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Full text of "Island life; or, The phenomena and causes of insular faunas and floras, including a revision and attempted solution of the problem of geological climates"






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ISLAND LIFE. 






ISLAND LIFE: 



OK, 



THE PHENOMENA AND CAUSES OF 

I^nsulnr dTaunas) anti dTloras!, 



INCLUDING A KEVISION AND ATTEMPTED SOLUTION OF THE 

PROBLEM OF 



a^fologiral ClimatrsJ. 



hy 



ALFRED RUSSEL WALLACE, 

ACTBOK OF "THE MALAY ARCHIPELAGO," "TROPICAL NATURE," " IBS OECGRAPniCAL 
I)I6TRIBUTI0N OF ANIMALS," &C, 



MACMILLAN AND CO. 

1880. 

The Jiight of Translation avd Reprodtictton it Etterved. 



LONDON : 

R. CLAY, SOXS, AXD TATLOR, 

BREAD 8TBEET HILL. 




26- 
liJSS 



TO 

SIR JOSEPH DALTOX HOOKER, 

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

WHO, MORE THAN ANY OTHER WRITER, 

HAS ADVANCED OUR KNOWLEDGE OF THE GEOGRAPHICAL 

DISTRIBUTION OF PLANTS, AND ESPECIALLY 

OF INSULAR FLOR/VS, 

I gcbifutc Ibis IToIume, 

ON A KINDRED SUBJECT, 
AS A TOKEN OF ADMIR.\TION AND REGARD. 



PREFACE. 

The present volume is the result of four years' additional 
thought and research on the lines laid down in my GeograpMcal 
Distributimi of Animals, and may be considered as a popular 
supplement to and completion of that work. 

It is, however, at the same time a complete work in itself ; 
and, from the mode of treatment adopted, it will, I hope, be well 
calculated to bring before the intelligent reader the wide scope 
and varied interest of this branch of natural history. Although 
some of the earlier chapters deal with the same questions as my 
former volumes, they are here treated from a different point of 
view ; and as the discussion of them is more elementary and at 
the same time tolerably full, it is hoped that they will prove 
both instructive and interesting. The plan of my larger work 
required that gciura only should be taken account of; in the 
present volume I often discuss the distribution of species, and 
this will help to render the work more intelligible to the 
unscientific reader. 

The full statement of the scope and object of the present 
essay given in the " Introductory " chapter, together with the 
" Summary " of the whole work and the general view of the 
more important arguments given in the " Conclusion," render it 
unnecessary for me to offer any further remarks on these points. 
I may, iowever, state generally that, so far as I am able to 



PEEFACE. 



judge, a real advance has here been made in the mode of treating 
problems in Geographical Distribution, owing to the firm estab- 
lishment of a number of preliminary doctrines or " principles," 
which in many cases lead to a far simpler and yet more com- 
plete solution of such problems than have been hitherto possible. 
The most important of these doctrines are those which establish 
and define — (1) The former wide extension of all groups now 
discontinuous, as being a necessary result of "evolution"; 
(2) The permanence of the great features of the distribution 
of land and water on the earth's surface ; and, (3) The nature 
and frequency of climatal changes throughout geological time. 

I have now only to thank the many friends and correspond- 
ents who have given me information or advice. Besides those 
whose assistance is acknowledged in the body of the work, I am 
especially indebted to four gentlemen who have been kiud 
enough to read over the proofs of chapters dealing with ques- 
tions on which they have special knowledge, giving me the 
benefit of valuable emendations and suggestions. Mr. Edward 
R. Alston has looked over those parts of the earlier chapters 
which relate to the mammals of Europe and the North 
Temperate zone ; Mr. S. B. J. Skertchley, of the Geological 
Survey, has read the chapters which discuss the glacial epoch 
and other geological questions ; Professor A. Newton has looked 
over the passages referring to the birds of the Madagascar 
group ; while Sir Joseph D. Hooker has given me the in- 
valuable benefit of his remarks on my two chapters dealing 
with the New Zealand flora. 

Croydon, August, 1880. 



CONTENTS. 

PAKT I. 

THE riSPEESAL OF ORGANISMS; ITS PHENOMENA, LAWS, AND CAUSES. 

CHAPTER I. 

INTHODUCTOHY. 

Remarkable Contrasts in the distribution of Animals— Britain and Japan — Australia 
and New Zealand— Bali and Lombok — Florida and Bahama Islands— Brazil and 
Africa — Borneo, Madagascar, and Celebcs^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 — Islan ds offer the best subjects for th e study of 
distribution — Outline of the subjects to be discussed in the present volume. 

Pages 3—11 

CHAPTER II. 

THE ELEUENTAltT FACTS OP DISTniBin'ION. 

Importance of Locality as an essential character of Species — Areas of Distribution — 
Extent and Limitations of Specific Areas — Specific range of Birds — Generic 
Areas — Separate and overlapping areas — The species of Tits as illustrating Areas 
of Distribution — Tlie distribution of the species of Jays — Discontinuous generic 
areas — Peculiarities of generic and family distribution — General features of over- 
lapping and discontinuous areas — Restricted areas of Families — The distribution 
of Orders Pages 12—30 

CHAPTER III. 

CUlSSrFICATIOS OF THE FACTS OP DISTKIBCTIOJt. — ZOOLOQICAI, RE0I0N3. 

The Geographical Divisions of the Globe do not correspond to Zoological Divisions — 
The range of British Mammals as indicating a Zoological Region — Range of East 
Asian and North African Mammals — The Range of British Birds — Range of East 
Asian Birds — The limits of the Palrearctic Region — Characteristic features of the 
Palaearctic Region — Definition and characteristic groups of the Ethiopian Region 
— Of the Oriental Region— Of the Australian Region— Of the Nearctic Region 
— Of the Neotropical Region — Comparison of Zoological Regions with the Geo- 
graphical Divisions of the Globe Pages 31 — 53 



CONTENTS. 



CHAPTEE IV. 

EVOHJTION AS THE KEY TO DISTBIBCTION. 

Importance of the Doctrine of Evolution— The Origin of New Species — Variation in 
Animals — The amount of variation in Xorth American Birds — How new species 
arise from a variable species — Definition and Origin of Genera— Cause of the 
extinction of Species — The rise and decay of Species and Genera— Discontinuous 
specific areas, why rare — Discontinuity of the area of Parus palustris — Disconti- 
nuity of Emberiza schsnidus — The European and Japanese Jays — Supposed ex- 
amples of discontinuity among North American Birds — Distribution and antiquity 
of Families — Discontinuity a proof of antiquity — Concluding Remarks 

rages 54-69 

CHAPl'ER V. 

THE POWERS OF DISPERSAL OP AhTMALS AXD PLANTS. 

Statement of the general question of Dispersal — The Ocean as a barrier to the dis- 
persal of Mammals — The dispersal of Birds — Tlie 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 disjjersal — Birds as agents in the dispersal of 
Seeds — Ocean currents as agents in Plant dispersal — Dispersal along mountain- 
chains — Antiquity of Plants as affecting their distribution . . Pages 70 — 80 



CHAPTER VI. 

GEOGRAPHICAL AKD GEOLOGICAL CHAXGES : THE PERMAN-EXCE OF COXTINESTS. 

Changes of Land and Sea, their nature and extent — Shore-deposits and stratified 
rocks — The Stovements of Continents — Supposed oceanic formations ; the Origin 
of Chalk— Fresh-water and Shore-deposits as proving the permanence of Conti- 
nents — Oceanic Islands as indications of the permanence of Continents and 
Oceans — General stability of Continents with constant change of form — Effect of 
Continental Changes on the Distribution of Animals — Changed distribution proved 
by the extinct animals of different epochs — Summary of evidence for the general 
permanence of Continents and Oceans ... , . Pages 81 — 103 

CHAPTER Vn. 

CHANGES OP CLIMATE WHICH HAVE INPLUESCED THE DISPERSAL OF 0RGAXIS.M9 : 
THE GLACIAL EPOCH. 

Proofs of the recent occurrence of a Glacial Epoch — Moraines — Travelled Blocks — 
Glacial deposits of Scotland: the "Till" — Inferences from the glacial phenomena 
of Scotland— Glacial phenomena of North America — Effects of the Glacial Epoch 
on animal life— Warm and cold periods— Palaeontological evidence of alternate 
cold and warm periods — Evidence of interglacial warm periods on the Continent 
and in North America — Migrations and extinctions of Organisms caused by the 
Glacial Epoch Pages 103-120 



CONTEXTS. 



CHAPTER YIU. 

THE CAfSES OF GLACIAL EPOCHS. 

Various suggested causes — Astronomical causes of changes of Climate— Difference 
of Temperature caused by varying distances of tlje .Sun— Properties of air and 
water, snow and ice, in relation to Climate — Effects of snow on Climate — High 
land and great moisture essential to the initiation of a Glacial Epoch— Per- 
petual snow nowhere exists on lowlands — Comiitions determining the presence or 
absence of perpetual Snow — EflSciency of Astronomical causes in producing Glaci- 
ation — Action of meteorological causes in intensifying Glaciation — Summary of 
causes of Glaciation— Effect of clouds and fog in cutting off the Sun's heat — 
South Temperate America as illustrating the influence of Astronomical causes on 
Chmate — Geographical changes how far a cause of Glaciation— Land acting as a 
barrier to ocean-currents— The theory of interglacial periods and their probabla 
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 aa 
betiriug on the theory of eccentricity as a cause of Glacial Epochs 

JPages 121—162 
CHAPTER IS. 

ANCIE'Tr GLACIAL EPOCH.S, AXD MILD CLIMATES IS THE AECnC EE0I0K3. 

Mr. CroU's views on ancient Glacial Epochs— Effects of Denudation in destroying 
the evidence of remote Glacial Epochs— Else of sea-level connected with Glacial 
Epochs a cause of further denudation— AVhat evidence of early Glacial Epochs 
may be expected— Evidences of Ice-action during the Tertiary Period— The 

weight of the negative evidence— Temperate climates in the Arctic Regions 

The Miocene Arctic flora— Mild Arctic climates of the Cretacious Period— Strati- 
grapiiical evidence of long-continued mild Arctic conditions— The causes of mild 
Arctic chmates— Geographical conditions favouring mild northern climates in Ter- 
tiary times— The Indian Ocean as a source of heat in Tertiary times— Condi- 
tion of Xorth America during the Tertiary Period— Effect of high excentricity on 
warm Polar climates— Evidences as to climate in the Secondary and Paleozoic 
Epochs— Warm Arctic climates in early Secondary and Paleozoic times— Con- 
clnsions 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 
producmg changes of climate Fages 163 — 202 

CH.iPTER X. 

THE earth's age, ANT) THE HATE OP DEVELOPMENT OP AMIUALS AST) 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 depositiou of the Sedimentary Rocks — The 
rate of Geological change probably greater in very remote times — Value of the 
preceding estimate of Geological Time— Organic modification dependent on 
Change of Conditions — Geographical mutations as a motive power in bringing 
about Organic Changes — Climatal revolutions as an agent in producing Organic 
Changes— Present condition of the Earth one of exceptional stability as regards 
Climate — Date of last Glacial Epoch and its bearing on the Measurement of 
Geological time — Concluding Remarks Fages 203—229 



CONTENTS. 



PART 11. 

ISSULAR FAUNAS AND FLOKAS. 
CHAPTER XI. 

THE CLASSIFICATION OF ISLiXDS. 

Importance of Islands in the study of the Distribution of Organisms — Classificatioa 
of Islands with reference to Distribution — Continental Islands — Oceanic Islands 

Pages 233-237 

CHAPTEK XIL 

OCEANIC ISLANDS : — THE AZORES AND BERMUDA. 

TUB AZORES, OB TTESTEES ISIASDS. 

Position and physical features— Chief Zoological features of the Azores— Birds- 
Origin of the Azorean bird-fauna — Insects of the Azores— Land-shells of the 
Azores — The 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 238 — 253 

BEEJICDA. 

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

CHAPTER Xni 

THE GALAPAGOS ISLANDS. 

Position and physical features— Absence 'of indigenous Mammaha and Amphibia — 
Reptiles- Birds— Insects and Land-shells — The Keelins Islands as illustrating the 
manner in which Oceanic Islands are peopled— Flora of the Galapagos— Origin of 
the Flora of the Galapagos— Coucluding Remarks . . . Pages 265—280 



CONTEXTS. 



CHAPTER XIY. 

ST. HELEXA. 

Position ami physical features of St. Helena — Change etfected by European occupa- 
tion — The Insects of St. Helena — Coleoptera — Peculiarities and origin of the 
Coleoptera of St. Helena — Land-shells of St. Helena —Absence of Fresh-water 
Organisms — Native vegetation of St. Helena — The relations of the St. Helena 
Compositse— Concluding remarks on St. Helena .... Paijes 281 — 297 

CHAPTER XV. 
", THE SANDWICH ISLANDS. 
Position and Physical features — Zoology of the Sandwich Islands — Birds— Reptiles — 
Land-shells— Insects — Vegetation of the Sandwich Islands— Peculiar features of 
the Hawaiian Flora — Antiquity of the Hawaiitm Fauna and Flora— Concluding 
observations on the Fauna and Flora of the Sandwich Islands — General Remarks 
on Oceanic Islands Vayes 298 — 311 

CHAPTER XVI. 

CONTINENTAL ISLANDS OF HECENT ORIGIN : UREAT BRITAIN. 

Characteristic Features of Recent Continental Islands — Recent Physical Changes of 
the British Isles — Proofs of Former Elevation— Submerged Forests — Buried River 
Channels— Time of Last Union with the Continent— Why Britain is poor in 
Species— Peculiar British Birds- Fresh-water Fishes — Cause of Great Speciality 
iu Fishes — Peculiar British Insects— Lepidoptera confined to the British Isles — 
Peculiarities of the Isle of JIan Lepidoptera— Coleoptera confined to the British 
Isles— Trichoptera peculiar to the Britisli Isles— Land and Fresh-water Shells — 
Pecuharitius of the British Flora -Peculiarities of the Irish Flora— Peculiar 
British Mosses and Hepaticse— Concluding Remarks on the Peculiarities of the 
British Fauna and I'lora I'ai/es 312 347 

CHAPTEK XVII. 

B0RNE.1 AND JAVA. 

Position and physical features of Borneo — Zoological features of Borneo : Mammalia 
-Birds— The afEuities of the Bornean fauna— Java, its position and physical fea- 
tures— General character of tlie 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 

Faffts 348—362 

CHAPTER XVIII. 

JAPAN AND FORMO.SA. 

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— I'ormosa— Physical features of For- 
mo.<:a— Animal life of Formosa— M.immalia— Land birds peculiar to Formosa— 
Formosan birds recurring in India or Malaya— Comparison of faunas of Hainan, 
Formosa, and Janau— General Remarks on Recent Continental Islands 

Fnt/es 3G3— 383 



CONTENTS. 



CHAPTER XIX. 

ASCIENT COXTIXEXTAI. ISLA>T)3 : THE MABAGASCAE GEOrP. 

Eemarks on Ancient Continental Islands— Physical features of Madagascar— Biolo- 
gical features of Madagascar— Mammalia- Reptiles— Relation of Madagascar to 
Africa— Early history of Africa and Madagascar— Anomalies of distribution and 
how to explain them— The birds of Madagascar as indicating a supposed Lemu- 
rian Continentr- Submerged Islands between Madagascar and India- Concluding 
remarks ou "Lemuria"- The Mascarene Islands— The Comoro Islands— The Sey- 
chelles Archipelago— Birds of the Seychelles— Reptiles and Amphibia— Fresh-water 
Fishes-Land SheUs- Mauritius, BDurbon, 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 . . . rages 383—420 



CHAPTER XX. 

ANOMALOUS ISI-AND3 : CEIXBES. 

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

CHAPTER XXI. 

AirOUALOUS ISLANDS : NEW ZEALAND. 

Position and Physical features of Xew Zealand— Zoological character of New Zea- 
land — Mammalia — Wingless birds living and extinct — Recent existence of the 
Moa — Past changes of New Zealand deduced from its wingless Birds — Birds and 
Reptiles of New Zealand — Conclusions from the peculiarities of the New Zealand 
Fauna Pages 442—456 

CHAPTER XXII. 

THE FLORA OF XEW ZEALAND : ITS AFFINITIES AND PEOBABLE OEIGIN. 

Relations of the New Zealand Flora to that of Australia — General features of the 
Australian Flora — The Floras of South-eastern and South-western Australia — 
Geological explanation of the differences of these two floras — The origin of the 
Australian element in the New Zealand Flora — Tropical chai'acter of the New 
Zealand Flora explained — Species common to New Zealand and Australia mostly 
temperate forms — "Why easily dispersed plants have often restricted ranges — 
Summary and Conclusion on the New Zealand Flora . . . Pages 457 — 478 



CONTENTS. 



CHAPTER XXIII. 

ox THE AECnC ELEMSlrr IN SOUTH TEMPEnATE FLORAS. 

European species and genera of plants in the Southern Hemisphere — Aggressive power 
of the Scandinavian flora— Means by which plants liave migrated from north to 

south — Newly moved soil as affording temporary stations to migrating plants 

Elevation and depression of the snow-liae as aiding the migration of plants 

C'h.inges of climate favourable to migration — The migration from north to south 
has been long going on— Geological changes as aiding migration — Proofs of mi- 
gration by way of the Andes— Proofs of migration by way of the Himalayas and 
Southern Asia— Proofs of migration by way of the African highlands— Supposed 
connection of South Africa and Australia — The endemic genera of plants in New 

Zealand — The absence of Southern types from the Northern Hemisphere 

Concluding remarks on the New Zealand and South Temperate floras 

Fagcs 477—498 

CHAPTER XXIV. 

S17MMABY ASD CONCLCSION. 

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



MAPS AND ILLUSTRATIONS. 

PAGE 

1. JIap showing the Distribution of the tece Jays . . Frontispiece. 

2. Map shotting the Zoological Regions Tuface 31 

3. 5Iap shottlno the Disthibction of Pakcs PALrST/iis . . . To face 64 

4. A Glacier with Moraines (From Sir C. Lyell's Principles of Geology) . 105 

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

of Man) 107 

6. Diagram showing the effects cf Excenteicity and Precession on 

C'ldiate 1-3 

7. Diagram of Escenthicitt and Trkcession 124 

8. Map showing the Extent of the North and South Polar Ice . . . 133 

9. Diagram showing Changes op Excenthiciit dvring Three Million 

Tears 165 

10. Outline Map of the Azores 239 

11. Map of Bermuda and the American Coast 254 

12. Section of Bermuda and adjacent Sea-bottom 255 

13. Map of the Galapagos and ad.iacext Coasts of South America . . 267 

14. Map of the Galapagos 267 

15. Map of the South Atlantic, showing position of St. Helena . . . 282 

16. Map of the Sandwich Islant)3 299 

17. Map of the North Pacific, with its submerged Banks 300 

18. Map showls-g the Bane connecting Britain with the Continent . 314 



MAPS AND ILLUSTRATIONS. xvii 

PAOE 

19. Map op Boeseo and Java, showing the Geeat Si/BMAeixe BAinc 

OF Socth-Eastekn Asia 349 

20. Map of Japan and Foemosa 364 

21. Physical Sketch Map of Madaoascae (From Nature) 385 

22. Map of Madagascae Geoup, showing Deiths of Sea 387 

23. Map oi' TUf Indian Ocean 396 

24. Map of Ceixbes and the scbboundino Islakds 423 

25. Map showing Depths of Sea abound Attstbalia and New Zealand . 443 

26. Map showing the peobadi.e condition of Acstealia doeino 

TILE Cretaceous Epoch 465 



ISLAND LIFE. 



ISLAND LIFE. 

PART I. 

THE DISPERSAL OF KG AN ISMS; 
ITS PHENOMENA, LAWS, AND CAUSES. 



A 



CHAPTER I. 

INTRODUCTORY. 

Remarkable Contrasts in distribution of Animals — Britain and Japan — 
Australia and New Zealand — Bali and Lonibok — Florida and Bahama 
Islands — Brazil and Africa — Borneo, Madagascar, and Celebes — 
Problems in distribution to be found in every country — Can be solved 
only by the combination of many distinct lines of inquiry, biological 
and physical — Islands offer the best subjects for the study of distribu- 
tion — Outline of the subjects to be discussed in the present volume. 

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

B 2 



ISLAND LIFE. [part u 



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

Now let an inhabitant of Australia s^l to New Zealand, a 
distance of less than thirteen hundred miles, and he will find 
himself in a country whose productions are totally unlike those 
of his own. Kangaroos and wombats there are none, the birds 
are almost all entirely new, insects are very scarce and quite 
unlike the handsome or strange Australian forms, while even 
the vegetation is all changed, and no gum-tree, or wattle, or 
gi-ass-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 aud 
Lombok, each about as large as Corsica, and separated by a 
strait only fifteen miles wide at its narrowest part. Yet these 
islands differ far more from each other in their birds and quad- 
rupeds than do England and Japan. The birds of the one are 
extremely unli/:c those of the other, the difference being such 
as to strike even the most ordinary observer. Bali has red and 
green woodpeckers, barbets, weaver-birds, and black-and-white 
magpie-robins, none of which are found in Lombok, where, 
however, we find screaming cockatoos and friar-birds, and the 
strange mound-building megapodes, which are all equally un- 
known in Bali. Many of the kingfishers, crow-shrikes, and 
other birds, though of the same general form, are of very distinct 
species ; and though a considerable number of birds are the same 
in both islands the difference is none the less remarkable — as 
proving that mere distance is one of the least important of the 
causes which have determined the likeness or unlikeness in the 
animals of different countries. 



f.UAV. I.] INTRODUCTORY. 



In the western hemisjihere we find equally striking examples. 
The Eastern United States possess very peculiar and interesting 
plants and animals, the vegetation becoming more luxuriant as 
we go south but not altering in essential character, so that when 
we reach the southern extremity of Florida we still find our- 
selves in the midst of oaks, sumachs, magnolias, vines, and 
other characteristic forms of the temperate flora ; while the 
birds, insects, and land-shells are almost identical with those 
found further north. But if we now cross over the naiTow 
strait, about fifty miles wide, which separates Florida from the 
Bahama Islands, we find ourselves in a totally different country, 
surrounded by a vegetation which is essentially tropical and 
generally identical with that of Cuba. The change is most 
striking, because there is no difference of climate, of soil, 
or apparently of position, to account for it ; and when we 
find that the birds, the insects, and especially the land- 
shells are almost all West Indian, while the North American 
types of plants and animals have almost all completely 
disappeared, we shall be convinced that such differences and 
resemblances cannot be due to existing conditions, but must 
depend upon laws and causes to which more 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-troiiical Florida there are less 
marked differences in the animal productions than between 
Florida and Cuba or Yucatan, so much more alike in climate and 
so much nearer together. So the differences between the birds 
and quadrupeds of temperate Tasmania and tropical North 
Australia are slight and unimportant as compared with the 
enormovis differences we find when we pass from the latter 
country to equally tro2:)ical Java. If we compare corresponding 
portions of different continents, we find no indication that the 
almost perfect similarity of climate and general conditions has 
any tendency to produce similarity in the animal world. The 
equatorial parts of Brazil and of the West Coast of Africa are 



6 ISLAND LIFE. [part i. 

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

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

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



CHAP. I.] IXTRODUCTORY. 



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

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

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

' I cannot avoid licic 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, whose value is often in inverse proportion to their bulk and cost. 
The same species have been collected again and again, often described 
several times over under new names, and not unfrequently stated to be 
from places they never inhabited. The result of this wretched system is 
that the productions of some of the most frequently visited and most in- 
teresting islands on the globe are still very imperfectly known, while their 
native plants and animals are being yearly exterminated, and this is the 
case even with eountries under the rule or protection of European 
governments. Such are the Sandwich Islands, Tahiti, the Marquesas, the 
Philippine Islands, and a host of smaller ones ; while Bourbon and Mauritius, 
St. Helena, and several others, have only been adequately explored after 
an important portion of their productions has been destroyed by cultiva- 
tion or the reckless introduction of goats and pigs. The employment in 
each of our possessions, and those of other European powers, of a resident 
naturalist at a very small annual expense, would have done more for 
the advancement of knowledge in this direction than all the expensive 
expeditions that have again and again circumnavigated the globe. 



ISLAND LIFE. [part i. 



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

' The general facts of Palaeontology, as bearing on the migrations of 
animal groups, are summarised in my Geographical Distribution of Animals, 
Vol. I. Chapters VL, VIL, and VIIL 



CHAP. ].] INTRODUCTORY. 



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

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



10 ISLAND LIFE. [pabt i. 

dispersal and existing distribution of organisms. The other 
important theory, or rather corollary from the preceding theory 
— that of the permanence of oceans and the general stability 
of continents throughout all geological time, is as yet very 
imperfectly understood, and seems, in fact, to many persons in 
the nature of a paradox. The evidence for it, however, appears 
to me to be conclusive; and it is certainly the most fundamental 
question in regard to the subject we have to deal with : since, 
if we once admit that continents and oceans may have changed 
j)laces over and over again (as many writers maintain), we lose 
all power of reasoning on the migrations of ancestral forms of 
life, and are at the mercy of every wild theorist who chooses to 
imagine the former existence of a now-submerged continent to 
explain the existing distribution of a group of frogs or a genus 
of beetles. 

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



CHAP. J.] INTRODUCTORY. 11 

accurate conception of the physical and organic changes whicli 
have resulted in the present state of the eaith. 

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



CHAPTER II. 

THE ELEMENTARY FACTS OF DISTRIBUTION. 

Importance of Locality as an essential character of Species — Areas of Dis- 
tribution — Extent and Limitations of Speciiic Areas — Specific range of 
Birds — Generic Areas — Separate and overlapping areas— The species of 
Tits as illustrating Areas of Distribution — The distribution of the species 
of Jays — Discontinuous generic areas — Peculiarities of generic and 
family distribution — General features of overlapping and discontinuous 
areas — Restricted areas of Families — The distribution of Orders. 

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

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



cHAr. II.] THE ELEMENTARV FACTS OF DISTRIBUTION. 13 

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

Areas of Distribution. — Every species of animal has a certain 
area of distribution to which, as a rule, it is i3ermanently 'rA^^. 
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 fretjuently to be met 
with, but there are many partial exceptions to this rule. Some 
animals are so adapted to certain kinds of country — as to forests 
or marshes, mountains or deserts — that they cannot live long 
elsewhere. These may be found scattered over a wide area in 
suitable spots only, but can hardly on that account be said to 
have several distinct areas of distribution. As an examjslo we 
may name the chamois, which lives only on high mountains, 
but is found in the Pyrenees, the Alps, the Car2:)athians, 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 discontinuous dis- 
tribution of a species, there being a gap of about a thousand miles 
between its southern limits in Russia, and its reappearance in 



U ISLAND LIFE. [part. i. 



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

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

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



CHAP. II.] THE ELEMEXTAEY FACTS OF DISTPJBUTION. 15 

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

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

Of very restricted continental ranges the best examples in 
Europe are, the little blue magpie {Cyanopica cooki) confined to 
the central portions of the Spanish peninsula ; and the Italian 
sparrow found only in Italy and Corsica. In Asia, Palestine 
affords some examples of birds of very restricted range — a 
beautiful sun-bird [JVcdarinca osca) a peculiar starling {Amy- 
tJrns Tristraiiiii) and some others, being almost or quite con- 
fined to the wanner portions of the valley of the Jordan. In 



IG ISLAND LIFE. [part i. 

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

The above details will sufiiciently 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 continent in an east and west direction, 
but considerable numbers are restricted either to the northern 
or the southern half. In Africa some species range over all the 
continent south of the desert, while large numbers are restricted 
to the equatorial forests, or to the upland plains. In North 
America, if we exclude the tropical and the arctic portions, a 
considerable nimiber of species range over all the temperate 
parts of the continent, while still more are restricted to the 
east, the centre, or the west, respectively. 

Generic Areas. — Having thus obtained a tolerably clear idea 
of the main facts as to the distribution of isolated species, let 
tis 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 

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



ciiAr. li.] THP: elementary facts of DISTRIBUTfON. 17 



wolves belong to the dog genus, Canis ; the tiger, lion, leopard, 
jaguar, and the wild cats, to the cat genus, Felis; the blackbird, 
song-thrush, missel-thrush, fieldfare, and many others, to the 
thrush genus, Turdus; the crow, rook, raven, and jackdaw, 
to the crow genus, Corvus ; but the magpie belongs to another, 
though closely-allied genus. Pica, distinguished by the ditfcrent 
form and proportions of its wings and tail from all the species 
of the crow genus. The number of species in a genus varies 
greatly, from one up to several hundreds. The giraffe, the 
glutton, the walrus, the bearded reedling, the secretary-bird, 
and many others, have no close 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 amono- 
the lower classes of animals genera are often very extensive, 
the fine genus Papilio, or swallow-tailed butterflies, containino- 
more than four hundred species; and Cicindela, which includes 
our native tiger beetles, has about the .same number. Many 
genera of shells are very extensive, and one of them — the 
genus Helix, including the commonest snails, and ranging 
all over the world — is probably the most extensive in the 
animal kingdom, numbering about two thou.sand described 
species. 

Separate and ovcrkqypina 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 each other, 
each species occupying an area of its own which rarely coin- 
cides exactly with that of any other species of the same genus. 
In some cases, when a river, a mountain-chain, or a change of 
conditions as from pasture to desert or forest, determines the 
range of species, the areas of two species of the same genus 
may just meet, one beginning where the other ends ; but this 
is comparatively rare. It occurs, however, in the Amazon 
valley, where several species of monkeys, birds, and insects 
come up to the .south bank of the river but do not pass it, 

c 



18 ISLAND LIFE. [part i. 

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

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



cnAr. 11.] THE ELEMEXTARY FACTS OF DISTRIBL'TION. 19 



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

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

c 2 



20 ISLAND LIFE. [part i. 

Pariis luguhris, allied to the marsh tit, is confined to South-east 
V Europe and Asia Minor, from Hungary and South Russia to 

Palestine ; and Parus cindus, another allied form, is confined 
to the extreme north in Lapland, Finland, and perhaps Northern 
Russia and Siberia. Another beautiful little bird, the crested tit- 
mouse {Parus cristatus) is sometimes placed in a separate genus. 
It inhabits nearly all Central and South Europe, wherever there 
are pine forests, from 6-4° 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 
Panis 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. 

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

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

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



CHAP. II.] THE ELEMENTARY FACTS OF DISTRIBUTION. 21 

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

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

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

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

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

6. Garndus 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 Eussia where it has 
been found as far west as Kazan in districts where the common 
jay also occurs. 

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

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

9. Garndus sbunsis. — The Chinese jay, is very closely allied 
to the Himalavan, of which it is sometimes classed as a 



22 ISLAND LIFE. [iaut i. 

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

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

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

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

In the accompanying map (see frontispiece) we have laid down 
the distribution of each species so far as it can be ascertained 
from the works of Sharpe and Dresser for Europe, Jerdon for 
India, Swinhoe for China, and Messrs. Blakiston and Pryer for 
Japan. There is, however, much uncertainty in many places, 
and gaps have to be filled up conjecturally, while such a large 
part of Asia is still very imperfectly explored, that considerable 
modifications may have to be made when the country becomes 
more accurately known. But though details may be modified 
we can hardly suppose that the great features of the several 
specific areas, or their relations to each other, will be much 
atFected; 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 overlapping of the several areas, and the iso- 
lation of many of the species; while the next most striking 
feature is the manner in which the Asiatic species almost sur- 
round a vast area in which no jays are found. The only species 
with large areas, are the European G. glandarius and the Asiatic 
G. Brandti. The former has three species overlapping it — in 
Algeria, in South-eastern and in North-eastern Europe respect- 
ively. The Syrian jay (No. 4), is not known to occur anywhere 



CHAP. II.] THE ELEMENTARY FACTS OF DISTRIBUTION. 23 

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

Discontinuous generic Areas. — It is not very easy to find 
good examples of genera whose species occupy two or more quite 
disconnected areas, for though such cases may not be rare, we 
are seldom in a position to mark out the limits of the several 
species with sufficient accuracy. The best and most remarkable 
case among European birds is that of the blue magpies, forming 
the genus Cyanopica. One species (6'. cooki) is confined (as 
already stated) to the wooded and mountainous districts of Spain 
and Portugal, while the only other species of the genus (C. cyanus) 
is found far away in North-eastern Asia and Japan, so that the 
two species are separated by about 5,000 miles of continuous 
land. Another case is that of the curious little water-moles 
forming the genus Mygale, one species M. muscmitica, being found 
only on the banks of the Volga and Don in South-eastern 
Russia, while the other, M. pyrenaica, is confined to streams on 
the northern side of the Pyrenees. In tropical America there 
are four different kinds of bell-birds beloncjintr to the genus 

DO O 

Chasmorhynchus, each of which appears to inhabit a restricted 



24 ISLAND LIFE. [iaet l. 

area completely separated from the others. The most northerly 
is C tricarunculatus of Costa Rica and Veragua, a brown bird with 
a white head and three long caruncles growing upwards at the 
base of the beak. Next comes C vxriegntus, in Venezuela, a 
white bird with a brown head and numerous caruncles on the 
throat, perhaps conterminous with the last; in Guiana, ex- 
tending to near the mouth of the Rio Negro, we have C. nivcus, 
the bell-bird described by Waterton, which is pure white, with 
a single long fleshy caruncle at the base of the beak ; the last 
species, C. nudicoUis, 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-rlncring notes like a bell or a blow on 
an anvil, as well as for their pecuhar colours. They are there- 
fore known to the native Indians wherever they exist, and we 
may be the more sure that they do not spread over the inter- 
vening areas where they have never been fouud, and where the 
natives know nothing of them. 

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

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



CHAP. 11.] THE ELEMKNTARY FACTS OF DISTRIBUTION. 25 

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

Pcndiaritics of Generic and Famihj Distribution. — Theexamples 
now given sufiSciently illustrate the mode in which the several 
species of a genus are distributed. We have ne.xt to consider 
genera as the component parts of families, and families of orders, 
from the same point of view. 

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



26 ISLAND LIFE. [par- i. 

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

As a great many genera consist of single species there is no 
lack of cases of great restriction, such as the curious lemur called 
the " potto " which is found only at Sierra Leone, and forms the 
genus Perodicticus ; the true chinchillas found onlj'in the Andes 
of Peru and Cliili south of 9° S. lat. and between 8,000 and 
12,000 feet elevation ; several genera of finches each confined to 
limited portions of the higher Himalayas, the blood-pheasants 
(Ithaginis) found only above 10,000 feet from Nej^al to East 
Thibet ; the bald-headed starling of the Philippine islands, the 
l3're-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 arc often as unmistakably allied as are the species 
of a genus : and it is these cases that furnish the most interest- 
ing problems to the student of distribution. We must therefore 
consider them somewhat more fully. 

Among mammalia the most remarkable of these divided 
fiimilies is that of the camels, of which one genus Camelus, 
the true camels, comprising the camel and dromedary, is con- 
fined to Asia, while the other, Auchenia, comprising the llamas 
and alpacas, is found only in the high Andes and in the plains 
of temperate South America. Not only are these two genera 
separated by the Atlantic and by the greater part of the land of 
two continents, but one is confined to the Northern and tlie 
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 con- 
fined to Madagascar and the large West Indian islands Cuba and 
Hayti, the former containing five genera and the latter a single 
genus with a species in each island. Here again w-e have the 
whole continent of Africa as well as the Atlantic ocean separat- 
ing allied genera. Two famihes of rat -like animals, Octodon- 
tidfe and Echimyidffi, are also divided by the Atlantic. Both are 
mainly South America, but the former has two genera in North 
and East Africa, and the latter also two in South and West 



cHAr. II.] THE ELEMENTARY FACTS OF DISTRIBUTION. 27 

Africa. Two other families of mammalia, tliough confined to 
the Eastern hemisphere, are yet markedly discontinuous. The 
Tragulidce 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, 
Hyomoschu.?, is confined to West Africa. The other family is 
the Simiidaj or arithropoid 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 Echimyidaj and other rodents of Africa and 
South America. 

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

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



28 ISLAND LIFE. [paet i. 

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

General features of Overlapping aiul Discontinuous Areas. — 
These numerous examples of discontinuous genera and families 
form an important section of the facts of animal dispersal which 
any true theory must satisfactorily account for. In greater or less 
l^rominence they are to be found all over the world, and in every 
group of animals, and they grade imperceptibly into those cases 
of conterminous and overlapping areas which we have seen to 
prevail in most extensive groups of species, and which are 
perhaps even more common in those large families which consist 
of many closely allied genera. A sufficient proof of the over- 
lapping of generic areas is the occurrence of a number of genera 
of the same family together. Thus in France or Italy about 
twenty genera of warblers (Sylviadte) are found, and as each 
of the thirty-three genera of this family inhabiting temperate 
Europe and Asia has a different area, a gi'eat number must here 
overlap. So, in most parts of Africa at least, ten or twelve 
genera of antelopes may be found, and in South America a 
large proportion of the genera of monkeys of the family Cebidie 
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 Bovidge, or hollow-horned ruminants, which have 
a few isolated genera in the Eocky 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 ftimilies sometimes consist 
of single genera and even single species, they often present 



CHAP. II.] THE ELEMENTARY FACTS OF DISTRIBUTION. 29 



examples of very restricted range ; but what is perhaps move 
interesting are those cases in which a family contains mimeroiis 
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 extra- 
tropical South Africa; the hill-tits (Liotrichid;e), a family of 
eleven genera and thirty-five species almost wholly limited to 
the Himalayas, but with a few straggling species in the Malay 
countries; the Pteroptocliid;e, large wren-like birds, consisting 
of eight genera and nineteen species, almost entirely confined 
to temperate South America and the Andes ; and the birds-of- 
paradise, consisting of nineteen or twenty genera and about 
thirty-five species, almost all inhabitants of New Guinea and 
the immediately surrounding islands, while a few, doubtfully 
belonging to the family, extend to East Australia. Among 
reptiles the most striking case of restriction is that of the 
rough-tailed burrowing snakes (Uropeltidaj), the five genera 
and eighteen species being strictly confined to Ceylon and 
the southern parts of the Indian Peninsula. 

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

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



30 ISLAND LIFE. [rAitr i. 

spiny Echidna, to Australia. Among birds the Stnithiones or 
ostrich tribe ai-e almost confined to the three Southern con- 
tinents, South America, Africa and AustraUa; 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 Geograpliical Divisions of tlie Globe do not correspond to Zoological 
divisions — Tlie range of British Mammals as indicating a Zoological 
Eegion — Range of East Asian and North African Mammals — The 
Range of British Birds — Range of East Asian Birds— The limits of the 
Pala;arctic Region — Characteristic features of the Pala^arctic Region — 
Definition and characteristic groups of the Ethiopian Region — Of the 
Oriental Region — Of the Australian Region — Of the Nearctic Region — 
Of the Neotropical Region — Comparison of Zoological Regions with 
the Geographical Divisions of the Globe. 

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

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



32 ISLAND LIFE. [parti. 

of distribution occupies a large portion of Europe. There are, 
indeeJ, a few species limited to Central or Western or Southern 
Europe, and these are almost the only cases in which we can 
use tlie 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 pi'obably no single 
animal or group contiued to Asia which is not also more or less 
nearly confined to the tropical or the temperate portion of it. 
The only exception is perhaps the tiger, which may really be 
called an Asiatic animal, as it occupies nearly two-thirds of the 
continent; but this is an unique example, while the cases in 
which Asiatic animals and groups are strictly limited to a 
portion of Asia, or extend also into Europe or into Africa or to 
the Malay Islands, are exceedingly numerous. So, in Africa, 
very few groups of animals range over the whole of it without 
going beyond either into Europe or Asia Minor or Arabia, 
while those which are purely African are generally confined to 
the portion south of the tropic of Cancer. Australia antl 
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 groujis especially characteristic of 
South America are found also beyond the isthmus of Panama, 
in what is geographically part of the northern continent. 

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



-CHAP. in.J 



ZOOLOGICAL REGIONS. 



13rimary zoological divisions of tbe 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 Mamnuds as indicating a Zoological 
Region. — We will first take our commonest wild mammalia and 
see how far they extend, and especially whether they are con- 
fined to Europe or range over parts of other continents : 



1. Wildcat. 

2. Fox 

3. Weasel.... 

4. Otter 

5. Badger 

6. Stag 

7. Hedgehog 

8. Mole 

9. Squirrel . 

10. Dormouse., 

11. Water-rat. 

12. Hare 

13. Rabbit 



Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 
Europe 



N. Africa 
N. Africa 
N. Africa 
N. Africa 
N. Africa 
N. Africa 



N. Africa 



Siberia, 
Central 
Central 
Siberia. 
Central 
Central 
Central 
Central 
Central 



Afghanistan. 
Asia to Anioor. 
Asia to Amoor. 

Asia to Amoor. 

Asi:i to Amoor. 

Asia to Amoor. 

Asia. 

Asia to Amoor. 



Central Asia to Amoor. 
W. Siberia, Persia. 



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

Range of East Asian and North African Mammcds. — 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 

D 



34 ISLAND LIFE. [fart i. 

latitude as Germany. We find that there are forty-four ter- 
restrial species (omitting the bats, the seals, and other marine 
animals), and of these no less than twenty-si.x: are identical with 
European species, and twelve or thirteen more are closely allied 
representatives, leaving only five or six which are peculiarly 
Asiatic. We can hardly have a more convincing proof of the 
essential oneness 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) because a con- 
siderable number of West Asiatic and desert forms occur. 
Having, however, shown that Europe and Western Asia have 
almost identical animals, we may treat all these as really 
European, and we shall then be able to compare the quadrupeds 
of North Africa with those of Eurojie and West Asia. Taking 
those of Algeria as the best known, we find that there ai'c 
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 fift}'- 
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. 

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



CHAP. III.] ZOOLOGICAL REGIONS. 25 

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

I. Britisd Birds wuich extend to North Africa and Central or 
North-east Asia. 

1. Lan'ius collurio Red-backed Slirike (a!eo all Africa). 

2. Oriolm Galhulo Golden Oriole (also all Africa). 

3. Turdus musicus Song-Thrush. 

4. „ iliacus Red-wing. 

5. „ pilaris Fieldfare. 

6. Monticola saxatUis Blue rock Thrush. 

7. Ruticilla suecica Bluethroat (also India in winter). 

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

9. „ cmanthe Wheatear (also N. America). 

10. Acrocephalus arundinaceus Great Reed-Warbler. 

11. Sylvia cunuca Lesser Whitethroat. 

12. Parus 7naJor Great Titmouse. 

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

14. „ ruii Yellow Wagtail. 

