour-bearing winds from the south, and the
result would probably be that three-fourths of the land would
be in the ice-clad condition of Greenland, while a comparatively
narrow belt of the more southern lowlands would alone afford.
habitable surfaces or produce any woody vegetation.
Notwithstanding, therefore, the criticism above referred to,
I believe that Sir Charles Lyell was substantially right, and
that the two ideal maps given in the Principles of Geology (11th
ed. Vol. i. p. 270), if somewhat modified so as to allow a freer
passage of currents in the tropics, do really exhibit a condition
of the earth which, by geographical changes alone, would bring
about a perpetual summer or an almost universal winter. But
we have seen in our sixth chapter that there is the strongest
cumulative evidence, almost amounting to demonstration, that
for all known geological periods our continents and oceans have
occupied the same general position they do now, and that no
such radical changes in the distribution of sea and land as
imagined by way of hypothesis by Sir Charles Lyell, have ever
occurred. Such an hypothesis, however, is not without its
use in our present inquiry, for if we obtain thereby a clear

CHAP, VIII.] THE CAUSES OF GLACIAL EPOCHS. 145

conception of the influence of such great changes on climate, we
are the better able to appreciate the tendency of lesser changes
such as have undoubtedly often occurred.

Land as a barrier to ocean currents.—We have seen already the
great importance of elevated land to serve as condensers and
ice-accumulators ; but there is another and hardly less important
effect that may be produced by an extension of land in high
latitudes, which is, to act as a barrier to the flow of ocean
currents. Jn the region with which we are more immediately
interested it is easy to see how a comparatively slight alteration
_ of land and sea, such as has undoubtedly occurred, would produce
an enormous effect on climate, Let us suppose, for instance,
that the British Isles again became continental, and that this
continental land extended across the Faroe Islands and Iceland
to Greenland. The whole of the warm waters of the Atlantic,
with the Gulf Stream, would then be shut out from Northern
Europe, and the result would almost certainly be that snow
would accumulate on the high mountains of Scandinavia till
they became glaciated to as great an extent as Greenland, and
the cold thus produced would react on our own country and
cover the Grampians with perpetual snow, like mountains of
the same height at even a lower latitude in South America.

If a similar change were to occur on the opposite side of
the Atlantic very different effects would be produced. Suppose,
for instance, the east side of Greenland were to sink consider-
ably, while on the west the sea bottom were to rise in Davis’
Strait so as to unite Greenland with Baffin’s Land, thus stopping

Itogether the cold Arctic current with its enormous stream of
icebergs from the west coast of Greenland. Such a change
might cause a great accumulation of ice in the higher polar
latitudes, but it would certainly produce a wonderful ameliorat-
ing effect on the climate of the east coast of North America,
and might raise the temperature of Labrador to that of Scot-
land. Now these two changes have almost certainly occurred,
either together or separately, during the Tertiary period, and
they must have had a considerable effect either in aiding or
checking the terrestrial and astronomical causes affecting climate
which were then in operation.

146 ISLAND LIFE. [PART I.

_ It would be easy to suggest other probable changes which would

produce a marked effect on climate; but we will only refer to
the subsidence of the Isthmus of Panama, which has certaialy
happened more than once in Tertiary times. If this subsidence
were considerable it would have allowed much of the accumulated
warm water which initiates the Gulf Stream to pass into the
Pacific; and if this occurred while astronomical causes were
tending to bring about a cold period in the northern hemisphere,
the resulting glaciation might be exceptionally severe. The
effect of this change would however be neutralised if at the
same epoch the Lesser and Greater Antilles formed a connected
land.

Now, as such possible and even probable geographical
changes are very numerous, they must have produced important
effects; and though we may admit that the astronomical causes
already explained were the most important in determining
the last glacial epoch, we must also allow that geographical
changes must often have had an equally important and perhaps
even a preponderating influence on climate. We must also
remember that changes of land and sea are almost always
accompanied by elevation or depression of the pre-existing
land: and whereas the former produces its chief effect by
diverting the course of warm or cold oceanic currents, the
latter is of not less importance in adding to or diminishing
those areas of condensation and ice-accumulation which, as
we have seen, are the most efficient agents in producing
glaciation.

If then Sir Charles Lyell may have somewhat erred in attach-
ing too exclusive an importance to geographical changes as
bringing about mutations of climate, his critics have, I
think, attached far too little importance to these changes. We
know that they have always been in progress to a sufficient
extent to produce important climatal effects; and we shall
probably be nearest the truth if we consider, that great extremes
of cold have only occurred when astronomical and geographical
causes were acting in the same direction and thus produced a
cumulative result, while, through the agency of warm oceanic
currents, the latter alone have been the chief cause of mild

CHAP, VIII. ] THE CAUSES OF GLACIAL EPOCHS. 147

climates in high latitudes, as we shall prove in our next
chapter.!

On the theory of inter-glacial Periods and their probable character.
—The theory by which the glacial epoch is here explained is
one which apparently necessitates repeated changes from glacial
to warm periods, with all the consequences and modifications
both of climate and physical geography which follow or ac-
company such changes. It is essentially a theory of alternation ;
and it is certainly remarkable in how many cases geologists have
independently deduced some alternations of climate as probable.
Such are the interglacial deposits indicating a mild climate, both
in Europe and America; an early phase of very severe glacia-
tion when the “till” was deposited, with later less extensive

1 The influence of geographical changes on climate is now held by
many geologists who oppose what they consider the extravagant hypotheses
of Dr. Croll, Thus, Prof. Dana imputes the glacial epoch chiefly, if not
wholly, to elevation of the land caused by the lateral pressure due to
shrinking of the earth’s crust that has caused all other elevations and
depressions. He says: “ Now, that elevation of the land over the higher
latitudes which brought on the glacial era is a natural result of the same
agency, and a natural, and almost necessary, counterpart of the coral-island
subsidence which must have been then in progress. The accumulating,
folding, solidification, and crystallisation of rocks attending all the rock-
making and mountain-making through the Paleozoic, Mesozoic, and
Cenozoic eras, had greatly stiffened the crust in these parts; and hence in
after times, the continental movements resulting from the lateral pressure
necessarily appeared over the more northern portions of the continent,
where the accumulations and other changes had been relatively small. To
the subsidence which followed the elevation the weight of the ice-cap may
have contributed in some small degree. But the great balancing move-
ments of the crust of the continental and oceanic areas then going
forward must have had a greatly preponderating effect in the oscillating
agency of all time—lateral pressure within the crust.” (American Journal
of Science and Arts, 3rd Series, Vol. IX. p. 318.)

‘In the 2nd edition of his Afanual of Geology, Professor Dana suggests
elevation of Arctic lands sufficient to exclude the Gulf Stream, as a source
of cold during glacial epochs. This, he thinks, would have made an
epoch of cold at any era of the globe. A deep submergence of Behring’s
Strait, letting in the Pacific warm current to the polar area, would have
produced a mild Arctic climate like that of the Miocene period. When
the warm current was shut out from the polar area it would yet reach
near to it, and bring with it that abundant moisture necessary for
glaciation.” (Manual of Geology, 2nd Edition, pp. 541-754, 756.)

L 2

148 ISLAND LIFE. [PART 1,

glaciation when moraines were left in the valleys; several succes-
sive periods of submergence and elevation, the later ones becom-
ing less and less in amount, as indicated by the raised beaches
slightly elevated above our present coast line; and lastly, the
occurrence in the same deposits of animal remains indicating
both a warm and a cold climate, and especially the existence
of the hippopotamus in Yorkshire soon after the period of
extreme glaciation.

But although the evidence of some alternations of climate
seems indisputable, and no suggestion of any adequate cause
for them other than the alternating phases of precession during
high excentricity has been made, it by no means follows that
these changes were always very great—that is to say, that the
ice completely disappeared and a warm climate prevailed
throughout the whole year. It is quite evident that during
the height of the glacial epoch there was a combination of
causes at work which led to a large portion of North-western
Europe and Hastern America being buried in ice to a greater
extent even than Greenland is now, since it certainly extended
beyond the land and filled up all the shallow seas between
our islands and Scandinavia. Among these causes we must
reckon a diminution of the force of the Gulf Stream, or its being
diverted from the north-western coasts of Europe; and what we
have to consider is, whether the alteration from a long cold
winter and short hot summer, to a short mild winter and long
cool summer would greatly affect the amount of ice af the
ocean currents remained the same. The force of these currents
are, it is true, by our hypothesis, modified by the increase
or diminution of the ice in the two hemispheres alternately,
and they then react upon climate; but they cannot be thus
changed till after the ice-accumulation has been considerably
affected by other causes. Their direction may, indeed, be
greatly changed by slight alterations in the outline of the land,
while they may be barred out altogether by other alterations
of not very great amount; but such changes as these have no
relation to the alteration lot climates caused by the changing
phases of precession.

Now, the existence at the ee time of an ice-clad

CHAP, VIII. | THE CAUSES OF GLACIAL EPOCHS. 149

Greenland is an anomaly in the northern hemisphere, only to
be explained by the fact that cold currents from the polar area
flow down both sides of it. In Eastern Asia we have the lofty
Stanivoi Mountains in the same latitude as the southern part
of Greenland, which, though their summits are covered with
perpetual snow, give rise to no ice-sheet, and, apparently, even
to no important glaciers ;—a fact undoubtedly connected with
the warm Japan current flowing partially into the Sea of
Okhotsk. So in North-west America we have the lofty coast
range, culminating in Mt. St. Ehas, nearly 15,000 feet high, and
an extensive tract of high land to the north and north-west, with
glaciers comparable in size with those of New Zealand, although
situated in Lat. 60° instead of in Lat. 45°. Here, too, we have
the main body of the Japan current turning east and south, and
thus producing a mild climate, little inferior to that of Norway,
warmed by the Gulf Stream. We thus have it made clear that
could the two Arctic currents be diverted from Greenland, that
country would become free from ice, and might even be com-
pletely forest-clad and inhabitable ; while, if the Japan current
were to be diverted from the coast of North America and a cold
current come out of Behring’s Strait, the entire north-western
extremity of America would even now become buried in ice.

Now it is the opinion of the best American geologists that
during the height of the glacial epoch North-eastern America
was considerably elevated. This elevation would bring the
wide area of the banks of Newfoundland far above water,
causing the American coast to stretch out in an immense curve
to a point more than 600 miles east of Halifax ; and this would
certainly divert much of the greatly reduced Gulf Stream straight
across to the coast of Spain. The consequence of such a state
of things would probably be that the southward flowing Arctic
currents would be much reduced in velocity ; and the enormous
quantity of icebergs continually produced by the ice-sheets of
all the lands bordering the North Atlantic would hang about
their shores and the adjacent seas, filling them with a dense
ice-pack, far surpassing that of the Antarctic regions, and chilling
the atmosphere so as to produce constant clouds and fog with

1Dana’s Manual of Geology, 2nd Edition, p. 540,

150 ISLAND LIFE. | i PPAaner

almost perpetual snow storms, even at midsummer, such as now
prevail in the worst portions of the Southern Ocean.

But when such was the state of the North Atlantic (and,
however caused, such must have been its state during the height
of the glacial epoch), can we suppose that the mere change from
the distant sun in winter and near sun in summer, to the
reverse, could bring about any important alteration — the
physical and geographical causes of glaciation remarning un-
changed? For, certainly, the less powerful sun of summer, even
though lasting somewhat longer, could not do more than the
much more powerful sun did during the phase of summer
in perihelion, while during the less severe winters the sun would
have far less power than when it was equally near and at a
very much greater altitude in summer. It seems to me,
therefore, quite certain that whenever extreme glaciation has
been brought about by high excentricity combined with favour-
able geographical and physical causes (and without this combi-
nation it is doubtful whether extreme glaciation would ever
occur), then the ice-sheet will not be removed during the alter-
nate phases of precession, so long as these geographical and
physical causes remain unaltered. It is true that the warm and
cold oceanic currents, which are the most important agents in
increasing or diminishing glaciation, depend for their strength
and efficiency upon the comparative extents of the northern
and southern ice-sheets; but these ice-sheets cannot, I believe,
Increase or diminish to any important extent unless some
geographical or physical change first occurs.’

1 Jn reply to an objection of a somewhat similar nature to this, Dr.
Croll has recently stated (Geol. Mag., Oct., 1879) that he “has not
assumed that the comparative disappearance of the ice on the warm
hemisphere during the period of high excentricity is due to any additional
heat derived from the sun in consequence of the greater length of the
summer,” but that “‘the real and effective cause of the disappearance of
the ice was the enormous transference of equatorial heat to temperate and
polar regions by means of ocean currents.” But this is surely arguing in
a circle; for the ocean currents are mainly due to the difference of tem-
perature of the polar and equatorial areas combined with the peculiar
form and position of the continents, and some one or more of these
factors must be altered before the ocean currents towards the north pole

CHAP, VIII. ] THE CAUSES OF GLACIAL EPOCHS. 151

If this argument is valid, then it would follow that, so long as
excentricity was high, whatever condition of climate was brought
about by it in combination with geographical causes, would
persist through several phases of precession ; but this would not
necessarily be the case when the excentricity itself changed, and
became more moderate. It would then depend upon the pro-
portionate effect of clmatal and geographical causes in produc-
ing glaciation as to what change would be produced by the
changing phases of precession; and we can best examine this
question by considering the probable effect of the change in
precession during the next period of 10,500 years, with the
present moderate degree of excentricity.

Probable effect of Winter in aphelion on the Climate of Britain.
—Let us then suppose the winters of the northern hemisphere
to become longer and much colder, the summers being propor-
tionately shorter and hotter, without any other change whatever.
The long cold winter would certainly bring down the snow-line
considerably, covering large areas of high land with snow during
the winter months, and extending all glaciers and ice-fields.
This would chill the supermcumbent atmosphere to such an
extent that the warm sun and winds of spring and early summer
would bring clouds and fog, so that the sun-heat would be cut
off and much vapour be condensed as snow. The greater sun-
heat of summer would no doubt considerably reduce the snow
and ice; but it is, I think, quite certain that the extra accumula-
tion would not be all melted, and that therefore the snow-line
would be permanently lowered. This would be a necessary result,
because the greater part of the increased cold of winter would be
stored up in snow and ice, while the increased heat of summer
could not be in any way stored up, but would be largely prevented

can be increased. The only factor available is the Antarctic ice, and if
this were largely increased, the northward-flowing currents might be so
increased as to melt some of the Arctic ice. But the very same argument
applies to both poles. Without some geographical change the Antarctic
ice could not materially diminish during its winter in perihelion, nor in-
crease to any important extent during the opposite phase. We there-
fore seem to have no available agency by which to get rid of the ice
over a glaciated country, so long as the geographical conditions remained
unchanyed and the excentricity continued high, me

152 ISLAND LIFE. | [PART 1.

from producing any effect, by reflection from the surface of the
snow and by the intervention of clouds and fog which would
carry much of the heat they received to other regions. It
follows that 10,000 years hence, when our winter occurs in
aphelion (instead of, as now, in perihelion), there will be produced
a colder climate, independently of any change of land and sea,
of heights of mountains, or the force of currents.

But if this is true, then the reverse change, bringing the sun
back into exactly the same position with regard to us as it is in
now (all geographical and physical conditions remaining un-
changed), would certainly bring back again our present milder
climate. The change either way would not probably be very
great, but it might be sufficient to bring the snow line down to
3,000 feet in Scotland, so that all the higher mountains had
their tops covered with perpetual snow. This perpetual snow,
down to a fixed line, would be kept up by the necessary supply
of snow falling during autumn, winter, and spring, and this
would, as we have seen, depend mainly on the increased length
and greatly increased cold of the winter. As both the duration
and the cold of winter decreased the amount of snow would
certainly decrease, and of this lesser quantity of snow a larger
proportion would be melted by the longer, though somewhat
cooler summer. This would follow because the total amount of
sun-heat received during the summer would be the same as
before, while it would act on a less quantity of snow; there
would thus be a smaller surface to reflect the heat, and a smaller
condensing area to produce fogs, while the diminished intensity
of the sun would produce a less dense canopy of clouds, which
have been shown to be of prime importance in checking the
melting of snow by the sun. Wee have considered this case, for
simplicity of reasoning, on the supposition that all geographical
and physical causes remained unchanged. But if an alteration
of the climate of the whole north temperate and Arctic zones
occurred, as here indicated, this would certainly affect both the
winds and currents, in the manner already explained (sce p. 137),
so as to react upon climate and increase the differences produced
by phases of precession. How far that effect would be again
increased by corresponding but opposite changes in the southern

i
alas

CHAP. VIII.] THE CAUSES OF GLACIAL EPOCHS. 153

hemisphere it is impossible to say. It may be that existing
geographical and physical conditions are there such potent agents
in producing a state of glaciation that no change in the phases
of precession would materially affect it. Still, as the climate of
the whole southern hemisphere is dominated by the great
mass of ice within the Antarctic circle, it seems probable that
if the winter were shorter and the summer longer the quantity
of ice would slightly diminish ; and this would again react on
the northern climate as already fully explained.

The essential principle of Climatal change restated—The pre-
ceding discussion has been somewhat lengthy, owing to the
varied nature of the facts and arguments adduced, and the
extreme complexity of the subject. But if, as I venture to
hope, the principle here laid down is a sound one, it will be
of the greatest assistance in clearing away some of the many
difficulties that beset the whole question of geological climates.
This principle is, briefly, that the great features of climate are
determined by a combination of causes, of which geographical
conditions and the degree of excentricity of the earth’s orbit
are by far the most important; that when these combine to
produce a severe glacial epoch, the changing phases of pre-
cession every 10,500 years have very little, if any, effect on
the character of the climate, as mild or glacial, though it may
modify the seasons ; but when the excentricity becomes moderate
and the resulting climate less severe, then the changing phases
of precession bring about a considerable alteration, and even
a partial reversal of the climate.

The reason of this may perhaps be made clearer by consider-
ing the stability of either very cold or very mild conditions,
and the comparative instability of an intermediate state of
climate. When a country is largely covered with ice, we may
look upon it as possessing the accumulated or stored-up cold of
a long series of preceding winters; and however much heat
is poured upon it, its temperature cannot be raised above the
freezing point till that store of cold is got rid of—that is, till
the ice is all melted. But the ice itself, when extensive, tends
to its own preservation, even under the influence of heat; for
the chilled atmosphere becomes filled with fog, and this keeps

154 ISLAND LIFE. [PART T.

off the sun-heat, and then snow falls even during summer, and
the stored-up cold does not diminish during the year, When,
however,only a small portion of the surface is covered with ice,
the exposed earth becomes heated by the hot sun, this warms
the air, and the warm air melts the adjacent ice. It follows,
that towards the equatorial limits of a glaciated country
alternations of climate may occur during a period of high ex-
centricity, while nearer the pole, where the whole country is
completely ice-clad, no amelioration may take place. Exactly
the same thing will occur inversely with mild Arctic climates; but
this is a subject which will be discussed in the next chapter.

This view of the character of the last glacial epoch strictly
corresponds with the facts adduced by geologists. The inter-
glacial deposits never exhibit any indication of a climate whose
warmth corresponded to the severity of the preceding cold,
but rather of a partial amelioration of that cold ; while it 1s only
the very latest of them, which we may suppose to have occurred
when the excentricity was considerably diminished, that exhibit
any indications of a climate at all warmer than that which now
prevails."

1Jn a recent number of the Geological Magazine (April, 1880) Mr. Searles
V. Wood adduces what he considers to be the “‘ conclusive objection ’’ to
Dr. Croll’s excentricity theory, which is, that during the last glacial epoch
Kurope and North America were glaciated very much in proportion to
their respective climates now, which are generally admitted to be due to
the distribution of oceanic currents. But Dr. Croll admits his theory “ to
be baseless unless there was a complete diversion of the warm ocean
currents from the hemisphere glaciated,” in which case there ought to be
no difference in the extent of glaciation in Europe and North America.
Whether or not this is a correct statement of Dr. Croll’s theory, the above
objection certainly does not apply to the views here advocated; but as I
also hold the “ excentricity theory ” in a modified form, it may be as well to
show why it does not apply. In the first place I do not believe that the
Gulf Stream was ‘‘completely diverted” during the glacial epoch, but
that it was diminished in force, and (as described “at p. 138) partly diverted
southward. A portion of. its influence would, however, still remain to
cause a difference between the climates of the two sides of the Atlantic;
and to this must be added two other causes—the far greater penetration
of warm sea-water into the European than into the North American conti-
nent, and the proximity to America of the enormous ice-producing mass
of Greenland. We have thus three distinct causes, all combining to

CHAP. VIII. ] THE CAUSES OF GLACIAL EPOCHS. 155

Probable date of the Glacial Epoch.—The state of extreme
glaciation in the northern hemisphere, of which we gave a
general description at the commencement of the preceding
chapter, is a fact of which there can be no doubt whatever,
and it occurred at a period so recent geologically that all the
_mollusca were the same as species still living. There is clear
geological proof, however, that considerable changes of sea and
land, and a large amount of valley denudation, took place during
and since the glacial epoch, while on the other hand the surface
markings produced by the ice have been extensively preserved ;
and taking all these facts into consideration, the period of about
200,000 years since it reached its maximum, and about 80,000
years since it passed away, 1s generally considered by geologists
to be ample. There seems, therefore, to be little doubt that in
increased excentricity we have found one of the chief exciting
causes of the glacial epoch, and that we are therefore able to
fix its date with a considerable probability of being correct.
The enormous duration of the glacial epoch itself (including
its interglacial, mild, or warm phases), as compared with the
lapse of time since it finally passed away, is a consideration of
the greatest importance, and has not yet been taken fully into
account in the interpretation given by geologists of the physical
and biological changes that were coincident with, and probably
dependent on, it.

Changes of the Sea-level dependent in Glaciation —It has been
pointed out by Dr. Croll, that many of the changes of level of

produce a more severe winter climate on the west than on the east of the
Atlantic during the glacial epoch, and though the first of these—the Gulf
Stream—was not nearly so powerful as it is now, neither is the difference
indicated by the ice-extension in the two countries so great as the present
difference of winter-temperature, which is the essential point to be con-
sidered. The ice-sheet of the United States is usually supposed to have
extended about ten, or, at most, twelve, degrees further south than it did
in Western Europe, whereas we must go twenty degrees further south in
the former country to obtain the same mean winter temperature we find
in the latter, as may be seen by examining any map of winter isothermals.
This difference very fairly corresponds to the difference of conditions
existing during the glacial epoch and the present time, so far as we are
able to estimate them, and it certainly affords no grounds of objection to
the theory by which the glaciation is here explained.

156 ISLAND LIFE. [PART I.

sea and land which occurred about the time of the glacial epoch
may be due to an alteration of the sea-level caused by a shifting
of the earth’s centre of gravity; and physicists have generally
admitted that the cause is a real one, and must have produced
some effect of the kind indicated. It is evident that if ice-
sheets several miles in thickness were removed from one polar
area and placed on the other, the centre of gravity of the earth
would shift towards the heavier pole, and the sea would
necessarily follow it, and would rise accordingly. Extreme
glacialists have maintained that during the height of the glacial
epoch, an ice-cap extended from about 50° N. Lat. in Europe,
and 40° N. Lat. in America, continually increasing in thickness,
till it reached at least six miles thick at the pole; but this view
is now generally given up. A similar ice-cap is however be-
lieved to exist on the Antarctic pole at the present day, and its
transference to the northern hemisphere would, it is calculated,
produce a rise of the ocean to the extent of 800 or 1,000 feet.
We have, however, shown that the production of any such
ice-cap is improbable if not impossible, because snow and ice
can only accumulate where precipitation is greater than melting
and evaporation, and this is never the case except in areas
exposed to the full influence of the vapour-bearing winds. The
outer rim of the ice-sheet would inevitably exhaust the air
of so much of its moisture that what reached the inner parts
would produce farless snow than would be melted by the long
hot days of summer. The accumulations of ice were therefore
probably confined, in the northern hemisphere, to the coasts
exposed to moist winds, and where elevated land and mountain
ranges afforded condensers to initiate the process of glaciation,
and we have already seen that the evidence strongly supports
this view. Even with this limitation, however, the mass of
accumulated ice would be enormous, as indeed we have positive
evidence that it was, and might have caused a sufficient shifting
of the centre of gravity of the earth to produce a submergence
of about 150 or 200 feet.

But this would only be the case if the accumulation of ice
on one pole was accompanied by a diminution on the other, and
this may have occurred to a limited extent during the earlier

CHAP. VIII. ] THE CAUSES OF GLACIAL EPOCHS. 157

stages of the glacial epoch, when alternations of warmer and
colder periods would be caused by winter occurring in perihelion
or aphelion. If, however, as we maintain, no such alternations
- occurred when the excentricity was near its maximum, then the
ice would accumulate in the southern hemisphere at the same
time as in the northern, unless changed geographical conditions,
of which we have no evidence whatever, prevented such accu-
mulations. That there was such a greater accumulation of ice
is shown by the traces of ancient glaciers in the Southern Andes
and in New Zealand, and also, according to several writers, in
South Africa; and the indications in all these localities point
to a period so recent that it must almost certainly have been
contemporaneous with the glacial period of the northern hemi-
sphere, This greater accumulation of ice in both hemispheres

1 The recent extensive glaciation of New Zealand is generally imputed by
the local geologists to a greater elevation of the land; but I cannot help
believing that the high phase of excentricity which caused our own glacial
epoch was at all events an assisting cause. This is rendered more pro-
bable if taken in connection with the following very definite statement of
glacial markings in South Africa. Captain Aylward in his Transvaal of
To-day (p. 171) says :—‘‘ It will be interesting to geologists and others to
learn that the entire country, from the summits of the Quathlamba to the
junction of the Vaal and Orange rivers, shows marks of having been swept
over, and that at no very distant period, by vast masses of ice from east to
west, The striations are plainly visible, scarring the older rocks, and
marking the hill-sides—getting lower and lower and less visible as, descend-
ing from the mountains, the kopjies (small hills) stand wider apart; but
wherever the hills narrow towards each other, again showing how the vast
ice-fields were checked, thrown up, and raised against their eastern
extremities,”

This passage is evidently written by a person familiar with the phe-
nomena of glaciation, and as Captain Aylward’s preface is dated from
Edinburgh, he has probably seen similar markings in Scotland. The
country described consists of the most extensive and lofty plateau in South
Africa, rising to a mountain knot with peaks more than 10,000 feet high,
thus offering an appropriate area for the condensation of vapour and the
accumulation of snow, At present, however, the mountains do not reach
the snow-line, and there is no proof that they have been much higher in
recent times, since the coast of Natal is now said to be rising. It is evi-
dent that no slight elevation would now lead to the accumulation of snow
and ice in these mountains, situated as they are between 27° and 30° S. Lat.;
since the Andes, which in 32°8, Lat. reach 23,300 feet high, and in 28°

158 , ISLAND LIFF. [PART I,

would lower the whole ocean by the quantity of water abstracted
from it, while any want of perfect synchronism between the
decrease of the ice at the two poles would cause a movement
of the centre of gravity of the earth, and a slight rise of the
sea-level at one pole and depression at the other. It is also
generally believed that a great accumulation of ice might cause
subsidence by its pressure on the flexible crust of the earth,
and we thus have a very complex series of agents leading to
elevations and subsidences of limited amount, such as seem
always to have accompanied glaciation. This complexity of
the causes at work may explain the somewhat contradictory
evidence as to rise and fall of land, some authors maintaining
that it stood higher, and others lower, during the glacial
period. 3

The state of the Planet Mars, as bearing on the Theory of
Excentricity as a cause of Glacial Periods.—It is well known
that the polar regions of the planet Mars are covered with white
patches or discs, which undergo considerable alterations of size
according as they are more or less exposed to the sun’s rays.

8. Lat. 20,000, with far more extensive plateaus, produce no ice-fields.
We cannot, therefore, believe that a few thousand feet of additional eleva-
tion, even if it occurred so recently as indicated by the presence of stria-
tions, would have produced the remarkable amount of glaciation above
described ; while from the analogy of the northern hemisphere, we may
well believe that it was mainly due to the same high excentricity that led to
the glaciation of Western and Central Europe, and Eastern North America.

These observations confirm those of Mr. G. W. Stow, who, in a paper
published in the Quarterly Journal of the Geological Society (Vol. xxvii. p.
539), describes similar phenomena in the same mountains, and also mounds
and ridges of unstratified clay packed with angular boulders ; while further
south the Stormberg mountains are said to be similarly glaciated, with im-
mense accumulations of morainic matter in all the valleys. We have here
all the chief surface phenomena characteristic of a glaciated country only
afew degrees south of the tropic; and taken in connection with the evi-
dence of Professor Hartt, who describes true moraines near Rio de Janeiro,
situated on the tropic itself, we can hardly doubt the occurrence of some
general and wide-spread cause of glaciation in the southern hemisphere at
a period so recent that the superficial phenomena are as well preserved as
in Europe. Such evidences of recent glaciation in the southern hemi-
sphere are quite inexplicable without calling in the aid of the recent phase of
high excentricity ; and they may be fairly claimed as adding another link
to the long chain of argument in favour of the theory here advocated.

| \ sil

CHAP, vit] THE CAUSES OF GLACIAL EPOCHS. 159

They have therefore been generally considered to be snow or
ice-caps, and to prove that Mars is now undergoing something
like a glacial period. It must always be remembered, however,
that we are very ignorant of the exact physical conditions of
the surface of Mars. It appears to have a cloudy atmosphere
like our own, but the gaseous composition of that atmosphere
may be different, and the clouds may be formed of other matter
besides aqueous vapour. Its much smaller mass and attractive
power must have an effect on the nature and extent of these
clouds, and the heat of the sun may consequently be modified
ina way quite different from anything that obtains upon our
earth. Bearing these difficulties and uncertainties in mind, let
us see what are the actual facts connected with the supposed
polar snows of Mars.'

Mars offers an excellent subject for comparison with the
Harth as regards this question, because its excentricity 1s now
a little greater than the maximum excentricity of the Earth
during the last million years,—(Mars excentricity 0.0931,
Harth excentricity, 850,000 years back, 0.0707) ; the inclina-
tion of its axis is also a little greater than ours (Mars 28° 51’,
Earth 23°, 27’), and both Mars and the Earth are so situated
that they now have the winter of their northern hemispheres
in perihelion, that of their southern hemisphere being in
aphelion. If, therefore, the physical condition of Mars were
the same or nearly the same as that of the Earth, all cir-
cumstances combine, according to Mr. Croll’s hypothesis, to
produce a severe glacial epoch in its southern, with a perpetual
spring or summer in its northern, hemisphere; while on the
hypothesis here advocated we should expect glaciation at both
poles. As a matter of fact Mars has two snow-caps, of nearly
equal magnitude at their maximum in winter, but varying very
unequally. The northern cap varies slowly and little, the
southern varies rapidly and largely.

1 The astronomical facts connected with the motions and appearance of
the planet are taken from a paper by Mr. Edward Carpenter, M.A., in the
Geological Magazine of March, 1877, entitled, ‘‘ Evidence afforded by
Mars on the subject of Glacial Periods,” but I arrive at somewhat different
conclusions from those of the writer of the paper.

160 ISLAND LIFE. [PART 1.

In the year 1830 the southern snow was observed, during the
midsummer of Mars, to diminish to half its former diameter in
a fortnight (the duration of such phenomena on Mars being
reckoned in Martian months equivalent to one-twelfth of a
Martian year). Thus on June 23rd it was 11° 30° in diameter,
and on July 9th had diminished to 5° 46’, after which it rapidly
increased again. In 1837 the same cap was observed near its
maximum in winter, and was found to be about 35° in diameter.

In the same year the northern snow-cap was observed during
its summer, and was found to vary as follows :—

May 4th. Diameter of spot 31° 24
June 4th, 5 Ny 287
os agen ‘ ‘5 22° 54
July 4th. 55 9 18° 24°
ree sie . i 1S 20"
3 2uth, ¥ ¥y 1G

We thus see that Mars has two permanent snow-caps, of nearly
equal size in winter but diminishing very unequally in summer,
when the southern cap is reduced to nearly one-third the size
of the northern; and this fact is held by Mr. Carpenter, as it
was by the late Mr. Belt, to be opposed to the view of the
hemisphere which has winter in aphelion (as the southern now
has both in the Earth and Mars), having been alone glaciated
during periods of high excentricity.}

Before, however, we can draw any conclusion from the case
of Mars, we must carefully scrutinise the facts, and the condi-
tions they imply. Im the first place, there is evidently this
radical difference between the state of Mars now and of the
Karth during a glacial period—that Mars has no great ice-
sheets spreading over her temperate zone, as the Earth un-
doubtedly had. This we know from the fact of the rapid

1 Tn an article in Nature of Jan. 1, 1880, the Rev. T. W. Webb states that
in 1877 the pole of Mars (? the south pole) was, according to, Schiaparelli,
entirely free of snow. He remarks also on the regular contour of the sup-
posed snows of Mars as offering a great contrast to ours, and also the
strongly marked dark border which has often been observed. On the whole
Mr. Webb seems to be of opinion that there can be no really close resem-
blance between the physical condition of the Earth and Mars, and that any
arguments founded on such supposed similarity are therefore untrustworthy,

CHAP. VIII. ] THE CAUSES OF GLACIAL EPOCHS. 161

disappearance of the white patches over a belt three degrees
wide in a fortnight (equal to a width of about 100 miles of our
measure), and in the northern hemisphere of eight degrees wide
(about 280 miles) between May 4th and July 12th. Even with
our much more powerful sun, which gives us more than twice
as much heat as Mars receives, no such diminution of an ice-
sheet, or of glaciers of even moderate thickness, could possibly
occur ; but the phenomenon is on the contrary exactly analogous
to what actually takes place on the plains of Siberia in summer.

_ These, as I am informed by Mr. Seebohm, are covered with snow

during winter and spring to a depth of six or eight feet, which
diminishes very little even under the hot suns of May, till warm
winds combine with the sun in June, when in about a fortnight
the whole of it disappears, and a little later the whole of Northern
Asia is free from its winter covering. As, however, the sun of
Mars is so much less powerful than ours, we may be sure that
the snow (if it 1s real snow) is much less thick—a mere surface-

coating in fact, such as occurs in parts of Russia where the

precipitation is less, and the snow accordingly does not exceed
two or three feet in thickness.

We now see the reason why the sowthern pole of Mars parts
with its white covering so much quicker and to so much greater
an extent than the northern, for the south pole during summer
is nearest the sun, and, owing to the great excentricity of Mars,
would have about one-third more heat than during the summer
of the northern hemisphere; and this greater heat would cause
the winds from the equator to be both warmer and more power-
ful, and able to produce the same effects on the scanty Martian
snows as they produce on our northern plains. The reason why
both poles of Mars are almost equally snow-covered in winter is
not difficult to understand. Owing to the greater obliquity of
the ecliptic, and the much greater length of the year, the polar
regions will be subject to winter darkness fully twice as long as
with us, and the fact that one pole is nearer the sun during
this period than the other at a corresponding period, will there-
fore make no perceptible difference. It is also probable that
the two poles of Mars are approximately alike as regards their
geographical features, and that neither of them is surrounded

162 ISLAND LIFE. [PART I.

by very high land on which ice may accumulate. With us at
the present time, on the other hand, geographical conditions
completely mask and even reverse the influence of excentricity,
and that of winter in perzhelion in the northern, and summer
in perthelion in the southern hemisphere. In the north we
have a preponderance of sea within the Arctic circle, and of
lowlands in the temperate zone. In the south exactly opposite
conditions prevail, for there we have a preponderance of land
(and much of it high land) within the Antarctic circle, and of
sea in the temperate zone, Ice, therefore, accumulates in the
south, while a thin coating of snow, easily melted in summer,
is the prevalent feature in the north ; and these contrasts react
upon climate to such an extent, that in the southern ocean,
islands in the latitude of Ireland have glaciers descending to
the level of the sea, and constant snowstorms in the height of
summer, although the sun is then actually nearer the earth
than it is during our northern summer!

It is evident, therefore, that the phenomena presented by the
varying polar snows of Mars are in no way opposed to that
modification of Dr. Croll’s theory of the conditions which
brought about the glacial epochs of our northern hemisphere,
which is here advocated ; but are perfectly explicable on the same
general principles, if we keep in mind the distinction between
an ice-sheet—which a summer's sun cannot materially diminish,
but may even increase by bringing vapour to be condensed into
snow—and a thin snowy covering which may be annually melted
and annually renewed, with great rapidity and over large areas.
Except within the small circles of perpetual polar snow there
can at the present time be no ice-sheets in Mars; and the
reason why this permanent snowy area is more extensive around
the northern than around the southern pole may be partly due
to higher land at the north, but is perhaps sufficiently explained
by the diminished power of the summer sun, owing to its greatly
increased distance at that season in the northern hemisphere, so
that it is not able to melt so much of the snow which has
accumulated during the long night of winter.

Le}

CHAPTER IX.

ANCIENT GLACIAL EPOCHS, AND MILD CLIMATES IN THE
ARCTIC REGIONS.

. 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—W hat
evidence of early Glacial Epochs may be expected—Evidences of Ice-
action during the Tertiary Period--The weight of the negative evi-
dence—Temperate climates inthe 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
—HEffect of high excentricity on warm Polar climates—Evidences as to
climate in the Secondary and Paleozoic Epochs—Warm Arctic climates
in early Secondary and Paleozoic times—Conclusions as to the climates
of Secondary and Tertiary Periods—General view of Geological Climates
as dependent on the physical features of the EHarth’s surface—Esti-
mate of the comparative effects of geographical and physical causes in
producing changes of climate.

Ir we adopt the view set forth in the preceding chapter as to
the character of the glacial epoch and of the accompanying
alternations of climate, it must have been a very important agent

producing changes in the distribution of animal and vegetable

life. The intervening mild periods, which almost certainly oc-
curred during its earlier and later phases, were sometimes more
equable than even our present insular climate, and severe frosts
were probably then unknown. During the eight or ten thousand
years that each such mild period lasted, some portions of the

“M 2

164 ISLAND LIFE. [PART I.

north temperate zone, which had been buried in snow or ice,
would become again clothed with vegetation and stocked with
anima! life, both of which, as the cold again came on, would be
driven southward, or perhaps partially exterminated. Forms
usually separated would thus be crowded together, and a.
struggle for existence would follow, which must have led to
the modification or the extinction of many species. When the
survivors in the struggle had reached a state of equilibrium, a
fresh field would be opened to them by the later ameliorations
of climate; the more successful of the survivors would spread
and multiply; and after this had gone on for thousands of
generations, another change of climate, another southward
migration, another struggle of northern and southern forms
would take place.

But if the last glacial epoch has coincided with, and has been
to a considerable extent caused by, a high excentricity of the
earth’s orbit, we are naturally led to expect that earlier glacial
epochs would have occurred whenever the excentricity:was
unusually large. Dr. Croll has published tables showing the
varying amounts of excentricity for three million years back ;
and from these it appears that there have been many periods
of high excentricity, which has often been far greater than
at the time of the last glacial epoch! The accompanying
diagram has been drawn from these tables, and it will be seen
that the highest excentricity occurred 850,000 years ago,
at which time the difference between the sun’s distance at
aphelion and perihelion was thirteen and a half millions of miles,
whereas during the last glacial period the maximum difference
was ten and a half million miles.

Now, judging by the amount of organic and physical change
that occurred during and since the glacial epoch, and that
which has occurred since the Miocene period, it is considered
probable that this maximum of excentricity coincided with some
part of the latter period; and Dr. Croll maintains that a glacial
epoch must then have occurred surpassing in severity that of
which we have such convincing proofs, and consisting like it of

1 London, Edinburgh and Dublin Philosophical Magazine, Vol. XXXVL.,
pp. 144-150 (1868).

OERP: 1x.| - ANCIENT GLACIAL EPOCHS. 165

alternations of cold and warm phases
every 10,500 years. The diagram
also shows us another long-continued
period of high excentricity from
1,750,000 to 1,950,000 years ago,
and yet another almost equal to the
maximum 2,500,000 years back.
These may perhaps have occurred
during the Eocene and Cretaceous
epochs respectively, or all may have
been included within the lhmits of
the Tertiary period. As two of these
high excentricities greatly exceed
that which caused our glacial epoch,
while the third is almost equal to it
and of longer duration, they seem to
afford us the means of testing rival
theories of the causes of glaciation.
If, as Dr. Croll argues, high excen-
tricity is the great and dominating
agency in bringing on glacial epochs,
geographical changes being subor-
dinate, then there must have been

Sie eo ee eee ek WN we ee AT,
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0168

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a bs
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bag = aT

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glacial epochs of gre severity at all =

these three periods; while if he is
also correct in supposing that the
alternate phases of precession would
inevitably produce glaciation in one 4S

hemisphere, and a proportionately
mild and equable climate in the
opposite hemisphere, then we should RS

have to look for évidence of ex- <Q =o

ceptionally warm and exceptionally

DIAGRAM SHOWING THE CHANGES OF EXCENTRICITY DURING THE LAST THREE MILLION YEARS.

cold periods, occurring alternately << — o is
and with several repetitions, with- _ \ S
in a space of time which, geo- | rf
logically speaking, is very short | rs
indeed, ahd =| “9

165 ISLAND LIFE. [PART I.

Let us then inquire first into the character of the evidence
we should expect to find of such changes of climate, if they
have occurred ; we shall then be in a better position to estimate
at its proper value the evidence that actually exists, and, after
giving it due weight, to arrive at some conclusion as to the
theory that best explains and harmonises it.

Lffects of Denudation im destroying the evidence of remote
Glacial Epochs—It may be supposed, that if earlier glacial
epochs than the last did really occur, we ought to meet with
some evidence of the fact corresponding to that which has
satisfied us of the extensive recent glaciation of the northern
hemisphere ; but Dr. Croll and other writers have ably argued
that no such evidence is likely to be found. It is now generally
admitted that sub-aérial denudation is a much more powerful
agent in lowering and modifying the surface of a country than
was formerly supposed. It has in fact been proved to be so
powerful that the difficulty now felt is, not to account for the
denudation which can be proved to have occurred, but to explain
the apparent persistence of superficial features which ought long
ago to have been destroyed.

A proof of the lowering and eating away of the land-surface
which every one can understand, is to be found in the quantity
of solid matter carried down to the sea and to low grounds by
rivers. ‘This is capable of pretty accurate measurement, and
has been so measured for several rivers, large and small, in
different parts of the world. The details of these measure-
ments will be given in a future chapter, and it is only necessary
here to state that the average of them all gives us this result—
that one foot must be taken off the entire surface of the land
each 3,000 years in order to produce the amount of sediment
and matter in solution which is actually carried into the sea.
To give an idea of the limits of variation in different rivers it
may be mentioned that the Mississippi is one which denudes
its valley at a slow rate, taking 6,000 years to remove one foot ;
while the Po is the most rapid, taking only 729 years to do the
same work in its valley. The cause of this difference is very
easy to understand. A large part of the area of the Mississippi

CaiAe. x. . ANCIENT GLACIAL EPOCHS. 167

basin consists of the almost rainless prairie and desert regions of
the west, while its sources are in comparatively arid mountains
with scanty snow-fields, or in a low forest-clad plateau. The
Po, on the other hand, is wholly in a district of abundant rainfall,
while its sources are spread over a great amphitheatre of snowy
Alps nearly 400 miles in extent, where the denuding forces
are ata maximum. As Scotland is a mountain region of rather
abundant rainfall, the denuding power of its rains and rivers is
probably rather above than under the average, but to avoid any
possible exaggeration we will take it at a foot in 4,000 years.

Now if the end of the glacial epoch be taken to coincide with
the termination of the last period of high excentricity, which
occurred about 80,000 years ago (and no geologist will consider
this too long for the changes which have since taken place), it
follows that the entire surface of Scotland must have been since
lowered an average amount of twenty feet. But over large areas
of alluvial plains, and wherever the rivers have spread during
floods, the ground will have been raised instead of lowered ; and
on all nearly level ground and gentle slopes there will have
been comparatively little denudation; so that proportionally
much more must have been taken away from mountain sides
and from the bottoms of valleys having a considerable down-
ward slope. One of the very highest authorities on the subject
of denudation, Mr. Archibald Geikie, estimates the area of these
more rapidly denuded portions as only one-tenth of the com-
paratively level grounds, and he further estimates that the
former will be denuded about ten times as fast as the latter. It
follows that the valleys will be deepened and widened on the
average about five feet in the 4,000 years instead of one foot ;
and thus many valleys must have been deepened and widened
100 feet, and some even more, since the glacial epoch, while
the more level portions of the country will have been lowered
on the average only about two feet.

Now Dr. Croll gives us the following account of the present
aspect of the surface of a large part of the country :—

“ Go where one will in the lowlands of Scotland and he shall
hardly find a single acre whose upper surface bears the marks
of being formed by the denuding agents now in operation. He

168 ISLAND LIFE. [PART I.

will observe everywhere mounds and hollows which cannot be
accounted for by the present agencies at work. . . . Inre-.
gard to the general surface of the country the present agencies
may be said to be just beginning to carve a new line of features
out of the old glacially-formed surface. But so little progress
has yet been made, that the kames, gravel-mounds, knolls of
boulder clay, &c., still retain in most cases their original form.” 4

The facts here seem a little inconsistent, and we must suppose
that Dr. Croll has somewhat exaggerated the universality and
complete preservation of the glaciated surface. The amount of
average denudation, however, is not a matter of opinion but of
measurement; and its consequences can in no way be evaded.
They are, moreover, strictly proportionate to the time elapsed ;
and if so much of the old surface of the country has certainly
been remodelled or carried into the sea since the last glacial
epoch, it becomes evident that any surface-phenomena produced
by still earlier glacial epochs must have long since entirely
disappeared.

fiise of the Sea-level connected with Glacial Epochs, a cause of
further Denudation—tThere is also another powerful agent that
must have assisted in the destruction of any such surface deposits
or markings. During the last glacial epoch itself there were
several oscillations of the land, one at least of considerable extent,
during which shell-bearing gravels were deposited on the flanks
of the Welsh and Irish mountains, now 1,300 feet above sea-
level ; and there is reason to believe that other subsidences of
the same area, though perhaps of less extent, may have occurred
at various times during the Tertiary period. Many writers, as
we have seen, connect this subsidence with the glacial period
itself, the unequal amount of ice at the two poles causing the
centre of gravity of the earth to be displaced, when, of course,
the surface of the ocean will conform to it and appear to rise in
the one hemisphere and sink in the other. If this is the case,
subsidences of the land are natural concomitants of a glacial
period, and will powerfully aid in removing all evidence of its
occurrence. We have seen reason to believe, however, that during
the height of the glacial epoch the extreme cold persisted through

1 Climate and Time in their Geological Relations, p. 341.

CHAP, IX.] ANCIENT GLACIAL EPOCHS. 169

the successive phases of precession, and if so, both polar areas
would probably be glaciated at once. This would cause the
abstraction of a large quantity of water from the ocean, and a
proportionate elevation of the land, which would react on the
accumulation of snow and ice, and thus add another to that
wonderful series of physical agents which act and react on each
other so as to intensify glacial epochs.

But whether or not these causes would produce any important
fluctuations of the sea-level is of comparatively little import-
ance to our present inquiry, because the wide extent of marine
Tertiary deposits in the northern hemisphere and their occur-
rence at considerable elevations above the present sea-level,
afford the most conclusive proofs that great changes of sea and
land have occurred throughout the entire Tertiary period; and
these repeated submergences and emergences of the land com-
bined with sub-aérial and marine denudation, would undoubtedly
destroy all those superficial evidences of ice-action on which we
mainly depend for proofs of the occurrence of the last glacial
epoch.

What evidence of early Glacial Epochs may be expected.—
Although we ‘may admit the force of the preceding argument
as to the extreme improbability of our finding any clear evidence
of the superficial action of ice during remote glacial epochs,
there is nevertheless one kind of evidence that we ought to find,
because it is both wide-spread and practically indestructible.

One of the most constant of all the phenomena of a glaciated
country is the abundance of icebergs produced by the breaking
off of the ends of glaciers which terminate in arms of the sea, or
of the terminal face of the ice-sheet which passes beyond the
land-into the ocean. In both these cases abundance of rocks
and débris, such as form the terminal moraines of glaciers on land,
are carried out to sea and deposited over the sea-bottom of the
area occupied by icebergs. In the case of an ice-sheet it is
almost certain that much of the ground-moraine, consisting of
mud and imbedded stones, similar to that which forms the “ till”
when deposited on land, will be carried out to sea with the ice
and form a deposit of marine “till” near the shore.

It has indeed been objected that when an ice-sheet covered

170 ISLAND LIFE. [PART I.

an entire country there would be no moraines, and that rocks or
débris are very rarely seen on icebergs. But during every
glacial epoch there will be a southern limit to the glaciated
area, and everywhere near this limit the mountain-tops will
rise far above the ice and deposit on it great masses of débris ;
and as the ice-sheet spreads, and again as it passes away,
this moraine-forming area will successively occupy the whole
country. But even such an ice-clad country as Greenland is
now known to have protruding peaks and rocky masses which
give rise to moraines on its surface ;* and, as rocks from Cumber-
land and Ireland were carried by the ice-sheet to the Isle of Man,
there must have been a very long period during which the ice-
sheets of Britain and Ireland terminated in the ocean and sent
off abundance of rock-laden bergs into the surrounding seas;
and the same thing must have occurred along all the coasts of
Northern Europe and Eastern America.

We cannot therefore doubt that throughout the greater part
of the duration of a glacial epoch the seas adjacent to the
glaciated countries would receive continual deposits of large
rocks, rock-fragments, and gravel, similar to the material of
modern and ancient moraines, and analogous to the drift and the
numerous travelled blocks which the ice has undoubtedly scat-
tered broadcast over every glaciated country; and these rocks
and boulders would be imbedded in whatever deposits were then
forming, either from the matter carried down by rivers or from
the mud ground off the rocks and carried out to sea by the
glaciers themselves. Moreover, as icebergs float far beyond the
limits of the countries which gave them birth, these ice-borne
materials would be largely imbedded in deposits forming from
the denudation of countries which had never been glaciated, or
from which the ice had already disappeared.

But if every period of high excentricity produced a glacial
epoch of greater or less extent and severity, then, on account of
the frequent occurrence of a high phase of excentricity during
the three million years for which we have the tables, these
boulder and rock-strewn deposits would be both numerous and
extensive. our hundred thousand years ago the excentricity

1 Nature, Vol. XXI., p. 345, “The Interior of Greenland.”

CHAP. IX.] ANCIENT GLACIAL EPOCHS. vial

was almost exactly the same as it is now, and it continually in-
creased from that time up to the glacial epoch. Now if we take
double the present excentricity as being sufficient to produce
some glaciation in the temperate zone, we find (by drawing out
the diagram at p. 165 on a larger scale) that daring 1,150,000
years out of the 2,400,000 years immediately preceding the last
glacial epoch, the excentricity reached or exceeded this amount,
consisting of sixteen separate epochs, divided from each other by
periods varying from 30,000 to 200,000 years. But if the last
glacial epoch was at its maximum 200,000 years ago, a space
of three million years will certainly include much, if not all, of
the Tertiary period; and even if it does not, we have no reason
to suppose that the character of the excentricity would suddenly
change beyond the three million years.

It follows, therefore, that if periods of high excentricity, like
that which appears to have been synchronous with our last glacial
epoch and is generally admitted to have been one of its efficient
causes, always produced glacial epochs (with or without alternat-
ing warm periods), then the whole of the Tertiary deposits in the
north temperate and Arctic zones should exhibit constantly
alternating boulder and rock-bearing beds, or coarse rock-strewn
gravels analogous to our existing glacial drift, and with some
corresponding change of organic remains. Let us then see what
evidence can be adduced of the existence of such deposits, and
whether it is adequate to support the theory of repeated glacial
epochs during the Tertiary period.

Lvidences of LIce-action during the Tertiary Period. —The
Tertiary fossils both of Europe and North America indicate
throughout warm or temperate climates, except those of the
more recent Pliocene deposits which merge into the earlier
glacial beds. The Miocene deposits of Central and Southern
Europe, for example, contain marine shells of some genera now
only found farther south, while the fossil plants often resemble
those of Madeira and the southern states of North America.
Large reptiles, too, abounded, and man-like apes lived in the south
of France and in Germany. Yet in Northern Italy, near Turin,
there are beds of sandstone and conglomerate full of character-
istic Miocene shells, but containing in an intercalated deposit

V2 ISLAND LIFE. [PART I,

angular blocks of serpentine and greenstone often of enormous
size, one being fourteen feet long, and another twenty-six feet.
Some of the blocks were observed by Sir Charles Lyell to be
faintly striated and partly polished on one side, and they are
scattered through the beds for a thickness of nearly 150 feet.
It is interesting that the particular bed in which the blocks occur
yields no organic remains, though these are plentiful both in
the underlying and overlying beds, as if the cold of the icebergs
had driven away the organisms adapted to live only in a com-
paratively warm sea. Rock similar in kind to these erratics
occurs about twenty miles distant in the Alps.

The Eocene period is even more characteristically tropical in
its flora and fauna, since palms and Cycadacez, turtles, snakes.
and crocodiles then inhabited England. Yet on the north side
of the Alps, extending from Switzerland to Vienna, and also
south of the Alps near Genoa, there is a deposit of finely-
stratified sandstone several thousand feet in thickness, quite
destitute of organic remains, but containing in several places
in Switzerland enormous blocks either angular or partly rounded,
and composed of oolitic limestone or of granite. Near the Lake
of Thun some of the granite blocks found in this deposit are of
enormous size, one of them being 105 feet long, ninety feet wide,
and forty-five feet thick! The granite is red, and of a peculiar
kind which cannot be matched anywhere in the Alps, or indeed
elsewhere. Similar erratics have also been found in beds of the
same age in the Carpathians and in the Apennines, indicating
probably an extensive inland European sea into which glaciers
descended from the surrounding mountains, depositing these
erratics, and cooling the water so as to destroy the mollusca
and other organisms which had previously inhabited it. It is
to be observed that wherever these erratics occur they are
always in the vicinity of great mountain ranges; and although
these can be proved to have been in great part elevated during
the Tertiary period, we must also remember that they must
have been since very much lowered by denudation, of the
amount of which, the enormously thick Eocene and Miocene
beds now forming portions of them is in some degree a measure

as well asa proof. It is not therefore at all improbable that -

CHAP. IX. | ANCIENT GLACIAL EPOCHS. 173

during some part of the Tertiary period these mountains may
have been far higher than they are now, and this we know
might be sufficient for the production of glaciers descending to
the sea-level, even were the climate of the lowlands somewhat
warmer than at present.!

The weight of the negative evidence.—But when we proceed to
examine the Tertiary deposits of other parts of Europe, and
especially of our own country, for evidence of this kind, not
only is such evidence completely wanting, but the facts are of
so definite a character as to satisfy most geologists that it can
never have existed; and the same may be said of temperate
North America and of the Arctic regions generally.

In his carefully written paper on ‘The Climate Controversy ”
Mr. Searles V. Wood, Jun., remarks on this point as follows:
‘‘ Now the Eocene formation is complete in England, and is
exposed in continuous section along the north coast of the Isle
of Wight from its base to its junction with the Oligocene (or
Lower Miocene according to some), and along the northern
coast of Kent fromits base to the Lower Bagshot Sand. It has
been intersected by railway and other cuttings in all directions
and at all horizons, and pierced by wells innumerable; while
from its strata in England, France, and Belgium, the most

1 Prof. J. W. Judd says: “In the case of the Alps I know of no glacial
phenomena which are not capable of being explained, like those of New
Zealand, by a great extension of the area of the tracts above the snow-line
which would collect more ample supplies for the glaciers protruded into
surrounding plains. And when we survey the grand panoramas of ridges,
pinnacles, and peaks produced for the most part by sub-aérial action, we
may well be prepared to admit that before the intervening ravines and
valleys were excavated, the glaciers shed from the elevated plateaux must
have been of vastly greater magnitude than at present.” (Contributions
to the Study of Volcanoes, Geological Magazine, 1876, p. 536.) Profess or
Judd applies these remarks to the last as well as to previous glacial periods
inthe Alps; but surely there has been no such extensive alteration and
lowering of the surface of the country since the erratic blocks were de-
posited on the Jura and the great moraines formed in North Italy, as this
theory would imply. We can hardly suppose wide areas to have been
lowered thousands of feet by denudation, and yet have left other adjacent
areas apparently untouched ; and it is even very doubtful whether such
an extension of the snow-fields would alone suffice for the effects which
were certainly produced.

174 ISLAND LIFE. [PART I.

extensive collections of organic remains have been made of any
formation yet explored, and from nearly all its horizons, for at one
place or another in these three countries nearly every horizon
may be said to have yielded fossils of some kind. These fossils,
however, whether they be the remains of a flora such as that of
Sheppey, or of a vertebrate fauna containing the crocodile and
alligator, such as is yielded by beds indicative of terrestrial
conditions, or of a molluscan assemblage such as is present in
marine or fluvio-marine beds of the formation, are of unmis-
takably tropical or sub-tropical character throughout; and no
trace whatever has appeared of the intercalation of a glacial
period, much less of successive intercalations indicative of more
than one period of 10,500 years’ glaciation. Nor can it be urged
that the glacial epochs of the Eocene in England were intervals
of dry land, and so have left no evidence of their existence
behind them, because a large part of the continuous sequence
of Eocene deposits in this country consists of alternations of
fluviatile, fluvio-marine, and purely marine strata; so that it
seems impossible that during the accumulation of the Eocene
formation in England a glacial period could have occurred
without its evidences being abundantly apparent. The Oligocene
of Northern Germany and Belgium, and the Miocene of those
countries and of France, have also afforded a rich molluscan
fauna, which, like that of the Eocene, has as yet presented no
indication of the intrusion of anything to interfere with its
uniformly sub-tropical character.” ! |

This is sufficiently striking ; but when we consider that this
enormous series of deposits, many thousand feet in thickness,
consists wholly of alternations of clays, sands, marls, shales, or
limestones, with a few beds of pebbles or conglomerate, not one
of the whole series containing irregular blocks of foreign matc-
rial, boulders, or gravel such as we have seen to be the essen-
tial characteristic of a glacial epoch; and when we find that
this very same general character pervades all the extensive
Tertiary deposits of temperate North America, we shall, I think,
be forced to the conclusion that no general glacial epochs could

1 Geological Magazine, 1876, p. 392,

CHAP. 1X.] MILD ARCTIC CLIMATES. 175

have occurred during their formation. It must be remembered
that the “imperfection of the geological record” will not help
us here, because the series of Tertiary deposits is unusually
complete, and we must suppose some destructive agency to have
selected all the intercalated glacial beds and to have so com-
pletely made away with them that not a fragment remains,
while preserving all or almost all the interglacial beds; and to
have acted thus capriciously, not in one limited area only, but
over the whole northern hemisphere, with the local exceptions
on the flanks of great mountain ranges already referred to.

Temperate Climates wn the Arctic regions.—As we have just
seen, the geological evidence of the persistence of sub-tropical
or warm climates in the north temperate zone during the
greater part of the Tertiary period is almost irresistible, and we
have now to consider the stil] more extraordinary series of ob-
servations which demonstrate that this amelioration of climate
extended into the Arctic zone, and into countries now almost
wholly buried in snow and ice. These warm Arctic climates
have been explained by Dr. Croll as due to periods of high
excentricity with winter in perihelion, a theory which implies
alternating epochs of glaciation far exceeding what now prevails ;
and it is therefore necessary to examine the evidence pretty
closely in order to see if this view is more tenable in the case
of the north polar regions than we have found it to be in that
of the north temperate zone.

The most recent of these milder climates 1s perhaps indicated
by the abundant remains of large mammalia—such as the
mammoth, woolly rhinoceros, bison and horse, in the icy alluvial
plains of Northern Siberia, and especially in the Liakhov
Islands in the same latitude as the North Cape of Asia. These
remains occur not in one or two spots only, as if collected by
eddies at the mouth of a river, but along the whole borders of
the Arctic Ocean ; and it 1s generally admitted that the animals
must have lived upon the adjacent plains, and that a consider-
ably milder climate than now prevails could alone have enabled
them to do so. At what period this occurred we do not know,
but one of the last intercalated mild periods of the glacial
epoch itself seems to offer all the necessary conditions. Again,

176 ISLAND LIFE. [PARNy a

Sir Edward Belcher discovered on the dreary shores of Welling-
ton Channel in 753° N. Lat., the trunk and root of a fir-
tree which had evidently grown where it was found. It
appeared to belong to the species Adzes alba, or white fir, which
now reaches 68° N. Lat. and is the most northerly conifer
known. Similar trees, one four feet in circumference and
thirty feet long, were found by Lieut. Mecham im Prince Patrick’s
Island in Lat. 76° 12° N., and other Arctic explorers have
found remains of trees in high latitudes which may all probably —
be referred to the same mild period as that of the ice-preserved
Arctic mammalia.

Similar indications of a recent milder climate are found in
Spitzbergen. Professor Nordenskjéld says: ‘At various places
on Spitzbergen, at the bottom of Lomme Bay, at Cape
Thordsen, in Blomstrand’s strata in Advent Bay, there are
found large and well-developed shells of a bivalve, Mytilus
edulis, which is not now found living on the coasts of Spitzbergen,
though on the west coast of Scandinavia it everywhere covers
he rocks near the sea-shore. These shells occur most plenti-
fully in the bed of a river which runs through Reindeer Valley
at Cape Thordsen. They are probably washed out of a thin
bed of sand at a height of about twenty or thirty feet above
the present sea-level, which is intersected by the river. The
geological age of this bed cannot be very great, and it has
clearly been formed since the present basin of the Ice Sound,
or at least the greater part of it, has been hollowed out by
glacial action.” +

The Miocene Arctic flora.—One of the most starthng and
important of the scientific discoveries of the last twenty years
has been that of the relics of a luxuriant Miocene flora in
various parts of the Arctic regions. It is a discovery that was
totally unexpected, and 1s even now considered by many men of
science to be completely unintelligible; but it is so thoroughly
established, and it has such a direct and important bearing on
the subjects we are discussing in the present volume, that it is
necessary to lay a tolerably complete outline of the facts before
our readers.

1 Geological Magazine, 1876, “ Geology of Spitzbergen,” p. 267.

CHAP: 1X.| MILD ARCTIC CLIMATES. 177

The Miocene flora of temperate Europe was very like that of
Eastern Asia, Japan, and the warmer part of Eastern North
America of the present day. It is very richly represented in
Switzerland by well preserved fossil remains, and after a close
comparison with the flora of other countries Professor Heer
concludes that the Swiss Lower Miocene flora indicates a climate
corresponding to that of Louisiana, North Africa, and South
China, while the Upper Miocene climate of the same country
would correspond to that of the south of Spain, Southern
Japan, and Georgia (U.S. of America). Of this latter flora,
found chiefly at Cininghen in the northern extremity of
Switzerland, 465 species are known, of which 166 species are
trees or shrubs, half of them being evergreens. They comprise
sequoias like the California giant trees, camphor-trees, cimna-
mons, sassafras, bignonias, cassias, gleditschias, tulip-trees, and
many other American genera, together with maples, ashes,
planes, oaks, poplars, and other familiar European trees repre-
sented by a variety of extinct species. If we now go to the
west coast of Greenland in 70° N. Lat., we find abundant
remains of a flora of the same general type as that of Gininghen
but of a more northern character. We have a sequoia identical
with one of the species found at Gininghen, a chestnut, salisburia,
liquidambar, and sassafras, and even a magnolia. We have also
seven species of oaks, two planes, two vines, three beeches,
four poplars, two willows, a walnut, a plum, and several shrubs,
supposed to be evergreens; altogether 137 species, mostly well
and abundantly preserved !

But even further north, in Spitzbergen, in 78° and 79° N.
Lat. and one of the most barren and inhospitable regions on
the globe, an almost equally rich fossil flora has been discovered
including several of the Greenland species, and others peculiar,
but mostly of the same genera. There seem to be no ever-
greens here except conifers, one of which is identical with the
swamp-cypress (Taxodium distichunv) now found living in the
Southern United States! There are also eleven pines, two
Libocedrus, two sequoias, with oaks, poplars, birches, planes,
limes, a hazel, an ash, and a walnut; also water-lilies, pond-
weeds, and an iris—altogether about a hundred species of

178 ISLAND LIFE. [PART 1,
flowering plants. Even in Grinnell Land, within 8} degrees of
the pole, a similar flora existed, twenty-five species of fossil
plants having been collected by the last Arctic expedition, of
which eighteen were identical with the species from other Arctic
localities. This flora comprised poplars, birches, hazels, elms,
viburnums, and eight species of conifers, including the swamp
cypress, and the Norway spruce (Pinus abies) which does not
now extend beyond 693° N.

Fossil plants closely resembling those just mentioned have
been found at many other Arctic localities, especially in Iceland,
on the Mackenzie River in 65° N. Lat. and in Alaska. As an
intermediate station we have, in the neighbourhood of Dantzic
in Lat. 55° N.,a similar flora, with the swamp-cypress, sequoias,
oaks, poplars, and some cinnamons, laurels, and figs. A little
further south, near Breslau north of the Carpathians, a rich
flora has been found allied to that of Gininghen, but wanting in
some of the more tropical forms. Again, in the Isle of Mull
in Scotland, in about 564° N. Lat., a plant-bed has been dis-
covered containing a hazel, a plane, and a sequoia, apparently
identical with a Swiss Miocene species.

We thus find one well-marked type of vegetation spread from
Switzerland and Vienna to North Germany, Scotland, Iceland,
Greenland, Alaska, and Spitzbergen, some few of the species
even ranging over the extremes of latitude between Cininghen —
and Spitzbergen, but the great majority being distinct, and ex-
hibiting decided indications of a decrease of temperature accord-
ing to latitude, though much less in amount than now exists.
Some writers have thought that the great similarity of the floras
of Greenland and Cininghen is a proof that they were not con-
temporaneous, but successive ; and that of Greenland has been
supposed to be as old as the Kocene. But the arguments yet
adduced do not seem to prove such a difference of age, because
there is only that amount of specific and generic diversity between
the two which might be produced by distance and difference of
temperature, under the exceptionally equable climate of the
period. We have even now examples of an equally wide range
of well-marked types; as in temperate South America, where
many of the genera and some of the species range from the

CHAP. IX.] MILD ARCTIC CLIMATES. 179

Straits of Magellan to Valparaiso—places differing as much in
latitude as Switzerland and West Greenland ; and the same may
be said of North Australia and Tasmania, where, at a greater
latitudinal distance apart, closely allied forms of Eucalyptus,
Acacia, Casuarina, Stylidium, Goodenia, and many other genera
would certainly form a prominent feature in any fossil flora now
being preserved.

Mild Arctic Climates of the Cretaceous Period.—In the Upper
Cretaceous deposits of Greenland (in a locality not far from
those of the Miocene age last described) another remarkable flora
has been discovered, agreeing generally with that of Europe and
North America of the same geological age. Sixty-five species
of plants have been identified, of which there are fifteen ferns,
two cycads, eleven conifers, three monocotyledons, and thirty-
four dicotyledons. One of the ferns is a tree-fern with thick
stems, which has also been found in the Upper Greensand of
England. Among the conifers the giant sequoias are found,
and among the dicotyledons the genera Populus, Myrica, Ficus,
Sassafras, Andromeda Diospyros, Myrsine, Panax, as well as
magnolias, myrtles, and leguminose. Several of these groups
occur also in the much richer deposits of the same age in North
America and Central Europe ; but all of them evidently afford
such fragmentary records of the actual flora of the period, that
it is impossible to say that any genus found in one locality was
absent from the other merely because it has not yet been found
there. On the whole, there seems to be less difference between
the floras of Arctic and temperate latitudes in Upper Cretaceous
than in Miocene times.

In the same locality in Greenland (70° 33’ N. Lat. and 52°
W. Long.), and also in Spitzbergen, a more ancient flora, of Lower
Cretaceous age, has been found ; but it differs widely from the
other in the great abundance of cycads and conifers and the
scarcity of exogens, which latter are represented by a single
poplar. Of the thirty-eight ferns, fifteen belong to the genus
Gleichenia now almost entirely tropical. There are four genera
of cycads, and three extinct genera of conifers, besides Glyptos-
trobus and Torreya now found only in China and California, six
species of true pines, and five of the genus Sequoia one of which

N 2

aed

180 ~ ISLAND LIFE. [PART I.

occurs also in Spitzbergen. The Kuropean deposits of the same
age closely agree with these in their general character, conifers,
cycads, and ferns forming the mass of the vegetation, while
exogens are entirely absent, the above-named Greenland poplar
being the oldest known dicotyledonous plant.!

If we take these facts as really representing the flora of the
period, we shall be forced to conclude that, measured by the
change effected in its plants, the lapse of time between the Lower
and Upper Cretaceous deposits was far greater than between the
Upper Cretaceous and the Miocene—a conclusion quite opposed
to the indications afforded by the mollusca and the higher
animals of the two periods. It seems probable, therefore, that
these Lower Cretaceous plants represent local peculiarities of
vegetation such as now sometimes occur in tropical countries.
On sandy or coralline islands in the Malay Archipelago there
will often be found a vegetation consisting almost wholly of
cycads, pandani, and palms, while a few miles off, on moderately
elevated land, not a single specimen of either of these families
may be seen, but a dense forest of dicotyledonous trees covering
the whole country. A lowland vegetation, such as that above
described, might be destroyed and its remains preserved by a
slight depression, allowing it to be covered up by the detritus of
some adjacent river, while not only would the subsidence of
high land be a less frequent occurrence, but when it did occur
the steep banks would be undermined by the waves, and the
trees falling down would be floated away, and would either be
cast on some distant shore or slowly decay on the surface or in
the depths of the ocean.

From the remarkable series of facts now briefly summarized,
we learn, that whenever plant-remains have been discovered
within the Arctic regions, either in Tertiary or Cretaceous
deposits, they show that the climate was one capable of support-
ing a rich vegetation of trees, shrubs, and herbaceous plants,
similar in general character to that which prevailed in the tem-
perate zone at the same periods, but showing the influence of
a less congenial climate. These deposits belong to at least four

1 The preceding account is mostly derived from Professor Heer’s great
work Flera Fossilis Arctica,

CHAP. Ix.] MILD ARCTIC CLIMATES. 181

distinct geological horizons, and have been found widely scattered
within the Arctic circle, yet nowhere has any proof been obtained
of intercalated cold periods, such as would be indicated by the
remains of a stunted vegetation, or a molluscan fauna similar
to that which now prevails there.

Stratigraphical Evidence of long-continued mild Arctic con-
ditions.—Let us now turn to the stratigraphical evidence, which,
as we have already shown, offers a crucial test of the occurrence
or non-occurrence of glaciation during any extensive geological
period ; and here we have the testimony of perhaps the greatest
living authority on Arctic geology—Professor Nordenskjold. In
his lecture on “ The Former Climate of the Polar Regions” he
says: “The character of the coasts in the Arctic regions is
especially favourable to geological investigations. While the
valleys are for the most part filled with ice, the sides of the
mountains in summer, even in the 80th degree of latitude, and
to a height of 1,000 or 1,500 feet above the level of the sea, are
almost wholly free from snow. Nor are the rocks covered with
any amount of vegetation worth mentioning ; and, moreover, the
sides of the mountains on the shore itself frequently present
perpendicular sections, which everywhere expose their bare
surfaces to the investigator. The knowledge of a mountain’s
geognostic character, at which one, in the more southerly
countries, can only arrive after long and laborious researches,
removal of soil and the like, is here gained almost at the first
glance ; and as we have never seen in Spitzbergen nor in Green-
land, in these sections often many miles in length, and including
one may say all formations from the Silurian to the Tertiary,
any boulders even as large as a child’s head, there is not the
smallest probability that strata of any considerable extent, con-
taining boulders, are to be found in the polar tracts previous to
the middle of the Tertiary period. Since, then, both an exami-
nation of the geognostic condition, and an investigation of the
fossil flora and fauna of the polar lands, show no signs of a
glacial era having existed in those parts before the termination
of the Miocene period, we are fully justified in rejecting, on the
evidence of actual observation, the hypotheses founded on
purely theoretical speculations, which assume the many times

182 ISLAND LIFE. [PART I.

repeated alternation of warm and glacial climates between the
present time and the earliest geological ages.”! And again, in
his Sketch of the Geology of Spitzbergen, after describing the
various formations down to the Miocene, he says: “All the
fossils found in the foregoing strata show that Spitzbergen, dur-
ing former geological ages, enjoyed a magnificent climate, which
indeed was somewhat colder during the Miocene period, but
was still favourable for an extraordinarily abundant vegetation,
much more luxuriant than that which now occurs even in
the southern part of Scandinavia; and I have in these strata
sought in vain for any sign, that, as some geologists have of late
endeavoured to render probable, these favourable climatic con-
ditions have been broken off by intervals of ancient glacial
periods. The profiles I have had the opportunity to examine
during my various Spitzbergen expeditions would certainly, if
laid down on a line, occupy an extent of a thousand English
miles; and if any former glacial period had existed in this
region, there ought to have been some trace to be observed of
erratic blocks, or other formations which distinguish glacial
action. But this has not been the case. In the strata, whose
length I have reckoned alone, I have not found a single
fragment of a foreign rock so large as a child’s head.”

Now it is quite impossible to ignore or evade the force of
this testimony as to the continuous warm climates of the north
temperate and polar zones throughout Tertiary times. The
evidence extends over a vast area, both in space and time,
it is derived from the work of the most competent living
geologists, and it is absolutely consistent in its general tendency.
We have in the Lower Cretaceous period an almost tropical
climate in France and England, a somewhat lower temperature
in the United States, and a mild insular climate in the Arctic
regions. In each successive period the climate becomes some-
what less tropical; but down to the Upper Miocene it remains
warm temperate in Central Europe, and cold temperate within
the polar area, with not a trace of any intervening periods of
Arctic cold. It then gradually cools down and merges through

1 Geological Magazine, 1875, p. 531.
2 Geological Magazine, 1876, p. 266.

CHAP. IXx.] MILD ARCTIC CLIMATES. 183

the Pliocene into the glacial epoch in Europe, while in the
Arctic zone there is a break in the record between the Miocene
and the recent glacial deposits.

Accepting this as a substantially correct account of the
general climatic aspect of the Tertiary period in the northern
hemisphere, let us see whether the principles we have already
laid down will enable us to give a satisfactory explanation of
its causes.

The Causes of mild Arctic Climates—In his remarkable
series of papers on ‘‘Ocean Currents,’ Dr. James Croll has
proved, with a wealth of argument and illustration whose
cogency is irresistible, that the very habitability of our globe
is due to the equalising climatic effects of the waters of the
ocean; and that itis to the same cause that. we owe, either
directly or indirectly, almost all the chief diversities of climate
between places situated in the same latitude. Owing to the
peculiar distribution of land and sea upon the globe, more than
its fair proportion of the warm equatorial waters is directed
towards the western shores of Europe, the result being that the
British Isles, Norway, and Spitzbergen, have all a milder climate
than any other parts of the globe in corresponding latitudes.
A very small portion of the Arctic regions, however, obtains
this benefit, and it thus remains, generally speaking, a land
of snow and ice, with too short a summer to nourish more than
a very scanty and fugitive vegetation. The only other opening
than that between Iceland and Britain by which warm water

1 It is interesting to observe that the Cretaceous flora of the United
States (that of the Dakota group), indicates a somewhat cooler climate
than that of the following Eocene period. Mr. De Rance (in the geological
appendix to Capt. Sir G. Nares’ Narrative of a Voyage to the Polar Sea)
remarks as follows: ‘ In the overlying American Eocenes occur types of
plants occurring in the European Miocenes and still living, proving the
truth of Professor Lesquereux’s postulate, that the plant types appear in
America a stage in advance of their advent in Europe. These plants
point to a far higher mean temperature than those of the Dakota group,
to a dense atmosphere of vapour, and a luxuriance of ferns and palms.”
This is very important as adding further proof to the view that the
climates of former periods are not due to any general refrigeration, but
to causes which were subject to change and alternation in former ages

as now.

184 ISLAND LIFE. [PART I.

penetrates within the Arctic circle, is through Behring’s Straits ;
but this is both shallow and limited in width, and the con-
sequence is that the larger part of the warm currents of the
Pacific turns back along the shores of the Aleutian Islands and
North-west America, while a very small quantity enters the
icy ocean.

But if there were other and wider openings into the Arctic
Ocean, a vast quantity of the heated water which is now turned
backward would enter it, and would produce an amelioration
of the climate of which we can hardly form a conception. A
great amelioration of climate would also be caused by the
breaking up or the lowering of such Arctic highlands as now
favour the accumulation of ice; while the interpenetration of
the sea into any part of the great continents in the tropical
or temperate zones would again tend to raise the winter
temperature, and render any long continuance of snow in
their vicinity almost impossible.

Now geologists have proved, quite independently of any
such questions as we are here discussing, that changes of the
very kinds above referred to have occurred during the Tertiary
period ; and that there has been, speaking broadly, a steady
change from a comparatively fragmentary and insular condition
of the great north temperate lands in early Tertiary times, to
that more compact and continental condition which now pre-
vails. It is, no doubt, difficult and often impossible to deter-
mine how long any particular geographical condition lasted, or
whether the changes in one country were exactly coincident
with those in another; but it will be sufficient for our purpose
briefly to indicate those more important changes of land and
sea during the Tertiary period, which must have produced a
decided effect on the climate of the northern hemisphere,

Geographical Changes favouring mud Northern Climates in
Tertiary times—The distribution of the Eocene and Miocene
formations shows, that during a considerable portion of the
Tertiary period, an inland sea, more or less occupied by an
archipelago of islands, extended across Central Europe between
the Baltic and the Black and Caspian Seas, and thence by
narrower channels south-eastward to the valley of the Euphrates

CHAP. 1X.] MILD ARCTIC CLIMATES. 185

and the Persian Gulf, thus opening a communication between
the North Atlantic and the Indian Ocean. From the Caspian
also a wide arm of the sea extended during some part of the
Tertiary epoch northwards to the Arctic Ocean, and there 1s
nothing to show that this sea may not have been in existence
during the whole Tertiary period. Another channel probably
existed over Egypt! into the eastern basin of the Mediterranean
and the Black Sea; while it is probable that there was a com-
munication between the Baltic and- the White Sea, leaving
Scandinavia as an extensive island. Turning to India, we find
that an arm of the sea of great width and depth extended
from the Bay of Bengal to the mouths of the Indus; while the
enormous depression indicated by the presence of marine fossils
of Eocene age at a height of 16,500 feet in Western Tibet,
renders it not improbable that a more direct channel across
Afghanistan may have opened a communication between the
West Asiatic and Polar seas.

It may be said that the changes here indicated are not war-
ranted by an actual knowledge of continuous Tertiary deposits
over the situations of the alleged marine channels; but it 1s
no less certain that the seas in which any particular strata were
deposited were always more extensive than the fragments of
those strata now existing, and often immensely more extensive.
The Eocene deposits of Europe, for example, have certainly
undergone enormous denudation both marine and subaérial,
and may have once covered areas where we now find older de-
posits (as the chalk once covered the weald), while they certainly
exist concealed under some Miocene, Pliocene, or recent beds.
We find them widely scattered over Europe and Asia, and often
elevated into lofty mountain ranges; and we should certainly
err far more seriously in confining the Eocene seas to the
exact areas where we now find Eocene rocks, than in liberally
extending them, so as to connect the several detached portions
of the formation whenever there is no valid argument against

1 Mr. 8S. B. J. Skertchley informs me that he has himself observed thick
Tertiary deposits, consisting of clays and anhydrous gypsum, at Berenice
on the borders of Egypt and Nubia, at a height of about 600 feet above
the sea-level; but these may have been of fresh-water origin.

186 ISLAND LIFE. [PART I.

our doing so. Considering then, that some one or more of the
sea-communications here indicated almost certainly existed
during Eocene and Miocene times, let us endeavour to estimate
the probable effect such communications would have upon the
climate of the northern hemisphere.

The Indian Ocean as a source of Heat in Tertiary times.—
If we compare the Indian Ocean with the South Atlantic we
shall see that the position and outline of the former are very
favourable for the accumulation of a large body of warm water
moving northwards. Its southern opening between South
Africa and Australia is very wide, and the tendency of the
trade-winds would be to concentrate the currents towards
its north-western extremity, just where the two great channels
above described formed an outlet to the northern seas, As
will be shown in our nineteenth chapter, there were probably,
during the earlier portion of the Tertiary period at least, several
large islands in the space between Madagascar and South India ;
but these had wide and deep channels between them, and
their effect would probably have been favourable to the con-
veyance of heated water northward, by concentrating the
currents, and thus producing massive bodies of moving water
analogous to the Gulf Stream of the Atlantic." Less heat
would thus be lost by evaporation and radiation in the tropical
zone, and an impulse would be acquired which would carry
the warm water into the north polar area. About the same
period Australia was divided into two islands, separated by a
wide channel in a north and south direction, (see Chapter
XXIT.), and through this another current would almost certainly
set northwards, and be directed to the north-west by the
southern extension of Malayan Asia. The more insular con-
dition at this period of Australia, India, and North Africa,
with the depression and probable fertility of the Central Asiatic
plateau, would lead to the Indian Ocean being traversed by
regular trade-winds instead of by variable monsoons, and thus

1 By referring to our map of the Indian Ocean showing the submarine
banks indicating ancient islands (Chap. XIX.), it will be evident that the
south-east trade winds—then exceptionally powerful—would cause a vast
body of water to enter the deep Arabian Sea.

CHAP. IX.] MILD ARCTIC CLIMATES. 187

the constant vis a tergo, which is so efficient in the Atlantic,
would keep up a steady and powerful current towards the
northern parts of the Indian Ocean, and thence through the
midst of the European archipelago to the northern seas.

Now it is quite certain that such a condition as we have
here sketched out would produce a wonderful effect on the
climate of Central Europe and Western and Northern Asia.
Owing to the warm currents being concentrated in inland
seas, instead of being dispersed over a wide ocean like the
North Atlantic, much more heat would be conveyed into the
Arctic Ocean, and this would altogether prevent the formation
of ice on the northern shores of Asia, which continent did not
then extend nearly so far north and was probably deeply inter-
penetrated by the sea. This open ocean to the north, and the
warm currents along all the northern lands, would so equalise
temperature, that even the northern parts of Europe might
then have enjoyed a climate fully equal to that of the warmer
parts of New Zealand at the present day, and might have well
supported the luxuriant vegetation of the Miocene period, even
without any help from similar changes in the western hemi-
sphere.?

Condition of North America during the Tertiary Period.—But
changes of a somewhat similar character have also taken place
in America and the Pacific. An enormous area west of the

1 In his recently published Lectures on Physical Geography, Professor
Haughton calculates, that more than half the solar heat of the torrid zone
is carried to the temperate zones by ocean currents. The Gulf Stream itself
carries one-twelfth of the total amount, but it is probable that a very small
fraction of this quantity of heat reaches the polar seas owing to the wide
area over which the current spreads in the North Atlantic. The corres-
ponding stream of the Indian Ocean in Miocene times would have been
fully equal to the Gulf Stream in heating power, while, owing to its being
so much more concentrated, a large proportion of its heat may have
reached the polar area. But the Arctic Ocean occupies less than one-tenth
of the area of the tropical seas; so that, whatever proportion of the heat
of the tropical zone was conveyed to it, would, by being concentrated into
one-tenth of the surface, produce an enormously increased effect. Taking
this into consideration, we can hardly doubt that the opening of a suffi-
cient passage from the Indian Ocean to the Arctic seas would produce the
effects above indicated.

188 ISLAND LIFE. Trapt 1.

Mississippi, extending over much of the Rocky Mountains, con-
sists of marine Cretaceous beds 10,000 feet thick, indicating
great and long-continued subsidence, and an insular condition
of Western America with a sea probably extending northwards
to the Arctic Ocean. As marine Tertiary deposits are found
conformably overlying these Cretaceous strata, Professor Dana
is of opinion that the great elevation of this part of America
did not begin till early Tertiary times. Other Tertiary beds
in California, Alaska, Kamschatka, the Mackenzie River, the
Parry Islands, and Greenland, indicate partial submergence
of all these lands with the possible influx of warm water from
the Pacific; and the considerable elevation of some of the
Miocene beds in Greenland and Spitzbergen renders it probable
that these countries were then much less elevated, in which
case only their higher summits would be covered with perpetual
snow, and no glaciers would descend to the sea.

In the Pacific there was probably an elevation of land coun- |

terbalancing, to some extent, the great depression of so much
of the northern continents. Our map in Chapter XV. shows
the islands that would be produced by an elevation of the
great shoals under a thousand fathoms deep, and it is seen that
these all trend in a south-east and north-west direction, and
would thus facilitate the production of definite currents im-
pelled by the south-east trades towards the north-west Pacific,
where they would gain access to the polar seas through
Behring’s Straits, which were, perhaps, sometimes both wider
and deeper than at present.

Liffect of these Changes on the Climate of the Arctic Regions.—
These various changes of sea and land, all tending towards a
transference of heat from the equator to the north temperate
zone, were not improbably still further augmented by the
existence of a great inland South American sea occupying
what are now the extensive valleys of the Amazon and
Orinoco, and forming an additional reservoir of super-heated
water to add to the supply poured into the North Atlantic.
~ It is not of course supposed that all the modifications here
indicated co-existed at the same time. We have good reason to
believe, from the known distribution of animals in the Tertiary

CHAP. IXx.]| MILD ARCTIC CLIMATES. 189

period, that land-communications have at times existed between
Europe or Asia and North America, either by way of Behring’s
Straits, or by Iceland, Greenland, and Labrador. But the same
evidence shows that these land-communications were the excep-
tion rather than the rule, and that they occurred only at long
intervals and for short periods, so as at no time to bring about
anything like a complete interchange of the productions of the
two continents! We may therefore admit that the com-
munication between the tropical and Arctic oceans was occa-
sionally interrupted in one or other direction; but if we look
at a globe instead of a Mercator’s chart of the world, we shall
see that the disproportion between the extent of the polar and
tropical seas is so enormous that a single wide opening, with an
adequate impulse to carry in a considerable stream of warm
water, would be amply sufficient for the complete abolition of
polar snow and ice, when aided by the absence of any great
areas of high land within the polar circle, such high land
being, as we have seen, essential to the production of perpetual
snow even at the present time.

Those who wish to understand the effect of oceanic currents
in conveying heat to the north temperate and polar regions,
should study the papers of Dr. Croll already referred to. But
the same thing is equally well shown by the facts of the actual
distribution of heat due to the Gulf Stream. The difference
between the mean annual temperatures of the opposite coasts
of Kurope and America is well known and has been already
quoted, but the difference of their mean winter temperature is
still more striking, and it is this which concerns us as more
especially affecting the distribution of vegetable and animal
life. Our mean winter temperature in the west of England is
the same as that of the Southern United States, as well as that
of Shanghae in China, both about twenty degrees of latitude
further south; and as we go northward the difference increases,
so that the winter climate of Nova Scotia in Lat. 45° 1s found
within the Arctic circle on the coast of Norway ; and if the latter

1 For an account of the resemblances and differences of the mammalia

of the two continents during the Tertiary epoch, see my Geographical
Distribution of Animals, Vol. I. pp. 140-—156.

190 ISLAND LIFE. [PART I.

country did not consist almost wholly of precipitous snow-clad
mountains, it would be capable of supporting most of the vegetable
products of the American coast in the latitude of Bordeaux.}
With these astounding facts before us, due wholly to the
transference of a portion of the warm currents of the Atlantic
to the shores of Europe, even with all the disadvantages of
an icy sea to the north-east and ice-covered Greenland
to the north-west, how can we doubt the enormously
greater effect of such a condition of things as has been shown
to have existed during the Tertiary epoch? Instead of one
great stream of warm water spreading widely over the North
Atlantic and thus losing the greater part of its store of heat
before it reaches the Arctic seas, we should have several streams
conveying the heat of far more extensive tropical oceans by
comparatively narrow inland channels, thus being able to

1 Professor Haughton has made an elaborate calculation of the differ-
ence between existing climates and those of Miocene times, for all the
places where a Miocene flora has been discovered, by means of the actual
range of corresponding species and genera of plants. Although this
method is open to the objection that the ranges of plants and animals are
not determined by temperature only, yet the results may be approxi-
mately correct, and are very interesting. The following table which
summarizes these results is taken from his Lectures on Physical Geography
(p. 344) :—

Eatttede: tens tee sera
1. ‘Switzerland 5° 200) APP OO" S376. 69°.8 EF. | 167.2 FF.
2 MVAMEZAG 3. bi eget uel ea OA ace A5°.7 ,, 627.6%,, LOTD 55
3, Leeland eg.) a es Oo so0) salad, 20m, 48°.2 5, 12°26 5,
4, Mackenzie River . . | 65°.00 19°:4 48°.2 ,, ZO -8 5;
5, Disco (Greenland) . | ° 70°,.00.| 19°:6 ,, 55°.6 ,, 36°.0 ,,
6. Spitzbergem:.)). 9. 4S nOO. ly AG ce DLS. 35°.3 ,,
7. Grinnell Land. . .| 81°.44 HT 55 42°.3 4, 44°.0 ,,

It is interesting to note that Iceland, which is now exposed to the full
influence of the Gulf Stream, was only 12°°6 F. warmer in Miocene times,
while Mackenzie River, now totally removed from its influence, was
28° warmer. This, as well as the greater increase of temperature as we
go northward and the polar area becomes more limited, is quite in
accordance with the view of the causes which brought about the Miocene
climate which is here advocated.

