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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ISLAND LIFE 



ISLAND LIFE 

OR 

THE PHENOMENA AND CAUSES OF 

INSULAR FAUNAS AND FLORAS 

INCLUDING A REVISION AND ATTEMPTED SOLUTION OF 
THE PROBLEM OF 

GEOLOGICAL CLIMATES 



ALFEED EUSSEL WALLACE 

AUTHOR OF "the MALAY ARCHIPELAGO," "THE GEOGRAPHICAL DISTRIBUTION OF 
ANIMALS," " DARWINISM," ETC. 



SECOND AND REVISED EDITION 



ILonlJon 
MACMILLAN AND CO. 

AND NEW YORK 
1892 

The Eight of Translation and Reproduction is Reserved 






Richard Clay akd Soks, Limited, 
london and bungay. 

First edition 2^rinted ISSO {Med. Svo) 
Second edition 1892 (Cr. Svo) 



TO 

SIR JOSEPH DALTON HOOKER, 

K.C.S.I., C.B., F.R.S., ETC., ETC. 

WHO, MORE THAN ANY OTHER WRITER, 

HAS ADVANCED OUR KNOWLEDGE OF THE GEOGRAPHICAL 

DISTRIBUTION OF PLANTS, AND ESPECIALLY 

OF INSULAR FLORAS, 

Jf g^bitatc tins ®0lume ; 

ON A KINDRED SUBJECT, 
AS A TOKEN OF ADMIRATION AND REGARD. 



PREFACE TO THE SECOND EDITION 

This edition has been carefully revised througliont, and 
owing to the great increase to onr knowledge of the Natural 
History of some of the islands during the last twelve years 
considerable additions or alterations have been required. 
The more important of these changes are the following : — 

Chapter YII. The account of the migrations of animals 
and plants during and since the Glacial Epocli, has been 
modified to accord with newer information. 

Chapters VIII and IX. The discussion of the causes of 
Glacial Epochs and Mild Arctic Climates has been some- 
what modified in view of the late Dr. Croll's remarks, and 
the argument rendered clearer. 

Chapter XIII. Several additions to the Fauna of the 
Galapagos have been noted. 

Chapter XV. Considerable additions have been made 
to this chapter embodying the recent discoveries of birds 
and insects new to the Sandwich Islands, while a much 
fuller account has been given of its highly peculiar and 
very interesting flora. 

Chapter XVI. Important additions and corrections have 
been made in the lists of peculiar British animals and 
plants embodying the most recent information. 

Chapter XVII. Very large additions have been made 
to the mammalia and birds of Borneo, and full lists of the 
peculiar species are given. 



PREFACE TO SECOND EDITION 



Chapter XVIII. A more accurate account is given of 
the birds of Japan. 

Chapter XIX. The recent additions to the mammals 
and birds of Madagascar are embodied in this chapter, and 
a fuller sketch is given of the rich and peculiar flora of the 
island. 

Chapter XXI. and XXII. Some important additions 
have been made to these chapters owing to more accurate 
information as to the depth of the sea around New Zealand, 
and to the discovery of abundant remains of fossil plants 
of the tertiary and cretaceous periods both in New Zealand 
and Australia. 

In the body of the work I have in each case acknowledged 
the valuable information given me by naturalists of 
eminence in their various departments, and I return my 
best thanks to all who have so kindly assisted me. I am 
however indebted in a special manner to one gentleman — 
Mr. Theo. D. A. Cockerell, now Curator of the Museum of 
the Jamaica Institute — who supplied me with a large 
amount of information by searching the most recent works 
in the scientific libraries, by personal inquiries among 
naturalists, and also by giving me the benefit of his own 
copious notes and observations. Without his assistance it 
would have been difficult for me to have made the present 
edition so full and complete as I hope-it now is. In a w^ork of 
such wide range, and dealing with so large a body of facts 
some errors will doubtless be detected, though, I trust few 
of impoi&tance. 

Paekstoxe, Dorset, December, 1891. 



PREFACE TO THE FIRST EDITION 



The present voliunc is the result of four years' additional 
tiiought and research on the lines laid down in my 
Gcograpliical Distribution of Animals, and may be con- 
sidered as a popular supplement to and completion of that 
work. 

It is, however, at the same time a complete w^ork in 
itself: and, from the mode of treatment adopted, it will, I 
hope, be well calculated to bring before the intelligent 
reader the wide scope and varied interest of this branch of 
natural history. Although some of the earlier chapters 
deal with the same questions as my former volumes, they 
are here treated from a different point of view ; and as the 
discussion of them is more elementary and at the same 
time tolerably full, it is hoped that they Avill 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 intelli- 
gible 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 imj^ortant arguments given in the " Conclu- 
sion," render it unnecessary for me to offer any further 
remarks on these points. I may, however, state 



PREFACE TO FIRST EDITIO?^^ 



gerferally that/ so far as I am able to judge, a real 
advance lias here been made in the mode of treating 
problems in Geogi'aphical Distribution, owing to the firm 
establishment of a number of preliminary doctrines or 
" principles/' which in many cases lead to a far simpler and 
yet more complete solution of such problems than have 
been hitherto jDossible. The most important of these 
doctrines are those which establish and define — (1) The 
former wide extension of all gi'oups 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 noAV only to thank the many friends and 
correspondents who have given me information or advice. 
Besides those whose assistance is acknowledged hi the body 
of the work, I am especially indebted to four gentlemen 
who have been kind enough to read over the 2iroofs of chap- 
ters dealing with questions on which they have special 
knowledge, giving me the benefit of valuable emendations 
and suggestions. Mr. Edward R. Alston has looked' over 
those parts of the earlier chapters which relate to the 
mammals of Europe and the North Temperate zone ; Mr. 
S. B. J. Skertchley, of the Geological Survey, has read the 
cha2iters 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 Josejih D. Hooker has given me the invaluable 
benefit of his remarks on my two chapters dealing with tlie 
New Zealand flora. 

CiiOYDON, August, 1880. 



CONTENTS 



PART I 

THE DISPERSAL OF ORGANISMS ; ITS PHENOMENA, LAWS, AND 
CAUSES 



CHAPTER I 

INTRODUCTORY 

Remarkable Contrasts in tlie 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. 

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 Ovei'lapping Areas — The 
Species of Tits as illustrating Areas of Distribution — The Distribution 
of the Sj)ecies of Jays — Discontinuous Generic Areas — Peculiarities of 
Generic and Family Distribution — General Features of Overlapping 
and Discontinuous Areas — Restricted Areas of Families — The Distribu- 
tion of Orders Pages 12—30 



CONTETTTS 



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 I\Iammals — The 
Range of British Birds — Range of East Asian Birds — The Limits of the 
Palfearctic Region — Characteristic Features of the Palsearctic Region — 
Definition and Characteristic Groups of the Ethiopian Region — Of the 
Oriental Region — Of the Australian Region — Of the Nearctic Region 
— Of the Neotropical Region — Comparison of Zoological Regions with 
the Geographical Divisions of the Globe . , . Pages 31-^54 

CHAPTER IV 

EVOLUTION AS THE KEY TO DISTRIBUTION 

Importance of the Doctrine of Evolution — The Origin of New Species — 
Variation in Animals — The amount of Variation in North American 
Birds — How New Species Arise from a Variable Species — Definition 
and Origin of Genera — Cause of the Extinction of Species — The Rise 
and Decay of Species and Genera — Discontinuous Specific Areas, why 
Rare — Discontinuity of the Area of Parus Palustris — Discontinuity of 
Emberiza Schoeniclus — The European and Japanese Jays — Supposed 
examples of Discontinuity among North American Birds — Distribution 
and Antiquity of Families — Discontinuity a Proof of Antiquity — Con- 
cluding remarks Pages 55—71 



CHAPTER V 

THE POWERS OF DISPERSAL OF ANIMALS AND PLANTS 

Statement of the General Question of Dispersal — The Ocean as a Barrier 
to the Dispersal of Mammals — The Disj^ersal of Birds — The Dispersal 
of Reptiles — The Dispersal of Insects — The Disjiersal of Land iMollusca 
— Great Antiquity of Land-shells — Causes Favouring the Abundan-ce of 
Land-shells — ^The Dispersal of Plants — Special Adaptability of Seeds 
for Dispersal — Birds as Agents in the Disj^ersal of Seeds — Ocean 
Currents as Agents in Plant Dispersal — Dispersal along Mountain Chains 
— Antiquity of Plants as Etfecting their Distribution . Pages 72 — 82 



CHAPTER VI 

GEOGRAPHICAL AND GEOLOGICAL CHANGES : THE PERMANENCE OF 
CONTINENTS 

Changes of Land and Sea, their Nature and Extent — Shore-Deposits and 
Stratified Rocks — The Movements of Continents — Supposed Oceanic 



CONTEXTS 



Formations ; the Origin of Chalk — Fresh-water and Shore- deposits as 
Proving the Permanence of Continents — Oceanic Islands as Indications 
of the Permanenee of Continents and Oceans — General Stability 
of Continents with Constant Change of Form — Effect of Continental 
Changes on the Distribution of Animals — Changed Distribution Proved 
by the Extinct Animals of Different Epochs— Summary of Evidence 
for the General Permanence of Continents and Oceans. Pages 83 — 105 



CHAPTER YII 



CHANGES OF CLIMATE WHICH HAVE INFLUENCED THE DISPERSAL OF 
ORGANISMS : THE GLACIAL EPOCH 



Proofs of the Recent Occurrence of a Glacial Epoch — Moraines — Travelled 
lilocks — Glacial Deposits of Scotland : the "Till" — Inferences from 
the Glacial Phenomena of Scotland — Glacial Phenomena of North 
America — Efiects of the Glacial Epoch on Animal Life — Wann and 
Cold Periods — Palteontological Evidence of Alternate Cold and Warm 
Periods — Evidence of Interglacial Warm Periods on the Continent and 
in North America — Migrations and Extinctions of Orc;anisms Caused 
by the Glacial Epoch >af/cs 106— 124 



CHAPTER VIII 



THE CAUSES OF GLACIAL EPOCHS 



Various Suggested Causes — Astronomical Causes of Changes of Climate — 
Difference of Temperature Caused by Varying Distances of the Sun — 
Properties of Air and Water, Snow and Ice, in Relation to Climate — 
Effects of Snow on Climate — High Land and Great Moisture Essential 
to the Initiation of a Glacial Epoch— Perpetual Snow nowhere Exists 
on Lowlands — Conditions Determining the Presence or Absence of 
Perpetual Snow — Efficiency of Astronomical causes in Producing 
Glaciation — Action of Meteorological Causes in Intensifying Glaciation 
— Summary of Causes of Glaciation — Effect of Clouds and Fog in 
Cutting off the Sun's Heat — South Temperate Amer'ca as Illustrating 
the Influence of Astronomical Causes on Climate — Geographical Changes 
how far a Cause of Glaciation — Land Acting as a Barrier to Ocean- 
cuiTents — 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 IMars as Bearing on the Theory 
of Excentricity as a Cause of Glacial Epochs . . Pages 125 — 168 



co:n'tejN'ts 



CHAPTER IX 

ANCIENT GLACIAL ErOCHS, AND MILD CLIMATES IN THE AECTIC 
EEGIONS 

Mr. Croll's Views on Ancient Glacial Epochs — Effects of Denudation in 
Destroying the Evidence of Remote Glacial Ei)ochs — Rise of Sea-level 
Connected with Glacial Epochs a Cause of Further Denudation — What 
Evidence of Early Glacial Epochs may be Expected — Evidences of Ice- 
action During the Tertiary Period — The Weight of the Negative 
Evidence — Temperate Climates in the Arctic Regions — The ]\Iiocene 
Arctic Flora — Mild Arctic Climates of the Cretaceous Period — Strati- 
graphical Evidence of Long-continued Mild Arctic Conditions — The 
Causes of Mild Arctic Climates — Geographical Conditions Favouring 
Mild Northern Climates in Tertiary Times — The Indian Ocean as a 
Source of Heat in Tertiary Times — Condition of North America During 
the Tertiary Period — Effect of High Excentricity on Warm Polar 
Climates — Evidences as to Climate in the Secondary and Paleozoic 
Epochs — AVarm Arctic Climates in Early Secondary and Palaeozoic Times 
— Conclusions as to the Climates of Secondary and Tertiary Periods — 
General View of Geological Climates as Dependent on the Physical 
Features of the Earth's'Surface — Estimate of the Comparative Effects 
of Geographical and Phvsical Causes in Producing Changes of Climate. 

Pages 169—209 



CHAPTER X 

THE earth's AGE, AND THE RATE OF DEVELOPMENT OF ANIMALS AND 

PLANTS 

Various Estimates of Geological Time — Denudation and Deposition of 
Strata as a Measure of Time — How to Estimate the Thickness of the 
Sedimentary Rocks — How to Estimate the Average Rate of Deposition 
of the Sedimentary Rocks — The Rate of Geological Change Probably 
Greater in very Remote Times — Value of the Preceding Estimate of 
Geological Time — Organic Modification Dependent on Change of 
Conditions — Geographical Mutations as a ]\Iotive Power in Bringing 
about Organic Changes — Cliniatal Revolutions as an Agent in Produc- 
ing Organic Changes — Present Condition of the Earth One of Excep- 
tional Stability as Regards Climate — Date of Last Glacial Epoch and 
its Bearing on the Measurement of Geological Time — Concluding 
Remarks Pages 210—240 



CONTENTS 



PART II 

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 241 — 245 

CHAPTER XII 

OCEANIC ISLANDS : — THE AZORES AND BEEMUDA 

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 tlie 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 Pages 246—262 

Bermuda 
Position and Physical Features — The Red Clay of Bennuda — 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 

Pages 263—274 

CHAPTER XIII 

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 Pages 273 — 291 

CHAPTER XIV 

ST. HELENA 

Position and Physical Features of St. Helena — Change Effected by Euro- 
pean 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. ....... Pa^^cs 292— 309 



CONTEN'TS 



CHAPTER XY 

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 

Pages 310—330 

CHAPTER XYI 

CONTINENTAL ISLANDS OF EECENT ORIGIN : GREAT BRITAIN 

Characteristic Features of Recent Continental Islands — Recent Physical 
Changes of the Britisli 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 Britisli Isles — Peculiarities 
of the Isle of Man Lepidoptera — Coleoptera Confined to the British 
Isles — Trichoptera Peculiar to the Britisli Isles — Land and Fresh- water 
Shells — Peculiarities of the British Flora — Peculiarities of the Irish 
Flora — Peculiar British Mosses and Hepaticse — Concluding Remarks on 
the Peculiarities of the British Fauna and Flora . Pages 331 — 372 



CHAPTER XVII 

BORNEO AND JAVA 

Position and Physical Features of Borneo — Zoological Features of .Borneo : 
Mammalia— Birds— The Affinities of the Borneo Fauna— Java, its 
Position and Phj^sical Features— General Character of the Fauna of 
Java— DitFerences Between the Fauna of Java and that of the other 
]\Ialay Islands— Special Relations of the Javan Fauna to that of the 
Asiatic Continent— Past Geogi-aphical Changes of Java and Borneo— 
The Philippine Islands— Concluding Remarks on the Malay Islands 

Pages 373—390 

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 . Pages 391—410 



CONTENTS 



CHAPTER XIX 

ANCIENT CONTINENTAL ISLANDS : THE MADAGASCAR GROUP 

Remarks 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 
" Lemuria " — The Mascarene Islands — The Comoro Islands — The Sey- 
chelles 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. . . Pa^cs411— 449 



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 Deriva- 
tion 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 

Pages 450 — 470 



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 . . Pages 471—486 



CONTENTS 



CHAPTER XXII 

THE FLOKA OF XEW 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 Exj^lanation of tlie 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 487 — 508 



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 Migi'ating Plants — Elevation and Depression of 
the Snow-line as Aiding the Migration of Plants — Changes of Climate 
Favourable to Migration — The JMigration 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 ]\Iigration by way of the 
African Highlands — Suj^posed 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 509 — 530 



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 — Investi- 
gation of the Facts of Dispersal — Of the Means of Dispersal — Of Geo- 
graphical 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 ]\Ir. CroU — 
Supposed Limitations of Geological Time — Time Amply Sufficient both 
for Geological and Biological Development — Insular Faunas and Floras 
— The North Atlantic Islands — Tlie 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 

Pages 531—545 



MAPS AND ILLUSTRATIONS 



PAGE 

1. Map shoavixo the Disteibution of the true Jays 

Frontispiece. 

2. Map showing the Zoological Regions To face 31 

3. Map showing the Distribution of Farus Falustris 

To face 66 

4. A Glacier with Moraines (From Sir C. Lyell's Frinci'ples 

of Geology) 109 

5. Map of the Ancient Rhone Glacier (From Sir C. Lyell's 

Antiquity of Man) 110 

6. Diagram showing the effects of Excentricity and 

Precession on Climate 127 

7. Diagram of Excentricity and Precession 129 

8. Map shoaving the Extent of the North and South 

Polar I(^e 138 

9. Diagram showing Changes of Excentricity during Three 

Million Years 171 

10. Outline Map of the Azores 248 

11. Map of Bermuda and the American Coast 263 

12. Section of Bermuda and adjacent Sea-bottom 264 



XX MAPS AND ILLUSTRATIOXS 

PAGE 

13. Map of the Galapagos and adjacent Coasts of South 

America 27o 

14. Map of the Galapagos 277 

15. Map of the South Atlantic, showing position of St. 

Helena ; 293 

16. Map of the Sandwich Islands 311 

17. Map of the North Pacific, with its submerged Banks'. 312 

18. Map showing the Bank connecting Britain with the 

Continent ; 333 

19. Map of Borneo and Java, showing the Great Submarine 

Bank of South-Eastern Asia 373 

20. Map of Japan and Formosa 392 

21. Physical Sketch Map of Madagascar (From Nature) . . 413 

22. ;Map of Madagascar Group, showing Depths of Sea . . 415 

23. Map of the Indian Ocean 424 

24. Map of Celebes and the surrounding Islands 451 

25. Map showing Depths of Sea around Australia and J5'ew 

Zealand 471 

26. Map showing the probable condition of Australia 

during the Cretaceous Epoch • 496 



ISLAND LIFE 

PAET I 

THE DISPERSAL OF ORGANISMS 

ITS PHENOMENA, LAWS, AND CAUSES 



CHAPTER I 

INTKODUCTORY 

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 countr}^ — 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. 
B B 2 ' 



ISLAND LIFE 



thrushes, buntings, and house-sparrows, some absokitely 
identical with our own feathered friends, others so closely 
resembling them that it requires a joractised 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 Avhat 
might be expected in any -pscrt 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 Avhose 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 grass-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 quadrupeds than do England 
and Japan. The bii'ds of the one are extremely unlike 
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 unknown in Bali. Many of the kingfishers, crow- 
shrikes, and other birds, thouoli 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 



INTRODUCTORY 



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. 

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 Alabama or 
Florida we still find ourselves in the midst of pines, oaks, 
sumachs, masfnolias, vines, and other characteristic forms 
of the temperate flora; while the birds, insects, and land-, 
shells are of the same general character with those found 
further north. ^ But if we now cross over the narrow strait, 
about fifty miles Avide, 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 
chanoe is most striking^, because there is little 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 of the Bahamas 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 

^ A small number of species belonging to the "West Indies are found in 
the extreme southern portion of the Florida Peninsula. 



ISLAND LIFE 



Australia are slight and unimportant as comjDared 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 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 ; Avhile 
among birds, the toucans, chatterers, and humming-birds 
of Brazil are replaced 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, thouq;h closer tooether, 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, 
offers 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 



CHAP. I INTRODUCTORY 



years study of this class of subjects has couvmced 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 not there, a problem which involves all the migi-ations 
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 extinction 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 know- 
ledge 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 ; ^ and in many cases it can 

^ I cannot avoid liere referring to tlie 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 or f^uartos, 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 unfref[uently 
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 interesting 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 countries under the rule or protection of 



ISLAND LIFE 



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 furtlier have to make use of the 
theory of '' descent with modification " as the only ]30ssible 
key to the interpretation of the facts of distribution, and 
this theoiy 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 explan- 
ation 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. An- 
other important factor in our interpretation of the phe- 
nomena 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 t<^ 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 al- 
ready obtained remarkable evidence of the migrations of 
many animals and plants in past ages, tlirowing an often 
unexpected light on the actual distribution -of many 
groujDs.^ 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 

European governments. Such are the Sandwich Islands, Tahiti, the 
Marquesas, the Philippine Islands, and a host of smaller ones ; while 
Bourbon and j\Iauritius, St. Helena, and several others, have only been 
adequately explored after an important portion of their productions has 
been destroyed by cultivation or the reckless introdudion 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 circumnavi- 
gated the globe. 

^ The general facts of Paleontology, as bearing on the migrations of 
animal groups, are summarised in my Geoqrcvphical Distribution of Animals. 
Voh I. Chapters YL, YII., and YIII. 



INTRODUCTORY 



have to trust to collateral evidence and more or less prob- 
able hypothetical explanations. Hardly less valuable is 
the evidence of stratigrajDhical 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 
tlora allowed time for special development. Here, too, 
our knowledge is exceedingly imperfect, though the 
blanks upon the geological map of the world are yearly 
diminishing in extent. Lastly, as a most valuable supple- 
ment to geology, we require to know approximately, the 
depth and contour of the ocean-bed, since this affords an im- 
portant clue to the former existence of now-submerged lands, 
uniting islands to continents, or affording intermediate 
stations which have aided the migTations of many organ- 
isms. This kind of information has only been partially 
obtained during the last few years ; and it will be seen in 
the latter j)art 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 importance of which is only now beginning to be 
recognised by students of nature. These are, firstly, the 
wonderful alterations of climate which have occurred in 
the temperate and polar zones, as proved by the evidences 
of o'laciation in the one and of luxuriant ves^etation in the 
other; and, secondly, the theory of the permanence of exist- 
ing continents and oceans. If glacial ejDOchs 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 
geological changes of sea and land. It is therefore neces- 
sary to consider the evidence for these climatal changes ; 



10 ISLAND LIFE 



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 terrestrial 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 ej)Ochs and warm polar climates, we have the 
key to explain and harmonize many of the most anom- 
alous biological and geological phenomena, and one which 
is especially valuable for the light it throws on the dis- 
persal 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 sontinents 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 i:)laces over and 
over again (as many writers maintain), we lose all power 
of reasonino: on the mis^rations 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 contin- 
ent 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 chajDter, some of the most remarkable and inter- 
esting facts in the distribution and affinities of organic 
forms are j)resented 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 continent — aj)pears 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 whicli 
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 



IXTRODUCTORY 11 



been recognised ; and it is 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 jDresent to us. By far the larger 
part of the islands of the globe are but portions of contin- 
ents undergoing some of the various changes to which they 
are ever subject ; and the correlative proposition, that every 
portion of our continents has again and again passed 
through insular conditions, has not been sufficiently con- 
sidered, but is, I believe, the statement of a great and 
most suo'o^estive truth, and one Avhich lies at the founda- 
tion of all accurate conce23tion of the physical and organic 
changes which have resulted in the jDresent state of the 
earth. 

The indications now given of the scope and j^urjDose 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 comi^lex 
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 oreo- 
logical 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 Jsivs — 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 S^Decies 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 re- 
quired no explanation. 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 conditions of that country were not 
suitable to it, but in Avhat 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 gener- 
ally adopted, and it was seen that each animal could only 
have come into existence in some area where ancestral 



CHAi'. II THE ELEMENTAKY FACTS OF DISTRIBUTION 13 

forms closely allied to it already lived, a real and important 
relation was 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 diver sities 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 knowledge 
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 pre- 
sent state of the organic world was brought about, until we 
have ascertained with some accuracy the general laws of 
the distribution 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 per- 
manently 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 
apparent and some real 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, 
permanently, live elsewhere. These maybe 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 
mountains 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 dis- 



14 ISLAND LIFE 



continuous distribution of a species, there being a gap of 
about a thousand miles between its southern limits in 
Russia, and its reappearance in 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 furtlier on. Other cases are believed to exist 
of still Avider separation of a species, as with the marsh 
titmice and the reed buntings of Euro23e and Jaj^an, where 
similar forms are found in the extreme localities, while 
distinct varieties or sub-sj^ecies, inhabit the intervening 
districts. 

Extent and Limitations of Speeijic 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, the elk, the 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 identity 
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 hemispheres. Among the undisjDuted 
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 sjiecies, Vesperugo serotinus, which is found over 
the larger part of North America, Europe and Asia, as far 



CHAr. II THE ELEMEXTARY FACTS OF DISTRIBUTION 15 

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 species or as to its geographical limits being really 
known. In Europe we have a distinct sj^ecies of ibex 
{Caq)ra Pyrenaica) confined to the Pyrenean mountains, 
while the true marmot is restricted to the Alpine range. 
More remarkable is the Pyrenean water-mole {Mygalc 
Pyrenaica), a curious small insectivorous 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 ajjj^arent 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 joowers of flight ; but, what 
is very curious, we also find more striking (though 
perhaps not more frequent) examples of extreme limita- 
tion 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 Jlammea) 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 iDasserine birds the raven has probably the Avidest 
range, extending from the arctic regions to Texas and New 
Mexico in America, and to North India and Lake Baikal 
in Asia ; whde the little northern willow- wren (PJiylloscojms 
horealis) ranges from arctic 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 (Cyanojnca cooki) 
confined to the central portions of the Spanish peninsula ; 
and the Italian sparrow found only in Italy and Corsica. 



16 ISLAND LIFE 



In Asia, Palestine affords some examples of birds of very 
restricted range — a beautiful sun-bird {Nectarinca osea) a 
peculiar starling {Amydrus tristramii) and some others, 
being almost or quite confined to the warmer jDortions of 
the valley of the Jordan. In 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 AvonderfuUy 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 volcano of Chiriqui in Yeragua has a species con- 
fined to its wooded crater. One of the most strange and 
beautiful of the humming-birds {Zoddigcsia mirahilis) was 
obtained once only, more than forty years ago, near 
Chachapoyas in the Andes of northern Peru ; and though 
Mr. Gould sent many drawings of the bird to people visiting 
the district and for many years offered a high reward for a 
specimen, no other has ever been seen ! ^ 

Tlie 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 European birds range over the whole conti- 
nent 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 

^ Since these lines were written, a fine series of specimens of this rare 
humming-bird has been obtained from the same locality. (See Proc. Zool. 
Soc. 1881, pp. 827-834.) 



CHAP. II THE ELEMENTARY FACTS OF DISTRIBUTION 17 



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 
sjDecies, 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 wolves belong to the 
dog genus, Canis ; the tiger, lion, leopard, jaguar, and the 
wild cats, to the cat grenus, Felis ; the blackbird, son2:-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 varies greatl}^ from one up to several hundreds. 
The giraffe, the glutton, the walrus, the bearded reedling, 
the secretary-bird, and many others, have no close allies, 
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 hun- 
dred 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. ^ 

Sefccratc mid Ovcrlcipijing Areas. — The species of a genus 
are distributed in two ways. Either they occupy distinct 
areas which do not touch each other and are sometimes 
widely separated, or they touch and occasionally overlap 

^ Many of these large genera are now subdivided, the divisions being 
sometimes termed genera, sometimes siib-genera. 



18 ISLAND LIFE 



each other, each species occupying an area of its own 
Avhich rarely coincides exactly with that of any other 
species of the same genus. In some case.s, 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 compara- 
tively 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, 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 Ave find 
another species {Pithecia Qmjiba7'hata ?). Among birds we 
have the green jacamar {Galhula viridis), abundant on the 
north bank of the Lower Amazon, while on the south 
bank we have two allied species (Galhula rufoviridis and 
G. cyaneicollis) ; and among insects we have at Santarem 
on the south bank of the Amazon, the beautiful blue 
butterfly, Callithca sa^^plmxt, while almost opposite to it, at 
Monte-alegre, an allied species, Callithca JjCiwicuri is alone 
found. Perhaps the most interesting and best known 
case of a series of allied species, Avhose ranges are separate 
but conterminous, is that of the beautiful South* American 
wading birds, called trumpeters, and forming the genus 
Psophia. There are five sj^ecies, 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 jDart 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 



CHAP. II THE ELEMENTARY FACTS OF DISTRIBUTION 19 

species extending over a considerable portion of the area 
occupied by the genus and inckiding 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 examj)les. One of the best is to be found 
in the genus Dcndroica, a group of American wood- warblers. 
These little birds all migTate in the winter into the troi^ical 
regions, but in the summer they come north, each having 
its particular range. Thus, D. dominica comes as far as 
the middle Eastern States, D. cceruka keeps west of the 
Allesfhanies, D. discolor comes to Michiccan and New 
England ; four other species go farther north in Canada, 
while several extend to the borders of the Arctic zone. 

The Species of Tits as Ilhistratinr/ Areas of Distrihution. 
— In our own hemisphere the overlapping of allied species 
may be well illustrated by the various kinds of titmice, 
constituting the genus Parus, several of which are among 
our best known English birds. The great titmouse (Pants 
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 {Panes 
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 and Japan. 
The marsh tit {Parus j)cdustris) 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 
{Panes horealis), which overlaps 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 camtscliathensis) ranges from North-eastern 
Russia across Northern Siberia to Lake Baikal and to 
Hakodadi in Japan, thus overlapping Parus horealis in the 

c 2 



20 ISLAND LIFE 



w6stem portion of its area. Our little favourite, the blue 
tit (Farus cceruleits) 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 
ci/ancus) overlaps the range of P. ccerulcns in Western 
Eurojje as far as St. Petersburg and Austria, rarely 
stras^orlinor to Denmark, 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. Panes 
tcneriffce, a beautiful dark blue form of our blue tit, inhabits 
North-west Africa and the Canaries ; Pants ledouci, closely 
allied to our coal tit, is found only in Algeria ; Paoms 
Inguhris, alHod to the marsh tit, is confined to South-east 
Europe and Asia Minor, from Hungary and South Russia 
to Palestine ; and Panes cindns, another allied form, is 
confined to the extreme north in Lapland, Finland, and 
perhaps Northern Russia and Siberia. Another beautiful 
little bird, the crested titmouse (Panes cristatns) is some- 
times 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 ascertaining their actual distribution, it has 
not been found practicable 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 



•HAF. II THE ELEMENTARY FACTS OF DLSTRIBUTIOX 21 



birds tliey 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 passing 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 Palsearctic ^ genera. The 
following are the species, beginning with the most westerly 
and proceeding towards the east. The numbers prefixed 
to each sjDOcies correspond to those on the coloured map 
which forms the frontispiece to this volume. 

1. Garrulus glandarius. — The common jay, inhabits the 
British Isles and all Europe except the extreme north, 
extending 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 witli the common species. 

3. Garrulus hryrdchi. — The black-headed jay, is closely 
allied to the common sj^ecies, but quite distinct, inhabiting 
a comparatively small area in South-eastern Euroj^e, 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 Jn/rcanus. — The Persian jay, is a small 
species allied to our jay and only known from the Elburz 
Mountains in the north of Persia. 

6. Garridus hrandti. — 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 

^ The Palfearctic region includes temperate Asia and Europe, as will be 
explained in tlic next chapter. 



22 ISLAND LIFE taut i 

Russia Avhere it lias been found as far west as Kazan in 
districts where the common jay also occurs. 

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

8. Garntlus hispecularis. — 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 tlie eastern division, thouoh accordins^ to the 
Abbe David it reaches Moupin in East Thibet. 

9. Garrulus sinensis. — The Chinese jay, is very closely 
allied to the Himalayan, of which it is sometimes classed 
as a sub-species. It seems to be found in all the southern 
mountains of China, from Foocliow on the east to Sze-chuen 
and East Thibet on the west, as it is recorded fi'om Mou- 
pin by the Abbe David as well as the Himalayan bird — a 
tolerable proof that it is a distinct form. 

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

11. Garrulus jarjonicus.- — The Japanese jay is nearly 
allied to our common British species, being somewhat 
smaller and less brightly coloured, and with black orbits ; 
yet these are the most Avidely separated species of the 
genus. According to Mr. Seebohm this species is equally 
allied to the Chinese and Siberian jays. 

In the accompanying map (see frontisi^iece) 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 Mr. 
Seebohm's recent work 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 im23erfectly explored, that considerable modi- 
fications may have to be made wdien 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 



CHAP. II THE ELEMENTARY FACTS OF DISTRIBUTION 23 

will be much affected ; and these are what we have chiefly 
to consider as bearing on the questions here discussed. 

The first thing that strikes us on looking at the map, is, 
the small amount of overlaj^ping of the several areas, and 
the isolation of many of the species ; while the next most 
striking feature is the manner in which the Asiatic species 
almost surround a vast area in which no jays are found. 
The only species with large areas, are the European G. 
glandarius and the Asiatic G. Branclti. The former has 
three species overlapping it — in Algeria, in South-eastern 
and North-eastern Europe respectively. The Syrian jay 
(No. 4), is not known to occur anywhere with the black- 
headed jay (No. 8), and perhaps the two areas do not meet. 
The Persian jay (No. 5), is quite isolated. The Himalayan 
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 it is nearly 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 assiduously, 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 occujoy 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 European birds is 



24 ISLAND LIFE part i 

that of the bhie magpies, forming the genus Cyanopica. 
One species ( C. cooki) is confined (as ah'eady stated) to the 
wooded and mountainous districts of Spain and Portugal, 
while the only other species of the genus {C. cyayius) 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 My gale, one species M. 
muscovitica, being found only on the banks of the Volga 
and Don in South-eastern Russia, while the other, M. 
injrenaica, 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 area com- 
pletely separated from the others. The most northerly 
is C. tricarunculahts of Costa Rica and Veragua, a brown 
bird Avith a white head and three long caruncles growing 
ujjwards at the base of the beak. Next comes C. variegatus, 
in Venezuela, a white bird with a brown head and nu- 
merous caruncles on the throat, perhaj^s conterminous with 
the last ; in Guiana, extending to near the mouth of the 
Rio Negro, Ave have C. nivcus, the bell-bird described by 
Waterton, Avhich is pure wdiite, with a single long fleshy 
caruncle at the base of the beak ; the last species, C. 
nndicoUis, 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, rinoino- notes, like a bell 
or a blow on an anvil, as Avell as for their peculiar colours. 
They are therefore known to the native Indians wherever 
they exist, and we may be the more sure that they do not 
spread over the intervening areas where they have never 
been found, and Avhere the natiA^es knoAV nothing of 
them. 

A good example of isolated species of a group nearer 
home, is afforded by the snoAv-partridges of the genus 
Tetraogallus. One species inhabits the Caucasus range 
and noAvhere else, keeping to the higher slopes from 6,000 
to 11,000 feet above the sea, and accompanying the ibex in 
its Avanderings, as both feed on the same plants. Another 



CHAP. II THE ELEMENTARY FACTS OF DISTRIBUTION 25 



has a wider range in Asia Minor and Persia, from the 
Tav.rus mountains to the South-east corner of the Caspian 
Sea ; a third species inhabits the Western Himalayas, 
between the forests and perpetual snow, extending east- 
wards to Nepal ; while a fourth is found on the north side 
of the moimtains in Thibet, and the ranges of these two 
perhaps overlap ; the last species inhabit the Altai moun- 
tains, and like the two first ajDpears 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 
named Urotrichus, of which one species inhabits Japan 
and the other British Columbia. The cuckoo-like honey- 
guides, forming the genus Indicator, are tolerably abund- 
ant in tropical Africa, but there are two outlying species, 
one in the Eastern Himalaya mountains, the other in 
Borneo, both very rare, and 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 and Eastern China, 
while the third is confined to Java ; the curious genus 
Eupetes, supposed to be allied to the dippers, has one 
species in Sumatra and Malacca, while four other species 
are found 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, 

Pemdiariiies 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 j^oint of 
view. 



26 ISLAXD LIFE 



All the phenomena presented by the species of a genus 
are reproduced by the genera of a family, and often in a 
more marked deOTee. Owino^, however, to the extreme 
restriction of genera by modern naturalists, there are not 
many among the higher animals 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 as a 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 (tlie 
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 birds which are 
truly cosmopolites ; but there are many genera of hawks, 
owls, wading and swimming birds, which have a world-wide 
rano^e. 

As a great many genera consist of single species there is 
no lack of cases of great restriction, such as the curi'ous 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-jDheasants (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 interesting problems to the student of distribution. 



CHAP. II THE ELEMENTARY FACTS OF DISTRIBUTIOX 27 



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 confined to Asia, while the other Auchenia, 
comprisng 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 Centetida?, a family 
of small insectivorous animals, which are wholly confined 
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 separating allied genera. Two families (or 
subfamilies) of rat-like animals, Octodontida? and 
Echimyidse, are also divided by the Atlantic. Both are 
mainly South American, but the former has two genera in 
North and East Africa, and the latter also two in South 
and West Africa. Two other families of mammalia, 
though confined to the Eastern hemisphere, are yet 
markedly discontinuous. The Tragulidse 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 
fimiily is the Simiida? or anthropoid 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 Echimyida? 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 Megakemidie or barbets are gaily coloured 



28 ISLAXD LIFE 



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 
siDecies in Africa. 

Among reptiles we have two families of snakes — the 
Dendrophidas or tree-snakes, and the Dryiophidse or green 
whip-snakes — wdiich 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 family 
Amphisbsenidai are divided between tropical Africa and 
America, a few sj^ecies only occurring in the southern 
portion of the adjacent temperate regions ; wdiile even the 
peculiarly American family of the iguanas is represented 
by two genera in Madagascar, and one in the Fiji and 
Friendly Islands. Passing on to the Amphibians the 
"vvorm-like Cseciliadse are troiDicopolitan, as are also the 
toads of the family EngystomatidfB. Insects also furnish 
some analogous cases, three genera of Cicindelida^, 
(Pogonostoma, Ctenostoma, and Peridexia) showing a 
decided connection between this family in South America 
and Madagascar ; while the beautiful family of "diurnal 
moths, Uraniida^ is confined to the same two countries. 
A somewdiat similar but better known illustration is 
afforded by the two genera of ostriches, one confined to 
Africa and Arabia, the other to tlie plains of temperate 
South America. 

General features of Ovcrlapimig and Discoiitinuous 
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 grou}^ of animals, 
and they grade impercei^tibly into those cases of conter- 
minous and overlapping areas which w^e have seen to 



CHAP. IT THE ELE:\IEXTARY facts of distribution 29 

prevail in most extensive groujDS 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 overlapping 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 (Sylviadge) 
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 crenera of 
antelopes may be found, and in South America a laro-e 
proportion of the genera of monkeys of the family Cebid^e 
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 Bovidse, 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 examples of very restricted range ; but "Avhat 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 (Chrysochloridse) consisting of two 
genera and three species, confined to extratropical South 
Africa ; the hill-tits (Liotrichidas), a family of numerous 
genera and sjDecies mainly confined to the Himalayas, but 
with a few straggling species in the Malay countries and 
the mountains of China ; the Pteroptochidse, large wren- 
like birds, consisting of eight genera and nineteen species, 
almost entirely confined to temperate South America and 



30 ISLAND LIFE part i 

the Andes ; and the birds-of-paradise, consisting of nine- 
teen or twenty genera and about thirty-five species, ahnost 
all inhabitants of New Guinea and the immediately 
surrounding islands, while a few, doubtfully belonging to 
the family, extend to East Australia. Among reptiles the 
most striking case of restriction is that of the rough-tailed 
burrowing snakes (Uropeltidse), the five genera and 
eighteen species being strictly confined to Ceylon and the 
southern parts of the Indian Peninsula. 

The DistrihUion of Orders. — When we pass to the larger 
groups, termed orders, comprising several families, we find 
comparatively few cases of restriction and many of world- 
wide distribution ; and the families of wdiich they are 
composed are strictly comparable to the genera of which 
families are composed, inasmuch as they present examples 
of overlapping, or conterminous, or isolated areas, though 
the latter are comparatively 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 Marsapialia 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 MarsujDials to Australia and America ; "and the 
Monotremata, the lowest of all mammals — comprising the 
duck-billed PlatyjDus and the spiny Echidna, to Australia 
and New Guinea. Among birds the Struthiones or ostrich 
tribe are almost confined to the three Southern continents. 
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. 



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 ]\Iammals 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 
Palfiearetic Region — Characteristic features of the Palaearctic Region — 
Definition and characteristic groups of the Ethiopian Region — Of the 
Oriental Region — Of the Australian Region — Of the Nearctic Region — 
Of tlie 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 sm'face, whether as single 
species or as collected in those groups termed genera, 
families, and orders, it will be w^ell, 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 anytbing beyond species, and very seldom, or 
perhaps never, even those accurately. Thus the term 
" Euroj^e " will not give, with any approacli to accuracy, 
the range of any one genus of mammals or birds, and 



32 ISLAND LIFE part i 

jDerhaps not that of lialf-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 of distribution occupies a large portion of Europe. 
There are, indeed, a few species limited to Central or 
Western or Southern Europe, 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 excej)tion is perhaps the tiger, which may 
really be called an Asiatic animal, as it. occupies nearly 
two-thirds of the continent ; but this is an uniqiie example, 
while the cases in which Asiatic animals and groups are 
strictly limited to a portion of Asi^, or extend also into 
Europe or into Africa or to the Malay Islands, are exceed- 
ingly 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 tlie 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 character- 
istic 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 Avill 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 



ZOOLOGICAL REGIONS 



abroad ; we shall therefore proceed to explain its nature 
and the principles on which it is established, as it will 
Imve to be often referred to in future chapters of this work, 
and will take the jDlace of the old geographical divisions 
whose inconvenience has already been pointed out. The 
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 indicatinr/ a Zoological 
Region. — We will first take our coinmonest wild mammalia 
and see how far they extend, and especially whether they 
are confined to Europe or range over parts of other 
continents : 



1. AVildCat 

2. Fox 

3. AVeasel ... 

4. Otter 

5. Badger ... 

6. Stag 

7. Hedgehog 

8. Mole 

9. Squirrel... 
10. Dormou.se 
11 



Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 

Water-rat \ Europe 

Hare Europe 

Rabbit ! Europe 



X. Africa 

N. Africa 

N. Africa 

N. Africa 

N. Africa 

N. Africa 



X. Africa 



Siberia, 
Central 
Central 
Siberia. 
Central 
Central 
Central 
Central 
Central 



Afghanistan. 
A.sia to Amoor. 
A.sia to Amoor. 

Asia to Amoor. 

Asia to Amoor. 

Asia to Amoor. 

Asia. 

Asia to Amoor. 



Central Asia to Amoor. 
W. Siberia, Per.sia. 



We thus see that out of thirteen of our commonest 
quadrupeds 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 inhabitants of the New World, 
being as common in the northern parts of North America 
as they are with us ; but with these exceptions 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 examjDle, 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 

D 



34 ISLAND LIFE 



more arctic kinds, as already stated, extend into the colder 
regions of North America. 

Eange of East 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 latitude as Germany. We find 
that there are forty-four terrestrial species (omitting the 
bats, the seals, and other marine animals), and of these no 
less than twenty-six are identical with European species, 
and twelve or thirteen more are closely allied representa- 
tives, leaving only five or six which are peculiarly Asiatic. 
We can hardly have a more convincing proof of the 
essential oneness of 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) be- 
cause a considerable number of West Asiatic and desert 
forms occur. Having, hoAvever, 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 Eange of British Birds. — As it is very imjDortant 
that no doubt should exist as to the limits of the zoological 



CHAP. Ill ZOOLOGICAL REGIONS 35 

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 Ave are now 
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 History of Jjritish Birds edited by 
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. In order to confine our exami- 
nation withiD 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. 

1. Lanius coUurio Red backed Shrike (also all Africa). 

2. Oriolus Galbv.la Golden Oriole (also all Africa), 

3. Turdus musicus SoHg-Tlirusli. 

4. ,, iliacus Red-wing. 

5. ,, pilaris Fieldfare. 

G. Monticola saxatilis Blue rock Thrush. 

7. raUicilla succica Bluethroat (also India in winter). 

8. Saxicola ruhicola Stonechat (also India in winter). 

9. , , ccnanthc Wheatear (also N, America). 

10. Acroccphalus arundinaccus. Great Reed- Warbler. 

I I . Sylvia curruca Lesser Whitethroat. 

1 2. Pants major Great Titmouse. 

1 3. Motacilla sulphurca Grey Wagtail (also China and 2Lalaya). 

14. , , raii Yellow Wagtail. 

15. A nthus trivialis Tree Pipit. 

16. , , spilolcUa Water Pipit. 

17. , , campestris Tawny Pipit. 

18. A lauda arvensis Skylark. 

19. , , crisiata Crested Lark. 

D 2 



ISLAND LIFE 



20. Emheriza schceniclus Reed Bunting. 

21. ,, citrinclla Yellow-liammer. 

22. "Fringilla montifrincjilla ... Brambling. 

23. Passer montanus Tree Sparrow (also S. Asia). 

24. „ domcsticus House Sparrow. 

25. Coecothraustes vulgaris Hawfincli. 

26. CarducUs sjjinus Siskin (also CMnaj. 

27. Loxia curxirostra Crossbill. 

28. Sturmis vulgaris Starling. 

29. Pyrrhocorax graculus Chough. 

SO. Corvus coroJie Crow. 

31, Hirundo rustica Swallow (all Africa and Asia). 

32. Cotylc riparia Sand ]\Iartin (also India and N. America). 

II. British Birds which raxge to Central or Xorth-east Asia. 

1. Laniiis excubitor Great Grey Shrike, 

2. Turdus varius White's Thrush (also to Japan). 

3. ,, atrigularis Black-throated Thrush. 

4. Acrocephalus 7icevii(s Grasshopper "Warbler. 

5. Phylloscoims supcrciliosus . . . Yellow-browed "Warbler. 

6. Certhia familiar is Tree-creeper. 

7. Parus cccruleus Blue Titmouse. 

8. , , atcr Coal Titmouse, 

9. , , paZ?,is^?-z's JMarsh Titmouse. 

10. Acrcdula cauda'.a Long-tailed Titmouse. 

11. Ampelis garrulus AVax-wing. 

12. Anthus richardi Richard's Pipit. 

13. Alauda alpcstris Shore Lark (also IsT. America). 

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

15. ,, la'pponicus ... Lapland Bunting. 

16. Emheriza rustica Rustic Bunting (also China). 

17. ,, pusilla Little Bunting. 

18. Linota linaria Mealy Redpole (also N. America). 

19. Pyrrliula eryihrina Scarlet Grosbeak (also N. India, China). 

20. ,, cnucleator Pine Grosbeak (also N. America), 

21 . Loxia hifasciata Tv.-o-barred Crossbill , 

22. Pastor roseus Rose-coloured Starling (also India). 

23. C'orvus corax Raven (also N. America), 

24. Pica riLsiica Magpie, 

25. Nucifraga caryocatactcs Nutcracker. 

in. British Birds ranging into N. Africa and W. Asia. 

1 . Lanius minor Lesser Grey Shrike, 

2. ,, auriculatus Woodchat (also Tropical Africa), 

3. Muscicapa grisola Spotted Flycatcher (also E, and S, 

Africa). 

4. ,, atricajnllct Pied Flycatcher (also Central Africa). 

5. Tardus viscivorus Mistletoe-Thrush (N. India in winter). 

6. ,, mcrulct Blackbird. 

7. , , torguatais Ring Ouzel. 

8. Accentor raodular is Hedge Sparrow. 

9. Eritliacus ruhecula Redbreast. 

10. Daulias luscinia Nightingale. 



cHAr. Ill ZOOLOGICAL REGIONS 37 



1 1 . Ruiicilla 2}hcenicurus Redstart. 

12. , , t ithys Black Redstart. 

13. Saxicola ruhclra Whinchat. 

14. Aedon galadodcs Rufous Warbler. 

15. Acroccxihalus strcpcrus Reed AVarbler. 

10. ,, sducnohcnns... Sedge Warbler. 

17. Mdizo2)hilus undatus Dartford Warbler. 

18. Sylvia rufci Greater Whitethroat. 

19. , , salicaria Garden Warbler. 

20. ,, cdriccqnlla Blackcap. 

21 . , , oiyhca Orphean Warbler. 

22. Phylloscoioiis sibilatrix Wood Wren. 

23. ,, trochilus Willow Wren. 

24. ,, collyhita Cliiffchaff. 

25. Ecgulus cristatus Golden-crested Wren. 

26. , , ignicapillus Fire-crested Wren. 

27. Troglodytes imrvulus Wren, 

28. Siita cccsia Nuthatch. 

29. Motacilla alba White Wagtail (also W. Africa). 

30. ,, Jlava Blue-headed Wagtail. 

31. Anthus 2yratensis Meadow- Pipit. 

S2. A lauda arhorca Woodlark. 

33. Calandrcllahrachydadyla.. Short-toed Lark. 

34. Emhcriza miliaria Common Bunting. 

35. ,, cirlus Cirl Bunting. 

36. ,, hortulana Ortolan. 

37. Fringilla ccelcbs Chaffinch. 

38. Coccothraudcs diloris Greenfinch. 

39. Scrinus liortulanus Serin. 

40. Cardudis degans Goldfinch. 

41 . Linota cannahina Linnet. 

42. Corviis moncdula Jackdav/. 

43. Chdidon urbica House-Martin. 

IV. British Birds ranging to North Africa. 

1 . Ilyjjolais idcrina Icterine AVarbler. 

2. Ac7vccphalus aquaticus Aquatic Warbler. 

3. ,, luscinioidcs Savi's Warbler. 

4. Motacilla luguh^is Pied Wagtail. 

5. Pyrrhula curopcca Bullfinch. 

6. Garrulus glandarius Jay. 

V. British Birds ranging to West Asia only. 

1 . Accentor collaris Alpine Accentor. 

2. Muscicapa 2Mrva R«d-breasted Flycatcher (to N. W India). 

3. Panurus biarmicus Bearded Titmouse. 

4. Mdanocoryijlia sibirica . . . White-winged Lark. 

5. Euspiza mclanoee2}liala . . . Black-headed Bunting. 
G. Linota flavirostris Twite. 

7. Corvus frugilegus Rook. 

VI. British Birds confined to Europe. 

1 . C Indus aqucctictis Dipper (closely allied races inhabit other 

parts of the Palaearctic Region). 

2. Pai'ios cristatuc Crested Titmouse. 



38 ISLAND LIFE 



3. Anthus dbscurus Rock Pipit. 

4. Linota rvfcscens Lesser Redpoll (closely allied races in 

N. Asia and N. America). 

5. Loxia 2nlyopsiUacus Parrot Crossbill (a closely allied form in 

jS". Asia). 

We find, that out of a total of 118 British Passeres 
there are : 

32 species which range to North Africa and Central 

or East 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. 

7 species which range to West Asia, but not to North 
Africa. 

5 species which do not range out of Europe. 

These figures agree essentially Avith those furnished by 
the mammalia, and complete the demonstration that all 
the temperate 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 East 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 Europe. The birds of Eastern 
Siberia have been carefully studied by Eussian naturalists 
and afford us the means of making the required comj^arison. 
There are 151 species belonging to the orders Passeres and 
Picarige (the perching and climbing birds), and of these no 
less than 77, or more than half, are absolutely identical 



CHAP. Ill ZOOLOGICAL REGIONS 39 

with European species ; 68 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 which- 
ever 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, our first zoological region, which has been termed the 
" Palsearctic " by Mr. Sclater, meaning the " northern 
old-world " region — a name now well known to naturalists. 
The Limits of the Palceardic 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 sandy 
ocean 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 matter of convenience, to consider 
the geographical line of the tropic of Cancer to form the 
boundary. We are thus enabled to define the Palsearctic 
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 Palsearctic region, and Baluchistan should 
probably go with these. The boundary in the north- 
western part of India is again difficult to determine, but it 



40 ISLAND LIFE 



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 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 demarkation between the temperate and tropical 
faunas, though this line will be so irregular, owing to the 
complex system of valleys and ridges, that in our joresent 
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 Palsearctic region a little south of 
Shanghai on the east coast. Several tropical genera come 
as far north as iNingpo or even Shanghai, but rarely 
beyond; while in Formosa and Amoy tropical forms 
predominate. Such decidedly northern forms as bullfinches 
and hawfinches are found at Shanghai ; hence w^e may 
commence the boundary line on the coast between Shanghai 
and Ningpo, but inland it probably bends a little southward, 
and then northward to the mountains and valleys of West 



CHAP. Ill ZOOLOGICAL REGIONS 41 

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 Pala3arctic, although its extreme southern portion, 
owing to its mild insular climate and evergreen vegetation, 
gives shelter to a number of tropical forms. 

Characteristic Features of the Falccaretic Pvcgion. — Ha vino 
thus demonstrated the unity of the Palsearctic region by 
tracing out the distribution of a large proportion of its 
mammalia and birds, 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 
TaljDidse or moles, consisting of eight genera and sixteen 
species, all of which are confined to it except one which is 
found in North-west America, and two which extend to 
Assam and Formosa. Among carnivorous animals the 
lynxes (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 Bovidse, chiefly antelopes ; while 
the entire group of goats and sheep, comj^rising twenty-two 
species, is almost confined to it, one species only occurring 
in the Rocky Mountains of North America and another 
in the Nilgiris 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 dor- 
mice, and the 23ikas, have only a few species elsewhere. 

In birds there are a large number of j^eculiar genera of 
which Ave need only mention a few of the more important, 
as the grasshojDper-warblers (Locustella) with seven species, 
the Accentors with twelve species, and about a dozen other 
genera of warblers, including the robins ; the bearded tit- 
mouse and several allied genera ; the long-tailed titmice 
forming the genus Acredula ; the magpies, chouglis, and 
nutcrackers ; a host of finches, among which the bull- 
finches (Pyrrhula) and the buntings (Emberiza) are the 



42 ISLAND LIFE 



most important. The true pheasants (Phasianus) are 
wholly Palsearctic, except one species in Formosa, as are 
several genera of wading birds. Though the reptiles of 
cold countries are few as compared with those of the 
tropics, the Palsearctic region in its warmer portions has a 
considerable number, and among these are many which 
are peculiar to it. Such are four genera of snakes, seven of 
lizards, five of frogs and toads, and twelve 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 
j)eculiar genus (Parnassius), only found elsewhere in the 
Rocky Mountains of North America, Avhile the beautiful 
genus Thais of the south of Europe and Sericinus of North 
China are equally remarkable. Among other insects we 
can only now refer to the great family of Carabida^, 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 aUies Pro- 
cerus and Procrustes, containing nearl}^ 800 species, is almost 
wholly confined to this region, and would alone serve to dis- 
tinguish it zoologically from all other parts of the globe. 

^ The following list of the genera of reptiles and amphibia peculiar to 
the Palfearctic Region has been furnished me by Mr. G. A, Boulenger, of 
the British Museum : — 

Snakes. Progs and Toads. 

Achalinus— Chinas, Japan. Pclohates—Ewr., S.W. Asia. 

C(elopcUis—'&. Y.xn\, N. Af., S.W. PcZ<!/^^.?— W.Em-ope. 

jYsia Dwcoglossus — S. Eur., is.AV. At. 

Macroprotodon—k'. Eur., X. Af. Boinhinator—Ex\x., Tenip. Asia. 

T(q)hromcto2wn— Cent. Asia. Ahjius—Cawt. and W. Eur. 

Newts. 

Lizards. Salamandra—Kux.,^ "N. Af , S.W. 
Phrynoccphahts — Cent, and S.W. Asia. 

Asia. GMogloasa — Spain and Portugal. 

Anguis—E\\YO])e, W. Asia. >Salamandrina— Italy. 

Blanus—Q.^V. Eur., N.W.Africa, Fackytriton— 'E.Sist Thibet 

S.W. Asia. Jlynohius — China and Japan. 

TrogonopMs—k.^\ Africa. Gcomolgc—^. :Manchuria. 

Laccrta—Ewr. Temp. Asia, N. O^iychodac-tylits— J ^^an. 

Africa (one sp. in Salaviandrclla — Siberia. 

W. Af.). Ranidcns — Siberia. 

Psammodroimis—^AN . Eur., N.W. 7?«^?-«c%^cnw— East Tliibet. 

Africa. Myalohatraclius — China, Japan. 

Algiroidcs S. Eur. Proteus — Caverns of S. Austria. 



ZOOLOGICAL REGIONS 43 



Having given so full an exposition of the facts whick 
determine the extent and boundaries of the Palsearctic 
region, there is less need of entering into much detail as 
regards the other regions of the Eastern Hemisj^here ; 
their boundaries being easily defined, vdiile their forms of 
animal life are Avell marked and strongly contrasted. 