15. Anthus (rivialis Tree Pipit. 

16. „ spiloletia Water Pipit. 

17. „ campestris Tawny Pipit. 

18. Alauda arvensis ..: Skylark. 

19. „ cristata Crested Lark. 

20. Emberiza sclxenicltis Reed Bunting. 

21. „ citrinella Yellow-hammer. 

22. Fringilla montifringilla ... Brambling. 

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

24. ,, domesticus House Sparrow. 

25. Coccothraustes vulgans ... Hawfinch. 

26. Carduelis spinas Siskin (also China). 

27. Ldxia currirnsira Crossbill. 

28. Sturnus vulgaris Starling. 

D 2 



3G ISLAND LIFE. [paut i, 

29. Pyrrhocorax graculus Chough. 

30. Corvus corone Crow. 

31. Jlirundo rustica Swallow (all Africa and Asia). 

32. Cotyle riparia Sand Martin (also India and N. America). 



II. Beitish Birds which eange to Cestral ob North-east Asia. 

1 . Lanius excuhitor Great Grey Shrike. 

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

3. „ afrigularis Black-throated Thrusk 

4. Acrocephalus nav'ius Grasshopper Warbler. 

5. Phylloscopus siiperciliosus Yellow-browed Warbler. 

6. Certhia familiaris Tree-creeper. 

7. Parus cceruleus Blue Titmouse. 

8. ,, ater Coal Titmouse. 

9. „ pahistris Marsh Titmouse. 

10. Acredula caudata Long-tailed Titmouse. 

11. Ampelis garrulus Wax-wing. 

12. Anthus richardi Richard's Pipit. 

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

14. Pleclrop?tanes nivalis Snow-Bunting (also X. America). 

15. „ lapponicus Lapland Bunting. 

16. Emieriza rustica Rustic Bunting (also China). 

17. „ pusilla Little Bunting. 

18. L'mota linaria Mealy Redpole (also N. America). 

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

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

21. Loxia hi/asciata Two-barred Crossbill. 

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

23. Corvus corax Raven (also N. America). 

24. Pica rustica Magpie. 

25. Nucifraga caryocatactes Nutcracker. 



III. British Birds easgisg isto 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. „ atricapilla Pied Flycatcher (also Central Africa). 

5. Turdus viscivorus Mistletoe-Thrush (N. India in ■wTnter). 

6. „ merula Blackbird. 

7. „ torquatus Ring Ouzel. 

8. Accentor modnlaris Hedge Spirrow. 

9. Erithacus rubecula Redbreast. 

10. Daulias luscinia Nightingale. 

11. RuticiUa phcEnicurus Redstart. 

12. „ tithys Black Redstart 

13. Saxicola rubetra Whinchat. 

14. Aedon galactodes Rufous Warbler. 

15. AcTocephalus streperus Reed Warbler. 

16. „ schxnohenus... Sedge Warbler. 



CHAT. III.] 



ZOOLOGICAL REGIONS. 



37 



17. Afelizophilus uiidatus Dartford Warbler. 

18. SylviaTufa Greater Whitethroat. 

19. ,, salicaria Garden Warbler. 

20. „ atricapUla Blackcap. 

21. „ orphea Orphean Warbler. 

22. PhjUoscopus sibilalrix ...... Wood Wren. 

23. „ trochilus Willow Wren. 

24. „ collybila Cbiffchaflf. 

25. Regulus crUtatus ■ Golden-crested Wren. 

26. „ ignicapillm Fire-crested Wren. 

27. Troglodytes parvulm Wren. 

28. Sitta cwsia Nuthatch. 

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

30. ,, flava Blue-headed Wagtail. 

31. Anthus pratensis Meadow-Pipit. 

32. Alauda arborea Woodlark. 

33. Calandrella brachydactyUi... Short-toed Lark. 
3-t. Emberiza miUaria Common Bunting. 

35. „ cirlus Cirl Bunting. 

36. „ hortulaiia Ortolan. 

37. Fringilla caslebs Chafiinch. 

38. Coccothrausles chloris Greenfinch. 

39. Serinus hortulanas Serin. 

40. Carduelis elegans Goldfinch. 

41. Linota cannabina Linnet. 

42. Corvus monedula Jackdaw. 

43. Chelklon urbka House-Martin. 



IV. British Birds rangiso to North Africa. 

1. Hypolais icterina Icterine Warbler. 

2. Acroceplialus aquaticus Aquatic Warbler, 

3. ,, luscinioides Savi's Warbler. 

4. MotaciUa lug ubris Pied Wagtail. 

5. Pyrrliula europma Bullfinch. 

6. Garrulus glandarius Jay. 

V. British Birds ranging to Wkst Asu only. 

1. Muscicapa jiarva Red-breasted Flycatcher (to N. W. India). 

2. Panurus biarmicus ... Bearded Titmouse. 

3. Melanocorypha sibirica White-winged Lark. 

4. Euspiza melanocephala Black-headed Bunting. 

5. Lhwta Jlavirostris Twite. 

6. Corvus frugilegus Rook. 



YI. British Birds confined to Europe. 

1. Cinclus aquaticus Dipper. 

2. Accentor collar is Alpine Accentor.' 

3. Parus cristatus Crested Titmouse. 

4. Anthus obscurus Bock Pipit. 

5 Linota rufescens Lesser Redpoll. 

6. Loxia pityopsittacus Parrot Crossbill. 



38 ISLAND LIFE. [iart i. 

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. 

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

6 species which do not range out of Europe. 
These figures agree essentially with those furnished by the 
mammalia, and complete the demonstration that all the tem- 
perate portions of Asia and North Africa must be added to Europe 
to form a natural zoological division of the earth. We must also 
note how comparatively few of these overpass the limits thus 
indicated ; only seven species extending their range occasionally 
into tropical or South Africa, eight into some parts of tropical 
Asia, and six into arctic or temperate North America. 

Range of East Asian Birch. — 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 neces-sarily, because it is 
jiossible that a totally distinct North Asiatic fauna might there 
prevail ; and, although our birds go eastward to the remotest 
jmrts of Asia, their birds might not come westward to Europe. 
The birds of Eastern Siberia have been carefully studied by 
Russian naturalists and afford us the means of making the 
required comparison. There are 151 species belonging to the 
orders Passeres and Picarias (the perching and climbing birds), 
and of these no less than 77, or more than half, are absolutely 
identical with European species; G3 are peculiar to North 
Asia, but all except five or six of these are allied to European 
forms ; the remaining 11 species are migrants from South- 
eastern Asia. The resemblance is therefore equally close 
whichever extremity of the Euro-Asiatic continent we take 
as our starting point, and is equally remarkable in birds as in 
mammalia. We have now only to determine the limits of this. 



CHAP. III.] ZOOLOGICAL REGIONS. 39 

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

The Limits of the Falcearctic 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 jJaces, 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 chajiterj 
so that the southern boundary alone remains, but as this runs 
across Ihe 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 difSculty. The Euro-Asiatic animals 
undoubtedly extend to the northern borders of the Sahara, 
while those of tropical Africa come up to its southern margin, 
the desert itself forming a kind of dry sea between them. Some 
of the species on either side penetrate and even cross the 
desert, but it is impossible to balance these with any accuracy, 
and it has therefore been thought best, as a more matter of 
convenience, to consider the geographical line of the tropic of 
Cancer- to form the boundary. We are thus enabled to define 
the Pala?arctic region as including all north temperate Africa ; 
and, a similar interminghng of animal tyjjes occurring in Arabia, 
the same boundary line is continued to the southern shore of 
the Persian Gulf Persia and Afghanistan undoubtedly belong 
to the Palaearctic region, and Baluchistan should probably go 
with these. The boundary in the north-western part of India 
is again difficult to determine, but it cannot be far one way or 
the other from the river Indus as far up as Attock, opposite the 
mouth of the Cabool river. Here it will bend to the south-east, 
passing a little south of Cashmeer, and along the southern 
slopes of the Himalayas into East Thibet and China, at heights 
varying from 0,000 to 11,000 feet according to soil, a.spect, 
and shelter. It may, perhaps, be defined as extending to the 
upper belt of forests as far as coniferous trees prevail ; but 



40 ISLAND LIFE. [pinr i, 

the temperate and tropical faunas are here so intermingled that 
to draw any exact parting line is impossible. The two faunas 
are, however, very distinct. In and above the pine woods there 
are abundance of warblers of northern genera, with wrens, 
numerous titmice, and a great variety of buntings, grosbeaks, 
bullfinches, and rosefinches, all more or less nearly allied to the 
birds of Europe and Northern Asia ; while a little lower down 
we meet with a host of peculiar birds allied to those of tropical 
Asia and the Malay Islands, but often of distinct genera. There 
can be no doubt, therefore, of the existence here of a pretty 
sharp line of demarcation between the temperate and tropical 
faunas, though this line will be so irregular, owing to the com- 
plex system of valleys and ridges, that in our j)resent ignorance of 
much of the country it cannot be marked in detail vn an}- 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 Palaearctic region 
a Uttle south of Shanghae on the coast. Several tropical genera 
come as far as Ningpo or even Shanghae, but rarely beyond ; 
while in Formosa and Amoy tropical forms predominate. Such 
decidedly northern forms as bullfinches and hawfinches are found 
at Shanghae ; hence we may commence the boundary line on 
the coast between Shanghae and Ningpo, but inland it probably 
bends a little southward, and then northward to the mountains 
and valleys of West China and East Thibet in about 32° N. 
latitude; where, at Moupin, a French missionary, Pere David, 
made extensive collections showing this district to be at the 
junction of the tropical and temperate faunas. Japan, as a 
whole, is decidedly Paltearctic, although its extreme southern 
portion, owing to its mild insular climate and evergreen vege- 
tation, gives shelter to a number of tropical forms. 

Characteristic feafuns of the Palcearctic Region. — Having thus 
demonstrated the unity of the Palaearctic region by tracing out 
the distribution of a large proportion of its mammalia and birds. 



CHAP. 111.] ZOOLOGICAL REGIONS. 41 

it only remains to show how far it is characterised by peculiar 
groups such as genera and families, and to say a few words on 
the lower forms of life which prevail in it. 

Taking first the mammalia, we find this region is distinguished 
by its possession of the entire family of Talpidae or moles, 
consisting of eight genera and sixteen species, all of which are con- 
fined to it except one which is found in North-west America, and 
two which extend to Assam and Formosa. Among carnivorous 
animals the 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 Bovidas, chiefly antelopes ; while the entire group of 
goats and sheep, comprising twenty-two species, is almost confined 
to it, one species only occurring in the Rocky Jilountains of North 
America and another in the Neilgherries of Southern India. 
Among the rodents there are nine genera, with twenty-seven 
species wholly confined to it, while several others, as the voles, 
the dormice, and the pikas, have only a few sjjecies elsewhere. 

In birds there are a large number of peculiar genera of 
which wc need only mention a few of the more important, as 
the grasshopper-warblers (Locustella) with seven sj)ecies, the 
Accentors with twelve species, and about a dozen other genei-a 
of warblers, including the robins; the bearded titmouse and 
several allied genera ; the long-tailed titmice forming the genus 
Acredula ; the magpies, choughs, and nutcrackers ; a host of 
finches, among which the bullfinches (Pyrrhula) and the buntings 
(Emberiza) are the most important. The true pheasants 
(Phasianus) are wholly Patearctic, except one species in For- 
mosa, as are several genera of wading birds. Though the 
reptiles of cold countries are few as compared with those of the 
tropics, the Pala;arctic region in its warmer portions has a 
considerable number, and among these are many which are 
peculiar to it. Such are two genera of snakes, seven of lizards, 
eight of frogs and toads, and eight of newts and salamanders; 
while of fresh-water fishes there are about twenty peculiar 
genera. Among insects we may mention the elegant Apollo 
butterflies of the Alps as forming a peculiar genus (Parnassius), 



42 ISLAND LIFE. [paet. i. 



only found elsewhere in the Rocky Mountains of North America, 
while the beautiful genus Thais of tlie south of Europe and 
Sericiuus 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 allies 
Procerus and Procrustes, containing nearly 300 species, is almost 
wholly confined to this region, and would alone serve to distin- 
guish it zoologically from all other parts of the globe. 

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

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

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



CHAr. iii.J ZOOLOGICAL REGIONS. 43 

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

Among birds the most conspicuous and remarkable are, the 
gi'cat-billcd vulture-crows (Corvultur), the long-tailed why- 
dah finches (Vidua), the curious ox-peckers (Buphaga), the 
splendid metallic starlings (Lamprocolius), the handsome plan- 
tain-eaters (Musophaga), the ground-hornbills (Bucorvus), the 
numerous guinea-fowls belonging to four distinct genera, the 
serpent-eating secretary-bird (Serpcntarius), the huge boat- 
billed heron (BaUeniceps), and the true ostriches. Besides 
these there arc three quite peculiar African families, the 
Musophagidae, or plantain-eaters, including the elegant crested 
touracos; the curious little finch-like colies (Coliida;), and the 
Irrisoridtt', 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 jjossesses an immense number of peculiar forms. These are 
not sufficiently known to require notice in a work of this cha- 
racter, but we may mention a few as mere illustrations; the 
puff-adders, the most hideous of poisonous snakes; the chame- 
leons, the most remarkable of lizards; the goliath-beetles, the 
largest and handsomest of the Cetoniido? ; and .some of the 
Achatina% which are the largest of all known land-shells. 

Definition and Cliaraderistic Groups of the Oriental Region. 
— The Oriental region comprise.^ all Asia south of the Palre- 
arctic limits, and along with this the Malay Islands as far as 
the Philippines, Borneo, and Java. It was called the Indian 
region by Mr. Sclater, but this term has been objected to 
because the Indo-Chinese and Malayan districts are the rich- 
est and most characteristic, while the peninsula of India is 
the poorest portion of it. The name " Oriental " has therefore 
been adopted in my work on Tlie Gcoriraphical Distrihntion of 



44 ISLAND LIFE [part i. 



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

The great features of the Oriental region are, the lon^-armed 
apes, the orang-utans, the tiger, the sun-bears and honey- 
bears, the tapir, the chevrotains or mouse-deer, aad the Indian 
elephant. Its most conspicuous birds are the immense number 
and variety of babbling-thrushes (Timaliidse), its beautiful 
little hill-tits (Liotrichidae), its green bulbuls (Phyllornithida3), 
its many varieties of the crow-family, its beautiful gapers and 
pittas adorned with the most delicate colours, its great variety 
of hornbills, and its magnificent Phasianidiv, comprising the 
peacocks, argus-pheasants, fire-backed pheasants, and jungle - 
fowl. Many of these are, it is true, absent from the peninsula 
of Hindostan, but sufficient remain there to ally it with the 
other parts of the region. 

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

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



CHAP. III.] ZOOLOGICAL EEGIONS. 45 

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

Reptiles are as abundant as in Africa, but they present no 
well-known groups which can be considered as specially cha- 
racteristic. Among insects we may notice the magnificent 
golden and green Papilionidas of various genera as being un- 
equalled in the world ; while the great Atlas moth is probably 
the most gigantic of Lepidoptera, being sometimes ten inches 
across the wings, which are also very broad. Among the beetles 
the strange flat-bodied Malayan mormolyce is the largest of all 
the Carabida', while the catoxantha is equally a giant among 
the Buprestidae. On the wliole, 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 Groups of the Australian 
Begion. — The Australian region is .so well marked off from 
the Oriental, as well as from all other parts of the world, by 
zoological peculiarities, that we need not take up much time in 
describing it, especially as some of its component islands will 
come under review at a subsequent stage of our work. Its 
most important portions are Australia and New Guinea, but 
it also includes all the Malayan and Pacific Islands to the 
east of Borneo, Java, and Bali, the Oriental region termi- 
nating with the submarine bank on which those islands are 
situated. The island of Celebes is included in this region 
from a balance of considerations, but it almost equally well 
belongs to the Oriental, and must be left out of the account 
in our general sketch of the zoological features of the Austra- 
lian region. 

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



46 ISLAND LIFE. [fabt i. 

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

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



CHAP. III.] ZOOLOGICAL REGIONS. 47 

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

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

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

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



48 ISLAND LIFE. [pabt i. 

quite so conspicuous but nevertheless very important. We have 
first, three peculiar genera of moles, one of which, the star- 
nosed mole, is a most extraordinary creature, quite unlike 
anything else. Then there are three genera of the weasel 
family, including the well-known skunk (Mephitis), all quite 
different from Eastern forms. Then we come to a peculiar 
family of carnivora, the racoons, very distinct from anything in 
Europe or Asia ; and in the "Rocky Mountains we find the 
prong-horn antelope (Antilocapra) and the mountain goat of 
the trappers (Aplocerus), both peculiar genera. Coming to 
the rodents we find that the mice of America differ in some 
dental peculiarities from those of the rest of the world, and 
thus form several dLstinct genera; the jumping mouse (Xapus) 
is a peculiar form of the jerboa family, and then we come to the 
pouched rats (Geomyidse) 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 
pecuhar 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 Palffiarctic region. 

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



CHAP. III.] ZOOLOGICAL BEGIOXS. 49 

like starlings to the hang-uests, loteridue ; aud these four 
peculiar families comprise more than a hundred species, and 
give a special character to the ornithology of the country. 
Add to these such peculiar birds as the mocking thrushes 
(Mimus), the blue jays (Cyanocitta), the tanagers, the peculiar 
genera of cuckoos (C'occygus and Crotophaga), the humming- 
birds, the -wild turkeys (Meleagris), and the turkey-buzzards 
(Catharte.s), and we see tliat if there is any doubt as to the 
mammals of North America being sufficient!}' distinct to justify 
the creation of a separate region, the evidence of the birds 
would alone settle the question. 

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

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

E 



50 ISLAND LIFE. [part i. 

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

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

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



CHAP. 111.] ZOOLOGICAL REGIONS. 51 

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

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

We must also notice the preponderance of low or archaic 
types among the animals of South America. Edentates, 
marsupial.s, 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 tlie absence of the 
singing muscles, is excessively prevalent, the enormous groups 
of the aut-tliruslies, tyrants, tree-creepers, manakius, and 
chatterers belonging to it. The Picariaj (a lower group) also 
prevail to a far greater extent than in any other regions, both 
in variety of forms and number of species ; and the chief 
representatives of the gallinaceous birds — the curassows and 
tinamous, are believed to be allied, the former to the brush- 
turkeys of Australia, the latter (very remotely) to the ostriches, 
two of the least developed types of birds. 

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

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

K 2 



52 ISLAND LIFE. [pabt i. 

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

In Central America, and especially in Mexico, we have an 
intermixture of Soutii American and North American animals, 
but the former undoubtedly predominate, and a large proportion 
of the peculiar Neotropical groups extend as far as Costa Rica. 
Even in Guatemala and Mexico we have howling and spider- 
monkeys, coati-mundis, tapirs, and armadillos ; while chatterers, 
manakins, ant -thrashes, and other peculiarly Neotropical groups 
of birds are abundant. There is therefore no doubt as to Mexico 
forming part of this region, although it is comparatively poor, 
and exhibits the intermingling of temperate and tropical forms. 
The West Indies are less clearly Neotropical, their poverty 
in mammals as well as in most other groups being extreme, 
while great numbers of North American birds migrate there 
in winter. The resident birds, however, comprise trogons, 
sugar-birds, chatterers, with many humming-birds and parrots, 
representing eighteen peculiar Neotropical genera ; a fact which 
decides the region to which the islands belong. 

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

ComjMrison of Zoological Begioiis vjith the Geograjihiccd 
Divisions of the Globe. — Having now completed our survey 



fHAi'. III.] ZOOLOGICAL liKGIUXS. 53 

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

Regions. Geographical Equivalent. 

Paliearctic EuRorE, with north temperate Africa and Asia. 

Ethiopian Africa (south of the Saliara) with Madaga.scar. 

Oriental Tropical Asia, to Philippines and Java. 

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

Nearctic North America, to North 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 C T I C P A L .E A R C T I C 

I I 

I Oriental 

Ethiopian I 

Neo - I 

TROPICAL Australian 



CHAPTER IV. 

EVOLUTION THE KEY TO DISTRIBUTION. 

Importance of tlie Doctrine of Evolution — Tlie Origin of Xew Species — 
Variation in Animals — The amount of variation in North American 
Birds — How new species arise from a variable species — Definition and 
Origin of Genera — Cause of the extinction of Species — The rise and 
decay of Species and Genera — Discontinuous specific areas, why rare — 
Discontinuity of the area of Parus palustris — Discontinuity of Emberiza 
schceniclus — Tlie European and Japanese Jays — Supposed examples of 
discontinuity among North American Birds — Distribution and antiquity 
of Families— Discontinuity a proof of antiquity — Concluding Beiuarks. 

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

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



CHAP. IV.] EVOLUTION THE KEY TO DISTRIBUTION. 55 

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

The Oriijin of Kcir S/mies. — 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 wc must remember that new species can only be 
formed when and where there is room for tliem. If a continent 
is fully stocked with animals, each species being so well adapted 
for its mode of life that it can overcome all the dangers to 
which it is exposed, and maintain on the average a tolerably 
uniform population, then, so long as no change takes place, no 
new species will arise. For everj' place or station is supposed 
to be filled by creatures perfectly adapted to all surrounding 
conditions, able to defend themselves from all enemies, and to 
obtain food notwithstanding the rivalry of many competitors. 
But such a perfect balance of organisms nowhere exists upon 
the eartE, and probably never has existed. The well-known 
fact that some species are very common, while others are very 
rare, is an almost certain proof that the one is better adapted 
to its position than the other ; and this belief is strengthened 
when we find the individuals of one species ranging into 
different climates, subsisting on ditferent food, and competing 
with ditferent 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 occur.s, either of 
climate or geograj)hy, some of the small and ill-adapted species 



,/ 



56 ISLAND LIFE. [part t. 

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

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

'^, centuries, or perhaps even a few generations, one or more new 

(^_jpecies 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 fully. Few persons consider how largely and universally 
all animals are varying. We know, however, that in every 
generation, if we could examine all the individuals of any 
common species, we should find considerable differences, not 
only in size and colour, but in the form and proportions of all 
the parts and organs of the body. In our domesticated animals 
we know this to be the case, and it is by means of the continual 
selection of such shght varieties to breed from that all our ex- 
tremely different domestic breeds have been produced. Think 
of the difference in every limb, and every bone and muscle, and 
probably in every part, internal and external of the whole body, 
between a greyhound and a bull-dog ! Yet, if we had the whole 
series of ancestors of these two breeds before us, we should pro- 
bably find that in no one generation was there a greater differ- 
ence than now occurs in the same breed, or sometimes even the 
same litter. It is often thought, however, that wild species do 
not vary sufiBciently 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 are able to adduce 
positive proof of their opinion. 



CHAP. IV.] EVOLUTION THE KEY TO DISTRIBUTION. 57 



The Amount of Variation in North American Birds. — An 
American naturalist, Mr. J. A. Allen, has made elaborate 
observations and measurements of the birds of the United 
States, and he finds a wonderful and altogether unsuspected 
amount of variation between individuals of the same species. 
They differ in the general tint, and in the markings and distri- 
bution of the colours; in size and proportions ; in the length of 
the wings, tail, bill, and feet ; in the length of particular feathers, 
altering the shape of the wing or tail ; in the length of the tarsi 
and of the separate toes, and in the length, width, thickness, and 
curvature of the bill. These variations are very considerable, 
often reaching to one-sixth or one-seventh of the average 
dimensions, and sometimes more. Thus Tardus fuscescens 
(Wilson's thrush), varied in length of wing from 3-58 to 416 
inches, and in the tail from 3'.55 to 400 inches ; and in twelve 
specimens, all taken in the same locality, the wing varied in length 
from 14'5 to 21 per cent, and the tail from 14 to 22-o 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 Dendneca coronata (the yeliow- 
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 ami marking vary to an equal extent; the 
dark streaks on the under surface of Melospiza mclodia (the 
American song-sparrow) being sometimes reduced to narrow 
lines, while in other specimens they are so enlarged as to cover 
the greater part of the breast and sides of the bodj', sometimes 
uniting on the middle of the breast into a nearly continuous 
patch. In one of the small spotted wood-thrushes, Turdus 
fuseescens, the colours are sometimes very pale, and the maidv- 
ings on the breast reduced to indistinct narrow lines, w'hile in 
other specimens the general colour is much darker, and the 
breast markings dark, broad, and triangular. Al^the variations 
here mentioned occur between adult males, so that there is no 



58 ISLAND LIFE. [part. i. 

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

These interesting facts entirely support the belief in the 
variability of all animals in all their parts and organs, to an ex- 
tent amply sufEcient for natural selection to work with. We may, 
indeed, admit that these are extreme cases, and that the majority 
of species do not vary half or a quarter so much as shown in the 
examples quoted, and we shall still have ample variation for all 
purposes of specific modification. Instead of an extreme varia- 
tion in the dimensions and proportions of the various organs of 
from 10 to 25 per cent, as is here proved to occur, we may as- 
sume from 3 to G 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 groups 
of equal extent, with regard to any particular character — as 
length of wing, or of toes, or thickness or curvature of bill, or 
strenglh of markings — we should have one group in which the 
mean or average character prevailed with little variation, one in 
which the character was greatly, and one in which it was little, 
developed. If we formed our groups, not by equal numbers, 
but by equal amount of variation, we should probably find, in 
accordance with the law of averages, that the central group in 
which the mean characteristics prevailed was much more nume- 
rous than the extremes, perhaps twice, or even three times, as 
great as either of them, and forming such a series as the follow- 
ing — 10 maximum, 30 mean, 10 minimum development. In 
ordinary cases we have no reason to believe that the mean cha- 
racters or the amount of variation of a species changes materially 
from year to year or from century to century, and we may there- 

1 These facts are taken from a memoir on The Mammals and Winter 
Birds of Florida, by J. A. Allen ; forming Vol. II., No. 3, of the Bulletin 
of the Museum of Comparative Zoology at Harvard College, Cambridge, 

Massachusetts. 



ciiAr. IV.] EVOLUTION THE KEY TO DISTRIBUTION. 59 



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

ILnn new Species arise from a variable Sjjecic.s. — It is now 
very easy to understaml 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 nmltiply at the 
expense^ of the rest. If the change of conditions spreads over 
~TEe^whole area occupied by the species, this one extreme form 
will replace the others ; while if the area shoiild be cut in two 
by subsidence or elevation, the conditions of the two parts may 
be modified in opposite directions, so as to be each adapted to 
one extreme form ; in which case the original type will become 
extinct, being replaced by two species, each foimed by a com- 
bination of certain extreme characters which had before existed 
in some of its varieties. 

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



fif^ ISLAND LIFE. [part i. 

greater wariness can escape their new foes. We may thus easily 
understand how a series of changes may occur at distant inter- 
vals, each leading to the selection and preservation of a special 
set of variations, and thus what was a single species may become 
/ transformed into a group of allied species ditlering from each 

/ other in a variety of ways, just as we find them in nature. 

— Among these species, however, there will be some which will 
have become adapted to very local or special conditions, and 
wiU 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 

I of structure, will be better adapted to succeed in the struggle 
for existence with other animals, will spread over a wider area, 
and increase so as to become common species. Sometimes these 
wUl acquire such a perfection of organisation by successive 
favourable modifications that thej' will be able to spread greatly 
beyond the range of the parent form. They then become what 
are termed dominant species, maintaining themselves in vigour 
and abundance over very wide areas, displacing other species 
with which they come into competition, and, under still further 
changes of conditions, becoming the parents of a new set of 
diverging species. 

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

A genus is a group of allied species which difi"ers 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. ^\lien 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 



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

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

A creature which has been thus modified in important 
characters will be a new type, specially adapted to fill its 
place in the economy of nature. It will almost certainly 
have arisen from au extensive or dominant group, because 
only such are sufficiently rich in individuals to afford an ample 
supply of the necessary variations, and it will inherit the r -v \ 
vigour of constitution and adaptability' to a wide range of '^u)oo^ 
conditions wlncli gave success to its ancestors. It will there- 
fore have every chance in its favour in the struggle for existence ; 
it may spread widely and displace many of its nearest allies, 
and in doing so will itself become modified superficially and 
become the parent of a number of subordinate sjiecies. It 
will now have become a dominant ffenm, occupying an entire 
continent, or perhaps even two or more continents, spreading in 
every direction till it comes in contact with competing forms 
better adapted to tlie different environments. Such a genus 
may continue to exist during long geological epochs ; but the_ 
time wiU generaJly_c^me when either physical changes, or '^ 
competing forms, or new enemies are too much for it, and it -^--^^ 
begins3o"Iosen[ts supremacy. First one then another of its 
component species will dwindle away and become extinct, till 
at last only a few species remain. Sometimes these soon follow 
the others and the whole genus dies out, as thousands of genera 
have died out during the long course of the earth's life-history ; 
but it will also sometimes happen that a few species will 
continue to maintain themselves in areas where they are removed 
from the influences that exterminated their fellows. 

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



62 ISLAND LIFE. [part 



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

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



CHAP. IV.] EVOLUTION THE KEY TO DISTEIBUTIOX. 63 

portions. This is the more likely to be the case because the"^ 
most recently formed species, probably adapted to local condi- ^ 
tions and therefore most removed from the general type of the 
group, will have the best chance of surviving, and these may 
exist at several isolated points of the area once occupied by the J 
whole group. We may thus understand how the phenomena' 
of discontinuous areas has come about, and we may be sure 
that when aUied 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. 

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

Among birils 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 ; w hile another reason 
may be that their powers of flight cause them to occupy on the 
average wider and less precisely defined areas than do the species 



64 ISLAND LIFE. [part i. 

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

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

Discontinuity of Emhcriza scJiamiclus. — 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 replaced by another smaller 

' See Ibis, 1879, p. 32. 




1 

I 

I 
1 



15 

a; 



THAP. IV.] EVOLUTION THE KEY TO DISTRIBUTION. fi5 

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

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

Supposed Examples of Eiscontinvity 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 

' Ibis, 1879, p. 40. 

F 



66 ISLAND LIFE. [part i. 

central plains and the vast ranges of the Rocky Mountains and 
Sierra Nevada, that we can hardly expect to find species whose 
areas may he 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 main- 
tained their continuity towards the north, while even when 
differentiated into two or more allied species their areas are 
often conterminous or overlapping. 

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

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

Distribution and Antiquity of Families. — Just as genera are 



CHAP. IV.] EVOLUTION THE KEY TO DISTBIBUTION. 67 

groups of allied species distinguished from all other groups by 
some well-marked structural characters, so fatinUes are groups 
of allied genera distinguished by more marked and more im- 
portant characters, which are generally accompanied by a pecu- 
liar outward form and style of colouration, and by distinctive 
habits and mode of life. As a genus is usually more ancient 
than any of the species of which it is composed, because during 
its growth and development the original rudimentary species 
becomes supplanted by more and more perfectly adapted forms, 
so a family is usually older than its component genera, and 
during the long period of its life-history may have survived 
man}' 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 there- 
fore be an indication of antiquity, and the more widely the 
fragments are scattered the more ancient we may usually pre- 
sume the parent group to be. A striking example is furnished 
by the strange reptilian fishes forming the order or sub-order 
Dipnoi, which includes the Lepidosiren and its allies. Only 
three or four living species are know-n, and these inhabit tropical 
rivers situated in the remotest continents. The Lepidostren 
paradoxa is only known from the Amazon and some other South 
American rivers. An allied species, Lqndosiren annedens, some- 
times placed in a distinct genus, inhabits the Gambia in West 
Africa, while the recent discovery in Eastern Australia of the 
Ceratodus or mud-fish of Queensland, adds another form to the 
same isolated group. Numerous fossil teeth, long known from 
the Triassic beds of this country, and also found in Germany 
and India in beds of the same age, agree so closely with those 
of the living Ceratodus that both are referred to the same genus. 
No more recent traces of any such animal have been discovered, 
but the Carboniferous Ctenodus and the Devonian Dipterus 
evidently belong to the same group, while in North America 
the Devonian rocks have yielded a gigantic allied form which 

F 2 



68 ISLAND LIFE. [pabt i. 

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

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

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



CHAP. IV.] EVOLUTION THE KEY TO DISTEIBUTIOX. 69 

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



CHAPTER Y. 

THE POWERS OF DISPERSAL OF ANIMALS AND PLANTS. 

Statement of the general question of Dispersal — Tlie Ocean as a barrier to 
the dispersal of Mammals — The dispersal of Birds — The dispersal of 
Reptiles — The dispersal of Insects — The dispersal of Land Mollusca — 
Great antiquity of Land-shells — Causes favouring the abundance of 
Land-shells — The dispersal of Plants — Special adaptability of Seeds for 
dispersal — Birds as agents in the dispersal of Seeds — Ocean currents as 
agents in Plant dispersal — Dispersal along mountain-chains — Antiquity 
of Plants as affecting their distribution. 

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

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



CHAP, v.] DISPERSAL OF ANIMALS AND PLANTS. 71 



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

The Ocean as a Barrier to the Dispersal of Mammals. — A 
wide extent of ocean forms an almost absolute barrier to the 
dispersal of all land animals, and of most of those which 
are aerial, since even birds cannot fly for thousands of miles 
without rest and without food, unless they are aquatic birds 
who can find both rest and food on the surface of the ocean. 
We may be sure, therefore, that without artificial help neither 
mammalia nor land birds can pass over very wide oceans. The 
exact width they can pass over is not determined, but we have 
a few facts to guide us. Contrary to the common notion, pigs 
can swim very well, and have been known to swim over five or 
six miles of sea, and the wide 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 endeavour to return to the shore. We 
cannot therefore believe that they would ever swim over fifty or 
a hundred miles of sea, and the same may be said of all the 
larger mammalia. Deer also swim well, but there is no reason 
to believe that they would venture out of sight of land. With 
the smaller, and especially with the arboreal, mammalia, there is 
a much more eifectual way of passing over the sea, by means of 



72 ISLAND LIFE. [part i. 

floating trees, or those floating islands which are often formed 
at the mouths of great rivers. Sir Charles Lyell describes such 
floating islands which were encountered among the Moluccas, on 
which trees and shrubs were growing on a stratum of soil which 
even formed a white beach round the margin of each raft. 
Among the Philippine 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 mice might 
have been carried away on the trees which formed part of such 
a raft, and might thus colonise a new island ; though, as it 
would require a pair of the same species to be carried away 
together, such accidents would no doubt be rare. Insects, how- 
ever, and land-shells would almost certainly be abundant on such 
a raft or island, and in this way we may account for the wide 
dispersal of many species of both these groups. 

Notwithstanding the occasional action of such causes, we 
cannot suppose that they have been effective in the dispersal of 
mammalia as a whole ; and whenever we find that a considerable 
number of the mammals of two countries exhibit distinct 
marks of relationship, we may be sure that an actual land con- 
nection, or at all events an approach to within a very few miles 
of each other, has at one time existed. But a considerable 
number of identical ' mammalian families and even genera are 
actually found in all the great continents, and the present 
distribution of land upon the globe renders it easy to see how 
they have been able to disperse themselves so widely. All the 
great land masses radiate from the arctic regions as a common 
centre, the only break being at Behrings Strait, which is so 
shallow that a rise of less than a thousand feet would form a 
broad isthmus connecting Asia and America as far south as the 
parallel of C0° N. Continuity of land therefore may be said to 
exist already for all parts of the world (except Australia and a 
number of large islands, which will be considered separately), 
and we have thus no difficulty in the way of that former wide 



CHAP, v.] DISPERSAL OF ANIMALS AND PLANTS. 73 

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

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

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

The Dispersal of Amphibia and Fresh-irnter Fishes. — 
The two lower groups of vertebrates. Amphibia and fresh- 
water fishes, possess special facilities for dispersal, in the fact of 
1 Lyell'B Principles of Geology, II., p. 3C9. 



74 ISLAND LIFE. [i'Art i. 

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



CHAP, v.] DISPEESAL OF AMJIALS AND PLANTS. 75 

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

Hie Dispersal 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 hghtness they can be carried immense 
distances by gales of wind. Others can survive exposure to 
salt water for many days, and may thus be floated long distances 
by marine currents. The eggs and larvaj often inhabit solid 
timber, or lurk under bark or in crevices of logs, and may 
thus reach any countries to which such logs are floated. Another 
important factor in the problem is the immense antiquity of 
insects, and the long persistence of many of the best marked 
types. The rich insect fauna of the .Miocene period in Switzer- 
land consisted largely of genera still inhabiting Europe, and 
even of a considerable number identical, or almost so, with living 
species. Out of 1-56 genera of Swiss fossil beetles no less than 
114 are still living; and the general character of the species is 
exactly like that of the existing fauna of the northern hemi- 
sphere in a somewhat more southern latitude. There is, there- 
fore, evidently no difficulty in accounting for any amount of 
dispersal among insects ; and it is all the more surprising that 
with such powers of migration they should yet be often as 
restricted in their range as the reptiles or even the 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 carried into a new country they cannot live. Many can 
only feed in the larva state on one species of plant ; others are 
bound up with certain groups of animals on whom they are 
more or less parasitic. Climatal influences have a great 
effect on their delicate bodies; w^hile, 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 



76 ISLAND LIFE. [part i. 

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

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

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

^ Mr. Darwin found that the large 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 
water in calm weather, the distance might extend to a thousand miles or 
more. The eggs of fresh-water luoUusca are known to attach themselves 
to the feet of aquatic birds, and this is supposed to account for their very 
wide diffusion. 



CHAP, v.] DISPERSAL OF ANIMALS AND PLANTS. 77 

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

Land-shells have therefore survived all the revolutions the 
earth has undergone since 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 with them, 
though the variety of species and genera bears a direct relation 
to the facilities of transfer, and the shell fauna is never very 
rich and varied, except in countries which have at one time or 
other been united to some continental land. 

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

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



78 ISLAND LIFR. [part i. 

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

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

When, however, we consider the enormous quantity of seeds 
produced by plants, — that great numbers of these are more or 
less adapted to be carried by the wind, — and that winds of great 
violence and long dui'ation occur in most parts of the world, we 
ai-e as sure that seeds must be cariied 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 



CHAP, v.] DISPERSAL OF ANIMALS AND PLANTS. 79 

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

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

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

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



80 ISLAND LIFE. [part i. 



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



CHAPTER VI. 

GEOGRAPHICAL AND GEOLOGICAL CHANGES : THE 
PERMANENCE OF CONTINENTS. 

Changes of Land and Sea, their nature and extent — Shore-deposits and 
stratified Kucks — The Movements of Continents — Supposed Oceanic 
formations ; the Origin of Clialk — Fresh-water and Sliore-deposits as 
proving the permanence of Continents — Oceanic Islands as indications 
of tlie permanence of Continents and Oceans — General stability of 
Continents with constant change of form — Effect of Continental 
Changes on the Distribution of Animils — 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 wliich have occurred in 
particular cases will be described when we discuss the origin 
and relations of the faunas of the different classes of islands. 
We have here only to consider the general character and extent 
of such changes, and to correct some erroneous ideas which are 
prevalent on the subject. 

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 diy land has undoubtedly, at one time or other, formed 
part of a sea-bottom, and we can hardly exclude the surfaces 
occupied by volcanic and fresh-water deposits, since, in many 
cases, if not in all, these rest upon a substratum of marine 
formations. At first sight, therefore, it seems a necessary 
inference that when the present continents were under water 
there must have been other continents .situated where we now 



82 ISLAND LIFE. [part i. 

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

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

• Principles of Geology, 11th Ed., Vol. I., p. 258. 

* On Limestone as an Index of Geological Time. 



CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 83 

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

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

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

G 2 



84 ISLAND LIFE. [part i. 

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

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

* In liis PreUminarij Report on Oceanic Deposit, Mr. Murray says: — "It 
has been found that the deposits taking place near continents and islands 
have received their chief characteristics from the presence of the debris 
of adjacent hinds. 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 deposited 
\\ itliin 200 miles of the land." {Proceedings of the Royal Society of Edin- 
burgh, 1876-77, p. 253.) 



CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 85 



thickest masses of sedimentary rock — those of the ancient 
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 nuiddy pool. These 
phenomena unequivocally point to shallow and even littoral 
waters. They occur from bottom to top of formations, which 
reach a thickness of several thousand feet. They can be in- 
terpreted only in one way, viz., that the formations in question 
began to be laid down in shallow water; that during their 
formation the area of deposit gradually subsided for thou.sands 
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 cliaracter of the deposits remained, even 
after the original sea-bottom had been buried under a vast mass 
of sedimentary 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 among them, which can 
legitimately be considered those of a deep sea. They have all 
been deposited in comparatively shallow water."' 

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

' Geographical Evohttivn. (Proceedings of the Royal Geographical Society, 
1879, p. 426.) 



\ 



86 ISLAND LIFE. [part i. 

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

ITie Movements of Continents. — As we find tliese stratified 
rocks of different periods spread over almost the whole surface 
of existing continents where not occupied by igneous or meta- 
morphic rocks, it follows that at one period or another each, 
part of the continent has been under tbe 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 
jjortions in succession without perceptibly affecting their nearly 
horizontal position, and also of intense lateral compression, 
supposed to be produced by partial subsidence along certain 
lines of weakness in the earth's crust, the effect of which is to 
crumple the strata and force up certain areas in great eontorted 
masses, which, when carved out by subaerial denudation into 
peaks and valleys, constitute our great mountain systems.^ In 
this way every part of a continent may again and again have 
sunk beneath the sea, and yet as a whole may never have 
ceased to exist as a continent or a vast continental archipelago. 

■ Professor Dana points out that the regions whicli, after long under- 
going subsidence, and accumulating vast piles of sedimentary deposits, 
have been elevated into mountain ranges, have thereby become stiff and 
unyielding, and that the next depression and subsequent upheaval will be 
situated on one or the other sides of it; and he shows that, in North 
America, this is the case with all the mountains of the successive geological 
formations. Thus, depressions and elevations of extreme slowness but 
often of vast amount, have occurred successively in restricted adjacent 
areas ; and the effect has been to bring each portion in succession beneath 
the ocean but always bordered on one or both sides by the remainder of 
the continent, from the denudation of which the deposits are formed which, 
on the subsequent upheaval, become mountain ranges. (^Manual of Geology, 
2nd Ed., p. 751.) 