CHAP. 1X] MILD ARCTIC CLIMATES. 191

transfer a large proportion of their heat info the northern and
Arctic seas. The heat that they gave out during the passage,
instead of being widely dispersed by winds and much of it lost
in the higher atmosphere, would directly ameliorate the climate
of the continents they passed through, and prevent all accumu-
lation of snow except on the loftiest mountains. The formation
of ice in the Arctic seas would then be impossible; and the
mild winter climate of the latitude of North Carolina, which
by the Gulf Stream is transferred 20° northwards to our islands,
might certainly, under the favourable conditions which prevailed
during the Cretaceous, Eocene, and Miocene periods, have been
carried another 20° north to Greenland and Spitzbergen ; and
this would bring about exactly the climate indicated by the fossil
Arctic vegetation. For it must be remembered that the Arctic
summers are, even now, really hotter than ours, and if the
winter's cold were abolished and all ice-accumulation prevented,
the high northern lands would be able to support a far more
luxuriant summer vegetation than is possible in our unequal
and cloudy climate.’

Lffect of High Excentricity on the warm Polar Climates.—
If the explanation of the cause of the glacial epoch given in
the last chapter is a correct one, it will, I believe, follow
that changes in the amount of excentricity will produce no

1 The objection has been made, that the long polar night would of itself
be fatal to the existence of such a luxuriant vegetation as we know to have
existed as far as 80° N. Lat., and that there must have been some
alteration of the position of the pole, or diminution of the obliquity of the
ecliptic, to permit such plants as magnolias and large-leaved maples to
flourish. But there appears to be really no valid grounds for such an
objection. Not only are numbers of Alpine and Arctic evergreens deeply
buried in the snow for many months without injury, but a variety of
tropical and sub-tropical plants are preserved in the hot-houses of St.
Petersburg and other northern cities, which are closely matted during
winter, and are thus exposed to as much darkness as the night of the
Arctic regions. We have besides no proof that any of the Arctic trees or
large shrubs were evergreens, and the darkness would certainly not be
prejudicial to deciduous plants. With a suitable temperature there is
nothing to prevent a luxuriant vegetation up to the pole, and the long con-
tinued day is known to be highly favourable to the development of foliage,
which in the same species is larger and better developed in Norway than in
the south of England.

192 ISLAND LIFE. [PART 1.

important alteration of the climates of the temperate and Arctic
zones so long as favourable geographical conditions, such as
have been now sketched out, render the accumulation of ice
impossible. The effect of a high excentricity in producing a
glacial epoch was shown to be due to the capacity of snow and
ice for storing up cold, and its singular power (when in large
masses) of preserving itself unmelted under a hot sun by itself
causing the interposition of a protective covering of cloud and
vapour. But mobile currents of warm water have no such
power of accumulating and storing up heat or cold from one
year to another, though they do in a pre-eminent degree possess
the power of equalising the temperature of winter and summer
and of conveying the superabundant heat of the tropics to
ameliorate the rigour of the Arctic winters. However great
was the difference between the amount of heat received from the
sun in winter and summer in the Arctic zone during a period of
high excentricity and winter in aphelion, the inequality would be
greatly diminished by the free ingress of warm currents to
the polar area; and if this was sufficient to prevent any
accumulation of ice, the summers would be warmed to the full
extent of the powers of the sun during the long polar day,
which is such as to give the pole at midsummer more heat
during the twenty-four hours than the equator receives during
its day of twelve hours. The only difference, then, that would
be directly produced by the changes of excentricity and pre-
cession would be, that the summers would be at one period
almost tropical, at the other of a more mild and uniform
temperate character; while the winters would be at one time
somewhat longer and colder, but never, probably, more severe
than they are now in the west of Scotland.

But though high excentricity would not directly modify the
mild climates produced by the state of the northern hemisphere
which prevailed during Cretaceous, Eocene, and Miocene times,
it might indirectly affect it by increasing the mass of Antarctic
ice, and thus increasing the force of the trade-winds and the re-
sulting northward-flowing warm currents. Now there are many
peculiarities in the distribution of plants and of some groups of
animals in the southern hemisphere, which render it almost certain

CHAP. 1X.] MILD ARCTIC CLIMATES, 193

that there has sometimes been a greater extension of the Antarctic
lands during Tertiary times ; and it is therefore not improbable
that a more or less glaciated condition may have been a long
persistent feature of the southern hemisphere, due to the
peculiar distribution of land and sea which favours the pro-
duction of ice-fields and glaciers. And as we have seen that
during the last three million years the excentricity has been
almost always much higher than it is now, we should expect
that the quantity of ice in the southern hemisphere will usually
have been greater, and will thus have tended to increase the force
of those oceanic currents which produce the mild climates of
the northern hemisphere.

Evidences of Climate in the Secondary and Paleozoic epochs.—
We have already seen, that so far back as the Cretaceous period
there is the most conclusive evidence of the prevalence of a
very mild climate not only in temperate but also in Arctic lands,
while there is no proof whatever, or even any clear indication,
of early glacial epochs at all comparable in extent and severity
with that which has so recently occurred; and we have seen
reason to connect this state of things with a distribution of
land and sea highly favourable to the transference of warm water
from equatorial to polar latitudes. So far as we can judge by
the plant-remains of our own country, the climate appears to
have been almost tropical in the Lower Eocene period; and as
we go further back we find no clear indications of a higher, but
often of a lower temperature, though always warmer or more
equable than our present climate. The abundant corals and
reptiles of the Oolite and Lias indicate equally tropical condi-
tions ; but further back, in the Trias, the flora and fauna become
poorer, and there is nothing incompatible with a climate no
warmer than that of the Upper Miocene. This poverty is still
more. marked in the Permian formation, and it is here that
clear indications of ice-action are found in the Lower Permian
conglomerates of the west of England. These beds contain
abundant fragments of various rocks, often angular and some-
times weighing half a ton, while others are partially rounded,
and have polished and striated surfaces, just like the stones of

the “ till.” They lie confusedly bedded in a red unstratified marl,
O

194 ISLAND LIFE. [PART 1,

and some of them can be traced to the Welsh hills from
twenty to fifty miles distant. This remarkable formation was
first pointed out as proving a remote glacial period, by Professor
Ramsay; and Sir Charles Lyell agreed that this is the only
possible explanation, that, with our present knowledge, we can
give of them.

Permian breccias are also found in Ireland, containing blocks
of Silurian and Old Red sandstone rocks which Professor Hull
believes could only have been carried by floating ice. Similar
breccias occur in the south of Scotland, and these are stated
to be ‘overlain by a deposit of glacial age, so similar
to the breccia below as to be with difficulty distinguished
from: it, *+

These numerous physical indications of ice-action over a
considerable area during the same geological period, coinciding
with just such a poverty of organic remains as might be pro-
duced by a very cold climate, are very important, and seem
clearly to indicate that at this remote period geographical
‘conditions were such as to bring about a glacial epoch in our
part of the world.

Boulder-beds also occur in the Carboniferous formation, both
in Scotland, on the continent of Europe, and in North America ;
and Professor Dawson considers that he has detected true
glacial deposits of the same age in Nova Scotia. Boulder-beds
also occur in the Silurian rocks of Scotland and North America,
and according to Professor Dawson, even in the Huronian, older
than our Cambrian. None of these indications are however
so satisfactory as those of Permian age, where we have the very
kind of evidence we looked for in vain throughout the whole of
the Tertiary and Secondary periods. Its presence in several
localities in such ancient rocks as the Permian is not only most
important as indicating a glacial epoch of some kind in Paleozoic
times, but confirms us in the validity of our conclusion, that the
total absence of any such evidence throughout the Tertiary and
Secondary epochs demonstrates the absence of recurring glacial
epochs in the northern hemisphere, notwithstanding the frequent
recurrence of periods of high excentricity.

1 Geological Magazine, 1873, p. 320.

CHAP. IX. | GEOLOGICAL CLIMATES. 195

Warm Arctic Climates in early Secondary and Paleozoic times.
—The evidence we have already adduced of the mild climates
prevailing in the Arctic regions throughout the Miocene, Eocene,
and Cretaceous periods is supplemented by a considerable body
of facts relating to still earlier epochs.

In the Jurassic period, for example, we have proofs of a mild
Arctic climate, in the abundant plant-remains of East Siberia
and Amurland, with less productive deposits in Spitzbergen,
and at Ando in Norway just within the Arctic circle. But even
more remarkable are the marine remains found in many places
in high northern latitudes, among which we may especially
mention the numerous ammonites and the vertebre of huge
reptiles of the genera Ichthyosaurus and Teleosaurus found in
the Jurassic deposits of the Parry Islands in 77° N. Lat.

In the still earlier Triassic age, nautili and ammonites in-
habited the seas of Spitzbergen, where their fossil remains are
now found. |

In the Carboniferous formation we again meet with plant-
remains and beds of true coal in the Arctic regions, Lepido-
dendrons and Calamites, together with large spreading ferns,
are found at Spitzbergen, and at Bear Island in the extreme
north of Hastern Siberia; while marine deposits of the same
age contain abundance of large stony corals.

Lastly, the ancient Silurian limestones, which are widely
spread in the high Arctic regions, contain abundance of corals
and cephalopodous mollusca resembling those from the same
deposits in more temperate lands.

Conclusions as to the Climates of Tertiary and Secondary periods.
—If now we look at the whole series of geological facts as to the
animal and vegetable productions of the Arctic regions in past
ages it is certainly difficult to avoid the conclusion that they
indicate a climate of a uniformly temperate or warm character.
Whether in Miocene, Upper or Lower Cretaceous, Jurassic,
Triassic, Carboniferous or Silurian times, and in all the
numerous localities extending over more than half the polar
regions, we find one uniform climatic aspect in the fossils.
This is quite inconsistent with the theory of alternate cold
and mild epochs during phases of high excentricity, and

Orn

196 ISLAND LIFR, [parr 1.

persistent cold epochs when the excentricity was as low as it
is now or lower, for that would imply that the duration of cold
conditions was greater than that of warm. Why then should
the fauna and flora of the cold epochs never be preserved ?
Mollusca and many other forms of life are abundant in the
Arctic seas, and there is often a luxuriant dwarf woody vegeta-
tion on the land, yet in no one case has a single example of
such a fauna or flora been discovered of a date anterior to the
last glacial epoch. And this argument is very much strength-
ened when we remember that an exactly analogous series of
facts is found over all the temperate zones. Everywhere we
have abundant floras and faunas indicating warmer conditions
than such as now prevail, but never in a single instance one
which as clearly indicates colder conditions. The fact that.
drift with Arctic shells was deposited during the last glacial
epoch, as well as gravels and crag with the remains of arctic
animals and plants, shows us that there is nothing to prevent
such deposits being formed in cold as well as in warm periods ;
and it is quite impossible to believe that in every place and at
all epochs all records of the former have been destroyed, while
in a considerable number of mstances those of the latter have
been preserved. When to this uniform testimony of the paleeon-
tological evidence we add the equally uniform absence of any
indication of those ice-borne rocks, boulders, and drift, which
are the constant and necessary accompaniment of every period
of glaciation, and which must inevitably pervade all the marine
deposits formed over a wide area so long as the state of glacia-—
tion continues, we are driven to the conclusion that the last
glacial epoch of the northern hemisphere was exceptional,
and was not preceded by numerous similar glacial epochs
throughout Tertiary and Secondary time.

But although glacial epochs (with the one or two excep-
tions already referred to) were certainly absent, considerable
changes of climate may have frequently occurred, and these
would lead to important changes in the organic world. We can
hardly doubt that some such change occurred between the Lower
and Upper Cretaceous periods, the floras of which exhibit such
an extraordinary contrast in general character. We have also

CHAP. IX.] GEOLOGICAL CLIMATES, 197

—

the testimony of Mr. J. 8. Gardner, who has long worked at the
fossil floras of the Tertiary deposits, and who states, that there
is strong negative and some positive evidence of alternating
warmer and colder conditions, not glacial, contained not only
in English Eocene, but all Tertiary beds throughout the world.?
In the case of marine faunas it is more difficult to judge, but
the numerous changes in the fossil remains from bed to bed only
a few feet and sometimes a few inches apart, may be sometimes
due to change of climate; and when it is recognised that such
changes have probably occurred at all geological epochs and
their effects are systematically searched for, many peculiarities
in the distribution of organisms through the different members
of one deposit may be traced to this cause.

General view of Geological Climates as dependent on the
Physical Features of the Harth’s Surface—In the preceding
chapters I have earnestly endeavoured to arrive at an explana-
tion of geological climates in the temperate and Arctic zones,
which should be in harmony with the great body of geological
facts now available for their elucidation. If my conclusions as
here set forth diverge considerably from those of Dr. Croll, it is
not from any want of appreciation of his facts and arguments,
since for many years I have upheld and enforced his views to the
best of my ability. But a careful re-examination of the whole
question has now convinced me that an error has been made in
estimating the comparative effect of geographical and astro-
nomical causes on changes of climate, and that, while the
latter have undoubtedly played an important part in bringing
about the glacial epoch, it 1s to the former that the mild climates
of the Arctic regions are almost entirely due. If I have now
succeeded in approaching to a true solution of this difficult
problem, I owe 1t mainly to the study of Dr. Croll’s writings,
since my theory is entirely based on the facts and principles so
clearly set forth in his admirable papers on ‘‘ Ocean Currents in
relation to the Distribution of Heat over the Globe.” The
main features of this theory as distinct from that of Dr. Croll
I will now endeavour to summarise.

Looking at the subject broadly, we see that the climatic

1 Geological Magazine, 1877, p. 137,

1 98 ISLAND LIFE. [PART I.

condition of the northern hemisphere is the result of the
peculiar distribution of land and water upon the globe; and
the general permanence of the position of the continental
and oceanic areas—which we have shown to be _ proved
by so many distinct lines of evidence—is also implied by
the general stability of climate throughout long geological
periods. The land surface of our earth appears to have always
consisted of three great masses in the north temperate zone,
narrowing southward, and terminating in three compara-
tively narrow extremities represented by Southern America,
South Africa and Australia. Towards the north these masses
have approached each other, and have sometimes become
united ; leaving beyond them a considerable area of open polar
sea. Towards the south they have never been much further
prolonged than at present, but far beyond their extremities
an extensive mass of land has occupied the south polar
area.

This arrangement is such as would cause the northern hemi-
sphere to be always (as it is now) warmer than the southern,
and this would lead to the preponderance of northward winds
and ocean currents, and would bring about the concentration of
the latter in three great streams carrying warmth to the north-
polar regions. These streams would, as Dr. Croll has so well
shown, be greatly increased in power by the glaciation of the
south polar land; and whenever any considerable portion of this
land was elevated, such a condition of glaciation would certainly
be brought about, and would be heightened whenever a high
degree of excentricity prevailed.

It appears to be the general opinion of geologists that the
great continents have undergone a process of developmeat from
earlier to later times. Professor Dana says: ‘The North
American continent, which since early time had been gradually
expanding in each direction from the northern Azoic, eastward,
westward, and southward, and which, after the Palseozoic, was
finished in its rocky foundation, excepting on the borders of the
Atlantic and Pacific and the area of the Rocky Mountains, had
reached its full expansion at the close of the Tertiary period.
The progress from the first was uniform and systematic: the

CHAP. IX. | GEOLOGICAL CLIMATES, 199
land was at all times simple in outline; and its enlargement
took place with almost the regularity of an exogenous plant.” }

A similar development undoubtedly took place in the Euro-
pean area, which was apparently never so compact and so little
interpenetrated by the sea as it 1s now, while Europe and Asia
have only become united into one unbroken mass since late
Tertiary times.

If, however, the greater continents have become more compact
and massive from age to age, and have received their chief
extensions northward at a comparatively recent period, while
the antarctic lands had a corresponding but somewhat earlier
development, we have all the conditions requisite to explain
the persistence, with shght fiuctuations, of warm climates far
into the north-polar area throughout Palzeozoic, Mesozoic, and
Tertiary times. At length, during the latter part of the
Tertiary epoch, a considerable elevation took place, closing up
several of the water passages to the north, and raising up ex-
tensive areas in the Arctic regions to become the receptacle of
snow and ice-fields. This elevation is indicated by the abundance
of Miocene and the absence of Pliocene deposits in the Arctic
zone and the considerable altitude of many Miocene rocks in
Europe and North America; and the occurrence at this time of
a long-continued period of high excentricity necessarily brought
on the glacial epoch in the manner already described in our
last chapter.

We thus see that the last glacial epoch was the climax of a
great process of continental development which has been going
on throughout long geological ages; and that it was the direct
consequence of the north temperate and polar land having
attained a great extension and a considerable altitude just at
the time when a phase of very high excentricity was coming on.
Throughout earlier Tertiary and Secondary times an equally
high excentricity often occurred, but it never produced a glacial
epoch, because the north temperate and polar areas had less
high land, and were more freely open to the influx of warm
oceanic currents. But wherever great plateaux with lofty
mountains occurred in the temperate zone a considerable /ocad
1 Manual of Geology, 2nd Ed. p, 525,

200 ISLAND LIFE. [PART I.

glaciation might be produced, which would be specially intense
during periods of high excentricity; and it 1s to such causes we
must impute the indications of ice-action in the vicinity of the
Alps during the Tertiary period. The Permian glaciation appears ©
to have been more extensive, and it is quite possible that at
this remote epoch a sufficient mass of high land existed in
our area and northwards towards the pole, to have brought on a
true glacial period comparable with that which has so recently
passed away. .

Estumate of the comparative effects of Geographical and
Astronomical Causes in producing Changes of Climate.—It
appears then, that while geographical and physical causes alone,
by their influence on ocean currents, have been the main agents
in producing the mild climates which for such long periods
prevailed in the Arctic regions, the concurrence of astronomical
causes—high excentricity with winter in aphelion—was neces-
sary to the production of the great glacial epoch. If we reject
this latter agency, we shall be obliged to imagine a concurrence
of geographical changes at a very recent period of which we
have no evidence. We must suppose, for example, that a large
part of the British Isles—Scotland, Ireland, and Wales at all
events—were simultaneously elevated so as to bring extensive
areas above the line of perpetual snow; that about the same
time Scandinavia, the Alps, and the Pyrenees received a similar
increase of altitude ; and that, almost simultaneously, Eastern
North America, the Sierra Nevada of California, the Caucasus,
Lebanon, the southern mountains of Spain, the Atlas range, and
the Himalayas, were each some thousands of feet higher than
they are now; for all these mountains present us with indica-
tions of a recent extension of their glaciers, in superficial phe-
nomena so similar to those which occur in our own country
and in Western Europe, that we cannot suppose them to belong
to a different epoch. Such a supposition is rendered more diffi-
cult by the general concurrence of scientific testimony to a partial
submergence during the glacial epoch, not only in all parts of
Britain, but in North America, Scandinavia, and, as shown by
the wide extension of the drift, in Northern Europe; and when
to this we add the difficulty of understanding how any probable

CHAP. IX.] GEOLOGICAL CLIMATES, 201
addition to the altitude of our islands could have brought about
the extreme amount of glaciation which they certainly under-
went, and when, further, we know that a phase of very high
excentricity did occur at a period which is generally admitted
to agree well with physical evidence of the time elapsed since
the cold passed away, there seems no sufficient reason why such
an agency should be ignored.

No doubt a prejudice has been excited against it in the minds
of many geologists, by its being thought to lead necessarily to
frequently recurring glacial epochs throughout all geological
time. But I have here endeavoured to show that this is not a
necessary consequence of the theory, because a concurrence of
favourable geographical conditions is essential to the initiation
of a- glaciation, which when once initiated has a tendency to
maintain itself throughout the varying phases of precession
occurring during a period of high excentricity. When, however,
geographical conditions favour warm Arctic climates—as it has
been shown they have done throughout the larger portion
of geological time—then changes of excentricity, to however
great an extent, have no tendency to bring about a state of
glaciation, because warm oceanic currents have a preponderating
influence, and without very large areas of high northern land
to act as condensers, no perpetual snow is possible, and hence
the initial process of glaciation does not occur.

The theory as now set forth should commend itself to geolo-
gists, since it shows the direct dependence of climate on physical
processes which are guided and modified by those changes in
the earth’s surface which geology alone can trace out. It is in
perfect accord with the most recent teachings of the science as
to the gradual and progressive development of the earth’s crust
from the rudimentary formations of the Azoic age, and it lends
support to the view that no important departure from the great
lines of elevation and depression originally marked out on the
earth’s surface have ever taken place.

It also shows us how important an agent in the production of
a habitable globe with comparatively small extremes of climates
over its whole area, is the great disproportion between the
extent of the land and the water surfaces. For if these

202 ISLAND LIFE. [PART I,
proportions had been reversed, large areas of land would
necessarily have been removed from the beneficial influence of
aqueous currents or moisture-laden winds ; and slight geolo-
gical changes might easily lead to half the land surface becom-
ing covered with perpetual snow and ice, or being exposed
to extremes of summer heat and winter cold, of which our
water-permeated globe at present affords no example. We thus
see that what are usually regarded as geographical anomalies—
the disproportion of land and water, the gathering of the land
mainly into one hemisphere, and the singular arrangement of
the land in three great southward-pointing masses—are really
facts of the greatest significance and importance, since it 1s to
these very anomalies that the universal spread of vegetation
and the adaptability of so large a portion of the earth’s surface
for human habitation is directly due.

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.

THE subjects discussed in the last three chapters introduce us to
a difficalty which has hitherto been considered a very formidable
one—that the maximum age of the habitable earth, as deduced
from physical considerations, does not afford sufficient time either
for the geological or the organic changes of which we have evidence.
Geologists continually dwell on the slowness of the processes of
upheaval and subsidence, of denudation of the earth’s surface,
and of the formation of new strata; while on the theory of
development, as expounded by Mr. Darwin, the variation and
modification of organic forms is also a very slow process, and
has usually been considered to require an even longer series of
ages than might satisfy the requirements of physical geology
alone.

As an indication of the periods usually contemplated by geolo-
gists, we may refer to Sir Charles Lyell’s calculation in the tenth

204 ISLAND LIFE. [PART 1.

edition of his Principles of Geology (omitted in later editions),
by which he arrived at 240 millions of years as having probably
elapsed since the Cambrian period—a very moderate estimate
in the opinion of most geologists. This calculation was founded
on the rate of modification of the species of mollusca; but
much more recently Professor Haughton has arrived at nearly
similar figures from a consideration of the rate of formation
of rocks and their known maximum thickness, whence he
deduces a maximum of 200 millions of years for the whole
duration of geological time, as indicated by the series of
stratified formations! But in the opinion of all our first natu-
ralists and geologists, the period occupied in the formation of
the known stratified rocks only represents a portion, and perhaps
a small portion, of geological time. In the last edition of the
Origin of Species (p. 286), Mr. Darwin says :—“‘ Consequently, if
the theory be true, it is indisputable that before the lowest Cam-
brian stratum was deposited long periods elapsed, as long as, or
probably far longer than, the whole interval from the Cambrian
age to the present day; and that during these vast periods the
world swarmed with living creatures.” Professor Huxley, in his
anniversary address to the Geological Society in 1870, adduced
a number of special cases showing that, on the theory of de-
velopment, almost all the higher forms of life must have
existed during the Paleozoic period. Thus, from the fact that
almost the whole of the Tertiary period has been required to
convert the ancestral Orohippus into the true horse, he believes
that, in order to have time for the much greater change of the
ancestral Ungulata into the two great odd-toed and even-toed
divisions (of which change there is no trace even among the
earliest Eocene mammals), we should require a large portion,
if not the whole, of the Mesozoic or Secondary period. Another
case is furnished by the bats and whales, both of which strange
modifications of the mammalian type occur perfectly developed
in the Eocene formation. What countless ages back must we
then go for the origin of these groups, the whales from some
ancestral carnivorous animal, and the bats from the insectivora !
And even then we have to seek for the common origin of
1 Nature, Vol. XVIII. (July, 1878), p. 268.

CHAP. X.| THE EARTH’S AGE. 205

carnivora, insectivora, ungulata, and marsupials at a far earlier
period ; so that, on the lowest estimate, we must place the origin
of the mammalia very far back in Paleozoic times. Similar
evidence is afforded by reptiles, of which Professor Huxley says :
-—“Tf the very small differences which are observable between
the crocodiles of the older Secondary formations and those of the
present day furnish any sort of an approximation towards an
estimate of the average rate of change among reptiles, it is
almost appalling to reflect how far back in Paleozoic times
we must go before we can hope to arrive at that common stock
from which the crocodiles, lizards, Ornithoscelida, and FPlesiosauria,
which had attained so great a development in the Triassic
epoch, must have been derived.” Professor Ramsay has expressed
similar views, derived from a general study of the whole series
of geological formations and their contained fossils. He says,
speaking of the abundant, varied, and well-developed fauna of
the Cambrian period: “In this earliest known varied life
we find no evidence of its having lived near the beginning of
the zoological series. In a broad sense, compared with what
must have gone before, both biologically and physically, all the
phenomena connected with this old period seem, to my mind,
to be of quite a recent description ; and the climates of seas and
lands were of the very same kind as those the world enjoys at
the present day.” 1

These opinions, and the facts on which they are founded, are
so weighty, that we can hardly doubt that, if the time since the
Cambrian epoch is correctly estimated at 200 millions of years,
the date of the commencement of life on the earth cannot be
much less than 500 millions ; while 1t may not improbably have
been longer, because the reaction of the organism under changes
of the environment is believed to have been less active in
low and simple, than in high and complex forms of life, and
thus the processes of organic development may for countless
ages have been excessively slow.

But according to the physicists, no such periods as are here

1 “On the Comparative Value of certain Geological Ages considered as
items of Geological Time.” (Proceedings of the Royal Society, 1874,
p. 334.)

206 ISLAND LIFE. [PART I.

contemplated can be granted. From a consideration of the
possible sources of the heat of the sun, as well as from calcula-
tions of the period during which the earth can have been
cooling to bring about the present rate of increase of tempera-
ture as we descend beneath the surface, Sir William Thomson
concludes that the crust of the earth cannot have been solidi-
fied much longer than 100 million years (the maximum possible
being 400 millions), and this conclusion is held by Dr. Croll and
other men of eminence tobe almost indisputable It will
therefore be well to consider on what data the calculations of
geologists have been founded, and how far the views here set
forth, as to frequent changes of climate throughout all geological
time, may affect the rate of biological change.

Denudation and Deposition of Strata as a measure of Time.—The
materials of all the stratified rocks of the globe have been ob-
tained from the dry land. Every point of the surface is exposed
to the destructive influences of sun and wind, frost, snow, and
rain, which break up and wear away the hardest rocks as well
as the softer deposits, and by means of rivers convey the worn
material to the sea. The existence of a considerable depth of soil
over the greater part of the earth’s surface; of vast heaps of
rocky débris at the foot of every inland cliff; of enormous
deposits of gravel, sand, and loam; as well as the shingle,
pebbles, sand, or mud, of every sea-shore, alike attest the uni-
versality of this destructive agency. It is no less clearly shown
by the way in which almost every drop of running water—
whether in gutter, brooklet, stream, or large river—becomes
discoloured after each heavy rainfall, since the matter which
causes this discolouration must be derived from the surface of
the country, must always pass from a higher to a lower level,
and must ultimately reach the sea, unless it is first deposited in
some lake, or by the overflowing of a river goes to form an
alluvial plain. The universality of this subaérial denudation,
both as regards space and time, renders it certain that its cumu-
lative effects must be very great; but no attempt seems to have

1 Trans. Royal Society of Edinburgh, Vol. XXIII. p.161. Quarterly Jour-

nal of Science, 1877. (Croll on the “ Probable Origin and Age of the
Sun,’’)

CBAP, X.| THE EARTHS AGE. 207

been made to determine the magnitude of these effects till Mr.
Alfred Tylor, in 1853,! pointed out that by measuring the
quantity of solid matter brought down by rivers (which can be
done with considerable accuracy), we may obtain the amount of
lowering of the land-area, and also the rise of the ocean level,
owing to the quantity of matter deposited on its floor. A few
years later Dr. Croll applied the same method in more detail to
an estimate of the amount by which the land is lowered in a
given period ; and the validity of this method has been upheld
by Prof. Geikie, Sir Charles Lyell, and all our best geologists, as
affording a means of actually determining with some approach
to accuracy, the time occupied by one important phase of
geological change.

The quantity of matter carried away from the land by a river
is greater than at first sight appears, and is more likely to be
under- than over-estimated. By taking samples of water near
the mouth of a river (but above the influence of the tide) at a
sufficient number of points in its channel and at different
depths, and repeating this daily or at other short intervals
throughout the year, it is easy to determine the quantity of
solid matter held in suspension and solution; and if corre-
sponding observations determine the quantity of water that is
discharged, the total amount of solid matter brought down
annually may be calculated. But besides this, a considerable
quantity of sand or even gravel is carried along the bottom or
bed of the river, and this has rarely been estimated, so that the
figures hitherto obtained are usually under the real quantities.
There is also another source of error caused by the quantity of
matter the river may deposit in lakes or in flooded lands during
its course, for this adds to the amount of denudation performed
by the river, although the matter so deposited does not come
down to the sea. After a careful examination of all the best
records, Professor A. Geikie arrives at the following results, as
to the quantity of matter removed by seven rivers from their
basins, estimated by the number of years required to lower the
whole surface an average of one foot:

1 Philosophical Magazine, April 1853,

208 ISLAND LIFE. [PART I.

The Mississippi removes one foot in 6,000 years.

4» Ganges ” ” 2,358,
5). loan: Elo 1,464 ,

» Rhone Ae .5 13528 oe
», Danube a 3 6,846 ,,
3) Po oP) 23 729 ee)
Nath “5 5% A 2s ues

Here we see an intelligible relation between the character of
the river basin and the amount of denudation. The Mississippi
has a large portion of its basin in an arid country, and its sources
are either in forest-clad plateaux or in mountains free from
glaciers and with a scanty rainfall. The Danube flows through
Eastern Europe where the rainfall is considerably less than in
the west, while comparatively few of its tributaries rise among
the loftiest Alps. The proportionate amounts of denudation
being then what we might expect, and as all are probably
under rather than over the truth, we may safely take the aver-
age of them all as representing an amount of denudation which,
if not true for the whole land surface of the globe, will certainly
be so for a very considerable proportion of it. This average is
almost exactly one foot in three thousand years! The mean
altitude of the several continents has been estimated to be as

1 Jt has usually been the practice to take the amount of denudation in
the Mississippi valley, or one foot in six thousand years, as a measure of the
rate of denudation in Europe, from an idea apparently of being on the
‘“‘safe side,” and of not over-estimating the rate of change. But this
appears to me a most unphilosophical mode of proceeding and unworthy
of scientific inquiry. What should we think of astronomers if they always
took the lowest estimates of planetary or stellar distances, instead of the
mean results of observation, ‘‘in order to be on the safe side!”’? As if
error in one direction were any worse than error in another. Yet this is
what geologists do systematically. Whenever any calculations are made
involving the antiquity of man, it is those that give the lowest results that
are always taken, for no reason apparently except that there was, for so long
a time, a prejudice, both popular and scientific, against the great antiquity
of man; and now that a means has been found of measuring the rate of
denudation, they take the slowest rate instead of the mean rate, apparently
only because there is now ascientific prejudice in favour of extremely slow
geological change. I take the mean of the whole; and as this is almost
exactly the same as the mean of the three great European rivers—the
Rhone, Danube, and Po—I cannot believe that this will not be nearer the
truth for Europe than taking one North American river as the standard.

CHAP, X, | THE EARTH'S AGE. 209

follows: Europe 671 feet, Asia 1,132 feet, Africa 900 feet,
North America 748 feet, and South America 1,151 feet. At
the rate of denudation above given, it results that, were no
other forces at work, Kurope would be planed down to the sea-
level in about two million years; while if we take a somewhat
slower rate for North America, that continent might last about
three million years.! This also implies that the mean height of
these continents would have been double what it is now two
million and three million years ago respectively : and as we have
no reason to suppose this to have been the case, we are led to
infer the constant action of that upheaving force which the
presence of sedimentary formations even on the highest
mountains also demonstrates.

We have already discussed the unequal rate of denudation on
hills, valleys, and lowlands, in connection with the evidence of
remote glacial epochs (p. 166); what we have now to consider
is, what becomes of all this denuded matter, and how far the
known rate of denudation affords us a measure of the rate of
deposition, and thus gives us some indication of the lapse of
geological time from a comparison of this rate with the observed
thickness of stratified rocks on the earth’s surface.

How to estumate the Thickness of the Sedimentary Rocks.—
The sedimentary rocks of which the earth’s crust is mainly
composed consist, according to Sir Charles Lyell’s classification,
of fourteen great formations, of which the most ancient is the
Laurentian, and the most recent the Post-Tertiary ; with thirty
important sub-divisions, each of which again consists of a more
or less considerable number of distinct beds or strata. _Thus, the

1 These figures are merely used to give an idea of the rate at which de-
nudation is actually going on now; but if no elevatory forces were at
work, the rate of denudation would certainly diminish as the mountains
were lowered and the slope of the ground everywhere rendered flatter.
This would follow not only from the diminished power of rain and rivers,
but because the climate would become more uniform, the rainfall prcbably
less, and no rocky peaks would be left to be fractured and broken up by
the action of frosts. Itis certain, however, that no continent has ever
remained long subject to the influences of denudation alone, for, as we
have seen in our sixth chapter, elevation and depression have always been
going on in one part or other of the surface.

210 ISLAND LIFE. [PART I.

Silurian formation is divided into Upper and Lower Silurian,
each characterised by a distinct set of fossil remains, and the
Upper Silurian again consists of a large number of - separate
beds, such as the Wenlock Limestone, the Upper Llandovery
Sandstone, the Lower Llandovery Slates, &c., each usually
characterised by a difference of mineral composition or me-
chanical structure, as well as by some peculiar fossils. These
beds and formations vary greatly in extent, both above and
beneath the surface, and are also of very various thicknesses in
different localities. A thick bed or series of beds often thins
out in a given direction, and sometimes disappears altogether,
so that two beds which were respectively above and beneath it
may come into contact. As an example of this thinning out,
American geologists adduce the Paleozoic formations of the
Appalachian Mountains, which have a total thickness of 42,000
feet, but as they are traced westward thin out till they become
only 4,000 feet in total thickness. In like manner the Carboni-
ferous grits and shales are 18,000 feet thick in Yorkshire and
Lancashire, but they thin out southwards, so that in Leicester-
shire they are only 3,000 feet thick; and similar phenomena
occur in all strata and in every part of the world. It must be
observed that this thinning out has nothing to do with denuda-
tion (which acts upon the surface of a country so as to produce
great irregularities of contour), but is a regular attenuation of
the layers of rock, due to a deficiency of sediment in certain
directions at the original formation of the deposit. Owing to
this thinning out of stratified rocks, they are on the whole of far
less extent than is usually supposed. When we see a geological
map showing successive formations following each other in long
irregular belts across the country (as is well seen in the case of
the Secondary rocks of England), and a corresponding section
showing each bed dipping beneath its predecessor, we are apt to
imagine that beneath the uppermost bed we should find all the
others following in succession like the coats of an onion. But °
this is far from being the case, and a remarkable proof of the
narrow limitation of these formations has been recently obtained
by a boring at Ware through the Chalk and Gault Clay, which
latter immediately rests on the Upper Silurian Wenlock

CHAP. X. ] THE EARTHS AGE. 211

Limestone full of characteristic fossils, at a depth of only 800
feet. Here we have an enormous gap, showing that none of
earlier Secondary or late Palzeozoic formations extend to this
part of England, unless indeed they had been all once elevated
and entirely swept away by denudation.!

But if we consider how such deposits are now forming, we
shall find that the thinning out of the beds of each formation,
and their restriction to irregular bands and patches, is exactly
what we should expect. ‘he enormous quantity of sediment
continually poured into the sea by rivers, gradually subsides to
the bottom as soon as the motion of the water is checked. All
the heavier material must be deposited near the shore or in
those areas over which it is first spread by the tides or currents
of the ocean ; while only the very fine mud and clay is carried
out to considerable distances. Thus all stratified deposits will
form most quickly near the shores, and will thin out rapidly at
greater distances, little or none being formed in the depths of
the great oceans. This important fact was demonstrated by
the specimens of sea-bottom examined during the voyage of
the Challenger, all the “shore deposits” being usually confined
within a distance of 100 or 150 miles from the coast, while the
‘deep-sea deposits” are either purely organic, being formed of
the calcareous or siliceous skeletons of globigerine, radiolarians,
and diatomacex, or are clays formed of undissolved portions of

1 The following statement of the depths at which the Paleozoic forma-
tions have been reached in various localities in and round London was
given by Mr. H. B. Woodward in his address to the Norwich Geological
Society in 1879 :—

Deep Wells through the Tertiary and Cretaceous Formations.

Wario eh secess. ocr0s se at 1,022 feet reached Carboniferous Rock.

Kentish 'Town........... il LAY as » Old Red Sandstone.
Tottenham Court Road ,, 1,064 ,, 33 4 Wevonian,

Brae Wall voc. esse esses i OOE s, » Devonianor Old Red Sandstone,
WIRE de Ms Nau sasions , 800 ,, ,, Silurian (Wenlock Shale).

We thus find that over a wide area, extending from London to Ware and
Harwich, the whole of the formations from the Oolite to the Permian are
wanting, the Cretaceous resting on the Carboniferous or older Palzozoic
rocks; and the same deficiency extends across to Belgium, where the
Tertiary beds are found resting on Carboniferous at a depth of less than

400 feet.
Po

212 ISLAND LIFE. [PART 1.

these, together with the disintegrated or dissolved materials of
pumice and volcanic dust, which being very light are carried by
wind or by water over the widest oceans.

From the preceding considerations we shall be better able to
appreciate the calculations as to the thickness of stratified
deposits made by geologists. Professor Ramsay has calculated
that the sedimentary rocks of Britain alone have a total maai-
mum thickness of 72,600 feet ; while Professor Haughton, from
a survey of the whole world, estimates the maximum thickness
of the known stratified rocks at 177,200 feet. Now these mazi-
mum thicknesses of each deposit will have been produced only
where the conditions were exceptionally favourable, either in
deep water near the mouths of great rivers, or in inland seas,
or in places to which the drainage of extensive countries was
conveyed by ocean currents ; and this great thickness will neces-
sarily be accompanied by a corresponding thinness, or complete
absence of deposit, elsewhere. How far the series of rocks found
in any extensive area, as Europe or North America, represents
the whole series of deposits which have been made there we
cannot tell; but there is no reason to think that it is a very
inadequate representation of their maximum thickness, though
it undoubtedly is of their extent and bulk. When we see in how
many distinct localities patches of the same formation occur, it
seems improbable that the whole of the deposits formed during
any one period should have been destroyed, even in such an area
as Europe, while it is still more improbable that they should
be so destroyed over the whole world; and if any considerable
portion of them is left, that portion may give a fair idea of their
average, or even of their maximum, thickness. In his admi-
rable paper on “The Mean Thickness of the Sedimentary
Rocks,”! Dr. James Croll has dwelt on the extent of denuda-
tion in diminishing the mean thickness of the rocks that have
been formed, remarking, “‘ Whatever the present mean thick-
ness of all the sedimentary rocks of our globe may be, it must
be small in comparison to the mean thickness of all the
sedimentary rocks which have been formed. This is obvious
from the fact that the sedimentary rocks-of one age are partly

1 Geological Magazine, Vol. VIII., March, 1871.

CHAP. X.] THE EARTH’S AGE, 213

formed from the destruction of the sedimentary rocks of former
ages. From the Laurentian age down to the present day the
stratified rocks have been undergoing constant denudation.”
This is perfectly true, and yet the mean thickness of that
portion of the sedimentary rocks which remains may not be
very different from that of the entire mass, because denudation
acts only on those rocks which are exposed on the surface of a
country, and most largely on those that are upheaved; while,
except in the rare case of an extensive formation being guste
horizontal, and wholly exposed to the sea or to the atmosphere,
denudation can have no tendency to diminish the thickness of
any entire deposit.1_ Unless, therefore, a formation is completely
destroyed by denudation in every part of the world (a thing very
improbable), we may have in existing rocks a not very inade-
quate representation of the mean thickness of all that have been
formed, and even of the maximum thickness of the larger
portion. This will be the more likely because it is almost
certain that many rocks contemporaneously formed are counted
by geologists as distinct formations, whenever they differ in litho-
logical character or in organic remains. But we know that
limestones, sandstones, and shales, are always forming at the
same time; while a great difference in organic remains may
arise from comparatively slight changes of geographical features,
or from difference in the depth or purity of the water in which
the animals lived.”

1 Mr. C. Lloyd Morgan has well illustrated this point by comparing the
generally tilted-up strata denuded on their edges, to a library in which a
fire had acted on the exposed edges of the books, destroying a great mass
of literature but leaving a portion of each book in its place, which portion
represents the thickness but not the size of the book. (Geological Magazine,
1878; p. 161.)

2 Professor J. Young thinks it highly probable that—“ the Lower Green-
sand is contemporaneous with part of the Chalk, so were parts of the
Wealden; nay, even of the Purbeck a portion must have been forming
while the Cretaceous sea was gradually deepening southward and west-
ward.” Yet these deposits are always arranged successively, and their
several thicknesses added together to obtain the total thickness of the
formations of the country. (See Presidential Address, Sect. C, British
Association, 1876.)

214 ISLAND LIFE. [PART I,

How to estimate the average rate of Deposition of the Sedimentary
Rocks.—But if we take the estimate of Professor Haughton
(177,200 feet), which, as we have seen, is probably excessive, for
the maximum thickness of the sedimentary rocks of the globe
of all known geological ages, can we arrive at any estimate of
the rate at which they were formed? Dr. Croll has attempted
to make such an estimate, but he has taken for his basis the
mean thickness of the rocks, which we have no means whatever
of arriving at, and which he guesses, allowing for denudation, to
be equal to the maximum thickness as measured by geologists.
The land-area of the globe is, according to Dr. Croll, 57,000,000
square miles, and he gives the coast-line as 116,000 miles. This,
however, is, for our purpose, rather too much, as it allows for
bays, inlets, and the smaller islands. An approximate mea-
surement on a globe shows that 100,000 miles will be nearer
the mark, and this has the advantage of being an easily remem-
bered even number. The distance from the coast, to which
shore-deposits usually extend, may be reckoned at about 100 or
150 miles, but by far the larger portion of the matter brought
down from the land will be deposited comparatively close to the
shore; that is, within twenty or thirty miles. If we suppose
the portion deposited beyond thirty miles to be added to the
deposits within that distance, and the whole reduced to a uni-
form thickness in a direction at right angles to the coast, we
should probably include all areas where deposits of the maxi-
mum thickness are forming at the present time, along with a
large but unknown proportion of surface where the deposits
were far below the maximum thickness. This follows, if we
consider that deposit must go on very unequally along different
parts of a coast, owing to the distance from each other of the
mouths of great rivers and the limitations of ocean currents ;
and because, compared with the areas over which a (legate
deposit is forming annually, those where there is little or none
are probably at least twice as extensive. If, therefore, we take
a width of thirty miles along the whole coast-line of the globe as
representing the area over which deposits are forming, corre-

sponding to the maximum thickness as measured by geologists,

CHAD. x.] THE EARTH'S AGH. 215

we shall certainly over- rather than under-estimate the possible
rate of deposit.!

Now a coast-line of 100,000 miles with a width of 30 gives
an area of 3,000,000 square miles, on which the denuded matter
of the whole land-area of 57,000,000 square miles is deposited.
As these two areas are as 1 to 19, it follows that de-
position, as measured by maximum thickness, goes on at least
nineteen times as fast as denudation—probably very much
faster. But the mean rate of denudation over the whole earth
is about one foot in three thousand years; therefore the rate of
maximum deposition will be at least 19 feet in the same
time ; and as the total maximum thickness of all the stratified
rocks of the globe is, according to Professor Haughton, 177,200
feet, the time required to produce this thickness of rock, at the

1 As by far the larger portion of the denuded matter of the globe passes
to the sea through comparatively few great rivers, the deposits must
often be confined to very limited areas.: Thus the denudation of the vast
Mississippi basin must be almost all deposited in a limited portion of the
Gulf of Mexico, that of the Nile within. a small area of the Eastern
Mediterranean, and that of the great rivers of China—the Hoang Ho and
Yang-tse-kiang, in a small portion of the Eastern Sea. Enormous lengths
of coast, like those of Western America and; Eastern Africa, receive very
scanty deposits ; so that thirty miles in width along the whole of the coasts
of the globe will probably give an area greater than that of the area of
average deposit, and certainly greater than that of maximum deposit, which
is the basis on which I have here made my estimates. In the case of the
Mississippi, it is stated by Count Pourtales that along the plateau between
the mouth of the river and the southern extremity of Florida for two
hundred and fifty miles in width the bottom consists of clay with some
sand and but few Rhizopods; but beyond this distance the soundings
brought up either Rhizopod shells alone, or these mixed with coral sand,
Nullipores, and other calcareous organisms (Dana’s Manual of Geology,
2nd Ed. p. 671). It is probable, therefore, that a large proportion of the
entire mass of sediment brought down by the Mississippi is deposited on
the limited area above indicated.

Professor Dana further remarks: “‘ Over interior oceanic basins as well
as off a coast in quiet depths, fifteen or twenty fathoms and beyond, the
deposits are mostly of fine silt, fitted for making fine argillaceous rocks,
as shales or slates. When, however, the depth of the ocean falls off
below a hundred fathoms, the deposition of silt in our existing oceans
mostly ceases, unless in the case of a great bank along the border of

a continent.”’

216 ISLAND LIFE. [PART I.

present rate of denudation and deposition, is only 28,000,000
years.

The hate of Geological Change probably greater vn very remote
times.—The opimion that denudation and deposition went on
more rapidly in early times owing to the frequent occurrence of
vast convulsions and cataclysms was strenuously opposed by Sir
Charles Lyell, who so well showed that causes of the very same
nature as those now in action were sufficient. to account for all
the phenomena presented by the rocks throughout the whole
series of geological formations. But while upholding the
soundness of the views of the “ uniformitarians” as opposed to the
“ convulsionists,’ we must yet admit that there is reason for
believing in a gradually increasing intensity of all telluric
action as we go back into past time. This subject has been well
treated by Mr. W. J. Sollas,? who shows that, if, as all physicists
maintain, the sun gave out perceptibly more heat in past ages
than now, this alone would cause an increase in almost all the
forces that have brought about geological phenomena. With
greater heat there would be a more extensive aqueous atmo-
sphere, and a greater difference between equatorial and polar
temperatures ; hence more violent winds, heavier rains and snows,
and more powerful oceanic currents, all producing more rapid
denudation. At the same time, the internal heat of the earth
being greater, it would be cooling more rapidly, and thus the
forces of contraction—which cause the upheaving of mountains,
the eruption of volcanoes, and the subsidence of extensive
areas—would be more powerful and would still further aid the
process of denudation. Yet again, the earth’s rotation was
certainly more rapid in very remote times, and this would cause
more impetuous tides and still further add to the denuding

1 From the same data Professor Haughton estimates a minimum of
200 million years for the duration of geological time; but he arrives at .
this conclusion by supposing the products of denudation to be uniformly
spread over the whole sea-bottom instead of over a narrow belt near the
coasts, a supposition entirely opposed to all the known facts, and which
had been shown by Dr. Croll, five years previously, to be altogether erro-
neous. (See Nature, Vol. XVIII, p. 268, where Professor Haughton’s
paper is given as read before the Royal Society.)

# See Geological Magazine for 1877, p. 1.

CHAP, X. | THE EARTH'S AGE. 217

power of the ocean. It thus appears that, as we go back into
the past, all the forces tending to the continued destruction and
renewal of the earth’s surface would be in more powerful action,
and must therefore tend to reduce the time required for the
deposition and upheaval of the various geological formations.
It may be true, as many geologists assert, that the changes here
indicated are so slow that they would produce comparatively
little effect within the time occupied by the known sedimentary
rocks, yet, whatever effect they did produce would certainly be
in the direction here indicated, and as several causes are acting
together, their combined effect may have been by no means un-
important. It must also be remembered that such an increase
of the primary forces on which all geologic change depends
would act with great effect in still further intensifying those
alternations of cold and warm periods in each hemisphere, or,
more frequently, of excessive and equable seasons, which have
been shown to be the result of astronomical, combined with
geographical, revolutions; and this would again increase the
rapidity of denudation and deposition, and thus still further
reduce the time required for the production of the known
sedimentary rocks. It is evident therefore that these various
considerations all combine to prove that, in supposing that the
rate of denudation has been on the average only what it is now,
we are almost certainly over-estimating the dime required to have
produced the whole series of formations from the Cambrian
upwards. .

Value of the preceding estimate of Geological Tvme.—It is not
of course supposed that the calculation here given makes any
approach to accuracy, but it is believed that it does indicate the
order of magnitude of the time required. We have a certain
number of data, which are not guessed but the result of actual
measurement; such are, the amount of solid matter carried
down by rivers, the width of the belt within which this matter is
mainly deposited, and the maximum thickness of the known
stratified rocks.1 A considerable but unknown amount of

1 In his reply to Sir W. Thompson, Professor Huxley assumed one foot

in a thousand years as a not improbable rate of deposition. The above
estimate indicates a far higher rate; and this follows from the well

218 ISLAND LIFE. [PART I.

denudation is effected by the waves of the ocean eating away
coast lines. This was once thought to be of more importance
than sub-aérial denudation, but it is now believed to be com-
paratively slow in its action.1 Whatever it may be, however, it
adds to the rate of formation of new strata, and its omission
from the calculation is again on the side of making the lapse of
time greater rather than less than the true amount. Evenif a
considerable modification should be needed in some of the
| assumptions it has been necessary to make, the result must still
show that, so far as the time required for the formation of the
known stratified rocks, the hundred million years allowed by
physicists 1s not only ample, but will permit of even more than
an equal period anterior to the lowest Cambrian rocks, as
demanded by Mr. Darwin—a demand supported and enforced
by the arguments, taken from independent standpoints, of
Professor Huxley and Professor Ramsay.

Organic Modification dependent on Change of Conditions.—
Having thus shown that the physical changes of the earth’s
surface may have gone on much more rapidly and occupied
much less time than has generally been supposed, we have now
to inquire whether there are any considerations which lead to
the conclusion that organic changes may have gone on with
corresponding rapidity.

There is no part of the theory of natural selection which is
more clear and satisfactory than that which connects changes of

ascertained fact, that the area of deposition is many times smaller than the
area of denudation.

1 Dr. Croll and Professor Geikie have shown that marine denudation is
very small in amount as compared with sub-aérial, since it acts only locally
on the edge of the land, whereas the latter acts over every foot of the
surface. Mr. W. T. Blanford argues that the difference is still greater in
tropical than in temperate latitudes, and arrives at the conclusion that—
“Tf over British India the effects of marine to those of fresh-water denu-
dation in removing the rocks of the country be estimated at 1 to 100, I .
believe that the result of marine action will be greatly overstated’’ (Geo-
logy and Zoology of Abyssinia, p. 158, note). Now, as our estimate of
the rate of sub-aérial denudation cannot pretend to any precise accuracy,
we are justified in neglecting marine denudation altogether, especially as
we have no method of estimating it for the whole earth with any approach
to correctness. :

CHAP. X.] THE RATE OF ORGANIC CHANGE. 219

specific forms with changes of external conditions or environ-
ment. If the external world remains for a moderate period
unchanged, the organic world soon reaches a state of equilibrium
through the struggle for existence ; each species occupies its
place in nature, and there is then no inherent tendency to
change. But almost any change whatever in the external
world disturbs this equilibrium, and may set in motion a whole
series of organic revolutions before it is restored. A change of
climate in any direction will be sure to injure some and benefit
other species. The one will consequently diminish, the other
increase in number ; and the former may even become extinct.
But the extinction of a species will certainly affect other species
which it either preyed upon, or competed with, or served for
food; while the increase of any one animal may soon lead to
the extinction of some other to which it was inimical. These
changes will in their turn bring other changes; and before an
equilibrium is again established, the proportions, ranges, and
numbers, of the species inhabiting the country may be materi-
ally altered. The complex manner in which animals are related
to each other is well exhibited by the importance of insects,
which in many parts of the world limit the numbers or deter-
mine the very existence of some of the higher animals. Mr.
Darwin says:—“ Perhaps Paraguay offers the most curious
instance of this; for here neither cattle, nor horses, nor dogs
have ever run wild, though they swarm southward and north-
ward in a wild state; and Azara and Rengger have shown that
this 1s caused by the greater number in Paraguay of a certain
fiy, which lays its eggs in the navels of these animals when first
born. The increase of these flies, numerous as they are, must
be habitually checked by some means, probably by other para-
sitic insects. Hence, if certain insectivorous birds were to
decrease in Paraguay, the parasitic insects would probably
merease ; and this would lessen the number of navel-frequenting
flies—then cattle and horses would run wild ; and this would
certainly alter (as indeed I have observed in parts of South
America) the vegetation: this again would largely affect the in-
sects, and this, as we have seen in Staffordshire, the insectivorous
birds, and so onwards in ever increasing circles of complexity.”

220 ISLAND LIFE. [PART T,

Geographical changes would be still more important, and it
is almost impossible to exaggerate the modifications of the
organic world that might result from them. A subsidence of
land separating a large island from a continent would affect the
animals and plants im a variety of ways. It would at once
modify the climate, and so produce a series of changes from this
cause alone; but more important would be its effect by isolating
small groups of individuals of many species and thus altering
their relations to the rest of the organic world. Many of these
would at once be exterminated, while others, being relieved from
competition, might flourish and become modified into new
species. Even more striking would be the effects when two
continents, or any two land areas which had been long separated,
were united by an upheaval of the strait which divided them.
Numbers of animals would now be -brought into competition
for the first time. New enemies and new competitors would
appear in every part of the country; and a struggle would
commence which, after many fluctuations, would certainly result
in the extinction of some species, the modification of others,
and a considerable alteration in the proportionate numbers and
the geographical distribution of almost all.

Any other changes which led to the intermingling of species
whose ranges were usually separate would produce corresponding
results. Thus, increased severity of winter or summer tempera-
ture, causing southward migrations and the crowding together
of the productions of distinct regions, must inevitably produce
a struggle for existence, which would lead to many changes both
in the characters and the distribution of animals: Slow eleva-
tions of the land would produce another set of changes, by
affording an extended area in which the more dominant species
might increase their numbers;'and, by a greater range and
variety of alpine climates and mountain stations, affording
room for the development of new forms of life.

Geographical Mutations as a Motive Power in bringing about
Organic Changes.—Now, if we consider the various geographical
changes which, as we have seen, there is good reason to believe
have ever been going on in the world, we shall find that the
motive power to initiate and urge on organic changes has never

CHAP. X.] THE RATE OF ORGANIC CHANGE, 221

been wanting. In the first place, every continent, though per-
manent in a general sense, has been ever subject to innumerable
physical and geographical modifications. At one time the total
area has increased, and at another has diminished ; great plateaus
have gradually risen up, and have been eaten out by denudation
into mountain and valley ; volcanoes have burst forth, and, after
accumulating vast masses of eruptive matter, have sunk down
beneath the ocean, to be covered up with sedimentary rocks, and
at a subsequent period again raised above the surface; and the
loci of all these grand revolutions of the earth’s surface have
changed their position age after age, so that each portion of
every continent has again and again been sunk under the ocean
waves, formed the bed of some inland sea, or risen high into
plateaus and mountain ranges. How great must have been the
effects of such changes on every form of organic life! and it is
to such as these we may perhaps trace those great changes of
the animal world which have seemed to revolutionise it, and
have led us to class one geological period as the age of rep-
tiles, another as the age of fishes, and a third as the age of
mammals.

But such changes as these must necessarily have led to re-
peated unions and separations of the land masses of the globe,
joining together continents which were before divided, and
breaking up others into great islands or extensive archipelagoes.
Such alterations of the means of transit would probably affect
the organic world even more profoundly than the changes of
area, of altitude, or of climate, since they afforded the means, at
long intervals, of bringing the most diverse forms into competi-
tion, and of spreading all the great animal and vegetable types
widely over the globe. But the isolation of considerable masses
of land for long periods also afforded the means of preservation
to many of the lower types, which thus had time to become
modified into a variety of distinct forms, some of which became
so well adapted to special modes of life that they have continued
to exist to the present day, thus affording us examples of the
life of early ages which would probably long since have become
extinct had they been always subject to the competition of the
more highly organised animals. As examples of such excessively

222. ISLAND LIFE. . [PARP

archaic forms, we may mention the mud-fishes and the ganoids,
confined to limited fresh-water areas; the frogs and toads, which
still maintain themselves vigorously in competition with higher
forms ; and among mammals the Ornithorhynchus and Echidna
of Australia; the whole order of Marsupials—which, out of
Australia where they are quite free from competition, only
exist abundantly in South America, which was certainly long
isolated from the northern continents; the Insectivora, which,
though widely scattered, are generally nocturnal or subterranean
in their habits; and the Lemurs, which are most abundant in
Madagascar, where they have long been isolated, and almost
removed from the competition of higher forms.

Climatal Revolutions as an agent in producing Organic
Changes.—The geographical and geological changes we have
been considering are probably those which have been most
effective in bringing about the great features of the distribution
of animals, as well as the larger movements in the development
of organised beings; but it is to the alternations of warm and
cold, or of uniform and excessive climates—of almost perpetual
spring in arctic as well as in temperate lands, with occasional
phases of cold culminating at remote intervals in glacial epochs,
—that we must impute some of the more remarkable changes
both in the specific characters and in the distribution of
organisms.| Although the geological evidence is opposed to
the belief in early glacial epochs except at very remote and
distant intervals, there is nothing which contradicts the occur-
rence of repeated changes of climate, which, though too small
in amount to produce any well-marked physical or organic
change, would yet be amply sufficient to keep the organic world
in a constant state of movement, and which, by subjecting the
whole flora and fauna of a country at comparatively short
intervals to decided changes of physical conditions, would
supply that stimulus and motive power which, as we have seen,

1 Agassiz appears to have been the first to suggest that the principal
epochs of life extermination were epochs of cold ; and Dana thinks that
two at least such epochs may be recognised, at the close of the Paleozoic
and of the Cretaceous periods—to which we may add the last glacial
epoch.

CHAP. X.| THE RATE OF ORGANIC CHANGE. 223

is all that is necessary to keep the processes of “ natural
selection” in constant operation.

The frequent recurrence of periods of high and of low excen-
tricity must certainly have produced changes of climate of
considerable importance to the life of animals and_ plants.
During periods of high excentricity with summer in perchelion,
that season would be certainly very much hotter, while the
winters would be longer and colder than at present; and al-
though geographical conditions might prevent any permanent
increase of snow and ice even in the extreme north, yet we
cannot doubt that the whole northern hemisphere would then
have a very different climate than when the changing phase of
precession brought a very cool summer and a very mild winter
—a perpetual spring, in fact. Now, such a change of climate
would certainly be calculated to bring about a considerable
change of species, both by modification and migration, without
any such decided change of type either in the vegetation or
the animals that we could say from their fossil remains that any
change of climate had taken place. Let us suppose, for in-
stance, that the climate of England and that of Canada were to
be mutually exchanged, and that the change took five or six
thousand years to bring about, it cannot be doubted that con-
siderable modifications in the fauna and flora of both countries
would be the result, although it is impossible to predict what
the precise changes would be. We can safely say, however, that
some species would stand the change better than others, while
it is highly probable that some would be actually benefited by
it, while others would be injured. But the benefited would
certainly increase, and the injured decrease, in consequence, and
thus a series of changes would be initiated that might lead to
most important results. Again, we are sure that some species
would become modified in adaptation to the change of climate
more readily than others, and these modified species would
therefore increase at the expense of others not so readily
modified, and hence would arise on the one hand extinction of
species, and on the other the production of new forms.

But this is the very least amount of change of climate that
would certainly occur every 10,500 years when there was a high

224 ISLAND LIFE. [PART I.

excentricity, for it is impossible to doubt that a varying distance
of the sun in summer from 86 to 99 millions of miles (which
is what occurred during—as supposed—the Miocene period,
850,000 years ago) would produce an important difference in
the summer temperature and in the actinic influence of sun-
shine on vegetation. For the intensity of the sun’s rays would
vary as the square of the distance, or nearly as 74 to 98, so
that the earth would be actually receiving one-fourth less sun-
heat during summer at one time than at the other. An equally
high excentricity occurred 2,500,000 years back, and no doubt
was often reached during still earlier epochs, while a lower but
still very high excentricity has frequently prevailed, and is
probably near its average value. Changes of climate, therefore,
every 10,500 years, of the character above indicated and of
varying intensity, have been the rule rather than the exception
in past time; and these changes must have been variously
modified by changing geographical conditions so as to produce
climatic alterations in different directions, and giving to the
ancient lands either dry or wet seasons, storms or calms, equable
or excessive temperatures, in a variety of combinations of which
the earth perhaps affords no example under the present low
phase of excentricity and consequent slight inequality of sun
heat.

Present Condition of the Earth one of exceptional Stability as
regards Climate.—It will be seen, by a reference to the diagram
at page 165, that during the last three million years the excen-
tricity has been Jess than it is now on eight occasions, for short
periods only, making up a total of about 280,000 years; while
it has been more than it is now for many long periods, of from
300,000 to 700,000 years each, making a total of 2,720,000
years, or nearly as 10 to 1. For nearly half the entire period,
or 1,400,000 years, the excentricity has been nearly double what
it is now, and this is not far from its mean condition. We have
no reason for supposing that this long period of three million
years, for which we have tables, was in any way exceptional
as regards the degree or variation of excentricity; but, on the
contrary, we may pretty safely assume that its variations during
this time fairly represent its average state of increase and

CHAP. X.] THE RATE OF ORGANIC CHANGE. 225

decrease during all known geological time. But when the
glacial epoch ended, 72,000 years ago, the excentricity was
about double its present amount; it then rapidly decreased
till, at 60,000 years back, it was very little greater than it is
now, and since then it has been uniformly small. It follows
that, for about 60,000 years before our time, the mutations
of climate every 10,500 years have been comparatively unim-
portant, and that the temperate zones have enjoyed an eacep-
tional stability of climate. During this time those powerful
causes of organic change which depend on considerable changes
of climate and the consequent modifications, migrations,
and extinctions of species, will not have been at work; the
slight changes that did occur would probably be so slow
and so little marked that the various species would be able
to adapt themselves to them without much disturbance ;
and the result would be an epoch of exceptional stability of
species.

But it is from this very period of exceptional stability that we
obtain our only scale for measuring the rate of organic change.
It includes not only the historical period, but that of the Swiss
Lake dwellings, the Danish shell-mounds, our peat-bogs, our
sunken forests, and many of our superficial alluvial deposits—
the whole in fact, of the iron, bronze, and neolithic ages. Even
some portion of the paleolithic age, and of the more recent
gravels and cave-earths may come into the same general period
if they were formed when the glacial epoch was passing away.
Now throughout all these ages we find no indication of change
of species, and but little, comparatively, of migration. We thus
get an erroneous idea of the permanence and stability of specific
forms, due to the period immediately antecedent to our own
being a period of exceptional permanence and stability as regards
climatic and geographical conditions.!

1 This view was, I believe, first put forth by myself in a paper read
before the Geological Section of the British Association in 1869, and
subsequently in an article in Nature, Vol. I. p. 454. It was also stated
by Mr. 8S. B. K. Skertchley in his Physical System of the Universe, p. 363
(1878) ; but we both founded it on what I now consider the erroneous

doctrine that actual glacial epochs recurred each 10,500 years during
periods of high excentricity.

226 ISLAND LIFE. [PART T.

Date of last Glacial Epoch and its bearing on the Measurement of
Geological Time.—Directly we go back from this stable period
we come upon changes both in the forms and in the distribution
of species; and when we pass beyond the last glacial epoch into
the Phocene period we find ourselves in a comparatively new
world, surrounded bya considerable number of species altogether
different from any which now exist, together with many others
which, though still living, now inhabit distant regions. . It seems
not improbable that what is termed the Pliocene period, was really
the coming on of the glacial epoch, and this is the opinion of
Professor Jules Marcou.t According to our views, a considerable
amount of geographical change must have occurred at the change
from the Miocene to the Pliocene, favouring the refrigeration of
the northern hemisphere, and leading, in the way already pointed
out, to the glacial epoch whenever a high degree of excentricity
prevailed. As many reasons combine to make us fix the height
of the glacial epoch at the period of high excentricity which
occurred 200,000 years back, and as the Pliocene period was
probably not of long duration, we must suppose the next great
phase of very high excentricity (850,000 years ago) to fall within
the Miocene epoch. Dr. Croll believes that this must have
produced a glacial period, but we have shown strong reasons
for believing that, in concurrence with favourable geographical
conditions, it led to uninterrupted warm climates in the tem-
perate and northern zones. This, however, did not prevent the
occurrence of local glaciation wherever other conditions led to
its Initiation, and the most powerful of such conditions is a great
extent of high land. Now we know that the Alps acquired
a considerable part of their elevation during the latter part of
the Miocene period, simce Miocene rocks occur at an elevation of
over 6,000 feet, while Eocene beds occur at nearly 10,000 feet.
But since that time there has been a vast amount of denudation,
so that these rocks may have been first raised much higher
than we now find them, and thus a considerable portion of the
Alps may have been once more elevated than now. This would
certainly lead to an enormous accumulation of snow, which

1 Explication d’une seconde édition de la Carte Geologique de la Terre
(1875), p. 64,

OHAP. X.] MEASUREMENT OF GEOLOGICAL TIME. 227

would be increased when the excentricity reached a maximum,
as already fully explained, and may then have caused glaciers to
descend into the adjacent sea, carrying those enormous masses
of rock which are buried in the Upper Miocene of the Superga
in Northern Italy. An earlier epoch of great altitude in the
Alps coinciding with the very high excentricity 2,500,000 years
ago, may have caused the local glaciation of the Middle Eocene
period when the enormous erratics of the Flysch conglomerate
were deposited in the inland seas of Northern Switzerland, the
Carpathians, and the Apennines. This is quite in harmony with
the indications of an uninterrupted warm climate and rich
vegetation during the very same period in the adjacent low
countries, just as we find at the present day in New Zealand a
delightful climate and a rich vegetation of Metrosideros, fuchsias
and tree-ferns on the very borders of huge glaciers, descending
to within 700 feet of the sea-level. It is not pretended that
these estimates of geological time have any more value than
probable guesses ; but it is certainly a curious coincidence that
two remarkable periods of high excentricity should have occurred,
at such periods and at such intervals apart, as very well accord
with the comparative remoteness of the two deposits in which
undoubted signs of ice-action have been found, and that both
these are localised in the vicinity of mountains which are known
to have acquired a considerable elevation at about the same
period of time.

In the tenth edition of the Principles of Geology, Sir Charles
Lyell, taking the amount of change in the species of mollusca
as a guide, estimated the time elapsed since the commencement
of the Miocene as one-third that of the whole Tertiary epoch,
and the latter at one-fourth that of geological time since the
Cambrian period. Professor Dana, on the other hand, estimates
the Tertiary as only one-fifteenth of the Mesozoic and Paleozoic
combined. On the estimate above given, founded on the dates
of phases of high excentricity, we shall arrive at about four
million years for the Tertiary epoch, and sixteen million years for
the time elapsed since the Cambrian, according to Lyell, or sixty
millions according to Dana. The estimate arrived at from the
rate of denudation and deposition (twenty-eight million years)

228 ISLAND LIFE. [PART I.

is nearly midway between these, and it is, at all events,
satisfactory that the various measures result in figures of the
same order of magnitude, which is all one can expect on so
difficult and exceedingly speculative a subject.

The only value of such estimates is to define our notions of
geological time, and to show that the enormous periods, of
hundreds of millions of years, which have sometimes been
indicated by geologists, are neither necessary nor warranted
by the facts at our command; while the present result places us
more in harmony with the calcalations of physicists, by leaving a
very wide margin between geological time as defined by the
fossiliferous rocks, and that far more extensive period which
includes all possibility of life upon the earth.

Concluding Remarks.—In the present chapter I have endea-
voured to show that, combining the measured rate of denudation
with the estimated thickness and probable extent of the known
series of sedimentary rocks, we may arrive at a rude estimate of
the time occupied in the formation of those rocks. From
another point of departure—that of the probable date of the
Miocene period, as determined by the epoch of high excentricity
supposed to have aided in the production of the Alpine glaciation
during that period, and taking the estimate of geologists as to
the proportionate amount of change in the animal world since
that epoch—we obtain another estimate of the duration of geolo-
- gical time, which, though founded on far less secure data, agrees
pretty nearly with the former estimate. The time thus arrived
at is immensely less than the usual estimates of geologists, and
is so far within the limits of the duration of the earth as cal-
culated by Sir William Thomson, as to allow for the develop-
ment of the lower organisms an amount of time anterior to the
Cambrian period several times greater than has elapsed between
that period and the present day. I have further shown that, in
the continued mutations of climate produced by high excentri-
city and opposite phases of precession, even though these did
not lead to glacial epochs, we have a motive power well calcu-
lated to produce far more rapid organic changes than have
hitherto been thought possible; while in the enormous amount
of specific variation (as demonstrated in an earlier chapter), we

CHAP. X.] MEASUREMENT OF GEOLOGICAL TIME. 229

have ample material for that power to act upon, so as to keep
the organic world in a state of rapid change and development
proportioned to the comparatively rapid changes in the earth’s
surface.

We have now finished the series of preliminary studies of the
biological conditions and physical changes which have affected
the modification and dispersal of organisms, and have thus
brought about their actual distribution on the surface of the
earth. These studies will, it is believed, place us in a condition
to solve most of the problems presented by the distribution of
animals and plants, whenever the necessary facts, both as to their
distribution and their affinities, are sufficiently well known; and
we now proceed to apply the principles we have established to
the interpretation of the phenomena presented by some of the
more important and best known of the islands of our globe,
limiting ourselves to these for reasons which have been already
sufficiently explained in our preface.

PART II. |

INSULAR FAUNAS AND FLORAS.

CEA PIER Xl

THE CLASSIFICATION OF ISLANDS.

Importance of Islands in the study of the Distribution of Organisms—
Classification of Islands with reference to Distribution—Continental
Islands—Oceanic Islands.

In the preceding chapters, forming the first part of our work,
we have discussed, more or less fully, the general features pre-
sented by animal distribution, as well as the various physical
and biological changes which have been the most important
agents in bringing about the present condition of the organic
world.

We now proceed to apply these principles to the solution of
the numerous problems presented by the distribution of animals ;
and in order to limit the field of our inquiry, and at the same
time to deal only with such facts as may be rendered intelligible
and interesting to those readers who have not much acquaintance
with the details of natural history, we propose to consider only
such phenomena as are presented by the islands of the globe.

Importance of Islands in the study of the Distribution of
Organisms.—Islands possess many advantages for the study of
the laws and phenomena of distribution. As compared with
continents they have a restricted area and definite boundaries,
and in most cases their geographical and biological limits
coincide. The number of species and of genera they contain
is always much smaller than in the case of continents, and their
peculiar species and groups are usually well defined and strictly
limited inrange. Again, their relations with other lands are often

234 ISLAND LIFE. [PART II.

direct and simple, and even when more complex are far easier tc
comprehend than those of continents; and they exhibit besides
certain influences on the forms of life and certain peculiarities of
distribution which continents do not present, and whose study
offers many points of interest.

In islands we have the facts of distribution often presented
to us in their simplest forms, along with others which become
gradually more and more complex; and we are therefore able to
proceed step by step in the solution of the problems they present.
But as in studying these problems we have necessarily to take
into account the relations of the insular and continental faunas,
we also get some knowledge of the latter, and acquire besides so
much command over the general principles which underlie all
problems of distribution, that it is not too much to say that when
we have mastered the difficulties presented by the peculiarities
of island life we shall find it comparatively easy to deal with the
more complex and less clearly defined problems of continental
distribution.

Classification of Islands with reference to Distribution.—Islands
have had two distinct modes of origin; they have either been
separated from continents of which they are but detached frag-
ments, or they have originated in the ocean and have never
formed part of a continent or any large mass of land. This
difference of origin is fundamental, and leads to a most
important difference in their animal inhabitants; and we
may therefore first distinguish the two classes—oceanic and
continental islands.

Mr. Darwin appears to have been the first writer who called
attention to the number and importance, both from a geological
and biological point of view, of oceanic islands. He showed that
with very few exceptions all the remoter islands of the great
oceans were of volcanic or coralline formation, and that none
of them contained indigenous mammalia or amphibia. He also
showed the connection of these two phenomena, and maintained
that none of the islands so characterised had ever formed part of
a continent. This was quite opposed to the opinions of the
scientific men of the day, who almost all held the idea of
continental extensions, and of oceanic islands being their

CHAP. XI.] THE CLASSIFICATION OF ISLANDS. 235

fragments, and it was long before Mr. Darwin’s views obtained
general acceptance. Even now the belief still lingers; and
we continually hear of old Atlantic or Pacific continents, of
“Atlantis” or “ Lemuria,” of which hypothetical lands many
existing islands, although wholly volcanic, are thought to be the
remnants. We have already seen that Darwin connected the
peculiar geological structure of oceanic islands with the per-
manence of the great oceans which contain them, and we have
shown that several distinct lines of evidence all point to the same
conclusion. We may therefore define oceanic islands, as follows :
—Islands of volcanic or coralline formation, usually far from
continents and always separated from them by very deep sea,
entirely without indigenous land mammalia or amphibia, but
with abundance of birds and insects, and usually with some
reptiles. This definition will exclude only two islands which
have been sometimes classed as oceanic—New Zealand and the
Seychelles. Rodriguez, which was once thought to be another
exception, has been shown by the explorations during the Tran-
sit of Venus Expedition to be essentially volcanic, with some
upraised coralline limestone.

Continental Islands Continental islands are always more
varied in their geological formation, containing both ancient
and recent stratified rocks. They are rarely very remote from
a continent, and they always contain some land mammals and
amphibia, as well as representatives of the other classes and
orders in considerable variety. They may, however, be divided
into two well-marked groups—ancient, and recent, continental
islands—the characters of which may be easily defined.

Recent continental islands are always situated on submerged
banks connecting them with a continent, and the depth of the
intervening sea rarely exceeds 100 fathoms. They resemble the
continent in their geological structure, while their animal and
vegetable productions are either almost identical with those of the
continent, or if otherwise, the difference consists in the presence
of closely allied species of the same types, with occasionally a
very few peculiar genera. They possess in fact all the character-
istics of a portion of the continent, separated from it at a recent,
geological period.

236 ISLAND LIFE. [PART IT.

Ancient continental islands differ greatly from the preceding
in many respects. They are not united to the adjacent continent
by a shallow bank, but are usually separated from it by a depth
of sea of a thousand fathoms or upwards. In geological structure
they agree generally with the more recent islands; like them
they possess mammalia and amphibia, usually in considerable
abundance, as well as all other classes of animals; but these are
highly peculiar, almost all being distinct species, and many form-
ing distinct and peculiar genera or families. They are also well
characterised by the fragmentary nature of their fauna, many of
the most characteristic continental orders or families being quite
unrepresented, while some of their animals are allied, not to
such forms as inhabit the adjacent continent, but to others found
only in remote parts of the world. This very remarkable set of
characters marks off the islands which exhibit them as a
distinct class, which often present the greatest anomalies and
most difficult problems to the student of distribution.

Oceanic Islands.—The total absence of warm-blooded terrestrial
animals in an island otherwise well suited to maintain them, is
held to prove that such island is no mere fragment of any ex-
isting or submerged continent, but one that has been actually
produced in mid-ocean. It is true that if a continental island
were to be completely submerged for a single day and then again
elevated, its higher terrestrial animals would be all destroyed;
and if it were situated at a considerable distance from land 1t
would be reduced to the same zoological condition as an oceanic
island. But such a complete submergence and re-elevation
appears never to have taken place, for there is no single island
on the globe which has the physical and geological features of a
continental, combined with the zoological features of an oceanic
island. It is true that some of the coral-islands may be formed
upon submerged lands of a continental character, but we have no
proof of this ; and even if it were so, the existing islands are to all
intents and purposes oceanic.

We will now pass on to a consideration of some of the more
interesting examples of these three classes, beginning with
oceanic islands.

All the animals which now inhabit such oceanic islands must

CHAP. XI. ] OCEANIC ISLANDS. 237

either themselves have reached them by crossing the ocean, or be
the descendants of ancestors who did so. Let us then see what
are, in fact, the animal and vegetable inhabitants of these islands,
and how far their presence can be accounted for. We will begin
with the Azores, or Western Islands, because they have been .
thoroughly well explored by naturalists, and in their peculiarities
afford us an important clue to some of the most efficient means
of distribution among several classes of animals.

CHAPTER XII.
OCEANIC ISLANDS :—THE AZORES AND BERMUDA.

THE AZORES, OR WESTERN ISLANDS.

Position and physical features—Chief zoological features of the Azores—
Birds—Origin of the Azorean bird fauna—lInsects of the Azores—
Land-shells of the Azores—The flora of the Azores—The dispersal of
seeds—Birds as seed-carriers—Facilities for dispersal of Azorean plants
—Important deduction from the peculiarities of the Azorean fauna
and flora,

BERMUDA.

Position and physical features—The Red Clay of Bermuda—Zoology of
Bermuda—Birds of Bermuda—Comparison of the bird faunas of Ber-
muda and the Azores—Insects of Bermuda—Land Mollusca—Flora of
Bermuda—Concluding remarks on the Azores and Bermuda.

We will commence our investigation into the phenomena, pre-
sented by oceanic islands, with two groups of the North
Atlantic, in which the facts are of a comparatively simple
nature, and such as to afford usa valuable clue to a solution of
the more difficult problems we shall have to deal with further on.
The Azores and Bermuda offer great contrasts in physical features,
but striking similarities in geographical position. The one is
voleanic, the other coralline; but both are surrounded by a wide
expanse of ocean of enormous depth, the one being about as far
from Europe as the other is from America. Both are situated
in the temperate zone, and they differ less than six degrees in
latitude, yet the vegetation of the one is wholly temperate,
while that of the other is almost tropical. The productions of
the one are related to Europe, as those of the other are to
America, but they present instructive differences; and both

CHAP, XII. | OCEANIC ISLANDS, 239

afford evidence of the highest value as to the means of dispersal
of various groups of organisms across a wide expanse of ocean.

THE AZORES, OR WESTERN ISLANDS.

These islands form a widely scattered group, nine in number,
situated between 37° and 39° 40’ N. Lat. and stretching in
a south-east and north-west direction over a distance of nearly

OUTLINE MAP OF THE AZORES.

Notr.—The light tint shows where the sea is less than 1,000 fathoms deep.
The dark tint _,, 53 Ae more than 1,000 fathoms deep.
The figrres show depths in fathoms.

400 miles. The largest of the islands, San Miguel, is about forty
miles Jong, and is one of the nearest to Europe, being rather
under 900 miles from the coast of Portugal, from which it is
separated by an ocean 2,500 fathoms deep. The depth between
the islands does not seem to be known, but the 1,000 fathom
line encloses the whole group pretty closely, while a depth of
about 1,800 fathoms is reached within 300 miles in all direc-
tions. These great depths render it in the highest degree

240 ISLAND LIFE. [PART II,

improbable that the Azores have ever been united with the
European continent; while their being wholly volcanic’ is
equally opposed to the view of their having formed part of an
extensive Atlantis including Madeira and the Canaries. The
only exception to their volcanic structure is the occurrence
in one small island only (Santa Maria) of some marine deposits
of Upper Miocene age—a fact which proves some alterations of
level, and perhaps a greater extension of this island at some
former period, but in no way indicates a former union of the
islands, or any greater extension of the whole group. It
proves, however, that the group is of considerable antiquity,
since it must date back to Miocene times; and this fact may be
of importance in considering the origin and peculiar features of
the fauna and flora. It thus appears that in all physical
features the Azores correspond strictly with our definition of
“oceanic islands,” while their great distance from any other
land, and the depth of the ocean around them, make them
typical examples of the class.) We should therefore expect
them to be equally typical in their fauna and flora; and this is
the case as regards the most important characteristics, although
in some points of detail they present exceptional phenomena.
Chief Zoological Features of the Azores1—The great feature
of oceanic islands—the absence of all indigenous land-mammalia
and amphibia—is well shown in this group; and it is even
carried further, so as to include all terrestrial vertebrata, there
being no snake, lizard, frog, or fresh-water fish, although the
islands are sufficiently extensive, possess a mild and equable
climate, and are in every way adapted to support all these
groups. On the other hand, flying creatures, as birds and
insects, are abundant; and there is also one flying mammal—a
small European bat. It is true that rabbits, weasels, rats and
mice, and a small lizard peculiar to Madeira and Teneriffe, are
now found wild in the Azores, but there is good reason to
believe that these have all been introduced by human agency.

1 For most of the facts as to the zoology and botany of these islands, I
am indebted to Mr, Godman’s valuable work—Natural History of the
Azores or Western Islands, by Frederick Du Cane Godman, F.L.S.,
F.Z.S., &c., London, 1870

CHAP, XII. THE AZORES. 241
The same may be said of the gold-fish and eels now found in
some of the lakes, there being not a single fresh-water fish
which is truly indigenous to the islands. When we consider
that the nearest part of the group is about 900 miles from
Portugal, and more than 550 miles from Madeira, it is not
surprising that none of these terrestrial animals can have passed
over such a wide expanse of ocean unassisted by man.

Let us now see what animals are believed to have reached
the group by natural means, and thus constitute its indigenous
fauna. These consist of birds, insects, and land-shells, each of
which must be considered separately.

Birds.—Fifty-three species of birds have been observed at the
Azores, but the larger proportion (thirty-one) are either aquatic
or waders—birds of great powers of flight, whose presence in the
remotest islands is by no means remarkable. Of these two
groups twenty are residents, breeding in the islands, while eleven
are stragglers only visiting the islands occasionally, and all are
common European species. The land-birds, twenty-two in
number, are more interesting, four only being stragglers, while
eighteen are permanent residents. The following is a list of

these resident land-birds :—

1. Common Buzzard (Buieo vulgaris)

2. Long-eared Owl (Asio otus)

3. Barn Owl (Strix flammea)

4, Blackbird (Turdus merula)

5. Robin (Lrythacus rubecula)
6. Blackcap (Sylvia atricapilla)
7. Gold-crest (Regulus cristatus)

8. Wheatear (Saxicola enanthe)

9. Grey Wagtail (Motacilla sulphurea)
10. Atlantic Chaffinch (fringilla tintillon)

11, Azorean Bullfinch (Pyrrhula murina)
12. Canary (Serinus canarius)
13. Common Starling _ ... He (Sturnus vulgaris)
14, Lesser Spotted Woodpecker ... (Dryobates minor)
15. Wood-pigeon ee (Columba palumbus)
16. Rock Dove ae (Columba livia)

17. Red-legged Partridge... (Caccabis rufa)

18. Common Quail " ( Coturnix communis)

All the above-named birds are common in Europe and North

242 ISLAND LIFE. [PART It.

Africa except three—the Atlantic chaffinch and the canary
which inhabit Madeira and the Canary Islands, and the Azorean
bullfinch, which is peculiar to the islands we are considering.

Origin of the Azorean Bird-fauna.—The questions we have
now before us are—how did these eighteen species of birds first
reach the Azores, and how are we to explain the presence of a
single peculiar species while all the rest are identical with
European birds? In order to answer them, let us first see what
stragglers now actually visit the Azores from the nearest con-
tinents. The four species given in Mr. Godman’s list are the
kestrel, the oriole, the snow-bunting, and the hoopoe; but he
also tells us that there are certainly others, and adds: “ Scarcely
a storm occurs in spring or autumn without bringing one or
more species foreign to the islands; and I have frequently been
told that swallows, larks, grebes, and other species not referred
to here, are not uncommonly seen at those seasons of the year.”

We have, therefore, every reason to believe that the birds
which are now residents originated as stragglers, which occa-
sionally found a haven in these remote islands when driven out
to sea by storms. Some of them, no doubt, still often arrive
from the continent, but these cannot easily be distinguished as
new arrivals among those which are residents. Many facts men-
tioned by Mr. Godman show that this is the case. A barn-owl,
much exhausted, flew on board a whaling-ship when 500 miles
S.W. of the Azores; and even if it had come from Madeira it
must have travelled quite as far as from Portugal to the islands.
Mr. Godman also shot a single specimen of the wheatear in
Flores after a strong gale of wind. and as no one on the island
knew the bird, it was almost certainly a recent arrival. Sub-
sequently a few were found breeding in the old crater of Corvo, a
small adjacent island; and as the species is not found in any
other island of the group, we may infer that this bird is a
recent immigrant in process of establishing itself.

Another fact which is almost conclusive in favour of the bird-
population having arrived as stragglers is, that they are most
abundant in the islands nearest to Hurope and Africa. The
Azores consist of three divisions—an eastern, consisting of two
islands, St. Michael’s and St. Mary’s; a central of five, Terceira,

CHAP. XII. | THE AZORES. 243

Graciosa, St. George’s, Pico, and Fayal; and a western of two,
Flores and Corvo. Now had the whole group once been united
to the continent, or even formed parts of one extensive Atlantic
island, we should certainly expect the central group, which is
more compact and has a much larger area than all the rest, to
have the greatest number and variety of birds. But the fact
that birds are most numerous in the eastern group, and diminish
as we go westward, is entirely opposed to this theory, while it is
strictly in accordance with the view that they are all stragglers from
Europe, Africa, or the other Atlantic islands. Omitting oceanic
wanderers, and including all birds which have probably arrived in-
voluntarily, the numbers are found to be forty species in the eastern
group, thirty-six in the central, and twenty-nine in the western.

To ‘account for the presence of one peculiar species—the
bullfinch (which, however, does not differ from the common
European bullfinch more than do some of the varieties of
North American birds from their type-species) is not difficult ;
the wonder rather being that there are not more peculiar forms.
In our third chapter we have seen how great is the amount of
individual variation in birds, and how readily local varieties
become established wherever the physical conditions are suffi-
ciently distinct. Now we can hardly have a greater difference of
conditions than between the continent of Kurope or North Africa,
and a group of rocky islands in mid-Atlantic, situated in the full
course of the Gulf Stream and with an excessively mild though
stormy climate. We have every reason to believe that special
modifications would soon become established in any animals
completely isolated under such conditions. But they are not,
as a rule, thus completely isolated, because, as we have seen,
stragglers arrive at short intervals; and these, mixing with the
residents, keep up the purity of the breed. It follows, that only
those species which reach the Azores at very remote intervals
will be likely to acquire well-marked distinctive characters ;
and this appears to have happened with the bullfinch alone, a
bird which does not migrate, and is therefore less likely to be
blown out to sea, more especially as it inhabits woody districts.
A few other Azorean birds, however, exhibit slight differences
from their European alles.

R 2

244 ISLAND LIFE. [PART II.

There is another reason for the very slight amount of pecu-
larity presented by the fauna of the Azores as compared with
many other oceanic islands, dependent on its comparatively
recent origin. ‘The islands themselves may be of considerable
antiquity, since a few small deposits, believed to be of Miocene
age, have been found on them, but there can be little doubt
that their present fauna, at all events as concerns the birds,
had its origin since the date of the last glacial epoch. Even
now icebergs reach the latitude of the Azores only a little to
the westward, and when we consider the proofs of extensive
ice-action in North America and Europe, we can hardly doubt
that these islands were at that time surrounded with pack-ice,
while their own mountains, reaching 7,600 feet high in Pico,
would almost certainly have been covered with perpetual snow
and have sent down glaciers to the sea. They might then
have had a climate almost as bad as that now endured by the
Prince Edward Islands in the southern hemisphere, nearly ten
degrees farther from the equator, where there are no land-birds
whatever, although the distance from Africa is not much greater
than that of the Azores from Europe, while the vegetation is
limited to a few alpine plants and mosses. This recent origin
of the birds accounts in a great measure for their identity with
those of Europe, because, whatever change has occurred must
have been effected in the islands themselves; and in a time limited
to that which has elapsed since the glacial epoch passed away.

Insects of the Azores.—Having thus found no difficulty in ac-
counting for the peculiarities presented by the birds of these
islands, we have only to see how far the same general principles
will apply to the insects and land-shells. The butterflies,
moths, and hymenoptera, are few in number, and almost all
seem to be common European species, whose presence is
explained by the same causes as those which have introduced
the birds. Beetles, however, are more numerous, and have been
better studied, and these present some features of interest. The
total number of species yet known is 212, of which 175 are
European; but out of these 101 are believed to have been
introduced by human agency, leaving seventy-four really
indigenous. Twenty-three of these indigenous species are not

CHAP, x11.] THE AZORES. 245

found in any of the other Atlantic islands, showig that they
have been introduced directly from Europe by causes which
have acted more powerfully here than farther south. Besides
these there are thirty-six species not found in Europe, of which
nineteen are natives of Madeira or the Canaries, three are
American, and fourteen are altogether pecuhar to the Azores.
These latter are mostly allied to species found m Europe or in
the other Atlantic islands, while one is allied to an American
species, and two are so distinct as to constitute new genera.
The following list of these peculiar species will be mteresting :—

CARABIDE,

Anchomenus aptinoides ...... Allied to a species from the Canaries.

Bembidium hesperus ......... Allied to the European B, latum.
DYTISCIDA.