Definition and Characteristic Groups of the Ethiojnan 
Region. — The Ethiopian region consists of all tropical and 
south Africa, to which are appended the large island of 
Madagascar and the Mascarene Islands to the east and 
north of it, though these differ materially from the con- 
tinent, and will have to be discussed in a separate 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 Palsearctic region. 

Taking first the mammalia, vv^e find the following re- 
markable animals at once separating it from the Palsearctic 
and every other region. The gorilla and chimpanzee, the 
baboons, numerous lemurs, the spotted hysena, the aard- 
wolf and hysena-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 characterised by the 
absence of others which are not only abundant in the 
Palsearctic region but in many tropical regions as well. 
The most remarkable of these deficiencies are the bears 
the deer and the vv'ild oxen, all of vrhich 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, 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, Potamogalidse ; the goldenmoles, also 
forming a peculiar family, Chrysochloridse ; as do the 
elephant-shrews, Macroscelididse ; the singular aard-varks, 
or earth -pigs, forming a peculiar family of Edentata called 
OrycteropodidiB ; while there are numerous peculiar genera 
of monkeys, swine, civets, and rodents. 

Among birds the most conspicuous and remarkable are, 
the great-billed vulture-cro^^s (Corvultur), the long-tailed 



44 ISLAND LIFE pakt i 



wliydah finches (Vidua), the curious ox-peckers (Buphaga), 
the, splendid metalHc stariings (LaniprocoUus), the hand- 
some plantain-eaters (Musophaga), the ground-hornbills 
(Bucorvus), the numerous guinea-fowls belonging to four 
distinct genera, the serpent-eating secretary-bird (Ser^Dent- 
arius), the huge boat-billed heron (Bateniceps), and the 
true ostriches. There are also three quite peculiar 
African farailies, the Musophagida3 or plantain-eaters, 
includino^ the eleo-ant crested touracos ; the curious 
little finch-like colies (Coliidse), and the Irrisoridse, 
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 familiar to require notice in a 
work of this character, but we may mention a few as mere 
illustrations : the puff-adders, the most hideous of poisonous 
snakes ; the chameleons, the most remarkable of lizards ; 
the o-oliath-beetles, the laro^est and handsomest of the 
Cetoniida3 ; and some of the Achatinse, which are the 
largest of all known land-shells. 

Dejlniiion and Ckaracia^istic Groups of the Oriental 
Region. — The Oriental region comprises all Asia south of 
the Pala^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 richest 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 
The Geographical Distribution of Animals as preferable to 
either Malayan or Indo-Australian, both of which have 
been proposed, but are objectionable, as being already in 
use in a different sense. 

The oreat features of the mammals of the Oriental reofion 
are, the long-armed aj^es, the oriing-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 (Timaliidse), its beautiful little hill-tits (Liotrich- 
idse), its green bulbuls (Phyllornithidse), its many varieties 



CHAr. Ill ZOOLOGICAL REGIOXS 



45 



of the crow-family, its beautiful gapers and pittas adorned 
with the most delicate colours, its great variety of hornbills, 
and its magnificent Phasianidag, 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 
mammalia 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 
arborepJ 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 grouj^s of birds we can only mention a 
few. The curious little tailor-birds of the genus Ortho- 
tomus are found over the whole region and almost alone 
serve to characterise it, as do the fine laughing-thrushes, 
forming the genus Garrulax; while the beautiful grass- 
green fruit-thrushes (Phyllornis), 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 distributed, 
and which may be said to characterise the region, is Gallus, 
comprising the true jungle-fowl, one of which, Gallus ban- 
kiva, is found from the Himalayas and Central India to 
Malacca, Java, and even eastward to Timor, and is the 
undoubted origin of almost all our domestic poultry. South- 
ern India and Ceylon each possesses distinct species of 
jungle-foYv^l, and a third very handsome green bird (Gallus 
seneus inhabits Java.) 

Eeptiles are as abundant as in Africa, but they j)resent 
no well-known groups which can be considered as specially 
characteristic. Among insects we may notice the magni- 



46 ISLAND LIFE 



ficent golden and green Papilionidse of various genera as 
being unequalled in the world ; while the great Atlas moth 
is probably the most gigantic of Lepidoj3tera, being some- 
times 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 Carabidoe, while the 
catoxantha is equally a giant among the BuprestidaB. 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. 

Definition and Characteristic Grotqos 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 23ortions 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 terminating with the submarine bank on which 
those islands are situated. The island of Celebes is in- 
cluded 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 Australian region. 

The great feature of the Australian region is the almost 
total absence of all the forms of terrestrial 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 Insectivora, Carnivora, nor Ungulata, 
while even the rodents are only represented by a few small 
rats and mice. In the remoter 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 

^ Remains of the dingo have been found fossil in Pleistocene deposits but 
the antiquity of man in Australia is not known. It is not, however, im- 



CHAP. Ill ZOOLOGICAL RECxIOXS 47 

are so great that every naturalist agrees that AustraHa 
must be made a separate region, the only difference of 
opinion being as to its extent, some thinking 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 characteristic Oriental families are 
absent. Thus there are no vultures, woodpeckers, pheas- 
ants, 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 (Meli- 
phagidse), 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 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 

probable that it may be as great as in Europe. My friend A. C. Swinton, 
Esq., Avhile working in the then almost unknown gold-tiekl of j\Iaryborough, 
Victoria, in January, 1855, found a fragment of a well-formed stone axe 
resting on the metamorphic schistose bed-rock about five feet beneath the 
surface. It was overlain by the compact gravel drift called by the miners 
" cement," and by an included layer of hard iron-stained sandstone. The 
fragment is about an inch and three-eighths wide and the same length, and 
is of very hard fine-grained black basalt. One side is ground to a very 
smooth and regular surface, terminating in a well-formed cutting edge more 
than an inch long, the return face of the cutting part being about a ciuarter 
of an inch wide. The other side is a broken surface. The weapon appears 
to have been an axe or tomahawk closely resembling that figured at p. 335 
of Lumholtz's Among Cannibals, from Central Queensland. The fragment 
was discovered by Mr. Swinton and the late Mr. Mackworth Shore, one of 
the discoverers of the gold-field, before any rush to it had taken place, and 
it seems impossible to avoid the conclusion that it was formed prior to the 
deposit of the gravel drift and iron-stained sandstone under which it lay. 
This would indicate a great antiquity of man in Australia, and would enable 
us to account for the fossilised remains of the dingo in Pleistocene deposits 
as those of an animal introduced by man. 



48 ISLAND LIFE part i 

never sit upon their eggs, but allow them to be hatched, 
reptile-like, by the heat of the sand or of fermenting vege- 
table matter; and lastly, the emus and cassowaries, in 
which the Avings are far more rudimentary than in the 
ostriches of Africa and South America. New Guinea and 
the surrounding islands are remarkable for their tree- 
kangaroos, their birds-of-paradise, their raquet-tailed 
kingfishers, their great crown-pigeons, their crimson lories, 
and many other remarkable birds. This brief outline being 
sufficient to show the distinctness and isolation of the 
Australian region, we will now jmss to the consideration 
of the Western Hemisphere 

Definition and Characteristic Groups of the Near die 
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 high- 
lands and volcanic peaks of Mexico and Guatemala, while 
a few which are characteristic of the troi^ics 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 mos't 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 con- 
tinued along the higher ridges of Guatemala. 

The Nearctic region is so similar to the Palsearctic 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 Avhich 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 fea- 
tures of this region, and see how far it resembles, and how 
far differs from, the Palsearctic. 

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 



CHAP. Ill ZOOLOGICAL REGIOXS 49 

hares, all very similar to those of the Eastern Hemisphere, 
and several hardly distinguishable. Even the bison or 
" buffalo " of the prairies, once so abundant and character- 
istic, 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 
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 un- 
like anything else. Then there are three genera of the 
weasel family, including the well-known skunk (Mej)hitis), 
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 (Geomyidoe), 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 (Erethizon), 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 Palsearctic 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 exam- 
ination shows the ornithologist that what he took for the 

E 



50 ISLAND LIFE 



latter are really quite distinct, and that there is not a single 
true- flycatcher of the family Muscicapidse, or a single 
starling of the family Sturnidse in the whole continent, 
while there are very few true warblers (Sylviidge), their 
place being taken by the quite distinct families MniotiltidaB 
or wood-warblers, and Vireonidse or greenlets. In like 
manner the flycatchers of America belong to the totally 
distinct family of tyrant-birds, Tyrannidse, and those that 
look like starlings to the hang-nests, Icterida3 ; and these 
four peculiar families comjDrise about a hundred and 
twenty 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 j^eculiar genera of cuckoos 
(Coccygus and CrotojDhaga), the humming-birds, the wild 
turkeys (Meleagris), and the turkey-buzzards (Cathartes), 
and we see that if there is 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 animials, 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 
Iguanidse. Nowhere in the world are the tailed bat- 
rachians so largely developed as in this region, the Sirens 
and the Amphiumidse forming two peculiar families, while 
there are nine j^eculiar genera of salamanders, and two 
others allied respectively to the Proteus of Euroj^e and the 
Sieboldia or giant salamander of Jaj)an. There are seven 
l^eculiar families and about thirty 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 lind the Nearctic region to be exceedingly well 
characterised, and to be amply distinct from the Palsearctic. 
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 tlie debatable ground 
between the Pala3arctic, Ethiopian, and Oriental regions. 



CHAP. Ill ZOOLOGICAL REGIONS 51 



If, however, we compare the number of species, which are 
common to the Nearctic and Palsearctic 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 Ave 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 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 Neotroincal 
Begion. — The Neotropical region requires very little defi- 
nition, 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 Austraha, which, however, it far ex- 
ceeds 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 pecu- 
liar 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 conti- 
nent can boast of. Among birds we have the charming 
sugar-birds, forming the family Coerebidse ; the immense 
and wonderfully varied group of tanagers ; the exquisite 
little manakins, and the gorgeously-coloured chatterers ; 
the host of tree-creepers of the family Dendrocolaptida3 ; 
the wonderful toucans; the puff-birds, jacamars, todies and 
motmots ; the marvellous assemblage of four hundred dis- 
tinct 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 Avonderful is its richness in species, 
since these fully equal, if they do not surpass, those of the 



52 ISLAND LIFE part i 

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 from South America, 
though a few species are found in Central America and 
the West Indies ; the Viverrida^ or civet family is wholly 
wanting, as are every form of sheeiD, 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, sunbirds, starlings, larks (except a soli- 
tary 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, 
marsuj^ials, 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 grou23s of 
the ant-thrushes, tyrants, tree-creepers, manakins, and 
chatterers belonging to it. The Picarise (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 j^revalence 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, 



CHAP. Ill ZOOLOGICAL REGIONS 53 

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. 

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 por- 
tion 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 jDroportion of the peculiar Neotropical groups extend 
as far as Costa Rica, Even 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 abund- 
ant. 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 hum- 
ming-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 considerable proportion of north temperate forms. But 
it contains armadillos, cavies and opossums ; and its birds 
all belong to 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 abundance of hang-nests, 
tyrant-birds, ant-thrushes, tree-creepers, and a fair pro- 



54 ISLAND LIFE 



portion of liumming-birds, tanagers and parrots. The zoology 
is therefore thoroughly Neotropical, although somewhat 
poor ; and it has a number of jDeculiar forms of strictly Neo- 
tropical types — as the chinchillas, alpacas, &c., which are 
not found in the tropical regions except in the high Andes. 
Comparison of Zoological Regions tcitli the Geographical 
Divisions of the Glohe. — Having now completed our survey 
of the great zoological regions of the globe, we find that 
they do not differ so much from the old geogi-aphical 
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 Palsearctic 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 with the zoological pri- 
mary divisions of the earth is sufficiently clear. In order 
to make these relations visible to the eye and more easily 
remembered, we will j^ut them into a tabular form : 

Regions. Geographical Equivalent. 

Palsearctic Europe, with north temperate Africa and Asia. 

Ethiopian Africa (south of the Sahara) with Madagascar. 

Oriental Tropical Asia, to Philippines and Java. 

Australian ... Australia, with Pacific Islands, Moluccas, &c. 

Nearctic North America, to Xorth Mexico. 

Neotropical . . . South America, with tropical N. America and W. Indies. 

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



N E A R G T I C P AL^ARCTIC 

I I 

I Oriental 

Ethiopian I 

Neo- I 

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 
Schoeniclus — The European and Japanese Jays — Supposed Examples of 
Discontinuity among North American Birds — Distribution and Antiquity 
of Families — Discontinuity a proof of Antiquity — Concluding Remarks. 

In the preceding chapters we have explained the general 
nature of the jijhenomena presented by the distribution of 
animals, and have illustrated and defined the new 
geographical division of the earth which is found best to 
a^ree with them. Before we s^o further into the details of 
our subject, and especially before we attempt to trace the 
causes which have brought about the existing 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, such as geological and climatal 
changes, and the origin and development of species and 
groups by natural selection. This last is of the most 
fundamental importance, and its bearing on the dispersal 



56 ISLAND LIFE 



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 
distribution of species, of genera, and of families, present 
almost 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 comprehensive 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 thirty years ago, and 
have now come to be ado23ted by naturalists as established 
propositions in the theory of evolution. 

The Origin of Nno SjJccics. — 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 Avell 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 23lace, no new 
species will arise. For every place or station is supposed 
to be filled by creatures in all respects adapted to sur- 
rounding 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 sj^ecies 
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 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 57 

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

But the change will most likely affect even flourishing 
species in different ways, some beneficially, others inju- 
riously. Or, again, it may affect a great many injuri- 
ously, to such an extent as to require some change in their 
structure or habits to enable them to get on as well as be- 
fore. Now " variation " and the " struggle for exist- 
ence " 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 
neio sjMcies will be almost sure to be formed. 

Variation in Animals. — 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 fally. 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 extremely 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 grey- 
hound and a bull-dog ! Yet, if we had the complete series 
of ancestors of these two breeds before us, we should prob- 



58 ISLAND LIFE 



ably find that in no one generation was there a greater 
difference 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 well aware that this is a mistake, it is only 
recently that they have been able to adduce positive proof 
of their opinion. 

The Amount of Variation in JSortli Amoncan Birds. — 
An American naturalist, Mr. J. A. Allen, has made elabor- 
ate 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 distribution 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, Avidth, thickness, and 
curvature of the bill. These variations are very consider- 
able, often reaching to one-sixth or one-seventh of the 
average dimensions, and sometimes more. Thus Turdus 
fusccscens (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 2 2' 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 Dcndraca 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 Mclospiza mclodia (the American 
song-sparrow) being sometimes reduced to narrow lines. 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 59 



while in other specimens they are so enlarged as to cover 
the greater part of the breast and sides of the body, some- 
times uniting on the middle of the breast into a nearly 
continuous patch. In one of the small spotted wood- 
thrushes, Turdus fuscescens, the colours are sometimes very 
pale, and the markings 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 be- 
tween adult males, so that there is no question of differences 
of age or sex, and the pair last referred to Avere 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 
extent 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 variation in the 
dimensions and proportions of the various organs of from 
10 to 25 per cent, as is here proved to occur, we may assume 
from 3 to 6 per cent, as generally occurring in the majority 
of species ; and if we further remember that the above 
excessive variations were found by comparing 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 grouj^s 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, 

^ 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 Comparative Zoology at Harvard College, Cambridge, 
Massachusetts. 



60 ISLAND LIFE part i 

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 pre- 
vailed w^as much more numerous than the extremes, 
perhajjs twice, or even three times, as great as either of 
them, and forming such a series as the following — 10 
maximum, 30 mean, 10 minimum development. In or- 
dinary cases we have no reason to believe that the mean 
characters or the amount of variation of a species changes 
materially from year to year or from century to century, 
and we may therefore look upon the central group as the 
type of the species which is best adapted to the conditions 
in wdiich it has actually to exist. This type wdll therefore 
always form the majority, because the struggle for existence 
will lead to the continual suppression of the less perfectly 
adapted extremes. But sometimes a species has a wide 
range into countries wdiich differ in physical conditions, 
and then it often happens that one or other of the extremes 
wdll predominate in a jDortion of its range. These form 
local varieties, but as they occur mixed with the other 
forms, they are not considered to be distinct species, al- 
though they maj differ from the other extreme form quite 
as mach as species often do from each other.^ 

Hoiv Neiv Species arise from a Variahle 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 Avill become extinct, being replaced by two species, 

^ The great variation in wild animals is more fully discussed and 
illustrated in the author's Darwinism (Chapter III.). 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 61 



each formed by a combination 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 sjoecies 
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 requirino- a 
corresponding change of constitution, of covering, of vege- 
table 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 
greater wariness can escape their new foes. We may thus 
easily understand how a series of changes may occur at 
distant intervals, each leading to the selection and pre- 
servation of a special set of variations, and thus what was 
a single sj^ecies 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 condi- 
tions, 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 strusfSfle 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 modi- 
fications that they Avill be able to s]3read 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 



62 ISLAND LIFE 



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 whicli 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 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 become 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 a 
new place in the economy of nature. It Avill almost cer- 
tainly have arisen from an extensive or dominant species, 
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 adaiDtability to 
a wide range of conditions which gave success to its 
ancestors. It will therefore 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, sj^reading 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 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 63 

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 con- 
tinue to maintain themselves in areas where they are 
removed from the influences that exterminated their 
fellows. 

Cause of the Extinction of S'pccies. — 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 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 places that we find the most striking 
examples of the preservation of fragments of primeval 
groujDS of animals, often widely separated from each other, 
owing to their having been preserved at remote portions of 
the area of the once widesf)read 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 ty^^es 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 
o^eneral assemblao^e of hio^her 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 primitive of 
all vertebrates ; while the Galeopithecus and Tarsius of the 
Malay islands and the i3otto of West Africa, survive amid 
the hiofher mammalia of the Asiatic and African continents 



64 ISLAND LIFE 



owmo- to their nocturnal habits and concealment in the 

o 

densest forests. , 

The Fdsc and Decay of S2)ecics 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 con- 
tinuous area which gets larger and larger till it reaches a 
maximum ; and Ave accordingly find that almost all exten- 
sive groups are thus continuous. When decay commences, 
and the group, ceasing to be in harmony with its environ- 
ment, 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 portions. This is the more likely to 
be the case because the most recently formed species, 
probably adapted to local conditions and therefore most 
removed from the general type of the grou23, 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 phenomenon 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. 

BisccntinuotLS SjJcciJic Areas, why Bare. — But although 
discontinuous generic areas, or the separation from each 
other of species whose ancestors must once have occupied 
conterminous or overlapping areas, is of frequent occur- 
rence, yet undoubted cases of discontinuous specific areas 
are very rare, except, as already stated, wlien 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 com- 
mon phenomenon of a species being only found in the 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 65 

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 explanation; but in one of the cases 
refeiTed 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 
of mammalia. It will be interesting therefore to examine 
the few cases on record, as we shall thereby obtain ad- 
ditional knowledge of the steps and processes by which 
the distribution of varieties and species has been brought 
about. 

Discontinuity of the Area of Farus 2^alustris. — Mr. See- 
bohm, who has travelled and collected in Europe, Siberia, 
and India, and possesses extensive and accurate knowledge 
of Palsearctic birds, has recently called attention to the 
varieties and sub-species of the marsh tit {Parus j^cihistris), 
of which he has examined 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, forming the 
sub-species F. borealis.^ In Japan and Kamschatka other 

1 See Ibis, 1879, p. 32. 

2 In Mr. Seebohm's latest work, Bi7xls of the Japanese Emjyirc (1890), 
he says, " Examples from North. China are indistinguishable from those 
obtained in Greece " (p. 82). 

F 



66 ISLAND LIFE 



varieties are found, which have been named respectively 
P. jcfponicus and P. camschatJcensis and another P. songarus 
in Turkestan and Mongoha. Now it all depends upon 
these forms being classed as sub-sjDecies or as true species 
whether this is or is not a case of discontinuous specific 
distribution. If Parus horealis is a distinct species from 
Parus 2'>cthistris, as it is reckoned in Gray's Hand List of 
Birds, and also in Sharpe and Dresser's Birds of EuropCy 
then Parus palustris has a most remarkable discontinuous 
distribution, as shown in the accompanying map, one 
portion of its area comprising 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 miles between them. If, how- 
ever, these two forms are reckoned as sub-species only, 
then the area of the species becomes continuous, while 
only one of its varieties or sub-species has a discontinuous 
area. It is a curious fact that P. palustris and P. horealis 
are found toofether 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. 

Disco7itinuity of Bmhcri^a schceniclus. — The other case 
is that of our reed bunting {Emheriza schmniclus), which 
ranges over almost all Europe and Western Asia as far as 
the Yenesai valley and North-west India. It is then 
rejilaced by another smaller species, B. j^f^sserina, which 
ranges eastwards to the Lena river, and in winter as far 
soutli as Amoy in China ; but in Japan the original species 
appears again, receiving a new name {B. 'pyrrhulina), but 
Mr. Seebohm assures us that it is quite indistinguishable 
from the European bird. Although the distance between 
these two portions of tlie species is not so great as in the 
last example, being about 2,000 miles, in other respects 
the case is an interesting one, because the forms which 
occupy the intervening space are recognised by Mr. 
Seebohm himself as undoubted species.^ 

i Ihls, 1879, p. 40. In his Birds of the Japanese Empire (1890), Mr. 
Seebohm classes the Japanese and European forms as E. schceniclus, 
and thinks that their range is probably continuous across the two 
continents. 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 67 



The European cmd Japanese Jays. — Another case some- 
what resembling that of the marsh tit is afforded by the 
European and Japanese ja^^s {Gamdus glandarius and G. 
japonietcs). Our common jay inhabits the whole of Europe 
except the extreme north,, but is not known to extend any- 
where into Asia, where it is represented by several quite 
distinct species. (See Map, Frontispiece.) But the great 
central island of Japan is inhabited 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. 

Supposecl Examples of Discontinuity among North 
American Birds.— 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 central plains and the vast ranges of the 
Rocky Mountains and Sierra Nevada, that we can hardly 
expect to find species wdiose 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 is 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 maintained tlieir continuity towards the north, 
while even when differentiated into two or more allied 

F 2 



68 ISLAND LIFE part i 



species their areas are often conterminous or over- 
lapping. 

Almost the only bird that seems to have a really discon- 
tinuous range is the species of wren, Thryotliorus hcwicJdi, 
of which the type form ranges from the east coast to 
Kansas and Minnesota, while a longer-billed variety, 
T. leioickii sioilurus, is found in the wooded parts of 
California and as fa5r 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 Vireo hellii of the middle United 
States and the sub-species intsillus of California ; and of 
the purple red-finch, Carjpodacusinirpureus, with its variety 
C. califo7micus ; 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 that 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 re- 
markable 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 phenome- 
non — 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. 

DistrilmtiGn and Antiquity of Families. — Just as genera 
are groups of allied species distinguished from all other 
groups by some well-marked structural characters, so 
families are groups of allied genera distinguished by more 
marked and more important characters, which are generally 
accompanied by a peculiar 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 de- 
velopment the original rudimentary species becomes sup- 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTION 69 

planted 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. 

Discontinuity a Proof of Antiquity. — Discontinuity will 
therefore be an indication of antiquity, and the more widely 
the fragments are scattered the more ancient we may 
usually presume the parent group to be. A striking- 
example is furnished by the strange reptilian fishes form- 
ing 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 iKcracloxa is 
only known from the Amazon and some other South 
American rivers. An allied species, Zejnclosiren anneetens, 
sometimes 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 Dip- 
terus evidently belong to the same group, while in North 
America the Devonian rocks have yielded a gigantic allied 
form which 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 
belonging 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 



70 ISLAND LIFE 



find them now isolated in remote parts of the globe, the 
natm^al 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 exist- 
ing 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 
distribution 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 betAveen the isolated genera which in many cases now 
alone exist ; while it is almost an axiom of " natural selec- 
tion " that such numerous 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 kno^A^ and 
l^robable changes of sea and land, the knoAMi changes of 
climate, and the actual powers of dispersal of the different 
groups of animals, were such as would have enabled all the 
now disconnected gi'oups to have once formed parts of a 
continuous series. Proofs of such former continuity are 
continually being obtained by the discovery of allied extinct 
forms in intervening lands, but the extreme imperfection 
of the o-eolooical record as reo^ards land animals renders it 



CHAP. IV EVOLUTION THE KEY TO DISTRIBUTIOX 71 

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, notwithstanding 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 IMamraals — 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 arc confined 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 WTiters, 
and it wnll 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 



CHAP. V DISPERSAL OF ANIMALS AND PLANTS 73 

particular cases that arise in regard to the faunas and floras 
of remote islands. But the other side of the question of 
dispersal — that which depends on geological and cUmatal 
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 
comprehension of these intricate problems. The four 
chapters which follow this are devoted to a full examin- 
ation of these profoundly interesting and important 
questions, after wdiich 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 which 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 distribution of pigs in the islands 
of the Eastern 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 endeav- 
our 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 tlie larger mammalir.. 



74 ISLAND LIFE part i 

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 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 
OTowincr on a stratum of soil which even formed a white 
beach round the margin of each raft. Among the 
Philippine Islands 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 field-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 thus conveyed at the same time, such 
accidents would no doubt be rare. Insects, however, 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 connection, 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 



75 



CHAP. V DISPERSAL OF ANIMALS AND PLANTS 

form a broad isthmus connecting Asia and America as fur 
south as the parallel of 60° N. Continuity of land there- 
fore 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 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 Dupersal of Birds. — Wherever mammals can mi- 
grate 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 Avith 
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 Dis]3crsal of ReiMlcs. — 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 the 
reptile 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 
^ Lyell's Principles of Geology, ii., p. 369. 



76 ISLAND LIFE 



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 Disjjersal of Am'phibia and Frcsh-iuaUr Fishes. — 
The two lower groups of vertebrates, Amphibia and fresh- 
water fishes, possess special facilities for dispersal, in the 
fact of their eggs being deposited in water, and in their 
aquatic or semi-aquatic habits. They have another ad- 
vantage 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 productions of the globe. 
Some genera of Batrachia have almost a w^orld-wide dis- 
tribution ; 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 depressions 
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, 
however, 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 ice may have come into play. High ranges of moun- 
tains, 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 



CHAP, r DISPERSAL OF ANIMALS AND PLANTS 77 



antiquity of the group, which has survived so many- 
changes in physical geography that it has been able, step 
by step, to reach countries Avhich are separated by barriers 
impassable 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 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 Disjjersal of Insects. — 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 lightness 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 
larvae 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 Switzerland con- 
sisted 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 hemisphere in a somewhat more southern latitude. 
There is, therefore, 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 mammalia. 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 



ISLAND LIFE 



carried into a new country they cannot live. Many 
caix only feed in the larva state on one species of plant ; 
others are bound up with certain groups of animals on 
Avhom 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 it happens, that among insects 
are to be found examples of the widest and most erratic 
dispersal and also of the extremest restriction to limited 
areas ; and it is only by bearing these considerations in 
mind that we can find a satisfactory explanation of the 
many anomalies we meet with in studying their distribu- 
tion. 

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 Avide, and often a cosmo- 
politan 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 
ojDcrculum, or which close the mouth of the shell with a 
diaphragm of secreted mucus, may float across narrow 
arms of the sea, especially w^hen 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, 

^ ]\Ir. Darwin found that the hirge Helix pomatia 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 



CHAP. T DISPERSAL OF ANIMALS AND PLANTS 79 

their powers of voluntary dispersal, even on land, are very 
limited, and this will explain the extreme restriction of their 
range m many cases. 

Great Antiquity of Land-Shells. — The clue to the almost 
imiversal 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 closety 
allied to them, 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 
Palaeozoic 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 Palaeozoic 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 Avith 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 
abundance 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 

water in calm weatlier, the distance might extend to a thousand miles or 
more. The eggs of fresh-water mollusca, as well as the young animals, are 
known to attach themselves to the feet of aquatic birds, and this is probably 
the most efficient cause of their very wide diffusion. 



80 ISLAXD LIFE part i 

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 continent. 
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 gToup of 
animals whatever, but which is perhaps explained by the 
considerations now suggested. 

The Dis]oersal of Plants.— Th.Q ways in which plants are 
dispersed over the earth, and the special facilities they often 
possess 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 tAvo 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 argu- 
ment in particular cases. A few general remarks only will 
therefore be made here. 

Special Adaptahility of Seeds for Dispersal. — Plants pos- 
sess 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 



CHAP. V DISPERSAL OF ANIMALS AND PLANTS 81 

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 in the air, while 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 
undoubtedly imj)ortant 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 iDlumage 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 Avill be found in Chapter XII. 
when discussing the origin of the flora of the Azores and 
Bermuda. 

Ocean-currents as Agents in Tlant-dispersal. — Ocean-cur- 
rents 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 experi- 
ments have been collected proving that seeds may some- 
times be carried in this way many thousand miles and 
afterwards germinate. Mr. Darwin made a series of in- 
teresting experiments on this subject, some of which will 
be given in the chapter above referred to. 

Bisperzal 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 

G 



82 ISLAXD LIFE 



relation to that of the nearest continent ; but there are 
other phenomena presented 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 
mountains chains has probably been effective ; and the 
exact mode in Avhich 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 succession of moderate steps, owing to the frequent 
exposure of fresh surfaces of soil or dSbris on mountain 
sides and summits, offering stations on which foreign 
plants can temporarily establish themselves. 

Antiquity of Plants as affecting their Distonhution. — We 
h?.ve already referred to the importance of great antiquity 
in enabling 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. Eich 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 therefore 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, ren- 
ders it far less difficult to understand the examples of wide 
distribution of the genera and species of plants than in the 
case of similar instances among animals. This subject 
wdll be further alluded to when discussing the origin of 
the New Zealand flora, in Chapter XXII. 



CHAPTER YI 

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 par- 
ticular 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. 

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 occujiied by volcanic and 
fresh- water dejoosits, 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 there must 

G 2 



84 ISLAND LIFE 



have been other continents situated where we now 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 : — 
" Continents, therefore, although permanent for whole 
geological ej^ochs, 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 is impossible to resist other evidences that they 
have once been land. The very continuity of animal and 
vegetable life on the globe points to it. The molluscous 
fauna of the eastern coast of North America is very simi- 
lar 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 g-eologist should not remember the recent and lono- 
continued warm climates of the Arctic regions, and see 
that a connection of Northern Euroi:)e by Iceland with 
Greenland and Labrador over a sea far less than a thousand 
fathoms deep would furnish the "littoral continuity" re- 
quired. 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 oscillations, of the 
level of the land with respect to the sea were confined within 
limits near the present continents, the results would have 
been a gradual diminution instead of develojoment 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 continental 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 sand- 
stones and argillaceous shales. The evidence of chemistry 
thus confirms the inductions drawn from the distribution 
of animal life upon the globe." 

^ Principles of Geology, lltli Ed., Vol, I., p. 258. 
- On Limestone as an Index of Geological Time. 



CHAP. Yi GEOGRAPHICAL AND GEOLOGICAL CHAXGES 85 



So far from this being a " mathematical demonstration," 
it appears to me to be a complete misinterpretation of 
the facts. 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 orio-in- 
ally supplied it still keep up that supply, though perhaps 
in dimmished 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 accumulation 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 develop- 
ment 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, by supplying 
more calcareous matter in solution for secretion by lime- 
stone-forming organisms, lead to their comparative 
abundance in later as compared with earlier formations. 

However weak we may consider the above-quoted argu- 
ments 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 almost always find a 
considerable belt of shallow water, meaning thereby water 
from 100 to 150 fathoms deep. The distance from the 



86 ISLAND LIFE part i 

coast line at which such dejDths 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 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 (witli few exceptions) are organic, con- 
sisting 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 consist of sand or pebbles or any visible frag- 
ments of rock, must have been formed within 50 or 100 
miles of then existing continents, or if at a greater distance, 
in shallow inland seas receiving dej^osits from more sides 
than one, or in certain exceptional areas where deep ocean 
currents carry the d^hris of land to greater distances.^ 

^ In liis Preliminary Eejjort on Oceanic Deijosit, Mr. Murray says : — "It 
lias been found that the deposits taking place near continents and islands 
have received their chief characteristics from the presence of the debris 
of adjacent lands. In some cases these deposits extend to a distance of 
over 150 miles from the coast." [Proceedings of the Royal Society, 
Vol. XXIV. p. 519.) 

' ' The materials in suspension appear to be almost entirely dei)Osited 
within 200 miles of the land," [Proceedings of the Royal Society of Edin- 
burgh, 1876-77, p. 253.) 



CHAP. VI GEOGRAPHICAL AND GEOLOGICAL CHANGES 87 

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 de23osited within 
a comjDaratively short distance of a sea-shore. Sir 
Archibald Geikie says : — " Among the thickest masses of 
sedimentary rock — those of the ancient Palaeozoic 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 interpreted 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 sedi- 
mentary matter." He goes on to say, that this general 
statement applies to the more recent as well as to the more 
ancient formations, and concludes — "In short, the more 
attentively the stratified rocks of the earth are studied, the 
more striking becomes the absence of any formations amoug 
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 Avidth 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 

1 Geographical Evolution. {Proceedings of the Royal Grngrajthical Society. 
1879, p.' 426.) 



88 ISLAND LIFE 



from the cUhris of which they were origmally foi-med. 
Again quoting Sir Archibald Geikie : — " The materials car- 
ried down to the sea would arrange themselves 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. 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 igne- 
ous or metamorphic 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 perceiD- 
tibly affecting their nearly horizontal position ; and also of 
intense lateral compression, suj^posed 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 subaerial denudation into peaks and 
valleys, constitute our great mountain systems.^ In this 

^ Professor Dana was, I believe, the first to point out that the regions 
which, after long undergoing subsidence and accumulating vast piles of 
sedimentary deposit have been elevated into mountain ranges, 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 has shown 
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 occiirred successively in 



CHAP. VI GEOGRAPHICAL AND GEOLOGICAL CHANGES 89 

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 archi- 
pelago. And, as subsidence will always be accompanied 
by deposition, of sediments from the adjacent land, 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 alter- 
nate subsidences and elevations, each of moderate amount. 
Supposed Oceanic Formations ; — tlic Origin of Chalk. — 
There seems very good reason to believe that few, if any, of 
the rocks known to geologists correspond exactly to the de- 
posits 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 corre- 
spond 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 proportion of 
both deposits, more especially the pelagic Foraminifera, 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 coccoliths and discoliths, are also found in both 
formations, while there is a considerable general resem- 
blance between the higher forms of life. Sir Wyville 
Thomson tells us, that — ''' Sponges are abundant in both, 
and the recent chalk-rnud has yielded a large number of 
examples of the group porifcra xitrea, which find their 
nearest representatives among the Ventriculites of the 
white chalk. The echinoderm fauna of the deeper parts of 

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 whicli the deposits 
are formed which, on the subsei|uent upheaval, become mountain ranges. 
(Manual of Geology , 2nd Ed., p. 751.) 



90 ISLAND LIFE 



the Atlantic basin is very characteristic, and yields an 
assemblage of forms which represent in a remarkable 
degree the corresponding group in the white chalk. 
Species of the genus Cidaris are numerous ; some remark- 
able flexible forms of the Diademidse 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 shoA\Ti to exist 
between it and some kinds of oceanic mud should have 
been at once seized upon, and the conclusion arrived at 
tiiat 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 approximately with chalk in chemical compo- 
sition, only containing from 44 to 79 jDer 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 car- 
bonate of lime, and a very minute quantity of alumina and 
silica. This large proportion of carbonate of lime implies 
some other source of this mineral, and it is j)robably to be 
found in the excessively fine mud produced by the decom- 
jDosition 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 dej)osit 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 Lyell well remarks 

1 Nature, Vol. 11. , p. 297. 

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

Carbonate of Lime 92-800 per cent. 

Carbonate of Magnesia 2'385 

Alumina 0'250 

Oxideoflron 0-543 

Silica 0-750 

Phosphoric Acid and Fluorine 2 '113 " 

Waterandloss 1-148 



CHAP. VI GEOGRAPHICAL AND GEOLOGICAL CHANGES 91 

that the pure calcareous mud joroduced by the decompo- 
sition of the shelly coverings of mollusca and zoophytes 
would be much ligiiter than argillaceous or arenaceous mud, 
and being thus transported to greater distances would be 
completely separated from all impurities. 

Now the Globigerinse have been shown by the Challenger 
explorations to abound in all moderately warm seas ; livino- 

This chalk consists simply of comminuted corals and shells of the reef. 
It has been examined microscopically and found to he destitute of the 
minute organisms abounding in the chalk of England. {Geology of the 
United States Exj)loring Expedition, p. 150.) Mr. Guppy also found 
chalk-like coral limestones containing 95 p.c, of carbonate of lime in the 
Solomon Islands. 

The absence of GloMgerince is a local x>lienomenon. They are quite 
absent in the Arafura Sea, and no Glohigerina-ooze, was found in any of 
the enclosed seas of the Pacific, but with these exceptions the Gloligeriiwn 
"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 GloMgerina-QdZQ of the Atlantic, four specimens of which given by 
Sir "W. Thomson {Voyage of the Challenger Vol. II. Appendix, pp. 374- 
376, Nos. 9, 10, 11 and 12) from the mid-Atlantic, show the following 
proportions : — 

Carbonate of Lime 43*93 to 79*17 i)er cent. 

Carbonate of Magnesia 1*40 to 2*58 

Alumina and Oxide of Iron. 6*00? to 32*98 

Silica 4*60 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 Glohigerina-oozQ of the mid-Atlantic, where it 
seems to be always present ; and the small projwrtion 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. 

Carbonate of Lime 94*09 98*40 

Carbonate of Magnesia 0*31 0*08 

Alimiina and Phosphoric Acid . . a trace 0*42 

Chloride of Sodium 1*29 — 

Insoluble debris 3*61 1*10 

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

The large proportion of carbonate of lime, and the very small quantity 

of silica, alumina, and insoluble debris, at once distinguish true chalk from 

the Glohigerina-ooze of the deep ocean bed. 



92 ISLAND LIFE part i 

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 dred.cjings and surface-gatherings of the 
Chcdlenr/er by 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 supported by the fact that in 
many stations not far from our own shores Globigerinse 
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 ; but Mr. Brady says that a dwarf variety of Globi- 
gerina was found in the soundings of the North Polar 
Expedition in Lat. 83° 19' N. 

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 sup23orted 
in a striking manner by the nature of the molluscan fauna 
of the chalk. Dr. Gwyn Jeffi'eys, one of our greatest 

^ Xotes on Reticularian Rhizopoda \ iw MicroscopicalJmuniaJ , Vol. XIX., 
New Series, p, 84. 

2 Proceedings of tlie Royal Society, Vol. XXIV. p. 532. 



CHAP. Yi GEOGRAPHICAL AND GEOLOGICAL CHANGES 93 

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 declared that they are all com- 
paratively 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 
Atlantic ooze — Leda, Verticordia, Nesera, 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 1,500 
geographical miles ; and in an ojoposite 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 is 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 Scan- 
dinavian highlands, extending to Northern Germany and 
North-western Russia, where Palaeozoic 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 extending 
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 
Sivitzerland, p. 175. To the north the sea may have had 

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



94 ISLAND LIFE 



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 naiTow 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, and even pure sands and sandstones, charac- 
terised 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 
anything like oceanic conditions having prevailed in 
Europe during the Cretaceous period ; but they are quite 
consistent with the existence of a great Mediterranean sea 
of considerable de]3th in its central j^ortions, and occuj^ying 
either at one or successive periods, the whole area of the 
Cretaceous formation. We may also note that the Maes- 
tricht beds in Belgium and the Faxoe chalk in Denmark 
are both highly coralline, the latter being, in fact, as com- 
pletely 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 snj^pose that during this period the 
comjDaratively 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 Avould bring with it that abun- 
dance of Globigerinse, 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 con- 
ditions for the production of the true chalk, as well as the 
other members of the Cretaceous formation. The products 



CHAP, vi GEOGKAPHICAL AXD GEOLOGICAL CHANGES 95 

of the denudation of its shores and islands would form the 
various sandstones, marls, and clays, which Avould be 
deposited 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 and often much less, would 
receive only the impalpable mud of the coral-reefs and the 
constantly falling tests of Foraminifera. These would 
imbed and preserve for us the numerous echinoderms, 
sponges, and moUusca, which lived upon the bottom, the 
fishes and turtles which swam in its waters, and some- 
times the winged reptiles that flew overhead. The abun- 
dance of ammonites, and other cephalopods, in the chalk, 
is another indication that the water in which they lived 
was not very deep, since Dr. S. P. Woodward thinks that 
these organisms Avere 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 lime mud. 
The lime-bottom, which consists almost entirely of Poly- 
thalamia, 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, Kotalia cultrata in large numbers, 
several Textilarise, Marginulinse, &c. Beside these, small 
free corals, Alcyonidse, Ophiurse, 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 Cretaceous times. No fact is more certain than 
the considerable break, indicative of a great lapse of time, 
intervening between the Cretaceous and Tertiary for- 

1 Geological Magazine, 1871, p. 426. 



96 ISLAND LIFE 



mations. 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 Creta- 
ceous 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, 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 ; and even 
these need not have been all under water at the same 
time. 

The several considerations now adduced are, I think, 
sufficient to show that the view put forth by some natural- 
ists (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 con- 
dition of Europe during that period. Instead of being a 
wide ocean, with a few scattered islands, comjDarable to 
some parts of the Pacific, it formed as truly a portion of the 
great northern continent as it does now, although the in- 
land seas of that epoch may have been more extensive 
and more numerous than they are at the present day.^ 

^ In his lecture on GcograpMcal Evolution (which was published after the 
greater part of this chapter had been written) Sir Archibald 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 Euroj^e and into Asia. 
But they v.cre probably nowhere more than a few hundred feet deep over 



CHAP. VI GEOGRAPHICAL AXD GEOLOGICAL CHANGES 



Fresli-waUr 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 con- 
tinents 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 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 
continuous 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 formations 
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 Cretaceous formation we have the same 
indications of persisting lands in the rich plant-beds of 
Aix-la-Chapelle, and a few other localities on the Continent, 
as well as in coniferous fruits from the Gault of Folkestone ; 
while in North America cretaceous plant-beds occur in 

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-General of the Geological Survey 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. 

H 



ISLAND LIFE 



New Jersey, Alabama, Kansas, the sources of the Missouri, 
the' Rocky Mountains from New Mexico to the Arctic 
Ocean, Alaska, California, and in Greenland and Spitz- 
bergen; while birds and land reptiles are found in the 
Cretaceous deposits of Colorado and other districts near the 
centre of the Continent. 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 West- 
phalia. In the older Oolite or Jurassic formation we have 
abundant proofs of continental conditions in the fresh-water 
and " dirt "-beds of the Purhecks in the south of England, 
with plants, insects and mammals; the Bavarian litho- 
graphic 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- 
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 
yet known to have existed on the earth. Professor O. C. 
Marsh describes it as having been between fifty and sixty 
feet long, and when standing erect at least thirty feet 
high ! 1 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 East Siberia and 
the Amur valley. The older Triassic deposits are very 
extensively developed in America, and both in the Con- 
necticut 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 j^lants. Here too are found the ancient 
mammal, Microlestes, of Wurtemberg, with the ferns, 
conifers, and Labyrinthodonts of the Bunter Sandstone in 
Germany ; while the beds of rock-salt in this formation, 

- Introduction and Succession of Vertebrate Life in America, by Professor 
0. C, Marsh. Reprinted from the Popular Science Monthly, March, April, 
1878. 



CHAP. VI GEOGRAPHICAL A^^D GEOLOGICAL CHANGES 99 



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 Palaeozoic formations, 
but find no diminution in the proofs of continental condi- 
tions. The Permian formation has a rich flora often pro- 
ducing coal in England, France, Saxony, Thuringia, Silesia, 
and Eastern Russia. Coalfields of the same age occur in 
Ohio in North America. In the still more ancient Carbon- 
iferous formation we find the most remarkable proofs of the 
existence of our present land massses 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 New Zealand. In North America there are immense 
coal fields, in Nova Scotia and New Brunswick, from Penn- 
sylvania southward to Alabama, in Indiana and Illinois, 
in Missouri, and even so far west as Colorado ; and there 
is also a true coal formation in South Brazil. This wonder- 
fully 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 consider- 
ation the fresh-water deposits that still remain to be 
discovered, and those extensive areas Avhere 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 
^ Physical Geography and Geology of Great Britain, 5tli Ed. p. 61. 

II 2 



100 ISLAND LIFE 



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 Con- 
tinents 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 gi'eat oceans. 
He says {Origin of Species, 6th Ed. 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 afford even a fragment of any Palseozoic or Secondary 
formation. Hence Ave may perhaps infer that during the 
Palaeozoic and Secondary periods neither continents nor 
continental islands existed where our oceans now extend ; 
for had they existed, Palaeozoic and Secondary formations 
would in all probability have been accumulated from sedi- 
ment derived from their wear and tear ; and these would 
have been at least j^artially 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 great oscillations of level, since the 
Cambrian period." This argument standing by itself has 
not received the attention it deserves, but coming in sup- 
port 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.^ 

^ 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 at one time adopted this view, speaking of the great belt of 



CHAP. VI GEOGRAPHICAL AND GEOLOGICAL CHANGES 101 



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 subjected 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 gro^vn 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 

Tertiary volcanoes " which extended through Greenland, Iceland, the Faroe 
Islands, the Hebrides, Ireland, Central France, the Iberian Peninsula, the 
Azores, ^Madeira, Canaries, Cape de Yerde Islands, Ascension, St. Helena, 
and Tristan d'Acunha, and which constituted as shown by the recent 
sonndings of H.M.S. 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 Ridge " 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 vokanic upheaval and 
the accumulation 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 may 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. 

In my Darwinism (pp. 344-5) I have given an additional argument 
founded on the comparative height and area of land with the depth and 
area of ocean, which seems to me to add considerably to the weight of the 
evidence here submitted for the permanence of oceanic and continental 
areas. 



102 ISLAND LIFE 



upraised coral reefs of inland seas. The mountains of one 
period have disappeared by denudation or subsidence, 
while the mountains of the succeedicg 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. 

Effect of Conti7iental Changes on the Distrihutio7i of Ani- 
mals. — It is 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 
livino' thinos must have been driven backward and forward 
from east to west, or from north to south, from one side of 
a continent or a hemisphere to the other. Owing to the 
remarkable continuity of all the land masses, animals and 
plants must have often been compelled to migTate into 
other continents, where in the struggle for existence under 
new conditions many would succumb ; while such as were 
able to survive would constitute 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 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 develop- 
ment and preservation of every weapon, every habit, and 
every instinct, which could in any way conduce to the 
safety and preservation of the several species. 

Changed DistoHbution proved hy the Extinct Animals of 
Different Epochs. — We thus find that, while the inorganic 
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 pre- 
served 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 



CHAP. VI GEOGRAPHICAL AND GEOLOGICAL CHAJiTGES 103 

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 migrations 
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 geological 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. 

Summary of Evidence for the General Permanence of 
Continents and Oceans. — As this question of the permanence 
of our continents or, rather, of the continental areas, 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 

^ In a review of Mr. T. Mellard Reade's Chemical Bnmdation 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 thepresent 
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 j^lants and the fact that 
the bulk of the strata on land are of marine origin are opposed to the hypo- 



104 ISLAND LIFE 



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 Avere 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 con- 
tained fossils, to be a comparatively shallow water forma- 
tion — 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. Everywhere 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 formations 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 lacustrine deposits can be traced back through 
every period, from the newer Tertiary to the Devonian and 
Cambrian, and in every continent which has been geo- 
logically explored ; and thus complete the proof that our 
continents have been in existence under ever changing 

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 Sir 
Archibald Geikie, who, in the lecture already quoted saj^s : — "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 
lain 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." 



CHAP, vi GEOGRAPHICAL AXD GEOLOGICAL CHANGES 105 

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 theii^ permanence and stability. 
In addition to their enormous depths and great extent, 
and the circumstance that the deposits now forming in 
them are distinct from anything found upon the land- 
surfa<;e, we have the extraordinary fact that the countless 
islands scattered over their whole area (with one or two 
exceptions only and those comparatively near to continental 
areas) never contain any Palaeozoic 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 and 
not really oceanic, 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 OcciuTence of a Glacial Epoch — Moraines — Travelled 
Blocks — Glacial Deposits of Scotland : the " Till " — Inferences from the 
Glacial Phenomena of Scotland — Glacial Phenomena of K"orth America 
— Effects of the Glacial Epoch on Animal Life — Warm and Cold Periods 
— Palaeontological Evidence of Alternate Cold and Warm Periods — 
Evidence of Interglacial W^arm Periods on the Continent and in North 
America — Migrations and Extinctions of Organisms caused by the 
Glacial Epoch. 

We have now to coosider another set of physical revolu- 
tions 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 has 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 o^Dposite phases of the 
same great phenomenon — cold or even glacial e230chs in 
the Temperate zones on the one hand, and mild or even 
warm periods extending into the Arctic regions on the 



CHAP. VII THE GLACIAL EPOCH 107 

other. The evidence for both these changes having oc- 
curred is conclusive ; and as they must be taken account of 
wlienever we endeavour to explain the past 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 Oeeurrence 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 glacia- 
tion 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 
gTOOves several inches wide, smaller furrows, and strise 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 direc- 
tion — 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 striae 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 phe- 
nomenon, the rounding off or planing down of the hardest 
rocks to a smooth undulating surface. Hard crystalhne 
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 



108 ISLAND LIFE 



are termed rocJies inoutonn6cs, from their often having the 
appearance at a distance of sheep lying down. 

Now these two phenomena are actually j^i'oduced by 
existing glaciers, while there is no other known or even 
conceivable cause that could have produced them. When- 
ever 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, gi'ooved, and striated just as 
are those of Wales and Scotland. The two sets of phe- 
nomena 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 
evidence. Glaciers j^roduce many other effects besides 
these two, and whatever effects they produce in Switzer- 
land, 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. 

Moraines. — Almost every existing glacier carries down 
with it great masses of rock, stones, and earth, which fall 
on its surface from the precipices and mountain slopes 
which hem it in, or the rocky peaks which rise above it. 
As the glacier slowly moves downward, this ddhris 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 teiTninal moraine. The de- 
crease 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 distinguished almost at a glance. Their position is 
most remarkable, having no apiDarent natural relation to 
the form of the valley or the surrounding slopes, so that 
they look like huge earthworks formed by man for pur- 
poses 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 Avhere no other 
natural force but that of ice could have placed them. 



CHAP, vit THE GLACIAL EPOCH 109 



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 Bloeks. — The phenomenon of travelled or 
jDerched blocks is also a common one in all glacier 




A GLACIER WITH MORAINES. 



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 circumstances the end of 
the glacier not being confined laterally will spread out, 



no ISLAND LIFE 



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 giaciation 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 hlochs 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 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 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 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 traceable 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 (/ e d), while those found 
towards Geneva have all come from the west side (p ^^)- 
It is also very suggestive that the highest blocks on the 



CHAP. VII 



THE GLACIAL EPOCH 



111 



Jura at G have come from the eastern shoulder of Mont 
Blanc in the dkect line 7^ B F G. Here the glacier would 
naturall}^ preserve its greatest thickness, while as it spread 
out eastward and Avestward it would become thinner. We 
accordingly find that the travelled blocks on either side of 




Blanc 



MAP SHOWING THE fOX-RSE OP THE ANCIENT GLACIER OP THE RHONE AND THE 
DISTRIBUTION OF ERRATIC BLOCKS ON THE JURA. 



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 conclusive that, after 
personal examination of the district in company with 
eminent Swiss geologists. Sir Charles Lyell gave up the 



112 ISLAND LIFE part i 



view he had first adopted — that the blocks had been 
carried by floating ice during a period of submergence — as 
altogether untenable.^ 

The jDhenomena now described demonstrate a change of 
climate suflicient 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 Switzer- 
land. 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 geolo- 
gists are acquainted with the weight of evidence 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 Dejjosits 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 lacustrine deposits, while others again have been 
formed or modified by the sea during periods of sub- 
mergence. But below them all, and often resting directly 
on the rock-surface, there are extensive layers of a very 
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 striae 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 

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

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



THE GLACIAL EPOCH ns 



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 j^atches, but in some 
of the broader valleys forms terraces which have been cut 
through by the streams. Occasionally it is found as high 
as two thousand feefc 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 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 
striae, perched blocks, rochcs moutonndes, and other marks 
of glacial action, occur very high up the mountains to at 
least 8,000 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 Glcicial Phenomena of Seotlctncl. — 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 con- 
clusion ; 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 corroborative evidence 
as to amount to absolute demonstration. The weight of 
this vast ice-sheet, at least three thousand feet in maxi- 
mum thickness, and continually moving seaward with a 
slow grinding motion like that of all existing glaciers, 

I 



114 ISLAND LIFE part i 

must have ground down the whole surface of the country, 
especially all the prominences, leaving the rounded rocks 
as well as the grooves and striae we still see marking the 
direction of its motion. All the loose stones and rock- 
masses which lay on the surface would he pressed into the 
ice ; the harder blocks would serve as scratching and grind- 
ing 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 
moutonn^es. 

The peculiar characters of the " till," its fineness and 
tenacity, 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 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 comparatively 
little drainage water, and thus the mud and stones collected 
in vast compact masses in all the hollows, and especially 
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 This view of the formation of 'ftill" 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, includ- 
ing the late Mr. Searles V. Wood, Jun., that mud ground off the rocks 
cannot remain beneath the ice, forming sheets of great thickness, because 
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 constantly 
receiving as the ice from one valley after another joined together, and 
at last produced an ice-sheet covering the whole country. The grind 



THE GLACIAL EPOCH 115 



There is good evidence that, when the ice was at its maxi- 
mum, 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.^ 

ing 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, and the ice 
extended, say, twenty miles in every direction from a given part of a valley 
where the ice was of less than the average thickness, the mud would 
necessarily accumulate at this part simply because there was no escape for 
it. Whenever the pressure all round any area Avas greater than the pressure 
on that area, the debris of the surrounding parts would be forced into it, 
and would even raise up the ice to give it room. 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 
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 
glaciers 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 debris. 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 gi-eat bulk of the debris must have 
gathered 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. 

^ That the ice-sheet was continuous from Scotland to Ireland is proved 
by the glacial phenomena in the Isle of ]\Ian, 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 Gcologv of the Isle of Man, bv John Home, 
F.G.S. Trans, of the Edin. Geol. Soc. Vol. II. pt. 3, 1874.) 

I 2 



11 G ISLAND LIFE 



It is evident that the change of climate requisite to 
proditce 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 witli 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 de- 
posited them at a height of 8,450 feet above the sea; 
while to the south, in the plains of Italy, the terminal 
moraines left by the retreating glaciers have formed exten- 
sive 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 than in Europe, stretching over the whole of 
Canada and to the south of the great lakes as far as 
latitude SO". There is, in all these countries, a wide-spread 
deposit like the " till " of Scotland, produced by the grind- 
ing 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, in Britain, Scandin- 
avia, 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 wdiole 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 



THE GLACIAL EPOCH n; 



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 deducino- the 
unknown 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. — It is hardly necessary to jDoint out what an 
important effect this great climatal cycle must have had 
upon all living things. When an icy mantle crept gradu- 
ally over much of the northern hemisphere till laro-e 
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 southward, causing a 
struggle for existence which must have led to the exter- 
mination of many forms, and the migration of others 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 suffi- 
ciently 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 



118 ISLAND LIFE 



distinct formations of " till " separated from each other by 
bed^ 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.^ Mr. 
Searles V. Wood, Jun., classes the most recent (Hessle) 
boulder clay as '• post-glacial," but he admits an inter- 
vening warmer period, characterised by southern forms of 
mollusca and insects, after which glacial conditions again 
prevailed wdth northern types of mollusca.^ Elsewhere he 
says : " Looking at the presence of such fluviatile mollusca 
as Cyrena flitmincdis and Unio littoralis and of such 
mammalia as the hippopotamus and other great pachy- 
derms, 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 j^artially accompanied, by a 
limited submergence, which nowhere 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 
dcjiression 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. 

^ 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, pp. 158, 160. 

^ Geological Magazine, 1876, p. 396. 



THE GLACIAL EPOCH 119 



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. 

Palceontological Evidence of Alternate Cold and Warm 
Periods. — Especially suggestive of a period warmer than 
the present, immediately following glacial conditions, is 
the occurrence of the hippopotamus in caves, brick-earths, 
and gravels of palaeolithic 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 abun- 
dantly along with those of the Elephas antiquus, Rhino- 
ceros hemitcechics, reindeer, bear, horse, and other quadru- 
peds, and with countless remains of the hyaenas which 
devoured them ; while it has also been found in cave de- 
posits in Glamorganshire, at Durdham Down near Bristol, 
and in the post-Pliocene drifts of England and France. 