CHAP. VI.] GEOGHAPHICAL AND GEOLOGICAL CHANGES. 87 



And, as subsidence will always be accompanied by deposition, 
piles of marine strata many thousand feet thick may have been 
formed in a sea which was never very deep, by means of a 
slow depression either continuous or intermittent, or through 
alternate subsidences and elevations, each of moderate amount. 
Supposed Oceanic Formations ; — the Orijin of Chalk. — There 
seems very good reason to believe that few, if any, of the rocks 
known to geologists correspond exactly to the deposits now 
forming at the bottom of our great oceans. The white oceanic 
mud, or Globigerina-ooze, found in all the great oceans at depths 
varying from 250 to nearly 3,000 fathoms, and almost constantly 
in depths under 2,000 fathom.s, has, however, been supposed to 
be an exception, and to corrcsjiond exactly to our white and 
grey chalk. Hence some naturalists have maintained that 
there has probably been one continuous formation of chalk in 
the Atlantic from the Cretaceous epoch to the present day. 
This view has been adopted chiefly on account of the similarity 
of the minute organisms found to compose a considerable 
portion of both deposits, more especially the pelagic Fora- 
miuifera, 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 resemblance between the 
higher forms of life. Sir Wyville Thomson tells us, that — 
" Sponges are abundant in both, and the recent chalk-mud 
has yielded a large number of examples of the group porifera 
■vitrea, w^iich find their nearest representatives among the 
Ventriculites of the white chalk. The echinoderm fauna of 
the deeper parts of the Atlantic basin is very characteristic, 
and yields an assemblage of forms which represent in a remark- 
able degree the corresponding gi-oup in the white chalk. Species 
of the genus Cidaris are numerous; some remarkable flexible 
forms of the Diademida; seem to approach Echinothuria." ''■ 
jNow as some explanation of the origin of chalk had long been 
desired by geologists, it is not surprising that the amount of 
resemblance shown to exist between it and some kinds of 
1 Nature, Vol. II., p. 297. 



8S ISLAND LTFE. [part i. 

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

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

' Sir W. Tlioiuson, Voyage of Challenger, Vol. II,, 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 0250 „ 

Oxideoflron 0-543 „ 

Silica 0-750 „ 

Phosphoric Acid and Fluorine 2-113 „ 

Water and loss 1-148 „ 

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

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

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



CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 89 

Lyell well remarks that the pure calcareous miid produced by 
the decomposition of the shelly coverings of mollusca and 
zoophytes would be much lighter than argillaceous or arena- 
ceous 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 ; living 
both at the surface, at various depths in the water, and at the . 
bottom. It was long thought that they were surface-dwellers 
only, and that their dead tests sank to the bottom, producing 
the Globigerina-ooze in those areas where other deposits 
were absent or scanty. But the examination of the whole 
of the dredgings and surface-gatherings of the Challenger by 

Sir W. Thomson ( Voyage of the Challenger. Vol. 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 per cent. 

Carbonate of Magnesia 140 to 258 ,, 

Alumina and Oxide of Iron GOO? 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 833 per cent, of the Globigerina-oozc of the mid-Atlantic, where it 
seems to be always present ; and the small proportion of similar matter 
in true chalk is another proof that its origin is different, and that it was 
deposited far more rapidly than tlie oceanic ooze. 

The following analysis of chalk by Mr. D. Forbes will show the difference 

between the two formations : — 

Grey Chalk. White Chalk, 
FtAke^tune. Slutreham. 

Carbonate of Lime 9409 9840 

Carbonate of Magnesia OSl ('8 

Alumina and Phosphoric Acid a trace 042 

Chloride of Sodium 129 — 

Insoluble rfeftm 3-61 110 

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

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

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

the Globigerina-ooze of the deep ocean bed. 



90 ISLAND LIFE. [part i. 

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

Now witli 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 Globigeriua-oozes which we get in 
shallow water resemble the chalk much more than those in 
deeper water, say over 1,000 fathoms." ^ This is important and 
weighty evidence, and it is supported in a striking manner by 
the nature of the molluscan fauna of the chalk. Mr. Gwyu 
Jeffries, one of our greatest authorities on shells, who has 
himself dredged largely both in deep and shallow water and 
who has no theory to support, has carefully examined this 
question. Taking the whole series of genera which are found 
in the Chalk formation, seventy-one in number, he declares 
that they are all comparatively shallow-water forms, many 
living at depths not exceeding 40 to 50 fathoms, while some 
are confined to still shallower waters. Even more important 
is the fact that the genera especially characteristic of the deep 

I Notes on Reticularian Ehizopoda ; in MicroscopicalJournal, Vol. XIX., 
New Series, p. 84. 

' Proceedings of the Royal Society, Vol. XXIV. p. 532. 



CHAP. VI,] GEOGRAPHICAL AXD GEOLOGICAL CHANGES. 91 

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 e.^plain the peculiar characteristics of the chalk 
formation. Sir Charles Lyell tells us that "pure chalk, of 
nearly uniform aspect and compo.sition, is met with in a north- 
west and south-east direction, from the north of Ireland to the 
Crimea, a distance of about 1,140 geographical miles; and in 
an opposite direction it e.Ktends 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 Scandinavian highlands, ex- 
tending 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 extend- 
ing through Austria, South Germany, and the south of France, 
as shown in the map of Central Europe during the Cretaceous 
period in Professor Heer's Primeval World of Switzerland, p. 175. 
To the north the sea may have had an outlet to the Arctic Ocean 
between the Ural range and Finland. South of the Alps there 
was probably another sea, which may have communicated with 
the northern one just described, and there was also a narrow 
strait across Switzerland, north of the Alps, but, as might be 
expected, in this only marls, clays, sandstones, and limestones 
were deposited instead of true chalk. It is also a suggestive 
fact that both above and below the true chalk, in almost all the 
countries where it occurs, are extensive depo.sits of marls, clays. 



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



92 ISLAND LIFE. [part i. 

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

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



CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 93 

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

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

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

There is yet another consideration which seems to have been 
altogether overlooked by those who suppose that a deep and 
open island-studded ocean occupied the place of Europe in Cre- 
taceoiis times. No fact is more certain than the considerable 
break, indicative of a great lapse of time, intervening between 
the Cretaceous and Tertiary formations. A few deposits of 
intermediate age have indeed been found, but these have been 
generally allocated either with the Chalk or the Eocene, leaving 
the gap almost as pronounced as before. Now, what does this 
gap mean ? It implies that when the deposition of the various 
Cretaceous beds of Europe came to an end they were raised 
above the sea-level and subject to extensive denudation, and 
that for a long but unknown period no extensive portion of 
what is now European land was below the sea-level. It was 
only when this period terminated that large areas in 
several parts of Europe became submerged and received the 
earliest Tertiary deposits known as Eocene. If, therefore, 
' Geohvjkal Magazine, 1871, p. 426. 



94 ISLAND LIFE. [part i. 

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 
dui-ing that period ; or in fact that any part of it was submerged, 
except those areas on which we actually find Cretaceous deposits, 
or where we have good reason to believe they have existed. 

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

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

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



CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 95 

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



96 ISLAND LIFE. [rART I. 

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

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

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



CHAP. VI.] GEOUEAPHICAL AND GEOLOGICAL CHANGES. 97 

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

Oceanic Islands as IndicatioTis of the Permanence of Continents 
and Oceans. — Coming to the question from the other side, 
Mr. Darwin has adduced an argument of considerable weight 
in favour of the permanence of the great oceans. He says 
{Origin of Species, 6th Ed. p. 288): "Looking to existing oceans, 
which aie thrice as extensive as the laud, 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 &fforl even a fragment of 
any Palaeozoic or Secondary formation. Hence we may perhaps 
infer that during the Palaeozoic and Secondary periods neither 

' riiijskfd Gcof/ntpliy and GeoJogy of Great Britain, 5tli Ed. p. GL 

a 



93 ISLAND LIFE. [part i. 

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

' Of late it has been the custom to quote the so-called " ridge " down 
the centre of the Atl.intic as indicating an extensive ancient land. Even 
Professor Jiidd adopts this view, for he speaks of tlie great belt of Tertiary 
volcanoes " which extended througli Greenland, Iceland, the Faroe Islands, 
the Hebrides, Ireland, Central France, the Iberian Peninsula, the Azores, 
Madeira, Canaries, Cape de Verde Islands, Ascension, St. Helena, and 
Tristan d'Acunlia,and which constituted as shown by the recent soundings 
of II. 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 Heporls, No. 7, a considerable part of this ridge is found 
to be more than 1,9U0 fathoms deep, while the portion called the " Connecting 
Kidge " seems to be due in part to the deposits carried out by the Kiver 
Amazon. In the neighbourhood of the Azores, St. Paul's Bocks, Ascension, 
and Tristan d'Acunh:i are considerable areas varj-ing from 1,200 to 1,500 
fathoms deep, while the rest of the ridge is usually 1,800 or 1,900 fathoms. 
The shallower water is no doubt due to volcanic upheaval and the accumu- 
lation of volcanic ejections, and there may be many other deeply submerged 
old volcanoes on the ridge ; but that it ever formed a chain of mountains 
"comparable in elevation with the Andes," there seems not a particle of 
evidence to prove. It is however probable that this ridge indicates the 
former existence of some considerable Atlantic islands, which will serve 
to explain the presence of a few identical genera, and even species of 
plants and insects in Africa and South America, while the main body 
of the fuuna and flora of these two continents remains radicallv distinct. 



CHAP, vi] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 99 

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

Effect of Continental Changes on the Distrihution of Animals. — 
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 living things must 
have been driven backward and forward from oast to west, or 
from north to south, from one side of a continent or a hemi- 
sphere to the other. Owing to the remarkable continuity of 
ail the land masses, animals and plants must have often been 
compelled to migrate into other continent?, where in the 
straggle for existence under new conditions many would 
succumb ; while such as were able to survive would consti- 
tute those wide-spread groups whose distribution often puzzles 
us. Owing to the repeated isolation of portions of continents 
for long periods, special forms of life would have time to be 

H 2 



100 ISLAND LIFE. [part i. 

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

Changed Distribution proved hy the Extinct Animals of Different 
epoclis. — 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 preserved in the rocks. Everywhere the animals 
which have most recently become extinct resemble more or less 
closely those which now live in the same country ; and where 
there are exceptions to the rule, we can generally trace them to 
some changed conditions which have led to the extinction of 
certain types. But when we go a little further back, to the late 
or middle Tertiary deposits, we almost always find, along with 
forms which micrht have been the ancestors of some now living, 
others which are only now found in remote regions and often in 
distinct continents — clear indications of those extensive migra- 
tions which have ever been going on. Every large island 
contains in its animal inhabitants a record of the period when 
it was last separated from the adjacent continent, while some 
portions of existing continents still show by the comparative 
poverty and speciality of their animals that at no distant epoch 
they were cut off by arms of the sea and formed islands. If 
the geological record w^ere 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. 



CHAP. VI.] GEOGRAPHICAL AND GEOLOGICAL CHANGES. 101 



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

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



102 ISLAND LIFE. [part i. 

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

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



CHAPTER VII. 

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

Proofs of the recent occurrence of a Glacial Epoch — Moraines — Travelled 
Blocks — Glacial deposits of Scotland : the "Till " — Inferences from the 
gla^^'ial phenomena of Scotland — Glacial phenomena of North America 
— Effects of the Glacial Epoch on animal life- — Warm and cold periods 
— Paljcontological evidence of alternate cold and warm periods — 
Evidence of interglacial warm periods on the Continent and in North 
America — Migrations and extinctions of Organisnis caused by the 
Glacial Epoch. 

We have now to consiiler another set of physical revolutions 
which have profoundly atiected 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 woild, there 
have been also a long succession of climatal changes, which, 
though very slow and gradual when measured by centuries, may 
have sometimes been rapid as compared with the slow march of 
geological mutations. 

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



104 ISLAND LIFE. [parti. 

migrations and actual distribution of the animal worLl, a Lrit-f 
outline of the more important facts and of the conclusions they 
lead to must be here given. 

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

Perhaps the most striking of all the evidences of glaciation 
arc the grooved, scratched, or striated rocks. These occur 
abundantly in Scotland, Cumberland, and North Wales, and uo 
rational explanation of them has ever been given except that 
they were formed by glaciers. In many valleys, as, for instance, 
that of Llanberris in North Wales, hundreds of examples may 
be seen, consisting of deep grooves several inches wide, smaller 
furrows, and striie of extreme fineness wherever the rock is of 
sufficiently close and hard texture to receive such marks. These 
grooves or scratches are often many yards long, they are found 
in the bed of the valley as well as high up on its sides, and they 
are almost all without exception in one general direction— that 
of the valley itself, even though the particular surface they are 
upon slopes in another direction. When the native covering of 
turf is cleared away from the rock the grooves and stri:v are often 
found in great perfection, and there is reason to believe that 
such markings cover, or have once covered, a large part of the 
surface. Accompanying these markings we find another, hardly 
less curious phenomenon, the rounding oflf or planing down of 
the hardest rocks to a smooth imdulating surface. Hard crys- 
talline schists with their strata nearly vertical, and which one 
would expect to find exposing jagged edges, are found ground 
off to a perfectly smooth but never to a flat surface. These 
rounded surfaces are found not only on single rocks but over 
whole valleys and mountain sides, and form what are termed 
rochcs moiitonnScs, from their often having the aj)pearance at a 
distance of sheeji lying down. 

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



ciiAr. VII.] 



TIIK GLACIAL EPOCH. 



105 



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




.\ CiL.Vf-K ; Willi Mu::.viN^S 



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



106 ISLAND LIFK. [pAnr i. 



rocky peaks which rise above it. As the glacier slowly moves 
downward, this debris forms long lines on each side, or on the 
centre whenever two glacier-streams unite, and is deposited at 
its termination in a huge mound called the terminal moraine. 
The decrease of a glacier may often be traced by successive old 
moraines across the valley up which it has retreated. When 
once seen and examined, these moraines can alwa3'S be distin- 
guished almost at a glance. Their position is most remarkable, 
having no apparent natural relation to the form of the valley or 
the surrounding slopes, so that they look like huge earthworks 
formed by man for purposes of defence. Their composition is 
equally peculiar, consisting of a mixture of earth and rocks of 
all sizes, usually without any arrangement, the rocks often 
being huge angular masses just as they had fallen from the sur- 
rounding precipices. Some of these rock masses often rest on the 
very top of the moraine in positions where no other natural 
force but that of ice could have placed them. Exactly similar 
mounds are found in the valleys of North Wales and Scotland, 
and always where the other evidences of ice-action occur 
abundantly. 

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



CRAP. VII.] 



THE GLACIAL EPOCH. 



107 



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




MAP SHOWING THE COURSE OF THE ANCIENT OLACIKR PF THE RHONE, AND THE PISIRIDUTION 
UF ERRATIC BLOCKS ON THE JURA. 



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



108 ISLAND LIFE. [part i. 

head of the Lake of Geneva, since it spread over the whole of 
the great valley of Switzei'land, extending from Geneva to 
Neufchatel, Berue, and Soleure, and even on the flanks of the 
Jura, reached a maximum height of 2,015 feet ahove the valley. 
The numerous blocks scattered over the Jura for a distance of 
about a hundred miles vary considerably in the material of 
which they are composed, but they are found to be each trace- 
able to a part of the Alps corresponding to their position, on 
the theor}' 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 (/ c d), while those found towards 
Geneva have all come from the west side (p /')• ^^ '^ ^'^o verj' 
suggestive that the highest blocks on the Jura at G have come 
i'rom the eastern shoulder of Mont Blanc in the direct line 
/< B F G. Here the glacier would naturally j)reserve its 
greatest thickness, while as it spread out eastward and westward 
it would become thinner. We accordingly find that the 
travelled blocks on either side of the central point become lower 
and lower, till near Soleure and Geneva they are not more than 
500 feet above the valley. The evidence is altogether so con- 
clusive that, after personal e.xamination of tlie district in com- 
pany with eminent Swiss geologists. Sir Charles Lyell gave up 
the view he had first adopted — that the blocks had been car- 
ried by ice during a period of submergence — as altogether 
untenable.' 

The phenomena now described demonstrate a change of 
climate sufficient to cover all our higher mountains with 
perpetual snow, and fill the adjacent valleys with huge glaciers 
at least as extensive as those now found in Switzerland. But 
there are other jjhenomena, best developed in the northern part 
of our islands, which show that even this state of things was 
but the concluding phase of the glacial period, which, during 
its maximum development, must have reduced the northern 
half of our island to a condition only to be paralleled now in 
Greenland and the Antarctic regions. As few persons besides 
professed geologists are acquainted with the weight of evidence 
' Antiquity of Man, 4tli Ed. pji. 310-318. 



CHAP. VII.] THE GLACIAL EPOCH. 109 

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

Glacial Deposits of Scotland: the " Till." — Over almost all 
the lowlands and in most of the highland valleys of Scotland 
there are immense superficial deposits of clay, sand, gravel, 
or drift, which can be traced more or less directly to glacial 
action. Some of these are moraine matter, others are lacus- 
trine deposits, while others again have been formed or modified 
by the sea during periods of submergence. But below them 
all, and often resting directly on the rock-surface, there arc 
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 strire often crossing each other in 
various directions. Sometimes the stones are so numerous that 
there seems to be only just enough clay to unite them into a 
solid mass, and they are of all sizes, from mere grit up to rocks 
nan}- feet in diameter. The " till " is found chiefly in the low- 
lying districts, where it covers extensive areas sometimes to a 
depth of a hundred feet ; while in the highlands it occurs in 
much smaller patches, but in some of the broader valleys forms 
terraces which have been cut through by the streams. Occa- 
sionally it is f jund as high as two thousand feet above the sea, 
in hollows or hill-sides, where it seems to have been protected 
from denudation. 

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

' The Great Ice Age and its Relation to tlie AnCiqiiitij of Man. Dy James 
Geikie, F.R.S. (Isbister and Co., 1874.) 



no ISLAND LIFE. [parti. 

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, roches moutonnics, and other marks of glacial 
action, occur very high up the mountains to at least 3,000 and 
often even to 3,500 feet above the sea, while all lower hills and 
mountains are rounded and grooved on their very summits ; 
and these grooves always radiate outwards from the highest 
peaks and ridges towards the valleys or the sea. 

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

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



CHAP. VII] THE GLACIAL EPOCH. Ill 



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

' Tliis view of the formation of "till" is tliat adopted by Dr. Geikie, 
and upheld by almost all the Scotch, Swiss, and Scandinavian geologists. 
The objection iiowever is made by many eminent English geologists, 
including Mr. Searles V. Wood, Jun., that mud ground off the rucks 
cannot remr.in beneath the ice, forming sheets of great thickness, be- 
cause the glacier cannot at the same time grind down solid rock and 
yet pass over the surface of soft mud and loose stones. But this 
difficulty will disappear if we consider the numerous fluctuations in the 
glacier with increasing size, and the additions it must have been con- 
stantly receiving as the ice from one valley after another joined together, 
and at last produced an ice-sheet covering the whole country. The 
grinding power is the motion and pressure of the ice, and the pressure 
will depend on its thickness. Now the points of maximum thickness 
must have often changed their positions, and the result would be that the 
matter ground out in one place would be forced into another place where 
the pressure was less. If there were no lateral escape for the mud, it 
would necessarily support the ice over it just as a water-bed supports the 
person lying on it ; and when there was little drainage water, and the ice 
extended, say, twenty miles in every direction from a given part of a valley 
where the ice was of less than tlie average thickness, the mud would ne- 
cessarily accumulate at this part simply because there was no escape for 
it. Whenever the pressure all round any area was greater than the pressure 
on that area, the 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 



112 ISLAND LIFE. [part i. 

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

It is evident that the change of climate requisite to produce 
such marvellous eHects in the British Isles could not have been 
local, and we accordingly find strikingly similar proofs that 
Scandinavia and all northern Europe have also been covered 
with a huge ice-sheet ; while we have already seen that a similar 
gigantic glacier buried the Alps, carr3'ing granitic blocks to the 
Jura, where it deposited them at a height of 3,450 feet above 
the sea ; while to the south, in the plains of Italy, the terminal 
moraines left by the retreating glaciers have formed extensive 
hills, those of Ivrea, the work of the great glacier from the 
Val d'Aosta being fifteen miles across, and from 700 to 1,500 
feet high. 

Glacial Phenomena in Nm-fh Amcn'ca. — In jSforth America 
the marks of glaciation are even more extensive and striking 

these openings in the valleys that the "till" is said to be found, and also in 
the lowlands where an ice-sheet must have extended for many miles in 
every direction. In these lowland valleys the '• till " is both thickest and 
most wide-spread, and this is what we might expect. At first, when the 
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 great bulk of the debris must gather 
under the ice wherever the pressure was least, and the ice would 
necessarily rise as it accumulated. Some of the mud would no doubt be 
forced out along lines of least resistance to the sea, but the friction of the 
stone-charged " till " would bo 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 JIan, 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 ilan, where they met and flowed southwards down the Irish Sea. Ice- 
marks are traced over the top? of the nioimtains which are nearly 2.000 feet 
high. (See A Sketch of the Geolog;/ of the Isle of Mun, by John Home, 
F.G.S. Trans, of the Edin. Geol. Soc. Vol. II. pt. 3, 1«74.) 



rHAP. VII.] THE GLACIAL EPOCH. 113 

than in Europe, stretching over the whole of Canada and to the 
south of the great lakes as far as latitude 39". There is, in all 
these countries, a wide-spread deposit like the " till " of Scotland, 
produced by the grinding of the great ice-sheet when it was at its 
maximum thickness ; and also extensive beds of moraine-matter, 
true moraines, and travelled blocks, left by the glaciers as they 
retreated towards the mountains and finally withdrew into the 
upland valleys. There are, also, both in Britain, Scandinavia, 
and North America, proofs of the submersion of the land 
beneath the sea to a depth of upwards of a thousand feet ; but 
this is a subject we need not here enter upon, as our special 
object is to show the reality and amount of that wonderful and 
comparatively recent change of climate termed the glacial epoch. 
Many persons, even among scientific men, who have not given 
much attention to the question, look upon the whole subject of 
the glacial epoch as a geological theory made to explain certain 
phenomena which are otherwise a puzzle ; and they would not 
be much surprised if they were some day told that it was all a 
delusion, and that Mr. So-and-so had explained the whole thing 
in a much more simple way. It is to prevent my readers being 
imjwsed upon by any such statements or doubts, that I have 
given this very brief and imperfect outline of the nature, extent, 
and completeness of the evidence on which the existence of the 
glacial epoch depends. There is perhaps no great conclusion in 
any science which rests upon a surer foundation than this ; and 
if we are to be guided by our reason at all in deducing the un- 
known from the known, the past from the present, we cannot 
refuse our assent to the reality of the glacial epoch of the 
northern hemisphere in all its more important features. 

Effects of the Glacial Epoch on Animal Life : Trarm and Cold 
Periods. — It is hardly necessary to point out what an important 
effect this great climatal cycle must have had upon all living 
things. Wlien an icy mantle crept gradually over much of the 
northern hemisphere till large portions of Europe and North 
America were reduced to the condition of Greenland now, the 
greater part of the animal life must have been driven south- 
ward, causing a struggle for existence which must have led to 
the extermination of many forms, and the migiation of others 

I 



114 ISLAND LIFE. [pabt i. 

into new areas. But these effects must have been greatly 
multipHed 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 verj' thin, but in other cases they are twenty or thirty 
feet thick, and in them have been found remains of the extinct 
ox, the Irish elk, the horse, reindeer and mammoth. Here we 
have evidence of two distinct periods of intense cold, and an 
intervening milder period sufficiently prolonged for the country 
to become covered with vegetation and stocked with animal 
life. In some districts borings have proved the existence of no 
less than four distinct formations of " till " separated from each 
other by beds of sand from two to twenty feet in thickness.^ 
Facts of a similar nature have been observed in other parts of 
our islands. In the east of England, ilr. Skertchly (of the 
Geological Survej') 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 intervening warmer period, 
characterised by southern forms of moUusca and insects, after 
which glacial conditions again prevailed with northern types of 
moUusca.^ Elsewhere he says : " Looking at the presence of 
such fluviatile mollusca as Cyrena fluviinalis and IJnio littoi-alia 
and of such mammalia as the hippopotamus and other great 

' 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 tlie Post-Glacial Period." Geological Magazine, 
1872, p. 158, 160. 



THAr. VII.] THE GLACIAL EPOCH. 115 

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

Further evidence of this alternation is found both in the 
Isle of Man and in Ireland, where two distinct boulder clays 
have been described with intervening beds of gravels and sands. 
Palccontological cvUlence of alternate Cold and Warm j^eriods. — 
Especially suggestive of a period warmer than the present, im- 
mediately following glacial conditions, is the occurrence of the 
hippopotamus in caves, brick-earths, and gravels of 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 abundantly along with those of the ox, elephant, horse, 
and other quadrupeds, and with countless remains of tlie 
hyaenas which devoured them ; while it has also been found 
in cave deposits in Glamorganshire, at Durdham Down, near 
Bristol, and in the post-Pliocene drifts of Dorsetshire. It is im- 
portant to note that where it is associated with other mammals 
in caves — which are hyo&na-dens, and not mere receptacles of 
water-carried remains — these always imply a mild climate, the 
elephant and rhinoceros found with it being species character- 
' Geulogical Magazine, 1876, p. 396. 

I 2 



110 ISLAND LIFE. [parti. 

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

The fact of the hippopotamus having lived at oi'' N. Lat. in 
England, quite close to the time of the glacial epoch, is absolutely 
inconsistent with a mere gradual amelioration of climate from 
that time till the present day. The immense quantity of vege- 
table food which this creature requires, implies a mild and 
uniform climate with hardly any severe winter ; and no theory 
that has yet been suggested renders this possible except that of 
alternate cold and warm periods during the glacial epoch itself 
In order that the hippopotamus could have reached Yorkshire 
and retired again as the climate changed, we may suppose it to 
have been a permanent inhabitant of the lower Rhone, between 
which river and the Rhine there is an easy communication by 
means of the Doubs and the 111, some of whose tributaries 
approach within a mile or two of each other about fifteen miles 
south-west of Mulhausen. Thence the passage would be easy 

' A. Tylor, on " Quaternary Gravels." Quarterly Journal of Geological 
Society of London, 1869, pp. 83 95 (woodcuts). 



CHAP. VII.] THE GLACIAL EPOCH. 117 

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

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

In Sweden also there are two " tills," the lower one ha\-ing 
been in places partly broken up and denuded before the upper 
1 Heer's Prinueval Wwld of Switxcrland . Vol. IL, pp. 148-168. 



118 ISLAND LIFE. [fart. i. 

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

This remarkable series of observations, spread over so wide 
an area, seems to afford ample proof that the glacial epoch did 
not consist merely of one process of change, from a temperate 
to a cold and arctic climate, which, having reached a maximum, 
then passed slowly and completely away ; but that there were 
certainlj' 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 dow-n 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 
woidd 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 earher. Of such 
deposits as were formed on land during the coming on of the 
' Dr. James Geikie in Geological Magazine, 1878, p. 77. 



CHAP. Til] THE GLACIAL EPOCH. 119 



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



120 ISLAND LIFE. [iart i. 

the Alps, and then by the Mediterranean ; whereas in eastern 
America and Asia the mountain chains run in a north and 
south direction, and there is nothing to prevent the flora from 
having been preserved by a southward migration into a milder 
region. 

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



CHAPTER YIII. 

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 — 
Etfects 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 — Eifect 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 aphelum on the climate of Britain — The essential 
principle of climatal change restated — Probable date of the last 
Glacial Epoch — Changes of the sea-level dependent on Glaciation — The 
planet Mars as bearing on the theory of excentricity as a cause of 
Glacial Epochs. 

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

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

2. Changes in the obliquity of the ecliptic. 

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



122 ISLAND LIFE. [part i. 

4. Changes in the distribution of land and water. 

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

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

7. A variation in the temperature of space. 

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

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



CHAP, viii.] THE CAUSES OF GLACIAL EPOCHS. 123 

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

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





GLACIAL EPOCH IN GLACIAL EPOCH IN 

N.HEMISPHERE S.HEMISPHERE 

DIAGRAM 8HOWISO THE ALTERED POSITION OF THE POLF8 AT INTERVALS OF 10,500 YEAR8 
PRODUCED BY THE PRECESSION OF THE EQCINOXFS AND TOE MOTION OF THE APHEUON ; 
AND ITS EFFECT ON CLIMATE DURING A PERIOD OF HIGH EXCENTRICITY. 



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



124 



ISLAND LIFE. 



[PABT I. 



eight and a half millions of miles between our distance from the 
sun in aphdion and perehelion (as the most distant and nearest 
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 si.vfy thousand years (commencing 



(CPROBABLE DURAHON Or THC GLACIAL EPOCH')) 




200 ISO too so 

THOUSAND YEARS AGO FROM 
A.D.I80O. 
DlAORAJi Of EXCENTRICITV AXD PRECESSION. 



The dark and li,::ht bands mark the phases of precession, the dark showing short mild winters, 
and the U;:ht Ion;: cold wrinters. the contrast being greater as the excentricitv is higher. 
The horizontal dotted line marks the present excentricit.v. The figures show the maxima 
and minima of excentricity during the last 300,000 years fi"om Dr. Croll's Tables. 

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



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

two things — first, what actual difference of temperature would 
be caused by varying distances of the sun, and, secondly, what 
are the properties of snow and ice in regard to climate. 

Bifferencc of Temperature caitsed hy varyiny 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. Our zero is thirty-two degi'ees below the freezing 
point of water, or, in the centigrade thermometer, the freezing 
point itself, both of which are equally misleading when applied 
to cosmical problems. If we say that ths mean temperature of 
a place is 50° F. or 10° C, these figures tell us nothing of how 
much the sun warms that place, because if the sun were with- 
drawn the temperature w ould fall far below either of the zero 
points. In the last Arctic Expedition a temperature of — 74° 
F. was registered, or 106° below the freezing point of water; 
and as at the same time the earth, at a depth of two feet, was 
only — 13° F. and the sea water + 28° F., we may be sure that 
even this intense cold was not near the possible minimum 
temperature. By various calculations and experiments which 
cannot be entered upon here, it has been determined that the 
temperature of space, independent of solar (but not of stellar) 
influence, is about — 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 by the sun to an amount 
measured by .")0 + 239 = 289° F., which is hence termed its 
absolute temperature. Now during the time of the glacial 
epoch the greatest distance of the sun in winter was 97i 
millions of miles, whereas it is now, in winter, only 91 millions 
of miles. But the quantity of heat received from the sun is 
inversely as the square of the distance, so that it would then be 
in the proportion of 8,281 to 9,506 now, or nearly one eighth 
less than its present amount. The mean temperature of Eng- 
land in January is about 39° F., which equals 278° F. of absolute 
temperature. But the above named fraction of 278° is 3G°, 
representing the amount which must be deducted to obtain the 
January temperature during the glacial epoch, which will there- 
fore be 3° F. Our actual temperature at that time might, 



126 ISLAND LIFE. [part i. 

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

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



' In a letter to Nature of October 30th, 1879, the Rev. 0. Fislier calls 
attention to a result arrived at by Pouillet, that the temperature which the 
surface of the ground would assiinie 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 daring the glacial 
epoch would come out 17° F.,and this Mr. Fisher thinks not low enough to 
cause any extreme difference from the present climate. In this opinion, 
however, I cannot agree with him. On the contrary, it would, I think, be 
a relief to the theory were the amounts of decrease of temperature in 
winter and increase in summer rendered more moderate, since according 
to the usual calculation (which I have adopted) the differences are un- 
necessarily great. I cannot therefore think that this modification of the 
temperatures, should it be ultimately proved to be correct (which is 
altogether denied by Dr. Croll), would be any serious objection to the 



CHAP, viii.] THE CAUSES OF GLACIAL EPOCHS. 127 



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

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

adoption of Dr. Croll's tlieory of the Astronomical and Pliysical causes of 
the Glacial Epoch. 

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



128 ISLAND LIFE. [parti. 

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

The power of water in carrying away heat is well exhibited 
by the fact of the abnormally high temperature of arid deserts 
and of very dry countries generally ; while the still more power- 
ful influence of moving air may be appreciated, by considering 
the effects of even our northern sun in heating a tightly-closed 
glass house to far above the temperature produced by tie 
vertical sun of the equator where the free air and abundance of 
moisture exert their beneficial influence. Were it not for the 
large proportion of the sun's heat carried away by air and 
water the tropics would become uninhabitable furnaces — as 
would indeed «7i// part of the earth where the sun shone brightly 
throughout a summer's day. 

We see, therefore, that the excess of heat derived from the sun 
at any place cannot be stored up to an important amount owing 
to the wonderful dispersing agency of air and water; and 
though some heat does penetrate the ground and is stored up 
there, this is so little in proportion to the whole amount received, 
and the larger part of it is so soon given out from the surface 
layers, that any surplus heat that may be thus preserved during 
one summer rarely or never remains in suflicient 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 



CHAP, VIII.] THE CAUSES OF GLACIAL EPOCHS. 129 

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

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

K 



130 ISLAND LIFE. [part i. 

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

HiglL Land and great Moisture essential to tlie initiation of a 
Glacial ejioch. — Another point of great importance in connection 
with this subject, is the fact, that this permanent storing up of 
cold depends entirely on the annual amount of snow-fall in jjro- 
portion to that of the sun and air-heat, and not on the actual 
cold of winter, or even on the average cold of the year. A 
place may be intensely cold in winter and may have a short 
arctic summer, yet, if so little snow falls that it is quickly melted 
by the returning sun, there is nothing to jirevent 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. 02° N., or than in 
Heard Island and South Georgia, both in Lat. 53° S. in the 
Southern Ocean, and almost wholly covered with perpetual snow 
and ice. At the " Jardin " on the Mount Blanc range, above 
the line of jierpetual snow, a thermometer in an exposed situa- 
tion marked — 6^ F. as the lowest winter temperature: while in 
many parts of Siberia mercury freezes several weeks in winter, 
showing a temperature below — 40° F. ; yet here the summers 
are hot, all the snow disappears, and there is a luxuriant vege- 
tation. Even in the very highest latitudes reached by our last 
Arctic Expedition there is very little perpetual snow or ice, for 
Captain Nares tells us that north of Haye's Sound, in Lat. 79° 
N., the mountains were remarkably free from ice-cap, while 
extensive tracts of land were free from snow during summer, 



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



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

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

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

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



132 ISLAND LIFE. [part i. 

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 laud, or is at least inclosed 
by a ring of high and mountainous land. The result is that in 
the north the polar area is free from any accumulation of per- 
manent ice (e.Kcept on the highlands of Greenland and Grin- 
nell's Land), while in the south a complete barrier of ice of 
enormous thickness appears to surrouml the pole. Dr. CroU 
shows, from the measured lieight of numerous Antarctic ice- 
bergs (often miles in length) that the ice-sheet from which they 
are the broken outer fragments must be from a mile to a mile 
and a half in thickness.^ As this is the thickness of the outer 
edge of the ice it must be far thicker inland ; and we thus find 
that the Antarctic continent is at this very time suffering glacia- 
tion to quite as great an extent as we have reason to believe 
occurred in the same latitudes of the northern hemisphere 
during the la.st glacial epoch. 

The accompanying diagrams show the comparative state of 
the two polar areas both a.9 regards the distribution of land and 
sea, and the extent of the ice-sheet and floating icebergs. The 
much greater quantity of ice at the south pole is undoubtedly 
due to the presence of a large extent of high land, which acts as 
a condenser, and an unbroken surrounding ocean, which affords 
a constant supply of vapour; and the effect is intensified by 
winter being there in aphelion, and thus several days longer 
than with us, while the whole southern hemisphere is at that 
time farther from the sun, and therefore receives less heat. 

We see, however, that with less favourable conditions for the 
production and accumulation of ice, Greenland is glaciated 
down to Lat. 61°. What, then, would be the effect if the 
Antarctic continent, instead of being confined almost wholly 
within the south polar circle, were to extend in one or two 
great mountAinous promontories far into the temperate zone? 
The comparatively small Heard Island in S. Lat. 5.3'' is even 
now glaciated down to the sea. What would be its condition 

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



ciiAr. viii] THE CAUSES OF GLACIAL EPOCHS. 



133 




134 ISLAND LIFE. [part i. 

were it a northerly extension of a lofty Antarctic continent ? 
We may be quite sure that glaciation would then be far more 
severe, and that an ice-sheet corresponding to that of Greenland 
might extend to beyond the parallel of 50° S. Lat. Even 
this is probably too low an estimate, for on the west coast of 
New Zealand in S. Lat. 43" 85' 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 thej- would be nearly in the ice-covered 
condition of Greenland, although situated in the latitude of 
Marseilles. 

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



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

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

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

1 "The general absence of recent marks of glacial action in Eastern 
Europe is well known ; and tlio series of clianges wliich 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. 
Mr. Campbell, whose ability to recognise the physical evidence of glaciers 
will scarcely be questioned, finds quite the same absence of the proof of 
extensive ice-action in North America, westward of the meridian of 
Chicago." (Prof. J. W. Judd in Geol. Mag. 1876, p. 535.) 

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



136 ISLAND LIFE. [rABT i. 

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

Efficiency of Astronomical Causes in producing Glaciafion. — 
Having now collected a sufficient body of facts, let us endeavour 
to ascertain what would be the state to which the northern 
hemisphere would be reduced by a high degree of excentricity 
and a winter in aphelion. When the glacial epoch is supposed 
to have been at its maximum, about 210,000 years ago, the 
excentricity was more than three times as great as it is now, 
. and, according to Dr. Croll's calculations, the mid-winter tem- 
perature of the northern hemisphere would have been lowered 
36° F., while the winter half of the year would have been 
twenty-six days longer than the summer half This would 
bring the January mean temperature of England and Scotland 
almost down to zero or about 30^ F. of frost, a winter climate 
corresponding to that of Labrador, or the coast of Greenland on 
the Arctic circle. But we must remember that the summer 
would be just as much hotter than it is now, and the problem 
to be solved is, whether the snow that fell in winter would 
accumulate to such an extent that it would not be melted in 
summer, and so go on increasing year by year till it covered the 
whole of Scotland, Ireland, and Wales, and much of England. 
Dr. CroU and Dr. Geikie answer without hesitation that it 
wouldi Sir Charles Lyell maintained that it would only do so 
when geographical conditions were favourable ; while the late 
Mr. Belt has argued, that excentricity alone would not produce 
the effect unless aided by increased obliquity of the ecliptic, 
which, by extending the width of the polar regions, would 
increase the duration and severity of the winter to such an 
extent that snow and ice would be formed in the Arctic and 
Antarctic regions at the same time whether the winter were in 
pierihelion or aphelion. 

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



CHAP, viii] THE CAUSES OF GLACIAL EPOCHS. 13T 



because we have no case at all parallel to it from which we can 
draw direct conclusions. It is, however, clear from the various 
considerations we have already adduced, that the increased 
cold of winter when the excentricity was great and the sun in 
aphelion during that season, would not of itself produce a glacial 
epoch unless the amount of vapour supplied for condensation 
was also exceptionally great. The greatest quantity of snow 
falls in the Arctic regions in summer and autumn, and with us 
the greatest quantity of rain falls in the autumnal months. It 
seems probable, then, that in all northern lands glaciation would 
commence when autumn occurred in aphelion. All the raiu 
which falls on our mountains at that season would then fall as 
snow, and, being further increased by the snow of winter, would 
form accumulations which the summer might not be able to 
melt. As time went on, and the apIielio7i occurred in winter, 
the perennial snow on the mountains wovdd have accumulated 
to such an extent as to chill the sj)riug and summer vapours, so 
that they too would fall as snow, and thus increase the amount 
of deposition ; but it is probable that this would never in our 
latitudes have been sufficient to produce glaciation, were it not 
for a series of climatal reactions which tend still further to 
increase the production of snow. 

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



138 ISLAND LIFE. [rAnr i. 

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

But this is only one-half of the effect that would be produced, 
for the increased force of the trades sets up another action which 
still further helps on the accumulation of snow and ice. It is 
now generally admitted that we owe much of our mild cUmatc 
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 hues, so that Drontheim in N. Lat. 02" 
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. 
CroU thinks, that a large portion of it miglit be diverted south- 
ward owing to the peculiar form of the east coast of South 
America, and so go to swell the Brazilian current and ameliorate 
the climate of the southern hemisphere. 

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



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

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

Summary of principal Causes of Gladalion. — I have now suf- 
ficiently answered the question, why the short hot summer would 
not melt the snow which accumulated during the long cold 
winter (produced by high excentricity and winter in aphelion), 
although the annual amount of heat received from the sun was 
exactly the same as it is now, and equal in the two hemispheres. 
It may be well, before going further, briefly to summarise the 
essential causes of this apparent paradox. These are — primarilj', 
the fact that solar heat cannot be stored up ow'ing 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 bj' 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 begim, and by their action and reaction pro- 
duce a maximum of effect which, without their aid, would be 
altogether unattainable. 

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



140 ISLAND LIFE. [part i. 

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 iu space. It must also be 
remembered that an enormous quantity of heat is used up in 
melting snow and ice, without raising its temperature ; each 
cubic foot of ice requiring as much heat to melt it as would 
raise nearly six cubic feet of water 30° F. It has, however, 
been argued that because when water is frozen it evolves just 
as much heat as it requires to melt it again, there is no loss of 
heat on the whole ; and as this is adduced as a valid arjrument 
over and over again 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 nir still remains below the freezing 
jjoint or freezing would not take place. The heat liberated by 
freezing is, therefore, what may be termed low-grade heat — 
heat incapable of melting snow or ice ; while the heat absorbed 
while ice or snow is melting is high-grade heat, such as is 
capable of melting .snow and supporting vegetable groNvtli. 
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 b}' 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. 

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



CHAP. VIII.] THE CAUSES OF GL.4CIAL EPOCHS. 141 

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

In reply to the objections of a recent critic Dr. Croll has 
given a new proof of this important fact by comparing the 
known amount of snow-fall with the equally well-known melting 
power of direct sun-heat in different latitudes. He says : " The 
annual precipitation on Greenland in the form of snow and rain, 
according to Dr. Rink, amounts to only twelve inches, and two 
inches of this he considers is never melted, but is carried away 
in the form of icebergs. The quantity of heat received at the 
equator from sunrise to sunset, if none were cut off by the 
atmosphere, would melt 3J inches of ice, or 100 feet in a year. 
The quantity received between latitude 00° and S0°, which is 

' For numerous details and illustrations see tlie paper — " On Ocean 
Currents in relation to the Pliy.sical Theory of Secular Changes of Climate' 
— in the Philosophical Magazine, 1870. 