A gabus godmanni .......0.05. Allied to the European A. dispar.
CoLYDIIDA,

Tarphius wollastont ......... A genus almost peculiar to the Atlantic islands,
ELATERIDE.,

Heteroderes AzZ0ricus ......06. Allied to a Brazilian species.

FMOASITUS COLOSUS..6.005: 600000 Belongs to a peculiar Madagascar genus !
MELYRIDA,

Aitalus miniaticollis ......... Allied to a Canarian species.

RHYNCOPHORA.

Phleophagus variabilis...... Allied to European and Atlantic species.

Acalles droueti .......... ......A Mediterranean and Atlantic genus.

LAparocerus AZOVICUS «1.06... Allied to Madeiran species.

Asynonychus godmanni ....A peculiar genus, allied to Brachyderes, of the
south of Europe.

Neocnemis occidentalis ...... A peculiar genus, allied to the Kuropean genus
Strophosomus.
HETEROMERA.
FHELODS QZOVICUS. so0....ececseas Allied to H. vulcanus of Madeira.
STAPHYLINIDA.

Xenomma melanocephala ...Allied to X. filiforme from the Canaries.

This greater amount of speciality in the beetles than in the
birds may be due to two causes. In the first place many of
these small insects have no doubt survived the glacial epoch,
and may, in that case, represent very ancient forms which have

246 ISLAND LIFE. [PART II.

become extinct in their native country ; and in the second place,
insects have many more chances of reaching remote islands than
birds, for not only may they be carried by gales of wind, but
sometimes, in the egg or larva state or even as perfect insects,
they may be drifted safely for weeks over the ocean, buried in
the hight stems of plants or in the solid wood of trees in which
many of them undergo their transformations. Thus we may
explain the presence of three common South American species
(two elaters and a longicorn), all wood-eaters, and therefore
liable to be occasionally brought in floating timber by the Gulf
Stream. But insects are also immensely more numerous in
species than are land-birds, and their transmission would be im
most cases quite involuntary, and not dependent on their own
powers of flight as with birds; and thus the chances against the
same species being frequently carried to the same island would
be considerable. If we add to this the dependence of so many
insects on local conditions of climate and vegetation, and their
liability to be destroyed by insectivorous birds, we shall see that,
although there may be a greater probability of insects as a whole
reaching the islands, the chance against any particular insect
arriving there, or against the same species arriving frequently,
is much greater than in the case of birds. The result is, that
(as compared with Britain for example) the birds are, pro-
portionately, much more numerous than the beetles, while the
peculiar species of beetles are much more numerous than among
birds, both facts being quite in accordance with what we know
of the habits of the two groups. We may also remark, that the
small size and obscure characters of many of the beetles renders
it probable that species now supposed to be peculiar, really
inhabit some parts of Europe or North Africa.

It is interesting to note that the two families which are pre-
eminently wood, root, or seed eaters, are those which present the
greatest amount of speciality. The two Hlateride alone exhibit
remote affinities, the one with a Brazilian the other with a
Madagascar group; while the only peculiar genera belong to the
Rhyncophora, but are allied to European forms. These last
almost certainly form a portion of the more ancient fauna of the
islands which migrated to them in pre-glacial times, while the

CHAP, XII.] THE AZORHS. 247

Brazilian elater appears to be the solitary example of a living
insect brought by the Gulf Stream to these remote shores.
The elater, having its nearest living ally in Madagascar
(Llastrus dolosus), cannot be held to indicate any independent
communication between these distant islands; but is more
probably a relic of a once more widespread type which has
only been able to maintain itself in these localities. Mr.
Crotch states that there are some species of beetles common to
Madagascar and the Canary Islands, while there are several
genera, common to Madagascar and South America, and some to
Madagascar and Australia. The clue to these apparent anomalies
is found in other genera being common to Madagascar, Africa,
and South America, while others are Asiatic or Australian.
Madagascar, in fact, has insect relations with every part of the
globe, and the only rational explanation of such facts is, that
they are indications of very ancient and once widespread groups,
maintaining themselves only in a few widely separated portions
of what was at one time or another the area of their distribution.

Land-shells of the Azores.—Like the imsects and birds, the
land-shells of these islands have a generally European aspect,
but with a larger proportion of peculiar species. This was to be
expected, because the means by which molluscs are carried over
the sea are far less numerous and varied than in the case of
insects ;! and we may therefore conclude that their mtroduction
is a very rare event, and that a species once arrived remains for
long periods undisturbed by new arrivals, and is therefore more
likely to become modified by the new conditions, and then fixed
as a distinct type. Out of the sixty-nine known species, thirty-
seven are common to Europe or the other Atlantic islands, while
thirty-two are peculiar, though almost all are distinctly allied to
European types. The majority of these shells, especially the
peculiar forms, are very small, and many of them may date
back to beyond the glacial epoch. The eggs of these would be
exceedingly minute, and might occasionally be carried on leaves
or other materials during gales of exceptional viclence and
duration, while others might be conveyed with the earth that
often sticks to the feet of birds. There are also, probably, other

1 See Chap. V. p. 76.

248 ISLAND LIFE. [PART II.

unknown means of conveyance; but however this may be, the
general character of the land-molluscs is such as to confirm
the conclusions we have arrived at from a study of the birds
and insects,—that these islands have never been connected
with a continent, and have been peopled with living things by
such forms only as in some way or other have been able to reach
them across many hundred miles of ocean.

Lhe Flora of the Azores.—The flowering-plants of the Azores
have been studied by one of our first botanists, Mr. H. C.
Watson, who has himself visited the islands and made extensive
collections; and he has given a complete catalogue of the
species in Mr. Godman’s volume. As our object in the present
work is to trace the past history of the more important islands
by means of the forms of life that inhabit them, and as for
this purpose plants are sometimes of more value than any class of
animals, it will be well to take advantage of the valuable materials
here available, in order to ascertain how far the evidence derived
from the two organic kingdoms agrees in character; and also
to obtain some general results which may be of service in our
discussion of more difficult and more complex problems.

There are in the Azores 480 known species of flowering-plants
and ferns, of which no less than 440 are found also in Europe,
Madeira, or the Canary Islands ; while forty are peculiar to the
Azores, but are more or less closely allied to European species.
As botanists are no less prone than zoologists to invoke former
land-connections and continental extensions to account for the
wide dispersal of objects of their study, it will be well to
examine somewhat closely what these facts really imply.

The Dispersal of Seeds.—The seeds of plants are liable to be
dispersed by a greater variety of agents than any other organisms,
while their tenacity of life, under varying conditions of heat and
cold, drought and moisture, is also exceptionally great. They
have also an advantage, in that the great majority of flowering
plants have the sexes united in the same individual, so that a
single seed in a state fit to germinate may easily stock a whole
island. The dispersal of seeds has been studied by Sir Joseph
Hooker, Mr. Darwin, and many other writers, who have made
it sufficiently clear that they are in many cases liable to be

CHAP. XII.] THE AZORES. 249

carried enormous distances. An immense number are specially
adapted to be carried by the wind, through the possession of
down or hairs, or membranous wings or processes; while others
are so minute, and produced in such profusion, that it is difficult
to place a limit to the distance they might be carried by gales
of wind or hurricanes. Another class of somewhat heavier
seeds or dry fruits are capable of being exposed for a long
time to sea-water without injury. Mr. Darwm made many
experiments on this point, and he found that many seeds,
especially of Atriplex, Beta, oats, Capsicum, and the potato,
grew after 100 days’ immersion, while a large number survived
fifty days. But he also found that most of them sink after a few
days’ immersion, and this would certainly prevent them being
floated to very great distances. It is very possible, however,
that dried branches or flower-heads containing seeds would float
longer, while it is quite certain that many tropical seeds do float
for enormous distances, as witness the double cocoa-nuts which
cross the Indian ocean from the Seychelle Islands to the coast
of Sumatra, and the West Indian beans which frequently reach
the west coast of Scotland. There is therefore ample evidence
of the possibility of seeds being conveyed across the sea for
great distances by winds and surface currents.!

1 Some of Mr. Darwin’s experiments are very interesting and suggestive.
Ripe hazel-nuts sank immediately, but when dried they floated for ninety
days, and afterwards germinated. An asparagus-plant with ripe berries,
when dried, floated for eighty-five days, and the seeds afterwards germi-
nated. Out of ninety-four dried plants experimented with, eighteen floated
for more than a month, and some for three months, and their powers of
germination seem never to have been wholly destroyed. Now, as oceanic
currents vary from thirty to sixty miles a day, such plants under the most
favourable conditions might be carried 90 x 60 = 5,400 miles! But even half
of this is ample to enable them to reach any oceanic island, and we must re-
member that till completely water-logged they might be driven along at a
much greater rate by the wind. Mr. Darwin calculates the distance by the
average time of flotation to be 924 miles; but in such a case as this we
are entitled to take the extreme cases, because such countless thousands of
plants and seeds must be carried out to sea annually that the extreme cases
in a single experiment with only ninety-four plants, must happen hundreds
or thousands of times and with hundreds or thousands of species, naturally,
and thus afford ample opportunities for successful migration. (See Origin
of Species, 6th Edition, p. 325.) ae

250 ISLAND LIFE. [PART II,

Birds as Seed-carriers.—The great variety of fruits that are
eaten by birds afford a means of plant-dispersal in the fact that
seeds often pass through the bodies of birds in a state well-fitted
for germination ; and such seeds may occasionally be carried long
distances by this means. Of the twenty-two land-birds found in
the Azores, half are, more or less, fruit-eaters, and these may have
been the means of introducing some plants into the islands.

Birds also frequently have small portions of earth on their
feet; and Mr. Darwin has shown by actual experiment that
almost all such earth contains seeds. Thus in nine grains of
earth on the leg of a woodcock a seed of the toad-rush was
found which germinated; while a wounded red-legged partridge
had a ball of earth weighing six and a half ounces adhering to its
leg, and from this earth Mr. Darwin raised no less than eighty-
two separate plants of about five distinct species. Still more re-
markable was the experiment with six and three-quarter ounces
of mud from the edge of a little pond, which, carefully treated
under glass, produced 537 distinct plants! This is equal to a
seed for every six grains of mud, and when we consider how
many birds frequent the edges of ponds in search of food, or
come there to drink, it is evident that great numbers of seeds
may be dispersed by this means.

Many seeds have hispid awns, hooks, or prickles which readily
attach them to the feathers of birds, and a great number of
aquatic birds nest inland on the ground; and as these are pre-
eminently wanderers, they must often aid in the dispersal of
such plants.?

1 The following remarks, kindly communicated to me by Mr, H. N.
Moseley, naturalist to the Challenger, throw much light on the agency of
birds in the distribution of plants :—‘‘ Grisebach (Veg. der Erde, Vol. II. p.
496) lays much stress on the wide ranging of the albatross (Diomedea)
across the equator from Cape Horn to the Kurile Islands, and thinks that
the presence of the same plants in Arctic and Antarctic regions may be
accounted for, possibly, by this fact. I was much struck at Marion Island
of the Prince Edward group, by observing that the great albatross breeds
in the midst of a dense, low herbage, and constructs its nest of a mound
of turf and herbage. Some of the indigenous plants, e.g. Acena, have
flower-heads which stick like burrs to feathers, &c., and seem specially

adapted for transportation by birds. Besides the albatrosses, various
species of Procellaria and Puffinus, birds which range over immense dis-

CHAP, XII] THE AZORES. 251

Facilities for Dispersal of Azorean Plants.—Now in the course
of very long periods of time the various causes here enumerated
would be sufficient to stock the remotest islands with vegetation,
and a considerable part of the Azorean flora appears well adapted
to be so conveyed. Of the 439 flowering-plants in Mr. Watson’s
list, I find that about forty-five belong to genera that have either
pappus or winged seeds; sixty-five to such as have very minute
seeds ; thirty have fleshy fruits such as are greedily eaten by birds ;
several have hispid seeds; and eighty-four are glumaceous plants,
which are all probably well-adapted for being carried partly by
winds and partly by currents, as well as by some of the other
causes mentioned. On the other hand we have a very suggestive
fact in the absence from the Azores of most of the trees and shrubs
with large and heavy fruits, however common they may be in
Europe. Suchare oaks, chestnuts, hazels, apples, beeches, alders,
and firs; while the only trees or large shrubs are the Portugal
laurel, myrtle, laurestinus, elder, Lawrus canariensis, Myrica faya,
and a doubtfuily peculiar juniper—all small berry-bearers, and
therefore likely to have been conveyed by one or other of the
modes suggested above.

tances may, I think, have played a great part in the distribution of plants,
and especially account, in some measure, for the otherwise difficult fact
(when occurring in the tropics), that widely distant islands have similar
mountain plants. The Procellaria and Puffinus in nesting, burrow in the
ground, as far as I have seen choosing often places where the vegetation
is the thickest. The birds in burrowing get their feathers covered with
vegetable mould, which must include spores, and often seeds. In high
latitudes the birds often burrow near the sea-level, as at Tristan d’Acunha
or Kerguelen’s Land, but in the tropics they choose the mountains for their
nesting-place (Finsch and Hartlaub, Orn. der Viti- und Tonga-Inseln, 1867,
Kinleitung, p. xvui.), Thus, Puffinus megasi nests at the top of the Koro-
basa basaga mountain, Viti Levu, fifty miles from the sea. A Procellaria
breeds in like manner in the high mountains of Jamaica, I believe at 7,000
feet. Peale describes the same habit of Procellaria rostrata at Tahiti, and
I saw the burrows myself amidst a dense growth of fern, &c., at 4,400 feet
elevation in that island. Phaethon has a similar habit. It nests at the
crata of Kilauea, Hawaii, at 4,000 feet elevation, and also high up in Tahiti.
In order to account for the transportation of the plants, it is not of course
necessary that the same species of Procellaria or Diomedea should now
range between the distant points where the plants occur. The ancestor of

the now differing species might have carried the seeds. The range of the
genus is sufficient.”

252 ISLAND LIFE, [PART IL.

There can be little doubt that the truly indigenous flora of
the islands is far more scanty than the number of plants recorded
would imply, because a large but unknown proportion of the
species are certainly importations, voluntary or involuntary, by
man. As, however, the general character of the whole flora is
that of the south-western peninsula of Europe, and as most of
the introduced plants have come from the same country, it is
almost impossible now to separate them, and Mr. Watson has
not attempted todoso. The whole flora contains representatives
of eighty natural orders and 250 genera ; and even if we suppose
that one-half the species only are truly indigenous, there will
still remain a wonderfully rich and varied flora to have been
carried, by the various natural means above indicated, over 900
miles of ocean, more especially as the large proportion of species
identical with those of Europe shows that their introduction
has been comparatively recent, and that it is, probably (as in the
case of the birds) still gomg on. We may therefore feel sure
that we have here by no means reached the limit of distance
to which plants can be conveyed by natural means across the
ocean; and this conclusion will be of great value to us in
investigating other cases where the evidence at our command
is less complete, and the indications of origin more obscure or
conflicting.

Of the forty species which are considered to be peculiar to the
islands, all are allied to European plants except six, whose nearest
affinities are in the Canaries or Madeira. Two of the Composite
are considered to be distinct genera, but in this order generic
divisions rest on slight technical distinctions; and the Campa-
nula vidalit is very distinct from any other known species. With
these exceptions, most of the peculiar Azorean species are closely
allied to European plants, and are in several cases little more
than varieties of them. While therefore we may believe that
the larger part of the existing flora reached the islands since the
glacial epoch, a portion of it may be more ancient, as there is
no doubt that a majority of the species could withstand some
lowering of temperature ; while in such a warm latitude and
surrounded with sea, there would always be many sunny and
sheltered spots in which even tender plants might flourish.

CHAP, XII. | BERMUDA. 258

Important deduction from the peculiarities of the Azorean Fauna
and Flora.—There is one conclusion to be drawn from the almost
wholly European character of the Azorean fauna and flora which
deserves special attention, namely, that the peopling of remote
islands is not due so much to ordinary or normal, as to extra-
ordinary and exceptional causes. These islands lie in the course of
the south-westerly return trades and also of the Gulf Stream, and
we should therefore naturally expect that American birds, insects,
and plants would preponderate if they were conveyed by the
regular winds and currents, which are both such as to prevent
European species from reaching them. But the violent storms to
which the Azores are liable blow from all points of the compass ;
and it is evidently to these, combined with the greater proximity
and more favourable situation of the coasts of Europe and North
Africa, that the presence of a fauna and flora so decidedly
European is to be traced.

The other North Atlantic Islands—Madeira, the Canaries,
and the Cape de Verdes—present analogous phenomena to those
of the Azores, but with some peculiarities dependent on their
more southern position, their richer vegetation, and perhaps
their greater antiquity. These have been sufficiently discussed
in my Geographical Distribution of Animals (Vol. I. pp. 208-
215); and as we are now dealing with what may be termed
typical examples of oceanic islands, for the purpose of illus-
trating the laws, and solving the problems presented by the
dispersal of animals, we will pass on to other cases which have
been less fully discussed in that work.

BERMUDA.

The Bermudas are a small group of low islands formed of coral,
and blown coral-sand consolidated into rock. They are situated
in 32° N. Lat., about 700 miles from North Carolina, and some-
what farther from the Bahama Islands, and are thus rather
more favourably placed for receiving immigrants from America
and its islands than the Azores are with respect to Europe.
There are about 100 islands and islets in all, but their total area

264 ISLAND LIFE. [PART II.

does not exceed fifty square miles. They are surrounded by reefs,
some at a distance of thirty miles from the main group; and
the discovery of a layer of earth with remains of cedar-trees
forty-eight feet below the present high-water mark shows that
the islands have once been more extensive and probably included

MAP OF BERMUDA AND THE AMERICAN COAST.

Notrt.—The light tint indicates sea less than 1.000 fathoms deep.
The dark tint ny », more than 1,000 fathoms deep.
The figures show the depth in fathoms,

the whole area now occupied by shoals and reefs.'_ Immediately
beyond these reefs, however, extends a very deep. ocean, while
about 450 miles distant ina south-east direction, the deepest part

1 Nature, Vol. VI. p. 262, “Recent Observations in the Bermudas,”’ by
Mr. J. Matthew Jones.

CHAP, XII.| BERMUDA, 255

of the North Atlantic is reached, where soundings of 3,825 and
3,875 fathoms have been obtained. It is clear therefore that
these islands are typically oceanic.

Soundings were taken by the Challenger in four different
directions around Bermuda, and always showed a rapid deepen-
ing of the sea to about 2,500 fathoms. This was so remarkable,
that in his reports to the Admiralty, Captain Nares spoke of
Bermuda as “a solitary peak rising abruptly from a base only
120 miles in diameter ;” and in another place as “an isolated
peak rising abruptly from a very small base.”” These expressions
show that Bermuda is looked upon as a typical example of an
“oceanic peak ”’ ; and on examining the series of official reports
of the Challenger soundings, I can find no similar case, although
some coasts, both of continents and islands, descend more
abruptly. In order to show, therefore, what is the real char-
acter of this peak, | have drawn a section of it on a true scale

x BERMUDA s

<——— 55. MILES ><-18 MILES 3<——— 46 MILES.————=»>

SECTION OF BERMUDA AND ADJACENT SEA-BOTTOM.

The figures show the depth in fathoms at fifty-five miles north and forty-six miles south os
the islands respectively.

from the soundings taken in a north and south direction where
the descent is steepest. It will be seen that the slope is on
both sides very easy, being 1 in 16 on the south, and 1 in 19
on the north. The portion nearest the islands will slope more
rapidly, perhaps reaching in places 1 in 10; but even this is
not steeper than many country roads in hilly countries, while
the remainder would be a hardly perceptible slope. Although
generally very low, some parts of these islands rise to 250 feet
above the sea-level, consisting of various kinds of limestone
rock, sometimes soft and friable, but often very hard and even
crystalline. It consists of beds which sometimes dip as much
as 30°, and exhibit besides great contortions, so that at first
sight the islands appear to exhibit on a small scale the pheno-
mena of a disturbed Paleozoic district. It has however long

256 ISLAND LIFE. [PART 11,

been known that these rocks are all due to the wind, which
blows up the fine calcareous sand, the product of the disinte-
gration of coral, shells, serpulz, and other organisms, forming
sand-hills forty and fifty feet high, which move gradually along,
overwhelming the lower tracts of land behind them. These
are consolidated by the percolation of rain-water, which dissolves
some of the lime from the more porous tracts and deposits it
lower down, filling every fissure with stalagmite.

The Red Clay of Bermuda.—Besides the calcareous rocks
there is found in many parts of the islands a layer of red earth
or clay, containing about thirty per cent. of oxide of iron. This
very closely resembles, both in colour and chemical composition,
the red clay of the ocean floor, found widely spread in the Atlantic
at depths of from 2,300 to 3,150 fathoms, and occurring abund-
antly all round Bermuda. It appears, therefore, at first sight,
as if the ocean bed itself has been here raised to the surface,
and a portion of its covering of red clay preserved; and this is
the view adopted by Mr. Jones in his paper on the “ Botany of
Bermuda.” He says, after giving the analysis: ‘This analysis
tends to convince us that the deep chocolate-coloured red clay
of the islands found in the lower levels, and from high-water
mark some distance into the sea, originally came from the ocean
floor, and that when by volcanic agency the Bermuda column was
raised from the depths of the sea, 1ts summit, most probably broken
in outline, appeared above the surface covered with this red mud,
which in the course of ages has but slightly changed its com-
position, and yet possesses sufficient evidence to prove its identity
with that now lying contiguous to the base of the Bermuda
column.” But in his Guide to Bermuda Mr. Jones tells us that
_ this same red earth has been found, two feet thick, under coral
rock at a depth of forty-two feet below low-water mark, and
that it ‘rested on a bed of compact calcareous sandstone.” Now
it is quite certain that this “calcareous sandstone” was never
formed at the bottom of the deep ocean 700 miles from land ;
and the occurrence of the red earth at different levels upon
coralline sand rock is therefore more probably due to some process
of decomposition of the rock itself, or of the minute organisms
which abound in the blown sand. The forthcoming volumes on

CHAP! X11. | BERMUDA. 257

the results of the Challenger expedition will probably clear up
the difficulty.

Zoology of Bermuda—As might be expected from their
extreme isolation, these islands possess no indigenous land
mammalia, frogs, or snakes. There is however one lizard, which
Professor Cope considers to be distinct from any American
species, and which he has named Plestiodon longirostris. It is
said to be most nearly allied to P. fasciatus of the south-eastern
States, from which it differs in having nearly ten more rows of
scales, the tail thicker, and the muzzle longer. In colour it is
ashy brown above, greenish blue beneath, with a white line:
black-margined on the sides, and it seems to be tolerably
abundant in the islands. This lizard is especially interesting
as the only vertebrate animal which exhibits any peculiarity.

Birds.—Notwithstanding its small size, low altitude, and
remote position, a great number of birds visit Bermuda annually,
some in large numbers, others only as accidental stragglers.
Altogether, over 180 species have been recorded, rather more
than half being wading and swimming birds, whose presence is
not so much to be wondered at as they are great wanderers ;
while about eighty-five are land birds, many of which would
hardly be supposed capable of filymg so great a distance. Of
the 180 species, however, about thirty have only been seen once,
and a great many more are very rare; but about twenty species
of land bird are recorded as tolerably frequent visitors, and nearly
half these appear to come every year.

There are only ten species which are permanent residents on
the island—eight land, and two water birds, and of these one
has been almost certainly introduced. These resident birds are
as follows :

1. Galeoscoptes carolinensis. (The Cat bird.) Migrates along the east
coast of the United States.

2. Sialia sialis. (The Blue bird.) Migrates along the east coast.

3. Vireo noveboracensis. (The White-eyed green Tit.) Migrates along
the east coast.

4. Passer domesticus. (The English Sparrow.) ? Introduced.

5. Corvus americanus. (The American Crow.) Common over all North
America.

258 ISLAND LIFE. [PART If,

6. Cardinalis virginianus. (The Cardinal bird.) Migrates from Carolina
southward.

7. Chamepelia passerina. (The Ground Dove.) Louisiana, W. Indies,
and Mexico.

8. Ortyx virginianus. (The American Quail.) New England to Florida.

9. Ardea herodias. (The Great Blue Heron.) All North America,

10. Fulica americana. (The American Coot.) Temperate and tropical

North America.

It will be seen that these are all very common North
American birds, and most of them are constant visitors from —
the mainland, so that however long they may have mhabited
the islands there has been no chance for them to have acquired
any distinctive characters through isolation.

Among the most regular visitants which are not resident, are
the common N. American kingfisher (Ceryle alcyon), the wood
wactail (Sevrus noveeboracensis), the wide ranging rice-bird
(Dolichonyx oryzivora), and a moorhen, (Gallinula galeata); the
first three being very common over almost all North America,
and the last abundant in the southern portion of it.

Comparison of the Bird-faunas of Bermuda and the Azores.—
The bird-fauna of Bermuda thus differs from that of the
Azores, in the much smaller number of resident species, and
the presence of several regular migrants. This is due, first, to
the small area and little varied surface of these islands, as well
as to their limited fiora and small supply of insects not affording
conditions suitable for the residence of many species all the
year round; and, secondly, to the peculiarity of the climate of
North America, which causes a much larger number of its birds
to be migratory than in Europe. The Northern United States
and Canada, with a sunny climate, luxuriant vegetation, and
abundant insect-life during the summer, supply food and shelter.
to an immense number of insectivorous and frugivorous birds ; so
that durmg the breeding season Canada is actually richer in
bird-life than Florida, But as the severe winter comes on all
these are obliged to migrate southward, some to Carolina,
Georgia, and Florida, others as far as the West Indies, Mexico,
or even to Guatemala and South America.

Every spring and autumn, therefore, a vast multitude of
birds, belonging to more than a hundred distinct species, migrate

CHAP, XII. ] BERMUDA. 259

northward or southward in EKastern America. A large proportion
of these pass along the Atlantic coast, and it has been observed
that many of them fly some distance out to sea, passing straight
across bays from headland to headland by the shortest route.

Now as the time of these migrations is the season of storms,
especially the autumnal one, which nearly coincides with the
hurricanes of the West Indies and the northerly gales of the
coast of America, the migrating birds are very liable to be
carried out to sea. Sometimes they may, as Mr. Jones suggests,
be carried up by local whirlwinds to a great height, where meet-
ing with a westerly or north westerly gale, they are rapidly
driven sea-ward. The great majority no doubt perish, but some
reach the Bermudas and form one of its most striking autumnal
features. In October, Mr. Jones tells us, the sportsman enjoys
more shooting than at any other time. The violent revolving
gales, which occur almost weekly, bring numbers of birds of
many species from the American continent, the different
members of the duck tribe forming no inconsiderable portion
of the whole; while the Canada goose, and even the ponderous
American swan, have been seen amidst the migratory host. With
these come also such delicate birds as the American robin (TZurdus
magratorius), the yellow-rumped warbler (Dendreca coronata), the
pine warbler (Dendreca pinus), the wood wagtail (Siwrus novebor-
acensis), the summer red bird (Pyranga estiva), the snow-bunt-
ing (Plectrophanes nivalis), the red-poll (Agiothus linarius), the
king bird (Tyrannus carolinensis), and many others. It is no doubt
in consequence of this repeated immigration that none of the
Bermuda birds have acquired any special peculiarity constituting
even a distinct variety; for the few species that are resident
and breed in the islands are continually crossed by individual
immigrants of the same species from the mainland,

Four European birds also have occurred in Bermuda ;—the
wheatear (Saxicola enanthe), which visits Iceland and Lapland
and sometimes the northern United States; the skylark
(Alauda arvensis), but this was probably an imported bird or an
escape from some ship; the land-rail (Crex pratensis), which
also wanders to Greenland and the United States; and the com-
mon snipe (Scolopax gallinago), which occurs not unfrequently

s 2

260 ISLAND LIFE, FPART If.)

in Greenland but has not yet been noticed in North America.
It is however so like the American snipe (S. wilsont), that a
straggler might easily be overlooked.

Two small bats of N. American species also occasionally
reach the island, and these are the only wild mammalia except
rats and mice.

Insects of Bermuda.—Insects appear to be very scarce; but it
is evident from the lists given by Mr. Jones that only the more —
conspicuous species have been yet collected. ‘These comprise
nineteen beetles, eleven bees and wasps, twenty-six butterflies
and moths, nine flies, and the same number of Hemiptera,
Orthoptera, and Neuroptera respectively. All appear to be
common North American or West Indian species; but until
some competent entomological collector visits the islands it is
impossible to say whether there are or are not any peculiar
species.

Land Mollusca.—The land-shells of the Bermudas are some-
what more interesting, as they appear to be the only group of
animals except reptiles in which there are any peculiar species.
The following list has been kindly furnished me by Mr. Thomas
Bland of New York, who has made a special study of the
terrestrial molluscs of the West Indian Islands. The species
which are peculiar to the islands are indicated by italics.

List of THE LAND-SHELLS OF BERMUDA.

1, Succinea fulgens. (Lea.)... ... Also in Cuba.

2 M Bermudensis. (Pfeifier.) 3, Darbadoes (?)

3. o margarita, (Pfr.) we Phen Sleyii rs

4, Hyalina Bermudensis. (Pfr.) ... A peculiar form, which, according

to Mr. Binney, “cannot be placed
in any recognised genus.” A
larger sub-fossil variety also
occurs, named H. Nelsoni, by
Mr. Bland, and which appears
sufficiently distinct to be classed
as another species,

‘ circumfpirmata. ee)

ns discrepans. (Pfr.)

. Patula Reiniana. (Pik):

» hypolepta. (Shuttleworth. ) Probably the same as P. minuscula

(Binney), a wide-spread Ameri-
can species.
o. ‘Helix vortex: SF OPinyine is ... Southern Florida and West Indies.

DONIAMN

CHAP. XII.] BERMUDA. 261

10. Helix microdonta. (Desh.) ... Bahama Islands.

times. appressa.. (Say.)..... ... Virginia and adjacent states; per-
haps introduced into Bermuda.

io) is, -pulchella, (Mill)... ... Europe; very close to H. minuta

(Say) of the United States.
Introduced into Bermuda (?)

13. ,, ventricosa, (Drap.) ... Azores, Canary Islands, and South
Europe.

14, Bulimulus nitidulus. (Pfr.) ... Cuba, Haiti, &c.

15. Stenogyra octona. (Ch.)... ... West Indies and South America.

16. Cionella acicula, (Mull.)... ... Florida, New Jersey, and Europe.

i Pupa pellucida. (Pfr.). ... ... West Indies, generally.

1, s;.. Barbadensis: -(Pfr.) ... Barbadoes (?)

19. ,, Jamaicensis. (C.B, Ad.) ... Jamaica,

20. Helicina convexa. (Pfr.) ... Barbuda.

Mr. Bland indicates only four species as. certainly peculiar to
Bermuda, and another sub-fossil species ; while one or two of the
remainder are indicated as doubtfully identical with those of other
countries. We have thus at least one-fourth of the land-shells
peculiar, while almost all the other productions of the islands are
identical with those of the adjacent continent and islands.
This corresponds, however, with what occurs generally in islands
at some distance from continents. In the Azores only one
land-bird is peculiar out of eighteen resident species; the beetles
show about one-eighth of the probably non-introduced species
as peculiar; the plants about one-twentieth; while the land-
shells have about half the species peculiar. This difference is
well explained by the much greater difficulty of transmission
over wide seas, in the case of land-shells, than of any other
terrestrial organisms. It thus happens that when a species has
once been conveyed it may remain isolated for unknown ages,
and has time to become modified by local conditions unchecked
by the introduction of other specimens of the original type.

Flora of Bermuda—Unfortunately no good account of the
plants of these islands has yet been published. Mr. Jones, in
his paper “‘On the Vegetation of the Bermudas” gives a list of
no less than 480 species of flowering plants; but this number
includes all the culinary plants, fruit-trees, and garden flowers,
as well as all the ornamental trees and shrubs from various
parts of the world which have been introduced, mixed up with
the European and American weeds that have come with agricul-
tural or garden seeds, and the really indigenous plants, in one

262 ISLAND LIFE. [PART IT.

undistinguished series. It appears too, that the late Governor,
Major-General Lefroy, ‘“‘has sown and distributed throughout
the islands packets of seeds from Kew, representing no less than
600 species, principally of trees and shrubs suited to sandy
coast soils ’’—so that it will be more than ever difficult in
future years to distinguish the indigenous from the imtroduced
vegetation.

From the researches of Dr. Rein and Mr. Moseley there
appear to be about 250 flowering plants in a wild state, and of
these Mr. Moseley thinks less than half are indigenous. The
majority are tropical and West Indian, while others are common
to the Southern States of North America; the former class
having been largely brought by means of the Gulf Stream, the
latter by the agency of birds or by winds. Mr. Jones tells us
that the currents bring numberless objects animate and inani-
mate from the Carribean Sea, including the seeds of trees,
shrubs, and other plants, which are continually cast ashore and
sometimes vegetate. The soap-berry tree (Sapindus saponaria)
has been actually observed to originate in this way.

Professor Oliver informs me that he knows of no undoubtedly
distinct species of flowering plants peculiar to Bermuda, though
there are some local forms of continental species,—instancing
Sisyrinchium, Bermudianum and Rhus toxicodendron. There are
however, two ferns—an Adiantum and a Nephrodium, which
are unknown from any other locality, and this renders it pro-
bable that some of the flowering plants are also peculiar. The
juniper, which is so conspicuous a feature of the islands, is said
to be a West Indian species (Juniperus barbadensis) found in
Jamaica and the Bahamas, not the North American red cedar ;
but there seems to be still some doubt about this common plant.

Mr. Moseley, who visited Bermuda in the Challenger, has well
explained the probable origin of the vegetation. The large
number of West Indian plants is no doubt due to the Gulf
Stream and constant surface drift of warm water in this direc-
tion, while others have been brought by the annual cyclones
which sweep over the intervening ocean. The great number of
American migratory birds, including large flocks of the American
golden plover, with ducks and other aquatic species, no doubt

CHAP, XI1.] BERMUDA. 263

occasionally bring seeds, either in the mud attached to their feet
or in their stomachs! As these causes are either constantly in —
action or recur annually, it is not surprising that almost all the
species should be unchanged owing to the frequent intercrossing
of freshly-arrived specimens. If a competent botanist were
thoroughly to explore Bermuda, eliminate the species introduced
by human agency, and investigate the source from whence the
others were derived and the mode by which they had reached
so remote an island, we should obtain important information as
to the dispersal of plants, which might afford us a clue to
the solution of many difficult problems in their geographical
distribution. |

Concluding Remarks.—The two groups of islands we have now
been considering furnish us with some most instructive facts as
to the power of many groups of organisms to pass over from
700 to 900 miles of open sea. There is no doubt whatever that
all the indigenous species have thus reached these islands, and
in many cases the process may be seen going on from year to
year. We find that, as regards birds, migratory habits and the
hability to be caught by violent storms are the conditions which
determine the island-population. In both islands the land-birds
are almost exclusively migrants ; and in both, the non-migratory
eroups—wrens, tits, creepers, and nuthatches—are absent ; while
the number of annual visitors is greater in proportion as the
migratory habits and prevalence of storms afford more efficient
means for their introduction.

We find also, that these great distances do not prevent the
immigration of some insects of most of the orders, and espe-
cially of a considerable number and variety of beetles; while
even land-shells are fairly represented in both islands, the large
proportion of peculiar species clearly indicating that, as we
might expect, individuals of this group of organisms arrive
only at long and irregular intervals.

Plants are represented by a considerable variety of orders and
genera, most of which show some special adaptation for dispersal
by wind or water, or through the medium of birds; and there is

1‘ Notes on the Vegetation of Bermuda,’ by H. N. Moseley. (Journal
of the Linnean Society, Vol. XIV., “ Botany,” p. 317.)

264 ISLAND LIFE. [PART II.

no reason to doubt that besides the species that have actually
established themselves, many others must have reached the
islands, but were not suited to the climate and other physical
conditions, or did not find the insects necessary to their
fertilisation.

If now we consider the extreme remoteness and isolation of
these islands, their small area, and comparatively recent origin,
and that, notwithstanding all these disadvantages, they have
acquired avery considerable and varied flora and fauna, we shall,
I think, be convinced, that with a larger area and greater
antiquity, mere separation from a continent by many hundred
miles of sea would not prevent a country from acquiring a very
luxuriant and varied flora, and a fauna also rich and peculiar as
regards all classes except terrestrial mammals, amphibia, and
some groups of reptiles. This conclusion will be of great im-
portance in many cases, where the evidence as to the exact
origin of the fauna and flora of an island is less clear and satis-

factory than in the case of the Azores and Bermuda.

=| eaaeiaail

CHAPTER XIIL.

THE GALAPAGOS ISLANDS.

Position and physical features—Absence of indigenous Mammalia and
Amphibia— Reptiles—Birds—Insects and Land-shells—The Keeling
Islands as illustrating the manner in which Oceanic Islands are
peopled—Flora of the Galapagos—Origin of the Flora of the
Galapagos—Concluding Remarks,

THe Galapagos differ in many important respects from the
islands we have examined in our last chapter, and the differences
are such as to have affected the whole character of their animal
inhabitants. Like the Azores, they are volcanic, but they are
much more extensive, the islands being both larger and more
numerous; while volcanic action has been so recent and exten-
sive that a large portion of their surface consists of barren lava-
fields. They are considerably less distant from a continent than
either the Azores or Bermuda, being about 600 miles from the
west coast of South America and a little more than 700 from
Veragua, with the small Cocos Islands intervening ; and they are
situated on the equator instead of being inthe north temperate
zone. They stand upon a deeply submerged bank, the 1,000
fathom line encircling all the more important islands at a few
miles’ distance, whence there appears to be a comparatively
steep descent all round to the average depth of that portion of
the Pacific, between 2,000 and 3,000 fathoms.

The whole group occupies a space of about 300 by 200 miles.
It consists of five large and twelve small islands; the largest
(Albemarle Island) being about eighty miles long and of very

266 ISLAND LIFE, [PART II.

irregular shape, while the four next in importance—Chatham,
Indefatigable, James, and Narborough Islands, are each about
twenty-five or thirty miles long, and of a rounded or elongate
form. The whole are entirely volcanic, and in-the western
islands there are numerous active volcanoes. Unlike the other

MAP OF THE GALAPAGOS AND ADJACENT COASTS OF SOUTH AMERICA.

The light tint shows where the sea is less than 1,000 fathoms deep.
The figures show the depth ia fathoms.

groups of islands we have been considering, these are situated
in a comparatively calm sea, where storms are of rare occurrence
and even strong winds almost unknown. They are traversed by
ocean currents which are strong and constant,, flowing towards

CHAP, X111.] THE GALAPAGOS ISLANDS. 267

the. north-west from the coast of Peru; and these physical
conditions have had a powerful influence on the animal and
vegetable forms by which the islands are now inhabited. The
Galapagos have also, during three centuries, been frequently
visited by Europeans, and were long a favourite resort of
buccaneers and traders, who found an ample supply of food in

==5 0 INGDON=———

SS BINDLOE 3

{CS ————————
/ =

MAP OF THE GALAPAGOS.

he light tint shows a depth of less than 1,000 fathoms.
The figures show the depth in fathoms.

the large tortoises which abound there ; and to these visits we
may perhaps trace the introduction of some animals whose
presence it is otherwise difficult to account for. The vegetation
is generally scanty, but still amply sufficient for the support of
a considerable amount of animal life, as shown by the cattle,

268 ISLAND LIFE. [PART II,

horses, asses, goats, pigs, dogs, and cats, which now run wild
in some of the islands.

Absence of indigenous Mammalia and Amphibia.—As in all
other oceanic islands, we find here no truly indigenous mam-
malia, for though there is a mouse of the American genus
Hesperomys, which differs somewhat from any known species, we
can hardly consider this to be indigenous; first, because these
creatures have been little studied in South America, and there
may yet be many undescribed species, and in the second place
because even had it been introduced by some European or
native vessel, there is ample time in two or three hundred years
for the very different conditions to have established a marked
diversity in the characters of the species. This is the more
probable because there is also a true rat of the Old World
genus Mus, which is said to differ slightly from any known
species; and as this genus is not a native of the American
continents we are sure that it must have been recently intro-
duced into the Galapagos. There can be little doubt therefore
that the islands are completely destitute of truly indigenous
mammalia; and frogs and toads, the only tropical representatives
of the Amphibia, are equally unknown.

Reptiles.—Reptiles, however, which at first sight appear as
unsuited as mammals to pass over a wide expanse of ocean,
abound in the Galapagos, though the species are not very
numerous. They consist of land-tortoises, lizards and snakes.
The tortoises consist of two peculiar species, Testudo macrophyes,
found in most of the islands, and 7. abingdoniw recently dis-
covered on Abingdon Island, as well as one extinct species,
T. ephippium, found on Indefatigable Island. These are all
of very large size, like the gigantic tortoises of the Mascarene
Islands, from which, however, they differ in structural characters ;
and Dr. Giinther believes that they have been originally derived
from the American continent.) Considering the well known
tenacity of life of these animals, and the large number of
allied forms which have aquatic or sub-aquatic habits, it is not
a very extravagant supposition that some ancestral form, carried

1 Gigantic Land Tortoises Inving- and Extinct in the collection of the
British Museum. By A. C. L. G. Giinther, F.R.S. 1877.

CHAP. XIII. ] THE GALAPAGOS ISLANDS. 269

out to sea by a flood, was once or twice safely drifted as far
as the Galapagos, and thus originated the races which now
inhabit them. |

The lizards are five in number; a peculiar species of
gecko, Phyllodactylus galapagensis, and four species of the
American family Iguanide. Two of these are distinct species
of the genus Liocephalus, the other two being large, and so
very distinct as to be classed in peculiar genera, One of these
is aquatic and found in all the islands, swimming in the sea at
some distance from the shore and féeding on seaweed ; the other
is terrestrial, and is confined to the four central islands. These
were originally described by Mr. Bell as Amblyrhynchus cristatus
and A. suberistatus; they were afterwards placed in two
other genera Trachycephalus and Oreocephalus (see Brit. Mus.
Catalogue of Lizards), while in a recent paper by Dr. Giinther,
the marine species is again classed as Amblyrhynchus, while
the terrestrial form is placed in another genus Conolophus.

How these lizards reached the islands we cannot tell. The
fact that they all belong to American genera or families indicates
their derivation from that continent, while their being all
distinct species is a proof that their arrival took place at a
remote epoch, under conditions perhaps somewhat different
from any which now prevail. It is certain that animals of this
order have some means of crossing the sea not possessed by
any other land vertebrates, since they are found in a consider-
able number of islands which possess no mammals nor any
other land reptiles; but what those means are has not yet been
positively ascertained.

It is unusual for oceanic islands to possess snakes, and it is
therefore somewhat of an anomaly that two species are found
in the Galapagos. Both are closely allied to South American
forms, and one is hardly different from a Chilian snake, so that
they indicate a more recent origin than in the case of the
lizards. Snakes it is known can survive a long time at sea,
since a living boa-constrictor once reached the island of St.
Vincent from the coast of South America, a distance of two
hundred miles by the shortest route. Snakes often frequent
trees, and might thus be conveyed long distances if carried out

270 ISLAND LIFE. [PART II.

to sea on a tree uprooted by a flood such as often oecurs in
tropical climates and especially during earthquakes. To some
such accident we may perhaps attribute the presence of
these creatures in the Galapagos, and that it is a very rare one
is indicated by the fact that only two species have as yet
succeeded in obtaining a footing there.

Birds —We now come to the birds, whose presence here may
not seem so remarkable, but which yet present features of in-
terest not exceeded by any other group. Fifty-seven species
of birds have now been obtained on these islands, and of these
thirty-eight are peculiar to them. But all the species found
elsewhere, except one, belong to the aquatic tribes or the waders
which are pre-eminently wanderers, yet even of these eight are
peculiar. The true land-birds are thirty-one in number, and all
but one are entirely confined to the Galapagos; while more than
half present such peculiarities that they are classed as distinct
genera. All are allied to birds inhabiting tropical America,
some very closely ; while one—the common American rice-bird,
which ranges over the whole northern and part of the southern
continents—is the only land-bird identical with those of the
mainland. The following is a list of these land-birds taken
from Mr. Salvin’s memoir in the Zransactions of the Zoological
Society for the year 1876 :—

TuRDID&.
1. Mimus trifasciatus .... ... ... ) This and the two allied species are
2. . 4; melanotus related to a Peruvian bird Mimus
B77 45 6 (Darvulus lengicaudus.
MNIOTILTIDA.
Closely allied to the wide-ranging D
1 A :
4, Dendreeca aureola | tow
HIRUNDINIDA.

et to P. purpurea of North and

_ 1
5. Progne conco:or South America.

C@REBIDA.
6. Certhidea olivacea ... .. A peculiar genus allied to the Andean.
f

‘ fusea’ lise eee OP ens Conirestrim:

CHAP. XIII] THE GALAPAGOS ISLANDS. 271

FRINGILLIDA.

8. Geospiza magnirostris ... ... )
9. 9 strenua :
10. oe dubia...

fi, is fortis... distinct genus, but allied to the

12. 3 nebulosa 2.00 wee. South American genus Guiraca.
3. 5, fuliginosa... ue
14, 43 parvula =
15. ‘ dentirostris ed
16. Cactornis scandens ... aa)
£7, similis ... Sees 3
18 # Di edoth r A genus allied to the last.
° be) Cc ¢ oe eooe
19, 5 abil: ces otye lls
20. Camarhynchus psittaculus ...)

erassirostris ... | A very peculiar genus allied to Neo-

° 99 | ‘
22. ‘5 variegatus ...} rbynchus of the west coast of
23. Le prosthemelas... | Peru.
24, Be habeli a)
IcTERIDA.

25. Delichonyx oryzivorus ...... Ranges from Canada to Paraguay.

TYRANNIDA.

26. Pyrocephalus nanus... ... ... Allied to P. rubineus of Ecuador.
27. Myiarchus magnirostris... ... Allied to West Indian species,

CoLUMBID ZA.

i. peculiar species of a 8. American

28, Zenaida galapagensis
: genus.

FALCONIDA.

29 Buteo galapagensis... ... .... A buzzard of peculiar coloration.

STRIGID.A.

f Hardly distinct from the wide-spread
A. brachyotus.
31, Strix punctatissima... ... ... Allied to S. flammea but quite distinct.

30, Asio galapagensis

We have here every gradation of difference from perfect
identity with the continental species to genera so distinct that
it is difficult to determine with what forms they are most nearly
allied; and it is interesting to note that this diversity bears a
distinct relation to the probabilities of, and facilities for, migra-
tion to the islands. The excessively abundant rice-bird, which
breeds in Canada and swarms over the whole United States,
migrating to the West Indies and South America, visiting the

272 , ISLAND LIFE. [PART IT;

distant Bermudas almost every year, and extending its range as
far as Paraguay, is the only species of land-bird which remains
completely unchanged in the Galapagos; and we may therefore
conclude that some stragglers of the migrating host reach the
islands sufficiently often to keep up the purity of the breed.
Next, we have the almost cosmopolite short-eared owl (Asto
brachyotus), which ranges from China to Ireland, and from Green-
land to the Straits of Magellan, and of this the Galapagos bird
is probably only one of the numerous varieties. The little
wood warbler (Dendreca aureola) is closely allied to a species
which ranges over the whole of North America and as far south
as New Grenada. It has also been occasionally met with in
Bermuda, an indication that it has considerable powers of flight
and endurance. The more distinct species—as the mocking-
thrushes (Mimus), the tyrant fly-catchers (Pyrocephalus and
Myiarchus), and the ground dove (Zenaida), are all allied to non-
migratory species peculiar to tropical America, and of a more
restricted range; while the distinct genera are allied to South
American groups of finches and sugar-birds which have usually
restricted ranges, and whose habits are such as not to render
them likely to be carried out to sea. The remote ancestral
forms of these birds which, owing to some exceptional causes,
reached the Galapagos, have thus remained uninfluenced by
later migrations, and have, in consequence, been developed into
a variety of distinct types adapted to the peculiar conditions of
existence under which they have been placed. Sometimes the
different species thus formed are confined to one or two of the
islands only, as the two species of Certhidea, which are divided
between the islands but do not appear ever to occur together,
Mimus parvulus is confined to Albemarle Island, and JL. trifascia-
tus to Charles Island; Cactoriis pallida to Indefatigable Island,
and C. abingdont to brasion Island.

Now all these phenomena are strictly consistent with the
theory of the peopling of the islands by accidental migrations,
if we only allow them to have existed for a sufficiently long
period ; and the fact that vclcanic action has ceased on many of
the islands, as well as their great extent, would certainly
indicate a considerable antiquity.

CHAP, XT1I, | THE GALAPAGOS ISLANDS. 273

The great difference presented by the birds of these islands
as compared with those of the equally remote Azores and
Bermudas, is sufficiently explained by the difference of climatal
conditions. At the Galapagos there are none of those periodic
storms, gales, and hurricanes which prevail in the North
Atlantic, and which every year carry some straggling birds of
Europe or North America to the former islands ; while, at the same
time, the majority of the tropical American birds are non-migra-
tory, and thus afford none of the opportunities presented by the
countless hosts of migrants which pass annually northward and
southward along the European, and especially along the North
American coasts. It is strictly in accordance with these different
conditions that we find in one case an almost perfect identity
with, and in the other an almost equally complete diversity from,
the continental species of birds.

Insects and Land-shells.—The other groups of land-animals
add little of importance to the facts already referred to. The
insects are very scanty; the most plentiful group, the beetles,
only furnishing about thirty-five species belonging to twenty-
nine genera and eighteen families. The species are almost all
peculiar, as are some of the genera. They are mostly small
and obscure insects, allied either to American or to world-wide
groups. The Carabide and the Heteromera are the most abun-
dant groups, the former furnishing six and the latter eight
species.1

1 The following list of the beetles yet known from the Galapagos shows
their scanty proportions and accidental character; the thirty-seven species
belonging to thirty-one genera and eighteen families. It is taken from
Mr. Waterhouse’s enumeration in the Proceedings of the Zoological Society
for 1877 (p. 81) :—

CARABIDA. MALACODERMS.
Feronia calathoides. Ablechrus darwinii.

» Insularis. Corynetes rufipes.

» galapagoensis. Bostrichus unciniatus.
Amblygnathus obscuricornis. LAMELLICORNES,
Solenophorus galapagoensis. Copris lugubris,

Notaphus galapagoensis. Oryctes galapagoensis.
DYTISCIDA. HKLATERID2.
Eunectes occidentalis, Physorhinus galapagoensis,

274 ISLAND LIFE. [PART. IT.

The land-shells are not abundant—about twenty in all,
most of them peculiar species, but not otherwise remarkable.
The observation of Captain Collnet, quoted by Mr. Darwin in
his Journal, that drift-wood, bamboos, canes, and the nuts of a
palm, are often washed on the south-eastern shores of the
islands, furnishes an excellent clue to the manner in which many
of the insects and land-shells may have reached the Galapagos.
Whirlwinds also have been known to carry quantities of leaves
and other vegetable debris to great heights in the air, and —
these might be then carried away by strong upper currents and
dropped at great distances, and with them small insects and
mollusca, or their eggs. We must also remember that volcanic
islands are subject to subsidence as well as elevation; and it is
quite possible that during the long period the Galapagos have
existed some islands may have intervened between them and
the coast, and have served as stepping-stones by which the
passage to them of various organisms would be greatly facilitated.
Sunken banks, the relics of such islands, are known to exist in
many parts of the ocean, and countless others, no doubt, remain
undiscovered.

The Keeling Islands as illustrating the manner in which Oceanie
Islands are Peopled.—That such causes as have been here ad-
duced are those by which oceanic islands have been peopled, is
further shown by the condition of equally remote islands which

Acilius incisus. HETEROMERA.
Copelatus galapagoensis, Stomion helopoides.
levigatum.
PALPICORNES. a ea
: ie Ammophorus obscurus,
Tropisternus lateralis. ‘
Philhydrus s te Oo
y g P. ee oe bifoveatus.
sae Cerra eaigy Pedoneeces galapagoensis.
Creophilus villosus. i pubescens,
Ti f 4
NECROPHAGA. Phaleria manicata.
Acribis serrativentris. ANTHRIBIDA.
Phalacrus darwinil. Ormiscus variegatus,
Dermestes vulpinus, PHYTOPHAGA,

CURCULIONIDA, Diabrotica limbata.

Otiorhynchus cuneiformis
Anchonus galapagoensis,

LoNGICORNIA,
Eburia amabilis,

Docema galapagoensis,

Longitarsus lunatus.
SECURIPALPES,

Scymnus galapagoonsis,

CHAP, XI1I.] THE GALAPAGOS ISLANDS. 275

we know are of comparatively recent origin. Such are the
Keeling or Cocos Islands in the Indian Ocean, situated about
the same distance from Sumatra as the Galapagos from South
America, but mere coral reefs, supporting abundance of cocoa-
nut palms as their chief vegetation. These islands were visited
by Mr. Darwin, and their natural history carefully examined.
The only mammals are rats, brought by a wrecked vessel and
said by Mr. Waterhouse to be common English rats, “but
smaller and more brightly coloured ;”’ so that we have here an
illustration of how soon a difference of race is established under
a constant and uniform difference of conditions. There are no
true land-birds, but there are snipes and rails, both apparently
common Malayan species. Reptiles are represented by one
small lizard, but no account of this is given in the Zoology of the
Voyage of the Beagle, and we may therefore conclude that it was
an introduced species. Of insects, careful collecting only pro-
duced thirteen species belonging to eight distinct orders. The
only bettle was a small Elater, the Orthoptera were a Gry!lus
and a Blatta; and there were two flies, two ants, and two small
moths, one a Diopzea which swarms everywhere in the eastern
tropics in grassy places. All these insects were no doubt brought
either by winds, by floating timber (which reaches the islands
abundantly), or by clinging to the feathers of aquatic or wading
birds; and we only require more time to introduce a greater
variety of species, and a better soil and more varied vegetation,
to enable them to live and multiply, in order to give these
islands a fauna and flora equal to that of the Bermudas. Of
wild plants there were only twenty species, belonging to nine-
teen genera and to no less than sixteen natural families, while
all were common tropical shore plants. These islands are thus
evidently stocked by waifs and strays brought by the winds and
waves ; but their scanty vegetation is mainly due to unfavourable
conditions—the barren coral rock and sand, of which they are
wholly composed, together with exposure to sea-air, being
suitable to a very limited number of species which soon mono-
polise the surface. With more variety of soil and aspect a
ereater variety of plants would establish themselves, and these
would favour the preservation and increase of more insects,

276 ISLAND LIFE. [PART IT.

birds, and other animals, as we find to be the case in many
small and remote islands.’

Flora of the Galapagos.—The plants of these islands are so
much more numerous than the known animals, even including
the insects, they have been so carefully studied by eminent
botanists, and their relations throw so much light on the past
history of the group, that no apology is needed for giving a
brief outline of the peculiarities and affinities of the flora. The
statements we shall make on this subject will be taken from the
Memoir of Sir Joseph Hooker in the Linnwan Transactions for

1 Juan Fernandez is a good example of a small island which, with time
and favourable conditions, has acquired a tolerably rich and highly peculiar
flora and fauna. It is situated in 34°S. Lat., 400 miles from the coast
of Chile, and so far as facilities for the transport of living organisms are
concerned is by no means in a favourable position, for the ocean-currents
come from the south-west in a direction where there is no land but the
Antarctic continent, and the prevalent winds are also westerly. No doubt,
however, there are occasional storms, and there may have been intermediate
islands, but its chief advantages are, no doubt, its antiquity and its varied
surface, offering many chances for the preservation and increase of what-
ever plants and animals have chanced to reach it. The island consists of
basalt, greenstone, and other ancient rocks, and though only about twelve
miles long its mountains are three thousand feet high. Enjoying a moist
and temperate climate it is especially adapted to the growth of ferns, which
are very abundant; and as the spores of these plants are as fine as dust,
and very easily carried for enormous distances by winds, it is not surprising
that there are twenty-four species on the island, while the remote period
when they first received their vegetation may be indicated by the fact
that four of the species are quite peculiar. The same general character
pervades the whole flora and fauna. For so small an island it is rich,
containing a considerable number of flowering plants, four true land-birds,
about fifty species of insects, and twenty of land-shells. Almost all these
belong to South American genera, and a large proportion are South American
species ; but several of the plants and insects, half the birds, and the whole
of the land-shells are peculiar. This seems to indicate that the means of
transmission were formerly greater than they are now, and that in the case
of land-shells none have been introduced for so long a period that all have
become modified into distinct forms, or have been preserved on the island
while they have become extinct on the continent.—For a detailed examina-
tion of the causes which have led to the modification of the humming-
birds of Juan Fernandez see the author’s Tropical Nature, p. 140; while
a general account of the fauna of the island is given in his Geographical
Distribution of Animals, Vol, I. p. 49.

CHAP. XILJ.] THE GALAPAGOS ISLANDS. Vari

1851, founded on Mr. Darwin’s collections, and a later paper by
N. J. Andersson in the Linnea of 1861, embodying more recent
discoveries.

The total number of flowering plants known at the latter
date was 332, of which 174 were peculiar to the islands, while
158 were common to other countries. Of these latter about
twenty have been introduced by man, while the remainder are
all natives of some part of America, though about a third part
are species of wide range extending into both hemispheres. Of
those confined to America, forty-two are found in both the
northern and southern continents, twenty-one are confined to
South America, while twenty are found only in North America,
the West Indies, or Mexico. This equality of North American
and South American species in the Galapagos is a fact of great
significance in connection with the observation of Sir Joseph
Hooker, that the peculiar species are allied to the plants of
temperate America or to those of the high Andes, while the
non-peculiar species are mostly such as inhabit the hotter
regions of the tropics near the level of the sea. He also
observes that the seeds of this latter class of Galapagos plants
often have special means of transport, or belong to groups whose
seeds are known to stand long voyages and to possess great
vitality. Myr. Bentham also, in his elaborate account of the
Composite,! remarks on the decided Central American or
Mexican affinities of the Galapagos species, so that we may
consider this to be a thoroughly well-established fact.

The most prevalent families of plants in the Galapagos are
the Composite (40 sp.), Graminez (32 sp.), Leguminose (30
sp.), and Euphorbiaceze (29 sp.). Of the Composite most of
the species, except such as are common weeds or shore plants,
are peculiar, but there are only two peculiar genera allied to
Mexican forms and not very distinct ; while the genus Lipocheta,
represented here by a single species, is only found elsewhere in
the Sandwich Islands, though it has American affinities.

Origin of the Galapagos Flora.—These facts are explained
by the past history of the American continent, its separation at

1 Journal of the Linnean Society, Vol. XIII., “ Botany,” p. 556.

278 ISLAND LIFE. [PART IT,

various epochs by arms of the sea uniting the two oceans across
what is now Central America (the last separation being of recent
date, as shown by the identical species of fishes on both sides
of the isthmus), and the influence of the glacial epoch in driving
the temperate American flora southward along the mountain
plateaus. At the time when the two oceans were united a
portion of the Gulf Stream may have been diverted into the
Pacific, giving rise to a current, some part of which would
almost certainly have reached the Galapagos, and this may have
helped to bring about that singular assemblage of West Indian
and Mexican plants now found there. And as we now believe
that the duration of the last glacial epoch in its successive
pnases was much longer than the time which has elapsed since
it finally passed away, while throughout the Miocene epoch the
snow-line would often be lowered during periods of high ex-
centricity, we are enabled to comprehend the nature of the
causes which may have led to the islands being stocked
with those northern or sub-alpine types which are so char-
acteristic a feature of that portion of the Galapagos flora
which consists of peculiar species.

On the whole, the flora agrees with the fauna in indicating
a moderately remote origin, great isolation, and changes of con-
ditions affording facilities for the introduction of organisms from
various parts of the American coast, and even from the West
Indian Islands and Gulf of Mexico. As in the case of the birds,
the several islands differ considerably in their native plants, many
species being lmited to one or two islands only, while others
extend to several. This is, of course, what might be expected
on any theory of their origin; because, even if the whole of the
islands had once been united and afterwards separated, long
continued isolation would often lead to the differentiation of
species, while the varied conditions to be found upon islands
differing in size and altitude as well as in luxuriance of vegeta-
tion, would often lead to the extinction of a species on one island
and its preservation on another. If the several islands had been
equally well explored, it might be interesting to see whether, as
in the case of the Azores, the number of species diminished in

1 Geographical Distribution of Animals, Vol. II. p. 81.

CHAP. XU. ] THE GALAPAGOS ISLANDS. 297

those more remote from the coast; but unfortunately our know-
ledge of the productions of the various islands of the group is
exceedingly unequal, and, except in those cases in which repre-
sentative species inhabit distinct islands, we have no certainty
on the subject. All the more interesting problems in geoera-
phical distribution, however, arise from the relation of the fauna
and flora of the group as a whole to those of the surrounding
continents, and we shall therefore for the most part confine
ourselves to this aspect of the question in our discussion of the
phenomena presented by oceanic or continental islands.

Concluding Remarks.——The Galapagos offer an instructive
contrast with the Azores, showing how a difference of condi-
tions that might be thought unimportant may yet produce very
striking results in the forms of life. Although the Galapagos
are much nearer a continent than the Azores, the number of
species of plants common to the continent is much less in the
former case than in the latter, and this is still more prominent
a characteristic of the insect and the bird faunas. This differ-
ence has been shown to depend, almost entirely, on the one
archipelago being situated in a stormy, the other in a calm,
portion of the ocean; and it demonstrates the preponderating
importance of the atmosphere as an agent in the dispersal of
birds, insects, and plants. Yet ocean-currents and surface-drifts
are undoubtedly efficient carriers of plants, and, with plants, of
insects and shells, especially in the tropics ; and it is probably to
this agency that we may impute the recent introduction of a
number of common Peruvian and Chilian littoral species, and
also at a more remote period of several West Indian types when
the Isthmus of Panama was submerced.

In the case of these islands we see the importance of taking
past conditions of sea and land and past changes of climate into
account, in order to explain the relations of the peculiar or ende-
mic species of their fauna and flora; and we may even see an
indication of the effects of climatal changes in the northern hemi-
sphere, in the north temperate or alpine affinities of so many of
the plants, and even of some of the birds. The relation between
the migratory habits of the birds and the amount of difference
from continental types is strikingly accordant with the fact that

280 ISLAND LIFE. (PART IL,

it is almost exclusively migratory birds that annually reach the
Azores and Bermuda; while the corresponding fact that the
seeds of those plants, which are common to the Galapagos and the
adjacent continent, have all—as Sir Joseph Hooker states—some
special means of dispersal, is equally intelligible. The reason
why the Galapagos possess four times as many peculiar species
of plants as the Azores is clearly a result of the less constant
introduction of seeds, owing to the absence of storms; the
greater antiquity of the group, allowing more time for specific
change ; and the influence of cold epochs and of alterations
of sea and land, in bringing somewhat different sets of plants at
different times within the influence of such modified winds and
currents as might convey them to the islands.

On the whole, then, we have no difficulty in explaining the
probable origin of the flora and fauna of the Galapagos, by
means of the illustrative facts and general principles already

adduced.

CE APT ER): XoDY,

ST. HELENA.

Position and physical features of St. Helena—Change effected by European
occupation—The Insects of St. Helena—Coleoptera—Peculiarities and
origin of the Coleoptera of St. Helena—Land-shells of St. Helena—
Absence of Fresh-water organisms—Native vegetation of St. Helena—
The relations of the St. Helena Composite—Concluding Remarks on
St. Helena.

In order to illustrate as completely as possible the peculiar
phenomena of oceanic islands, we will next examine the organic
productions of St. Helena and of the Sandwich Islands, since
these combine in a higher degree than any other spots upon the
globe, extreme isolation from all more extensive lands, with a
tolerably rich fauna and flora whose peculiarities are of surpass-
ing interest. Both, too, have received considerable attention
from naturalists; and though much still remains to be done in
the latter group, our knowledge is sufficient to enable us to
arrive at many interesting results.

Position and Physical features of St. Helena.—This island
is situated nearly in the middle of the South Atlantic Ocean,
being more than 1,100 miles from the coast of Africa, and
1,800 from South America. It is about ten miles long by eight
wide, and is wholly volcanic, consisting of ancient basalts, lavas,
and other volcanic products. It is very mountainous and rugged,
bounded for the most part by enormous precipices, and rising to
a height of 2,700 feet above the sea-level. An ancient crater,
about four miles across, is open on the south side, and its

GHAP:.Xtv. | ST, HELENA. 283

northern rim forms the highest and central ridge of the island.
Many other hills and peaks, however, are more than two thousand
feet high, and a considerable portion of the surface consists of a
rugged plateau, having an elevation of about fifteen hundred to
two thousand feet. Everything indicates that St. Helena is an
isolated voleanic mass built up from the depths of the ocean.
Mr. Woilaston remarks: ‘There are the strongest reasons for
believing that the area of St. Helena was never very much larger
than it is at present—the comparatively shallow sea-soundings
within about a mile and a half from the shore revealing an
abruptly defined ledge, beyond which no bottom is reached at a
depth of 250 fathoms; so that the original basaltic mass, which
was gradually piled up by means of successive eruptions from
beneath the ocean, would appear to have its limit definitely
marked out by this suddenly-terminating submarine cliff—the
space between it and the existing coast-lme being reasonably
referred to that slow process of disintegration by which the
island has been reduced, through the eroding action of the
elements, to its present dimensions.” If we add to this that
between the island and the coast of Africa, in a south-easterly
direction, is a profound oceanic gulf known to reach a depth of
2,860 fathoms, or 17,160 feet, while an equally deep, or perhaps
deeper, ocean, extends to the west and south-west, we shall be
satished that St. Helena is a true oceanic island, and that it
owes none of its peculiarities to a former union with any
continent or other distant land.

Change effected by Huropean occupation. — When first dis-
covered, 378 years ago, St. Helena was densely covered with a
luxuriant forest vegetation, the trees overhanging the seaward
precipices and covering every part of the surface with an ever-
green mantle. This indigenous vegetation has been almost
wholly destroyed ; and although an immense number of foreign
plants have been introduced, and have more or less completely
established themselves, yet the general aspect of the island is
now so barren and forbidding that some persons find it difficult
to believe that it was once all green and fertile. The cause of
the change is, however, very easily explained. The rich soil
formed by decomposed volcanic rock and vegetable deposits

284 ISLAND LIFE. [PART IT.

could only be retained on the steep slopes so long as it was
protected by the vegetation to which it in great part owed its
origin. When this was destroyed, the heavy tropical rains soon
washed away the soil, and has left a vast expanse of bare rock
or sterile clay. This irreparable destruction was caused in the
first place by goats, which were introduced by the Portuguese in
1513, and increased so rapidly that in 1588 they existed in
thousands. These animals are the greatest of all foes to trees,
because they eat off the young seedlings, and thus prevent the
natural restoration of the forest. They were, however, aided by
the reckless waste of man. The Hast India Company took
possession of the island in 1651, and about the year 1700 it
began to be seen that the forests were fast diminishing, and
required some protection. Two of the native trees, redwood
and ebony, were good for tanning, and to save trouble the bark
was wastefully stripped from the trunks only, the remainder
being left to rot; while in 1709 a large quantity of the rapidly
disappearing ebony was used to burn hme for building fortifica-
tions! By the MSS. records quoted in Mr. Melliss’ interesting
volume on St. Helena,’ it is evident that the evil consequences
of allowing the trees to be destroyed were clearly foreseen, as
the following passages show: ‘We find the place called the
Great Wood in a flourishing condition, full of young trees, where
the hoggs (of which there is a great abundance) do not come to
root them up. But the Great Wood is miserably lessened and
destroyed within our memories, and is not near the circuit and
length it was. But we believe it does not contain now less than
fifteen hundred acres of fine woodland and good ground, but no
springs of water but what is salt or brackish, which we take to
be the reason that that part was not inhabited when the people
first chose out their settlements and made plantations ; but if
wells could be sunk, which the governor says he will attempt
when we have more hands, we should then think it the most
pleasant and healthiest part of the island. But as to healthi-
ness, we don’t think it will hold so if the wood that keeps the
land warm were destroyed, for then the rains, which are violent

1 St. Helena: a Physical, Historical, and Topographical Description of the
Island, &c. By John Charles Melliss, F.G.S., &c. London: 1875,

CHAP. XIV. ] ‘ST, HELENA. 285

here, would carry away the upper soil, and it being a clay marl
underneath would produce but little ; as it is, we think in case
it were enclosed it might be greatly improved”... . “ When
once this wood is gone the island will soon be ruined”... .
“We viewed the wood’s end which joins the Honourable Com-
pany’s plantation called the Hutts, but the wood is so destroyed
that the beginning of the Great Wood is now a whole mile
beyond that place, and all the soil between being washed away,
that distance is now entirely barren.” (JZSS. Records, 1716.) In
1709 the governor reported to the Court of Directors of the
Kast India Company that the timber was rapidly disappearing,
and that the goats should be destroyed for the preservation of the
ebony wood, and because the island was suffering from droughts.
The reply was, “The goats are not to be destroyed, being more
valuable than ebony.” Thus, through the gross ignorance -of
those in power, the last opportunity of preserving the peculiar
vegetation of St. Helena, and preventing the island from be-
coming the comparatively rocky desert it now is, was allowed to
pass away.1 Even in a mere pecuniary point of view the error .
was a fatal one, forin the next century (in 1810) another gover-
nor reports the total destruction of the great forests by the

1 Mr, Marsh in his interesting work entitled, The Earth as Modified by
Human Action (p. 51), thus remarks on the effect of browsing quadrupeds
in destroying and checking woody vegetation.—‘“‘I am convinced that
forests would soon cover many parts of the Arabian and African deserts
if man and domestic animals, especially the goat and the camel, were
banished from them.. The hard palate and tongue, and strong teeth and
jaws of this latter quadruped enable him to break off and masticate tough
and thorny branches as large as the finger. He is particularly fond of the
smaller twigs, leaves, and seed-pods of the Sont and other acacias, which,
like the American robinia, thrive well on dry and sandy soils, and he
spares no tree the branches of which are within his reach, except, if I
remember right, the tamarisk that produces manna, Young trees sprout
plentifully around the springs and along the winter water-courses of the
desert, and these are just the halting stations of the caravans and their
routes of travel. In the shade of these trees annual grasses and perennial
shrubs shoot up, but are mown down by the hungry cattle of the Bedouin
as fast as they grow. A few years of undisturbed vegetation would suffice
to cover such points with groves, and these would gradually extend them-
selves over soils where now scarcely any green thing but the bitter
colocynth and tlie poisonous foxglove is ever seen.’’

236 ISLAND LIFE. [PART I,

goats, and that in consequence the cost of importing fuel for
government use was 2,729/. 7s. 8d. for a single year! About
this time large numbers of European, American, Australian, and
South African plants were imported, and many of these ran
wild and increased so rapidly as to drive out and exterminate
much of the relics of the native flora; so that now English
broom gorse and brambles, willows and poplars, and some
common American, Cape, and Australian weeds, alone meet the
eye of the ordinary visitor. These, in Sir Joseph Hooker’s
opinion, render it absolutely impossible to restore the native
flora, which only lingers in a few of the loftiest ridges and
most inaccessible precipices, and is rarely seen except by some
exploring naturalist.

This almost total extirpation of a luxuriant and highly pecu-
har vegetation must inevitably have caused the destruction of
a considerable portion of the lower animals which once existed
on the island, and it is rather singular that so much as has
actually been discovered should be left to show us the nature
of the aboriginal fauna. Many naturalists have made small
collections during short visits, but we owe our present complete
knowledge of the two most interesting groups of animals, the
insects, and the land-shells, mainly to the late Mr. T. Vernon
Wollaston, who, after having thoroughly explored Madeira and
the Canaries, undertook a voyage to St. Helena for the express
purpose of studying its terrestrial fauna, and resided for six
months (1875-76) in a high central position, whence the loftiest -
peaks could be explored. The results of his labours are con-
tained in two volumes,! which, like all that he wrote, are
models of accuracy and research, and it is to these volumes
that we are indebted for the interesting and suggestive facts
which we here lay before our readers.

Insects—Coleoptera.—The total number of species of beetles
hitherto observed at St. Helena is 203, but of these no less
than seventy-four are common and wide-spread insects, which
have certainly, in Mr. Wollaston’s opinion, been introduced by
human agency. There remains 129 which are believed to be

1 Coleoptera Sancte Helence, 1877; Testacea Atlantica, 1878.

CHAP. XIV. | ST. HELENA. 287

truly aborigines, and of these all but one are found nowhere else
on the globe. But in addition to this large amount of specific
peculiarity (perhaps unequalled anywhere else in the world) the
beetles of this island are equally remarkable for their generic
isolation, and for the altogether exceptional proportion in
which the great divisions of the order are represented. The
species belong to thirty-nine genera, of which no less than
twenty-five are peculiar to the island; and many of these are
such isolated forms that it is impossible to find their alhes in
any particular country. Still more remarkable is the fact, that
more than two-thirds of the whole number of indigenous species
are Rhyncophora or weevils, while more than two-fifths (fifty-
four species) belong to one family, the Cossonide. Now although
the Rhyncophora are an immensely numerous group and always
form a large portion of the msect population, they nowhere
else approach such a proportion as this. For example, in
Madeira they form one-sixth of the whole of the indigenous
Coleoptera, in the Azores less than one-tenth, and in Britain
one-seventh. Even more interesting is the fact that the twenty
genera to which these insects belong are every one of them
peculiar to the island, and im many cases have no near allies
elsewhere, so that we cannot but look on this group of beetles
as forming the most characteristic portion of the ancient insect
fauna. Now, as the great majority of these are wood borers,
and all are closely attached to vegetation, and often to par-
ticular species of plants, we might, as Mr. Wollaston well
observes, deduce the former luxuriant vegetation of the island
from the great preponderance of this group, even had we not
positive evidence that it was at no distant epoch densely forest-
clad. We will now proceed briefly to indicate the numbers
and peculiarities of each of the families of beetles which enter
into the St. Helena fauna, taking them, not in systematic order,
but according to their importance in the island.

1, RuyNcopHora.—This great division includes the weevils
-and allied groups, and, as above stated, exceeds in number of
species all the other beetles of the island. Four families are re-
presented ; the Cossonide, with fifteen peculiar genera comprising
fifty-four species, and one minute insect (Slenoscelis hylastoides)

288 ISLAND LIFE. [PART Il.

forming a peculiar genus, but which has been found also at the
Cape of Good Hope. It is therefore impossible to say of which
country it is really a native, or whether it is indigenous to both,
and dates back to the remote period when St. Helena received its
early emigrants. All the Cossonide are found in the highest
and wildest parts of the island where the native vegetation still
lingers, and many of them are only found in the decaying stems
of tree-ferns, box-wood, arborescent Composite, and other in-
digenous plants. They are all pre-eminently peculiar and
isolated, having no direct affinity to species found in any
other country. The next family, the Tanyrhynchide, has one
peculiar genus in St. Helena, with ten species. This genus
(Nesiotes) 1s remotely allied to European, Australian, and
Madeiran insects of the same family: the habits of the species
are similar to those of the Cossonide. The Trachyphlceide are
represented by a single species belonging to a peculiar genus
not very remote from a European form. The Anthribide again
are highly peculiar. There are twenty-six species belonging to
three genera, all endemic, and so extremely peculiar that they
form two new subfamilies. One of the genera, Acarodes, is
said to be allied to a Madeiran genus.

2. GEODEPHAGA.—These are the terrestrial carnivorous beetles,
very abundant in all parts of the world, especially in the tem-
perate regions of the northern hemisphere. In St. Helena
there are fourteen species belonging to three genera, one of
which is peculiar. This is the Haplothorax burchellu, the largest
beetle on the island, and now very rare. It resembles a large
black Carabus. There is also a peculiar Calosoma, very distinct,
though resembling in some respects certain African species.
The rest of the Geodephaga, twelve in number, belong to the
wide-spread genus Bembidium, but they are altogether peculiar
and isolated, except one, which is of European type, and alone
has wings, all the rest being wingless.

3. HETEROMERA.—This group is represented by three peculiar
genera containing four species, with two species belonging to
European genera. They belong to the families Opatride,
Mordellide, and Anthicida.

4. BRACHYELYTRA.—Of this group there are six peculiar

CHAP. XIV. ] ST. HELENA. 289

species belonging to four European genera—Homalota, Philon-
thus, Xantholinus, and Oxytelus.

5. PRIOCERATA.—The families Elateridee and Anobiide are
each represented by a peculiar species of a European genus.

6. PayropHacaA.—tThere are only three species of this tribe,
belonging to the European genus Longitarsus.

7. LAMELLICORNIS.—Here are three species belonging to
two genera. One is a peculiar species of ‘Trox, allied to South
African forms; the other two belong to the peculiar genus
Melissius, which Mr. Wollaston considers to be remotely allied
to Australian insects.

8. PSEUDO-TRIMERA.—Here we have the fine lady-bird Chzlo-
menus lunata, also found in Africa, but apparently indigenous in
St. Helena; and a peculiar species of Euxestes, a genus only
found elsewhere in Madeira.

9. TRICHOPTERYGIDZ.—These, the minutest of beetles, are
represented by one species of the Huropean and Madeiran genus
Ptinella.

10. NEcRopHAGA.—One indigenous species of Cryptophaga
inhabits St. Helena, and this is said to be very closely allied to
a Cape species.

Peculiarities and Origin of the Coleoptera of St. Helena.—We
see that the great mass of the indigenous species are not only
peculiar to the island, but so isolated in their characters as to
show no close affinity with any existing insects; while a small
number (about one-third of the whole) have some relations,
though often very remote, with species now inhabiting Europe,
Madeira, or South Africa. These facts clearly point to the
very great antiquity of the insect fauna of St. Helena, which
has allowed time for the modification of the originally introduced
species, and their special adaptation to the conditions prevailing
in this remote island. This antiquity is also shown by the re-
markable specific modification of a few types. Thus the whole
of the Cossonide may be referred to three types, one species only
(Hexacoptus ferrugineus) being allied to the European Cossonidee
though forming a distinct genus; a group of three genera and
seven species remotely allied to the Stenoscelis hylastoides, which
occurs also at the Cape; while a group of twelve genera with

290 ISLAND LIFE, [PART II.

forty-six species have their only (remote) allies in a few insects
widely scattered in South Africa, New Zealand, Europe, and the
Atlantic Islands. In like manner, eleven species of Bembidium
form a group by themselves; and the Heteromera form two
groups, one consisting of three genera and species of Opatride
allied to a type found in Madeira, the other, Anthicodes, alto-
gether peculiar.

Now each of these types may well be descended from a single
species which originally reached the island from some other
land; and the great variety of generic and specific forms into
which some of them have diverged is an indication, and to
some extent a measure, of the remoteness of their origin. The
rich insect fauna of Miocene age found in Switzerland consists
mostly of genera which still inhabit Europe, with others which
now inhabit the Cape of Good Hope or the tropics of Africa and
South America; and it is not at all improbable that the origin of
the St. Helena fauna dates back to at least as remote, and not
improbably to a still earlier, epoch. But if so, many difficulties
in accounting for its origin will disappear. We know that at
that time many of the animals and plants of the tropics, of
North America, and even of Australia, inhabited Europe; while
during the changes of climate, which, as we have seen, there is
good reason to believe periodically occurred, there would be
much migration from the temperate zones towards the equator,
and the reverse. If, therefore, the nearest ally of any insular
group now inhabits a particular country, we are not obliged to
suppose that it reached the island from that country, smce we
know that most groups have ranged in past times over wider
areas than they now inhabit. Neither are we limited to the
means of transmission across the ocean that now exist, because
we know that those means have varied greatly. During
such extreme changes of conditions as are implied by glacial
periods and by warm polar climates, great alterations of winds
and of ocean-currents are inevitable, and these are, as we have
already proved, the two great agencies by which the trans-
mission of living things to oceanic islands has been brought
about. At the present time the south-east trade-winds blow
almost constantly at St. Helena, and the ocean-currents flow in

CHAP. XIV.] ST. HELENA. 291
the same direction, so that any transmission of insects by their
means must almost certainly be from South Africa. Now there
is undoubtedly a South African element in the insect-fauna, but
there is no less clearly a European, or at least a north-temperate
element, and this is very difficult to account for by causes now
in action. But when we consider that this northern element is
chiefly represented by remote generic affinity, and has therefore
all the signs of great antiquity, we find a possible means of
accounting for it. We have seen that during early Tertiary
times an almost tropical climate extended far into the northern
hemisphere, and a temperate climate to the Arctic regions.
But if at this time (as is not improbable) the Antarctic regions
were as much ice-clad as they are now, it is certain that an
enormous change must have been produced in the winds. In-
stead of a great difference of temperature between each pole
and the equator, the difference would be mainly between one
hemisphere and the other, and this might so disturb the trade
winds as to bring St. Helena within the south temperate region
of storms—a position corresponding to that of the Azores and
Madeira in the North Atlantic, and thus subject it to violent
gales from all points of the compass. Atthis remote epoch the
mountains of equatorial Africa may have been more extensive
than they are now, and may have served as intermediate stations
by which some northern insects may have migrated to the
southern hemisphere.

We must remember also, that these peculiar forms are said
to be northern only because their nearest allies are now found
in the North Atlantic islands and Southern Europe; but it is
not at all improbable that they are really widespread Miocene
types, which have been preserved mainly in favourable insular
stations. They may therefore have originally reached St.
Helena from Southern Africa, or from some of the Atlantic
islands, and may have been conveyed by oceanic currents as
well as by winds,’ This is the more probable, as a large

1 On Petermann’s map of Africa, in the new edition of Stieler’s Hand-
Atlas (1879), the Island of Ascension is shown as seated on a much larger
and shallower submarine bank than St. Helena. The 1,000 fathom line
round Ascension encloses an oval space 170 miles long by 70 wide, and

U 2

292 ISLAND LIFE. [PART IL,

proportion of the St. Helena beetles live evenin the perfect state
within the stems of plants or trunks of trees, while the eggs
and larvee of a still larger number are likely to inhabit similar
stations. Drift-wood might therefore be one of the most
important agencies by which these insects reached the island.

Let us now see how far the distribution of other groups sup-
port the conclusions derived from a consideration of the beetles.
The Hemiptera have been studied by Dr. F. Buchanan White,
and though far less known than the beetles, indicate somewhat
similar relations. Eight out of twenty-one genera are peculiar,
and the thirteen other genera are for the most part widely
distributed, while one of the peculiar genera is of African type.
The other orders of insects have not been collected or studied
with sufficient care to make it worth while to refer to them
in detail; but the land-shells have been carefully collected and
minutely described by Mr. Wollaston himself, and it is interest-
ing to see how far they agree with the insects in their
peculiarities and affinities.

Land-shells of St. Helena.—The total number of species is
only twenty-nine, of which seven are common in Europe or the
other Atlantic islands, and are no doubt recent introductions.
Two others, though described as distinct, are so closely allied to
European forms, that Mr. Wollaston thinks they have probably

even the 300 fathom line, one over 60 miles long; and it is therefore
probable that a much larger island once occupied this site. Now Ascension
is nearly equidistant between St. Helena and Liberia, and such an island
might have served as an intermediate station through which many of the
immigrants to St. Helena passed. As the distances are hardly greater
than in the case of the Azores, this removes whatever difficulty may have
been felt of the possibility of any organisms reaching so remote an island.
The present island of Ascension is probably only the summit of a huge
volcanic mass, and any remnant of the original fauna and flora it might
have preserved may have been destroyed by great volcanic eruptions. Mr,
Darwin collected some masses of tufa which were found to be mainly
organic, containing, besides remains of fresh-water infusoria, the siliceous
tissue of plants! In the light of the great extent of the submarine bank
on which the island stands, Mr. Darwin’s remark, that—‘‘we may feel
sure, that at some former epoch, the climate and productions of Ascension
were very different from what they are now,”—has received a striking
confirmation. (See Naturalist’s Voyage Round the World, p. 495.)

CHAP. XIV. | ST. HELENA, 293

been introduced and have become slightly modified by new
conditions of life; so that there remain exactly twenty species
which may be considered truly indigenous. No less than
thirteen of these, however, appear to be extinct, being now
only found on the surface of the ground or in the surface soil
in places where the native forests have been destroyed and
the land not cultivated. These twenty peculiar species belong
to the following genera: Hyalina (3 sp.), Patula (4 sp.), Bulimus
(7 sp.), Subulina (3 sp.), Succinea (3 sp.) ; of which, one species
of Hyalina, three of Patula, all the Bulimi, and two of Subulina
are extinct. The three Hyalinas are allied to European species,
but all the rest appear to be highly peculiar, and to have no
near allies with the species of any other country. Two of the
Bulimi (LB. auris vulpine and B. darwinianus) are said to
somewhat resemble Brazilian, New Zealand, and Solomon
Island forms, while neither Bulimus nor Succinea occur at
all in the Madeira group.

Omitting the species that have probably been introduced by
human agency, we have here indications of a somewhat recent
immigration of European types which may perhaps be referred
to the glacial period; and a much more ancient immigration
from unknown lands, which must certainly date back to Miocene,
if not to Eocene, times.

Absence of Fresh-water Organisms.—A singular phenomenon
is the total absence of indigenous aquatic forms of life in
St. Helena. Nota single water-beetle or fresh-water shell has
been discovered; neither do there seem to be any water-plants
in the streams, except the common water-cress, one or two
species of Cyperus, and the Australian Jsapis prolifera. The
same absence of fresh-water shells characterises the Azores,
where, however, there is one indigenous water-beetle. In the
Sandwich Islands also recent observations refer to the absence
of water-beetles, though here there are a few fresh-water shells.
It would appear therefore that the wide distribution of the
same generic and specific forms which so generally characterises
fresh-water organisms, and which has been so well illustrated
by Mr. Darwin, has its limits in the very remote oceanic islands,
owing to causes of which we are at present ignorant,

294 ISLAND LIFE. [PART IT,

The other classes of animals in St. Helena need occupy us
little. There are no indigenous mammals, reptiles, fresh-water
fishes or true land-birds; but there 1s one species of wader—a
small plover (digialitis sancte-helene)—very closely allied to a
species found in South Africa, but presenting certain differences
which entitle it to the rank of a peculiar species. The plants,
however, are of especial interest from a geographical point of
view, and we must devote a few pages to their consideration as
supplementing the scanty materials afforded by the animal life,
thus enabling us better to understand the biological relations
and probable history of the island.

Native Vegetation of St. Helena—Plants have certainly more
varied and more effectual means of passing over wide tracts
of ocean than any kinds of animals. Their seeds are often so
minute, of such small specific gravity, or so furnished with
downy or winged appendages, as to be carried by the wind for
enormous distances. The bristles or hooked spines of many
small fruits cause them to become easily attached to the
feathers of aquatic birds, and they may thus be conveyed for
thousands of miles by these pre-eminent wanderers; while
many seeds are so protected by hard outer coats and dense
inner albumen, that months of exposure to salt water does not
prevent them from germinating, as proved by the West Indian
seeds that reach the Azores or even the west coast of Scotland,
and, what is more to the point, by the fact stated by Mr. Melliss,
that large seeds which have floated from Madagascar or
Mauritius round the Cape of Good Hope, have been thrown on
the shores of St. Helena and have then sometimes germinated !

We have therefore little difficulty in understanding how the
island was first stocked with vegetable forms. When it was
so stocked (generally speaking), is equally clear. For as the
peculiar coleopterous fauna, of which an important fragment
remains, is mainly composed of species which are specially
attached to certain groups of plants, we may be sure that the
plants were there long before the insects could establish them-
selves. However ancient then is the insect fauna the flora
must be more ancient still. It must also be remembered that
plants, when once established in a suitable climate and soil, soon

CHAP. xIv.] ST. HELENA. 295

take possession of a country and occupy it almost to the complete
exclusion of later immigrants. The fact of so many European
weeds having overrun New Zealand and temperate North
America may seem opposed to this statement, but it really is
not so. For in both these cases the native vegetation has first
been artificially removed by man and the ground cultivated ;
and there is no reason to believe that any similar effect would
be produced by the scattering of any amount of foreign seed
on ground already completely clothed with an indigenous
vegetation. We might therefore conclude @ priori, that the
flora of such an island as St. Helena would be of an excessively
ancient type, preserving for us in a slightly modified form
examples of the vegetation of the globe at the time when
the island first rose above the ocean. Let us see then what
botanists tell us of its character and affinities.

The truly indigenous flowering plants are about fifty in
number, besides twenty-six ferns. Forty of the former and ten
of the latter are absolutely peculiar to the island, and, as Sir
Joseph Hooker tells us, “ with scarcely an exception, cannot
be regarded as very close specific allies of any other plants
at all. Seventeen of them belong to peculiar genera, and of
the others, all differ so markedly as species from their congeners,
that not one comes under the category of being an insular
form of a continental species.” The affinities of this flora are,
Sir Joseph Hooker thinks, mainly African and especially South
African, as indicated by the presence of the genera Phylica,
Pelargonium, Mesembryanthemum, Oteospermum, and Wahlen-
bergia, which are eminently characteristic of southern extra-
tropical Africa. The sixteen ferns which are not peculiar are
common either to Africa, India, or America, a wide range
sufficiently explained by the dust-like spores of ferns, capable
of being carried to unknown distances by the wind, and the
great stability of their generic and specific forms, many of those
found in the Miocene deposits of Switzerland being hardly
distinguishable from living species. This shows, that identity
of species of ferns between St. Helena and distant countries
does not necessarily imply a recent origin.