The fact of the hippopotamus having lived at 54'' N. Lat. 
in England immediately after the glacial period seems 
quite inconsistent with a mere gTadual amelioration of 
climate from that time till the present day. The entirely 
tropical distribution of the existing animal and the large 
quantity of vegetable food which it requires both indicate 
a much warmer climate than now prevails in any part of 
Europe. The problem, however, is comjDlicated by the fact 
that, both in the cave-deposits and river gravels, its remains 
are often found associated with those of animals that 
imply a cold climate, such as the reindeer, the mammoth, 
or the woolly rhinoceros. At this time the British Isles 
were joined to the Continent, and a great river formed by 
the union of the Rhine, the Elbe and all the eastern rivers 
of England, flowed northward through what is now the 
German Ocean. The hippopotamus appears to have been 
abundant in Central Europe before the glacial epoch, but 
during the height of the cold was probably driven to the 
south of France, whence it may have returned by way of 
the Rhone valley, some of the tributaries of that river 
approaching those of the Rhine within a mile or two a 
little south-west of Mulhausen, whence it would easily 



120 ISLAND LIFE 



reach Yorkshire. Professor Boyd Dawkins supposes that 
at this time our summers were warm, as in Middle Asia 
and the United States, while the winters were cold, and 
that the southern and northern animals misfrated to and 
fro over the great plains which extended from Britain to 
the Continent. The following extract indicates how such 
a migration was calculated to bring about the peculiar 
association of sub-tropical and arctic forms. 

" It must not, however, be supposed that the southern 
animals migrated from the Mediterranean area as far 
north as Yorkshire in the same year, or the northern as 
far south as the Mediterranean. There were, as we shall 
see presently, secular changes of climate in Pleistocene 
Europe, and while the cold was at its maximum the 
arctic animals arrived at the southern limit, and while 
it was at its minimum the spotted hyaena and hippo- 
potamus and other southern animuls roamed to their 
northern limit. Thus every part of the middle zone has 
been successively the frontier between the northern and 
southern groups, and consequently their remains are 
mingled together in the caverns and river-deposits, under 
conditions which prove them to have been contemporaries 
in the same region. In some of the caverns, such as that 
of Kirkdale, the hyaena preyed upon the reindeer at one 
time of the year and the hippopotamus at another. In 
this manner the association of northern and southern 
animals may be explained by their migration according to 
the seasons ; and their association over so wide an area as 
the middle zone, by the secular changes of climate by 
which each part of the zone in turn was traversed by the 
advancing and retreating animals." ^ 

When we consider that remains of the hippopotamus 
have been found in the caves of North Wales and Bristol 
as well as in those of Yorkshire, associated in all with 
the reindeer and in some with the woolly rhinoceros or 
the mammoth, and that the animal must have reached 
these localities by means of slow-flowing rivers or flooded 
marshes by very circuitous routes, we shall be convinced 
that these long journeys from the Avarmer regions of South 
^ Early Man in Britain and his Place in the Tcrtianj Period, p. 113. 



THE GLACIAL EPOCH 121 



Europe could not have been made during the short sum- 
mers of the glacial period. Thus the very existence of 
such an animal in such remote localities closely associated 
with those implying almost an arctic winter climate ap- 
pears to afford a strong suj)port to the argument for the 
existence of warm inter-glacial or post-glacial periods. 

Evidence of Intco^ glacial Warm Periods on the Continent and 
in North Aynerica. — 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 lig- 
nite 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 numer- 
ous animal remains are also found, showing that the 
country was then inhabited by an elephant (Ulephas 
antiquus), a rhinoceros {Rhinoceros megarhinus), the urus 
(Bos primigcnius), the red deer (Cerviis elephas), and the 
cave-bear, (Ursus sj^elceics); 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 one was deposited, but no interglacial 
deposits have yet been found. In North America more 
comj^lete 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 fossiliferous 
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, 

^ lieev's Primceval World of Stoitzerland Vol. IL, pp. 148-168. 
■^ Dr. James Geikie in Geological Magazine, 1878, p. 77. 



122 ISLAND LIFE 



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

Migrations and Extinction of Organisms caused hy the 
Glacial UjJocJi. — Our last glacial epoch was accompanied 
by at least two considerable submergences and elevatious 
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 elevations would increase and 
aggravate the migrations and extinctions that a glacial 
epoch is calculated to produce. We can therefore hardly 
fail to be right in attributing the wonderful changes in 



THE GLACIAL EPOCH 123 



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 migration, leading to a much greater 
difference between the vegetable and animal forms of the 
eastern and western hemisphere than before existed. 
Many large and powerful mammalia lived in our own 
country in Pliocene times and apparently survived a part 
of the glacial epoch ; but when it finally passed away they 
too had disappeared, some having become altogether ex- 
tinct 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, two bears, five species of 
deer, and the gigantic beaver ; among the latter are the 
hyaena, bear, aud 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. The late Professor Asa Gray has pointed out 
that hundreds of species of trees and shrubs of peculiar 
genera which still flourish in those countries are now coqi- 
pletely Avanting in Europe, and there is good reason to 
believe that these were exterminated during the glacial 
period, being cut off from a southern migration, first by 
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 

^ This subject is admirably discussed in Professor Asa Gray's Lecture on 
"Forest Geography and Archaeology" in the American Journal of Science 
and Arts, Vol. XVI. 1878. 



124 ISLAND LIFE 



mild climate and luxuriant vegetation of tlie Arctic zone. 
If -my readers will follow me with the care and attention 
so difficult and interesting a problem requires and deserves, 
they will find that I have grappled with all the more im- 
portant facts which have to be accounted for, and have 
offered what I believe is the first complete and sufficient 
explanation of them. The im23ortant influence of climatal 
changes on the dispersal of animals and plants is a suffi- 
cient justiiication for introducing such a discussion into 
the present volume. 



CHAPTER VIII 

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 — 
Effectsof Snow on Climate — Higli Land and Great Moisture Essential to 
the Initiation of a Glacial Epoch — Perpetual Snow nowhere Exists on 
Lowlands — Conditions Determining the Presence or Absence of Perpetual 
Snow — Efficiency of Astronomical Causes in Producing Glaciation — 
Action of Meteorological causes in Intensifying Glaciation — Summary 
of Causes of Glaciation — Efiect 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 
liave 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. 

4. Chansfes in the distribution of land and water. 



126 ISLAND LIFE 



5. Changes in the position of the earth's axis of rota- 
tion. 

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 realities ; 
but it is now generally admitted that they are utterly in- 
adequate 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 de- 
monstrated facts, and which are universally 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 com- 
plex and wide reaching effects have been so admirably ex- 
plained and discussed by Dr. Croll in numerous papers and 
in his work — " Climate and Time in their Geological 
Relations." 

Astrooiomical 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 tliat 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 hemi- 
sphere. 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 as long as our summer is now 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 127 



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 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 comparative 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 

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. 



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 were produced 
with us at the 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 i3revalence 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 besides this change in the re- 
lation of our seasons to the earth's ajjJielion and 'perihelion 
there is another and still more important astronomical 



128 



ISLAND LIFE 



PART I 



factor in the change of magnitude of the excentricity itself. 
This 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 w^hen we come to a hun- 
dred thousand years ago there is a difference of eight and 
a half milHons of miles between our distance from the sun 
in a]jhelion and 2^<^rihdion (as the most distant and nearest 




lOO 50 O 

THOUSAND YEARS AGO FROM 
A. D. 1800. 



DIAGRAM OF EXCEKTRICITY AND PRECESSIOK. 

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 excen- 
tricity is higher. The horizontal dotted line shows the amount of the present 
excentricity. The figures show the maxima and minima of excentricity during the 
last 300,000 years from Dr. Croll's Tables. 



points of the earth's orbit are termed). At a 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 and a quarter, 
and at two hundred and ten thousand years ten and a half 
millions of miles. By reference to the accompanying 
diagram, which includes the last great period of excentricity, 
we find, that for the immense period of a hundred and 
sixty thousand years (commencing about eighty thousand 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 129 



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 hve 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 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. 

Differences of Temperatio'e Caused hy Varying Distances of 
the, Sun. — On this subject comparatively few persons have 
correct ideas owing to the unscientific manner in which we 
reckon heat by our thermometers. The zero of Fahren- 
heit's thermometer is thirty-two degrees below the freezing 
point of water, and that of 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 j^lace is 50° F., or 10° C, 
these figures tell us nothing of how much the sun warms 
that place, because if the sun were withdrawn the temper- 
ature 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., both influencing 
the temperature of the air, we may be sure that even this 
intense cold was not near the possible minimum tempera- 
ture. 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 —239^ 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 



130 ISLAND LIFE part i 

by the sun to an amount measured by 50 + 289 = 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 98 J millions of miles, whereas it 
is now, in winter, only 91:|- millions of miles, the mean 
distance being taken as 93 million 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 
8,372 to 9,613 now, or nearly one seventh less than its 
present amount. The mean temperature of England in 
January is about 37° F., which equals 276° F. of absolute 
temperature. But the above-named fraction of 276° is 237, 
the difference, 39, representing the amount which must be 
deducted to obtain the January temperature during the 
glacial epoch, which will therefore be — 2° F. But this is 
a purely theoretic result. The actual temperature at that 
time might 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 largely 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 will be 
more nearly correct for very large areas, because all the 
sensible surface-heat which produces climates necessarily 
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 winter, 
at the time of the glacial epoch, the northern hemi- 
sphere was receiving so much less heat from the sun 
as was calculated to lower its surface temperature on an 
average about 39° F., while during the height of summer 
of the same period it would be receiving so much more 
heat as would suffice, other conditions being equal, to raise 
its mean temj)erature about 48"" above what it is now. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 131 

The winter, moreover, would be long and the summer 
short, the difference being twenty-six days. 

We have here certainly an amount of cold in winter 
amply sufficient to produce a glacial period,^ especially as 
this cold would be long continued ; but at the same time 
we should have almost trojjical heat in summer, although 
that season would be somewhat 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. 

Fropcrtics 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 con- 
tact with it, and also to a considerable extent by the heat 
radiated from the warm earth, because, although pure dry 

1 In a letter, to Nature of October 30th, 1879, the Rev. 0. Fisher calls 
attention to a result arrived at by Pouillet, that the temijerature 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 thi;j 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 
wanter 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 
adoption of Dr. CroU's theory of the Astronomical and Physical causes of 
the Glacial Epoch. 

The reason of the theoretical increase of summer heat being greater than 
the decrease of winter cold is because we are now nearest the sun in winter 
and farthest in summer, whereas we calculate the temperatures of the 
glacial epoch for the phase of precession when the aphelion was in winter. 
A large part of the increase of temperature would no doubt be used up 
in melting ice and evaporating water, so that there would be a much less 
increase of sensible heat ; while only a portion of the theoretical lowering 
of temperature in ^vinter wouLl be actually produced owing to equalising 
effect of winds and currents, and the storing up of heat by the earth and 
ocean. 

K 2 



132 ISLAND LIFE 



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, owing to the greater weight of the cooler air 
which forces it up and takes its place ; and thus heat can 
never accumulate in the atmosphere beyond a very mode- 
rate 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 w^hich 
brings doAvn 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 impelled by the winds, forms great cur- 
rents, which carry off the 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 powerful 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 projDortion 
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 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 133 

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 of the 
temperate zones 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 Climate. — Let us then examine the 
very different effects produced by water falling as a liquid 
in the 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, a small portion only sinking 
into the earth and another portion evaporating into the 
atmosphere. If cold it cools the air and the earth some- 
what while passing through or over them, but produces no 
permanent effect on temperature, because a few hoars 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, hecciuse it has no mobility . 
It remains where it fell and becomes compacted into a 
mass, and it then keej^s 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 



134 isla:n'd life 



sun-heat Avarming the air or the earth much above the 
freezing-point. This is illustrated by the often-quoted fact 
that, at 80° N. Lat., CajDtain 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 tAvo 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 ice-cold 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 1^ inches 
thick would require as much heat as would raise a stratum 
of air 800 feet thick from the freezing point to the tropical 
heat of 88° F. 1 We thus obtain a good idea, both of the 
wonderful power of snow and ice in keejDing 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 iDermanent. These ])ro23erties would, 
however, 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 
extraordinary effects in physical geography and in. climate, 
as we see in the glaciers of Switzerland and the ice-capped 
interior of Greenland. 

Hifjli Land and great Moisture Essential to the Initiation 
of a Glacial EiJoch. — Another point of great importance in 
connection with this subject, is the fact, that this perma- 
nent storing up of cold depends entirely on the annual 
amount of snow-fall in jjroportion 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 
^ Dr. Croll says this "is one of the most widespread aud fimdaniental 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 135 

SO little snow falls that it is quickly melted by the return- 
ing 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 per- 
petual snow and ice. At the " Jardin " on the Mount 
Blanc range, above the line of perpetual snow, a thermo- 
meter in an exposed situation marked - 6° F. as the lowest 
winter temperature : while in many parts of Siberia mer- 
cury freezes during 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 
vegetation. 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 duriag summer, and covered with a rich vege- 
tation 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 Snoiu Noivliere Exists on Lowland Areas. — 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 ; ^ and it is 

errors within the whole range of geological climatology." The temperature 
of the snow itself is, he says, one of the main factors. [Climate and 
Cosmology, p. 85.) But surely the temperature of the snow must depend 
on the temperature of the air through which it falls. 

^ In an account of Prof. Nordenskj old'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, althouiih 



136 ISLiND LIFE 



only where there are lofty moimtains or plateaus — as in 
Greenland, Spitzbergen, and Grmnell's Land — that glaciers, 
accompanied by perpetual snow, cover the country, and de- 
scend 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 Ave find the nearest 
approach to a true ice-cap covering the whole circum- 
ference of the Antarctic continent, and forming a girdle of 
ice-cliffs which almost everywhere 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 mountainous, 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 
necessary condition of glaciation, is well shown by the 
general state of the tw^o polar areas at the present time. 
The northern part of the north temperate zone is almost 
all land, mostly low but with 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 permanent ice (except on the highlands 
of Greenland and Grinnell'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 icebergs (often miles in 
length) that the ice-sheet from which they are the broken 
outer fraOTnents must be from a mile to a mile and a half 

o 

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. 

^ Dr. Croll objects to this argument on the ground that Greenland and 
the Antarctic continent are probably lowlands or groups of islands. 
{Climate and Cosmology, Chap. Y.) 



CHAP. Yiii THE CAUSES OF GLACIAL EPOCHS 137 

in thickness.^ As this is the thickness of the outer edo-e 
of the ice it must be far thicker inland ; and we thus find 
tliat the Antarctic continent is at this very time sufferino- 
giaciation 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 floatino- 
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 supj^ly of 
vapour; and the effect is intensified by winter being 
there in aiolielion, 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 great mountainous promontories far into the 
temperate zone ? The comparatively small Heard Island 
in S. Lat. 53° is even now glaciated down to the sea. What 
would be its condition were it a northerly extension of a 
lofty Antarctic continent? We may be quite sure that 
giaciation would then be far more severe, and that an ice- 
sheet corresponding to that of Greenland might extend to 
beyond the parallel of 50° S. Lat. Even this is probably 
much too low an estimate, for on the west coast of New 
Zealand in S. 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. 

^ "On the Glacial Epoch," by James CroU. Gcol. Mag. July, August, 
1874. 



iiiiiilililllliiiiiiiiiiiil!;!' 



iill 




CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 139 

Conditions Determining the Presence or Absence of Ferpet- 
ual Snoiv. — It is clear, then, that the vicinity of a sea or ocean 
to supply moisture, together with high land to serve as a 
condenser of that moisture into snow, are the prime essen- 
tials 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 havinof abundance of hisfli 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 tlie two northern continents — Eastern 
Siberia and the north-Avestern shores of Hudson's Bay — 
there is no perennial 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 Scotltmd, then follows the Avest 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 glacia- 
tion, 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 with North-eastern Canada 
seems to have been the source of much of the glaciation 
of that continent.^ 

^ "The general absence of recent marks of glacial action in Eastern 
Europe is well known ; and the series of changes Avhich have been so well 
traced and described by Prof. Szabo 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. 
ilr. 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 Xortli America, westward of the meridian of 
Chicago." (Prof. J. AV. 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 



140 ISLAND LIFE parti 

The reason why no accumulation of snow or ice ever 
takes i^lace on Arctic lowlands is explained by the observa- 
tions'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 low- 
lands 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 dis- 
appears in a few days and the vegetable kingdom bursts 
into full luxuriance. This is very important as showing 
the imjDotence 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, 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, depending 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. 

Efficiency of Astronomical Causes in Producing Glacia- 
tion. — 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 

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. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS Ul 



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 is now, and, according 
to Dr. Croll's calculations, the mid-winter temperature 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 very much hotter than it is 
now, and the problem to be solved is, Avhether, suj^posing 
the geography of the northern hemisphere to have been 
identical with what it is now, 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 
that it would. Sir Charles Lyell maintained that it 
would only do so if geographical conditions were then 
more favourable than they are now ; 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 snoAV and ice would be formed in the 
Arctic and Antarctic resfions at the same time whether 
the winter were in yerihelion or aphelion} 

The problem we have now to solve is a very difficult one, 
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 apthelion during that season, would 
not of itself produce a glacial epoch unless the amount of 

^ I have somewhat modified this whole passage in the endeavour to 
represent more accurately the difference between the views of Dr. Croll and 
Sii' Charles Lyell. 



142 ISLAND LIFE 



vapour supplied for condensation was also exceptionally- 
great. The greatest quantity of snow falls in tlie 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 apkelion. All the 
rain which falls on our mountains at that season Avould 
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 
ccphclion 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 de- 
position ; 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 differ- 
ence 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 differ- 
ence of temperature and the extent of the cooled and 
heated masses of air, and this effect is now greatest be- 
tween 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 
upi^er return current which carries the warm moisture- 
laden air of the tropics towards the poles, descending in 
the temperate zone as west and south-west winds. These 
are now strongest in the southern 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 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 143 

partially reversed. The south polar area, having its winter 
in 2^crihelion, 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 con- 
dition of glaciation. 

But this is only one-half of the effect that Avould be 
produced, for the increased force of the trades sets up 
another action which still further helps on the accumula- 
tion 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. 
La.t. 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 jDortion of it might be diverted southward 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 in- 
crease 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 supj^ly of moisture leads to an extension 
of the ice, which reacts in still further increasing the 
supply of moisture. The same increase of snow and ice, 
by causing the north-east to be stronger than the south-east 



144 ISLAND LIFE 



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 hemi- 
sphere, increasing yet further the supply of moisture by 
the more powerful south-westerly winds, while still fur- 
ther lowering the temperature by the southward diversion 
of the Gulf Stream. 

Summary of Frind'pal Causes of Glaciati'on. — I have now 
sufficiently answered the question, why the short hot 
summer would not melt the snow Avhich accumulated 
during the long cold winter (produced by high excentricity 
and winter in a'phclion), 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 j^aradox. 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 
produce 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 Avater. 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 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 145 

portion of the reflected heat would no 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 ad- 
duced over and over again as a valid argument in every 
criticism of Dr. Croll'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 still o'cmains heloio the freezing ^96»m?J or freezino- 
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 up in 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. 

Uffcd of Clouds and Fog in cutting off the Smis 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 snoAV 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 



146 ISLAND LIFE 



shown that the existence of perpetual snow often 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 conditions equal — in- 
stead of Avhich 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 is 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 Avinter is not so 
excessively cold, but the summer is far less hot (than in 
the north),/(9?' the clouded shy seldom alloivs the sun to vjao^m 
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. 
CroU shows that this is a constant j^henomenon accom- 
panying the presence of large masses of ice in every part 
of the world.^ 

In rejDly 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 

^ For numerous details and illustrations see the paper— "On Ocean 
Currents in Relation to the Physical Theory of Secular Changes of Climate. " 
— in the Phihso2}hical Magazine, IS 70. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 147 

equator from sunrise to sunset, if none were cut off by the 
atmosphere, would melt 3J inches of ice, or 100 feet in a 
year. The quantity received between latitude 60° and 80°, 
which is 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 wdiich 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 clouds 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 Influence of 
Astronomical 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 w^e have exactly the condition of 
things to which England and Western Europe were sub- 
jected during the latter portion of the glacial epoch, wdien 
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 southvv^ards and termin- 
ates altogether in about the latitude of Edinburgh ; the 

^ See Darwin's Naturalist's Voyage Hound the Vv^orld, 2nd Edition, pp. 
244-251. 

L 2 



148 ISLAND LIFE part i 

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 hemisjDhere. The 
only important differences are : the open southern ocean, 
the longer and colder winter, and the general low tempera- 
ture caused by the south polar ice. But the great ac- 
cumulation 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 ex- 
centricity 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. 

Gcogvo'phical Ghanfics, how far a Ccmse of Glaciation. — 
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 v/ould 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 Avould retain more of the heat, and by means of cur- 
rents 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 
^lerhaps no such thing as ice anywhere produced. This 



CHAP, viri THE CAUSES OF GLACIAL EPOCHS 149 



would result from there being no land near the poles to 

retain snow, while the constant interchange 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 state of almost perjoetual glaciation of much of the 
land would result, notAvithstanding that the whole earth 
should thoretically 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 j^olar areas, warm oceanic cur- 
rents 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 neces- 
sarily offer an almost continuous 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 aftord 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, 



150 ISLAND LIFE 



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 w^ay of hypothesis by Sir Charles Lyell, have 
ever occurred. Such an hypothesis, however, is not with- 
out its use in our present inquiry, for if we obtain thereby 
a clear 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 gi^eat 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. In 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 con- 
tinental 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 cer- 
tainly be that snow would accumulate on the high moun- 
tains 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. 
SujDpose, for instance, the east side of Greenland were to 
sink considerably, w^hile on the west the sea bottom were 
to rise in Davis' Strait so as to unite Greenland with 
Baffin's Land, thus stopping altogether 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 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 151 

would certainly produce a vv onderful ameliorating effect on 
the climate of tlie east coast of North America, and might 
raise the temi^erature of Labrador to that of Scotland. 
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 action of the terrestrial and astro- 
nomical causes affecting climate which were then in 
operation. 

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 certainly 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 geograjDhical 
changes are very numerous, they must have produced im- 
portant effects ; and though we may admit that the astro- 
nomical 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 con- 
densation 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 
attaching too exclusive an importance to geographical 
changes as bringing about mutations of climate, his critics 



152 ISLAND LIFE 



have, I think, attached far too little importance to these 
chan^ges. We know that they have always been in pro- 
gress 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 climates in high 
latitudes, as we shall attempt to prove in our next chapter.^ 
On the Theory of Intcr-glacial Periods and their Prolable 
Chareicter. — 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 conse- 
quences and modifications both of climate and physical 
geography which follow or accompany such changes. It is 
essentially a theory of alternation; and it is certainly 

^ The influence of geographical changes on climate is now held by 
many geologists who oppose what they consider the extravagant hypotheses 
of Dr. CroU. 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 : " Kow, 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 necessarj^, 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 Palreozoic, 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." {A^ncrican Journal (^Science 
and Arts, Srd Series, Vol. IX. p. 318.) 

" In the 2nd edition of his Manual 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 glacia- 
tion." {Manual of Geology, 2nd Edition, pp. 541-755, 756.) 



CHAr. Mil THE CAUSES OF GLACIAL EPOCHS 153 



remarkable in how many cases geologists have independ- 
ently 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 glaciation when the " till " was deposited, with 
later less extensive glaciation when moraines were left in 
the valleys ; several successive periods of submergence and 
elevation, the later ones becoming 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 not long 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 atw^ork which led 
to a large portion of North-western Europe and Eastern 
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 betvv^een 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, w^hether 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 if the ocean currents remained the 
same. The force of these currents is, 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 



154 ISLAND LIFE part i 

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 of climates caused by the 
changing phases of precession. 

Now, the existence at the present time of an ice-clad 
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 Ckhotsk. So in 
North-west America we have the lofty coast range, culmi- 
nating in Mt. St. Elias, 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 completely 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 
1 Dana's Manual of Geology, 2nd Edition, p. 540. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 155 



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, equalling that of the Antarctic regions, 
and chilling the atmosphere so as to produce constant 
clouds and fog with almost perpetual snowstorms, 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 ])hysical and gcograijliical causes of glaciation 
remaining unchanged ? 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 iKrihclion, 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 favourable 
geographical and physical causes (and without this combina- 
tion it is doubtful whether ext^xme glaciation Avould ever 
occur), then the ice-sheet will not be removed during the 
alternate phases of precession, so long as these geogra]3hical 
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 compara- 
tive 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.^ 

^ Dr. CroU says that I here assume an impossible state of things. He 
maintains "that the change from the distant sun in winter, and near sun 



156 ISLAND LIFE part i 



If this argument is valid, then it would follow that, so 
long, as excentricity was high, whatever conditiop 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 proportionate 
effect of climatal and geograjDhical causes in producing 
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 Ai^liclion on. the Climcite e-f 
Britain. — Let us then suppose the winters of the northern 
hemisphere to become longer and much colder, the 

in summer to the near sun in winter and distant sun in summer, aided by 
the change in the physical causes which this would necessarily bring about, 
would certainly be sufficient to cause the snow and ice to disappear." 
{Climate and Cosmology, J). IQQ.) But I demur to his "necessarily." It 
is not the direct effect of the nearer sun in winter that is supposed to melt 
the snow and ice, but the "physical causes," such as absence of fogs and 
increase of warm equatorial currents. But the near sun in winter acting 
on an ice-clad surface would only increase the fogs and snow, while the 
currents could only change if a large portion of the ice were first melted, 
in which case they would no doubt be modified so as to cause a further 
melting of the ice. Dr. Croll says: "The warm and equable conditions 
of climate which would then prevail, and the enormous quantity of 
intertropical water carried into the Southern Ocean, Avould soon produce a 
melting of the ice," {Loc. cit. p. 111.) This seems tome to be assuming the 
very point at issue. He has himself shown that the presence of large 
quantities of ice prevents "a warm and equable climate" however great 
may be the sun-heat ; the ice therefore would not be melted, and there 
would be no increased flow of intertropical water to the Southern Ocean. 
The ocean currents are mainly due to the difierence of temperature 
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 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 Avinter in perihelion, nor in- 
crease to any important extent during the opposite phase. We therefore 
seem to have no available agency by which to get rid of the ice over a 
glaciated hemisphere, so long as the geographical conditions remained 
unchanged and the excentricity continued high. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 157 

summers being proportionately shorter and hotter, without 
any other change whatever. The long cold Avinter would 
certainly bring down the snow-line considerably, covering 
large areas of high land with snow during the winter 
months, and causing all glaciers and ice-fields to become 
larger. This would chill the superincumbent atmosphere 
to such an extent that the warm sun and winds of spring 
and early summer w^oald bring clouds and fog, so that the 
sun-heat w^ould 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 tha.t the extra accumulation would not be all 
melted, and that therefore the snow-line would be per- 
manently lowered. This would be a necessary result, 
because the gi'eater 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 from producing any effect, by 
reflection from the surface of the snow and by the inter- 
vention 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 will occur in aphelion (instead 
of, as now, in ^^^^'^^ihelion) , there will be produced a colder 
climate, independently of any change of land and sea, of 
heights of mountains, or in the force of oceanic 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 unchanged), would certainly bring back again 
our present milder climate. The change either w^ay 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 would have their tops covered 
with perpetual snow. This perpetual snow, down to a 
fixed line, would be kept up by the needful 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 dura- 
tion and the cold of winter decreased the amount of snoAV 
would certainly decrease, and of this lesser quantity of snow 



158 ISLAND LIFE 



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. We have considered this case, for 
simplicity of reasoning, on the supposition that all geo- 
graphical 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 (sec p. 142), 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 
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 Frincijylc of Climated Change Restatcel. — 
The preceding 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 urge, 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 



CHAP, viir THE CAUSES OF GLACIAL EPOCHS 159 

far the most important ; that, when these combine to pro- 
duce a severe glacial epoch, the changiag 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 be- 
comes moderate and the resulting glaciation less severe, 
then the changing phases of precession bring about a con- 
siderable alteration, and even a partial reversal of the 
glacial conditions. 

The reason of this may perhaps be made clearer by con- 
sidering the stability of either extreme glacial conditions 
or the entire absence of perpetual ice and snow, 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 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 ex- 
posed earth becomes heated by the hot sun, this w^arms 
the air, and the warm air melts the adjacent ice. It fol- 
lows, that towards the equatorial limits of a glaciated 
country alternations of climate may occur during a period 
of high excentricity, while nearer the pole, where the sur- 
face is almost completely ice-clad, no amelioration may 
take place. The same argument will, to some extent 
apply, 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 ap- 
pears to correspond very closely 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 is only the very latest 



160 ISLAND LIFE paet i 

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.^ 

Prolable Date of the Glacial Epoch. — The state of extreme 
glaciation in the northern hemisjDhere, of which we gave 
a general description at the commencement of the pre- 
ceding 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, 

^ In 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 Europe 
and jSTorth 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. CroU 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. 144) partly diverted 
southward. A portion of its influence would, however, still remain to 
cause a diff'erence 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 
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 diff'erence 
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 AVestern 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 fixirly corresponds to the diff'erence of conditions 
existing during the glacial epoch and the present time, so far as we are 
able to estimate them, and it certainly aff'ords no grounds of objection to 
the theory by which the glaciation is here explained. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 161 

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, is 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 consider- 
able 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 on Glaeiation. — It has 
been pointed out by Dr. Croll, that many of the changes 
of level of 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 w^ould rise accordingly. Extreme giacialists 
have maintained that durinof the heioiit 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 believed 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, how- 
ever, shown that the production of any such ice-cap is 
improbable if not impossible, because snow and ice can 

M 



162 ISLAND LIFE part i 

only accumulate where precipitation is greater than melt- 
ing 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 far less snow than 
would be melted by the long hot days of summer.^ The 
accumulations of ice were therefore probably confined, in 
the northern hemisj)here, 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 sup- 
ports 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 stages of the glacial epoch, when alter- 
nations of warmer and colder periods would be caused by 
winter occurring in 2^crihelion or aphelion. If, however, as 
is here maintained, 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 condi- 
tions, of which we have no evidence whatever, prevented 
such accumulations. That there was such a greater ac- 
cumulation 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 in- 
dications 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 hemisphere.^ 

^ Dr. Croll objects to this argument, and adduces the case of Greenland 
as showing that ice may accumulate far from sea. But the width of 
Greenland is small compared Anth that of the supposed Antarctic ice-cap. 
{Climate and Cosmology, p. 78.) 

2 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 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 163 

This greater accumulation of ice in both hemispheres 
would lower the whole ocean by the quantity of water 

believing that the high phase of excentricity which caused our own glacial 
e[)Och was at all events an assisting cause. This is rendered more prob- 
able 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 Yaal 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 andless 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 Avere 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 momitain knot with peaks more than 10,000 feet high, 
thus ottering 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 o(f S. Lat. ; 
since the Andes, which in 32° S. Lat. reach 23,300 feet high, and in 28° 
S. 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, Ave 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 
most of the surface phenomena characteristic of a glaciated country, only 
a few degrees south of the tropic ; and taken in connection with the indica- 
tions of recent glaciation in New Zealand, and those discovered by Dr. R. 
von Lendenfeld in the Australian Alps between 6,000 and 7,000 feet ele- 
vation {Nature, Vol. xxxii. p. 69), Ave can hardly doubt the occurrence of 
some general and AA'ide-spread cause of glaciation in the southern hemisphere 
at a period so recent that the superficial phenomena are almost as well pre- 
served as in Europe. Such evidences of recent glaciation in the southern 
hemisphere 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. 

M 2 



164 ISLAND LIFE 



abstracted from it, while any want of perfect synchronism 

betwjeen 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 would 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 sub- 
sidences 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, durino: the orlacial 
period. 

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 altera- 
tions of size according as they are more or less exposed to 
the sun's rays. They have therefore been generally con- 
sidered 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 dif- 
ferent, 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 con- 
sequently be modified in a way quite different from any- 
thing that obtains upon our earth. Bearing these diffi- 
culties and uncertainties in mind, let us see what are the 
actual facts connected with the sujDposed polar snows of 
Mars.i 

^ 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 con- 
clusions from those of the writer of the paper. 



CHAP. VIII THE CAUSES OF GLACIAL EPOCHS 165 

Mars offers an excellent subject for comparison with the 
Earth as regards this question, because its excentricity is 
now a little greater than the maximum excentricity of the 
Earth during the last million years, — (Mars excentricity 
00031, Earth excentricity, 850,000 years back, 0-0707); 
the inclination 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 pcrilielion, that of their southern 
hemisphere being in afJidion. If, therefore, the physical 
condition of Mars were the same or nearly the same as that 
of the Earth, all circumstances combine, according to Dr. 
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. 

In the year 1830 iha so^tthern ^xio^\ 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-caj^ was observed 
during its summer, and was found to vary as follows : — 



May 4tli. 


Diameter of spot 


31° 24' 


June 4th. 




55 


28° 0' 


„ 17th. 




55 


22° 54' 


July 4th. 




55 


18° 24' 


„ 12th. 




55 


15° 20' 


„ 20th. 




55 35 


18° 0' 



We thus see that Mars has two permanent snow-caps, of 
nearly equal size in winter but diminishing very unequallv 



166 ISLAND LIFE parti 

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 Avhich has winter in 
cfphdiooi (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 conditions they imply. In the first place, there is 
evidently this radical difference between the state of Mars 
now and of the Earth during a glacial period — that Mars 
has no great ice-sheets spreading over its temperate zone, 
as the Earth undoubtedly had. This we know from the 
fact of the rapid 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) be- 
tween 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 fortniglit 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 

1 In an article in Nature of Jan. 1, ISSO, the Rev. T. ^\. Webb states that 
in 1877 the pole of IMars (? the south i)ole) was, according to Schiaparelli, 
entirely free of snow. He remarks also on the regular contour of the sup- 
posed snows of JMars 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 untrust- 
worthy. 



CHAP. VIII THE CAUSES OF QLACIAL EPOCHS 167 

sure that the snow (if it is real snow) is much less thick 
— a mere surface-coating in fact, such as occurs in parts 
cf 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 southern pole of Mars 
parts with its white covering so much more quickly 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 hemi- 
sphere ; and this greater heat would cause the winds from 
the equator to be both warmer and more powerful, and able 
to produce the same effects on the scanty Martian snows as 
they produce on our northern snow-plains. The reason 
why both poles of Mars are almost equally snow-covered in 
winter is not difficult to understand. Owingf to the sreater 
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 therefore 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 sur- 
rounded by very high land on which ice may accumulate. 
With us at the present time, on the other hand, geograph- 
ical conditions completely mask and even reverse the 
influence of excentricity, and that of winter in perihelion 
in the northern, and summer in 2^(^'i^ihelion 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 



168 ISLAND LIFE part i 

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 
wliich 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 vajDour 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 dimi- 
nished power of the summer sun, owing to its greatly 
increased distance at that season in the northern hemi- 
sphere, so that it is not able to melt so much of the snow 
which has accumulated durins: the lonof nio^ht of winter. 



CHAPTER IX 

ANCIENT GLACIAL EPOCHS, AND MILD CLIMATES IN THE 
ARCTIC REGIONS 



Dr. Croll's A^iews on Ancient Glacial Epochs — Effects of Denudation in 
Destroying the Evidence of Remote Glacial Epochs — Rise of Sea-level 
Connected with Glacial Epochs a Cause of Further Denudation — What 
Evidence of Early Glacial Epochs may be Expected — Evidences of Ice- 
action During the Tertiary Period — The Weight of the Negative Evi- 
dence — Temperate Climates in the Arctic Regions — The ]\Iioccne Arctic 
Flora — Mild Arctic Climates of the Cretaceous Period — Stratigi-aphical 
Evidence of Long-continued Mild Arctic Conditions — The Causes of j\Iild 
Arctic Climates — Geographical Conditions Favouring ]\Iild Northern 
Climates in Tertiary Times — The Indian Ocean as a Source of Heat in 
Tertiary Times^Condition of North America During the Tertiary Period 
— Effect of High Excentricity on Warm Polar Climates — Evidences as to 
Climate in the Secondary and Palneozoic Epochs— AVarm 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 Earth's Surface — Estimate 
of the Comparative Effects of Geographical and Physical Causes in Pro- 
ducing Changes of Climate. 



If Ave adopt the vieAV set forth in the preceding chapter as 
to the character of the glacial epoch and of the accom- 
jDanying alternations of climate, it must have been a very 
important agent in 23rodi icing changes in the distribution 
of animal and vegetable life. The intervening mild 
periods, which almost certainly occurred during its earlier 
and later phases, may have been sometimes more equable 
than even our present insular climate, and severe frosts 
were probably then unknoAvn. During the four or five 



170 ISLAKD LIFE 



thousand years that each specially mild period may have 
lasted, some portions of the north temperate zone, which 
had 'been buried in snow or ice, would become again 
clothed with vegetation and stocked with animal life, both 
of which, as the cold again came on, would be driven 
southward, or perhaps jDartially 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, afresh 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 excen- 
tricity 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 excen- 
tricity for three million years back ; and from these it 
appears that there have been many periods of high excen- 
tricity, 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 2yc'^'ihelio7i 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 j^art of the latter period ; and Dr. 
Croll maintains that a glacial epoch must then have 

^ London, Edinburgh and Duhlin Philosophical Magazine, \o\. XXXVI., 
pp. 144-150(1868). 



ANCIENT GLACIAL EPOCHS 



171 



occurred surpassing in severity 
that of which we have such con- 
vincing proofs, and consisting like 
it of alternations of cold and 
warm phases every 10,500 years. 
The diagfram also shows us another 
long-continued period of high ex- 
centricity from 1,750,000 to 
1,950,000 years ago, and yet 
another almost equal to the maxi- 
mum 2,500,000 years back. These 
may perhaps have occurred during 
the Eocene and Cretaceous epochs 
resjDectively, or all may have been 
included within the limits 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 excentricity is 
the great and dominating agency 
in bringing on glacial epochs, geo- 
graphical changes being subor- 
dinate, then there must have 
been glacial epochs of great 
severity at all these three periods ; 
while if he is also correct in su23- 
posing that the alternate phases 
of precession Avould inevitably 
produce glaciation in one hemi- 
sphere, and a proportionately 
mild and equable climate in the 
opposite hemisphere, then we 
should have to look for evidence 
of exceptionally warm and excep- 
tionally cold periods, occurring 






172 ISLAND LIFE part i 



alternately and with several repetitions, within a space of 
time which, geologically speaking, is very short indeed. 

Let ns then inquire first into the character of the 
evidence we should exj^ect 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. 

Effects of Denudation in Destroying the Emdence 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 liave 
ably argued that no such evidence is likely to be found. 
It is now generally admitted that sub-aerial denudation is 
a much more powerful agent in lowering and modifying 
the surface of a country than was formerly sujDjDOsed. It 
has in fact been proved to be so powerful that the diffi- 
culty 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 it has been carefully measured for 
several rivers, large and small, in different parts of the 
world. The details of these measurements 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, on an average, 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 



ANCIENT GLACIAL EPOCHS 173 



years to remove one foot ; while the Po is the most rapid, 
taking only 729 years to do the same work in its valle3^ 
The cause of this difference is very easy to understand. 
A large part of the area of the Mississippi 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 rain- 
fall, while its sources are spread over a great amphitheatre 
of snowy Alps nearly 400 miles in extent, where the 
denudino- forces are at a maximum. As Scotland 



IS a 



mountain region of rather abundant rainfall, the denudino- 
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 coin- 
cide 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 downward slope. One of the very 
highest autliorities on the subject of denudation, Mr. 
Archibald Geikie, estimates the area of these more rapidly 
denuded portions as only one-tenth of the comparatively 
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. 



174 ISLAND LIFE 



Now Dr. Croll gives us the following account of the 
present asj^ect of the surface of a large j^art of the coun- 
try :— 

''Go where one will in the lowlands of Scotland and he 
shall hardly find a single acre w^iose upper surface bears 
the marks of being formed by the denuding agents now in 
operation. He will observe everywhere mounds and 
hollows which 'cannot be accounted for by the present 
agencies at work. ... In regard to the general sur- 
face 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." ^ 

The facts here seem a little inconsistent, and we must 
suppose that Dr. Croll has somewhat exaggerated the uni- 
versality and complete preservation of the glaciated sur- 
face. The amount of average denudation, however, is not 
a matter of opinion but of measurement ; and its conse- 
quences 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 re- 
modelled or earned into the sea since the last glacial epoch, 
it becomes evident that any surface-phenomena produced 
by still earlier glacial epochs mttst have long since entirely 
disappeared. 

Rise of the Sea-level Connected ^vitli Glacial Epochs, a Cause 
of Fihrther Denudation. — There 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 wi'iters, 
as we have seen, connect this subsidence with the glacial 
^ Climate and Time in tlieir Geological Relations, p. 341. 



ANCIENT GLACIAL EPOCHS 175 



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 power- 
fully 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 the successive phases of precession, and if so, both 
polar areas would j^robably 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 an}^ 
important fluctuations of the sea-level is of comparatively 
little importance to our present inquiry, because the wide 
extent of marine Tertiary deposits in the northern hemi- 
sphere and their occurrence at considerable elevations above 
the present sea-level, afford the most conclusive proofs that 
great changes of sea and land have occuiTed throughout 
the entire Tertiary period ; and these repeated sub- 
mergences and emergences of the land combined with 
sub-aerial 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 he 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 ofi" of the ends of glaciers which terminate 



176 ISLAND LIFE 



in arms of the sea, or of the terminal face of the ice-sheet 
whicli passes beyond the land into the ocean. In both 
these cases abundance of rocks and cUhris, 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 whicli 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 v^hen an ice-sheet 
covered an entire country there would be no moraines, and 
that rocks or ddhris are very rarely seen on icebergs. 
But during every glacial epoch there will be a southern 
limit to the glaciated area, and every where' near this limit 
the mountain-tops will rise far above the ice and deposit 
on it great masses of cUhris ; 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 Cumberland 
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 throuo^hout the oTeater 
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 scattered 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 
1 Nature, Vol. XXL, p. 345, "The Interior of Greenland. " 



CHAP. IX ANCIENT GLACIAL EPOCHS 177 



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 deiDosits forming from the 
denudation of countries which had never been glaciated, or 
from which the ice had already disajjpeared. 

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. Four hundred 
thousand years ago the excentricity was almost exactly the 
same as it is now, and it continually increased 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. 171 on a larger scale) that during 1,150,000 
years out of the 2,400,000 years immediately ^^recedhig 
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 alternating warm j^eriods), then the whole 
of the Tertiary deposits in the north temperate and Arctic 
zones should exhibit frequent alternations of 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 

N 



178 ISLAND LIFE part i 

theory of repeated glacial epochs during the Tertiary- 
period. 

Evidences of Ice-action cluo^ing 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 characteristic 
Miocene shells, but containing in an intercalated deposit 
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, combined 
with the turbidity produced by the glacial mud, had driven 
away the organisms adapted to live only in a comparatively 
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 Cycadacese, 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 con- 
taining 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. 



CHAP. IX ANCIENT GLACIAL EPOCHS 179 

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 sur- 
rounding 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 as a proof. It is not therefore at 
all improbable that during some part of the Tertiary j)eriod 
these mountains may have been far higher than they 
are now, and this we know might be sufficient for the pro- 
duction 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 

^ Prof. J. "\V. Jiidd 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 gi'and panoramas of ridges, 
pinnacles, and peaks produced for the most part by sub-aerial 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 A-'olcanoes, Geological Magazine, 1876, p. 536.) Professor 
Judd applies these remarks to the last as Avell as to previous glacial periods 
in the 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. 

N 2 



180 ISLAND LIFE 



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 Con- 
troversy " the late 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 LoAver Miocene ac- 
cording to some), and along the northern coast of Kent 
from its 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 extensive collections of organic remains have 
been made of any formation yet exj)lored, 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 condi- 
tions, or of a molluscan assemblage such as is present in 
marine or fluvio-marine beds of the formation, are of 
unmistakably tropical or sub-tropical character through- 
out ; and no trace whatever has appeared of the inter- 
calation of a glacial period, much less of successive inter- 
calations 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 ac- 
cumulation of the Eocene formation in England a glacial 
period could have occurred without its evidences being 



CHAP. IX MILD AKCTIC CLIMATES 181 

abundantly apparent. The Oligocene of Northern Ger- 
many and Belgium, and the Miocene of those countries 
and of France, have also afforded a rich molluscan fauna, 
which, Kke 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 Avliole series containing 
irreo'ular blocks of foreiojn material, boulders or OTavel, such 
as we have seen to be the essential characteristic of a glacial 
epoch ; and when we find that this same general character 
pervades all the extensive Tertiary deposits of temperate 
North America, we shall, I think, be forced to the con- 
clusion that no general glacial epochs could 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 completely made away with them that not a 
fragment remains, while preserving all or almost all the 
inter glacicd 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. 

Tem]jerate Climates in 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 still more 
extraordinary series of observations 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 
^ Geological Magazine, 1876, p. 392 



182 ISLAND LIFE 



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 is 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 is generally admitted that the animals must have 
lived upon the adjacent plains, and that a considerably 
milder climate than now prevails could alone have enabled 
them to do so. How long ago 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 condi- 
tions. Again, Sir Edward Belcher discovered on the dreary 
shores of Wellington Channel in 75J° 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 Abies 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 in 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 Nordenskjold says : " At various 
l^laces 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 coast 
of Spitzbergen, though on the west coast of Scandinavia it 
everywhere covers the rocks near the sea-shore. These 
shells occur most plentifully in the bed of a river which 
runs through Reindeer Valley at Cape Thordsen. They 



CHAP. IX MILD ARCTIC CLIMATES 183 



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 b}^ 
glacial action."^ 

The Miocene Arctic Flora. — One of the most startling 
and important of the scientific discoveries of the last 
forty 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 is even now 
considered by many men of science to be completely un- 
intelligible ; 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. 

The Miocene flora of temperate Europe was very like 
that of Eastern Asia, Japan, and the warmer part of East- 
ern 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 coun- 
tries Professor Heer concludes that the Swiss Lower Mio- 
cene flora indicates a climate corresponding to that of 
Louisiana, North Africa, and South China, while the 
L^pjDer Miocene climate of the same country would corre- 
spond to that of the south of Spain, Southern Japan, and 
Georgia (U.S. of America). Of this latter flora, found 
chiefly at CEninghen in the northern extremity of Switzer- 
land, 465 sjDecies are known, of which 166 species are trees 
or shrubs, half of them being evergreens. They comprise 
sequoias like the Californian giant trees, camphor-trees, 
cinnamons, sassafras, bignonias, cassias, gleditschias, tulip- 
trees, and many other American genera, together with 
maples, ashes, planes, oaks, poplars, and other familiar 
European trees represented by a variety of extinct species. 
If we now go to the Avest coast of Greenland in 70° N. Lat. 
we find abundant remains of a flora of the same general 

^ Geological ]\Rigazine, 1876, " Geology of Spitzbergen, " p. 267. 



184 ISLAND LIFE 



type as that of CEninghen but of a more northern character. 
We have a sequoia identical with one of the species found 
at CEninghen, a chestnut, sahsburia, liquidambar, sas- 
safras, and even a magnoUa. We have also seven species 
of oaks, two planes, two vines, three beeches, four poplars, 
two willows, a walnut, a j^lum, 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. Tliere 
seem to be no evergreens here excej^t coniferse, one of 
which is identical with the swamp-cypress {Taxodium 
distichum) 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 flowering plants. 
Even in Grinnell Land, within 8J degrees of the pole, a 
similar flora existed, twenty-five sj^ecies of fossil plants 
having been collected by the last Arctic expedition, of 
which eighteen Avere 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 
(Finus alics) which last does not now extend beyond 
69-1-° N. 

Fossil plants closely resembling those just mentioned 
have been found at many other Arctic localities, es2oecially 
in Iceland, on the Mackenzie River in 65° N. Lat. and in 
Alaska. As an intermediate station we have, in the neigh- 
bourhood 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 (Eninoiien, but wantino^ in some of the 
more tropical forms. Again, in the Isle of Mull in Scotland, 
in about 56V N. Lat., a plant-bed has been discovered con- 



CHAP. IX MILD AKCTIC CLIMATES 185 

taining a hazel, a plane, and a sequoia, apjDarently 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 (Eninghen and Spitzbergen, but the great ma- 
jority being distinct, and exhibiting decided indications 
of a decrease of temperature according to latitude, though 
much less in amount than now exists. Some writers have 
thought that the great similarity of the floras of Greenland 
andQj]ninghen is a proof that they were not contemporane- 
ous, but successive ; and that of Greenland has been sup- 
posed to be as old as the Eocene. 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 j^roduced by dis- 
tance 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 Straits of Magellan 
to Valparaiso — places differing as much in latitude as Swit- 
zerland and West Greenland ; and the same may be said 
of North Australia and Tasmania, where, at a greater lati- 
tudinal 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 
Uj^per 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 geo- 
logical age. Sixty-five species of plants have been identi- 
fied, of which there are fifteen ferns, two cycads, eleven 
coniferse, 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 



186 ISLAND LIFE 



the dicotyledons the genera Populus, Myrica, Ficus, Sassa- 
fras, Andromeda, Diospyros, Myrsine, Panax, as well as 
magnolias, myrtles, and leguminosse. 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 evidentl}^ 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 tlie 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° 38' 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 pojDlar. Of the thirty- 
eio'ht ferns, fifteen belonsf to the o^enus 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 Cali- 
fornia, six species of true pines, and five of the genus 
Sequoia, one of which occurs also in Spitzbergen. The 
European 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 po23lar being 
the oldest known dicotyledonous plant.^ 

If we take these facts as really representing the flora of 
the period, Ave shall be forced to conclude that, measured 
by the change effected in its plants, the lapse of time be- 
tween the Lower and Upper Cretaceous dejDosits 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 j^i^o^^^ble, therefore, that these 
Lower Cretaceous plants represent local peculiarities of 

^ The preceding account is mostly derived from Professor Heer's great 
work Flora Fossilis Arctica. 



CHAP. IX MILD ARCTIC CLIMATES 187 

vegetation sucli as now sometimes occur in tropical 
countries. On sandy or coralline islands in the Malay- 
Archipelago there will often be found a vegetation con- 
sisting 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 de- 
scribed, might be destroyed and its remains preserved by a 
slight depression, allowing it to be covered up by the de- 
tritus 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 f\icts liow briefly sum- 
marized, 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 supporting a rich vegetation of trees, shrubs, 
and herbaceous plants, similar in general character to that 
which prevailed in the temperate zone at the same periods, 
but showing the influence of a less congenial climate. 
These deposits belong to at least four 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. 

StTatigra])hiccd Evidence of Long-Continued Mild Arctic 
Conditions. — 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 ideological investic^ations. While the valleys are for the 



188 ISLAND LIFE part i 

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 jjerpendicular 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 
Grained almost at the first piance ; and as we have never 
seen in Spitzbergen nor in Greenland, 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, contain- 
ing boulders, are to be found in the polar tracts previous to 
the middle of the Tertiary period. Since, then, both an 
examination of the geognostic condition, and an investiga- 
tion of the fossil flora and fauna of the j^olar lands, show 
no signs of a glacial era having existed in those parts before 
the termination of the Miocene period, we are fully jus- 
tified in rejecting, on the evidence of actual observation, 
the hypotheses founded on purely theoretical speculations, 
which assume the many times 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 Spitzhergen, after describing the various forma- 
tions down to the Miocene, he says : " All the fossils found 
in the foregoing strata show that Spitzbergen, during 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 conditions have been broken off 

^ Geological Magazine, 1875, p. 531. 



CHAP. IX MILD ARCTIC CLIMATES 189 

by intervals of ancient glacial periods. The profiles I have 
had the opportunity to examine during my various Spitz- 
bergen 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 throughoat 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 somewhat less 
tropical ; but down to the UpiDer 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 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.^ 

^ Geological Magazine, 1876, p. 266. In his recent work — Climate and 
Cosmology (pp. 164, 172) — tlic late Dr. Croll has appealed to the imperfection 
of the geological record as a reply to these arguments ; in this case, as it 
appears to me, a very unsuccessful one. 

^ 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 Rauce (in the geological 
appendix to Capt. Sir G. Nares's 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 



190 ISLAND LIFE part i 

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 princijDles 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," the late Dr. James 
Croll has jDroved, with a wealth of argument and illustra- 
tion whose cogency is irresistible, that the very habitability 
of our globe is due to the equalizing climatic effects of the 
waters of the ocean ; and that it is 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 
Avarm equatorial waters is directed towards the western 
shores of Europe, the result being that the British Isles, 
Norway, and Sj^itzbergen, 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 sj^eaking, a land 
of snow and ice, with too short a summer to nourish more 
than a very scanty and fugitive vegetation. The only 
other oj)ening than that between Iceland and Britain by 
which warm water penetrates within the Arctic circle, is 
through Behring's Straits ; but this is both shallow and 
limited in width, and the consequence 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 tlie 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 

climates of former periods are not due to any general refrigeration, but 
to causes which were subject to change and alternation in former ages 



CHAP, rx MILD ARCTIC CLIMATES 191 

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 
imjDossible. 

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 prevails. It is, no doubt, difficult and 
often impossible to determine how long any particular 
geographical condition lasted, or Avhether 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. 

Gcogrcqjhical Changes Faxouring Mild 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 and the Persian 
Gulf, thus opening a communication between the North 
Atlantic and the Indian Oceans. 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 
is 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 

^ Mr, S, B. J. Skertchley informs me that lie has liimself observed thick 
Tertiary deposits, consisting of clays and anhydrous gypsum, at Berenice 
on the borders of Eg3-pt and Nubia", at a height of about 600 feet above the 
sea-level ; but these may have been of fresh-water origin. 



192 ISLAND LIFE 



basin of the Mediterranean and the Black Sea ; while it is 
probable that there was a communication 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 
warranted by an actual knowledge of continuous Tertiary 
dejDOsits over the situations of the alleged marine channels ; 
but it is no less certain that the seas in which any partic- 
ular 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 subaerial, and may have once 
covered areas where we now find older deposits (as the 
chalk once covered the weald), while a portion of them 
may lie concealed under 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 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 hemis23here. 

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 



CHAP. IX MILD AKCTIC CLIMATES 193 

opening between South Africa and Australia is very wide, 
and the tendency of the trade-winds would be to concen- 
trate 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 was 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 existence may 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 probably 
divided into two islands, separated by a wide channel in a 
north and south direction (see Chapter XXII.), and 
through this another current would almost certainly set 
northAvards, and be directed to the north-west by the 
southern extension of Malayan Asia. The more insular 
condition 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 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. 
Owincr to the warm currents beinof concentrated in inland 
seas instead of being dispersed over a wide ocean like the 

^ 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. 

O 



194 ISLAND LIFE 



North Atlantic, mucli 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 with- 
out 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 Mississippi, extending over much of the 
Rocky Mountains, consists of marine Cretaceous beds 
10,000 feet thick, indicating great and long-continued sub- 
sidence, and an insular condition of Western America with 
a sea probably extending northwards to the Arctic Ocean. 
As marine Tertiary deposits are found conformably over- 
lying 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 

^ In his recently published Lectui^es on Physical Gcogra'pliy, 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 corre- 
sponding stream of the Indian Ocean in ^Miocene times would have been 
fully equal to the Gulf Stream in heating power, Avhile, 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 sufficient 
passage from the Indian Ocean to the Arctic seas would produce the effects 
above indicated. 



CHAP. IX MILD ARCTIC CLD.IATES 195 

of all these lands with the jDossible 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 perj)etual snow, and no glaciers would 
descend to the sea. 

In the Pacific there was probably an elevation of land 
counterbalancing, to some extent, the gTeat depression of 
so much of the northern continents. Our map in Chapter 
XV. shows the islands that would be produced by an eleva- 
tion 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 impelled 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. 