142 ISLAND LIFE. [part i. 

that of Greenland, is, according to Meech, one-half that received 
at the equator. The heat received hy Greenland from the sun, 
if none were cut off by the atmosphere, would therefore melt 
fifty feet of ice per annum, or fifty times the amount of snow 
which falls on that continent. What then cuts off the ninety- 
eight per cent of the sun's heat ? " The only possible answer 
is, that it is the 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 infliierux of Astro- 
nomical Causes on Climate. — Those persons who still doubt the 
effect of winter in ajjhelion 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 C,000 feet in the same latitude as 
the Pyrenees ; in the latitude of the Swiss Alps mountains only 
6,200 feet high produce immense glaciers which descend to the 
sea-level ; while in the latitude of Cumberland mountains only 
from 3,000 to 4,000 feet high have every valley filled with 
streams of ice descending to the sea-coast and giving off 
abundance of huge icebergs.' Here we has-e exactly the con- 
dition of things to which England and Western Europe were 
subjected during the latter portion of the glacial epoch, when 
every valley in Wales, Cumberland, and Scotland had its glacier; 
and to what can this state of things be imputed if not to the 
fact that there is now a moderate amount of excentricity, 
and the winter of the southern hemisphere is in aphelion ? 
The mere geographical position of the southern extremity of 
America does not seem especially favourable to the production 
of such a state of glaciation. The land narrows from the tropics 
southwards and terminates altogether in about the latitude of 
Edinburgh ; the mountains are of moderate height ; while during 
summer the sun is three millions of miles nearer, and the heat 
received from it is equivalent to a rise of 20" F. as compared 
with the same season in the northern hemisphere. The only 

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



ciiAr. vm.] THE CAUSES OF GLACIAL EPOCHS. 143 

important differences are : the open southern ocean, the longer 
and colder winter, and the general low temperature caused by 
the south polar ice. But the great accumulation of south polar 
ice is itself due to the great extent of high land within the 
Antarctic circle acted upon by the long cold winter and furnished 
with moisture by the surrounding wide ocean. These conditions 
of high land and open ocean we know did not prevail to so 
great an extent in the northern hemisphere during the glacial 
epoch, as they do in the southern hemisphere at the present 
time ; but the other acting cause — the long cold winter — existed 
in a far higher degree, owing to the excentricity being about 
three times as much as it is now. It is, so far as we know or 
are justified in believing, the only efficient cause of glaciation 
which was undoubtedly much more powerful at that time ; and 
we are therefore compelled to accept it as the most probable 
cause of the much greater glaciation which then prevailed. 

Geographical changes, hoiv far a Cause 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 would be lowered, 
not raised, as Sir Charles Lyell maintained. The reason given 
is, that the land being heated heats the air, which rises and thus 
gives off much of the heat to space, while the same area covered 
with water would retain more of the heat, and by means of 
cuiTcnts carry it to other parts of the earth's surface. But 
although the mean temperature of the whole earth might be 
somewhat lowered by such a disposition of the land, there can 
be little doubt that it would render all extremes of temperature 
impossible, and that even during a period of high excentricity 
there would be no glacial epochs, and perhaps no such thing as 
ice anywhere produced. This would result from there being no 
land near the poles to retain snow, while the constant inter- 
change of water by means of currents between the polar and 
tropical regions would most likely prevent ice from ever forming 
in the sea. On the other hand, were all the land accumulated in 
the polar and temperate regions there can be little doubt that a 



144 ISLAND LIFE. [pabt i. 

state of almost perpetual glaeiation of much of the land would 
result, notwithstanding that the whole earth should theoretically 
he at a somewhat higher temperature. Two main causes would 
bring about this glaeiation. A very large area of elevated land 
in high latitudes would act as a powerful condenser of the 
enormous quantity of vapour produced by the whole of the 
equatorial and much of the temperate regions being areas of 
evaporation, and thus a greater accumulation of snow and ice 
would take place around both poles than would be possible 
under any other conditions. In the second place there would 
be little or no check to this accumulation of ice, because, owing 
to the quantity of land around the polar areas, warm oceanic 
currents could not reach them, while the warm winds would 
necessarily bring so much moisture that they would help on 
instead of checking the process of ice-accumulation. If we 
suppose the continents to be of the same total area and to have 
the same extent and altitude of mountain ranges as the present 
ones, these mountains must necessarily offer an almost continu- 
ous barrier to the vapour-bearing winds from the south, and the 
result would probably be that three-fourths of the land would 
be in the ice-clad condition of Greenland, while a comparatively 
narrow belt of the more southern lowlands would alone afford 
habitable surfaces or produce any woody vegetation. 

Notwithstanding, therefore, the criticism above referred to, 
I believe that Sir Charles Lj^ell was substantially right, and 
that the two ideal maps given in the Principles of Geology (11th 
ed. Vol. i. p. 270), if somewhat modified so as to allow a freer 
passage of currents in the tropics, do really exhibit a condition 
of the earth which, by geographical changes alone, would bring 
about a perpetual summer or an almost universal winter. But 
we have seen in our sixth chapter that there is the strongest 
cumulative evidence, almost amounting to demonstration, that 
for all known geological periods our continents and oceans have 
occupied the same general position they do now, and that no 
such radical changes in the distribution of sea and land as 
imagined by way of hypothesis by Sir Charles Lyell, have ever 
occurred. Such an hypothesis, however, is not without its 
use in our present inquiry, for if we obtain thereby a clear 



CHAi>. VIII.] THE CAUSES OF GLACIAL EPOCHS. 1-15 

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

Land as a barrier to ocean currents. — We have seen already the 
great importance of elevated land to serve as condensers and 
ice-accumulators ; but there is another and hardly less important 
etfect tliat may be produced by an extension of laud in high 
latitudes, which is, to act as a barrier to the flow of ocean 
currents. In the region with wliich 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 eft'ect on climate. Let us suppose, for instance, 
that the British Isles again became continental, and that this 
continental land extended across the Fiiroe Islands and Iceland 
to Greenland. The whole of the warm waters of the Atlantic, 
with the Gulf Stream, would then be shut out from Northern 
Europe, and the result would almost certainly be that snow 
would accumulate on the high mountains of Smndinavia 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 heiglit at oven a lower latitude in Soutli America. 

If a similar change were to occur on the opposite side of 
the Atlantic very dififerent effects would be produced. Suppose, 
for instance, the east side of Greenland were to sirdv consider- 
ably, while on the west the sea bottom were to rise in Davis' 
Strait so as to unite Greenland with Baffin's Land, thus stopping 
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 would certainly produce a wonderful ameliorat- 
ing effect on the climate of the east coast of North America, 
and might raise the temperature of Labrador to that of Scot- 
land. Now these two changes have almost certainly occurred, 
either together or separately, during the Tertiary period, and 
they must have had a considerable effect either in aiding or 
checking the terrestrial and astronomical causes affecting climate 
which were then in operation. 

L 



146 ISLAND LIFE. [part i. 

It would be easy to suggest other probable changes which would 
produce a marked effect oa 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 
w^arra water which initiates the Gulf Stream to pass into the 
Pacific ; and if this occuri-ed 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 geogi-aphical 
changes are very numerous, they must have produced important 
effects; and though we may admit that the astronomical causes 
already explained were the most important in determining 
the last glacial epoch, we must also allow that geographical 
changes must often have had an equally important and perhaps 
even a preponderating influence on climate. We must also 
remember that changes of land and sea are almost always 
accompanied by elevation or depression of the pre-existing 
land : and whereas the former produces its chief effect by 
diverting the course of warm or cold oceanic currents, the 
latter is of not less importance in adding to or diminishing 
those areas of condensation and ice-accumulation which, as 
we have seen, are the most efficient agents in producing 
glaciation. 

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



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

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

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

' The influence of geograpliical changes on climate is now held by 
many geologists who oppose what tliey consider (he 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 lias caused all other elevations and 
depressions. He says : " Now, that elevation of the land over the higher 
latitudes which brought on the glacial era is a natural result of the same 
agency, and a natural, and almost necessary, counterpart of the coral-island 
subsidence which must have been then in progress. The accumulating, 
folding, solidification, and crystallisation of rocks attending all the rock- 
making and mountain-making through the Palieozoic, Mcsozoic, 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 tlie continent, 
where the accumulations and other changes had been relatively small. To 
the subsidence which followed the elevation tlic weight of the ice-cap may 
have contributed in some small degree. But the great balancing move- 
ments of the crust of the continental and oceanic areas then going 
forward must have had a greatly preponderating effect in the oscillating 
agency of all time — lateral pressure within the crust." {American Journal 
of Science and Art/, 3rd 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 
glaciation." (Manual of Geology, 2nd Edition, pp. 541-755, 756.) 

L 2 



148 ISLAND LIFE. [part i. 

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

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

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



CHAP. VIII. ] THE CAUSES OF GLACIAL EPOCHS. 149 



Greenland is an anomaly in the northern hemisphere, only to 
be explained by the fact that cold currents from the polar area 
flow down both sides of it. In Eastern Asia we have the lofty 
Stanivoi Mountains iu the same latitude as the southern part 
of Greenland, which, though their summits are covered with 
perpetual snow, give rise to no ice-sheet, and, apparently, even 
to no important glaciers ; — a fact undoubtedly connected with 
the warm Japan current flowing partially into the Sea of 
Okhotsk. So in North-west Amei'ica we have the lofty coast 
range, culminating iu Mt. St. Elias, nearly 15,000 feet high, and 
an extensive tract of highland to the north and north-west, with 
glaciers comparable in size with those of New Zealand, although 
situated in Lat. G0° instead of in Lat. 45°. Here, too, we have 
the main body of the Japan current turning east and south, and 
thus producing a mild climate, little inferior to that of Norway, 
warmed by the Gulf Stream. We thus have it made clear that 
could the two Arctic currents be diverted from Greenland, that 
country would become free from ice, and might even be com- 
pletely forest-clad and inhabitable ; while, if the Jajwn 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 heiglit 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 000 miles east of Halifax ; and this would 
certainly divert much of the greatly reduced Gulf Stream straight 
across to the coast of Spain. The consequence of such a state 
of things would probably be that the southward flowing Arctic 
currents would be much reduced in velocity ; and the enormous 
quantity of icebergs continually produced by the ice-sheets of 
all the lands bordering the North Atlantic would hano- about 
their shores and the adjacent seas, filling them with a dense 
ice-pack, far surpassing that of the Antarctic regions, and chilling 
the atmosphere so as to produce constant clouds and fog with 
J Dana's Manual of Geolnrjii, 2nd Edition, p. 540. 



150 ISLAND LIFE. [part i. 

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

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

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



fHAP. viii.] THE CAUSES OF GLACIAL EPOCHS. 151 



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

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

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



152 ISLAND LIFE. [part i. 

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

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



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

hemisphere it is impossible to say. It may be that existing 
geograpliical ami physical conditions are there such potent agents 
in producing a state of glaciation that no change in the phases 
of procession 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 case ntial principle of Climnfid clunxjc restated. — The pre- 
ceding discussion has been somewhat lengthy, owing to the 
varied nature of the facts and arguments adduced, and the 
extreme complexity of the subject. But if, as I venture to 
hope, the principle here laid down is a sound one, it will be 
of the greatest assistance in clearing away some of the many 
difficulties that beset the whole question of geological climates. 
This principle is, briefly, that the great features of climate are 
determined by a combination of causes, of which geographical 
conditions and the degree of excentricity of the earth's orbit 
are by far the most important ; that when these combine to 
produce a severe glacial epoch, the changing phases of pre- 
cession every 10,500 years have very little, if any, effect on 
the character of the climate, as mild or glacial, though it may 
modify the seasons ; but when the excentricity becomes moderate 
and the resulting climate less severe, then the changing phases 
of precession bring about a considerable alteration, and even 
a partial reversal of the climate. 

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



154 ISLAND LIFE. [pabt r. 



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

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



avails.* 



' In a recent number of the Geological .l/a^oji/ie (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 North America were glaciated very much in proportion to 
their respective climates now, which are generally admitted to be due to 
the distribution of oceanic currents. But Dr. 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. \Z%) partly diverted 
southward. A portion of its influence would, however, still remain to 
cause a difference between the climates of the two sides of the Atlantic ; 
and to this must be added two other causes — the far greater penetration 
of warm sea-water into the European than into the North American conti- 
nent, and the proximity to America of the enormous ice-producing mass 
of Greenland. We have thus three distinct causes, all combining to 



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

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

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

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



I5S ISLAND LIFE. [lAiiT i. 

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

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



CHAP, vui.] THE CAUSES OF GLACIAL EPOCHS. 157 

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

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

This passage is evidently written by a person familiar with the phe- 
nomena of glaciation, and as Captain Aylward's preface is dated from 
Edinburgh, he has probably seen similar markings in Scotland. The 
country described consists of the most extensive and lofty plateau in South 
Africa, rising to a mountain knot with peaks more than 10,000 feet high, 
thus oflEering an appropriate area for the condensation of vapour and the 
accmnulation of snow. At present, however, the mountains do not reach 
the snow-line, and there is no proof that they have been much higher in 
recent times, since the coast of Natal is now said to be rising. It is evi- 
dent that no slight elevation would now lead to the accumulation of snow 
and ice in these mountains, situated as they are between 27^ and 30° S. Lat. ; 
since the Andes, which in 32° S. Lat. reach 2.3,300 feet high, and in 28' 



158 ISLAND LIFE. [rARr i. 

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

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

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 liave produced the remarkable amount of glaciation above 
described ; while from the analogy of the northern hemisphere, we may 
well believe that it was mainly due to the same high excentricity that led to 
the glaciation of Western and Central Europe, and Eastern North America. 
These obser\-ations confirm those of Mr. G. W. Stow, who, in a paper 
published in the Quarterly Journal of the Geologiral Society (Vol. xxvii. p. 
539), describes similar phenomena in the same mountains, and also mounds 
and ridges of unstratified clay packed witli angular boulders ; while further 
south the Stormberg mountains are said to be similarly glaciated, with im- 
mense accumulations of morainic matter in all the vallej's. We have here 
all the chief surface phenomena characteristic of a glaciated country only 
a few degrees south of the tropic ; and taken in connection with the evi- 
dence of Professor Hartt, who describes true moraines near Rio de Janeiro, 
situated on the tropic itself, we can hardly doubt the occurrence of some 
general and wide-spread cause of glaciation in the southern hemisphere at 
a period so recent that the superficial phenomena are as well preserved as 
in Europe. Such evidences of recent glaciation in the southern hemi- 
sphere are quite inexplicable without calling in the aid of the recent phase of 
high excentricity ; and they may be fairly claimed as adding another link 
to the long chain of argument in favour of the theory here advocated. 



CHAP, vin.] THE CAUSES OF GLACIAL EPOCHS. 159 



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

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 0.0931, 
Earth excentricity, 850,000 years back, 0.0707) ; tiie inclina- 
tion of its axis is also a little greater than ours (Mars 28° 51', 
Earth 23°, 27'), and both Mars and the Earth are so situated 
that they now have the winter of their northern hemispheres 
in perihelion, that of their southern hemisphere being in 
aphelion. If, therefore, the physical condition of Mars were 
the same or nearly the same as that of the Earth, all cir- 
cumstances combine, according to Mr. CroU's hypothesis, to 
produce a severe glacial epoch in its southern, with a perpetual 
spring or summer in its northern, hemisphere ; wliile 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 vaiying very 
unequally. The northern cap varies slowly and httle, the 
southern varies rapidly and largely. 

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



160 ISLAND LIFE. [pabt i. 

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

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

!May 4tli. Diameter of spot 31° 24 

Juno 4tli. „ „ 28= Of 

„ 17th. „ „ 22° 54' 

July 4th. „ „ 18' 24' 

„ 12th. „ „ lo- 20' 

„ 20th. „ „ 18' C 

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

Before, however, we can draw any conclusion from the ca.se 
of Mars, we must carefully scrutinise the facts, and the condi- 
tions 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 her temperate zone, as the Earth un- 
doubtedly had. This we know from the fact of the rapid 

' In an article in Xatvre of Jan. 1, 1880, the Rev. T. W. Webb states that 
in 1877 the pole of Mars (V the south pole) was, according toSchiaparelli, 
entirely free of snow. He remarks also on the regular contour of the sup- 
posed snows of Mars as offering a great contrast to ours, and also tlie 
strongly marked dark border which has often been observed. On the whole 
Mr. Webb seems to be of opinion that there can be no really close resem- 
blance between the physical condition of the Earth and Mars, and that any 
arguments founded on such supposed similarity are therefore untrustworthy. 



CHAP, viri.] THE CAUSES OF GLACIAL EPOCHS. 161 



disappearance of the white patches over a belt three degrees 
wide in a fortnight (equal to a width of about 100 miles of our 
measure), and in the northern hemisphere of eight degrees wide 
(about 280 miles) between May 4th and July 12th. Even with 
our much more powerful sun, which gives us more than twice 
as much heat as Mars receives, no such diminution of an ice- 
sheet, or of glaciers of even moderate thickness, could possibly 
occur ; but the phenomenon is on the contrary exactly analogous 
to what actually takes place on the plains of Siberia in summer. 
These, as I am informefl by Mr. Seebohm, are covered with snow 
during winter and spring to a depth of si.\ or eight feet, which 
diminishes very little even under the hot suns of May, till warm 
winds combine with the sun in June, when in about a fortnight 
the whole of it disappears, and a little later the whole of Northern 
Asia is free from its winter covering. As, however, the sun of 
Mars is so much less powerful than ours, we may be sure that 
the snow (if it is real snow) is much less thick — a mere surface- 
coating in fact, such as occurs in parts of Russia where the 
precipitation is less, and the snow accordingly does not exceed 
two or three feet in thickness. 

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

H 



Ifi2 ISLAND LIFE. [part i. 

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

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



CHAPTER IX. 

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

Dr. Croll's views on ancient Glacial Epochs— Effects of Denudation in 
destroying the evidence of remote Glacial Epochs— Rise of sea-level 
connected with Glacial Epochs a cause of further denudation— What 
evidence of early Glacial Epochs may be expected— Evidences of Ice- 
action during tlie Tertiary Period— The weight of the negative evi- 
dence—Temperate climates in the Arctic Regions — The Miocene Arctic 
flora — Mild Arctic climates of the Cretaceous Period— Stratigraphical 
evidence of long-continued mild Arctic conditions— The causes of mild 
Arctic climates — Geographical conditions favouring mild northern 
climates in Tertiary times— The Indian Ocean as a source of Heat in 
Tertiary times— Condition of North America during the Tertiary Period 
— Effect of high excentricity on warm Polar climates— Evidences as to 
climate in the Secondary and Palaozoic Epochs — Warm Arctic climates 
in early Secondary and Palaeozoic times — Conclusions as to the climates 
of Secondary and Tertiary Periods — General view of Geological Climates 
as dependent on the physical features of the Earth's surface— Esti- 
mate of the comparative effects of geographical and physical causes in 
producing changes of climate. 

If we adopt the view set forth in the preceding chapter as to 
the character of the glacial epoch and of the accompanj-ing " 
alternations of climate, it must have been a very important agent 
in producing changes in the distribution of animal and vegetable 
life. The intervening raild periods, which almost certainly oc- 
curred during its earlier and later phases, were sometimes more 
equable than even our present insular climate, and severe frosts 
were probably then unknown. During the eight or ten thousand 
years that each such mild period lasted, some portions of the 

M 2 



\ 



164 ISLAND LIFE. [part i. 

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

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

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

' London, Edinburgh and Dublin Philosophical Magazine, Vol. XXXVI., 
pp. 1-14-160 (1868). 



CHAP. IX.] 



ANCIENT GLACIAL EPOCHS. 



1G5 



alternations of cold and warm phases 
every 10,500 years. The diagram 
also shows us another long-continued 
period of high excentricity from 
1,750,000 to 1,950,000 years ago, 
and yet another almost equal to the 
maximum 2,500,000 years back. 
These may perhaps have occun-ed 
during the Eocene and Cretaceous 
epochs respectively, or all may have 
been included within the limits of 
the Tertiary period. As two of these 
high exceutricities greatly exceed 
that which caused our glacial epoch, 
while the third is almost equal to it 
and of longer dui-ation, they seem to 
afford us the means of testing rival 
theories of the causes of glaciation. 
If, as Dr. Croll argues, high excen- 
tricity is the great and dominating 
agency in bringing on glacial epochs, 
geographical changes being subor- 
dinate, then tliere must have been 
glacial epochs of great severity at all 
these three periods ; while if he is 
also correct in su2525osing that the 
alternate phases of precession would 
inevitably produce glaciation in one 
hemisphere, and a proportionately 
mild and equable climate in the 
opposite hemisphere, then we should 
have to look for evidence of ex- 
ceptionally warm and exceptionally 
cold periods, occurring alternately 
and with several repetitions, with- 
in a space of time which, geo- 
logically speaking, is very short 
indeed. 




"^' 



€r.i 







166 ISLAND LIFE. [part i. 

Let us then inquire first into the character of the e^ddence 
■we should expect to find of such changes of climate, if they 
have occurred ; we shall then he 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 evidence of remote 
Glacial Epochs. — It may be supposed, that if earlier glacial 
epochs than the last did really occur, we ought to meet with 
some evidence of the fact corresponding to that which has 
satisfied us of the extensive recent glaciation of the northern 
hemisphere ; but Dr. Croll and other writers have ably argued 
that no suxjh evidence is likely to be found. It is now generally 
admitted that sub-aiirial denudation is a much more powerful 
agent in lowering and modifying the surface of a country than 
was formerly supposed. It has in fact been proved to be so 
powerful that the difficulty now felt is, not to account for the 
denudation which can be proved to have occurred, but to explain 
the apparent persistence of superficial features which ought long 
ago to have been destroyed. 

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



CHAP. IX.] ANCIENT GLACIAL EPOCHS. 167 

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

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

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

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



168 ISLAND LIFE. [part i. 

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

The facts here seem a little inconsistent, and we must suppose 
that Dr. Croll has somewhat exaggerated the universality and 
complete preservation of the glaciated surface. The amount of 
average denudation, however, is not a matter of opinion but of 
measurement ; and its consequences can in no way be evaded. 
They are, moreover, strictly proportionate to the time elapsed ; 
and if so much of the old surface of the country has certainly 
been remodelled or carried into the sea since the last glacial 
epoch, it becomes evident that any surface-phenomena produced 
by still earlier glacial epochs 7nust have long since entirely 
disappeared. 

Hise of (he Sea-level connected toith Glacial Upochs, a cause of 
further 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 writers, as 
we have seen, connect this subsidence with the glacial period 
itself, the unequal amount of ice at the two poles causing the 
centre of gravity of the earth to be displaced, when, of course, 
the surface of the ocean will conform to it and appear to rise iii 
the one hemisphere and sink in the other. If this is the case, 
subsidences of the land are natural concomitants of a glacial 
period, and will powerfully aid in removing all evidence of its 
occurrence. We have seen reason to believe, however, that during 
the height of the glacial epoch the extreme cold persisted through 
' Climate and Time in their Geological Relations, p. 341. 



CHAP. IX.] ANCIENT GLACIAL EPOCHS. 169 



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

But whether or not these causes would produce any important 
fluctuations of the sea-level is of com2iaratively little import- 
ance to our present iuquiry, because the wide extent of marine 
Tertiary deposits in the northern hemisphere and their occur- 
rence at considerable elevations above the present sea-level, 
afford the most conclusive proofs that great cliaiiges of sea aud 
laud have occurred throughout the entire Tertiary period ; and 
these reiaeated submergences and emergences of the land com- 
bined 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. 

Mliat 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 
off of the ends of glaciers which terminate in arms of the sea, or 
of the terminal face of the ice-sheet which passes beyond the 
land into the ocean. In both these eases abundance of rocks 
aud dihris, such as form the terminal moraines of glaciers on land, 
are carried out to sea aud deposited over the .sea-bottom of the 
area occupied by icebergs. In the case of an ice- sheet it is 
almost certain that much of the ground-moraine, consisting of 
mud and imbedded stones, similar to that which forms the " till" 
■when deposited on land, will be carried out to sea with the ice 
and form a deposit of marine " till " near the shore. 

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



170 ISLAND LIFE. [part i. 

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

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

But if every period of high excentricity produced a glacial 
epoch of greater or less extent and severity, then, on account of 
the frequent occuiTence 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 
1 Nature, Vol. XXL, p. 345, "The Interior of Greenland." 



CHAP. IX.] ANCIENT GLACIAL EPOCHS. 171 

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

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

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



172 ISLAND LIFE. [pAitT i. 

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

The Eocene period is even more characteristically tropical in 
its flora and fauna, since palms and 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 containing in several places 
in Switzerland enormous blocks cither 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 10.5 feet long, ninety feet wide, 
aud 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 ago in the Carpathians and in the Apennines, indicating 
probably an extensive inland European sea into which glaciers 
descended from the surrounding mountains, depositing these 
erratics, and cooling the water so as to destroy the mollusca 
and other organisms which had previously inhabited it. It is 
to be observed that wherever these en-atics 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 



CHAP. IX.] ANCIENT GLACIAL EPOCHS. 173 

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

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

In his carefully written paper on " The Climate Controversy " 
Mr. Searles V. Wood, Jun., remarks on this point as follows : 
"Now the Eocene formation is complete in England, and is 
exposed in continuous section along the north coast of the Isle 
of Wight from its base to its junction with the Oligocene (or 
Lower Miocene according to some), and along the northern 
coast of Kent 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 i^ierced by wells innumerable; while 
from its strata in England, France, and Belgium, the most 

1 Prof. J. W. Judd snys : " In llie 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-lino 
which would collect more ample supplies for the glaciers protruded into 
surrounding plains. And when we survey the granil 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 Volcanoes, Geological Magazine, 1876, p. 536.) Professor 
Judd applies these remarks to the last as well 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. 



174 ISLAND LIFE. [i-art i. 

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

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

> Geological Magazine, 1876, p. 392. 



CHAP. IX.] MILD ARCTIC CLIMATES. 175 



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

Temperate Climates 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 con.sider the still more extraordinary series of ob- 
servations which demonstrate that this amelioration of climate 
extended into the Arctic zone, and into countries now almost 
wholly buried in snow and ice. These warm Arctic climates 
have been explained by Dr. Croll as due to periods of high 
excentricity with winter in perihelion, a theory which implies 
alternating epochs of glaciation far exceeding what now prevails ; 
and it is therefore necessary to examine the evidence pretty 
closely in order to see if this view is more tenable in the case 
of the north polar regions than we have found it to be in that 
of the north temperate zone. 

The most recent of these milder climates 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 consider- 
ably milder climate than now prevails could alone have enabled 
them to do so. At what period this occurred we do not know, 
but one of the last intercalated mild periods of the glacial 
epoch itself seems to offer all the necessary conditions. Again, 



176 ISLAND LIFE. [part i. 



Sir Edward Belcher discovered on the dreary shores of Welling- 
ton Channel in 75i° 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 places 
on Spitzbergen, at the bottom of Lomme Bay, at Cape 
Thordsen, in Blomstrand's strata in Advent Bay, there are 
found large and well-developed shells of a bivalve, Mytilus 
edidis, which is not now found living on the coasts of Spitzbergen, 
though on the west coast of Scandinavia it everywhere covers 
the rocks near the sea-shore. These shells occur most plenti- 
fully in the bed of a river which runs through Reindeer Valley 
at Cape Thordsen. They are probably washed out of a thin 
bed of sand at a height of about twenty or thirty feet above 
the present sea-level, which is intersected by the river. The 
geological age of this bed cannot be very great, and it has 
clearly been formed since the present basin of the Ice Sound, 
or at least the greater part of it, has-been hollowed out by 
glacial action." ^ 

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

' Geological Magazine, 1876, " Geology of Spitzbergen,"' p. 267. 



CHAP. IX.] MILD ARCTIC CLIJUTES. 177 



The Miocene flora of temperate Europe was very like that of 
Eastern Asia, Japan, and the warmer part of Eastpm North 
America of the present day. It is very richly represented in 
Switzerland by well preserved fossil remains, and after a close 
comparison with the flora of other countries Professor Heer 
concludes that the Swiss Lower Miocene flora indicates a climate 
corresponding to that of Louisiana, North Africa, and South 
China, while the Upper Miocene cUmate of the same country 
would correspond to that of the south of Spain, Southern 
Japan, and Georgia (U.S. of America). Of this latter flora, 
found chiefly at CEningben in the northern extremity of 
S^vitzerland, 4G5 species are known, of which 166 species are 
trees or shrubs, half of them being evergreens. Thev comprise 
sequoias like the California giant trees, camphor-trees, cinna- 
mons, sassafras, bignonias, cassias, gleditschias, tulip-trees, and 
many other American genera, together with maples, ashes, 
planes, oaks, poplars, and other familiar European trees repre- 
sented by a variety of extinct species. If we now go to the 
west coast of Greenland in 70° N. Lat., we find abundant 
remains of a flora of the same general type as that of (Eninghen 
but of a more northern character. We have a sequoia identical 
with one of the species found at (Eninghen, a chestnut, saUsburia, 
liquidambar, and sassafras, and even a magnolia. We have also 
seven species of oaks, two planes, two vines, three beeches, 
four poplars, two willows, a walnut, a plum, and several shrubs, 
supposed to be evergreens; altogetlier 137 species, mostly well 
and abundantly preserved ! 

But even further north, in Spitzbergen, in 78° and 79° N. 
Lat. and one of the most barren and inhospitable regions on 
the globe, an almost equally rich fossil flora has been discovered 
including several of the Greenland species, and others peculiar, 
but mostly of the same genera. There seem to be no ever- 
greens here except coniferae, 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 



178 ISLAND LIFE. |paet i. 

flowering plants. Even in Grinnell Land, within 8^ degrees of 
the pole, a similar flora existed, twenty-five species of fossil 
plants having been collected by the last Arctic expedition, of 
which eighteen were identical with the species from other Arctic 
localities. This flora comprised poplars, birches, hazels, elms, 
viburnums, and eight species of conifers, including the swamp 
cypress, and the Norway spruce {Pinus abies) which does not 
now extend beyond G9^° N. 

Fossil plants closely resembling those just mentioned have 
been found at many other Arctic localities, especially in Iceland, 
on the Mackenzie River in 6-5° N. Lat. and in Alaska. As an 
intermediate station we have, in the neighbourhood of Dantzic 
in Lat. 55° N., a similar flora, with the swamp-cypress, sequoias, 
oaks, poplars, and some cinnamons, laurels, and figs. A little 
further south, near Breslau north of the Carpathians, a rich 
flora has been found allied to that of (Eninghen, but wanting in 
some of the more tropical forms. Again, in the Isle of Mull 
in Scotland, in about 56i° N. Lat., a plant-bed has been dis- 
covered containing a hazel, a plane, and a sequoia, apparently 
identical with a Swiss Miocene species. 

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



CHAP. IX.] MILD ARCTIC CLIMATES. 179 



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

Mild Arctic Climates of the Cretacemis Period. — In the Upper 
Cretaceous deposits of Greenland (in a locality not far from 
those of the Miocene age last described) another remarkable flora 
has been discovered, agreeing generally with that of Europe and 
North America of the same geological age. Sixty-five species 
of plants have been identified, of which there are fifteen ferns, 
two cycads, eleven coniferaj, 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, 
.ind among the dicotyledons the genera Populus, Myrica, Ficus, 
Sassafras, Andromeda Diospyros, Myrsine, Pana.x, 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 evidently afiord 
such fragmentary records of the actual flora of the period, that 
it is impossible to say that any genus found in one locality was 
absent from the other merely because it has not yet been found 
there. On the whole, there seems to be less difference between 
the floras of Arctic and temperate latitudes in Upper Cretaceous 
than in Miocene times. 

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

X 2 



IRO ISLAND LIFE. [parti. 



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 poplar 
being the oldest known dicotyledonous plant. ^ 

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

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

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



CHAP, n-.] 5JILD AECTIC CLIMATES. 181 



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

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



182 ISLAND LIFE. [part i. 

repeated alternation of warm and glacial climates between the 
present time and the earliest geological ages."* And again, in 
his Sketch of the Geology of Spitzbergen, after describing the 
various formations down to the Miocene, he says : " All the 
fossils found in the foregoing strata show that Spitzbergen, dur- 
ing former geological ages, enjoyed a magnificent climate, which 
indeed was somewhat colder during the Miocene period, but 
was still favourable for an extraordinarily abundant vegetation, 
much more luxuriant than that wliich now occurs even in 
the southern part of Scandinavia ; and I have in these strat;i 
sought in vain for any sign, that, as some geologists have of late 
endeavoured to render probable, these favourable climatic con- 
ditions have been broken off by intervals of ancient glacial 
periods. Tho profiles I have had tlie opportunity to examine 
during my various Spitzbergen expeditions would certainly, if 
laid down on a line, occupy an extent of a thousand English 
miles; and if any former glacial pei'iod 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 tdone, I have not found a single 
fragment of a foreign rock so large as a child's head."^ 

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

' Geological Magazine, 1875, p, 531. 
* Geological Magazine, 1876, p. 266. 



CHA1-. IX.] MILD ARCTIC CLIMATES. 183 

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

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

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

' 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. Jlr. De Ranee (in the geological 
appendix to Capt. Sir G. Nares' Nairative of a Vui/age 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 higlier mean temperature than those of the Dakota group, 
to a dense atmosphere of vapour, and a luxuriance of ferns and palms." 
This is very important as adding further proof to the view that the 
climates of former periods are not due to any general refrigeration, but 
to causes which were subject to change and alternation in former ages 
as now. 



184 ISLAND LIFE. [part i. 

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

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

Now geologists have proved, quite independently of any 
suoh 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 nortli temperate lands in early Tertiary times, to 
that more compact and continental condition which now pre- 
vails. It is, no doubt, difficult and often impossible to deter- 
mine how long any particular geographical condition lasted, or 
whether the changes in one country were exactly coincident 
with those in another; but it will be sufficient for our purpose 
briefly to indicate those more important changes of land and 
sea during the Tertiary period, which must have produced a 
decided effect on the climate of the northern hemisphere. 

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



CHAP. IX.] MILD ARCTIC CLIMATES. 185 

and the Persian Gulf, thus opening a communication between 
the Xorth Atlantic and the Indian Ocean. From the Caspian 
also a wide arm of the sea extended during some part of the 
Tertiary epoch northwards to the Arctic Ocean, and there 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 basin of the Mediterranean 
and the Black Sea ; wliile it is probable that there was a com- 
munication between tlie 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 impi-obable that a more direct channel across 
Afghanistan may have opened a communication between the 
West Asiatic and Polar seas. 

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

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



186 ISLAND LIFE. [rART r. 

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

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

' By referring to our map of the Indian Ocean showing the submarine 
banlcs 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 Ssa. 



CHAr. IX.] MILD ARCTIC CLIMATES. 187 

the constant vk a tergo, which is so eflScient in the Atlantic, 
would keep up a steady and powerful cun-ent towards the 
northern parts of the Indian Ocean, and thence through the 
midst of the European archipelago to the northern seas. 

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

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

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



188 ISLAND LIFE. [i-art i. 

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

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

Effect of these Changes on the Climate of the Arctic Regions. — 
These various changes of sea and land, all tending towards a 
transference of heat from the equator to the north temperate 
zone, were not improbably still further augmented by the 
existence of a great inland South American sea occupying 
what are now the extensive valleys of the Amazon and 
Orinoco, and forming an additional reservoir of super-heated 
water to add to the supply poured into the North Atlantic. 

It is not of course supposed that all the modifications here 
indicated co-existed at the same time. We have good reason to 
believe, from the known distribution of animals in the Tertiary 



CHAP. IX.] >riLD ARCTIC CLIMATES. 189 



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

Those who wish to understand the effect of oceanic currents 
in conveying heat to the north temperate and polar regions, 
should study the papers of Dr. Croll already referred to. But 
the same thing is equally well shown by the facts of the actual 
distribution of heat due to the Gulf Stream. The difference 
between the mean annual temj)eratures of the opposite coasts 
of Europe and America is well known and has been already 
quoted, but the difference of their mean winter temperature is 
still more striking, and it is this which concerns us as more 
especially affecting the distribution of vegetable and animal 
life. Our mean winter temperature in the west of England is 
the same as that of the Southern United States, as well as that 
of Shanghae in China, both about twenty degi-ees of latitude 
further south ; and as we go northward the difference increases, 
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 

' For an account of the resemblances and differences of the mammalia 
of the two continents during the Tertiary epoch, see my Geographical 
Dixtn'bu/ion nf Animah, Vol. T. pp. 140 — 156. 



190 



ISLAND LIFE. 



[part I. 



country did not consist almost wholly of precipitous snow-clad 
mountains, it would be capable of supporting most of the vegetable 
products of the American coast in the latitude of Bordeaux. ^ 

With these astounding facts before us, due wholly to the 
transference of a portion of the warm currents of the Atlantic 
to the shores of Europe, even with all the disadvantages of 
an icy sea to the north-east and ice-covered Greenland 
to the north-west, how can we doubt the enormously 
screater effect of such a condition of thinsrs as has been shown 
to have existed during the Tertiary epoch ? Instead of ane 
great stream of warm water spreading widely over the North 
Atlantic and thus losing the greater part of its store of heat 
before it reaches the Arctic seas, we should have several streams 
conveying the heat of far more extensive tropical oceans by 
comparatively narrow inland channels, thus being able to 



• Professor Hiiugliton has made an elaborate calculation of the differ- 
ence between existing climates and those of Miocene times, for all the 
places where a lliocene flora has been discovered, by means of the actual 
range of corresponding species and genera of plants. Altliouffh this 
method is open to the objection that tlie ranges of plants and animals are 
not determined by temperature only, 3et the results may be approxi- 
mately correct, and are very interesting. The following table which 
summarizes these results is taken from his Lectures on Physical Geography 
(p. 344) :- 



Latitude. 


Present | Miocene DiH-eience. 
Temperature. Temperature. 


1. Switzerland . . . 

2. Dantzig .... 
3 Iceland .... 


47=.00 
54^21 
fi5=..S0 


53'.6 F. 
45".7 „ 
35'.6 „ 
19^4 „ 
19°.6 „ 
16=.5 „ 

r.7 „ 


69°.8 F. 
62=.6 „ 
48=.2 „ 
48^.2 „ 
65^6 „ 
61°.8 „ 
42°.3 „ 


16°.2 F. 
16°.9 „ 
12°.6 „ 
28°.8 „ 
36°.0 „ 
35°.3 „ 
44=.0 „ 


4. Mackenzie River . 

5. Disco (Greenland) 

6. Spitzbergen . . . 

7. Grinnell Land . , 




65°.0O 
70'.00 
78%00 
81°.44 



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



CHAP. IS.] MILD ARCTIC CLIMATES. 191 

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

Effect of High E.ccentridly on the wnrm Polar Climates. — 
If the exjilanation 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 

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



192 ISLAND LIFE. [part i. 

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

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



CHAP. IX ] MILD ARCXrC CLIMATES. 193 



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

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

o 



194 ISLAND LIFE. [part i. 

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

Permian breccias are also found in Ireland, contaiaing blocks 
of Silurian and Old Red .sandstone rocks which Professor Hull 
believes could only have been carried by floating ice. Similar 
breccias occur ia 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 distiugui-shed 
from it."i 

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

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

' Geoloyical ^fagf^:ine, 1873, p. 3'JO. 



CHAP. IX.] GEOLOGICAL CLIMATES. 195 

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. 

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 northei-n latitudes, among which we may especially 
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 in- 
habited the seas of Spitzbergen, where their fossil remains are 
now found. 

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

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

Cmiclusions as to the Climates of Tertiary and Secondary 2')eriods. 
— 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. 
WTiether in Miocene, Upper or Lower Cretaceous, Jurassic, 
Triassic, Carboniferous or Silurian times, and in all the 
numerous localities extending over more than half the polar 
I'egions, 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 

o 2 



106 ISLAND LIFE. [part i. 

persistent cold epochs when tlie exceutricity was as low as it 
is now or lower, for that would imply that the duration of cold 
conditions was greater than that of warm. Why then should 
the fauna and flora of the cold epochs never be preserved ? 
jMollusca and many other forms of hfe are abundant in the 
Arctic seas, and there is often a luxuriant dwarf woody vegeta- 
tion on the land, yet in no one case has a single example of 
such a fauna or flora been discovered of a date anterior to the 
last glacial epoch. And this argument is very much strength- 
ened when we remember that an exactly analogous series of 
facts is found over all the temperate zones. Everywhere we 
have abundant floras and founas indicating warmer conditions 
than such as now prevail, but never in a single instance one 
which as clearly indicates colder conditions. The fact that 
drift with Arctic shells w^as 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 v.-ell 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 palseon- 
tological evidence we add the equally uniform absence of any 
indication of those ice-borne rocks, boulders, and drift, which 
are the constant and necessary accompaniment of every period 
of glaciation, and which must inevitably pervade all the marine 
deposits formed over a wide area so long as the state of glacia- 
tion continues, we are driven to the conclusion that the last 
glacial epoch of the northern hemisphere was exceptional, 
and was not preceded by numerous similar glacial epochs 
throughout Tertiary and Secondary time. 

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



CHAP. IX.] GEOLOGICAL CLIMATE?. 197 

the testimony of Mr. J. S. Gardner, who has long worked at the 
fossil floras of the Tertiary deposits, and who states, that there 
is strong negative and some positive evidence of alternatino- 
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 tlie fossil remains from bed to bed only 
a few feet and sometimes a few inches apart, may be sometimes 
due to change of climate ; and when it is recognised that such 
changes have probably occurred at all geological epochs and 
their effects are systematically searched for, many peculiarities 
in the distribution of organisms througli the different members 
of one deposit may be traced to this cause. 

Gemral view of Geological Climates as dependent on the 
Physical Features of the Earth's Surface. — In the preceding 
chapters I have earnestly endeavoured to arrive at an explana- 
tion of geological climates in the temperate and Arctic zones, 
which should be in harmony with the great body of geological 
facts now available for their elucidation. If my conclusions as 
here set forth diverge considerably from those of Dr. Croll, it is 
not from any want of appreciation of his facts and arguments, 
since for many years I have uplield and enfi^rced his views to the 
best of my ability. But a careful re-e.\amination of the whole 
question has now convinced me that an error has been made in 
estimating tlie comparative effect of geograpliical and astro- 
nomical causes on changes of climate, and tliat, wliile the 
latter have undoubtedly played an important part in bringing 
about the glacial epoch, it is to tlie 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 principles so 
clearly set forth in his admirable papers on " Ocean Currents in 
relation to the Distribution of Heat over the Globe." The 
main features of this theory as distinct from that of Dr. Croll 
I will now endeavour to summarise. 