The Relation of the St. Helena Composite.—In an elaborate

296 ISLAND LIFE. [par T I

paper on the Compositz,! Mr. Bentham gives us some valuable
remarks on the affinities of the seven endemic species belonging
to the genera Commidendron, Melanodendron, Petrobium, and
Pisiadia, which form so important a portion of the existing
flora of St. Helena. He says: ‘‘ Although nearer to Africa
than to any other continent, those composite denizens which
bear evidence of the greatest antiquity have their affinities for
the most part in South America, while the colonists of a more
recent character are South African.” . . . “Commidendron and
Melanodendron are among the woody Asteroid forms exemplified
in the Andine Diplostephium, and in the Australian Olearia.
Petrobium is one of three genera, remains of a group probably
of great antiquity, of which the two others are Podanthus in
Chile and Astemma in the Andes. The Pisiadia is an endemic
species of a genus otherwise Mascarene or of Eastern Afiica,
presenting a geographical connection analogous to that of the
St. Helena Melhaniz,? with the Mascarene Trochetia.”
Whenever such remote and singular cases of geographical
affinity as the above are pointed out, the first impression is
to imagine some mode by which a communication between
the distant countries implicated might be effected; and this
way of viewing the problem is almost universally adopted, even
by naturalists. But if the principles laid down in this work
and in my CGeoyraphical Distribution of Animals are sound,
such a course is very unphilosophical. For, on the theory of
evolution, nothing can be more certain than that groups now
broken up and detached were once continuous, and that frag-
mentary groups and isolated forms are but the relics of once
widespread types, which have been preserved in a few localities
where the physical conditions were especially favourable, or
where organic competition was less severe. The true explana-
tion of all such remote geographical affinities is, that they date
back to a time when the ancestral group of which they are the
common descendants had a wider or a different distribution ;

1 “Notes on the Classification, History, and Geographical Distribution
of Composite.’’—Journal of the Linnean Society, Vol. XIII. p. 563 (1873).

* The Melhaniz comprise the two finest timber trees of St, Helena, now
almost extinct, the redwood and native ebony.

CHAP. XIV. ] ST. HELENA. 297

and they no more imply any closer connection between the
distant countries the allied forms now inhabit, than does the ex-
istence of living Equidze in South Africa and extinct Equide in
the Pliocene deposits of the Pampas, imply a continent bridging
the South Atlantic to allow of their easy communication.

Concluding Remarks on St. Helena.—The sketch we have now
given of the chief members of the indigenous fauna and flora of
St. Helena shows, that by means of the knowledge we have
obtained of past changes in the physical history of the earth,
and of the various modes by which organisms are conveyed
across the ocean, all the more important facts become readily
intelligible. We have here an island of small size and great
antiquity, very distant from every other land, and probably at no
time very much less distant from surrounding continents, which
became stocked by chance immigrants from other countries at
some remote epoch, and which has preserved many of their more
or less modified descendants to the present time. When first
visited by civilised man it was in all probability far more richly
stocked with plants and animals, forming a kind of natural
museum or vivarium in which ancient types, perhaps dating
back to the Miocene period, or even earlier, had been saved from
the destruction which has overtaken their allies on the great
continents. Unfortunately many, we do not know how many,
of these forms have been exterminated by the carelessness and
improvidence of its civilised but ignorant rulers; and it is only
by the extreme ruggedness and inaccessibility of its peaks and
crater-ridges that the scanty fragments have escaped by which
alone we are able to obtain a glimpse of this interesting chapter
in the life-history of our earth.

CHAPTER XV.
THE SANDWICH ISLANDS.

Position and Physical features—Zoology of the Sandwich Islands—Birds
—Reptiles—Land-shells—Insects— Vegetation of the Sandwich Islands
—Peculiar features of the Hawaiian Flora—Antiquity of the Hawaiian
Fauna and Flora—Concluding observations on the Fauna and Flora of
the Sandwich Islands—General Remarks on Oceanic Islands.

THE Sandwich Islands are an extensive group of large islands
situated in the centre of the North Pacific, bemg 2,350
miles from the nearest part of the American coast—the bay
of San Francisco, and about the same distance from the
Marquesas and the Samoa Islands to the south, and the
Aleutian Islands a httle west of north. They are, therefore,
wonderfully isolated in mid-ocean, and are only connected with
the other Pacific Islands by widely scattered coral reefs and
atolls, the nearest of which, however, are six or seven hundred
miles distant, and are all nearly destitute of animal or vegetable
life. The group consists of seven large inhabited islands besides
four rocky islets; the largest, Hawaii, being seventy miles across
and having an area of 3,800 square miles—being somewhat
larger than all the other islands together. A better conception
of this large island will be formed by comparing it with Devon-
shire, with which it closely agrees both in size and shape, though
its enormous volcanic mountains rise to nearly 14,000 feet high.
Three of the smaller islands are each about the size of Hertford-
shire or Bedfordshire, and the whole group stretches from north-
west to south-east for a distance of about 350 miles. Though so.

CHAP. XV. | THE SANDWICH ISLANDS. 299

extensive, the entire archipelago is volcanic, and the largest island
is rendered sterile and comparatively uninhabitable by its three
active voleanoes and their widespread deposits of lava.

The ocean depths by which these islands are separated from
the nearest continents are enormous. North, east, and south,
soundings have been obtained a little over or under three thousand
fathoms, and these profound deeps extend over a large part of

~ {eow

MAP OF THE SANDWICH ISLANDS. i

The light tint shows where the sea is less than 1,000 fathoms deep.
The figares show the depth in fathoms.

the North Pacific. We may be quite sure, therefore, that the
Sandwich Islands have, during their whole existence, been as
completely severed from the great continents as they are now ;
but on the west and south there is a possibility of more exten-
sive islands having existed, serving as stepping-stones to the
island groups of the Mid-Pacific. This is indicated by a few
widely-scattered coral islets, around which extend considerable

300 ISLAND LIFE, [Part I,

areas of less depth, varying from two hundred to a thousand
fathoms, and which may therefore indicate the sites of submerged
islands of considerable extent. When we consider that east
of New Zealand and New Caledonia, all the larger and loftier
islands are of volcanic origin, with no trace of any ancient strati-

MAP OF THE NORTH PACIFIC WITH ITS SUBMERGED BANKS.

The light tint shows where the sea is less than 1,000 fathoms deep.
The dark tint ,, 2 ab more than 1,000 fathoms deep.
The figures show the depths ia fathoms.

fied rocks (except, perhaps, in the Marquesas, where, according
to Jules Marcou, granite and gneiss are said to occur) it seems
probable that the innumerable coral-reefs and atolls, which occur
in groups on deeply submerged banks, mark the sites of bygone
volcanic islands, similar to those which now exist, but which, after

CHAP. XV. | THE SANDWICH ISLANDS, 301

becoming extinct, have been lowered or destroyed by denudation,
and finally, by subsidence of the earth’s crust, have altogether
disappeared except where their sites are indicated by the upward-
growing coral-reefs. If this view is correct we should give up all
idea of there ever having been a Pacific continent, but should
look upon that vast ocean as having from the remotest geological
epochs been the seat of volcanic forces, which from its profound
depths have gradually built up the islands which now dot its
surface, as well as many others which have sunk beneath its
waves. ‘The number of islands, as well as the total quantity of
land-surface, may sometimes have been greater than it is now,
and may thus have facilitated the transfer of organisms from one
group to another, and more rarely even from the American,
Asiatic, or Australian continents. Keeping these various facts
and considerations in view, we may now proceed to examine the
fauna and flora of the Sandwich Islands, and discuss the special
phenomena they present.

Zoology of the Sandwich Islands: Birds.—It need hardly be
said that indigenous mammalia are quite unknown in the Sand-
wich Islands, the most interesting of the higher animals being
the birds, which are tolerably numerous and highly peculiar. Many
aquatic and wading birds which range over the whole Pacific
visit these islands, twenty-four species having been observed,
but even of these five are peculiar—a coot, Pulica alai; a
moorhen, Gallinula sandvichensis ; a rail with rudimentary
wings, Pennula miller; and two ducks, Anas Wyvilliana and
Bernicla sandvichensis. The birds of prey are also great wan-
derers. Four have been found in the islands—the short-eared
owl, Otus brachyotus, which ranges over the greater part of the
globe, but is here said to resemble the variety found in Chile
and the Galapagos; the barn owl, Strix flammea, of a variety
common in the Pacific; a peculiar sparrow-hawk, <Accipiter
hawati ; and Buteo solitarius, a buzzard of a peculiar species,
and coloured so as to resemble a hawk of the American sub-
family Polyborine. It is to be noted that the genus Buteo
abounds in America, but is not found in the Pacific; and this
fact, combined with the remarkable colouration, renders it almost
certain that this peculiar species is of American origin.

302 ISLAND LIFE. | [pier

Coming now to the Passeres, or true perching birds, we find
sixteen species, all peculiar, belonging to ten genera, all but one
of which are also peculiar. The following is a list of these
extremely interesting birds :—

I. Muscicarip# (Flycatchers). Drepanidide —continued,

1. Chasiempis sandvichensis. 11. Hemignathus olivaceus.

2. Pheornis obscura. 12; Be obscurus.

13. ; lucidus.
II. MetipHacip& (Honeysuckers.) 14. ards cones

3. Mohoa nobilis. 1, a ea:

4, »5 braccata. 16. Loxioides bailloni.

5. 5» aprealis. 17. Psittirostra psittacea.

6. Chetoptila angustipluma. 18. Fringilla anna (recently de-

scribed, perhaps belongs also

III. DREPANIDIDA. to this group).

7. Drepanis coccinea.

8. syne Sosed.

i { -
9. Penns 101010 IV. Corvip (Crows).
10. 5» sanguinea, 19. Corvus hawaiensis.

Taking the above in the order here given, we have, first, two
peculiar genera of flycatchers, a family confined to the Old
World, but extending over the Pacific as far as the Marquesas
Islands. Next we have two peculiar genera (with four species)
of honeysuckers, a family confined to the Australian region, and
also ranging over all the Pacific Islands to the Marquesas. We
now come to the most important group of birds in the Sandwich
Islands, comprising five peculiar genera, and eleven or twelve
species, which are believed to form a peculiar family allied to the
Oriental flower-peckers (Diceidz), and perhaps remotely to the
American greenlets (Vireonidze), or tanagers (Tanagride). They
possess singularly varied beaks, some having this organ much
thickened like those of finches, to which family some of
them have been supposed to belong. In any case they form a
most peculiar group, and cannot be associated with any other
known birds. The last species, and the only one not belonging
to a peculiar genus, is the Hawaiian crow, belonging to the almost
universally distributed genus Corvus.

On the whole, the affinities of these birds are, as might be

« sie

CHAP. XV. | THE SANDWICH ISLANDS. 303

expected, chiefly with Australia and the Pacific Islands ; but they
exhibit in the buzzard, one of the owls, and perhaps in some of
the Drepanidide, slight indications of very rare or very remote
communication with America. The amount of speciality 1s,
however, wonderful, far exceeding that of any other islands; the
only approach to it being made by New Zealand and Madagascar,
which have a much more varied bird fauna anda smaller pro-
portionate number of peculiar genera. These facts undoubtedly
indicate an immense antiquity for this group of islands, or the
vicinity of some very ancient land (now submerged), from which
some portion of their peculiar fauna might be derived.
Reptiles.—The only other vertebrate animals are two lizards.
One of these is a very widespread species, Ablepharus pacilo-
pleurus, said by Dr. Giinther to be found in Timor, Australia,
the Samoa Islands, and the Sandwich Islands. It seems
hardly likely that such a range can be due to natural causes.
The other is said to form a peculiar genus of geckoes, but both
its locality and affinities appear to be somewhat doubtful.
Land-shells—The only other group of animals which has
been carefully studied, and which presents features of especial
interest, are the land-shells. These are very numerous, about
thirty genera, and between three and four hundred species having
been described ; and it is remarkable that this single group con-
tains as many species of land-shells as all the other Polynesian
Islands from the Pelew Islands and Samoa to the Marquesas. All
the species are peculiar, and about three-fourths of the whole
belong to peculiar genera, fourteen of which constitute the sub-
family Achatinelline, entirely confined to this group of islands
and constituting its most distinguishing feature. Thirteen genera
(comprising sixty-four species) are found also in the other Poly-
nesian Islands, but three genera of Auriculide (Plecotrema,
Pedipes, and Blauneria) are not found in the Pacific, but in-
habit—the former genus Australia, China, Bourbon, and Cuba,
the two latter the West Indian Islands. Another remarkable
peculiarity of these islands is the small number of Opercu-
lata, which are represented by only one genus and five species,
while the other Pacific Islands have twenty genera and 115
species, or more than half the number of the Inoperculata.

304 ISLAND LIFE. [PART IT.

This difference is so remarkable that it is worth stating in a
comparative form :—

Tnoperculata. Operculata. Auricwide.
Sanciwieln Ustamdin eu, a... ncn Joe 5 9
Rest, of. Pacitie Islamds; nasccocseccnrese 200 115 16

When we remember that in the West Indian Islands the
Operculata abound in a greater proportion than even in the
Pacific Islands generally, we are led to the conclusion that lime-
stone, which is plentiful in both these areas, is especially favour-
able to them, while the purely volcanic rocks are especially
unfavourable. The other peculiarities of the Sandwich Islands,
however, such as the enormous preponderance of the strictly
endemic Achatinelline, and the presence of genera which occur
elsewhere only beyond the Pacific area in various parts of the
great continents, undoubtedly point to a very remote origin, at a
time when the distribution of many of the groups of mollusca
was very different from that which now prevails.

A very interesting feature of the Sandwich group is the extent
to which the species and even the genera are confined to separate
islands. Thus the genera Carelia and Catinella with eight
species are peculiar to the island of Kaui; Bulimella, Apex,
Frickella, and Blauneria, to Oahu ; Perdicella to Maui; and Ebur-
nella to Lanai. The Rev. John T. Gulick, who has made a
special study of the Achatinellinze, informs us that the average
range of the species in this sub-family is five or six miles, while
some are restricted to but one or two square miles, and only very
few have the range of a whole island. Hach valley, and often
each side of a valley, and sometimes even every ridge and peak
possesses its peculiar species.! The island of Oahu, in which
the capital is situated, has furnished about half the species
already known. ‘This is partly due to its being more forest clad,
but also, no doubt, in part to its being better explored, so that
notwithstanding the exceptional riches of the group, we have
no reason to suppose that there are not many more species to be

1 Journal of the Linnean Society, 1873, p. 496. ‘On Diversity of
Evolution under one set of External Conditions.” Proceedings of the
Zoological Society of London, 1873, p. 80. ‘On the Classification of the
Achatinellidz.”

CHAP. XV. ] THE SANDWICH ISLANDS. 3305)

found in the less explored islands. Mr. Gulick tells us that
the forest region that covers one of the mountain ranges of
Oahu is about forty miles in length, and five or six miles in
width, yet this small territory furnishes about 175 species of
Achatinellide, represented by 700 or 800 varieties. The most
important peculiar genus, not belonging to the Achitinella group,
is Carelia, with six species and several named varieties, all
peculiar to Kaui, the most westerly of the large islands.
This would seem to show that the small islets stretching
westward, and situated on an extensive bank with less than a
thousand fathoms of water over it, may indicate the position
of a large submerged island whence some portion of the
Sandwich Island fauna was derived.

Insects. — Unfortunately we have as yet no such knowledge of
the insects of these islands as we possess in the case of the
Azores and St. Helena, but some considerable collections have
been sent over by Mr. T. Blackburn, now resident there, and we
may therefore soon possess fuller and more accurate information.
Although insects are said to be very scarce, yet all the chief tribes
of Coleoptera appear to be represented, though as yet by very
few species. These appear to be for the most part peculiar, but
to have widespread affinities. The majority, as might be ex-
pected, are allied to Polynesian, Australian, or Malayan forms;
some few are South American (perhaps introduced), while others
show north temperate affinities. There are several new genera,
and one peculiar group of six species is said to form a new family
allied to the Anthribide. A new genus of Lucanidz is said to
be allied to a Chilian genus. If we consider the greater facilities
of insects for dispersal when compared with birds or land-shells,
the characteristics of the insect fauna, so far as yet known, are
sufficiently in harmony with the amount of speciality and
isolation presented by the latter groups.

Vegetation of the Sandwich Islands.—The flora of these islands
is In many respects so peculiar and remarkable, and so well sup-
plements the information derived from its interesting but scanty
fauna, that a brief account of its more striking features will not
be out of place; and we fortunately have a pretty full know-
ledge of it, owing to the researches of the American botanist

306 ISLAND LIFE. [PART I,

Horace Mann, and of Dr. Pickering, who accompanied the
United States Exploring Expedition.

Considering their extreme isolation, their uniform volcanic
soil, and the large proportion of the chief island which consists
of barren lava-fields, the flora of the Sandwich Islands is ex-
tremely rich, consisting, so far as at present known, of 554
species of flowering plants and 135 ferns. This is considerably
richer than the Azores (439 Phanerogams and 39 ferns), which
though less extensive are far better known, or than the Gala-
pagos (332 Phanerogams), which are more strictly comparable,
being equally volcanic, while their somewhat smaller area may
perhaps be compensated by their proximity to the American
continent. Even New Zealand with more than twenty times
the area of the Sandwich group, whose soil and climate
are much more varied, and whose botany has been thoroughly
explored, has not double the number of flowering plants
(935 species), while in ferns it is barely equal.

Peculiar Features of the Flora.—This rich insular flora 1s won-
derfully peculiar, for if we deduct sixty-nine species, which are
believed to have been introduced by man, there remain 620
species of which 377, or more than three-fifths, are quite peculiar
to the islands. There are no less than 39 peculiar genera out of
a total of 253, and these 39 genera comprise 153 species, so that
the most isolated forms are those which most abound and thus
give a special character to the flora. Besides these peculiar
types, several genera of wide range are here represented by
highly peculiar species. Such are Lobelia, the Hawaiian species
of which are woody shrubs from six to twenty feet high, one
even being a tree, reaching a height of forty feet. Shrubby
geraniums fifteen feet high grow as epiphytes on forest trees, as
do some Vacciniums and Epacrids. Violets, and plantains also
form tall shrubby plants, and there are many strange arborescent
composite, as in other oceanic islands.

The affinities of the flora generally are very wide. Although
there are many Polynesian groups, yet Australian, New Zealand,
and American forms are equally represented. Dr. Pickering
notes the total absence of a large number of families found in
Southern Polynesia, such as Dilleniaceee, Anonacee, Olacacez,

CHAP, xv. | THE SANDWICH ISLANDS. 307

Aurantiaces, Guttiferze, Malpighiacez, Meliaceee, Combretaceze,
Rhizophoracese, Melastomaceze, Passifloraceee, Cunoniaces,
Jasminacee, Acanthaces, Myristicacese, Casuaraceze, Scita-
mines, and Aracze, as well as the genera Clerodendrum, Ficus,
and epidendric orchids. Australian affinities are shown by the
genera Exocarpus, Cyathodes, Melicope, Pittosporum, and by a
phyllodinous Acacia. New Zealand is represented by Ascarina,
Coprosma, Acna, and several Cyperaceze; while America is
represented by the genera Nama, Gunnera, Phyllostegia, Sisy-
rinchium, and by a red-flowered Rubus and a yellcw-flowered
Sanicula allied to Oregon species.

There is no true alpine flora on the higher summits, but
several of the temperate forms extend to a great elevation.
Thus Mr. Pickering records Vaccinium, Ranunculus, Silene,
Gnaphalium and Geranium, as occurring above ten thousand
feet elevation ; while Viola, Drosera, Aczena, Lobelia, Edwardsia,
Dodonea, Lycopodium, and many Composite, range above six
thousand feet. Vaccinium and Silene are very interesting, as
they are peculiar to the North Temperate zone, except one Silene
in South Africa.

The proportionate abundance of the different families in this
interesting flora is as follows :—

1. Composite, A7 species, 11. Piperacee, 12 species.
2. Cyperacee, Ones 12. Convolvulacer, 12 ,,
3. Lobeliacee, Deets 13. Malvaceae, 12k te
4, Rubiaceae, DOE ye 14. Amarantacee, Oe (ae
5. Labiate, Wile 15. Araliacee, So 7h:
6. Leguminose, 20 ,, 16. Violacee, Gets
7. Rutacee, Lely is 17. Pittosporacer, 6 ,,
8. Caryophyllacee, 14 __,, 18. Myrtacee, OF gs
9. Gesneriacee, 14 ce 19. Goodeniacee, Oo os
10. Urticacee, 1s une 20. Thymelacee, Gig

Four other orders, Geraniacese, Rhamnacez, Rosacesz, and
Cucurbitaceze, have five species each; and among the more im-
portant orders which have less than five species each are Ranun-
culacee, Ericaceat, Primulaceze, Polygonacez, Orchidacez, and
Juncacese. In the above enumeration the grasses (Graminacee)
are omitted, as they were not described at the time Mr. Mann’s

x 2

808 ISLAND LIFE. [part 1.

article was written. The most remarkable feature here is the
great abundance of Lobeliacez, a character of the flora which is
probably unique; while the superiority of Labiatz to Legumi-
nosze and the scarcity of Rosaceze and Orchidacez are also very
unusual. Composites, as in most temperate floras, stand at the
head of the list, and as these have been carefully studied by Mr.
Bentham, it will be interesting to note the affinities which they
indicate. Omitting four genera and species which are cosmo-
politan, and have no doubt entered with civilised man, there
remain twelve genera and forty-four species of Compositee in the
islands. All the species are peculiar, as are six of the genera ;
and in another genus, Coreopsis, the six species form a peculiar
named section or subgenus, Campylotheca; while the genus
Lipocheta with ten species is only known elsewhere in the
Galapagos, where a single species occurs. We may therefore
consider that eight out of the twelve genera of Hawaiian Com-
posits are really confined to the Archipelago. The relations of
the genera are thus given by Mr. Bentham :—

No of
Species. External Relations of the Species.

Lagenophora 1 With the Old World and Extra-Tropical America.
Aster 1 . American and Extra-Tropical Old World.
Tetramolobium 6 South Extra-Tropical American.
Vittadinia 1 South Extra-Tropical American and Australian.
Campylotheca (s.g) 6 With the Tropical American and very few Old
World species of Coreopsis and Bidens.

Bidens 1 The Tropical American species.
Lipocheeta 10 American Wedelioide and Helianthioide.
Argyroxiphium 2 With Madiez of the Mexican region.
Wilkesia 1 With Madiez of the Mexican region,

Dubantia Distantly with Madiez and Galinsogee of the
Mexican region.

Raillardia 11 With Raillardella of the Mexican region.

Hesperomannia 1 With Stifftia and Wunderlichia of the Brazilian
region.

The great preponderance of American relations of the Com-
posite, as above indicated, is very interesting and suggestive.
It is here that we meet with some of the most isolated and re-
markable forms, implying great antiquity ; and when we consider
the enormous extent and world-wide distribution of this order

CHAP. XV.] THE SANDWICH ISLANDS. 509

(comprising about ten thousand species), its distinctness from all
others, the great specialisation of its flowers to attract insects,
and of its seeds for dispersal by wind and other means, we can
hardly doubt that its origin dates back to a very remote epoch.
We may therefore look upon the Compositz as representing the
most ancient portion of the existing flora of the Sandwich Islands,
carrying us back to a very remote period when the facilities for
communication with America were greater than they are now.
This may be indicated by the two deep submarine banks in the
North Pacific, between the Sandwich Islands and San Francisco,
which, from an ocean floor nearly 3,000 fathoms deep, rise up to
within a few hundred fathoms of the surface, and seem to indi-
cate the subsidence of two islands, each about as large as Hawaii.
The plants of North Temperate affinity may be nearly as old, but
these may have been derived from Northern Asia by way of
Japan and the extensive line of shoals which run north-west-
ward from the Sandwich Islands, as shown on our map. Those
which exhibit Polynesian or Australian affinities, consisting for
the most part of less highly modified species usually of the same
genera, may have had their origin at a later, though still some-
what remote period, when large islands, indicated by the exten-
sive shoals to the south and south-west, offered facilities for the
transmission of plants from the tropical portions of the Pacific
Ocean.

Antiquity of the Hawauan Kaunaand Flora.—The great anti-
quity implied by the peculiarities of the fauna and flora, no less than
by the geographical conditions and surroundings, of this group,
will enable us to account for another peculiarity of its flora—
the absence of so many families found in other Pacific Islands.
For the earliest immigrants would soon occupy much of the
surface, and become specially modified in accordance with the
conditions of the locality, and these would serve as a barrier
against the intrusion of many forms which at a later period
spread over Polynesia. The extreme remoteness of the islands,
and the probability that they have always been more isolated
than those of the Central Pacific, would also necessarily result in
an imperfect and fragmentary representation of the flora of
surrounding lands.

S10) ISLAND LIFE. | [PART IL

Concluding Observations on the Fauna and Flora of the Sand-
wich Islands.—The indications thus afforded by a study of the
flora seem to accord well with what we know of the fauna of the
islands. Plants having so much greater facilities for dispersal
than animals, and also having greater specific longevity and
greater powers of endurance under adverse conditions, exhibit
in a considerable degree the influence of the primitive state of
the islands and their surroundings; while members of the
animal world, passing across the sea with greater difficulty and
subject to extermination by a variety of adverse conditions,
retain much more of the impress of a recent state of things,
with perhaps here and there an indication of that ancient
approach to America so clearly shown in the Composite and
some other portions of the flora.

General Remarks on Oceante Islands.—We have now reviewed
the main features presented by the assemblages of organic forms
which characterise the more important and best known of the
Oceanic Islands. They all agree in the total absence of indi-
genous mammalia and amphibia, while their reptiles, when they
possess any, do not exhibit indications of extreme isolation and
antiquity. Their birds and insects present just that amount of
specialisation and diversity from continental forms which may
be best explained by the known means of dispersal acting
through long periods ; their land shells indicate greater isolation,
owing to their admittedly less effective means of conveyance
across the ocean; while their plants show most clearly the
effects of those changes of conditions which we have reason to
believe have occurred during the Tertiary epoch, and preserve
to us in highly specialised and archaic forms some record of the
primeval immigration by which the islands were originally
clothed with vegetation. But in every case the series of forms
of life in these islands is scanty and imperfect as compared with
far less favourable continental areas, and no one of them presents
such an assemblage of animals or plants as we always find in an
island which we know has once formed part of a continent.

It is still more important to note that none of these oceanic
archipelagoes present us with a single type which we may
suppose to have been preserved from Mesozoic times; and this

CHAP, XV. ] OCEANIC ISLANDS. 311

fact, taken in connection with the volcanic or coralline origin of
all of them, powerfully enforces the conclusion at which we have
arrived in the earlier portion of this volume, that during the
whole period of geologic time as indicated by the fossiliferous
rocks, our continents and oceans have, speaking broadly, been
permanent features of our earth’s surface. For had it been
otherwise—had sea and land changed place repeatedly as was
once supposed—had our deepest oceans been the seat of great
continents while the site of our present continents was occupied
by an oceanic abyss—is it possible to imagine that no fragments
of such continents would remain in the present oceans, bringing
down to us some of their ancient forms of life preserved with
but little change? The correlative facts, that the islands of our
great oceans are all volcanic (or coralline built probably upon
degraded and submerged volcanic islands), and that their pro-
ductions are all more or less clearly related to the existing in-
habitants of the nearest continents, are hardly consistent with
any other theory than the permanence of our oceanic and
continental areas.

We may here refer to the one apparent exception, which,
however, lends additional force to the argument. New Zealand
is sometimes classed as an oceanic island, but it is not so really ;
and we shall discuss its peculiarities and probable origin
further on.

CHAPTER XVI.
CONTINENTAL ISLANDS OF RECENT ORIGIN: GREAT BRITAIN.

Characteristic Features of Recent Continental Islands—Recent Physical
Changes of the British Isles—Proofs of Former Elevation—Submerged
Forests—Buried River Channels—Time of Last Union with the Conti-
nent—Why Britain is poor in Species—Peculiar British Birds—Fresh-
water Fishes—Cause of Great Speciality in Fishes—Peculiar British
Insects—Lepidoptera confined to the British Isles—Peculiarities of the
Isle of Man—Lepidoptera—Coleoptera confined to the British Isles—
Trichoptera peculiar to the British Isles—Land ‘and Freshwater
Shells—Peculiarities of the British Flora—Peculiarities of the Irish
Flora—Peculiar British Mosses and Hepatice—Concluding Remarks
on the Peculiarities of the British Fauna and Flora.

WE now proceed to examine those islands which are the very
reverse of the “oceanic” class, being fragments of continents or
of larger islands from which they have been separated by sub-
sidence of the intervening land at a period which, geologically,
must be considered recent. Such islands are always still con-
nected with their parent land by a shallow sea, usually indeed
not exceeding a hundred fathoms deep; they always possess
mammalia and reptiles either wholly or in large proportion
identical with those of the mainland; while their entire flora
and fauna is characterised either by the total absence or com-
p2rative scarcity of those endemic or peculiar species and genera
which are so striking a feature of all oceanic islands. Such
islands will, of course, differ from each other in size, in antiquity,
and in the richness of their respective faunas, as well as in their
distance from the parent land and the facilities for intercom-
munication with it; and these diversities of conditions will
manifest themselves in the greater or less amount of speciality
of their animal productions.

CHAP. XVI. ] THE BRITISH ISLES. 313

This speciality, when it exists, may have been brought about
in two ways. A species or even a genus may on a continent
have a very limited area of distribution, and this area may be
wholly or almost wholly contained in the separated portion or
island, to which it will henceforth be peculiar. Even when the
area occupied by a species is pretty equally divided at the time
of separation between the island and the continent, it may
happen that it will become extinct on the latter, while it may
survive on the former, because the limited number of individuals
after division may be unable to maintain themselves against the
severer competition or more contrasted climate of the continent,
while they may flourish under the more favourable insular
conditions. On the other hand, when a species continues to
exist in both areas, it may on the island be subjected to some
modifications by the altered conditions, and may thus come to
present characters which differentiate it from its continental
allies and constitute it a new species. We shall in the course of
our survey meet with cases illustrative of both these processes.

The best examples of recent continental islands are Great
Britain and Ireland, Japan, Formosa, and the larger Malay
Islands, especially Borneo, Java, and Celebes; and as each of
these presents special features of interest, we will give a short
outline of their zoology and past history in relation to that of
the continents from which they have recently been separated,
commencing with our own islands, to which the present chapter
will be devoted.

Recent Physical Changes in the British Isles —Great Britain
is perhaps the most typical example of a large and recent con-
tinental island now to be found upon the globe. It is joined to
the continent by a shallow bank which extends from Denmark
to the Bay of Biscay, the 100 fathom line from these extreme
points receding from the coasts so as to include the whole of the
British Isles and about fifty miles beyond them to the westward.
(See Map.) Beyond this line the sea deepens rapidly to the 500
and 1,000 fathom lines, the distance between 100 and 1,000
fathoms being from twenty to fifty miles, except where there is
a great outward curve to include the Porcupine Bank 170 miles
west of Galway, and to the north-west of Caithness where a

514 ISLAND LIFH, [PART IT

narrow ridge less than 500 fathoms below the surface joins the ex-
tensive bank under 300 fathoms, on which are situated the Faroe
Islands and Iceland, and which stretches across to Greenland.
In the North Channel between Ireland and Scotland, and in the

i
J IGE

MAP SHOWING THE SHALLOW BANK CONNECTING THE BRITISH ISLES WITH THE CONTINENT.
The light tint indicates a depth of less than 100 fathoms.

The figures show the depth in fathoms.
The narrow channel between Norway and Denmark is 2,580 feet deep.

Minch between the outer Hebrides and Skye, are a series of
hollows in the sea-bottom from 100 to 150 fathoms deep.
These correspond exactly to the points between the opposing

CHAP, XVI.] THE BRITISH ISLES. 315

highlands where the greatest accumulations of ice would
necessarily occur during the glacial epoch, and they may well
be termed submarine lakes, of exactly the same nature as
those which occur in similar positions on land.

Proofs of Former Elevation—Submerged Lorests.—W hat renders
Britain particularly instructive as an example of a recent con-
tinental island is the amount of direct evidence that exists, of
several distinct kinds, showing that the land has been sufficiently
elevated (or the sea depressed) to unite it with the continent,
—and this at a very recent period. The first class of evidence
is the existence, all round our coasts, of the remains of sub-
marine forests often extending far below the present low-water
mark. Suchare the submerged forests near Torquay in Devon-
shire, and near Falmouth in Cornwall, both containing stumps
of trees in their natural position rooted in the soil, with deposits
of peat, branches, and nuts, and often with remains of insects
and other land animals. These occur in very different conditions
and situations, and some have been explained by changes in the
height of the tide, or by pebble banks shutting out the tidal
waters from estuaries; but there are numerous examples to
which such hypotheses cannot apply, and which can only be
explained by an actual subsidence of the land (or rise of the
sea-level) since the trees grew.

We cannot give a better idea of these forests than by quoting
the following account by Mr. Pengelly of a visit to one which
had been exposed by a violent storm on the coast of Devonshire,
at Blackpool near Dartmouth :—

“We were so fortunate as to reach the beach at spring-tide
low-water, and to find, admirably exposed, by far the finest
example of a submerged forest which I have ever seen. It
occupied a rectangular area, extending from the small river or
stream at the western end of the inlet, about one furlong east-
ward; and from the low-water line thirty yards up the strand.
The lower or seaward portion of the forest area, occupying about
two-thirds of its entire breadth, consisted of a brownish drab-
coloured clay, which was crowded with vegetable débris, such
as small twigs, leaves, and nuts. There were also numerous
prostrate trunks and branches of trees, lying partly imbedded

316 ISLAND LIFE. [PART I.

in the clay, without anything like a prevalent direction. The
trunks varied from six inches to upwards of two feet i diameter.
Much of the wood was found to have a reddish or bright pink
hue, when fresh surfaces were exposed. ‘Some of it, as well
as many of the twigs, had almost become a sort of ligneous
pulp, while other examples were firm, and gave a sharp crackling
sound on being broken. Several large stumps projected above
the clay in a vertical direction, and sent roots and rootlets into
the soil in all directions and to considerable distances. It was
obvious that the movement by which the submergence was
effected had been so uniform as not to destroy the approximate
horizontality of the old forest ground. One fine example was
noted of a large prostrate trunk having its roots still attached,
some of them sticking up above the clay, while others were
buried in it. Hazelnuts were extremely abundant—some entire,
others broken, and some obviously gnawed. ... It has been
stated that the forest area reached the spring-tide low-water
line; hence as the greatest tidal range on this coast amounts
to eighteen feet, we are warranted in inferring that the sub-
sidence amounted to eighteen feet as a minimum, even if we
suppose that some of the trees grew in a soil the surface of
which was not above the level of high water. There is satis-
factory evidence that in Torbay it was not less than forty feet,
and that m Falmouth Harbour it amounted to at least sixty-
seven feet.” }

On the coast of the Bristol Channel similar deposits occur,
as well as along much of the coast of Wales and in Holyhead
Harbour. It is believed by geologists that the whole Bristol
Channel was, at a comparatively recent period, an extensive
plain, through which flowed the River Severn; for im addition
to the evidence of submerged forests there are on the coast of
Glamorganshire numerous caves and fissures in the face of high
sea cliffs, in one of which no less than a thousand antlers of the
reindeer were found, the remains of animals which had been
devoured there by bears and hyzenas; facts which can only be
explained by the existence of some extent of dry land stretching
seaward from the present cliffs, but since submerged and washed

1 Geological Magazine, 1870, p. 165.

lio»

CHAP, XVI.] THE BRITISH ISLES. 317

away. ‘This plain may have continued down to very recent times,
since the whole of the Bristol Channel to beyond Lundy Island
is under twenty-five fathoms deep. In the east of England
we have a similar forest-bed at Cromer in Norfolk; and in the
north of Holland an old land surface has been Sand fifty-six
feet below high-water mark.

Buried River Channels.— Still more remarkable are the buried
river channels which have been traced on many parts of our
coasts. In order to facilitate the study of the glacial deposits
of Scotland, Dr. James Croll obtained the details of about 250
bores put down in all parts of the mining districts of Scotland
for the purpose of discovering minerals." These revealed the
interesting fact that there are ancient valleys and river channels
at depths of from 100 to 260 feet below the present sea-level.
These old rivers sometimes run in quite different directions from
the present lines of drainage, connecting what are now distinct
valleys; and they are so completely filled up and hidden by
boulder clay, drift, and sands, that there is no indication of their
presence on the surface, which often consists of mounds or low
hills more than 100 feet high. One of these old valleys connects
the Clyde near Dumbarton with the Forth at Grangemouth, and
appears to have contained two streams flowing in opposite directions
from a watershed about midway at Kalsith. At Grangemouth
the old channel is 260 feet below the sea-level. The watershed
at Kilsith is now 160 feet above the sea, the old valley bottom
being 120 feet deep or forty feet above the sea. In some places
the old valley was a ravine with precipitous rocky walls, which
have been found in mining excavations. Dr. Geikie, who has
himself discovered many similar buried valleys, is of opinion
that ey unquestionably belong to the period of the boulder
clay.”

We have here a clear proof that, when these rivers were
formed, the land must have stood in relation to the sea at least
260 feet higher than it does now, and probably much more ; and
this is sufficient to jom England to the continent. Supporting
this evidence, we have freshwater or littoral shells found at great
depths off our coasts. Mr. Godwin Austen records the dredging

1 Transactions of the Edinburgh Geological Society, Vol. I. p. 330.

318 ISLAND LIFE. [PART II.

up of a freshwater shell (Unio pictorum) off the mouth of the
English Channel between the fifty fathom and 100 fathom
lines, while in the same locality gravel banks with littoral shells
now lie under sixty or seventy fathoms water. More recently
Mr. Gwyn Jeffreys has recorded the discovery of eight species
of fossil arctic shells off the Shetland Isles in about ninety
fathoms water, all being characteristic shallow water species,
so that their association at this great depth is a distinet indication
of considerable subsidence.”

Time of last Union with the Continent.—-The period when
this last union with the continent took place was comparatively
recent, as shown by the identity of the shells with living species,
and the fact that the buried river channels are all covered with
clays and gravels of the glacial period, of such a character as
to indicate that most of them were deposited above the sea-
level. From these and various other indications geologists are
all agreed that the last continental period, as it is called, was
subsequent to the greatest development of the ice, but probably
before the cold epoch had wholly passed away. But if so
recent, we should naturally expect our land still to show an
almost perfect community with the adjacent parts of the con-
tinent in its natural productions; and such is found to be the
case. All the higher and more perfectly organised animals are,
with but few exceptions, identical with those of France and
Germany ; while the few species still considered to be peculiar
may be accounted for either by an original local distribution,
by preservation here owing to favourable insular conditions, or
by slight modifications having been caused by these conditions
resulting in a local race, sub-species, or species.

Why Britain ts poor in Species.—The former union of our islands -
with the continent, is not, however, the only recent change they -
have undergone. There is equally good evidence that a consider-
able portion, if not the entire area, has been submerged to a depth
of nearly 2,000 feet (see Chap. IX. p. 168), at which time only
what are now the highest mountains would remain as groups
of rocky islets. This submersion must have destroyed the

1 Quarterly Journal of Geological Society, 1850, p. 96.
2 British Association Report, Dundee, 1867, p. 431.

CHAP. XVI.] THE BRITISH ISLES. alg

greater part of the life of our country; and as it certainly
occurred during the latter part of the glacial epoch, the sub-
sequent elevation and union with the continent cannot have
been of very long duration, and this fact must have had an
important bearing on the character of the existing fauna and
flora of Britain. We know that just before ae during the
glacial period we possessed a fauna almost or quite identical
with that of adjacent parts of the continent and equally rich
in species. The submergence destroyed this fauna; and the per-
manent change of climate on the passing away of the glacial
conditions appears to have led to the extinction or migration
of many species in the adjacent continental areas, where they
were succeeded by the assemblage of animals now occupying
Central Europe. When England became continental, these
entered our country; but sufficient time does not seem to have
elapsed for the migration to have been completed before sub-
sidence again occurred, cutting off the further influx of purely
terrestrial animals, and leaving us without the number of species
which our favourable climate and varied surface entitle us to.

To this cause we must impute our comparative poverty in
mammalia and reptiles—more marked in the latter than the
former, owing to their lower vital activity and smaller powers
of dispersal. Germany, for example, possesses nearly ninety
species of land mammalia, and even Scandinavia about sixty,
while Britain has only forty, and Ireland only twenty-two. The
depth of the Irish Sea being somewhat greater than that of the
German Ocean, the connecting land would there probably be
of small extent and of less duration, thus offering an additional
barrier to migration, whence has arisen the comparative zoological
poverty of Ireland. This poverty attains its maximum in the
reptiles, as shown by the following figures :—

Belgium has 22 species of reptiles and amphibia.
Bmtain, -..,, 13 . ef 7
Ireland ,, 4 33

”? yp

Where the power of flight existed, and thus the period of
migration was prolonged, the difference is less marked; so that
Ireland has seven bats to twelve in Britain, and about 110 as
against 130 land-birds.

320 ISLAND LIFE. [part it,

Plants, which have considerable facilities for passing over the
sea, are somewhat intermediate in proportionate numbers, there
being about 970 flowering plants and ferns in Ireland to 1425 in
Great Britain,—or almost exactly two-thirds, a proportion inter-
mediate between that presented by the birds and the mammalia.

Peculiar British birds.— Among our native mammalia, reptiles,
and amphibia, it is the opinion of the best authorities that we
possess neither a distinct species nor distinguishable variety. In
birds, however, the case is different, since some of our species,
in particular our coal-tit (Parus ater) and long-tailed tit (Parus
caudatus) present well-marked differences of colour as compared
with continental specimens; and in Mr. Dresser’s work on the
Birds of Europe they are considered to be distinct species, while
Professor Newton, in his new edition of Yarrell’s British Birds,
does not consider the difference to be sufficiently great or suffi-
ciently constant to warrant this, and therefore classes them as
insular races of the continental species. We have, however,
one undoubted case of a bird peculiar to the British Isles, in the
red grouse (Lagopus scoticus), which abounds in Scotland, Ireland,
the North of England, and Wales, and is very distinct from any
continental species, although closely allied to the willow grouse
of Scandinavia. This latter species resembles it considerably in
its summer plumage, but becomes pure white in winter ; whereas
our species retains its dark plumage throughout the year, be-
coming even darker in winter than In summer. We have here
therefore a most interesting example of an insular form in our
own country ; but it is difficult to determine how it originated.
On the one hand, it may be an old continental species which
during the glacial epoch found a refuge here when driven from
its native haunts by the advancing ice; or, on the other hand, it
may be a descendant of the Northern willow grouse, which has
lost its power of turning white in winter owing to its long re-
sidence in the lowlands of an island where there is little permanent
snow, and where assimilation in colour to the heather among
which it lurks is at all times its best protection. In either case
it is equally interesting, as the one large and handsome bird
which is peculiar to our islands notwithstanding their recent
separation from the continent.

CHAP, XVI. | THE BRITISH ISLES. 321

The following is a list of the birds now held to be peculiar to
the British Isles :—
1. Parus BRITANNICUS ...Closely allied to P. ater of the continent ; a local
race or sub-species,

PeMRRUS ROSHA .....e.0068. Allied to P. caudatus of the continent.
3. LAGOPUS SCOTICUS...... Allied to LZ. albus of Scandinavia, but very distinct.

Freshwater Fishes.—Although the productions of fresh waters
have generally, as Mr. Darwin has shown, a wide range, fishes
appear to form an exception, many of them being extremely
limited in distribution. Some are confined to particular river
valleys or even to single rivers, others inhabit the lakes of a
limited district only, while some are confined to single lakes,
often of small area, and these latter offer examples of the most
restricted distribution of any organisms whatever. Cases of this
kind are found in our own islands, and deserve our especial atten-
tion. It has long been known that some of our lakes possessed
peculiar species of trout and charr, but how far these were un-
known on the continent, and how many of those in different
parts of our islands were really distinct, had not been ascertained
till Dr. Giinther, so well known for his extensive knowledge of
the species of fishes, obtained numerous specimens from every
part of the country, and by comparison with all known con-
tinental species determined their specific differences. The
striking and unexpected result has thus been attained, that
no less than fifteen well-marked species of freshwater fishes
are altogether peculiar to the British Islands. The following
is the list, with their English names and localities :—!

Freshwater Fishes peculiar to the British Isles.

land, the N. of Eng-
land, and Wales.

1 The list of names was furnished to me by Dr, Giinther, and I have
added the localities from the papers containing the original descriptions;
and from Dr. Haughton’s British Freshwater Fishes.

322 ISLAND LIFE. [PART Il.

Latin Name. English Name. Locality.

5. SALMO STOMACHIcUS. | Gillaroo trout ........ Lakes of Ireland.

6. » NIGRIPENNIS.. | Black-finned trout.. | Mountain lochs of
Wales and Scotland.

7. » LEVENENSIS... | Loch Leven trout... | Loch Leven, Loch

‘Lomond, Winder-

mere.

8. 5) COP BRISM Ga ssas. Welsh charr........+. Llanberris lakes, N.
Wales.

9. » WiLLuensil.. | Windermere charr... | Lake Windermere and

others in N. of Eng-
land, and Lake Brui-
ach in Scotland.

10. » KILLINENSIS.. | Lough Killincharr.. | Killin lake in Mayo,
Ireland.

ee POOL Geka caeuns Cole's charr i. Joccaeere Lough Eske and Lough

Dan, Ireland.

12. ppt GRAM as acuta Gray's char ou.\...k Lough Melvin, Leitrim,
N. W. Ireland.

13. Coregonus cLUPE- | The gwyniad, or | Loch Lomond, Ulles-

OIDES schelly water, Haweswater,

and Bala lake.

14, a VANDEsIUs | The vendace ......... Loch Maben, Dum-
friesshire.

15. : POLDAN..25° |) Che pollam 0.003. Lough Neagh and
Lough Earne, N. of
Treland.

These fifteen peculiar fishes differ from each other and from
all British and continental species, not in colour only, but in
such important structural characters as the form and size of the
fins, the number of the fin-rays, and the form or proportions of
the head, body, or tail. They are in fact, as Dr. Giinther
assures me, just as good and distinct species as any other re-
cognised species of fish. It may indeed be objected that, until
all the small lakes of Scandinavia are explored, and their fishes
compared with ours, we cannot be sure that we have any peculiar
species. But this objection has very little weight if we consider
how our own species vary from lake to lake and from island to
island, so that the Orkney species is not found in Scotland, and
not one of the peculiar British species extends to Ireland, which
has no less than six species altogether peculiar to it. If the
species of our own two islands are thus distinct, what reason have
we for believing that they will be otherwise than distinct from
those of Scandinavia? At all events, with the amount of evi-
dence we already possess of the very restricted ranges of many of

CHAP.. XVI. | THE BRITISH ISLES, O20

our species, we must certainly hold them to be peculiar till they
have been proved to be otherwise.

The great speciality of the Irish fishes is very interesting,
because it is just what we should expect on the theory of
evolution. In Ireland the two main causes of specific change—
isolation and altered conditions—are each more powerful than in
Britain. Whatever difficulty continental fishes may have in
passing over to Britain, that difficulty will certainly be increased
by the second sea passage to Ireland ; and the latter country has
been longer isolated, for the Irish Sea with its northern and
southern channels is considerably deeper than the German Ocean
and the eastern half of the English Channel, so that, when the
last subsidence occurred, Ireland would have been an island for
some length of time while England and Scotland still formed
part of the continent. Again, whatever differences have been
produced by the exceptional climate of our islands will have been
greater in Ireland, where insular conditions are at a maximum,
the abundance of moisture and the equability of temperature
being far more pronounced than in any other part of Europe.

Among the remarkable instances otf lmited distribution
afforded by these fishes, we have the Loch Stennis trout
confined to the little group of Jakes in the mainland of Orkney,
occupying altogether an area of about ten miles by three; the
Welsh charr confined to the Llanberris lakes, about three miles
in length; Gray’s charr confined to Lough Melvin, about seven
miles long; while the Lough Killin charr, known only from a
small’ mountain lake in Ireland, and the vendace, from the
equally small lakes at Lochmaben in Scotland, are two examples
of restricted distribution which can hardly be surpassed.

Cause of Great Speciality in Fishes—The reason why fishes
alone should exhibit such remarkable local modifications in lakes
and islands is sufficiently obvious. It is due to the extreme
rarity of their transmission from one lake to another. Just as
we found to be the case in Oceanic Islands, where the means
of transmission were ample hardly any modification of species
occurred, while where these means were deficient and individuals
once transported remained isolated during a long succession of
ages, their forms and characters became so much changed as to

¥2

324 ISLAND LIFE. [PART IL.

bring about what we term distinct species or even distinct genera,
—so these lake fishes have become modified because the means
by which they are enabled to migrate so rarely occur. It is quite
in accordance with this view that some of the smaller lakes
contain no fishes, because none have ever been conveyed to them.
Others contain several; and some fishes which have peculiarities
of constitution or habits which render their transmission somewhat
less difficult occur in several lakes over a wide area of country,
though none appear to be common to the British and Ivish lakes.

The manner in which fishes are enabled to migrate from lake
to lake is unknown, but many suggestions have been made. It
is a fact that whirlwinds and waterspouts sometimes carry living
fish in considerable numbers and drop them on the land. Here
is one mode which might certainly have acted now and then in
the course of thousands of years, and the eggs of fishes may have
been carried with even greater ease. Again we may well suppose
that some of these fish have once inhabited the streams that
enter or flow out of the lakes as well as the lakes themselves;
and this opens a wide field for conjecture as to modes of migra-
tion, because we know that rivers have sometimes changed their
courses to such an extent as to form a union with distinct
river basins. This has been effected either by floods connect-
ing low watersheds, by elevations of the land changing lines of
drainage, or by ice blocking up valleys and compelling the
streams to flow over watersheds to find an outlet. This is known
to have occurred during the glacial epoch, and is especially
manifest in the case of the Parallel Roads of Glenroy, and it
probably affords the true solution of many of the cases in which
existing species of fish inhabit distinct river basins whether in
streams or lakes. Ifa fish thus wandered out of one river-basin
into another, it might then retire up the streams to some of the
lakes, where alone it might find conditions favourable to it. By
a combination of the modes of migration here indicated it is not
difficult to understand how so many species are now common to
tle lakes of Wales, Cumberland, and Scotland, while others less
able to adapt themselves to different conditions have survived
only in one or two lakes in a single district ; or these last may
have been originally identical with other forms, but have become

CHAP. XV1.] THE BRITISH ISLES, 325

modified by the particular conditions of the lake in which they
have found themselves isolated.

Peculiar British Insects—We now come to the class of insects,
and here we have much more difficulty in determining what are
the actual facts, because new species are still being yearly dis-
covered and considerable portions of Europe are but imperfectly
explored. It often happens that an insect is discovered in our
islands, and for some years Britain is its only recorded locality ;
but at length it is found on some part of the continent, and not
unfrequently has been all the time known there, but disguised
by another name, or by being classed as a variety of some other
species. This has occurred so often that our best entomologists
have come to take it for granted that all our supposed peculiar
British species are really natives of the continent and will one
day be found there; and owing to this feeling little trouble
has been taken to bring together the names of such as from
time to time remain known from this country only. The view of
the probable identity of our entire insect-fauna with that of the
continent 1s held by such well-known authorities as Mr. E. C. Rye
and Dr. D. Sharp for the beetles, and by Myr. H. T. Stainton
for butterflies and moths; but as we have already seen that
among two orders of vertebrates—birds and fishes—there are
undoubtedly peculiar British species, it seems to me that all the
probabilities are in favour of there being a much larger number
of peculiar species of insects. In every other island where
some of the vertebrates are peculiar—as in the Azores, the
Canaries, the Andaman Islands, and Ceylon—the insects show an
equal if not a higher proportion of speciality, and there seems
no reason whatever why the same law should not apply to us.
Our climate is undoubtedly very distinct from that of any part
of the continent, and in Scotland, Ireland, and Wales we possess
extensive tracts of wild mountainous country where a moist
uniform climate, an alpine or northern vegetation, and a con-
siderable amount of isolation, offer all the conditions requisite
for the preservation of some species which may have become
extinct elsewhere, and for the slight modification of others
since our last separation from the continent. I think, therefore,
that it will be very interesting to take stock, as it were, of our

326 ISLAND LIFE. [PART If.

recorded peculiarities in the insect world, for it is only by so
doing that we can hope to arrive at any correct solution of the
question on which there is at present so much difference of opinion.
For the list of Coleoptera with the accompanying notes I am
indebted to Mr. E. C. Rye; and Dr. Sharp has also given me
valuable information as to the recent occurrence of some of the
supposed peculiar species on the continent. For the Lepidoptera
I first noted all the species and varieties marked as British only
in Staudinger’s Catalogue of European Lepidoptera. This list
was carefully corrected by Mr. Stainton, who weeded out all the
species known by him to have been since discovered, and
furnished me with valuable information on the distribution and
habits of the species. This information often has a direct bear-
ing on the probability of the insect being peculiar to Britain,
and in some cases may be said to explain why it should be so.
For example, the larvees of some of our peculiar species of
Tineina feed during the winter, which they are enabled to do
owing to our mild and insular climate, but which the severer
continental winters render impossible. A curious example of
the effect this habit may have on distribution is afforded by one
of our commonest British species, Hlachista rufocinerea, the larva
of which mines in the leaves of Holcus mollis and other grasses
from December to March. This species, though common every-
where with us, extending to Scotland and Ireland, is quite
unknown in similar latitudes on‘ the continent, but appears
again in Italy, the South of France, and Dalmatia, where the
mild winters enable it to live in its accustomed manner.

Such cases as this afford an excellent illustration of those |
changes of distribution, dependent probably on recent changes
of climate, which may have led to the restriction of certain
species to our islands. For should any change of climate lead
to the extinction of the species in South Europe, where it
is far less abundant than with us, we should have a common
and wide-spread species entirely restricted to our islands.
Other species feed in the larva state on our common gorse, a
plant found only in limited portions of Western and Southern
Europe; and the presence of this plant in a mild and insular
climate such as ours may well be supposed to have led to the

CHAP. XVI.] THE BRITISH ISLES, 327

preservation of some of the numerous species which are or have
been dependent on it.

Mr. McLachlan has kindly furnished me with some valuable
information on certain species of Trichoptera or Caddis flies
which seem to be peculiar to our islands; and this completes
the list of orders which have been studied with sufficient care to
afford materials for such a comparison. We will now give the
list of peculiar British Insects, beginning with the Lepidoptera,
and adding such notes as have been kindly supplied by the
gentlemen already referred to.

List of the Species or Varieties of Lepidoptera which, so far as at present
known, are confined to the British Islands. (The figures show the dates
when the species was first described.)

DiuRNI,

1, Potyommatus pvispar. “The large copper.” This fine insect, once
common in the fens, but now extinct owing to extensive drainage, is
generally admitted to be peculiar to our island, at all events as a variety
or local form. Its continental ally differs constantly in being smaller
and in having smaller spots ; but the difference, though constant, is so
slight that it is now classed as a variety under the name of rutilus,
Our insect may therefore be stated to be a well-marked local form of a
continental species.

2, Lyceena astrarche, var, ARTAXERXES. This very distinct form is con-
fined to Scotland and the north of England. The species of which
it is considered a variety (more generally known to English entomo-
logists as P. agestis) is found in the southern half of England, and
almost everywhere on the continent.

BoMBYCES.

3. LirHosia sERIcEA. North of England (1861).

4. Hepialus humuli, var. HETHLANDICA. Shetland Islands (1865). A
remarkable form, in which the male is usually yellow and buff instead
of pure white, as in the common form, but exceedingly variable in
tint and markings.

5. EPICHNOPTERYX RETICELLA. Sheerness, Gravesend, and other localities
along the Thames (1847).

6. E. pulla, var. RApIELLA, Near London, rare (18307) ; the species in
Central and Southern Europe. (Doubtfully peculiar in Mr. Stainton’s
opinion. )

Nocrvuz.

7. AcRonycTA MyRic#. Scotland only (1852). <A distinct species.
8. AGROTIS SUBROSEA. Cambridgeshire and Huntingdonshire fens, perhaps
extinct (1835). The var. subcerulea is found in Finland and Livonia.

328 ISLAND LIFE. [PART I.

9. A. ASHWoRTHII. South and west (1855). Distinct and not uncommon.
10. DIANTHECIA BARRETTI. Ireland (1864). Perhaps a form of the con-
tinental D. luteago, Mr. McLachlan thinks. :
11. Aporophyla australis, var. PascuEA. South of England (1830?). This
is a variety of a species otherwise confined to the South of Kurope,
and is thus especially interesting.

GEOMETRA.

12. Boarmia gemmaria, var. PERFUMARIA. Near London (1866). A large
dark variety of a common species, distinctly marked ; perhaps a good
species, as the larva feeds on ivy, while the larva of B. gemmaria is
said to refuse this plant, and to die if it has nothing else to eat ; but
Mr. McLachlan thinks this wants confirmation.

13. Cidaria albulata, var. ertszaTA. East of England (1835). A variety of
a Species otherwise confined to Central and Southern Europe.

14, EupITHeciA consTRicTATA. Widely spread, but local (1857). Larva
on thyme.

PYRALIDINA.
15. Aglossa pinguinalis, var. STREATFIELDI. Mendip Hills, unique! (1830?)
A remarkable and distinct variety of the common “ tabby.”
16. AsopiA PICTALIS. Unique (1830?). Perhaps an imported species.
17. ScopaRiA ALPINA. Scotland (1859).

TORTRICINA.

18. TERAS SHEPHERDANA. Fens of Cambridgeshire (1852).

19, CocuyLis DiLucIDANA. South of England (1829). Scarce, larva in
stems of the wild parsnip.

20. APHELIA NIGROVITTANA. Scotland (1852). A local form of the
generally distributed A. lanceolana.

21. EupEmis FULIGANA. South-east of England (1828). Rare, on fleabane.

22. GRAPHOLITHA N#HVANA. Generally distributed (1845). Doubtfully
distinct from continental species in Mr, Stainton’s opinion.

23. G. PARVULANA. Isle of Wight (1858?). Rare. A distinct species.

24. G. werrana. South of England (1850). A distinct species.

TINEINA,

25. TINEA COCHYLIDELLA. Sanderstead near Croydon (1854). Unique!

26. T. PALLESCENTELLA. Near Liverpool (1854). Abundant ; probably
imported in wool, Mr. Stainton thinks. :

27. T. FLAVESCENTELLA, Near London (1829). Scarce, perhaps imported. °

28, ACROLEPIA BETULETELLA. Yorkshire and county of Durham (1840).
Rare.

29, ARGYRESTHIA sEMIFUSCA. North and West of England (1829). Scarce;
a distinct species,

30. GELECHIA DIVISELLA, A fen insect (1854), Rare.

CHAP, XVI.] THE: BRITISH ISLES. 329

32.
33.

34,
35.
36.
ole
38.
39.

40,
Al,

42,
43.
44,
45.
46,

47.

48.
49,

50.
51.

57,

58.

G. CELERELLA. West of England (1854),

BRYOPHILA POLITELLA. Moors of N. of England (1854).

LITA FRATERNELLA. Widely scattered (1834). Larva feeds in shoots
of Stellaria uliginosa in spring. Mr. Stainton thinks it has been over-
looked abroad.

ANACAMPSIS SIRCOMELLA. North and West England (1854). Perhaps
a melanic variety of the more widely spread A. teniolella.

A. IMMACULATELLA, West Wickham (1834). Unique! A distinct
species.

GLYPHIPTERYX CLADIELLA. Eastern Counties (1859), Abundant.

G. SCHGNICOLELLA. In several localities (1859).

GRACILLARIA STRAMINELLA. North Britain (1850), Perhaps a local
form of the more southern G. elongella.

ORNIX LOGANELLA. Scotland (1848). Abundant, and a distinct species.

O. DEVONIELLA. In Devonshire (1854). Unique!

CoLEOPHORA ALBICOSTA. Widely spread (1829). Common on furze
(Ulex ewropeus). May probably be found in the North-west of
France, where the food-plant abounds.

. SATURATELLA. South of England (1850), Abundant on broom.

. INFLAT#&. South of England (1857), On Silene inflata.

. SQUAMOSELLA. Surrey (1856). Very rare, but an obscure species.

. SALINELLA. On Sea-coast (1859). Abundant.

ERITTIA OBSCUREPUNCTELLA. Widely scattered (1848). Larva feeds
on common honeysuckle in July. Mr. Stainton thinks it must have
been overlooked on the continent.

ELACHISTA FLAVICOMELLA, Dublin (1856). Excessively rare, two

specimens only known.

E. CONSORTELLA, Scotland (1854). A doubtful species.

EK. MEGERLELLA. Widely distributed (1854). Common. Larva feeds
in grass during winter and early spring.

E. oBLIQUELLA. Near London (1854). Unique!

H, ELEOCHARIELLA. North and Kast of England (1854). An obscure
form.

"ie Oe @

2, E. suBOCELLEA. Widely distributed (1835). An obscure form. Perhaps

mixed on the continent with other species.

. E. rrratomea. In chalk and limestone districts (1812). Abundant

and distinct.

. E, TRISERIATELLA, South of England (1854). Very local ; an obscure

species.

. LITHOCOLLETIS NIGRESCENTELLA. Northumberland (1850). Rare; a

dark form of LZ. Bremiella, which is widely distributed.

. L. iRRADIELLA. North Britain (1854). A northern form of the more

- southern and wide-spread L. lautella.

L. TRIGUTTELLA. Sanderstead, near Croydon (1848). Unique! very
peculiar.

L, uLIcIcOLELLA, In a few wide-spread localities (1854). A peculiar
form.

330 ISLAND LIFE. [PART Il.

59. L. CALEDONIELLA. North Britain (1854). A local variety of the more
widespread L. corylifoliella.
60. L. punninereLLA. North of England (1852). A somewhat doubtful

species.

61. BuccULATRIX DEMARYELLA. Widely distributed (1848). Rather
common.

62. TRIFURCULA SQUAMATELLA. South of England (1854). <A doubtful
species.

63. T. ATRIFRONTELLA. South of England, also in Lancashire (1854). Very

rare and peculiar.
64, NEPTICULA IGNOBILIELLA. Widely scattered (1854). On hawthorn,

not common.
65. N. poreri. South of England (1858). Bred from Larve in Poteriwm
sanguisorba.
66. N. quinquELLA. South of England (1848). On oak-leaves, very local.
67. N. aprcetia. Local (1854). Probably confused with allied species on
the continent.
68, N. HEADLEYELLA. Local (1854), A rare species.
PTEROPHORINA.
69. AGDISTIS BENNETTII. East coast (1840). Common on Statice limonium.

We have here a list of sixty-nine species, which, according
to the best authority, are, in the present state of our know-
ledge, pecuhar to Britam. It isa curious fact that only five of
these have been described less than twenty years ago; and as
during all that time they have not been recognised on the
continent, notwithstanding that good coloured figures exist of
almost all of them, it seems highly probable that many of them
are really confined to our island. At the same time we must
not apply this argument too rigidly, for the very day before my
visit to Mr. Stainton he had received a letter from Professor
Zeller announcing the discovery on the continent of a species of
our last family, Pterophorina, which for more than forty years had
been considered to be exclusively British. This insect, Platyptila
similidactyla (Pterophorus isodactylus, Stainton’s Manual), had
been taken rarely in the extreme north and south of our islands—
Teignmouth and Orkney, a fact which seemed somewhat indica-
tive of its being a straggler. Again, seven of the species are
unique, that is, have only been captured once; and it may be
supposed that, as they are so rare as to have been found only
once in England, they may be all equally rare and not yet found
on the continent. But thisis hardly in accordance with the laws

CHAP. XVI.] THE BRITISH ISLES. 351

of distribution. Widely scattered species are generally abun-
dant in some localities; while, when a species is on the point of
extinction, it must for a time be very rare in the single locality
where it last maintains itself. It is then more probable that
some of these unique species represent such as are almost
extinct, than that they have a wide range and are equally rare
everywhere ; and the peculiarity of our insular climate, combined
with our varied soil and vegetation, offer conditions which may
favour the survival of some species with us after they have
become extinct on the continent.

In the list here given nine are recorded as varieties, while
ten more, in Mr. Stainton’s opinion, ought probably to be
classed as varieties or local forms of other species, making
nineteen in all. This leaves no less than fifty undoubted species
not yet found beyond our islands; and though Mr. Stainton
thinks that most of these will ultimately be found on the
continent, we can hardly doubt, both from general considerations
dependent on the laws of distribution, and from the peculiar
habits, conspicuous appearance and restricted range of many of
our species, that a very considerable number will remain
permanently as peculiar British insects.

Peculiarities of the Isle of Man Lepidoptera.—Before quitting
the Lepidoptera, it will be well to notice some very interest-
ing examples of local modification, apparently brought abbut
by extreme conditions of exposure and insulation, and which
throw some light on the way in which local forms, varieties, or
species may be produced. This interesting phenomenon occurs
in the Isle of Man, where Mr. Edwin Birchall has collected
Lepidoptera assiduously, and has discovered a number of varieties,
apparently peculiar to the island, of which he has been so
good as to send me specimens accompanied by some valuable
notes.

The Isle of Man has no woods, bogs, or heaths, the moun-
tains being mostly covered with grass and rocks, so that a very
abundant insect-fauna cannot be expected. Sixteen species of
butterflies have been observed, and of these only one—the
common tortoise-shell (Vanessa urtice) presents any peculiarity.
This, however, is always remarkably small, a specimen rarely

332 ISLAND LIFE. [PART IT,

being found to equal the smallest English specimens; so that
we must look upon it as dwarf race developed in the Island and
confined to it.

The following moths also present definite peculiarities :

1. Agrotis lucernea, var. This is of a grayish-black colour, with hardly any
markings. All are alike, and are very distinct from the common type
of the species, which is abundant in Wales.

2. Corrhedia xerampelina, var. This is much darker and more richly
coloured than the English form, the yellow band being reduced to a
narrow line, sometimes a mere thread. This would doubtless be
regarded as a distinct species if it occurred with equal constancy in
some more remote island.

3. Dianthecia capsophila, var. This is an exceedingly dark and richly
marked form of the Irish D. capsophila, itself a local variety, Mr.
Birchall thinks, of D. carpophaga.

4. Dianthecia cesia, var, This is another dark form of a rare Irish and
continental species.

5. Tephrosia biundularia, var. This is an exceedingly dark form, and differs
so much from North of England specimens as to have all the appear-
ance of another species. Mr. Birchall has bred it from captured
parents, and finds that the produce is this dark form only.

We will now pass on to the Coleoptera, or beetles, an order
which has been of late years energetically collected and
carefully studied by British entomologists.

List of the Species of Beetles which, so far as at present known, are confined
to the British Islands.

CARABIDA,

1. DRomius vecTensis (Rye). Common in the Isle of Wight, not known
elsewhere,

2. *Harpalus latus, var. METALLESCENS (Rye). Unique, but very marked !
South coast..,

3. STENOLOPHUS DERELICTUS (Dawson). Unique! North Kent.

HELOPHORIDA.
4. *OcHTHEBIUS PowERI (Rye). Very marked. S, coast. A few specimens
only.
BRACHYELYTRA.

5. *ALEOCHARA HIBERNICA (Rye). Ireland. Mountain tops.
6. *OxypopA RuPIcOoLA (Rye). Scotland. Mountain tops; several
specimens,

CHAP, XV1. | THE BRITISH ISLES. 333 _

°@

35.

*“OXYPODA EDINENSIS (Sharp). Scotland.
e VERECUNDA (Sharp). Scotland.
3 WATERHOUSEI (Rye). London district.
HoMALOTA EXIMIA (Sharp).
iS CLAVIPES (Sharp). Scotland on mountains ; not rare.
a OBLONGIUSCULA (Sharp). [Scotland, perhaps also Swiss.
y PRINCEPS (Sharp). A coast insect.
ii CURTIPENNIS (Sharp).
$3 WXARATA (Sharp).
s PUBERULA (Sharp).
. INDISCRETA (Sharp).
_ ATRICOLOR (Sharp). {Some continental authors deny that
is GERMANA (Sharp). there are good species (Sharp).
* SETIGERKA (Sharp).
eee SHARPI (Rye). Very marked, unique!

2. *BRYOPORUS CASTANEUS (Hardy and Bold). Very marked, unique !

Northumberland Hills.

. *STENUS OSCILLATOR (Rye). Unique! South coast.
. *Scop#us rye1 (Wollaston). Very distinct; Dorset coast; several

specimens.

. *TROGOPHLHUS SPINICOLLIS (Rye). Mersey estuary, unique! Most

distinguishable, nothing like it in Europe.

. Lesteva sHArPI (Rye). Scotch hills.
. Eupretus wurter (Sharp). Scotch hills. Probably a variety of Z.

Giraudi of Austria (the only Europexn species) fide Kraatz (Sharp).

. *HOMALIUM RUGULIPENNE (Rye). Hxceedingly marked form. Northern,

western, and southern coasts ; rare.

PsELAPHIDA.

. Bryaxts cotus (Sharp). Coast.

, WATERHOUSE! (Rye). Coast.

. *BYTHINUS GLABRATUS (Rye). Sussex coast; a few specimens ; very

distinguishable ; myrmecophilous (lives in ants’ nests).

TRICHOPTERYGID &.
. PTINELLA MARIA (Matthews)
. TRICHOPTERYX SAR ( aie ue)
5 POWERI Chine area)
es EDITHTA ( see)
5 CANTIANA ( saat)
ee FUSCULA ( ee)
” KIRBII ( ” )
Bs FRATERCULA ( ae)
i WATHRHOUSIT AG...) )
- CHAMETONIS tn (hi, hy)
r JANSONI Cae ae tes)

334 ISLAND LIFE. [PART IT,

43. TRICHOPTERYX SEMINITENS (Matthews).

44, i SUFFOCATA (Haliday). Ireland.

A5, DISPAR (Matthews).

46. i CARBONARIA (Matthews).

47, Prinium HALIDAYI (Matthews).

48, > CALEDONICUM (Sharp). Scotland ; very marked form.

49, i INSIGNE (Matthews).
50. AcTIDIUM concoLoR (Sharp). Scotland; very marked.
1, PTENIDIUM KRAATZII (Matthews).

ANISOTOMIDZ.

52. *AGATHIDIUM RHINOCEROS (Sharp). Old fir-woods in Perthshire ;
local, many specimens ; a very marked species.
53. ANISOTOMA SIMILATA (Rye). Unique! South of England.

es a LUNICOLLIS (Rye). North-east and South of England, a
very marked form ; several specimens.
55. * is CLAVICORNIS (Rye). Unique! Scotland.

PHALACRID.
56. *PHALACRUS BRISOUTI (Rye). A few specimens. South of England,

CRYPTOPHAGIDZ..
57. ATOMARIA WOLLASTONI (Sharp). Unique! Scotland.
58, 9 DIVISA (Rye). Unique! South of England.
LATHRIDIDE.

59. CoRTICARIA WOLLASTONI (Waterhouse). South coast.

BYRRHID.
60. SYNCALYPTA HIRSUTA (Sharp).

ELATERID.
61. Eater coccinatus (Rye). Very marked, but possibly a variety of the
European £. preustus, South of England.

TELEPHORIDZ.

62, *TELEPHORUS DARWINIANUS (Sharp). Scotland, sea-coast. A stunted
form of abnormal habits.

CYPHONIDA.
63. CYPHON PUNCTIPENNIS (Sharp). Scotland.

ANTHICIDA.

64. AnTuicus saALinus (Crotch). South coast.

60.9% » scoricus (Rye). Loch Leven ; very distinct; many specimens.

CHAP, XVI. | THE BRITISH ISLES. 335

CURCULIONIDA.

66. *CATHORMIOCERUS MARITIMUS (Rye). A few specimens on our south
coast. A curious genus, only found elsewhere on the coasts of the
Mediterranean !

67. *Ceuthorhynchus contractus, var. PALLIPES (Crotch). Lundy Island ;
several specimens. A curious variety only known from this island.

68. *Lriosomus TROGLODYTES (Rye). A very queer form. Two or three
specimens. South of England.

69. *Apion RYEI (Blackburn). Shetland Islands. Several specimens.

HALTICIDA.
70. THYAMIs AGILIS (Rye). South of England ; many specimens.
y DISTINGUENDA (Rye). South of England; many specimens.

71. *PSYLLIODES LURIDIPENNIS (Kutschera). Lundy Island. <A very
curious form, not uncommon in this small island, to which it appears
to be confined.

CoccINELLID&.
72. ScYMNUS LivipUsS (Bald). Northumberland. A doubtful species.

Of the seventy-two species of beetles in the preceding list, a
considerable number no doubt owe their presence there to the -
fact that they have not yet been discovered or recognised on
the continent. This is almost certainly the case with many of
those which have been separated from other species by very
minute and obscure characters, and especially with the exces-
sively minute Trichopterygide described by Mr. Matthews.
There are others, however, to which this mode of getting rid of
them will not apply, as they are so marked as to be at once
recognised by any competent entomologist, and often so plentiful
that they can be easily obtained when searched for. Of this
class are the twenty-three species whose names are marked
with an asterisk (*), being those which, in Mr. Rye’s opinion,
are most likely to be peculiar to the localities where they are
found if any are,—but of this he is still somewhat sceptical.
Six of these are unique, leaving seventeen which have occurred
either rarely or in some abundance. Dividing the probably
peculiar species according to locality, we find that the South of
England has produced 9, North of England 2, Scotland 6,
Ireland 1, Shetland Islands 1, and Lundy Island 2. These

336 ISLAND LIFE. [PART Il,

numbers are, generally speaking, proportionate to the richness of
the district and the amount of work bestowed upon it ; Scotland,
however, giving more than its due proportion in this respect,
which must be imputed to its really possessing a greater amount
of speciality. The single peculiar Irish species stands as a monu-
ment of our comparative ignorance of the entomology of the
sister isle. The peculiar species of Apion in the Shetland
Tslands is interesting, and may be connected with the very
peculiar climatal conditions there prevailing, which have led in
some cases to a change of habits, so that a species of weevil
(Otiorhynchus maurus) always found on mountain sides in Scotland
here occurs on the sea-shore. Still more curious is the occur-
rence of two distinct forms (a species and a well-marked variety)
on the small granitic Lundy Island in the Bristol Channel.
This island is about three miles long and twelve from the coast
of Devonshire, consisting mainly of granite with a little of the
Devonian formation, and the presence here of peculiar insects
can only be due to isolation with special conditions, and im-
munity from enemies or competing forms. When we consider
the similar islands off the coasts of Scotland and Ireland, with
the Isle of Man and the Scilly Islands, none of which have
been yet thoroughly explored for beetles, it is probable that
many similar examples of peculiar isolated forms remain to be
discovered.

Mr. Rye hardly thinks it possible that the Dromius vectensis
can really be peculiar to the Isle of Wight, although it is abun-
dant there, and has never been found elsewhere ; but the case
of Lundy Island renders it less improbable; and when we con-
sider that the Arwm italicum, Calamintha sylvatica, and perhaps
one or two other plants are found nowhere else in the British Isles,
we must admit that the same causes which have acted to restrict
the range of a plant may have had a similar effect with a beetle.

I must also notice the Cathormiocerus maritimus, because
its only near ally inhabits the coasts of the Mediterranean; and
it thus offers an analogous case to the small moth, Hlachista
rufocinerea, which is found only in Britain and the extreme
South of Europe. Looking, then, at what seem to me the proba-
bilities of the case from the standpoint of evolution and natural

_ CHAP. XVI.) THE BRITISH ISLES, 337

selection, and giving due weight to the facts of local distribution
as they are actually presented to us, I am forced to differ from
the opinion held by our best entomological authorities, and to
believe that some considerable proportion of the species which,
in the present state of our knowledge, appear to be peculiar to
our islands, are, not only apparently, but really, so peculiar.

I am indebted to Mr. Robert McLachlan for the following in-
formation on certain Trichopterous Neuroptera (or caddis-flies)
which appear to be confined to our islands. The peculiar
aquatic habits of the larve of these insects, some living in
ponds or rivers, others in lakes, and others again only in clear
mountain streams, render it not improbable that some of them
should have became isolated and preserved in the mountain
districts of our western coasts, or that they should be modified
owing to such isolation. In these insects the characters depended
on to separate the species are wholly structural, and the care
with which Mr. McLachlan has studied them renders it certain
that the species here referred to are not mere varieties of known
continental forms, however closely they may resemble them in
form and coloration.

Trichoptera peculiar to the British Isles.

1, SETODES ARGENTIPUNCTELLA.—This species is known only from the
Lakes Windermere and Killarney. It has recently been described by Mr.
McLachlan, and is quite distinct from any known species though allied to
S. punctata and S. viridis, which inhabit France and Western Europe.

2. RHYACOPHILA MUNDA.—Described by Mr. McLachlan in 1863. A
very distinct species, found only in mountain streams in Wales and
Devonshire.

3, PHILOPOTAMUS INSULARIS. (? A variety of P. montanus.)—This can
hardly be termed a British species or variety, because, so far as at present
known, it is peculiar to the island of Guernsey. It agrees structurally
with P. montanus, a species found both in Britain and on the continent,
but it differs in its strikingly yellow colour, and less pronounced markings,
All the specimens from Guernsey are alike, and resident entomologists
assured Mr. McLachlan that no other kind is known. Strange to say,
some examples from Jersey differ considerably, resembling the common
European and British form. Even should this peculiar variety be at some
future time found on the continent it would still be a remarkable fact that
the form of insect inhabiting two small islands only twenty miles apart
should constantly differ ; but as Jersey is between Guernsey and the coast, it
seems just possible that the more insular conditions, and perhaps some

338 ISLAND LIF. [PART II.

peculiarity of the soil and water in the former island, have really led to
the production or preservation of a well-marked -variety of insect.

Land and Fresh-water Shells—As regards the land and
fresh-water mollusca it seems difficult to obtain accurate infor-
mation. Several species have been recorded as British only,
but Iam informed by Mr. Gwyn Jeffries that most of these are
decidedly continental, while a few may be classed as varieties of
continental species. According to the late Mr. Lovell Reeve
the following species are peculiar to our islands; and although
the first two seem extremely doubtful, yet the last two, to which
alone we accord the dignity of capital type, may not improbably
be peculiar to Ireland, being only found in the remote south-
western mountain region, where the climate possesses in the
highest degree the insular characteristics of a mild and uniform
temperature with almost perpetual moisture, and where several
of the peculiar Irish plants alone occur.

1. Cyclas pisidioides.—A small bivalve shell found in canals. Perhaps
a variety of C. corneum or C. rivicola according to Mr Gwyn Jeffries,

2. Assiminia grayana.—A small univalve shell allied to the periwinkles,
found on the banks of the Thames between Greenwich and Gravesend, on
the mud at the roots of aquatic plants.

3. GEOMALACUS MACULOSUS.—A beautiful slug, black, spotted with yellow
or white. It is found on rocks on the shores of Lake Carogh, south of
Castlemain Bay, in Kerry, It was discovered in 1842, and has never been
found in any other locality. An allied species is found in Portugal and
France, which Mr, Gwyn Jeffries thinks may be identical.

4, Limna@A INvoLUTA.—A_ beautiful pond-snail with a small polished
amber-coloured shell, found only in a small alpine lake and its inflowing
stream on Cromaghaun mountain near the lakes of Killarney. It appears
to be a very distinct species, most nearly allied to ZL. glutinosa which is
not found in Ireland. It was discovered in 1832, and has frequently been
obtained since in the same locality.

The facts—that these two last-named species have been known
for about forty or fifty years respectively, that they have never
been found in any other locality than the above named very
restricted stations, and that they have not yet been clearly iden-
tified with any continental species, all point to the conclusion
that they are the last remains of peculiar forms which have
everywhere else become extinct.

Peculiarities of the British Flora.—Thinking it probable

CHAP. XV1.] THE BRITISH ISLES. ~ 339

that there must also be some peculiar British plants, but
not finding any enumeration of such in the British Floras of
Babington, Hooker, or Bentham, I applied to the greatest living
authority on the distribution of British plants—Mr. H. C.
Watson, who has very kindly given me all the information I
required, and I cannot do better than quote his words. He
says: “It may be stated pretty confidently that there is no
‘species’ (generally accepted among botanists as a good species)
peculiar to the British Isles. ‘True, during the past hundred
years, nominally new species have been named and described on
British specimens only, from time to time. But these have
gradually come to be identified with species described elsewhere
under other names—or they have been reduced in rank by suc-
ceeding botanists, and placed or replaced as varieties of more
widely distributed species. In his Sritish Rubi Professor
Babington includes as good species, some half-dozen which he
has, apparently, not identified with any foreign species or variety.
None of these are accepted as ‘true species,’ nor even as ‘sub-
species’ in the Students’ Flora, where the brambles are
described by Baker, a botanist well acquainted with the plants
of Britain. And as all these nominal species of Rubi are of late
creation, they have truly never been subjected to real or critical
tests as ‘ species.’ ”

But besides these obscure forms, about which there is so much
difference of opinion among botanists, there are a few flowering
plants which, as varietves or sub-species, are apparently peculiar
to our islands. These are:—(1) Helianthemum Breweri, an
annual rock-rose found only in Anglesea and Holyhead
Island (classed as a sub-species of A. guttatum by Hooker
and Babington); (2) Rosa hibernica, found only in North
Britam and Ireland (a species long thought peculiar to the
British Isles, but said to have been recently found in France) ;
(8) Gnanthe fluviatilis, a water-dropwort, found only in the
south of England and in one locality in Ireland (classed
as a sub-species of @. phellandrium by Hooker) ; (4) Hieracium
wricum, a hawk-weed found in North Britain and Ireland (classed
by Hooker as a sub-species of H. Lawsoni, and said to be

“confined to Great Britain).”
Z 2

340 ISLAND LIFE. [PART II.

Two other species are, so far as the European Flora is con-
cerned, peculiar to Britain, being natives of North America,
and they are very interesting because they are certainly both
truly indigenous, that is, not introduced by human agency. These
are,— (1) Spiranthes romanzoviana, an orchid allied to our
ladies’ tresses, widely distributed in North America, but only
found elsewhere in the extreme south-west corner of Ireland ;
and (2) Hriocaulon septangulare—the pipewort—a curious
North American water-plant, found in lakes in the Hebrides and
the west of Ireland. Along with these we may perhaps class
the beautiful Irish filmy fern—TZrichomanes radicans, which
inhabits the Azores, Madeira and Canary Islands, the south-
west of Ireland, Wales, and formerly Yorkshire, but is not
certainly known to occur in any part of continental Europe
(except perhaps the south-west of Spain), though found in many
tropical countries.

We may here notice the interesting fact that Ireland possesses
no less than twenty species or sub-species of flowering plants not
found in Britain, and some of these may be altogether peculiar.
As a whole they show the effect of the pre-eminently mild and
insular climate of Ireland in extending the range of some south
Kuropean species. The following lists of these plants, with a
few remarks on their distribution, will be found interesting :—

List oF IRISH FLOWERING PLANTS WHICH ARE NOT FOUND IN BRITAIN.

1. Helianthemum guttatum. Ireland, near Cork, and on an island off
the coast of Galway (also Channel Islands, France, Italy).
2. Arenaria ciliata. S. W. Ireland (also Auvergne, Pyrenees, Crete), A
variety of this species has been recently found in Pembrokeshire.
3. Sawifraga umbrosa. W. Ireland (also N. Spain, Portugal).
A, » .geum. §. W. Ireland (also Pyrenees),
5. Pe hirsuta. SS. W. Ireland (also Pyrenees),
6. Saxifraga hirta (hypnoides sub. sp.). 8. Ireland, apparently unknown
on the continent.
7. Inula salicina. W. Ireland (Middle and South Europe).
8, Erica mediterranea. W. Ireland (W. France, Spain, Mediterranean).
9. ,, mackiana (tetraliz sub.-sp.) W. Ireland (Spain).
10. Arbutus unedo. S. W. Ireland (8. of France and Spain).
11. Dabeocia polifolia, W. Ireland (W. of France and Spain).
12, Pingiucula grandiflora. 8. W. Ireland (W. of France, Spain, Alps, &c.).
13. Neotinea intacta. W. Ireiand (France, 8. Europe).

CHAP, av, | THE BRITISH ISLES. o4l

14, Spiranthes romanzoviana 8. W. Iveland (North America).

15. (Sisyrinchium bermudianum. W. Ireland? introduced; (North America. )

16. Potamogeton longifolius (lucens. var.) W. Ireland, unique specimen !

17. 3 kirkii (natans sub.-sp.). W. Ireland (Arctic Europe),

18. Eriocaulon septangulare. W. Ireland, Skye, Hebrides (North America).

19. Carex buxbaumit. N. EH. Ireland, on an island in Lough Neagh (Arctic
and Alpine Europe, North America).

20. Calamagrostis stricta (var. Hooker’), On the shores and islands of Lough
Neagh. The species occurs at one locality in Cheshire (Germany,
Arctic Europe, and North America).

We find here nine south-west European species which
probably had a wider range in mild preglacial times, and have
been preserved in the south and west of Ireland owing to its
milder climate. It must be remembered that during the height
of the glacial epoch Ireland was continental, so that these plants
may have followed the retreating ice to their present stations and
survived the subsequent depression. This seems more probable
than that so many species should have reached Ireland for the
first time during the last union with the continent subsequent
to the glacial epoch. The Arctic, Alpe, and American plants
may all be examples of species which once had a wider range,
and which, owing to the more favourable conditions, have con-
tinued to exist in Ireland while becoming extinct in the adjacent
parts of Britain and Western Europe.

As contrasted with the extreme scarcity of peculiar species
among the flowering plants, it 1s the more interesting and un-
expected to find a considerable number of peculiar mosses and
Hepatice, some of which present us with phenomena of distri-
bution of a very remarkable character. For the following lists
and the information as to the distribution of the genera and
species Tam indebted to Mr. Wiliam Mitten, one of the first
authorities on these beautiful little plants.

List oF THE Species oF Mosses AND HEPATIC WHICH ARE PECULIAR TO
THE Brirish Istes (OR NOT FOUND IN EUROPE).

(Those belonging to non-European genera in Italics. )

MossEs.
1, Systegium multicapsulare ...... Central and South England.
2. ‘3 MATE CTMG os eee inth oe South of England. . |
3. Campylopus shawil............666 North Britain.
4, BeLILONIUS Vis skces. Ireland.

+P)

342 ISLAND LIFE. [PART JI.
5. Seligeria calcicola (sy. ...00.) sesso South of England,
Go Pottia, virmdatoliay s,s. geese South of England.
7. Leptodontium recurvifolium... Ireland and Scotland.
8. Lortula wooduss sczcsccuncue. Ireland.
o oe MAD STMICa sn serene Jreland.
10. Streptopogon gemmascens ....... Sussex.
11. Grimmia subsquarrosa............ North Britain.
12; re SEITE OMI nasvo.ssesacceton North Britain.
13. Glyphomitrium daviesii......... On basalt generally.
14. Zygodon nowellii ................ North Britain.
15. SBryini bamMesit io cc, . 0s esa sans North Britain.
16. Hookeria laetevirens............045 Ireland and Cornwall (also Madeira).
17, Daltonia splachnoides ......... we Ireland.
HEPATION.
1. Gymnomitrium crenulatum ... West England, Ireland.
Ay radula volabar ai. ceciuse sacs setts Ireland and Wales.
B. Acrobolbus Wilson .ccecessscst es Treland.
A, Lejeunia calyptrifolia ........065. Cornwall, Lake district, Ireland.
5. 539). ANIAETOSCOPLCE.. vwcenes see Treland.
6. Lophocolea spicata ............... Treland.
7, Jungermannia cuneifolia ....... Treland.
8. i domiana?, Wess. Scotland.
9. ‘Petalophyllum ralfsit.........00 West Britain, Ireland.

Many of the above are minute or obscure plants, and are
closely allied to other European species with which they may
have been confounded. We cannot therefore lay any stress on
these individually as being absent from the continent of Europe
so much of which is imperfectly explored, though it is probable
that some of them are really confined to Britain. But there are
a few—uindicated by italics—which are in a very different
category; for they belong to genera which are altogether un-
known in any other part of Europe, and their nearest allies are
to be found in the tropics or in the southern hemisphere. The
three non-European genera of mosses to which we refer all have
their maximum of development in the Andes, while the three
non-European Hepatice appear to have their maximum in the
temperate regions of the southern hemisphere. Mr. Mitten
has kindly furnished me with the following particulars of the
distribution of these genera :—

STREPTOPOGON is a comparatively small genus, with seven species in the
Andes, one in the Himalayas, and three in the south temperate zone, besides
our English species.

DALTONIA is a large genus of inconspicuous mosses, having seventeen
epecies in the Andes, two in Brazil, two in Mexico, one in the Galapagos,

——

CHAP, XVI.] THE BRITISH ISLES. 343

six in India and Ceylon, five in Java, two in Africa, and three in the
Antarctic Islands, and one in Ireland.

HOOKERIA (restricting that terin to the species referable to Cyclodictyon)
is still a large genus of handsome and remarkable mosses, having twenty-
six species in the Andes, eleven in Brazil, eight in the Antil'es, one in Mexico,
two in the Pacific Islands, one in New Zealand, one in Java, one in India,
and five in Africa—besides our British species, which is found also in
Madeira and the Azores but in no part of Europe proper.