Effect of these Changes on the Climate of the Arctic Begions. 
— These various chans^es of sea and land, all tendinor to- 
wards 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 ]30ured 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 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, Green- 
land, and Labrador. But the same evidence shows that 
these land-communications were the exception rather than 
the rule, and that tliey occurred only at long intervals and 
for short periods, so as at no time to bring about anything 
like a com])lete interchange of the productions of the two 
continents.^ We may therefore admit that the communi- 

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

2 



196 ISLAIs'D LIFE 



cation between the tropical and Arctic oceans was occasion- 
ally 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 cur- 
rents in conveying heat to the north temperate and polar 
regions, should study the papers of Dr. Croll already re- 
ferred 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 tem- 
peratures of the opposite coasts of Europe and America is 
well known and has been already quoted, but the diiference 
of their mean vjintcr temperature is still more striking, and 
it is this which concerns us as more especially aflecting 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 
Shanghai in China, both about twenty degrees of latitude 
further south ; and as we go northward the difference in- 
creases, so that the winter climate of Nova Scotia in Lat. 
45° is found within the Arctic circle on the coast of Norway ; 
and if the latter countr}^ 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.^ 

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

^ 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 



CHAP. IX 



MILD ARCTIC CLIMATES 



19: 



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 disad- 
vantages of an icy sea to the north-east and ice-covered 
Greenland to the north-west, how can we doubt the enor- 
mously greater eifect 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 hcfore 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 transfer a large proportion of 
their heat into 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 impos- 
sible ; and the mild winter climate of the latitude of North 



summarizes these results is taken from his Lectures on Physical Gcograpluj 
(p. 344) :- 




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 Itlackenzie River, now totally removed from its influence was 
28" warmer. This, as well as the gi-eater increase of temperature as we 
go northward and the polar area becomes more limited, is quite in accord- 
ance with the view of the causes which brought about the Miocene climate 
which is here advocated. 



198 ISLAND LIFE part i 



Carolina, which by the Gulf Stream is transferred 20° 
northwards to our islands, might certainly, under the 
favourable conditions which prevailed during the Creta- 
ceous, 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-accumu- 
lation jDre vented, the high northern lands would be able to 
support a far more luxuriant summer vegetation than is 
possible in our unequal and cloudy climate.^ 

Effect of High Excentricity on the Warm Polar Climates. — 
If the ex23lanation 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 
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 accumu- 
lation 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 inter- 
position of a protective covering of cloud and vapour. 
But mobile currents of water have no such power of 

^ The objection has been made, that the long pohar 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 nmst have been some altera- 
tion 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 numbeis 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 
prejudical to deciduous plants. With a suitable temperiture 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. 



CHAP. IX MILD ARCTIC CLIMATES 199 

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 cqjhelion, the inequality would be greatly dim- 
inished by the free ingress of warm currents to the polar 
area; and if this was sufficient to prevent any accumu- 
lation 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 actually 
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 precession 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 in- 
creasing the mass of Antarctic ice, and thus increasing the 
force of the trade-winds and the resulting 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 
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 hemi- 
sphere, due to the peculiar distribution of land and sea 
which favours the production 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 



200 ISLAXD LIFE 



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 Palceozoic 
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 com- 
parable 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 coTmtry, 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 conditions ; but further back, in the Trias, the 
flora and fauna, in the Brittish area, 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 some 
indications of ice-action are found in the Lower Permian 
conglomerates of the Avest of England. These beds contain 
abundant fragments of various rocks, often angular and 
sometimes 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, 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 Eamsay ; 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, containino- 



CHAP. IX GEOLOGICAL CLIMATES 201 

blocks of Silurian and Old Red sandstone rocks which 
Professor Hull believes could only have been carried by 
fioating 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 produced by a very cold climate, are very import- 
ant, and seem clearly to indicate that at this remote 
period geographical conditions were such as to bring about 
a glacial epoch, or perhaps only local glaciation, 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, Avhere 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 Palaeozoic times, but confirms us in the validity 
of our conclusion, that the total absence of any such evidence 
throughout the Tertiary and Secondary epochs demon- 
strates the absence of recurring glacial epochs in the 
northern hemisphere, notwithstanding the frequent recur- 
rence of periods of high excentricity. 

Warm Arctic Climates in Early Secondary and Palceozoic 
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. 

^ Geological Magazir.e, 1873, i\ 320. 



202 ISLAXD LIFE 



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 es23ecially mention the numerous 
ammonites and the vertebrae 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 
inhabited the seas of Spitzbergen, where their fossil re- 
mains are now found. 

In the Carboniferous formation we again meet with 
plant-remains and beds of true coal in the Arctic regions. 
Lepidodendrons and Calamites, together with large spread- 
ing ferns, are found at Spitzbergen, and at Bear Island in 
the extreme north of Eastern 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 abund- 
ance of corals and cei^halopodous 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, Carbonif- 
erous 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 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 



CHAP. IX GEOLOGICAL CLIMATES 203 

preserved ? Mollusca and many other forms of life are 
abundant in the Arctic seas, and there is often a hixuriant 
dwarf woody vegetation 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 strengthened 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 w^armer 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 
instances those of the latter have been preserved. When 
to this uniform testimony of the palseontological 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 glaciation continues, we are driven to the conclu- 
sion that the last glacial epoch of the northern hemisphere 
was exceptional, and was not preceded by numerous 
similar glacial epochs throughout Tertiary and Second- 
ary time. 

But although glacial epochs (with the one or two excep- 
tions already referred to) were certainly absent, consider- 
able 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 the testi- 
mony of Mr. J. S. Gardner, who has long worked at the 
fossil floras of the Tertiary deposits, and who states, that 



204 ISLAND LIFE part i 

there is strong negative and some positive evidence of 
alte-rnatinof ' 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 feAV inches apart, may be sometimes due to 
chano-e 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 dcpenclcnt on the 
Physical Features of the Earth's Surface. — In the pre- 
ceding chapters I have earnestly endeavoured to arrive at 
an explanation 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 eluci- 
dation. If my conclusions as here set forth diverge consid- 
erably 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 astronomical causes on changes of climate, and that, 
while the latter have undoubtedly played an important 
part in bringing about the glacial epoch, it is 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 it mainly to 
the study of Dr. Croll's writings, since my theory is entirely 
based on the facts and princij)les so clearly set forth in his 
admirable pajDers 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 
^ Geological Magazine, 1877, p. 137. 



CHAP. IX GEOLOGICAL CLIMATES 205 

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 con- 
tinental and oceanic areas — which we have shown to be 
proved by so many distinct lines of evidence — is also im- 
plied by the general stability of climate throughout loDg 
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 termi- 
nating in three comparatively narrow extremities re- 
presented by Southern America, South Africa, and Aus- 
tralia. Towards the north these masses have approached 
each other, and have sometimes become united ; leavino- 
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 
hemisphere 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 Dorth-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 ele- 
vated, such a condition of glaciation would certainly be 
brought about, and would be heightened whenever a high 
degree of excentricity prevailed. 

It is now the general opinion of geologists that the 
great continents have undergone a process of development 
from earlier to later times. Professor Dana appears to 
have been the first who taught it explicitly in the case of 
the North American continent, and he has continued the 
development of his views from 1856, when he discussed 
the subject in the American Journal, to the later editions 
of his Manual of Geology in which the same views are ex- 
tended to all the great continents. He says : — 

"The North American continent, which since early 



206 ISLAND LIFE 



time had been gradually expanding in each direction from 
the .northern Azoic, eastward, westward, and southward, 
and which, after the Palaeozoic, 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 
land was at all times simple in outline ; and its enlarge- 
ment took place with almost the regularity of an ex- 
ogenous plant."^ 

A similar develoj^ment undoubtedly took place in the 
European area, which was apparently never so compact and 
so little interpenetrated by the sea as it is now, while 
Europe and Asia have only become united into one un- 
broken 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 slight fluctua- 
tions, of warm climates far into the north-polar area 
throughout Palseozoic, Mesozoic, and Tertiary times. At 
length, during the latter part of the Tertiary epoch, a con- 
siderable elevation took place, closing up several of the 
water passages to the north, and raising up extensive 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. A depression seems 
to have occurred during the glacial period itself in North 
America as in Britain, but this may have been due jDartly 
to the weight of the ice and partly to a rise of the ocean 

1 Manual of Geology, 2nd Ed. p. 525. See also letter in Nature^ Vol. 
XXIII. p. 410. 



CHAP. IX GEOLOGICAL CLIMATES 207 

level caused by the earth's centre of gravity being shifted 
towards the north. 

We thus see that the last glacial epoch was the climax 
of a great process of continental development which had 
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 con- 
siderable 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, be- 
cause 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 
local glaciation might be produced, which would be 
specially intense during periods of high excentricity ; and 
it is 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. 

Estimate of the com^parative effects of Geograpliical 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 con- 
currence of astronomical causes — high excentricity with 
winter in aphelion — was necessary 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 



208 ISLAND LIFE 



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 indications 
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 difficult 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 addition 
to the altitude of our islands could have brought about 
the extreme amount of glaciation which they certainly 
underwent, 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 through- 
out 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 con- 
ditions 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 



CHAP. IX GEOLOGICAL CLIMATES 209 

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 
geologists, since it shows the direct dej)endence 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 inportant departure from the great lines of 
elevation and depression originally marked out on the 
earth's surface has ever taken place. 

It also shows us how important an agent in the pro- 
duction of a habitable globe with comjDaratively small 
extremes of climates over its whole area, is the great dis- 
proportion between the extent of the land and the water 
surfaces. For if these 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 geological changes might easily 
have led to half the land surface becoming 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 
sino^ular arrano^ement of the land in three ofreat southward- 
pointing masses — are really facts of the greatest signific- 
ance and importance, since it is to these very anomalies 
that the universal spread of vegetation and the adapt- 
ability 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 ]\Ieasure of Tim.e — 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 jMotivo PoAver 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 tlie 
Measurement of Geological Time — Concluding Remarks. 



The subjects discussed in the last three chapters intro- 
duce us to a difficulty 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. Geolo- 
gists continually dwell on the slowness of the processes of 
upheaval and subsidence, of denudation of the earth's sur- 
face, and of the formation of nev/ 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 



THE EARTH'S AGE 211 



even longer series of ages than might satisfy the require- 
ments of physical geology alone. 

As an indication of the periods usually contemplated by 
geologists, we may refer to Sir Charles Lyell's calculation 
in the tenth 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 geolo- 
gists. This calculation was founded on the rate of modi- 
fication 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 naturalists 
and geologists, the period occupied in the formation of the 
known stratified rocks only represents a portion, and per- 
haps a small portion, of geological time. In the sixth edition 
of the Origin of Species (p. 286), Mr. Darwin says : " Con- 
sequently, if the theory be true, it is indisputable that 
before the lowest Cambrian 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 num- 
ber of special cases showing that, on the theory of develop- 
ment, almost all the higher forms of life must have existed 
during the Palaeozoic 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 gTeater change of 
the ancestral Ungulata into the two great odd-toed and 
even-toed d ivisions (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 Second- 
ary period. Another case is furnished by the bats and 
whales, both of which strange modifications of the mam- 
1 Nature, Yol. XVIII. (July, 1878), p. 268. 

p 2 



212 ISLAND LIFE 



malian type occur perfectly developed in the Eocene for- 
mation. 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 car- 
nivora, insectivora, ungulata, and marsupials at a far earlier 
period ; so that, on the lowest estimate, Ave must jDlace the 
origin of the mammalia very far back in Palaeozoic times. 
Similar evidence is afforded by reptiles, of which Professor 
Huxley says : " If 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 Palaeozoic times we must go before 
Ave can hope to arrive at that common stock from Avhich 
the crocodiles, lizards, Ornitlioscclida, and Pksiosauo'ia, 
Avhich 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 Avhole series of sfeolog^ical formations and their con- 
tained fossils. He says, speaking of the abundant, varied, 
and Avell-developed fauna of the Cambrian period : " In 
this earliest knoAvn I'aried life AA^e find no evidence of its 
havino' lived near the bes^innins; of the zooloo-ical series. 
In a broad sense, compared AAdth Avhat must have gone 
before, both biologically and 23hysically, all the phenomena 
connected Avith this old period seem, to my mind, to be of 
quite a recent description; and the climates of seas and 
lands Avere of the very same kind as those the Avorld enjoys 
at the present day." ^ 

These opinions, and the facts on Avhich they are founded, 
are so Aveighty, that Ave 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 ; Avhile it 
may not imjDrobably have been longer, because the reaction of 

^ " On the Comparative Value of certain Geological Ages considered as 
items of Geological Time." {^Proceedings of the lluyal Society ^ 1874, p. 
334.) 



THE EARTH'S AGE 213 



the organism under changes of the environment is believed 
to have been less active in low and simple, than in hio-h 
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 contemplated can be granted. From a consideration 
of the possible sources of the heat of the sun, as well as 
from calculations of the period during which the earth can 
have been cooling to bring about the present rate of in- 
crease of temperature as we descend beneath the surface. 
Sir William Thomson concludes that the crust of the 
earth cannot have been solidified 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 to be 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 Stratct as a Measure of 
Time. — The materials of all the stratified rocks of the 
globe have been obtained 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 
ddhris 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 univer- 
sality of this destructive agency. It is no less clearly shown 
by the way in which almost every dro]) 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 

1 Trans. Royal Society of Edinhurgh, Vol. XXIIL p. 161. Quarterly 
Journal of Science, 1877. (Croll on the "Probable Origin and Age of the 

Sun.") 



214 ISLAND LIFE 



of the country, must always pass from a higher to a lower 
level', and must ultmiately 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 
subaerial denudation, both as regards space and time, 
renders it certain that its cumulative effects must be very 
great; but no attempt seems to have been made to deter- 
mine 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 Sir A. 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 tlie 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 corres23onding 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 uuder 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 
^ PhUosopMcal Magazine, April, 1853. 



THE EARTH'S AGE 215 



the matter so deposited does not come down to the sea. 
After a careful examination of all the best records, 
Sir 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 : 

The Mississippi removes one foot in 6,000 years. 

„ Ganges ,, ,, 2,358 ,, 

,, Hoang Ho ., ,, 1,464 ,, 

,, Rhone .. .. 1,528 ,, 

„ Danube ., ., 6,846 ,, 

„ Po „ ., 729 „ 

,, Xith ., ., 4,723 ,, 

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 
average of them all as representing an amount of denuda- 
tion which, if not true for the whole land surface of the 
globe, will certainly be so for a very considerable propor- 
tion of it. This average is almost exactly one foot in 
three thousand years.^ The mean altitude of the several 

^ It 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. AYhenever any calculations are made 
involving the antiquity of man, it is those that give the loivcst 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 



216 ISLAND LIFE part i 



continents has been recently estimated by Mr. John 
Murray,! to be as follows : Europe 989 feet, Asia 8,189 
feet, Africa 2020 feet, North America 1,888 feet, and South 
America 2,078 feet. At the rate of denudation above given, 
it results that, were no other forces at work, Europe would be 
planed down to the sea-level in about two million eight 
hundred thousand years ; while if we take a somewhat 
slower rate for North America, that continent might last 
about four or five million years." This also implies that 
the mean height of these continents would have been 
about double what it is now three million and five 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 denuda- 
tion on hills, valleys, and lowlands, in connection with the 
evidence of remote glacial epochs (p. 173) ; 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. 

denudation, tliey take the slowest rate instead of tlie mean rate, apparently 
only because there is now a scientific 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 Euro])e than taking one Xorth American river as the standard. 

^ " On the Height of the Land and the Depth of the Ocean," in the 
Scottish Gcograj)hical Magazine, 1888. 

- These figures are merely used to give an idea of the rate at Avhich 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 probably 
less, and no rocky peaks would be left to be fractured and broken up by 
the action of frosts. It is 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. 



THE EARTH'S AGE 217 



Hoiu to Estimate the Thickness of the Sedimentary Rocks. 
■ — The sedimentary rocks of which the earth's crust is 
mainly comi^osed consist, according to Sir Charles Lyell's 
classification, of fourteen great formations, of which the 
niost ancient is the Laurentian, and the most recent the 
Post-Tertiary or Pleistocene; with thirty important sub- 
divisions, each of which again consists of a more or less 
considerable number of distinct beds or strata. Thus, the 
Silurian formation is divided into Upper and Lower 
Silurian, each characterized by a distinct set of fossil 
remains, and the Upper Silurian again consists of a laro-e 
number of separate beds, such as the Wenlock Limestone, 
the Upper Llandovery Sandstone the Lower Llandovery 
Slates, &c., each usually characterised by a diiference of min- 
eral composition or mechanical 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 Palaeozoic formations of the Appalachian Moun- 
tains, 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 
Leicestershire 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 denudation (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 geologi- 
cal map showing successive formations following each 
other in long irregular belts across the country (as is well 



218 ISLAND LIFE 



seen in the case of the Secondary rocks of Englandj, and a 
correspondmg 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 Limestone full of characteristic fossils, at a depth 
of only 800 feet. Here we have an enormous gap, show- 
ing that none of earlier Secondary or late Palaeozoic 
formations extend to this part of England, unless indeed 
they had been all once elevated and entirely swept away 
by denudation.^ 

But if Ave 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. The 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 



^ Tlie following statement of the depths at which the Palaeozoic forma- 
tions have been reached in various localities in and round London was 
given by Mr, H. B. Woodward in his address to the Xorwich Geological 
Society in 1879 : — 

Deep Wells throurjh the Tertiary and Cretaceous Formations. 

Harwich at 1, 022 feet reached Carboniferous Rock. 

Kentish Town ,, 1,114 ,, ,, Old Red Sandstone. 

Tottenham Court Road,, 1,064 ,, ,, Devonian. 

Blackwall ,. 1,004 ,, ,, Devonian or Old Red Sandstone. 

Ware ,, 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 Palaeozoic 
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. 



CHAr. X THE EARTH'S AGE 210 



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 globigerinse, radiolarians, and 
diatomaceas, or are clays formed of undissolved portions of 
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 dei30sits made by geologists. Professor Ramsay 
has calculated that the sedimentary rocks of Britain alone 
have a total maximum 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 maximum thicknesses of 
each deposit will have been produced only where the con- 
ditions 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 
necessarily 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 representa- 
tion of their maximum thickness, though it undoubtedly is 
of their extent and hulk. 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 



220 ISLAND LIFE 



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 admirable paper on " The Mean Thick- 
ness of the Sedimentary Rocks," ^ Dr. James Croll has 
dwelt on the extent of denudation in diminishing the mean 
thickness of the rocks that have been formed, remarking, 
" Whatever the present mean thickness 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 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 denuda- 
tion." This is perfectly true, and j^et 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 quite Iwonzontal, and wholly 
exposed to the sea or to the atmosphere, denudation can 
have no tendency to diminish the thickness of any entire 
deposit.^ 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 inadequate representation of the mean thickness of all 
that have been formed, and even of the maximum thick- 
ness of the larger portion. This will be the more likely 
because it is almost certain that many rocks contempor- 
aneously formed are counted by geologists as distinct for- 
mations, whenever they differ in lithological character or 
in organic remains. But we know that limestones, sand- 
stones, and shales, are always forming at the same time ; 

^ Geological Magazine, Vol, YIIL, March, 1871. 

- Mr. C. Lloyd IMorgan has Avell 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 Maga-Jac^ 
1878, p. 161.) 



THE EARTH'S AGE 221 



while a great difference in organic remains may arise from 
comjoaratively slight changes of geographical features, or 
from difference in the depth or purity of the water in which 
the animals lived,^ 

Hotv to Estimate the Average Hate of Deposition of the 
Sedimentary Eoeks. — 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 denuda- 
tion, to be equal to the maxiiintm 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 measurement on a 
globe shows that 100,000 miles will be nearer the mark, 
and this has the advantage of being an easily remembered 
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 com- 
paratively 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 uniform thickness in 
a direction at right angles to the coast, we should probably 
include all areas where deposits of the maximum thickness 

^ Professor J, Young thinks it highly probable that — " the Lower Green- 
rand 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.) 

2 Mr. John Murray in his more careful estimate makes it about 51 J 
millions. 



222 ISLAND LIFE part i 

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 con- 
sider 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 thick deposit is forming annually, those where 
there is little or none are probably at least twice as exten- 
sive. 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, corresjDonding to the 
maximum thickness as measured by geologists, 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 

^ 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 tlie 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 viaximum 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 lew 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 ]\Iississippi 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. " 



THE EARTH'S AGE 223 



miles is deposited. As these two areas are as 1 to 19, it 
follows that deposition, as measured by inaxiniiviii thickness, 
goes on at least nineteen times as fast as denudation — 
probably very much faster. But the mean rate of denuda- 
tion 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 present rate of 
denudation and deposition, is only 28,000,000 years.^ 

The Rate of Geological Change Prohahly Greater in mry 
Remote Times. — The opinion that denudation and deposition 
went on more rapidly in earlier times owing to the frequent 
occurrence of vast convulsions and cataclysms was strenu- 
ously ojDposed 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 "con- 
vulsionists," 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 atmosphere, and, perhaps, a 
greater difference between equatorial and polar tempera- 
tures ; hence more violent winds, heavier rains and snows, 

•^ 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 vJwle sca-hoUom 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. XVlli., p. 268, where Professor Haughton's 
paper is given as read before the Royal Society. ) 

- See Geological Magazine for 1877, p. 1. 



224 ISLA^^D LIFE 



and more powerful oceanic currents, all producing more 
rapid denudation, At the same time, the internal heat of 
the earth being greater, it Avould be cooling more rapidly, 
and thus the forces of contraction — which cause the 
U23heaving of mountains, the eruj^tion 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 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 jDOwerful 
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 actino; toofether, 
their combined effects may have been by no means un- 
imjDortant. 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 in- 
tensifying 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 time required 
to have produced the whole series of formations from the 
Cambrian upwards. 

Value of the Preceding Estimate of Geologieal Time. — It 
is not of course supposed that the calculation here given 



THE EARTH'S AGE 225 



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 dei30sited, and the 
maximum thickness of the known stratified rocks.^ A 
considerable but unknown amount of denudation is effected 
by the waves of the ocean eating away coast lines. This 
was once thought to be of more importance than sub-aerial 
denudation, but it is now believed to be comparatively 
slow in its action.^ Whatever it may be, however, it adds 
to the rate of formation of new strata, and its omission 
from the calculation is ao^ain on the side of making the 
lapse of time greater rather than less than the true amount. 
Even if 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 is 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 Pro- 
fessor Huxley and Professor Ramsay. 

Organic Modification Dependent on Change of Conditions. 

^ In his reply to Sir AV. Thomson, 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-ascer- 
tained fact, that the area of deposition is many times smaller than the area 
of denudation. 

^ Dr. Croll and Sir Archibald Geikie have shown that marine denudation 
is very small in amount as compared with sub-aerial, since it acts only locally 
on the edge of the land, whereas the latter acts over every foot of the 
surface. Mr. AV. T. Blanford argues that the difference is still greater iu 
tropical than in temperate latitudes, and arrives at the conclusion that — 
"If 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). Xow, as our estimate of 
the rate of sub-aerial 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. 



226 ISLAND LIFE 



— 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 noAv to inquire whether there are any considera- 
tions 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 specific forms with changes of external con- 
ditions or environment. 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 materially 
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 determine 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 northward in a wild state ; and 
Azara and Rengger have shown that this is caused by the 
greater number in Paraguay of a certain fly, which lays 
its eggs in the navels of these animals when first born. 
The increase of these flies, numerous as they are, must be 



CHAP. X THE RATE OF ORGANIC CHAXCxE 227 

habitually checked by some means, probably by other 
parasitic insects. Hence, if certain insectivorous birds were 
to decrease in Paraguay, the parasitic . insects would 
probably increase ; 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 insects, and this, as we have 
seen in Staffordshire, the insectivorous birds, and so on- 
wards in ever increasing circles of complexity." 

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 sub- 
sidence of land separating a large island from a continent 
would affect the animals and plants in a variety of ways. 
It would at once modify the climate, and so produce a 
series of changes from this cause alone ; but more import- 
ant would be its effect by isolating small groups of in- 
dividuals 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 fluc- 
tuations, would certainly result in the extinction of some 
species, the modification of others, and a considerable 
alteration in the proportionate numbers and the geograph- 
ical 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 temperature, 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 

Q 2 



228 ISLAND LIFE 



the distribution of animals. Slow elevations of the land 
would produce another set of changes, by affording an ex- 
tended area in which the more dominant species might in- 
crease 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. 

Geograi^liical 3futatio7is as a Motive Poiver 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 been wanting. In the 
first place, every continent, though permanent 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 reptiles, another 
as the age of fishes, and a third as the age of mammals. 

But such changes as these must necessarily have led to 
repeated 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 aflect the organic world even 
more profoundly than the changes of area, of altitude, or 



THE RATE OF ORGANIC CHANGE 229 



of climate, since they afforded the means, at long intervals, 
of bringing the most diverse forms into competition, and 
of si^reading 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 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 comj^etition 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. 

Climated Ecvolutions as an Agent in Prochicing Organic 
Cliangcs. — 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 sjmng in arctic as well as 
in temperate lands, with occasional phases of cold culmin- 
ating at remote intervals in glacial epochs, — that Ave must 
impute some of the more remarkable changes both in the 
specific characters and in the distribution of organisms.^ 
^ Agassiz appears to have been the first to suggest that the principal 



230 ISLAND LIFE part i 

Although the geological evidence is opposed to the belief 
in eajly glacial epochs excej^t at very remote and distant 
intervals, there is nothing which contradicts the occurrence 
of rej^eated 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 w^e have seen, is all that is 
necessary to keep the processes of " natural selection " in 
constant operation. 

The frequent recurrence of periods of liigh and of low 
excentricity 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 j9cr^^<?/^c»9^, that season would be certainly very 
much hotter, while the winters w^ould be longer and 
colder than at present ; and although geographical con- 
ditions might prevent any permanent increase of snow 
and ice even in the extreme north, yet we cannot doubt 
that the whole northern hemispliere 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 j^erpetual spring, in fact. Now, such a change 
of climate would certainly be calculated to bring about a 
considerable change of sjMcics, botli by modification and 
migration, without any such decided change of tyj^e either 
in the vegetation or the animals that Ave could say from 
their fossil remains that any change of climate had taken 
place. Let us supj^ose, for instance, that the climate of 
England and that of Canada w^ere to be mutually ex- 
changed, and that the change took five or six thousand 
years to bring about, it cannot be doubted that consider- 
able modifications in the fauna and flora of both countries 
would be the result, although it is impossible to predict 

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 Palaeozoic 
and of the Cretaceous periods — to which we may add the last glacial epoch. 



CHAP. X THE RATE OF ORGANIC CHANGE 231 

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 jDrobable that some would be 
actually benefited by it, and that 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 pro- 
duction 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 excentricity, for it is impossible to doubt that 
a varying distance of the sun in summer from 86 to 99 
millions of miles (Avhich is what occurred during — as 
supposed — the Miocene period, 850,000 years ago) would 
produce an important difference in the summer tem- 
perature and in the actinic influence of sunshine 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 excen- 
tricity 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 condi- 
tions so as to produce climatic alterations in different 
directions, 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 jiresent low phase of 



232 ISLAND LIFE part t 

excentricity and consequent slight inequality of sun- 
lieat. 

PrCsait Condition of the Earth One of Exceptional Stability 
as Regards Climate. — It will be seen, by a reference to the 
diagram at page 171, that during the last three million 
years the excentricity has been less 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 de- 
gree 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 
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 unimportant, and that the temperate zones 
have enjoyed an exceptional stability of elimeite. During 
this time those powerful causes of organic change which 
depend on considerable changes of climate and the con- 
sequent 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 adaj^t 
themselves to them without much disturbance ; and 
the result would be cm 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, 



CHAP. X MEASUREMENT OF GEOLOGICAL TIME 233 

but that of the Swiss Lake dwellings, the Danish shell- 
mounds, our peat-bogs, our sunken forests, and many of our 
suj^erficial alluvial deposits — the whole in fact, of the iron, 
bronze, and neolithic ages. Even some j^ortion of the 
jmlseolithic 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 throuo-hout all these aoes we find no indication of 
change of species, and but little, comparatively, of migra- 
tion. We thus get an erroneous idea of the idcrmancnce 
and stahility of siKcific forms, due to the period immediately 
antecedent to our own being a iJCQ^iod of exccptioncd fcr- 
manence and stahility as regards climatic and geographical 
conditions.^ 

Date of Last Glacial Epoch and its Becoming on the 
Measurement of Geological Time. — Directly we go back 
from this stable j)eriod we come upon changes both in the 
forms and in the cristribution of species ; and when we 
pass beyond the last glacial epoch into the Pliocene period 
we find ourselves in a comparatively new world, surrounded 
by a 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.^ 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 

^ Tills view was, I believe, iirst put forth by myself in ca paper read 
before the Geological Section of the British Association in 1869, and 
subsequently in an article in Nature, Vol. L p. 454. It was also stated 
by :Mr. S. B. K. Skertchlev 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. 

2 Explication d'une scconde edition de la Carle Geoloyiqnc dc la Terre 
(1875), p. 64. 



234 ISLAND LIFE 



prevailed. As many reasons combine to make us fix the 
height of the glacial epoch at the period of high excen- 
tricity which occurred 200,000 years back, and as the Plio- 
cene period was probably not of long duration, w^e must 
suppose the next great jDhase of very high excentricity 
(850,000 years ago) to fall within the Miocene ei^och. 
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 condi- 
tions, it led to uninterrupted warm climates in the 
temperate 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, 
since 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 denuda- 
tion, so that these rocks may have been at first raised much 
higher than we now find them, and thus a considerable 
portion of the Alps may have been more elevated than 
they are now. This would certainly lead to an enormous 
accumulation of snow, which 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 indic- 
tions of an uninterrupted warm climate and rich vegetation 
during the very same period in the adjacent low countries, 
just as we find at the j^resent day in New Zealand a 
delightful climate and a rich vegetation of Metrosideros, 



CHAP. X MEASUREMENT OF GEOLOGICAL TIME 235 

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 com^Darative 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 Frincij^les 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 Palaeozoic 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) 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 w^hen discussing so difficult and ex- 
ceedingly 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 calculations of 
jihysicists, by leaving a very wide margin between geo- 
logical time as defined by the fossiliferous rocks, and that 



236 ISLAND LIFE 



far more extensive period whicli includes all possibility of 
life upon the earth. 

Concluding Remarks. — In the present chapter I have 
endeavoured 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 for- 
mation of those rocks. From another point of departure— 
that of the probable date of the Miocene period, as deter- 
mined 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 
pro23ortionate amount of change in the animal world since 
that epoch — we obtain another estimate of the duration of 
geological 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 oreolooists, and is so far within the limits of 
the duration of the earth as calculated by Sir William 
Thomson, as to allow for the development 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 
excentricity and opj^osite j)hases of precession, even though 
these did not lead to glacial epochs, we have a motive 
power well calculated 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 have ample 
material for that power to act upon, so as to keep the 
organic world in a state of rapid change and develojjment 
proportioned to the comparatively ra2)id changes in the 
earth's surface. 

We have now finished the series of preliminary studies 
of the biological conditions and j^hysical changes which 
have affected the modification and dispersal of organisms, 
and have thus brought about their actual distribution on 



MEASUREMENT OF GEOLOGICAL TIME 237 



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, when- 
ever the necessary facts, both as to tlieir 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 IT 

INSULAR FAUjVAS 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. 

In the preceding chapters, forming the first part of our 
work, we have discussed, more or less fully, the general 
features presented 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 23resented 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 phenom- 
ena as are presented by the islands of the globe. 

Im])OTtancG 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 



242 ISLAND LIFE 



case of continents, and their peculiar species and groups 
are usually well , defined and strictly limited in range. 
Again, their relations with other lands are often direct 
and simple, and even when more complex are far easier to 
comprehend than those of continents ; and they exhibit 
besides certain influences on the forms of life and certain 
peculiarities in their distribution which continents do not 
present, and whose study offers many points of interest. 

In islands we have the facts of distribution pre- 
sented to us, sometimes in their simplest forms, in other 
cases becoming 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 de- 
fined problems of continental distribution. 

Classificatio7i of Islands vnth Reference to Distrilmtion. — 
Islands have had two distinct modes of origin — they have 
either been separated from continents of which they are 
but detached fragments, 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 funda- 
mental, 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 



CHAr. xr THE CLASSIFICATION OF ISLANDS 243 

part of a continent. This was quite opposed to the 
opinions of the scientific men of the day, who ahnost all 
held the idea of continental extensions, and of oceanic 
islands being their 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 permanence 
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 a fair number 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 Transit of Venus Expedition to be essentially 
volcanic, with some upraised coralline limestone. 

Continental Islands. — Continental islands are always 
more varied in their oreoloofical formation, containino^ 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 sub- 
merged 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 other- 

R 2 



244 ISLAND LIFE 



wise, the difference consists in the presence of closely allied 
specie^ 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. 

Ancient continental islands differ greatly from the pre-' 
ceding in many respects. They are not united to the adja- 
cent continent by a shallow bank, but are usually separated 
from it by a depth of sea of several hundreds to more than 
a thousand fathoms. 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 forming 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 existing 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 sub- 
merged 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 it would be 
reduced to the same zoological condition as an oceanic 
island. But such a complete submergence and re-eleva- 
tion appears never to have taken place, for there is no 
single island on the globe Avhich has the physical and geo- 
logical features of a continental, combined with the zoo- 
logical features of an oceanic island. It is true that some 
of the coral-islands may be formed upon submerged lands 



OCEANIC ISLANDS. 245 



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, beginnino- 
with oceanic islands. 

All the animals which now inhabit such oceanic islands 
must 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 in- 
habitants 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 Pliysical Features — Chief Zoological Features of tlie Azores — 
Birds — Origin of tlie Azorean Bird Fauna — Insects 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 JMollusca — Flora of 
Bermuda — Concluding Remarks on the Azores and Bermuda. 

We will commence our investigation into the phenomena 
presented 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 us a valuable clue to a solu- 
tion 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 volcanic, the other coral- 
line ; 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 



CHAP. XII OCEANIC ISLANDS 247 



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 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, nine in number, form a widely scattered 
group, situated between 37° and 39° 40' N. Lat. and 
stretching in a south-east and north-west direction over a 
distance of nearly 400 miles. The largest of the islands, 
San Miguel, is about forty miles long, and is one of the 
nearest to Europe, being rather under 900 miles from the 
coast of Portugal, from Avhich 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 directions. 
These great dej^ths render it in the highest degree imj)rob- 
able 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 Ui)23er 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 gTeater 
extension of the whole grouj). It proves, however, that 
the group is of considerable antiquity, since it must date 
back to Miocene times ; and this fact may be of im- 
portance in considering the origin and peculiar features of 
the fauna and flora. It thus apjjears that in all physical 
features the Azores correspond strictly with our^physical 
definition of " oceanic islands," while their oreat distance 



ISLAND LIFE 



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. 




OUTLINE MAP OE' THE AZORES. 

Note. — The light tint shows where the sea is less than 1,000 fathoms deep. 
The dark tint „ ,, ,, more than 1,000 fathoms deep. 

The figures show depths in fathoms. 



Chief Zoological Features of the Azores} — The great 
feature of oceanic islands — the absence of all indigenous 
land-mammalia and am23hibia — is well shown in this 

^ For most of tlie facts as to the zoology and botany of these islands, I 
am indebted to Mr. Godman's valuable work — Natural History of the 
chores or Western Islands, by Frederick Du Cane Godman, F.L.S., F.Z.S., 
&c., London, 1870. 



CHAP. xiT THE AZORES 249 

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 exten- 
sive, possess a mild and equable climate, and are in every 
way adapted to support all these grouj)s. 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. 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 Blizzard {Butco vulgaris) 

2. Long-eared Owl {Asio otus) 

3 Barn Owl {strix fiammea) 

4. Blackbird ( Turdus mcrula) 

5. Robin {Erythacics rubemla) 

6. Blackcap {Sylvia atricapilla) 



250 


ISLA:N'D life part II 


7. 


Gold-crest 


[Regulus cristatus) 


8. 


Wheatear 


{Saxicola cenanthc) 


-9. 


Grey Wagtail 


{Motacilla sulphurca) 


10. 


Atlantic Chaffinch 


{Fringilla tintillon) 


11. 


Azorean Bullfinch 


{Pyrrhula murina) 


12. 


Canary 


{Scrinus canarius) 


13. 


Common Starling 


{SHrnus vulgaris) 


14. 


Lesser Spotted Woodijccker 


[Dryohatcs minor) 


15. 


Wood-pigeon 


( Cohnnba palumhiLs) 


16. 


Rock Dove 


{Columha livia) 


17. 


Red-legged Partridge 


[Caccahis rufa) 


18. 


Common Quail 


[Coturnix communis) 



All the above-named birds are common in Europe and 
North 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 exj^lain 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 continents. 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 occasionally 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 permanent inhabitants. Many facts mentioned 
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 



CHAP. XII THE AZORES 251 

Madeira it must have travelled quite as far as from 
Portugal to tlie 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. Subsequently 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 Europe 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, Graciosa, St. George's, Pico, and 
Fayal ; and a westei-n 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 involuntarily, 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 cha2Dter 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 sufficiently distinct. 
Now we can hardly have a greater difference of conditions 



252 ISLAND LIFE 



than between the continent of Europe 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 ha23pened 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 allies. 

There is another reason for the very slight amount of 
peculiarity j^resented by the fauna of the Azores as com- 
pared with many other oceanic islands, dependent on its 
comparatively recent origin. The islands themselves may 
be of considerable antiquit}^, 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 but a little to the west of them ; 
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 sun'ounded with pack-ice, 
while their own mountains, reaching 7,600 feet high in 
Pico, would almost certainly have been covered with per- 
petual 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 



CHAP. XII THE AZORES 253 

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 accounting 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 num- 
ber, 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 found in 
any of the other Atlantic islands, showing 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 
peculiar to the Azores. These latter are mostly allied to 
species found in 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 interesting : — 

Carabid^. 

Anchomcmts apiinoidcs . . .Allied to a species from the Canaries. 
Bcvihidium hesperus Allied to the European B. Itetuin. 

Dytiscid^. 
Agahiis godmanni Allied to the European A. disimr. 

COLYDIID^. 

Ttirphias u'oUctstoni A genus almost peculiar to the Atlantic islands. 



25i ISLAND LIFE paet ii 

Elaterid^. 

Heteroderes azoricus Allied to a Brazilian species. 

Elastnis dolosus ' Belongs to a peculiar Madagascar genus I 

Melyrid^. 
Attains miniaticollis Allied to a Canarian species. 

Rhyncophora. 

Phlcco2)hagus variahilis ...Allied to European and Atlantic species. 

Acalles droueti A Mediterranean and Atlantic genus. 

La'paroccrus azoricus Allied to Madeiran species. 

Asynonychun godmansi ... A peculiar genus, allied to Bracliyderes, of the 

soutli of Europe. 
Neocnemis ocddentalis . . A peculiar genus, allied to the European genus 
Stropliosoiinis. 

Heteromera. 
Hclops azoricus Allied to H. mdcanus of Madeira. 

Staphylinid^. 
Xenomma QnclanocepJiala.. Allied to X. filiformc from the Canaries. 



This greater amount of speciality in the beetles than in 
the birds may be due to two causes. In the first jDlace 
many of these small insects have no doubt survived the 
glacial epoch, and may, in that case, represent very ancient 
forms which have 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 light 
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 in 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 



CHAP. XII THE AZORES 255 

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 proba- 
bility of insects as a whole reaching the islands, the chance 
against any particular species 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, proportionately, 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 gToups. 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 Euroj)e 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 
Elaterida3 alone exhibit remote affinities, the one with a 
Brazilian the other with a Madagascar group ; while the 
only peculiar genera belong to the Bhyncophora, but are 
allied to European forms. These last almost certainly 
form a portion of the more ancient fauna of the islands 
which mig'rated to them in jDre-giacial times, while the 
Brazilian elater appears to be the solitary examj^le of a 
living insect brought by the Gulf Stream to these remote 
shores. The elater, having its nearest living ally in 
Madagascar {Elastrus dolosus), cannot be held to indicate 
any independent communication between these distant 
islands ; but is more iDrobably a relic of a once more wide- 
spread type which has only been able to maintain itself in 
these localities. Mr. Crotch states that there are some 
Impedes of beetles common to Madagascar and the Canary 
Islands, while there are several genera, common to Mada- 
gascar 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 



256 ISLAND LIFE 



the globe, and the only rational exi^lanation of such facts 
is, that they are indications of very ancient and once wide- 
spread 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 insects 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 introduction is a very rare event, and 
that a species once arrived remains for long periods un- 
disturbed 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 violence and duration, 
while others might be conveyed with the earth that often 
sticks to the feet of birds. There are also, probably, other 
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. 

The 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 
1 See Chap. V. p. 78. 



CHAP. XII THE AZORES 257 



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 j)urpose plants are some- 
times of more value than any class of animals, it will be 
well to take advantage of the valuable materials here avail- 
able, 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 Avhich 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 conti- 
nental 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 dis- 
persal 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 
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 pro- 
cesses ; 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 with- 
out injury. Mr. Darwin made many experiments on this 
point, and he found that many seeds, esj^ecially of Atriplex, 

S 



258 ISLAND LIFE 



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' im- 
mersion, and this would certainly prevent them being 
floated to very great distances. It is very possible, how- 
ever, that dried branches or flower-heads containing seeds 
would float longer, while it is quite certain that many 
trojDical 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 Vvdiich 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.^ 

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 many plants into the islands. 

Birds also frequently have small portions of earth on 
their feet; and Mr. Darwin has shown by actual experi- 
ment that almost all such earth contains seeds. Thus in 

^ Some of ]\Ir, 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 90x60 — 5, 400 miles I 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. ]\Ir. Darwin calciilates 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 migi-ation. (See Origin 
of Species, 6th Edition, p. 325. ) 



THE AZORES 259 



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 remarkable 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.^ 

^ 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 ( Vcg. clcrErde, 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. Acsena, have 
flower-heads which stick like burrs to feathers, &c., and seem specially 
adapted for transporation by birds. Besides the albatrosses, various 
species of Procellaria and Puffinus, birds which range over immense dis- 
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 (Finschand Hartlaub, Orn.der Viti-uncl Tonga-Inseln, 1867, 
Einleitung, p. xviii. ). Thus, Puffimts 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. Phaetlion has a similar habit. It nests at the 

s 2 



260 ISLAND LIFE part ii 

Facilities for Dispersal of AzoQ^ean 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 
giumaceous plants, which are all j)robably 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. Such are oaks, chestnuts, hazels, apples, 
beeches, alders, and firs ; while the only trees or large 
shrubs are the Portugal laul'el, myrtle, laurestinus, elder, 
Lanrus canaricnsis, Myrica faya, and a doubtfully peculiar 
juniper — all small berry-bearers, and therefore likely to 
have been conveyed by one or other of the modes suggested 
above. 

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, vol- 
untary 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 
to do so. 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, 

crater of Kilauea, Hawaii, at 4, 000 feet elevation, and also high up in Tahiti. 
In order to account for the transporation 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 jdants occur. The ancestor of 
the now differing species might have carried the seeds. The range of the 
genus is sullicient. '' 



CHAP. XII THE AZORES 261 

there will still remain a wonderfully rich ancj 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 
going 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 Camjmnula vidalii 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 jDortion 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. 

Important Deduction from the Peculiarities of the Azor- 
ean Fauna aiid 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 extraordinary 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 



262 ISLA^'D LIFE 



conveyed by the regular winds and currents, which are 
both such as to prevent European species from reaching 
the islands. 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 Cao- 
aries, and the Cape de Yerdes — present analogous phen- 
omena 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 Dis- 
trilmtion of Animals (Vol. I. pp. 208-215) ; and as we are 
noAV dealing with what may be termed typical examples 
of oceanic islands, for the purpose of illustrating 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 somewhat farther from the Bahama 
Islands, and are thus rather more favourably placed for 
receiving immigrants from America and its islands than the 
Azores are Avith respect to Europe. There are about 100 
islands and islets in all, but their total area does not ex- 
ceed 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 the whole area now occupied by 
shoals and reefs.^ Immediately beyond these reefs, liow- 

1 Nature, Vol. VI. p. 262, "Recent Observations in the Bermudas, " by- 
Mr. J. Matthew Jones. 



CHAP. XII 



BERMUDA 



263 



ever, extends a very deep ocean, while about 450 miles 
distant in a south-east direction, the deepest part of the 
North Atlantic is reached, where soundings of 3,825 and 




MAP OF BERMUDA AND THE AMERICAN COAST. 



Note.— The light tint indicates sea less than 1,000 fathoms deep 
The dark tint ,, ,, more than 1,000 fathoms deep. 
The figures show the depth in fathoms. 



3,875 fathoms have been obtained. It is clear therefore 
that these islands are typically oceanic. 

Soundings were taken by the ChalUnger in four differ- 



PAliT II 



264 ISLAND LIFE 

ent directions around Bermuda, and always showed a rapid 
deepening of the , sea to about 2,500 fathoms. Tliis was 
so remarkable, that in his reports to the Admiralty, Captain 
Nares spoke of Bermuda as " a solitary peak rising abru^Dtly 
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 
character of this peak, I have drawn a section of it on a 



BERMUDA 


d 








46 MILES. > 



SECTION OF BERMUDA AND ADJACENT SEA BOTTOM. 

The figiu'es show the depth in fathoms at fifty-five miles north and forty-six miles south 
of the islands respectively. 

true scale 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 which also show great contortions, so that 
at first sight the islands appear to exhibit on a small scale the 
phenomena of a disturbed Palaeozoic district. It has however 
lonor been known that these rocks are all due to the wind, 



CHAP. XII BERMUDA 265 



which blows up the fine calcareous sand, the product of the 
disintegration of coral, shells, serpulse, and other organisms, 
forming sand-hills forty and fifty feet high, which move 
gradually along, overwhelming the lower tracts of land be- 
hind 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 Bed 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 abundantly 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, its 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 composition, 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, 



266 ISLAND LIFE paut ii 

or of the minute organisms which abound in the 
blown sand/ 

Zoology of Bermuda. — As might be expected from their 
extreme isolation, these islands possess no indigenous 
terrestrial 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 
Plesticdoii (Uumeces) longirostris. It is said to be most 
nearly allied to Eumeces quinquelineatus 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 being the only vertebrate animal 
which exhibits any peculiarity. 

Birds. — Notwithstanding its small size, low altitude and 

^ ' ' The late Sir C. Wyville Thomson was of opinion that the ' red 
earth ' which largely forms the soil of Bermuda had an organic origin, as 
well as the 'red clay' which the Challenge?' discovered in all the greater 
depths of the ocean basins. He regarded the red earth and red clay as an 
ash left behind after the gi-adnal removal of the lime by water charged witli 
carbonic acid. This ash he regarded as a constituent part of the shells of 
Foraminifera, skeletons of Corals, and j\Iolluscs, [vide Voyage of the 
Challenger, Atlantic, Vol. I. p. 316]. This theory does not seem to be in 
any way tenable. Analysis of carefully selected shells of Foraminifera, 
Heteropods, and Pteropods, did not show the slightest trace of alumina, 
and none has as yet been discovered in coral skeletons. It is most 
probable that a large part of the clayey matter found in red clay and the 
red earth of Bermuda is derived from the disintegration of pumice, which 
is continually found floating on the surface of the sea. [See Murray, *' On 
the Distribution of Volcanic Debris Over the Floor of the Ocean ; " Proc. 
Roy. Sac. Edin. Vol. IX. pp. 247-261. 1876-1877.] The naturalists of the 
Challenger found it among the floating masses of gulf weed, and it is 
frequently picked up on the reefs of Bermuda and other coral islands. 
The red earth contains a good many fragments of magnetite, augite, felspar, 
and glassy fragments, and when a large quantity of the rock of Bermuda 
is dissolved away with acid, a small number of fragments are also met with. 
These mineral particles most probably came originally from the pumice 
which had been cast up on the island for long ages (for it is known that 
these minerals are present in pumice), although possibly some of them may 
have come from the volcanic rock, which is believed to form the nucleus 
of the island." The Voyage of H.M.S. Challenger, Narrative of the Cruise, 
Vol. I. 1885, pp. 141—142. 

- Four bats occur rarely, two being N. American, and two West Indian 
Species. The Bermuda Islands, by Angelo Heilprin, Philadelphia. 
1889. 



BERMUDA 267 



remote position, a great number of birds visit Bermuda 
annually, some in large numbers, others only as accidental 
stragglers. Altogether, over ISO species have been 
recorded, rather more than half being wading and swim- 
ming 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 flying 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 birds are recorded as tolerably frequent visitors, and 
nearly half these appear to come every year. 

There are only eleven species which are permanent 
residents on the island — eight land, and three water birds, 
and of these one has been almost certainly introduced. 
These resident birds are as follows : — 



1. Gakoscoptcs 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 novmboracensis. (The White-eyed green Tit. ) Migrates along 

the east coast. 

4. Passer domesticus. (The English Sparrow. ) ? Introduced. 

5. Corviis amcricanus. (The American Crow.) Common over all 

North America. 

6. Cardinalis virginianus. (The Cardinal bird.) Migrates from 

Carolina southward. 

7. ChamceiJcliapasserina. (The ground Dove. ) Louisiana, W. Indies, 

and Mexico. 

8. Ortijx virginianus. (The- American Quail.) Xew England to 

Florida. 

9. Ardca herodias. (The Great Blue Heron.) All North America. 

10. Gallinula galcata. (The Florida Gallinule.) Temperate and 

tropical North America. 

11. Phaeton Jiavirostris. (The Tropic Bird.) 

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 inhabited the islands there has been no chance 
for them to have acquired any distinctive characters 
owing to the want of isolation. 

Among the most regular visitants which are not resident, 
are the common N. American kingfisher (CGrylc alcyon), 



268 ISLAND LIFE 



the night-hawk (Chordeiles virginianus), the wood wagtail 
(Siurus novceboraccnsis), the snow-bunting {Plectwphanes 
nivalis), and the wide-ranging rice-bird {Dolichonyx 
oo'yzivora) , all very common and widespread in North 
America. 

Com.2^ariso)i of the Bird-faunas of Bcrwuda 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 flora 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 im- 
mense number of insectivorous and frugivorous birds ; so 
that during the breedirag season Canada is actually richer 
in bird-life than Florida. But as the severe Avinter 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 northward or southward in Eastern 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 meeting with a westerly or north 
westerly gale, they are rapidly driven sea-ward. The great 
majority no doubt perish, but some reach the Bermudas 



CHAP. XII BERMUDA 



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 por- 
tion 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 {Turclus migratorius) , the yellow- 
rumped warbler {Dcndrceca coronata), the pine warbler 
{Dcndrceca inmts), the wood wagtail {Siunos novcchoracensis), 
the summer red bird (Pyranga cestiva), the snow-bunting 
{Plcctro2Jhanes nivalis)^ the red-poll (j^giotlius Unarms), 
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 cenanthe), which visits Iceland and 
Lapland and sometimes the northern United States ; the 
skylark (Alauda arvensis), but this was probably an im- 
ported bird or an escape from some ship ; the land-rail 
{Crex pratensis), which also wanders to Greenland and the 
United States ; and the common snipe (ScolojJax gallinago), 
which occurs not unfrequently in Greenland but has not 
yet been noticed in North America. It is however so like 
the American snipe {S. ivilsoni), that a straggler might 
easily be overlooked. 

Two small bats of N. American species also occasionally 
reach the island, while two others from the West Indies 
have more rarely occurred, 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, and 
more recently by Professor Heilprin, that only the more 
conspicuous species have been yet collected. These com- 



270 ISLAND LIFE part ii 

prise 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 
somewhat more interesting, as they appear to be the only 
group of animals except reptiles in which there are any 
peculiar species. The following list was 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, from Avhich those of the Bermudas have undoubt- 
edly been derived. The nomenclature has been corrected 
in accordance with the list given in Professor Heilprin's 
work on the islands. The siDCcies which are peculiar to 
the islands are indicated by italics. 



List of the Land-Shells of Bermuda. 

1. Sitccinea fnlgens. (Lea.) Also in Cuba. 

2. ,, Bernmclensis. (Pfeiffer.)... ,. Barbadoes (?) 

3. ,, margarita. (Pfr.) ... ,, Haiti. 

4. Pcecilozonites Bermuclensis.^Ph-.) ... 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. 

5. ,, circumfirmatas {^edi^Ql^.) 

6. ,, discrepans. (Pfr.). 

7. ,, Beinianus. (Pfr.) 

8. Patula (Thysanophora) hypolepta. (Shuttleworth.) 

9. ,, vortex. (Pfr.) Southern Florida and West Indies. 

10. Helix microdonta. (Desh.) ... Bahama Islands, Florida, Texas. 

11. ,, appressa. (Say.) Virginia and adjacent states ; per- 

haps introduced into Bermuda. 

1 Fourteen species of Spiders were collected by Prof. A. Heilprin, all 
American or cosraopolitian species except one, Lycosa atlantica, which Dr. 
Marx of Washington describes as new and as peculiar to the islands. 
(Heilprin's The Bermudas, p. 93.) 



CHAP. XTI 



BERMUDA 



271 



12. Helix pulchella. (Miill.) 



13. „ ventricosa. (Drap. ) ... 

14. Bulimulus nitidulus. (Pfr.) 

15. Stenogyra octona. (Ch.) ... 

16. Stenogyra decollata (Linn.) 

17. Coecilianella acicula. (Miill.) 

18. Pupa pellucida. (Pfr.) 

19. ,, Barbadensis, (Pfr.) ... 

20. ., Jamaicensis. (C B. Ad.) 

21. Helicina convexa. (Pfr.) 



. . . Europe ; very close to H. minuta 

(Say) of the United States. 

Introduced into Bermuda (?) 
. . . Azores, Canary Islands, and South 

Europe. 
... Cuba, Haiti, &c. 
... West Indies and South America. 
... A South European species. 

Introduced. 
... Florida, New Jersey, and Europe. 
... "West Indies, and Yucatan. 
... Barbadoes (?) 
... Jamaica. 
... 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 about one- 
fifth 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 ter- 
restrial organisms. It thus happens that when a species 
has once been conveyed it may remain isolated for un- 
known ages, and has time to become modified by local 
conditions unchecked by the introduction of other in- 
dividuals of the original type. 

Flora of Bermuda. — Unfortunately no good account of 
the plants of these islands has yet been published. Mr. 

^ Mr. Theo. D. A. Cockerell informs me that there are two slugs in 
Bermuda of which specimens exist in the British Museum, — AmaUagagates 
Drap. common in Europe, and AgrioUmam campestris of the United States. 
Both may therefore have been introduced by human agency. Also 
Vaginulus Mordctc var. schivelyca which seems to be a variety of a Mexican 
species ; perha]is imported. 



272 ISLAND LIFE part ii 

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 aOTicultural or warden seeds, 

o o 

and the really indigenous plants, in one 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 introduced 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 indige- 
nous. 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 inanimate 
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 
{Scqmidus saponaria) has been actually observed to 
originate in this way. 

Professor Oliver informs me that he knows of no un- 
doubtedly distinct sjjccics of flowering j^lants peculiar to 
Bermuda, though there are some local forms of continental 
species, — instancing SisyrincJiium Bcrmudianum and Rhus 
toxicodendron. There are, however, two ferns — an Adiantum 
and a Nephrodium, which are unknown from any other 
locality, and this renders it probable that some of the 
flowering plants are also 23eculiar. The juniper, which is 
so conspicuous a feature of the islands, is said to be a 
West Indian species (Junijjcrus harhadensis) found in 
Jamaica and the Bahamas, not the North American red 



BERMUDA . 273 



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 direction, 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 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 w^ere derived and the 
mode by which they had reached so remote an island, we 
should obtain important information as to the dispersal of 
plants, wdiich might afford us a clue to the solution of 
many difficult problems in their geographical distribution. 

Ccndnding Manarks. — The tw^o groups of islands we 
have now been considering furnish us with some most in- 
structive 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 wdiatever 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 re- 
gards birds, migratory habits and the liability to be caught 
by violent storms are the conditions which determine the 
island -population. In both islands the land-birds are al- 
most exclusively migrants ; and in both, the non-migratory 
groups — wrens, tits, creepers, and nuthatches — are absent ; 
while the number of annual visitors is greater in propor- 
tion as the migratory habits and prevalence of storms 
afford more efficient means for their introduction. 

^ " Notes on the Vegetation of Bermuda, " by H. N. Moseley. {Journal 
of the Linncan Society, Vol. XIV., Botany, p. 317.) 

T 



274 ISLAND LIFE pakt ii 

We find also, that these great distances do not prevent 
the immigration, of some insects of most of the orders, and 
especially of a considerable number and variety of beetles ; 
while even land-shells are fairly represented in both islands, 
the large joroportion 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 no reason to doubt that besides the 
species that have actually established themselves, many 
others must have reached the islands, but were either not 
suited to the climate and other physical conditions, or did 
not find the insects necessary to their fertilisation, and 
were therefore unable to maintain themselves. 

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 a very 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 imj^ortance in 
those cases where the evidence as to the exact origin of 
the fauna and flora of an island is less clear and satisfactory 
than in the case of the Azores and Bermuda. 