Looking at the subject broadly, we see that the climatic 
' Gfolng'tcal Magazine, 1877, p. 137. 



198 ISLAND LIFE. [part i. 

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

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

It appears to be the general opinion of geologists that the 
great continents have undergone a process of development from 
earher to later times. Professor Dana says : " The North 
American continent, which since early time had been graduaUy 
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 



CHAP. 15.] GEOLOGICAL CLIJIATES. 199 

land Avas at all times simple in outline ; and its enlargement 
took place with almost the regularity of an exogenous plant." ' 

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

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

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



200 ISLAND LIFE. [rART i. 

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



cnAP. IX.] GEOLOGICAL CLIMATES. 201 



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

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

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

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



202 ISLAND LIFE. [part i. 

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



CHAPTER X. 

THE earth's age, and the rate of development of 

ANIMALS AND PLANTS. 

Various estimates of Geological Time — Denudation and Deposition of 
Strata as a measure of Time — How to estimate the thickness of tlie 
Sedimentary Rocks — How to estimate the average rate of deposition of 
the Sedimentary Rocks — The rate of Geological Change probably greater 
in very remote times — Value of the preceding estimate of Geological 
Time — Organic modification dependent on Change of Conditions — 
Geographical mutations as a Motive power in bringing about Organic 
Changes^Climatal revolutions as an agent in producing Organic 
Changes — Present condition of the Karth one of exceptional stability as 
regards Climate — Date of last Glacial Epocli and its bearing on the 
Measurement of Geological Time — Concluding Remarks. 

The subjects discussed in the last three cliapters iutroduce 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. 
Geologists continually dwell on the slowness of the processes of 
upheaval and subsidence, of denudation of the earth's surface, 
and of the formation of new strata; while on the theory of 
development, as expounded by Mr. Darwin, the variation and 
modification of organic forms is also a very slow process, and 
has usually been considered to require an even longer series of 
ages than might satisfy the requirements of physical geology 
alone. 

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



204 ISLAND LIFE. [part i. 

edition of his Principles of Geology (omitted in later editions), 
by which he arrived at 240 millions of years as having probably 
elapsed since the Cambrian period — -a very moderate estimate 
in the opinion of most geologists. This calculation was founded 
on the rate of modification of the species of mollusca ; but 
much more recently Professor Haughton has amved at nearly 
similar figures from a consideration of the rate of formation 
of rocks and their known maximum thickness, whence he 
deduces a maximum of 200 millions of years for the whole 
duration of geological time, as indicated by the series of 
stratified formations.' But in the opinion of all our first natu- 
rahsts and geologists, the period occupied in the formation of 
the known stratified rocks only represents a portion, and perhaps 
a small portion, of geological time. In the last edition of the 
Oi-igin of Species (p. 286), Mr. Darwin says : — " Consequently, if 
the theory be true, it is indisputable that before the lowest Cam- 
brian stratum was deposited long periods elapsed, as long as, or 
probably far longer than, the whole interval from the Cambrian 
age to the present day ; and that during these vast periods the 
world swarmed with living creatures." Professor Huxley, in his 
anniversary address to the Geological Society in 1870, adduced 
a number of special cases showing that, on the theory of de- 
velopment, almost all the higher forms of hfe 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 greater change of the 
ancestral Ungulata into the two great odd-toed and even-toed 
divisions (of which change there is no trace even among the 
earliest Eocene mammals), we should require a large portion, 
if not the whole, of the Mesozoic or Secondary period. Another 
case is furnished by the bats and nhales, both of which strange 
modifications of the mammalian type occur perfectly developed 
in the Eocene formation. What countless ages back must we 
then go for the origin of these groups, the whales from some 
ancestral carnivorous animal, and the bats from the insectivora ! 
And even then we have to seek for the common origin of 
1 Nature, Vol. XVIII. (July, 1878), p. 2C8. 



CHAP. X.] THE EARTH'S AOE. 205 



camivora, insectivora, ungulata, and marsupials at a far earlier 
period ; so that, on the lowest estimate, we must place the origin 
of the mammalia very far back in Palseozoic 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 avenige rate of change among reptiles, it is 
almost appalling to reflect how far back in Paleozoic times 
we must go before we can hope to arrive at that common stock 
from which the crocodiles, lizards, OrnithosccUda, and Flesiosauria, 
which had attained so gi'eat a development in the Triassic 
epoch, must have been derived." Professor Ramsay has expressed 
similar views, derived from a general study of the whole series 
of geological formations and their contained fossils. He says, 
speaking of the abundant, varied, and well-developed fauna of 
the Cambrian period : " In this earliest known varied life 
we find no evidence of its having lived near the beginning of 
the zoological series. In a broad sense, compared with what 
must have gone before, both biologically and physically, all the 
phenomena connected with this old period seem, to my mind, 
to be of quite a recent description ; and the climates of seas and 
lands were of the very same kind as those the world enjoys at 
the present day." ^ 

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

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

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



206 ISLAND LIFE. [part i. 

contemplated can be granted. From a consideration of the 
possible sources of the heat of the sun, as well as from calcula- 
tions of the period during which the earth can have been 
cooling to bring about the present rate of increase of tempera- 
ture as we descend beneath the surface, Sir William Thomson 
concludes that the crust of the earth cannot have been soHdi- 
fied much longer than 100 million years (the maximum possible 
being 400 millions), and this conclusion is held by Dr. CroU 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 Depositio7i of Strata as a measure of Time. — The 
materials of aU the stratified rocks of the globe have been ob- 
tained from the dry land. Every point of the surface is exposed 
to the destructive influences of sun and wind, frost, snow, and 
rain, which break up and wtar 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 tlie earth's surface ; of vast heaps of 
rocky cUhris at the foot of every inland clifif; of enormous 
deposits of gravel, sand, and loam ; as well as the shingle, 
pebbles, sand, or mud, of every sea-shore, alike attest the uni- 
versality of this destructive agency. It is no less clearly shown 
by the way in which almost every drop of running water — 
whether in gutter, brooklet, stream, or large river — becomes 
discoloured after each heavy rainfall, since the matter which 
causes this discolouration must be derived from the surface of 
the country, must always pass from a higher to a lower level, 
and must ultimately reach the sea, unless it is first deposited in 
some lake, or by the overflowing of a river goes to form an 
alluvial plain. The universality of this subaerial denudation, 
both as regards space and time, renders it certain that its cumu- 
lative effects must be very great ; but no attempt seems to have 

' Trans. Royal Society of Edinburgh, Vol. XXIII. p. 161. Quarterly Jour- 
nal of Science, 1877. (Croli on the " Probable Origin and Age of the 
Sun.") 



tiiAr. X.] THE EARTH'S AGE. 207 



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

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

^ Philrisnjtliical Magazine, April 1853. 



208 ISLAND LIFF. [part i. 

The Mississippi removes one foot in 6,000 yeara. 

Ganges „ ,, 2,358 ,, 

Hoang Ho ,, „ 1,464 , 

Rhone ,, ,, 1,528 „ 

Danube „ „ 6,840 „ 

Po „ „ 729 „ 

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

' It has usually been the practice to take the amount of denudation in 
the Slississippi 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 tliey always 
took the lowest estimates of planetary or stellar distances, instead of the 
mean results of observation, " in order to be on the safe side ! " ? As if 
error in one direction were any worse than error in another. Yet this is 
what geologists do systematically. Whenever any calculations are made 
involving the antiquity of man, it is those that give the lowest results that 
are always taken, for no reason apparenth' except that there was, for so long 
a time, a prejudice, both popular and scientific, against the great antiquity 
of man ; and now that a means has been found of measuring the rate of 
denudation, they take tlie slowest rate instead of the 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 Europe than taking one North American river as the standard. 



CDAP. X.] THE EAHTH'S AGE. 209 

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

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

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

' These figures are merely used to give an idea of tlie rate at which de- 
nudation is actually going on now ; but if no elevatory forces were at 
work, the rate of denudation would certainly diminish as the mountains 
were lowered and the slope of the ground everywhere rendered flatter. 
This would follow not only from tlie diminished power of rain and rivers, 
but because the climate would become more imiform, the rainfall probably 
less, and no rocky peaks would be left to be fractured and broken up by 
tlie action of frosts. It is certain, however, that no continent has ever 
remained long subject to the influences of denudation alone, for, as we 
liave seen in our sixth chapter, elevation and depression have always been 
going on in one part or other of the surface. 

P 



210 ISLAND LIFE. [paet i. 

Silurian formation is divided into Upper and Lower Silurian, 
each characterised by a distinct set of fossil remains, and the 
Upper Silurian again consists of a large number of sejDarate 
beds, such as the Wenlock Limestone, the Upper Llandovery 
Sandstone, the Lower Llandovery Slates, &c., each usually 
characterised by a difference of mineral composition or me- 
chanical structure, as well as by some peculiar fossils. These 
beds and formations vary greatly in extent, both above and 
beneath the surface, and are also of very various thicknesses in 
different localities. A thick bed or series of beds often thins 
out in a given direction, and sometimes disappears altogether, 
so that two beds which were respectively above and beueath it 
may come into contact. As an example of this thinning out, 
American geologists adduce the Palaeozoic formations of tlie 
Appalachian Mountains, which have a total thickness of 42,000 
feet, but as they are traced westward thin out till they become 
only 4,000 feet in total thickness. In hke manner the Carboni- 
ferous grits and shales are 18,000 feet thick in Yorkshire and 
Lancashire, but they thin out southwards, so that in Leicester- 
shire they are only 3,000 feet thick ; and similar phenomena 
occur in all strata and in every part of the world. It must be 
observed that this thinninij out has nothinsf to do with denuda- 
tiou (which acts upon the surface of a country so as to produce 
great irregularities of contour), but is a regular attenuation of 
tlie 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. Wlien we see a geological 
map showing successive formations following each other in long 
irregular belts across the country (as is well seen in the case of 
the Secondary rocks of England), and a corresponding section 
showing each bed dipping beneath its predecessor, we are apt to 
imagine that beneath the uppermost bed we should find all the 
others following in succession like the coats of an onion. But 
this is far from being the case, and a remarkable proof of the 
narrow limitation of these formations has been recently obtained 
by a boring at Ware through the Chalk and Gault Clay, which 
latter immediately rests on the L^pper Silurian Wenlock 



CHAP, s.] THE EARTH'S AGE. 211 

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

But if we consider how such deposits are now forming, we 
shall find that the thinning out of the beds of each formation, 
and their restriction to irregular bands and patches, is exactly 
what we should expect. 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 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 globigerina3, radiolarians, 
and diatomaceas, or are clays formed of undissolved portions of 

1 The 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 Norivich Geological 
Society in 1879 .— 

Deep Wells through the Tertiary and Cretaceous Formations. 

Harwich at 1,022 feet reached Carboniferous Rock. 

Kentish Town ,. l,lli >. » Old Red Sandstone. 

Tottenham Court Road „ 1,064 „ „ Devonian. 

Blackwall „ 1,00-1 ,, „ 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 Pal»ozoic 
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. 

P 2 



212 ISLAND LIFE. [part i. 

these, together with the disintegrated or dissolved materials of 
pumice and volcanic dust, which being very light are carried by 
wind or by water over the widest oceans. 

From the preceding considerations we shall be better able to 
appreciate the calculations as to the thickness of stratified 
deposits made by geologists. Professor Ramsay has calculated 
that the sedimentary rocks of Britain alone have a total maxi- 
mum thickness of 72,600 feet ; while Professor Haughton, from 
a survey of the whole world, estimates the maximum thickness 
of the known stratified rocks at 177,200 feet. Now these maxi- 
mum thicknesses of each deposit will have been produced only 
where the conditions were exceptionally favourable, either in 
deep water near the mouths of great rivers, or in inland seas, 
or in places to which the drainage of extensive coimtries was 
conveyed by ocean currents ; and this great thickness will neces- 
sarily be accompanied by a corresponding thinness, or complete 
absence of deposit, elsewhere. How far the series of rocks found 
in any extensive area, as Europe or North America, represents 
the whole series of deposits which have been made there we 
cannot tell ; but there is no reason to think that it is a very 
inadequate representation of their maximum thickness, though 
it undoubtedly is of their extent and bulk. When we see in how 
many distinct localities patches of the same formation occur, it 
seems improbable that the whole of the deposits formed during 
any one period should have been destroyed, even in such an area 
as Europe, while it is still more improbable that they should 
be so destroyed over the whole world ; and if any considerable 
portion of them is left, that portion may give a fair idea of their 
average, or even of their maximum, thickness. In his admi- 
rable paper on " The Mean Thickness of the Sedimentary 
Rocks," ' Dr. James Croll has dwelt on the extent of denuda- 
tion in diminishing the mean thickness of the rocks that have 
been formed, remarking, " Whatever the present mean thick- 
ness of all the sedimentary rocks of our globe may be, it must 
be small in comparison to the mean thickness of aU the 
sedimentary rocks which have been formed. This is obvious 
from the fact that the sedimentary rocks of one age are partly 
1 Geological Magazine, Vol. VIII., March, 1871. 



OHAP. X.] THE EARTH'S AGK. 213 

formed from the destruction of the sedimentary rocks of former 
ages. From the Laurentian age down to the present day the 
stratified rocks have been undergoing constant denudation." 
This is perfectly true, and yet the mean thickness of that 
portion of the sedimentary rocks wliich 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 
horizontal, 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 inade- 
quate representation of the mean thickness of all that have been 
formed, and even of the maximv.m thickness of the larger 
portion. This will be the more likely because it is almost 
certain that many rocks contemporaneously formed are counted 
by geologists as distinct formations, whenever they differ in litho- 
logical character or in organic remains. But we know that 
limestones, sandstones, and shales, are always forming at the 
same time ; while a great difference in organic remains may 
arise from comparatively slight changes of geograjjhical features, 
or from difference in the depth or purity of the water in wliich 
the animals lived. ^ 

1 Mr. C. Lloyd Morgan has well illustrated this point by comparing the 
generally tilted-up strata denuded on their edges, to a library in which a 
fire had acted on the exposed edges of the books, destroying a great mass 
of literature but leaving a portion of each book in its place, which portion 
represents the thickness but not the size of the book. {Geological Magazine, 
1878, p. 161.) 

2 Professor J. Young thinks it highly probable that — "the Lower Green- 
sand is contemporaneous with part of the Chalk, so were parts of the 
Wealden ; nay, even of the Purbeck a portion must have been forming 
while the Cretaceous sea was gradually deepening southward and west- 
ward." Yet these deposits are always arranged successively, and their 
several thicknesses added together to obtain the total thickness of the 
formations of the country. (See Presidential Address, Sect. C, British 
Association, 1876.) 



214 ISLAND LIFE. [part i. 

How to estimate the average rate of Deposition of the Sedimentary 
Rocks. — But if we take the estimate of Professor Haughton 
(177,200 feet), which, as we have seen, is probably excessive, for 
the maximum thickness of the sedimentary rocks of the globe 
of all known geological ages, can we arrive at any estimate of 
the rate at which they were formed ? Dr. CroU has attempted 
to make such an estimate, but he has taken for his basis the 
mean thickness of the rocks, which we have no means whatever 
of arriving at, and which he guesses, allowing for denudation, to 
be equal to the mojnmum thickness as measured by geologists. 
The land-area of the globe is, according to Dr. Croll, 57,000,000 
square miles, and he gives the coast-line as 116,000 miles. This, 
however, is, for our purpose, rather too much, as it allows for 
bays, inlets, and the smaller islands. An approximate mea- 
surement on a globe shows that 100,000 miles will be nearer 
the mark, and this has the advantage of being an easily remem- 
bered even number. The distance from the coast, to which 
shore-deposits usually extend, may be reckoned at about 100 or 
150 miles, but by far the larger portion of the matter brought 
down from the land will be deposited comparatively close to the 
shore ; that is, within twenty or thirty miles. If we suppose 
the portion deposited beyond thirty mUes to be added to the 
deposits within that distance, and the whole reduced to a uni- 
form thickness in a direction at right angles to the coast, we 
should probably include aU areas where deposits of the maxi- 
mum thickness are forming at the present time, along with a 
large but unkno\vn proportion of surface where the deposits 
were far below the maximum thickness. This follows, if we 
consider that deposit must go on very unequally along different 
parts of a coast, owing to the distance from each other of the 
mouths of great rivers and the limitations of ocean currents; 
and because, compared with the areas over which a thick 
deposit is forming annually, those where there is httle or none 
are probably at least twice as extensive. If, therefore, we take 
a width of thirty miles along the whole coast-hne of the globe as 
representing the area over which deposits are forming, corre- 
sponding to the maximum thickness as measured by geologists. 



CHAP. X.] THE EARTH'S AGE. 215 



we shall certainly over- rather than under-estimate the possible 
rate of deposit.^ 

Now a coast-line of 100,000 miles witli a width of 30 gives 
an area of 3,000,000 square miles, on which the denuded matter 
of the whole land-area of 57,000,000 square miles is deposited. 
As these two areas are as 1 to 19, it follows that de- 
position, as measured by maximum tbickness, goes on at least 
nineteen times as fast as denudation — probably very much 
faster. But the mean rate of denudation over the whole earth 
is about one foot in three thousand years ; therefore the rate of 
maximum deposition will be at least 19 feet in the same 
time ; and as the total maximum thickness of all the stratified 
rocks of the globe is, according to Professor Haughton, 177,200 
feet, the time required to produce this tliickness of rock, at the 

• As by far the larger portion of tlie denuded matter of the globe passes 
to the sea througli 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 witliiu- a small area of the Eastern 
Mediterranean, and that of the great rivers of China — the Hoang Ho and 
Yang-tse-kiang, in a small portion of tlie Eastern Sea. Enormous lengths 
of coast, like those of Western America andj 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 maxi'mum 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 tlie plateau between 
the mouth of the river and tlio southern extremity of Florida for two 
liundrcd and fifty miles in width the bottom consists of clay with some 
sand and but few Rhizopods; but beyond this distance the soundings 
brought up either Rhizopod shells alone, or these mixed with coral sand, 
Nullipores, and other calcareous organisms (Dana's Manual of Geology, 
2nd Ed. p. 671). It is probable, therefore, that a large proportion of the 
entire mass of sediment brought down by the Mississippi is deposited on 
the limited area above indicated. 

Professor Dana further remarks : " Over interior oceanic basins as well 
as off a coast in quiet depths, fifteen or twenty fatlioms and beyond, the 
deposits are mostly of fine silt, fitted for making fine argillaceous rocks, 
as shales or slates. When, liowever, the depth of the ocean falls off 
below a hundred fathoms, the deposition of silt in our existing oceans 
mostly ceases, unless in the case of a great bank along the border of 
a continent." 



216 ISLAND LIFE. [part i. 

present rate of denudation and deposition, is only 28,000,000 
years. 1 

The Rate of Geological Change prohahly greater in very remote 
times. — The opinion that denudation and deposition went on 
more rapidly in early times owing to the frequent occurrence of 
vast con\"ulsions and cataclysms was strenuously opposed by Sir 
Charles Lyell, who so well showed that causes of the very same 
nature as those now in action were sufficient to account for all 
the phenomena presented by the rocks throughout the whole 
series of geological formations. But while upholding the 
soundness of the views of the " uniformitarians " as opposed to the 
" convulsionists," we must yet admit that there is reason for 
believing in a gradually increasing intensity of aU 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 ahnost all the 
forces that have brought about geological phenomena. With 
greater heat there would be a more extensive aqueous atmo- 
sphere, and a greater difference between equatorial and polar 
temperatures ; hence more violent winds, heavier rains and snows, 
and more powerful oceanic currents, all producing more rapid 
denudation. At the same time, the internal heat of the earth 
being greater, it would be cooHng more rapidly, and thus the 
forces of contraction — which cause the upheaving of mountains, 
the eruption of volcanoes, and the subsidence of extensive 
areas — would be more powerful and would still further aid the 
process of denudation. Yet again, the earth's rotation was 
certainly more rapid in very remote times, and this would cause 
more impetuous tides and stiU further add to the denuding 

' 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 ichole sea-bottom instead of over a narrow belt near the 
coasts, a supposition entirely opposed to all the known facts, and which 
had been shown by Dr. Croll, five years previously, to be altogether erro- 
neous. (See Natvre, Vol. XVIIL, p. 268, where Professor Haughton's 
paper is given as read before the Royal Society.) 

' See Geological Magazine for 1877, p. 1. 



CHAP. X.] THE EARTH'S AGE. 217 



power of the ocean. It thus appears that, as we go back into 
the past, all the forces tending to the continued destruction and 
renewal of the earth's surface would be in more powerful action, 
and must therefore tend to reduce the time required for the 
deposition and upheaval of the various geological formations. 
It may be true, as many geologists assert, that the changes here 
indicated are so slow that they would produce comparatively 
httle effect within the time occupied by the known sedimentary 
rocks, yet, whatever effect they did produce would certainly be 
in the direction here indicated, and as several causes are acting 
together, their combined effect may have been by no means un- 
important. It must also be remembered that such an increase 
of the primary forces on which all geologic change depends 
would act with great effect in still further intensifying those 
alternations of cold and warm periods in each hemisphere, or, 
more frequently, of excessive and equable seasons, which have 
been shown to be the result of astronomical, combined with 
geographical, revolutions ; and this would again increase the 
rapidity of denudation and deposition, and thus still further 
reduce the time required for the production of the known 
sedimentary rocks. It is evident therefore that these various 
considerations all combine to prove that, in supposing that the 
rate of denudation has been on the average only what it is now, 
we are almost certainly over-estimating the time required to have 
produced the whole series of formations from the Cambrian 
upwards. 

Value of the preceding estimate of Geological Time. — It is not 
of course supposed that the calculation here given makes any 
approach to accuracy, but it is beheved that it does indicate the 
order of magnitude of the time required. We have a certain 
number of data, which are not guessed but the result of actual 
measurement; such are, the amount of solid matter carried 
down by rivers, the width of the belt within which this matter is 
mainly deposited, and the maximum thickness of the known 
stratified rocks.^ A considerable but unknown amount of 

1 In his reply to Sir W. Thompson, Professor Huxley assumed one foot 
in a thousand years as a not improbable rate of deposition. The above 
estimate indicates a far higher rate : and this follows from the well 



218 ISLAND LIFE. [part i. 

denudation is effected by the waves of the ocean eating away 
coast lines. This was once thought to be of more importance 
than sub-aerial denudation, but it is now believed to be com- 
paratively 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 again 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 stUl 
show that, so far as the time required for the formation of the 
known stratified rocks, the hundred milHon 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 
Professor Huxley and Professor Ramsay. 

Organic Modification dependent on CJiange of Conditions. — 
Having thus shown that the physical changes of the earth's 
surface may have gone on much more rapidly and occupied 
much less time than has generally been supposed, we have now 
to inquire whether there are any considerations which lead to 
tlie 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 

ascertaineil fact, tliat the area of deposition is many times smaller than the 
area of denudation. 

• Dr. Croll and Professor Geikie have shown that marine denudation is 
verj- small in amount as compared with sub-aerial, since it acts only locally 
on the edge of the land, whereas tlie latter acts over every foot of the 
surface. Mr. W. T. Blanford argues that the difference is still greater in 
tropical than in temperate latitudes, and arrives at the conclusion that — 
" If over British India the effects of marine to those of fresh-water denu- 
dation in remo\-ing the rocks of the country be estimated at 1 to 100, I 
believe that the result of marine action will be greatly overstated" (^Geo- 
logy and Zoology of Abyssinia, p. 158, note). Now, as our estimate of 
the rate of sub-aerial denudation cannot pretend to any precise accuracy, 
we are justified iu neglecting marine denudation altogether, especially as 
we have no method of estimating it for the whole earth with any approach 
to correctness. 



THAP. X.] THE RATE OF OEGANIC CHANGE. 219 

specific forms with changes of external conditions or environ- 
ment. If the external world remains for a moderate period 
unchanged, the organic world soon reaches a state of equilibrium 
through the stnrggle 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 oven become extinct. 
But the extinction of a species wiU certainly affect other species N 
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 wlucli it was inimical. These 
changes will in their turn bring other changes ; and before an 
equilibrium is again establisliod, tlie proportions, ranges, and 
numbers, of the species inhabiting the country may be materi- 
ally altered. The complex manner in wliieh animals are related 
to each other is well exhibited by the importance of insects, 
which in many parts of the world limit the numbers or deter- 
mine the very existence of some of the higher animals. Mr. 
Darwin says : — " Perhaps Paraguay offers the most curious 
instance of this ; for here neither cattle, nor horses, nor dogs 
have ever run wild, though they swarm southward and north- 
ward in a wild state ; and Azara and Rengger have shown that 
this is caused by the greater number in Paraguay of a certain 
fly, which lays its eggs in the navels of these animals when first 
bom. The increase of these flies, numerous as they are, must 
be habitually checked by some means, probably by other para- 
sitic insects. Hence, if certain insectivorous birds w^ere 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 in- 
sects, and this, as we have seen in Staffordshire, the insectivorous 
birds, and so onwards in ever increasing circles of complexity." 



220 ISLAXD LIFR. [part i. 

Geographical changes would be stiU more important, and it 
is almost impossible to exaggerate the modifications of the 
organic world that might result from them. A subsidence of 
land separating a large island from a continent would affect the 
animals and plants in a variety of ways. It would at once 
modify the cUmate, and so produce a series of changes from this 
cause alone ; but more important would be its effect by isolating 
small groups of individuals of many species and thus altering 
their relations to the rest of the organic world. Many of these 
would at once be exterminated, while others, being relieved from 
competition, might flourish and become modified into new 
species. Even more striking would be the effects when two 
continents, or any two land areas which had been long separated, 
were united by an upheaval of the strait which divided them. 
Numbers of animals would now be brought into competition 
for the first time. New enemies and new competitors would 
appear in every part of the country ; and a struggle would 
commence which, after many fluctuations, would certainly result 
in the extinction of some species, the modification of others, 
and a considerable alteration in the proportionate numbers and 
the geographical distribution of almost all. 

Any other changes which led to the intermingling of species 
whose ranges were usually separate would produce corresponding 
results. Thus, increased severity of winter or summer tempera- 
ture, causing southward migrations and the crowding together 
of the productions of distinct regions, must inevitably produce 
a struggle for existence, which woiild lead to many changes both 
in the characters and the distribution of animals. Slow eleva- 
tions of the land would produce another set of changes, by 
affording an extended area in which the more dominant species 
might increase their numbers ; and, by a greater range and 
variety of alpine cUmates and mountain stations, affording 
room for the development of new forms of life. 

Geographical Mutations as a Motive Power in bringing about 
Organic Changes. — Now, if we consider the various geographical 
changes which, as we have seen, there is good reason to beheve 
have ever been going on in the world, we shall find that the 
motive power to initiate and urge on organic changes has never 



CHAP. X.] THE RATE OF ORGANIC CHANGE. 221 

been wanting. In the first place, every continent, though per- 
manent in a general sense, has been ever subject to innumerable 
physical and geographical modifications. At one time the total 
area has increased, and at another has diminished ; great plateaus 
have gradually risen up, and have been eaten out by denudation 
into mountain and valley ; volcanoes have burst forth, and, after 
accumulating vast masses of eruptive matter, have sunk down 
beneath the ocean, to be covered up with sedimentary rocks, and 
at a subsequent period again raised above the surface ; and the 
loci of all these grand revolutions of the earth's surface have 
changed their position age after age, so that each portion of 
every continent has again and again been sunk under the ocean 
waves, formed the bed of some inland sea, or risen high into 
plateaus and mountain ranges. How great must have been the 
effects of such changes on every form of organic life ! and it is 
to such as these we may perhaps trace those great changes of 
the animal world which have seemed to revolutionise it, and 
have led us to class one geological period as the age of rep- 
tiles, another as the age of fishes, and a third as the a^e of 
mammals. 

But such changes as these must necessarily have led to re- 
peated unions and separations of the land masses of the globe, 
joining together continents which were before divided, and 
breaking up others into great islands or extensive archipelagoes. 
Such alterations of the means of transit would probably affect 
the organic world even more profoundly than the changes of 
area, of altitude, or of climate, since they afforded the means, at 
long inten'als, of bringing the most diverse forms into competi- 
tion, and of spreading all the great animal and vegetable types 
widely over the globe. But the isolation of considerable masses 
of land for long periods also afforded the means of preservation 
to many of the lower types, which thus had time to become 
modified into a variety of distinct forms, some of which became 
so well adapted to special modes of hfe that they have continued 
to exist to the present day, thus affording us examples of the 
life of early ages which would probably long since have become 
extinct had they been always subject to the competition of the 
more highly organised animals. As examples of such excessively 



222 ISLAND LIFE. [part i. 

archaic forms, we may mention the mud-fishes and the ganoids, 
confined to hmited fresh-water areas ; the frogs and toads, which 
still maintain themselves vigorously in competition with higher 
forms ; and among mammals the Ornithorhynchus and Echidna 
of Australia ; the whole order of Marsupials — which, out of 
Australia where they ai-e 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 Revolutions as an agent in producing Organic 
Changes. — The geographical and geological changes we have 
been considering are probably those which have been most 
effective in bringing about the great features of the distribution 
of animals, as well as the larger movements in the development 
of organised beings ; but it is to the alternations of warm and 
cold, or of uniform and excessive climates — of almost perpetual 
spring in arctic as well as in temperate lands, with occasional 
phases of cold culminating at remote intervals in glacial epochs, 
— that we must impute some of the more remarkable changes 
both in the specific characters and in the distribution of 
organisms.^ Although the geological evidence is opposed to 
the belief in early glacial epochs except at very remote and 
distant intervals, there is nothing which contradicts the occur- 
rence of repeated changes of climate, which, though too small 
in amount to produce any well-marked physical or organic 
change, would yet be amply sufficient to keep the organic world 
in a constant state of movement, and which, by subjecting the 
whole flora and fauna of a country at comparatively short 
intervals to decided changes of physical conditions, would 
supply that stimulus and motive power which, as we have seen, 

1 Agassiz appears to have been the first to suggest that the principal 
epochs of life extermination were epochs of cold ; and Dana thinks that 
two at least such epochs may be recognised, at the close of the Palaeozoic 
and of the Cretaceous periods — to which we may add the last glacial 
epoch. 



CHAP. X.] THE RATE OF ORGANIC CHANGE. 223 



is all tliat is necessary to keep the processes of "natural 
selection " in constant operation. 

The frequent recurrence of periods of high and of low excen- 
tricity must certainly have produced changes of cUmate of 
considerable importance to the life of animals and plants. 
During periods of high excentricity with summer in perihelion, 
that season would be certainly very much hotter, while the 
•\vinters would be longer and colder than at present ; and al- 
though geographical conditions might prevent any permanent 
increase of snow and ice even in the extreme north, yet we 
cannot doubt that the whole northern hemisphere would then 
have a very diiferent chmate than when the changing phase of 
precession brought a very cool summer and a very mild winter 
— a perpetual spring, in fact. Now, such a change of climate 
would certainly be calculated to bring about a considerable 
change of species, both by modification and migration, without 
any such decided change of type either in the vegetation or 
the animals that we could say from their fossil remains that any 
change of chmate had taken place. Let us suppose, for in- 
stance, that the chmate of England and that of Canada were to 
be mutually exchanged, and that the change took five or six 
thousand years to bring about, it cannot be doubted that con- 
siderable modifications in tlie fauna and flora of both countries 
would be the result, although it is impossible to predict what 
the precise changes would be. We can safely say, however, that 
some species would stand the change better than others, while 
it is highly probable that some would be actually benefited by 
it, while others would be injured. But the benefited would 
certainly increase, and the injured decrease, in consequence, and 
thus a series of changes would be initiated that might lead to , 
most important results. Again, we are sure that some species 
would become modified in adaptation to the change of cUmate 
more readily than others, and these modified species would 
therefore increase at the expense of others not so readily 
modified, and hence would arise on the one hand extinction of 
species, and on the other the production of new forms. 

But this is the very least amount of change of climate that 
would certainly occur every 10,500 years when there was a high 



224 ISLAND LIFE. [part i. 

excentricity, for it is impossible to doubt that a varying distance 
of the sun in summer from 86 to 99 millions of miles (which 
is what occurred during — as supposed — the Miocene period, 
850,000 years ago) would produce an important difference in 
the summer temperature and in the actinic influence of sun- 
shine on vegetation. For the intensity of the sun's rays would 
vary as the square of the distance, or nearly as 74 to 98, so 
that the earth would be actually receiving one-fourth less sun- 
heat during summer at one time than at the other. An equally 
high excentricity occurred 2,500,000 years back, and no doubt 
was often reached during still earlier epochs, while a lower but 
still very high excentricity has frequently prevailed, and is 
probably near its average value. Changes of climate, therefore, 
every 10,500 years, of the character above indicated and of 
varjnng intensity, have been the rule rather than the exception 
in past time ; and these changes must have been variously 
modified b}' changing geographical conditions so as to produce 
climatic alterations in different directions, and giving to the 
ancient lands either dry or wet seasons, storms or calms, equable 
or excessive temperatures, in a variety of combinations of which 
the earth perhaps affords no example under the present low 
phase of excentricity and consequent slight inequaKty of sun 
heat. 

Present Condition of the Earth one of exceptional Stability as 
regards Climate. — It will be seen, by a reference to the diagram 
at page 165, that during the last three million years the excen- 
tricity has been 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 degree or variation of excentricity ; but, on the 
contrary, we may pretty safely assume that its variations during 
tliis time fairly represent its average state of increase and 



CHAP. X.] THE RATE OF ORGANIC CHANGE. 225 

decrease during all known geological time. But when the 
glacial epoch ended, 72,000 years ago, the excentricity was 
about double its jjresent amount ; it then rapidly decreased 
till, at 60,000 years back, it was very little greater than it is 
now, and since then it has been uniformly small. It follows 
that, for about 60,000 years before our time, the mutations 
of climate every 10,500 years have been comparatively unim- 
portant, and that the temperate zones have enjoyed an excep- 
tioiuil stability of climate. During this time those powerful 
causes of organic change which depend on considerable changes 
of chmate and the consequent modifications, migrations, 
and extinctions of species, will not have been at work ; the 
slight changes that did occur would probably be so slow 
and so little marked that the various species would be able 
to adapt themselves to them without much disturbance ; 
and the result would be an epoch of e.cccptional utahility of 
species. 

But it is from this very period of exeeptional stability that we 
obtain our only scale for measuring the rate of organic change. 
It includes not only the historical period, but that of the Swiss 
Lake dwellings, the Danish shell-mounds, our peat-bogs, our 
sunken forests, and many of our superficial alluvial deposits — 
the whole in fact, of the iron, bronze, and neolithic ages. Even 
some portion of the palaeolithic age, and of the more recent 
gravels and cave-earths may come into the same general period 
if they were formed when the glacial epoch was passing away. 
Now throughout all these ages we find no indication of change 
of species, and but little, comparatively, of migration. We thus 
get an erroneous idea of the permanence and stability of specific 
form^, due to the period immediately antecedent to our own 
being a. period of exceptional permanence and stability as regards 
climatic and geographical conditions.^ 

' This view was, I believe, first put forth by myself in a paper read 
before the Geological Section of the British Association in 1869, and 
subsequently in an article in Nature, Vol. I. p. 454. It was also stated 
by Mr. S. B. K. Skertchley in his Phyniccd System of the Universe, p. 363 
(1878) ; but we both founded it on what I now consider the erroneoua 
doctrine that actual glacial epochs recurred each 10,500 years during 
periods of high excentricity. 

Q 



226 ISLAXK LIFE. [iaht i. 

Bate of last Glacial Sjjoch and its hearing on the Measurement of 
Geological Time. — Directly we go back from this stable period 
•\ve come upon changes both in the forms and in the distribution 
of species; and when we pass beyond the last glacial epoch into 
the Pliocene jieriod we find onrselves in a comparatively new 
world, surrounded by a considerable number of species altogether 
different from any which now exist, together \vith 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 opiuion 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 poiuteil 
out, to the glacial epoch whenever a high degree of excentricity 
prevailed. As many reasons combine to make us fix the height 
of the glacial epoch at the period of high excentricity which 
occurred 200,000 years back, and as the Pliocene period was 
jjrobably not of long duration, we must suppose the next great 
phase of very high excentricity (850,000 years ago) to fall within 
the Miocene epoch. Dr. Croll believes that this must have 
produced a glacial period, but wc have showTi strong reasons 
for believing that, in conciin-ence with favourable geograpliical 
conditions, it led to uninterrupted warm climates in the tem- 
perate and northern zones. This, however, did not prevent the 
occurrence of local glaciation wherever other conditions led to 
its initiation, and the most powerful of such conditions is a great 
extent of high land. Now we know that the Alps acquired 
a considerable pnrt of their elevation during the latter part of 
tlie 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 thei'e has been avast amount of denudation, 
so that these rocks may have been first raised much higher 
than we now find them, and thus a considerable portion of the 
Aljjs may have been once more elevated than now. This would 
cert;\inly lead to an enormous accumulation of snow, which 

' Explication tl'nne seconde edition de la Carte Geologique de la Terre 
(1875), p. W. 



i;hap. X.] MEASUREMENT OF GEOLOGICAL TIME. 227 

would be increased when the excentricity reached a maximum, 
as ah-eady 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 
jieriod when the enormous erratics of the Flysch conglomerate 
were deposited in the inland seas of Northern Switzerland, the 
Carpathians, and the Apennines. Tliis is quite in harmony with 
the indications of an uninterrupted warm climate and rich 
vegetation during the very same period in the adjacent low 
countries, ju.st as we find at the present day in New Zealand a 
delightful climate and a rich vegetation of Metrosideros, fuchsias 
anol tree-ferns on the very borders of huge glaciers, descending 
to within 700 feet of the sea-level. It is not pretended that 
these estimates of geological time have any more value than 
probable guesses ; but it is certainly a curious coincidence that 
two remarkable periods of high excentricity .should have occurred, 
at such periods and at such intervals apart, as very well accord 
with the comparative remoteness of the two ileposits in whicli 
undoubted signs of ice-action have been found, and that both 
tliese are localised in the vicinity of mountains whicli are known 
to have acquired a considerable elevation at about the same 
j^eriod of time. 

In the tenth edition of the Principks of Geology, Sir Ciiarles 
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 
milhon 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 milUon year.s) 



228 ISLAND LIFE. [iart i. 

is nearly midway between these, and it is, at all events, 
satisfactory that the various measures result in figures of the 
same order of magnitude, which is all one can expect on so 
difficult and exceedingly speculative a. subject. 

The only value of such estimates is to define our notions of 
geological time, and to show that the enormous periods, of 
hundreds of miUions 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 cdcalations of physicists, by leaving a 
very wide margin between geological time as defined by the 
fossUiferous rocks, and that far more extensive period which 
includes all pos.sibility of life upon the earth. 

Concluding Ecmnrls. — In the present chapter I have endea- 
voured to show that, combining the measured rate of denudation 
with the estimated thickness and probable extent of the known 
series of sedimentary rocks, we maj' arrive at a rude estimate of 
the time occupied in the formation of those rocks. From 
another point of departure — that of the probable date of the 
Miocene period, as determined by the epoch of high excentricity 
supposed to have aided in the production of the Alpine glaciation 
during that period, and taking the estimate of geologists as to 
the proportionate amount of change in the animal world since 
that epoch — we obtain another estimate of the duration of geolo- 
gical time, which, though founded on far less secure data, agrees 
pretty nearly with the former estimate. The time thus arrived 
at is immensely less than the usual estimates of geologists, and 
is so far within the limits of the duration of the earth as cal- 
culated by Sir William Thomson, as to allow for the develop- 
ment of the lower organisms an amount of time anterior to the 
Cambrian period several times greater than has elapsed between 
that period and the present day. I have further shown that, in 
the continued mutations of climate produced by high excentri- 
city and opposite phases of precession, even though these did 
not lead to glacial epochs, we have a motive power well calcu- 
lated to produce far more rapid organic changes than have 
hitherto been thought possible ; while in the enormous amount 
of specific variation (as demonstrated in an earher chapter), we 



CHAP. X.] MEASUREMENT OF GEOLOGICAL TIME. 229 

have ample material for that power to act upon, so as to keep 
the organic world in a state of rapid change and development 
proportioned to the comparatively rapid changes in the earth's 
surface. 

We have now finished the series of preliminary studies of the 
biological conditions and physical changes which have affected 
the modification and dispersal of organisms, and have thus 
brought about their actual distribution on the surface of the 
earth. These studies will, it is believed, place us in a condition 
to solve most of the problems presented by the distribution of 
animals and plants, whenever the necessary facts, both as to their 
distribution and their affinities, are sufficiently well known ; and 
we now proceed to apply the principles we have established to 
the interpretation of the phenomena presented by some of the 
more important and best known of the islands of our globe, 
limiting ourselves to these for reasons which have been already 
sufficiently explained in our preface. 



PART J[. 

n'SriAH FAUNAS AXD FLORAS. 



CHAPTER XI. 

THE CLASSIFICATION OF ISLANDS. 

Importance of Islands in tlie study of the Distribution of Organisms — 
Classification of Islands witli reference to Distribution — Continental 
Islands — Oceanic Islands. 

In the preceding chapters, forming the first part of our work, 
we have discussed, more or less fully, the general features pre- 
sented by animal distribution, as well as the various physical 
and biological changes which have been the most important 
agents in bringing about the present condition of the organic 
world. 

We now proceed to apply these principles to the solution of 
the numerous problems presented by the distribution of animals ; 
and in order to limit the field of our inquiry, and at the same 
time to deal only with such facts as may be rendered intelligible 
and interesting to those readers who have not much acquaintance 
with the details of natural history, we propose to consider only 
such phenomena as are presented by the islands of the globe. 

Import ance of Inlands in the study of the Distribution of 
Orf/nnism s. — 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 I 
coincide. The number of species and of genera they contain 
is always much smaller than in the case of continents, and their | 
peculiar species and groups are usually well defined and strictly I 
limited in range. Again, their relations with other lands are often 



•23-1 ISLAND LIFE. [i art ii. 

f direct and simple, and even wlien more complex are far easier to 

V. comprehend tlian tliose of continents; and they exhibit besides 

certain influences on the forms of life and certdn peculiarities of 

distribution which continents do not present, and whose study 

offers many points of interest. 

In islands we have the facts of distribution often presented 
to us in their simplest forms, along with others which become 
gradually more and more complex ; and we are therefore able to 
proceed step by step in the solution of the problems they present. 
But as in studying these problems we have necessarily to take 
into account the relations of the insular and continental faunas, 
we also get some knowledge of the latter, and acquire besides so 
much command over the general principles which underlie all 
problems of distribution, that it is not too much to say that when 
we have mastered the difficulties presented by the peculiarities 
of island life we shall find it comparatively easy to deal with the 
more complex and less clearly defined problems of continental 
distribution. 