These last two are very remarkable cases of distribution, since
Mr. Mitten assures me that the plants are so markedly different
from all other mosses that they would scarcely be overlooked in
Europe.

The distribution of the non-European genera of Hepaticz is
as follows :—

AcroBoLbus, A small! genus found only in New Zealand and the adjacent
islands, besides Ireland.

LeseuNIA. <A very extensive genus abounding in the tropical regions of
America, Africa, the Indian Archipelago, and the Pacific Islands, reaching
to New Zealand and Antarctic America, sparingly represented in the British
and Atlantic Islands, and in North America.

PreraLopHYLLUM. A small genus confined to Australia and New Zealand
_ in the southern hemisphere, and Ireland in the northern.

We have also a moss—Myurium hebridarum—found only in Scotland and
the Atlantic Islands; and one of the Hepatice—WJMastigophara woodsti—
found in Ireland and the Himalayas, the genus being most developed in
New Zealand, and unknown in any part of continental Europe.

These are certainly very interesting facts, but they are by no
means so exceptional in this group of plants as to throw any
doubt upon’ their accuracy. The Atlantic islands present very
similar phenomena in the khamphidiwm purpuratum, whose
nearest allies are in the West Indies and South America; and
in three species of Sciaromium, whose only allies are in New
Zealand, Tasmania, and the Andes of Bogota. An analogous
and equally curious fact is the occurrence in the Drontheim
mountains, in Central Norway, of a little group of four or five
peculiar species of mosses of the genus Mnium, which are found
nowhere else; although the genus extends over Europe, India,
and the southern hemisphere, but always represented by a very
few wide-ranging species except in this one mountain group !}

1 T am indebted to Mr, Mitten for this curious fact.

344 ISLAND LIFE. [PART IL,

Such facts show us the wonderful delicacy of the balance of
conditions which determine the existence of particular species
in any locality. The spores of mosses and Hepaticz are so
minute that they must be continually carried through the air
to great distances, and we can hardly doubt that, so far as its
powers of diffusion are concerned, any species which fruits
freely might soon spread itself over the whole world. That
they do not do so must depend on peculiarities of habit and con-
stitution, which fit the different species for restricted stations
and special climatic conditions; and according as the adaptation
is more general, or the degree of specialisation extreme, species
will have wide or restricted ranges. Although their fossil
remains have been rarely detected, we can hardly doubt that
mosses have as high an antiquity as ferns or Lycopods; and
coupling this antiquity with their great powers of dispersal we
may understand how many of the genera have come to occupy
a number of detached areas scattered over the whole earth, but
always such as afford the peculiar conditions of climate and
soil best suited to them. The repeated changes of temperature
and other climatic conditions, which, as we have seen, occurred
through all the later geological epochs, combined with those
slower changes caused by geographical mutations, must have
greatly affected the distribution of such ubiquitous yet delicately
organised plants as mosses. Throughout countless ages they
must have been in a constant state of comparatively rapid
migration, driven to and fro by every physical and organic
change, often subject to modification of structure or habit, but

always seizing upon every available spot in which they could —

even temporarily maintain themselves.

Here then we have a group in which there is no question of
the means of dispersal; and where the difficulties that present
themselves are not how the species reached the remote localities
in which they are now found, but rather why they have not
established themselves in many other stations which, so far as
we can judge, seem equally suitable to them. Yet it is a curious
fact, that the phenomena of distribution actually presented by
this group do not essentially differ from those presented by the
higher flowering plants which have apparently far less diffusive

—

CHAP. XVI. ] THE BRITISH ISLES: 345

power, as we shall find when we come to treat of the floras of
oceanic islands; and we believe that the explanation of this is,
that the life of species, and especially of genera, is often so
prolonged as to extend over whole cycles of such terrestrial
mutations as we have just referred to; and that thus the
majority of plants are afforded means of dispersal which are
usually sufficient to carry them into all suitable localities on the
globe. Hence it follows that their actual existence in such
localities depends mainly upon vigour of constitution and adap-
tation to conditions just as it does in the case of the lower and
more rapidly diffused groups, and only partially on superior
facilities for diffusion. This important principle will be used
further on to afford a solution of some of the most difficult
problems in the distribution of plant life.

Concluding remarks on the Peculiarities of the British Fauna and
Flora.—The facts, now I believe for the first time, brought to-
gether respecting the peculiarities of the British fauna and flora,
are sufficient to show that there is considerable scope for the study
of geographical distribution even in so apparently unpromising
a field as one of the most recent of continental islands. Looking
at the general bearing of these facts, they prove, that the idea
so generally entertained as to the biological identity of the
British Isles with the adjacent continent is not altogether
correct. Among birds we have undoubted peculiarities in at
least three instances; peculiar fishes are much more numerous,
and in this case the fact that the Irish species are all different
from the British, and those of the Orkneys distinct from those
of Scotland, renders it almost certain that the great majority of
the fifteen peculiar British fishes are really peculiar and will never
be found on the European Continent. The mosses and Hepatice
also have been sufficiently collected in Europe to render it
pretty certain that the more remarkable of the peculiar British
forms are not found there; why therefore, it may be well asked,
should there not be a proportionate number of peculiar British
insects? It is true that numerous species have been first dis-
covered in Britain, and, subsequently, on the continent; but we
have many species which have been known for twenty, thirty,
or forty years, some of which are not rare with us, and yet have

346 ISLAND LIFE. [PART Il.

never been found on the content. We have also the curious
fact of our outlying islands, such as the Shetland Isles, the Isle
of Man, and the little Lundy Island, possessing each some
peculiar forms which, certainly, do not exist on our principal
island which has been so very thoroughly worked. Analogy,
therefore, would lead us to conclude that many other species
would exist on our islands and not on the continent; and when
we find that a very large number (150) in three orders only, are
so recorded, we may I think be sure that a considerable portion
of these (though how many we cannot say) are really endemic
British species.

The general laws of distribution also lead us to expect such
phenomena. Very rare and very local species are such as are
becoming extinct; and it 1s among insects, which are so ex-
cessively varied and abundant, which present so many isolated
forms, and which, even on continents, afford numerous examples
of very rare species confined to restricted areas, that we should
have the best chance of meeting with every degree of rarity
down to the point of almost complete extinction. But we
know that in all parts of the world islands are the refuge of
species or groups which have become extinct elsewhere; and it
is therefore in the highest degree probable that some species
which have ceased to exist on the continent should be preserved
in some part or other of our islands, especiaily as these present
favourable climatic conditions such as do not exist elsewhere.

There is therefore a considerable amount of harmony in the
various facts adduced in this chapter, as well as a complete
accordance with what the laws of distribution in islands would
lead us to expect. In propurtion to the species of birds and
fresh-water fishes, the number of insect-forms is enormously
great, so that the numerous species here recorded as not yet
known on the continent are not to be wondered at; while it
would, I think, be almost an anomaly if, with peculiar birds
and fishes there were not a fair proportion of peculiar insects,
Our entomologists should, therefore, give up the assumption
that all our insects do exist on the continent, and will sometime
or other be found there, as not in accordance with the evidence ;
and when this is done, and the interesting peculiarities of some

CHAP. XVI. ] THE BRITISH ISLES. 347

of our smaller islands are remembered, the study of our native
animals and plants, in relation to those of other countries,
will acquire a new interest. The British Isles are said to
consist of more than a thousand islands and islets. How
many of these have ever been searched for insects? With
the case of Lundy Island before us, who shall say that there
is not yet scope for extensive and interesting investigations
into the British fauna and flora ?

CHAP TER sox Vil.

BORNEO AND JAVA.

Position and physical features of Borneo—Zoological features of Borneo:
Mammalia —Birds—The affinities of the Bornean fauna—Java,, its
position and physical features—General character of the.fauna of Java
—Differences between the fauna of Java and that of the other Malay
Islands—Special relations of the Javan fauna to that of the Asiatic
continent — Past geographical changes of Java and Borneo — The
Philippine Islands—Concluding remarks on the Malay Islands,

As a representative of recent continental islands situated in
the tropics, we will take Borneo, since, although perhaps not
much more ancient than Great Britain, it presents a considerable
amount of speciality; and, in its relations to the surrounding
islands and the Asiatic continent, offers us some problems of
great interest and considerable difficulty.

The accompanying map shows that Borneo 1s situated on the
eastern side of a submarine bank of enormous extent, being
about 1,200 miles from north to south, and 1,500 from east to
west, and embracing Java, Sumatra, and the Malay Peninsula.
This vast area is all included within the 100 fathom line, but by
far the larger part of it—from the Gulf of Siam to the Java
Sea—is under fifty fathoms, or about the same depth as the
sea that separates our own island from the continent. The
distance from Borneo to the southern extremity of the Malay
Peninsula is about 350 miles, and it 1s nearly as far from Sumatra
and Java, while it is more than 600 miles from the Siamase
Peninsula, opposite to which its long northern coast extends.
There is, I believe, nowhere else upon the globe, an island so far

CIIAP. XVII. | BORNEO AND JAVA. B49

ee = —————— ———— A
—SSSBILLIDmDDDDDmDmDDbbbBBpSSSSSSSSS—S5ESS= Oo
SESE Q

igo") me is yh _ido

/ MAP OF BORNEO AND JAVA, SHOWING THE GREAT SUBMARINE BANK OF SOUTH-EASTERN ASIA,

The light tint shows a less depth than 100 fathoms,
The figures show the depth of the sea in fathoms

350 ISLAND LIFE. [PART IT.

from a continent, yet separated from it by so shallow a sea.

Recent changes of sea and land must have occurred here on a
grand scale, and this adds to the interest attaching to the study

of this large island.

The internal geography of Borneo is somewhat peculiar. A
large portion of its surface is lowland, consisting of great alluvial
valleys which penetrate far into the interior; while the moun-
tains except in the north, are of no great elevation, and there
are no extensive plateaux. A subsidence of 500 feet would allow
the sea to fill the great valleys of the Pontianak, Banjarmassing,
and Coti rivers, almost to the centre of the island, greatly reducing
its extent, and causing it to resemble in form the island of Celebes
to the east of it.

In geological structure Borneo is thoroughly continental,
possessing formations of all ages, with basalt and crystalline
rocks, but no recent volcanoes. It possesses vast beds of coal of
Tertiary age ; and these, no less than the great extent of alluvial
deposits in its valleys, indicate great changes of level in recent
geological times. |

Having thus briefly indicated those physical features of Borneo
which are necessary for our inquiry, let us turn to the organic
world.

Neither as regards this great island nor those which surround
it, have we the amount of detailed information in a convenient
form that is required for a full elucidation of its past history-
We have, however, a tolerable acquaintance with the two higher
groups—mammalia and birds, both of Borneo and of all the
surrounding countries, and to these alone will it be necessary to
refer in any detail. The most convenient course, and that which
will make the subject easiest for the reader, will be to give,
first, a connected sketch of what is known of the zoology of
Borneo itself, with’ the main conclusions to which they point ; and
then to discuss the mutual relations of some of the adjacent
islands, and the series of geographical changes that seem required
to explain them.

CHAP, XVII.] BORNEO AND JAVA. 351

ZOOLOGICAL FEATURES OF BORNEO.

Mammalia.—About ninety-six species of mammalia have
been discovered in Borneo, and of these nearly two-thirds are
identical with those of the surrounding countries, and nearly
one half with those of the continent. Among these are two
lemurs, three civets, three cats, three deer, the tapir, the elephant,
and several squirrels, an assemblage which could certainly only
have reached the country by land. The following species of
mammalia are supposed to be peculiar to Borneo :—

QUADRUMANA, 17. Sciurus pluto.
1. Simia morio. A smallorang-utan 15. ,, macrotis. —
with large incisor teeth. 19, » Sarawakensis.
2. Hylobates concolor. 20. », borneonensis.
3. Nasalis larvatus. 21. » rufogularis.
4, Semnopithecus rubicundus. 22. » atricapillus.
5. ‘5 chrysomelas. 23. » Tufogaster. —
e i frontatus. 2A. Acanthion crassispinis.
7. Macacus melanotus. 25. Trichys lipura.
CARNIVORA, INSECTIVORA.
8. Cynogale bennettii. 26. Tupaia splendidula.
9. Paradoxurus stigmaticus. 27, ,, minor (Giinther, P. Z. 8.
10. Herpestes semitorquatus. 1876, p. 426).
ll. , ~~ brachyurus. ast Dendrogale murina.
12. Felis badia. 29. Ptilocerus lowii.

13. Lutra lovii (Giinther, P. Z. S.
1876, p. 736).

CHIROPTERA.
UNGULATA. : : i
14 Gieshawhatus 30. Phyllorina dori.
; 31. Vesperugo stenopterus.
RopENTIA. 39. is dorize.
15. Pteromys pheeomelas. 30: “ tylopus.
16. Sciurus ephippium. 34. Taphozous affinis.

Of the thirty-four peculiar species here enumerated, it is
probable that when they are more carefully studied some
will be found to be identical with those of Malacca or Sumatra ;
but. there are also four peculiar genera which are less likely
to be discovered elsewhere. These are Nasalis, the remarkable
long-nosed monkey; Cynogale, a semi-aquatic civet; Trichys,
a tailless porcupine ; and Ptilocerus, a feather-tailed arboreal
insectivore. These peculiar forms do not, however, imply
that the separation of the island from the continent is of very
ancient date, for the country is so vast and so much of the

352 ISLAND LIFE. [PART II.

connecting land is covered with water, that the amount of
speciality is hardly, if at all, greater than occurs in many con-
tinental areas of equal extent, This will be more evident if we
consider that Borneo is as large as the Indo-Chinese Peninsula,
or as the Indian Peninsula south of Bombay, and if either of
these countries were separated from the continent by the sub-
mergence of the whole area north of them as far as the Hima-
layas, they would be found to contain about as many peculiar
genera and species as Borneo actually does now. A more deci-
sive test of the lapse of time since the separation took place is
to be found in the presence of a number of representative
species closely allied to those of the surrounding countries, such
as the tailel monkeys and the numerous squirrels. These, how-
ever, are best seen among the birds, which have been more
thoroughly collected and more carefully studied than the
mammalia,

Lirds.—About 400 species of birds are known to inhabit
Borneo, of which 340 are land birds. There are about seventy
peculiar species ; and, according to Count Salvadori, thirty-four
of these (thirty-nine with later additions) are very distinct forms,
while no less than thirty-one are slight modifications of species
found in Sumatra or the Malay Peninsula. The following are
the species of birds considered by Count Salvadori to be peculiar
to Borneo, with the addition of a few species since added :—

First SERIES. SECOND SERIES,
Very distinct Species. Representative Species.
StTRIGIDE (Owls).
1. Ninox borneensis.
2. Ciccaba leptogrammica,

MEGALAMID/ (Barbets).

3. Chotorea chrysopsis.
4, Calorhamphus fuliginosus.

Pictpa& (Woodpeckers).

5. Hemilophus fischeri.
6. Jungipicus aurantiiventris.
7. Micropternus badiosus.

CucuLip® (Cuckoos).

1. Indicator archipelacus, 8. Rhopodytes borneensis.
2. Heterococeyx neglectus.

CHAP, XVII. | BORNEO AND JAVA.

se a

26.

. Zosterops melanura.

. Pycnonotus gourdinii.
. Criniger diardi.

. Turdinus leucogrammicus.
. Setaria pectoralis.

. Pitta bert.

353

First SERIES. SECOND SERIES.
Very distinct Species. Representative Species.

ALCEDINID& (Kingfishers).

. Ceyx sharpei. 9. Pelargopsis leucocephala.

, dillwynni. 10. Dacelo melanops.

PoODARGIDE.
| 11. Batrachostomus adspersus.

CAPRIMULGIDH (Goatsuckers).
Caprimulgus arundinaceus. 12. Caprimulgus bulweri.
9 concretus.
Hd salvadorii.

HIRUNDINID& (Swallows).

. Delichon dasypus. |

MuscicaPip#& (Flycatchers).

. Cyornis rufifrons.

5 bturcosa.
», beccariara.

. Schwaneria ccerulata.

ArTAMID (Swallow-shrikes).

. Artamus clemenciz. |

LANIIDe (Shrikes).

. Lanius schwaneri. 13. Volvocivora schierbrand1.
. Pityriasis gymnecephala.

NEcTARINUDZ (Sunbirds).

. Arachnothera crassirostris. |

Dicr1p# (Flower-peckers).

14, Prionochilus xanthopygius.
15. Diceum nigrimentum,

16. Zosterops parvula.

Pycnonotip#& (Bulbuls).

5) 6nschil.
TIMALIIDZ (Babblers).

17. Pomatorhinus borneensis.
18. Mixornis borneensis.

» cinereicapilla.
20. Brachypteryx umbratilis.
21, Malacocincla rufiventris,

Pitrip# (Pittas).

22. Pitta granatina.
23. 4, schwaneri.
245 ose sishert:

y) arcuata,
y> baudii.

19. Drymocataphus capistratioides.

354 ISLAND LIFE. [PART IT.

First SERIES. SEcoND SERIES.
Very distinct Species. Representative Species,
Syivipz# (Warblers).
27. Abrornis schwaneri.

28. Prinia superciliaris. 25. Orthotomus borneonensis.
29. Calamodyta doriz.
30. Kittacincla stricklandi. 26. Kittacincla suavis.

Corvip& (Crows and Jays).

27. Dendrocitta cinerascens.
28. Platysmurus aterrimus.

ALAUDID# (Larks).

31. Mirafra borneensis.

Puiocei1p#& (Weaver Finches).
32. Munia fuscans. |

PHASIANID& (Pheasants).
(33. Polyplectron emphanum, I. of | 29. Argusianus grayl.

Palawan.)
34, P. schleiermacheri.
35. Lobiophasis bulweri. 30. Euplocamus nobilis.
36. 9 castaneicauda. dl. 59 pyronotus.

RALLID# (Rails).
37. Rallina rufigenis. |
TETRAONIDZ (Partridges &c.).

38. Hematortyx sanguiniceps.
39. Bambusicola hyperythra.

Representative forms of the same character as these are
no doubt found in all extensive continental areas, but they are
rarely so numerous. Thus in Mr. Elwes’ paper on the “ Distri-
bution of Asiatic Birds,” he states that 12°5 per cent. of the land
birds of Burmah and Tenasserim are peculiar species, whereas we
find that in Borneo they are about 20 per cent., and the difference
may fairly be imputed to the greater proportion of slightly
modified representative species due to a period of complete
isolation. Of peculiar genera, the Indo-Chinese Peninsula has
one—Ampeliceps, a remarkable yellow-crowned starling, with
bare pink-coloured orbits; while two others, Temnurus and
Crypsirhina—singular birds allied to the jays—are found in
no other part of the Asiatic continent though they occur in
some of the Malay Islands. Borneo has three peculiar genera,
Schwaneria, a flycatcher ; Hematortyx, a crested partridge; and
Lobiophasis, a pheasant hardly distinct from Euplocamus ; while

Ry 3

CHAP. XVII. | BORNEO AND JAVA. 355

two others, Pityriasis, an extraordinary bare-headed bird
between a jay and a shrike, and Carpococcyx, a pheasant-like
ground cuckoo formerly thought to be peculiar, are said to have
been discovered also in Sumatra.

The insects and land-shells of Borneo and of the surrounding
countries are too imperfectly known to enable us to arrive at
any accurate results with regard to their distribution. They
agree, however, with the birds and mammals in their general
approximation to Malayan forms, but the number of peculiar
species is perhaps larger.

The proportion here shown of one-third peculiar species of
mammalia to about one-fifth peculiar species of land-birds,
teaches us that the possession of the power of flight only affects
the distribution of animals in a limited degree, and gives us
confidence in the results we may arrive at in those cases where
we have, from whatever cause, to depend on a knowledge of the
birds alone. And the difference we here find to exist is almost
wholly due to the wide range of certain groups of powerful flight
—as the birds of prey, the swallows and swifts, the king-crows,
and some others; while the majority of forest-birds appear to
remain confined, by even narrow watery barriers, to almost as
great an extent as do the mammalia.

The affinities of the Bornean Fauna.—The animals of Borneo
exhibit an almost perfect identity in general character, and a
close similarity in species, with those of Sumatra and the Malay
Peninsula. So great is this resemblance that it is a question
whether it might not be quite as great were the whole united ;
for the extreme points of Borneo and Sumatra are 1,500 miles
apart—as far as from Madrid to Constantinople, or from Bombay
to Rangoon. In this distance we should expect to meet with
many local species, and even representative forms, so that we
hardly require a lapse of time sufficient to have produced specific
change. So far as the forms of life are concerned, Borneo, as an
island, may be no older than Great Britain ; for the time that has
elapsed since the glacial epoch would be amply sufficient to pro-
duce such a redistribution of the species, consequent on their
mutual relations being disturbed, as would bring the islands into
‘their present zoological condition. There are, however, other

1 Ny

353 ISLAND LIFE. | [PART IT.

facts to be considered, which seem to imply much greater
and more complex revolutions than the recent separation of
Borneo from Sumatra and the Malay Peninsula, and that these
changes must have been spread over a considerable lapse of time.
In order to understand what these changes probably were, we
must give a brief sketch of the fauna of Java, the peculiarities
of which introduce a new element into the question we have to
discuss.

JAVA.

The rich and beautiful island of Java, interesting alike to the
politician, the geographer, and the naturalist, is more especially
attractive to the student of geographical distribution, because
it furnishes him with some of the most curious anomalies and
difficult problems in a place where such would be least expected.
As Java forms with Sumatra one almost unbroken line of
volcanoes and volcanic mountains, interrupted only by the
narrow Straits of Sunda, we should naturally expect a close
resemblance between the productions of the two islands. But
in point of fact there is a much greater difference between them
than between Sumatra and Borneo, so much further apart, and
so very unlike in physical features. Java differs from the three
great land masses—Borneo, Sumatra, and the Malay Peninsula,
far more than either of these do from each other; and this is
the first anomaly we encounter. But a more serious difficulty
than this remains to be stated. Java has certain close resem-
blances to the Siamese Peninsula, and also to the Himalayas,
which Borneo and Sumatra do not exhibit, and looking at the
relative position of these lands respectively, this seems most
incomprehensible. In order fully to appreciate the singularity
and difficulty of the problem, it will be necessary to point out
the exact nature and amount of these peculiarities in the fauna
of Java.

General character of the Fauna of Java.—If we were only to
take account of the number of peculiar species in Java, and the
relations of its fauna generally to that of the surrounding lands,
we might pass it over as a less interesting island than Borneo or
Sumatra. Its mammalia (ninety species) are nearly as numerous

CHAP. XVII.] BORNEO AND JAVA. £57

as those of Borneo, but are apparently less peculiar, none of
the genera and only five or six of the species being confined to
the island. In land-birds it is decidedly less rich, having
only 270 species, of which forty are peculiar, and only one or two
belong to peculiar genera; so that here again the amount of
speciality is less than in Borneo. It is only when we proceed to
analyse the species of the Javan fauna, and trace their distri-
bution and affinities, that we discover its interesting nature.
Difference between the Fauna of Java and that of the other
great Malay Islands.—Comparing the fauna of Java with that
which may be called the typical Malayan fauna as exhibited in
Borneo, Sumatra, and the Malay Peninsula, we find the follow-
ing differences. No less than thirteen genera of mammalia,
each of which is known to inhabit at least two, and generally all
three, of the above-named Malayan countries, are yet totally
absent from Java; and they include such important forms as the
elephant, the tapir, and the Malay bear. It cannot be said that
this difference depends on imperfect knowledge, for Java is one
of the oldest European settlements in the East, and has been
explored by a long succession of Dutch and English naturalists.
Every part of it is thoroughly well known, and it would be
almost as difficult to find a new mammal of any size in Europe
as in Java. Of birds there are twenty-five genera, all typically
Malayan and occurring at least in two, and for the most part
in all three of the Malay countries, which are yet absent from
Java. Most of these are large and conspicuous forms, such
as jays, gapers, bee-eaters, woodpeckers, hornbills, cuckoos,
parrots, pheasants, and partridges, as impossible to have remained
undiscovered in Java as the large mammalia above referred to.
Besides these absent genera there are some curious illus-
trations of Javan isolation in the species; there being several
cases in which the same species occurs in all three of the typical
Malay countries, while in Java it is represented by an allied
species. Such appear to be the Malayan monkey, Semno-
pithecus cristatus, replaced in Java by S. maurus; and the
large Malay deer, Rusa equinus, represented in Java by £&,
hippelaphus. Among birds there are more numerous examples,
no less than seven species which are common to the three great

358 ISLAND LIFE. [PART If.

Malay countries being represented in Java by distinct but
closely allied species.

From these facts it is impossible to doubt that Java has
had a history of its own, quite distinct from that of the other
portions of the Malayan area.

Special relations of the Javan Fauna to that of the Asiatic
Continent.—These relations are indicated by comparatively
few examples, but they are very clear and of great im-
portance. Among mammalia, the genus Helictis is found in
Java but in no other Malay country, though it inhabits also
North India; while two species, Rhinoceros javanicus and Lepus
kurgosa, are natives of Indo-Chinese countries and Java, but not
of typical Malaya. In birds there are three genera—Zoothera,
Notodela, and Crypsirhina, which inhabit Java and Indo-China ;
while four others—Brachypteryx, Allotrius, Cochoa, and Psal-
tria, inhabit Java and the Himalayas, but no intervening
country. There are also two species of birds—a trogon (Harpactes
oreskios), and the Javanese peacock (Pavo muticus), which inhabit
only Java and the Indo-Chinese Peninsula.

Here, then, we find a series of remarkable similarities between
Java and the Asiatic continent, quite independent of the typical
Malay countries—Borneo, Sumatra, and the Malay Peninsula,
which latter have evidently formed one connected land, and
thus appear to preclude any independent union of Java
and Siam.

The great difficulty in explaining these facts is, that all the
required changes of sea and land must have occurred within
the period of existing species of mammalia. Sumatra, Borneo,
and Malacca are, as we have seen, almost precisely alike as
regards their species of mammals and birds; while Java, though
it differs from them in so curious a manner; has no greater
degree of speciality, simce its species, when not Malayan, are
almost all Indian or Siamese.

There is, however, one consideration which may help us over
this difficulty. It seems highly probable that in the equatorial
regions species have changed less rapidly than in the north
temperate zone, on account of the equality and stability of
the equatorial climate. We have seen, in Chapter X., how

CHAP. XVII] BORNEO AND JAVA. —— 859

important an agent in producing extinction and modification of
species must have been the repeated changes from cold to warm,
and from warm to cold conditions, with the inevitable migrations
and crowding together that must have been their necessary con-
sequence. But in the lowlands, near the equator, these changes
would be very little felt, and thus one great cause of specific
modification would be wanting. Let us now see whether we
can sketch out a series of not improbable changes which may
have brought about the existing relations of Java and Borneo to
the continent.

Past Geographical Changes of Java and Borneo.—Although
Java and Sumatra are mainly volcanic, they are by no means
wholly so. Sumatra possesses in its great mountain masses
ancient crystalline rocks with much granite, while there are
extensive Tertiary deposits of Eocene age, overlying which are
numerous beds of coal now raised up many thousand feet above
the sea! The volcanoes appear to have burst through these
older mountains, and to have partly covered them as well as
great areas of the lowlands with the product of their erup-
tions. In Java either the fundamental strata were less extensive
and less raised above the sea, or the period of volcanic action
has been of longer duration ; for here no crystalline rocks have
been found except a few boulders of granite in the western
part of the island, perhaps a relic of a formation destroyed by
denudation, or covered up by volcanic deposits. In the southern
part of Java, however, there is an extensive range of low
mountains, about 3,000 feet high, consisting of basalt with
limestone apparently of Miocene age.

During this last-named period, then, Java would have been
at least 3,000 feet lower than it is now, and such a depression
would probably extend to considerable parts of Sumatra and
Borneo, so ag to reduce them all to a few small islands. At
some later period a gradual elevation occurred, which ultimately
united the whole of the islands with the continent. This
may have continued till the glacial period of the northern hemi-
sphere, during the severest part of which a few Himalayan

1 «Qn the Geology of Sumatra,” by M. R.D.M. Verbeck. Geological
Magazine, 1877,

360 ISLAND LIFE. [PART II.

species of birds and mammals may have been driven south-
ward, and ranged over suitable portions of the whole area.
Java was then separated by subsidence, and these species
became imprisoned there; while those in the remaining part of

the Malayan area again migrated northward when the cold had:

passed away from their former home, the equatorial forests of
Borneo, Sumatra, and the Malay Peninsula being more especially
adapted to the typical Malayan fauna which is there developed
in rich profusion. A little later the subsidence may have
extended farther north, isolating Borneo and Sumatra, but pro-
bably leaving the Malay Peninsula as a ridge between them as
far as the islands of Banca and Biliton. Other slight changes
of climate followed, when a further subsidence separated these
last-named islands from the Malay Peninsula, and left them
with two or three species which have since become slightly
modified. We may thus explain how it is that a species is
sometimes common to Sumatra and Borneo, while the inter-
vening island (Banca) possesses a distinct form.’

In my Geographical Distribution of Animals, Vol. I., p. 357, I
have given a somewhat different hypothetical explanation of the
relations of Java and Borneo to the continent, in which I took
account of changes of land and sea only ; but a fuller consideration
of the influence of changes of climate on the migration of animals,
has led me to the much simpler, and, I think, more probable,
explanation above given. The amount of the relationship be-
tween Java and Siam, as well as of that between Java and the
Himalayas, is too small to be well accounted for by an indepen-
dent geographical connection in which Borneo and Sumatra did
not take part. It is, at the same time, too distinct and indisput-
able to be ignored; and a change of climate which should drive
a portion of the Himalayan fauna southward, leaving a few
species in Java, from which they could not return owing to
its subsequent isolation by subsidence, seems to be a cause
exactly adapted to produce the kind and amount of affinity
between these distant countries that actually exists.

1 Pitta megarhynchus (Banca) allied to P. brachyurus (Borneo, Suma-
tra, Malacca) ; and Pitta bangkanus (Banca) allied to P. sordidus (Borneo
and Sumatra).

OHAP, XVII. | THE PHILIPPINES: 361

The Philippine Islands.—A. sufficiently detailed account of the
fauna of these islands, and their relation to the countries which
form the subject of this chapter, has been given in my (eo-
graphical Distribution of Anmmals., Vol. I. pp. 345-349 ; but since
that time considerable additions have been made to their fauna,
and these have had the effect of diminishing their isolation from
the other islands. Six genera have been added to the terrestrial
mammalia—Crocidura, Felis, Tragulus, Hystrix, Pteromys, and
Mus, as well as two additional squirrels; while the black ape
(Cynopithecus niger) has been struck out as not inhabiting the
Philippines. This brings the known mammalia to twenty-one
species, and no doubt several others remain to be discovered.
The birds have been increased from 219 to 288 species, and the
additions include many Malayan genera which were thought to be
absent. Such are Phyllornis (green bulbuls); Euryleemus (gaper),
Malacopteron, one of the babblers ; and Criniger, one of the fruit-
thrushes; as well as Batrachostomus, the frog-mouthed goat-
sucker. There still remain, however, a large number of Malayan
genera absent from the Philippines, while there are a few
Australian and Indian or Chinese genera which are not Malayan.
We must also note that about nine-tenths of the mammalia and
two-thirds of the land-birds are peculiar species, a very much
larger proportion than is found on any other Malay island.

The origin of these peculiarities is not difficult to trace. The
Philippines are almost surrounded by deep sea, but are connected
with Borneo by means of two narrow submarine banks, on the
northern of which is situated Palawan, and on the southern the
Sooloo Islands. Two small groups of islands, the Bashees and
Babuyanes, have also afforded a partial connection with the
continent by way of Formosa. It is evident that the Philippines
once formed part of the great Malayan extension of Asia, but
that they were separated considerably earlier than Java; and
having been since greatly isolated and much broken up by
volcanic disturbances, their species have for the most part
become modified into distinct local species. They have also
received a few Chinese types by the route already indicated,
and a few Australian forms owing to their proximity to the
Moluccas. The reason of their comparative poverty in genera

362 ISLAND LIFE. [PART I,

and species of the higher animals is, that they have been
subjected to a great amount of submersion in recent times,
greatly reducing their area, and causing, no doubt, the ex-
tinction of a considerable portion of their fauna. This is not
a mere hypothesis, but is supported by direct evidence ; for I am
informed by Mr. Everett, who has made extensive explorations
in the islands, that almost everywhere are found large tracts of
elevated coral-reefs, containing shells similar to those hvmg in
the adjacent seas; an indisputable proof of recent elevation.

Concluding remarks on the Malay Islands.—This completes our
sketch of the great Malay islands, the seat of the typical
Malayan fauna. It has been shown that the peculiarities
presented by the individual islands may be all sufficiently well
explained by a very simple and comparatively unimportant series
of geographical changes, combined with a limited amount of
change of climate towards the northern tropic. Beginning in late
Miocene times when the deposits on the south coast of Java
were upraised, we suppose a general elevation of the whole of the
extremely shallow seas uniting what are now Sumatra, Java,
Borneo, and the Philippines with the Asiatic continent, and
forming that extended equatorial area in which the typical
Malayan fauna was developed. After a long period of stability,
giving ample time for the specialisation of so many peculiar
types, the Philippines were first separated; then at a con-
“siderably later period Java; a little later Sumatra and Borneo ;
and finally the islands south of Singapore to Banca and Biliton.
This one simple series of elevations and subsidences, combined
with the changes of climate already referred to, and such local
elevations and depressions as must undoubtedly have occurred,
appears sufficient to have brought about the curious, and at first
sight puzzling, relations, of the faunas of Java and the Philip-
pines, as compared with those of the larger islands.

We will now pass on to the consideration of two other groups
which offer features of special interest, and which will complete
our illustrative survey of recent continental islands.

=
ae ea

CHAPTER XVIII.
JAPAN AND FORMOSA,

Japan, its position and Physical features—Zoological features of Japan-~
Mammalia—Birds—Birds common to Great Britain and Japan —Birds
peculiar to Japan—Japan birds recurring in distant areas—Formosa—
Physical features of Formosa—Animal life of Formosa—Mammalia—
Land-birds peculiar to Formosa—Formosan birds recurring in India or
Malaya—Comparison of faunas of Hainan, Formosa, and Japan—
General remarks on Recent Continental Islands,

JAPAN,

Tue Japanese Islands occupy a very similar position on the
eastern shore of the great Euro-Asiatic continent to that of the
British Islands on the western, except that they are about
sixteen degrees further south, and having a greater extension
in latitude, enjoy a more varied as well as a more temperate
climate. Their outline is also much more irregular and their
mountains loftier, the volcanic peak of Fusiyama being 14,177
feet high ; while their geological structure is very complex, their
soil extremely fertile, and their vegetation in the highest degree
varied and beautiful. Like our own islands, too, they are con-
nected with the continent by a marine bank less than a hundred
fathoms below the surface—at all events towards the north and
south ; but in the intervening space the Sea of Japan opens out
to a width of six hundred miles, and in its central portion is
very deep, and this may be an indication that the connection
between the islands and the continent is of rather ancient
date. At the Straits of Corea the distance from the main
land is about 120 miles, while at the northern extremity of

ISLAND LIFE.

MAP OF JAPAN AND FORMOSA (with depths in fathoms).

Light tint, sea under 100 fathoms. Medium tint, under 1,000 fathoms.
1,000 fathoms. The figures show the depth in fathoms,

Dark tint, over

CHAP. XVIII] JAPAN AND FORMOSA. 565

Yesso it is about 200. The island of Saghalien, however,
separated from Yesso by a strait only twenty-five miles wide,
forms a connection with Amoorland in about 52° N. Lat. A
southern warm current flowing a little to the eastward of the
islands, ameliorates their climate much in the same way as the
Gulf Stream does ours, and added to their insular position enables
them to support a more tropical vegetation and more varied
forms of life than are found at corresponding latitudes in China.

Zoological features of Japan.—As we might expect from the
conditions here sketched out, Japan exhibits in all its forms of
animal life a close general resemblance to the adjacent continent,
but with a considerable element of specific individuality ; while
it also possesses some remarkable isolated groups. It also ex-
hibits indications of there having been two or more lines of
migration at different epochs. The majority of its animals are
related to those of the temperate or cold regions of the continent,
either as identical or allied species; but a smaller number have a
tropical character, and these have in several instances no allies
in China but occur again only in Northern India or the Malay
Archipelago. There is also a slight American element in the
fauna of Japan, a relic probably of the period when a land
communication existed between the two continents over what
are now the shallow seas of Japan, Ochotsk, and Kamschatka.
We will now proceed to examine the peculiarities and relations
of the fauna. |

Mammalia.—The mammalia of Japan at present known are
forty in number; not very many when compared with the rich
fauna of China and Manchuria, but containing monkeys, bears,
deer, wild goats and wild boars, as well as foxes, badgers, moles,
squirrels, and hares, so that there can be no doubt whatever
that they imply a land connection with the continent. No
complete account of Japan mammals has been given by any
competent zoologist since the publication of Von Siebold’s
Fauna Japonica in 1844, but by collecting together most of the
scattered observations since that period the following list has
been drawn up, and will, it is hoped, be of use to naturalists.
The species believed to be peculiar to Japan are printed in
italics. These are very numerous, but it must be remembered

366 ’ ISLAND LIFE, [PART I.

that Corea and Manchuria (the portions of the continent
opposite Japan) are comparatively little known, while in very
few cases have the species of Japan and of the continent been
critically compared. Where this has been done, however, the
peculiar species established by the older naturalists have been
in many cases found to be correct.

List oF THE MAMMALIA OF THE JAPANESE ISLANDS.

1. Macacus spectosus. A monkey with rudimentary tail and red face,
allied to the Barbary ape. It inhabits the island of Niphon up to
4i° N. Lat., and has thus the most northern range of any living
monkey. ;

2. Pteropus dasymallus. A peculiar fruit-bat, found in Kiusiu Island
only (Lat. 33° N.), and thus ranging further north of the equator
than any other species of the genus.

3. Rhinolophus ferrum-equinum. The great horse-shoe bat, ranges from
Britain across Europe and temperate Asia to Japan. It is the
fi. nippon of the Fauna Japonica according to Mr. Dobson’s Mono-
graph of Asiatic Bats.

4. R. minor. Found also in Burma, Yunan, Java, Borneo, &e.

5. Vesperugo pipistrellus. From Britain across Europe and Asia.

6. V. abramus. Also in India and China.

7. V. noctula. From Britain across Europe and Asia.

8. V. molossus, Also in China.

9. Vespertilio capaccinii. Philippine Islands, and Italy! This is V,
macrodactylus of the Fauna Japonica according to Mr. Dobson.

10. Miniopterus schreibersii. Philippines, Burma, Malay Islands. This is
Vespertilio blepotis of the Fauna Japonica.

11. Talpa wogura. Closely resembles the common mole of Europe, but
has six incisors instead of eight in the lower jaw.

12. Urotrichus talpoides. A peculiar genus of moles confined to Japan
and the north-west coast of N. America. The American species has
been named Urotrichus gibsiz, but Mr. Lord after comparing the two
says that he “can find no difference whatever, either generic or
specific. In shape, size, and colour, they are exactly alike.”

13. Sorex myosurus. A shrew, found also in India and Malaya.

14. Sorex dzi-nezume.

15. S. wmbrinus. :

16. S. platycephalus.

17. Ursus arctos. var. A peculiar variety of the European brown bear
which inhabits also Amoorland and Kamschatka. It is the Ursus
ferox of the Fauna Japonica.

18. Ursus japonicus. <A peculiar species allied to the Himalayan and For-
uuosan species. Named U. tibetanus in the Fauna Japonica,

CHAP. XVIII.] JAPAN AND FORMOSA. 367

19. Meles anakuma. Differs from the European and Siberian badgers in
the form of the skull.

20. Mustela brachyura. A peculiar marten found also in the Kurile
Islands.

21. Mustela melanopus. The Japanese sable.

22. M. Japonica. <A peculiar marten (See Proc. Zool. Soc. 1865, p. 104).

23, M. Sibericus. Also Siberia and China. This is the M. ttalsc of the
Fauna Japonica according to Dr. Gray.

24, Lutronectes whiteleyi. A new genus and species of otter (P. Z.S.
1867, p. 180). In the Fauna Japonica named Lutra vulgaris.

25. Enhydris marina. The sea-otter of California and Kamschatka.

26. Canis hodophylax. According to Dr. Gray allied to Cuon sumatranus
of the Malay Islands, and C. alpinus of Siberia, if not identical
with one of them (P. Z. 8. 1868, p. 500).

27. Vulpes japonica. <A peculiar fox. Canis vulpes of Fauna Japonica.

28. Nyctereutes procyonoides. The racoon-dog of N. China and Amoor-
land.

29. Lepus brachyurus. A peculiar hare.

30. Sciurus lis. A peculiar squirrel.

31. Pteromys leucogenys. The white-cheeked flying squirrel.

32. P. momoga. Perhaps identical with a Cambojan species (P. Z. S.
1861, p. 137).

33. Myoxus japonicus. A peculiar dormouse. WM. elegans of the Fauna
Japonica; MW. javanicus, Schinz (Synopsis Manvmalium, ii, p. 530).

34. Mus argenteus. China.

35. Mus molossinus.

36, Aus nezumt.

37. M. speciosus.

38. Cervus sika. A peculiar deer allied to C. pseudaxis of Formosa and
C. mantchuricus of Northern China.

39. Nemorhedus crispa. A goat-like antelope allied to N. sumatranus of
Sumatra, and N. Swonhoer of Formosa.

40. Sus leucomystax. A wild boar allied to S, taevanus of Formosa.

We thus find that no less than twenty-six out of the forty
Japanese mammals are peculiar, and if we omit the aérial bats
(nine in number), as well as the marine sea-otter, we shall have
remaining only thirty strictly land mammalia, of which twenty-
five are peculiar, or five-sixths of the whole. Nor does this .
represent all their speciality ; for we have a mole differing in
its dentition from the European mole; another closely allied to
an American species; a peculiar genus of otters; and an antelope
whose nearest allies are in Formosa and Sumatra. The import-
ance of these facts will be best understood when we have examined
the corresponding affinities of the birds of Japan.

368 ISLAND LIFE. [PART II.

Birds.—Owing to the recent researches of some English resi-
dents we have probably a fuller knowledge of the birds than of
the mammalia; yet the number of true land-birds ascertained
to inhabit the islands either as residents or migrants is only
165, which is less than might be expected considering the
highly favourable conditions and the extreme riches of the
adjacent continent,—Mr. Swinhoe’s list of the birds of China
containing more than 400 land species, after deducting all which
are peculiar to the adjacent islands. Only sixteen species, or
about one-tenth of the whole, are now considered to be peculiar
to Japan; but even of these, five are classed by Mr. Seebohm as
sub-species or slightly modified forms of continental birds, so
that eleven only are well-marked species, undoubtedly distinct
from those of any other country.

The great majority of the birds are decidedly temperate forms
identical with those of Northern Asia and Europe; while no less
than forty of the species are also found in Britain, or are such
slight modifications of British species that the difference is only
perceptible to a trained ornithologist. The following list of the
birds common to Britain and Japan is very interesting, when we
consider that these countries are separated by the whole extent
of the European and Asiatic continents, or by almost exactly
one-fourth of the circumference of the globe :—

BIRDS COMMON TO GREAT BRITIAN AND JAPAN.!

1. Common Creeper (Certhia fami- 11. Swallow, sub-sp. (Hirundo gut-
liaris). turalis).
2. Nuthatch (Sitta europea). 12. Sand martin (Cotyle riparia).
3. Coal tit (Parus ater). 13. Brambling (F'ringilla _ montifrin-
4, Marsh tit, sub-sp. (P. japonicus). gilla).
5, Long-tailed tit (Acredula cau- 14. Siskin (Chrysomitris spinus).
data). 15, Lesser redpole (4 giothus linaria).
6. Great grey shrike (Lanius eacu- 16. 'Tree-sparrow (Passer montanus. )
bitor). 17. Pine grosbeak (Pyrrhula enu-
7. Nutcracker (Nucifraga caryoca- cleator).
tactes). 18. Reed bunting, sub-sp. (EHmberiza
8. Carrion Crow (Corvus corone). pyrrhulina).
9. Raven (Corvus coraz). 19. Snow bunting (Plectrophanes
10. Wax wing (Ampelis garrula). nivalis),

1 Extracted from Messrs. Blakiston and Pryer’s Catalogue of Birds of
Japan (Ibis, 1878, p. 209), with Mr. Seebohm’s additions and corrections
(Ibis, 1879, p. 18).

CHAP. XVIII. ] JAPAN AND FORMOSA. 369
20. Grey wagtail, sub-sp. (Motacilla 30. Golden eagle (Aquilachrysaétos).
melanope). 31, White-tailed eagle (Haliaetus
21. Great spotted woodpecker (Picus albicilla),
major). 32, Kestrel (Falco tinnunculus).
22. Great black woodpecker (Dry- 33. Hobby (I. subbuteo).
ocopus martius). 34. Merlin (£”. esalon).
23. Cuckoo (Cuculus canorus),. 35. Peregrine falcon (J. peregrinus).
24. Hoopoe (Upupa epops). 36, Greenland falcon (£". candicans),
25. Rock-dove (Columba livia). 37. Osprey (Pandion haliaetus).
26. Hen harrier (Circus cyaneus). 38. Eagle owl (Bubo maximus).
27. Gos-hawk (Astur palumbarius). 39. Short-eared owl (Asio accipitri-
28. Sparrow-hawk (Accipiter nisus). nus).
29. Rough-legged buzzard (Buteo 40. Long-eared owl (A. otus).
lagopus).

But these forty species by no means fairly represent the
amount of resemblance between Britain and Japan as regards
birds ; for there are also wrens, hedge-sparrows, gold-crests, sedge-
warblers, pipits, larks, rock-thrushes, jays, and many others,
which, though distinct species from our own, have the same
general appearance, and give a familiar aspect to the ornithology.
There remains, however, a considerable body of Chinese and.
Siberian species, which link the islands to the neighbouring
parts of the continent; and there are also a few which are
Malayan or Himalayan rather than Chinese, and thus afford us
an interesting problem in distribution.

The sixteen species and sub-species which are altogether
peculiar to Japan are for the most part allied to birds of North
China and Siberia, but three are decidedly tropical, and one of
them—a fruit pigeon (Z'reron sieboldi)—has no close ally nearer
than Java and the Himalayas. In the following list the affini-
ties of the species are indicated wherever they have been
ascertained :—

LIST OF THE SPECIES OF LAND BIRDS PECULIAR TO JAPAN,

1. Parus japonicus. A sub-species of P. palustris, very like Siberian

7 varieties. |

2. Parusvarius. Very distinct. It nearest ally is in Formosa.

3. Hypsipetes amaurosis. A tropical genus. Allied to species of 8. China
and India.

4. Garrulus japonicus. Allied to our European jay. In Niphon only.

5. Garrulus lidthi. A very distinct and handsome species. (See Ibis
1873, p. 478.)

370 ISLAND LIFE. [PART Il.

6. Zosterops japonica. Allied to a migratory Chinese species.
7. Chelidon blakistoni. Allied to C. whiteleyi of N. China.
8. Chlorospiza kawarahiba. Allied to C. sinica of China and Japan.
9. Emberiza ciopsis, A sub-species of the EL. cioides of N. China.
10. Emberiza yessoensis, Allied to the Siberian £. passerina.
11. Euspiza variabilis. A very distinct species.
12. Picus kisuki. Allied to P. pygmeus of Central Asia.
13. Gecinus awokera. Allied to G. canus (N. China), and G‘. viridis, Europe.
14. Mulleripicus richardsi. Allied to M. crawfurdi of Pegu. In Tzus
Sima Island (P. Z. S. 1879, p. 386).
15. Treron sieboldi, Allied to T. sphenwra (Himalayas), and T. korthalsi,
Java.
16. Accipiter gularis. A sub-species of the Malayan A. virgatus (also in
Formosa).
17. Buteo hemilasius. A distinct species.
18. Syrnium rufescens. A sub-species of S. uralense of E. Europe and
Siberia,

Japan birds recurring in distant avreas.—The most interesting
feature in the ornithology of Japan is, undoubtedly, the pre-
sence of several species which indicate an alliance with such
remote districts as the Himalayas, the Malay Islands, and
Kurope. Among the peculiar species, the most remarkable of
this class are,—the fruit-pigeon of the genus Treron, entirely un-
known in China, but reappearing in Formosa and Japan; the
Hypsipetes, whose nearest ally is in South China at a distance
of nearly 500 miles; and the jay (Garrulus japonicus), whose
close ally (G@. glandarius) inhabits Europe only, at a distance of
3,700 miles. But even more extraordinary are the following
non-peculiar species :—Spizaetus orientalis, a crested eagle, in-
habiting the Himalayas, Formosa, and Japan, but unknown in
China; Ceryle guttata, a spotted kingfisher, entirely confined to
the Himalayas and Japan; and Halcyon coromanda, a brilliant
red kingfisher inhabiting Northern India, the Malay Islands to
Celebes, Formosa, and Japan. We have here an excellent illus-
tration of the favourable conditions which islands afford both
for species which elsewhere live further south (Halcyon coro-
manda), and for the preservation in isolated colonies of species
which are verging towards extinction ; for such we must consider
the above-named eagle and kingfisher, both confined to a very
limited area on the continent, but surviving in remote islands.

CHAP. XVIII. ] JAPAN AND FORMOSA. | 371

The spotted kingfisher, indeed, affords us one of the best ex-
amples of that rare phenomenon—a species with a discontinuous
range; for although an island is considered, for purposes of
distribution, to form part of one continuous area with the
adjacent continent (as when a species is found in France and
Britain, or in Siam and Borneo, we do not say that the area of
distribution is discontinuous), yet in this case we have to pass
over three thousand miles of land after quitting the island,
before we come to the continental portion of the area occupied
by the species. Referring to our account of the birth, growth,
and death of a species (in Chapter IV.) 1t can hardly be doubted
that the Ceryle guttata formerly ranged from the Himalayas to
Japan, and has now died out in the intervening area owing to
geographical and physical changes, a subject which will be
better discussed when we have examined the interesting fauna
of the island of Formosa.

The other orders of animals are not yet sufficiently known to
enable us to found any accurate conclusions upon them. The
main facts of their distribution have already been given in my
Geographical Distribution of Animals (Vol L, pp. 227-231), and
they sufficiently agree with the birds and mammalia in showing
a mixture of temperate and tropical forms with a considerable
proportion of peculiar species. Owing to the comparatively
easy passage from the northern extremity of Japan through the
island of Saghalien to the main land of Asia, a large number of
temperate forms of insects and birds are still able to enter the
country, and thus diminish the proportionate number of peculiar
species. In the case of mammals this is more difficult; and the
large proportion of specific difference in their case is a good in-
dication of the comparatively remote epoch at which Japan was
finally separated from the continent. How long ago this sepa-
ration took place we cannot of course tell, but we may be sure
it was much longer than in the case of our own islands, and
therefore probably in the earlier portion of the Pliocene period.

FORMOSA,

Among recent continental islands there is probably none that
surpasses in interest and instructiveness the Chinese island
BB 2

372 | ISLAND LIFE. [PART IT.

named by the Portuguese Formosa, or “The Beautiful.” Till
quite recently it was a terra incognita to naturalists, and we
owe all our present knowledge of it to a single man, the late
Mr. Robert Swinhoe, who, in his official capacity as one of our
consuls in China, visited it several times between 1856 and 1866,
besides residing on it for more than a year. During this period
he devoted all his spare time and energy to the study of natural
history, more especially of the two important groups, birds and
mammals; and by employing a large staff of native collectors
and hunters, he obtained a very complete knowledge of its
fauna. In this case, too, we have the great advantage of a very
thorough knowledge of the adjacent parts of the continent, in
great part due to Mr. Swinhoe’s own exertions during the twenty
years of his service in that country. We possess, too, the
further advantage of having the whole of the available materials
in these two classes collected together by Mr. Swinhoe himself
after full examination and comparison of specimens; so that
there is probably no part of the world (if we except Europe,
North America, and British India) of whose warm-blooded
vertebrates we possess fuller or more accurate knowledge than
we do of those of the coast districts of China and its islands.?
Physical features of Formosa.—The island of Formosa is
nearly half the size of Ireland, being 220 miles long, and from
twenty to eighty miles wide, It is traversed down its centre by
a fine mountain range, which reaches an altitude of about 8,000
feet in the south and 12,000 feet in the northern half of the
island, and whose higher slopes and valleys are everywhere
clothed with magnificent forests. It is crossed by the line of the
Tropic of Cancer a little south of its centre; and this position,
combined with its lofty mountains, gives it an unusual variety
of tropical and temperate climates. These circumstances are
all highly favourable to the preservation and development of
animal life, and from what we already know of its productions,
1 Mr. Swinhoe died in October, 1877, at the early age of forty-two. His
writings on natural history are chiefly scattered through the volumes of the
Proceedings of the Zoological Society and The Ibis ; the whole being sum-
marised in his Catalogue of the Mammals of South China and Formosa

(P. Z.8., 1870, p. 615), and his Catalogue of the Birds of China and its
Islands (P. Z. S., 1871, p. 337).

CHAP, XVIII] - JAPAN AND FORMOSA. 373

it seems probable that few, if any islands of approximately the
same size and equally removed from a continent will be found to
equal it in the number and variety of their higher animals. The
outline map (at page 364) shows that Formosa is connected with
the mainland by a submerged bank, the hundred-fathom line
including it along with Hainan to the south-west and Japan on
the north-east ; while the line of two-hundred fathoms includes
also the Madjico-Sima and Loo-Choo Islands, and may, perhaps,
mark out approximately the last great extension of the Asiatic
continent, the submergence of which isolated these islands
from the mainland.

Animal Life of Formosa.—We are at present acquainted
with 35 species of mammalia, and 128 species of land-birds
from Formosa, fourteen of the former and forty-three of the
latter being peculiar, while the remainder inhabit also some
part of the continent or adjacent islands. This proportion of
peculiar species is perhaps (as regards the birds) the highest to
be met with in any island which can be classed as both conti-
nental and recent, and this, in all probability, implies that the
epoch of separation is somewhat remote. It was not, however,
remote enough to reach back to a time when the continental
fauna was very different from what it is now, for we find all the
chief types of living Asiatic mammalia represented in this small
island, Thus we have monkeys; insectivora; numerous car-
nivora; pigs, deer, antelopes, and cattle among ungulata;
numerous rodents, and the edentate Manis,—a very fair repre-
sentation of Asiatic mammals, all being of known genera, and of
species either absolutely identical with some still living else-
where or very closely allied to them. The birds exhibit analo-
gous phenomena, with the exception that we have here two
peculiar and very interesting genera.

But besides the amount of specific and generic modification
that has occurred, we have another indication of the lapse
of time in the peculiar relations of a large proportion of the
Formosan animals, which show that a great change in the dis-
tribution of Asiatic species must have taken place since the
separation of the island from the continent. Before pointing
these out it will be advantageous to give lists of the mammalia

374 ISLAND LIFE. | [PART II.

and peculiar birds of the island, as we shall have frequent occa-
sion to refer to them.

List oF THE MAMMALIA oF Formosa. (The peculiar species are printed
in italics. )

1. Macacus cyclopis, A rock-monkey more allied to If. rhesus of India
than to M. sancti-johannis of South China.

2. Pteropus formosus. <A fruit-bat closely allied to the Japanese species.
None of the genus are found in China. .

3. Vesperugo abramus. China.

4, Vespertilio formosus. Black and orange Bat. China.

5. Nyctinomus cestonii. Large-eared Bat. China, 8. Europe.

6. Lalpa insularis. A blind mole of a peculiar species.

7. Sorex murinus. Musk Rat. China.

8. Sorex sp. A shrew, undescribed.

9. Erinaceus sp. A Hedgehog, undescribed.
10. Ursus tibetanus. The Tibetan Bear. Himalayas and North China.
11. Helictis subaurantiaca. The orange-tinted Tree Civet. Allied to H.

nipalensis of the Himalayas more than to H. moschata of China.

. Martes flavigula, var. The yellow necked Marten. India, China,

. Felis macroscelis. The clouded Tiger of Siam and Malaya.

. Felis viverrina. The Asiatic wild Cat. Himalayas and Malacca.

. Felis chinensis. ‘The Chinese Tiger-cat. China.

. Viverricula malaccensis. Spotted Civet. China, India.

. Paguma larvata. Gem-faced Civet. China.

. Sus taivanus. Allied to the wild Pig of Japan.

19. Cervulus reevesii. Reeve’s Muntjac. China.

. Cervus pseudaxis. Formosan Spotted Deer. Allied to C. sika of
Japan.

. Cervus swinhoti. Swinhoe’s Rusa Deer. Allied to Indian and Malayan
species,

. Nemorhedus swinhoit. Swinhoe’s Goat-antelope. Allied to the species
of Sumatra and Japan.

. Bos chinensis. South China wild Cow.

. Mus bandicota. The Bandicoot Rat. Perhaps introduced from India.

. Mus indicus. Indian Rat.

. Mus coxinga. Spinous Country-rat.

. Mus canna. Silken Country-rat.

. Mus losea, Brown Country-rat.

. Sciurus castaneoventris. Chestnut-bellied Squirrel. China and Hainan,

. Sciurus m’clellandi. M/‘Clelland’s Squirrel. Himalayas, China,

. Scturopterus kaleensis. Small Formosan Flying Squirrel. Allied to
S. alboniger of Nepal.

. Pteromys grandis. Large Red Flying Squirrel. Allied to Himalayan
and Bornean species. From North Formosa.

cee Sl cee on ee oe
conto oF & bO

bo bo bo
bo Le jo)

WwWNMNNNMNNW WD bd wo
me OO CON O Ore &

CHAP. XVIII. ] JAPAN AND FORMOSA. 375

33. Pteromys pectoralis, White-breasted Flying Squirre!. From South

Formosa.
34, Lepus sinensis. Chinese Hare. Inhabits South China.
35. Manis dalmanni. Scaly Ant-eater, China and the Himalayas.

The most interesting and suggestive feature connected with
these Formosan mammals is the identity or affinity of several of
them, with Indian or Malayan rather than with Chinese species.
We have the rock-monkey of Formosa allied to the rhesus
monkeys of India and Burma, not to those of South China and
Hainan. The tree civet (Helictis subaurantiaca), and the small
flying squirrel (Sciwropterus kaleensis), are both allied to Hima-
layan species. Swinhoe’s deer and goat-antelope are nearest to
Malayan species, as are the red and white-breasted flying squir-
rels; while the fruit-bat, the wild pig, and the spotted deer are
all allied to peculiar Japanese species. ‘The clouded tiger is a
Malay species unknown in China, while the Asiatic wild cat is
a native of the Himalayas and Malacca. It is clear, therefore,
that before Formosa was separated from the main land the above
named animals or their ancestral types must have ranged over
the intervening country as far as the Himalayas on the west,
Japan on the north,and Borneo or the Philippines on the south ;
and that after that event occurred, the conditions were so mate-
rially changed as to lead to the extinction of these species
in what are now the coast provinces of China, while they or
their modified descendants continued to exist in the dense forests
of the Himalayas and the Malay islands, and in such detached
islands as Formosaand Japan. We will now see what additional
light is thrown upon this subject by an examination of the

birds.

List OF THE LAND BIRDS PECULIAR TO FORMOSA,

Turpip& (Thrushes).
1, Turdus albiceps, Allied to Chinese species,

SYLVIDIZ (Warblers).
2. Cisticola volitans. Allied to C. schenicola of India and China,
3. Herbivox cantans, Sub-species of H. cantillaus of N. China and
Japan.
4, Notodela montium. Allied to N. leucura of the Himalayas; no ally in
China.

376

13.

14,

15.

ite

18,

WS),

20.

22.

23,

ISLAND LIFE. [PART II.

TIMALIIDE (Babblers).

. Pomatorhinus musicus. Allies in 8. China and the Himalayas,
. P. erythrocnemis, Do. do.
. Garrulax ruficeps. Allied to G. albogularis of N. India and East

Thibet, not to the species of 8. China (G. sannio).

. Janthocincla pecilorhyncha, Allied to J. cerulata of the Himalayas,

None of the genus in China.

. Trochalopteron taivanus. Allied to a Chinese species.

. Alcippe morrisoniana.\ Near the Himalayan A. nipalensis. None of
. A. brunnea.

. Stbia auricularis. Allied to the Himalayan S. capistrata. The genus

the genus in China,

not known in China.

PANURIDE (Bearded Tits, &c).
Suthora bulomachus, Allied to the Chinese S. suffusa.

CincLIDz (Dippers and Whistling Thrushes),
Myiophoneus insularis, Allied to M, horsfieldi o£ South India.

PaRip# (Tits),

Parus insperatus. Sub-species of P. monticola of the Himalayas and
East Thibet.
P. castaneiveniris, Allied to P. varius of Japan,

LIOTRICHID (Hill Tits).

Inocichla steerti. A peculiar genus of a specially Himalayan family,
quite unknown in China,

PYCNONOTIDA (Bulbuls),

Pycnonotus (Spizixos) cinereicapillus. Very near P. semitorques of
China.

Hypsipetes nigerrimus. Allied to H. concolor of Assam, not to H,
macclellandi of China.

ORIOLID& (Orioles).
Analcipus ardens, Allied to A. traillii of the Himalayas and Tenas-
gérini,
CAMPEPHAGID& (Caterpillar Shrikes),
Graucalus rea-pineti. Closely allied to the Indian G. macei. No ally
in China.
DicruRrIp& (King Crows),

Chaptia brauniana. Closely allied to C. enea of Assam, No ally in
China,

MuscicaPip& (Flycatchers),
Cyornis vivida, Allied to C. rubeculoides of India.

| usec

CHAP, XVIII. ] JAPAN AND FORMOSA. od7

24,
25.

26.

27.

28.
29.

30.

31.

33,

42.
43,

CorviD& (Jays and Crows).

Garrulus taivanus. Allied to G sinensis of S. China.

Urocissa cerulea, A very distinct species from its Indian and Chinese
allies,

Dendrocitta formose. A sub-species of the Chinese D. sinensis.

PLOCEIDEH (Weaver Finches).

Muma formosana. Allied to M. rubronigra of India and Burmah.

ALAUDID (Larks),

Alauda sala. 1 ates in South China.

A, watiersi,
PITTID& (Pittas).

Pitia oreas, Allied to P. cyanoptera of Malaya and §. China.
Pictp& (Woodpeckers),

Picus insularis, Allied to P. leucunotus of Japan and Siberia.

MEGALEMIDA.

. Megalema nuchalis, Allied to M. oortii of Sumatra and M. faber of

Hainan. No allies in China.

CAPRIMULGIDE (Goatsuckers),

Caprimulgus stictomus. A sub-species of C. monticolus of India and
China.
CoLUMBID& (Pigeons).

. Treron formose. Allied to Malayan species.
. Sphenocercus sororius. Allied to Malay species and to S. sieboldi of

Japan. No allies of these two birds inhabit China.

. Chalcophaps formosana. Allied to the Indian species which extends to

Tenasserim and Hainan.

TETRAONID& (Grouse and Partridges).

. Oreoperdix crudigularis. A peculiar genus of partridges.
. Bambusicola sonorivox. Allied to the Chinese B. thoracica.
. Areoturni« rostrata. Allied to the Chinese A. blakistoniz.

PHASIANIDZE (Pheasants).

. Phasianus formosanus, Allied to P. torquatus of China.
. Luplocamus swinhoit. A very peculiar and beautiful species allied to

the tropical fire-backed pheasants, and to- the silver pheasant of
North China.

STRIGIDEZ (Owls).

Athene pardalota. Closely allied to a Chinese species,
Lempigius hambroekit, Allied to a Chinese species,

378 ISLAND LIFE. [PART II.

This list exhibits to us the marvellous fact that more than
half the peculiar species of Formosan birds have their nearest
allies in such remote regions as the Himalayas, South India, the.
Malay Islands, or Japan, rather than in the adjacent parts
of the Asiatic continent. Fourteen species have Himalayan
allies, and six of these belong to genera which are unknown in
China. One has its nearest ally in the Nilgherries, and five in.
the Malay Islands ; and of these six, four belong to genera which
are not Chinese. Two have their only near allies in Japan.
Perhaps more curious still are those cases in which, though the
genus is Chinese, the nearest allied species is to be sought for in
some remote region. ,Thus we have the Formosan babbler.
(Garrulax ruficeps) not allied to the species found in South
China, but to one inhabiting North India and East Thibet;
while the black bulbul (Hypsipetes nigerrimus), is not allied to
the Chinese species but to an Assamese form.

In the same category as the above we must place eight:
species not peculiar to Formosa, but which are Indian or
Malayan instead of Chinese, so that they offer examples of dis-
continuous distribution somewhat analogous to what we found
to occur in Japan. ‘These are enumerated in the following
list. 7

Srecies OF Brrps common To Formosa AND INDIA OR MALAYA, BUT NOT
FOUND IN CHINA.

1. Siphia superciliaris. The Rufous-breasted Flycatcher of the S.F,

Himalayas.

2. Halcyon coromanda, The Great Red Kingfisher of India, Malaya, and
Japan.

3. Palumbus pulchricollis. The Darjeeling Wood-pigeon of the S.E.
Himalayas.

. Turnic dussumierit. The larger Button-quail of India.

Spizaetus nipalensis. The Spotted Hawk-eagle of Nepal and Assam.
. Lophospiza trivirgata. The Crested Gos-hawk of the Malay Islands.
. Bulaca newarensis. The Brown Wood-owl of the Himalayas.

. Strix candida. The Grass-owl of India and Malaya.

CON OO

The most interesting of the above are the pigeon and the
flycatcher, both of which are, so for as yet known, strictly con-
fined to the Himalayan mountains and Formosa. They thus
afford examples of discontinuous specific distribution exactly

CHAP, XVIII. | JAPAN AND FORMOSA. 379

parallel to that of the great spotted kingfisher, already referred
to as found only in the Himalayas and Japan.

Comparison of the Faunas of Hainan, Formosa, and Japan.—
The island of Hainan on the extreme south of China, and only
separated from the mainland by a strait fifteen miles wide,
appears to have considerable similarity to Formosa, inasmuch as
it possesses seventeen peculiar land-birds (out of 130 obtained
by Mr. Swinhoe), two of which are close allies of Formosan
species, while two others are identical. We also find four
species whose nearest allies are in the Himalayas. Our know-
ledge of this island and of the adjacent coast of China is not
yet sufficient to enable us to form an accurate judgment of its
relations, but 1t seems probable that 1t was separated from the
continent at, approximately, the same epoch as Formosa and
Japan, and that the special features of each of these islands
is mainly due to their geographical position. Formosa, being
more completely isolated than either of the others, possesses a
larger proportion of peculiar species of birds, while its tropical
situation and lofty mountain ranges has enabled it to preserve
an unusual number of Himalayan and Malayan forms. Japan,
almost equally isolated towards the south, and having a much
greater variety of climate as well as a much larger area, pos-
sesses about an equal number of mammalia with Formosa, and
an even larger proportion of peculiar species. Its birds, how-
ever, though more numerous are less peculiar; and this is
probably due to the large number of species which migrate
northwards in summer, and find it easy to enter Japan through
the Kurile Isles or Saghalien. Japan too, is largely peopled by
those northern types which have an unusually wide range, and
which, being almost all migratory, are accustomed to cross over
seas of moderate extent. The regular or occasional influx of
these species prevents the formation of special insular races,
such as are almost always produced when a portion of the popu-
lation of a species remains for a considerable time completely
isolated. We thus have explained the curious fact, that while
the mammalia of the two islands are almost equally peculiar,
(those of Japan being most so in the present state of our

330 ISLAND LIFE. [parr a.

knowledge), the birds of Formosa show a far greater number
of peculiar species than those of Japan.

General remarks on recent Continental Islands.—We have now
briefly sketched the zoological peculiarities of an illustrative
series of recent continental islands, commencing with one of the
most recent—Great Britain—in which the process of formation
of peculiar species has only just commenced, and terminating
with Formosa, probably one of the most ancient of the series,
and which accordingly presents us with a very large proportion
of peculiar species, not only in its mammalia, which have no
means of crossing the wide strait which separates it from the
mainland, but also in its birds, many of which are quite able to
cross over. :

Here, too, we obtain a glimpse of the way in which species
die out and are replaced by others, which quite agrees with
what the theory of evolution assures us must have occurred.
On a continent, the process of extinction will generally take
effect on the circumference of the area of distribution, because
it is there that the species comes into contact with such adverse
conditions or competing forms as prevent it from advancing
further. A very slight change will evidently turn the scale and
cause the species to contract its range, and this usually goes on
till it is reduced to a very restricted area, and finally becomes
extinct. It may conceivably happen (and almost certainly has |
sometimes happened) that the process of restriction of range by
adverse conditions may act in one direction only, and over a
limited district, so as ultimately to divide the specific area into
two separated parts, in each of which a portion of the species
will continue to maintain itself. We have seen that there is
reason to believe that this has occurred in a very few cases both
in North America and in Northern Asia. (See pp. 64-66.) But
the same thing has certainly occurred in a considerable number
of cases, only it has resulted in the divided areas being occupied
by representative forms instead of by the very same species. The
cause of this is very easy to understand. We have already
shown that there is a large amount of local variation in a

CHAP. XVIII. ] JAPAN AND FORMOSA. 381

considerable number of species, and we may be sure that were
it not for the constant intermingling and intercrossing of the
individuals inhabiting adjacent localities this tendency to local
variation would soon form distinct races. But as soon as the
area is divided into two portions the intercrossing 1s stopped,
and the usual result is that two closely allied races, classed
as representative species, become formed. Such pairs of allied
species on the two sides of a continent, or in two detached areas,
are very numerous; and their existence is only explicable on the
supposition that they are descendants of a parent form which
once occupied an area comprising that of both of them,—that
this area then became discontinuous,—and, lastly, that, as a
consequence of the discontinuity, the two sections of the parent
species became segregated into distinct races or new species.

Now, when the division of the area leaves one portion of the
species in an island, a similar modification of the species, either
in the island or in the continent, occurs, resulting in closely-
allied but distinct forms ; and such forms are, as we have scen,
highly characteristic of island-faunas. But islands also favour
the occasional preservation of the unchanged species—a pheno-
menon which very rarely occurs in continents. This is probably
due to the absence of competition in islands, so that the parent
species there maintains itself unchanged, while the continental
portion, by the force of that competition, is driven back to some
remote mountain area, where it too obtains a comparative free-
dom from competition. Thus may be explained the curious fact,
that the species common to Formosa and India are generally
confined to limited areas in the Himalayas, or in other cases are
found only in remote islands, as Japan or Hainan.

The distribution and affinities of the animals of continental
islands thus throws much light on that obscure subject—the
decay and extinction of species ; while the numerous and delicate
gradations in the modification of the continental species, from
perfect identity, through slight varieties, local forms, and insular
races, to well-defined species and even distinct genera, afford
an overwhelming mass of evidence in favour of the theory of
“descent with modification.”

382 ISLAND LIFE. [PART II.

We shall now pass on to another class of islands, which,
though originally forming parts of continents, were separated
from them at very remote epochs. This antiquity is clearly
manifested in their existing faunas, which present many pecu-
liarities, and offer some most curious problems to the student
of distribution.

CHAPTER XIX.

ANCIENT CONTINENTAL ISLANDS: THE MADAGASCAR GROUP.

Reinarks on Ancient Continental Islands—Physical features of Madagascar
—Biological features of Madagascar—Mammalia—Reptiles—Relation
of Madagascar to Africa—Early history of Africa and Madagascar—
Anomalies of distribution and how to explain them—The birds of
Madagascar as indicating a supposed Lemurian Continent—Submerged
Islands between Madagascar and India—Concluding remarks on ‘‘ Lemu-
ria’’—The Mascarene Islands—The Comoro Islands—The Seychelles
Archipelago—Birds of the Seychelles—Reptiles and Amphibia—Fresh-
water Fishes—Land Shells—Mauritius, Bourbon, and Rodriguez—Birds
—HExtinct Birds and their probable origin—Reptiles—Flora of Mada-
gascar and the Mascarene Islands—Curious relations of Mascarene
plants—Endemic genera of Mauritius and Seychelles—Fragmentary
character of the Mascarene Flora—Flora of Madagascar allied to that
of South Africa—Preponderance of Ferns in the Mascarene Flora—
Concluding remarks on the Madagascar Group.

WE have now to consider the phenomena presented by a very
distinct class of islands—those which, although once forming
part of a continent, have been separated from it at a remote
epoch when its animal forms were very unlike what they are
now. Such islands preserve to us the record of a by-gone
world,—of a period when many of the higher types had not
yet come into existence and when the distribution of others
was very different from what prevails at the present day. The
problem presented by these ancient islands is often complicated
by the changes they themselves have undergone since the period
of their separation. <A partial subsidence will have led to the
extinction of some of the types that were originally preserved,

384 ISLAND LIFE. [PART II.
and may leave the ancient fauna in a very fragmentary state ;
while subsequent elevations may have brought it so near to the
continent that some immigration even of mammalia may have
taken place. If these elevations and subsidences occurred several
times over, though never to such an extent as again to unite the
island with the continent, it is evident that a very complex
result might be produced ; for besides the relics of the ancient
fauna, we might have successive immigrations from surrounding
lands reaching down to the era of existing species. Bearing in
mind these possible changes, we shall generally be able to arrive
at a fair conjectural solution of the phenomena of distribution
presented by these ancient islands.

Undoubtedly the most interesting of such islands, and that
which exhibits their chief peculiarities in the greatest perfec-
tion, is Madagascar, and we shall therefore enter somewhat fully
into its biological and physical history.

Physical features of Madagascar.—This great island is situated
about 250 miles from the east coast of Africa, and extends
from 12° to 253° 8. Lat. It is almost exactly 1,000 miles
long, with an extreme width of 360 and an average width of
more than 260 miles. A lofty granitic plateau, from eighty to
160 miles wide and from 3,000 to 5,000 feet high, occupies its
central portion, on which rise peaks and domes of basalt and
granite to a height of nearly 9,000 feet; and there are also
numerous extinct volcanic cones and craters. All round the
island, but especially developed on the south and west, are
plains of a few hundred feet elevation, formed of rocks which
are shown by their fossils to be of Jurassic age, or at all events
to belong to somewhere near the middle portion of the Secondary
period. The higher granitic plateau consists of bare undulating
moors, while the lower Secondary plains are more or less wooded ;
and there is here also a continuous belt of dense forest, varying
from six or eight to fifty miles wide, encircling the whole island,
usually at about thirty miles distance from the coast but in the
north-east coming down to the sea-shore.

The sea around Madagascar, when the shallow bank on which it
stands is passed, is generally deep. This 100-fathom bank is only
from one to three miles wide on the east side, but on the west

CHAP. XIX. ] THE MADAGASCAR GROUP. 3895

20 bedi

Reunion.

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ENGLAND
to the sazne scale

MADAGASCAR,

The Shaded Part shews the Elevated Grani- |
tic region; the Black dots,the Volcanicaistricts, |
while Dense Forests surround the Island

Cae

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386 ISLAND LIFE. [PART IT.

it is much broader, and stretches out opposite Mozambique to a
distance of about eighty miles, The Mozambique Channel varies
from less than 500 to more than 1,500 fathoms. deep, the shal-
lowest part being where the Comoro Islands and adjacent shoals
seem to form stepping-stones to the continent of Africa. The
500-fathom line includes Aldabra and the small Farquhar
Islands to the north of Madagascar; while to the east the sea
deepens rapidly to the 1,000-fathom line, and then more slowly,
a profound channel of 2,400 fathoms separating Madagascar from
Bourbon and Mauritius. To the north-east of Mauritius are a
series of extensive shoals, forming four large banks less than 100
fathoms below the surface, while the 1,000-fathom line includes
them all, with an area about half that of Madagascar itself.
A little further north is the Seychelles group, also standing
on an extensive 1,000-fathom bank, while all around the sea
is more than 2,000 fathoms deep.

It seems probable, then, that to the north-east of Madagascar
there was once a series of very large islands, separated from it
by not very wide straits; while eastward across the Indian
Ocean we find the Chagos and Maldive coral atolls, marking
the position of other large islands, which together would form
a line of communication, by comparatively easy stages of 400
or 500 miles each between Madagascar and India. These sub-
merged islands, as shown in our map at p. 396, are of great
importance in explaining some anomalous features in the zoology
of this great island.

If the rocks of Secondary age which form a belt around the
island are held to indicate that Madagascar was once of less
extent than it is now (though this by no means necessarily
follows), we have also evidence that it has recently been con-
siderably larger ; for along the east coast there is an extensive
barrier coral-reef about 350 miles in length, and varying in
distance from the land from a quarter of a mile to three or
four miles. This is good proof of recent subsidence; while
we have no record of raised coral rocks inland which would
certainly mark any recent elevation, because fringing coral reefs
surround a considerable portion of the northern, eastern, and
south-western coasts. We may therefore conclude that during

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388 ISLAND LIFE. [PART II,

Tertiary times the island was usually as large as, and often
probably much larger than, it is now.

iological features of Madagascar.—Madagascar possesses an
exceedingly rich and beautiful fauna and flora, rivalling in
some groups most tropical countries of equal extent, and even
when poor in species, of surpassing interest from the singularity,
the isolation, or the beauty of its forms of life. In order to
exhibit the full peculiarity of its natural history and the nature
of the problems it offers to the biological student, we must
give an outline of its more important animal forms -in systematic
order.

Mammalia, — Madagascar possesses no less than sixty-six
species of mammals—a certain proof in itself that the island
has once formed part of a continent; but the character of these
animals is very extraordinary and very different from the as-
semblage now found in Africa or in any other existing continent.
Africa is now most prominently characterised by its monkeys,
apes, and baboons; by its lions, leopards, and hyenas; by its
zebras, rhinoceroses, elephants, buffaloes, giraffes, and numerous
species of antelopes. But no one of these animals, nor any
thing like them, is found in Madagascar, and thus our first
impression would be that it could never have been united with
the African continent. But, as the tigers, the bears, the tapirs,
the deer, and the numerous squirrels of Asia are equally
absent, there seems no probability of its having been united
with that continent. Let us then see to what groups the
mammalia of Madagascar belong, and where we must look for
their probable allies.

First and most important are the lemurs, consisting of six
genera and thirty-three species, thus comprising just half the
entire mammalian population of the island. This group of
lowly-organised and very ancient creatures still exists scattered
over a wide area; but they are nowhere so abundant as in the
island of Madagascar. They are found from West Africa to
India, Ceylon, and the Malay Archipelago, consisting of a
number of isolated genera and species, which appear to main-
tain their existence by their nocturnal and arboreal habits, and
by haunting dense forests. It can hardly be said that the

CHAP; XIX. | THE MADAGASCAR GROUP. 389

African forms of lemurs are more nearly allied to those of
Madagascar than are the Asiatic, the whole series appearing to
be the disconnected fragments of a once more compact and
extensive group of animals.

Next, we have about a dozen species of Insectivora, consisting
of one shrew, a group distributed over all the great continents ;
and five genera of a peculiar family, Centetide, which family
exists nowhere else on the globe except in the two largest West
Indian Islands, Cuba and Hayti, thus adding still further to
our embarrassment in seeking for the original home of the
Madagascar fauna.

We then come to the Carnivora, which are represented by a
peculiar cat-like animal, Cryptoprocta, forming a distinct family,
and having no allies in any part of the globe; and eight civets
belonging to four peculiar genera. Here we first meet with
some decided indications of an African origin; for the civet
family is more abundant in this continent than in Asia, and some
of the Madagascar genera seem to be decidedly allied to African
groups—as, for example, Eupleres to Suricata and Crossarchus,!

The Rodents consist only of four rats and mice of peculiar
genera, one of which is said to be allied to an American genus ;
and lastly we have a river-hog of the African genus Potamo-
cheerus, and a small sub-fossil hippopotamus, both of which being
semi-aquatic animals might easily have reached the island from
Africa, by way of the Comoros, without any actual land-connection.

Reptiles of Madagascar, — Passing over the birds for the
present, as not so clearly demonstrating land-connection, let us
see what indications are afforded by the reptiles. The large
and universally distributed family of Colubrine snakes is repre-
sented in Madagascar, not by African or Asiatic genera, but by
two American genera—Philodryas and Heterodon, and by Her-
petodryas, a genus found in America and China. The other
genera are all peculiar, and belong mostly to widespread tropical
families ; but two families—Lycodontide and Viperids, both
abundant in Africa and the Eastern tropics—are absent.
Lizards are mostly represented by peculiar genera of African or

1 See Dr. J. EH, Gray’s ‘‘ Revision of the Viverride,” in Proc. Zool. Soc,
1864, p. 507, 3

390 : ISLAND LIFE. [PAR®T 11,

tropical families, but several African genera are represented by
peculiar species, and there are also some species belonging to
two American genera of the Iguanide, a family which is ex-
clusively American; while a genus of geckoes, inhabiting
America and Australia, also occurs in Madagascar.

fielatwon of Madagascar te Africa.—These facts taken all
together are certainly very extraordinary, since they show in a
considerable number of cases as much affinity with America as
with Africa; while the most striking and characteristic groups
of animals now inhabiting Africa are entirely wanting in Mada-
gascar. Let us first deal with this fact, of the absence of so
many of the most dominant African groups. The explanation
of this deficiency is by no means difficult, for the rich deposits
of fossil mammals of Miocene age in France, Germany, Greece,
and North-west India, have demonstrated the fact that all the
great African mammals then inhabited Europe and temperate
Asia. We also know that a little earlier Gn Eocene times)
tropical Africa was cut off from Europe and Asia by a sea
stretching from the Atlantic to the Bay of Bengal, at which
time Africa must have formed a detached island-continent such
as Australia is now, and probably, like it, very poor in the
higher forms of life. Coupling these two facts, the inference seems
clear, that all the higher types of mammalia were developed
in the great Euro-Asiatic continent (which then included
Northern Africa), and that they only migrated into tropical
Africa when the two continents became united by the upheaval
of the sea-bottom, probably in the latter pee of the Miocene
or early in the Pliocene period.

1 This view was, I believe, first advanced by Professor Huxley in his
‘Anniversary Address to the Geological Society,’’ in 1870. He says :—‘‘In
fact the Miocene mammalian. fauna of Europe and the Himalayan regions
contain, associated together, the types which are at present separately
ocated in the South African and Indian provinces of Arctogea. Now
there 1s every reason to believe, on other grounds, that both Hindostan
south of the Ganges, and Africa south of the Sahara, were separated by a
wide sea from Europe and North Asia during the Middle and Upper Eocene
epochs. Hence it becomes highly probable that the well-known similar-
ities, and no less remarkable differences, between the present faune of
India and South Africa have arisen in some such fashion as the following :

CHAP, XIX. ] THE MADAGASCAR GROUP. oul

It is clear, therefore, that if Madagascar had once formed
part of Africa, but had been separated from it before Africa
was united to Kurope and Asia, it would not contain any of
those kinds of animals which then first entered the country.
But, besides the African mammals, we know that some birds
now confined to Africa then inhabited Europe, and we may there-
fore fairly assume that all the more important groups of birds,
reptiles, and insects, now abundant in Africa but absent from
Madagascar, formed no part of the original African fauna, but
entered the country only after it was joined to Europe and Asia.

Karly History of Africa and Madagascar.— We have seen that
Madagascar contains an abundance of mammals, and that most
of them are of types either peculiar to, or existing also in, Africa ;
it follows that that continent must have had an earlier union
with Europe, Asia, or America, or it could never have obtained
any mammals at all. Now these ancient African mammals are
Lemurs, Insectivora, and small Carnivora, chiefly Viverride ;
and all these groups are known to have inhabited Europe in
Eocene and Miocene times; and that the union was with
Europe rather than with America is clearly proved by the fact
that even the Insectivorous Centetidz, now confined to Mada-
gascar and the West Indies, inhabited France in the Lower
Miocene period, while the Viverride, or civets, which form so

Some time during the Miocene epoch, the bottom of the nummulitic sea
was upheaved and converted into dry land in the direction of a line ex-
tending from Abyssinia to the mouth of the Ganges. By this means the
Dekkan on the one hand and South Africa on the other, became connected
with the Miocene dry land and with one another. The Miocene mammals
spread gradually over this intermediate dry land ; and if the condition of
its eastern and western ends offered as wide contrasts as the valleys of the
Ganges and Arabia do now, many forms which made their way into Africa
must have been different from those which reached the Dekkan, while
others might pass into both these sub-provinces.”

This question is fully discussed in my G'eographical Distribution of
Animals (Vol. I., p. 285), where I expressed views somewhat different from
those of Professor Huxley and made some slight errors which are corrected
in the present work. As I did not then refer to Professor Huxley’s prior
statement of the theory of Miocene immigration into Africa (which I had
read but the reference to which I could not recall) I am happy to give
his views here.

392 ISLAND LIFE. [PART II.

important a part of the fauna of Madagascar as well as of
Africa, were abundant in Europe throughout the whole Ter-
tiary period, but are not known to have ever lived in any part
of the American continent. We here see the application of
the principle which we have already fully proved and illustrated
(Chapter LV., p. 62), that all extensive groups have a wide range
at the period of their maximum development; but as they
decay their area of distribution diminishes or breaks up into
detached fragments, which one after another disappear till the
group becomes extinct. Those animal forms which we now
find isolated in Madagascar and other remote portions of the
globe all belong to ancient groups which are in a decaying or
nearly extinct condition, while those which are absent from it
belong to more recent and more highly-developed types, which
range over extensive and continuous areas, but have had no
opportunity of reaching the more ancient continental islands.
Anomalies of Distribution and how to explain them.—If these
considerations have any weight, it follows that there 1s ho reason
whatever for supposing any former direct connection between
Madagascar and the Greater Antilles merely because the In-
sectivorous Centetide now exist only in these two groups of
islands ; for we know that the ancestors of this family must
once have had a much wider range, which almost certainly
extended over the great northern continents. We might as
reasonably suppose a land-connection across the Pacific to ac-
count for the camels of Asia having their nearest existing
allies in the llamas and alpacas of the Peruvian Andes, and
another between Sumatra and Brazil, in order that the ances-
tral tapir of one country might have passed over to the other.
In both these cases we have ample proof of the former wide
extension of the group. Extinct camels of numerous species
abounded in North America in Miocene, Pliocene, and even
Post-pliocene times, and one has also been found in North-
western India, but none whatever among all the rich deposits
of mammalia in Europe. We are thus told, as clearly as pos-
sible, that from the North American continent as a centre the
camel tribe spread westward, over now-submerged land at the
shallow Behring Straits and Kamschatka Sea, into Asia, and

CHAP. XIX.] THE MADAGASCAR GROUP. 393

southward along the Andes into South America. Tapirs are
even more interesting and instructive. Their remotest known
ancestors appear in Western Europe in the early portion of the
Eocene period; in the later Eocene and the Miocene other
forms occur both in Europe and North America. These seem
to have become extinct in North America, while in Europe
they developed largely into many forms of true tapirs, which at
a mueh later period found their way again to North, and thence
to South, America, where their remains are found in caves and
gravel-deposits. It is an instructive fact that in the Hastern
continent, where they were once so abundant, they have
dwindled down to a single species, existing in small numbers
in the Malay Peninsula, Sumatra, and Borneo only; while in
the Western continent, where they are comparatively recent
immigrants, they occupy a much larger area, and are repre-
sented by three or four distinct species. Who could possibly
have imagined such migrations, and extinctions, and changes of
distribution as are demonstrated in the case of the tapirs, if we
had only the distribution of the existing species to found an
opinion upon? Such cases as these—and there are many others
equally striking—show us with the greatest distinctness how
nature has worked in bringing about the examples of anomalous
distribution that everywhere meet us; and we must, on every
ground of philosophy and common sense, apply the same method
of interpretation to the more numerous instances of anomalous
distribution we disccver among such groups as reptiles, birds,
and insects, where we rarely have any direct evidence of their
past migrations through the discovery of fossil remains. When-
ever we can trace the past history of any group of terrestrial
animals, we invariably find that its actual distribution can be
explained by migrations effected by means of comparatively
slight modifications of our existing continents. In no single
case have we any direct evidence that the distribution of land
and sea has been radically changed during the whole lapse of
the Tertiary and Secondary periods, while, as we have already
shown in our fifth chapter, the testimony of geology itself, if
fairly interpreted, upholds the same theory of the stability of
our continents and the permanence of our oceans. Yet so easy

394 ISLAND LIFE. [PART 11.

and pleasant is it to speculate on former changes of land and
sea with which to cut the gordian knot offered by anomalies
of distribution, that we still continually meet with suggestions
of former continents stretching in every direction across the
deepest oceans, in order to explain the presence in remote parts
of the globe of the same genera even of plants or of insects—
organisms which possess such exceptional facilities both for ter-
restrial, aérial, and oceanic transport, and of whose distribution
in past ages we generally know absolutely nothing.