CHAPTER XIII 

THE GALAPAGOS ISLANDS 

Position tand Physical Features — Absence of Indigenous Mammalia and 
Amphibia — Reptiles — Birds — Insects and Land-Shells — Tlie Keeling 
Islands as Illustrating the Manner in which Oceanic Islands are Peopled 
— Flora of the Galapagos — Origin of the Flora of the Galapagos — Con- 
cluding 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 that a large j^ortion 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 the}^ are 
situated on the equator instead of being in the north tem- 
perate zone. They stand upon a deeply submerged bank, 
the 1,000 fathom line encircling all the more imj^ortant 
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. 



276 



ISLAND LIFE 



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 




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 in fathoms. 



long and of very irregular shaj^e, while the four next in 
importance — Chatham, Indefatigable, James, and Nar- 
borough Islands, are each about twenty-five or thirty miles 



CHAP. XIII THE aALAPAGOS ISLANDS 277 

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 groups of 
islands we have been considering, these are situated in a 




MAP OF THE GALAPAGOS. 

The light tint shows a depth of less than 1,000 fathoms. 
The figures show the depth in lathoms. 

comparatively calm sea, where storms are of rare occur- 
rence and even strong winds almost unknown. They are 
traversed by ocean currents which are strong and constant, 
flowino- towards the north-west from the coast of Peru ; 



ISLAND LIFE PART II 



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 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 
tlie support of a considerable amount of animal life, as 
shown by the cattle, horses, asses, goats, pigs, dogs, and 
cats, which now run wild in some of the islands. 

Absence of Indigenous Mammalia and Amijhihia. — As in 
all other oceanic islands, we find here no truly indigenous 
mammalia, 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 intro- 
duced 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 
introduced into the Galapagos. There can be little doubt 
therefore that the islands are comj^letely destitute of truly 
indigenous mammalia ; and frogs and toads, the only 
tropical representatives of the Amphibia, are equally 
unknown. 

Reptiles. — Re23tiles, 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, 
Tcstudo mic7'0])]iyes, found in most of the islands, and T, 



CHAP. XIII THE GALAPAGOS ISLANDS 279 

abingdonii recently discovered on Abingxlon Island, as well 
as one extinct species, T. cpliipinum, 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 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 galcqxtgensis, and four species of 
the American family Iguanidse. Two of these are distinct 
species of the genus Tropidurus, 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, swim- 
ming in the sea at some distance from the shore and 
feeding on seaweed ; the other is terrestrial, and is confined 
to the four central islands. These last were originally 
described as AmMyrliynchus cristatus by Mr. Bell, and 
A. suljcristahts by Gray ; they were afterwards placed in 
two other genera Trachycephalus and Oreocephalus {see 
Brit. Mus. Catalogue of Lizards), while in a recent paper 
by Dr. Steindachner, the marine species is again classed as 
Amblyrhynchus, while the terrestrial form is placed in 
another genus Conolophus, both genera being peculiar to 
the Galapagos. 

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 j)ossessed by any other land vertebrates, 

^ Gigantic Land Tortoises Living and Extinct in the Collection of the 
British Museum. By A. C. L. G. Giinther, F.R.S. 1877. 



280 ISLAND LIFE 



since they are found in a considerable number of islands 
which possess no mammals nor any other land reptiles ; 
but Avhat those means are has not yet been positively 
ascertained. 

It is unusual for oceanic islands to possess snakes, and it is 
therefore somcAvhat 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 tlius be 
conveyed long distances if carried out to sea on a tree 
uprooted by a flood such as often occurs 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, Avhose presence here 
may not seem so remarkable, but which yet present 
features of interest not exceeded by any other group. 
About seventy species of birds have now been obtained on 
these islands, and of these forty-one are peculiar to them. 
But all the species found elsewhere, excej^t one, belong to 
the aquatic tribes or the Avaders which are pre-eminently 
wanderers, yet even of these eight are peculiar. The true 
land-birds are forty-two in number,^ and all but one are 
entirely confined to the Galapagos ; Avhile three-fourths 
of them present such peculiarities that they are classed in 
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 Transactions of the Zoological Society for the year 1876, 
to which are added nine species collected in 1888 and 



CHAP. XIII 



THE GALAPAGOS ISLANDS 



281 



described by Mr. Ridgway in the Proceedings of the 
U.S. National Museum (XII. p. 101) and some additional 
species obtained in 1880. 



TUIIDID^. 



Xesomimiis trifasciatus 

,, melanotus 

,, parvulus 

,, niacdonakli (Ridg. ) 

,, iievsonatiis (Ridg.) 



...\ Thisai 
... Y are r 
. J Mim 



and the two allied species 
I related to a Peruvian bird 
Mimus longicaudus. 



6. Dendrceca aureola 



MNIOTILTIDiE. 



/ Closely allied to the wide-rang- 
[ ing D. ccsiiva. 



7. Progne concolor 



HlRUNDINID^. 



f Allied to r. purpurea of Xortl; 
[ and South America. 



8. Certhidea olivacea ... 

9. " fusca 

10. " cinerascens 



CCEREBID^. 



A peculiar genus allied to the 
Andean genus Conirostrmn. 







FllINGILLID^. 


11. 


Geospiza niagnirostris 




12. 


,j 


strenua 




13. 


J, 


dubia 


A distinct genus, but allied to the 


14. 


)) 


fortis 


South American genus Guiraca. 


15. 


J J 


nebulosa 




16. 


J ) 


fuliginosa 


> 


17. 




parvula 




18. 


5 J 


dentirostris 




19. 




conirostris (Ridg.) 




20. 


jj 


media (Ridg.) 


, 


21. 


,, 


difficilis (Sharpe) > 




22. 


Cactornis scandens 




23. 




assimilis 




24. 


5) 


abingdoni 




25. 


J> 


■ pallida 


A genus allied to the last. 


26. 




Drevirostris (Ridg.) 




27. 


JJ 


hy poleuca ( Ridg. ) ^ 


A very peculiar genus allied to 


28. 


Camarhynchus psittaculus ^ 


Neorhynchus of the west coast 


29. 


5 J 


crassirostris 


of Peru. 


30. 


») 


variegatus 




31. 


35 


3rosthenielas 


/ 


32. 




labeli 




33. 


,j 


townsendi (Ridg.) ... 




34. 


,, 


pauper (Ridg.) ...J 





ISLAND LIFE 



35. Dolichonyx oryzivonis 



36. Pyrocephalus nanus 

37. P. minimus (Ridg.) ... 

38. Myiarchus magnirostri.- 



39. Zenaida galapagensis 

40. Buteo galapagensis .., 

41. Asio galapagensis 

42. Strix ])unctatissima 



ICTERID^. 

Ranges from Canada to Para- 
guay. 

Tyraxnid.e. 

Allied to P. ruhincits of Ecua- 
dor. 
Allied to "West Indian species. 



Columbid.t:. 



/ A peculiar species of a S. 
( American genus. 



Falconid^. 



A buzzard of peculiar coloration. 



SXRIGIDiE. 



] Hardly distinct from the wide- 
■■■ \ spread A. hrachyotus. 
. . . Allied to S. flammea but (juite 
distinct. 



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, migration 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 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 {Asio hrachyotus), which ranges from 
China to Ireland, and from Greenland to the Straits of 
Magellan, and of this the Galapagos bird is probably only 
one of the numerous varieties. The little wood warbler 
(Bendrceca aureola) is closely allied to a species which 



CHAP. XIII THE GALAPAGOS ISLANDS 283 



rano-es 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 
tyrant fly-catchers (Pyrocephalus and Myiarchus), the 
ground-dove (Zenaida), and the buzzard (Buteo), 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 thrushes, 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 con- 
ditions 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 three species of 
Certhidea, which are divided between the islands but do 
not appear ever to occur together. Nesomimus imrvulus is 
confined to Albemarle Island, and N. trifascieitus to Charles 
Island ; Ccictornis iKillida to Indefatigable Island, C. 
Irevirostris to Chatham Island, and C. ahingcloni to 
Abingdon 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 volcanic action 
has ceased on many of the islands, as well as their great 
extent, would certainly indicate a considerable antiquity. 

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- 



284 ISLAND LIFE 



migratory, and thus afford none of the opportunities 
presented by the countless hosts of migrants which pass 
annually northward and southward along the European, 
and esj)ecially 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 forty 
species belonging to thirty-two genera and nineteen 
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 
Carabidse and the Heteromera are the most abimdant 
groups, the former furnishing six and the latter nine 
species.^ 

^ The following list of the beetles yet known from the Galapagos shows 
their scanty proportions and accidental character ; the forty species be- 
longing to thirty-three genera and eighteen families. It is taken from 
]\Ir. Waterhoiise's enumeration in the Froccedinq^ of the Zoological Society 
for 1877 (p. 81), Avith a few additions collected by the U. S. Fish Com- 
mission Steamer Albatross, and published by the i]. S. National Museum 
in 1889. 

CaKABID^. ilALACODERMS. 

Feronia calathoides. Ablechrus darwiuii. 

,, insularis. Corynetes rufipes. 

,, galapagoensis. Bostrichus unciniatus. 

Amblygnathus obscuricornis. Tetrapriocerca sp. 
Solenophorus galapagoensis. Lamellicorxes. 

Notaphus galapagoensis. Copris lugubris. 

Dytiscid^. Oryctes galapagoensis. 
Eunectes occidentalis. Elaterid^. 

Acilius incisus. Physorhinus galapagoensis. 
Copelatus galapagoensis. Heteromera. 

PALPicoRNrs. AUecula n. s. 

Tropisternus lateralis. Stomion helopoides. 
Philhydrus sp. ,, Icevigatum. 

Staphylinid^. Ammophorus obscurus. 
Creophilus villosus. , , cooksoni, 

Necrophaga. ,, bifoveatus. 

Acribis serrativentris. Pedonoeces galapagoensis. 
Phalacrus darwinii. ,, pubescens. 

Dermestes vulpinus. Piialeria manicata. 



CHAP. XIII THE GALAPAGOS ISLANDS 285 

The land-shells are not abundant — about twenty in all, 
most of them peculiar species, but not otherwise remark- 
fuble. 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 dehris 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 wliieli 
Oceanic Islctnds cere Peopled. — That such causes as have 
been here adduced are those by which oceanic islands have 
been peopled, is further shown by the condition of equally 
remote islands which 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. 



CURCULIOXID/E. PhYTOPHAGA 

Otiorhynchus cuneiformis. Diabrotica limbata. 

Anchonus galapagoensis. Docema galapagoensis. 

LoNGicoPtNiA. Longitarsus lunatus, 
Mallodou sp. Securipalpes. 

Eburia amabilis. Scymuns galapagoensis. 

A NTHRIBID^, 

Ormiscus variegatus. 



286 ISLAND LIFE part ii 

Darwin, and tlieir 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 produced thirteen species belonging to 
eight distinct orders. The only beetle was a small Elater, 
the Orthoptera were a Gryllus and a Blatta; and there 
were two flies, two ants, and two small moths, one a 
Diopsea 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 nineteen genera and 
to no less than sixteen natural lamilies, wliile 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 
exj^osure to sea-air, being suitable to a very limited 
number of species which soon monopolise the surface. 
With more variety of soil and aspect a greater variety of 
plants would establish themselves, and these would favour 
the preservation and increase of more insects, birds, and 

1 ]\Ir. H. O, Forbes, who visited these islands in 1878, increased the 
number of wikl plants to thirty-six, and these lielonged to twenty-six 
natural orders. 



CHAP. XIII THE GALAPAGOS ISLANDS 287 

other animals, as we find to be the case in many small 
and remote islands.^ 

Flora of the GalajKcgos. — 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 Linnccan Transactions for 1851, founded 
on Mr. Darwin's collections, and a later paper by N. J. 
Andersson in the Liniia^a of 1861, embodying more recent 
discoveries. 

^ Juan Fernandez is a good example of a small island whicii, 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. JSTo doult, 
however, there are occasional storms, and there may have been intermediate 
island:^ but its chief advantages are its antiquity, its varied surface, and its 
favourable soil and climate, offering many chances for the preservation and 
increase of whatever 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 tliere are nearly fifty species on the island, while the 
remote period when it first received its vegetation may be indicated by the 
fact that nearly half the species are quite peculiar ; while of 102 species of 
flowering plants seventy are peculiar, and there are ten peculiar genera. 
The same general character pervades the fauna. For so small an island 
it is rich, containing 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 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 in- 
troduced 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 examination of the causes which have 
led to the modification of the humming birds of Juan Fernandez see the 
chapter on Humming Birds in the s.\\\hov'& Xatnral Selection and Tropical 
Nature, p. 324 ; while a general account of the fauna of the island is given 
in his Geographical Distribution of Animals, Vol. II. p. 49. 



288 ISLAXD LIFE part it 



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 ex- 
tending 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 oTeat sioiiificance in connection with the 
observation of Sir Joseph Hooker that the 'pcculiciQ^ 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 joossess great vitality. 
Mr. Bentham also, in his elaborate account of the Com- 
positre,- remarks on the decided Central American or 
Mexican aflinities of the Galapagos species, so that we may 
consider this to be a thoroughly well-established fact. 

The most prevalent families of j^lants in the Galapagos 
are the Compositse (40 sp.), Graminese (32 sp), Legumi- 
nos8e (30 sp.), and Euphorbiaceae (29 sp.). Of the Com- 
posit^e 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 Lipocha^^ta, represented 
here by a single S23ecies, is only found elsewhere in the 
Sandwich Islands though it has American affinities 

Origin of the Galajmgos Flora. — These facts are ex- 
plained by the past history of the American continent, its 

^ No additions appear to have been made to this flora down to 1885, 
when Mr. Hemsley published his Report on the Present State of our Know - 
ledge of Insular Floras. 

- Journal of the Linncan Society, Vol. XIII., "Botany," p. 556. 



CHAP, xiii THE GALAPAGOS ISLANDS 289 



separation at 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 consider- 
able number of 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 dura- 
tion of the last glacial epoch in its successive phases 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 excentricity, we are enabled to comprehend the 
nature of the causes which may have led to the islands 
being stocked with those north tropical or mountain types 
which are so characteristic a feature of that portion of the 
Galapagos flora which consists of peculiar species. 

On the whole, the flora agrees with the fauna in in- 
dicating a moderately remote origin, great isolation, and 
chano'es of conditions affordino; facilities for the introduc- 
tion 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 limited to one or two islands only, while others 
extend to several. This is, of course, what might be ex- 
pected 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 vegetation, would often lead to the ex- 
tinction of a species on one island and its preservation on 
another. If the several islands had been equally well 
^ Geofjrapliical Distribuiioii of Animals, Vol. IL p. 81. 

U 



290 ISLAND LIFE part ii 



explored, it might be interesting to see whether, as in the 
case of the Azores, the number of species diminished in 
those more remote from the coast ; but unfortunately our 
knowledge of the productions of the various islands of the 
group is exceedingly unequal, and, except in those cases 
in which representative species inhabit distinct islands, we 
have no certainty on the subject. All the more interesting- 
problems in geographical 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 23resented by 
oceanic or continental islands. 

Concluding Bern arks. — The Galapagos offer an instructive 
contrast with the Azores, showing how a difference of con- 
ditions that might be thought unimportant may yet pro- 
duce very striking results in the forms of life. Although 
the Galapagos are much nearer a continent than the 
Azores, the number of species of 23lants common to the 
continent is much less in the former case than in the latter, 
and this is still more jDrominent a characteristic of the 
insect and the bird faunas. This difference has been 
shown to dej)end, 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 im- 
j^ortance of the atmosjDhere 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 of several West Indian 
types at a more remote period when the Isthmus of Panama 
was submerged. 

In the case of these islands we see the importance of 
taking account of past conditions of sea and land and past 
changes of climate, in order to exj^lain the relations of the 
peculiar or endemic species of their fauna and flora ; and 
we may even see an indication of the effects of climatal 
changes in the northern hemisj)here, in the north tern- 



CHAP. XIII THE GALAPAGOS ISLANDS 291 



perate or alpine affinities of many of the plants, and even 
cf 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 
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 wdiy the Galapagos pos- 
sess 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. 



CHAPTER XIV 

ST, HELENA 

Position and Physiccal Featiu-es of St. Helena — Change Efiected by 
European Occupation — Tlie Insects of St. Helena — Coleopteva — Pecu- 
liarities and Origin of the Coleoptera of St. Helena — Land-shells of St. 
Helena — Absence of Fresh-water Organisms — Xative Vegetation of St. 
Helena — The Relations of the St. Helena Compositse — Concluding 
Remarks on St. Helena. 

Ix order to illustrate as completely as possible the peculiar 
IDlienomena of oceanic islands, we will next examine the 
organic j^roductions 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 surpassing 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 



294 ISLAND LIFE part ii 

the most jDart 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 northern rim forms the hio'hest and central rido^e 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 volcanic 
mass built up from the dejDths of the ocean. Mr. 
Wollaston remarks : " There are the strongest reasons for 
believing that the area of St. Helena w^as 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, hcyoncl 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 ap23ear to have its limit definitely marked out by 
this suddenly-terminating submarine cliff — the space 
between it and the existing coast-line being reasonably 
referred to that slow process of disintegration by which the 
island has been reduced, throuo-h the erodinq; 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 satisfied 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 Efedcd hy Eurcpean Ocmpaticn. — When first 
discovered, in the year 1501, St. Helena was densely 
covered with a luxuriant forest vegetation, the trees over- 
hanging the seaward precijDices and covering every part of 
the surface with an evergreen 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, 



CHAP. XIV ST. HELENA 295 

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 could 
oiily 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 East 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 lime for building fortifications ! 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 re?tSon 
that that part was not inhabited when the people first 

^ St. Helena: a Physical, Historical, and Topogra2}hical Description of 
the Island, d.-c. By John Charles Melliss, F.G.S., c^c. London : 1875. 



296 ISLAI^TD LIFE 



chose out their settlements and made plantations ; but if 
wells, could be sunk, which the governor says he will 
attempt w^hen we have more hands, we should then think 
it the most pleasant and healthiest part of the island. 
But as to healthiness, we don't think it will hold so if the 
wood that keeps the land w^arm w^ere destroyed, for then 
the rains, which are violent here, w'ould carry away the 
upper soil, and it being ^ clay marl underneath would 
produce but little ; as it is, w^e think in case it were 
enclosed it might be greatly improved "....'•' AYhen 
once this wood is gone the island will soon be ruined " . . . , 
" We viewed the wood's end wdiich joins the Honourable 
ComiDany's plantation called the Hutts, but the w^ood 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." (MSS. 
records, 1716.) In 1709 the governor rejDorted to the 
Court of Directors of the East India Company that the 
timber w as rapidly disappearing, and that the goats should 
be destroyed for the preservation of the ebony wood, and 
because the island w'as suffering from droughts. The reply 
w^as, " 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 j^re venting the 
island from becoming the comparatively rocky desert it 
now is, w^as allowed to pass away.^ Even in a mere 

^ Mr. Marsh in liis interesting work entitled The Earth as Modified hy 
Human Action (p. 51), thu3 remarks on the elfect of browsing quadrupeds 
in destroying and cheeking 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, Avere 
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 j^articularly fond of the 
smaller twigs, leaves, and seed-jiods of the Sent 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 



CHAP, xrv ST. HELENA 297 

pecuniary point of view the error was a fatal one, for in the 
next century (in 1810) another governor reports the total 
destruction of the great forests by the 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 rajDidly 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 jDrecipices, 
and is rarely seen except by some exploring naturalist. 

This almost total extirpation of a luxuriant and highly 
peculiar 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 contained 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. 

as fast as tliey grow. A few years of undisturbed vegetation would suffice 
to cover sucli points with groves, and these would gradually extend them- 
selves over soils where now scarcely any green thing but the bitter 
colocynth and the poisonous foxglove is ever seen." 

^ Coleox>tera Sanctcc Hclcnce, 1877 ; Testacca Atlantica, 1878. 



298 ISLAND LIFE paet ii 

Insects — ColcG2:)tcra. — The total number of species of 
beettes 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 remain 129 
which are believed to be 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 allies 
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 
Cossonidse. Now although the Rhyncophora are an 
immensely numerous group and always form a large por- 
tion of the insect population, they nowhere else apj^roach 
such a proportion as this. For example, in Madeira they 
form one-sixth of the whole of the indigenous Coleoi^tera, 
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 in 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 particular species of plants, we 
might, as Mr. Wollaston well observes, deduce the former 
luxuriant vegetation of the island from the great pre- 
ponderance 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 



CITAr, XTV 



ST. HELENA 299 



systematic order, but according to their importance in the 
island. 

1. Rhyxcophora. — This great division includes the 
weevils and allied grou^DS, and, as above stated, exceeds in 
number of species all the other beetles of the island. Four 
families are represented ; the Cossonidoe, with fifteen 
peculiar genera comprising fifty-four species, and one 
minute insect (StenosccH^ liylastoidcs) 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 Cossonidse 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 Composita?, and other indigenous plants. 
They are all pre-eminently peculiar and isolated, having 
no direct affinity to species found in any other country. 
The next family, the Tanyrhynchida?, has one peculiar 
genus in St. Helena, with ten species. This genus (Nesiotes) 
is remotely allied to European, Australian, and Madeiran 
insects of the same family : the habits of the species are 
similar to those of the Cossonidge. The Trachyphloeid?e are 
represented by a single species belonging to a peculiar 
genus not very remote from a European form. The An- 
thribidee 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 temperate regions of the northern hemisphere. In 
St. Helena there are fourteen species belonging to three 
genera, one of which is peculiar. This is the Hai^lotliorax 
hurchellii, 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 



300 ISLAND LIFE 



Geodephaga, twelve in number, belong to the wide-spread 
genus Bembidium, but tbey 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 
Opatridse, Mordellidoe, and Anthicidye. 

4. Brachyelytra. — Of this gTOup there are six peculiar 
species belonging to four European genera — Homalota, 
Philonthus, Xantholinus, and Oxytelus. 

5. Priocerata. — The families Elaterida} and Anobiidse 
are each represented by a peculiar sj^ecies of a European 
genus. 

6. Phytophaga. — There are only three species of this 
tribe, belonging to the European genus Longitarsus. 

7. Lamellicorxis. — 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 
ofenus Melissius, which Mr. Wollaston considers to be 
remotely allied to Australian insects. 

8. Pseudo-TRIMERA. — Here we have the fine lady-bird 
Cliilomenus litnata, also found in Africa, but apparently 
indigenous in St. Helena; and a peculiar species of 
Euxestes, a genus only found elsewhere in Madeira. 

9. TRICHOPTERYGID.E. — These, the minutest of beetles, 
are represented by one species of the European and 
Madeiran genus Ptinella. 

10. Necrophaga. — One indigenous species of Crypto- 
phaga inhabits St. Helena, and this is said to be very 
closely allied to a Cape species. 

Peculiarities and Origin of the Coleo'ptcraof 8t. 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 anti- 
quity of the insect fauna of St. Helena, which has allowed 



C) 



CHAP. XIV ST. HELEiSTA 301 

time for the modification of the originally introduced 
species, and their special adaptation to the conditions pre- 
vailing in this remote island. This antiquity is also shown 
by the remarkable specific modification of a few types. 
Thus the whole of the Cossonidse may be referred to three 
types, one species only {Hexacoptus ferrugincus) being allied 
to the European Cossonidie though forming a distinct 
genus ; a group of three genera and seven species remotely 
allied to the Stcnoscelis hylastoidcs, which occurs also at the 
Cape ; while a group of twelve genera with 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 Bem- 
bidium form a group by themselves ; and the Heteromera 
form two groups, one consisting of three genera and species 
of Opatridse allied to a type found in Madeira, the other, 
Anthicodes, altogether 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 indica- 
tion, and to some extentameasure, 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, man}^ difiiculties in 
accounting for its origin will disappear. We know that 
at that time many of the animals and j)lants 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 tem- 
perate zones towards the equator, and the reverse. If, 
therefore, the nearest ally of any insular group now in- 
habits a particular country, we are not obliged to suppose 
that it reached the island from that country, since we 
know that most groups have ranged in past times over 



302 ISLAND LIFE 



wider areas tlian tliey 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 transmission of living 
things to oceanic islands has been brought about. At the 
present time the south-east trade-winds blow almost con- 
stantly at St. Helena, and the ocean-currents flow in 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 con- 
sider 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. Instead of a great difference of temperature be- 
tween each pole and the equator, the difference v^^ould be 
mainly between one hemisphere and the other, and this 
miofht 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. At this 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 



CHAP. XIV ST. HELENA. 303 

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 there- 
fore 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 proportion of the St. 
Helena beetles live even in the perfect state within the 
stems of plants or trunks of trees, while the eggs and 
larvae 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 
support 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 

^ Oil Petermann's map of Africa, in Sticlcrs 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 even the 300 
fathom line, one over 60 miles long ; and it is therefore probable that 
a much larger island once occupied this site. Xow 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 im- 
migrants 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 b}^ 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 wliat they are now," — has received a- striking 
confirmation, {^qq Naturalist's Voyage Eound the World, p. 495.) 



304 ISLAND LIFE 



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 
interesting 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 been introduced and have 
become slightly modified by new conditions of life ; so that 
there remain exactly twenty species which may be con- 
sidered 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 23eculiar 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 sj)ecies, 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 
(B. cncris ruljnna: a.iid B. claricinianus) are said to some- 
what resemble Brazilian, New Zealand, and Solomon 
Island forms, wliile neither Bulimus nor Succinea occur 
at all in the Madeira group. 

Omitting the species that have j^robably 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 pheno- 
menon is the total absence of indigenous aquatic forms of 
life in St. Helena. Not a single water-beetle or fresh- 
water shell has been discovered ; neither do there seem to 
be any water-j)lants in the streams, except the common 



CHAr. XIV ST. HELENA 305 

water-cress, one or two species of Cyperus, and the 
Australian Isapis prolifcra. 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 vvater- 
beetles, though here there are a few fresh-Avater shells. It 
would appear therefore that the wide distribution of the 
same generic and specific forms which so generally 
characterises fresh-Avater 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. 

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 is one 
species of wader — a small plover (yEgicditis sanckc-hclence) 
— 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 
enablinor us better to understand the biolos^ical 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 sj)ines 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 j^oiiit, by the fact stated by Mr. 
Melhss, that lars^e seeds which have floated from 



'O 



306 ISLAND LIFE part ii 

Madagascar or Mauritius rouud the Cape of Good Hoj^e, 
have, been thrown on the shores of St. Helena and have 
then sometimes germinated ! 

We have therefore little difficulty in understanding lioiv 
the island Avas first stocked with vegetable forms. When 
it was so stocked (generally speaking), is equally clear. 
For as the peculiar coleopterous fauna, of which an im- 
portant 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 themselves. 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 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 opjDosed to this state- 
ment, but it really is not so. For in both these cases the 
native vegetation has first been artifically removed by man 
and the ground cultivated ; and there is no reason to 
believe that any similar effect w^ould be produced by the 
scattering of any amount of foreign seed on ground already 
completely clothed w4th an indigenous vegetation. We 
might therefore conclude a jJriori, 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 
wdiat botanists tell us of its character and affinities. 

The truly indigenous flowering j^lants 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 alhes of any other 
plants at all. Seventeen of them belong to pecuhar 
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, 



CHAP. XIV ST. HELENA 307 



mainly African and especially South African, as indicated 
by the presence of the genera Phylica, Pelargonium, 
Mesembryanthemum, Oteospermum, and Wahlenbergia, 
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 rano^e 
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 sjDecific forms, 
many of those found in the Miocene dejoosits of Switzer- 
land, being hardly distinguishable from living species. 
This shows, that identity of sjjecies of ferns between St. 
Helena and distant countries does not necessarily imply a 
recent origin. 

The Relation of the St. Helena Comiiositcc. — In an 
elaborate j^ajoer on the Compositse,^ 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 forms 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 Africa, presenting a 
geographical connection analogous to that of the St. Helena 
Melhanise,^ with the Mascarene Trochetia." 

Whenever such remote and singular cases of geo- 
graphical affinity as the above are pointed out, the first 

^ "Notes on the Classification, History, and Geographical Distribution 
of Compositce." — Journal of the Linnran Society, Vol. XIII. j). 563 (1873). 

- The Melhanioe comprise the two finest timber trees of St. Helena, now 
almost extinct, the redwood and native ebony. 

X 2 



308 ISLAND LIFE part ii 

im23re.ssion is to imagine some mode by Avhicli a com- 
munication between the distant countries imj^licated 
might be effected ; and this way of viewing the problem is 
ahnost universally adopted, even by naturalists. But if 
the principles laid down in this work and in my Gco- 
grapliical 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 widesjDread 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 explanation 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 ; and they no more 
imply any closer connection between the distant countries 
the allied forms now inhabit, than does the existence of 
living Equidse in South Africa and extinct Equidse in the 
Pliocene deposits of the Pampas, imply a continent 
bridging the South Atlantic to allow of their easy com- 
munication. 

Concluding Remarhs on St. Helena. — The sketch Ave 
have nov\r 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 Avas 
in all i3robabihty 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 



cHAi'. XIV ST. HELENA 309 



period, or even earlier, had been saved from tlie destruc- 
tion which has overtaken their aUies on the great con- 
tinents. Unfortunatel}^ many, we do not know how 
many, of these forms have been exterminated by tlie 
carelessness and improvidence of its civilised but ignorant 
rulers ; and it is only by the extreme ruggedness and 
inaccessibility of its j^eaks and crater-ridges that the 
scanty fragments have escaped by Avhich 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 — Zoolog_Y of the Sandwich IsLinds — 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 Sandwdch Islands — General Remarks on Oceanic Islands. 

The Sandwich Islands are an extensive group of large 
islands situated in the centre of the North Pacific, being 
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 little 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 3,800 square miles — being 
somewhat larger than all the other islands together. A 
better conception of this large island Avill be formed by 
comparing it with Devonshire, with which it closely 
agrees both in size and shape, though its enormous 
volcanic mountains rise to nearly 14,000 feet high. 



THE SANDWICH ISLANDS 



311 



Three of the smaller islands are each about the size of 
Hertfordshire or Bedfordshire, and the Avhole group 
stretches from north-Avest to south-east for a distance of 
about 350 miles. Though so extensive, the entire archi- 
pelago is volcanic, and the largest island is rendered 




MAP OF TIIIC SANDWICH ISLANE:- 



Tlie light tint shows wliere the sea is less than 1,000 fathoms deeii, 
The figrres show the dejith in fathoms. 



sterile and comparatively uninhabitable by its three active 
volcanoes and their widespread deposits of lava. 

The ocean de23ths by which these islands are sej^arated 
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 the North Pacific. We may 



312 



ISLAND LIFE 



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 



160 E. 170 180 I70 160 150 



130 I20 




MAP OF THE NORTH PACIFIC WITH ITS SUEMEP.GED BANKS. 

The light tint shows where the sea is less than 1,000 fathoms deep. 
The dark tint ,, ,, ,, more than 1,000 fathoms deep. 

The figures show the depths in fathoms. 



Avest and south there is a possibility of more extensive 
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 



ciiAr. XV THE SANDWICH ISLANDS 313 

considerable 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 stratified rocks 
(except, perhaps, in the Marquesas, where, according to 
Jules !RIarcou, 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 
Avliich now exist, but which, after becoming extinct, have 
been lowered or destroyed by denudation, and finally 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 considera- 
tions 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 Sandwich 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- 
five species having been observed, but even of these six 
are peculiar — a coot, Fulica alai ; a moorhen, Gallinula 
galeata var sandvichensis ; a rail with rudimentary wings, 
Pennula millci ; a stilt-plover, Jlimantojms hmdscni ; and 



314 ISLAND LIFE 



two ducks, Anas Wyvilliana and Bernida sandmclioisis. 
The birds of prey are also great wanderers. Four have 
been found in the islands — the short-eared owl, Otus 
hracfiyotns, which ranges over the greater 23art of the globe, 
but is here said to resemble the variety found in Chile 
and the Galapagos; tlie barn owl, Sti^ix flammca, of a 
variety common in the Pacific ; a peculiar sparrow-hawk, 
Accipiterlw.waii ; and Buteo solitarius, a buzzard of a peculiar 
species, and coloured so as to resemble a hawk of the 
American subfamily Polyborina^. 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. 

The Passeres, or true perching birds, are especially 
interesting, being all of peculiar species, and, all but one, 
belonging to peculiar genera. Their numbers have been 
greatly increased since the first edition of this work 
aj^peared, j)artly by the exertions of American naturalists, 
and very largely by the researches of Mr. Scott B. Wilson, 
who visited the Sandwich Islands for the j^urpose of 
investigating their ornithology, and collected assiduously 
in the various islands of the group for a year and a half. 
This gentleman is now publishing a finely illustrated 
work on Hawaiian birds, and he has kindly furnished me 
v/ith the following list. 

Passeres of the Saxdwich Islands. 

MusciCAPiD.E (Flyeatcliers). 

1 . Chasicmpis ridgwayi 1 law;iii. 

2. ,, sclatcri Ivauai. 

3. ,, dolci Kauai. 

4. ,, gayi Oalni, 

.5. ,, ibidis Oahu. 

6. Phaoru is ohscura Hawaii. 

7. ,, myadestina Kauai. 

Melipiiagid^. (Honey suckers). 

8. Acrulcccrcns nohilis Hawaii. 

9. ,, hraccatm, Kauai. 

10. ,, rtjozmZis (extinct) Oahu or Maui. 

1 1 . ChtctoiMla anfjustipluma (extinct) Hawaii. 



THE SANDWICH ISLANDS 315 



Bueva^idida:. 

1 2. Brcpanis 2)cicljica (extinct) Hawaii. 

1 3. Vastiaria coccinea All the Islands. 

14. Hiniationc vircus Hawaii. 

15. ,, doUi Maui. 

16. ,, sanguinca All the Islands. 

17. , , viontana Lanai. 

18. ,, chloria Oahu. 

19. ,, maculala Oahu. 

20. ,, parva Kauai. 

21. ,, stcjiicgeri Kauai. 

22. Oreoiuyza bairdi Kauai. 

23. Hcviignafhtos ohscurus Hawaii. 

24. , , oUvaccus Hawaii. 

25. ,, lichtensteini Oahu. 

26. ,, liicidas Oahu. 

27. ,, stejncgcri :. Kauai. 

28. ,, haua2Jr.ps Kauai. 

29 . Loxo]is coccinea Hawaii. 

30. , , flammca Molokai. 

31. ,, aurca Maui. 

32. ChrysomitridoiJs cceiiUcorostria Kaui. 

33. , , anna (extinct) 

FiiixGiLLiDJ^ (Fiuchea). 

34. Loxioidcs haillcui Hawaii. 

35. Psittirostra psittacca All the Islands. 

36. Chloridops kona Hawaii. 

CoRViD^ (Crows). 

37. Corvus haicaiiensis Hawaii. 

Many of the birds recently described are representative 
forms found in the several islands of the group. 

Taking the above in the order here given, we have, 
first, two peculiar genera of true flycatchers, a family con- 
fined to the Old World, but extending over the Pacific as 
far as the Marquesas Islands. Next we have two peculiar 
genera (Avith 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 seven or eight peculiar genera, and 
twenty-two species which are believed to form a peculiar 
family allied to the Oriental flower-peckers (Diceid^e), and 
perhaps remotely to the American greenlets ( Vireonidee), or 



316 ISLAND LIFE pakt ii 



tanagers (Tanagridae). 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 expected, chiefly with Australia and the Pacific Islands ; 
but they exhibit in the buzzard, one of the owls, and 
perhaiDS in some of the Drepanididse, slight indications of 
very rare or very remote communication with America. 
The amount of speciality is, however, -wonderful, far 
exceeding that of any other islands ; the only aj^proach to 
it being made by New Zealand and Madagascar, which 
have a much more varied bird fauna and a smaller ]jro- 
]jOTtionate number of peculiar genera. The Galapagos, 
among the true oceanic islands, while presenting many 
peculiarities have only four out of the ten genera of Passeres 
peculiar. 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 i^eculiar fauna might be derived. For 
further details as to the affinities and geographical dis- 
tribution of the genera and species, the reader must consult 
Mr. Scott Wilson's work The Birds of the Sandwich Islands, 
already alluded to. 

Reptiles. — The only other vertebrate animals are two 
lizards. One of these is a very widespread species, 
Ahlc])harus p)ccciloi}leuTus, ranging from the Pacific Islands 
to West Africa. The other is said to form a peculiar 
genus of geckoes, but both its locality and affinities apj^ear 
to be somewhat doubtful. 

Land-shells. — The only other grouj) of animals which 
has been carefully studied, and which presents features of 
especial interest, are the land-ahells. These are very 
numerous, about thirty genera, and between three and four 
hundred species having been described ; and it is remark- 
able that this single group contains as many species of 



THE SANDWICH ISLAXDS 317 



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 
subfamily Achatinellinse, 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 Polynesian Islands, but three genera of 
Auriculidte (Plecotrema, Pedipes, and Blauneria) are not 
found in the Pacific, but inhabit — 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 Operculata, 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. This 
difference is so remarkable that it is worth stating in a 
comparative form : — 

Inoperculata Operculata. Auriculidse. 

Sandwich Islands 332 5 9 

Rest of Pacific Islands 200 115 16 

When we remember that in the West Indian Islands 
the Operculata abound in a greater projDortion than even 
in the Pacific Islands generally, we are led to the con- 
clusion that limestone, which is plentiful in both these 
areas, is especially favourable 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 Achati- 
nellinse, 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 novr 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 Eburnella to Lanai. 



318 ISLAND LIFE part ii 

The Kev. John T. Gulick, who has made a special study of 
the Achatinellinge, mforms 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. Each 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 
excejDtional riches of the group, we have no reason to 
suppose that there are not many more species to be 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 Achatinellidse, represented by 700 or 800 
varieties. The most important peculiar genus, not belong- 
ing to the Achatinella 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 sub- 
merged island whence some portion of the Sandwich 
Island fauna was derived. 

Insects. — Owing to the researches of the Rev. T. 
Blackburn we have now a fair knowledge of the Coleop- 
terous fauna of these islands. Unfortunately some of the 
most jDroductive islands in plants — Kaui and Maui — were 
very little exjDlored, but during a residence of six years the 
equally rich Oahu was well worked, and the general 
character of the beetle fauna must therefore be considered 
to be pretty accurately determined. Out of 428 species 
collected, many being obviously recent introductions, no 

1 Journal of the Linncan Society, 1873, p. 496, "On Diversity of 

Evolution under one set of External Conditions." Proceedings of the 

Zoolofjical Society of London, 1873, p. 80. "On the Classification of the 
Achitinellidpe. " 



CHAP. XV THE SANDWICH ISLANDS 319 



less than 352 species and 99 of the genera appear to be 
quite peculiar to the archipelago. Sixty of these S23ecies 
are Carabida3, forty-two are Stapliylinidse, forty are 
NitidulidfB, twenty are Ptinidse, twenty are Ciodidse, thirty 
are Aglycyderidae, forty-five are Curculionida3, and fourteen 
are Cerambycidse, the remainder being distributed among 
twenty-two other families. Many important families, such 
as Gicindelidse, Scaraboeidse, Buprestida^, and the whole of 
the enormous series of the Phytophaga are either entirely 
absent or are only represented by a few introduced species. 
In the eight families enumerated above most of the species 
belong to peculiar genera which usually contain numerous 
distinct species ; and we may therefore consider these to re- 
13resent the descendants of the most ancient immigrants into 
the islands. 

Two important characteristics of the Coleopterous fauna 
are, the small size of the species, and the great scarcity of 
individuals. Dr. Sharp, who has described many of them,^ 
says they are " mostly small or very minute insects," and 
that " there are few — probably it would be correct to say 
absolutely none — that would strike an ordinary observer as 
being beautiful." Mr. Blackburn says that it was not an 
uncommon thing for him to pass a morning on the 
mountains and to return home with perhaps two or three 
specimens, having seen literally nothing else except the 
few species that are generally abundant. He states that 
he " has frequently spent an hour sweeping flower-covered 
herbao^e, or beating branches of trees over an inverted 
white umbrella without seeing the sign of a beetle of any 
kind." To those Avho have collected in any tro23ical or 
even temperate country on or near a continent, this 
poverty of insect life must seem almost incredible ; and it 
affords us a striking proof of how erroneous are those now 
almost obsolete views which imputed the abundance, 
variety, size, and colour of insects to the warmth and sun- 
light and luxuriant vegetation of the tropics. The facts 
become quite intelligible, however, if we consider that only 

^ " Memoirs on the Coleoptera of tlie Hawaiian Islands." By the Rev. T. 
Blackburn, B.A., and Dr. D. Sharp. ScienUfic Transactions of the Royal 
Dublin Society. Vol. III. Series II, 1885. 



320 ISLAND LIFE 



minute insects of certain groujDS could ever reach the islands 
by natural means, and that these, already highly speciaUsed 
for certain defined modes of life, could only develop 
slowly into slightly modified forms of the original tjrpes. 
Some of the groups, however, are considered by Dr. Sharp 
to be very ancient generalised forms, especially the peculiar 
family Aglycyderidse, wdiich he looks upon as being 
" absolutely the most primitive of all the known forms of 
Coleojitera, it being a synthetic form linking the isolated 
Rhynchophagous series of families w'ith the Clavicorn series. 
About thirty species are known in the Hawaiian Islands, 
and they exhibit much difference inter sd' A few remarks 
on each of the more important of the families w^ll serve to 
indicate their probable mode and period of introduction into 
the islands. 

The Carabidae consist chiefly of seven peculiar genera of 
Anchomenini comprising fifty-one species, and several 
endemic species of Bembidiin^e. They are highly peculiar 
and are all of small size, and may have originally reached 
the islands in the crevices of the drift w^ood from N.W. 
America which is still thrown on their shores, or, more 
rarely, by means of a similar drift from the N.- Western 
islands of the Pacific.^ It is interesting to note that 
peculiar species of the same groups of Carabidse are found 
in the Azores, Canaries, and St, Helena, indicating that 
they j^ossess some special facilities for transmission across 
wude oceans and for establishing themselves upon oceanic 
islands. The Staphylinidas present many peculiar species 
of know^n genera. Being still more minute and usually 
more ubiquitous than the Carabidse, there is no difficulty in 
accounting for their presence in the islands by the same 
means of dispersal. The Nitidulida^, Ptinidse, and Ciodida? 
being very small and of varied habits, either the perfect 
insects, their eggs or larvse, may have been introduced 
either by water or wind carriage, or through the agency of 
birds. The Curculionidse, being w^ood bark or nut borers, 
would have considerable facilities for transmission by 
floating timber, fruits, or nuts ; and the eggs or larvae of the 

^ See Hildebrand's Flora of the Hawaiian Islands. Introduction, p. 
xiv. 



CHAP, xv THE SANDWICH ISLANDS 321 

peculiar Cerambycidse must have been introduced by the 
same means. The absence of so many important and 
cosmopolitan groups whose size or constitution render them 
incapable of being thus transmitted over the sea, as well 
as of man}^ which seem equally w^ell adapted as those 
w^hich are found in the islands, indicate how rare have been 
the conditions for successful immigration; and this is still 
further emphasized by the extreme specialisation of the 
fauna, indicating that there has been no repeated 
immigration of the same species which would tend, as in 
the case of Bermuda, to preserve the originally intro- 
duced forms unchanged by the effects of relocated inter- 
crossing. 

Vegetation of the Sandicich Islands. — The flora of these 
islands is in many respects so peculiar and remarkable, 
and so well supplements 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 knowledge of it, owing to 
the researches of the German botanist Dr. W. Hilde- 
brand.^ 

Considering their extreme isolation, their uniform 
volcanic soil, and the large projDortion of the chief island 
which consists of barren lava-fields, the flora of the 
Sandwich Islands is extremely rich, consisting, so far as at 
present known, of 844 species of flowering plants and 155 
ferns. This is considerably richer than the Azores (439 
Phanerogams and 39 ferns), which though less extensive 
are perhaps better known, or than the Galapagos (332 
Phanerogams), which are more strictly comparable, being 
equally volcanic, w^hile 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 rot a very much larger 
number of flowering plants (935 species), while in ferns it 
is barely equal. 

^ Flora of the Haivaiian Islands, by W. Hildebrand, M.D., annotated 
and publislied after the author's death by W. F. Hildebrand, 1888. 

Y 



322 



ISLAND LIFE 



PART II 



The following list gives the number of indigenous 
species in each natural order. 

Number of Sjyccies in each Natural Order in the Haicaiinn Flora, 
excluding the introduced Plants. 



I 48. 
49. 
50. 
51. 



Dicotyledons. 

1. Ranimculacefe 2 

2. Menispermaceae 4 

3. Papaveracene 1 

4. Cruciferse 3 

5. Capparidace£e 2 

6. Violacefe 8 

7. Bixaceffi 2 

8. Pittosporacciii 10 

9. Caryophyllaceai 23 

10. Portulaceffi 3 

11. Guttiferse 1 i 58. 

12. Ternstraemiace^e 1 J 59. 

13. Malvaceoe 14 j 60. 

14. vSterculiacepe 2 i 61. 

15. Tiliaceai 1 | 62. 

16. Geraiiiace?e 6 : 63. 

17. ZygopliyllacecB 1 j 64. 

18. Oxalidaceae 1 ■ 65. 

19. Rutaceai 30 ; 66. 

20. Ilicineai 1 I 67. 

21. Celastraeea? 1 68. 

22. Rhamiiace;e 7 i 69. 

23. Sapindaceai 6 \ 70. 

24. Anacardiaceffi 1 ■ 71. 

25. Leguminosffi 21 i 72. 

26. Eosacese 6 ; 73. 

27. Saxifragaceai (trees) 2 j 

28. Droseracea; : 1 

29. Haloragete 1 

30. Myrtaceai 6 

31. Lythraeea; 

32. Ouagraceaj 

33. Ciiciirbitaceai 

34. Ficoideai 

35. l?egoniace;ie 

36. Umbellifera 

37. Araliaceai 

38. Rubiacea? 

39. Compositai 

40. Lobeliacese 

41. Goodeniacese 

42. Vaccinacere 2 ! 87. 

43. Epacridacene 2 88. 

44. Sapotacene 3 

45. Myrsinaceai 5 j 

46. Primulaceai (Lysimacliia) 

shrubs 6 

47. Plumbaginaceai 1 



74. 
6 i 75. 
1 i 76. 

1 I 77. 
8 ! 78. 

79. 

80. 

81. 

82. 

83. 



1 

1 

5 

12 

49 

70 ! 84. 

58 85. 

8 I 86. 

'2 



Gentianacese (Erythrsea) ... 1 

Loganiacefe 7 

Apocynacese 4 

Hydrophyllaceffi (Xama — 

allies Andes) 1 

Oleacete 1 

Solanaceie 12 

Convolviilacea3 14 

Boraginacese 3 

Scrophulariaccfe 2 

Gesneriacepe ^A 

]\Iyoporacetie 1 

Verbenacefie 1 

Labiatffi ...-. 30 

PlantaginacccC 2 

Nyctaginacejc 5 

Ainarantaceaj 9 

Pbytolaccace;e 1 

Polygonacero 3 

Chenopodiacere 2 

Lauracene 2 

TliynielcTeacea} 7 

Santalaceoe 5 

Lorauthaceae 1 

Eupliorbiaceffi 12 

XJrticacese 15 

Piperacese 20 

Monocotyledons. 

Orchidacese 3 

Scitaminaceai 4 

Iridacese 1 

Taccacese 1 

Dioscoreacefe 2 

Liliacese 7 

Coinmelinaceje 1 

Flagellariacese 1 

Juncacefe 1 

Palmacese 3 

PandanaccjB 2 

Aracese 2 

Naiadacese 4 

Cyperacese 47 

Graminacese 57 

Vascular Cryptogams. 

Ferns 136 

Lycopodiaceae 17 

Rhizocarpeie 2 



CHAP. XV 



THE SAXDWICH ISLANDS 323 



Peculiar Features of the Flora. — This rich insular flora \z 
wonderfully peculiar, for if we deduct 115 species, which 
are believed to have been introduced by man, ^there 
remain 705 species of flowering plants of which 574, or 
more than four-fifths, are quite peculiar to the islands. 
There are no less than 88 pecuhar genera out of a total of 
265 and these 38 genera comprise 254 species, so that the 
most isolated forms are those Avhich 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 the Hawaiian species of 
Lobelia which are woody shrubs either creeping or six feet 
high, while a species of one of the peculiar genera of Lobe- 
liacea? is a tree reaching a height of forty feet. Shrubby 
geraniums grow twelve or fifteen feet high, and some 
vacciniams grow as epiphytes on the trunks of trees. 
Violets and plantains also form tall shrubby plants, and 
there are many strange arborescent compositse, as in other 
oceanic islands. 

The affinities of the flora generally are very wide. 
Although there are many Polynesian groups, yet Austra- 
lian, New Zealand, and American forms are equally re- 
presented. Dr. Pickering notes the total absence of a large 
number of families found in Southern Polynesia, such as 
Dilleniacese, Anonacese, Olacaceae, Aurantiacese, Guttiferoe. 
Malpighiacea^, Meliacese, Combretacese, Rhizophoracese, 
Melastomacea^, Passifloracese, Cunoniacese, Jasminacese, 
Acanthaceae, Myristicaceae, and Casuarace?e, as well as the 
genera Clerodendron, 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, Acsena, and several Cyperacea? ; while America is 
represented by the genera Nama, Gunnera, Phyllostegia, 
Sisyrinchium, and by a red-flowered Rubus and a yellow- 
flowered Sanicula allied to Oregon species. 

There is no true alj^ine flora on the higher summits, but 
several of the temjDerate forms extend to a great elevation. 
Thus Mr. Pickering records Vaccinium, Ranunculus, Silene, 
Gnaphalium and Geranium, as occarring above ten 

Y 2 



324 



ISLAND LIFE 



thousand feet elevation ; while Viola, Drosera, Acsena, 
Lobelia, Edwardsia, Dodon^a, Lycopodium, and many 
Compositse, range above six thousand feet. Vacciniuni 
and Silene are very interesting, as they are almost peculiar 
to the North Temperate zone ; while many plants allied 
to Antarctic sj)ecies are found in the bogs of the high 
plateaux. 

The proportionate abundance of the different families 
in this interesting flora is as follows : — 



1. Compositse 70 species. 

2. Lobeliaceae 58 ,, 

3. Graminaceae 57 ., 

4. Rubiaceaj 49 

5. Cyperaceoe 47 

6. Labiatffi 39 

7. Rutacece 80 

8. Gesneriacese 24 

9. Caryophyllacese 23 

10. Leguminosse 21 ., 



11. Piperacece 



20 



1 2. Urticacete 15 species. 

13. Malvaceae 14 ., 

14. Convolviilacese 14 ,, 

15. Araliaceee 12 ,, 

16. Solanacete 12 ,, 

17 Euphorbiaceas 12 ., 

18. Pittosj)oraceae 10 ., 

19. Amarantacece 9 ., 

20. Violacese 8 , , 

21. Goodeniaceae 8 ,. 



Nine other orders, Geraniacea?, Rhamnacese, Rosacese, 
Myrtaceae, Primulacese, Loganiaceae, Liliaceae, Thymelacege, 
and Cucurbitacese, have six or seven species each ; and 
among the more important orders which have less than 
five species ea^ch are Ranunculace^e, Cruciferae, Vaccinace^, 
Apocynacege, Boraginacese, Scrophulariacea?, Polygonaceae, 
Orchidacese, and Juncacese. The most remarkable feature 
here is the great abundance of Lobeliaceae, a character of 
the flora which is probably unique ; while the sui^eriority 
of Labiata3 to Leguminosae and the scarcity of Rosacea^ 
and Orchidacese are also very unusual. Composites, as in 
most temperate floras, stand at the head of the list, and it 
will be interesting to note the affinities which they indi- 
cate. Omitting eleven species Avhich are cosmopolitan, 
and have no doubt entered with civilised man, there re- 
main nineteen genera and seventy species of Compositse 
in the islands. Sixty-one of the species are peculiar, as 
are eight of the genera ; while the genus Lipocha?ta with 
eleven species is only known elsewhere in the Galapagos, 
where a single species occurs. We may therefore consider 
that nine out of the nineteen aenera of Hawaiian Com- 



cnAP. XV THE SAXDWICH ISLAXDS 325 



positse are really confined to the Archipelago. The rela- 
tions of the peculiar genera and species are indicated in 
the following table. ^ 

Affinities of Hawaiian Composites. 

Xo. of 
Peculiar Genera. Species. External Affinities of tlie Genus. 

Remya 2 Very peculiar. Allied to the North American 

genus Grindelia. 

Tetramolobium ... 7 South Temperate America and Australia. 

Lipochseta 11 Allied to American genera. 

Campylothreca ... 12 With Tropical American species of Bidens and 

Coreopsis. 

Argyroxipliium... 2 With the Me.vican Madiese. 

Wilkesia 2 Same affinities. 

Dubantia 6 With the Mexican Raillardella. 

Raillardia 12 Same affinities. 

Hesperomannia... 2 Allied to Stifftia and Wunderlichia of Brazil. 

Peculiar Species. 

Lagenophora 1 Australia, New Zealand, Antarctic America, Fiji 

Islands, 

Senecio 2 Universally distributed. 

Artemisia 2 Xorth Temperate Regions. 

The great preponderance of American relations in the 
Compositse, as above indicated, is very interesting and 
suggestive, since the Compositse of Tahiti and the other 
Pacific Islands are allied to Malaysian types. It is here 
that we meet with some of the most isolated and remark- 
able forms, implying great antiquity ; and when we con- 
sider the enormous extent and world-wide distribution of 
this order (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 Compositae as representing the most ancient 
portion of the existing flora of the Sandwich Islands, 
carrying us back to a very remote period when the facili- 
ties for communication Avith America were greater than 
they are now. This may be indicated by the two deep 
submarine banks in the North Pacific, between the Sand- 
wich Islands and San Francisco, which, from an ocean floor 

^ These are obtained from Hildebrand's Flora supplemented by Mr. 
Bcntham's paper in the Journal of the Lin/iean Society. 



326 ISLAND LIFE 



nearly 3,000 fathoms deep, rise up to within a few hun- 
dred fathoms of the surface, and seem to indicate the sub- 
sidence 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-westward from the Sandwich Islands, as shown 
on our map. Those which exhibit Polynesian or Australian 
affinities, consisting for the most part of less highly modi- 
fied species, usually of .the same genera, may have had 
their origin at a later, though still somewhat remote 
period, Avhen large islands, indicated by the extensive 
shoals to the south and south-west, offered facilities for the 
transmission of plants from the tropical portions of the 
Pacific Ocean. 

It is in the smaller and most woody islands in the 
westerly portion of the group, especially in Kauai and 
Oahu, that the greatest number and variety of plants are 
found and the largest proportion of peculiar species and 
genera. These are believed to form the oldest portion of 
the group, the volcanic activity having ceased and allowed 
a luxuriant vegetation more completely to cover the 
islands, while in the larger and much newer islands of 
Hawaii and Maui the surface is more barren and the 
vegetation comparatively monotonous. Thus while twelve 
of the arborescent Lobeliacese have been found on Hawaii 
no less than seventeen occur on the much smaller Oahu, 
which has even a genus of these plants confined 
to it. 

It is interesting to note that while the non-peculiar 
genera of flowering plants have little more than two 
species to a genus, the endemic genera average six and 
three-quarter species to a genus. These may be con- 
sidered to represent the earliest immigrants v^diich became 
firmly established in the comparatively unoccupied islands, 
and have gradually become modified into such complete 
harmony with their new conditions that they have de- 
veloped into many diverging forms adapting them to 
different habitats. The following is a list of the peculiar 
genera with the number of species in each. 



THE SAXDWICH ISLANDS 



327 



Peculiar Eaicaiian Genera of Flowering Plants. 

Genus. No. of Species. Natural Order. 

1. Isodendrion 3 Violacese. 

2. Schiedea (seeds rugose or muricate) 17 Caryopliyllacese. 

3. Alsinidendron 1 ,, 

.4. Pelea 20 Kutacese. 

5. Platydesma 4 ,, 

6. Mahoe 1 Sapindaceae. 

7. Broussaisia 2 Saxifragaeece. 

8. Hildebrandia 1 Begoniaceaj. 

9. Cheirodendron (fleshy fruit) 2 Araliacete. 

10. Pterotropia (succulent) 3 ,, 

11. Triplasandra (drupe) 4 ,, 

12. Kadua (small, flat, winged seeds) 16 Rubiacese. 

13. Gouldia (berry) 5 ,, 

14. Bobea (drupe) .5 ,, 

15. Straussia (drupe) 5 ,, 

16. Remya 2 C'onipositse. 

17. Tetramolobium 7 ,, 

18. Lipoehffita 11 ,, 

19. Campylotlieca 12 ,, 

20. Argyroxiphium 2 ,, 

21. Wilkesia 2 

22. Dubautia 6 

23. Raillardia 12 \, 

24. Hesperoinauuia 2 ,, 

25. Brighamia 1 Lobeliaeea:>. 

26. Clermontia (berry) 11 ,, 

27. Rollandia 6 ,, 

28. Delissea 7 ,, 

29. Cyauea 28 

30. Labordea 9 Logaiiiaceoe. 

31. Nothocestrum 4 Solanaces. 

32. Haplostachys (nucules dry) 3 Labiatai. 

33. Phyllostegia (nucules flesh)') 16 ,, 

34. Stenogyne (nucules fleshy) 16 ,, 

35. Nototrichiuni 3 Amarantacete. 

36. Charpentiera 2 ,, 

37. Touchardia 1 Urticacea. 

38. jSTeraudia 2 ,, 

Total 254 species. 