Classijication of Islands vjilh reference to Bislribution. — Islands 
have had two distinct modes of origin ; they have either been 
separated from continents of which tliey are but detaclied fi"ag- 
ments, or they have originated in the ocean and have never 
formed part of a continent or any large mass of land. This 
difiference of origin is fundamental, and leads to a most 
important difference in their animal inhabitants; and we 
may therefore first distinguish the two classes — oceanic and 
continental islands. 

Mr. Darwin appears to have been tlie 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 pai't of 
a continent. This was quite opposed to the opinions of the 
scientific men of the day, who almost all held the idea of 
continental extensions, and of oceanic islands being their 



CHAP, xi.] THE CLASSIFICATION OF ISLANDS. 235 

fragments, and it wns lono; before Mr. Darwin's views obt^iined 
general acceptance. Even now the belief still lingers ; and 
we continually hear of old Atlantic or Pacific continents, of 
"Atlantis" or " Leniuria," of which hypothetical lands many 
existing islands, although wholly volcanic, are thought to be the 
remnants. We have already seen that Darwin connected the 
peculiar geological structure of oceanic islands with the per- 
manence of the great oceans which contain them, and wc have 
shown that several distinct lines of evidence all point to the same 
conclusion. We may therefore define oceanic islands, as follows : 
— Islands of volcanic or coralline formation, usually far from 
continents and always separated from them by very deep sea, 
entirely without indigenous land mammalia or amphibia, but 
with abundance of birds and insects, and usually with some 
reptiles. This definition will exclude only two islands which 
have been sometimes classed as oceanic — New Zealand and the 
Seychelles. Rodriguez, which was once thought to be another 
exception, has been shown by the explorations during the Tran- 
sit of Venus Expedition to be essentiaUy volcanic, with some 
upraised coraUine limestone. 

Continental Mauds. — Continental islands are always more 
varied in their geological formation, conUiining both ancient 
and recent stratified rocks. They are rarely very remote from 
a continent, and they always contain some land manmials 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. 

Eecent continental islands are always situated on submerged 
banks connecting them with a continent, and the depth of the 
intervening sea rarely exceeds 100 fathoms. They resemble the 
continent in their geological structure, while their animal and 
vegetable productions are eitlier almost identical with those of the 
continent, or if otherwise, the difference consists in the presence 
of closely allied species of the same types, with occasionally a 
very few peculiar genera. They possess in fact all the character- 
istics of a portion of the continent, separated from it at a recent 
geological period. 



236 ISLAND LIFE. [part h. 

Ancient continental islands differ greatly from the preceding 
in many respects. They are not united to the adjacent continent 
by a shallow bank, but are usually separated from it by a depth 
of sea of a thousand fathoms or upwards. In geological structure 
they agree generally with the more recent islands ; like them 
they possess mammalia and ampliibla, usually in considerable 
abundance, as well as all other da.sses of animals ; but these are 
highly peculiar, almost all being distinct species, and many form- 
ing distinct and peculiar genera or families. They are also well 
characterised by the fragmentai-y natvire of their fauna, many of 
the most characteristic continental orders or families being quite 
unrepresented, while some of their animals ai-e 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 anomahes and 
most difficult problems to the student of distribution. 

Oceanic Islands. — The total absence of warm-blooded terrestrial 
animals in an island otherwise well suited to maintain them, is 
held to prove that such island is no mere fragment of any ex- 
isting or submerged continent, but one that has been actually 
produced in mid-ocean. It is true that if a continental island 
were to be completely submerged for a single day and then again 
elevated, its higher terrestrial animals would be all destroyed. 
and if it were situated at a considerable distance from land it 
would be reduced to the same zoological condition as an oceanic 
island. But such a complete submergence and re -elevation 
appears never to have taken place, for there is no single island 
on the globe which has the physical and geological features of a 
continental, combined with the zoological features of an oceanic 
island. It is true that some of the coral-islands may be formed, 
upon submerged lands of a continental character, but we have no 
proof of this ; and even if it were so, the existing islands are to all 
intents and purposes oceanic. 

We will now pass on to a consideration of some of the more 
interesting examples of these three classes, beginning with 
oceanic islands. 

All the animals which now inhabit such oceanic islands must 



CHAP. XI.] OCEANIC ISLANDS. 237 

either themselves have reached them by crossing the ocean, or he 
the descendants of ancestors who did so. Let us then see what 
are, in fact, the animal and vegetable inhabitants of these islands, 
and how far their presence can be accounted for. We will begin 
with the Azores, or Western Islands, because they have been 
thoroughly well explored by naturalists, and in their peculiarities 
afford us an important clue to some of the most efficient means 
of distribution among several classes of animals. 



/; 



CHAPTER XII. 

OCEANIC ISLANDS: — THE AZORES AND BERMUDA. 

The Azores, or Western Islands. 
Position .ind physical features — Chief zoological features of the Azores — 
Birds — Origin of the Azorean bird fauna — Insects of the Azores — 
Land-shells of the Azores — The 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 Re<l Clay of Beriiuida — Zoology of 
Bermuda — Birds of Bermuda — Comparison of the bird faunas of Ber- 
muda and the Azores — Insects of Bermuda — Land llollusca — Flora of 
Bermuda — Concluding remarks on the Azores and Bernnida. 

We will commence our investigation into the phenomena pre- 
sented by oceanic islands, with two groups of the North 
Atlantic, in which the facts are of a comparatively simple 
nature, and such as to afford us a valuable clue to a solution of 
the more difficult problems we shall have to deal with further on. 
The Azores and Bermuda offer great contrasts in physical features, 
Init striking similai-ities in geograpliical position. The one is 
volcanic, the other coralline ; but both are sun-ounded by a wide 
expanse of ocean of enormous depth, the one being about as far' 
from Europe as the other is from America. Both are situated 
in the temperate zone, and they differ less than si.K degrees in 
I 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 



:hap. XII.] 



OCEANIC ISLANDS. 



239 



afford evidence of the highest vahie as to the means of dispersal 
of various groujjs of organisms across a wide expanse of ocean. 



THE AZORES, OR WESTERN ISLANDS. 

These islands form a widely scattered group, nine in number, 
situated betweeu 37° and 39° 40' N. Lat. and stretching in 
a south-east and north-west direction over a distance of nearly 





- " 30 


20 - 


2790 


'" 


40 


^ ^=^ 




2t 


50 




b::_;^3 


AZORES! 


8 .00 




mmm 




- 15C 
3C 


aooo 


J 








c 


^^ 


WJW 





fiUlI.lNi: MAP OF THE AZORES. 



Note. — Tlie light tint sliows where the sea is less tlmn 1.000 fatlmms deep. 
The rlnrk lint .. ., .. more Ihiin l.otio I'fithonis deep. 

The figures show (lei>tlis in fathoms. 

4110 iiiile.s. The largest of the islands, Sau Miguel, is about forty 
miles l<ing, and is one of the nearest to Europe, being rather 
under 900 miles from the coast of Portugal, from which it is 
separated by an ocean 2,500 fathoms deep. The depth between 
the islands does not seem to be known, but the 1,000 fathom 
line encloses the whole group j)retty closely, while a depth of 
about 1,800 fathoms is reached within 300 miles in all direc- 
tions. The.se great drpths render it in tlir liighe.st degree 



240 ISLAND LIFE. [part ii. 

improbable that the Azores have ever been united with the 
European continent ; while their being wholly volcanic is 
equally opposed to the view of their having formed part of an 
extensive Atlantis including Madeira and the Canaries. The 
only exception to their volcanic stracture is the occurrence 
in one small island only (Santa Maria) of some marine deposits 
of Upper Miocene age — a fact which proves some alterations of 
level, and perhaps a greater extension of this island at some 
former period, but in no way indicates a former union of the 
islands, or any greater extension of the whole group. It 
proves, however, that the group is of considerable antiquity, 
since it must date back to Miocene times ; and this fact may be 
of importance in considering the origin and peculiar features of 
the fauna and flora. It thus appears that in all physical 
features the Azores correspond strictly with our definition of 
" oceanic islands," while their great distance from any other 
land, and the depth of the ocean around them, make them 
typical examples of the class. We should therefore expect 
^them to be equally typical in their fauna and flora ; and this is 
the case as regards the most important characteristics, although 
in some points of detail they present exceptional phenomena. 

Chii'f Zoological Features of the Azores} — The great feature 
of oceanic islands — the ab.?ence of all indigenous land-mammalia 
and amphibia — is well shown in this group ; and it is even 
carried further, so as to include all terrestrial vertebrata, there 
being no snake, lizard, frog, or fresh-water fish, although the 
islands are sufficiently extensive, possess a mild and equable 
climate, and are in every way adapted to support all these 
groups. On the other hand, flying creatures, as birds and 
insects, are abundant ; and there is also one flying mammal — a 
small European bat. It is true that rabbits, weasels, rats and 
mice, and a small lizard peculiar to Madeira and Teneriffe, are 
now found wild in the Azores, but there is good reason to 
believe that these have all been introduced by human agency. 

' 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 
Azores or Weitern Islands, by Frederick Du Cane Godman, F.L. S., 
F.Z.S., &c., London, 1870 



CHAP. XII.] THE AZORES. 2-Jl 



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 trulj' 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 tnan. 

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 (tliirty-one) are either aquatic 
or waders — birds of great powers of flight, whose presence in the 
remotest islands is by no means remarkable. Of these two 
groups twenty are residents, breeding in the islands, while eleven 
are stragglers only visiting the islands occasionally, and all are 
common European species. The land-birds, twenty-two in 
number, are more interesting, four only being stragglers, while 
eighteen are permanent residents. The following is a list of 
these resident land-birds : — 



1. 


Common Buzzard 


{Biiteo vulgaris) 


2. 


Long-eared Owl 


(Asio olus) 


3. 


Barn Owl 


{Sln'xjlaiiimea) 


4. 


Blackbird 


{Turdus merula) 


5. 


Kobin 


{Erylhacus rubecula) 


6. 


Blackcap 


{Sylvia atricapilla) 


7. 


Gold-crest 


{Jiegulus cristatus) 


8. 


Wheatear 


{Saxicola ccnanthe) 


9. 


Grey Wagtail 


{Motacilla sulphurea) 


10. 


Atlantic Chaffinch 


(Fringilla lintillon) 


11. 


Azorean Bullfinch 


{Pyrrhula murina) 


12. 


Canary 


{Serinus canarius) 


13. 


Common Starling 


{Sturnus vulgaris) 


14. 


Lesser Spotted Woodpecker ... 


{Dryobates minor) 


15. 


Wood-pigeon 


{Columba palumbus) 


16. 


Rock Dove 


{Columba licia) 


17. 


Red-legged Partridge 


(Caccabis rufa) 


18. 


Common Quail 


( Colurnix communis) 



All the above-named birds are common in Europe and North 



f 



2+2 ISLAXn LIFE. [iaht n. 

Africa except three — the Atlantic chaffinch and the canary 
whicli inliabit Madeira and the Canary Islands, and the Azorean 
bullfinch, which is peculiar to the islands we are considering. 

Origin of ike Azorean Bird-fauna. — The questions we have 
now before us are — how did these eighteen sjjecies of birds first 
reach the Azores, and how are we to explain the presence of a 
single peculiar species while all the rest are identical with 
^ European birds ? In order to answer them, let us first see_SEh_at 
stragglers now actually visit the Azores from the nearest con- 
tinents. The four species given in Mr. Godman's list are the 
kestrel, the oriole, the snow-bunting, and the hoopoe ; but he 
also tells us that there are certainly others, and adds : " Scarcely 
a storm occurs in spring or autumn without bringing one or 
more species foreign to the islands ; and I have frequently been 
told that swallows, larks, grebes, and other species not referred 
V— to here, are not uncommonly seen at those seasons of the year." 
We have, therefore, every reason to believe that the birds 
which are now residents originated as stragglers, which occa- 
sionally found a haven in these remote islands when driven out 
to sea by storms. Some of tliem, no doubt, still often arrive 
from the continent, but these cannot easily be distinguished as 
V new arrivals among those which ai-e residents. Many facts men- 
tioned by Mr. Godman sliow that this is the case. A barn-owl, 
mueii exhausted, flew on board a whaling-ship when 500 miles 
S. W. of the Azoi-es ; and even if it had come from Madeira it 
must have travelled quite as far as from Portugal to the islands. 
Mr. Godman also shot a single specimen of the wheatear in 
Flores after a strong gale of wind, and as no one on the island 
knew the bird, it was almost certainly a recent arrival. Sub- 
sequently a few were found breeding in the old crater of Corvo, a 
small adjacent island ; and as the species is not found in any 
; other island of the group, we may infer that this bird is a 
I recent immigrant in process of establishing itself. 

Another fact which is almost conclusive in favour of the bird- 

r 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, 



CHAP. XII 1 THE AZOKKS. 2-13 

Graciosa, St. George's, Pico, and Fayal; and a western of two, 
Floras 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 tlie 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 wliich have probably arrived in- 
voluntarily, the numbers are found to be forty species in the eastern 
group, thirty-six in the central, and twenty-nine in the western. 
To account for the presence of oixe 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 tiieir type-species) is not difficult ; 
tho wonder rather being that there are not more peculiar forms.^)— 
In our third chapter v/e have seen how great is the amount of 
individual variation in birds, and how readily local varieties 
become established wherever the physical conditions are suffi- 
ciently distinct. Now we can hardly have a greater difference of 
conditions than between the continent of Eurojie 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 siich conditions. But they are not, 
as a rule, thus completely isolated, because, as we have seen, 
stragglers arrive at short intervals ; and these, mixing with the"/* 
residents, keep up the purity of the breed. It follows, that only 
those species which reach the Azores at very remote intervals 
will be likely to acquire well-marked distinctive characters; 
and this appears to have happened vnth 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. 

R 2 



244 ISLAND LIFE. [part ii- 

There is another reason for the very slight amount of pecu- 
liarity presented by the fauna of the Azores as compared with 
many other oceanic islands, dependent on its comparatively 
recent origin. The islands themselves may be of considerable 
antiquity, since a few small deposits, beUeved 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, 
I had its origin since the date of the last glacial epoch. Even 
Vnow icebergs reach the latitude of the Azores only a little to 
the westward, and when we consider the proofs of extensive 
ice-action in North America and Europe, we can hardly doubt 
that these islands were at that time surrounded with pack-ice, 
wliile their own mountains, reaching 7,600 feet high in Pico, 
would almost certainly have been covered with perpetual snow 
and have sent down glaciers to the sea. They might then 
/have had a climate almost as bad as that now endured by the 
Prince Edward Islands in the southern hemisphere, nearly ten 
degrees farther from the equator, where there are no land-birds 
whatever, although the distance from Africa is not much greater 
V than that of the Azores from Europe, while the vegetation is 
limited to a few alpine plants and mosses. This recent origin 
of the birds accounts in a great measure for their identity with 
those of Europe, because, whatever change has occurred must 
have been effected ia the islands themselves, and in a time hmited 
to that which has elapsed since the glacial epoch passed away. 

Insects of the Azores. — Having thus found no difficulty in ac- 
counting for the peculiarities presented by the birds of these 
islands, we have only to sBBr-tow far the same general principles 
wiU apply to the insects and land-shells. The butterflies, 
moths, and hymenoptera, are few in number, and almost all 
seem to be common European Species, whose presence is 
explained by the same causes as those which have introduced 
the birds. Beetles, however, are more numerous, and have been 
better studied, and these present some features of interest. The 
total number of species yet kno^-n is 212, of which 175 are 
Eurojjean ; but out of these 101 are believed to have been 
introduced bj' human agency, leaving seventy-four really 
indigenous. Twenty-three of tliese indigenous species are not 



rnAP. XII. ] THE AZORES. 245 

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 : — 

C'ARABIDiE. 

Anchomenus aptinoides Allied to a species from the Canaries. 

Bcmhldium hesperus Allied to the European B. Itetuiii. 

Dytiscidjs. 
Agabus godmanni Allied to the European A. dispai: 

CoLYDlIDJi. 

Tarphius u-ollasloni A genus almost peculiar to the Atlantic islands. 

Elaterid^. 

ITeieroderes azoricus Allied to a Brazilian species. 

Elastrus dolosus Belongs to a peculiar Madagascar genus I 

Melybidje. 
Attalus miniatknUis Allied to a Canarian species. 

Ehtncophoea. 

PhhvopluKjus variahilts Alliod to European nnd Atlantic species. 

Acalles droueii A Mediterranean and Atlantic genus. 

Laparocerus azoricus Allied to Madeiran species. 

Asynonychus godmanni ....A peculiar genus, allied to Brachyderes, of the 

south of Europe. 
Neocnemls occidentaVis A peculiar genus, allied to the European genus 

Str02>liosomus. 

Heteromera. 
Helops azoricus Allied to H. vulcanus of Madeira. 

Staphtlinid^. 
Xenomma melanocephala ...Allied to X.Jiliforine from the Canaries. 

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



216 ISLAND LIFK. [lAur ii. 

become extiuct 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 wliich 
many of them undergo their transformations. Thus we may 
explain the presence of three common South American species 
(two elaters and a longieorn), all wood-eat€rs, 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 many 
insects on local conditions of climate and vegetation, and their 
liability to be destroyed by insectivorous birds, we shall see that, 
although there may be a greater probability of insects as a whole 
reaching the islands, the chance against any particular insect 
arriving there, or against the same species arriving frequently, 
is much greater than in the case of birds. The result is, that 
(as compared with Britain for example) the birds are, pro- 
portionately, much more numerous than the beetles, while the 
pecuhar species of beetles are much more numerous than among 
birds, both facts being quite in accordance with what we know 
of the habits of the two groups. We may also remark, that the 
small size and obscure characters of many of the beetles renders 
it probable that species now supposed to be peculiar, really 
inhabit some parts of Europe or North Africa. 

It is interesting to note that the two families which are pre- 
eminently wood, root, or seed eaters, are those which present the 
greatest amount of speciality. The two Elateridse alone exhibit 
remote affinities, the one with a Brazilian the other with a 
Madagascar group ; while the only peculiar genera belong to the 
Rhyncophora, but are allied to European forms. These last 
almost certainly form a portion of the more ancient fauna of the 
islands which migrated to them in pre-glacial times, while the 



CHAP. XII.] THE AZORES. 247 



Brazilian elater appeal's to be the solitary example of a living 
insect brouglit 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 
probably a relic of a once more widespread type which has 
only been able to maintain itself in these localities. Mr. 
Crotch states that there are some species of beetles common to 
Madagascar and the Canary Islands, while there are several 
genera, cotnmon to Madagascar and South America, and some to 
Madagascar and Australia. The clue to these apparent anomalies 
is found in otlier genera being common to Madagascar, Africa, 
and South America, while others are Asiatic or Australian. 
Madagascar, in fact, lias insect relations witli every part of the 
globe, and the only rational explanation of such facts is, that 
they are indications of very ancient and once widespread groups, 
maintaining themselves only in a few widely separated portions 
of what was at one time or another the area of their distribution^ 
Land-shells of the Azores. — Like the 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 undisturbed by new arrivals, and is therefore more 
likely to become modified by the new conditions, and then fixed 
as a distinct type. Out of the sixty-nine known species, thirty- 
seven are common to Europe or the other Atlantic islands, while 
thirty-two are peculiar, though almost all are distinctly allied to 
European types. The majority of these shells, especially the 
peculiar forms, are very small, and many of them may date 
back to beyond the glacial epoch. The eggs of these would be 
exceedingly minute, and might occasionally be carried on leaves 
or other materials during gales of exceptional violence and 
duration, while others might be conveyed with the earth that 
often sticks to the feet of birds. There arc also, probably, other 
1 See Chap. V. p. 76. 



248 ISLAND LIFE. [part ii. 

unknown means of conveyance ; but however this may be, the 
general character of the land-molluscs is such as to confirm 
the conclusions we have arrived at from a study of the birds 
and insects, — that these islands have never been connected 
with a continent, and have been peopled wdth 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 ALr. Godman's volume. As our object in the present 
work is to trace the past history of the more important islands 
by means of the forms of life that inhabit them, and as for 
this purpose plants are sometimes of more value than any class of 
animals, it will be well to take advantage of the valuable materials 
here available, in order to ascertain how far the evidence derived 
from the two organic kingdoms agrees in character : and also 
to obtain some general results which may be of service in our 
discussion of more difficult and more complex problems. 

There are in the Azores 480 known species of flowering-plants 
and ferns, of which no less than 440 are found also in Europe, 
Madeira, or the Canary Islands ; while forty are peculiar to the 
Azores, but are more or less closely allied to European species. 
As botanists are no less prone than zoologists to invoke former 
land-connections and continental extensions to account for the 
■wade dispersal of objects of their study, it will be well to 
examine somewhat closely what these facts really imply. 

Tlie 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 di-spersal of seeds has been studied by Sir Joseph 
Hooker, Mr. Darwin, and many other writers, who have made 
it suflfieiently clear that they are in many cases liable to be 



OHAP. xn.] THE AZORES. 249 



earned enormous distances. An immense number are specially 
adapted to be carried by the wind, through the possession of 
down or hairs, or membranous wings or processes ; while others 
are so minute, and produced in such profusion, that it is difficult 
to place a limit to the distance they might be carried by gales 
of wind or hurricanes. Another class of somewhat heavier 
seeds or dry fruits are capable of being exposed for a long 
time to sea- water without injur}^ Mr. Darwin made many 
experiments on this point, and he found that many seeds, 
especially of Atriplex, Beta, oats, Capsicum, and the potato, 
grew after 100 days' immersion, while a large number survived 
fifty days. But he also found that most of them sink after a few 
days' immersion, and tliis would certainly prevent them being 
floated to veiy great distances. It is very possible, however, 
that dried branches or flower-heads containing seeds would float 
longer, while it is quite certain that many tropical seeds do float 
for enormous distances, as witness the double cocoa-nuts which 
cross the Indian ocean from the Seychelle Islands to the coast 
of Sumatra, and tiie West Indian beans which frequently reach 
the west coast of Scotland. There is therefore ample evidence 
of the possibility of seeds being conveyed across the sea for 
great distances by winds and surface currents.^ 

' Some of Mr. Dar\vin's experiments are very interesting and suggestive. 
Eipe hazel-nuts sank immediately, but when dried tliey floated for ninety 
days, and afterwards germinated. An asparagus-plant with ripe berries, 
when dried, floated for eighty-five daj-s, and the seeds aftei-wards 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 
germuiatiou 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 he carried 90 x 60 = 5,400 miles ! But even half 
of this is ample to enable them to reach an}' oceanic island, and we must re- 
member that till completely water-logged they might he driven along at a 
much greater rate by the wind. Mr. Danvin calculates the distance by the 
average time of flotation to be 924 miles ; but in such a ease 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 onlj' ninety-four plants, mustliappen himdreds 
or thousands of times and with hundreds or thousands of species, naturally, 
and thus afford ample opportunities for .succespful migration. (See Origin 
of Species, Gth Edition, p. 325.) 



250 Island life. [part n. 

Birds as Seed-carriers. — The great variety of fruits that are 
eaten hy 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 twent3--two land-birds found in 
the Azores, half are, more or less, fruit-eaters, and these may have 
been the means of introducing some plants into the islands. 

Birds also frequently have small portions of earth on their 
feet ; and Mr. Darwin has shown by actual experiment that 
almost all such earth contains seeds. Thus in nine grains of 
earth on the leg of a woodcock a seed of the toad-rush was 
found which germinated ; while a wounded red-legged partridge 
had a ball of earth weighing six and a half ounces adhering to its 
leg, and from this earth Mr. Darwin raised no less than eighty- 
two separate plants of about five distinct species. Still more re- 
markable was the experiment with six and three-quarter ounces 
of mud from the edge of a little pond, which, carefully treated 
under glass, produced 537 distinct plants ! This is equal to a 
seed for every six grains of mud, and when we consider how 
many birds frequent the edges of ponds in search of food, or 
come there to drink, it is evident that great numbers of seeds 
may be dispersed by tliis means. 

Many seeds have hispid awns, hooks, or prickles which readily 
attach them to the feathers of biixis, 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, n.aturalist to the Challenger, throw much light on the agencj- of 
birds in the distribution of plants : — "Grisebach {Veg. cler Erde, Vol. II. p. 
496) lays much stress on the wide rang-ing of the albatross (Diomedoa) 
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, bj' this fact. I was much struck at Marion Island 
of the Prince Kdward 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. Acaena, have 
flower-heads which stick like burrs to feathers, &c., and seem specially 
adapted for transportation by birds. Besides the albatrosses, various 
species of Procellaria and PiifFinus, birds which range over immense dis- 



cuAr. XII.] THE AZOKES. 251 



Facilities for JJisjxriKd of Azormn Flanls. — Now in the course 
of very long pei'iods of time the various causes here enumerated 
would be sutticient to stock the remotest islands with vegetation, 
and a considerable part of the Azorean flora appears well adapted 
to be so conveyed. Of the 439 flowering-plants in Mr. Watson's 
list, I find that about forty-five belong to genera that have either 
pappus or winged seeds; sixty-five to such as have very minute 
seeds ; thirty have fleshy fruits such as are greedily eaten by birds ; 
several have hispid seeds ; and eighty-four are glumaceous plants, 
which are all probably well-adapted for being carried partly by 
winds and jwrtly by currents, as well as by some of the other 
causes mentioned. On the other hand we liave a very suggestive 
fact in the absence from the Azores of most of the trees and shrubs 
witii lui-ge and heavy fruits, however common they may be in 
Europe. Such are oaks, ciiestnuts, hazels, apples, beeches, alders, 
and firs ; while the only trees or lai-ge shrubs are tlie Portugal 
laurel, myrtle, laurestinus, elder, Zaurus canaricnsis, Myricafaya, 
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. 



^ao^ 



lances way, I think, have plujeJ a jjreat part in the distribution of plants, 
and especially account, in some measure, for the otherwise diflicult fact 
(when occurring in the tropics), tliut widely distant islands have similar 
mountain plants. The Procellaria and Puflinus 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 In'gh 
latitudes the birds often burrow near the sea-level, as at Tristan d'Acunha 
or Kerguelen's Land, but in the tropics they choose the mountains for their 
nesting-place (Finsch and Hartlaub, Orn. der Viti- uiid Tonga-Insdn, 1807, 
EinleituDg, p. xviii.). Thus, Puffinvs 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 roslrata at Tahiti, and 
I saw the burrows myself amidst a dense growth of fern, &c., at 4,400 feet 
elevation in that island. Phaethon has a similar habit. It nests at the 
crata of Kilauea, Hawaii, at 4,000 feet elevation, and also high up in Tahiti. 
In order to accovmt for the transportation of the plants, it is not of course 
necessary that the same species of Procellaria or Diomedea should now 
range between the distant points where the plants occur. The ancestor of 
the now differing species might have carried the seeds. The range of the 
genus is sufficient.'' 



25-2 ISLAND LIFE. [rABX. u. 

There can be little doubt that the truly indigenous flora of 
the islands is far more scanty than the number of plants recorded 
Avould imply, because a large but unknown proportion of the 
species are certainly importations, voluutarj' 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 suppo.se 
that one-half the species only are truly indigenous, there will 
stiU remain a wonderfully rich aud 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) stiU 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 ; aud 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 Compositae 
are considered to be distinct genera, but in tliis order generic 
divisions rest on slight technical distinctions ; and the Campa- 
nula ridalii 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 mor.e 
than varieties of them. While therefore we may believe that 
the larger part of tlie existing flora reached the islands since the 
glacial epoch, a portion of it may be more ancient, as there is 
no doubt that a majority of the species could withstand some 
lowering of temperature ; while in such a warm latitude and 
surrounded with sea, there would always be many sunny and 
sheltered spots in which even tender plants might flourish. 



CHAP. XII.] BERMUDA. 25.S 

Important deduction from the peculiarities of th-e Azorean Fauna 
and Flora. — There is one conclusion to be drawn from the almost 
wholly European character of the Azorean fauna and flora which 
deserves special attention, namely, that the peopling of remote 
islands is not due so much to ordinary or normal, as to extra- 
ordinary and exceptional causes. These islands lie in the course of 
the south-westerly return trades and also of the Gulf Stream, and 
we should therefore naturally expect that American birds, insects, 
and plants would preponderate if they were conveyed by the 
regular winds and currents, which are both such as to prevent 
European species from reaching them. But the violent storms to 
which the Azores are liable blow from all points of the compass ; 
and it is evidently to these, combined with tlie greater proximity 
and more favourable situation of tlie coasts of Europe and North 
Africa, that the presence of a fauna and flora so decidedly 
European is to be traced. 

The other North Atlantic Islands — Madeira, the Canaries, 
and the Cape de Verdes — present analogous phenomena to those 
of the Azores, but with some peculiarities dependent on their 
more southern position, their richer vegetation, and perhaps 
their greater antiquity. These have been sufficiently discussed 
in my Geographical Bistrihution of Animals (Vol. I. j^p. 208- 
215) ; and as we are now dealing with what may be termed 
typical examples of oceanic islands, for the purpose of illus- 
trating the laws, and solving the problems presented by the 
dispersal of animals, we will pass on to other cases which have 
been less fully discussed in that work. 



BERMUDA. 

The Bermudas arc a small group of low islands formed of coral, 
and blown coral-sand consolidated into rock. They are situated 
in 32° N. Lat, about 700 miles from North Carolina, and some- 
what farther from the Bahama Islands, and are thus rather 
more favourably placed for receiving immigrants from America 
and its islands than the Azores are with respect to Europe. 
There are about 100 islands and islets in all, but their total area 



^ 



254 



ISLAND LIFE. 



[part II. 



does not exceed fifty square miles. They are surrounded by reefs, 
some at a distance of thirty miles from the main gi'oup ; and 
the discovery of a layer of earth with remaius of cedar-trees 
forty-eight feet below the present liigh-water mark shows that 
the islands have once been more extensive and probably included 




MAP OF BEBMDDA AND THE AMERICAS COAST. 

Note. — The light tint indicates sea less than 1.000 fathoms deep. 
The dark tint .. .. more than 1,000 fathoms <!eei>. 
The figures show the depth in fathoms. 



the whole area now occupied by shoals and reefs.' Immediately 
beyond these reefs, however, extends a very deep ocean, while 
about 450 miles distant in a south-east direction, the deepest part 

• N'atiu-e, VoL VI. p. 262, "Recent Obserratioiis in the Beniiuda.e," by 
Sir. J. Mittliew Jones. 



CBAP. xn.] BERMUDA. 255 



of the North Atlantic is reached, where soundings of 3,825 and 
3,875 fathoms have been obtained. It is clear therefore that 
these islands are typically oceanic. 

Soundings were taken by the Challenger in four different 
directions around Bermuda, and always showed a rapid deepen- 
ing of the sea to about 2,500 fathoms. This was so remarkable, 
that in his reports to the Admiralty, Captain Nares spoke of 
Bermuda as " a solitary peak rising abruptly from a base only 
120 miles in diameter;" and in another place as " an isolated 
peak rising abruptly from a very small base." These expressions 
show that Bermuda is looked upon as a typical example of an 
" oceanic peak " ; and on examining the series of official reports 
of the Challenger soundings, I can find no similar case, although 
some coasts, both of continents and islands, descend more 
abruptly. In order to show, therefore, what is the real char- 
acter of this peak, I have drawn a section of it on a true scale 









BERMUDA 








^^^^-t--~ 






' 






) 




ss 


M!LES 


><-l8 M!LES-X 


46 MILES.— 


% 





SECTION OF BKRMrO.V AND ADJACENT SEA-BOTTOM. 

The ngiucs show Ihc depth in fall is nt nfiy-flvc miles north and forty-six miles south of 

llir islands respecti\ely. 

from the soundings taken in a north aiid 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 Hmestone 
rock, sometimes soft and friable, but often very hard and even 
crystalline. It consi.sts of beds which sometimes dip as much 
as 30°, and exhibit besides great contortions, so that at first 
sight the islands appear to exhibit on a small scale the pheno- 
mena of a disturbed Palaeozoic district. It has however long 



25r, ISLAND LIFE. [rAui ii. 

been known that these rocks are all due to the Vidnd, which 
blows up the fine calcareous sand, the product of the disinte- 
gration 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 behind them. These 
are consolidated by the percolation of rain-water, which dissolves 
some of the hrae from the more porous tracts and deposits it 
lower down, filling every fissure with stalagmite. 

The Red Clay of Bermuda. — Besides the calcareous rocks 
there is found in many parts of the islands a layer of red earth 
or clay, containing about thirty per cent, of oxide of iron. This 
very closely resembles, both in colour and chemical composition, 
the red clay of the ocean floor, found widely spread in the Atlantic 
at depths of from 2,300 to 3,150 fathoms, and occurring abund- 
antly all round Bermuda. It appears, therefore, at first sight, 
as if the ocean bed itself has been here raised to the surfixce, 
and a portion of its covering of red clay preser\'ed ; 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 com- 
position, and yet possesses sufficient evidence to prove its identity 
with that now lying contiguous to the base of the Bermuda 
column." But in his Guide to Bermuda Mr. Jones tells us that 
this same red earth has been found, two feet thick, under coral 
rock at a depth of forty-two feet below low-water mark, and 
that it "rested on abed 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 difi"erent levels upon 
coralline sand rock is therefore more probably due to some process 
of decomposition of the rock itself, or of the minute organisms 
which abomid in the blown sand. The forthcoming volumes on 



CHAP. XII.] BERMUDA. 257 

the results of the Challenger expedition will probably clear up 
the difficulty. 

Zoology of Bermuda. — As might be expected from their ' 
extreme isolation, these islands possess no indigenous land 
mammalia, frogs, or snakes. There is however one lizard, which ■^ 
Professor Cope considers to be distinct from any American 
species, and which he has named Plestiodon longirostris. It is 
said to be most nearly allied to P. fasciahis of the south-eastern 
States, from which it differs in having nearly ten more rows of 
scales, the tail thicker, and the muzzle longer. In colour it is 
ashy brown above, greenish blue beneath, with a white line 
black-margined on the sides, and it seems to be tolerably 
abundant in the islands. This lizard is especially interesting 
as the only vertebrate animal which exhibits any pecuUarity. 

Birds. — Notwithstanding its small size, low altitude, and 
remote position, a great number of birds visit Bermuda annually, \\ 
some in large numbers, others only as accidental stragglers. 
Altogether, over ISO sjaecies have been recorded, rather more A 
than half being wading and swimming birds, whose presence is / 
not so much to be wondered at as they are great wanderers ; 
while about eighty-five are land birds, many of which would 
hardly be supposed capable of 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 bird are recorded as tolerably frequent visitors, and nearly 
half these appear to come every year. 

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

1. Galeoscoples carolinensis. (The Cat bird.) Migrates along tlie east 

coast of the United States. 

2. S'laUa sialis. (The Bhie bird.) Migrates along the east coast. 

i5. Vireo novcchoracemh. (The White-eyed green Tit.) Migrates along 
the east coast. 

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

5. Corvus amerkanus. (The American Crow.) Common over all North 

America. 

S 



258 ISLAND LIFE. [paut it. 

6. Cardinalis mrginianus. (The Cardinal bird.) Migrates from Carolina 

southward. 

7. Chama-peUa passerina. (The Ground Dove.) Louisiana, \V. Indies, 

and Mexico. 

8. Orfyx virgiiiiaiuis. (The American Quail.) New England to Florida. 

9. Ardea herodius. (The Great Blue Heron.) All North America. 

10. FuUca americana. (The American Coot.) Temperate and tropical 
North America. 

It will be seen that these are all very common North 
American birds, and most of them are constant visitors from 
the mainland, so that however long they may have inhabited 
the islands there has been no chance for them to have acquired 
any distinctive characters through isolation. 

Among the most regular visitants which are not resident, are 
the common N. American kingfisher [Ceryle alcyon), the wood 
wagtail [Siurus novmhoracensis), the wide ranging rice-bird 
{Dolichonyx oryzivora), and a moorhen, (Gallinida gcdeata) ; the 
first three being very common over almost all North America, 
and the last abundant in the southern portion of it. 
_ Comparison of the Bird-faunas of Bermuda and tlic 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 Ameri ca, which causes a much larger number of its birds 
to be migratory than in Europe. The Northern United States 
and Canada, with a sunny climate, luxuriant vegetation, and 
abundant insect-life during the summer, supply food and shelter 
to an immense number of insectivorous and frugivorous birds ; so 
that during the breeding season Canada is actually richer in 
bird-life than Florida. But as the severe winter comes on all 
the.se 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 tlian a hundred distinct sj^ecies, migrate 



CHAP. XII.] BERMUDA. 259 

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 carriedlip hy local whirlwinds to a great height, where meet- 
ing with a westerly or north westerly gale, they are rapidly 
driven sea-ward. The great majority no doubt perish, but some 
reach the Bermudas and form one of its most striking autumnal 
features. In October, Mr. Jones tells us, the sportsman enjoys 
more shooting than at any other time. The violent revolving 
gales, which occur almost weekly, bring numbers of birds of 
many species from the American continent, tiie different 
members of the duck tribe forming no inconsiderable portion 
of the whole ; while the Canada goose, and even the ponderous 
American swan, have been seen amidst the migratory ho.st. With 
these come also such delicate birds as the American robin {Ttirdus 
migratorius), the yellow-rumped warbler {Bendroeca coronata), the 
pine warbler {Dendrceco finvs), the wood wagtail (Siurus normhor- 
acensis), the summer led bird (Pyrcmga crsliva), the snow-bunt- 
ing {Plectrophanes nivalis), the red-poll {^giothus linarivs), the 
king bird (Tyrannvs 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 vaiiety ; 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 arvcnsis), but this was probably an imported bird or an 
escape from some ship; the land-rail (C'rcx pratensis), which 
also wanders to Greenland and the United States ; and the com- 
mon snipe {Scolopax gallinago), which occurs not unfrequently 

s 2 



260 ISLAND LIFE. [pakt u. 

in Greenland but has not yet been noticed in North America. 
It is howevei- so like the American snipe {S. wilsoni), that a 
straggler might easily be overlooked. 

Two small bats of N. American species also occasionally 
reach the island, and these are the only wild mammalia except 
rats and mice. 

Insects of Bermuda. — Insects appear to be very scarce ; but it 
is evident from the lists given by Mr. Jones that only the more 
conspicuous species have been yet collected. These comprise 
nineteen beetles, eleven bees and wasps, twenty-sis 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 pecuhar 
species. 

Land Mollusca. — The land-shells of the Bermudas are some- 
what more interesting, as they appear to be the only group of 
animals except reptiles in which there are any pecuhar species. 
The fullowng list has been kindly furnished me b}' Mr. Thomas 
Bland of New York, who has made a special study of the 
terrestrial molluscs of the West Indian Islands. The species 
which are peculiar to the islands are indicated by italics. 

List of the Land-Suells of Beumcda. 

1. Succinea fiilgens. (Lea.) Also in Cuba. 

2. „ Bermudeiisis. (Pfeiiier.) „ Barbadoes (?) 

3. ,, raargarita. (Pfr.) ... „ Haiti. 

4. Hyalina Berinudensis. (Fir.) ... A peculiar form, which, according 

to Mr. Binney, '-cannot be placed 
in any recognised genus." A 
larger sub-fossil variety also 
occurs, named H. Nelxoni, by 
llr. Bland, and which appears 
sufficiently distinct to be classed 
as another species. 

5. „ circitmjirmatit. (Redfield.) 

6. ,, dhcrejmits. (Pfr.) 

7. Patula Reiniaaa. (Pfr.) 

8. „ hypolepta. (Shuttleworth.) Probably the same as P. 7?i!ni/scM?a 

(Binney), a wide-spread Ameri- 
can species. 

9. Helix vortex. (Pfr.) Southern Florida and Westlndies. 



CHAP. XII.] 



BERMUDA. 



261 



10. Helix microdonta. (Desh.) 

11. „ appre.'isa. (Say.) 

12. „ pulchella. (Mull.)... 



... Baliiima Islands. 

... Virginia and adjacent states ; per- 

liai)s introduced into Bermuda. 
... Europe; verj' olose to //. ininuta 

(Say) of the United States. 

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

Europe. 
... Cuba, Haiti, &c. 
... West Indies and South America. 
... Florida, New Jersey, and Europe. 
,.. West Indies, gpiierally. 
... Barhadocs (V) 
. .. Jamaica. 
... Barbuda. 



13. „ ventricoga. (Drap. ) 

14. Bulimuhis nitididus. (Pfr.) 

15. Stenogyra octoiia. (Cli.)... 

16. Cionella acicula. (Miill.)... 

17. Pupa pellucida. (Pi'r.) ... 

18. „ Barbadensis. (Pfr.) 

19. ,, Jamaicensis. (O.B. Ad.) 

20. Helicina convexa. (Pfr.) 

Mr. Bland indicates only four species as certainly peculiar to 
Bermuda, and another sub-fossil species ; while one or two of the 
remainder arc indicated as doubtfully identical with those of other 
countries. We have thus at least one-fourth of the land-shells 
peculiar, while almost all the other productions of the islands are 
identical with those of the adjacent continent and islands. 
This con-esponds, 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-eiglith of the probably non-introduced species 
as peculiar; the plants about one-twentieth; while the land- 
shells have about half the species peculinr. This difference is 
well explained by the much greater difficulty of transmission 
over wide seas, in the case of land-shells, than of any other 
terrestrial organisms. It thus happens that when a species has 
once been conveyed it may remain isolated for unknown ages, 
and has time to become modified by local conditions unchecked 
by the introduction of other specimens of the original tj'pe. 

Flora of Bermvda. — Unfortunately no good account of the 
plants of these islands has yet been published. Mr. Jones, in 
his paper " On the Vegetation of the Bermudas " gives a list of 
no less than 480 species of flowering plants ; but this number 
includes all the culinary plants, fruit-trees, and garden flowers, 
as well as all the ornamental trees and shrubs from various 
parts of the world which have been introdticed, mixed up with 
the European and American weeds that have come with agricul- 
tural or garden seeds, and the really indigenous plants, in one 



262 ISLAND LIFE. [part ii. 

undistinguished series. It appears too, that the late Governor, 
Major-General Lefroy, " has so^vn 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 yeai"s to distinguish the indigenous from the introduced 
vegetation. 