The Birds of Madagascar, as indicating a supposed Lemurrvan
continent.—Having thus shown how the distribution of the land
mammalia and reptiles of Madagascar may be well explained by
the supposition of a union with Africa before the greater part of its
existing fauna had reached it, we have now to consider whether,
as some ornithologists think, the distribution and affinities of
the birds present an insuperable objection to this view, and
require the adoption of a hypothetical continent—Lemuria—
extending from Madagascar to Ceylon and the Malay Islands,

There are about one hundred land birds known from the island
of Madagascar, all but four or five being peculiar; and about
half of these peculiar species belong to peculiar genera, many
of which are extremely isolated, so that it is often difficult to
class them in any of the recognised families, or to determine
their affinities to any living birds. Among the other moiety,
belonging to known genera, we find fifteen which have un-
doubted African affinities, while five or six are as decidedly
Oriental, the genera or nearest allied species being found in
India or the Malay Islands. It is on the presence of these
peculiar Indian types that Dr. Hartlaub, in his recent work on
the Birds of Madagascar and the Adjacent Islands, lays great
stress, as proving the former existence of “ Lemuria;” while he
considers the absence of such peculiar African families as the
plantain-eaters, glossy-starlings, ox-peckers, barbets, honey-
guides, hornbills, and bustards—besides a host of peculiar
African genera—as sufficiently disproving the statement in my
Geographical Distribution of Animals that Madagascar is “ more
nearly related to the Ethiopian than to any other region,” and
that its fauna was evidently “ mainly derived from Africa.”

supe |

CHAP. X1x.] THE MADAGASCAR GROUP. 395

But the absence of the numerous peculiar groups of African
birds is so exactly parallel to the same phenomenon among
mammals, that we are justified in imputing it to the same
cause, the more especially as some of the very groups that
are wanting—the plantain-eaters and the trogons, for example,
—are actually known to have inhabited Europe along with the
large mammalia which subsequently migrated to Africa. As to
the peculiarly Eastern genera—such as Copsychus and Hyp-
sipetes, with a Dicrurus, Ploceus, a Cisticola, and a Scops, all
closely allied to Indian or Malayan species—although very
striking to the ornithologist, they certainly do not outweigh
the fourteen African genera found in Madagascar. Their pre-
sence may, moreover, be accounted for more satisfactorily than
by means of an ancient Lemurian continent, which, even if
granted, would not explain the very facts adduced in its support.

Let us first prove this latter statement. :

The supposed “Lemuria” must have existed, if at all, at so
remote a period that the higher animals did not then inhabit
either Africa or Southern Asia, and it must have become par-
tially or wholly submerged before they reached those countries ;
otherwise we should find in Madagascar many other animals
besides Lemurs, Insectivora, and Viverride, especially such
active arboreal creatures as monkeys and squirrels, such hardy
grazers as deer or antelopes, or such wide-ranging carnivores as
foxes or bears. This obliges us to date the disappearance of the
hypothetical continent about the earlier part of the Miocene
epoch at latest, for during the latter part of that period we
know that such animals existed in abundance in every part of
the great northern continents wherever we have found organic
remains. But the Oriental birds in Madagascar, by whose pre-
sence Dr. Hartlaub upholds the theory of a Lemuria, are slightly
modified forms of existing Indian genera, or sometimes, as Dr.
Hartlaub himself points out, speeies hardly distinguishable from
those of India. Now all the evidence at our command leads
us to conclude that, even if these genera and species were in
existence in the carly Miocene period, they must have had a
widely different distribution from what they have now. Along
with so many African and Indian genera of mammals they then

396 ISLAND LIFE. [PART II,

probably inhabited Europe, which at that epoch enjoyed a sub-
tropical climate; and this is rendered almost certain by the
discovery in the Miocene of France of fossil remains of trogons
and jungle-fowl. If, then, these Indian birds date back to the
very period during which alone Lemuria could have existed,
that continent was quite unnecessary for their introduction into
Madagascar, as they could have followed the same track as the
mammalia of Miocene Europe and Asia ; while if, as I maintain,
they are of more recent date, then Lemuria had ceased to
exist, and could not have been the means of their introduction.

Ay
Ag AGO Hy, alll
iy ty MAUR My, gO

wy,

& 9 yy MS
gn Merny yy Ww
\) : =

MAP OF THE INDIAN OCEAN.
Showing the position of banks less than 1,000 fathoms deep between Africa and the Indian
Peninsula. “

Submerged Islands between Madagascar and India—Looking at
the accompanying map of the Indian Ocean, we see that between
Madagascar and India there are now extensive shoals and coral-
reefs, such as are always held to indicate subsidence; and we
may therefore fairly postulate the former existence here of
several large islands, some of them not much inferior to Mada-

gascar itself, These reefs are all separated from each other by

CHAP. XIX. | THE MADAGASCAR GROUP. 397

very deep sea—much deeper than that which divides Mada-
gascar from Africa, and we have therefore no reason to imagine
their former union. But they would nevertheless greatly facili-
tate the introduction of Indian birds into the Mascarene Islands
and Madagascar; and these facilities existing, such an immigra-
tion would be sure to take place, just as surely as American birds
have entered the Galapagos and Juan Fernandez, as European
birds now reach the Azores, and as Australian birds reach such
a distant island as New Zealand. This would take place the
more certainly because the Indian Ocean 1s a region of violent
periodical storms at the changes of the monsoons, and we have
seen in the case of the Azores and Bermuda how important a
factor this is in determining the transport of birds across the
ocean.

Mr. Darwin’s theory of the formation of atolls is now almost
universally accepted as the true one, and this theory implies
that the areas in question are still, or have very recently been,
subsiding. The final disappearance of these now sunken islands
does not, therefore, in all probability, date back to a very re-
mote epoch; and this exactly accords with the fact that some
of the birds, as well as the fruit-bats of the genus Pteropus, are
very closely allied to Indian species, if not actually identical,
others being distinct species of the same genera. The fact that
not one closely-allied species or even genus of Indian or Malayan
mammals is found in Madagascar, sufficiently proves that it is
no land-connection that has brought about this small infusion of
Indian birds and bats; while we have sufficiently shown, that,
when we go back to remote geological times no land-connection
in this direction was necessary to explain the phenomena of the
distribution of the Lemurs and Insectivora, A land-connection
with some continent was undoubtedly necessary, or there would
have been no mammalia at all in Madagascar; and the nature
of its fauna on the whole, no less than the moderate depth of
the intervening strait and the comparative approximation of the
opposite shores, clearly indicate that the connection was with
Africa.

Concluding remarks on “ Lemuria.”—I have gone into this
question in some detail, because Dr. Hartlaub’s criticism on my

398 ISLAND LIFE. [PART Il.

views has been reproduced in a scientific periodical,! and the
supposed Lemurian continent is constantly referred to by quasi-
scientific writers, as well as by naturalists and geologists, as if its
existence had been demonstrated by facts, or as if it were abso-
lutely necessary to postulate such a land in order to account for
the entire series of phenomena connected with the Madagascar
fauna, and especially with the distribution of the Lemuride.?
I think I have now shown, on the other hand, that it was
essentially a provisional hypothesis, very useful in calling atten-
tion to aremarkable series of problems in geographical distri-
bution, but not affording the true solution of these problems,
any more than the hypothesis of an Atlantis solved the problems
presented by the Atlantic Islands and the relations of the
European and North American flora and fauna. The Atlantis
is now rarely introduced seriously except by the absolutely
unscientific, having received its death-blow by the chapter on
Oceanic Islands in the Origin of Species, and the researches of
Professor Asa Gray on the affinities of the North American
and Asiatic floras. But “Lemuria” still keeps its place—a good
example of the survival of a provisional hypothesis which offers

1 The Ibis, 1877, p. 334.

2 In a paper read before the Geological Society in 1874, Mr. H. F. Blan-
ford, from the similarity of the fossil plants and reptiles, supposed that
India and South Africa had been connected bya continent, ‘‘and remained
so connected with some short intervals from the Permian up to the end of
the Miocene period,” and Mr. Woodward expressed his satisfaction with
“ this further evidence derived from the fossil flora of the Mesozoic series of

India in corroboration of the former existence of an old submerged conti-
nent—Lemuria.”’

Those who have read the preceding chapters of the present work will
not need to have pointed out to them how utterly inconclusive is the frag-
mentary evidence derived from such remote periods (even if there were no
evidence on the other side) as indicating geographical changes. The notion
that a similarity in the productions of widely separated continents at any
past epoch is only to be explained by the existence of a direct land-con-
nection, is entirely opposed to all that we know of the wide and varying
distribution of all types at different periods, as well as to the great powers
of dispersal over moderate widths of ocean possessed by all animals except
mammalia, It is no less opposed to what is now known of the general
permanency of the great continental and oceanic areas; while in this par-
ticular case it is totally inconsistent (as has been shown above) with the
actual facts of the distribution of animals,

CHAP, XIX. | THE MADAGASCAR GROUP. 399

what seems an easy solution of a difficult problem, and has
received an appropriate and easily remembered name, long after
it has been proved to be untenable.

It is now more than four years since I first showed, by a
careful examination of all the facts to be accounted for, that
the hypothesis of a Lemurian continent was alike unnecessary
to explain one portion of the facts, and inadequate to explain
the remaining portion! Since that time I have seen no
attempt even to discuss the question on general grounds in
opposition to my views, nor on the other hand have those who
have hitherto supported the hypothesis taken any opportunity
of acknowledging its weakess and inutility. I have therefore
here explained my reasons for rejecting it somewhat more fully
and in a more popular form, in the hope that a check may thus
be placed on the continued re-statement of this unsound theory
as if it were one of the accepted conclusions of modern science.

The Mascarene Islands.2—In the Geographical Distribution of
Animals, a summary is given of ali that was known of the
zoology of the various islands near Madagascar, which to some ex-
tent partake of its peculiarities, and with it form the Malagasy
sub-region of the Ethiopian region. As no great additions have
since been made to our knowledge of the fauna of these islands,
and my object in this volume being more especially to illustrate
the mode of solving distributional problems by means of the
most suitable examples, I shall now confine myself to pointing
out how far the facts presented by these outlying islands
support the views already enunciated with regard to the origin
of the Madagascar fauna.

The Comoro Islands.—This group of islands is situated
nearly midway between the northern extremity of Madagascar
and the coast of Africa. The four chief islands vary between
sixteen and forty miles in length, the largest being 180 miles from
the coast of Africa, while one or two smaller islets are less than
100 miles from Madagascar. All are volcanic, Great Comoro being

1 Geographical Distribution of Animals, Vol. I., p. 272—292.

2 The term “ Mascarene ” is used here in an extended sense, to include
all the islands near Madagascar which resemble it in their animal and
vegetable productions,

400. ISLAND LIFE. [PART IL.

an active volcano 8,500 feet high ; and, as already stated, they
are situated on a submarine bank with less than 500 fathoms
soundings, connecting Madagascar with Africa. There is reason
to believe, however, that these islands are of comparatively
recent origin, and that the bank has been formed by matter
ejected by the volcanoes or by upheaval. Any how there is
no indication whatever of there having been here a land-con-
nection between Madagascar and Africa; while the islands
themselves have been mainly colonised from Madagascar, to
the 100-fathom bank surrounding which some of them make
a near approach.

The Comoros contain two land mammals, a lemur and a civet,
both of Madagascar genera and the latter an identical species,
and there is also a peculiar species of fruit-bat (Pteropus
comorensis), a group which ranges from Australia to Asia and
Madagascar, but is unknown in Africa. Of land-birds forty-one
species are known, of which sixteen are peculiar to the islands,
twenty-one are found also in Madagascar, and three found in
Africa and not in Madagascar; while of the peculiar species,
six belong to Madagascar or Mascarene genera.

These facts point to the conclusion that the Comoro Islands
have been formerly more nearly connected with Madagascar
than they are now, probably by means of intervening islets
and the former extension of the latter island to the westward,
as indicated by the extensive shallow bank at its northern
extremity, so as to allow of the easy passage of birds, and
the occasional transmission of small mammalia by means of
floating trees.?

The Seychelles Archipelago.—This interesting group consists
of about thirty small islands situated 700 miles N.N.E. of
Madagascar, or almost exactly in the line formed by continuing
the central ridge of that great island. The Seychelles stand
upon a rather extensive shallow bank, the 100-fathom line
around them enclosing an area nearly 200 miles long by 100
miles wide, while the 500-fathom line shows an extension of
nearly 100 miles in a southern direction. All the larger islands

1 For the birds of the Comoro Islands see Proc. Zool, Soc., 1877, p. 295,
and 1879, p. 673.

CHAP, X1X. | THE MADAGASCAR GROUP. 401

are of granite, with mountains rising to 3,000 feet in Mahé, and
to from 1,000 to 2,000 feet in several of the other islands, We
can therefore hardly doubt that they form a portion of the great
line of upheaval which produced the central granitic mass
of Madagascar, intervening poits being indicated by the
Amirantes, the Providence, and the Farquhar Islands, which,
though all coralline, probably rest on a granitic basis. Deep
channels of more than 1,000 fathoms now separate these.
islands from each other, and if they were ever sufficiently
elevated to be united, it was probably at a very remote epoch.

The Seychelles may thus have had ample facilities for
receiving from Madagascar such immigrants as can pass over
narrow seas; and, on the other hand, they were equally favour-
ably situated as regards the extensive Saya de Malha and
Cargados banks, which were probably once large islands, and
may have supported a rich insular flora and fauna of mixed
Mascarene and Indian type. The existing fauna and flora of
- the Seychelles must therefore be looked upon as the remnants
which have survived the partial submergence of a very extensive
island; and the entire absence of mammalia may be due, either
to this island having never been actually united to Madagascar,
or to its having since undergone so much submergence as to
have led to the extinction of such mammals as may once have
inhabited it. The birds and reptiles, however, though few in
number, are very interesting, and throw some further light on
the past history of the Seychelles,

Birds of the Seychelles.—¥Fifteen indigenous land-birds are
known to inhabit the group, thirteen of which are peculiar
species,’ belonging to genera which occur also in Madagascar or

1 The following is a list of these peculiar birds. (See the Zbis, for 1867,
p..359; and 1879, p. 97.)

PASSERES, PSITTACI.
Ellisia seychellensis. Coracopsis barklyi,
Copsychus seychellarum. Paleornis wardi,
flypsipetes crassirostris. CoLUMBA.

Tchitrea corvina.
Nectarinia dussumiert,

Zosterops modesta.
. semiflava. ACCIPITRES.

Foudia seychellarum. Tinnunculus gracilis.
DD

Alectorenas pulcherrimus,
Turtur rostratus,

402 ISLAND LIFE, |. [PART a.
Africa. The genera which are more peculiarly Indian are,—Cop-
sychus and Hypsipetes, also found in Madagascar ; and Palzornis,
which has species in Mauritius and Rodriguez, as well as one
on the continent of Africa. A black parrot (Coracopsis), con-
generic with two species that inhabit Madagascar and with one
that is peculiar to the Comoros; and a beautiful red-headed
blue pigeon (Alectorenas pulcherrimus) allied to those of Mada-
gascar and Mauritius, but very distinct, are the most remarkable
species characteristic of this group of islands.

Reptiles and Amphibia of the Seychelles.— The reptiles
and amphibia are rather numerous and very interesting, indicat-
ing clearly that the islands can hardly be classed as oceanic.
There are five species of lizards, three being peculiar to the
islands, while the two others have a rather wide range. The
first is a chameleon—defenceless slow-moving lizards, especially
abundant in Madagascar, from which no less than twenty-one
species are now known, about the same number as on the
continent of Africa. The Seychelles species (Chameleo tigris) is
peculiar to the islands. The next is one of the skinks (Huprepes
cyanogaster), small ground-lizards with a very wide distribution
in the Eastern Hemisphere. This species is, however, peculiar
to the islands. The other peculiar species is one of the geckoes
(Phelsuma seychellensis). An East African species (P. cepedianus)
is also found in the Seychelles, as well as in the Comoro Islands,
Bourbon, Mauritius, Madagascar, and Rodriguez; and there is
also a third gecko of another genus (Peropus mutilatus)
which is found also in Mauritius, Bourbon, Rodriguez, and
Ceylon, and even in Penang and the Philippine Islands. These
lizards, clinging as they do to trees and timber, are exceedingly
liable to be carried in ships from one country to another, and I
am told by Dr. Giinther that some are found almost every year
in the London Docks. It is therefore probable, that when species
of this family have a very wide range they have been assisted
in their migrations by man, though their habit of clinging to
trees also renders them likely to be floated with large pieces of
timber to considerable distances. Dr. Percival Wright, to whom
I am indebted for much information on the productions of the
Seychelles Archipelago, informs me that the last-named species

CHAP, XIX. | THE MADAGASCAR GROUP. 463

varies greatly in colour in the different islands, so that he could
always tell from which particular island a specimen had been
brought. This is analogous to the curious fact of certain lizards
on the small islands in the Mediterranean being always very
different in colour from those of the mainland, usually becoming
rich blue or black (see Nature, Vol. XIX. p. 97); and we thus
learn how readily in some cases differences of colour are brought
about by local conditions.

Snakes, as is usually the case in small or remote islands, are
far less numerous than lizards, only two species being known.
One, Dromicus seychellensis, is a peculiar species of the family
Colubridz, the rest of the’ genus being found in Madagascar and
South America. The other, Boodon geometricus, one of the
Lycodontide, or fanged ground-snakes, inhabits also South and
West Africa. So far, then, as the reptiles are concerned, there is
nothing but what is easily explicable by what we know of the
general means of distribution of these animals.

We now come to the Amphibia, which are represented in the
Seychelles by two tailless and two serpent-like forms. The frogs
are, Rana mascariensis, found also in Mauritius, Bourbon, An-
gola, and Abyssinia, and probably all over tropical Africa; and
Megalixalus infrarufus, a tree-frog altogether peculiar to the
islands, and forming a peculiar genus of the widespread tropical
family Polypedatide. It is found, Dr. Wright informs me, on
the Pandani or screw-pines; and as these form a very character-
istic portion of the vegetation of the Mascarene Islands, all
the species being peculiar and confined each to a single island
or small group, we may perhaps consider it as a relic of the
indigenous fauna of that more extensive land of which the
present islands are the remains.

The serpentine Amphibia are represented by two species of
Cecilia. These creatures externally resemble large worms,
except that they have a true head with jaws and rudimentary
eyes, while internally they have of course a true vertebrate
skeleton. They live underground, burrowing by means of the
ring-like folds of the skin which simulate the jointed segments
of a worm’s body, and when caught they exude a viscid slime.
The young have external gills which are afterwards replaced by

DD eZ

404 ISLAND LIFE. [PART If.

true lungs, and this peculiar metamorphosis shows that they
belong to the amphibia rather than to the reptiles. The Ceecilias
are widely but very sparingly distributed through all the tropical
regions; a fact which may, as we have seen, be taken as an
indication of the great antiquity of the group, and. that it is
‘now verging towards extinction. In the Seychelles Islands two
species have been found, named respectively Cecilia oxyura
and C. rostrata. - The former also inhabits the Malabar coast of
India, while the latter has been found in West Africa and also
South America.’ This is certainly one of the most remark-
able cases of the wide and discontinuous distribution of a species
known ; and when we consider the habits of life of these animals
and the extreme slowness with which it is likely they can mi-
erate into new areas, we can hardly arrive at any other conclu-
sion than that this species once had an almost world-wide range,
and that in the process of dying out it has been left stranded, as
it were, in these three remote portions of the globe. The ex-
treme stability and long persistence of specific form which this
implies is extraordinary, but not unprecedented, among the lower
vertebrates. The crocodiles of the Eocene period differ but
slightly from those of the present day, while a small fresh-water
turtle from the Miocene deposits of the Siwalik Hills is abso-
lutely identical with a still living Indian species, Himys tectus.
The mud-fish of Australia, Ceratodus forstert is a very ancient
type, and may well have remained specifically unchanged since

early Tertiary times. It is not, therefore, incredible that the |

Seychelles Ceecilia may be the oldest land vertebrate now living
on the globe; dating back to the early part of the Tertiary period,
when the warm climate of the northern hemisphere in high
latitudes and the union of the Asiatic and American continents
allowed of the migration of such types over the whole northern
hemisphere, from which they subsequently passed imto the
southern hemisphere, maintaining themselves only in certain

1 Specimens are recorded from West Africa in the Proceedings of the
Academy of Natural Science, Philadelphia, 1857, p. 72, while specimens in
the Paris Museum were brought by D’Orbigny from 8. America, Dr,
Wright’s specimens from the Seychelles have, as he informs me, been
determined to be the same species by Dr. Peters of Berlin.

CHAP. XIX. ] THE MADAGASCAR GROUP. 405
ccc peo A ae
limited areas where the physical conditions were especially
favourable, or where they were saved from the attacks of enemies
or the competition of higher forms.

fresh-water Fishes—The only other vertebrates in the Sey-
chelles are two fresh-water fishes abounding in the streams and
rivulets. One, Haplochilus playfairie is peculiar to the islands,
but there are allied species in Madagascar. It is a pretty little
fish about four inches long, of an olive colour, with rows of red
spots, and is very abundant in some of the mountain streams.
The fishes of this genus, as I am informed by Dr. Giinther,
often inhabit both sea and fresh water, so that their migration
from Madagascar to the Seychelles and subsequent modification,
offers no difficulty. The other species is Lundulus orthonotus,
found also on the east coast of Africa; and as both belong to
the same family — Cyprinodontide—this may possibly have
migrated in a similar manner.

Land-shells. —The only other group of animals inhabiting
the Seychelles which we know with any approach to complete-
ness, are the land and fresh-water mollusca, but they do not
furnish any facts of special interest. About forty species are
known, and Mr. Geoffrey Nevill, who has studied them, thinks
their meagre number is chiefly owing to the destruction of so
much of the forests which once covered the islands. Seven of the
species—and among them one of the most conspicuous, Achatina
fulica—have almost certainly been introduced; and the remainder
show a mixture of Madagascar and Indian forms, with a prepon-
derance of the latter. Five genera—Streptaxis, Cyathoponea,
Onchidium, Helicina and Paludomus, are mentioned as being
especially Indian, while only two—Tropidophora and Giubbus,
are found in Madagascar but not in India.t About two-thirds
of the species appear to be peculiar to the islands.

Mauritius, Bourbon and Rodriguez. — These three islands
are somewhat out of place in this chapter, because they
really belong to the oceanic group, being of volcanic formation,
surrounded by deep sea, and possessing no indigenous mammals
oramphibia. Yet their productions are so closely related to those
of Madagascar, to which they may be considered as attendant

1 « Additional Notes on the Land-shells. of the Seychelles Islands.” By
Geoffrey Nevill, C.M.Z.S. Proc, Zool. Soe. 1869, p. 61.

406 ISLAND LIFE. [PART II,

= ee

satellites, that it is absolutely necessary to associate them together
if we wish to comprehend and explain their many interesting
features.

Mauritius and Bourbon are lofty volcanic islands, evidently of
great antiquity. They are about 100 miles apart, and the sea
between them is less than 1,000 fathoms deep, while on each
side it sinks rapidly to depths of 2,400 and 2,600 fathoms. We
have therefore no reason to believe that they have ever been
connected with Madagascar, and this view is strongly supported
by the character of their indigenous fauna. Of this, however,
we have not a very complete or accurate knowledge, for though
both islands have long been occupied by Europeans, the study of
their natural products was for along time greatly neglected, and
owing to the rapid spread of sugar cultivation, the virgin forests,
and with them no doubt many native animals, have been almost
wholly destroyed. There is, however, no good evidence of there
ever having been any indigenous mammals or amphibia, though
both are now found and are often recorded among the native
aninials.?

1 In Maillard’s Notes sur l’Isle de Reunion, a considerable number of
mammalia are given as “wild,” such as Lemur mongoz and Centetes setosus,
both Madagascar species, with such undoubtedly introduced animals as a
wild cat, a hare, and several rats and mice. He also gives two species of
frogs, seven lizards, and two snakes. The latter are both Indian species
and certainly imported, as are most probably the frogs. Legouat, who
resided some years in the island nearly two centuries ago, and who was
a close observer of nature, mentions numerous birds, large bats, land-
tortoises, and lizards, but no other reptiles or venomous animals except
scorpions. We may be pretty sure, therefore, that the land-mammalia,
snakes, and frogs, now found wild, have all been introduced. Of lizards,
on the other hand, there are several species, some peculiar to the island,
others common to Africa and the other Mascarene Islands. The following
list by Prof. Dumeril is given in Maillard’s work :—

Platydactylus cepedianus. — Hemidactylus frenatus.
4 ocellatus. Gongylus bojerii.
HHemidactylus peronit. A blepharus peronit.
ee mutilatus.

Four species of chameleon are now recorded from Bourbon and one
from Mauritius (J. Reay Greene, M.D., in Pop. Science Rev. April, 1880),
but as they are not mentioned by the o!d writers, it is pretty certain that

these creatures are recent introductions, and this is the more ets as
they are favourite domestic pets.

CHAP, XIX.] THE MADAGASCAR GROUP. 407

The smaller and more remote Rodriguez is also volcanic; but it
has, besides, a good deal of coralline rock, an indication of partial
submergence and helping to account for the poverty of its faunas
and flora. Itstands ona 100-fathom bank of considerable extent,
but beyond this the sea rapidly deepens to more than 2,000
fathoms, so that it is truly oceanic like its larger sister isles,

Birds.—The living birds of these islands are few in number
and consist mainly of peculiar species of Mascarene types,
together with two peculiar genera—Oxynotus belonging to the
Campephagidee or caterpillar-catchers, a family abundant in the
old-world tropics; and a dove, Trocazza, forming a peculiar sub-
genus. The origin of these birds offers no difficulty, looking at
the position of the islands and of the surrounding shoals and
islets.

Katinet Birds.—These three islands are, however, pre-eminently
remarkable as being the home of a group of large ground-birds,
quite incapable of flight, and altogether unlike anything found
elsewhere on the globe; and which, though once very abundant,
have become totally extinct within the last two hundred years.
The best known of these birds is the dodo, which inhabited
Mauritius; while allied species certainly lived in Bourbon and
Rodriguez, abundant remains of the species of the latter island
—the “solitaire,” having been discovered, corresponding with the
figure and description given of it by Legouat, who resided in
Rodriguez in 1692. These birds constitute a distinct family,
Didide, allied to the pigeons but very isolated. They were
quite helpless, and were rapidly exterminated when man intro-
duced dogs, pigs, and cats into the islands, and himself sought
them for food. The fact that such perfectly defenceless creatures
survived in great abundance to a quite recent period in these
three islands only, while there is no evidence of their ever
having inhabited any other countries whatever, is itself almost
demonstrative that Mauritius, Bourbon, and Rodriguez are very
ancient but truly oceanic islands. From what we know of the
general similarity of Miocene birds to living genera and families,
it seems clear that the origin of so remarkable a type as the
dodos must date back to early Tertiary times. If we suppose
some ancestral ground-feeding pigeon of large size to have

408 ISLAND LIFE. [PART II.

reached the group by means of intervening islauds afterwards
submerged, and to have thenceforth remained to increase and
multiply unchecked by the attacks of any more powerful
animals, we can well understand that the wings, being useless,
would in time become almost aborted! It is also not im-
probable that this process would be aided by natural selection,
because the use of wings might be absolutely prejudicial to the
birds in their new home. Those that flew up into trees to roost,
or tried to cross over the mouths of rivers, might be blown out
to sea and destroyed, especially during the hurricanes which
have probably always more or less devastated the islands; while
~ on the other hand the more bulky and short-winged individuals,
who took to sleeping on the ground in the forest, would be pre-
served from such dangers, and perhaps also from the attacks of
birds of prey which may always have visited the islands. But
whether or no this was the mode by which these singular birds
acquired their actual form and structure, it is perfectly certain
that their existence and development depended on complete
isolation and on freedom from the attacks of enemies. We
have no single example of such defenceless birds having ever
existed on a continent at any geological period, whereas analogous

1 That the dodo is really an abortion from a more perfect type, and nota
direct development from some lower form of wingless bird, is shown by its
possessing a keeled sternum, though the keel is exceedingly reduced, being
only three-quarters of an inch deep in a length of seven inches. The most
terrestrial pigeon—the Didunculus of the Samoan islands, has a far deeper
and better developed keel, showing that in the case of the dodo the
degradation has been extreme. We have also analogous examples in other
extinct birds of the same group of islands, such as the flightless Rails—
Aphanapteryx of Mauritius and Erythromachus of Rodriguez, as well as
the large parrot—Lophopsittacus of Mauritius, and the Night Heron,
Nycticorax megacephala of Rodriguez, the last two birds probably having
been able to fly a little. The commencement of the same process is to be
seen in the peculiar dove of the Seychelles, Turtur rostratus, which, as
Mr. Edward Newton has shown, has much shorter wings than its close
ally, T. picturatus, of Madagascar. For a full and interesting account of
these and other recently extinct birds see Professor Newton’s article on
“Fossil Birds” in the Encyclopedia Britannica, ninth edition, vol. iil.,
p. 732; and that on “The Extinct Birds of Rodriguez,’ by Dr. A.
Giinther and Mr. E. Newton, in the Royal Society’s volume on the Transit
of Venus Expedition.

CHAP. XIX. | THE MADAGASCAR GROUP. 409

though totally distinct forms do exist in New Zealand, where
enemies are equally wanting. On the other hand, every con-
tinent has always produced abundance of carnivora adapted to
prey upon the herbivorous animals inhabiting it at the same
period; and we may therefore be sure that these islands have
never formed part of a continent during any portion of the time
when the dodos inhabited them.

It is a remarkable thing that an ornithologist of Dr. Hart-
laub’s reputation, looking at the subject from a purely ornitho-
logical point of view, should yet entirely ignore the evidence of
these wonderful and unique birds against his own theory, when
he so confidently characterises Lemuria as “that sunken land
which, containing parts of Africa, must have extended far east-
ward over Southern India and Ceylon, and the highest points of
which we recognise in the volcanic peaks of Bourbon and
‘Mauritius, and in the central range of Madagascar itself—the
last resorts of the mostly extinct Lemurine race which formerly
peopled it.”1 Itis here implied that lemurs formerly inhabited
Bourbon and Mauritius, but of this there is not a particle of
evidence, and we feel pretty sure that had they done so the
dodos would never have been developed there. In Madagascar
there are no traces of dodos, while there are remains of extinct
gigantic struthious birds of the genus Aupyornis, which were no
doubt as well able to protect themselves against the smaller
carnivora as are the ostriches, emus, and cassowarles in their
respective countries at the present day.

The whole of the evidence at our command, therefore, tends to
_ establish in a very complete manner the “ oceanic” character of
the three islands— Mauritius, Bourbon, and Rodriguez, and that
they have never formed part of “ Lemuria,” or of any continent.

Reptiles.—Mauritius, like Bourbon, has lizards, some of which
are peculiar species; but no snakes, and no frogs or toads
but such as have been introduced? Strange to say, however, a
small islet called Round Island, only about a mile across, and

1 See Ibis, 1877, p. 334.

2 A common Indian and Malayan toad (Bufo melanostictus) has been
introduced into Mauritius and also some European toads, as 1 am informed
by Dr. Gunther.

410 ISLAND LIFE. [PART II,

situated about fourteen miles north-east of Mauritius, possesses
a snake which is not only unknown in Mauritius, but also in any
other part of the world, being altogether confined to this minute
islet! It belongs to the python family, and forms a peculiar
and very distinct genus, Casarea, whose nearest allies seem to
be the Ungalia of Cuba and Bolgeria of Australia. It is hardly
possible to believe that this serpent has very long maintained
itself on so small an island; and though we have no record of
its existence on Mauritius, it may very well have imhabited the
lowland forests without being met with by the early settlers ;
and the introduction of swine, which soon ran wild and effected
the final destruction of the dodo, may also have been fatal to
this snake. It is, however, now almost certainly confined to
the one small islet, and is probably the land-vertebrate of most
restricted distribution on the globe.

On the same island there is a small lizard, Thyrus boyeri,
also a peculiar species and genus, but this is recorded from
Mauritius and Bourbon as well, though it appears to be rare in
both islands. As Round Island is connected with Mauritius by
a bank under a hundred fathoms below the surface, it has pro-
bably been once joined to it, and when first separated would
have been both much larger and much nearer the main island,
circumstances which would greatly facilitate the transmission
of these reptiles to their present dwelling-place.

Flora of Madagascar and the Mascarene Islands.—The botany
of the great island of Madagascar has been perhaps more
thoroughly explored than that of the opposite coasts of Africa, so
that its peculiarities may not be really so great as they now
appear to be. Yet there can be no doubt of its extreme
richness and grandeur, its remarkable speciality, and its anoma-

lous external relations. It is characterised by a great abundance
of forest-trees and shrubs of peculiar genera or species, and
often adorned with magnificent flowers. Some of these are
allied to African forms, others to those of Asia, and it is said
that of the two affinities the latter preponderates. But there
are also, as in the animal world, some decided South American
relations, while others point to Australia, or are altogether
isolated.

x >

CHAP, XIX.] THE MADAGASCAR GROUP. 411

Among the most prominent characteristics of the Mada-
gascar flora is the possession of a peculiar and isolated family,
Chleenacex, allied somewhat to the balsams, but presenting very
anomalous characters. It consists of four genera and a number
of species all entirely confined to the island. They are hand-
some trees or shrubs, mostly with showy red flowers. One of
them, Rhodolena altivola, is a semi-scandent shrub with magni-—
ficent campanulate flowers the size of a camellia and of a
brilliant purple colour. The genus Chrysopia consists of large
forest trees with spreading crowns adorned with umbels or co-
rymbs of large purple flowers. It belongs to the Clustacez, and
is most nearly allied to the South American genus Moronobea.
The Colvillea, a peculiar genus of Leguminose, is a tree with
splendid scarlet flowers; and there are a large number of
other peculiar genera more or less remarkable. Combretaceze
with splendid flowers abound in Madagascar itself, though they
are rare in the Mascarene islands; while the Ravenala, or
“traveller's tree;” the extraordinary lattice-leaved Ouvirandra ;
the Poinciana regia, one of the most gorgeous of flowering trees ;
and the long-spurred Angrecum sesquipedale, one of the most
elegant and remarkable of orchids, are among its vegetable
wonders.’

Of the flora of the smaller Madagascarian islands we possess
a much fuller account, owing to the recent publication of Mr.
Baker’s Flora of the Mauritius and the Seychelles, including also
Rodriguez. The total number of species in this flora is 1,058,
more than half of which (536) are exclusively Mascarene—that
is, found only in some of the islands of the Madagascar group,
while nearly a third (804) are endemic or confined to single islands.
Of the widespread plants sixty-six are found in Africa but nct
in Asia, and eighty-six in Asia but not in Africa, showing a similar
Asiatic preponderance to what is said to occur in Madagascar.
With the genera, however, the proportions are different, for I
find by going through the whole of the generic distributions as
given by Mr. Baker, that out of the 440 genera of wild plants

1 This sketch of the Flora of Madagascar is taken chiefly from a series
of articles by M. Emile Blanchard in the Revue des Deua Mondes. Vol.
CI. (1872).

412 ISLAND LIFE. [PART IT.

fifty are endemic, twenty-two are Asiatic but not African, while
twenty-eight are African but not Asiatic, ‘This implies that the
more ancient connection has been on the side of Africa, while
a more recent immigration, shown by identity of species, has
come from the side of Asia; and it is probable that when the
flora of Madagascar is more thoroughly worked out, the same, or
a still greater African preponderance, will be found in that island.

A few Mascarene genera are found elsewhere only in South
America, Australia, or Polynesia; and there are also a con-
siderable number of genera whose metropolis is South America,
but which are represented by one or more species in Mada-
gascar, and by a single often widely distributed species in
Africa. This fact- throws light upon the problem offered by
those mammals, reptiles, and insects of Madagascar which now
have their only allies in South America, since the two cases
would be exactly parallel were the African plants to become
extinct. Plants, however, are undoubtedly more long-lived
specifically than animals—especially the more highly organised
groups, and are less lable to complete extinction through the
attacks of enemies or through changes of climate or of physical
geography ; hence we find comparatively few cases in which
groups of Madagascar plants have their only allies in such
distant regions as America and Australia, while such cases are
numerous among animals, owing to the extinction of the allied
forms in intervening areas, for which extinction, as we have
already shown, ample cause can be assigned.

Curious Relations of Mascarene Plants—Among the curious
affinities of Mascarene plants we have culled the following
from Mr. Baker’s volume. Trochetia, a genus of Sterculiacee,
has four species in Mauritius, one in Madagascar, and one in
the remote island of St. Helena. Mathurina, a genus of Turner-
aces, consisting of a single species peculiar to Rodriguez, has
its nearest ally in another monotypic genus, Erblichia, confined
to Central America. Siegesbeckia, one of the Composite, con-
sists of two species, one inhabiting the Mascarene islands, the
other Peru. Labourdonasia, a genus of Sapotaces, has two
species in Mauritius, one in Natal, and one in Cuba. Neso-
genes, belonging to the verbena family, has one species in

——

aaa a

CHAP, XIX. | THE MADAGASCAR GROUP. 413

Rodriguez and one in Polynesia: Mespilodaphne, an extensive
genus of Lauracez, has six species in the Mascarene islands,
and all the rest (about fifty species) in South America. Ne-
penthes, the well-known pitcher plants, are found chiefly in the
Malay Islands, South China, and Ceylon, with species in the
Seychelles Islands, and in Madagascar. Milla, a large genus of
Liliacez, is exclusively American, except one species found in
Mauritius and Bourbon. Agauria, a genus of Ericacez, is con-
fined to the Mascarene islands and the Camaroon Mountains
in West Africa. An acacia, found in Mauritius and Bourbon
(A. heterophylla), can hardly be separated specifically from
Acacia koa of the Sandwich Islands. The genus Pandanus,
or screw-pine, has sixteen species in the three islands—
Mauritius, Rodriguez, and the Seychelles—all being peculiar,
and none ranging beyond a single island. Of palms there are
fifteen species belonging to ten genera, and all these genera are
peculiar to the islands. We have here ample evidence that
plants exhibit the same anomalies of distribution in these
islands as do the animals, though in a smaller proportion ; while
they also exhibit some of the transitional stages by which these
anomalies have, in all probability, been brought about, render-
ing quite unnecessary any other changes in the distribution of
sea and land than physical and geological evidence warrants.

1 It may be interesting to botanists and to students of geographical
distribution to give here an enumeration of the endemic genera of the
Flora of the Mauritius and the Seychelles, as they are nowhere separately
tabulated in that work,

POM BIX ACEH) jo. sce. ates eese 1 sp., a shrub, Maur., Rod., Sey., also
Madagascar.

Medusagyne (Ternstrémiacez)..1 sp., a shrub, Seychelles,

Aula (ObeLCUliacese) ..., 6s. ...0% 1 sp., a shrub, Mauritius.

Qutvasia, (Meéliaced) .... 2.0... 3 sp., shrubs, Mauritius (2 sp.), Rodriguez

(1 sp.), also Bourbon.
Cossignya (Sapindacez) .......1 sp., a shrub, Mauritius, also Bourbon,

Hornea Shoo a eeeees 1 sp., a shrub, Mauritius.

Stadtmannia iessayi Wisd'd ntti’, 1 sp., a shrub, Mauritius.

Doratoxylon BB Secale atecimlst 1 sp., a shrub, Mauritius and Bourbon.
Gagnebina (Leguminose) ........1 sp., a shrub, Mauritius, also Madagascar.
Roussea (Saxifragace®) ......... 1 sp., a climbing shrub, Mauritius and

Bourbon,

414 ISLAND LIFE. [PART 12.

‘Fragmentary Character of the Mascarene Flora.—Although the
peculiar character and affinities of the vegetation of these islands
is sufficiently apparent, there can be little doubt that we only
possess a fragment of the rich fiora which once adorned them.
The cultivation of sugar, and other tropical products, has led to
the clearing away of the virgin forests from all the lowlands,
plateaus, and accessible slopes of the mountains, so that

Tetrataxis (Lythracez)........ ...1 sp., a shrub, Mauritius.

Psiloxylon i ah ae i sp., a shrub, Mauritius and Bourbon.

Mathurina (Turneracee) ..... -««l Sp., a shrub, Rodriguez,

Foetidia (Myrtace®) .............06 1 sp., a tree, Mauritius,

Danais (Rubiaceze) ......-......00 4 sp., climbing shrubs, Maur. (1 sp.), Rodr.,
(1 sp.), also Bourbon and Madagascar.

Fernelia (Rubiacée) 2.0.0.0... 1 sp., a shrub, Mauritius and Rodriguez.

Scyphochlamys (Rubiaceae) ...... 1 sp., a shrub, Rodriguez.

Myonima Sal Seer 3 sp., shrubs, Mauritius, also Bourbon,

Cylindrocline (Composite) ....... 1 sp., a shrub, Mauritius.

Monarrhenus We ata uRL ORs Ter 2 sp., shrubs, Mauritius, also Bourbon and
Madagascar.

Faujasia (Composite) ...........6 3.sp., shrubs, Mauritius, also Bourbon and
Madagascar.

Heterochenia (Campanulacez)..1 sp., a shrub, Mauritius, also Bourbon,

Tanulepis (Asclepiadacee) ...... 1 sp., a climber, Rodriguez.

Decanema a | Milani 1 sp., a climber, Mauritius, also Madagascar.

Nicodemia (Loganiacez) ...... 2 sp., shrubs, Mauritius (1 sp.), also Comoro
Islands and Madagascar,

Bryodes (Serophulariacee) ...... 1 sp., herb, Mauritius.

Radamea ayer Ec ae 2 sp., herb, Seychelles (1 sp.), and Mada-
gascar.

Colea (Rignoniacez) ........... 10 sp., Mauritius’ (1 sp.), Seychelles (1

sp.), also Bourbon and Madagascar.
(Shrubs, trees, or climbers.)

Obetia (Uirticacea)?... to. .cse: 2 sp., shrubs, Mauritius, Seychelles, and
Madagascar.

Bosquiea (Mores) co. senasessncoes.2 3 sp., trees, Seychelles (1 sp.), also Mada-
gascar.

Monimia (Monimiacez)..........+ 3 sp., trees, Mauritius (2 sp.), also Bourbon.

Cynorchis (Orchidew) ~70.2....... 3 sp., herb, ter., Mauritius,

Amphorchis Panes ae cet 1 sp., herb, ter., Mauritius, also Bourbon.

Arnottia Gee aoe onchr 2sp., herb, ter., Mauritius, also Bourbon.

A plostellis a ssstesscsarel Sp., herb, ter, Mauritiug;

Cryptopus Par ae ier ratio 1 sp. herb, Epiphyte, Mauritius, also

Bourbon and Madagascar,

CHAP. XIX.] THE MADAGASCAR GROUP. 415
remains of the aboriginal woodlands only linger in the recesses
of the hills, and numbers of. forest-haunting plants must in-
evitably have been exterminated. The result is, that nearly
three hundred species of foreign plants have run wild in
Mauritius, and have in their turn helped to extinguish the native
species. In the Seychelles, too, the indigenous flora has been
almost entirely destroyed in most of the islands, although the
peculiar palms, from their longevity and comparative hardiness,
have survived. Mr. Geoffrey Nevill tells us, that at Mahé, and
most of the other islands visited by him, it was only in a few
spots near the summits of the hills that he could perceive any
remains of the ancient flora. Pine-apples, cinnamon, bamboos,
and other plants, have obtained a firm footing, covering large
tracts of country and killing the more delicate native flowers
and ferns. The pine-apple, especially, grows almost to the tops
of the mountains. Where the timber and shrubs have been
destroyed, the water falling on the surface immediately cuts
channels, runs off rapidly, and causes the land to become dry
and arid ; and the same effect is largely seen both in Mauritius,

Lomatophyllum (Liliacez) ....... 3 sp., shrubs (succulent), Mauritius, also
Bourbon.

Lodoicea (ie aimate) 2 eel ae 1 sp., tree, Seychelles.

Latania Scent mt 3.sp., trees, Mauritius (2 sp.), Rodriguez,
also Bourbon.

Hyophorbe Niele pore 3 sp., trees, Mauritius (2 sp.), Rodriguez,
also Bourbon.

Dictyosperma Ae we eh ey 1 sp., tree, Mauritius, Rodriguez, also
Bourbon.

Acanthopheenix AS eum eens 2 sp., trees, Mauritius, also Bourbon.

Deckenia TOP ener 1 sp., tree, Seychelles,

Nephrosperma PLN Sree ee 1 sp., tree, Seychelles.

Roscheria Si ee re OA 1 sp., tree, Seychelles.

Verschaffeltia Paha Parent 1 sp., tree, Seychelles.

Stevensonia Sha aries teug ss 1 sp., tree, Seychelles.

Ochropteris CHtGeS) ae) onan 1 sp., herb, Mauritius, also Bourbon and
Madagascar.

Among the curious features in this list are the great number of endemic
shrubs in Mauritius, and the remarkable assemblage of five endemic genera
of palms in the Seychelles Islands. We may also notice that one palm
(Latania loddigesii) is confined to Round Island and two other adjacent
islets, offering a singular analogy to the peculiar snake also found there.

416 ISLAND LIFE. [PART II.

and Bourbon, where, originally, dense forest covered the entire
surface, and perennial moisture, with its ever-accompanying
luxuriance of vegetation, prevailed.

Flora of Madagascar allied to that of South Africa.—In my
Geographical Distribution of Animals 1 have remarked on the

relation between the insects of Madagascar and those of south

temperate Africa, and have speculated on a great southern exten-
sion of the continent at the time when Madagascar was united
with it. As supporting this view I now quote Mr. Bentham’s
remarks on the Composite. He says: “The connections of the
Mascarene endemic Composite, especially those of Madagascar
itself, are eminently with the southern and sub-tropical African
races; the more tropical races, Plucheinee, &c., may be rather
more of an Asiatic type.” He further says that the Composite
flora is almost as strictly endemic as that of the Sandwich
Islands, and that it is much diversified, with evidences of great
antiquity, while it shows insular characteristics in the tendency
to tall shrubby or aborescent forms in several of the endemic
or prevailing genera.

Preponderance of Ferns in the Mascarene Flora.—A striking
character of the flora of these smaller Mascarene islands is the
great preponderance of ferns, and next to them of orchidez. The
following figures are taken from Mr. Baker’s Flora for Mauritius
and the Seychelles, and from an estimate by M. Frappier of the
flora of Bourbon given in Maillard’s volume already quoted :—

Mauritius, &e. Bourbon.
Pers ct tocscnacle coun anne 168 Pern 4. ....42. cn pee 240
Oneiidecer eo ta.cncvssmare 19 Orchide.. .c:in-eenes: 120
CQLAMMAM ER denice tea cdo eee 69 Gramimes oc usasceeeee 60
Cypenaceds....,cchoueemomaece 62 Composite... /.esece 60
Rubiaceae yo: ania e. 57 Leguminose..........+ 36
Huphorbiaces: cele. 45 Rubiaces. cciizcceaees 24
COMPOSI. cy uasaneceeces 43 Cy peraces.... .cc.2c. caer 24
Tie Cumin se. coe dy concoscs ss 41 Euphorbiacee.......... 18

The cause of the great preponderance of ferns in oceanic
islands has already been discussed in my book on Tropical Nature ;
and we have seen that Mauritius, Bourbon, and Rodriguez must
be classed as such, though from their proximity to Madagascar
they have to be considered as satellites to that great island,

CHAP. XIX.] THE MADAGASCAR GROUP. 417

The abundance of orchids may be in part due to analogous
causes. Their usually minute and abundant seeds would be as
easily carried by the wind as the spores of ferns, and their
frequent epiphytic habit affords them an endless variety of
stations on which to vegetate, and at the same time removes
them in a great measure from the competition of other plants.
When, therefore, the climate is sufficiently moist and equable,
and there is a luxuriant forest vegetation, we may expect to
find orchids abundant on such tropical islands as are not too
far removed from other lands or continents from which their
seeds might be conveyed.

Concluding remarks on Madagascar and the Mascarene Islands.
—There is probably no portion of the globe that contains within
itself so many and such varied features of interest connected with
geographical distribution, or which so well illustrates the mode
of solving the problems it presents, as the comparatively small
insular region which comprises the great island of Madagascar
and the smaller islands and island-groups which immediately
surround it. In Madagascar we have a continental island of
the first rank, and undoubtedly of immense antiquity; we
have detached fragments of this island in the Comoros and
Aldabra; in the Seychelles we have the fragments of another
very ancient island, which may perhaps never have been
continental; in Mauritius, Bourbon, and Rodriguez we have
three undoubtedly oceanic islands ; while in the extensive banks
and coral reefs of Cargados, Saya de Malha, the Chagos, and the
Maldive Isles, we have indications of the submergence of many
large islands which may have aided in the transmission of organ-
isms from the Indian Peninsula. But between and around all
these islands we have depths of 2,500 fathoms and upwards,
which renders it very improbable that there has ever been here
a continuous land surface, at all events during the Tertiary or
Secondary periods of geology.

It is most interesting and satisfactory to find that this conclu-
sion, arrived at solely by a study of the form of the sea-bottom
and the general principle of oceanic permanence, is fully sup-
ported by the evidence of the organic productions of the several
islands; because it gives us confidence in those principles, and

418 ISLAND LIFE. [PART 11.

helps to supply us with a practical demonstration of them. We
find that the entire group contains just that amount of Indian
forms which could well have passed from island to island; that
many of these forms are slightly modified species, indicating
that the migration occurred during late Tertiary times, while
others are distinct genera, indicating a more ancient connec-
tion; but in no one case do we find animals which necessitate
an actual land-connection, while the numerous Indian types of
mammalia, reptiles, birds, and insects, which must certainly
have passed over had there been such an actual land-connection,
are totally wanting. The one fact which has been. supposed to
require such a connection—the distribution of the lemurs—
can be far more naturally explained by a general dispersion of
the group from Europe, where we know it existed in Eocene
times; and such an explanation applies equally to the affinity
of the Insectivora of Madagascar and Cuba; the snakes (Herpe-
todryas, &c.) of Madagascar and America; and the lizards (Cryp-
toblepharus) of Mauritius and Australia. To suppose, in all these
cases, and in many others, a direct land-connection, is really
absurd, because we have the evidence afforded by geology of
wide differences of distribution directly we pass beyond the most
recent deposits; and when we go back to Mesozoic—and still
more to Palzozoic—times, the majority of the groups of animals
and plants appear to have had a world-wide range. A large
number of our European Miocene genera of vertebrates were
also Indian or African, or even American; the South American
Tertiary fauna contained many European types; while many
Mesozoic reptiles and mollusca ranged from Europe and North
America to Australia and New Zealand.

By direct proof (the occurrence of wide areas of marine
deposits of Eocene age), geologists have established. the fact
that Africa was cut off from Europe and Asia by an arm of
the sea in early Tertiary times, forming a large island-continent.
By the evidence of abundant organic remains we know that all
the types of large mammalia now found in Africa (but which are
absent from Madagascar) inhabited Europe and Asia, and many
of them also North America, in the Miocene period. At a
still earlier époch Africa may have received its lower types of

CHAP. XIX.] THE MADAGASCAR GROUP. 419

mammals—lemurs, insectivora, and small carnivora, together
with its ancestral struthious birds, and its reptiles and insects
of American or Australian affinity ; and at this period it was
joined to Madagascar. Before the later continental period of
Africa, Madagascar had become an island; and thus, when the
large mammalia from the northern continent overran Africa,
they were prevented from reaching Madagascar, which thence-
forth was enabled to develop its singular forms of low-type mam-
malia, its gigantic ostrich-like Aipyornis, its isolated birds, its
remarkable insects, and its rich and peculiar flora. From it the
adjacent islands received such organisms as could cross the sea ;
while they transmitted to Madagascar some of the Indian birds
and insects which had reached them.

The method we have followed in these investigations is to
accept the results of geological and paleontological science,
and the ascertained facts as to the powers of dispersal of the
various animal groups; to take full account of the laws of
evolution as affecting distribution, and of the various ocean
depths as implying recent or remote union of islands with
their adjacent continents; and the result is, that wherever
we possess a sufficient knowledge of these various classes of
evidence, we find it possible to give a connected and intelligible
explanation of all the most striking peculiarities of the organic
world. In Madagascar we have undoubtedly one of the most
difficult of these problems; but we have, I think, fairly met
and conquered most of its difficulties. The complexity of the
organic relations of this island is due, partly to its having
derived its animal forms from two distinct sources—from one
continent through a direct land-connection, and from another
by means of intervening islands now submerged; but, mainly
to the fact of its having been separated from a continent
which is now, zoologically, in a very different condition from
what it was at the time of the separation; and to its having
been thus able to preserve a number of types which may
date back to the Hocene, or even to the Cretaceous, period.
Some of these types have become altogether extinct else-
where ; others have spread far and wide over the globe, and
have survived only in a few remote countries—and especially in

EE 2

420 ISLAND LIFE. [PART. 11.
those which have been more or less secured by their isolated
position from the incursions of the more highly-developed
forms of later times. This explains why it is that the nearest
allies of the Madagascar fauna and flora are now so often to be
found in South America or Australia—countries in which low
forms of mammalia and birds still largely prevail ;—it beg on
account of the long-continued isolation of all these countries
that similar forms (descendants of ancient types) are preserved
in them. Had the numerous suggested continental extensions
connecting these remote continents at various geological periods
been realities, the result would have been that all these interest-
ing archaic forms, all these helpless insular types, would long
ago have been exterminated, and one comparatively monotonous
fauna have reigned over the whole earth. So far from explain-
ing the anomalous facts, the alleged continental extensions, had
they existed, would have left no such facts to be explained.

CHAPTER XX.

ANOMALOUS ISLANDS: CELEBES.

Anomalous relations of Celebes—Physical features of the Island—Zoo-
logical character of the Islands around Celebes—The Malayan and
Australian Banks—Zoology of Celebes : Mammalia—Probable derivation
of the Mammals of Celebes— Birds of Celebes—Bird-types peculiar to
Celebes—Celebes not strictly a Continental Island—Peculiarities of
the Insects of Celebes—Himalayan types of Birds and Butterflies in
Celebes—Peculiarities of shape and colour of Celebesian Butterflies—.
Concluding Remarks—Appendix on the Birds of Celebes.

THE only other islands of the globe which can be classed as
“ancient. continental” are the larger Antilles (Cuba, Haiti,
Jamaica, and Porto Rico), Iceland, and perhaps Celebes. The
Antilles have been so fully discussed and illustrated in my
former work, and there is so little fresh information about
them, that I do not propose to treat of them here, especially
as they fall short of Madagascar in all points of biological
interest, and offer no problems of a different character from
such as have already been sufficiently explained.

Iceland, also, must apparently be classed as belonging to the
“ Ancient Continental Islands,” for though usually described as
wholly volcanic, it is, more probably, an island of varied geolo-
gical structure buried under the lavas of its numerous volcanoes.
But of late years extensive Tertiary deposits of Miocene age
have been discovered, showing that it is not a mere congeries of
voleanoes ; it is connected with the British Islands and with
Greenland by seas less than 500 fathoms deep; and it possesses
a few mammalia, one of which is peculiar, and at least three
peculiar species of birds. It was therefore almost certainly

492 ISLAND LIFE. [PART II.

united with Greenland, and probably with Europe by way of —

Britain, in the early part of the Tertiary period, and thus
afforded one of the routes by which that intermigration of
American and European animals and plants was effected which
we know occurred during some portion of the Eocene and Mio-
cene periods, and probably also in the Pliocene. The fauna
and flora of this island are, however, so poor, and offer so few
peculiarities, that it 1s unnecessary to devote more time to
consideration here.

There remains the great Malay island—Celebes, which, owing
to its possession of several large and very peculiar mammalia,
must be classed, zoologically, as ‘“‘ancient continental”; but
whose central position and relations both to Asia and to Australia
render it very difficult to decide in which of the primary zoological
regions it ought to be placed, or whether it has ever been united
with either of the great continents. Although I have pretty
fully discussed its zoological peculiarities and past history in my
Geographical Distribution of Animals, it seems advisable to review
the facts on the present occasion, more especially as the systematic
investigation of the characteristics of continental islands we have
now made will place us in a better position for determining its
true zoo-geographical relations.

Physical features of Celebes.—This large and still comparatively
unexplored island is interesting to the geographer on account
of its remarkable form, but much more so to the zoologist
for its curious assemblage of animal forms. The geological
structure of Celebes is almost unknown. The extremity of the
northern peninsula is volcanic ; while in the southern peninsula
there are extensive deposits of a crystalline limestone, in some
places overlying basalt. Gold is found in the northern peninsula
and in the central mass, as well as iron, tin, and copper in small
quantities; so that there can be little doubt that the mountain
ranges of the interior consist of ancient stratified rocks.

It is not yet known whether Celebes is completely separated
from the surrounding islands by a deep sea, but the facts at our
command render it probable that it is so. The northern and
eastern portions of the Celebes Sea have been ascertained to be
from 2,000 to 2,600 fathoms deep, and such depths may extend

CHAP. XX.] CELEBES. 423

over a considerable portion of it, or even be much exceeded in
the centre. In the Molucea passage a single sounding on the
Gilolo side gave 1,200 fathoms, and a large part of the Molucca

MAP OF CELEBES AND THE SURROUNDING ISLANDS.

The depth of sea is shown by three tints: the lightest indicating less than 100 fathoms, the
medium tint less than 1,000 fathoms, and the dark tint more than 1,000 fathoms. The
figures show depths in fathoms.

and Banda Seas probably exceed 2,000 fathoms. The southern
portion of the Straits of Macassar is full of coral reefs, and a
shallow sea of less than 100 fathoms extends from Borneo to

424 ISLAND LIFE. [PART 11.

within about forty miles of the western promontory of Celebes;
but farther north there is deep water close to the shore, and it
seems probable that a deep channel extends quite through the
straits, which have no doubt been much shallowed by the deposits
from the great Bornean rivers as well as by those of Celebes
itself. Southward again, the chain of volcanic islands from Baly
to Timor appear to rise out of a deep ocean, the few soundings
we possess showing depths of from 670 to 1,300 fathoms almost
close to their northern shores. We seem justified, therefore, in
concluding that Celebes is entirely surrounded by a deep sea,
which has, however, become partially filled up by river deposits,
by volcanic upheaval, or by coral reefs. Such shallows, where
they exist, may therefore be due to antiquity and isolation, in-
stead of being indications of a former union with any of the
surrounding islands.

Zoological character of the Islands around Celebes.—In order to
have a clear conception of the peculiar character of the Cele-
besian fauna, we must take into account that of the surrounding
countries from which we may suppose it to have received immi-
erants. ‘These we may divide broadly into two groups, those
on the west belonging to the Oriental region of our zoological
geography, and those on the east belonging to the Australian
region. Of the first group Borneo isa typical representative ; and
from its proximity and the extent of its opposing coasts it is
the island which we should expect to show most resemblance to
Celebes. We have already seen that the fauna of Borneo is essen-
tially the same as that of Southern Asia, and that it is excessively
rich in all the Malayan types of mammalia and birds. Java and
Baly closely resemble Borneo in general character, though some-
what less rich and with several peculiar forms; while the
Philippine Islands, though very much poorer, and with a greater
amount of speciality, yet exhibit essentially the same character.
These islands, taken as a whole, may be described as having a
fauna almost identical with that of Southern Asia ; for no family
of mammalia is found in the one which is absent from the other,
and the same may be said, with very few and unimportant
exceptions, of the birds; while hundreds of genera and of species
are common to both.

CHAP. XX.] CELEBES. 425

In the islands east and south of Celebes—the Moluccas, New
Guinea, and the Timor group from Lombok eastward—we find,
on the other hand, the most wonderful contrast in the forms of
life. Of twenty-seven families of terrestrial mammals found in
the great Malay islands, all have disappeared but four, and of
these it is doubtful whether two have not been introduced by
man. We also find here four families of Marsupials, all totally
unknown in the‘ western islands. Even birds, though usually
more widely spread, show a corresponding difference, about
eleven Malayan families being quite unknown east of Celebes,
where six new families make their appearance which are equally
unknown to the westward.'

We have here a radical difference between two sets of islands
not very far removed from each other, the one set belonging
zoologically to Asia, the other to Australia. The Asiatic or
Malayan group is found to be bounded strictly by the eastward
limits of the great bank (for the most part less than fifty
fathoms below the surface) which stretches out from the Siamese
and Malayan peninsulas as far as Java, Sumatra, Borneo, and
the Philippines. To the east another bank unites New Guinea
and the Papuan Islands as far as Aru, Mysol, and Waigiou, with
Australia ; while the Moluccas and Timor groups are surrounded
by much deeper water, which forms, in the Banda and Celebes
Seas and perhaps in other parts of this area, great basins of
enormous depths (2,000 to 3,000 fathoms or even more) enclosed
by tracts under a thousand fathoms, which separate the basins

1 Families of Malayan Birds not Families of Moluccan Birds not
found in islands East of found in islands West of

Celebes. Celebes.
Troglodytide. Paradiseide.
Sittidee. Meliphagide.
Paride. Cacatuidee.
Liotrichide. Platycercide.
Phyllornithide. Trichoglosside.
Kurylemide. Nestoride.
Picida.

Indicatoride.
Megalemide.
Trogonide.

Phasianide.

426 ISLAND LIFE. [PART II.

from each other and from the adjacent Pacific and Indian
Oceans (see map). This peculiar formation of the sea-bottom
probably indicates that this area has been the seat of great local
upheavals and subsidences; and it is quite in’accordance with
this view that we find the Moluccas, while closely agreeing with
New Guinea in their forms of life, yet strikingly deficient in
many important groups, and exhibiting an altogether poverty-
striken appearance as regards the higher animals. It is a
suggestive fact that the Philippine Islands bear an exactly
parallel relation to Borneo, being equally deficient in many of
the higher groups; and here too, in the Sooloo Sea, we find a
similar enclosed basin of great depth. Hence we may in both
cases connect, on the one hand, the extensive area of land-surface
and of adjacent shallow sea with a long period of stability and a
consequent rich development of the forms of life; and, on the
other hand, a highly broken land-surface with the adjacent seas
of great but very unequal depths, with a period of disturbance,
probably involving extensive submersions of the land, resulting
in a scanty and fragmentary vertebrate fauna.

Zoology of Celebes—The zoology of Celebes differs so rn
ably from that of both the great divisions of the Archipelago
above indicated, that it is very difficult to decide in which
to place it. It possesses only about sixteen species of terrestrial
mammalia, so that it is at once distinguished from Borneo and
Java by its extreme poverty in this class. Of this small number
four belong to the Moluccan and Australian fauna—there being
two marsupials of the genus Cuscus, and two forest rats said
to be allied to Australian types.

The remaining twelve species are, generally speaking, of
Malayan or Asiatic types, but some of them are so peculiar
that they have no near allies in any part of the world; while
the rest are of the ordinary Malay type or even identical with
Malayan species, and some of these may be recent introductions
through human agency. These twelve species of Asiatic type
will be now enumerated. They consist of five peculiar squirrels
—a group unknown farther east; a peculiar species of wild
pig; a deer so closely allied to the Cervus hippelaphus of
Borneo that it may well have been introduced by man bot

CHAP, XX.] CELEBES. 427
here and in the Moluccas; a civet, Viverra tangalunga, common
in all the Malay Islands, and also perhaps introduced; the
curious Malayan tarsier (Tarsius spectrum) said to be only
found in a small island off the coast ;—and besides these, three
remarkable animals, all of large size and all quite unlike any-
thing found in the Malay Islands or even in Asia. These are
a black and almost tailless baboon-like ape (Cynopithecus
nigrescens); an antelopean butlalo (Anoa depressicornis), and
the strange babirusa (babirusa alfurus).

Neither of these three animals last mentioned have any close
allies elsewhere, and their presence in Celebes may be considered
the crucial fact which must give us the clue to the past history
of the island. Let us then see what they teach us. The ape
is apparently somewhat intermediate between the great baboons
of Africa and the short-tailed macaques of Asia, but its cranium
shows a nearer approach to the former group, in its flat project-
ing muzzle, large superciliary crests, and maxillary ridges. The
anoa, though anatomically allied to the buffaloes, externally
more resembles the bovine antelopes of Africa; while the
babirusa is altogether unlike any other living member of the
swine family, the canines of the upper Jaws growing directly
upwards like horns, forming a spiral curve over the eyes, instead
of downwards, as in all other mammalia. An approach to
this peculiarity is made by the African wart-hogs, in which
the upper tusk grows out laterally and then curves up; but
these animals are not otherwise closely allied to the babirusa.

Probable derwation of the Mammals of Celebes.—It is clear
that we have here a group of extremely peculiar, and, in all
probability, very ancient forms, which have been preserved to
‘us by isolation in Celebes, just as the monotremes and mar-
supials have been preserved in Australia and so many of the
lemurs and Insectivora in Madagascar. And this compels us
to look upon the existing island as a fragment of some ancient
land, once perhaps forming part of the great northern continent,
but separated from it far earlier than Borneo, Sumatra, and
Java. The exceeding scantiness of the mammalian fauna, how-
ever, remains to be accounted for. We have seen that Formosa,
a much smaller island, contains more than twice as many

428 ISLAND LIFE. [PART H.

species; and we may be sure that at the time when such
animals as apes and buffaloes existed, the Asiatic continent
swarmed with varied forms of mammals to quite as great an
extent as Borneo does now. If the portion of separated land
had been anything like as large as Celebes now is, it would
certainly have preserved a far more abundant and varied fauna.
To explain the facts we have the choice of two theories ;—
either that the original island has since its separation been
greatly reduced by submersion, so as to lead to the extinction
of most of the higher land animals; or, that it originally formed
part of an independent land stretching eastward, and was only
united with the Asiatic continent for a short period, or perhaps
even never united at all, but so connected by imtervening
islands separated by narrow straits that a few mammals might
find their way across. The latter supposition appears best to
explain the facts. The three animals in question are such as
might readily pass over narrow straits from island to island;
and we are thus better enabled to understand the complete
absence of the arboreal monkeys, of the Insectivora, and of the
very numerous and varied Carnivora and Rodents of Borneo,
all of which are entirely unrepresented in Celebes by any
peculiar and ancient forms except the squirrels.

The question at issue can only be finally determined by
geological investigations. If Celebes has once formed part of
Asia, and participated in its rich mammalian fauna which has
been since destroyed by submergence, then some remains of
this fauna must certainly be preserved in caves or late Tertiary
deposits, and proofs of the submergence itself will be found
when sought for. If, on the other hand, the existing animals
fairly represent those which have ever reached the island, then
no such remains will be discovered, and there need be no
evidence of any great and extensive subsidence in late Tertiary
times. ;

Birds of Celebes—Having thus clearly placed before us the
problem presented by the mammalian fauna of Celebes, we
may proceed to see what additional evidence is afforded by
the birds, and any other groups of which we have sufficient
information. About 164 species of true land-birds are now

CHAP, XX.] CELEBES. 429

known to inhabit the island of Celebes itself. Considerably
more than half of these (ninety-four species) are peculiar to it ;
twenty-nine are found also in Borneo and the other Malay
Islands, to which they specially belong; while sixteen are common
to the Moluccas or other islands of the Australian region; the
remainder being species of wide range and not characteristic
of either division of the Archipelago. We have here a large pre-
ponderance of western over eastern species of birds inhabiting
Celebes, though not to quite so great an extent as in the mam-
malia; and the inference to be drawn from this fact is, simply,
that more birds have migrated from Borneo than from the
Moluccas—which is exactly what we might expect both from
the greater extent of the coast of Borneo opposite that of
Celebes, and also from the much greater richness in species of
the Bornean than the Moluccan bird-fauna.

It is, however, to the relations of the peculiar species of
Celebesian birds that we must turn, in order to ascertain the
origin of the fauna in past times; and we must look to the
source of the generic types which they represent to give us this
information. The ninety-four peculiar species above noted
belong to about sixty-six genera, of which about twenty-three
are common to the whole Archipelago, and have therefore little
significance. Of the remainder, twelve are altogether peculiar
to Celebes; twenty-one are Malayan, but not Moluccan or
Australian; while ten are Moluccan or Australian, but not
Malayan. This proportion does not differ much from that
afforded by the non-peculiar species; and it teaches us that, for
a considerable period, Celebes has been receiving immigrants
from all sides, many of which have had time to become modified
into distinct representative species. These evidently belong to
the period during which Borneo on the one side, and the Moluc-
cas on the other, have occupied very much the same relative
position as now. ‘There remains the twelve peculiar Celebesian
genera, to which we must look for some further clue as to the
origin of the older portion of the fauna; and as these are
especially interesting we must examine them somewhat closely.

Bird-types peculiar to Celebes.—First we have Artamides, one
of the Campephaginz or caterpillar-shrikes—a not very well-

430 ISLAND LIFE. [PART II.

marked genus, and which may have been derived, either from
the Malayan or the Moluccan side of the Archipelago. Two
peculiar genera of kingfishers—Monachalcyon and Cittura—seem
allied, the former to the widespread Todiramphus and to the
Caridonax of Lombok, the latter to the Australian Melidora.
Another kingfisher, Ceycopsis, combines the characters of the
Malayan Ceyx and the African Ispidina, and thus forms an
example of an ancient generalised form analogous to what
occurs among the mammalia. Streptocitta is a peculiar form
allied to the magpies; while Basilornis (found also in Ceram),
Enodes, and Scissirostrum, are very peculiar starlings, the latter
altogether unlike any other bird, and perhaps forming a distinct
sub-family. Meropogon is a peculiar bee-eater, allied to the
Malayan Nyctiornis; Rhamphococyx is a modification of
Phzenicophaes, a Malayan genus of cuckoos; Prioniturus (found
also in the Philippines) is a genus of parrots distinguished by
raquet-formed tail feathers, altogether unique in the order;
while Megacephalon is a remarkable and very isolated form of
the Australian Megapodiide, or mound-builders.

Omitting those whose affinity may be pretty clearly traced to
groups still inhabiting the islands of the western or the eastern
half of the Archipelago, we find four birds which have no near
allies at all, but appear to be either ancestral forms, or extreme
modifications, of Asiatic or African birds—Basilornis, Enodes,
Scissirostrum, Ceycopsis. These may fairly be associated with
the baboon-ape, anoa, and babirusa, as indicating extreme
antiquity and some communication with the Asiatic continent
at a period when the forms of life and their geographical dis-
tribution differed considerably from what they are at the
present time.

But here again we meet with exactly the same difficulty as
in the mammalia, in the comparative poverty of the types of
birds now inhabiting Celebes. Although the preponderance of
affinity, especially in the case of its more ancient and peculiar
forms, is undoubtedly with Asia rather than with Australia;
yet, still more decidedly than in the case of the mammalia, are
we forbidden to suppose that it ever formed a part of the old
Asiatic continent, on account of the total absence of so many

| ischial

CHAP. XX. ] CELEBES. 431

important and extensive groups of Asiatic birds. It is not
single species or even genera, but whole families that are thus
absent, and among them families which are pre-eminently
characteristic of all tropical Asia. Such are the Timaliide, or
babblers, of which there are twelve genera in Borneo, and
nearly thirty genera in the Oriental Region, but of which one
species only, hardly distinguishable from a Malayan form, in-
habits Celebes; the Phyllornithidz, or green bulbuls, and the
Pycnonotide, or bulbuls, both absolutely ubiquitous in tropical
Asia and Malaya, but unknown in Celebes; the Eurylemide,
or gapers, found everywhere in the great Malay Islands; the
Megalemidz, or barbets; the Trogonide, or trogons; and the
Phasianide, or pheasants, all pre-eminently Asiatic and Malayan
but all absent from Celebes, with the exception of the common
jungle-fowl, which, owing to the passion of Malays for cock-
fighting, may have been introduced. To these important
families may be added Asiatic and Malayan genera by the score ;
but, confining ourselves to these seven ubiquitous families,
we must ask,—is it possible, that, at the period when the
ancestors of the pecuhar Celebes mammals entered the island,
and when the forms of life, though distinct, could not have been
quite unlike those now living, it could have actually formed a
part of the continent without possessing representatives of the
greater part of these extensive and important families of birds ?
To get rid altogether of such varied and dominant types of
bird-life by any subsequent process of submersion is more
difficult than to exterminate mammalia; and we are therefore
again driven to our former conclusion—that the present land of
Celebes has never (in Tertiary times) been united to the Asiatic
continent, but has received its population of Asiatic forms by
migration across narrow straits and intervening islands. ‘Taking
into consideration the amount of affinity on the one hand, and
the isolation on the other, of the Celebesian fauna, we may
probably place the period of this earlier migration in the early
part of the latter half of the Tertiary period, that is, in middle
or late Miocene times.

Celebes not strictly a Continental Island.—A study of the
mammalian and of the bird-fauna of Celebes thus leads us in

432 ISLAND LIFE. [PART II,

both cases to the same conclusion, and forbids us to rank it as
a strictly continental island on the Asiatic side. But facts of
a very similar character are equally opposed to the idea of
a former land-connection with Australia or New Guinea, or
even with the Moluccas. The numerous marsupials of those
countries are all wanting in Celebes, except the phalangers of
the genus Cuscus, and these arboreal creatures are very liable
to be carried across narrow seas on trees uprooted by earth-
quakes or floods. The terrestrial cassowaries are equally absent 5
and thus we can account for the presence of all the Moluccan
or Australian types actually found in Celebes without supposing
any land-connection on this side during the Tertiary period.
The presence of the Celebes ape in the island of Batchian,
and of the babirusa in Bouru, can be sufficiently explained by
a somewhat closer approximation of the respective lands, or by
a few intervening islands which have since disappeared, or it
may even be due to human agency.

If the explanation now given of the peculiar features presented
by the fauna of Celebes be the correct one, we are fully justified
in classing it as an “anomalous island,” since it possesses a
small but very remarkable mammalian fauna, without ever
having been directly united with any continent or extensive
land; and, both by what it has and what it wants, occupies
such an exactly intermediate position between the Oriental and
Australian regions that it will perhaps ever remain a mere
matter of opinion with which it should properly be associated.
Forming, as it does, the western limit of such typical Aus-
tralian groups as the Marsupials among mammalia, and the
Trichoglossidz and Meliphagide among birds, and being so
strikingly deficient in all the more characteristic Oriental
families and genera of both classes, I have always placed it in
the Australian Region; but it may perhaps with equal propriety
be left out of both till a further knowledge of its geology enables
us to determine its early history with more precision.

Peculiarities of the Insects of Celebes.—The only other class of
animals in Celebes, of which we have a tolerable knowledge, is
that of insects, among which we meet with peculiarities of a
very remarkable kind, and such as are found in no other island

CHAP. Xx. | CELEBES. 433

on the globe. Having already given a full account of some
of these peculiarities in a paper read before the Linnean
Society—republished in my Contributions to the Theory of
Natural Selection,—while others have been discussed in my
Geographical Distribution of Animals (Vol. I. p. 434)—I will
only here briefly refer to them in order to see whether they
accord with, or receive any explanation from, the somewhat
novel view of the past history of the island here advanced.

The general distribution of the two best known groups of
insects—the butterfiies and the beetles—agrees very closely
with that of the birds and mammalia, inasmuch as Celebes
forms the eastern limit of a number of Asiatic and Malayan
genera, and at the same time the western limit of several
Moluccan and Australian genera, the former perhaps pre-
ponderating as in the higher animals,

Himalayan Types of Birds and Butterflies in Celebes—A
curious fact of distribution exhibited both among butterflies
and birds, is the occurrence in Celebes of species and genera
unknown to the adjacent islands, but only found again when
we reach the Himalayan mountains or the Indian Peninsula.
Among birds we have a small yellow flycatcher (Myialestes
helianthea), a flower-pecker (Pachyglossa aureolimbata), a finch
(Munia brunnerceps), and a roller (Coracias temminckit), all
closely allied to Indian (not Malayan) species,—all the genera,
except Munia, being, in fact, unknown in any Malay island.
iixactly parallel cases are two butterflies of the genera Dichor-
rhagia and Euripus, which have very close allies in the Hima-
layas, but nothing like them in any intervening country. These
facts call to mind the similar case of Formosa, where some of
its birds and mammals occurred again, under identical or closely
allied forms, in the Himalayas; and in both instances they can
only be explained by going back to a period when the distribu-
tion of these forms was very different from what it is now.

Peculiarities of Shape and Colour in Celebesian Butterflies —
Even more remarkable are the peculiarities of shape and colour
in a number of Celebesian butterflies of different genera. These
are found to vary all in the same manner, indicating some
general cause of variation able to act upon totally distinct

F F

434 ISLAND LIFE, [PART 11.

groups, and produce upon them all a common result. Nearly
thirty species of butterflies, belonging to three different families,
have a common modification in the shape of their wings, by
which they can be distinguished at a glance from their allies
in any other island or country whatever ; and all these are
larger than the representative forms inhabiting most of the
adjacent islands.! No such remarkable local modification as
this is known to occur in any other part of the globe; and
whatever may have been its cause, that cause must certainly
have been long in action, and have been confined to a limited
area. We have here, therefore, another argument in favour of
the long-continued isolation of Celebes from all the surrounding
islands and continents—a hypothesis which we have seen to
afford the best, if not the only, explanation of its peculiar
vertebrate fauna.

Concluding Remarks—If the view here given of the origin
of the remarkable Celebesian fauna is correct, we have in this
island a fragment of the great eastern continent which has pre-
served to us, perhaps from Miocene times, some remnants of its
ancient animal forms. There is no other example on the globe
of an island so closely surrounded by other islands on every
side, yet preserving such a marked individuality in its forms of
life ; while, as regards the special features which characterise its
insects, 1t is, so far as yet known, absolutely unique. Unfortu-
nately very little is known of the botany of Celebes, but it
seems probable that its plants will to some extent partake of
the speciality which so markedly distinguishes its animals ;
and there is here a rich field for any botanist who is able to
penetrate to the forest-clad mountains of its interior.

1 For outline figures of the chief types of these butterflies, see my
Malay Archipelago, Vol. I. p. 441, or p. 281 of the second edition.

APPENDIX TO CHAPTER XX.

The following list of the Land Birds of Celebes and the adjacent

islands which partake of its zoological peculiarities, in which are incor-

porated all the species discovered up to the present year, has been drawn

up from the following sources :—

10.

A List of the Birds known to inhabit the Island of Celebes. By Arthur,
Viscount Walden, F.R.S. (Trans. Zool. Soc, 1872. Vol. viii. pt. ii.)

Intorno 4l Genere Hermotimia, (Rchb.) Nota di Tommaso Salvadori.
(Atti della Reale Accademia delle Scienze di Torino. Vol. x. 1874.)

Intorno a due Collezioni di Ucelli di Celebes—Note di Tommaso
Salvadori. (Annali del Mus. Civ. di St. Nat. di Genova. Vol. vii.
1875.)

. Beitrége zur Ornithologie von Celebes und Sangir. Von Dr. Friedrich

Bruggemann. Bremen, 1876.

. Intorno a due piccole Collezioni di Ucelli di Isole Sanghir e di Tifore.

Nota di Tommaso Salvadori, (Annali del Mus, Civ. di St. Nat, di
Genova. Vol. ix. 1876-77.)

. Intorno alle Specie di Nettarinie delle Molucche e del Gruppo di

Celebes. Note di Tommaso Salvadori. (Atti della Reale Accad.
delle Scienze di Torino. Vol. xii. 1877.)

. Descrizione di tre Nuove Specie di Ucelli, e note intorno ad altre poco

conosciute delle Isole Sanghir. Per Tommaso Salvadori. (L. ec.
Vol. xiii. 1878.)

. Field Notes on the Birds of Celebes. By A. B. Meyer, M.D., &c.

(Ibis, 1879.)

. On the Collection of Birds made by Dr, Meyer during his Expedition

to New Guinea and some neighbouring Islands. By R. Boulder
Sharpe. (Mitth. d. kgl. Zool. Mus, Dresden, 1878. Heft 3.)
New species from the Sula and Sanghir Islands are described.

List of Birds from the Sula Islands (Hast of Celebes) with Descrip-
tions of the New Species. By Alfred Russel Wallace, F.Z.S.
(Proc. Zool. Soc. 1862, p. 333.)

LIST OF LAND BIRDS OF CELEBES.

NB, The Spectes marked with an * are not included in Viscount Walden’s list. For
these only, an authority ts usually given.

~
| Celebes. Sula Is. |Sanghir Is. | Range and Remarks,
\ fo) fo}

TURDIDA, |

' 1. Geocichla erythronota ... x |
2. Monticola solitaria ...... all Gee: Phil., China, Japan

SYLVIIDA.'

Cisticola cursitans ...
Ae orayi .

3 Assam
4, a al

5. Acrocephalus orientalis ...

| China, Japan
— x (Salv.)} Moluceas
Asia, Java, Timor

a insularis
Pratincola caprata ..,

| ee

|
|
|
|
|
|
r
|
|
|
|
|

*8. Gerygone flaveola (Cab.)... | x(Meyer), | (Near G. sulphurea, Timor)

TIMALIIDA, |
9. Trichostomacelebense ... | x

PYCNONOTIDA. |
*10. Criniger longirostris (Wall.)

ae | Oriental genus (near Bouru

sp.)
ae ne aureus (Wald.)... x |

ORIOLIDA.

|
12. Oriolus celebensis ... ... x (Var. of O. coronatus, Java)
13, », formosus ( (Cab.) .. — —_ x(Brugg.) (Var. of Philipp. sp.)
14, » frontalis (Wall. ne —

CAMPEPHAGIDA.

15. Graucalus atriceps x Ceram, Flores
16. ue leucopygius x
les FA temminckii *
18. Campephagamorio ... ...
*19; a melanotis —
*20, »» _ Salvadorii (Sharpe) —
21, Lalage leucopygialis... x
#22, », dominica ... ...|x(Meyer)) — — Java,
23. Artamides bicolor

*24, », schistaceus (Shar -pe) -— *

x (Wall ) Moluccas

DicavuRIpm.

25. Dicrurusleucops _... x
*26. ce axillaris (Salv. e ois x
*27. pectoralis (Wall. ) peel

CHAP. XX. | LIST OF LAND BIRDS OF CELEBES. 437

MUSCICAPIDZE.

28. Cyornis rufigula
29. banyumas ...
30. Myialestes Hemeniiee
31. Hypothymis puella ..
32, 5 menadensis Be
¥*33. Monarcha commutata
(Brugg.) ...

#34, os cinerascens

PACHYCEPHALIDA,

35. Hylocharis sulfuriventra ..
*36. Pachycephala lineolata
(CELE Se eae ae
*37. Pachycephala — rufescens
CWall.j~ 3. Beit ut
*38. Pachycephala clio (Wall)

LAND.
*39. Laniusmagnirostris(Meyer)

CorvIDz.

40. Corvus enca

41, »» annectens (Brugg. )
42, », (Gazzola) typica ...
43. Streptocitta caledonica
44, torquata

¥45, (Charitornis) albertize (Schl. )

MELIPHAGIDE.
46. Myzomela chloroptera

NECTARINIDA.

47, Anthreptes malaccensis

(celebensis, Shelley) ... |

48. Chalcostethia porphyolema
*49, Ae auriceps As

*50. »» sangirensis (Meyer) |
51, Arachnecthra frenata
52. Nectarophila grayi ...
53. AEthopyga flavostriata

*54, 397 beecari (Salv.) ..

*55. ;, duyvenbodei(Schl.) |

DicHID.A,

56. Zosterops intermedia

ye 3 atrifrons ...

58. Diceum celebicum ..._...
#59, », sanghirense (Salv. )

60, Pachyglossa aureolimbata ,

HIRUNDINIDS.

Celebes.

61. Hirundo gutturalis ..,
62. i. javanica

x KX & XX

| exec ex

Sula Is.

- | =

x (Wall.)

x Var.

x (Wall.).

fanghir Is.

Range and Remarks.

Java and Borneo
(Indian ally)

Moluccas

Bouru

Bouru
Bouru

Java

(Nearest IL, sunguinolenta
of Australia)
; Siam, Malaya
Ternate
Moluccas and N. Guinea.

(An Oriental genus)

|
|

Lomboek

| Indian region
| Indo-Malaya

448

PLOCEIDA.

63. Munia oryzivora

64. sy.) sonia, 3

65. > amolaces,

66, so) DruUmMeIEeps:...
*67, »> jagori

STURNIDZ.

. Basilornis celebensis

. Acridotheres cinereus
. Sturnia pyrrhogenys

. Calornis neglecta
Rls »» Metallica

. Enodes erythrophrys
. Scissirostrum pagel ...

ARTAMIDA.,

75. Artamus monachus... ...
LGs i leucorhynchus . ae

MoraciLuipa,
77. Corydalla gustavi
78. Budytes viridis
*79.. Calobates melanope ‘
(= Motac. sulfurea, Brugg. )

PITTIDA,
80. Pitta forsteni
*8], ,, sanghirana (Schl. i
S28 oes celebensis
*83. ,, palliceps (Brugge. ye.
*84. ,, ccruleitorques (Salv. )
*85. ,, irena(=crassirostris)
PICIDA,

86. Mulleripicus aly use
87. Yungipicus temminckii ...

CuCcULIDA.

88. Rhamphococcyx pees
chus..

89. Centropus celebensis

G0. Ae affinis

91. ve javanensis

92. Cuculus canorus Bien cee
93, Cacomantes lanceolatus ...
94, vs sepulchralis ...
95, Hierococcyx crassirostris...
96. Eudynamis melanorhyncha
*97, oH facialis (Wall. )
*98, Be orientalis 4
99. Scythrops novehollandiz..

CoRACIIDA.
100. Coracias temminckii
101, Eurystomus orientalis ...

ISLAND LIFE.

Celebes.

x
x
x
~
x (Meyer)

lela xe KX XX X

Sula ls. |Sanghir Is.
x x var.
x(Wall.)} —
x
— x
pan | x
——a | x
CWall)) es
x
x(Brugg.

[PART II,
Range and Remarks.
Java
Java
Moluccas

(Near M. ruwbronigra, India)
Philippines

Malaya

Moluceas

Malay Archipel.

Java, Moluccas

China, Philipp.

Timor, Ternate ?

Java
Java, Borneo

Java

Moluccas ?
Moluccas, &2.

Asia

CHAP, XX. | LIST OF LAND BIRDS OF CELEBES. 459

Celebes. | SulaIs. |Sanghir Is. Range and Remarks.

MEROPIDA.

102. Meropogon forsteni _.... x
103. Merops philippinus ee x Oriental region
104, PRE TORMAGUS: 2c ak. x x Java, Australia

ALCEDINIDA,

x Moluceas
Indo-Malaya

105. Alcedo moluccensis

106, », asiatica as

107. Pelargopsis melanorhyncha
*108. Ceyx wallacei (Sharpe) ...

109, Ceycopsis fallax aN

110. Halcyon chloris

Td. an sancta

112. ss forsteni

113. af MUP ees, ck abe
- 114. Monachalcyon princeps..
*115. __,, cyanocephala (Brugge. )

116, Cittura cyanotis
*117. 4, sanghirensis (Schl. )

x (Allied to Mol. sp.)

x x All Archipel.
| All Archipel.

[eX Ke MEK UK exe x
x

BuUcEROTIDA.

118. Hydrocissa exarata a :
119. Cranorhinus cassidix ... x

CAPRIMULGIDA,

120. Caprimulgus affinis on x
Th, a Spaew : x
122, Lyncornis macr opterus .. x

CYPSELIDA,

123. Dendrochelidon wallacei.
124. Collocalia esculenta

125. a fuciphaga

126, Chetura gigantea ...

| Mol. to Aru Is.
India, Java
India, Java

x xX X X

ISEPTACT.

127. Cacatua sulphurea ...

128. Prioniturus platurus

129. flavicans
*130. Platycercus dorsalis, var.

131. Tanygnathus mulleri
*132. ‘5 megalorhynchus

Lombok, Flores

x (Wall. ) N. Guinea ?
x

MEXS [POX x

— x Moluccas. An island near

eee Menado (Meyer)

*133. 4p luzoniensis
134, Loriculus stigmatus ...
PSB 95 lor wie)
136, ,, sclatert . :
Wee ey COXUIS .., 62
*138, ,, catamene (Schl. \=
139. Trichoglossus ornatus ..,
*140. om ‘flavoviridis (Wall.)
141, »> meyeri

*142, Eos histrio = E. coccinea

— |x(Brugg.)|

Togian Is., Gulf of Tomini.

[axe de (xe se 3c |

449

ISLAND LIFE.

Sula Is.

Sanghir Is.

[PART 11,

Range and Remarks.

COLUMB2.

148,
144,

145.
146.

147.
*148.
149.
*150.

ou.
152.
*153.
154,
MDD:
156.
LOG:
158.
159.
*160.
GT,
raz.
163.
164,
165.
166.
167,
168.

Treron vernans

» griseicauda

Ptilopus formosus ... .
‘ melanocephalus...

gularis

3 father! (Brugg. )
Carpophaga paulina... ...
pulchella (Wald.)

concinna
Py rosacea
5, pecilorrhoa (Brugg.)
luctuosa
“ bicolor
5 radiata
forstenl
Macropyg sia albicapilla ..
», Macassariensis .
5, sanghirensis (Salv.)
Turaccena menadensis
Reinwardtenas reinwardti
Turtur tigrina.. .:
Chaleophaps stephani
HA indica
Phlogeenas tristigmata ...
Geopelia striata
Calenas nicobarica

GALLINA.

169.
170.
lyf
“Whe.
173.
174.

Gallus bankiva
Coturnix minima
Turnix rufilatus

»» beccarii (Salv.) ..
Megapodius gilberti
Megacephalon malleo

i: ACCIPITRES,

175.
176.2
*177,
178.
179.
180.
Sai:
182.
183.
184,
85.

Cireus assimilis
Astur griseiceps
7?

», Thodogastra ...

53) EEO tata i
Accipiter sulaensis (Schl. )
be soloensis ..