The great preponderance of the two orders Compositse 
and Lobehacese are what first strike us in this hst. In the 
former case the facilities for wind-dispersal afforded by the 
structure of so many of the seeds render it compara- 
tively easy to account for their having reached the islands 
at an early period. The Lobelias, judging from Hilde- 
brand's descriptions, may have been transported in several 



323 ISLAXD LIFE part ii 



different ways. Most of the endemic genera are berry- 
bearers and thus offer the means of dispersal by fruit- 
eating birds. The endemic species of the genus Lobeha 
have sometimes very minute seeds, which might be carried 
long distances by wind, while other species, especially 
Lobelia gaudichaudii, have a " hard, almost woody capsule 
which opens late," apparently well adapted for floating 
long distances. Afterwards "the calycine covering 
withers aAvay, leaving a fenestrate woody network '"' en- 
closing the capsule, and the seeds themselves are " com- 
pressed, reniform, or orbicular, and margined," and thus 
of a form well adapted to be carried to great heights and 
distances by gales or hurricanes. 

In the other orders which present several endemic 
genera indications of the mode of transit to the islands 
are afforded us. The Araliacea^ are said to have fleshy 
fruits or drupes more or less succulent. The Rubiacese 
have usually berries or drupes, while one genus, Kadua, 
has " small, flat, winged seeds." The two largest genera 
of the Labiatse are said to have " fleshy nucules," which 
would no doubt be swallowed by birds.^ 

Antiquity of the Haivaiian Fauna and Flora. — The 
great antiquity 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 condi- 
tions of the locality, and these woidd serve as a barrier 
against the intrusion of many forms which at a later 

^ Among the curious features of the Hawaiian flora is the extraordinary 
development of what are usually herbaceous plants into shrubs or trees. 
Three species of Yiola are shrubs from three to five feet high. A shrubby 
Silene is nearly as tall ; and an allied endemic genus, Schiedea, has 
numerous shrubby species. Geraniuvi arhorciivi is sometimes twelve feet 
high. The endemic Compositse are mostly shrubs, while several are trees 
reaching twenty or thirty feet in height. The numerous Lobeliacete, all 
endemic, are mostly shrubs or trees, often resembling palms or yuccas 
in habit, and sometimes twenty-five or thirty feet high. The only native 
genus of Primulacese — Lysimachia — consists mainly of shrubs ; and even a 
plantain has a woody stem sometimes six feet high. 



CHAP. XV OCEAXIC ISLANDS 329 

period spread over Polynesia. The extreme remoteness 
of the islands, and the probability that they have always 
heen more isolated than those of the Central Pacific, 
Avould also necessarily result in an imperfect and frag- 
mentary representation of the flora of surrounding lands. 

Goncluding Observations on the Fauna and Flora, of the 
Sandiuich Islands. — The indications thus afforded by a 
study of the flora seem to accord Avell 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 exter- 
mination by a variety of adverse conditions, retain much 
more of the impress of a recent state of things, with per- 
haps here and there an indication of that ancient a23proach 
to America so clearly shown in the Compositse and some 
other portions of the flora. 

Genekal Remarks ox Oceaxic Islaxds. 

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 indigenous mam- 
malia 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 sjoecialisation and diversity from continental 
forms which may be well 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 



330 ISLAND LIFE part ii 

clothed with vegetation. But in every case the series 
of forms of life in these islands is scanty and im- 
perfect as compared with far less favourable continental 
areas, and no one of them j^resents 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 sujjpose to have been preserved from Mesozoic 
times ; and this 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 j^ortion 
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 frag- 
ments 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 volcanic islands 
or extinct submarine volcanoes), and that their productions 
are all more or less clearly related to the existing inhabit- 
ants 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 — 
Trichoi)tera Peculiar to the British Isles — Land and Freshwater Shells 
— Pecidiarities of the British Flora — Peculiarities of the Irish Flora — 
Peculiar British Mosses and Hepaticee — 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 subsidence of the intervening land at a period 
which, geologically, must be considered recent. Such 
islands are always still connected 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 comparative 
scarcity of those endemic or peculiar species and genera 
which are so striking a feature of almost all oceanic 
islands. Such islands will, of course, differ from each 



332 ISLAJs'D LIFE 



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 intercommunication with 
it ; and these diversities of conditions will manifest them- 
selves in the greater or less amount of speciality of their 
animal jDroductions. 

This siDeciality, when it exists, may have been brought 
about in two ways. A species or even a genus may on a 
continent have had a very limited area of distribution, and 
this area may be wholly oralmost 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 sei^aration 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 favour- 
able 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 examjDles 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 Clmnges in the British Isles. — Great 
Britain is perhaps the most typical example of a large and 
recent continental 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 



CHAP. XTI 



THE BRITISH ISLES 



333 



coasts SO as to include the whole of the British Isles and 
about fifty miles beyond them to the westward. (See Map.) 




MAP SHOWIXG 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. 

Beyond this line the sea deepens rapidly to the 500 and 
1,000 fathom lines, the distance between 100 and 1,000 



334 ISLAND LIFE 



fathoms being from twenty to fifty miles, except where 
there is a great outward curve to inckide the Porcupine 
Banli 170 miles west of Gal way, and to the north-west of 
Caithness where a narrow ridge less than 500 fathoms 
below the surface joins the extensive 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 
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 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 Elcration — Suhmergcd Forests. — What 
renders Britain particularly instructive as an example of a 
recent continental 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 submarine forests often 
extending far below the present low-water mark. Such 
are the submerged forests near Torquay in Devonshire, and 
near Falmouth in Cornwall, both containing stumjis 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 examj^les 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 Devonshii>e, at Blackpool near Dartmouth : — 



CHAP. XVI THE BRITISH ISLES 335 

" 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 eastward ; 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 ddbris, such as small twigs, 
leaves, and nuts. There were also numerous prostrate 
trunks and branches of trees, lying partly imbedded in the 
clay, without anything like a prevalent direction. The 
trunks varied from six inches to upwards of two feet in 
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 subsidence 
amounted to eighteen feet as a minimum, even if we 
sujDpose that some of the trees grew in a soil the surface 
of which was not above the level of high water. There is 
satisfactory evidence that in Torbay it was not less than 
forty feet, and that in Falmouth Harbour it amounted to 
at least sixty-seven feet." ^ 

^ Geological Magazine, 1870, i>. 155. 



ISLAND LIFE 



On the coast of tlieBristol Channel similar deposits occur, 
as well as along much of the coast of Wales and in Holy- 
head' 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 in 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 hysenas ; facts which can only be explained by 
the existence of some extent of dry land stretching sea- 
ward from the present cliffs, but since submerged and 
washed away. This j^l^in 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 found fifty-six feet beloAV high-water 
mark. 

Buried Fuvcr Channels. — Still more remarkable are the 
buried river channels which have been traced on many 
jmrts 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 dejjths 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 Dum- 
barton with the Forth at Grangemouth, and appears to 
have contained two streams flowing in opposite directions 
from a watershed about midway at Kilsith. At Grange- 
^ Transactions of the Edinhiirgh Geological Society, Vol. I. p. 330. 



CHAP. XVI THE BRITISH ISLES 337 

mouth 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. Sir A. Geikie, who has him- 
self discovered many similar buried valleys, is of opinion 
that " they unquestionably belong to the period of the 
boulder clay." 

We have here a clear j^roof 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 join 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 up of a freshwater 
shell {Uiiio 2^iciorum) 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 distinct indication of considerable sub- 
sidence.^ 

Time of Last Union with the Continent. — The period 
when this last union with the continent took place Avas 
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 j^assed away. 
But if so recent, we should naturally expect our land still 

^ Quarterly Journal of Geological Society, 1850, p. 9G. 
- British Association Ec'port, Dundee, 1867, p. 431. 



338 ISLAND LIFE 



to show an almost perfect community with the adjacent 
parts . of the continent 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. 
TVhp Britain is Poor in ^ijecics. — 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 considerable portion, if not the 
entire area, has been submerged to a depth of nearly 
2,000 feet (see Chap. IX. p. 174), at which time only 
what are now the highest mountains would remain as 
groups of rocky islets. This submersion must have 
destroyed the greater part of the life of our country ; and 
as it certainly occurred during the latter part of the 
glacial epoch, the subsequent 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 and during the glacial period we 
23ossessed a fauna almost or quite identical with that of 
adjacent parts of the continent and equally rich in S23ecies. 
The submergence destroyed this fauna ; and the perman- 
ent change of climate on the jjassing aAvay of the glacial 
conditions appears to have led to the extinction or 
migration of many sjDecies 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 subsidence 
again occurred, cutting off the further influx of jDurely 
terrestrial animals, and leaving us without the number of 
species which our favourable climate and varied surface 
entitle us to. 



CHAP. XVI THE BRITISH ISLES 330 

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, 
2^ossesses 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 
comiDarative zoological poverty of Ireland. This poverty 
attains its maximum in the reptiles, as shown by the 
folio win Of fissures : — 

Belgium has 22 species of reptiles and amphibia. 

Britain ,,13 

Ireland ,,4 ,, ., :, 

Where the power of flight existed, and thus the period 
of migration Avas prolonged, the difference is less marked ; 
so that Ireland has seven bats to twelve in Britain, and 
about 110 as against 130 land-birds. 

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 1,425 in Great Britain, — or almost exactly 
two-thirds, a proportion intermediate between that pre- 
sented by the birds and the mammalia. 

Peculiar British Birds. — Among our native mammalia, 
reptiles, and amphibia, it is the 023inion 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 and long-tailed tit, present well-marked differences 
of colour as compared with continental specimens; and 
in Mr. Dresser's work on the Birds of Buropc they are 
considered to be distinct sj^ecies, while Professor Newton, 
in his new edition of Yarrell's British Birds, does not 
consider the differencer to be sufficiently great or suffi- 
ciently constant to warrant this, and therefore classes 

Z 2 



340 ISLAXD LIFE part ii 

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 {Lagoims 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, becoming even darker in winter 
than in summer. We have here therefore a most inter- 
esting 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 residence 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. 

The followino- is a list of the birds now held to be 

o 

peculiar to the British Isles : — 

1. Parus ater, stcb. sp. britannicus Closely allied to P. ater of the 

continent ; a local race or 
sub-species. 

2. Acredula caudata, si4&, s;j>. rosea Allied to A. caudata of the 

continent. 

3. Lagoptjs scoTicus Allied to X. alhus of Scandin- 

avia, a distinct species. 

FrcsliwaUr 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 



CHAP. XVI 



THE BRITISH ISLES 



341 



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 attention. It has 
long been known that some of our lakes possessed peculiar 
species of trout and charr, but how far these were 
unknown on the continent, and how many of those in 
different parts of our islands were really distinct, had not 
been ascertained till Dr. Gilnther, 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 continental species deter- 
mined their sjDecific 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 : — ^ - 





Freslncatcr 1 


'Wishes '2^cculiar to the 


British Isks. 




Latin Name. 


English Name. 


Locality. 


1, 


Salmo BEACHYPOMA 


Short-headed salmon 


Firth of Forth, Tweed, 
Ouse. 


2. 


,, GALLIVENSIS 


Gahvay sea-trout 


Gahvay, West Ireland. 


3. 


,, ORCADENSIS. 


Loch Stennis trout... 


Lakes of Orkney. 


4. 


,, FEKOX 


Great lake- trout 


Larger lakes of Scotland, 
Ireland, the N. of 
England, and Wales. 


5. 


,, STOMACHICUS 


Gillaroo trout 


Lakes of Ireland. 


6. 


,, NIGPJPINNIS 


Black-finned trout . . . 


Mountain lochs of Wales 
and Scotland. 


/. 


,, LEVENENSIS. 


Loch Leveu Trout . . . 


Loch Leven, Loch Lo- 
mond, Windermere. 


8. 


,, Perish 


Welsh charr 


Llanberris lakes, N. 
Wales. 


0. 


,. WlLLUGHBII 


Windermere charr ... 


Lake Windermere and 
others in N. of Eng- 
land, and Lake Brui- 
ach in Scotland. 


10. 


,, KILLINEXSIS 


Loch Killin charr ... 


Killin lake in Inverness- 
shire. 


11. 


,, COLII 


Cole's charr 


Lough Eske and Lough 
Dan, Ireland. 


12. 


„ CtKAyi 


Gray's charr 


Lough Melvin, Leitrim, 
N.W. Ireland. 



^ 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 Freshicatcr Fishes. 



342 


ISLAND LIFE 


PART II 


Lati7i Name. 
13. COREGOXUS CLITPE- 
OIDES 


English Name. 
The gwyniad, or 
sclielH' 


Locality. 
Loch Lomoud, Ulles- 
water, Derweutwater, 


14. ,, YANDESIUS 

15. ,, POLLAN ... 


The veudace 

Thepollan 


HawesAvater, and Bala 
lake. 

Loch J\Iaben, Dumfries- 
shire. 

Lough Neagh and Lough 
Eariie, N. of Ireland. 



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 
number and size of the scales, form and size of tlie fins, 
and the form or proportions of the head, body, or tail. 
Some of them, like >S'. killinensis and the Coregoni are in 
fact, as Dr. Glinther assures me, just as good and distinct 
species as any other recognised species of fish. It may 
indeed be objected that, until all the small lakes of 
Scandinavia are exj^lored, 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 only one of the peculiar British species 
extends to Ireland, which has no less than five species 
altogether peculiar to it. If the sj^ecies 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 evidence 
we already possess of the very restricted ranges of many of 
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 
wdll 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 



CHAP. XVI THE BRITISH ISLES 343 

Eastern half of the Englisli Channel, so that, when the 
last subsidence occurred, Ireland would have been an 
island for some length of time Avhile 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 of limited distribution 
aftbrded by these fishes, we have the Loch Stennis trout 
confined to the little group of lakes 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 Loch 
Killin charr, known only from a small mountain lake in 
Inverness-shire, and the vendace, from the equally small 
lakes at Loch Maben 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 modifica- 
tions 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 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 only 
one appears to be common to the British and Irish lakes. 



344 ISLAND LIFE 



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 some- 
times 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 rising over 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 afibrds the true 
solution of many of the cases in which existing species of 
fish inhabit distinct river basins whether in streams or 
lakes. If a 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 the 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 
modified by the particular conditions of the lake in which 
they have found themselves isolated. 

Fcculiar British Insects. — We now come to the class of 
insects, and here we have much more difficulty in deter- 
mining what are the actual facts, because new species are 
still being yearly discovered and considerable portions of 
Europe are but imperfectly explored. It often happens 
that an insect is discovered in our islands, and for some 



THE BRITISH ISLES 345 



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 entomo- 
logists 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 
has been held by such well-known authorities as the late 
Mr. E. C. Rye and Dr. D. Sharp for the beetles, and by 
Mr. 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 Is- 
lands, and Ceylon — the insects show an equal if not a higher 
proportion of speciality, and there seems no reason what- 
ever 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 
considerable amount of isolation, offer all the conditions re- 
([uisite 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 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 was 
originally indebted to the late Mr. E. C. Rye ; and Dr. 
Sharp also gave me valuable information as to the recent 



346 ISLA^^D LIFE part ii 

occurrence of some of tlie siipi^osed peculiar siDccies on the 
continent. The list has now been revised by the Rev. Canon 
Fowler, author of the best modern work on the British 
Coleoptera, who has kindly furnished some valuable notes. 

For the Lepidoj^tera 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 bearing on the 
probability of the insect being peculiar to Britain, and in 
some cases may be said to exj)lain why it should be so. 
For example, the larvae 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, 
Elacliista rufocincrea, the lava of which mines in the leaves 
of Holcus mollis and other grasses from December to 
Marcli. This species, though common everywhere with 
us, extending to Scotland and Ireland, is quite unknown in 
similar latitudes on the continent, but ajDpears 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 pre- 
servation of some of the numerous species which are or 
have been dependent on it. Since the first edition was 



CHAP. XVI THE BRITISH ISLES 347 

published many new British species have been discovered, 
while some of the supposed peculiar species have been found 
on the continent. Information as to these has been kindly 
furnished by Mr. W. Warren, Mr. C. G. Barrett, Lord 
Walsingham, and other students of British Lepidoptera, 
and the first-named gentleman has also looked over the 
proofs. 

Mr. McLachlan has kindly furnished me with some 
valuable information on certain species of Triclioptera 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 com- 
parison. We will now give the list of peculiar British 
Insects, beginning with the Lepidoj)tera and adding such 
notes as have been sup^Dlied by the gentlemen already 
referred to. 

List of the Species or Varieties of Leindopterct ivhicli, so far as at 2oresent 
knoivn, arc confinecl to the British Islands. {The figures shoio the dates 
when the sjjecies loas first descrihcd. Species added since the first edAtion 
are marked xoith an asterisk.) 

DiUIlNI. 

1. PoLYOMMATUS DisPAE. " The large copper. " This fine inseci, 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. Lycffina astrarche, var. a]itaxerxes. 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. Lithosia com plana, var. sericea. North of England (1S61). 

'1. 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. Epichxopteryx reticella. Sheerness, Gravesend, and other locali- 

ties along the Thames (1847) ; Hayling Island, Sussex. 

6. E. pulla, var. radiella. Near London, rare (1830?) ; the species in 

Central and Southern Europe. (Doubtfully peculiar in Mr. 
Stainton's opinion. ) 



34$ ISLATs^D LIFE 



NOCTU^. 

7. Acronyct.a enjihorbipe, var. myric^. Scotland only (1852). A 

melanic form of a continental species, 

8. Agrotis subrosea. Cambridgeshire and Huntingdonshire fens, 

perhaps extinct (1835). The rar. suhcccrulea is found in Finland 
and Livonia. 

9. Agrotis candelarum var. ASHWORTHii. South and "West (1855). 

Distinct and not uncommon. 

10. Luperina luteago, rar. barretti. Ireland (1864). 

11. Aporophyla australis, var. pascuea. South of England (1830), A 

variety of a species otherwise confined to South Europe. 

12. Hydroscia nictitans, var. PAi-rDRis. 

Geometry. . 

13. Boarmia gemmaria, var. perfumaria. Xear London and elsewhere. 

A large dark variety of a common species. 

14. *B. repandata, var. soDOREXSirisr. Outer Hebrides. 

15. *Emmelesia albulata, va.r. hebridium. Outer Hebrides. 

16. *E. albulata, var. thules. Shetland Islands. 

17. *^relanippe montanata, var. shetlaxdica. Shetland Islands. 

18. *jM. sociata, var. obscurata. Outer Hebrides. A dark form. 

19. Cidaria albulata, t"«r. GRiSEATA. East of England (1835). A variety 

of a species otherwise confined to Central and Southern Europe. 

20. EuPiTHECiA CONSTEICTATA. Widely Spread, but local (1835). Larva 

on thyme. 

21. *E. satjTata, var. curzoni. N. Scotland. 

22. *E. nanata var. CURZOXI. Shetland Islands. 

Pyralidina. 

23. Aglossa pinguinalis, var. streatfieldi. IMendip Hills (1830). A 

remarkable variety of the common " tabby." 

24. *Scoparia cembr», va.r. SCOTICA. Scotland (1872). 

25. *]\h-elois ceratonise, rar. pryerella. Xorth London (1871). 

26. *Howceosoma nimbella, var. saxicola. England, Scotland, Isle of 

Man (1871). 

27. *Epischnia bankesiella. Isle of Portland (1888). 

TORTRICINA. 

28. Aphelia xiGROViTTANA. Scotland (1852). A local form of the 

generally distributed A. lanceolaim. 

29. Grapholita paryulana. Isle of Wight (1858). Rare. A distinct 

species. 

30. CoNCHYLis erigerana. South-east of England (1866). 

31. *Brachyt^nia woodiaxa. Herefordshire (1882\ 

32. *Eupfecilia angustana, var. thuleaxa. Shetland Islands. 

33. *ToRTRix doxelaxa. Connemara, Ireland (1890). 

Tixeixa. 

34. TiXEA rocHYLiDELLA. SandcTstead, near Croydon (1854). Unique ! 

35. AcROLEPiA BETUL^TELLA, Yorkshire and Durham (1840). Rare. 

36. Argyresthia semifusca. North and West of England (1829). 

Rather scarce. A distinct species. 

37. Gelechia diyisella. A fen insect (1856). Rare. 



OHAP. xvi. BRITISH ISLES 349 

38. G. CELERELLA. West of England (1854). A doubtful species. 

39. *G. TETRAGONELLA. Yorkshire. Norfolk. Salt marshes. 

40. *G. SPARSICILIELLA. Pembroke. 

41.. *G. PLANTAGINELLA. A salt-niarsli species. 

42. G. OcELLATELLA (Barrett nee Stainton). Bred from Beta maritima. 

Very distinct. 

43. .Bryotropha POLITELLA. Moors of North of England. Norfolk (1854). 

44. *B. portlandicella. Isle of Portland (1890). 

45. LiTA FRATERNELiiA. "Widely scattered (1834). Larva feeds on shoots 

of Stellaria uliginosa in spring. 

46. L. BLANDULELLA. Kent. 

47. AxACAMPSis siRCOMELLA. North and West England (1854). 

Perhaps a melanic variety of the more widely spread A. Ueniolclla. 

48. A. IMMACULATELLA. West Wickham (1834). Unique I A distinct 

species. 

49. *(EC0PH0RA WOODIELLA ? 

50. Glyphipteryx cladiella. Eastern Counties (1859). Abundant. 

51. G. sciicENicoLELLA. In Several localities (1859). 

52. Gracilaria stramineella. (1850). On birch. Perhaps a local 

form of G. elongclla, found on alder. 

53. Ornix loganella. Scotland (1848). Abundant, and a distinct 

species. 

54. 0. devoniella. In Devonshire (1854). Unique ! 

55. CoLEOPHORA saturatella. South of England (1850). Abundant on 

broom. 

56. C. iNFLATiE. South and East of England. On Silenc inflata. ? con- 

tinental. 

57. C. SQUAMOSELLA. Surrey (1856). Very rare, but an obscure species. 

58. C, SALINELLA. On Sea-coast (1859), Abundant. 

59. *C. POTENTiLLiE. South of England. 

60. *C, ADJUXCTELLA. Essex salt niarslies. ? Lancashire (1882). 

61. *C. LiMOXiELLA. Isle of Wight. Feeds on Staticc limonium. 

02. Elachista flavicomella. " Dublin (1856). Excessively rare, two 

specimens only known. 
63, *E. sciRPi. AVales and Sussex. Salt marshes. 
G4. E. coxsoRTELLA. Scotland (1854). A doubtful species. 
65. E. MEGERLELLA. Widely distributed (1854). Common. Larva 

feeds in grass during winter and early spring. 
Q>Q. E. OBLIQUELLA. Near London (1854). Unique ! 

67. E. TRISERIATELLA. South of England (1854). Very local; an 

obscure species. 

68. *TiXAGMA BETUL^. East Dorset (1891). 

69. LiTHOCOLLETis xiGRESCEXTELLA. Northumberland (1850). Rare ; 

a dark form of X. Breyiiiella, which is widely distributed. 

70. *L. AXDERiD^. Sussex. Dorset (1886). 

71. L. IRRADIELLA. North Britain (1854). A northern form of the 

more southern and wide-spread L. Icmtclla. 

72. L. TRIGUTTELLA. Sanderstead, near Croydon (1848). Unique ! very 

peculiar. 

73. L. ULicicoLELLA. In a few wide-spreadlocalities (1854). A peculiar 

form. 

74. L. CALEDOXIELLA. North Britain (1854). A local variety of the 

more widespread L. corylifoUcUa. 



350 ISLAXD LIFE part ii 

75. L. DUXNINGIELLA. Xortli of England (1852). A somewhat doubt- 

ful species. 

76. BuccuLATRix DEMARYELLA. Widely distributed (1848). Rather 

common. 

77. Teifurcula squamatella. South of England (1854). A doubtful 

species. 

78. :NrErTicuLA igxobiliella. Widely scattered (1854). On hawthorn, 

not common. ? on continent. 

79. X. POTEPJi. South of England (1858). Bred from Larvai in Po^enw??i 

sanguisorha. 

80. X. quinquella. South of England (1848). On oak leaves, very 

local. ? continental. 

81. N. apicella. Local (1854). Probably confused with allied species 

on the continent. 

82. N. headleyella. Local (1854). A rare species. 

83. *N'. HODGKixsoxi. Lancashire. 

84. *jS'. woolhopiella. Herefordshire. 

85. *]Sr. serella. Westmoreland and S. England. 

86. *N. AUROMARGINELLA. Dorset (1890). 

87. *mlcropteryx sangii. (1891). 

88. *m. salopiella. 

Pterophorina. 

89. Agdistis BENNETTii. East coast. L of Wight (1840). Common on 

Statice limonmm. 

We have here a list of eighty-nine species, which, 
according to the best authorities, are, in the jDresent state 
of our knowledge, peculiar to Britain. It is a curious fact 
that no less than fifty of these have been described more 
than twenty-five years ; and as during all that time they 
have not been recognised on the continent, notwith- 
standing 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 exclu- 
sively British. This insect, Platyptilia similidactyla 
(FkropJiorus isodadylus, Stainton's Manual), had been 
taken rarely in the extreme north and south of our islands 
— Teignmouth and Orkney, a fact which seemed some- 
what indicative 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 



CHAP. XTi THE BRITISH ISLES 351 

equally rare and not yet found on the continent. But 
this is hardly in accordance with the laws of distribution. 
Widely scattered species are generally abundant 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 j^eculiarity 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. 

Of the sixty-nine species recorded in my first edition 
fourteen have been since discovered on the continent, while 
no less than twenty-two species and eleven varieties have 
been added to the list. As we can hardly suppose con- 
tinental entomologists to be less thorough collectors than 
ourselves, it ought to be more and more difficult to find 
any insects which are unknown on the continent if all ours 
really exist there ; and the fact that the list of apparently 
peculiar British species is an increasing one renders it 
probable that many of them are not only apparently but 
really so. Both general considerations dependent on the 
known laws of distribution, and the peculiar habits, con- 
spicuous appearance, and restricted range, of many of our 
species, alike indicate that some considerable proportion of 
them will remain permanently as peculiar British species. 

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 and Varieties of Beetles which, so far as at present knoicn, 
are confined to the British Islands. Those added since the first edition 
are marked tcith an asterisk. 

CARABIDiE. 

1. *BembidmTn saxatile, rar. vectensis (Fowler), Isle of Wight. 

2. Dromius yectexsis (Rye). Common in the Isle of Wight, also in 

Kent, and at Weymouth and Seaton. Closely allied to D. sicjma. 

3. Harpahis latus, var. metallescexs (Rye). Unique, but very 

marked ! South coast. " Perhaps a sport or a hybrid " (Fowler). 

4. AcuPALPUS DEUELiCTUS (Dawson). Unique ! North Kent. Canon 

Fowler thinks it may be a variety of A. dorscdis. 



352 ISLAND LIFE part ii 

DYTICIDiE. 

5. *Acilius sulcatus, var. scoxicus (Curtis). Scotland. A melanic 

' variety. 

Helophorid^. 

6. OcHTHEBirs rowERi (Rye). Very marked, S. coast. A few speci- 

mens only. 

7. *0. ^NEUS (Stsph). 

Brachyelytra. 

8. OcYUSA HIBERXICA (Rye). Ireland, moimtain tops, and at Braemai\ 

9. *OxYPODA TARDA (Sharp), 

10. ,, PECTiTA (Sharp). Scotland. 

11. ,, VERECUNDA (Sharp). Scotland, also London districts. 

12. HoMALOTA DiVERSA (Sharp). 

13. ,, FULViPENNis (Rye). 

14. ,, OBLONGiuscuLA (Sharp). Scotland, also England and 
Ireland. 

15. ,, PRixcEPS (Sharp). A coast insect. 

16. ,, CURTIPENNIS (Sharp). Scotland and near Birmingham. 

17. H. levana, var. setigera (Sharp), 

IS. Stenus oscillator (Rye). Unique ! South coast. May be a 
hybrid. 

19. TROGOPHL^rs SPINICOLLIS (Rye). Mersey estuary, unique ! ]\[ost 

distinguishable, nothing like it in Europe. Perhaps imported from 
another continent. 

20. EuDECTUS AVHiTEi (Sharp). Scotch hills. A variety of E. Giraudi 

of Germany (the only European species) /fZc Kraatz (Sharp). 

21. HoMALiUM RUGULIPEXXE (Rj^e). Exceedingly marked form. 

Northern and western coasts ; rare. 

22. *Mycetoporus moxticola (Fowler). Cheviots and Invemess-shire. 

SCYDM^XID^. 

23. *ScYDMiEXUS POWERi (Fowler) S, England. A recent discovery. 

24. *S, plaxifroxs (Fowler). .. ,, 

PSELAPHID^. 

25. Bryaxis cotfs (De Sauley). Scotland. 

26. Bythixus glabratus (Rye). Sussex coast ; also Isle of Wight ; a 

few specimens ; very distinguishable ; myrmecophilous (lives in ants' 
nests), 

Trichopterygid^. 



27. 


Ptixella 


MARIA 


(Matthews) Derbyshire. 


28. 


TrICHOPTERYX SARJ3 


( „ ) Notts. 


29. 


JJ 


POWERI 


( ,, ) Oxon. 


30. 




EDITHIA 


( „ ) Kent. 


31. 




*AXGUSTA 


( ,, ) Leicestershire. 


32. 




kirbii 


( „ ) Norfolk. 


33. 




fratercula( ,, ) 


34. 




WATERHOUSIl( ,, ) 


35. 




CHAMPIOX 


is( ,, ) Wicken Fen. 


36. 




JAXSOXI 


( ,, ) Leicestershire. 


37. 




suFFOCATA (Haliday). Ireland, Co. Cork. 


38. 




carboxaria (Matthews). Notts. 



CHAP. XVI THE BRITISH ISLES 353 



39. Ptilium halidayi (Matthews). Sherwood Forest. 

40. ,, CALEDONiciiM (Sharp). Scotlaixl ; very marked form. 

41. ,, INSIGNE (Matthews). London district. 

42. "OirrHOPERUS mundus (Matthews). Oxfordshire. 

43. *0. PUNCTULATUS (Mattliews). Lincolnshire. 

Anisotomid.e. 

44. x^fiATHiDiUM RHiNOCEE,0.s (Sharp). Old fir-woods in Perthshire ; 

local, many specimens ; a ver}' marked species. 

45. Anisotoma .similata (Rye). South of England. Two specimens. 

46. ,, LUNicoLLis (Rye). North-east and South of England, a 
very inarked form ; several specimens. 

Phalacp.id^. » 

47. Phalacrus BPtisouTi (Rye). South of England. Rare. "Perhaps 

a small form of P. coruscus " (Fowler). 

CrYPTOPHAGIDvE. 

4S. Atomaria divisa (Rye). Unique ! South of England. 
Lathridiid^. 

49. Melanopthalma transversalis, var. wollastoni (Waterhouse). South 

coast, and Lincolnshire. 

Byrrhid/E. 

50. Syncalypta hirsuta (Sharp). South of England, local. "Closely 

fillied to S. sdigera " (Fowler). 

MORDELLID^. 

51. *Anaspis sEPTENTRiONALis. Scotland (1891 ). (Champion.) 
52.* ,, GARNEYSi (Fowler), London District. (1890.) 

Telephorid.e. 

53. Telephorus darwinianus (Sharp). Scotland, sea-coast. A stunted 

form of abnormal habits. Perhaps a variety of T. Hfvratus. 

Cyphonii)^. 

54. Cyphon punctipennis (Sharp). Scotland. 

Anthicid^. 

55. Anthicus salinus (Crotch). South coast. 

5(J. ,, scoTicus (Rye). Loch Leven ; very distinct : many speci- 

mens. 

CiOIDjE. 

57. *Cis BiLAMELLATUS (Wood). West Wickliam, Kent. '• Perhaps im- 

ported. Has the appearance of an exotic Cis " (Fowler). 

TOMICID^. 

58. * Pityopthorus lichtensteinii, WM-. SCOTICUS (Blandford). Scotland. 

CURCULIONID^. 

59. Ceuthorhynchus contractus, var. pallipes (Crotch). Lundy Island ; 

several specimens. A curious variety only known from this island. 

60. LiosoMUs TROGLGDYTEs (Rye). A very queer form. Two or three 

specimens. South of England. 

61. *Orcheites ilicis, m?\ NiGRi pes (Fowler). London District. (1890.) 

A A 



354 ISLAND LIFE 



62. Apion ryei (Blackburn). Shetland Islands. Several specimens. 

Perhaps a var. of A. fagi. 

Chrysomelid^, 

63. Chrysoniela staphylea, ran shaepi (Fowler). Sohvay district. 

Halticid^. 

64. LoxGiTARSiTS AGiLis (Rye). South of England ; many specimens. 

65. ,, DiSTiNGUEXDA (Rye). South of England ; many speci- 
mens. 

66. PsYLLiODES LCRiDiPENNis (Kutscliera). Lundy Island. A very 

curious form, not uncommon in this small island, to which it 
appears to be confined. "An extreme and local variety of 
P. clirysoccijhala " (Fowler). 

COCCINELLII)^. 

67. ScYMXI^s LiviDUS (Bold). Northumberland. A doubtful species. 

Of the sixty-seven species and varieties of beetles in the 
preceding hst, a considerable number no doubt owe their pre- 
sence 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 excessively minute Trichopterygidse 
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. The peculiar 
species of Aj^ion in the Shetland Islands is interesting, and 
may be connected with the very peculiar climatal con- 
ditions there prevailing, which have led in some cases to a 
change of habits, so that a species of weevil {Otiorhynchus 
mcmrus) 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 Avell-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 immunity from enemies or com- 
petir.g forms. When we consider the similar islands off 



CHAP. XVI THE BRITISH ISLES 355 

the coast 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 ex- 
amples of peculiar isolated forms remain to be discovered. 

Looking, then, at what seem to me the probabilities of 
the case from the standpoint of evolution and natural 
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 entomo- 
logical authorities, and to believe that some at least, 
perhaps many, of the species which, in the present state of 
our knowledge, appear to be peculiar to our islands, are, 
not only apj^arently, but really, so peculiar. 

I am indebted to Mr. Robert McLachlan for the follow- 
ing information on certain Trichopterous Neuroptera (or 
caddis-flies) which appear to be confined to our islands. 
The jDeculiar aquatic habits of the larvae of these insects, 
some living in ponds or rivers, others in lakes, and others 
again only in dear mountain streams, render it not improb- 
able that some of them should have become isolated and 
preserved in our islands, or that they should be modified 
owing to such isolation. 

Trichoptcra peculiar to the British Isles. 

1, Philopotamus iNSULARis. (? A. y&xiQt J oi P. montanus.) — This can 
hardly be termed a British species or A'ariety, because, so far as at present 
known, it is peculiar to the Island of Guernsey. It agrees structurally 
with P. montaiuis, 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 ]\Ir. McLachlan that no other kind is known. Strange to say, 
some examples from Jersey differ considerabl}^ resembling the common 
European and British form. Even should this peculiar variety be at some 
future time found on the continent it \yould 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 
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. In the 
first edition of this work two other species were named as then, peculiar 
to Britain — Setodes argentipunctella and Rhyacophila munda. but both 
have now been taken on the continent. 

2. Mesophylax impuxctatus, var. zetlandicus. — A variety of a 
South and Central European species, one specimen of which has been 
found in Dumfriesshire. The variety is distinguished by its small size and 
dark colour. 

A A 2 



856 ISLAND LIFE 



Land and Freshwater Shells. — In the first edition of this 
work four species were noted as being, so far as was then 
known, exclusively British. One of these, Cyclas 'pisi- 
dioides (now called Sjyha^ri'itm pisidioidcs) has been dis- 
covered on the continent, but the other three remain still 
apparently confined to these islands ; and to these another 
has been added by the discovery of a new species of 
Hydrobia in the estuary of the Thames. The peculiar 
species now stand as follows : — 

1. Geomalacus MACULOsrs. — A beautiful sing, black spotted vnili 
yellow or white, found on rocks on the sliores of Lake Caragh in Kerry. 
It was discovered in 1842, and has recently been found also at Glengarriff 
in Cork. An allied species is found in France and Portugal. 

2. LiMNEA INVOLUTA. — A pond snail Avith a small polished amber- 
coloured sliell found only in a small alpine lake, and its inflowing stream 
on Cromagloun mountain near the lakes of Killarney. It was discovered 
in 1838, and has frequently been obtained since in the same locality. It 
is sometimes clas:;ed as a variety of Limnca pcregra, and is at all events 
closely allied to that species. 

3. Hydrobia jenkinsii. — A small shell of the family Rissoidoe inhabit- 
ing the Thames estuary both in Essex and Kent. It was discovered only 
a few years ago, and was first described in 1889. 

4. AssiMiNEA cjrayana. — A small estuarine pulmonobranch found on 
the banks of the Thames between Greenwich and Gravesend, on mutl at 
the roots of aquatic plants. It has been discovered more than sixty years. 

But besides the above-named species there are a con- 
siderable number of well-marked varieties of shells which 
seem to be peculiar to our islands. A list of these has 
been kindly furnished me by Mr. Theo. D. A. Cockerell, 
who has paid much attention to the subject ; and after 
omitting all those whose peculiarities are very slight or 
whose absence from the continent is doubtful, there remain 
a series of forms some of which are in all ])robability really 
endemic with us. This is the more j^robable from the fact 
that an introduced colony of Helix nemoralis at Lexington, 
Virginia, presents numerous varieties among which are 
several which do not occur in Europe.^ The following list 
is therefore given in the hope that it may be useful in 
calling attention to those varieties which are not yet posi- 
tively known to occur elsewhere than in our islands, and 

^ See "The Virginia Colony of Helix nemoralis," T. D. A. Cockerell. 
in The Nautilus, Vol. III. No. 7, p. 73. 



cHAr. XVI THE BRITISH ISLES 357 

thus lead, ultimately, to a more accurate knowledge of the 
facts. It is only by obtaining a full knowledge of varieties, 
their distribution and their comparative stability, that we 
can ever hope to detect the exact process by which nature 
works in the formation of species. 

List of the Species and Varieties of Land and Freshwater 

Shells which, so far as at present known, are believed to be 

Peculiar to the British Isles or not found on the Continent. 

LlMACID^. 

1 . Limax marginatus, var. M ACULATUS. Ireland ; frequent, very distinct, 

2. ,, ,, ,, decipiens. Ireland and England. 

3. ,, flavus, far. suffusus. England ; Melanic form. 

4. ,, ,, ,, griseus. England ; Melanic form. 

5. Agriolimax agrestis, var. niger. Yorkshire. Melanic. Azores. 

6. ,, ,, ,, GRISEUS. England. Melanic. 

7. Amalia gagates, var. rava. W. of England. 

8. ,, sowerbyi, var. rustica. England. 

9. ,, ,, ,, NiGRESCENS. Surrey and Middlesex. 

10. ,, ,, ,, BicoLOR. Ealing. 

11. Hyalina crystallina, var. complanata. Near Bristol. 

12. ,, fulva, var. alderi. 

13. Yitrina pellucida, var. depressiuscula. S. England, Wales. 

Helicid^. 

14. Arion ater, var. albo-lateralis. England, Wales, Isle of Man : 

very distinct. 

15. ,, liortensis, var. fall AX. England. Common at Boxliill. 

16. Geomalacus :iiACUL0SUs. Kerry and Cork. Three varieties have 

been described, one of which occurs in Portugal. 

17. Helix aspersa, var. lutescens. England. Kot rare perhaps in 

France. 

18. ,, nemoralis, var. hibernica. Ireland. 

19. ,, rufescens, var. manchesteriensis. England. 

20. ,, hispida, var. subglobosa. England. 

21. ,, ,, ,, depilata. England. 

22. ,, ,, ,, MINOR. England, Ireland. 

23. ,, granulata, var. cornea. Lulworth, Dorset. 

24. ,, virgata, var. subaperta. Bath. 

25. ,, ,, ,, subglobosa, England, Wales, Bantry Bay. 

26. ,, ,, ,, carinata. Wareham, Dorset. 

27. ,, caperata, var. major. England, AVales, Scotland. Distinct. 

28. ,, ,, ,, NANA. England. 

29. ,, ,, ,, suBSCALARik Wales, Ireland. 

30. ,, ,, ,, ALTERNATA. England, Kent. 

31. ,, acuta, var. nigrescens. England. 

PUPID^. 

32. Pupa anglica, var. pallida. Not rare. 

33. ,, lilljeborgi, var. bidentata. Ireland. 



358 ISLAND LIFE part ii 

34. Pupa pygmea, var. pallida. Dorset aud Devon. 

35. Clausilia rugosa, %-ar. parvula. Ireland. 

StENOGYRIDwE. 

36. Cochlicopa lubrica, var. hyalina. Wales, Scotland. 

37. Coecilianella acicula, var. anglica. England. 

SUCCINEID^. 

38. Succinea putris, var. solidula. Wiltshire. 

39. ,, virescens, var. AUREA. Ireland. 

40. \, pfeifferi, ,, rufe.«!CEN8. England, Ireland. 

41. ., ,, ,, MINOR. England. 

LlMN^ID.^;. 

42. Planorbis fontanus, var. :minor. England. 

43. ,, carinatus, ,, disciformis. England. 

44. ,, contortus, ,, excavatus, Ireland. 

45. ,, ,, ,, MINOR. 

46. Physa fontinalus, var. oblong A. England, AVales, Ireland. 

47. LiMN^A INVOLUTA. Ireland. 

48. Limnsea glutinosa, var. mucronata. 

49. ., peregra, var. burnetti. Scotland. Very distinct. 

50. ,, ,, ,, LACusTRis. Perhaps in C. Yerde Islands. 

51. ,, ,, ,, maritima. Great Britain. 

52. ,, ,, ,, LINEATA. England. 

53. ,, ,, ,, stagnaliformis. England. 

54. ., stagnalis, var. elagantula. Curious. In a })ond at 
Chislehurst. 

55. ,, palustris, var. conica. England, Ireland. 

56. ,, ,, ,, TiNCTA. England, AVales. 

57. ,, ,, 5, ALBIDA. England. 

58. ,, truncatula, var. elegans. England, Ireland. Distinct. 

59. ,, ,, ,, FUSCA. Wales. 

60. Ancylus lacustris, var. compressus. England. 

Paludinid^. 

61. Paludina vivipara, var. efasciata. England. Xot uncommon. 

62. ,, ,, ,, atropurpurea. Pontyi)ool. 

RlSSOID^. 

63. Hydrobia jenkinsii. Thames Estuary. 

64. ,, ventrosa, var. minor. 

65. ,, ,, ;, decollata. 

66. „ ,, ;, OVATA. 

67. ,, ,, ;, ELONGATA. 

68. ,, ,, ;, PELLUCIDA. 

CYRENIDJ3. 

69. Sphierium corneum, var. compressum. 

70. ,, ;, 5, minor. 

71. ., ,, ,, iSTAGNICOLA. 

72. ,, ovale, va.r. pallidum. England. 

73. ,, lacustre, var. rotundum. Wales. 

74. Pisidium pusillum, var. grandis. 

75. ,, ,, ., circularpl Wales. 

76. ,, nitidum, var. gloeosum. 



CHAP. XVI THE BRITISH ISLES 359 

Unionid^. 

77. Unio tumidiTs, var. richexsis. Regent's Park. Peculiar form. 

78. „ pictorum, tar. latior. England. 

79. ,, ,, ,, coMPRESSUS. England. 
SO. ,, margaritifer, var. oliyacetjs. 

81. Anodonta cvgnsea, var. ixcrassata. England. 

82. ,, \, ,, pallida. England, Ireland. 

ESTUARINE OR MARINE PULMONOTRANCHS. 

8.3. As-siMiNEA GRAYAXA. Thames Estuary. 

Feculiaritics of the British Flora.- — Thinking it probable 
that there must also be some peculiar British plants, but 
not finding any enumeration of such in the British Moras 
of Babington, Hooker, or Bentham, I applied to the 
greatest living authority on the distribution of British 
plants — the late Mr. H. C. Watson, who very kindly gave 
me the information I required, and I cannot do better 
than quote his words : " It may be stated pretty con- 
fidently that there is no ' species ' (generally accepted 
among botanists as a good species) peculiar to the British 
Isles. True, daring 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 succeeding botanists, and placed or replaced 
as varieties of more widely distributed species. In his 
British RvM Professor Babington includes as good species, 
some half-dozen wdiich he has, apparently, not identified 
with any foreign species or variety. None of these are 
accepted as ' true species,' nor even as ' sub-sj^ecies ' in 
the Students Flora, where the brambles are described 
by Baker, a botanist well acquainted Avith 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.'" 

In my first edition I was only able to name four species, 
sub-species, or varieties of flowering plants which were 
believed to be unknown on the continent. But much 
attention has of late years been paid to the critical ex- 
amination of British plants in comparison with continental 
specimens, and I am now enabled to give a much more 



360 ISLAND LIFE 



extensive list of the species or forms which at present seem 
to be peculiar. For the following list I am prmiarily in- 
debted to Mr. Arthur Bennett of Croydon. Sir Joseph 
Hooker has been so kind as to examme it carefully and to 
give me his conclusions on the relative value of the differ- 
ences of the several forms, and Mr. Baker, of Kew, has also 
assisted with his extensive knowledge of British jDlants. 

List of Species, Sub-species, and Vapjeties of Flowering Plants 
FOUND IN Great Britain or Ireland, but not at present known 
IN Continental Europe. By Arthur Bennett, F.L.S. The 
most distinct and best determined forms are marked with an 

asterisk. 

1. *Caltlia radicans (Forst.). "A much disputed species, or form of C. 

pal'ustrirs. It is a relativelj' rare plaut." (J. D. H.) "Certainly 
distinct from the Scandinavian form." (Ar. Bennett.) 

2. *Arabis petrsea (Lam.) rar. grandifolia (Druce). -Scotch mountains. 

"The Larger flowers alone distinguish this." (J. D. H. ) 

3. Arabis ciliata (R. Br.). In Nj^man's ConsiJcctus Florcc Europcccc 

this species is given as found in England and Ireland only. 

' ' A very much disputed form of a plant of very wide distribution 
in Europe and North America." (J. D. H.) 

4. Brassica monensis (Huds. ). " This and the continental B. cheiranthus 

(also found in Cornwall) are barely distinguishable from one 
another." (J. D. H.) 

5. Diplotaxis muralis (D. C. ) var. Babingtonii (Syme), South of England. 

"A biennial or perennial form; considered to be a denizen by 
Watson." (J. D. H.) 

6. "Helianthemum guttatum (Mill), var. Breweri (Planch). Anglesea. 

" Very doubtful local plant. H. quttatum (true) has lately been 
found in the same locality." (J. D. H.) 

7. '"'Polygala vulgaris (L.), -yar. grandiflora (Bab). Sligo, Ireland. "A 

very distinct variety. " (J. D. H.) 

8. Viola lutea (Huds.), var. amoena (Symons»). " V. lutca itself is con- 

sidered to be a form of V. tricolor, and V. aiiKxnathe. better coloured 
of the two forms of V. lutca." (J. D. H. ) 

9. *Cerastium arcticum (Lange), var. Edmonstonii (Beeby). Shetland Is. 

"But C. arcticum is referable to the very variable 0. alpimnu." (J. 
D. H.) "Near to the European C. laf (folium." (Ar. Bennett.) 

10. *Geranium sanguineum (L.), var. Lancastriense (With.). Lancashire. 

"A prostrate local form growing out of its native soil in sand by the 
sea. " (J. D. H. ) Mr. Bennett writes : " I have grown G. savfiui7icum 
and its prostrate variety in sand, and neither became Lancastriense. " 

11. Genista tinctoria (L.), var. humifusa (Dickson). C^ornwall. "A 

decumbent hairy form confined to the Lizard." (J. D. H. ) 

12. Cytisus scoparius (Link.), ?wr. prostratus (Bailey). Cornwall. "A 

liro.strateform." (J. D. H.) 

13. Anthyllis vulncraria (L.), var. ovata (Bab.). Shetland Is. "A slight 

variety that Mr. Baker tells me reverted at once under cultivation." 
(J. D. H.) 

14. *Trifolium repens (L.), var. Townsendii (Bab.). Scilly Isles. "A well- 



cHAr. XVI THE BRITISH ISLES 361 

marked form by its rose-purple flowers. Confined, to the Scilly 
Isles." (J. D. H.) 

15. *E,osa involuta (Sm.), 'car. Wilsoni. (Borrer.) Wales. "There are a 

multitude of forms or varieties of it. involuta, andiv. u-ilsoniis one of 
the best-marked, found on the Menai Straits and Derry," (J. D. H.) 

16, Rosa involuta var. gracilis (Woods). "This is considered by many as 

one of the commonest forms of -ff. invohUa." (J. D. H.) 
17.' Rosa involuta var. Nicholsoni (Crepin). " Another slight variety of 
E. invohUa." (J. D. H.) 

18. Rosa involuta var. Woodsiana (Groves). "A Wimbledon Common 

variety of it. villosa." (J. D. H. ) 

19. Rosa involuta var. Grovesii (Baker). "Mr. Baker thinks this of no 

account." (J. D. H.) 

20. Rubus echinatus (Lind. ). "A variety of the widely spread E. Badula., 

itself a form of ii. /rit^zcosMS, " (J. D. H.) 

21. *Rubus longithyrsiger (Lees). "Mr. Baker informs me that this is a 

very distinct plant never yet found on the continent." (J. D. H. ) 

22. Pyrus aria (Sm.) var. rupicola (Syme). " A very local form, contine(l 

to Gt. Britain, and owing its characters to its starved position '"' 
(Baker.) 

23. Callitriche obtusangula (Le Gall), var. Lachii (Warren). Cheshire. 

' ' This is intermediate between two sub-species of C. vcrna. " ( J. D. H. ) 

24. */Enanthe fluviatilis (Coleman). South of England. "The fluitant 

form of ^. PheUandrium." (J. D. H.) 

25. Anthemis arvensis (L. ), va,r. anglica (Spreng). X. Coast of England. 

"A maritime form with more fleshy leaves formerly found near 
Durham. It has other very trifling characters. " (J. D. H.) 

26. Arctium intermedium (Bab. ). ' ' There are two sub-species of A. lappa, 

ma jus and minus, each with varieties, and this is one of the inter- 
mediates." (J. D. H.) 

27. Hieracium holosericium (Backli.). Scotch Alps. 

28. H. gracilentum (Backh.). 

29. H. lingulatum (Backh.). ,, A var, of this in Scand- 

inavia. 

30. H. senescens (Backh.), ,, 
31 H, chrysanthenum (Backh,). ,, 

32. H. iricum (Fr. ). Teesdale and Scotland. 

33. H. gibsoni (Backh. ), Yorkshire and Westmoreland. 

34. Hieracium nitidum (Backh.). Lower glens of the Scotch Alps. Mr. 

Bennett writes : — "The following Hieracia have been named by 
Mr. F. J. Hanbury as endemic forms. One can only safely say they 
are certainly not known in Scandinavia, as they have all been sub- 
mitted to Dr. Lindeberg, But usually Scotch species are not 
represented in Central Europe to any great extent, though several 
do occur. Still these new forms ought to be critically compared 
with all Dr. Peters' new species." 

35. H. Langewellense (Hanb.). Caithness. 

36. H. pollinarium (Hanb.). Sutherland. 

37. H. scoticum (Hanb.). Sutherland and Caithness. 

38. H. Backhousei (Hani).). Aberdeen, Bantt", Inverness, 
39- H. caledonicum (Hanb.). Caithness and Sutherland, 

40. H. Farrense (Hanb.). Sutherland and Shetland Is, 

41. H, proximum (Hanb.). Caithness. With regard to all these 



362 ISLAND LIFE 



Hieracia Sir Joseph Hooker and Mr. Baker say: — "No case can 
he made of these. They are local forms with the shadowest of shady 
• characters."' Mr. Bennett writes : " H. iricum and H. Gibsoni are 
the best marked forms." 

42. *Campanula rotundifolia (L.), wr. speciosa (A. G. More). W. Ireland. 

" Very well distinguished by its large flowers and small calyx lobes, 
approaching the Swiss C. Scheuzeri." (J. D. H.) 

43. Statice reticulata (Sm.). "Baker agrees with me that this is also a 

Mediterranean species." (J. D. H.) 

44. Erythn^a capitata (Willd.), var. sphrerocephala (Towns. )._ Isle of 

Wio-ht. ' ' A form of E. centauriitvi utterly anomalous in its genus 
in the insertion of the stamens. A monster rather than a species." 
(J. D. H.) 

45. *Erythrfealatifolia (Sm.). On the sandy dunes near Liverpool "A 

local form." (J. D. H.) 

46. Myosotis collina (Hoflfim.), var. Mittenii (Baker). Sussex. 

47. Veronica officinaKs (L.), var. hirsuta (Hopk.). Ayr, Scotland. 

48. Veronica arvensis (L.), var. eximia (Towns.). Hampshire. 

49. Mentha alopecuroides (Hull). Nearest to M. duldssvma (Dum.). 

50. Mentha pratensis (Sole). Only once found. 

51. Chenopodium rubrum (L.), var. pseudobotryoides (H. C. Watson). 

52. Salix ferruginea (Forbes). England, Scotland. " Probably a hybrid 

between *S'. viminalis and aS'. cincrcaJ' (J. D. H. ) 

53. Salix Grahami (Borr. ). Sutherland, Perth. ' ' A hybrid ? " (J. D. H. ) 

54. Salix Sadleri (Syme). Aberdeen. "A hybrid?" (J. D. H.) 

55. *Spiranthes Romanzoviana (Cham.). Ireland (N. America). 

56. *Sisyrinchiumangustifolium (Mill.). Ireland. (Arctic and Temp. N. 

America. ) 

57. Allium Babingtonii (Borrer). West England, West Ireland. "A 

form of ^. anqjcloprasuni, itself a naturalised species." (J. D. H.) 

58. *PoTAMOGETON LANCEOLATUS (Sm.). Auglesca, Cambridgeshire, Ire- 

land. Mr. Bennett writes : — " Endemic ! I have taken a good amount 
of trouble to ascertain this. Nearly 400 specimens I have distributed 
all over the world with requests for information as to anything like 
it. The response is everywhere the same, 'nothing.' The nearest to 
it occurs in the Duchy of Lauenberg but is referable to P. hetcro- 
lyhyllus.'' 

59. Potamogeton Griffithii (Ar. Bennett). Carnarvon. "Nearest to this 

is a probable hybrid from N. America, but not identical." (Ar. 
Bennett.) 

60. Potamogeton pusillus (L.), suh-sp. Sturrockii (Ar. Benn.). Perth. 

61. Potamogeton pusillus (L.), var. rigidus (Ar. Benn.). Orkneys, 

Shetlands. 
02. R,ui)piarostellata (Koch.), var. nana(Bosw.). Orkneys. 

63. *Eriocaulon septangulare (With. ). Hebrides, Ireland. N. America. 

64. Scirpus uniglunus (Link), var. Watsoni (Bab.). Scotland, England. 

"This is a variety of a sub-species of the common S. palustris." 
(J. D. H.) 

65. Luzula pilosa (Willd. ), var. Borreri ( Bromf). 

m. *Carex involuta (Bab.). Cheshire. " A distinct enough plant but 
probably a hybrid between C. vcsicaria and C. ampuUacca, ibund in 
one ])lace only." (J. D. H.) 

67. Carex glauca (Murr.), var. stictocarpa (Sm.). Scotland. 



CHAP. XVI THE BRITISH ISLES 363 

68. Carex precox (Jacq.), var. capitata (Ar. Benn. ). Ireland. "A 

remarkable plant (monstrosity?) simulating C. caintata (L.)." (Ar. 
Bennett. ) 

69. *Carex Grahami (Boott). " A mountain form of C. vcsicaricf,." (J. 

D. H.) 

70. *Spartina Townsendi (Groves). Hampshire. " A distinct but very 

local form of *S'. stricta, found in one place only." (J. D. H.) 