From the researches of Dr. Eein and ilr. Moseley there 
appear to be about 250 flowering plants in a wild state, and of 
these Mr. Moseley thinks less than half are indigenous. The 
majority are tropical and West Indian, while others are common 
to the Southern States of North America; the former class 
having been largely brought by means of the Gulf Stream, the 
latter by the agency of birds or by winds. Mr. Jones tells us 
that the currents bring numberless objects animate and inani- 
mate from the Carribean Sea, including the seeds of trees, 
shrubs, and other plants, which are continually cast ashore and 
sometimes vegetate. The soap-berrj^ tree (Scqniidus saponaria) 
has been actually observed to originate in this way. 

Professor Oliver informs me that he knows of no undoubtedly 
distinct species of flowering plants peculiar to Bermuchi, tliough 
there are some local forms of continental species, — instancing 
Sisyrincliium, Bcrmudianum and Rhus toxicodendron. There are 
however, two ferns — an Adiantura and a Nephrodium, which 
are unknown from any other locality, and tliis renders it pro- 
bable that some of the flowering plants are also peculiar. The 
juniper, which is so conspicuous a feature of the islands, is said 
to be a West Indian species (Juniperus harbadensis) found in 
Jamaica and the Bahamas, not the North American red cedar ; 
but there seems to be still some doubt about this common plant. 

Mr. Moseley, who visited Bermuda in the Challenger, has well 
explained the probable origin of the vegetation. The large 
number of West Indian plants is no doubt due to the Gulf 
Stream and constant surface drift of warm water in this direc- 
tion, while others have been brought by the annual cyclones 
which sweep over the intervening ocean. The great number of 
American migratory birds, including large flocks of the American 
golden plover, with ducks and other aquatic species, no doubt 



CHAP, sii.] . BERMUDA. 263 

occcasionally bring seeds, either in the mud attached to theii- 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 vmchanged owing to the frequent intercrossing 
of freshly-arrived specimens. If a competent botanist were 
thoroughly to explore Bermuda, eliminate the species introduced 
by human agency, and investigate the source from whence the 
others were derived and the mode by which they had reached 
so remote an island, we should obtain important information as 
to the dispersal of plants, which might afford us a clue to 
the solution of many difficult problems in their geograj)hical 
distribution. 

Concluding Remarks. — The two groups of islands we have now 
been considering furnish us with some most instructive facts as 
to the power of many groups of organisms to pass over from 
700 to 900 miles of open sea. There is no doubt whatever that 
all the indigenous species have thus reached these islands, and 
in many cases the process may be seen going on from year to 
year. We find that, as regards birds, migratory habits and the 
liability to be caught by violent storms are the conditions which- 
determine the island -population. In both islands the land-birds 
are almost exclusively migrants ; and in both, the non-migratory 
groups — wrens, tits, creepers, and nuthatches — are absent ; while 
the number of annual visitors is greater in proportion as the 
migratory habits and prevalence of storms afford more efficient 
means for their introduction. 

We find also, that these great distances do not prevent the 
immigration of some insects of most of the orders, and espe- 
cially of a considerable number and variety of beetles ; while 
even land-shells are fairly represented in both islands, the large 
proportion of peculiar species clearly indicating that, as we 
might expect, individuals of this grovip of organisms arrive 
only at long and in-egular 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 

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



264 - ISLAND LIFE. [part ir. 

no reason to doubt that besides the species that have actually 
established themselves, many others must have reached the 
islands, but were not suited to the climate and other physical 
conditions, or did not find the insects necessary to their 
fertilisation. 

If now we consider the extreme remoteness and isolation of 
these islands, their small area, and comparatively recent origin, 
and that, notwithstanding all these disadvantages, they have 
acquired 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 terresti'ial mammals, amphibia, and 
some groups of reptiles. This conclusion will be of great im- 
portance ia many cases, where the evidence as to the exact 
origin of the fauna and flora of an island is less clear and satis- 
factory than in the case of the Azores and Bermuda. 



CHAPTER XIII. 

THE GALAPAGOS ISLANDS. 

Position and physical features — Absence of indigenous Mammalia and 
Amphibia — Kcptiles — Birds — Insects and Land-shells — The Keeling 
Islands as illustrating the manner in which Oceanic Islands are 
peopled — Flora of the Galapagos — Origin of the Flora of the 
Galapagos — Concluding Remarks. 

The Galapagos differ in many important respects from the 
islands we have examined in our last chapter, aud the differences 
are such as to have affected the whole character of their animal 
inhabitants. Like the Azores, they are volcanic, but they are 
much more extensive, the islands being both larger and more 
numerous ; while volcanic action has been so recent and exten- 
sive that a large portion of their surface consists of barren lava- 
fields. They are considerably less distant from a continent than 
either the Azores or Bermuda, being about 000 miles from the 
west coast of South America and a little more than 700 from 
Yeragua, w ith the small Cocos Islands intervening ; and they are 
situated on the equator instead of being in the north temperate 
zone. They stand upon a deei^ly submerged bank, the 1,000 
fathom hne encircling all the more important islands at a few 
miles' distance, whence there appears to be a comparatively 
steep descent all round to the average depth of that portion of 
the Pacific, between 2,000 and .3,000 fathoms. 

The whole group occupies a space of about .300 by 200 miles. 
It consists of five large and twelve small islands ; the largest 
(Albemarle Island) being about eighty miles long and of very 



2S6 



ISLAND LIFE. 



[part II. 



irregular shape, while the four next in importance— Chatham, 
Indefatigable, James, and Narborough Islands, are each about 
twenty-five or thirty miles long, and of a rounded or elongate 
form. The whole are entirely volcanic, and in the western 
islands there are numerous active volcanoes. Unlike the other 




MAP OF THE GALAPAGOS AND ADJACENT COASTS OF SOUTH AMERICA. 

The light tint shows where the sea is less than 1,000 fathoms deep. 
The figures show the depth in fathoms. 



groups of islands we have been considering, these are situated 
in a comparatively calm sea, where storms are of rare occurrence 
and even strong winds almost unknown. They are traversed by 
ocean currents which are strong and constant, flowing towards 



CHAP. XIII.] 



THE GAL.\P.AlGOS ISLANDS. 



267 



the north-west from the coast of Peru ; and these physical 
conditions have had a powerful influence on the animal and 
vegetable forms by which the islands are now inhabited. The 
Galapagos have also, during three centuries, been frequently 
visited by Europeans, and were long a favourite resort of 
buccaneers and traders, who found an ample supply of food in 










======^== 


9l{ sol 89| 




f 


if 


-: -'. 


^^H 








^^ta=s»^yw£>^^^| 




1 


■ 






' COWEN >^^^^^H 


T 


^-^' 






p - 


* 






"2 


2 


1- 









onl 


ro| 



MAP OF THE GALAPAGOS. 



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



the large tortoises which abound there ; and to these visits we 
may perhaps trace the introduction of some animals whose 
presence it is otherwise diSicuIt to account for. The vegetation 
is generally scanty, but still amply sufficient for the support of 
a considerable amount of animal Hfe, as shown by the cattle, 



2G8 ISLAND LIFE. [part ii. 

horses, asses, goats, pigs, dogs, and cats, which now run wild 
in some of the islands. 

Absence of indigeiwns Mammalia and Amphibia. — As in all 
other oceanic islands, we find here no truly indigenous mam- 
malia, for though there is a mouse of the American genus 
Hesperomys, which differs somewhat from any known species, we 
can hardly consider this to he indigenous ; first, because these 
creatures have been little studied in South America, and there 
may yet be many undescribed species, and in the second place 
because even had it been introduced by some European or 
native vessel, there is ample time in two or three hundred years 
for the very different conditions to have established a marked 
diversity in the characters of the species. This is the more 
probable because there is also a true rat of the Old World 
genus Mus, which is said to differ slightly from any known 
species ; and as this genus is not a native of the American 
continents we are sure that it must have been recently intro- 
duced into the Galapagos. There can be little doubt therefore 
that the islands are completely destitute of truly indigenous 
mammalia ; and frogs and toads, the only tropical representatives 
of the Ampliibia, are equally unknown. 

Reptiles. — Reptiles, however, winch 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 pecidiar species, Testudo microphyes, 
found in most of the islands, and T. abingdonii recently dis- 
covered on Abingdon Island, as well as one extinct species, 
T. epliipipium, 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 kno^\^^ 
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 

' Gigantic Land Tortoises Living and Extinct in the collection of the 
British Museum. By A. C. L. G. Giinther, F.E.S. 1877. 



CHAP. XIII.] THE GALAPAGOS ISLAliJDS. 209 

out to sea by a flood, was once or twice safely drifted as for 
as the Galapagos, aud thus originated the races which now 
inhabit them. 

The lizards are five in number; a peculiar species of 
gecko, PhijUodadylus galapagensis, and four species of the 
American family Iguanidte. Two of these are distinct species 
of the genus Lioccphalus, the other two being large, and so 
very distinct as to be classed in peculiar genera. One of these 
is aquatic and found in all the islands, swimming in the sea at 
some distance fi-om the shore and feeding on seaweed ; the other 
is terrestrial, and is confined to the four central islands. These 
were originally described by ]Mr. Bell as Amhlyrlujnvhus cristntus 
and A. suhcristatus ; they were afterwards placed in two 
other genera Trachyccphalus and Oreocephalus {sec Brit. Mus. 
Catalogue of Lizards), while in a recent paper by Dr. Gunther, 
the marine species is again classed as Amblyrhynchus, while 
the teiTestrial form is placed in another genus Couolophus. 

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 sjiecies is a proof that their amval took place at a 
remote epoch, under conditions perhaps somewhat different 
from any which now prevail. It is certain that animals of this 
order have some means of crossing the sea not possessed by 
any other land vertebrates, since they are found in a consider- 
able number of islands which possess no mammals nor any 
other land reptiles ; but what those means are has not yet been 
positively ascertained. 

It is unusual for oceanic islands to possess snakes, and it is 
therefore somewhat of an anomaly that two species are found 
in the Galapagos. Both are closely alhed 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 readied the island of St. 
Vincent from the coast of South America, a distance of two 
hundred miles by the shortest route. Snakes often frequent 
trees, and might thus be conveyed long distances if canied out 



^ 



270 ISLAND LFFE. [part ii. 

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 maj' perhaps attribute the presence of 
these creatures in the Galapagos, and that it is a very rare one 
is indicated by the fact that only two species have as yet 
succeeded in obtaining a footing there. 

Birds. — We now come to the birds, whose presence here may 
not seem so remarkable, but which yet present features of in- 
terest not exceeded by any other gi'oup. Fifty-seven species 
of birds have now been obtained on these islands, and of these 
thirty-eight are peculiar to them. But all the species found 
elsewhere, except one, belong to the aquatic tribes or the waders 
which are pre-eminently wanderers, yet even of these eight are 
peculiar. The true laud-birds are thirty-one in number, and all 
but one are entirely confined to the Galapagos ; while more than 
half present such peculiarities that they are classed as distinct 
genera. All are allied to birds inhabiting tropical America, 
some very closely ; while one — the common American rice-bird, 
which ranges over the whole northern and part of the southern 
continents — is the only land-bird identical with those of the 
mainland. The following is a list of these land-birds taken 
from Mr. Salviii's memoir in the Transactions of the Zoological 
Society for the year 1876 : — 

Tlrdid^. 

1. Mimus trifasciatus "j Thi^ and the two allied species nre 

2. ,, nie'anotiis > related to a Peruvian bird Mimus 

3. „ pamihis I hngicaudut. 



MSIOTILTID.E. 



4. Dendroeca aureola f Closely allied to the wide-ranging D. 

I (estiva. 

HiRCNDIXID.f:. 

, T) „ „ i„, f Allied to P. purpurea of North and 

5. Progne concolor ^ South America. 



CCEREB1D.E. 

}A pec 
genus Conirostrum. 



fi. Certhidea olivacea \ A peculiar genus allied to the Andean, 



CHAP. XIII.] 



THE GALAPAGOS ISLANDS. 



271 



Fringillid^. 



8. Geospiza mtignirostris ... 

9. „ strenua 

10. „ (luliia 

11. ,, fortis 

12. „ iicbulosa 

13. „ fuliginosa 

14. „ pan-ula 

15. ,, (lentirostiis 

16. Cactomis scandens 

17. „ assiiiiilis 

18. „ abinsjdoui 

19. „ pallida 

20. Camarhjnchus pgittaculus 

21. „ crassirostris 

22. „ vaiipfjatus 

23. „ piostlieinelas 

24. ,, liabeli ... 



[\ distinct genus, but allied to the 
( Suutli American genus Guiraca. 



1 



(A genus allied to the last. 



I A verj' peculiar genus allied to Neo- 
}- ilivnclnis of the west coast of 
I Peru, 
J 



25. Dolichonjx oryzivorus 



26. Pyrocephalua nanus... 

27. Myiarclius magnirostris 



28. Zenaida galapagensis 



ICTKUID.«. 

Ranges from Canada to Paraguay. 

Tyuaxxid.b. 

Allied to P. rubineus of Ecuador. 

Allied to West Indian species. 

CoLUMBID^E. 

A peculiar species of a S. American 



(■ 



genus. 



29 Biiteo galapagensis. 



30. Asio galapagensis . 

31. Strix punctatissinia . 



Falconid^. 
... A buzzai-d of peculiar coloration. 

StRIGIDjE. 

f Hardly distinct from the wide-spread 
" \ A. hrachijnlus. 
. . . Allied to IS.flammea but quite 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, migra- 
tion to the islands. The excessively abundant rice-bird, which 
breeds in Canada and swarms over the whole United States, 
migrating to the West Indies and South America, visiting the 



272 ISLAND LIFE. [part ii. 

(listaut 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 Cliina to Ireland, and from Green- 
land to the Straits of Magellan, and of this the Galapagos bird 
is probably only one of the numerous varieties. The little 
wood warbler {Deiidrceca aureola) is closely allied to a species 
which ranges over the whole of North America and as far south 
as New Grenada. It has also been occasionally met with in 
Bermuda, an indication that it has considerable powers of flight 
and endurance. The more distinct specks — as the mocking- 
thrushes (Mimus), the tyrant fly-catchers (PjTocephalus and 
Myiarchus), and the ground dove (Zenaida), are all allied to non- 
migratory species peculiar to tropical America, and of a more 
restricted range ; while the distinct genera are allied to South 
American groups of finches and sugar-birds which have usually 
restricted ranges, and whose habits are such as not to render 
them likely to be carried out to sea. The remote ancestral 
forms of these birds which, owing to some exceptional causes, 
reached the Galapagos, have thus remained uninfluenced by 
later migrations, and have, in consequence, been developed into 
a variety of distinct types adapted to the pecuhar conditions of 
existence under which they have been placed. Sometimes the 
different species thus formed are confined to one or two of the 
islands only, as the two species of Certhidea, which are divided 
between the islands but do not appear ever to occur together. 
Mimus parvulus is confined to Albemarle Island, and M. trifascia- 
tns to Charles Island ; Cactornis pallida to Indefatigable Island, 
and C. ahingdoni to Abingdon Island. 

Now aU 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 gi-eat extent, would certainly 
indicate a considerable antiquity. 



f-HAr. xiii,] THE GALAPAGOS ISLANDS. 273 

The great difference presented by the birds of these islands 
as compared witli those of the equally remote Azores and 
Bermudas, is sufficiently explained by the difference of climatal 
conditions. At the Galapagos there are none of those periodic 
storms, gales, and hurricanes which prevail in the North 
Atlantic, and which every year carry some straggling birds of 
Europe or North America to the former islands ; while, at the same 
time, the majority of the tropical American birds are'non-migra- 
tory, and thus afford none of the opportunities presented by the 
countless hosts of migrants which pass annually northward and 
southward along the European, and especially along the North 
American coasts. It is strictly in accordance with these different 
conditions that we find in one case an almost perfect identity 
with, and in tlie other an almost equally complete diversity from, 
the continental species of birds. 

Insects and Land-sliells. — The other groups of land-animals 
add little of importance to the facts already referred to. The 
insects are very scanty ; the most plentiful group, the beetles, 
only furnishing about thirty-five species belonging to twenty- 
nine genera and eigliteen fiimilies. 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 Carabida; and the Heteromera are tlic most abun- 
dant groups, the former furnishing si.\ and the latter eight 
species. 1 

' The following list of tlie beetles yet known from tlie Galapiigos sliow.s 
their scanty proportions and accidental character ; the thirty-seven species 
belonging to thirty-one genera and eighteen families. It is taken from 
Mr. Waterhouse's enumeration in the Proceedivgs of the Zoological Society 
for 1877 (p. 81):— 

Cakaeid.e. Malacoderms. 

Feronia calathoides. Ablechrus darwinii. 

„ insularis. Corynetes rulipes. 

„ galapagoensLs. Bostrichus imciniatus. 
Aniblygnathus ob-scuricomis. Lamkllicornes. 

Solenopliorus galapagoensis. Copris lugubris. 

Notaphus galapagoensis. Oryctes galapagoensis. 

Dy-nscipyf;. Klatekid.e. 

Eunectes oecidentalis. Phyi^orliimis gahipagoensi,-!. 

T 



274 ISLAND LTFE. [lAitr. ii. 



The land-shells are not abiindaut — about twenty in all, 
most of them peculiar species, but not otherwise remarkable. 
The observation of Captain Coilnet, quoted by Mr. Darwin in 
his Journal, that drift-wood, bamboos, canes, and the nuts of a 
palm, are often washed on the south-ea.stem shores of the 
islands, furnishes an excellent clue to the manner in which many 
of the insects and land-shells m.ay have reached the Galapagos. 
Whirlwinds also have been known to carry quantities of leaves 
and other vegetable debris to great heights in the air, and 
these might be then carried awa}- 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 inten-ened between them and 
the coast, and have served as stepping-stones by Avhich the 
passage to tlicm of various organisms would be greatly facilitated. 
Sunken banks, the relics of such islands, are known to exist in 
manj' parts of the ocean, and countless others, no doubt, remain 
undiscovered. 

T/ic Keel in ff Islands as illustrating the manner in which Oceanic 
Islands are Peopled. — That such causes as have been here ad- 
duced are those by wliich oceanic islands have been peopled, is 
further shown by the (■f)ndition of equally remote islands whicli 

Aeiliu.s ini-isiis. Hkteromera. 

Copelatiis gjiliipagoeusis. iSloiuiori helopoides. 
Palpicornks. '■ , l»vigat„n,. 

X lopisternus lateralis. ' 



Philhydrus sp 

STArilYLINin.K 



cooksoni. 
„ bifovcatiis. 

Pedonoeccs ga]apageen>is. 
Creophilus villosus. ^ pubescent 

Necrophaga. Pl.aleiia manicata. 
Acribis serrativentii«. Axi HRiBm.s. 

Phalacrus darwiiiii. Onuiscus variegatus. 
Diimestes viilpiiiiis. PHVToril.\GA. 

CrRCDLioxin.K. Diidirotica Hnibata. 

Otiorbynchiis cuneiforinis Docenia galapagoeiisis. 

Aiiclioiius galapagocnsU. Loiigitarsus lunatus. 

LOXGICOK.N 1 A. SECUUirAI.PES. 

Ebiiria aiiial>ilis. Sf vmiiiis galapagoo*isi.«. 



CHAP, xni.] THE GALAPAGOS ISLANDS. 275 

we know aye^'O^rcomparallvely recent origin. Such are the 
KeeHng o^Cocos Islands in the Indian Ocean, situated about 
the same distance Trom Sumatra as the Galapagos from South 
America, but mere coral reefs, supporting abundance of cocoa- 
nut palms as their chief vegetation. These islands were visited 
by Mr. Darwin, and their natural history carefully examined. 
The only mammals are rats, brought by a A\'recked 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 ajjparently 
common Malayan species. Reptiles are represented by one 
small lizard, but no account of tlii.s is given in the Zoology of the 
Voyage of the Beagle, and we may therefore conclude that it was 
an introduced species. Of insects, careful collecting only pro- 
duced thirteen species belonging to eight distinct orders. The 
only bettle was a small Elatcr, the Orthoptera were a Gryllus 
and a Blatta ; and there were two flios, two ants, and two small 
moths, one a Dioptea which swarms everywhere in the eastei'n 
tropics in grassy places. All these insects were no doubt brought 
cither by winds, by floating timber (which reaches the islands 
abundantly), or b}' clinging to the feathers of acpiatic or wading 
birds ; and we only require more time to introduce a greater 
variety of species, and a better .soil and more varied vegetation, 
to enable them to live and multiply, in order to give these 
islands a fauna and flora equal to that of the Bermudas. Of 
wild plants there were only twenty species, belonging to nine- 
teen genera and to no less than sixteen natural families, while 
all were common tropical shore plants. These islands are thus 
evidently stocked by waifs and strays brought by tlie winds and 
waves ; but their scanty vegetation is mainly due to unfavourable 
conditions — the barren coral rock and sand, of which they are 
wholly composed, together with exposure to sea-air, being 
suitable to a very limited number of species which soon mono- 
polise the surface. With more variety ol soil and aspect a 
greater variety of plants would establish themselves, and these 
Would favour the preservation and increase of niore injects, 

T 2 



276 ISLAND LIFE. [paut ii. 

birds, and otlier animals, as we find to be the case in many 
small and remote islands.' 

Flora of the Galajxigos. — The plants of these islands are so 
much more numerous thau the known animals, even including 
the insects, they have been so carefully studied by eminent 
botanists, and their relations throw so mucli 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 Lianmai Transactions for 

' Juan Fernandez is a good example of a small i--land Aviiich, 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-current« 
come from the south-west in a direction where there is no land but the 
Antarctic continent, and the prevalent winds are also westerly. No doubt, 
however, there are occasional storms, and there may have been intermediate 
islands, but its chief advantages are, no doubt, its antiquity and its varied 
surface, offering many chances for tlie preservation and increase of what- 
ever plants and animals have chanced to reach it. The island consists of 
basalt, greenstone, and other ancient rocks, and though only about twelve 
miles long its mountains are three thousand feet high. Enjoying a moist 
and temperate climate it is especially adapted to the growth of ferus, which 
are very abundant ; and as the spores of these plants arc as line as dust, 
and very easily carried for enormous distances by winds, it is not surprising 
that there are twenty-four species on the island, while the remote period 
when they iirst received their vegetation may be indicated by the fact 
that four of the species are quite peculiar. The same general character 
pervades the whole flora and fauna. For so small an island it is rich, 
containing a considerable number of flowering plants, four true land-birds, 
about fifty species of insects, and twenty of land-shells. Almost all these 
belong to South American genera, and a large proportion are South American 
species ; but several of the plants and insects, half the birds, and the whole 
of the land-shells are peculiar. This seems to indicate that the means of 
transmission were formeily greater than they are now, and that in the case 
of land-shells none have been introduced for so long a period that all have 
become modified into distinct forms, or have been preserved on the island 
while they have become extinct on the continent. — For a detailed examina- 
tion of the causes which have led to the modification of the humming- 
birds of Juan Fernandez see the author's Tropical Nature, p. 140 ; while 
a general account of the fauna of the island is given in his GeograpMco,l 
Distribution of Animals, Vol. IL p. 49. 



CHAP. xiH.] THE GALAPAGOS ISLANDS. 277 

1851, founded on Mr. Darwin's collections, and a later paper by 
N. J. Audersson in the Linnwa of 1 SGI, embodying more i-ecent 
discoveries. 

The total number of flowering plants known at the latter 
date was 332, of which Hi 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 
aU natives of some p;irt of America, though about a third part 
are species of wide range extending into both hemispheres. Of 
those confined to America, forty-two are found in both the 
northern and southern continents, twenty-one are confined to 
South America, while twenty are found only in North America, 
the West Indies, or Mexico. This equality of North American 
and South American species in the Galapagos is a fact of great 
significance in connection with the observation of Sir Joseph 
Hooker, that the pemdiar species are allied to the plants of 
temperate America or to those of the high Andes, while the 
non-peculiar species are mostly such as inhabit the hotter 
regions of the tropics near the level of the sea. He also 
observes that the seeds of this latter class of Galapagos plants 
often have special means of transport, or belong to groups whose 
seeds are known to stand long voyages and to possess great 
vitality. Mr. Bentham also, in his elaborate account of the 
CompositiB,' remarks on the decided Central American or 
Mexican affinities of the Galapagos species, so that we may 
consider this to be a thoroughly well-established fact. 

The most prevalent families of plants in the Galapagos are 
the Compo-sita; (40 .sp.), Graminese (32 .sp.), Leguminosae (30 
sp.), and Euphorbiacese (29 sp.). Of the Compositae 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 Lipochseta, 
represented here by a single species, is only found elsewhere in 
the Sandwich Islands, though it has American aflinities. 

Origin of the Galapagos Flora. — These facts are explained 
by the past history of the American continent, its separation at 

' Journal of the L'wiiean Society, Vu!. XIII., '■ Butauy,' p. 556. 



278 ISLAND LIFE. [part u. 

various epochs by arms of the sea uniting the two oceans across 
what is now Central America (the last separation being of recent 
date, as shown by the identical species of fishes on both sides 
of the isthmus), and the influence of the glacial epo?h in driving 
tlie 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 wliich would 
almost certainly liave reached the Galapagos, and this may have 
helped to bring about that singular assemblage of West Indian 
and Mexican plants now found there. And as we now believe 
that the duration of the last glacial epoch in its successive 
phases was much longer than the time which has elapsed since 
it finally passed away, while throughout the Jliocene epoch the 
snow-line would often be lowered during periods of high ex- 
oentricity, we are enabled to comprehend the nature of the 
causes wdiich may Lave led to the islands being stocked 
with those northern or sub-alpine types which are so char- 
acteristic a feature of that portion of the Galapagos flora 
which consists of peculiar species. 

On the whole, the flora agrees with tlie fauna in indicating 
a moderately remote origin, great isolation, and changes of con- 
ditions affording facilities for the introduction of organisms from 
various p;u-ts 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 expected 
on any theory of their origin ; because, even if the whole of the 
islands had once been united and afterwards separated, long 
continued isolation would often lead to the differentiation of 
species, while the varied conditions to be found upon islands 
differing in size and altitude as well as in luxuriance of vegeta- 
tion, would often lead to the extinction of a species on one island 
and its preservation on another. If the several islands had been 
equally well explored, it might be interesting to see whether, as 
in the case of the Azores, the number of species diminished in 
1 Geographical Distribution of Animals, Vo!. II. p. 81. 



iii\r. xnr.] THE (.AI.Al'AGOS ISl.AXI 'S. 2!ii7 



those more remote from the coast ; but unfortunately our know- 
ledge of the jiroductions of the various islands of the group is 
exceedingly uneciual, and, except in those cases in which repre- 
sentative species inhabit distinct islands, we have no certainty 
on the subject. All the more interesting problems in geogi-a- 
phical distribution, however, arise from the relation of the fauna 
and flora of the group as a whole to those of the surrounding 
continents, antl we shall therefore for the most part confine 
ourselves to this aspect of the question in our discussion of the 
phenomena presented by oceanic or continental islands. 

Concluding Remarks. — The Galapagos offer an instructive 
contrast with the Azores, showing how a difference of condi- 
tions that might be thought unimportant may yet produce very 
striking results in tlie forms of life. Although the Galapagos 
are much nearer a continent than the Azores, the number of 
species of plants common to the continent is much less in the 
former case than in the latter, and this is still more prominent 
a characteristic of the insect and the bird faunas. This differ- 
ence has been shown to depend, almost entirely, on the one 
archipelago being situated in a stormy, the other in a calm, ^ 
portion of the ocean ; and it demonstrates the preponderating / 
importance of the atmosphere as an agent in the dispersal of 
birds, insects, and plants. Yet ocean-cun-ents and surface-drifts \ 
are undoubtedly efficient carriers of plants, and, with plants, of j 
insects and shells, especially in the ti-opics ; and it is probably to 
this agency that we may impute the recent introduction of a 
number of common Peruvian and Chilian littoral species, and 
also at a more remote period of several \^'est Indian types when 
tlie Isthmus of Panama was submerged. 

In the case of these islands we see the importance of taking 
past conditions of sea and land and past changes of climate into 
account, in order to explain the relations of the peculiar or ende- 
mic species of their fauna and flora ; and we may even see an 
indication of the effects of climatal changes in the northern hemi- 
sphere, in the north temperate or alpine affinities of so many of 
the plants, and even of some of the birds. The relation between 
the migratory habits of tlie birds and the amount of difference 
fium continental types is strikingly accordant with the fact that 



•2?0 ISLAND LIFE. [rAur ll. 

it is almost exclusively migratory birds that amiually reach the 
Azores and Bermuda; while the corresponding fact that the 
seeds of those plants, which are common to the Galapagos and the 
adjacent continent, have all — as Sir Joseph Hooker states — some 
special means of dispersal, is equally intelligible. The reason 
why the Galapagos possess four times as many peculiar species 
of plants as the Azores is clearly a result of the less constant 
introduction of seeds, owing to the absence of storms ; the 
greater antiquity of the group, allowing more time for specific 
change ; and the influence of cold epochs and of alterations 
of sea and land, in bringing somewhat different sets of plants at 
different times within the influence of such modified winds and 
currents as might convey them to the islands. 

On the whole, then, we have no ditficulty 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 ;inil pliysical features of St. Helena — Change effected by European 
ofcupation — The Insects of St. Helena — Coleoptera — Peculiarities anil 
origin of the Coleoptera of St. Helena — Land-shells of St. Helena — 
Absence of Fresli-water organisms — Native vegetation of St. Helena — 
The relations of the St. Helena Conipositoe — Concluding Remarks on 
St. Helen;i. 

In order to illustrate as completely as possible the peculiar 
phenomena of oceanic islands, we will next examine the organic 
productions of St. Helena and of the Sandwich Islands, since 
these combine in a higher degree than any other spots upon the 
globe, extreme isolation from all more extensive lands, with a 
tolerably rich fauna and flora whose peculiarities are of surpass- 
ing interest. Both, too, have received considerable attention 
from naturalists ; and though much still remains to be done in 
the latter group, our knowledge is sufficient to enable us to 
arrive at many interesting restdts. 

Position and Phi/sical featurffi of St. Helena. — This island 
is situated nearly in the midille of the South Atlantic Ocean, 
being more than 1,100 miles from the coast of Africa, and 
1,800 from South America. It is about ten miles long by eight 
wide, and is wholly volcanic, consisting of ancient basalts, lavas, 
and other volcanic products. It is very mountainous and rugged, 
bounded for the most part by enormous precipices, and rising to 
a height of 2,700 feet above the sea-level. An ancient crater, 
about four miles acros.s, is open on the south side, and its 



282 



ISLAXD LIFi: 



[part II. 




, a 

* 2 



CHAP. XIV.] ST. HELENA. 283 

northera riui forms the highest and central ridge of the island. 
Many other hills and peaks, however, are more than two thousaml 
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 depths of the ocean. 
Mr. '\Vollast<:>n remarks : " There are the strongest reasons for 
beheving that the area of St. Helena was never very much larger 
than it is at present — the comparatively shallow sea-soundings 
within about a mile and a half from the shore revealing an 
abruptly defined ledge, beyund which no bottom is reached at a 
depth of 2.50 fathoms ; so that the original basaltic mass, which 
was gradually piled up by means of successive eruptions from 
beneath the ocean, would appear to have its limit definitely 
marked out by this suddenly-terminating submarine cliff — the 
space between it and the existing coast-line being reasonably 
referred to that slow process of disintegration by which the 
island has been reduced, through the eroding action of the 
elements, to its present dimensions." If we add to this that 
between the island and the coa.st of Africa, in a south-easterly 
direction, is a profound oceanic gulf known to reach a depth of 
2,860 fathoms, or 17,100 feet, while an equally deep, or perhaps 
deeper, ocenn, 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 effected hy European occupation. — When first dis- 
covered, 378 years ago, St. Helena was densely covered with a 
luxuriant forest vegetation, the trees overhanging the seaward 
precipices and covering every pait of the surface with an ever- 
green mantle. This indigenous vegetation has been almost 
wholly destroyed ; and although an immense number of foreign 
plants have been introduced, and have more or less completely 
established themselves, yet the general aspect of the island is 
now so barren and forbidding that some persons find it difficult 
to believe that it was once all green and fertile. Tlie cause of 
the change is, however, very easily explained. The rich soil 
formed by decomposed volcanic rock and vegetable deposits 



284 ISLAND LIFE. [paet ii. 

could only be retained on the steep slopes so long as it was 
protected by the vegetation to which it in great part owed its 
origin. When this was destroyed, the heavy tropical rains soon 
washed away the soil, and has left a vast expanse of bare rock 
or sterile clay. Tliis irreparable destruction was caused in the 
first place by goats, which were introduced by the Portuguese in 
1.513, and increased so rapidly that in 1.588 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."- Tliey 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 fur building fortifica- 
tions ! By the MSS. records quoted in Mr. Melliss' interesting 
volume on St. Helena,' it is evident that the evil consequences 
of allowing the trees to be destroyed were clearly foreseen, as 
the following passages show : " We find the place called the 
Great Wood in a flourishing condition, full of young trees, where 
the hoggs (of which there is a great abundance) do not come to 
root them up. But the Great Wood is miserably lessened and 
destroyed within our memories, and is not near the circuit and 
length it was. But we beUeve it does not contain now less than 
fifteen hundred acres of fine woodland and good ground, but no 
springs of water but what is salt or brackish, which we take to 
be the reason that that part was not inhabited when the people 
first chose out their settlements and made plantations ; but if 
wells could be sunk, which the governor says he will attempt 
when we have more hand.s, we should then think it the most 
pleasant and healthiest pai-t of the island. But as to healthi- 
ness, we don't think it will hold so if the wood that keeps the 
land warm were destroyed, for then the rains, which are violent 

' SI. Helena : a Physical, Historical, and Topograj>hical De,icription of lite 
Island, etc. By John Charles Melliss, F.G.S., &c. London : 1875. 



cnAP. XIV.] ST. HELENA. 285 

here, would carry away the upper soil, and it being a clay marl 
underneath would pi'oduce but little ; as it is, we thiulv in case 
it were enclosed it might be greatly improved "...." When 
once this wood is gone the island will soon be ruined " . . . . 
" We viewed the wood's end which joins the Honourable Com- 
pany's plantation called the Hutts, but the wood is so destroyed 
that the besinnina: 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." {3fSS. Records, 1716.) In 
17U9 the governor reported to the Court of Directors of the. 
East India Company that the timber was ra]>idly disappearing, 
and that the goats should be destroyed for the preservation of the 
ebony wood, and because the island was suifering from drouglits. 
The reply was, " The goats are not to be destroyed, being more 
valuable than ebony." Thus, through the gross ignorance of 
those in power, the last opportunity of preserving the peculiar 
vegetation of St. Helena, and preventing the island from be- 
coming the comparatively rocky desert it now is, was allo\Yed to 
pass away.^ Even in a mere jiecuniary point of view the en'or 
was a fatal one, for in the next century (in 1810) another gover- 
nor reports the total destruction of the great forests by the 

' Jlr. Marsh in liis interesting work entitled, Tlic Earth as Modified by 
JTumati Action (p. 51), thus remarlis on the effect of browsing quadrupeds 
in destroying and checking woody vegetation. — " I am convinced that 
forests would soon cover many parts of the Arabian and African deserts 
if man and domestic animrils, especially the goat and the camel, were 
l)auished from them. The hard ])alate and tongue, and strong teeth and 
jaws of this latter quadruped enable him to break off and masticate tough 
and thorny branches as large as the finger. He is particularly fond of the 
smaller twigs, leave.s, and seed-pods of the Sont and other acacias, which, 
like the American robinia, thrive well on drj' and sandy soils, and he 
spares no tree the branches of which are within his reach, except, if I 
remember right, the tamarisk that produces manna. Young trees sprout 
plentifully around the springs and along the winter -water-courses of the 
desert, and these are just the halting stations of the caravans and their 
routes of travel. In the shade of these trees annual grasses and perennial 
shrubs shoot up, but are mown down by the hungry cattle of the Bedouin 
as fast as they grow. A few years of undisturbed vegetation would suffice 
to cover such points with groves, and these would gradually extend them- 
selves over soils where now scarcely any green thing but the bitter 
colocynth and the poisonous foxglove is ever seen.'' 



2«6 ISLAND LIFE. [part ii. 

goats, and that in consequence the cost of importing fuel for 
government use was 2,729^. 7s. 8d. for a single year 1 About 
this time large numbers of European, American, Australian, and 
South African plants were imprirted, and many of these ran 
wild and increased so rapidly as to drive out and exterminate 
much of the relics of the native flora; so that now English 
broom gorse and brambles, willows and poplars, and some 
common American, (^ape, and Australian weeds, alone meet the 
eye of the ordinary visitor. These, in Sir Joseph Hooker's 
opinion, render it absolutely impossible to restore the native 
flora, which only lingers in a few of the loftiest ridges and 
most inaccessible precipices, and is rarely seen except by some 
exploring naturalist. -- — -^ 

This almost total extirpation of a luxuriant and highly pecu- 
liar vegetation njust inevitably ha.ve 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 laud-shells, mainly to the late Mr. T. Vernon 
Wollaston, who, after having thoroughly explored Madeira and 
the Cixnaries, undertook a V(.>yage to St. Helena for the exprcs 
jiurpose of studying its terrestrial fauna, and resided for six 
months (1875-76) in a high central position, whence the loftiest 
peaks could be explored. The results of his labours are con- 
tained in two volumes,^ which, like all that he wrote, are 
models of accuracj" and research, and it is to these volumes 
that we are indebted for the interesting and suggestive facts 
Avhich we here lay before our readers. 

Insects— Coleoptcrn. — The total number of species of beetles 
hitherto obsen'ed at St. Helena is 203, but of these no less 
than seventy-four are common and wide-spread insects, which 
have certainly, in Mr. Wollaston's opinion, been introduced by 
human agency. There remains 120 which are believed to be 

1 Cnltoptcra Sanctcc Uclcnm, \?rri x Testacca AtlanlUv, 1878. 



cnAP. XIV.] ST. HELENA. 287 

truly aborigines, and of these all but one are found nowhere else 
on the globe. But in addition to this large amount of specific 
peculiarity (perhaps unequalled anywhere else in the world) the 
beetles of this island are equally remarkable for their generic 
isolation, and for the altogother exceptional proportion in 
which the great divisions of the order arc 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 RhjTicophora or weevils, while more than two-fifths (fifty- 
four species) belong to one family, the Cossonidaj. Now although 
the Rhyncopliora are an immensely numerous group and always 
form a large portion of the insect population, they nowhere 
else approach such a proportion as this. For example, in 
Madeira they form one-sixth of the whole of the indigenous 
Coleoptera, in the Azores less than one-tenth, and in Britain 
one-seventh. Even more interesting is the fact that the twenty 
genera to which these insects belong are every one of them 
peculiar to the island, and 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 par- 
ticular species of plants, we might, as Mr. Wollaston well 
observes, deduce the former luxuriant vegetation of tlie island 
from the great preponderance of this group, even had we not 
positive evidence that it was at no distant epoch densely forest- 
clad. We will now proceed briefly to indicate the numbers 
and peculiarities of each of the families of beetles which enter 
into the St. Helena fauna, taking them, not in systematic order, 
but according to their impoitance in the island. 

1. Rhyncophoea. — This great division includes the weevils 
and aUied groups, and, as above stated, exceeds in number of 
species all the other beetles of the island. Four families are re- 
presented ; the Cossonidce, with fifteen peculiar genera comprising 
fifty-fiiur P^^ecies, and one minute insect {Stenoscelis hi/lmtoiclcs) 



288 ISLAND LIFE. [part n. 

forming a peculiar genus, but wliich 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 CompositiE, and other in- 
digenous plants. They are all pre-eminently pecuHar and 
i-solated, having no direct iifRnity to species found in any 
other country. The next family, the Tanyrh3Tichidae, has one 
pecuUar genus in St. Helena, with ten species. This genus 
(Nesiotes) is remotely allied to European, AustraUan, and 
Madeiran insects of the same family : the habits of the species 
are similar to those of the Cossonidse. The Trachyphloeidte are 
represented by a single species belonging to a pecuUar genus 
not very remote from a European form. The Anthribidae again 
are highly peculiar. There are twenty-six species belonging to 
three genera, all endemic, and so extremely peculiar that they 
form two new subfamilies. One of the genera, Acarodes, is 
said to be allied to a Madeiran genus. 

2. Geodephaga. — These are the terrestrial carnivorous beetles, 
very abundant in all parts of the world, especially in the tem- 
perate regions of the northern hemisphere. In St. Helena 
there are fourteen species belonging to three genera, one of 
which is peculiar. This is the Hcqilothorax hurchcUii, the largest 
beetle on the island, and now very rare. It resembles a large 
black Carabus. There is also a peculiar Calosoma, very distinct, 
though resembling in some respects certain African species. 
The rest of the Geodephaga, twelve in number, belong to the 
wide-spread genus Bembidium, but tiiey are altogether peculiar 
and isolated, except one, which is of European type, and alone 
has wings, all the rest being \\ingless. 

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 Opatridae, 
Mordellidae, and Anthicidse. 

4. Brachyelttra. — Of this group there are six peculiar 



CHAP. XIV.] ST. IIELEN.\. 289 

species belonging to four European genera — Honialota, Pliilon- 
tbus, Xantholinus, and Oxytelus. 

5. Priocerata. — The families Elateridte and Anobiids are 
each represented by a peculiar species of a European genus. 

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

7. Lamellicornis. — Here are three species belonging to 
two genera. One is a peculiar species of Trox, allied to South 
African forms ; the other two belong to the peculiar genus 
Melissius, which Mr. Wollaston considers to be remotely allied 
to Australian insects. 

8. PsEULio-TRiMERA. — Here we have tlie fine lady-bird Chilo- 
menus lunata, also found in Africa, but apparently indigenous in 
St. Helena ; and a peculiar species of Euxcstcs, a genus only 
found elsewhere in Madeira. 

9. Tkichopterygid^. — These, the niinutcst nf beetles, are 
represented by one species of the European and Madeiran genus 
Ptinella. 

10. Necropuaga. — One indigenous species of Cryptophaga 
inhabits St. Helena, and tliis is said to be very closely allied to. 
a Cape species. 