Neopus malayensis
Spizaetus lanceolatus
Haliaetus leucogaster }
Spilornis rufipectus

tenuirostris( Brugg. a

De
H

x
ta
SOS Sar

SOS PS. ES oN OS

xxxx |xxxxx

Vv
“nN

eyer

SVs

x var.
Sanghi-
rensis.

x var.
Xanthor-
rhoa,
Salv.

x (Salv.)

Malacca, Java, Philipp.

Java, Lombock

Togian Is. (Ann. and Mag.
Nat, Hist., 1874.)

Ké Goram

Gilolo, Timor

New Guinea, Moluccas

Moluccas and New Guinea
Malaya, Moluccas

New Guinea

India and Archipelago

China, Java, Lombock
Malacca and New Guinea

Java, Timor

(Var. of C. Chinensis)

Australia

Malacca and New Guinea
Nepaul,Sum.,Java, Moluccas

Oriental region

a
4

CHAP, XXx.]

186.
hsv ie
188.
189.
190.
Toi,

192,
193.
194,
195.

Celebes.

Sula Is.

iSanghir Is.

LIST OF LAND BIRDS OF CELEB#S.

Range and Remarks.

Butastur liventer ..
be indicus

Haliastur leucosternus ...

Milvus affinis ...
Klanus hypoleucus...

celebensis) ...
Baza erythrothorax
Falco severus ...

Cerchneis moluccensis ...

Polioaetus humilis

STRIGIDA.

196

197.

198

199.
200.
*201.
202.

Athene punctulata

», ochracea
Scops magicus

», Mmenadensis ...
Ninox japonicus

». scutulata
Strix rosenbergi

: b aa
Pernis ptilorhyncha (var.

5GxKaxX

PS PG DgS

x [xxx x x

|
|

x (Salv.)

Java, Timor

India, Java

Moluccas, New Guinea
Australia

¢ Java, Borneo

(Var. Java, &c.)
All Archipel.

Java, Moluccas
India, Malaya

Amboyna, &c. ?
Flores, Madagascar

| China, Japan

Malacca

CHAPTER XXI.
ANOMALOUS ISLANDS: NEW ZEALAND.

Position and Physical Features of New Zealand—Zoological character of
New Zealand—Mammalia—Wingless Birds living and extinct—-Recent
Existence of the Moa—Past Changes of New Zealand deduced from
its Wingless Birds—Birds and Reptiles of New Zealand—-Conclusions
from the Peculiarities of the New Zealand Fauna.

THE fauna of New Zealand has been so recently described, and
its bearing on the past history of the islands so fully discussed
in my large work already referred to, that it would not be neces-
sary to introduce the subject again, were it not that we now
approach it from a somewhat different point of view, and with
some important fresh material, which will enable us to arrive
at more definite conclusions as to the nature and origin of this
remarkable fauna and flora. The present work is, besides,
addressed to a wider class of readers than my former volumes,
and it would be manifestly incomplete if all reference to one of
the most remarkable and interesting of insular faunas was
omitted.

The two great islands which mainly constitute New Zealand
are together about as large as the kingdom of Italy. They
stretch over thirteen degrees of latitude in the warmer portion
of the south-temperate zone, their extreme points correspond-
ing to the latitudes of Vienna and Cyprus. Their climate
throughout is mild and equable, their vegetation is luxuriant,
and deserts or uninhabitable regions are as completely unknown
as in our own islands.

CHAP. Xx. | NEW ZEALAND. 443

The geological structure of these islands has a decidedly
continental character. Ancient sedimentary rocks, granite,
and modern volcanic formations abound ; gold, silver, copper,
tin, iron, and coal are plentiful; and there are also some con-
siderable deposits of early or late Tertiary age. The Secondary
rocks alone are very scantily developed, and such fragments as
exist are chiefly of Cretaceous age, often not clearly separated
from the succeeding Eocene beds.

teow sibs

| so 100 10 \'20 [i890 40 {ISO 160 liZo0;

MAP SHOWING DEPTHS OF SEA AROUND AUSTRALIA AND NEW ZEALAND.:

The light tint indicates a depth of less than 1,000 fathoms.
The dark tint 5 si more than 1,000 fathoms.

The position of New Zealand, in the great Southern Ocean,
about 1,200 miles distant from the Australian continent, 1s very
isolated. It is surrounded by a moderately deep ocean; but
the form of the sea-bottom is peculiar, and may help us in the
solution of some of the anomalies presented by its living pro-
ductions. The line of 200 fathoms encloses the two islands
and extends their area considerably; but the 1,000-fathom
line, which indicates the land-area that would be produced if

444 ISLAND LIFE. [PART Il.

the sea-bottom were elevated 6,000 feet, has a very remarkable
conformation, extending in a broad mass westward, and then
sending out two great arms, one reaching to beyond Lord Howe’s
Island, while the other stretches over Norfolk Island to the
great barrier reef, thus forming a connection with tropical
Australia and New Guinea. Temperate Australia, on the other
hand, is divided from New Zealand by an oceanic gulf about.
700 miles wide and between 2,000 and 3,000 fathoms deep.
The 2,000-fathom line embraces ali the islands immediately
round New Zealand; and a submarine plateau at a depth
somewhere between one and two thousand fathoms stretches
southward to the Antarctic continent. Judging from these indi-
cations, we should say that the most probable ancient connections
of New Zealand were with tropical Australia and New Guinea,
and perhaps, at a still more remote epoch, with the great
Southern continent by means of intervening lands and islands ;
and we shall find that a land-connection or near approximation
in these two directions, at remote periods, will serve to ex-
plain many of the remarkable anomalies which these islands
present.

Zoological Character of New Zealand.—We see, then, that
both geologically and geographically New Zealand has more
of the character of a “continental” than of an “ oceanic” island,
yet its zoological characteristics are such as almost to bring it
within the latter category—and it is this which gives it its
anomalous character. It is usually considered to possess no
indigenous mammalia; it has no snakes, and only one frog ;
it possesses (living or quite recently extinct) an extensive group
of birds incapable of flight; and its productions generally are
wonderfully isolated, and seem to bear no predominant or close
relation to those of Australia or any other continent. These
are the characteristics of an oceanic island ; and thus we find
that the inferences from its physical structure and those from
its forms of life directly contradict each other. Let us see
how far a closer examination of the latter will enable us to
account for this apparent contradiction.

Mammalia of New Zealand.—The only undoubtedly indi-
genous mammalia appear to be two species of bats, one of which

CHAP, XXI. | NEW ZEALAND. 445

(Scotophilus tuberculatus) is, according to Mr. Dobson, identical
with an Australian form, while the other (Mystacina tuberculata)
forms a very remarkable and isolated genus of Emballonuride,
a family which extends throughout all the tropical regions of
the globe. The genus Mystacina was formerly considered to
belong to the American Phyllostomide, but this has been
shown to be an error.1 The poverty of New Zealand in bats
is very remarkable when compared with our own islands where
there are at least twelve distinct species, though having a far
less favourable climate. | |

Of the existence of truly indigenous land mammals in New
Zealand there is at present no positive evidence, but there is
some reason to believe that one if not two species may be found
there. The Maoris say that before Europeans came to their
country a forest-rat abounded and was largely used for food.
They believe that their ancestors brought it with them when
they first came to the country; butit has now become almost, if
not quite, exterminated by the European brown rat. What
this native animal was is still somewhat doubtful. Several
specimens have been caught at different times which have been
declared by the natives to be the true Kiore Maori—as they term
it, but these have usually proved on examination to be either
the European black rat or some of the native Australian rats
which now often find their way on board ships. But within
the last few years many skulls of a rat have been obtained from
the old Maori cooking-places, and from a cave associated with
moa bones; and Captain Hutton, who has examined them, states
that they belong to a true Mus, but differ from the Mus rattus.
This animal might have been on the islands when the Maoris
first arrived, and in that case would be truly indigenous ; while
the Maori legend of their “ ancestors” bringing the rat from their
Polynesian home may be altogether a myth invented to account
for its presence in the islands, because the only other land
mammal which they knew—the dog—was certainly so brought.
The question can only be settled by the discovery of remains

-! Dobson on the Classification of Chiroptera (Ann. and Mag. of Nat,
Hist. Nov. 1875).

446 ISLAND LIFE. [PART II.

of arat in some deposit of an age decidedly anterior to the
first arrival of the Maori race in New Zealand.!

Much more interesting 1s the reported existence in the moun-
tains of the South Island of a small otter-like animal. Dr.
Haast has seen its tracks, resembling those of our Huropean otter,
at a height of 3,000 feet above the sea in a region never before
trodden by man; and the animal itself was seen by two
gentlemen near Lake Heron, about seventy miles due west of
Christchurch. It was described as being dark brown and the
size of a large rabbit. On being struck at with a whip, it uttered
a shrill yelping sound and disappeared in the water.?, Ananimal
seen so closely as to be struck at with a whip could hardly have
been mistaken for a dog—the only other animal that it could
possibly be supposed to have been, and a dog would certainly not
have “ disappeared.in the water.” This account, as well as the
footsteps, point to an aquatic animal; and if it now frequents
only the high alpine lakes and streams, this might explain
why it has never yet been captured. Hochstetter also states
that it has a native name—Waitoteke—a striking evidence
of its actual existence, while a gentleman who lived many years
in the district assures me that it is universally believed in by
residents in that part of New Zealand. The actual capture of
this animal and the determination of its characters and affinities
could not fail to aid us greatly in our speculations as to the
nature and origin of the New Zealand fauna.

1 See Buller, “On the New Zealand Rat,” Trans. of the N. Z. Institute
(1870), Vol. IIL. p. 1, and Vol. IX. p. 348; and Hutton, “On the Geogra-
phical Relations of the New Zealand Fauna,’’ Trans. N. Z. Instit. 1872,
p. 229.

2 Hochstetter’s New Zealand, p. 161, note.

3 The animal described by Captain Cook as having been seen at Pick-
ersgill Harbourin Dusky Bay (Cook’s 2nd Voyage, Vol. I. p. 98) may have
been the same creature. He says, ‘‘ A four-footed animal was seen by three
or four of our people, but as no two gave the same description of it, I can-
not say what kind it is. All, however, agreed that it was about the size of
a cat, with short legs, and of a mouse colour. One of the seamen, and he
who had the best view of it, said it had a bushy tail, and was the most like
a jackal of any animal he knew.” It is suggestive that, so far as the
points on which ‘all agreed ’—the size and the dark colour—this description
would answer well to the animal so recently seen, while the “ short legs”

CHAP. XXI.| NEW ZEALAND. 447

Wingless Birds, living and extinct—Almost equally valuable
with mammalia in atfording indications of geographical changes
are the wingless birds for which New Zealand is so remarkable.
These consist of four species of Apteryx, called by the natives
‘“‘kiwis,”’—creatures which hardly look like birds owing to the
apparent absence (externally) of tail or wings and the dense
covering of hair-like feathers. They vary in size from that of
a small fowl up to that of a turkey, and have a long slightly
curved bill, somewhat resembling that of the snipe or ibis.
Two species appear to be confined to the South Island, and one
to the North Island, but all are becoming scarce, and they will
no doubt gradually become extinct. These birds are generally
classed with the Struthiones or ostrich tribe, but they form a
distinct family, and in many respects differ greatly from all
other known birds.

But besides these, a number of other wingless birds, called
“‘moas,” inhabited New Zealand during the period of human
occupation, and have only recently become extinct. These were
much larger birds than the kiwis, and some of them were even
larger than the ostrich, a specimen of Dinornis maximus
mounted in the British Museum in its natural attitude being
eleven feet high. They agreed, however, with the living
Apteryx in having four toes, and in the character of the pelvis
and some other parts of the skeleton, while in their short bill
and in some important structural features they resembled
the emu of Australia and the cassowaries of New Guinea.’
No less than eleven distinct species of these birds have
now been discovered; and their remains exist in such

correspond to the otter-like tracks, and the thick tail of an otter-like animal
may well have appeared “bushy” when the fur was dry. It has been
suggested that it was only one of the native dogs; but as none of those
who saw it took it for a dog, and the points on which they all agreed are
not dog-like, we can hardly accept this explanation ; while the actual exist-
ence of an unknown animal in New Zealand of corresponding size and
colour is confirmed by this account of a similar animal having been seen
about a century ago.

! Owen, “ On the Genus Dinornis,” Trans. Zool. Soc. Vol. X. p. 184.
Mivart, ‘‘On the Axial Skeleton of the Struthionide,” Trans. Zool. Soe.
Vol, X.p. 51,

448 ISLAND LIFE, fran i.

abuadance—in recent fiuviatile deposits, in old native cooking
places, and even scattered on the surface of the ground—that
complete skeletons of several of them have been put together,
illustrating various periods of growth from the chick up to the
adult bird. Feathers have also been found attached to portions
of the skin, as well as the stones swallowed by the birds to
assist digestion, and eges, some containing portions of the
embryo bird; so that everything confirms the statements of the
Maoris—that their ancestors found these birds in abundance on
the islands, that they hunted them for food, and that they
finally exterminated them only a short time before the arrival of
EKuropeans.' Bones of Apteryx are also found fossil, but appar-
ently of the same species as the living birds. How far back in
geological time these creatures or their ancestral types lived in
New Zealand we have as yet no evidence to show. Some
specimens have been found under a considerable depth of
fluviatile deposits which may be of Quaternary or even of
Pliocene age; but this evidently affords us no approximation to
the time required for the origin and development of such highly
peculiar insular forms.

Past Changes of New Zealand deduced from its Wingless Birds.

1 The recent existence of the Moa and its having been exterminated by
the Maoris appears to be at length set at rest by the statement of Mr.
John White, a gentleman who has been collecting materials for a history of
the natives for thirty-five years, who has been initiated by their priests into
all their mysteries, and is said to “know more about the history, habits,
and customs of the Maoris than they do themselves.” Hisinformation on
this subject was obtained from old natives long before the controversy on
the subject arose. He says that the histories and songs of the Maoris
abound in allusions to the Moa, and that they were able to give full
accounts of “its habits, food, the season of the year it was killed, its
appearance, strength, and all the numerous ceremonies which were enacted
by the natives before they began the hunt, the mode of hunting, how cut
up, how cooked, and what wood was used in the cooking, with an account
of its nest, and how the nest was made, where it usually lived, &c.” Two
pages are occupied by these details, but they are only given from memory,
and Mr. White promises a full account from his MSS. Many of the details
given correspond with facts ascertained from the discovery of native cook-
ing places with Moa’s bones; and it seems quite incredible that such an
elaborate and detailed account should be all invention. (See Transactions
of the New Zealand Institute, Vol. VIII. p. 79.)

CHAP, XX1.] NEW ZEALAND. 449

—It has been well observed by Captain Hutton, in his inter-
esting paper already referred to, that the occurrence of such a
number of species of Struthious birds living together in so
small a country as New Zealand is altogether unparalleled else-
where on the globe. This is even more remarkable when we
consider that the species are not equally divided between the
two islands, for remains of no less than ten out of the eleven
known species of Dinornis have been found in a single swamp
in the South Island, where also three of the species of Apteryx
occur. The New Zealand Struthiones, in fact, very nearly equal
in number those of all the rest of the world, and nowhere else
do more than three species occur in any one continent or island,
while no more than two ever occur in the same district. Thus,
there appear to be two closely allied species of ostriches inhabiting
Africa and South-western Asia respectively. South America
has three species of Rhea, eachin a separate district. Australia
has an eastern and a western variety of emu, and a cassowary
in the north; while eight other cassowaries are known from the
islands north of Australia—one from Ceram, two from the Aru
Islands, one from Jobie, one from New Britain, and three from
New Guinea—but of these last one is confined to the northern
and another to the southern part of the island.

This law, of the distribution of allied species in separate areas
—which is found to apply more or less accurately to all classes
of animals—is so entirely opposed to the crowding together of
no less than fifteen species of. wingless birds in the small area of
New Zealand, that the idea is at once suggested of great geogra-
-phical changes. Captain Hutton points out that if the islands
from Ceram to New Britain were to become joined together, we
should have a large number of species of cassowary (perhaps
several more than are yet discovered) in one land area. If now
this land were gradually to be submerged, leaving a central
elevated region, the different species would become crowded
together in this portion just as the moas and kiwis were in
New Zealand. But we also require, at some remote epoch, a more
or less complete union of the islands now inhabited by the
separate species of cassowaries, in order that the common
ancestral form which afterwards became modified into these

450 ISLAND LIFE. pPAmarat,

species, could have reached the places where they are now
found; and this gives us an idea of the complete series of
changes through which New Zealand is believed to have passed
in order to bring about its abnormally dense population of wing-
less birds. First, we must suppose a land connection with some
country inhabited by struthious birds, from which the ancestral
forms might be derived; secondly, a separation into many con-
siderable islands, in which the various distinct species might
become differentiated ; thirdly, an elevation bringing about the
union of these islands to unite the distinct species in one
area; and fourthly, a subsidence of a large part of the area,
leaving the present islands with the various species crowded
together.

If New Zealand has really gone through such a series of
changes as here suggested, some proofs of it might perhaps be
obtained in the outlying islands which were once, presumably,
joined with it. And this gives great importance to the state-
ment of the aborigines of the Chatham Islands, that the
Apteryx formerly lived there but was exterminated about 1835.
It is to be hoped that some search will be made here and also in
Norfolk Island, in both of which it is not improbable remains
either of Apteryx or Dinornis might be discovered.

So far we find nothing to object to in the speculations of
Captain Hutton, with which, on the contrary, we almost wholly
concur ; but we cannot follow him when he goes on to suggest an
Antarctic continent uniting New Zealand and Australia with
South America, and probably also with South Africa, in
order to explain the existing distribution of struthious birds.
Our best anatomists, as we have seen, agree that both Dinornis
and Apteryx are more nearly allied to the cassowaries and emus
than to the ostriches and rheas; and we see that the form of

the sea-bottom suggests a former connection with North Aus-

tralia and New Guinea—the very region where these types
most abound, and where in all probability they originated. The
suggestion that all the struthious birds of the world sprang
from a common ancestor at no very remote period, and that
their existing distribution is due to direct land communication
between the countries they now inhabit, is one utterly opposed

ee eee u

CHAP. XXI.| NEW ZEALAND. 451

to all sound principles of reasoning in questions of geographical
distribution. For it depends upon two assumptions, both of
which are at least doubtful, if not certainly false—the first,
that their distribution over the globe has never in past ages
been very different from what it is now; and the second, that
the ancestral forms of these birds never had the power of flight.
As to the first assumption, we have found in almost every case
that groups now scattered over two or more continents formerly
lived in intervening areas of existing land. Thus the marsupials
of South America and Australia are connected by forms which
lived in North America and Europe; the camels of Asia and
the llamas of the Andes had many extinct common ancestors
im North America; the lemurs of Africa and Asia had their
ancestors in Europe, as did the trogons of South America,
Africa, and tropical Asia. But besides this general evidence we
have direct proof that the struthious birds had a wider range
in past times than now. Remains of extinct rheas have been
found in Central Brazil, and those of ostriches in North India;
while remains, believed to be of struthious birds, are found in
the Eocene deposits of England; and the Cretaceous rocks of
North America have yielded the extraordinary toothed bird,
Hesperornis, which Professor O. Marsh declares to have been
“a carnivorous swimming ostrich.”

As to the second point, we have the remarkable fact that all
known birds of this group have not only the rudiments of wing-
bones, but also the rudiments of wings, that, is, an external
limb bearing rigid quills or largely-developed plumes. In the
cassowary these wing-feathers are reduced to long spines like
porcupine-quills, while even in the Apteryx, the minute
external wing bears a series of nearly twenty stiff quill-like
feathers." These facts render it probable that the struthious
birds do not owe their imperfect wings to a direct evolution
from a reptilian type, but to a retrograde development from
some low form of winged birds, analogous to that which has pro-
duced the dodo and the solitaire from the more highly-developed
pigeon-type. Professor Marsh has proved, that so far back as

1 See fig. in Trans. of N. Z. Institute, Vol. IIL, plate 120, fig. 2.
: GG 2

452 ISLAND LIFE. [PART 11,

the Cretaceous period, the two great forms of birds—those with
a keeled sternum and fairly-developed wings, and those with a
convex keel-less sternum and rudimentary wings—already
existed side by side; while in the still earlier Archzeopteryx of
the Jurassic period we have a bird with well-developed wings,
and therefore probably with a keeled sternum. We are evidently,
therefore, very far from a knowledge of the earlier stages of
bird life, and our acquaintance with the various forms that have
existed is scanty in the extreme ; but we may be sure that birds
acquired wings, and feathers, and some power of flight, before
they developed a keeled sternum, since we see that bats with no
such keel fly very well. Since, therefore, the struthious birds
all have perfect feathers, and all have rudimentary wings, which
are anatomically those of true birds, not the rudimentary fore-
legs of reptiles, and since we know that in many higher groups
of birds—as the pigeons and the rails—the wings have become
more or less aborted, and the keel of the sternum greatly
reduced in size by disuse, it seems probable that the very
remote ancestors of the rhea, the cassowary, and the apteryx,
were true flying birds, although not perhaps provided with a
keeled sternum, or possessing very great powers of flight. But
in addition to the possible ancestral power of flight, we have
the undoubted fact that the rhea and the emu both swim
freely, the former having been seen swimming from island to
island off the coast of Patagonia. This, taken in connection
with the wonderful aquatic ostrich of the Cretaceous period
discovered by Professor Marsh, opens up fresh possibilities of
migration; while the immense antiquity thus given to the
group and their universal distribution in past time, renders
all suggestions of special modes of communication between the
parts of the globe in which their scattered remnants now
happen to exist, altogether superfluous and misleading.

The bearing of this argument on our present subject is, that
so far as accounting for the presence of wingless birds in New
Zealand is concerned, we have nothing whatever to do with
any possible connection, by way of a southern continent or
antarctic islands, with South America and South Africa,
because the nearest allies of its moas and kiwis are the

CHAP. 3X1. | NEW ZEALAND. 453

cassowaries and emus, and we have distinct indications of a
former land extension towards North Australia and New Guinea,
which is exactly what we require for the original entrance of
the struthious type into the New Zealand area.

Winged Birds and lower Vertebrates of New Zealand.—Having
given a pretty full account of the New Zealand fauna else-
where’ I need only here point out its bearing on the hypo-
thesis now advanced, of the former land-connection having been
with North Australia, New Guinea, and the Western Pacific
Islands, rather than with the temperate regions of Australia.

Of the Australian genera of birds, which are found also in
New Zealand, almost every one ranges also into New Guinea
or the Pacific Islands, while the few that do not extend beyond
Australia are found in its northern districts. As regards the
peculiar New Zealand genera, all whose affinities can be traced
are allied to birds which belong to the tropical parts of the
Australian region; while the starling family, to which four of
the most remarkable New Zealand birds belong (the genera
Creadion, Heterolocha, and Calleas), is totally wanting in
temperate Australia and is comparatively scarce in the entire
Australian region, but is abundant in the Oriental region, with
which New Guinea and the Moluccas are in easy communication.
It is certainly a most suggestive fact that there are more than
sixty genera of birds peculiar to the Australian continent (with
Tasmania), many of them almost or quite confined to its tempe-
rate portions, and that no single one of these should be repre-
sented in temperate New Zealand.* The affinities of the living
and more highly organised, no less than those of the extinct and
wingless birds, strikingly accord with the line of communication
indicated by the deep submarine bank connecting these temperate
islands with the tropical parts of the Australian region.

The reptiles, so far as they go, are quite in accordance with

1 Geographical Distribution of Animals, Vol. I., p. 450.

2 In my Geographical Distribution of Animals (I. p. 541) I have given
two peculiar Australian genera (Orthonyx and Tribonyx) as occurring in
New Zealand. But the former has been found in New Guinea, while the
New Zealand bird is considered to form a distinct genus, Clitonyx; and

the latter inhabits Tasmania, and was recorded from New Zealand through
an error. (See bis, 1873, p. 427.)

454 ISLAND LIFE. [PART II.

the birds. The lizards belong to three genera,—Himulia and
Mocoa, which have a wide range in the Eastern tropics and the
Pacific and Malayan regions, as well as Australia ; and Naultinus,
a genus peculiar to New Zealand, but belonging to a family—
Geckotidee, spread over the whole of the warmer parts of the
world, Australia, on the other hand, has three small but
peculiar families, and no less than thirty-six peculiar genera of
lizards, many of which are confined to its temperate regions,
but no one of them extends to temperate New Zealand. The
extraordinary lizard-like Hatteria punctata of New Zealand
forms of itself a distinct order of reptiles, in some respects
intermediate between lizards and crocodiles, and having therefore
no affinity with any living animal.

The only representative of the Amphibia in New Zealand is
a solitary frog of a peculiar genus (Liopelma hochstetterr) ; but
it has no affinity for any of the Australian frogs, which are
numerous, and belong to eleven different families; while the
Liopelma belongs to a very distinct family (Bombinatorids),
confined to Europe and temperate South America.

Of the fresh-water fishes we need only say here, that none
belong to peculiar Australian types, but are related to those of
temperate South America or of Asia.

The Invertebrate classes are comparatively little known, and
their modes of dispersal are so varied and exceptional that the
facts presented by their distribution can add little weight to
those already adduced. We will, therefore, now proceed to the
conclusions which can fairly be drawn from the general facts of
New Zealand natural history already known to us.

Deductions from the peculiarities of the New Zealand Fauna.—
The total absence (or extreme scarcity) of mammals in New
Zealand obliges us to place its union with North Australia and
New Guinea at a very remote epoch. We must either go back
to a time when Australia itself had not yet received the ancestral
forms of its present marsupials and monotremes, or we must
suppose that the portion of Australia with which New Zealand
was connected was then itself isolated from the mainland, and
was thus without a mammalian population. We shall see in
our next chapter that there are certain facts in the distribution.

CHAP. XXI. | NEW ZEALAND. 455

of plants, no less than in the geological structure of the country,
which favour the latter view. But we must on any supposition
place the union very far back, to-account for the total want of
identity between the winged birds of New Zealand and those
peculiar to Australia, and a similar want of acgordance in the
lizards, the fresh-water fishes, and the more important insect-
groups of the two countries. From what we know of the long
geological duration of the generic types of these groups we
must certainly go back to the earlier portion of the Tertiary
period at least, in order that there should be such a complete
disseverance as exists between the characteristic animals of the
two countries; and we must further suppose that, since their
separation, there has been no subsequent union or sufficiently
near approach to allow of any important intermigration, even
of winged birds, between them. It seems probable, therefore,
that the Bampton shoal west of New Caledonia, and Lord
Howe’s Island further south, formed the western limits of that
extensive land in which the great wingless birds and other
isolated members of the New Zealand fauna were developed.
Whether this early land extended eastward to the Chatham
Islands and southward to the Macquaries we have no means of
ascertaining, but as the intervening sea appears to be not more
than about 1,500 fathoms deep it is quite possible that such an
amount of subsidence may have occurred. It is possible, too,
that there may have been an extension northward to the
Kermadec Islands, and even further to the Tonga and Fiji
Islands, though this is hardly probable, or we should find more
community between their productions and those of New
Aealand.

A southern extension towards the Antarctic continent at a
somewhat later period seems more probable, as affording an
easy passage for the numerous species of South American and
Antarctic plants, and also for the identical and closely allied
fresh-water fishes of these countries.

The subsequent breaking up of this extensive land into a
number of separate islands in which the distinct species of moa
and kiwi were developed—their union at a later period, and
the final submergence of all but the existing islands, is a pure

456 ISLAND LIFE. [PART I.

we Se Se —————

hypothesis, which scems necessary to explain the occurrence of
so many species of these birds in a small area but of which we
have no independent proof. There are, however, some other
facts which would be explained by it, as the presence of three
peculiar but allied genera of starlings, the three species of
parrots of the genus Nestor, and the six distinct rails of the
genus Ocydromus, as well as the numerous species In some cf
the peculiar New Zealand genera of plants, which seem less
likely to have been developed in a single area than when
isolated, and thus preserved from the counteracting influence
of intercrossing.

In the present state of our knowledge these seem all the
conclusions we can arrive at from a study of the New Zealand
fauna; but as we fortunately possess a very full and accurate
knowledge of the flora of New Zealand, as well as of that of
Australia and the south temperate lands generally, it will be
well to see how far these conclusions are supported by the facts
of plant distribution, and what further indications they afford us
of the early history of these most interesting countries. This
inquiry is of sufficient importance to occupy a separate chapter,

eee oe

CHAPTER XXII.

THE FLORA OF NEW ZEALAND: ITS AFFINITIES
AND PROBABLE ORIGIN.

Relations of the New Zealand Flora to that of Australia—General features
of the Australian Flora—The Floras of South-eastern and South-western
Australia—Geological explanation of the differences of these two
Floras—The origin of the Australian element in the New Zealand Flora
—Tropical character of the New Zealand Flora explained—Species
common to New Zealand and Australia mostly temperate forms—-Why
easily dispersed plants have often restricted ranges—Summary and
Conclusion on the New Zealand Flora.

ALTHOUGH plants have means of dispersal far exceeding those
possessed by animals, yet as a matter of fact comparatively few
species are carried for very great distances, and the flora of a
country taken as a whole usually affords trustworthy indications
of its past history. Plants, too, are more numerous in species
than the higher animals, and are almost always better known;
their affinities have been more systematically studied; and it may
be safely affirmed that no explanation of the origin of the fauna
of a country can be sound, which does not also explain, or at
least harmonise with, the distribution and relations of its flora.
The relations of the flora of New Zealand to that of Aus-
tralia have long formed an insoluble enigma for botanists. Sir
Joseph Hooker, in his most instructive and masterly essay on
the flora of Australia, says:—“ Under whatever aspect I -
regard the flora of Australia and of New Zealand, I find all
attempts to theorise on the possible causes of their community
of feature frustrated by anomalies in distribution, such as I

458 ISLAND LIFE. [PART II.

believe no two other similarly situated countries in the globe
present. Everywhere else I recognise a parallelism or harmony
in the main common features of contiguous floras, which
conveys the impression .of their generic affinity, at least, being
aifected by migration from centres of dispersion in one of them,
or in some adjacent country. In this case it is widely different.
Regarding the question from the Australian point of view, it is
impossible in the present state of science to reconcile the fact
of Acacia, Eucalyptus, Casuarina, Callitris, &c., being absent in
New Zealand, with any theory of trans-oceanic migration that
may be adopted to explain the presence of other Australian
plants in New Zealand ; and it is very difficult to conceive of a
time or of conditions that could explain these anomalies, except
by going back to epochs when the prevalent botanical as well
as geographical features of each were widely different from what
they arenow. On the other hand, if I regard the question from
the New Zealand point of view, I find such broad features of
resemblance, and so many connecting links that afford irre-
sistible evidence of a close botanical connection, that I cannot
abandon the conviction that these great differences will present
the least difficulties to whatever theory may explain the whole
case.” I will now state, as briefly as possible, what are the
facts above referred to as being of so anomalous a character,
and there is little difficulty in doing so, as we have them fully
set forth, with admirable clearness, in the essay above alluded
to, and in the same writer’s Jntroduction to the Flora of New
Zealand, only requiring some slight modifications, owing to
the later discoveries which are given in the Handbook of the
New Zealand Flora.

Confining ourselves always to flowerimg plants, we find that
the flora of New Zealand is a very poor one, considering the
extent of surface, and the favourable conditions of soil and
climate. It consists of 985 species, our own islands possessing
about 1,500; but a very large proportion of these are peculiar,
there being no less than 677 endemic species, and thirty-two
endemic genera.

Out of the 258 species not peculiar to New Zealand, no less
than 222 are Australian, but a considerable number of these

linea

ee a

CHAP, XXII] THE FLORA OF NEW ZEALAND. 459

are also Antarctic, South American, or European; so that there
are only about 100 species absolutely confined to New Zealand
and Australia, and, what is important as indicating a somewhat
recent immigration, only six of these belong to genera which
‘are peculiar to the two countries, and hardly any to the larger
and more important Australian genera. Many, too, are rare

species in both countries and are often alpines.

Far more important are the relations of the genera and
families of the two countries. All the Natural Orders of New
Zealand are found in Australia except three—Coriarie, a
widely-scattered group found in South Kurope, the Himalayas,
and the Andes; Escallonieze, a widely distributed group; and
Chloranthacese, found in Tropical Asia, Japan, Polynesia,
and South America. Out of a total of 303 New Zealand
genera, no less than 251 are Australian, and sixty of these are
almost peculiar to the two countries, only thirty-two however
being absolutely confined to them. In the three large orders—
Composite, Orchides, and Graminezx, the genera are almost
identical in the two countries, while the species—in the two
former especially—are mostly distinct.

Here then we have apparently a wonderful resemblance
between the New Zealand flora and that of Australia, indicated
by more than two-thirds of the non-peculiar species, and more
than nine-tenths of the non-peculiar genera (255) being
Australian. But now let us look at the other side of the
question.

There are in Australia seven great genera of plants, each
containing more than 100 species, all widely spread over the
country, and all highly characteristic Australian forms,—Acacia,
Eucalyptus, Melaleuea, Leucopogon, Stylidiwm, Grevillea, and
Hakea. ‘These are entirely absent from New Zealand, except
one species of Leucopogon, a genus which also has representatives
in the Malayan and Pacific Islands. Sixteen more Australian
genera have over fifty species each, and of these eight are totally
absent from New Zealand, five are represented by one or two
species, and only two are fairly represented; but these two—
Drosera and Helichrysum, are very widespread genera, and might
have reached New Zealand from other countries than Australia.

460 . ISLAND LIFE, [PART IL,

But this by no means exhausts the differences between New
Zealand and Australia. No less than seven important Australian
Natural Orders—Dilleniaceze, Buettneriacee, Polygalez, Tre-
mandrez, Casuarinex, Heemodoraceze, and Xyridez are entirely
wanting in New Zealand and several others which are excess-
ively abundant and highly characteristic of the former country
are very poorly represented in the latter. Thus, Leguminose
are extremely abundant in Australia, where there are over 1,000
species belonging to about 100 genera, many of them altogether
peculiar to the country; yet in New Zealand this great order
is most scantily represented, there being only five genera and
thirteen species; and only two of these genera, Swainsonia and
Clianthus, are Australian, and as the latter consists of but two
species 11 may as well have passed from New Zealand to
Australia as the other way, or more probably from some third
country to them both. Goodeniaceze with twenty genera and
230 species Australian, has but two species in New Zealand—
and one of these is a salt-marsh plant found also in Tasmania
and in Chile; and four other large Australian orders—Rhamnez
Myoporineze, Proteaceze and Santalacez, have very few repre-
sentatives in New Zealand.

We find, then, that the great fact we have to explain and
account for is, the undoubted affinity of the New Zealand flora
to that of Australia, but an affinity almost exclusively confined
to the least predominant and least peculiar portion of that flora,
leaving the most predominant, most characteristic, and most
widely distributed portion absolutely unrepresented. We must
however be careful not to exaggerate the amount of affinity with
Australia, apparently implied by the fact that nearly six-
sevenths of the New Zealand genera are also Australian, for,
as we have already stated, a very large number of these are
iZuropean, Antarctic, South American or Polynesian genera,
whose presence m1 the two contiguous areas only indicates a
common origin. About one-eighth, only, are absolutely confined
to Australia and New Zealand (thirty-two genera), and even of
these several are better represented in New Zealand than in
Australia, and may therefore have passed from the former to the
latter. No less than 174 of the New Zealand genera are

OHAP. XXII.] THE FLORA OF NEW ZEALAND. 461

temperate South American, many being also Antarctic or
European; while others again are especially tropical or Poly-
nesian; yet undoubtedly a larger proportion of the Natural
Orders and genera are common to Australia than to any other
country, so that we may say that the basis of the flora is
Australian with a large intermixture of northern and southern
temperate forms and others which have remote world-wide
affinities.
+ General features of the Australian Flora and tts probable
Origin.—Before proceeding to point out how the peculiarities
of the New Zealand flora may be best accounted for, it is
necessary to consider briefly what are the main peculiarities
of Australian vegetation, from which so important a part of
that of New Zealand has evidently been derived.

The actual Australian flora consists of two great divisions—
a temperate and a tropical, the temperate being again divisible
into an eastern and a western portion. Everything that is
characteristic of the Australian flora belongs to the temperate
division (though these often overspread the whole continent),
in which are found almost all the remarkable Australian types
of vegetation and the numerous genera peculiar to this part of
the world. Contrary to what occurs in most other countries, the
tropical is far less rich in species and genera than the temperate
region, and what is still more remarkable it contains com-
paratively few peculiar species, and very few peculiar genera.
Although the area of tropical Australia is about equal to that
of the temperate portions, and it has now been pretty well
explored botanically, it has less than half as many species.

1 Sir Joseph Hooker informs me that the number of tropical Australian
plants discovered within the last twenty years is very great, and that the
statement as above made may have to be modified. Looking, however, at
the enormous disproportion of the figures given in the “Introductory
Essay ” in 1859 (2,200 tropical to 5,800 temperate species) it seems hardly
possible that a great difference should not still exist, at all events as
regards species. Sir Joseph Hooker also doubts the generally greater
richness of tropical over temperate floras which I have taken as almost an
axiom. He says: “Taking similar areas to Australia in the Western
World, e.g., tropical Africa N. of 20° as against temperate Africa and
Europe up to 47°—I suspect that the latter would present more genera and

462 ISLAND LIFE. [PART II.

Nearly 500 of its species are identical with Indian or Malayan
plants, or are very close representatives of them; while there
are more than 200 Indian genera, confined for the most part to
the tropical portion of Australia. The remainder of the tro-
pical flora consists of certain species and genera of temperate
Australia which range over the whole continent, but these
form a very small portion of the peculiarly Australian genera.

These remarkable facts clearly point to one conclusion—that
the flora of tropical Australia is, comparatively, recent and
derivative. If we imagine the greater part of North Australia
to have been submerged beneath the ocean, from which
it rose in the middle or latter part of the Tertiary period,
offering an extensive area ready to be covered by such suitable
forms of vegetation as could first reach it, something like the
present condition of things would inevitably arise. From the
north widespread Indian and Malay plants would quickly
enter, while from the south the most dominant forms of tem-
perate Australia, and such as were best adapted to the tropical
climate and arid soil, would intermingle with them. LHven if
numerous islands had occupied the area of Northern Australia
for long periods anterior to the final elevation, very much the
same state of things would result.

The existence in North and North-east Australia of enormous
areas covered with Cretaceous and other Secondary deposits, as
well as extensive Tertiary formations, lends support to the view,
that during very long epochs temperate Australia was cut off
from all close connection with the tropical and northern lands
by a wide extent of sea; and this isolation is exactly what was
required, in order to bring about the wonderful amount of
specialisation and the high development manifested by the

species than the former.” This, however, appears to me to be hardly a
case in point, because Europe is a distinct continent from Africa and has
had a very different past history. A closer parallel may perhaps be found
in equal areas of Brazil and south temperate America, or of Mexico and
the Southern United States, in both of which cases I suppose there can be
little doubt that the tropical areas are far the richest. Temperate South
Africa is, no doubt, always quoted as richer than an equal area of tropical
Africa or perhaps than any part of the world of equal extent, but this is
admitted to be an exceptional case.

CHAP. XXII] THE FLORA OF NEW ZEALAND, 463

typical Australian flora. Before proceeding further, however,
let us examine this flora itself, so far as regards its component
parts and probable past history.

The Floras of South-eastern and South-western Australia.—
The peculiarities presented by the south-eastern and south-
western subdivisions of the flora of temperate Australia are
most interesting and suggestive, and are, perhaps, unparalleled
in any other part of the world. South-west Australia is far
less extensive than the south-eastern division—less varied in
soil and climate, with no lofty mountains, and much sandy
desert; yet, strange to say, it contains an equally rich flora and
a far greater proportion of peculiar species and genera of plants.
As Sir Joseph Hooker remarks :—“ What differences there are
in conditions would, judging from analogy with other countries,
favour the idea that South-eastern Australia, from its far
greater area, many large rivers, extensive tracts of mountainous
country and humid forests, would present much the most exten-
sive flora, of which only the drier types could extend into South-
western Australia. But such is not the case ; for though the far
greater area is much the best explored, presents more varied
conditions, and is tenanted by a larger number of Natural Orders
and genera, these contain fewer species by several hundreds.” !

The fewer genera of South-western Australia are due almost
wholly to the absence of the numerous European, Antarctic,
and South-American types found;im the south-eastern region,
while in purely Australian types it is far the richer, for while
it contains most of those found in the east it has a large
number altogether peculiar to it ; and Sir Joseph Hooker states
that “there are about 180 genera, out of 600 in South-western
Australia, that are either not found at all in South-eastern, or

1 Sir Joseph Hooker thinks that later discoveries in the Australian Alps
and other parts of East and South Australia may have greatly modified or
perhaps reversed the above estimate. But even if this should be the case
the small area of South-west Australia will still be, proportionally, far the
richer of the two. It is much to be desired that the enormous mass of
facts contained in Mr, Bentham’s Flora Australiensis should be tabulated
and compared by some competent botanist, so as to exhibit the various
relations of its wonderful vegetation in the same manner as was done by
Sir Joseph Hooker with the materials available twenty-one years ago.

464 ISLAND LIFE. [PART IT,

that are represented there by a very few species only, and these
180 genera include nearly 1,100 species.”

Geological explanation of the differences of these two Floras.—
These facts again clearly point to the conclusion, that South-
western Australia is the remnant of the more extensive and
more isolated portion of the continent in which the peculiar
Australian flora was principally developed. The existence there
of a very large area of granite—800 miles in length by nearly
500 in maximum width, indicates such an extension; for this
granitic mass was certainly once buried under piles of stratified
rock, since denuded, and then formed the nucleus of the old
Western Australian continent. If we take the 1000-fathom
line around the southern part of Australia to represent the
probable extension of this old land we shall see that 1t would
give a wide additional area south of the Great Australian
Bight, and form a continent which, even if the greater part of
tropical Australia were submerged, would be sufficient for the
development of a peculiar and abundant flora. We must also
remember that an elevation of 6000 feet, added to the vast
amount which has been taken away by denudation, would
change the whole country, including what are now the deserts
of the interior, into a mountainous and well-watered region.

But while this rich and peculiar flora was in process of forma-
tion, the eastern portion of the continent must either have been
widely separated from the western or had perhaps not yet risen
from the ocean. The whole of this part of the country consists
of Paleeozoic and Secondary formations with granite and meta-
morphic rocks, the Secondary deposits being largely developed
on both sides of the central range, extending the whole length
of the continent from Tasmania to Cape York, and constituting
the greater part of the plateau of the Blue Mountains and other
lofty ranges. During some portion of the Secondary period,
therefore, this side of Australia must have been almost wholly
submerged beneath the ocean; and if we suppose that during
_ this time the western part of the continent was at nearly its
maximum extent and elevation, we shall have a sufficient ex-
planation of the great difference between the flora of Western
and Eastern Australia, since the latter would only have been

CHAP. X¥I11.] THE FLORA OF NEW ZEALAND, 465

able to receive immigrants from the former, at a later period,
and in a more or less fragmentary manner.

If we examine the geological map of Australia (given in
Stanford’s Compendium of Geography and Travel, volume
“ Australasia’), we shall see good reason to conclude that the
eastern and the western divisions of the country first existed as
separate islands, and only became united at a comparatively
recent epoch. This is indicated by an enormous stretch of
Cretaceous and Tertiary formations extending from the Gulf of
Carpentaria completely across the continent to the mouth of the
Murray River. During the Cretaceous period, therefore, and
probably throughout a considerable portion of the Tertiary
epoch,’ there must have been a wide arm of the sea occupying
this area, dividing the great mass of land on the west—the true
seat and origin of the typical Australian flora—from a long but
narrow belt of land on the east, indicated by the continuous
mass of Secondary and Palzozoic formations already referred to
which extend uninterruptedly from Tasmania to Cape York.
Whether this formed one continuous land, or was broken up
into islands, cannot be positively determined ; but the fact
that no marine Tertiary beds occur in the whole of this area,
renders it probable that it was almost, if not quite, continuous,
and that it not improbably extended across to what is now
New Guinea. At this epoch, then (as shown in the accom-
panying map), Australia would consist of a very large and
fertile western island, almost or quite extra-tropical, and ex-
tending from the Silurian rocks of the Flinders range in South
Australia, to about 150 miles west of the present west coast,
and southward to about 350 miles south of the Great Australian
Bight. To the east of this, at a distance of from 250 to 400
miles, extended in a north and south direction a long but

1 From an examination of the fossil corals of the South-west of Victoria,
Professor P. M. Duncan concludes—‘‘ that, at the time of the formation of
these deposits the central area of Australia was occupied by sea, having
open water to the north, with reefs in the neighbourhood of Java.” The
age of these fossils is not known, but as almost all are extinct species, and
some are almost identical with European Pliocene and Miocene species
they are supposed to belong to a corresponding period. (Journal of Geol.
Soc., 1870.)

lelvael

466 ISLAND LIFE. | [PART IT.

comparatively narrow island, stretching from far south of
‘Tasmania to New Guinea; while the crystalline and Secondary
formations of central North Australia probably indicate the
existence of one or more large islands in that direction.

The eastern and the western islands—with which we are
now chiefly concerned—would then differ considerably in their

o> Ne a ee

TASMANIA

=1g0= SS ae ——7

MAP SHOWING THE PROBABLE CONDITION OF AUSTRALIA DURING THE CRETACEOUS PERIOD,

The white portions represent land; the shaded parts sea.
The existing land of Australia is shown in outline.

vegetation and animal life. The western and more ancient land
already possessed, in its main features, the peculiar Australian
flora, and also the ancestral forms of its strange marsupial
fauna, both of which it had probably received at some earlier
epoch by a temporary union with the Asiatic continent over
what isnow the Javasea. Eastern Australia, on the other hand,

CHAP. XxI1. | THE FLORA OF NEW ZEALAND. A67
possessed only the rudiments of its existing mixed flora, derived
from three distinct sources. Some important fragmeuts of the
typical Australian vegetation had reached it across the marine
strait, and had spread widely owing to the soil, climate and
general conditions being exactly suited to it ; from the north and
north-east a tropical vegetation of Polynesian type had occupied
suitable areas in the north; while the extension southward of
the Tasmanian peninsula, accompanied, probably, as now, with
lofty mountains, favoured the immigration of south-temperate
forms from whatever Antarctic lands or islands then existed.
The marsupial fauna had not yet reached this eastern land,
which was, however, occupied in the north by some ancestral
struthious birds, which had entered it by way of New Guinea
through some very ancient continental extension, and of which
the emu, the cassowaries, the extinct Dromornis of Queensland,
and the moas and kiwis of New Zealand, are the modified
descendants.

The Origin of the Australian element in the New Zealand Flora.
—We have now brought down the history of Australia, as
deduced from its geological structure and the strongly marked
features of its flora, to the period when New Zealand was first
brought into close connection with it, by means of a great north-
western extension of that country, which, as already explained
in our last chapter, is so clearly indicated by the form of the
sea bottom (See Map, p. 443). The condition of New Zealand
previous to this event is very obscure. That it had long existed
as a more or less extensive land is indicated by its ancient
sedimentary rocks; while the very small areas occupied by
Jurassic and Cretaceous deposits, imply that much of the present
land was then also above the sea-level. The country had pro-
bably at that time a scanty vegetation of mixed Antarctic and
Polynesian origin ;' but now, for the first time, it would be open

1 In Dr. Hector’s address as President of the Wellington Philosophical
Society, in 1872, he refers to the fluviatile deposits of early Tertiary or
Cretaceous age as containing valuable deposits of coal, and adds:—“ In
the associated sandstones and shales the flora of the period has been in
many cases well preserved, and shows that at a period anterior to the
deposit of the marine stratum the New Zealand area was clothed with a

Hin 2

468 . ISLAND LIFE. [PART II,

to the free immigration of such Australian types as were suitable
to its climate, and which had already reached the tropical and sub-
tropical portions of the eastern Australian island. It is here that
we obtain the clue to those strange anomalies and contradictions
presented by the New Zealand flora in its relation to Australia,
which have been so clearly set forth by Sir Joseph Hooker, and
which have so puzzled botanists to account for. But these appa-
rent anomalies cease to present any difficulty when we see that the
Australian plantsin New Zealand were acquired, not directly, but,
as it were, at second hand, by union with an island which itself
had as yet only received a portion of the flora. And then, further
difficulties were placed in the way of New Zealand receiving
such an adequate representation of that portion of the flora
which had reached East Australia as its climate and position
entitled it to, by the fact of the union being, not with the tem-
perate, but with the tropical and sub-tropical portions of that
island, so that only those groups could be acquired which were
less exclusively temperate, and had already established them-
selves in the warmer portion of their new home.

It is therefore no matter of surprise, but exactly what we

should expect, that the great mass of pre-emimently temperate
Australian genera should be absent from New Zealand, including
the whole of such important families as Dilleniacesee Treman-

drez, Buettneriace, Polygaleze, Casuarinese, and Hamodoracez ;

while others, such as Rutaces, Stackhousiez, Rhamnez, Myr-
tacex, Proteacez, and Santalacez, are represented by only a few
species. Thus, too, we can explain the absence of all the pecu-
liar Australian Leguminose ; for these were still mainly confined

mixed vegetation of dicotyledonous leaves and ferns, that in general char-
acter represent those which now constitute the flora of the country. It
would appear from the recent surveys of Dr. Haast that the large saurian
reptiles in the Amuri and Waipara beds, the collections of which have
been added to largely during the past year by the exertions of Mr. Henry
Travers, lived during the formation of these coal-seams, and coeval with
them was a species of the Kauri tree, the leaves of which have been found
imbedded with the reptilian bones.”” He goes on to suggest that “ even
at this remote period, New Zealand formed part of an area that possessed
an insular flora, the peculiar characters of which have been preserved to
the present time,” (Trans, N. Z. Inst., V. p. 423.)

|
a

CHAP. XXII. | THE FLORA OF NEW ZEALAND. 469
to the great western island, along with the peculiar Acacias and
Eucalypti, which at a later period spread over the whole con-
tinent. It is equally accordant with the view we are maintain-
ing, that among the groups which Sir Joseph Hooker enumerates
as “keeping up the features of extra tropical Australia in its
tropical quarter,” several should have reached New Zealand,
such as Drosera, some Pittosporeze and Myoporines, with a few
Proteacez, Loganiacez, and Restiaceee ; for most of these are not
only found in tropical Australia, but also in the Malayan and
Pacific islands.

Tropical character of the New Zealand Flora. explained.—In
this origin of the New Zealand fauna by a north-western route
from North-eastern Australia, we find also an explanation of the
remarkable number of tropical groups of plants found there:
for though, as Sir Joseph Hooker has shown, a moist and uni-
form climate favours the extension of tropical forms in the
temperate zone, yet some means must be afforded them for
reaching a temperate island. On carefully going through the
Handbook, and comparing its indications with those of Bentham’s
Flora Australiensis, I find that there are in New Zealand thirty-
eight thoroughly tropical genera, thirty-three of which are found
in Australia—mostly in the tropical portion of it, though a few
are temperate, and these may have reached it through New
Zealand.' To these we must add thirty-two more genera, which,

1 The following are the tropical genera common to New Zealand and
Australia :—

1, Melicope. Queensland, Pacific Islands,

2. Eugenia. Tropical Australia, Asia, and America.

3. Passiflora. Queensland, Tropics of Old World and America.
4, Myrsine. Tropical and Temperate Australia, Tropical and Sub-tropical

regions,

5. Sapota. Australia, Norfolk Islands, Tropics.

6. Cyathodes. Australia and Pacific Islands.

7. Parsonsia. Tropical Australia and Asia,

8. Geniostoma. Queensland, Polynesia, Asia.

9. Mitrasacme. ‘Tropical and Temperate Australia, India,
10. Ipomea. Tropical Australia, Tropics.
11. Mazus. Temperate Australia, India, China.

12. Vitex. Tropical Australia, Tropical and Sub-tropical.

13. Pisonia. Tropical Australia, Tropical and Sub-tropical.

0 ISLAND LIFE. [PART 11,

though chiefly developed in temperate Australia, extend into
the tropical or sub-tropical portions of it, and may well have
reached New Zealand by the same route.

On the other hand we find but few New Zealand genera
rtainly derived from Australia which are especially temperate,

and it may be as well to give a list of such as do occur with a
few remarks. They are sixteen in number, as follows :—

on OD

. Pennantia (1 sp.). This genus has a species in Norfolk Island, indi-
cating perhaps its former extension to the north-west.

. Pomaderris (3 sp.). Two species are common to Temperate Australia

and New Zealand, indicating recent trans-oceanic migration.

. Quintinia (2 sp.). This genus has winged seeds facilitating migration,

Olearia (20 sp.). Seeds with pappus.

. Craspedia (2 sp.). Seeds with pappus. Alpine ; identical with Australian

species, and therefore of comparatively recent introduction,

. Celmisia (25 sp.), Seeds with pappus. Only three Australian species,

two of which are identical with New Zealand forms, probably
therefore derived from New Zealand.

Ozothamnus (5 sp.). Seeds with pappus.

Hpacris (4 sp.). Minute seeds. Some species are sub-tropical, and
they are all found in the northern (warmer) is'and of New Zealand.

. Archeria (2 sp.). Minute seeds, Tasmania and New Zealand only.

. Alternanthera. Tropical Australia, India, and 8. America,

. Lretranthera. Tropical Australia, Tropics.

. Santalum. Tropical and Sub-tropical Australia, Pacific, Ma'ay Islands.
. Carumbium. Tropical and Sub-tropical Australia, Pacific Islands.

. Elatostenma. Sub-tropical Australia, Asia, Pacific Lalands.

. Peperomia. Tropical and Sub-tropical Australia, Tropics.

. Piper. Tropical and Sub-tropical Australia, Tropics.

. Dacrydium, Tasmania, Malay, and Pacific Islands.

. Dammara. Tropical Australia, Malay, and Pacific Islands.

. Dendrobium. Tropical Australia, Eastern Tropics.

. Bolbophyllum. Tropical and Sub-tropical Australia, Tropics.

. Sarcochilus. Tropical and Sub-tropical Australia, Fiji, and Malay

Islands.

. Freycinetia. Tropical Australia, Tropical Asia.

. Cordyline. Tropical Australia, Pacific Islands.

. Dianella. Australia, India, Madagascar, Pacific Islands,
. Cyperus. Australia, Tropical regions mainly.

. Fimbristylis. Tropical Australia, Tropical regions,

. Paspalum. Tropical and Sub-tropical grasses,

. Isachne. Tropical and Sub-tropical grasses.

. Sporobolus, Tropical and Sub-tropical grasses,

Oe a ee

rary XX11. | THE FLORA OF NEW ZEALAND. ATL

10. Logania (3 sp.). Small seeds. Alpine plants.

11. Hedycarya (1 sp.).

12. Chilogtottis (1 sp.). Minute seeds. In Auckland Islands; alpine in

_ Australia.

13. Prasophyllum (1 sp.). Minute seeds. Identical with Australian
species.

14, Orthoceras (1 sp.) Minute seeds. Close to an Australian species.

15, Alepyrum (1 sp.). Alpine, moss-like. An Antarctic type.

16. Dichelachne (3 sp.). Identical with Australian species. An awned
grass,

We thus see that there are special features in most of these
plants that would facilitate transmission across the sea between
temperate Australia and New Zealand, or to both from some
Antarctic island ; and the fact that in several of them the species
are absolutely identical shows that such transmission has
occurred in geologically recent times.

Species common to New Zealand and Australia mostly Tem-
perate forms.—Let us now take the species which are com-
mon to New Zealand and Australia, but found nowhere else,
and which must therefore have passed from one country to
the other at a more recent period than the mass of genera with
which we have hitherto been dealing. These are ninety-six in
number, and they present a striking contrast to the similarly
1estricted genera in being wholly temperate in character, the
entire list presenting only a single species which is confined to
sub-tropical East Australia—a grass (Apera arundinacea) only
found in a few localities on the New Zealand coast.

Now it is clear that the larger portion, if not the whole, of
these plants must have reached New Zealand from Australia
(or in a few cases Australia from New Zealand), by transmission
across the sea, because we know there has been no land con-
nection during the Tertiary period, as proved by the absence of
all the Australian mammalia, and almost all the most character-
istic Australian birds, insects, and plants. The form of the sea-
bed shows that the distance could not have been less than 600
miles, even during the greatest extension of Southern New
Zealand and Tasmania; and we have no reason to suppose it to
have been less, because in other cases an equally abundant fiora
of identical species has reached islands at astill greater distance

472 ISLAND LIFE. [PART IL.

—notably in the case of the Azores and Bermuda, The cha-
racter of the plants is also just what we should expect; for
about two-thirds of them belong to genera of world-wide range
in the temperate zones, such as Ranunculus, Drosera, Hpilobium,
Gnaphalium, Senecio, Convolvulus, Atriplex, Luzula, and many
sedges and grasses, whose exceptionally wide distribution shows
that they possess exceptional powers of dispersal and vigour of
constitution, enabling them not only to reach distant countries, but
also to establish themselves there. Another set of plants belong
to especially Antarctic or south temperate groups, such as Colo-
banthus, Acena, Gaultheria, Pernettya, and Muhlenbeckia, and
these may in some cases have reached both Australia and New
Zealand from some now submerged Antarctic island. Again,
about one-fourth of the whole are alpine plants, and these
possess two advantages as colonisers. Their lofty stations
place them in the best position to have their seeds carried away
by winds; and they would in this case reach a country which,
having derived the earlier portion of its flora from the side of
the tropics, would be likely to have its higher mountains and
favourable alpine stations to a great extent unoccupied, or
occupied by plants unable to compete with specially adapted
alpine groups.

Fully one-third of the exclusively Australo-New Zealand species
belong to the two great orders of the sedges and the grasses ;
and there can be no doubt that these have great facilities for dis-
persion in a variety of ways. Their seeds, often enveloped in
chaffy glumes, would be carried long distances by storms of
wind, and even if finally dropped into the sea would have so
much less distance to reach the land by means of surface cur-
rents; and Mr. Darwin’s experiments show that even cultivated
oats germinated after 100 days’ immersion in sea-water. Others
have hispid awns by which they would become attached to the
feathers of birds, and there is no doubt this is an effective mode
of dispersal. But a still more important point is, probably, that
these plants are generally, if not always, wind-fertilised, and
are thus independent of any peculiar insects, which might be
wanting in the new country. _

Why casily-dispersed plants have often restricted ranges.—

—"

CHAP, XXII] THE FLORA OF NEW ZEALAND. 473

This last consideration throws light on a very curious point,
which has been noted as a difficulty by Sir Joseph Hooker, that
plants which have most clear and decided powers of dispersal
by wind or other means, have noé generally the widest specific
range; and he instances the small number of Composite com-
mon to New Zealand and Australia. But in all these cases it
will, 1 think, be found that although the species have not a wide
range the genera often have. In New Zealand, for instance,
the Composite are very abundant, there being no less than 148
species, almost all belonging to Australian genera, yet only nine
species, or less than one-sixteenth of the whole, are identical in
the two countries. The explanation of this is not difficult.
Owing to their great powers of dispersal, the Australan Com-
posits reached New Zealand at a very remote epoch, and such
as were adapted to the climate and the means of fertilisation
established themselves ; but being highly specialised plants with
great flexibility of organisation, they soon became modified in
accordance with the new conditions, producing many special
forms in different localities; and these, spreading widely, soon
took possession of all suitable stations. Henceforth immigrants
from Australia had to compete with these indigenous and well-
established plants, and only in a few cases were able to obtain
a footing ; whence it arises that we have many Australian types,
but few Australian species, in New Zealand, and both phenomena
are directly traceable to the combination of great powers of dis-
persal with a high degree of specialisation. Exactly the same
thing occurs with the still more highly specialised Orchidez.
These are not proportionally so numerous in New Zealand
(thirty-eight species), and this is no doubt due to the fact that
so many of them require insect-fertilisation often by a particular
family or genus (whereas almost any insect will fertilise Com-
positee), and insects of all orders are remarkably scarce in New
Zealand. This would at once prevent the establishment of
many of the orchids which may have reached the islands, while
those which did find suitable fertilisers and other favourable
conditions would soon become modified into new species. It is
thus quite intelligible why only three species of orchids are
identical in Australia and New Zealand, although their minute

AT4 ISLAND LIFE. [PART. IT,

and abundant seeds must be dispersed by the wind almost as
readily as the spores of ferns.

Another specialised group—the Scrophularinez, abounds in
New Zealand, where there are sixty-two species; but though
almost all the genera are Australian only three species are so.
Here, too, the seeds are usually very small, and the powers of
dispersal great, as shown by several European genera— Vero-
nica, Huphrasia, and Limosella, being found in the southern
hemisphere.

Looking at the whole series of these Australo-New Zealand
plants, we find the most highly specialised groups—Composite,
Scrophularinee, Orchideze— with a small proportion of identical
species (one-thirteenth to one-twentieth), the less highly special-
ised—Ranunculacee, Onagrarize and Ericee—with a higher
proportion (one-ninth to one-sixth), and the least specialised—
Juncee, Cyperaceee and Gramineze—with the high proportion in
each case of one-fourth. These nine are the most important New
Zealand orders which contain species common to that country
and Australia and confined to them; and the marked corre-
spondence they show between high specialisation and want of
specific identity, while the generic identity is in all cases approx-
imately equal, points to the conclusion that the means of
diffusion are, in almost all plants ample, when long periods of
time are concerned, and that diversitiesin this respect are not
so important in determining the peculiar character of a derived
flora, as adaptability to varied conditions, great powers of multi-
plication, and inherent vigour of constitution. This point will
have to be more fully discussed in treating of the origin of the
Antarctic and north temperate members of the New Zealand
flora.

Summary and Conclusion on the New Zealand Flora.—Confining
ourselves strictly to the direct relations between the plants of
New Zealand and of Australia, as I have done in the preceding
discussion, I think I may claim to have shown, that the union
between the two countries in the latter part of the Secondary
epoch at a time when Eastern Australia was widely separated
from Western Australia (as shown by its geological formation
and by the contour of the sea-bottom) does sufficiently account

- CHAP, XX11.] THE FLORA OF NEW ZEALAND. 475

for all the main features of the New Zealand flora. It shows
why the basis of the flora is fundamentally Australian both as
regards orders and genera, for it was due to a direct land con-
nection between the two countries. It shows also why the great
mass of typical Australian forms are unrepresented, for the
Australian flora is typically western and temperate, and New
Zealand received its immigrants from the eastern island which
had itself received only a fragment of this flora, and from the
tropical end of this island, and thus could only receive such
forms as were not exclusively temperate in character. It shows,
further, why New Zealand contains such a very large proportion
of tropical forms, for we see that it derived the main portion of
its flora directly from the tropics. Again, this hypothesis shows
us why, though the specially Australian genera in New Zealand
are largely tropical or sub-tropical, the specially Australian
species are wholly temperate or alpine; for these are com-
paratively recent arrivals, they must have migrated across the
sea in the temperate zone, and these temperate and alpine
forms are exactly such as would be best able to establish them-
selves in a country already stocked mainly by tropical forms
and their modified descendants. This hypothesis further fulfils
the conditions implied in Sir Joseph Hooker’s anticipation that
—“these great differences (of the floras) will present the least
difficulties to whatever theory may explain the whole case,’—
for it shows that these differences are directly due to the history
and development of the Australian flora itself, while the resem-
blances depend upon the most certain cause of all such broad
resemblances—actual land connection.

One objection will undoubtedly be made to the above theory,
—that it does not explain why some species of the prominent
Australian genera Acacia, Hucalyptus, Melaleuca, Grevillea, &c.,
have not reached New Zealand in recent times along with
the other temperate forms that have established themselves,
But it is doubtful whether any detailed explanation of such
a negative fact is possible, while general explanations sufficient
to cover it are not wanting. Nothing is more certain than that
numerous plants never run wild and establish themselves in
countries where they nevertheless grow freely if cultivated;

476 ISLAND LIFE, [PART IT.

and the explanation of this fact given by Mr. Darwin—that
they are prevented doing so by the competition of better
adapted forms—is held to be sufficient. In this particular case,
however, we have some very remarkable evidence of the fact
of their non-adaptation. The intercourse between New Zealand
and Europe has been the means of introducing a host of common
European plants,—more than 150 in number, as enumerated at
the end of the second volume of the Handbook ; yet, although
the intercourse with Australia has probably been greater, only
two or three Australian plants have similarly established them-
selves. More remarkable still, Sir Joseph Hooker states: “I
am informed that the late Mr. Bidwell habitually scattered
Australian seeds during his extensive travels in New Zealand.”
We may be pretty sure that seeds of such excessively common and
characteristic groups as Acacia and Hucalyptus would be among
those so scattered, yet we have no record of any plants of these
or other peculiar Australian genera ever having been found wild,
still less of their having spread and taken possession of the soil
in the way that many European plants have done. We are,
then, entitled to conclude that the plants above referred to have
not established themselves in New Zealand (although their seeds
may have reached it) because they could not successfully com-
pete with the indigenous flora which was already well established
and better adapted to the conditions of climate and of the
organic environment. This explanation is so perfectly in
accordance with a large body of well-known facts, including
that which is known to every one—bow few of our oldest and
hardiest garden plants ever run wild—that the objection above
stated will, I feel convinced, have no real weight with any
naturalists who have paid attention to this class of questions.

CHAPTER XXIII.

ON THE ARCTIC ELEMENT IN SOUTH TEMPERATE FLORAS,

European species and genera of plants in the southern hemisphere—
Aggressive power of the Scandinavian flora—Means by which plants
have migrated from north to south—Newly moved soil as affording
temporary stations to migrating plants—Elevation and depression of
the snow-line as aiding the migration of plants—Changes of climate
favourable to migration—The migration from north to south has been
long going on—Geological changes as aiding migration—Proofs of
migration by way of the Andes—Proofs of migration by way of the
Himalayas and Southern Asia—Proofs of migration by way of tlie
African highlands—Supposed connection of South Africa and Australia
—The endemic genera of plants in New Zealand—The absence of
southern types from the northern hemisphere—Concluding remarks on
the New Zealand and south temperate floras.

WE have now to deal with another portion of the New
Zealand flora which presents perhaps equal difficulties—that
which appears to have been derived from remote parts of
the north and south temperate zones; and this will lead us
to inquire into the origin of the northern or Arctic element
in all the south temperate floras.

More than one-third of the entire number of New Zealand
genera (115) are found also in Europe, and even fifty-eight
species are identical in these remote parts of the world. Tem-
perate South America has seventy-four genera in common with
New Zealand, and there are even eleven species identical in the
two countries, as well as thirty-two which are close allies or
representative species. A considerable number of these northern

478 ISLAND LIFE. [PART 11.

or Antarctic plants and many more which are representative
species, are found also in Tasmania and in the mountains of
temperate Australia; and Sir Joseph Hooker gives a list of
thirty-eight species very characteristic of EHurope and Northern
Asia, but almost or quite unknown in the warmer regions, which
yet reappear in temperate Australia. Other genera seem
altogether Antarctic—that is, confined to the extreme southern
lands and islands; and these often have representative species
in Southern America, Tasmania, and New Zealand, while others
occur only in one or two of these areas. Many north temperate
genera also occur in the mountains of South Africa, On the
other hand, few if any of the peculiar Australian or Antarctic
types have spread northwards, except some of the former which
have reached the mountains of Borneo, and a few of the latter
which spread along the Andes to Mexico.

On these remarkable facts, of which I have given but the
barest outline, Sir Joseph Hooker makes the following suggestive
observations :—

‘When I take a comprehensive view of the vegetation of the
Old World, I am struck with the appearance it presents of there
being a continuous current of vegetation Gf I may so fancifully
express myself) from Scandinavia to Tasmania ; along, in short,
the whole extent of that arc of the terrestrial sphere which
presents the greatest continuity of land. In the first place
Scandinavian genera, and even species, reappear everywhere from
Lapland and Iceland to the tops of the Tasmanian Alps, in
rapidly diminishing numbers it is true, but in vigorous develop-
ment throughout, They abound on the Alps and Pyrenees, pass
on to the Caucasus and Himalaya, thence they extend along the
Khasia Mountains, and those of the peninsulas of India to —
those of Ceylon and the Malayan Archipelago (Java and
Borneo), and after a hiatus of 30° they appear on the Alps
of New South Wales, Victoria, and Tasmania, and beyond
these again on those of New Zealand and the Antarctic
Islands, many of the species remaining unchanged through-
out! It matters not what the vegetation of the bases and
flanks of these mountains may be; the northern species may
be associated with alpine forms of Germanic, Siberian, Oricntal,

CHAP. XXIII.] ARCTIC PLANTS IN NEW ZEALAND. 479

Chinese, American, Malayan, and finally Australian and Ant-
arctic types; but whereas these are all, more or less, local
assemblages, the Scandinavian asserts his prerogative of
ubiquity from Britain to beyond its antipodes.”’ 4

It is impossible to place the main facts more forcibly before
the reader than in the above striking passage. It shows clearly
that this portion of the New Zealand flora is due to wide-spread
causes which have acted with even greater effect in other south
temperate lands, and that in order to explain its origin we must
grapple with the entire problem of the transfer of the north
temperate flora to the southern hemisphere. Taking, therefore,
the facts as given by Sir Joseph Hooker in the works already
referred to, I shall discuss the whole question broadly, and shall
endeavour to point out the general laws and subordinate causes
that, in my opinion, have been at work in bringing about the
anomalous phenomena of distribution he has done so much
to make known and to elucidate.

Aggressive Power of the Scandinavian Flora.—The first impor-
tant fact bearing upon this question is the wonderful aggressive
and colonising power of the Scandinavian flora, as shown by the
way in which it establishes itself in any temperate country to
which it may gain access. About 150 species have thus estab-
lished themselves in New Zealand, often taking possession of large
tracts of country ; about the same number are found in Australia,
and nearly as many in the Atlantic states of America, where
they form the commonest weeds. Whether or not we accept
Mr. Darwin’s explanation of this power as due to development
in the most extensive land area of the globe where competition
has been most severe and long-continued, the fact of the exist-
ence of this power remains, and we can see how important an
agent it must be in the formation of the floras of any lands to
which these aggressive plants have been able to gain access.

But not only are these plants pre-eminently capable of holding
their own in any temperate country in the world, but they also
have exceptional powers of migration and dispersal over seas and
oceans. This is especially well shown by the case of the Azores,
where no less than 400 out of a total of 478 flowering plants are

1 Introductory Essay On the Flora of Australia, p.105.

480 ISLAND LIFE. [PART II.
identical with European species. These islands are more than
800 miles from Europe, and, as we have already seen in Chapter
XII., there is no reason for supposing that they have ever been
more nearly connected with it than they are now, since an exten-
sion of the European coast to the 1,000-fathom line would very
little reduce the distance. Now it is a most interesting and
suggestive fact that more than half the Huropean genera which
occur in the Australian flora occur also in the Azores, and in
several cases even tiie species are identical in both. The im-
portance of such a case as this cannot be exaggerated, because
it affords a demonstration of the power of the very plants in
question to pass over wide areas of sea, some no doubt wholly
through the air, carried by storms in the same way as the
European birds and insects which annually reach the Azores,
others by floating on the waters, or by a combination of the two
methods ; while some may have been carried by aquatic birds, to
whose feathers many seeds have the power of attaching them-
selves. We have in such facts as these a complete disproof of
the necessity for those great changes of sea and land which are
continually appealed to by those who think land-connection the
only efficient means of accounting for the migration of animals
or plants; but at the same time we do not neglect to make the
fullest use of such moderate changes as all the evidence at our
command leads us to believe have actually occurred, and
especially of the former existence of intermediate islands, so
often indicated by shoals in the midst of the deepest oceans.
Means by which Plants have migrated from North to South.—
But if plants can thus pass in considerable numbers and variety
over wide seas and oceans, 1t must be yet more easy for them to
traverse continuous areas of land, wherever mountain-chains
offer suitable stations at moderate intervals on which they might
temporarily establish themselves. The facilities afforded for
the transmission of plants by mountains has hardly received
sufficient attention. The numerous land-slips, the fresh sur-
faces of broken rock and precipice, the débris of torrents, and
the moraines deposited by glaciers, afford numerous unoccupied

1 Hooker, On the Flora of Australia, p. 95.—H. C. Watson, in Godman’s
Azores, pp. 278-286.

CHAP. XXIII.] ARCTIC PLANTS IN NEW ZEALAND. 481

stations on which wind-borne seeds have a good chance of
germinating. It is a well-known fact that fresh surfaces of soil
or rock, such as are presented by railway cuttings and embank-
ments, often produce plants strange to the locality, which survive
for a few years, and then disappear as the normal vegetation
gains strength and permanence. Butsuch a surface will, in the

1 As this is a point of great interest in its bearing on the dispersal]
of plants by means of mountain ranges, I have endeavoured to obtain
a few illustrative facts :—

1. Mr. William Mitten, of Hurstpierpoint, Sussex, informs me that when
the London and Brighton railway was in progress in his neighbourhood,
Melilotus vulgaris made its appearance on the banks, remained for several
years, and then altogether disappeared. Another case is that of Diplotazis
muralis, which formerly occurred only near the sea-coast of Sussex, and at
Lewes; but since the railway was made has spread along it, and still
maintains itself abundantly on the railway banks though rarely found
anywhere else.

2. A correspondent in Tasmania informs me that whenever the virgin
forest is cleared in that island there invariably comes up a thick crop of °
a plant locally known as fire-weed—a species of Senecio, probably S, Aus-
tralis. \t never grows except where the fire has gone over the ground,
and is unknown except in such places. My correspondent adds :—“ This
autumn I went back about thirty-five miles through a dense forest, along
a track marked by some prospectors the year before, and in one spot
where they had camped, and the fire had burnt the fallen logs, &c., there
was a fine crop of ‘fire-weed.’ All around for many miles was a forest of
the largest trees and dense scrub.” Here we have a case in which burnt
soil and ashes favour the germination of a particular plant, whose seeds
are easily carried by the wind, and it is not difficult to see how this
peculiarity might favour the dispersal of the species for enormous distances,
by enabling it temporarily to grow and produce seeds on burnt spots.

3. In answer to an inquiry on this subject, Mr. H. C. Watson has been
kind enough to send me a detailed account of the progress of vegetation
on the railway banks and cuttings about Thames Ditton. This account is
written from memory, but as Mr. Watson states that he took a great
interest in watching the process year by year, there can be no reason to
doubt the accuracy of his memory. I give a few extracts which bear
especially on the subject we are discussing.

‘One rather remarkable biennial plant appeared early (the second year,
as I recollect) and renewed itself either two or three years, namely, [satis
tinctoria—a species usually supposed to be one of our introduced, but
pretty well naturalised, plants. The nearest stations then or since known
to me for this Jsatis are on chalk about Guildford, twenty miles distant.
There were two or three plants of it at first, never more than half a dozen.
Once since I saw a plant of Jsatis on the railway bank near Vauxhall.

1 et

432 ISLAND LIFE. - [Parr II,

meantime have acted as a fresh centre of dispersal; and thus
a plant might pass on step by step, by means of stations
temporarily occupied, till it reached a district where, the

“Close by Ditton Station three species appeared which may be called
interlopers. The biennial Barbarea precox, one of these, is the least
remarkable, because it might have come as seed in the earth from some
garden, or possibly inthe Thames gravel (used as ballast), At first it
increased to several plants, then became less numerous, and will soon, in
all probability, become extinct, crowded out by other plants. The biennial
Petroselinum segetum was at first one very luxuriant plant on the slope of
the embankment. It increased by seed into a dozen or a score, and is now
nearly if not quite extinct. The third species is Linaria purpurea, not
strictly a British plant, but one established in some places on old walls.
A single root of it appeared on the chalk facing of the embankment by
Ditton Station. It has remained there several years and grown into a
vigorous specimen. ‘Two or three smaller examples are now seen by it,
doubtless sprung from some of the hundreds or thousands of seeds shed
by the original one plant. Thespecies is not included in Salmon and
Brewer's Flora of Surrey.

“The main line of the railway has introduced into Ditton parish the
perennial Arabis hirsuta, likely to become a permanent inhabitant. The
species is found on the chalk and greensand miles away from Thames

itton ; but neither in this parish nor in any adjacent parish, so far as

known to myself or to the authors of the flora of the county, does it
oceur. Some years after the railway was made a single root of this
Arabis was observed in the brickwork of an arch by which the railway is
earried over a public road. A vear or two afterwards there were three or
four plants. In some later year I laid some of the ripened seed-pods
between the bricks in places where the mortar had partly crumbled out.
Now there are several scores of specimens in the brickwork of the arch.
It is presumable that the first seed may have been brought from Guildford.
But how eould it get on to the perpendicular face of the brickwork ?

‘“‘The Bee Orchis (Ophrys apifera), plentiful on some of the chalk lands
in Surrey, is not a species of Thames Ditton, or (as I presume) of any
adjacent parish. Thus, I was greatly surprised some years back to see
about a hundred examples of it in flower in one clayey field either on the
outskirts of Thames Ditton or just within the limits of the adjoining
parish of Cobham. I had crossed this same field in a former year without
observing the Ophrys there. And on finding it in the one field I closely
searched the surrounding fields and copses, without finding it anywhere
else. Gradually the plants became fewer and fewer in that one field,
and some six or eight years after its first discovery there the species had
quite disappeared again. I guessed it had been introduced with chalk,
but could obtain no evidence to show this,”

4, Mr. A. Bennett, of Croydon, has kindly furnished me with some
information on the temporary vegetation of the banks and cuttings on the

— ™ ssi Sets

cuaP. xxu.J] ARCTIC PLANTS IN NEW ZEALAND. 483

general conditions being more favourable, it was able to
establish itself as a permanent member of the flora. Such,
generally speaking, was probably the process by which the
Scandinavian flora has made its way to the southern hemi-
sphere; but it could hardly have done so to any important

railway from Yarmouth to Caistor in Norfolk, where it passes over exten-
sive sandy Denes with a sparse vegetation. The first year after the
railway was made the banks produced abundance of (Hnothera odorata
and Delphinium Ajacis (the latter only known thirty miles off in corn-
fields in Cambridgeshire), with Atriplex patula and A, cdeltoidea. Gradually
the native sand plants—Carices, Grasses, Galzum verum, &c., established
themselves, and year by year covered more ground till the new introduc-
tions almost completely disappeared. The same phenomenon was observed
in Cambridgeshire between Chesterton and Newmarket, where, the soil
being different, Stellaria media and other annuals appeared in large patches ;
but these soon gave way to apermanent vegetation of grasses, composites,
&c., so that in the third year no Stellaria was to be seen.

5. Mr. T. Kirk (writing in 1878) states that—“in Auckland, where a
dense sward of grass is soon formed, single specimens of the European Milk
Thistle (Carduus marianus) have been known for the past fifteen years ;
but although they seeded freely, the seeds had no opportunity of germinat-
ing, so that the thistle did not spread. A remarkable exception to this
rule occurred during the formation of the Onehunga railway, where a few
seeds fell on disturbed soil, grew up and flowered. The railway works
being suspended, the plant increased rapidly, and spread wherever it cou'd
tind disturbed soil.”

Again:—‘ The fiddle-dock (Rumex pulcher) occurs in great abundance
on the formation of new streets, &c., but soon becomes comparatively rare.
It seems probable ihat it was one of the earliest plants naturalised here,
but that it partially died out, its buried seeds retaining their vitality.” .

Medicago sativa and Apium graveolens, are also noted as escapes from
cultivation which maintain themselves for a time but soon die out.!

The preceding examples of the temporary establishment of plants on
newly exposed soil, often at considerable distances from the localities they
usually inhabit, might, no doubt, by further inquiry be greatly multiplied ;
but, unfortunately, the phenomenon has received little attention, and is
not even referred to in the elaborate work of De Candolle (Géographie
Botanique Raisonnée) in which almost every other aspect of the dispersion
and distribution of plants is fully discussed. Enough has been advanced,
however, to show that it is of constant ovcurrence, and from the point of
view here advocated it becomes of great importance in explaining the
almost world-wide distribution of many common plants of the north
temperate zone.

1 Transactions of the New Zealand Institute, Vol, X. p. 367.
1 ae”

484 ISLAND LIFE, [PART IT.

extent without the aid of those powerful causes explained
in our eighth chapter—causes which acted as a constantly
recurrent motive-power to produce that “continuous cur-
rent of vegetation” from north to south across the whole
width of the tropics referred to by Sir Joseph Hooker. Those
causes were, the repeated changes of climate which, during all
geological time, appear to have occurred in both hemispheres,
culminating at rare intervals in glacial epochs, and which have
been shown to depend upon changes of excentricity of the
earth’s orbit and the occurrence of summer or winter in
aphelion, in conjunction with the slower and more irregular
changes of geographical conditions; these combined causes
acting chiefly through the agency of heat-bearmg oceanic
currents, and of snow- and ice-collecting highlands. Let us
now briefly consider how such changes would act in favouring
the dispersal of plants.

Elevation and depression of the Snow Line as aiding the
migration of Plants—We have endeavoured to show (in an
earlier portion of this volume) that wherever geographical or
physical conditions were such as to produce any considerable
amount of perpetual snow, this would be increased whenever
a high degree of excentricity concurred with winter in aphelion,
and diminished during the opposite phase. On all mountain
ranges, therefore, which reached above the snow-line, there
would be a periodical increase and decrease of snow, and
when there were extensive areas of plateau at about the
same level, the lowering of the snow-line might cause such an
increased accumulation of snow as to produce great glaciers
and ice-fields, such as we have seen occurred in South Africa
during the last period of high excentricity. But along with —
such depression of the line of perpetual snow there would
be a corresponding depression of the alpine and sub-alpine
zones suitable for the growth of an arctic and temperate vege-
tation, and, what is perhaps more important, the depression
would necessarily produce a great extension of the area of these
zones on all high mountains, thus affording a number of new
stations suitable for such temperate plants as might first reach
them. Bat just above and below the snow-line is the area of

CHAP, XXIH.] ARCTIC PLANTS IN NEW ZEALAND. 485

most powerful disintegration and denudation, from the alternate
action of frost and sun, of ice and water; and thus the more
extended area would be subject to the constant occurrence of
land-slips, berg-falls, and floods, with their accompanying accu-
mulations of débris and of alluvial soil, affording innumerable
stations in which solitary wind-borne seeds might germinate
and temporarily establish themselves.

This lowering and rising of the snow-line each 10,500 years

during periods of high excentricity, would occur in the nerthern
and southern hemispheres alternately ; and where there were high
mountains within the tropics the two would probably overlap
each other, so that the northern depression would make itself felt
ina slight degree even across the equator some way into the
southern hemisphere, and vice vers; and even if the difference of
the height of perpetual snow at the two extremes did not average
more than a few hundred feet, this would be amply sufficient to
supply the new and unoccupied stations needful to facilitate the
migration of plants.
_ But the differences of temperature in the two hemispheres
caused by the sun being in periiclion in the winter of the one
while it was in aphelion during the same season in the other,
would necessarily lead to increased aérial and marine currents,
as already explained; and whenever geographical conditions
were such as to favour the production of glaciation in any area
these effects would become more powerful, and would further
aid in the dispersal of the seeds of plants.

Changes of Climate favourable to Migration —It is clear then,
that during periods when no glacial epochs were produced in the
northern hemisphere, and even when a mild climate extended
over the whole polar area, alternate changes of climate favouring
the dispersal of plants would occur on all high mountains, and
with particular force on such as rise above the snow-line. But
during that long-continued, though comparatively recent, phase
of high excentricity which produced an extensive glaciation in
the northern hemisphere and local glaciations in the southern,
these risings and lowerings of the snow-line on all mountain
ranges would have been at a maximum, and would have been
increased by the depression of the ocean which must have

486 ISLAND LIFE. [PABA IL,

arisen from such a vast bulk of water being locked up in land-
ice, and which depression would have produced the same effect
as a general elevation of all the continents. At this time, too,
aérial currents would have attained their maximum of force
in both hemispheres; and this would greatly facilitate the
dispersal of all wind-borne seeds as well as of those carried in
the plumage cr in the stomachs of birds, since we have seen
how vastly the migratory powers of birds are increased by a
stormy atmosphere. 7

Migration from North to South has been long going on.—Now,
if each phase of colder and warmer mountain-climate—each
alternate depression and elevation of the snow-line, only helped
on the migration of a few species some stages of the long route
from the north to the south temperate regions, yet, during the
long course of the Tertiary period there might well have arisen
that representation of the northern flora in the southern hemis-
phere which is now so conspicuous. For it is very important to
remark that it is not the existing flora alone that 1s represented,
such as might have been conveyed during the last glacial epoch
only ; but we find a whole series of northern types evidently of
varying degrees of antiquity, while even some genera character-
istic of the southern hemisphere appear to have been originally
derived from Europe. Thus Lucalyptus and Metrosideros have
been determined by Dr. Ettinghausen from their fruits in the
Eocene becs of Sheppey, while Pumelea, Leptomeria and four
genera of Pioteacez have been recognised by Professor Heer in
the Miocene of Switzerland ; and the former writer has detected
fifty-five Australian forms in the Eocene plant beds of Hiring
(? Belgium)! Then we have such peculiar genera as Pachychla-

1 Sir Joseph Hooker informs me that he considers these identifications
worthless, and Mr. Bentham has also written very strongly against the
value of similar identifications by Heer and Unger. Giving due weight to
the opinions of these eminent botanists we must admit that Australian
genera have not yet been demonstrated to have existed in Europe during
the Tertiary period ; but, on the other land, the evidence that they did so
appears to have some weight, on account of the improbability that the
numerous resemblances to Australian plants which have been noticed by
different observers should a// be illusory ; while the well established fact
of the former wide distribution of many tropical or now restricted types of

CHAP. xx111.] ARCTIC PLANTS IN NEW ZEALAND. 487

don and Notothlaspi of New Zealand said to have affinities
with Arctic plants, while Stidbocarpa—another peculiar New
Zealand genus—has its nearest allies in the Himalayan and
Chinese Aralias. Following these are a whole host of very
distinct species of northern genera which may date back
to any part of the Tertiary period, and which occur in every
south temperate land. Then we have closely allied repre-
sentative species of European or Arctic plants; and, lastly,
a number of jdentical species,—and these two classes are
probably due entirely to the action of the last great glacial
epoch, whose long continuance, and the repeated fluctuations
of climate with which it commenced and terminated, ren-
dered it an agent of sufficient power to have brought about this
result,

Here, then, we have that constant or constantly recurrent
process of dispersal acting throughout long periods with varying
power—that “continuous current of vegetation” as it has
been termed, which the facts demand ; and the extraordinary
phenomenon of the species and genera of European and even
of Arctic plants being represented abundantly in South Africa,
Australia, and New Zealand, thus adds another to the long
series of phenomena which are rendered intelligible by frequent
alternations of warmer and colder climates in either hemisphere,
culminating, at long intervals and in favourable situations, in
actual glacial epochs.

Geological changes as aiding migration. —It will be well also to
notice here, that there is another aid to dispersion, dependent
upon the changes effected by denudation during the long periods
included in the duration of the species and genera of plants.
A considerable number of the plants of Europe of the Miocene

plants and animals, so frequently illustrated in the present volume, removes
the antecedent improbability which is supposed to attach to such identifi-
cations. I am myself the more inclined to accept them, because, according
to the views here advocated, such migrations must have taken place at
remote as well as at recent epochs; and the preservation of some of these
types in Australia while they have become extinct in Europe, is exactly
paralleled by numerous facts in the distribution of animals which have
been already referred to in Chapter XIX., and elsewhere in this volume,
and also repeatedly in my larger work.

483 ISLAND LIFS. [PART II.

period were so much like existing species that although they
have generally received fresh names they may well: have been
identical ; and a large proportion of the vegetation during the
whole Tertiary period consisted of genera which are still
living... But from what is now known of the rate of sub-aérial
denudation, we are sure, that during each division of this
period many mountain chains must have been considerably
lowered, while we know that some of the existing ranges have
been greatly elevated. Ancient volcanoes, too, have been de-
stroyed by denudation, and new ones have been built up, so
that we may be quite sure that ample means for the transmis-
sion of temperate plants across the tropics, may have existed in
countries where they are now no longer to be found. The great
mountain masses of Guiana and Brazil, for example, must have
been far more lofty before the sedimentary covering was
denuded from their granitic bosses and metamorphic peaks, and
may have aided the southern migration of plants before the
final elevation of the Andes. And if Africa presents us with
an example of a continent of vast antiquity, we may be sure
that its great central plateaux once bore far loftier mountain
ranges ere they were reduced to their present condition by
long ages of denudation.

Proofs of Migration by way of the Andes—We are now
prepared to apply the principles above laid down to the ex-
planation of the character and affinities of the various portions
of the north temperate flora in the southern hemisphere, and
especially in Australia and New Zealand.

At the present time the only unbroken chain of highlands
and mountains connecting the Arctic and north temperate with

the Antarctic lands is to be found in the American continent,.

the only break of importance being the comparatively low

1 Out of forty-two genera from the Eocene of Sheppey enumerated
by Dr. Ettinghausen in the Geological Magazine for January 1880, only
two or three appear to be extinct, while there is a mostextraordinary inter-
mixture of tropical and temperate forms—Musa, Nipa, and Victoria, with
Corylus, Prunus, Acer, &c. The rich Miocene flora of Switzerland,

described hy Professor Heer, presents a still larger proportion of living

genera.