71. Agrostis nigra (With.). 

72. Deschampsia flexuosa (Trin.), var. Voirlichensis ( J. C. Melvill). Perth. 

73. *Deyeuxia neglecta (Kunth), var. Hookeri (Syme). Ireland. "A 

distinct variety confined to Lough Neagh." (J. D. H. ) 

74. Glyceria maritima (Willd. ), var. riparia (Towns. ). Hampshire. 

75. Poa Balfouri'(Bab. ). Scotland. " An alpine sub-variety of a variety 

of the protean P. nemoralis." (J. D. H. ) 

In his comments on this extensive list of supposed 
peculiar British jilants, Sir Josej^h Hooker arrives at the 
following conclusions : — 

1. There are four unquestionably distinct species which do not occur in 
continental Europe : viz. — 

One absolutely endemic species, Potamogeton lanceolatus. 

Three American species, Sisyiunchium angustifolium, Spiranthes 

ROMANZOVIANA, ErIOCA-ULON SEPTAXGrLARE. 

2. There are sixteen endemic varieties of British species, viz. — 
Eleven of more or less variable species, Caltha palustris, var. radicans ; 

Polygala vulgaris, var. grandiflora ; Cerastium arcticum, var. edmons- 
TONii ; Trifolium repens, var. Townsendii ; Rosa involuta, var. wilsoni ; 
Rulnis fruticosus, sitb-sp. longithyrsiger ; Campanula rotundifolia, var. 
8PECI0.SA ; Erythrffia centaurium, suh-sp. latifolia ; Carex involuta, 
(?Hyb. ); Carex vesicaria, var. Grahami ; Deyeuxia neglecta, var. 
Hookeri, 

Five of comparatively well limited species. Arabis peti-fea, var. grandi- 
FOLIA ; Helianthemum guttatum, var. Breweri ; Geranium sangiuneum, 
var. Lancastriexse ; .ffinanthe Phellandrium, var. fluviatilis ; 
Spartium stricta, var. Townsendi. 

The above twenty species are marked in the list with 
an asterisk. Of the remaining fifty-five, Sir Joseph 
Hooker says, " that for various reasons it would not be 
safe to rely on them as evidence. In most cases the 
varietal form is so very trifling a departure from the type 
that this may be safely set down to a local cause, and is 
probably not constant. In others the plant is doubtfully 
endemic ; in still others a hybrid." 

Even should it ultimately prove that of the whole 
number of the fifty-five doubtful forms none are established 
as peculiar British varieties, the number admitted after so 



364 ISLAND LIFE 



rigorous an examination is about what we sliould expect in 
comparison with the hmited amount of speciality we have 
seen to exist in other groups. The three American species 
which inhabit the extreme west and north-west of the 
British Isles, but are not found on the continent of Europe 
are especially interesting, because they demonstrate the 
existence of some iDeculiar conditions such as would help 
to explain the presence of the other peculiar species. 
Whether we suppose these American forms to have 
migrated from America to Europe before the glacial epoch, 
or to be the remnants of a vegetation once spread over the 
north, temperate zone, we can only explain their j^resence 
with us and not further east by something favourable 
either in our insular climate or in the limited competition 
due to our comparative poverty in species. 

About half of the peculiar forms are found in the 
extreme west or north of Britain or in Ireland, where 
peculiar insular conditions are at a maximum ; and tlie 
influence of these conditions is further shown by the 
number of species of West or South European plants which 
occur in the same districts. 

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 European 
species. The following list of these plants, for which I am 
indebted to Mr. A. G. More, with a few remarks on their 
distribution, will be found interesting : — 
List of Irish Floweking Plants which are xot found ix Britain. 

1. Poly gala vulgaris {var. grandiflora). Sligo. 

2. Campanula rotundifolia {var. speciosa). W. Ireland. 

3. Arciiaria ciliata. W. Ireland (also Auvergne, Pyrenees, Crete). 

4. Saxifraga umhrosa. W. Ireland (also Pyrenees, N. Spain, Portngal). 
f). ,, gcum. S. W. Ireland (also Pyrenees). 

6. ,, hirstcta. S. W. Ireland (also Pyrenees). 

7. Inula salicina. W. Ireland (Scandinavia, ]\Iiddle and South Europe). 

8. Erica mcditcrranea. W. Ireland (W. France, Spain, Portugal). 

9. ,, macTcaiana {t/ilndix snh.-s]).)\^. Ireland (Spain). 

10. Arbutus uncdo. S. W. Ireland (W. of France, Spain, Portugal and 

shores of JMediterranean). 

11. Dabcocia iJolifolia. W. Ireland (W. of France, Spain and Portugal). 



CHAP. XYi THE BRITISH ISLES 365 

12. Pinquicula grandiflora. S. AV. Ireland (Spain, Pp-enees, Alps of 

France and Switzerland). 

13. Neotinia intada. W. Ireland (S. France, Portugal, Spain, and 

shores of Mediterranean). 

14. Sinraiithcs romanzoviana. S. W. Ireland (North America). 

15. Sisyr inch ium aiigusti folium. W. Ireland (jS'orth America, Arctic and 

Temp. ). 

16. Potamoij'ton lonchiles. Ireland, Mr. Arthur Bennett informs me that 

this is certainly not British or European, hut may j)ossibly be 
identical with P. flidtans var. Americanus of the U. States. 

17. Potamogdon kirkii {natans sxih.-s^.). AV. Ireland. (Arctic Europe ?) 

18. Eriocauloii scptangulare. AA". Ireland, Skye, Hebrides (North 

America). 

19. Carex huxhaumii. N. E. Ireland, on an island in Lough ISTeagh (Arctic 

and Alpine Europe, North America). 

20. Deyeuxia neglcda {var. Hookeri). On the shores and islands of Lough 

Neagh. (And in Gennany, 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 con- 
tinental, 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 sub- 
sequent to the glacial epoch. The Arctic, Alpine, and 
American plants may all be examples of species which 
once had a wider range, and which, owing to the more 
favourable conditions, have continued to exist in Ireland 
while becoming extinct in the adjacent parts of Britain 
and Western Euroj)e. 

As contrasted with the extreme scarcity of peculiar 
species among the flowering plants, it is the more interesting 
and unexpected to find a considerable number of j^eculiar 
mosses and Hepatic^, some of which present us with phe- 
nomena of distribution of a very remarkable character. 
For tlie following lists and the information as to the dis- 
tribution of the genera and species I am indebted to Mr. 
William Mitten, one of the first authorities on these beau- 
tiful little plants. That of the mosses has been corrected 
for this edition by Dr. R. Braithwaite, and several species 
of hepaticae have been added by Mr. Mitten. 



366 ISLAND LIFE 



LisTOF THE Species of Mosses and Hepatic^ which are PEcrLiAR to 
THE British Isles (or not found in Europe). 

( Those belonging to non-European genera in Italics. ) 

Mosses. 

1 . Systegium Mittenii South England. 

2. Campylopns Sliawii Xortli Britain. 

3. , , setifolius Ireland, Wales, and Hebrides. 

4. Seligeria caicicola South England. 

5. Pottia A'iridifolia South England. 

6. Leptodontium recurvifolium . . . Ireland and Scotland. 

7. Tortula Hybernica Ireland. 

8. Htrcptopogon gcmmasccns Sussex. 

9. Brjrum barbatum Scotland. 

10. Bartramidula Wilsoni Ireland, Wales, and Scotland. 

11. Daltonia sjilachnoides Ireland, Antilles, and Mexico. 

12. Hookeria laetevirens Ireland, Cornwall, and Madeira. 

1 3. Hypnuni niicans Ireland. 

14. Myurium Hebridariuui Hebrides and Atlantic Islands. 

15. Hedwigia ciliata rrtr. striata ... Wales and Scotland. 



Hepatic^. 

1. Frullania germana Ireland. 

2. ,, Hutchinsite.. Ireland, Scotland, Wales, Devon, 

Tropical regions. 

3. Lejeunia flava Ireland, Atlantic Islands, S. America, 

Africa. &c. 

4. ,, microscopica Ireland, Wales, Cumberland, Madeira. 

5. ,, Holtii Ireland (Killarney). 

6. , , diversiloba Ireland ( Killarney), Mexico ? 

7. ,, patens Ireland. 

8. Radula tenax Ireland. 

9. ,, Holtii Ireland. 

10. :, voluta Ireland, Wales, Cumberland, Mexico? 

11. , , Carringtonii Ireland. 

1 2. Lepidozia Pearsoni Wales. 

13. Adilocolia decipiens Ireland, AVales, Africa, and S.America. 

1 4. Cejihalozia aeraria Wal es. 

15. Lophocolia sjiicata Ireland, Cornwall, Anglesea. 

1 6. Martinellia ninibosa Ireland ( Brandon ^Mountain ). 

1 7. Plagiochila spinulosa Wales, Ireland, and Scotland, Atlan- 

tic Islands. 

18. ,, ambagiosa Ireland, India. 

19. Jamesoniella Carringtonii Scotland. 

20. Gymnocolea Xevicensis Scotland. 

21 . Jungermannia Doniana Scotland. 

22. Cesia crenulata Ireland, Wales. 

23. Chasmatocolea cuneifolia Ireland. 

24. Aerobolbus Wilsoni Ireland, S. America, New Zealand, 

25. Petalopliyllum Ralfsii Ireland, Cornwall, Devon. 



CHAP. XVI THE BRITISH ISLES 367 

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 several of them are 
really confined to Britain. But there are a few — indicated 
by italics — which are in a very different category ; for 
they belong to genera which are altogether unknown in 
any other part of Europe, and their nearest allies are to be 
found in the tropics or in the southern hemisphere. The 
four non-Euro2Dean genera of mosses to which we refer 
all have their maximum of develoj^ment in the Andes, 
while the three non-European Hepatica? 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 : — 

Barteamidula. Asia, Africa, S. America and Australia, but not 
Europe or N. America. 

Stkeptopogox 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 
species in the Andes, two in Brazil, two in ISIexico, one in the Galapagos, 
six in India and Ceylon, five in Java, two in Africa, and three in the 
Antarctic Islands, and one in Ireland. 

HooKERiA (restricting that term 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 Antilles, one in 
Mexico, two in the Pacific Islands, one in Xew 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 distribu- 
tion, 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 
Hepaticae is as follows : — 

Chasmatocolia, South America and Ireland. 

AcEOBOLBUS. A small genus found only in New Zealand and the 
adjacent islands, besides Ireland. 



368 ISLAND LIFE 



Petalophyllum. a small genxis confined to Australia and New Zealand 
in the southern hemisphere, Algeria, and Ireland in the northern. We 
have 'also one of the Hepaticte — Mastigojiliora JVoodsii — found in Ireland 
and the Himalayas, but unknown in any part of continental Europe. 
The genus is most developed in New Zealand. 

These are certainly very interesting facts, but they are 
by no means so exceptional in this gTonp of plants as to 
throw any donbt upon their accuracy. The Atlantic islands 
present very similar phenomena in the B.liaiwphiclmm 
pmjmratum, 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 sjDecies except in this one mountain 
group ! ^ 

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 
Hepaticse are so minute tliat 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 special- 
isation 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 

^ I am indebted to Mr. Mitten for this curious fact. 



CHAP. XVI THE BRITISH ISLES 36^ 



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 geograph- 
ical 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 Avhere 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 

^ The foUowiug remarks by Dr. Richard Spruce, who has made a special 
study of mosses and especially of hepaticte, are of interest. ' ' From what 
precedes, I conclude that no existing agency is capable of transporting the 
germs of our hepatics of tropical type from the torrid zone to Britain, and 
I venture to suppose that their existence at Killarney dates from the remote 
period when the vegetation of the whole northern hemisphere partook of a 
trojjical character. If I am challenged to account for their survival 
through the last glacial period, I reply that, granting even the existence of 
a universal ice-cap down to the latitude of 40° in America and 50"' in Europe, 
it is not to be assumed that the whole extent, even of land, was perennially 
entombed ' in thrilling legions of thick-ribbed ice.' Towards the southern 
margin of the ice the climate was probably very similar to that of Greenland 
and the northern part of Xorway at the present day. The summer sun would 
have great power, and on the borders of sheltered fjords the frozen snow 
would disappear completely, if only for a very short period, and I ask only 
for a month or two, not doubting the capacity of our hepatics to survive in 
a dormant state under the snow for at least ten months in the year. I have 
gathered mosses in the Pyrenees where the snow had barely left them on 
August -^nd ; by September 25th they were re-covered with snow, and would 
not be again uncovered tiil the following year. The mosses of Killarney 
might even enjoy a longer summer than this ; for the gulf-stream laves botli 
sides of the south-western angle of Ireland, and its te])id waters would exert 
great melting power on the ice-bound coast, preventing at the same time 
any formation of ice in the sea itself" This passage is the conclusion of a 
very interesting discussion on the distribution of hepaticre in a paper on 
"A New Hepatic from Killarney," in the Journal of Botany, vol. 25, 
(Feb. 1887), pp. 33 — 82, in which many curious facts are given as to the 
habits and distribution of these curious and beautiful little plants. 

B B 



870 ISLAND LIFE part ir 

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 power, as we shall find Avhen 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 Ave 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 
adaptation 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 j^roblems in the distribution of j^lant life.^ 

Concluding Jxemeirks on the Peculiarities of the British 
Fauna and Flora. — The facts, now I believe for the first 
time brought together, respecting the peculiarities of the 
British fauna and flora, are sufficient to sliow that there is 
considerable scope for the study of geographical distribu- 
tion 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 tlie fact that the Irish species 

^ While these pages are passing tliiougli the jiress I am iulbniied li}' my 
Mend Mr. W. fl. Beeby that in the Shetland Isles, where he has been 
collecting lor live summers, he lias found sev'eral plants new to the British 
flora, and a few altogether iindescribed. Among these latter is a very 
distinct species of Hieracium {H. Zetland Icioii), which is (luite unknown 
in Scandinavia, and is almost certainly peculiar to the British Islands. 
Here we have another proof that entirely new species are still to be dis- 
covered in the remoter portions of our country. 



CHAK xvt THE BRITISH ISLES 371 



are almost all different from the British, and those of the 
Orkneys distinct from those of Scotland, renders it ahiiost 
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 Hepaticai 
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 discovered in Britain, and, sub- 
sequently, 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 never 
been f<jund on the continent. 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 wdiich has been so very thoroughly 
w^orked. Analogy, therefore, would lead us to conclude 
that many other species or varieties 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 some 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 is among insects, whicli 
are so excessively varied and abundant, which present so 
many isolated forms, and which, even on continents, afford 
numerous examj^les of very rare species confined to re- 
stricted areas, that we should have the best cliance of 
meeting Avith 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, especially 

B B 2 



372 ISLAND LIFK part ii 

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 proportion to the 
species of birds and fresh-water fishes, the number of 
insect-forms is enormously great, so that the numerous 
species or varieties 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 assump- 
tion, that all our insects do exist on the continent, and 
will some time or other be found there, as not in accordance 
either with the evidence or the probabilities of the case ; 
and when this is done, and the interesting peculiarities of 
some 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 
interestinof investia'ations into the British fauna and flora ? 



CHAPTER XVII 



BORNEO A X D 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. 

Tlie accompanying map shows that Borneo is 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 j^art 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 




It^aUcr iy Bourull SC. 
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. 



CHAP. XVII BORNEO AND JAVA 375 



Peninsula is about 350 miles, and it is nearly as far from 
Sumatra and Java, while it is more than 600 miles frona 
the Siamese Peninsula, opposite to which its long northern 
coast extends. There is, I believe, nowhere else upon 
the globe, an island so far 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 mountains 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, Baujarmassing, 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 iskmd 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 acquaint- 
ance 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 



376 ISLAND LIFE part ii 

the adjacent islands, and the series of geographical changes 
that seem required to explain them. 

Zoological Features of Borneo. 

Mammalia. — Nearly a hundred and forty species of 
mammalia have been discovered in Borneo, and of these 
more than three-fourths are identical with those of the 
surrounding countries, and more than one half with those 
of the continent. Among these are two lemurs, nine 
civets, five cats, five deer, the tapir, the elephant, the 
rhinoceros, and many 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 : — 





QUAPKUMANA. 


13. 


Sciurus whiteheads (Th. ) Kini 


1. 


Simia morio. A small orang- 




Balu. 




utan with large incisor teeth. 


14. 


, , everetti. 


2_ 


Hylobates mulleri. 


15. 


Rheithrosciurus macrotis. 


3. 


Kasalis larvatus. 


16. 


Hystrix crassispinis. 


4. 


Semnopithecus rubicimdus. 


17. 


Trichvs guentheri. 


5. 


,, chrysomelas. 


18. 


Mus iiifraluteus. (Th. )Kini Balu. 


6. 


, , frontatns. 


19. 


,, alticola. (Th.) Kini Balu. 


7. 


,, hosei. (Thomas.) 




IXSECTIYORA. 




Kini Balu. 


20. 


Tupaia splendidula. 




Carniyora. 


21. 


,, minor. 


8. 
9. 


Herpestes semitorquatus. 
Felis badia. 


22. 
23. 


, , dorsalis. 
Dendrogale murina. 

Chiroptera. 


0. 


UXGULATA. 

Sus barbatus. 


24. 
25. 


Vesperugo stenopterus. 
,, doriiB. 




RODENTIA. 


26. 


Cynopterus brachyotus. 


1. 


Pteromys plmeomelas. 


27. 


,, lucasii. 


2. 


Sciunis jentinki. (Th.) Kini 


28. 


, , spadiceus. 




Balu 


29. 


Hipposideros dorian. 



Of the twenty-nine peculiar species here enumerated 
it is possible tliat a few may 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 ; Rheithrosciurus, a peculiar form of squirrel ; and 
Trichys, a tailless porcupine. These peculiar forms do not, 
however, imply that the separation of the island from the con- 
tinent is of very ancient date, for the country is so vast and 



CHAP. XVII BORNEO AND JAYA 377 



SO much of the once connecting land is covered with water, 
that the amount of speciality is hardly, if at all, greater 
than occurs in many continental areas of equal extent and 
remoteness. 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 sej^arated from the continent by the 
submergence of the whole area north of them as far as the 
Himalayas, they would be found to contain quite as many 
peculiar genera and species as Borneo actually does now. 
A more decisive 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 tailed monkeys and 
the numerous squirrels. These relationships, however, are 
best seen among the birds, which have been more 
thoroughly collected and more carefully studied than the 
mammalia. 

Birds. — About 580 species of birds are now known to 
inhabit Borneo, of which 420 species are land-birds.^ One 
hundred and eight species are supposed to be peculiar to 
the island, and of these one half have been noted, either by 
Count Salvadori or Mr. Everett, as being either representa- 
tive species of, or closely allied to birds inhabiting other 
islands or countries. The majority of these are, as might 
be expected, allied to species inhabiting the surrounding 
countries, especiall}^ Sumatra, the Malay Peninsula, or Java, 
a smaller number having their representative forms in the 
Philippine Islands or Celebes. But there is another grou23 
of eight species whose nearest allies are found in such 
remote lands as Ceylon, North India, Burma, or China. 
These last have been indicated in the following list by a 
double star (**) while those which are representative of 
forms found in the immediately surrounding area, and are 
in many cases very slightly differentiated from their allies, 
are indicated by a single star (*). 

1 In the first edition of tliis work the numbers were 400 and 340, 
showing the great increase of our knowledge during tlie last ten years, 
chiefly owing to the researches of Mr. A. H. Everett in Sarawak and Mr. 
John Whitehead in North Borneo and the great mountain Kini Iialu. 



378 



ISLAND LIFE 



PART II 



List of Birds which are supposed to be peculiar to Borneo. 



32. 
33. 
34. 
35. 
3G. 



48. 
49. 



f.l. 
52. 

54. 

56. 



TuRDiD^ (Tlmishes). 

**Cettia oreophila. 7. *Cittocincla suavis. 

*Meriila seebohmi. 8. * ,, strieklandi. 

**Geociclila aiirata. 9. *Heiiioiirus bonieensis 

**Myioplioiieus bonieensis. 10. ^Phj'llergates ciiiereieollis. 

Brachypteryx erythrogyna. : 11. Bnrnesia superciliaris. 
Copsyclius niger. 

TiMELiiD^ (Babbling Thrushes). 



*GaiTulax schistochlamys. 
Ehinocichla treacheri. 
Allocotops calvus. 
**Stachyiis borneeiLsis. 
Cyanoclerma bicolor. 
Chlorocharis a^milia?. 
Antlropliihis accentor. 
Malacopterum cinereocapilhim 
**Staplii(lia everetti. 
^Herporius brunnescens. 

Brachypodid^ (Bulbiils) 



22. 
23. 

24. 
25. 
26. 
27. 

28. 



*Mixornis bonieensis, 
* ,, iiiontana. 
*Turdinus canicapillns. 

, , atriguhiris. 
*Dryniocataphus capistratoides. 
Ptilophaga rufiventris. 

,, leucogrammica. 

29. *Corythocichla crassa. 

30. *Tnrdinuhis exsiil. 

31. Orinthocichla whiteheadi. 



*Heniixns connectens 
Criniger diardi. 
* ,, ruticrissus. 
Tricophoropsis typus. 
Oreostictes k^icops. 



37. Rubigiila niontis. 

38. * ., paroticalis. 

39. Chloropsis kinabalnensis. 

40. * ., irridinncha. 



Oviolns cnnsobrimis. 



Panis sarawakensis. 



OkioLiDrE (Orioh\s). 

j 42. *Oriohis vulneratus. 
Parid^ (Tits). 

I 44. *Dendro}ihila corallipes. 
Laniidj. (Shrikes). 
Pityriasis gymnocephala. j 46. *H3'lott:'rpe liypoxantha 

Dii RURID.E (Drougo-shrikes). 
^Chibia bonieensis. j 

CampophaCtID/E (Caterpillar-catchers). 
riilamodyclia?ra jeffreyi. | 50. Pericrocotus cinereigula 

*Artami(les normani. ] 

MusciCAPiD^ (Flycatchers). 



**Heniichelidon cinereicey)S. 
*Rhinomyias gularis. 
* , , ruficrissa. 

Cryptolopha schwaneri. 

., niontis. 

*Stoparola eerviniventris. 



57. Siphia coeruleata, 

58. . , beccariana. 

59. ,, elopurensis. 

60. , , obscura. 

61. ,, everetti. 

62. ,, nigrogularis. 



Xectarineid^ (Sun-birds). 



63. Arachnothera julir 



CHAP. XVII BORNEO AND JAVA 379 



Dic.BiD^ (Flower-peckers). 



67. **Prionoeliilu.s everetti 

68. *Zosterop,s rlara. 



61. *Diceum inoiitieoluin. 

6.1. * ,, pryeri. 

6ii. *Prioiioo]iilu.s Xcantliopygins. 

Ploceidj^ (Weavers). 
69; C'hlorura bonieensis. | 70. Munia fnseans. 

CoRviD^ (Crows). 

71. *Denclrocitta cinerasceiis. I 73. *Platysminus aterrimus. 

72. C'issa jeffreyi. | 

PiTTiT).?; (Clrnund Thrushes). 

74. Pitta bertffi. | 77. *Pitta usheri. 

75. ,, arcuata. i 78. * ,, gi'anatina. 

76. ,, liaudi. I 79. * ,, schwaiieri. 

EuRYL^MiDiE (Gapers). 

80. Calyptomena whiteheadi. | 

Cypselid.e (Swifts). 

81. Cypselus lowi. | 

PoDARGiDiB (Frocrmouths). 

82. *Batrachostomns adspersus. | 

C'APRiMrLaiDiE (GoatsiHckers). 

83. Caprimulgus borneensis. | 84, Caprimulgus coneretus. 

PiciDiR (Woodpeckers). 

85. *Jvngipicus aurantiiventris. I 87. *Micropternus badiosus. 

86. ' ,, i.icatus. ] 88. Sasia everetti. 

Aloedixid^. (Kingfi.shers). 
89. *Pelargop?^iis leucof^ephala. | 90. *Carcineutes melanops. 

Ti;of;oxiD.E (Trogons). 

91. Harpactes wliiteheadi. | 

CrcrLiPJ^ (Cuckoos). 

92. *Rhopodyte.s borneensis. | 

Capitoxip.t: (Barbets). 

93. Cyanops pulcherrimus. I 95. *]\IegahTema chr^'sopsis. 

94. ,, monticulus. j 

BUBOXID^ (Owls). 
96. Heteroscops Incite. I 97. *Syrnium leptogrammienm. 

Fat.coxid^ (Hawks, &c. ). 

98. Spilornis pallidus. I 100. Microhierax latifrons. 

99. *Accipiter nigrotibialis. | 

PHAf=;iAXiDiE (Phea.sants). 

101. Polyplectron .schliermacheri. | 103. ' Argusianus grayi. 

102. Lobiophasis bukvori. | 104. *Euplocamus pyrronotus. 



380 ISLAND LIFE 



Tetraonid^ (Grouse, &c. ). 

105. BambusicoLa hyperytlira. I 107. Hsematortyx sangiiiniceps. 

106. ' ,, erythroplirys. | 

RALLiDiE (Rails). 
108. Rallina rufigenys. | 

Representative forms of the same character as those noted 
above are found in all extensive continental areas, but they 
are rarely so numerous. Thus, in Mr. Ehves' paper on the 
"Distribution 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 25 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 Pen- 
insula has one — Ainpeliceps, a remarkable yellow-crowned 
starling, with bare j^ink-coloured orbits ; while two others, 
Temnurus and Crypsirhina — singular birds allied to the 
jays — are found in no other part of the Asiatic contir.ent 
though they occur in some of the Malay Islands. Borneo 
has seven peculiar genera of passeres,^ as well as 
Hasmatortyx, a crested partridge; and Lobiophasis, a 
pheasant hardly distinct from Euplocamus ; while 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 sur- 
rounding countries are too imperfectly known to eniblo us 
to arrive at any accurate results with regard to their distri- 
bution. 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 less than one -fourth 
peculiar species of mammalia and fully one-fourth peculiar 
species of land-birds, teaches us that the possession of the 
power of flight affects but little the distribution of land- 

^ These are Allocotops, Chlorocliaris, Aii(lro])]iilus, and Ptilopyga. 
among the Timeliidie ; Tricophoropsis and Oreoctistes among the Brachy- 
podidre ; Chlamydochcera among the Campophagidce. 



CHAP. XVII RORXEO AND JAVA 381 



animals, 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 
if we consider the wide range of certain grouj)s of powerful 
flight — as the birds of prey, the swallows and swifts, the 
king-crows, and some others, we shall be forced to con- 
clude that the majority of forest-birds are restricted . by 
even narrow watery barriers, to an even greater extent 
than 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 the Missouri 
valley to California. In such an extent of country we 
always meet with some local species, and representative 
forms, so that we hardly require any great lapse of time as 
an element in the production of the peculiarities we actually 
find. 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 produce such a redistribution of the 
species, consequent on their mutual relations being dis- 
turbed, as would bring the islands into their present 
zoological condition. There are, however, other 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. 



382 ISLAND LIFE 



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 soiue 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, Ave 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 Ave encounter. 
But a more serious difficulty than this remains to be stated. 
Java has certain close resemblances to the Siamese Penin- 
sula, and also to the Himalayas, which Borneo and Sumatra 
do not exhibit to so great a proportionate extent ; and 
looking at the relative position of these lands respectively, 
this seemis 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. 

GcncrcU Cliaradcr 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 interest- 
ing island than Borneo or Sumatra. Its mammalia 
(ninety species) are nearly as numerous as those of Borneo, 
but are apparently less peculiar, none of the genera and 
only five or six of the sju^cies being confined to the island. 
In land-birds it is decidedly less rich, having only 800 
species, of which about forty-five are peculiar, and only one 

^ In a letter from Darwin liesa^-s : — " Hooker writes to me, ' Miguel lias 
been telling me that the flora of Sumatra and Borneo are identical, and 
that of Java quite diflerent. ' " 



CHAP. XVII BORXEO AXD JAVA 



or two belong to peculiar genera ; so that here again the 
amount of speciality is considerably less than in Borneo. 
It is only when we proceed to analyse the species of the 
Javan fauna, and trace their distribution and affinities, that 
we discover its interesting nature. 

Difference Betiveen the Fauna of Java, and that of the otlur 
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 following diiferences. 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 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 re- 
mained undiscovered in Java as the large mammalia above 
referred to. 

Besides these absent ffciura. there are some curious 
illustrations of Javan isolation in the species ; there being 
several cases in which the same sjiecies occurs in all three 
of the typical Malay countries, while in Java it is 
represented by an allied species. These occur chiefly 
among birds, there being no less than seven species which 
are common to the three great Malay countries but are re- 
presented in Java by distinct though closely allied species. 

From these facts it is impossible to doubt thnt Java has 
had a history of its own, quite distinct from that of the 
other portions of the Malayan area. 



384 ISLAND LIFE 



SiKcial Relations of the Javcin Fctunct to tlicit of the Asiatic 
Gooitinent. — 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 Lc-ptis kurgosa, are natives of Indo-Chinese countries 
and Java, but not of typical Malaya. In birds there are 
five genera or sub-genera — Zoothera, Notodela, Crypsirhina, 
Allotrius, and Cochoa, which inhabit Java, the Himalayas, 
and Indo-China, all but the last extending south to 
Tenasserim, but none of them occurring in Malacca, 
Sumatra, or Borneo. There are also two species of birds 
— a trogon {Harpaetes oreshios), and the Javanese peacock 
{Pavo nmticus), which inhabit only Java and the Indo- 
Chinese countries, the former reaching Tenasserim and the 
latter Perak in the Malay Peninsula. 

Here, then, we find a series of remarkable similarities 
between Java and the Asiatic continent, quite independent 
of the tyj)ical Malay countries — Borneo, Sumatra, and the 
Malay Peninsula, which latter have evidently formed one 
connected land, and thus appear to preclude any in- 
dependent union of Java and Siam. 

The great difficulty in ex]3laining 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 have, as we have seen, a 
great similarity 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, since its 
species, when not Malayan, are almost all North 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 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 con- 



OHAr. XVII BOR]N'EO AND JAVA 385 

ditions, Avith the migrations and crowding together that 
must have been their necessary consequence. But in the 
lowlands, near the equator, these changes would be very 
little if at all 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 ami 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 i^roducts of their 
eruptions. 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 excej)t a few boulders of 
granite in the western part of the island, perhaps the relics 
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 as 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 hemisphere, during the 
severest part of which a few Himalayan species of birds 
and mammals may have been driven southward, and 

1 "On tlie Geology of Sumatra," by M, R. D. M. Verbeck. Geological 
Magazine, 1877. 

C C 



386 ISLAND LIFE ^art it 

have ranged over suitable portions of the whole area. Java 
then became separated by subsidence, and these species were 
imj^risoned in the island ; 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 ada]3ted to the tyj^ical 
Malayan fauna which is there developed in rich profusion. 
A little later the subsidence may have extended farther 
north, isolating Borneo and Sumatra, in which a few other 
Indian or Indo-Chinese forms have been retained, but jorob- 
ably 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 subsi- 
dence 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, Avhile the intervening island (Banca) 
possesses a distinct form.^ 

In my Geographical Disirihutioii 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, explan- 
ation above given. The amount of the relationship 
between Java and Siam, as well as of that between Java 
and the Himalayas, is too small to be well accounted for 
by an independent geographical connection in which 
Borneo and Sumatra did not take part. It is, at the same 
time, too distinct and indisputable to be ignored ; and a 
change of climate which should drive a portion of the 
Himalayan fauna southward, leaving a few species in Java 
and Borneo from which they could not return owing to the 
subsequent isolation of those islands by subsidence, seems 

^ Pitta megarhy^icMts {Banca) allied to P. hrachyurus (Borneo, Sumatra, 
Malacca) ; and Pitta hangkanus (Banca) allied to P. sordidus (Borneo and 
Sumatra). 



CHAP. XVII THE PHILIPPINES 387 

to be a cause exactly adapted to produce the kind 
and amount of affinity between these distant countries 
that actually exists. 

The Philippine Islands. 

A general account of the fauna of these islands, and of 
their biological relations to the countries Avhich form the 
subject of this chapter, has been given in my Gcogra'phical 
Distribution of Animals, Vol. I. pp. 345-349 ; but since 
the publication of that work considerable additions have 
been made to their fauna, having the effect of somewhat 
diminishing their isolation from the other islands. Four 
genera have been added to the terrestrial mammalia — Croci- 
dura, Felis, Pteromys, and Mus, as well as two additional 
squirrels ; while the black ape {Cynciyithecus niger) has 
been struck out as not inhabiting the Philippines. This 
brings the true land mammalia to twenty-one species, of 
which fourteen are peculiar to the islands ; but to these we 
must add no less than thirty-three species of bats of which 
only ten are peculiar.^ In these estimates the Palawan 

'^ The following list of the mammalia of the Philippines and the Sulu 
Islands has been kindly furnished me by Mr. Everett. 

QuADRUMANA. 19. Crociduraedwardsiana. Peculiar 

1. Macacus cvnoraolgus. species. 

2. Tarsius spectrum. -0- Dendrogale sp. 

p.„^„,„„, 21. Galeopithecus philippinensis. Peculiar 

OARNivoRA. species. 

3. Viverra taugalunga. Ptttroptfra 

4. Paradoxurus philippinensis. Also in i^hiroptera. 

Palawan. --• Pteropus leucopterus. 

5. Felis bengalensis. In Negi-os Island. 23. ,, edulis. 

Ungulata. 24. „ hypomelanus. 

2o. ,, jubatus. 

6. Bubalusmindorensis. Peculiar species. 26. Xantharpyia amplexicaule. 

7. Cervus philippinus. Peculiar species. 27. Cvnopterus marginatus. 

S. „ alfredi. Peculiar species. 28. " ,, jagorii. Peculiar species 

9. ,, nigricans. Peculiar species. 29. Carponycteris australis. 

10. „ pseudaxis. Sulu only. Prob- 30. Rhi-.iol6phus luctus. 

ably introduced. 31. ^^ philippinensis. Peculiar 

11. Sus marchesi. Peculiar species. species. 

Rodentia. 32. Rhiuolophus rufus. Peculiar species. 

12. Sciurus philippinensis. Peculiar f- Hipposideros diaderaa. 



species. 

13. Sciurus cagos. Peculiar species. „. ^.^l^^'^^??' , . 

14. „ concinnus. Peculiar. Min- ^o. Hipposideros larvatus._ 
danao and Basilan. 



36. ,, obscurus. Peculiar 



15. Plilaeomys cummingi. Peculiar genus „ ^r-^^"'^'^^?? ' 



Hipposideros coronatus. Peculiar 



16. Mus ephippium. 

17. ,j everetti. Peculiar species. „„ --..^P'^^^??- , . , 

" ^ ^ 38. Hipposideros bicolor. 

Insectivora. 39^ Megaderma spasma. 

18. Crocidura luzoniensis. Peculiar 40. Vesperugo pachj-pus. 

species. 41. ,, tenuis. 



c c 2 



ISLAHD LIFE 



PART II 



group has been omitted as these islands contain so many 
Bornean species, that if inckided they obscure the special 
features of the fauna. 

Birds. — The late Marquis of Tweeddale made 
a special study of Philippine birds, and in 1878 pub- 
lished a catalogue in the Transactions of the Zoological 
Society (Vol. IX. Pt. 2, pp. 125-247). But since that date 
large collections have been made by Everett, Steere, and 
other travellers, the result of which has been to more than 
double the known species, and to render the ornithological 
fauna an exceedingly rich one. Many of the Malayan 
genera which were thought to be absent when the first 
edition of this work was published have since been dis- 
covered, among which are Phyllornis, Criniger, Diceum, 
Prionochilus, and Batrachostomus. But there still remain 
a large number of highly characteristic Malayan genera 
whose absence gives a distinctive feature to the Philippine 
bird fauna. Among these are Tiga and Meiglyptes, 
genera of woodpeckers ; Phsenicophaes and Centropus, re- 
markable cuckoos ; the long-tailed paroquets, Palseornis ; 
all the genera of Barbets except Xantholsema ; the small 
but beautiful family Euryla^midae ; many genera allied to 
Timalia and Ixos ; the mynahs, Gracula ; the long-tailed 
flycatchers, Tchitrea; the fire-backed pheasants, Euploca- 
mus ; the argus pheasants, the jungle-fowl, and many others. 

The following tabular statement will illustrate the rapid 
growth of our knowledge of the birds of the Philippines : — 



Lord Tweeddale's Catalogue (1873) 

]\rr. Wardlaw Ramsay's List (1881) 

Mr. Everett's MSS. List of Additions (1891) 



Land-birds. 



158 
265 
370 



Water-birdi- 



60 

75 

102 



Total. 



218 
340 

472 



The number of peculiar species is very large, there being 
about 300 land and forty-two water birds, which are not 



42. Vesperugo abramus. 

43. Nycticejus kulilii. 

44. Vespertilio macrotarsiis. 

species. 

45. Vespertilio capaccinii. 

46. Harpiocephaliis cyclotis. 

47. Kerivoula hardwickii. 



48. Kerivoula pellucida. Peculiar species. 

49. ,, jagorii. Peculiar species. 
Peculiar 50. Miniopterus sclireibersii. 

•^'1- » ti-istis. Peculiar species, 

52. Emballonura monticola. 

53. Taphyzous melanopogon. 

54. Nyctinomus plicatus. 



CHAP. XVII THE PHILIPPINES. 389 



known to occur beyond the group. We have here, still more 
pronounced than in the case of Borneo, the remarkable 
fact of the true land birds presenting a larger amount of 
speciality than the land mammals ; for while more than 
four- fifths of the birds are peculiar, only a little more 
than half the mammals are so, and if we exclude the bats 
only two-thirds. 

The general character of the fauna of this group of 
islands is evidently the result of their physical conditions 
and geological history. The Philippines are almost sur- 
rounded by deep sea, but are connected Avith Borneo by 
means of two narrow submarine banks, on the northern of 
which is situated Palawan, and on the southern the Sulu 
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 exten- 
sion of Asia, but that they were separated considerably 
earlier than Java ; and having been since greatly isolated 
and much broken uj) by volcanic disturbances, their species 
have for the most part become modified into distinct local 
forms, representative species often occurring in the different 
islands of the group. 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. Their 
comparative poverty in genera and species of the mammalia 
is perhaps due to the fact that they have been subjected 
to a great amount of submersion in recent times, greatly 
reducing their area and causing the extinction of a con- 
siderable 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 explora- 
tions in the islands, that almost everywhere are found large 
tracts of elevated coral-reefs, containing shells similar to 
those living in the adjacent seas, an indisputable proof of 
recent elevation. 

Concluding Renmrks on the Malay Islands. — This com- 
pletes 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 



390 ISLAND LIFE part ii 

sufficieDtly well explained by a very simple and com- 
paratively unimjDortant series of geographical changes, com- 
bined 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 conti- 
nent, 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 tjq^es, the PhilijDpines were first separ- 
ated ; then at a considerably 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 Philippines, 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. 



CHAPTER XVIII 

JAPAX 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. 

The 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 connected 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 inter- 
vening space the Sea of Japan opens out to a width of 
six hundred miles, and in its central portion is very deep, 




MAP OF JAPAN AND FORMOSA (witll depths ill fatliOllls). 

Litjht tint, sea under 100 fathoms. Medium tint, under 1,000 fathoms. Dark tint, over 
1.000 fathoms. The figures show the depth in lathoms. 



CHAP. XVIII JAPAN AND FORMOSA 393 

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 
Yesso it is about 200. The island of Saghalien, however, 
separated from Yesso by a strait only twenty-five miles 
wide, forms a connection Avith 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 Jcvjian. — 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 
sjDecific individuality ; while it also possesses some remark- 
able isolated groups. Its fauna presents indications of there 
having been two or more lines of migTation 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 jDresent 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 Avild 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 comjDlete account of Japan 
mammals has been given by any competent zoologist since 
the publication of Von Siebold's Fauna Ja/ponica in 1844^, 



394 ISLAND LIFE paet ii 



but by collecting together most of the scattered observa- 
tions- smce 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 remem- 
bered 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 sjKciosus. A monkey with rnclimentary tail and red face, 

allied to the Barbary ape. It inhabits the island of Xiphon np to 
41° N. Lat., and has thus the most northern range of any living 
monkey, 

2. Ptcrojyus clasymallus. 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 R. 
nijjj^on of the Fauna Japonica according to Mr. Dobson's Monogra2)h 
of Asiatic Bats. 

4. R. minor. Found also in Burma, Yunan, Java, Borneo, &c. 
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. Talpa mizura. Glinth. Allied to T. u-ogura. 

13. Urotrichus talpoides. A peculiar genus of moles confined to Japan. 

An American species has been named Urotriclmis gihsii, and 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." But Dr. Giinther (P. Z. S. 1880, p. 441) states 
that U. qihsii differs so much in dentition from the Japanese species 
that it should be placed in a distinct genus, which he calls Neuro- 
trichus. 

14. Sorex myosurus. A shrew, found also in India and ]\Ialaya. 

15. Sorex dzi-nezumi. 

16. S. umhriniLS. 

17. S. platyccphalus. 



CHAP. XVIII JAPAN AND FORMOSA 395 

18. Ursus arctos. var. A peculiar variety of the European brown bear 

which inhabits also Anioorland and Kamschatka. It is the Ursus 
frrox of the Fauna Japonica. 

19. Ursus japonicus. A peculiar species allied to the Himalayan and For- 

mosan species. Named U. tihctanus in the Fauna Japonica. 

20. Meles anakuma. Differs from the European and Siberian badggrs in 

the form of the skull. 

21. Mustela hrachyura. A peculiar martin found also in the Kurile 

Islands. 

22. Mustela melanopus. The Japanese sable. 

23. M. Japonica. A peculiar martin (See Proc. Zool. Soc. 1865, p. 104). 

24. M. Sibericus. Also Siberia and China. This is the M. italsi of the 

Fauna Japonica according to Dr. Gray. 

25. Lutronedeswhitclcyi. A new genus and species of otter {P. Z. S. 1867, 

p. 180). In the Fauna Japonica named Lutra vulgaris. 

26. Enhydris marina. The sea-otter of California and Kamschatka. 

27. Canis liochphxilax. According to Dr. Gray allied to Cuon samatranus 

of the Malay Islands, and C. alpinns of Siberia, if not identical with 
one of them {P. Z. S. 1868, p. 500). 

28. Vulpcs japonica. A peculiar fox. C«/ii5 ritZjoes of Fauna Japonica. 

29. Nyctereutes procyonoides. The racoon-dog of N. China and Amoor- 

land. 

30. Lepus hrachyurus. A peculiar hare. 

31. Sciurus lis. A peculiar squirrel. 

32. Ptcromys lcucogc7iys. The white-cheeked flying squirrel. 

33. P. momoga. Perhaps identical with a Cambojan species {P. Z. S. 

1861, 1). 137). 

34. Myoxus ja2)onictLS. A peculiar dormouse. M. clegans of the Fauna 

Japonica ; M. javanicus, Schinz {Synopsis Mammalium, ii. p. 530). 

35. Mus argenteus. China. 

36. Mus molossinus. 

37. M. nezumi. 

38. JA spcciosiis. 

39. Ccrvits sika. A peculiar deer allied to C. pscudaxis of Formosa and 

C. mantcMiricus of Northern China, 

40. Ncmorhcclus crispa. A goat-like antelope allied to N. sumatranus of 

Sumatra, and A'. SwinJwri of Formosa. 

41. Sus leucomystax. A wild boar allied to ,S'. tacvanus of Formosa, 

We thus find that no less than twenty-six out of the 
forty-one Japanese mammals are peculiar, and if we omit 
the aerial 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 superficially resembling but quite 
distinct from an American species; a peculiar genus of 
otters ; and an antelope whose nearest allies are in 
Formosa and Sumatra. The importance of these facts will 



396 ISLAND LIFE part ii 

be best understood when we have exammed the corre- 
sjoonding affinities of the birds of Jaj^an. 

Birds. — Owing to the recent researches of some English 
residents 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 200, which is less than might be expected 
considering the highly favourable conditions of mild climate, 
luxuriant vegetation, and abundance of insect-life, 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 seventeen species, or about one-twelfth of 
the whole, are now considered to be peculiar to Japan 
projDer ; while seventeen more are peculiar to the various 
outlying small islands constituting the Benin and Loo Choo 
groups. Even of these, six or seven are classed by Mr. See- 
bohm as probably sub-species or slightly modified forms of 
continental birds, so that ten 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 of land-birds 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 land-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 "-lobe : — 

Land Birds Common to Great Britain and Japan. ^ 
{Eitlicr Identical Species or Reijresentative sub-species.) 

1 . Goldcrest Regulus cristatus sub-sp. orientalis. 

2. JMarsli tit Parus i^lustris sub-sp. japonicus. 

3. Coal tit Parus atcr sub-sp. pekinensis. 

4. Long-tailed tit Acredula caudata (the sub-sp. rosea is 

British). 

^ Extracted from Messrs. Blakistou and Fryer's Catalogue of Birds of 
Japan {Ibis, 1878, p. 209), with Mr. Seebohm's additions and corrections 
in his Bi7rls of tJic Jajjanese Empire 1890. Accidental stragglers are not 
reckoned as British birds. 



CHAP, xviii JAPAN AND FORMOSA 397 

5 . Common creeper Gerthia familiar is. 

6. Nuthatch Siita curopcea siib-sp. amurcnsls. 

7 . Carrion crow Corvus corone. 

8. Nutcracker Niccifraga earyoeatades. 

9 . Magpie Pica caudata. 

10. Pallass' grey shrike Laniios excitbitor snh-s]}. viajo?'. 

11. Waxwing Ampclis garrulas. 

12. Grey wagtail Motacilla hoarula sub-sp, mclanopc. 

13. Alpine Pipit Anthus spinolctta sub-sp. japonicus. 

14. Skylark A lauda arvoisis sub-sp. japonica. 

15. Common hawfincli Coccothraustes tmlgaris. 

16. Common Crossbill Loxia carvirostra. 

17. Siskin Fringilla spinus. 

18. Mealy redpolo , , ' linaria. 

19. Brambling ,, montifringilla. 

20. Tree sparrow Passer montanus. 

21. Reed bunting Emheriza schccniculus sub. sp. p)ctlustris^ 

22. Rustic bunting ,, rustica. 

23. Snow bunting , , nivalis. 

24. Chimney swallow Hirundo rustica ayxh-n]). gittturalis. 

25. Sand martin Cotyle riparia. 

26. Great spotted woodpecker Picus major sub-sp. japonicus. 

27. Lesser spotted woodpecker , , minor. 

28. Wryneck Jynx torquilla. 

29. Hoopoe TJpupa epops. 

30. Blue rock pigeon Golumha lima. 

31. Cuckoo Cucuiiis canorits. 

32. Kingfisher Alcedo is2nda sub-S'p. be7igale7isis. 

33. Eagle owl Bubo maximus. 

34. Snowy owl Surnia nyctea. 

35. Long-eared owl Strix otus. 

36. Short-eared owl , , brachyotus. 

37. Scops owl Scops scojjs. 

38. Jer falcon Falco gyrfalco. 

39. Peregrine falcon ,, peregrinus. 

40. Hobby ,, subbiUeo. 

41. Merlin Falco ccsalon. 

42. Kestrel Tinnunculus alaudarius sub-sp. japonicus. 

43. Osprey Pandion halidctus. 

44. Honey-buzzard Pernis apivorus. 

45. White-tailed eagle Halidctus albicilla. 

46. Golden eagle Aquila cJirysdetus. 

47. Common buzzard Buteo vulgaris sub-sp. plumipcs. 

48. Hen-harrier Circus cyaneus. 

49. Marsh-harrier ,, ceruginosus. 

50. Gos-hawk Astur palumharius. 

51. Sparrow-hawk Acciinter nisus. 

52. Ptarmigan Tctrao mutus. 

53. Common quail Coturnix communis. 

But even these fifty-three species by no means fairly 
represent the amount of resemblance between Britain and 



398 ISLAND LIFE 



Japan as regards birds ; for there are also thrushes, robins, 
stonechats, wrens, hedge-sparrows, sedge -warblers, jays, 
starlings, swifts, goatsuckers, and some others, which, 
though distinct sjjccics from our own, have the same 
general apjDearance, 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 Himalaj^an rather than 
Chinese, and thus afford us an interesting problem in 
distribution. 

The seventeen species and sub-species which are 
altogether peculiar to Japan proper, 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 {Trcroii 
sicholcU) — has no close ally nearer than Burmah and the 
Himalayas. In tbe following list the affinities of the species 
are indicated wherever they have been ascertained : — 

List of the Species of Land Birds peculiar to Japan. 

1. Accentor riibidus. Nearlj^ allied to our hedge-sparrow, and less closely 

to the Central Asian A. immaculatus. 
(la. Ky'psi'pctcs amaurotis. IMigrates to the Corea, otherwise peculiar. ) 

2. Zosterops japonica. Allied to two Chinese species. 

3. Lusciniola pryei^i. 

4. Garrulus japonicus. Allied to the Siberian and British Jays. 

5. Fringilla Jcaivarahiha. Allied to the Chinese greenfinch. 

6. Emhcriza ciopsis. Allied to the E. Siberian bunting E. cioides, of which 

it may be considered a sub-species. 

7. Emhcriza yessoensis. A distinct species. 

8. ,, personata. A snh-'ij^ecies oi E. s2)odoeephala. 

9. Gccinus aiookcra. A distinct species of green woodpecker. 

10. Picus namiyci. Allied to a Formosan species. 

11. Trcron sicholdi. Allied to T. sphenura of the Himalayas, and to a 

Formosan species. 

12. Garpophaga iaiithina, A distinct species of fruit-pigeon. 

13. Bubo blakistoni. Allied to a Philippine eagle-owl. 

14. Scops semitorgucs. A distinct species. 

15. Phasianus versicolor. A distinct species. 

16. ,, siemmcringi. A distinct species. 

17. ,, scintillaus. A sub-species of the last. 

The large number of seventeen peculiar species in the out- 
lying Bonin and Loo Choo Islands is an interesting feature 
of Japanese ornithology. The comparative remoteness of 



CHAP. XVIII JAPAN AND FORMOSA 399 

these islands, their mild sub-tropical climate and luxuriant 
vegetation, and perhaps the absence of violent storms and 
their being situated out of the line of continental 
migration, seem to be the conditions that have favoured 
the specialisation of modified types adaj^ted to the new 
environment. 

Japan Birds Recurring in Distant Areas. — The most 
interesting feature in the ornithology of Jaj^an is, un- 
doubtedly, the presence of several species which indicate 
an alliance with such remote districts as the Himalayas, 
the Malay Islands, and Europe. Among the peculiar 
species, the most remarkable of this class are, — the fruit- 
pigeon of the genus Treron, entirely unknown in China, 
but reappearing in Formosa and JajDan ; the HyjDsipetes, 
whose nearest ally is in South China at a distance of 
nearly 500 miles; and the jay (Garrnhtsj'ajyonicus), whose 
near ally (G. glandarius) inhabits Europe only, at a 
distance of 3,700 miles. But even more extraordinary are 
the following non-peculiar species : — Sinzactus oricntalis, a 
crested eagle, inhabiting the Himalayas, Formosa, and 
Japan, but unknown in Southern or Eastern China ; Cerylc 
guttata, a spotted kingfisher, almost confined to the 
Himalayas and Japan, though occurring rarely in Central 
China ; 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 Avhich islands afford 
both for species which elsewhere live further south 
(Halcyon coromanda), 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. Referring to 
our account of the birth, growth, and death of a species (in 
Chapter IV.) it can hardly be doubted that the Cerylc 
guttata formerly ranged from the Himalayas to Japan, and 
has now almost 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. 



400 ISLAND LIFE 



The other orders of animals are not yet sufficiently- 
known to enable us to found any accurate conclusions upon 
theni. The main facts of their distribution have already 
been given in my Gcografpliical Bistrihntion of Animals 
(Vol I., pf). 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 sjDecies. Owing to the comparatively easy passage 
from the northern extremity of Japan through the island 
of Saghalien to the mainland 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 j)roportion of specific difference in . 
their case is a good indication of the comparatively remote 
epoch at which Japan was finally separated from the 
continent. How long ago this separation 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. 

FOEMOSA. 

Among recent continental islands there is probably none 
that surpasses in interest and instructiveness the Chinese 
island named by the Portuguese, Formosa, or " The 
Beautiful." Till quite recently it was a terra incognita to 
naturalists, and we owe almost all our jDresent 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 know- 
ledge 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. SAvinhoe's 
own exertions during the twenty years of his service in 



CHAP. XVIII JAPAN AND FORMOSA 101 



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 verte- 
brates 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 pro- 
ductions, 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 
392) 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 

^ 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. S., 1870, p. 615), and his Catalogue of the Birds of China and its 
Islands (P. Z. S., 1871, p. 337). 

D D 



402 ISLAND LIFE 



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 jDart of the continent or adjacent islands. This 
proportion of peculiar species is perhajDS (as regards the 
birds) the highest to be met with in any island which can 
be classed as both continental and recent, and this, in all 
probability, implies that the epoch of separation is some- 
what 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 
carnivora ; pigs, deer, antelopes, and cattle among 
ungulata ; numerous rodents, and the edentate Manis, — 
a very fair representation of Asiatic mammals, all being 
of known genera, and of species either absolutely identical 
with some still living elsewhere or very closely allied to 
them. The birds exhibit analogous i^henomena, with the 
exception that we have here two peculiar and very inter- 
esting genera. 

But besides the amount of specific and generic modifica- 
tion 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 distribution 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 and peculiar birds of the island, as 
we shall have frequent occasion 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 M. 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. Vesper ugo abramus. China. 

4. A^'espertilio formosus. Black and orange Bat, China. 

f). Nyctinomus cestonii. Large-eared Bat. China, S. Europe. 
0. Talpa insularis. A blind mole of a peculiar species. 



CHAP. XVIII JAPAN AND FORMOSA 403 

7. Sorex niuriiiiis. ^Musk Rat. China. 

8. Sorex sp. A slirew, undescribed. 

9. Erinacens sp. A Hedgehog, undescribed. 

10. Ursus tibetanus. The Tibetan Bear. Himalayas and North China. 

11. Hclictis suhaurantiaca. The orange-tinted Tree Civet. Allied to ^. 

nipcdensis of the Himalayas more than to H. moschata of China. 

12. ^I^i-rtes flavigiila, var. The yellow-necked Marten. India, China. 

13. Felis macroscelis. The clouded Tiger of Siam and Malaya. 

14. Felis viverrina. The Asiatic wild Cat. Himalayas and Malacca. 

15. Felis chinensis. The Chinese Tiger Cat. China. 

16. Viverricuia malaccensis. Sjiotted Civet, China, India. 

17. Paguma larvata. Gem-faced Civet. China. 

18. Sus taivanus. Allied to the wild Pig of Japan. 

19. Cervulus reevesii. Reeve's Muntjac. China. 

20. Cervus x>seudaxis. Formosan Spotted Deer. Allied to C. sika of 

Japan. 

21. Cervus stcinhoii. Swinhoe's Rusa Deer. Allied to Indian and IMalayan 

species. 

22. Ncmoi'hcdus sicinhoii. Swinhoe's Goat-antelope. Allied to the species 

of Sumatra and Japan. 

23. Bos chinensis. South China wild Cow. 

24. JMus bandicota. The Bandicoot Rat. Perhaps introduced from India. 

25. Mus indicus. Indian Rat. 

26. 3Ius coxinga. Spinous Country-rat. 

27. Mies canna. Silken Country-rat. 

28. Mus losca. Brown Country-rat. 

29. Sciurus castaneoventris. Chestnut-bellied Squirrel. China and 

Hainan. 
30: Sciurus m'clellandi. M'Clelland's Squirrel. Himalayas, China. 

31. Sciurojjtcrits kalccnsis. Small Formosan Flying Squirrel, Allied to 

S. alhonigcr of Nepal. 

32. Pteromys grandis. Large Red Flying Squirrel, Allied to Himalayan 

and Bornean species. From North Formosa. 

33. Pteromys iKctoralis. White-breasted Flying Squirrel. 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 {Hclictis s^ibcturantiaca) , and the small flying 
squirrel {Scmroijterus kalccnsis), 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 squirrels ; while the friiit-bat, the wild pig 

D D 2 



404 ISLAND LIFE 



and the spotted deer are all allied to peculiar Japanese 
species. The clouded tiger is a Malay . species unkno^vn 
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 mainland 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 Philip- 
pines on the south ; and that after that event occurred, 
the conditions were so materially changed as to lead to 
the extinction of these species in what are now the coast 
provinces of China, while they or their modified descend- 
ants continued to exist in the dense forests of the 
Himalayas and the Malay Islands, and in such detached 
islands as Formosa and Japan. We will now see what 
additional light is thrown upon this subject by an exam- 
ination of the birds. 

List of the Land Birds peculiar to Formosa. 

TuRDiD^ (Thruslies). 

1. Tardus albicejjs. Allied to Cliinese species. 

Sylvidi^ (Warblers). 

2. Cisticola volitans. Allied to C. schcenicola of India and China, 

3. Herhivox cantam. Sub-species of H. cantillaus of N. China and 

Japan. 

4. Notodela montium. Allied to N. leucura of the Himalayas ; no ally in 

China. 

TiMALiiD^ (Babblers). 

5. Pomatorhinus musims. Allies in S. China and the Himalayas. 

6. P. erythrociicmis. Do, do. 

7. Garridax ruficcys. Allied to G. alhogularis of N. India and East 

Thibet, not to the species of S. China ( G. sannio). 

8. Janthocindct 2)cecilorhyncha. Allied to J. ccerulata of the Himalayas. 

Xone of the genus in China. 

9. Trochalopteron taivanus. AUied to a Chinese species. 

10. Alcippe morrisoniana. \ Near the Himalayan A. n.palensis. None of 

11. A. hrunnca. ] the genus in China. 

12. Sibia aurieiularis. Allied to the Himalayan *S'. capistrata. The genus 

not known in China. 

PANURiDiE (Bearded Tits, &c). 

13. Sufhora hulomacTius. Allied to the Chinese S. suffusa. 

CiNCLiD^ (Dippers and "Whistling Thrushes). 

14. 3fyio2:)ho7icus iiisiclaris. Allied to 31. horsfieldi of South India. 



CHAP. XVIII JAPAN" AND FORMOSA 405 

Paeid^ (Tits). 
15. Parus inspcratus. Sub-species of P. monticola of the Himalayas and 

East Thibet. 
IC. P. castaneivcntris. Allied to P. varms of Japan. 

LiOTRiCHiD^ (Hill Tits). 
17.. Liocichla stccrii. A peculiar genus of a specially Himalayan family, 
quite unknown in China. 

Pycnonotid^ (Bulbuls). 

18. Pycnonotus {Spizixos) cinercicapillus. Very near P. sremitorques of 

China. 

19. Bypsipetcs nigerrimus. Allied to H. concolor of Assam, not to H. 

macclellandi of China. 

Opjolid^ (Orioles). 

20. Analcipus ardens. Allied to A. traillii of the Himalayas and Tenas- 

serim. 

Campephagid^ (Caterpillar Shrikes). 

21. Graucalus rex-pincti. Closely allied to the Indian Cr. macei. No ally 

in China. 

DiCRURiD^ (King Crows). 

22. Chaptia hrauniana. Closely allied to C. ccnea of Assam. No ally in 

China. 

MusciCAPiD^ (Flj'catchers). 

23. Cyornis vivida. Allied to 0. rubeculoides of India. 

CoRViD^ (Jays and Crows). 

24. Garrulus taivanus. Allied to G. sinensis of S. China. 

25. Urocissa cosrulea. A very distinct species from its Indian and Chinese 

allies. 

26. Dendrocitta formosce. A sub-species of the Chinese D. sinensis. 

Ploceid^ (Weaver Finches), 

27. Munia formosana. Allied to M. ruhronigra of India and Burmah. 

Alaudid^ (Larks). 

28. Alauda sala. 



29, A. icattersi. S ^^^'^^ '"^ ^""''^^ ^^'''^• 

PiTTiD^ (Pittas). 

30, Pitta oreas. Allied to P. cyanoptcra of Malaya and S. China. 

PiciD^ (Woodpeckers). 

31, Picus insular is. Allied to P. fc?ico7io^w.9 of Japan and Siberia. 

Megal^mid^, 

32, Megalomia nuclialis. Allied to M. oortii of Sumatra and M. Jaber of 

Hainan, No allies in China, 

Caprimulgid^ (Goatsuckers). 

33, Caprimulqus stictomus. A sub-species of C. monticolus of India and 

China. 



406 ISLAND LIFE 



CoLUMBiD^ (Pigeons). 

34, T,reron formosoc: Allied to Malayan species. 

35, Sphenoccrcus sororius. Allied to J\lalay species and to S. sieholdi of 

Japan. No allies of these two birds inhabit China. 

36, Chalcophcqjs formosana. Allied to the Indian species which extends 

to Tenasserim and Hainan, 

TETRAONiDiE (Gi'ouse and Partridges). 

37. Oreoperdix crudigularis. A peculiar genus of partridges, 

38, Bambusieola sonorivox. Allied to the Chinese B. thoracica. 

39. Arcoturnix rostrata. Allied to the Chinese A. hlaJcistonii. 

Ph ASIAN ID J3 (Pheasants). 

40. Phasiamis formosanus. Allied to P. torquatiLS of China. 

41. Euplocamus sicinhoii. A very peculiar and beautiful species allied to 

the tropical fire-backed pheasants, and to the silver pheasant of 
North China, 

Strigid^e (Owls), 

42, Athene pardalota. Closely aUied to a Chinese species. 

43. Leriipigius liamhroeMi. Allied to a Chinese species. 

This list exhibits to us the marvellous fact that more 
than half the peculiar species of Formosau 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 Qmficcps) not allied to the 
species found in South China, but to one inhabiting North 
India and East Thibet ; while the black bulbul {Hyi:)si'petes 
nigerrwnis), 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 rather than Chinese, so that they offer examples 
of discontinuous distribution somewhat analogous to wdiat 



CHAP. XVIII JAPAN AND FORMOSA 407 

we found to occur in Japan. These are enumerated in 
the following list. 

Species of Birds common to Formosa and India or Malaya, but not 
FOUND IN China. 

1. SijjMa supercilmris. The Rufous -breasted Flycatcher of the S.E. 

Himalayas. 

2. Halcyon coromanda. The Great Red Kingfisher of India, ]\Ialaya, and 

Japan. 

3. Pahimhus 2ndchricollis. The Darjeeling Wood-pigeon of the S.E. 

Himalayas. 

4. Turnix dussumicri. The larger Button-quail of India. 

5. Spizaetus nipalcnsis. The Spotted Hawk-eagle of Nepal and Assam. 

6. Lophospiza trivirgata. The Crested Gos-hawk of the Malay Islands. 

7. Bulaca ncwarensis. The Brown Wood-owl of the Himalayas. 

8. Strix Candida. The Grass-owl of India and Malaya. 

The most interesting of the above are the pigeon and 
the flycatcher, both of which are, so far as yet known, 
strictly confined to the Himalayan mountains and Formosa. 
They thus afford examples of discontinuous specific 
distribution exactly parallel to that of the great sjiotted 
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, Avhile two others 
are identical. We also find four species whose nearest 
allies are in the Himalayas. Our knowledge 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 it seems probable that it was separated from the 
continent at, approximately, the same epoch as Formosa 
and Japan, and that the special features of each of these 
islands are 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 



408 ISLAND LIFE 



have enabled it to preserve an unusual number of Hima- 
layan and Malayan forms. Japan, almost equally isolated 
towards tlie south, and having a much greater variety of 
climate as well as a much larger area, possesses about an 
equal number of mammalia with Formosa, and an even 
larger proportion of peculiar species. Its birds, however, 
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 population 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 njost so in the present state of our 
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 accord- 
ingly 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 



^ Captain Blakistoii lias shown that the northern island — Yezo — is much 
more temperate and less peculiar in its zoology than the central and southern 
islands. This is no doubt deijendent cliiefly on the considerable change of 
climate that occurs on passing the Tsu-garu strait. 



CHAP, xviri JAPAN" AND FORMOSA 409 

species die out and are replaced by others, which quite 
agrees with what the theory of evohition 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 sjDecies comes into 
contact with such adverse conditions or competing forms 
as prevent it from advancing further. A very slight change 
Avill 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 haj^pen (and almost certainly has some- 
times 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. 65-68.) But the same thing has certainly 
occurred in a considerable number of cases, only it has 
resulted in the divided areas being occupied by representa- 
tive 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 
considerable number of s]3ecies, and we may be sure that 
were it not for the constant intermino^lino^ and inter- 
crossmg of the individuals inhabiting adjacent localities 
this tendency to local variation in adaptation to slightly 
different conditions, w^ould soon form distinct races. But 
as soon as the area is divided into two portions the inter- 
crossing is stojDped, 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 seerreo-ated into distinct races 



410 ISLAND LIFE 



Now, when the division of the a,rea 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 seen, highly characteristic of island- 
faunas. But islands also favour the occasional preservation 
of the unchanged species — a phenomenon 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 con- 
tinental portion, by the force of that competition, is driven 
back to some remote mountain area, where it also obtains 
a comparative freedom 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 con- 
tinental 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- 
detined species and even distinct genera, afford an over- 
whelming mass of evidence in favour of the theory of 
" descent with modification." 

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 joeculiarities, and ofier some most 
curious problems to the student of distribution. 



CHAPTER XIX 

ANCIENT CONTINENTAL ISLANDS : THE MADAGASCAR GROUP 

Remarks on Ancient Continental Islands — Physical Features of Madagascar 
— Biological Features of ]\Iadagascar- — Mammalia — Reptiles — Relation 
of j\Iadagascar to Africa — Early History of Africa and Madagascar — 
Anomalies of Distribution and How to Exjjlain Them — The Birds of 
Madagascar as Indicating a Supposed Lemm-ian Continent — Submerged 
Islands between ]\Iadagascar and India — Concluding Remarks on 
" Lemuria " — The Mascarene Islands — The Comoro Islands — The Sey- 
chelles Archipelago — Birds of the Seychelles — Reptiles and Amphibia — 
Freshwater Fishes — Land Shells — ]\Iauritius, Bourbon, and Rodriguez — 
Birds — Extinct Birds and their Probable Origin — Reptiles — Flora of 
Madagascar and the ]\Iascarene Islands — Curious Relations of Mascarene 
Plants — Endemic Genera of j^lauritius and Seychelles — Fragmentary 
Character of the JMascarene Flora — Flora of Madagascar Allied to that 
of South Africa — Preponderance of Ferns in the Mascarene Flora — Con- 
cluding Remarks on the Madagascar Group. 

We have now to consider the phenomena presented by a 
very distmct 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 
recard of a by-gone world, — of a period when many of the 
higher types had not yet come into existence and when 
tlie 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 



412 ISLAND LIFE PART It 

extinction of some of the tyj^es that were originally 
preserved, 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 immigra- 
tions 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 
perfection, is Madagascar, and Ave shall therefore enter 
somewhat fully into its biological and physical history. 

Phijsical Features of Madagascar. — This great island is 
situated about 250 miles from the east coast of Africa, and 
extends from 12° to 25 J° S. Lat. It is almost exactly 
1,000 miles long, with an extreme width of 860 and an 
average width of more than 260 miles. A lofty granitic 
plateau, from eighty to 160 miles wide and from 8,000 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 j)lains 
are more or less wooded ; and there is here also a con- 
tinuous 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. 



414 ISLAND LIFE part ii 



The sea around Madagascar, when the shallow bank on 
whiqh 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 it is much broader, and stretches 
out oj)posite Mozambique to a distance of about eighty 
miles. The Mozambique Channel is rather more than 
1,000 fathoms deep, but there is only a narrow belt of this 
depth opposite Mozambique, and still narrower where the 
Comoro Islands and adjacent shoals seem to form 
stepping-stones to the continent of Africa. The 1,000- 
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 separat- 
ing 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 
farther north is the Seychelles group, also standing on an 
extensive 1,000-fathom bank, while all round 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 east- 
ward across the Indian Ocean Ave find the Chagos and 
Maldive coral atolls, perhaps 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 
submerged islands, as shown in our map at p. 424, are of 
great imjiortance in exjilaining 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 considerably 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 



416 ISLAND LIFE 



a quarter of a mile to three or four miles. This seems 
to indicate recent subsidence ; while we have no record 
of raised coral rocks inland which would certainly mark 
any recent elevation, though fringing coral reefs surround 
a considerable portion of the northern, eastern, and south- 
western coasts. We may therefore conclude that during 
Tertiary times the island was usually as large as, and often 
probably much larger than, it is now. 

Biological Features of Madagasear. — Madagascar possesses 
an exceedingly rich and beautiful fauna and flora, rivalling 
in some groups most trojDical 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 cha- 
racter of these animals is very extraordinary and altogether 
different from the assemblage now found in Africa or in 
any other existing continent. Africa is now most promi- 
nently characterised by its monkeys, apes, and baboons; 
by its lions, leopards, and hyaenas ; by its zebras, rhino- 
ceroses, 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 



CHAP. XIX THE MADAGASCAR GROUP 417 

still exists scattered over a wide area; but they are 
noAvhere so abundant as in the island of Madagascar. 
They are found from West Africa to India, Ceylon, and 
the Malay Archii^elago, consisting of a number of isolated 
genera and species, which appear to maintain their 
existence by their nocturnal and arboreal habits, and by 
haunting dense forests. It can hardly be said that the 
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 comi3act 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, 
Centetidse, 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 seekino; for the orio'inal home of the Madasfascar fauna. 

We then come to the Carnivora, which are represented 
by a peculiar cat-like animal, Cryptoprocta, forming a 
distinct family, and having no close 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 Kodents 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 PotamocliDerus, 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-connec- 

1 See Dr. J. E. Gray's "Revision of the Viverridre," in Proc. Zool. Soe. 
1864, p. 507. 

- Some of the Bats of Madagascar and East Africa are said to have their 
nearest allies in Australia. (See Dobson in Nature, Vol. XXX. p. 575.) 

K E 



418 ISLAND LIFE 



tion, let us see what indications are afforded by the 
reptiles. The large and universally distributed family 
of Colubrine snakes is represented in Madagascar, not by 
African or Asiatic genera, bat by two American genera 
— Philodryas and Heterodon, and by Herpetodryas, a 
genus found in America and China. The other genera 
are all peculiar, and belong mostly to widespread tropical 
families; but two families — Lycodontida^ and Viperida?, 
both abundant in Africa and the Eastern tropics — are 
absent. Lizards are mostly represented by peculiar genera 
of African or tropical families, but several African genera 
are represented by peculiar species, and there are also 
some species belonging to two American genera of the 
Iguanidas, a family which is exclusively American ; while 
a genus of geckoes, inhabiting America and Australia, also 
occurs in Madagascar. 

Relation of Madagascar to 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 Madagascar. 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 or Pliocene age in France, 
Germany, Greece, and North-west India, have demon- 
strated the fact that all the g^reat African mammals then 
inhabited Europe and temperate Asia. We also know 
that a little earlier (in 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 Aus- 
tralia is now, and probably, like it, very j)oor 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 



CHAP. XIX THE MADAGASCAR GROUP 419 



in the latter portion of the Miocene or early in the 
Pliocene period.^ 

It is clear, therefore, that if Madagascar had once formed 
part of Africa, but had been separated from it before 
Africa was united to Europe 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 therefore fairly assume that all the 
more important groups of birds, reptiles, and insects, now 
abundant in Africa but absent from Madagascar, formed no 
jDart of the original African fauna, but entered the country 
only after it was joined to Europe and Asia. 

Early 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 mamm.als at all 

^ This view was, I believe, first advanced by Professor Huxley iu 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 
located in the South African and Indian provinces of Arctogtea. N"o'\\' 
there is 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 Xorth Asia during the Middle and Upper Eocene 
epochs. Hence it becomes highly probable that the well-known similari- 
ties, and no less remarkable differences, between the present faunas of 
India and South Africa have arisen in some such fashion as the following : 
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 extend- 
ing from Abyssinia to the mouth of the Ganges, By this means the 
Dekkan on the one hand and South Africa on tlfe other, became connected 
with the J^Iiocene dry land and with one another. The Miocene mammals 
spread gi-adually over this intermediate dry land ; and if the condition ol 
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 GeorjrapMcal Distribution of 
Anrnials (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 prioi- 
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, 

E E 2 



420 ISLAND LIFE 



Now these ancient African mammals are Lemurs, Insecti- 
vora,.and small Carnivora, chiefly Yiverrid^ ; 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 joroved by the fact that 
even the insectivorous Centetidse, now confined to Mada- 
gascar and the West Indies, inhabited France in the Lower 
Miocene period, while the Viverridse, or civets, which form 
so important a part of the fauna of Madagascar as well as 
of Africa, were abundant in Europe throughout the whole 
Tertiary 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 IV., p. 60), that all ex- 
tensive groups have a wade range at the period of their 
maximum development ; but as they decay their area of 
distribution diminishes or breaks up into detached frag- 
ments, 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 Ex2:)lain Them. — If 
these considerations have any weight, it follows that there 
is no reason whatever for supposing any former direct 
connection between Madagascar and the Greater Antilles 
merely because the insectivorous Centetid^e 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 account 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 ancestral tapir of 
one country might have passed over to the other. In both 



CHAP. XIX THE MADAGASCAR GROUP 421 



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 possible, that from the North American con- 
tinent as a centre the camel tribe spread westward, over 
now-submerged land at the shallow Behring Straits and 
Kamschatka Sea, into Asia, and southward along the 
Andes into South America. Tapirs are even more inter- 
esting and instructive. Their remotest known ancestors 
appear in Western Europe in the early portion of the 
Eocene period ; in the latter 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 much 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 Eastern continent, where they 
were once so abundant, they have dwindled down to a 
single species, existing in small numbers in the Malay 
Peninsula, Simiatra, and Borneo only; while in the 
Western continent, Avhere they are comparatively recent 
immigrants, they occupy a much larger area, and are re- 
presented by three or four distinct species. Who could 
possibly have imagined such migTations, 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 discover among such groups as 
reptiles, birds, and insects, where we rarely have any direct 
evidence of their past migrations through the discovery of 



422 ISLAND LIFE 



fossil remains. Whenever Ave 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 tlie jDermanence of our oceans. Yet 
so easy 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 
excejDtional facilities both for terrestrial, aerial, and oceanic 
transport, and of whose distribution in early geological 
periods we generally know little or nothing. 

The Birds of Madagascar, as Indicating a Sup^^osed 
Lcmnrian Continent. — Having thus shown how the distri- 
bution of the land mammalia and reptiles of Madagascar 
may be well explained by the supposition of a union with 
Africa before the gi'eater 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 and fifty land birds known 
from the island of Madagascar, of which a hundred and 
twenty-seven are 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, 

^ The total number of JMadagascar birds is 238, of which 129 are 



CHAP. XIX THE MADAGASCAR GROUP 423 



belonging to known genera, we find fifteen which have 
undoubted 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 t3^pes that Dr. Hartlaub, 
in his recent work on the BiQxh 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, horn- 
bills, and bustards — besides a host of peculiar African 
genera — as sufficiently disproving the statement in my 
Geogra]j]iiccd Distrilmtion of Animals that Madao-ascar is 
" more nearly related to the Ethiopian than to any other 
region," and that its fauna was evidently " mainly derived 
from Africa." 

But the absence of the numerous peculiar groujDS 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 Hypsipetes, with 
a Dicrurus, a Ploceus, a Cisticola, and a Scops, all closely 
allied to Indian or Malayan species — although very strikino- 
to the ornithologist, they certainly do not outweigh the 
fourteen African genera found in Madagascar. Their 
presence may, moreover, be accounted for more satisfac- 
torily than by means of an ancient Lemurian continent, 
which, even if granted, would not explain the very facts 
adduced in its suj^port. 

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 

absolutely peculiar to the islaud, as are thirty-five of the genera. All the 
peculiar birds but two are land birds. These are the numbers given in M. 
Grandidier's great work on Madagascar. 



424 ISLAND LIFE 



become partially or wholly submerged before they reached 
those, countries ; otherwise we should find in Madagascar 
many other animals besides Lemurs, Insectivora, and 
Yiverridse, especially such active arboreal creatures as 
monkeys and squirrels, such hardy grazers as deer or an- 
telopes, or such wide-ranging carnivores as foxes or bears. 
This obliges us to date the disappearance of the hypotheti- 
cal 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 presence Dr. Hartlaub upholds the theory of a 
Lemuria, are slightly modified forms of existing Indian 
genera, or sometimes, as Dr. Hartlaub himself points out, 
species hardly distingiiishahle 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 
early Miocene period, they must have had a widely differ- 
ent distribution from what they have now. Along with so 
many African and Indian genera of mammals they then 
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 Lemui'ia had ceased to exist, and could 
not have been the means of their introduction. 

Submerged Islands hetweeii 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 usually 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 Madagascar itself. 
These reefs are all separated from each other by very deep 



CHAP, XIX 



THE MADAGASCAR GROUP 



425 



sea — much deeper than that which divides Madagascar 
from Africa, and we have therefore no reason to imagine 
tl: eir former union. But they would nevertheless greatly 
facilitate the introduction of Indian birds into the Mas- 
carene Islands and Madagascar ; and these facilities existing, 
such an immigration 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, 



gO| 30| 40| 50l 60| 70! 80| 




MAP OF THE INDIAN OCEAN. 

Sliowiug the position of banks less than 1,000 fathoms deep between Africa and the 
Indian Peninsula. 



and as Australian birds reach such a distant island as New 
Zealand. This would take place the more certainly because 
the Indian Ocean is 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. 



426 ISLAND LIFE 



The final disappearance of these now sunken islands 
does, not, in all, probability, date back to a very remote 
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 j)roves 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 s^eoloo^ical times no land-connection in this 
direction was necessary to explain the phenomena of the 
distribution of the Lemurs and Insectivora. A land-con- 
nection with some continent was undoubtedly necessary, 
or there would have been no mammalia at all in Mada- 
gascar ; 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 " Lcmnria." — I have gone into 
this question in some detail, because Dr. Hartlaub's 
criticism on my 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 absolutely 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 Lemuridse.^ I 

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 by a continent, "and remained 
so connected with some short intervals from the Permian up to the end of 
the ]\Iiocene 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 



CHAP. XIX THE MADAGASCAR GROUP 427 



think I have now sliown, on the other hand, that it was 
essentially a provisional hypothesis, very useful in calling 
attention to a remarkable series of problems in geographical 
distribution, but not affording the true solution of those 
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 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 fifteen 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 
weakness and inutility. I have therefore here explained 
my reason«3 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 
modem science. 

that a similarity iu 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. 

^ Gcogra2)hical Distribution of Animals, Vol. I., pp. 272 — 292. 



428 ISLAND LIFE 



The Mascarene Islands} — In the Geographical Distri- 
hution of Animals, a summary is given of all that was 
known of the zoology of the various islands near 
Madagascar, which to some extent partake of its peculiari- 
ties, 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 23roblems by 
means of the most suitable examj)les, I shall now confine 
myself to pointing out how far the facts presented by these 
outlying islands* su23port the views already enunciated with 
resjard to the oris^in of the Madao-ascar fauna. 

O O o 

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 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. 
Anyhow, there is no indication whatever of there having 
been here a land-connection between Madagascar and 
Africa ; while the islands themselves have been mainly 
colonised from Madagascar, some of them making a near ap- 
proach to the 100-fathom bank which surrounds that island. 

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 {Pterojms como7''ensis), a group which ranges from 
Australia to Asia and Madagascar but is unknown in 
Africa. Of land-birds forty-one species are known, of 

^ The term " Mascarene " is used here in an extended sense, to include 
all the islands near ]\Iadagascar ^Yhich resemble it in their animal and 
vegetable productions. 



CHAP. XIX THE MADAGASCAR GROUP 429 



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. A species of 
Chameleon is also peculiar to the islands. 

These facts point to the conclusion that tlie 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 are of granite, with 
mountains rising to 3,000 feet in Mahe, 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 points 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 favourably situated as regards the extensive Saya 
de Malha and Cargados banks, which were probably once 

^ For the birds of the Comoro IsLancIs see Proc. Zool. Soc, 1877, p. 295, 
and 1879, p. 673. 



430 ISLAND LIFE paet ii 



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 non-aerial 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 Africa. The genera which are more 
peculiarly Indian are, — Copsychus and Hypsipetes, also 
found in Madagascar ; and Pal?eornis, which has species in 
Mauritius and Rodriguez, as well as one on the continent 
of Africa. A black parrot (Coracopsis), congeneric with 
two species that inhabit Madagascar and with one that is 
peculiar to the Comoros ; and a beautiful red-headed blue 
pigeon (Aledorcvnas loitkherrimus) 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, 
indicating clearly that the islands can hardly be classed as 
oceanic. There are seven species of lizards, three being 
peculiar to the islands, while the others have rather a 
wide range. The first is a chameleon — defenceless slow- 

^ The following is a list of these peculiar birds. (See the Ibis, for 1867.. 
p. 359 ;audl879, p. 97.) 

PaSSERES. PSITTACI. 

Ellisia seychellensis. Coracopsis barklyi. 

Copsychus seychellaru m. PalcBorivs wardi. 
Hypsixietes crassirostris. CoLrsiB^. 

Tchitrca cor villa. Alectormnas pvlcherrimrts 

Nectarinia dussuviifri. Turtur rostraius. 
Zostcropsmodcsia Accipitres. 

,, semifiava. 

Foudia sevcheUarinn. Tinmmcuhts gracilis. 



CHAP. XIX THE MADAGASCAR GROUP 431 



moving lizards, especially abundant in Madagascar, from 
which no less than eighteen species are now known, 
about the same number as on the continent of Africa. 
The Seychelles species {Chamceleoii tigris) also occurs at 
Zanzibar. The next are skinks (Scincidse), small gTound- 
lizairds with a wide distribution in the Eastern hemi- 
sphere. Two species are however peculiar to the islands 
— Mctbuia seycJiellensis and 31. lurigJitii. The other 
peculiar species is one of the geckoes (Geckotidjs) named 
JEluronyx seycJiellensis, and thei'e are also three other 
geckoes, Phelsitmct madagascarensis, Gehyra mutilata and 
Hcriiidaetylus frenatus, the two latter having a wide 
distribution in the tropical regions of both hemispheres. 
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 j^robable, 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 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, either directly or indirectly, 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, Dromieus seycJiellensis, is a peculiar species 
of the family Colubridae, the rest of the genus being found 
in Madagascar and South America. The other, Boodon 
geomctriens, one of the Lycodontid^, or fanged ground- 
snakes, is also joeculiar. So far, then, as the reptiles are 



432 ISLAND LIFE 



concerned, there is nothing but what is easily explicable 
by Ayhat 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 mascarenicnsis, found also in 
Mauritius, Bourbon, Angola, and Abyssinia, and probably 
all over tropical Africa ; and Mcgalixalus seyclicllensis a 
peculiar tree-frog having allies in Madagascar and tropical 
Africa. It is found, Dr. Wright informs me, on the 
Pandani or screw-pines ; and as these form a very 
characteristic 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 Csecilia. 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, burrow- 
ing 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 true lungs, 
and this peculiar metamorphosis shows that they belong to 
the amphibia rather than to the reptiles. The Csecilias 
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 there appear to be three species of these 
singular animals. Gryi^to'pso])lii8 omdiiiilicatus is confined 
to the islands; Ilcrpeh squalostoma is found also in 
Western India and in Africa ; while Hyi^ogcoi^his rodratus 
inhabits both West Africa and South America.^ This 
last is certainly one of the most remarkable cases of 
the wide and discontinuous distribution of a species ; and 

^ Specimens are recorded from West Africa in the Proceedings of the 
Academy of Natural Science, Philadelphia, 1857, p. 72, while specimens 



CHAP. XIX THE MADAGASCAR GROUP 433 



when we consider the habits of life of these animals and 
the extreme slowness with which it is likely they can 
migrate into new areas, we can hardly arrive at any other 
conclusion than that this species once had an almost 
Avorld-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 extreme stability and long 
persistence of specific form which this implies is extra- 
ordinary, but not unprecedented, among the lower verte- 
brates. The crocodiles of the Eocene period differ but 
slightly from those of the present day, while a small fresh- 
water turtle from the Pliocene deposits of the Siwalik 
Hills is absolutely identical with a still living Indian 
species, Emys tectus. The mud-fish of Australia, Corttochcs 
forsteri is a very ancient type, and may well have remained 
specifically unchanged since early Tertiary times. It is 
not, therefore, incredible that this Seychelles Csecilia may 
be the oldest land vertebrate now living on the globe ; 
dating back to the earl}^ part of the Tertiary period, when 
the warm climate of the northern hemisphere in high 
latitudes and the union of the Asiatic and American con- 
tinents allowed of the migration of such types over the 
whole northern hemisphere, from which they subsequently 
passed into the southern hemisphere, maintaining them- 
selves only in certain limited areas, Avhere the physical 
conditions were especially favourable, or where they were 
saved from the attacks of enemies or the competition of 
higher forms. 

Fresh-icater Fishes. — The only other vertebrates in the 
Seychelles are two fresh-water fishes abounding in the 
streams and rivulets. One, Haplochilus i^layfairii 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. Gilnther, often inhabit 
both sea and fresh water, so that their migration from 

in the Paris Museum were brought by D'Orbigny from S. America. Dr. 
AVright's specimens from the Seychelles liave, as he informs me, been 
determined to be the same species by Dr. Peters of Berlin. 

F F 



434 ISLAND LIFE tart ii 

Madagascar to tlie Seychelles and subsequent modification, 
offers no difficulty. The other species is Fnndulus 
ortlionohts, found also on the east coast of Africa ; and as 
both belong to the same family — Cyprinodontidae — 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 
completeness, 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, AcJiaiina fulicct — 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, Cyatho- 
ponea, Onchidium, Helicina and Paludomus, are mentioned 
as being especially Indian, while only two — Tropidophora 
and Gibbus, are found in Madagascar but not in India.^ 
About two-thirds of the species appear to be peculiar to 
the islands. 

Mauritius, Bourhon and Eodrigucz. — These three islands 
are somewliat 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 or amphibia. Yet their productions 
are so closely related to those of Madagascar, to which they 
may be considered as attendant 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 Mada- 

^ "Additional Notes on the Land-sliells of the Seychelles Islands." By 
Geoffrey Nevill, C.M.Z.S. Proc. ZooJ. Soc. 1869, p. 61. 



CHAP. XIX THE MADAGASCAR GROUP 435 



gascar, and this view is strongly supj)orted 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 a long time greatly 
neglected, and owing to the rapid spread of sugar cultiva- 
tion, 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 
animals.^ 

The smaller and more remote island, Rodriguez, is also 
volcanic ; but it has, besides a good deal of coralline rock, 
an indication of partial submergence helping to account 
for the j^overty of its fauna and flora. It stands on a 100- 
fathom bank of considerable extent, but beyond this the 

^ lu ]\Iciillartl's Notes sur VIslc dc lleiiniou, a cousiderable number of 
mammalia are given as "wild," such as Lemur viongoz and Ccntelcs sctosus 
Loth 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 certainl}^ imported, as are most probably the frogs. Legouat, who 
resided some years in the island nearly two centuries ago, and who was 
a closer observer of nature, mentions numerous birds, large bats, land- 
tortoises, and lizards, but no other reptiles or venomous animals except 
scorpions. AVe 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. Hemidaclylusfrenatus. 

,, ocellatus. Gonrjylus hojirii. 

Hemidactylus pcronii. AMepharus peronii. 

,, mutilatus. 

Four species of chameleon are now recorded from Bourbon and one from 
]\Iauritius (J. Reay Greene, M.D., in Pop. Science Rex. April, 1880), but 
as they are not mentioned by the old writers, it is pretty certain that these 
creatures are recent introductions, and this is the more probable as they 
are favourite domestic pets. 

Danvin informed me that in a work entitled Voyage a VIslc de France, 
-par un Ojpcier cholloi, published in 1770, it is stated that a fresh-water fish 
had been introduced from Batavia and had multiplied. The writer also 
says (p. 170) : " Ona essay e, mais sans sticcts. d'y transporter dcs grcnouilles 
qui mangent Ics ceicfs que les moustigues deposcnt sur les eaux stagnantcs." 
It thus appears that there were then no frogs on the island. 

F F 2 



436 ISLAND LIFE 



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 j^eculiar species of Mascarene 
types, together with two peculiar genera — Oxynotus 
belonging to the Campephagida3 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 diTiculty, looking at the position of the 
islands and of the surrounding shoals and islets. 

Extinct Birds. — These three islands are, however, pre- 
eminently remarkable as having been 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, Didida?, allied to 
the pigeons but very isolated. They were quite defenceless, 
and were rapid-ly exterminated when man introduced dogs, 
pigs, and cats into the island, and himself sought them for 
food. The fact that such perfectly unprotected 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 ances- 
tral ground-feeding pigeon of large size to have reached 
the group by means of intervening islands afterwards 
submerged, and to have thenceforth remained to increase 
and multiply unchecked by the attacks of any more power- 



CHAJ'. XIX THE MADAGASCAR GROUP m 



ful animals, we can well understand that the wings, being 
useless, would in time become almost aborted.^ It is also 
not improbable 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 preserved from such dangers, and perhaps also from 
the attacks of birds of prey v/hich 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 dejDended on comiDlete isolation and on free- 
dom from the attacks of enemies. We have no single 
example of such defenceless birds having ever existed on a 
continent at any geological period, Avhereas analogous 
though totally distinct forms do exist in New Zealand, where 
enemies are equally wanting. On the other hand, every 
continent 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 

^ That the dodo is really an abortion from a more perfect type, and not a 
direct development from some lower form of wingless bird, is shovrn by its 
jjossessing a keeled sternum, though the keel is exceedingly reduced, being 
only three-c^uarters of an inch deep in a length of seven inches. The most 
terrestrial pigeon — the Didunculus of the Samoan Islands, has a far deejier 
and better developed keel, showing that in the case of the dodo the degrada- 
tion has been extreme. "VVe have also analogous examples in other extinct 
bii'ds of the same group of islands, such as the flightless Rails — Aphanap- 
teryx of ]\Iauritius and Erythromachus of Rodriguez, as well as the 
large parrot — Lopliopsittacus of jMauritius, and the Night Heron, 
Nydicorax 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 
]\Ir. Edward Xewton 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 Xewton's article on 
"Fossil Birds" in the Enc^iclopmdia BrUcmnica, ninth eilition, vol. iii., 
p. 732 ; and that on "The Extinct Birds of Rodriguez," by Dr. A. Giinther 
ancl ]\Ir. E. Xewtou, in the Royal Society's volume on the Transit of Venus 
Expedition. 



438 ISLAND LIFE part ii 

these islands bave never formed part of a continent 
(iuri^g any portion of the time when the dodos inhabited 
them. 

It is a remarkable thing that an ornithologist of Dr. 
Hartlaub's reputation, looking at the subject from a purely 
ornithological 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 eastward 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."^ 
It is 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 
^pyornis, which were no doubt as well able to protect 
themselves against the smaller carnivora as are the 
ostriches, emus, and cassowaries 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. 

Beidtiles. — 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 Bound Island, only about a 
mile across, and 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 

1 See Ibis, 1877, p. 334. 

- A common Indian and Malayan toad {Bufo nielanostidus) lias been 
introduced into Mauritius and also some European toads, as I am informed 
by Dr. Giinther. 



CHAP. XIX THE MADAGASCAR GEOUP 439 



altogether confined to this minute islet ! It belongs to 
the boa family, and forms a peculiar and very distinct 
g(3nus, Casaria, whose nearest allies seem to be the Ungalia 
of Cuba and Bolyeria 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 
inhabited 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, how- 
ever, 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, Scclotes 
hojeri, recorded also from Mauritius and Bourbon, though 
it appears to be rare in both islands ; but a gecko, Fhclsuma 
guenthcri, is restricted to the island. As Round Island is 
connected with Mauritius by a bank under a hundred 
fathoms below the surface, it has probably been once 
joined to it, and when first separated w^ould have been 
both much larger and much nearer the main island, 
circumstances which would greatly facilitate the trans- 
mission of these reptiles to their 23resent dwelling-place, 
where they have been able to maintain themselves owing 
to thecomjDlete absence of competition, while some of them 
have become extinct in the larger island. 

Flora of Madagascar and the Mascarcnc 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 23eculiarities 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 remark- 
able speciality, and its anomalous 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 afiinities the latter preponderates. But there 
are also, as in the animal world, some decided South 



440 ISLAND LIFE 



American relations, while other groups point to Australia, 
or ar.e altogether isolated. 

No less than 3,740 flowering plants are now known from 
Madagascar with 360 ferns and fern-allies. The most 
abundant natural orders are the following : 

Species. Species. 

Leguminospe 346 Cyperacese 160 

Ferns 318 Kubiaceee 147 

Compositre 281 Acanthaceoe ......'. 131 

Euphorbiacese 228 Graminete 130 

Orchidese 170 

The flora contains representatives of 144 natural orders 
and 970 genera, one of the former and 148 of the latter 
being peculiar to the island. The peculiar order, 
Ch^elnacese, comprises seven genera and twenty-four 
species ; while Rubiaceae and Compositor have the largest 
number of peculiar genera, followed by Leguminosse and 
Melastomacese. Nearly three-fourths of the species are 
endemic. 

Beautiful flowers are not conspicuous in the flora of 
Madagascar, though it contains several magnificent 
flowering plants. A shrub with the dreadful name 
Harpagoijliytum Grandidieri has bunches of gorgeous 
red flowers ; Tridellatcia madagascariensis is a climbing 
plant with spikes of rich yellow flowers ; while Poinciana 
regia, a tall tree, Rhodolccna altivola and Astoupxa 
WallicJiii, shrubs, are amono^ the most mamiificent 
flowering plants in the world. Disa Buchenaxiana, Com- 
welina madagascarica, and Tachiademts jplatypterus are 
fine blue-flowered plants, while the superb orchid Angrcv- 
cujTi scfiquipcdale, Vinca rosea, Euphorhia splendcns, 
and StejjTianotis fionhunda , have been long cultivated 
in our hot-houses. There are also many handsome 
Combretacea3, Rubiaceae, and Leguminosae ; but, as in most 
tropical regions, this wealth of floral beauty has to be 
searched for, and produces little eflect in the landscape. 

The affinities of the Madag^ascar flora are to a sfreat 
extent m accordance with those of the fauna. The 
tropical portion of the flora agrees closely with that of 
tropical Africa, while the i^lants of the highlands are 



CHAP. XTX THE MADAGASCAR GROUP 441 



equally allied to those of the Cape and of the mountains 
of Central Africa. Some Asiatic types are present which 
do not occur in Africa ; and even the curious American 
affinities of some of the animals are reproduced in the 
vegetable kingdom. These last are so interesting that 
they deserve to be enumerated. An American genus of 
Euphorbiacece, Omphalea, has one species in Madagascar, 
and Pedilanthus, another genus of the same natural order, 
has a similar distribution. Myrosma, an American genus 
of Scitaminese has one Madagascar species; while the 
celebrated '* travellers' tree," Ravcnala maclagascaricnsis, 
belonging to the order Musacese, has its nearest ally in a 
plant inhabiting N. Brazil and Guiana. Echinolsena, a 
genus of grasses, has the same distribution.^ 

Of the flora of the smaller Madagascarian islands we 
possess a fuller account, owing to the recent publication 
of Mr. Baker's Fhra of the Mauritius and the Seychelles, 
including also Bodriguez. 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 
(304) are endemic or confined to single islands. Of the 
widespread plants sixty-six are found in Africa but not 
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 propor- 
tions 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 fifty are endemic, 
twenty-two are Asiatic but not African, Avhile 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 already certain 
that when the flora of Madagascar is more thoroughly 
worked out, a still greater African preponderance will be 
found in that island. 

^ This brief account of the Madagascar flora has been taken from a very 
interesting paper by the Rev. Richard Baron, F.L.S,, F.G.S., in the 
Journal of the Linnean Society , y o\. XXV., p. 246; where much informa- 
tion is given on the distribution of the flora within the island. 



442 ISLAND LIFE part ii 



A few Mascarene genera are found elsewhere only in 
South America, Australia, or Polynesia ; and there are 
also a considerable number of genera whose metropolis is 
South America, but which are represented by one or more 
species in Madagascar, 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 Avould be exactly 
parallel were the African plants to become extinct. 
Plants, however, are undoubtedly more long-lived speci- 
fically than animals — especially the more highly organised 
groups, and are less liable 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 Aus- 
tralia, while SQch cases are numerous among animals, 
owinof to the extinction of the allied forms in interveninsc 
areas, for which extinction, as we have already shown, 
ample cause can be assigned. 

Chcrious Relations of Mascarene Plants. — Among the 
curious affinities of Mascarene plants we have culled the 
following from Mr. Baker's volume. Trochetia, a s^enus 
of Sterculiaceoe, has four species in Mauritius, one in 
Madagascar, and one in the remote island of St. Helena. 
Mathurina, a genus of Turneracese, 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 Compositse, consists 
of two species, one inhabiting the Mascarene islands, the 
other Peru. Labourdonasia, a genus of Sapotacese, has 
two species in Mauritius, one in Natal, and one in Cuba. 
Nesogenes, belonging to the " verbena family, has one 
species in Rodriguez and one in Polynesia. Mespilodaphne, 
an extensive genus of Lauracese, has six species in the 
Mascarene islands, and all the rest (about fifty species) in 
South America. Nepenthes, the well-known pitcher 
plants, are found chiefly in the Malay Islands, South 
China, and Ceylon, with species in the Seychelles Islands, 



CHAP. XIX THE MADAGASCAE GROUP 443 



and in Madagascar. Milla, a large genus of Liliacea?, is 
exclusively American, except one species found in Mauri- 
tius and Bourbon. Agauria, a genus of Ericacese, is 
found in Madagascar, the Mascarene islands, the plateau 
of Central Africa, and the Camaroon Mountains in West 
Africa. An acacia, found in Mauritius and Bourbon (A. 
heterophi/lla), 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 — 
^lauritius, 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 anom- 
alies of distribution in these islands as do the animals, 
though in a smaller j^roportion ; while they also exhibit 
some of the transitional stages by which these anomalies 
have, in all probability, been brought about, rendering 
quite unnecessary any other changes in the distribution 
of sea and land than physical and geological evidence 
warrants.^ 

' 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 Mauritms and the Seychelles, as they are nowiicre separately tabulated 
in that work, 

Aphloia (Bixacese) 1 sp-, a sliruh, IMaiir., Rod., Sey., also Madagascar. 

Medusagyne (Ternstroraiacefe) ...1 sp., a shrul), Seychelles. 

Astiria (Sterciiliacese) 1 sji., a shnib, Mauritius. 

Quivisia (Meliaceee) 3 sp., .shrubs, Mauritius (2 sp.), Rodriguez (1 sp.), 

also Bourljon. 

Cossignya (Sapindacea-) 1 sp., a shrub, Mauritius, also Bourbon. 

Hornea ,, 1 sp., a shrub, Mauritius. 

Stadtmannia ,, 1 sp., a shrub, Mauritius. 

Doratoxylon ,, 1 sp., a shrub, Mauritius and Bourbon. 

Gagnebina (Leguminosa-) 1 sp., a shrub, Mauritius, also Madagascar. 

Roussea (Saxifragacea-) 1 sp., a climbing shrub, Mauritius and Bourbon. 

Tetrataxis (Lythraceie) 1 sp., a slii'ub, Mauritius. 

Psiloxylon ,, 1 sp., a shrub, Mauritius and Bourbon. 

3Iathurina (Turneracea-) 1 sp., a shrub, Rodriguez. 

Foetidia (Myrtacefe) 1 sp., a tree, Mauritius. 

Danais (Rubiaceaj) 4 sp., climbing shrubs, ]\ranr. (1 sp.), Rodr. (1 sp.), 

also Bourl)on and jMadagascar. 

Fernelia (Rubiacess) 1 sp., a shrub, Mauritius and Rodriguez. 

Pyrostria ,, G sp., shrubs, Mauritius (3 sp.), also Bourbon and 

Madagascar. 

Scyphochlamys (Rubiaceee) 1 sp., a shrub, Rodriguez. 

Myonima ,, .3 sp., shrubs, Maurifius, also Bourbon. 

Cylindrocline (CoraiJositse) 1 sp., a shrub, Mauritius. 

Jlonarrhenus ,, 2 sp., shrubs, Mauritius, also Bourbon and Mada- 

gascar. 



444 ISLAND LIFE 



Fragmentary Character of the Mascarene Flora. — 
AltliQugh the peculiar character and affinities of the 
vegetation of these islands is sufficiently aj^parent, there 
can be little doubt that we only possess a fragment of the 
rich flora 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 remains of 
the aboriginal woodlands only linger in the recesses of the 
hills, and numbers of forest-haunting plants must inevit- 
ably 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 



Faiijasia (Coinpositse) 3 sji., shrubs, Mauritius, also Bourbon and Mada- 
gascar. 

Heteroclirenia (Campanulaceis) 1 sp., a slirub, Mauritius, also Bourbon. 

Tanulepis (Asclepiadacese) 1 sp., a climber, Rodriguez. 

Decaneuia ,, i sji., a climber, Mauritius, also Madagascar. 

Nicodemia (Loganiaceae) 2 sp., shrubs, Mauritius (1 sp.), also Comoro Islands 

and Madagascar. 

Bryodes (Scrophulariacefe) 1 sp., herb, Mauritius. 

Radamsea ,, 2 sp., herb, Seychelles (1 sp.), and Madagascar. 

Colea (Bignoniacese) 10 sp., Mauritius (1 sp.), Seychelles (1 sp.), also 

Bourbon and Madagascar. (Shrubs, trees, or 
climbers.) 

Obetia (Urticacea) 2 sp., shrubs, Mauritius, Seychelles, and Mada- 
gascar. 

Bosquiea (Morea;) 3 sp., trees, Seychelles (1 sp.), also Madagascar. 

Monimia (Monimiacea') 3 sp., trees, Mauritius (2 sp.), also Bourbon. 

Cynorchis (Orchidea-) 3 sp., herb, ter., Mauritius. 

Amphorchis ,, ...i sp., herb, ter., Mam-itius, also Bourbon. 

Arnottia ,, 2 sp., herb, ter., Mauritius, also Bourbon. 

Aplostellis ,, 1 sp., herb, ter., Mauritius. 

Cryptopus ,, 1 sp., herb, Epiphyte, Mauritius, also^Bourbon and 

Madagascar. 

Lomatophyllum (Liliaceai) 3 sp., shrubs (succulent), Mauritius, also Bourbon. 

Lodoicea (PalmaO 1 sp., tree, Seychelles. 

Latania ,. 3 sp., trees, Mauritius (2 sp.), Rodriguez, also 

Bourbon. 

Hyophorbe ,, 3 .sji., trees, Mam-itius (2 sji.), Rodriguez, also 

Bourbon. 

Dictyosperma ,, 1 sp., tree, Mauritius, Rodriguez, also Bourbon. 

Acanthophsenix ,, -sp., trees, Mauritius, also Bourbon. 

Deckenia ,, 1 s])., tree, Seychelles. 

Nephrosperma , , 1 si>. , tree, Sej^chelles. 

Roscheria ,, 1 s})., tree, Seychelles. 

Verschaffeltia , 1 sj)., tree, Seychelles. 

Stevensonia ,, 1 f]>., tree, Seyehelles. 

Ochropteris (Filices) 1 sj'., herb, Mauritius, also Bourbon and Madagascar. 

Among the curious features in this list are the great number of endemic 
shrulis 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. 



CHAr. XIX THE MADAGASCAR GROUP 445 



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 Mahe, 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, es23ecially, grows almost to the tops 
of the mountains. Where the timber and shrubs have 
been destroyed, the water falling on the surface im- 
mediately cuts channels, runs off rapidly, and causes the 
land to become dry and arid ; and the same effect is 
largely seen both in Mauritius 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 Soutli Africa. — In 
my Geographical Distribution of Animals I have remarked 
on the relation between the insects of Madagascar and 
those of south temperate Africa, and have speculated on a 
great southern extension 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 Compositas. 
He says : " The connections of the Mascarene endemic 
Compositae, especially those of Madagascar itself, are 
eminently with the southern and sub-tropical African 
races ; the more tropical races, Plucheinese, &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 char- 
acteristics in the tendency to tall shrubby or arborescent 
forms in several of the endemic or prevailing genera. 

Prc20onderancc of Fans 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 orchideaB. The followins^ fibres are taken from 



^O ^-to ' 



446 ISLAND LIFE 



Mr. Baker's Flora for Mauritius and the Seychelles, and 

frora an estimate by M. Frappier of the flora of Bourbon 
given in Maillard's volume already quoted : — 

Mauritius, d-c. Bourbon. 

Ferns 168 Ferns 240 

OrcMdese 79 OrchidccC 120 

Gramineos 69 Gramine;ie 60 

CyperaeesB 62 Compositfe 60 

Rubiacese 57 Leguminosre 36 

Euphorbiacete 45 Rubiacese 24 

Composite 43 Cyperaceae 24 

LegiiminosEe 41 Euphorbiaceai 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. The abundance of orchids, 
the reverse of what occurs in remoter oceanic islands, 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 23lentiful on such tropical islands as possess 
an abundance of insects adapted to fertilise them, and 
which are not too far removed from other lands or conti- 
nents from which their seeds might be conveyed. 

Coiiduding 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 Avell 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 frasments of this island in the Comoros and 



CHAP. XIX THE MADAGASCAR GROUP 447 



Aldabra; in the Seychelles we have the fragments of 
another very ancient island, Avhich may perhaps never 
hc.ve 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 organisms 
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 
conclusion, arrived at solely by a study of the form of the 
sea-bottom and the general principle of oceanic per- 
manence, is fully supported by the evidence of the organic 
productions of the several islands ; because it gives us 
confidence in those principles, and 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, in- 
dicating that tlie migration occurred during late Tertiary 
times, while others are distinct genera, indicating a more 
ancient connection ; 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 supj^osed 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 (Herpetodryas, &c.) of Madagascar and America ; 
and the lizards (Cryptoblepharus) of Mauritius and 
Australia. To suppose, in all these cases, and in many 
others, a direct land-connection, is really absurd, because 



448 ISLAND LIFE 



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 Palseozoic — 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 very good evidence (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 w^e knoAv 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 epoch Africa may have received its lower types 
of 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 thenceforth was enabled 
to develop its singular forms of low-type mammalia, its 
gigantic ostrich-like iEpyornis, 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 ; v.diile 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 accejjt the results of geological and palteontological 
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, 



CHAP. XIX THE MADAGASCAR GROUP 449 

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 com- 
plexity 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-con- 
nection, 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 that which prevailed 
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 Eocene, or even to the Cretaceous, period. Some of 
these types have become altogether extinct elsewhere ; 
others have spread far and wide over the globe, and have 
survived only in a few remote countries — and especially in 
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 exj^lains 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 being 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 con- 
necting these remote continents at various geological 
periods been realities, the result would have been that all 
these interesting archaic forms, all these defenceless insular 
types, would long ago have been exterminated, and one 
comparatively monotonous fauna have reigned over the 
whole earth. So far from explaining the anomalous facts, 
the alleged continental extensions, had they existed, would 
have left no such facts to be explained. 

G G 



CHAPTER XX 

ANOMALOUS ISLANDS : CELEBES 



Auomalous 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 tlie 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 geological 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 



CHAP. XX CELEBES 45I 



volcanoes; 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 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 Miocene periods, and prob- 
ably also in the Pliocene. The fauna and flora of this 
island are, however, so poor, and offer so few peculiarities, 
that it is unnecessary to devote more time to their 
consideration. 

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 con- 
tinental " ; 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 dis- 
cussed its zoological peculiarities and past history in my 
Geographical DisMjution 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 Celches. — This large and still com- 
paratively unexplored island is interesting to the geo- 
grapher on account of its remarkable outline, 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 pen- 
insula 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 

G G 2 



452 



ISLAND LIFE 



doubt that the mountain ranges of the interior consist of 
ancient stratified rocks. 




i,,,,.™p,_ _r V A s 



MAP OF CELEBES AND THE SURROUNDING ISLANDS. 

The depth of sea is shown bv 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 dejiths in fathoms. 

It is not yet known whether Celebes is completely 
separated from the surrounding islands by a deep sea, but 



ctiAi'. x^ CELEBES 453 

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,G00 fathoms deep, 
and such depths may extend over a considerable portion of 
it, or even be much exceeded in the centre. In the 
Molucca passage a single sounding on the Gilolo side gave 
1,200 fathoms, and a large part of the Molucca and Banda 
Seas jDrobably exceed 2,000 fathoms. The southern jDortion 
of the Straits of Macassar is full of coral reefs, and a 
shallow sea of less than 100 fathoms extends from Borneo 
to 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 dej)osits from the great Bornean rivers as 
well as by those of Celebes itself. Southward again, the 
chain of volcanic islands from Bali to Timor ajDjDears 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. AVe seem justified, therefore, in con- 
cluding 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, instead of being indications of a 
former union with any of the surrounding islands. 

Zoological Character of the Isla7ids around Celebes. — In 
order to have a clear conception of the peculiar character 
of the Celebesian fauna, we must take into account that of 
the surrounding countries from which we may suppose it 
to have received immigrants. These we ma}^ 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 is a typical representative ; and from its 
proximity and the extent of its opposing coasts it is the 
island which we should expect to shoAV most resemblance 
to Celebes. We have already seen that the fauna of 
Borneo is essentially the same as that of Southern Asia, 
and that it is excessively rich in all the Malayan types of 



454 ISLAND LIFE part ii 

mammalia and birds. Java and Bali closely resemble 
Borneo in general character, though somewhat less rich 
and with several peculiar forms; w^hile the Philip23ine 
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. 

In the islands east and south of Celebes — the Moluccas, 
New Guinea, and the Timor group from Lombok east- 
ward — 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 disapi^eared 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 

^ Families of Malayan Birds not Families of Moluccan Birds not 
found in islands Fast of found in islands West of 
Celebes. Celebes. 

Troglodytidse. Paradiseidae. 

Sittidse. Meliphagida?. 

Paridae. Cacatuidaj. 

Liotrichidse. Platycercidse. 

Phyllornithidse. Triclioglossidae 

Eurylsemidffi. Nestorida-. 

Picidje. 

Indicatoridse. 

Megalsemidaj. 

Trogonid*. 

Phasianidse. 



CHAP. XX CELEBES 455 

stretches out from the Siamese and Malayan peninsula 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 Waigicu, 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 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 agi-eeing with 
New Guinea in their forms of life, yet strikingly deficient 
in many important groups, and exhibiting an altogether 
poverty-stricken 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 distur- 
bance, probably involving extensive submersions of the land^ 
resulting in a scanty and fragmentary vertebrate fauna. 

Zoology of Celebes. — The zoology of Celebes differs so 
remarkably 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. 



456 ISLAND LIFE 



The remaining twelve species are, generally speaking, 
of Malayan or Asiatic types, but some of tliem 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 M2?]3el(qjlms of 
Borneo that it may well have been introduced by man 
both here and in the Moluccas; a civet, Viverra 
tangcdunga, 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 anything found in the 
Malay Islands or even in Asia. These are a black and 
almost tailless baboon-like ape {Cynointhcus nigrescens) ; 
an antelopean buffalo {Anoa clcpressicornis), and the 
strange babirusa (Babirusa alfurus). 

None of these three animals last mentioned has any 
close allies elscAvhere, 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 in- 
termediate 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 projecting 
muzzle, large superciliary crests, and mnxillary ridges. 
The anoa, though anatomically allied to the buffaloes, ex- 
ternally 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 uj^wards like horns, forming a S23iral 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. 



CHAP. XX CELEBES 457 

Frohahle Derivation 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 mono- 
tremes and marsupials 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, however, remains to 
be accounted for. We have seen that Formosa, a much 
smaller island, contains more than twice as many 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 intervening 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 except the squirrels are entirely un- 
represented in Celebes by any peculiar and ancient forms. 

The question at issue can only be finally determmed by 
geolosfical investig^ations. If Celebes has once formed part 
of Asia, and participated in its rich mammalian launa, 
which has been since destroyed by submergence, then some 



458 ISLAND LIFE part il 

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 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 mammalia ; 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 Ave 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 Avhich 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 pro- 



GHAP. XX CELEBES 459 



portion does not differ much from that afforded by the 
non-peculiar species ; and it teaches us that, for a consider- 
able 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 Moluccas on the other, have occupied very much 
the same relative position as now. There remain 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 Campephaginse or caterpillar-shrikes — a not 
very well-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 Todiram23hus 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 form- 
ing a distinct sub-family. Meropogon is a peculiar bee- 
eater, allied to the Malayan Nyctiornis ; Rhamphococyx is 
a modification of Phsenicophaes, 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 Megace- 
phalon is a remarkable and very isolated form of the 
Australian Megapodiidse, or mound-builders. 

Omitting those Avhose affinity may be pretty clearly 
traced to groups still inhabiting the islands of the western 
or the ea