——

cuar. xxm1.] ARCTIC PLANTS IN NEW ZEALAND. 48)

Isthmus of Panama, where there is a distance of about 300
miles occupied by rugged forest-clad hills, between the lofty
peaks of Veragua and the northern extremity of the Andes of
New Grenada. Such distances are, as we have already seen,
no barrier to the diffusion of plants; and we should accordingly
expect that this great continuous mountain-chain has formed
the most effective agent in aiding the southward migration of
the Arctic and north temperate vegetation. We do find, in fact,
not only that a large number of northern genera and many
species are scattered all along this line of route, but that at the
end of the long journey, in Southern Chile and Fuegia, they
have established themselves in such numbers as to form an
important part of the flora of those countries. From the lists
given in the works already referred to, it appears that there
are between sixty and seventy northern genera in Fuegia and
Southern Chile, while about forty of the species are absolutely
identical with those of Europe and the Arctic regions. Con-
sidering how comparatively little the mountains of South
Temperate America are yet known, this is a very remarkable
result, and it proves that the transmission of species must have
gone on up to comparatively recent times. Yet, as only a few
of these species are now found along the line of migration, we
see that they only occupied such stations temporarily; and we
may connect their disappearance with the passing away of the
last glacial period which, by raising the snow-line, reduced the
area on which alone they could exist, and exposed them to
the competition of indigenous plants from the belt of country
immediately below them.

Now, just as these numerous species and genera have un-
doubtedly passed along the great American range of mountains,
although only now found at its two extremes, so others have
doubtless passed on further; and have found more suitable
stations or less severe competition in the Antarctic continent
and islands, in New Zealand, in Tasmania, and even in Aus-
tralia itself. The route by which they may have reached these
countries is easily marked out. Immediately south of Cape
Horn, at a distance of only 500 miles, are the South Shetland
Islands and Graham’s Land, whence the Antarctic continent or

490 i ISLAND LIFE. [PART ID.

a group of large islands probably extends across or around the
south polar area to Victoria Land and thence to Adélie Land.
The outlying Young Island, 12,000 feet high, is about 750
miles south of the Macquarie Islands, which may be considered
a southern outher of the New Zealand group; and the Mac-
quarie Islands are about the same distance from the 1,000-
fathom line, marking the probable southern extension of Tas-
mania. Other islands may have existed at intermediate points;
but, even as it 1s, these distances are not greater than we know
are traversed by plants both by flotation and by aérial currents,
especially in such a stormy atmosphere as that of the Antarctic
regions. Now, we may further assume, that what we know
occurred within the Arctic circle also took place in the Ant-
arctic—that is, that there have been alternations of climate
during which seme portion of what are now ice-clad lands
became able to support a considerable amount of vegetation.?
During such periods there would be a steady migration of plants
from all seuthern circumpolar countries to people the com-
paratively unoccupied continent, and the southern extremity
of America being considerably the nearest, and also being the
best stocked with those northern types which have such great
powers of migration and colonisation, such plants would form
the bulk of the Antarctic vegetation, and during the continuance
of the milder southern climate would occupy the whole area.
When the cold returned and the land again became ice-clad,
these plants would be crowded towards the outer margins of
the Antarctic land and its islands, and some of them would find
their way across the sea to such countries as offered on their
mountain summits suitable cool stations ; and as this process of
alternately receiving plants from Chile and Fuegia and trans-
mitting them in all directions from the central Antarctic land
may have been repeated several times during the Tertiary
period, we have no difficulty in understanding the general com-

1 The recent discovery of a rich flora on rocky peaks rising out of the
continental ice of Greenland, as well as the abundant vegetation of the
highest northern latitudes, renders it possible that even now the Antarctic
continent may not be wholly destitute of vegetation, although its climate
and physical condition are far less favourable than those of the Arctic lands.

CHAP. XXIUI.] ARCTIC PLANTS IN NEW ZEALAND. 491

munity between the Kuropean and Antarctic plants found in
all south temperate lands. Kerguelen’s Land and The Crozets
are within about the same distance from the Antarctic con-
tinent as New Zealand and Tasmania, and we need not there-
fore be surprised at finding in each of these islands some
Fuegian species which have not reached the others. Of course
there will remain difficulties of detail, as there always must
when we know so imperfectly the past changes of the earth’s
surface and the history of the particular plants concerned. Sir
Joseph Hooker notes, for example, the curious fact that several
Composite common to three such remote localities as the
Auckland Islands, Fuegia, and Kerguelen’s Land, have no
pappus or seed-down, while such as have pappus are in no
case common even to two of these islands. Without knowing
the exact history and distribution of the genera to which these
plants belong it would be useless to offer any conjecture, except
that they are ancient forms which may have survived great
geographical changes, or may have some peculiar and exceptional
means of dispersion.

Proofs of Migration by way of the Himalayas and Southern
Asia.—But although we may thus explain the presence of a
considerable portion of the European element in the floras of
New Zealand and Australia, we cannot account for the whole of
it by this means, because Australia itself contains a host of
Kuropean and Asiatic genera of which we find no trace in
New Zealand or South America, or any other Antarctic land.
We find, in fact, in Australia two distinct sets of European
plants. First we have a number of species identical with those
of Northern Europe or Asia (of the most characteristic of
which—thirty-eight in number—Sir Joseph Hooker gives a
list); and in the second place a series of European genera
usually of a somewhat more southern character, mostly re-
presented by very distinct species, and all absent from New
Zealand; such as Clematis, Papaver, Cleome, Polygala, Lava-
tera, Ajuga, &c. Now of the first set—the North European
species—about three-fourths occur in some parts of America, and
about half in South Temperate America or New Zealand ;
whence we may conclude that most of these, as well as some

492 ISLAND LIFE. [PART lI.

others, have reached Australia by the route already indicated.
The second set of Australo-Huropean genera, however, and
many others characteristic of the South Huropean or the Hima-
layan flora, have probably reached Australia by way of the
mountains of Southern Asia,-Borneo, the Moluccas, and New
Guinea, at a somewhat remote period when loftier ranges and
some intermediate peaks may have existed, sufficient to carry
on the migration by the aid of the alternate climatal changes
which are known to have occurred, The long belt of Secondary
and Paleozoic formations in East Australia from Tasmania to
Cape York, continued by the lofty ranges of New Guinea,
indicates the route of this immigration, and sufficiently explains
how it is that these northern types are almost wholly confined
to this part of the Australian continent. Some of the earlier
immigrants of this class no doubt passed over to New Zealand
and now form a portion of the peculiar genera confined to
these two countries; but most of them are of later date, and
have thus remained in Australia only.

Proofs of Migration by way of the African Highlands.—It
is owing to this twofold current of vegetation flowing into
Australia by widely different routes that we have in this
distant land a better representation of the European flora,
both as regards species and genera, than in any other part of
the southern hemisphere; and, so far as I can judge of the
facts, there is no general phenomenon—that is, nothing in the
distribution of genera and other groups of plants as opposed to
cases of individual species—that is not fairly accounted for by
such an origin. It further receives support from the case of
South Africa, which also contains a large and important repre-
sentation of the northern flora. But here we sce no indications
(or very slight ones) of that southern influx which has given
Australia such a community of vegetation with the Antarctic
lands. There are no less than sixty genera of strictly north
temperate plants in South Africa, none of which occur in
Australia; while very few of the species, so characteristic of
Australia, New Zealand, and Fuegia, are found there. It is
clear, therefore, that South Africa has received its Kuropean
plants by the direct route through the Abyssinian highlands

CHAP. XXITI.] ARCTIC PLANTS IN NEW ZEALAND. 493

and the lofty equatorial mountains, and mostly at a distant
period when the conditions for migration were somewhat more
favourable than they are now. The much greater directness
of the route from Northern Europe to South Africa than to
Australia; and the existence even now of lofty mountains and
extensive highlands for a large portion of the distance, will
explain (what Sir Joseph Hooker notes as ‘‘a very curious
fact”) why South Africa has more very northern European
genera than Australia, while Australia has more identical
species and a better representation on the whole of the
European flora—this being clearly due to the large influx of
species it has received from the Antarctic Islands, in addition
to those which have entered it by way of Asia. The greater
distance of South Africa even now from any of these islands,
and the much deeper sea to the south of the African continent,
than in the case of Tasmania and New Zealand, indicating a
smaller recent extension southward, is all quite in harmony
with the facts of distribution of the northern flora above
referred to.

Supposed Connection of South Africa and Australia.—There
remains, however, the small amount of direct affinity between
the vegetation of South Africa and that of Australia, New
Zealand, and Temperate South America, consisting in all of
fifteen genera, five of which are confined to Australia and
South Africa, while several natural orders are better represented
im these two countries than in any other part of the world.
This resemblance has been supposed to imply some former land-
connection of all the great southern lands, but it appears to
me that any such supposition is wholly unnecessary. The dif-
ferences between the faunas and floras of these countries are
too great and too radical to render it possible that any such
connection should have existed except at a very remote period-
But if we have to go back so far for an explanation, a much
simpler one presents itself, and one more in accordance with
what we have learnt of the general permanence of deep oceans
and the radical changes that have taken place in the distribu-
tion of all forms of life. Just as we explain the presence of
marsupials in Australia and America and of Centetide in

494 | ISLAND LIFE. [parr 11.

Madagascar and the Antilles, by the preservation in these
localities of remnants of once wide-spread types, so we should
prefer to consider the few genera common to Australia and
South Africa as remnants of an ancient vegetation, once spread
over the northern hemisphere, driven southward by the pressure
of more specialised types, and now finding a refuge in these
two widely separated southern lands. It is suggestive of such
an explanation that these genera are either of very ancient
groups—as Conifers aud Cycads—or plants of low organisation
as the Restiacese—or of world-wide distribution, as Melan-
thaceee.

Lhe Endemic Genera of Plants in New Zealand.—Returning
now to the New Zealand flora, with which we are more espe-
cially concerned, there only remains to be considered the pecu-
liar or endemic genera which characterise it. These are thirty-
two in number, and are mostly very isolated. A few have
affinities with Arctic groups, others with Himalayan, or
Australian genera; several are tropical forms, but the majority

appear to be altogether peculiar types of world-wide groups—as

Leguminose, Saxifrageze, Composite, Orchidee, &. We must
evidently trace bazk these peculiar forms to the earliest immi-
grants, either from the north or from the south; and the great
antiquity we are obliged to give to New Zealand—an antiquity
supported by every feature in its fauna and flora, no less than by
its geological structure, and its extinct forms of life’—affords
ample time for the changes in the general distribution of plants,
and for those due to isolation and modification under the influ-
ence of changed conditions, which are manifested by the

extreme peculiarity of many of these interesting endemic forms.

1 Dr. Hector notes the occurrence of the genus Dammara in Triassic
deposits, while in the Jurassic period New Zealand produced the genera
Paleozamia, Oleandrium, Alethopteris, Camptopteris, Cycadites, Echino-
strobus, &c., all Indian forms of the same age. Neocomian beds contain
a true dicotyledonous leaf with Dammara and Araucaria. ‘The Cretaceous
deposits have produced a rich flora of dicotyledonous plants, many of
which are of the same genera as the existing flora; while the Miocene and
other Tertiary deposits produce plants apparently almost identical with
those now inhabiting the country. (Trans. New Zealand Inst. Vol. XI.
1879, p. 536.) These facts agree well with the origin of the New Zealand
flora developed in the last chapter.

| heiaemaumiauali

a ae ae pias

CHAP. xx] ARCTIC PLANTS IN NEW ZEALAND. 495

The absence of Southern Types from the Northern Hemisphere.
—We have now only to notice the singular want of reciprocity
in the migrations of northern and southern types of vegetation.
In return for the vast number of European plants which have
reached Australia, not one single Australian plant has entered
any part of the north temperate zone, and the same may be
said of the typical southern vegetation in general, whether
developed in the Antarctic lands, New Zealand, South America,
or South Africa. The furthest northern outliers of the southern
flora are a few genera of Antarctic type on the Bornean Alps ;
the genus Acwna which has a species in California; two re-
presentatives of the Australian flora—Casuarina and Styliduum,
in the peninsula of India; while China and the Philippines
have two strictly Australian genera of Orchidee—Mverotis and
Thelymitra, as well as a Restiaceous genus. Several distinct
causes appear to have combined to produce this curious inability
of the southern flora to make its way into the northern hemis-
phere. The primary cause is, no doubt, the totally different
distribution of land in the two hemispheres, so that in the south
there is the minimum of land in the colder parts of the tempe-
rate zone and in the north the maximum. This is well shown
by the fact that on the parallel of Lat. 50° N. we pass over 240°
of land or shallow sea, while on the same parallel of south
latitude we have only 4°, where we cross the southern part of
Patagonia. Again the three most important south temperate
land-areas— South Temperate America, South Africa, and
Australia—are widely separated from each other, and have in all
probability always been so; whereas the whole of the north
temperate lands are practically continuous. It follows that,
instead of the enormous northern area, in which highly organised
and dominant groups of plants have been developed gifted with
great colonising and aggressive powers, we have in the south
three comparatively small and detached areas, in which rich
floras have been developed with special adaptations to soil,
climate, and organic environment, but comparatively impotent
and inferior beyond their own domain.

Another circumstance which makes the contest between the
northern and southern forms still more unequal, is the much

496 ISLAND LIFE. [CART 11,

greater hardiness of the former, from having been developed in
a colder region, and one where alpine and arctic conditions ex-
tensively prevail; whereas the southern floras have been mainly
developed in mild regions to which they have been altogether
confined. While the northern plants have been driven north or
south by each succeeding change of climate, the southern
species have undergone comparatively slight changes of this
nature, owing to the areas they occupy being unconnected with
the ice-bearing Antarctic continent. It follows, that whereas
the northern plants find in all these southern lands a milder and
more equable climate than that to which they have been accus-
tomed, and are thus often able to grow and flourish even more
vigorously than in their native land, the southern plants would
find in almost every part of Europe, North America or
Northern Asia, a more severe and less equable climate, with
winters that usually prove fatal to them even under cultivation.
These causes, taken separately, are very powerful, but when
combined they must, I think, be held to be amply sufficient to
explain why examples of the typical southern vegetation are
almost unknown in the north temperate zone, while a very few
of them have extended so far as the northern tropic.’

Concluding remarks on the last two chapters.—Our inquiry
into the external relations and probable origin of the fauna
and flora of New Zealand, has thus led us on to a general

1 The fact stated in the last edition of the Origin of Species (p. 340) on
the authority of Sir Joseph Hooker, that Australian plants are rapidly
sowing themselves and becoming naturalised on the Neilgherrie mountains
in the southern part of the Indian Peninsula, though an exception to the
rule of the inability of Australian plants to become naturalised in the
Northern Hemisphere, is yet quite in harmony with the hypothesis here
advocated. For not only is the climate of the Neilgherries more favour-
able to Australian plants than any part of the North Temperate zone, but
the entire Indian Peninsula has existed for unknown ages as an island and
thus possesses the “insular” characteristic of a comparatively poor and
less developed flora and fauna as compared with the truly “continental”
Malayan and Himalayan regions. Australian plants are thus enabled to
compete with those of the Indian Peninsula highlands with a fair chance
of success.

CHar. xxi.] ARCTIC PLANTS IN NEW ZEALAND. 497

theory as to the cause of the peculiar biological relations be-
tween the northern and the southern hemispheres; and no
better or more typical example could be found of the wide
range and great interest of the study of the geographical
distribution of animals and plants.

The solution which has here been given of one of the most
difficult of this class of problems, has been rendered possible
solely by the knowledge very recently obtained of the form of
the sea-bottom in the southern ocean, and of the geological
structure of the great Australian continent. Without this
knowledge we should have nothing but a series of guesses or
probabiJities on which to found our hypothetical explanation,
which we have now been able to build up on a solid foundation
of fact. The complete separation of East from West Australia
during the Cretaceous period, could never have been guessed
till it was established by the laborious explorations of the
Australian geologists ; while the hypothesis of a comparatively
shallow sea, uniting New Zealand by a long route with tropical
Australia, while a profoundly deep ocean always separated it
from temperate Australia, would have been rejected as too
improbable a supposition for the foundation of even the most
enticing theory. Yet it is mainly by means of these two facts,
that we are enabled to give an adequate explanation of the
strange anomalies in the flora of Australia and its relation to
that of New Zealand. |

In the more general explanation of the relations of the
various northern and southern floras, I have shown what an
important aid to any such explanation is the theory of repeated
changes of climate, not necessarily of great amount, given in
our eighth Chapter; while the whole discussion justifies the
importance attached to the theory of the general permanence
of continents and oceans, as demonstrated in Chapter VI,
since any rational explanation based upon facts (as opposed to
mere unsupported conjecture) must take such general perma-
nence as a starting-point. The whole inquiry into the pheno-
mena presented by islands, which forms the main subject of the
present volume has, I think, shown that this theory does afford

K K

498 ISLAND LIFE, [PART IT.

a firm foundation for the discussion of questions of distribution
and dispersal; and that by its aid, combined with a clear per-
ception of the wonderful powers of dispersion and modification
in the organic world when long periods are considered, the most

difficult problems connected with this subject cease to be
insoluble.

CHAPTER XXIV.

SUMMARY AND CONCLUSION.

The present volume is the development and application of a theory—State-
ment of the Biological and Physical causes of dispersal—Investigation
of the facts of dispersal-——of the means of dispersal—of geographical
changes affecting dispersal—of climatal changes affecting dispersal—
The glacial epoch and its causes—Alleged ancient glacial epochs—
Warm polar climates and their causes—Conclusions as to geological
climates—How far different from those of Mr. Croll—Supposed limita-
tions of geological time—Time amply sufficient both for geological and
biological development—Insuiar faunas and floras—The North Atlantic
Islands—The Galapagos—St. Helena and the Sandwich Islands—Great
Britain as a recent Continental Island—Borneo and Java—Japan and
Formosa—Madagascar as an ancient Continental Island—Celebes and
New Zealand as anomalous Islands—The Flora of New Zealand and
its origin—The European element in the South Temperate Floras—
Concluding Remarks,

THE present volume has gone over a very wide field both of
facts and theories, and it will be well to recall these to the
reader's attention and point out their connection with each other,
in a concluding chapter. I hope to be able to show that,
although at first sight somewhat fragmentary and disconnected,
this work is really the development of a clear and definite
theory, and its application to the solution of a number cf
biological problems. That theory is, briefly, that the distri-
bution of the various species and groups of living things over
the earth’s surface, and their aggregation in definite assem-
blages in certain areas, is the direct result and outcome of a
complex set of causes, which may be grouped as “ biological”
and “physical.” The biological causes are mainly of two
Kaz

509 ISLAND LIFE. [PART II.

kinds—firstly, the constant tendency of all organisms to in-
crease in numbers and to occupy a wider area, and their
various powers of dispersion and migration through which, when
unchecked, they are enabled to spread widely over the globe;
and, secondly, those laws of evolution and extinction which
determine the manner in which groups of organisms arise and
grow, reach their maximum, and then dwindle away, often
breaking up into separate portions which long survive in very
remote regions. ‘The physical causes are also mainly of two
kinds. We have, first, the geographical changes which at one
time isolate a whole fauna and flora, at another time lead to
their dispersal and intermixture with adjacent faunas and floras
—and it was here important to ascertain and define the exact
nature and extent of these changes, and to determine the
question of the general stability or instability of continents
and oceans; in the second place, it was necessary to determine
the exact nature, extent, and frequency of the changes of cli-
mate which have occurred in various parts of the earth,—
because such changes are among the most powerful agents in
causing the dispersal and extinction of plants and animals.
Hence the importance attached to the question of geological
climates and their causes, which have been here investigated
at some length with the aid of the most recent researches of
geologists, physicists, and explorers. These various inquiries
led on to an investigation of the mode of formation of strati-
fied deposits, with a view to fix within some limits their pro-
bable age; and also to an estimate of the probable rate of
development of the organic world; and both these processes
are shown to involve, in all probability, periods of time less
vast than have generally been thought necessary.

The numerous facts and theories established in the First
Part of the work are then applied to explain the phenomena
presented by the floras and faunas of the chief islands of the
globe, which are classified, in accordance with their physical
origin, in three group or classes, each of which are shown to
exhibit certain well-marked biological features.

Having thus shown that the work is a connected whole,
founded on the principle of tracing out the more recondite

CHAP. XXIV. | SUMMARY AND CONCLUSION. 501

causes of the distribution of organisms, we will briefly indicate
the scope and object of the several chapters, by means of which
this general conception has been carried out.

Beginning with simple and familiar facts relating to British
and European quadrupeds and birds, I have defined and shown
the exact character of ‘“‘areas of distribution,” as applied to
species, genera, and families, and have illustrated the subject
by maps showing the peculiarities of distribution of some well-
known groups of birds. Taking then our British mammals and
land-birds, I follow them over the whole area they inhabit, and
thus obtain a foundation for the establishment of “ zoological
regions,” and a clear insight into their character as distinct
from the usual geographical divisions of the globe.

The facts thus far established are then shown to be necessary
results of the “law of evolution.” The nature and amount of
‘variation’ is exhibited by a number of curious examples;
the origin, growth, and decay of species and genera are traced,
and all the interesting phenomena of isolated groups and dis-
continuous generic and specific areas are shown to follow as
logical consequences.

The next subject investigated is the means by which the
various groups of animals are enabled to overcome the natural
barriers which often seem to limit them to very restricted areas,
how far those barriers are themselves liable to be altered or
abolished, and what is the exact nature and amount of the
changes of sea and Jand which our earth has undergone in
past times. This latter part of the inquiry is shown to be
the most important as it is the most fundamental; and as it
is still a subject of controversy, and many erroneous views pre-
vail in regard to it, it is discussed at some length. Several
distinct classes of evidence are adduced to prove that the grand
features of our globe—the position of the great oceans and
the chief land-areas—have remained, on the whole, unchanged
throughout geological time. Our continents are shown to be
built up mainly of “shore-deposits ;” and even the chalk, which
is so often said to be the exact equivalent of the “ globigerina-
ooze” now forming in mid-Atlantic, is shown to be a com-
paratively shallow-water deposit formed in inland seas, or in

502 ISLAND LIFE. [PART Il.

the immediate vicinity of land. The general stability of con-
tinents has, however, been accompanied by constant changes of
form, and insular conditions have prevailed over every part in
succession; and the effect of such changes on the distribution
of organisms is pointed out.

We then approach the consideration of another set of
changes—those of climate—which have probably been agents
of the first importance in modifying the specific forms as well
as the distribution of animals. Here again we find ourselves
in the midst of fierce controversies. The occurrence of a re-
cent glacial epoch of great severity in the northern hemisphere
is now universally admitted, but the causes which brought it
on are matter of dispute. But unless we can arrive at these
causes, as well as at those which produced the equally well
demonstrated mild climate in the Arctic regions, we shall be
quite unable to determine the nature and amount of the changes
of climate which have occurred throughout past ages, and shall
thus be left without a most important clue to the explanation of
many of the anomalies in the distribution of animals and plants.

I have therefore devoted three chapters to a full investigation
of this question. I have first given such a sketch of the most
salient facts as to render the phenomena of the glacial epoch
clear and intelligible. I then review the various suggested
explanations, and, taking up the two which alone seem tenable,
I endeavour to determine the true principles of each. While
adopting generally Mr. Croll’s views as to the causes of the
‘‘slacial epoch,” I have introduced certain limitations and modi-
fications. I have pointed out with more precision than has, I
believe, hitherto been done, the very different effects on climate
of water in the liquid and in the solid state ; and I have shown,
by a variety of evidence, that without high land there can be
no permanent snow and ice. From these facts and principles
the very important conclusion is reached, that the alternate
phases of precession—causing the winter of each hemisphere
to be in aphelion and perthelion each 10,500 years—would pro-
duce a complete change of climate only where a country was
partially snow-clad; while, whenever a large area became
almost wholly buried in snow and ice—as was certainly the

CHAP, XXIv.] SUMMARY AND CONCLUSION. 503

case with Northern Europe during the glacial epoch—then the
glacial conditions would be continued and perhaps even inten-
sified when the sun approached nearest to the earth in winter,
instead of there being at that time, as Mr. Croll maintains,
an almost perpetual spring. This important result is supported
by reference to the existing differences between the climates
of the northern and southern hemispheres, and by what is
known to have occurred during the last glacial epoch ; and it
is shown to be in complete harmony with the geological evidence
as to interglacial mild periods.

Discussing next the evidence for glacial epochs in earlier
times, it is shown that Mr. Croll’s views are opposed by a vast
body of facts, and that the geological evidence leads irresistibly
to the conclusion that during a large portion of the Secondary
and Tertiary periods, uninterrupted warm climates prevailed in
the north temperate zone, and so far ameliorated the climate of
the Arctic regions as to admit of the growth of a luxuriant
vegetation in the highest latitudes yet explored. The geogra-
phical condition of the northern hemisphere at these periods is
then investigated, and it is shown to have been such as to
admit the warm tropical waters freely to penetrate the land,
and to reach the Arctic seas by several channels; and, adopt-
ing Mr. Croll’s views as to the enormous quantity of heat that
would thus be conveyed northwards, it is maintained that the
mild Arctic climates are amply accounted for. With such
favourable geographical conditions, it is shown, that changes of
excentricity and of the phases of precession would have no other
effect than to cause greater differences of temperature between
summer and winter; but, wherever there was a considerable
extent of very lofty mountains the snow-line would be lowered,
and the snow-collecting area being thus largely increased a con-
siderable amount of local glaciation might result. Thus may be
explained the presence of enormous ice-borne rocks in Eocene
and Miocene times in Central Europe, while at the very same
period all the surrounding country enjoyed a tropical or sub-
tropical climate.

The general conclusion is thus reached, that geographical
conditions are the primary causes of great changes of climate,

504 ISLAND LIFE. [PART 11.

and that the radically different distribution of land and sea in
the northern and southern hemispheres has generally led to
great diversity of climate in the Arctic and Antarctic regions,
The form and arrangement of the continents is shown to be
such as to favour the transfer of warm oceanic currents to the
north far in excess of those which move towards the south, and
whenever these currents had free passage through the northern
Jand-masses to the polar area, a mild climate must have pre-
vailed over the whole northern hemisphere. It is only in very
recent times that the great northern continents have become
so completely consolidated as they now are, thus shutting out
the warm water from their interiors, and rendering possible
a wide-spread and intense glacial epoch. But this great
climatal change was actually brought about by the high
excentricity which occurred about 200,000 years ago; and
it is doubtful if a similar glaciation in equally low latitudes
could be produced by means of any such geographical com-
binations as actually occur, without the concurrence of a high
excentricity.

A survey of the present condition of the earth supports this
view, for though we have enormous mountain ranges in every
latitude, there is no glaciated country south of Greenland in
N. Lat. 61° But directly we go back a very short period,
we find the superficial evidences of glaciation to an enormous
extent over three-fourths of the globe. In the Alps and Pyre-
nees, in the British Isles and Scandinavia, in Spain and the
Atlas, in the Caucasus and the Himalayas, in Eastern North
America and west of the Rocky Mountains, in the Andes, in
the Mountains of Brazil, in South Africa, and in New Zealand,
huge moraines and other unmistakable ice-marks attest the
universal descent of the snow-line for several thousand feet
below its present level. If we reject the influence of high
excentricity as the cause of this almost universal glaciation,~
we must postulate a general elevation of all these mountains
about the same time—for the close similarity in the state of
preservation of the ice-marks and the known activity of denu-
dation as a destroying agent, forbid the idea that they belong
to widely separated epochs. It has, indeed, been suggested,

onar. xxIv.] SUMMARY AND CONCLUSION. 505

that denudation alone has lowered these mountains so much
during the quarternary epoch, that they were previously of
sufficient height to account for the glaciation of all of them,
but this hardly needs refutation ; for it 1s clear that denudation
could not at the same time have removed some thousands of
feet of rock from many hundreds of square miles of lofty
snow-collecting plateaus, and yet have left moraines, and
blocks, and even glacial strive, undisturbed and uneffaced on
the slopes and in the valleys of these same mountains.

The theory of geological climates set forth in this volume,
while founded on Mr. Croll’s researches, differs from all that
have yet been made public, in clearly tracing out the compara-
tive influence of geographical and astronomical revolutions,
showing that, while the former have been the chief, if not the
exclusive, causes of the long-continued mild climates of the
Arctic regions, the concurrence of the latter has been essential
to the production of glacial epochs in the temperate zones, as
well as of those local glaciations in low latitudes, of which there
is such an abundance of evidence.

The next question discussed is that of geological time as
bearing on the development of the organic world. The periods
- of time usually demanded by geologists have been very great,
and it was often assumed that there was no occasion to limit
them. But the theory of development demands far more ; for
the earliest fossiliferous rocks prove the existence of many and
varied forms of life which require unrecorded ages for their
development—ages probably far longer than those which have
elapsed from that period to the present day. The physicists,
however, deny that any such indefinitely long periods are avail-
able. ‘The sun is ever losing heat far more rapidly than it can
be renewed from any known or conceivable source. The earth
is a cooling body, and must once have been too hot to support
life ; while the friction of the tides is checking the earth’s rota-
tion, and this cannot have gone on indefinitely without making
our day much longer than it is. A limit is therefore placed to
the age of the habitable earth, and it has been thought that
the time so allowed is not sufficient for the long processes of
geological change and organic development. It is therefore

506 ISLAND LIFE. [PART II.

important to inquire whether these processes are either of them
so excessively slow as has been supposed, and I devote a chapter
to the inquiry.

Geologists have measured with some accuracy the maximum
thickness of all the known sedimentary rocks. The rate of
denudation has also been recently measured by a method which,
if not precise, at all events gives results of the right order of
magnitude and which err on the side of being too slow rather
than too fast. If, then, the maximum thickness of the known
sedimentary rocks is taken to represent the average thickness
of all the sedimentary rocks, and we also know the amount of
sediment carried to the sea or lakes, and the avea over which
that sediment is spread, we have a means of calculating the
time required for the building up of all the sedimentary rocks
of the geological system. I have here inquired how far the
above suppositions are correct, or on which side they probably
err; and the conclusion arrived at is, that the time required is
very much less than has hitherto been supposed.

Another estimate is afforded by the date of the last glacial
epoch as coincident with the last period of high excentricity,
while the Alpine glaciation of the Miocene period is assumed to
have been caused by the next earlier phase of very high excen-
tricity. Taking these as data, the proportionate change of the
species of mollusca affords a means of arriving at the whole
lapse of time represented by the fossiliferous rocks; and these
two estimates agree in the order of their magnitudes.

It is then argued that the changes of climate every 10,500
years during the numerous periods of high excentricity have
acted as a motive power in hastening on both geological and
biological change. By raising and lowering the snow-line in all
mountain ranges it has caused increased denudation; while the
same changes have caused much migration and disturbance in
the organic world, and have thus tended to the more rapid
modification of species. The present epoch being a period of
very low excentricity, the earth is in a phase of exceptional
stabulity both physical and organic; and it is from this peried
of exceptional stability that our notions of the very slow rate
of change have been derived.

CHAP. XX1Y. ] SUMMARY AND CONCLUSION. 507

The conclusion is, on the whole, that the periods allowed by
physicists are not only far in excess of such as are required for
geological and organic change, but that they allow ample margin
for a lapse of time anterior to the deposit of the earliest fossili-
ferous rocks several times longer than the time which has
elapsed since their deposit to the present day.

Having thus laid the foundation for a scientific interpretation
of the phenomena of distribution, we proceed to the Second Part
of our work—the discussion of a series of typical Insular Faunas
and Floras with a view to explain the interesting phenomena they
present. Taking first two North Atlantic groups—the Azores
and Bermuda, it is shown how important an agent in the dispersal
of most animals and plants is a stormy atmosphere. Although
900 and 700 miles respectively from the nearest continents,
their productions are very largely identical with those of Europe
and America; and, what is more important, fresh arrivals of
birds, insects, and plants, are now taking place almost annually.
These islands afford, therefore, test examples of the great dis-
persive powers of certain groups of organisms, and thus serve as
a basis on which to found our explanations of many anomalies
of distribution. Passing on to the Galapagos we have a group less
distant from a continent and of larger area, yet, owing to special
conditions, of which the comparatively stormless equatorial at-
mosphere is the most important, exhibiting far more speciality
in.its productions than the more distant Azores. Still, however,
its fauna and flora are as unmistakably derived from the
American continent as those of the Azores are from the
uropean.

We next take St. Helena and the Sandwich Islands, both
wonderfully isolated in the midst of vast oceans, and no longer
exhibiting in their productions an exclusive affinity to one
continent. Here we have to recognise the results of immense
antiquity, and of those changes of geography, of climate,
and in the general distribution of organisms which we know
have occurred in former geological epochs, and whose causes
and: consequences we have discussed in the first part of our
volume. This concludes our review of the Oceanic Islands.

Coming now to Continental Islands we consider first those of

508 | ISLAND LIFE, [PART IT,

most recent origin and offering the simplest phenomena; and
begin with the British Isles as affording the best example of
very recent and well known Continental Islands. Reviewing
the interesting past history of Britain, we show why it is com-
paratively poor in species and why this poverty is still greater
in Ireland. By a careful examination of its fauna and flora it
is then shown that the British Isles are not so completely
identical, biologically, with the continent as has been supposed,
A considerable amount of speciality is shown to exist, and that
this speciality is real and not apparent is supported by the
fact, that small outlying islands, such as the Isle of Man, the
Shetland Isles, Lundy Island, and the Isle of Wight, all possess
certain species or varieties not found elsewhere.

Borneo and Java are next taken, as illustrations of tropical
islands which may be not more ancient than Britain, but which,
owing to their much larger area, greater distance from the
continent, and the extreme richness of the equatorial fauna and
flora, possess a large proportion of peculiar species, though these
are in general very closely allied to those of the adjacent parts
of Asia. The preliminary studies we have made enable us to
afford a simpler and more definite interpretation of the peculiar
relations of Java to the continent and its differences from
Borneo and Sumatra, than was given in my former work (The
Geographical Distribution of Animals).

Japan and Formosa are next taken, as examples of islands
which are decidedly somewhat more ancient than those pre-
viously considered, and which present a number of very inter-
esting phenomena, especially in their relations to each other,
and to remote rather than to adjacent parts of the Asiatic
continent.

We now pass to the group of Ancient Continental Islands,
of which Madagascar is the most typical example. It is sur-
rounded by a number of smaller islands which may be termed
its satellites since they partake of many of its peculiarities ;
though some of these—as the Comoros and Seychelles may be
considered continental, while others—as Bourbon, Mauritius,
and Rodriguez—are decidedly oceanic. In order to understand
the peculiarities of the Madagascar fauna we have to consider

CHAP. XXIV. ] SUMMARY AND CONCLUSION. 509

the past history of the African and Asiatic continents, which it
is shown are such as to account for all the main peculiarities of
the fauna of these islands without having recourse to the
hypothesis of a now-submerged Lemurian continent. Consider-
able evidence is further adduced to show that ‘‘ Lemuria” is a
myth, since not only is its existence unnecessary, but it can be
proved that 1t would not explain the actual facts of distribution.
The origin of the interesting Mascarene wingless birds is dis-
cussed, and the main peculiarities of the remarkable flora
of Madagascar and the Mascarene islands pointed out; while it
is shown that all these phenomena are to be explained on the
general principles of the permanence of the great oceans and
the comparatively shght fluctuations of the land area, and by
taking account of established palzontological facts.

There remain two other islands—Celebes and New Zealand,
which are classed as “ anomalous,” the one because it is almost
impossible to place it in any of the six zoological regions, or
determine whether it has ever been actually joined to a
continent—the other because it combines the characteristics
of continental and oceanic islands.

The peculiarities of the Celebesian fauna have already been
dwelt upon in several previous works, but they are so remark-
able and so unique that they cannot be omitted in a treatise
on “Insular Faunas;” and here, as in the case of Borneo and
Java, fuller consideration and the application of the general
principles laid down in our First Part, lead to a solution of the
problem at once more simple and more satisfactory than any
which have been previously proposed. JI now look upon Celebes
as an outlying portion of the great Asiatic continent of Miocene
times, which either by submergence or some other cause had
lost the greater portion of its animal inhabitants, and since then
has remained more or less completely isolated from every other
land. It has thus preserved a fragment of a very ancient fauna
along with a number of later types which have reached it from
surrounding islands by the ordinary means of dispersal. This
sufficiently explains all the peculiar affinities of its animals,
though the peculiar and distinctive characters of some of them
remain as mysterlous as ever.

510 ISLAND LIFE. [PART IT.

New Zealand is shown to be so completely continental in
its geological structure, and its numerous wingless birds so
clearly imply a former connection with some other land (as do
its numerous lizards and its remarkable reptile, the Hatteria),
that the total absence of indigenous land-mammalia was hardly
to be expected. Some attention is therefore given to the curious
animal which has been seen but never captured, and this is
shown to be probably identical with an animal referred to by
Captain Cook. The more accurate knowledge which has
recently been obtained of the sea bottom around New Zealand
enables us to determine that the former connection of that island
with Australia was towards the north, and this is found to agree
well with many of the peculiarities of its fauna.

The flora of New Zealand and that of Australia are now both
so well known, and they present so many peculiarities, and
relations of so anomalous a character, as to present in Sir Joseph
Hooker's opinion an almost insoluble problem. Much additional
information on the physical and geological history of these two
countries has, however, been obtained since the appearance of
Sir Joseph Hooker's works, and I therefore determined to apply
to them the same method of discussion and treatment which has
been usually successful with similar problems in the case of
animals. The fact above noted, that New Zealand was con-
nected with Australia in its northern, tropical portion only, of
itself affords a clue to one portion of the specialities of the New
Zealand flora—the presence of an unusual number of tropical
families and genera, while the temperate forms consist mainly of
species either identical with those found in Australia or closely
allied to them. Buta still more important clue is obtained in
the geological structure of Australia itself, which is shown to
have been for long periods divided into an eastern and a western
island, in the latter of which the highly peculiar flora of tem-
perate Australia was developed. This is found to explain with
great exactness the remarkable absence from New Zealand of
all the most abundant and characteristic Australian genera, both
of plants and of animals, since these existed at that time only
in the western island, while New Zealand was in connection
with the eastern is'and alone and with the tropical portion of

CHAP, XXIY.] SUMMARY AND CONCLUSION, 511

it. From these geological and physical facts, and the known
powers of dispersal of plants, all the main features, and many of
the detailed peculiarities of the New Zealand flora are shown
necessarily to result.

Our last chapter is devoted to a wider, and if possible more
interesting subject—the origin of the European element in the
floras of New Zealand and Australia, and also in those of South
America and South Africa. This is so especially a botanical
question, that 1t was with some diffidence I entered upon it, yet
it arose so naturally from the study of the New Zealand and
Australian floras, and seemed to have so much light thrown
upon it by our preliminary studies as to changes of climate and
the causes which have favoured the distribution of plants, that
I felt my work would be incomplete without a consideration
of it. The subject will be so fresh in the reader’s mind that
a complete summary of it is unnecessary. I venture to think,
however, that I have shown, not only the several routes by
which the northern plants have reached the various southern
lands, but have pointed out the special aids to their migration,
and the motive power which has urged them on.

In this discussion, if no where else, will be found a complete
justification of that lengthy investigation of the exact nature of
past changes of climate, which to some readers may have
seemed unnecessary and unsuited to such a work as the present.
Without the clear and definite conclusions arrived at by that
discussion, and those equally important views as to the per-
manence of the great features of the earth’s surface, and the
wonderful dispersive powers of plants which have been so
frequently brought before us in our studies of insular floras,
I should not have ventured to attack the wide and difficult
problem of the northern element in southern floras,

In concluding a work dealing with subjects which have oc-
cupied my attention for many years, I trust that the reader who
has followed me throughout will be imbued with the conviction
that ever presses upon myself, of the complete interdependence
of organic and inorganic nature. Not only does the marvellous
structure of each organised being involve the whole past history

512 ISLAND LIFE, [PART II.

of the earth, but such apparently unimportant facts as the
presence of certain types of plants or animals in one island
rather than in another, are now shown to be dependent on the
long series of past geological changes—on those marvellous
astronomical revolutions which cause a periodic variation of
terrestrial climates—on the apparently fortuitous action of
storms and currents in the conveyance of germs—and on the
endlessly varied actions and reactions of organised beings on
each other. And although these various causes are far too
complex in their combined action to enable us to follow them
out in.the case of any one species, yet their broad results are
clearly recognisable ; and we are thus encouraged to study more
completely every detail and every anomaly in the distribution
of living things, in the firm conviction that by so doing we shall
obtain a fuller and clearer insight into the course of nature, and
with increased confidence that the “mighty maze” of Being
we see everywhere around us is “ not without a plan.”

INDEX.

. : ra ‘
j a 5
’ j ,
X ‘ ] / ‘ ts
} ' i
: ' —
i ‘ :
at ! “ ‘ / . ‘ }
' x ‘
‘ ho é
oat) - of } =
: i ~ : y |
, . 1
5 ’ \
1 ; ‘
i
‘ 1
, '
iy = t : ; .
I B
‘ al A 3 . £
i \
. ' = ‘ 1
t A ; *
,
i 5 !
H
i.
x % + \
’ .
I i
y 4 :
: a - 7
i !
ts i ’ oo
‘
,
‘
‘ -
t : ae x 2
1 7 . .
‘ 4

INDEX.

A,
Acacia, 179
Acacia “heter ophylla, 413
Acacia koa, 413
Acena in California, 495
Achatinelline, average range of, 304
Accipiter hawaii, 301
Ltigialitis sancte- helence, 294
Africa, characteristic mammalia of, 288
former isolation of, 390
Africa and Madagascar, relations of, 290
early history of, 391
African highlands as aiding the migration
of plants, 492
African reptiles absent from Madagascar,
3

Aggressive power of the Scandinavian flora,
479

Air and water, properties of in relation to
climate, 127
Alectorenas pulcherrimus, 402
Allen, Mr. J. A., on variation, 57
Allied species occupy separate areas, 449
Alpine plants, their advantages as colo-
nisers, 472
Alternations of climate in Switzerland and
North America, 117
Alternations of climate,
evidence of, 115
Amblyrhynchus cristatus, 269
Amazon, limitation of species by, 17, 18
American genera of reptiles in Madagascar,
389
Amphibia, dispersal of, 73
Amphibia of the Seychelles, 402, 403
introduced, of Mauritius, 409
of New Zealand, 454
Amphioxus, 62
Amydrus Tristramit, restricted range of, 15
Anas Wyvilliana, 301
Ancient continental islands, 238, 383
Ancient glacial epochs, 163
what evidence of may be expected, 169
Ancient groups in Madagascar, 392
Andersson, N. J., on the flora of the Galapa-
gos, 277
Andes, migration of plants along the, 488
Andromeda, 179
Angrecum sesquipedale, 411
Animal life, effects of glacial epoch on, 118
Animal life of Formosa, 373
Anoa depressicornis, 427
Antarctic continent as a means of plant-
dispersion, 489
Antarctic islands with perpetual snow, 131

paleontological

Antelones, overlapping genera of, 28
Antiquity of Hawaiian fauna and flora, 809
of land-shells, 76
of New Zealand, 494
of plants as affecting
persal, 80
Apera arundinacea, 471
Apium graveolens in New Zealand, 483
Apteryx, species of, 447
Arabis hirsuta on railway arch, 482
Archaic forms still existing, 221
Arctic and Antarctic regions, contrasts of,

their dis-

132
Arctic current, effects of a stoppage of,
145

Arctic plants in the southern hemisphere,
477

Arctic regions, mild climates of, 175
recent interglacial mild period in, 175
Arctic warm climates of Secondary and
Paleozoic times, 195
Areas of distribution, 13
separate and overlapping, 17
Ascension, former climate and productions
of, 292
Astronomical and geographical causes, com-
parative effects of, on climate, 200
Astronomical causes of change of climate,
2
of glaciation, 136
Atlantic isles, peculiar mosses of, 343
Atlantosaurus, the largest land-animal, 96
Atriplex patula on a railway bank, 483
Auchenia, 26
Austen, Mr. Godwin, on littoral shells in
deep water, 317
eae two sets of Northern plants in,

South European plants in, 491
Australia and South Africa, supposed con-
nection of, 493
ae ees birds absent from New Zealand,
53
Australian flora, general features of, 461
richest in temperate zone, 461
Lorine and derivative in the tropics,
2
its south-eastern and south-western
divisions, 463
Sir Joseph Hooker on, 463
geological explanation of, 464
its presence in New Zealand, 467
natural orders of wanting in New Zea-
land, 460
Australian orchides in China, 495

516 INDEX.

Australian genera of plants in India, 495
Australian plants absent from New Zealand,
458-460
none in north temperate zone, 405
running wild in Neilgherrie moun-
tains, 496
Australian region, definition of, 45
mammals and birds of, 46
gueireten seeds scattered in New Zealand,
47

Aylward, Captain, on glaciation of South
Africa, 157
Azores, 239
Azores, absence from, of large-fruited trees
or shrubs, 251
Azores, zoological features of, 240
birds of, 241
insects of, 244
beetles of, 245
land-shells of, 247
flora of, 248
Azores and New Zealand, identical plants
in both, 480
Azorean bird-fauna, origin of, 242
Azorean fauna and flora, deductions from,
253
Azorean plants, facilities for the dispersal
of, 251

Babirusa alfurus, 427
Badgers, 41
Bahamas contrasted with Florida, 5
Baker, Mr., on flora of Mauritius and the
Seychelles, 411
Bali and Lombok, contrasts of, 4
Banca, peculiar species of, 86)
Barbarea precox on railway bank, 482
Barn-owl, wide range of, 1
Barriers to dispersal, 71
Bats in Bermuda, 260
Bears of Europe and America, 14
Beaver of Europe and America, 14
Beetles of the Azores, 245
remote affinities of some of, 246
Beetles of the Galapagos, 273
of St. Helena, 286
of the Sandwich Islands, 305
Beetles, peculiar British species of, 332
Bell-birds, distribution of, 23
Bennett, Mr. A., on the vegetation of railway
panks, 482
Bentham, Mr. ., on the composite of the
Galapagos, 277
on the composite of St. Helena, 296
on the Mascarene composite, 416
on Sandwich Island composite, 308
Bermuda, 253
soundings around, 255
red clay of, 256
zoology of, 257
reptiles of, 257
birds of, 257
insects of, 260
land-mollusca of, 260
flora of, 261
Bermuda and Azores, comparison of bird-
faunas of, 258
Bernicla sandvichensis, 301
Biological causes which determine distri u-
tion, 500
Biological features of Madagascar, 888
Birchall, Mr. Edwin, on Isle of Man lepi-
doptera, 331
Birds as plant-dispersers, 79

Birds as seed-carriers, 250
ce to Great Britain and Japan,
common to India and Japan, 370
ranges of, 15
specific range of, 15
dispersal of, 73
of the Azores, 241
of Bermuda, 257
of Bermuda and Azores compared, 258
of the Galapagos, 270
of the Sandwich Islands, 301
peculiar to Britain, 320
of Borneo, 252
of Java, 357
of the Philippines, 361
of Japan, 368
peculiar to Japan, 369
peculiar to Formosa, 875
common to Formosa and India or Ma-
laya, 478
of Madagascar, and their teachings, 394
of Comoro Islands, 400
of the Seychelles, 401
of the Mascarene islands, 407
of islands east and west of Celebes, 425
of Celebes, 428
peculiar to Celebes, 429
of New Zealand, 447, 453
wingless, of New Zealand, 447
Blackburn, Mr. T., on the beetles of the
Sandwich Islands, 805
Blakiston and Pryer on birds of Japan,

3
Blanchard, M. Emile, on flora of Mada-
gascar, 411
Bland, My., on land-shells of Bermuda, 260
Blanford, Mr. W. T., on small effect - of
marine denudation, 218
Blocks, travelled and perched, 106
Blue magpies, range of, 15
Borneo, geology of, 350
mammalia of, 851
birds of, 352
insects and land-shells of, 355
affinities of fauna of, 855
Borneo and Asia, resemblance of, 6
Borneo and Java, 348

Boulder-beds of the carboniferous forma-

tion, 194
Boulder clays of east of England, 114
Bovide, 28
Brady, Mr, H.B., on habitat of globigerine,
0

Britain, probable climate of with winter in
aphelion, 151

British birds, range of, 34-88

British Columbia, interglacial warm periods
in, 118

British fauna and flora, peculiarities of,

345
British Isles, recent changes in, 313

proofs of former elevation of, 315

submerged forests of, 315

buried river channels of, 317

last union of with continent, 318

why poor in species, 318

peculiar birds of, 320

fresh-water fishes of, 321

peculiar insects of, 325

peculiar Lepidoptera of, 827

peculiar Coleoptera of, 332

peculiar Trichoptera of, 337

peculiar land and fresh- water shells of,
338

peculiarities of the flora of, 339

reculiar mosses and Hepatice of, 341

INDEX.

British mammals as indicating a zoological
region, 33

Buried river-channels, 317

Buteo solitarius, 801

Butterflies of Celebes, peculiar shape of, 483

Butterflies, peculiar British, 327.

Cc.

Caddis-flies peculiar to Britain, 337

Cecilia, species of, in the Seychelles, 404
wide distribution of, 404

Ceciliadex, 27

Callithea Lepriewri, 18

Callithea sapphira, 18

Camels as destroyers of vegetation, 285

Camels, former wide distribution of, 392

Camelus, 17, 26

Campanula vidalii, 252

Canis, 17, 25

Carabus, 42

Carboniferous boulder-beds, 194

Carboniferous warm Arctic climate, 195

Carnivora in Madagascar, 389

Carpenter, Dr., on habitat of globigerine,

Carpenter, Mr. Edward, on Mars and glacial
periods, 159
Carduus marianus in New Zealand, 483
Carpodacus purpureus and P. californicus, 66
Castor, 17
Casuarina, 179
Casuarina in India, 495
Cause of extinction, 61
Caves of Glamorganshire, 316
Cebibe, overlapping genera of, 28
Celebes, physical features of, 422
islands around, 424
zoology of, 426
derivation of mammals of, 427
birds of, 428
not a continental island, 481
insect pecularities of, 432
Himalayan types in, 433
peculiarity of butterflies of, 433
list of land-birds of, 486
Centetide, 26
Centetide, formerly inhabited Europe, 391
Central America, 52
Ceratodus, or mud-fish, 67
Cervus, 17, 25
Chalk a supposed oceanic formation, 87
Chalk at Oahu, analysis of, 88
Chalk, analysis of, 89
Chalk mollusca indicative of shallow water,
90
Chalk sea, extent of, in Europe, 91
Chalk-formation, land-plants found in, 92
deposited in a shallow sea, 92
of Faxoe an ancient coral-reef, 92
modern formation of, 93
supposed oceanic origin of erroneous,
4

“Challenger” soundings and shore-deposits,
84

‘Challenger ” ridge in the Atlantic, 98
Chameleons very abundant in Madagascar,
402

Chamois, distribution of, 13
Changes of land and sea, 81
Chasmorhynchus, distribution of, 28
C. nudicollis, 24

C. tricarunculatus, 24
C. variegatus, 24
Chilomenus lunata, 289
Chinchillas, 26

517

Chrysochloride, 29
Cicindela, 17
Cicindelide common to South America and
Madagascar, 27
Climate affected by arrangement of the
great continents, 198
astronomical causes of changes of, 122
causes of mild Arctic, 183
changes of, during ‘Tertiary and
Secondary Periods, 196
changes of, as affecting migration of
plants, 485
Climate, nature of changes of, caused by
high excentricity, 223
exceptional stability of the present, 224
of Britain with winter in aphelion, 151
of Tertiary period ,in Europe and
N. America, 171
Climates of Tertiary and Secondary periods,
5

Climate of the Secondary and Paleozoic
epochs, 193, 195
Climate, properties of snow and ice in re-
lation to, 127
Climatal changes, 1038
Climatal change, its essential principle re-
stated, 153
Climatal changes as modifying organisms,
220, 222.
Clouds cut off the sun’s heat, 140
Coal in Sumatra, 358
Coast line of globe, extent of, 214
Cochoa, distribution of, 25
Cold alone does not cause glaciation, 130
how it can be stored up, 128
Coleoptera of the Azores, 245
of St. Helena, 286
of the Sandwich Islands, 305
peculiar British species of, €32
Comoro Islands, 399
mammals and birds of, 400
Composite of the Galapagos, 277
of St. Helena, 295
of the Sandwich Islands, 308
of the Mascarene Islands, 416
species often have restricted ranges, 473
Conclusions on the New Zealand flora,
ATA
Contemporaneous formation of
Greensand and Wealden, 213
Continental conditions throughout geo-
logical time, 94—97
changes and animal distribution, 99
extensions will not explain anomalous
facts of distribution, 420
Continental Islands, 235
of recent origin, 312
general remarks on recent, 330
Continental period, date of, 318
Continents, movements of, &6
permanence of, 94
general stability of, 99, 101
geological development of, 198
Continuity of land, 72
Continuity of now isolated groups, proof of,
69

Lower

Cook, Captain, on a native quadruped in
New Zealand, 446

Cope, Professor, on the Bermuda lizard,
257

Coracias temminckii, 433

Corvus, 17

Cossonide, in St. Helena, 287

ere ao etae deposits in North Australia, 462,
5

Cretaceous flora of Greenland, 179

Croll, Dr. James, on Antarctic icebergs, 182

518

Croll, Dr. James, on winter temperature of
Britain in glacial epoch, 135
on diversion of gulf-stream during the
glacial epoch, 1388
on loss of heat by clouds and fogs, 140
on geographical causes as affecting
climate, 143
on ancient glacial epochs, 164
on universality of glacial markings in
Scotland, 167
on mild climates of Arctic regions, 175
on ocean-currents, 183, 197
on age of the earth, 206
omeee thickness of sedimentary rocks,
2
on small amount of marine denudation,
218 :
on buried river-channels, 317
Ctenodus, 67
Cyanopica, distribution of, 23
Cyanopica cooki, restricted range of, 15, 23
Cyanopica cyanus, 23
Cynopithecus nigrescens, 427

Dacelo, 46
Dana on continental upheavals, 86
on chalk in the Sandwich Islands, 88
on elevation of land causing the glacial
epoch, 147
on elevation of Western America, 188
on the development of continents, 198
on shore-deposits, 215
on life extermination by cold epochs,
22
Darwin’s experiment on Helix pomatia, 76
experiments on seed-dispersal, 249
theory of formation of atolls, 397
Darwin, on the permanence of oceans, 97
on cloudy sky of Antarctic regions, 141
on glaciers of the Southern Andes, 142
on geological time, 204
on complex relations of organisms, 219
on seeds carried by birds, 250
on natural history of the Keeling
Islands, 275
on cultivated plants not running wild,
476

De Candolle on dispersal of seeds, 78

Deep-sea deposits, 211

Delphinium ajacis, on a railway bank, 483

Dendreca, 18

D. cerulea, 18

D. discolor, 18

D. dominica, 18

Dendreca coronata, variation of, 57

Dendrophide, 27

Denudation destroys the evidences of glacia-
tion, 166

Denudation and deposition as a measure of
time, 206

Denudation in river basins, measurement of,
208

Denudation, marine as compared with sub-
aerial, 218

Deposition of sediments, how to estimate
the average, 214

Deserts, cause of high temperature of, 128

Diagram of excentricity and precession, 124

Diagram of excentricity for three million
years, 165

Didide, how exterminated, 407

Didunculus, keeled sternum of, 408

Diospyros, 179

Diplotaxis muralis, on railway banks, 481

INDEX.

Dipnoi, discontinuity of, 67

Dipterus, 67

Discontinuous generic areas, 23
Discontinuity among North American birds,

Discontinuity a proof of antiquity, 67
Discontinuous areas, 63
why rare, 63
Dispersal of animals, 70
of land animals, how effected, 74
Dispersal of seeds by wind, 78
by birds, 79
by ocean-currents, 79
along mountain-chains, 79
Dispersal of Azorean plants, facilities for,
25
Distribution, changes of shown by extinct
animals, 100
how to explain anomalies of, 392
Drontheim mountains, peculiar mosses of,
343
Dobson, Mr., on bats of Japan, 366
on the affinities of Mystacina tuberculata,
445
Dodo, the, 407
aborted wings of, 408
Dryiophide, 27
Rome Professor, on lizards of Bourbon,
0

Dunean, Professor P. M., on ancient sea of
central Australia, 465

Early history of New Zealand, 455

Earth’s age, 203

East Asian birds, range of, 38

East and West Australian floras, geological
explanation of, 464

Echidna, 30

Echimyide, 26

Elevation of North America during glacial
period, 149

causing diversion of gulf-stream, 149

Emberiza scheniclus, discontinuity of, 64

E. passerina, range of, 65

E. ‘pyrrhulina, 65

Endemic genera of plants in Mauritius, &c.,
413

Endemic genera of plants in New Zealand,
49

English plants in St. Helena, 286
Environment, change of as modifying or-
ganisms, 219
Hriocaulon septangulare, 340
Ethiopian Region, definition of, 42
birds of, 43
Ettinghausen, Dr., on Australian plants in
England, 486
Eucalyptus, 179
Eucalyptus and Acacia, why not in New
Zealand, 475
Eucalyptus in Eocene of Sheppey, 486
Eupetes, distribution of, 25
Europe, Asia, &c., as zoological terms, 31
European birds, range of, 16
European birds in Bermuda, 259
European occupation, effects of
Helena, 283
European plants in New Zealand, 477
in Chile and Fuegia, 489
Everett, Mr., on raised coral-reefs in the
Philippines. 362
Evolution necessitates continuity, 68
Excentricity and precession, diagram of,
24

in Sf.

INDEX.

Excentricity, variations of during three mil-
lion years, 164

Excentricity a test of rival theories of cli-
mate, 165

Excentricity, high, its effects on warm and
cold climates, 192

Explanation of peculiarities of the fauna of
Celebes, 431

Extinct animals showing changes of distri-
bution, 100

Extinct birds of the Mascarene Islands, 407

of New Zealand, 447
Extinction caused by glacial epoch, 119

Families, restricted areas of, 28
distribution and antiquity of, 66
Fauna and flora, pecularities of British, 345
Fauna of Borneo, affinities of, 355
of Java, 356, 357
of Java and Asia compared, 358
Faunas of Hainan, Formosa, and Japan
compared, 379
Felis, 17, 25
Ferns, abundance of in Mascarene flora, 416
Ficus, 179
Fire-weed, the, of Tasmania, 481
Fisher, Rev. O., on temperature of space,
126
Fishes, dispersal of, 73
peculiar British, 321
cause of great speciality in, 323
mode of migration of freshwater, 324
freshwater, of New Zealand, 454
Floating islands and the dispersal of ani-
mals, 72
Flora of the Azores, 248
of Bermuda, 261
of the Galapagos, 276
of St. Helena, 294
of the Sandwich Islands, 305; peculiar
features of, 3806
pecularities of the British, 339
of Madagascar and the Mascarene
Islands, 410
of Madagascar and South Africa allied,
416

Flora of New Zealand, 457
very poor, 458
its resemblance to the Australian, 459
its differences from the Australian, 459,
460

origin of Australian element in, 467
tropical character of explained, 469
summary and conclusion on, 474
Floras of New Zealand and Australia,
summary of conclusion as to, 510
Florida and Canada, resemblances of, 5
and Bahamas, contrasts of, 5
Fogs cut off the sun’s heat in glaciated
countries, 140
Forbes, Mr. D., analysis of chalk, 89
Former continuity of scattered groups, 68
Formosa, 371
physical features of, 372
animal life of, 373
list of mammalia of, 874
list of land-birds peculiar to, 875
Forests, submerged, 315
Freezing water liberates low-grade heat,
140
Fresh-water deposits, extent of, 94, 95
Fresh-water organisms absent in St. Helena,
293
snail peculiar to Ireland, 338

519

Fresh-water fishes of the Seychelles 403
Frogs of the Seychelles, 403
of New Zealand, 454
Fuegia, European plants in, 489
Fulica alai, 301

Galapagos, absence of mammalia and am-
phibia from, 268
reptiles of, 268
birds of, 270
insects of, 273
land-shells of, 274
flora of, 276
Galapagos Islands, 265
and Azores contrasted, 279
Galbula cyaneicollis, 17
rufoviridis, 17
viridis, 17
Galeopithecus, 62
Gallinula sandvichensis, 301
Gardner, Mr. J. S., on Tertiary changes of
climate, 197
Garrulus, distribution of species of, 20
Garrulus glandarius, 20, 22, 65
. cervicalis, 21
krynicki, 21
. atricapillus, 21
. hyrcanus, 21
. brandti, 21, 22
. lanceolatus, 21
. bispecularis, 21
. sinensis, 21
. taivanus, 22
G. japonicus, 22, 65
G. lidthi, 22
Geikie, Dr. James, on interglacial deposits,
118
on age of buried river-channels, 317
Prof, A., on stratified rocks being found
near shores, 84, 85
on formation of chalk in shallow water,
94
on permanence of continents, 101
on variation in rate of denudation,
167
on the rate of denudation, 207
on small amount of marine denudation,
218
Genera, extent of, 17
origin of, 60
rise and decay of, 62
Generic areas, 16
Generic and Family distribution, 25
Genus, defined and illustrated, 16
Geographical change as a cause of glacia-
tion, 143
changes, influence of, on climate, 146,
147
changes, effect of on Arctic climates,
188

ARRAAARAAD

changes of Java and Borneo, 359
changes as modifying organisms, 220
Geological change, probably quicker in

remote times, 216

changes as aiding the migration of
plants, 487

climates and geographical conditions,
197

climates as affecting distribution, 502
climates, summary of causes of, 502
time, 203

time, value of the estimate of, 217
time, measurement of, 226

time, summary of views on, 505

520 INDEX.

Geology of Borneo, 350
of Madagascar, 384
of Celebes, 422
of New Zealand, 443
of Australia, 465
Geomalacus maculosus, 333
Glacial climate not local, 112
deposits of Scotland, 109
Glacial epoch, proofs of, 104
effects of on animal life, 113
alternations of climate during, 114
as Causing migration and extinction, 119
causes of, 121
the essentials to the production of, 130
probable date of the, 155
and the climax of continental develop-
ment, 199
date cf last, 225
Glacial phenomena in North America, 112
Glaciation was greatest where rainfall is
now greatest, 134
Glaciation, summary of chief causes of, 189
in Northern Hemisphere, the only
efficient cause of, 148
of New Zealand and South Africa, 157
local, due to high éxcentricity, 199
widespread in recent times, 504
Gleichenia in Greenland, 179
Globigerina-ooze, analysis of, 89
in relation to chalk, 87
Globigeringz, where found, 89, 90
Glyptostrobus, 179
Goats, destructiveness of, in St. Helena, 285
Gaye Mr., on birds reaching the Azores,
2
Godenia, 179
Great Britain and Japan, birds common to,

Greene, Dr. J. Reay, on chameleons in
Bourbon and Mauritius, 406

Greenland, loss of sun-heat by clouds in,
141

an anomaly in the Northern Hemi-
sphere, 149
Miocene flora of, 177
Cretaceous flora of, 179
flora of ice-surrounded rocks of, 450
Grinnell Land, fossil flora of, 178
Guernsey, peculiar caddis-fly in, 337
Gulick, Rev. J. T., on Achatinelline, 304
Giuther, Dr., on peculiar British fishes, 321
on lizards in the London Docks, 402

Haast, Dr., on otter-like mammal in New
Zealand, 446
on Kauri-tree in Cretaceous beds of New
Zealand, 468
Habitability of globe due to disproportion
of land and water, 201
Haplothorax burchellii, 288
Hartlaub, Dr., on ‘‘ Lemuria,” 394, 409
Hatteria punctata, 454
Haughton, Professor, on heat carried by
ocean-currents, 187
comparison of Miocene and existing
climates, 190
on geological time, 204, 216
on thickness of sedimentary rocks, 212
Hawaiian fauna and flora, antiquity of, 309
Heat and cold, how dispersed or s‘ored up,
128
Heat required to melt snow, 129
evolved by frozen water, its nature and
effects, 140

Heat cut off by cloud and fogs, 140

Hector, Dr., on ancient flora of New Zea-
land, 467

on Triassic and Jurassic flora of New

Zealand, 494

Hecr, Professor, on chalk sea in Central
Europe, 91

Helianthemum breweri, 389

Heliodus, 68

Helix, 17

Hemiptera of St. Helena, 292

Hepatice, peculiar British, 342

non-European geneva of in Britain, 343

Hesperomys, 25

Hesperornis allied to ostriches, 451

Hieracium iricwm, 339

High land essential to the production of a
glacial epoch, 130

Himalayan birds and insects in Celebes,
433

Hippopotamus in Yorkshire as proving a
mild climate, 115—117

Hirundo, 25

Hochstetter on the aquatic mammal of New
Zealand, 446

ae speic! Joseph, on the Galapagos flora,
O77

(
on affinities of St. Helena plants, 295
on the flora of New Zealand, 457
on proportion of temperate and tropical
Australian floras, 461
on current of vegetation from north to
south, 478
on supposed occurrence of Australian
plants in England in the Tertiary
period, 486
Humming-birds, restricted ranges of, 16
Hutton, Captain, on struthious birds of New
Zealand, 449
Huxley, Professor, on geological time, 204
on European origin of African animals,
890
Hyalina Bermudensis, 260
circumfirmata, 260
discrepans, 260
Hyomoschus, 27
Hyracoidea, restricted range of, 29

Ice-action, what evidences of during the
Tertiary period, 171
indications of ancient, 194
Ice-borne rocks, a test of a glacial epoch,
170
in Miocene of N. Italy, 171
in Eocene of Alps, 172
in Eocene of Carpathians and Apennines,
172
absence of, in English and N. American
Tertiaries, 174
Ice-cap, why improbable or impossible, 156
Tceland, a continental island, 421
Icteride, 49
Tguanide, 49
Indian birds in Formosa, 378
Indian ocean as a source of heat in Tertiary
times, 186
Indian genera of plants in Australia, 462
Indicator, distribution of, 25
Insectivora in Madagascar, 389
Insects, dispersal of, 75
of the Miocene period, 75
restriction of range of, 75
of the Azores, 244
of Bermuda, 286

INDEX.

521

Insects of the Galapagos, 273
of the Sandwich Islands, 305
peculiar British, 325
of Celebes, peculiarities of, 482
Insular faunas, summary of conclusions as
to, 507, 510
Interglacial warm periods on the continent
and in North America, 117
Interglacial periods and their probable
character, 147
Interglacial periods will not occur during an
epoch of extreme glaciation, 150
Interglacial climates never very warm, 154
Ireland, poverty of, in reptiles, 319
in plants, 820
Ireland, peculiar fishes of, 321, 823
Ireland, plants of not found in Great
Britain, 340
Islands, classification of, 234
importance of, in study of distribution,
233
Islands, remote, how stocked with plants
and animals, 2538
Islands submerged between Madagascar and
India, 396
Isle of Man, peculiarities of Lepidoptera of,
331

Isle of Wight, peculiar beetle of, 886
Isatis tinctoria, on railway bank, 481
Italian sparrow, restricted range of, 15
Ithaginis, 26

Japan birds in distant areas, 370
Japan, zoological features of, 265
mammalia of, 865
birds of, 868
birds peculiar to, 369
Japan and Formosa, 363
Java, fauna of, 356
Asiatic species in, 358
past history of, 359
Java and Borneo, past changes of, 3859
Jays, distribution of species of, 20
Jays of Europe and Japan, 65
Jeifreys, Dr. Gwyn, on shallow-water mol-
lusca in chalk, 90
on fossil shallow-water shells in deep
water, 318
Jones, Mr., on red clay of Bermuda, 256
on migration of birds to Bermuda, 259
on vegetation of the Bermudas, 261
Juan Fernandez, flora and fauna of, 276
Judd, Prof. J. W., on absence of glaciation
in east Europe, 135
on glaciation of the Alps produced by
elevation, 173
Juniperus barbadensis, 262
Jura, travelled blocks on, 107
Jurassic warm Arctic climate, 195

Keeling Islands, animals of, 274

Kirk, Mr. T, on temporary introduced
plants, 483

Knowledge of various kinds required for
study of geographical distribution,
7, 9

Lagopus scoticus, 320
Land as a barrier to ocean-currents, 145

Land and sea, changes of, 81
how changes of affect climate, 148, 144!
Land and water, disproportion of renders
globe habitable, 201
Land-birds of Celebes, list of, 486
Land-connection, how far necessary to dis-
persal of mammals, 72
Land-shells, great antiquity of, 76
universal distribution of, 77
causes favouring the abundance of, 77
Land-shells of the Azores, 247
of Bermuda, 250
of the Galapagos, 274
of St. Helena, 292
of the Sandwich Islands, 303
of the Seychelles, 405
Laurus canariensis, 251
Leguat on the Solitaire, 407
Leguminose, abundance of in Australia,
460

“Lemuria,” a supposed submerged conti-
nent, 394-399
Lemurs in Madagascar, 388
Leopard, enormous range of, 14
Lepidoptera, list of peculiar British, 327
Lepidoptera of the Isle of Man, 331
Lepidosiren, 62
Lepidosiren paradoxa, and L. annectens, 67
Lepidosternide, 27
Limestone as indicating change of sea and
land, 83
Limneea involuta, 338
Linaria purpurea, on railway bank, 482
Liopelma hochstetteri, 454
Liotrichide, 29
List of the land-birds of Celebes, 426
Lizards of the Galapagos, 269
local variation of colour of, 403
Lizard peculiar to the Mascarene Islands,
410

Lizards of New Zealand, 454
Lobeliaceez, abundance of in the Sandwich
Islands, 308
Locality of a species, importance of, 12
Loddigesia mirabilis, rarity of, 16
Lord, Mr., on species of Urotrichus, 366
Low-grade and high-grade heat, 140
Lowlands nowhere covered with perpetual
snow, 131
Lundy Island, peculiar beetles of, 326
Lyell, Sir Charles, on permanence of conti-
nents, 82
on calcareous mud, 88
on the distribution of chalk, 91
on geographical causes as modifying
climate, 143
on estimate of geological time, 203
st classification of sedimentary rocks,
09
Lynxes, 41

McLachlan, Mr., on peculiar British caddis-
flies, 827, 837

Madagascar, physical features of, 884
former condition of, 386
biological features of, 388
mammalia of, 388
reptiles of, 389
relation of to Africa, 390
early history of, 391
birds of in relation to ‘‘ Lemuria,” 394
conclusion on faunaand flora of, 417
great antiquity of, 417

Madagascar and Africa, contrast of, 6
relations of, 390

522 INDEX.

Maillard on animals of Bourbon, 406
Malay Islands, local peculiarities of flora in,
180

past history of, 362
Malayan birds in Formosa, 378
Mammalia of East Asia, range of, 33
of North Africa, range of, 34
of Britain, poverty of, 319
of Borneo, 351
of Java, 356
of the Philippines, 361
of Japan, 305
of Formosa, 374
common to Formosa and India, 375
of Madagascar, 388
of Comoro Islands, 400
of Celebes, 427; whence derived, 428
of New Zealand, 444
Mann, Horace, on the flora of the Sandwich
Islands, 806
Maori legend of origin of the forest-rat, 445
Maoris, their accounts of the moa, 448
Map of the old Rhone glacier, 107
Maps of North and South Polar Regions,
133
Map of the Azores, 239
of Bermuda, 254
of the Galapagos, 266, 267
of the South Atlantic Ocean, 282
of the Sandwich Islands, 299
of the North Pacific with its submerged
banks, 300
of British Isles and the 100-fathom
bank, 314
of Borneo and Java, 349
of Japan and Formosa, 364
physical, of Madagascar, 385
of the Madagascar group, 387
of the Indian Ocean, 396
of Celebes, 423
of sea-bottom around New Zealand, 443
of Australia in Cretaceous period, 466
Marcou, Professor Jules, on the pliocene and
glacial epochs, 226
Marmot, range of, 15
Mars as illustrating glacial theories, 158,
162
Mars, no true ice-cap on, 160
Marsupials, range of, 29
Marsh, Prof. O. C., on the Atlantosaurus,
96
on Hesperornis, 451
Marsh, Mr., on camels as desert-makers,
285

Mascarene Islands, 399, 409
Mascarene plants, curious relations of, 412
endemic genera of, 413
Mascarene flora, fragmentary character of.
414
abundance of ferns in, 416
Mauritius, Bourbon, and Rodriguez, 405
Measurements of geological time, 226
agreement of various estimates of, 227
concluding remarks on, 2238
Medicago sativa in New Zealand, 483
Megalemide, 27
Meleagris, 49
Melilotus vulgaris on railway banks, 481
Meliphagide, 46
Melliss, Mr., on the early history of St.
Helena, 284
Melospiza melodia, variation of, 57
Merycotherium, 119
Meteorological causes as intensifying glacia-
tion, 187-139
Migration caused by glacial epoch, 119

Migration of birds to Bermuda, 258
of plants from north to south, 480
of plants and alterations of snow line,
484

of plants due to changes of climate, 485
of plants from north to south, long
continued, 486
of Biante aided by geological changes,
487
of plants by way of Himalayas and
South Asia, 491
of plants by way of the Andes, 488
of plants through Africa, 492
Mild Arctic climates, str atigraphical evi-
dence of, 181
causes of, 183
dependent on geographical changes, 184
effects of high excentricity on, 191
summary of causes of, 503
Miocene Arctic flora, 176
Miocene flora of Europe, 117
Miocene or Eocene floras, 178
Miocene deposits of Java, 359
Miocene fauna of Europe and North India,
3} 390
Mississippi, matter carried away by, 166
Mitten, Mr. William, on peculiar British
mosses and hepatice, 341
on temporary appearance of plants, 481
Mniotiltide, 48
Mnium, peculiar species of in the Drontheim
mountains, 434
Moas of New Zealand, 447
Mollusca, dispersal of, 76
Monotremata, restricted range of, 29
Moraines, 105
of Ivrea, 112
Morgan, Mr. C. Lloyd, on thickness of for-
mations not affected by denudation,
218
Moseley, Mr. H. N., on seeds carried by
birds, 250
on the flora of Bermuda, 262
Mosses, peculiar British, 341
non-European genera of in Britain, 342
how diffused and why restricted, 344
Mt. St. Elias, why not ice-clad, 149
Mountain chains aiding the dispersal_ of
plants, 79
as aids to migration of plants, 480
Munia brunneiceps, 433
Mus, 17, 25
Murray, Mr. J., on oceanic deposits, 84
on chalk-like globigerina-ooze, 90
Mygale pyrenaica, range of, 15
Myrica faya, 251
Myialestes helianthea, 483
Myrsine, 179

Nares, Capt. Sir G., on snow and ice in
high latitudes, 130
on abrupt elevation of Bermuda, 255
Nearctic Region, definition of, 47
mammalia of, 47
birds of, 48
reptiles of, 49
Nectarinea osea, restricted range of, 15
Neilgherries, Australian plants naturalized
in, 496
Neotropical Region, definition of, 50
low types of, 51
Nevill, Mr. Geoffrey, on land-shells of the
Seychelles, 405
on destruction of Seychelles flora, 415

INDEX. 523

New species, origin of, 55

Newton, Mr. E., on short wings of the Sey-
chelles dove, 408

Newton, Professor, on recently extinct birds,

Newts, restricted range of, 30
New Zealand, recent glaciation of, 157
New Zealand, 442
geology of, 443
form of sea-bottom around, 443
zoological charicter of, 444
mammalia of, 444
wingless birds of, 447
European plants in, 447
past changes of, 448
winged birds. and lower vertebrates of,
4538
deductions from pecularities of fauna of,
4

period of its union with N. Australia,
454
the flora of, 457
route of Arctic plants to, 490
endemic genera of plants in, 494
great antiquity of, 494
Nordenskjéld, Prof.,on absence of perpetual
snow in N. Asia, 131
on Sout milder climate in Spitzbergen,
17
on former Polar climates, 181
on geology of Spitzbergen, 182
North America, glacial phenomena in, 112
interglacial warm periods in, 117
condition of in Tertiary period, 187
Northern genera of plants in S. temperate
America, 489
hemisphere, absence of southern plants
from, 495
flora, hardiness of, 496

Oceanic islands a proof of the permanence
of oceans, 97
Oceanic and continental islands, 234
Oceanic islands, 235, 238
—the Azores, 239
general remarks on, 310
Ocean-currents as carriers of plants, 79
as affecting interglacial periods, 148
as determining climate, 149
effects of in Tertiary times, 190
Ocean, Darwin on permanence of, 97
Octodontide, 26
Cininghen, Miocene flora of, 177
Gnanthe fluviatilis, 839
Gnothera odorata, on arailway bank, 483
Oliver, Professor, on peculiar Bermudan
plants, 262
Operculata, scarcity of in the Sandwich
Islands, 304
eee peers temporary appearance of,
2

rae species have restricted ranges,
73

Orchids, abundance of, in Bourbon and
Mauritius, 416
why almost universal in the tropics, 417
Orders, distribution of, 29
Organic change dependent on change of
conditions, 218
Oriental Region, definition of, 43
mammals and birds of, 44
reptiles of, 45
insects of, 45
Origin of new species, 55, 59

Ovigin of new genera, 60

of the Galapagos flora, 277

of the beetles of St. Helena, 289

of Australian element in the New

Zealand flora, 467

Orkney, peculiar fishes of, 321, 323
Orthonyx not a New Zeajand genus, 453
Osprey, wide range of, 15
Ostriches, 28
Otter-like mammal in New Zealand, 446
Overlapping and discontinuous areas, 28

Pachyglossa aureolimbata, 488
Palearctic Region, limits of, 39
characteristic features of, 40—42
Paleozoic formations, depth of,
London, 211
Palm confined to Round Island, 415
Panax, 179
Papilio, 17
Paraguay, no wild horses or cattle in, 219
Parnassius, 41
Parus ater, 19
. borealis, 19, 64
britannicus, 321
camtschatkensis, 19
cinctus, 20
. ceruleus, 19
cyaneus, 19
cristatus, 20
ledouci, 19
lugubris, 2)
major, 19
palustris, 19
palustris, discontinuous area of, 64
rosea, 821
P. tenerife, 19
Passeres of the Sandwich Islands, 302
Past changes of New Zealand, 448
Patula Reiniana, 260
Payer, Lieut., on evaporation of ice during
the Arctic summer, 135
Petroselinum segetum on railway bank, 482
Perodicticus, 26
Permian formation, indications of ice-action
in, 193
Permanence of continents, summary of
evidence for, 101
Pennula millei, 301
Pengelly, Mr., on submerged forests, 315
Peculiar fauna of New Zealand, deductions
from, 454
Philippine Islands, 361
recent additions to fauna of, 361
past history of, 361
Phryniscide, 27
Phyllodactylus galapagensis, 269
Phylloscopus borealis, range of, 15
Physical causes which determine distribu-
tion, 500
features of Formosa, 372
Pinus abies in Grinnell Land, 178
Pica, 17
Pickering, Dr., on the flora of the Sandwich
Islands, 806
on families absent from the Sandwich
Islands, 306
on temperate forms on mountains of the
Sandwich Islands, 307
Pithecia monachus, 18
P. rufibarbata, 18
Pitta, distribution of, 25
Plants, dispersal of, 77
seeds of, adapted for dispersal, 78

round

roth yatta hy yh

524

Plants, wide range of species and genera of,
178
poverty of, in Ireland, 320
peculiar British, 339
of Ireland not in Great Britain, 340
cause of their wide diffusion and narrow
restriction, 345
how they migrate from north to south,
480
of existing genera throughout the
Tertiary period, 488
southern migration of, by way of the
Himalayas, 491
southern migration of, through Africa,
492
endemic genera cof, in New Zealand, 494
Plestiodon longirostris of Bermuda, 257
Platypus, 29
Po, matter carried away by, 166
Podargus, 46
Poinciana regia, 411
Populus, 179
Pourtales, Count, on modern formation of
chalk, 93
on sedimentary deposits in Gulf of
Mexico, 215
Poverty in species of Britain, 318
Precession of Equinoxes, influence of on
climate, 123
Preservation of species, 62
Proboscidea, range of, 29
Proteus, 62
Psophia, range of species of, 18
Pteroptochide, 29
Pyrenean ibex, restricted range of, 15

Railways, new plants on, 481
Ramsay, Professor, on ancient land surfaces,
97

on geological time, 205
on thickness of sedimentary rocks, 212
Rat, native, of New Zealand, 445
Rats in the Galapagos, 268
Rate of organic change usually measured
by an incorrect scale, 225
Raven, wide range of, 15
Reade, T. Mellard, on changes of sea and
land, 82
Recent continental islands, 235
Red clay of Bermuda, 256
Reptiles, dispersal of, 73
of the Galapagos, 268
of the Sandwich Islands, 303
cause of scarcity of, in British Isles, 319
of Madagascar, 389
of the Seychelles, 402
of Mauritius and Round Island, 409
of New Zealand, 453
Rhodolena altivola, 411
Rhus toxicodendron, 262
River-channels, buried, 317
Roches moutonnées, 104
Rodents in Madagascar, 389
Rosa hibernica, 3389
Round Island, a snake and a palm peculiar
to, 410, 415
Rumex pulcher, in New Zealand, 483
Rye, Mr. E. C., on peculiar British insects,
825, 832, 335

St. Helena, 280
effects of European occupation on the
vegetation of, 283

INDEX.

St. Helena, insects of, 286
land-shells of, 292
absence of fresh-water organisms in, 293
native vegetation of, 294

Salvi Mr., on the birds of the Galapagos,

Sandwich Islands, the, 298

zoology of, 301

birds of, 301

reptiles of, 303

land-shells of, 303

insects of, 305

vegetation of, 305

antiquity of fauna and flora of, 809
Sassafras, 179
Scandinavian flora, aggressive power of, 479
Scientific voyages, comparative results of, 7
Sciurus, 25
Sclater, Mr. P. L., zoological regions of, 32,

39
Scotland, glacial deposits of, 109-112
probable rate of denudation in, 167
Miocene flora of, 178
peculiar fishes of, 321
Scotophilus tuberculatus, 445
Scrophularinez, why few species are com-
mon to Australia and New Zealand,
474
Sea, depth of around Madagascar, 894
depth of around Celebes, 422
Sea-bottom around New Zealand and Aus-

tralia, 443
Sea-level, changes of, dependent on glacia-
. tion, 155
complex effeets of glaciation on, 157,
158

rise of, a cause of denudatior, 168
Seas, inland in Tertiary period, 185
Section of sea-bottom near Bermuda, 255
Sedges and grasses common to Australia
and New Zealand, 472
Sedimentary rocks, how to estimate thick-
ness of, 209
thinning out of, 210
how formed, 211
thickness of, 209, 212
summary of conclusions on the rate oi
formation of the, 214, 506
Seebohm, Mr., on Parus palustris, 64
on Emberiza scheniclus, 65
on snow in Siberia, 161
on birds of Japan, 368
Seeds, dispersal of, 248
carried by birds, 250
Senecio australis, on burnt ground, 481
Sericinus, 42
Seychelles Archipelago, 400
birds of, 401
reptiles and amphibia of, 402
fresh-water fishes of, 405
land-shells of, 405
Sharp, Dr. D., on peculiar British beetles,
825

Shells, peculiar to Britain, 338
Shetland Isles, peculiar beetle of, 336
Shore deposits, 88, 211
proving the permanence of continents,
94, 95
distance from coast of, 214
Siberia, amount of snow and its. sudden
disappearance in, 135
Silurian boulder-beds, 194
warm Arctic climate, 195
Simiidae, 27
Sisyrinchium bermudianum, 262
Skertchley, Mr., on four distinct boulder
clays, 114

INDEX.

525

Slug peculiar to Ireland, 338
Snakes of the Galapagos, 269
of the Seychelles, 403 i
Snake peculiar to Round Island, 410
Snow and ice, properties of, in relation to
climate, 127
Snow, effects of on climate, 128
quantity of heat required to melt, 129
often of small amount in high latitudes,
130
never perpetual on lowlands, 181
conditions determining perpetual, 134
maintains cold by reflecting the solar
heat, 139
Snow-line, alterations of, causing migration
of plants, 484
Sollas, Mr. J. W., on greater intensity of
telluric action in past time, 216
South Africa, recent glaciation of, 157
many northern genera of plants in, 492
its supposed connection with Australia,
493
Southern plants, why absent in the Northern
Hemisphere, 495
South American plants in New Zealand, 494
South Temperate America, 52
climate of, 142
earn flora, comparative tenderness of,
49
Space, temperature of, 125
Specialisation antagonistic to diffusion of
species, 474
Species, extinction of, 61
rise and decay of, 62
epoch of exceptional stability of, 225
dying out and replacement of, 380
preservation of, in islands, 381
Specific areas, 14
Spiranthes romanzoviana, 340
Spitzbergen, Miocene flora of, 177
absence of boulder-beds in, 181
Stability of extreme glacial conditions, 153
Stainton, Mr. H. T., on peculiar British
moths, 825-330
Stanivoi mountains, why not ice-clad, 149
Starlings, genera of in New Zealand, 453,
456

Stellaria media, temporary appearance of,
483

Sternum, process of abortion of keel of, 408

Stow, Mr. G. W, on glacial phenomena in
South Africa, 157

Stratified rocks formed near shores, 83, 85

deposits, how formed, 211
Striated rocks, 104
blocks in the Permian formation, 193

Strix flammea, 15

Struthiones, 31

Struthious birds of New Zealand as indicat-
ing past changes, 449

Stylidium, 179

Submerged forests, 815

Subsidence of isthmus of Panama, 146

Sumatra, geology of, 359

Sweden, two deposits of ‘‘ till” in, 117

Swimming powers of mammalia, 71

Swinhoe, Mr. Robert, researches in Formosa,
372

Switzerland, interglacial warm periods in,

Sylviade, overlapping genera of, 28

; T.

Talpide, 41

Tapirs, distribution of, 24
former wide range of, 393

Tarsius, 62 .
Tarsius spectrum, 427
Tasmania and North Australia, resemblance
of, 5
route of Arctic plants to, 490
Taxodium distichum in Spitzbergen, 177

‘Temperate climates in Arctic Regions, 175

Australian genera of plants in New
Zealand, 470
Australian species of plants in New
Zealand, 471
Temperature, how dependent on sun’s dis-
ance, 125,
of space, 125
monary glacial epochs, evidence against,
5)

warm climates, continuous, 182
Test of glaciation at any period, 169
Testudo abingdonit, 268
T. microphyes, 268
Tetraogallus, distribution of, 24
Thais, 42
pee Sir William, on age of the earth,
20
Sir Wyville, on organisms
globigerina-ooze, 87
Thryothorus bewickii, discontinuity of, 66
‘Till ” of Scotland, 109
several distinct formations of, 114
Tits, distribution of species of, 19
Torreya, 179
Tortoises of the Galapagos, 268
Trade-winds, how modified by a glacial
epoch, 137
Tragulide, 27
Travelled blocks, 106
Tremarctos, an isolated genus, 28
Triassic warm Arctic climate, 195
Tribonyx not a New Zealand genus, 453
Trichoptera peculiar to Britain, 337
Trogons, 27
Tropical affinities of New Zealand birds, 453
character of the New Zealand flora, cause
of, 469
’ genera common to New Zealand and
Australia, 469
Turdus, 17, 25
Turdus fuscescens, variation of, 57
Tylor, A., on evidence of floods during de-
posit of gravels, 116
ep ce enns the rate of denudation,
7
Tyrannide, 48

in the

U.
Urania, 28
Ursus, 25
Uropeltide, 29
Urotrichus, distribution of, 25

Variation in animals, 50
amount of, in N. American birds, 57
Vegetation, local peculiarities of, 180
effects of Polar night on, 191
Vesperugo serotinus, range of, 14
Vireonide, 48
Vireosylvia gilvus and V. swainsonii, 66

W.
Wallich, Dr., on habitat of globigerineg, 90

Water, properties of in relation to climate,
127, 128

526 INDEX.

Waterhouse, Mr., on Galapagos beetles, 273
Wales, peculiar fish of, 322, 328
Warm climates of Northern latitudes, long
persistence of, 193
Watson, Mr. H. C., on the flora of the
Azores, 248
on peculiar British plants, 339
on vegetation of railway-banks, 481
Webb, Mr., on comparison of Mars and the
Earth, 160
West Australia, rich flora of, 463
former extent and isolation of, 465
West Indies, 52
White, Dr. F. Buchanan, on the Hemiptera
of St. Helena, 292
Mr. John, on native accounts of the
moa, 448
Winter temperature of Europe and America,
189

Winged birds of New Zealand, 453
Wingless birds never inhabit continents,
408
their evidence against ‘‘ Lemuria,’ 409
of New Zealand, 447
Wings of struthious birds show retrograde
development, 451
Wolf, range of, 14
Wollaston, Mr. T. V., on insular character
of St. Helena, 283
on St. Helena shells and insects, 236

Wood, Mr. Searles V., jun., on formation of
“tin,” 111
on alternations of climate, 114
on causes of glacial epochs, 121
conclusive objection to the excentricity
theory, 154
on continuous warm Tertiary climates,
173
Woodward, Mr., on ‘‘ Lemuria,” 398
Wright, Dr. Percival, on lizards of the Sey-
chelles, 402

Vie

Young, Professor J., on contemporaneous
formation of deposits, 213

Young Isiand, 490

Z.
Zoology of Bermuda, 257
of the Sandwich Islands, 301
of Borneo, 351
of islands round Celebes, 424
of Celebes, 426
Zoological and geograpical regions com-
pared, 52
Zoological features of Japan, 365
character of New Zealand, 444

THE END,

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Full text of "Island life, or, the phenomena and causes of insular faunas and floras : including a revision and attempted solution of the problem of geological climates"

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