Peculiarities and Oriijin of (he Cokoptcra of St. Helena.. — We 
see that the great mass of tiic 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 
(^eiy great antiquity of the insect fauna of St. Helena, which 
has allow^ed time for the modification of .the originally introduced 
species, and their special adaptation^ the conditions prevailing 
in this remote island. This antiquity is also shown by the re- 
markable specific modification of a few types. Thus the whole 
of the Cossonidaj may be referred to three types, one species only 
(Hexacoptus femigineus) being allied to the European Cossonidse 
though forming a distinct genus ; a group of three genera and 
seven species remotely allied to the Stenoscclis hi/lastoides, which 
occurs also at the Cape ; while a group of twelve genera with 

U 



290 ISLAXD LIFE. [i>art ii. 

forty-six species have their only (remote) aUies in a few insects 
widely scattered in South Africa, New Zealand, Europe, and the 
Atlantic Islands. In like manner, eleven species of Bembidium 
form a group by themselves ; and the Heteromera form two 
groups, one consisting of three genera and species of Opatridaa 
allied to a type found in Madeira, the other, Anthicodes, alto- 
gether peculiar. 

Now each of these types may well be descended from a single 
species which originally reached the island from some other 
land ; and the great variety of generic and specific forms into 
which some of them have diverged is an indication, and to 
some extent a measure, of the remoteness of their origin. The 
rich insect fauna of Miocene age found in Switzerland consists 
mostly of genera which still inhabit Europe, with others which 
now inhabit the Cape of Good Hope or the tropics of Africa and 
South America ; and it is not at all improbable that the origin of 
the St. Helena fauna dat<js back to at least as remote, and not 
improbably to a stiU earlier, epoch. But if so, many difficulties 
in accounting for its origin will disappear. We know that at 
that time many of the animals and plants of the tropics, of 
North America, and even of Australia, inhabited Europe ; while 
during the changes of climate, which, as we have seen, there is 
good reason to believe periodically occurred, there would be 
much migration from the temperate zones towards the equator, 
and the reverse. If, therefore, the nearest ally of any insular 
group now inhabits a particular country, we are not obliged to 
suppose that it reached the island from that country, since we 
know that most groups have ranged in past times over wider 
areas than they now inhabit. Neither are we limited to the 
means of transmission across the ocean that now exist, because 
we know tliat those means have varied greatly. During 
such extreme changes of conditions as are implied by glacial 
periods and by warm polar climates, great alterations of winds 
and of ocean-currents are inevitable, and these are, as we have 
already proved, the two great agencies by which the trans- 
mission of living things to oceanic islands has been brought 
about. At the present time the south-east trade-winds blow 
almost constantly at St. Helena, and the ocean-cuiTents flow in 



CHAP. XIV.] ST. HELENA. 291 

the same direction, so that any transmission of insects hy their 
means must almost certainly be from South Africa. Now thereV 
is undoubtedly a South African element in the insect-fauna, but \ 
there is no less clearly a European, or at least a nortli-tempcrate \ 
element, and this is very difficult to account for by causes now 
in action. But wlicn we consider that this nortliern element is 
chiefly represented by remote generic affinity, and has therefore 
all the signs of great antiquity, we find a possible means of 
account'ng 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 arc now, it is certain that an 
enormous change must have been produced in the wind.s. In- 
stead of a great difference of temperature between each pole 
and the equator, the difference would be mainly between one 
hemisphere and the other, and this might so disturb the trade 
winds as to bring St. Helena within the south temperate region 
of storms — a position corresponding to that of the Azores and 
Madeira in the North Atlantic, and thus subject it to violent 
gales from all points of the compass. 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, tliat tlicse peculiar furnis arc said 
to be northern only because their nearest allies are now found 
in the North Atlantic islands and Southern Europe ; but it is 
not at all improbable that they are really widespread Miocene 
types, which have been preserved mainly in favourable insular 
stations. They may therefore have originally reached St. 
Helena from Southern Africa, or horn 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 

* On Pctermann's map of Africa, in the new edition of Slieler's Hand- 
Atlas (1879), the Ishmd of Ascension is shown as seated on a much larger 
and shallower submarine bank than St. Helena. The 1,000 fathom line 
round Ascension encloses an oval space 170 miles long by 70 wide, and 

u 2 



202 ISLAND LIFE. [i'Aiit iiT 

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 stiU larger number are likely to inhabit similar 
stations. Drift-wood might therefore be one of the most 
important agencies by which these insects reached the island. 

Let us now see how far the distribution of other groups sup- 
port the conclusions derived from a consideration of the beetles. 
The Hemiptera have been studied by Dr. F. Buchanan White, 
and though far less known than the beetles, indicate somewhat 
similar relations. Eight out of twenty-one genera are pecidiar, 
and the thirteen other genera are for the most part widely 
distributed, while one of the peculiar genera is of African type. 
The other orders of insects have not been collected or studied 
with sufficient care to make it worth while to refer to them 
in detail ; but the land-shells have been carefully collected and 
minutely described by Mr. Wollaston himself, and it is interest- 
ing to see how far they agree with the insects in their 
peculiarities and affinities. 

Zund-shells of St. Helena. — The total number of species is 
only twenty-nine, of which seven are common in Europe or the 
other Atlantic islands, and are no doubt recent introductions. 
Two others, though described as distinct, are so closely allied to 
European forms, that Mr. Wollaston thinks they have probably 

even the 300 fatlioin line, one over 60 miles lon<i ; and it is therefore 
probable tliat a inucli larger island once occupied tbis site. Now Ascension 
is nearly equidistant between St. Helena and Liberia, and such an island 
might have served as an intermediate station through which many of the 
immigrants to St. Helena passed. As the distances are hardly greater 
than in the case of the Azores, this removes whatever difficulty may have 
been felt of the possibility of any organisms reaching so remote an island. 
The present island of Ascension is probably only the summit of a huge 
volcanic mass, and any remnant of the original fauna and flora it might 
have preserved may have been destroyed by great volcanic eruptions. Mr. 
Darwin collected some masses of tufa which were found to be mainlj' 
organic, containing, besides remains of fresh-water infusoria, the siliceous 
tissue of plants ! In the light of the great extent of the submarine bank 
on which the island stands, Mr. Darwin's remark, that — "we may feel 
sure, that at some former epoch, the climate and productions of Ascension 
were very different from what they are now," — has received a striking 
confirmation. (See Xaiuralist's Voyage Round the World, p. 495.) 



CHAP. XIV.] ST. HELENA. 293 

been introduced and have become slightly modified by new 
conditions of life ; so that there remain exactly twenty species 
which may be considered truly indigenous. No less than 
thirteen of these, however, apjjear to be extinct, being now 
only found on the surface of the ground or in the surface soil 
in places where the native forests have been destroyed and 
the land not cultivated. These twenty peculiar species belong 
to the folhjwing genera : Hyalina (3 sp.), Patula (4 sp.), Bulinius 
(7 sp.), Subulina (3 sp.), Succinca (3 sp.) ; of which, one species 
of Hyalina, three of Patula, all the Bulinii, and two of Subulina 
are extinct. The three Hynlinas are allied to European species, 
but all the rest appear to be liighly peculiar, and to have no 
near allies with the species of any other country. Two of the 
Bulimi {B. aurta vuljiiiur and B. dariciiiiaiins) are said to 
somewhat resemble Brazilian, New Zealand, and Solomon 
Island forms, wliile neither Bidimus nor Succinea occur at 
all in the Madeira group. 

Omitting the speies that have probably been introduced by 
human agency, we have here indications of a somewhat recent 
immigration of Eur<)j)ean types wliich 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 Organ.Ums. — A singular plienomenon 
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-plants 
in the streams, except the common water-cress, one or two 
species of Cyperus, and the Australian Isapis prolifera. The 
same absence of fresh-water shells characterises the Azores, 
where, however, there is one indigenous water-beetle. In the 
•Sandwich Islands also recent observations refer to the absence 
of water-beetles, though here there are a few fresh-water sliells. 
It would appear therefore that the wide distribution of the 
same generic and specific forms which so generally characterises 
fresh-water organisms, and wliich has been so well illustrated 
by Mr. Darwin, has its limits in the veri/ remote oceanic islands, 
owing to causes of which we are at present ignorant. 



204 ISLAND LIFE. [i-akt il. 

The other classes of animals in St. Helena need occupy lis 
little. There are no indigenous mammals, reptiles, fresh-water 
fishes or true land-birds ; but there is one speeies of wader — a 
small plover (^i/ialitis sanctoc-hdena:) — very closely allied to a 
species found in South Afnea, but presenting certain differences 
which entitle it to the rank of a pecuUar species. The plants, 
however, are of especial interest from a geographical point of 
view, and we must devote a few pages to their consideration as 
supplementing the scanty materials afforded by the animal life, 
thus enabling us better to understand the biological relations 
and probable history of the island. 

Xcdiie Vegetation of St. Helena. — Plants have certainly more 
varied and more effec-tual means of passing over wide tracts 
of ocean t!ian any kinds of animals. Their seeds are often so 
minute, of sxich small specific gravity, or so furnished with 
downy or winged appendages, as to be carried by the wind for 
enormous distances. The bristles or hooked spines of many 
small fruits cause them to become easily attached to the 
feathers of aquatic birds, and they may thus be conveyed for 
thousands of miles by these pre-eminent wanderers; while 
many seeds are so protected by hard outer coats and dense 
inner albumen, that montlis of exposure to salt water does not 
prevent them from germinating, as proved by the West Indian 
seeds that reach tiie Azores or even the west coast of Scotlami, 
and, what is more to the point, by the fact staled by Mr. MeUiss, 
that large seeds which have floated from Madagascar or 
Mauritius round the Cape of Good Hope, have been thrown on 
the shores of St. Helena and have then sometimes germinated ! 

We have therefore little difficulty in understanding how the 
island was first stocked with vegetable forms. Ulien it was 
so stocked (generally sjjeaking), is equally cleai-. For as the 
peculiar coleopterous fauna, of which an important fragment 
remains, is mainly composed of species which are spe:iallv 
attached to certain groups of plants, we maj' be sure that the 
plants were there long before the insects could establish them- 
selves. However ancient then is the insect fauna the flora 

ust be more ancient still. It must also be remembered that 
plants, when once established in a suitable climate and soil, soon 



\ se 
\m 



CHAP, xiv.] ST. IIELKXA. 295 

take possession of a country and occupy it almost to the complete 
exclusion of later immigrants. The fact of so many European 
weeds having overrun New Zealand and temperate North 
America may seem opposed to this statement, but it really is 
not so. For in both these cases the native vegetation has first 
been artificially removed by man and the ground cultivated ; 
and thei'c is no reason to believe that any similar ctfe^'t would 
be produced by the scattering of any amount of foreign seeil 
on ground already completely clothed witii an indigenous 
vegetation. We might therefoie conclude « priori, that the 
flora of such an island as St. Helena would be of an excessively 
ancient type, preserving for us in a slightly modified form 
examples of the vegetation of the globe at the time wlien 
the island first rose above the ocean. Let us see then what 
botanists tell us of its character and affinities. 

The truly indigenous flowering plants are about fifty in 
numV)er, besides twenty-six ferns. Forty of the former and ten 
of the latter are absolutely pe 'uUar to the island, and, as Sir 
Joseph Hooker tells us, " with scarcely an exception, cannot 
be regarded as very clo.se specific allies of any other plants 
at all. Seventeen of them belong to peculiar genera, and of 
tlie 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 speiies." The affinities of this flora are. 
Sir Joseph Hooker thinks, mainly African and espe:-ially South 
African, as indicated by the pre.^ence of the genera Phylica, 
Pelargonium, Mesembryanthemum, Oteospernium, and Wahlen- 
bergia, which are eminently characteristic of southern extra- 
tropical Africa. The sixteen ferns which are not peculiar are 
common either to Africa, India, or America, a wide range 
sufficiently explained by tlie dust-Hke spores of ferns, capable 
of being carried to unknown distances by the wind, and the 
great stability of theii" generic and specific forms, many of those 
found in the Miocene deposits of Switzerland being hardly 
distinguishable from living species. This shows, that identity 
of species of ferns between St. Helena and distant countries^, 
does not necessarily imply a recent origin. 

The Reiution of the St. Helena Compositce. — In an elaborate 



296 ISLAND LIFE. [par t n 

paper on the Composit;^,^ Mr. Bentham gives us some valuable 
remarks on the affiuities of the seven endemic species belonging 
to the genera Commidendron, Melanodendron, Petrobium, and 
Pisiadia, which form so important a portion of the existing 
flora of St. Helena. He says : " Although nearer to Africa 
than to any other continent, those composite denizens which 
bear evidence of the gi'eatest anti(|uity have their afiiuities 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 Audiue Diplostephium, and in the Australian Olearia. 
Petrobium is one of three genera, remains of a group probably 
of great antiquity, of which the two othere are Podanthus in 
Chile and Astemma in the Andes. The Pisiadia is an endemic 
species of a genus otherwise Mascarene or of Eastern Afiiea, 
presenting a geographical connection analogous to that of the 
St. Helena Melhaniae,^ with the Mascarene Trochetia." 

Whenever such remote and singular cases of geographical 
affinity as the above are pointed out, the first impression is 
to im.agine some mode by which a communication between 
the distant countries implicated might be effected ; and this 
way of viewing the problem is almost universally adopted, even 
by naturalists. But if the principles laid down in this work 
and in my Geojrajjhical DistribiUion of Animals are sound, 
such a course is very unphilosophical. For, on the theory of 
evolution, nothing can be more certain than that groups now 
broken up and detached were once continuous, and that frag- 
mentary groups and isolated forms are but the relics of once 
widespread types, which have been preserved in a few localities 
where the physical conditions were especially favourable, or 
where organic competition was less severe. The true explana- 
tion of all such remote geographical affinities i.s, 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 ; 

» "Notes on tlie Classification, History, and Geogripliieal Distribution 
of Compositse."— /oio-Hu? of the Linnean Societi/, Vol. XIII. p. 56.3 (1873). 

' The Mellianias comprise the two tinest timber trees of St. Helena, now 
almost extinct, the redwood and native ebonv. 



CHAP. XIV.] ST. HELENA. 297 

ami they no more imply any closer connection between tho 
distant countries the allied forms now inhabit, than does the ex- 
istence of living Equidae in South Africa and extinct Equidae in 
the Pliocene deposits of the Pampas, imply a continent bridging 
the South Atlantic to allow of their easy communication. 

Concluding Bemar/cs on St. Helena. — The sketch we have now 
given of the chief members of the indigenous fauna and flora of 
St. Helena shows, that by means of the knowledge we have 
obtained of past changes in the physical liistory of the earth, 
and of the various modes by which organisms arc 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 dist;\nt from surrounding continents, which 
became stocked by chance immigrants from other countries at 
some remote epoch, an<l which has preserved many of their more 
or less modified descendants to the present time. When first 
visited by civilised man it was in all proliability far more richly 
stocked witli ])lants and animals, fc^rming a kind of natural 
museum or vivarium in which ancient types, perhaps dating 
back to tiie Miocene period, or even earlier, had been saved from 
the destruction which has overtaken their alhes on the gi-eat • 
continents. Unfurtunately many, we do n<jt know how many, 
of these forms have been exterminated by the carelessness and 
improvidence of its civilised but ignorant rulers ; and it is only 
by the extreme ruggedness and inaccessibility of its peaks and 
crater-ridges tliat tlie scanty fragments have escaped by which 
alone we are able to obtain a glimpse of this interesting chapter 
in the life-history of our eartli. 



CHAPTER XV. 

THE SANDWICH ISLANDS. 

Position anil Physical features — Zoology of the Sindwicli Islands — Birds 
— lieptiles — L-.iud-sliells — Insects — Vegetation of the Sandwicli Islands 
— Peculiar features of the Hawaiian Flora — Antiquity of the Hawaiian 
Fauna and Flora — Concluding ohservations on the Fauna and Flora of 
the Sandwich Islands — General Remarks on Oceanic Islands. 

The Sandwich Islands are an extensive group of large islands 
situat<?d in the centre of" the North Pacific, being 2,350 
miles from the neare.'Jt part of the American coast — the bay 
of San Francisco, and about the same distance from the 
Marijuesas 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 P.vcific Islands by widely scattered coral reefs and 
atolls, the nearest of which, however, are six or seven hundred 
miles distant, and are all nearly destitute of animal or vegetable 
life. The group consists of seven large inhabited islands besides 
four rocky islets ; the largest, Hawaii, being seventy miles across 
and having an area of 3,800 square miles — being somewhat 
larger than all the other islands together. A better conception 
of this large island will be formed by comparing it with Devon- 
shire, with which it closely agrees both in size and shape, though 
its enormous volcanic mountains rise to nearly 1-1,000 feet high. 
Three of the smaller islands are each about the size of Hertford- 
shu'e or Bedfordshire, and the whole group stretches from north- 
west to south-east for a distance of about 350 miles. Though so 



CIlAl'. X\.] 



TIIK SAXLAVICII ISLAXDy. 



2!!9 



extensive, tlie entire arcliipelago is vulcanic, and tlie largest island 
is rendered sterile and cumparatively uninhabitable by its three 
active volcanoes and their widespread deposits of lava. 

The ocean depths by which these islands are separated from 
the nearest continents are enormous. North, east, and south, 
soundings have been obtained a little over or under three thousand 
fathoms, and these profound deeps extend over a large part of 




MAP OF THE SVNDWICH ISLANDS. 



The light tint shows whore the sen is less than 1,000 fnthoms deep. 
The lig .res s"i i\v the depth in fiilluiins. 



the North Pacific. "We may be quite sure, tlieref jre, that the 
Sandwich Lslaiids liave, during their whole existence, been as 
completely severed from the great continents as they are now ; 
but oil the west and Sfjuth there is a possibility of more exten- 
sive islands having existed, .serving as stepping-stones to the 
island groups of the Mid-Pacific. This is indicated by a few 
widely-.scattered coral islets, ar.iund wliidi extend coasiderable 



300 



ISLAND LIFK. 



[PAiir II. 



areas of less depth, varpng from two hundred to a thousand 
fathoms, and which tmiy therefore indicate tlie sites of submerged 
ishinds 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 anv ancient strati- 



I60E. na lyi ip> rra 



Ka 130 BO iio« 




=.. 170 160 170 

MAP OF THE NORTH P.^i;lrjc HJIU lis tiUBAlKHuKD BANKS. 

The light tint shows where the sen is le.ss than 1.000 fnthoms deep. 
The dark tint ,. .. ., m«r.; Ihiin 1,01)0 fiithoiiis deep. 

The figures show the depths in Tathoms. 



fied rocks (oxcejit, perhaps, in the Marq\iesas, where, according 
ti> Jules Marcou, granite and gneiss are said to occur) it seems 
probable that tlie innumerable coral-reefs and atolls, which occur 
in groups on deeply submerged banks, mark the sites of bygone 
Volcanic islands, similar to those whicli now exist, but which, after 



ciiAr. xv.J THE SANDWICH ISLAM'S. 301 

becoming extinct, have been lowered or destroyed by denudation, 
and finally, by subsidence of the earth's crust, have altogether 
disappeared except where their sites are indicated by the upward- 
growing coral-reefs. If this view is correct we sliould give up all 
idea of tlaere ever having been a Pacific continent, but should 
look upon that vast ocean as having from tlie remotest geologioil 
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 otliers 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 tlius have facilitated the transfer of organisms from one 
group to another, and more rarely even from tlie American, 
Asiatic, or Australian continents. Keeping these various facts 
and considerations in view, we may now proceed to examine the 
fauna and flora of the Sandwich Islands, and discuss the special 
phenomena they present. 

Zoology of the SandvAch Islands: Birds.— It need iKndly be 
said that indigenous mammalia are ([uitc unknown in the Sand- 
wich Islands, the most interesting of the higher animals being 
the birds, which are tolerably numerous and highly peculiar. Many 
aquatic and wading birds which range over the whole Pacific 
visit these islands, twenty-four species having been observed, 
but even of these five are peculiar — a coot, Fulica alai ; a 
moorhen, Gallinnla sandvicJicnsis ; a rail with i-udimentary 
wings, Pennnla mil lei ; and two ducks, A7ias Wyvilliana and 
Bernicla sandvichcnsis. The birds of prey are also great wan- 
derers. Four have been found in the islands — the short-eared 
owl, Oius hraclujotus, which ranges over the greater part of the 
globe, but is here said to resemble the variety found in Chile 
and the Galapagos ; the barn owl, Sti-ix Jlammea, of a variety 
common in the Pacific ; a peculiar sparrow-hawk, Accijnter 
hawaii ; and Butco solitarius, a buzzard of a peculiar species, 
and coloured so as to resemble a hawk of the American sub- 
family Polyborinse. It is to be noted that the genus Buteo 
abounds in America, but is not found in the Pa:-ific; and this 
fact, combined with the remarkable colouration, renders it almost 
certain that this ijeiuliar sjoecies is of American origin. 



302 



ISLAND LIFE. 



[I'ART II. 



Coming now to the Passeres, or true perching birds, we find 
sixteen species, all peculiar, belonging to ten genera, all but one 
of which are also peculiar. The following is a list of these 
extremely interesting birds : — 



I. MuscicAPiD.« (Flycatchers). 
1 . Chasiempii sandvichemis. 
'2. PhffornU obgeura. 

IL Meliphaoid^ (Honeysuckers.) 

.^. Mohoa nohilis. 

4. „ braccota. 

5. „ apicalin. 

6. Chcetoptila anguslipluma. 





III. Drepanidid-e 


7. 


Drrpanis rocciiiea. 


H. 


„ rosea. 


0. 


„ flavii. 


10. 


,, saiiguinea. 



DrepanididjB — continued. 

11. Hemignuthus olivaceus. 

12. „ ohscurus. 

13. „ lucidus. 
It. Loxops corcinea. 

1.5. ,, aurea. 

16. Lo-rioirlcs bailloni. 

1 7. Psitti'roxlra i>sitlarea. 

18. Frinr/illa anna (recently de- 

scribed, perhaps belongs also 
to this group). 

IV. CoRviD.E (Crows). 

19. Corvus hatcaiensis. 



Taking the above in the order here given, we have, first, two 
peculiar genera of flycatchers, a family confined to the Old 
World, but extending over the Pacific as far as the Marquesas 
Islands. Next we have two peculiar genera (with four species) 
of honeysuckers, a family confined to the Australian region, and 
also ranging over all the Pacific Islands to the Marquesas. We 
now come to the most important group of birds in the Sandwich 
Islands, comprising five peculiar genera, and eleven or twelve 
species, which are believed to form a peculiar family allied to the 
Oriental flower-peckers (Diceidse), and perhaps remotely to the 
American greenlets (Vireonidse), or tanagers (Tanagridse). 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 wdth any other 
knowTi 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 Comis. 

On the whole, the affinities of these birds are, as misrht be 



CHAP. XV.] THE SANDWICH ISLANDS. 30.^ 

expected, cliiefly witli Au.•^tralia and the Pacific Islands ; but they 
exhibit in the buzzard, one ot" tlie owls, and perhaps in sume 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 approach to it being made by New Zealand and Madagascar, 
which have a much more varied bird fauna and a smaller pro- 
IwHionate number of peculiar genera. These facts undoubtedly 
indicate(an immense antirpiity foi^ this group of islands, or the 
vicinity of some very ancient land (now submerged), from which 
some portion of their peculiar fauna might be derived. 

Reptiles. — The only other vertebrate animals are two lizards. 
One of these is a very widespread species, Ahlepharus pncilo- 
j)leun(,<s, said by Dr. Giinther to be fjund in Timor, Australia, 
the Samoa Islands, and the Sandwich Islands. It seems 
hardly likely that such a range can be due to natural causes. 
The other is said to form a peculiar genus of geckoes, but both 
its locality and affinities apjx>ar to be somewhat doubtful. 

Land-shells. — The only other group of anim.ils wiiicli has 
been carefully studied, and which presents features of especial 
interest, are tlie land-shelLs. These are very luimerous, about 
thirty genera, and between three and four hundred species having 
been described ; and it is remarkable that this single group con- 
tains as many species of land-shells as all the other Polynesian 
Islands from the Pelew Islan<ls and Samoa to the Marquesas. All 
the species are peculiar, and about three-fourths of the whole 
belong to peculiar genera, fourteen of which constitute the sub- 
family Achatinellinae, entirely confined to this group' of islands 
and constituting its most distinguishing feature. Thirteen genera 
(comprising sixty-four species) are found also in the other Poly- 
nesian Islands, but three genera of Auriculidse (Plecotrema, 
Pedipes, and Blauneria) are not found in the Pacific, but in- 
habit — the former genus Australia, China, Bourbon, and Cuba, 
the two latter the West Indian Islands. Another remarkable 
peculiarity of the.se islands is the small number' of Opercu- 
lata, which are represented by only one genus and five species, 
while the other Pacific Islands have twenty genera and 115 
species, or more than half the number of tlie Inrtperculata. 



304 ISLAND LIFE. [part ii. 

This difference is so remarkable that it is worth stating in a 
comparative form : — 

Inoperou'ala. OperculaU. Auriclf.id^ 

Sandwich Islands •->32 5 9 

Rest of Tacific Islands 200 115 16 

When we remember that in tlie West Indian Islands the 
Operculata abound in a greater proportion than even in the 
Pacific Islands generally, we are led to the conclusion that lime- 
stone, which is plentiful in both these areas, is especially favour- 
able to them, wliile the purely volcanic rocks are especially 
unfavourable. The other peculiarities of the Sandwich Islands, 
however, such as the enormous preponderance of the strictly 
endemic Achatinellinse, and the presence of genera which occur 
r elsewliere only beyond the Pacific area in various parts of the 
great continents, vindoubtcdl}' point to a very remote origin, at a 
time wlien the distribution of many of the groups of mollusca 
was very different from that which now prevails. 

A very interesting feature of the Sandwich group is the extent 
to which the species and even the genera are confined to separate 
islands. Thus tlie genera Carelia and Catinella with eight 
species are poniliar to the island of Kaui ; Bulimella, Apex, 
Frickella, and Blauneria, to Oahu ; Perdicella to Maui ; and Ebur- 
nella to Lanai. The Kev. John T. Gulick, who has made a 
special study of the Achatinellinpe, informs us that the average 
range of the species in this sub-family is five or six miles, while 
some are restricted to but one or two square miles, and only very 
few have the range of a whole island. 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 kno\vn. This is partly due to its being more forest clad, 
but also, no doubt, in part to its being better explored, so that 
notwithstanding the exceptional riches of the group, we have 
no reason to suppose that there are not many more species to be 

' Journal of the Lhmean Society, 1873, p. 496. "On Diversity of 
Evolution under one set of External Conditions." Proceedings of the 
Zoological Society of London, 1873, p. 80. "On the Classification of the 
Acliatinellidie." 



CHAP. XV.] THE SANDWICH ISLA^'DS. 3.')5 



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 
Achatiuellidse, represented by 700 or 800 varieties. The most 
important peculiar genus, not belonging to the Achitinella group, 
is Carelia, with six species and several named varieties, all 
peculiar to Kaui, the most westerly of the large islands. 
This would seem to show that the small islets strctchinsr 
westward, and situated on an extensive bank with less than a 
thousand fathoms of water over it, may indicate the position 
of a large submerged island whence some portion of the 
Sandwich Island fauna was derived. 

Insects. — Unfortunately we have as yet no such knowledge of 
the insects of these islands as we posse.ss in the case of the 
Azores and St. Helena, but some considerable collections have 
been sent over by Mr. T. Blackburn, now resident there, and we 
may therefore soon possess fuller and more accurate information. 
Although insects are said to be very scarce, yet all tlie chief tribes 
of Coleoptera appear to be represented, though as yet by very 
few species. These appear to be for the most part peculiar, but 
to have widespread afSnities. The majority, as might be ex- 
pected, aie allied to Polynesian, Australian, or Malayan forms ; 
some few are South American (perhaps introduced), while others 
show north temperate affinities. There are several new genera, 
and one peculiar group of six species is said to form a new family 
allied to the Anthribidee. A new genus of Lucanidae is said to 
be allied to a Chilian genus. If we consider the greater facilities 
of insects for dispersal when compared with birds or land-shells, 
the characteristics of the insect fauna, so far as yet known, are 
sufficiently in harmony with the amount of speciality and 
isolation presented by the latter groups. 

Vegetation, of the Sandwich Islands. — The flora of these islands 
is in many respects so peculiar and remarkable, and so well sup- 
plements the information derived from its interesting but scanty 
fauna, that a brief account of its more striking features will not 
be out of place; and we fortunately have a pretty full know- 
ledge of it, owing to the researches of the American botanist 

X 



306 ISLAND LIFE. [i'aut ii. 

Horace Mann, and of Dr. Pickering, who accompanied the 
United States Exploring Expedition. 

Considering their extreme isolation, their uniform volcanic 
soil, and the large proportion of the chief island which consists 
of barren lava-fields, the flora of the Sandwich Islands is ex- 
tremely rich, consisting, so far as at present known, of 554 
species of flowering plants and 135 ferns. This is considerably 
richer than the Azores (439 Phanerogams and 39 ferns), which 
though less extensive are far better known, or than the Gala- 
pagos (332 Phanerogams), which are more strictly comparable, 
being equally volcanic, while their somewhat smaller area may 
perhaps be compensated by their proximity to the American 
continent. Even New Zealand with more than twenty times 
the area of the Sandwich group, whose soil and climate 
are much more varied, and whose botany has been tlioroughly 
explored, has not double the number of flowering plants 
(935 species), while in ferns it is barely equal. 

Peculiar Features of the Flora. — This rich insular flora is won- 
derfully peculiar, for if we deduct sixty-nine species, which are 
believed to have been introduced by man, there remain 620 
species of which 377, or more than three-fifths, are quite pecuhar 
to the islands. There are no less than 39 peculiar genera out of 
a total of 253, and these 39 genera comprise 153 species, so that 
the most isolated forms are those which most abound and thus 
give a special character to the flora. Besides these peculiar 
types, several genera of wide range are here represented by 
highly peculiar species. Such are Lobelia, the Hawaiian species 
of which are woody shi'ubs from six to twenty feet high, one 
even being a tree, reaching a height of forty feet. Shrubby 
geraniums fifteen feet high giow as epiphytes on forest trees, as 
do some Vacciniums and Epacrids. Violets, and plantains also 
form tall shrubby plants, and there are many strange arborescent 
composita?, as in other oceanic islands. 

The affinities of the flora generally are very wide. Although 
there are many Polynesian groups, yet Australian, New Zealand, 
and American forms are equally represented. Dr. Pickering 
notes the total absence of a large number of famihes found in 
Southern Polynesia, such as Dilleniaceae, Anonacese, Olacacese, 



CHAP. XV.] THE SANDWICH ISLAN US. 307 

Aurantiaceee, Guttiferaj, Malpighiacese, Meliacese, Combretaceae, 
RhizophoracetC, Melastomacese, Passifloracese, Cunoniacese, 
Jasniinaceje, Acautliacese, Myristicace£e, Casuaracese, Scita- 
minese, and Aracae, as well as the genera Clerodendrum, Ficus, 
and epidendric orchids. Austrahan affinities are shown by the 
genera Exocarpus, Cyathodes, Melicope, Pittosporum, and by a 
phyllodinous Acacia. New Zealand is represented by Ascariua, 
Coprosma, Acsena, and several Cyperaceae; while America is 
represented by the genera Nama, Gunnera, Phyllostegia, Sisy- 
rinchium, and by a red-flowered Rubus and a yellcw-flowered 
Sanicula allied to Oregon species. 

There is no true alpine flora on the higher summits, but 
several of the temperate forms extend to a great elevation. 
Thus Mr. Pickering records Vaccinium, Ranunculus, Silene, 
(inaphaliuni and Geranium, as occurring above ten thousand 
feet elevation ; while Viola, Drosera, Acsna, Lobelia, Edwardsia, 
DodoniBa, Lycopodium, and many Coinpositai, range above six 
thousand feet. Vaccinium and Silene are very interesting, as 
they are peculiar to the North Temperate zone, except one Silene 
in South Africa. 

The proportionate abundance of the different families in tliis 
interesting flora is ;is follows : — 

12 species. 



1. 


Composita?, 


47 species. 


11. 


Piperace.-c, 


12 


2. 


Cyiicracete, 


39 


>i 


12. 


Convolviilacea', 


12 


3. 


LobeliaceiC, 


35 


j» 


13. 


Malvacejp, 


12 


4. 


Eubiiice^, 


33 


jj 


14. 


Amarantaceae, 


9 


5. 


Labiatffi, 


27 


J) 


15. 


Araliacea;, 


8 


6. 


LeguininosiP, 


20 


j> 


16. 


Violacea;, 


6 


7. 


Rutacefe, 


17 


>j 


17. 


Pittosporacese, 


6 


8. 


Caryo])liyllaceje 


>14 


jj 


18. 


Myrtaceie, 


6 


9. 


(icsueriaceiB, 


u- 


?» 


19. 


Goodeniacese, 


6 


10. 


Urticaceas, 


13 


>» 


20. 


Tljyiuelaceffi, 


6 



Four other orders, Geraniacese, Rhamnacea3, Rosacese, ami 
Cucurbitaceas, have five species each ; and among the more im- 
portant orders which have less than five species each are Ranun- 
culacese, Ericaceaj, Primulacese, Polygonacese, Orchidacese, and 
JuncacesE. In the above enumeration the grasses (Graminacese) 
are omitted, as they were not described at the time Mr. Mann's 

X 2 



■% 



308 



ISLAND LIFE. 



[I'ART 11. 



article was written. The most remarkable feature here is the 
great abundance of Lobeliacese, a character of the flora which is 
probably unique ; while the superiority of Labiatae to Legumi- 
nosse and the scarcity of Rosacese and Orchidaceae are also very 
unusual. Composites, as in most temperate floras, stand at the 
head of the hst, and as these have been carefully studied by Mr. 
Bentham, it will be interesting to note the afiinities which they 
indicate. Omitting four genera and species which are cosmo- 
politan, and have no doubt entered with civihsed man, there 
remain twelve genera and forty-four species of Compositaj in the 
islands. All the species are peculiar, as are sis of the genera ; 
and in another genus, Coreopsis, the sis species form a peculiar 
named section or subgenus, CamjJylotheca ; while the genus 
Lipochasta with ten species is only known elsewhere in the 
Galapagos, where a single species occurs. We may therefore 
consider that eight out of the twelve genera of Hawaiian Com- 
positte are really confined to the Archipelago. The relations of 
the genera are thus given by ilr. Bentham : — 





No of 
Species. 


Lagenopliora 
Aster 


1 

1 


Tetramolobiuiu 


G 


Vittadinia 


1 


Cumpylotlieca (s 


■g)6 


Bideus 


1 


Lipoclia^ta 


10 


Arfryroxipliiuin 
Wilkesia 


2 

1 


Dubantia 


3 


Baillardia 


11 


Hesperomannia 


1 



External Relations of the Species. 
Witli the Old World and Extra-Tropical America. 
American and Extra-Tropical Old World. 
South Extra-Tropical American. 
South Extra-Tropical American and Australian. 
With the Tropical American and verj' few Old 

World species of Coreopsis and Bidens. 
The Tropical American species. 
American Wedelioida; and Helianthioidoe. 
With MadieiB of the Mexican region. 
With Mudiea? of the Mexican region. 
Distantly with Madiea3 and Galinsogea; of the 

Mexican region. 
With Raillardella of the Mexican region. 
With Stifftia and Wunderlichia of the Brazilian 
region. 

The great preponderance of American relations of the Com- 
posite, as above indicated, is very interesting and suggestive. 
It is here that we meet with some of the most isolated and re- 
markable forms, implying great antiquity ; and when we consider 
the enormous extent and world-wide distribution of this order 



cn.w. X v.] THE SANDWICH ISLANDS. 309 

(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 tliat its origin dates back to a very remote epocli. 
We may therefore look upon the Compositae as representing the 
most ancient portion of the existing flora of the Sandwich Tslnnds, 
carrying us back to a very remote period when the facilities for 
communication with America were greater than they are now. 
This may be indicated by the two deep submarine banks in the 
North Pacific, between the Sandwich Islands and San Francisco, 
which, from an ocean floor nearly 3,000 fathoms deep, rise up to 
within a few hundred fathoms of the surface, and seem to indi- 
cate the subsidence of two islands, each about as Lu-ge as Hawaii. 
The plants of Nortli Temperate affinity may be nearly as old, but 
these may have been derived from Nortliern Asia by way of 
Japan and tiie extensive line of shoals which run north-west- 
ward from the Sandwich Islands, as shown on our map. Those 
which exhibit Polynesian or Australian affinities, consisting for 
tlie most part of less highly modified species usually of the same 
genera, may have had their origin at a later, though still some- 
what remote period, when large islands, indicated by the exten- 
sive shoals to the south and soutii-west, off"ered facilities for the 
transmission of plants from the tropical portions of the Pacific 
Ocean. 

Antiquity of the Hawaiian Fauna and Flora. — The great auti- '« 
quity implied by the peculiaritiesof thefauna andflora, no lessthan 
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 I.slands. 
FoiLjlie— eSfliest immigrants would soon occupy much of the 
surface, and become specially modified in accordance with the 
conditions of the locality, and these would serve as a barrier 
against the intrusion of many forms which at a later period 
spread over Polynesia. The extreme remoteness of the islands, 
and the probability that they have always been more isolated 
than those of the Central Pacific, would also necessarily result in 
an imperfect and fragmentary representation of the flora of 
surrounding lands. 



310 ISLAND LIFE. [pabt ii. 

Concluding OhservcUiov.s o)i the Fauna and Flora of tlie Sand- 
wich Islands. — The indications tlius afforded by a stiidy of the 
flora seem to accord well with what we know of the fauna of the 
islands. Plants having so much greater facilities for dispersal 
than animals, and also having greater specific longevity and 
greater powers of endurance under adverse conditions, exhibit 
in a considerable degree the influence of the primitive state of 
the islands and their surroundings; while members of the 
animal world, passing across the sea w4th greater difficulty and 
subject to extermination b) a variety of adverse conditions, 
retain much more of the impress of a recent state of things, 
with perhaps here and there an indication of that ancient 
approach to America so clearly shown in the Compositas and 
some other portions of the flora. 

General licmarks on Oceanic Islands. — We have now reviewed 
the main features presented by the assemblages of organic forms 
which characterise the more important and best known of the 
Oceanic Islands. They all agree in the total absence of indi- 
genous mammalia and amphibia, while their reptiles, when they 
possess any, do not exhibit indications of extreme isolation and 
antiquity. Their birds and insects present just that amount of 
specialisation and diversity from continental forms which may 
be best explained by the known means of dispersal acting 
through long periods ; their land shells indicate greater isolation, 
owing to their admittedly less effective means of conveyance 
across the ocean ; while their plants show most clearly the 
effects of those changes of conditions which we have reason to 
believe have occun-ed during the Tertiary epoch, and preserve 
to us in highly specialised and archaic forms some record of the 
primeval immigration by which the islands were originally 
clothed with vegetation. But in every case the series of forms 
of life in these islands is scanty and imperfect as compared with 
fai- less favourable continental ai-eas, and no one of them presents 
such an assemblage of animals or plants as we always find in an 
island which we know has once formed part of a continent. 

It is still more important to note that none of these oceanic 
archipelagoes present us with a single type which we may 
suppose to have been preserved from Mes(jzoic times ; and this 



CHAP. XV.] OCEANIC ISLANDS. 311 

fact, taken in connection with the volcanic or coralline origin of 
all of them, powerfully enforces the conclusion at wliich we have 
arrived in the earUer portion of this volume, that during the 
whole period of geologic time as indicated by tlie 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 laud changed place repeatedly as was 
once supposed — had our deepest oceans been the seat of great 
continents while the site of our present continents was occupied 
by an oceanic abyss — is it possible to imagine that no fragments 
of such continents would remain in the present oceans, bringing 
down to us some of their ancient forms of life preserved with 
but Httle change ? The correlative facts, that the islands of our 
great oceans are all volcanic (or coralline built probably upuu 
degraded and submerged volcanic islands), and that their pro- 
ductions are all more or less clearly related to the existing in- 
habitants of the nearest continents, are hardly consistent with 
any other theory than the permanence of our oceanic and 
continental areas. 

We may here refer to the one apparent exception, which, 
however, lends additional force to the argument. New Zealand 
is sometimes classed as an oceanic island, but it is not so really ; 
and we shall discuss its peculiarities and probable origin 
further on. 



I 



CHAPTER XVI. 

CONTINENTAL ISLANDS OF RECENT ORIGIN : GREAT BRITAIN. 

Characteristic Features of Recent Continental Islands — Recent Physical 
Changes of the Britisli Isles — Proofs of Former Elevation — Submerged 
Forests — Biiried River Channels — Tune of Last Union with the Conti- 
nent — Why Britain is poor in Species — Peculiar British Birds — Fresh- 
water Fislies — Cause of Great Speciality in Fishes — Peculiar British 
Insects — Lepidoptera confined to the British Isles — Peculiarities of the 
Isle of Man — Lepidoptera — Coieoptera confined to the British Isles — 
Trichoptera peculiar to the British Isles — Land and Freshwater 
Shells — Peculiarities of the British Flora — Peculiarities of the Irish 
Flora — Peculiar British Mosses and Hepaticas — Concluding Remarks 
on the Peculiarities of the British Fauna and Flora. 

We now pmcecd to examine those islands which are the very 
reverse of tlie "oceanic" cla.ss, being fragments of continents or 
of larger islands from which they have been separated by sub- 
sidence of the intervening land at a period which, geologically, 
must be considered recent. Such islands are always still con- 
nected with their parent land by a shallow sea, usually indeed 
not exceeding a hundred fathoms deep ; they always possess 
mammalia and reptiles either wholly or in large proportion 
identical with those of the mainland ; while their entire flora 
and fauna is characterised either by the total absence or com- 
parative scarcity of those endemic or peculiar species and genera 
1 which are so striking a feature of all oceanic islands. Such 
islands will, of course, differ from each other in size, in antiquity, 
and in the richness of their respective faunas, as well as in their 
distance from the parent land and the facilities for intercom- 
munication with it ; and these diversities of conditions will 
manifest themselves in the greater or less amount of speciality 
of their animal pr(idtictions. 



CHAP. XVI.] THE BRITISH ISLES. 313 

This speciality, when it exists, may have been brought about 
in two ways. A species or even a genus may on a continent 
have a very limited area of distribution, and this area may be 
wholly or almost wholly contained in the separated portion or 
island, to which it will henceforth be peculiar. Even when the 
area occupied by a species is pretty equally divided at the time 
of separation between the island and the continent, it may 
happen that it will become extinct on the latter, while it may 
survive on the former, because the limited number of individuals 
after division may be unable to maintain themselves against the 
severer competition or more contrasted climate of the continent, 
while they may flourish under the more favourable insular 
conditions. On the other hand, when a species continues to 
exist in both areas, it may on the island be subjected to some 
modifications by the altered conditions, and may thus come to 
present characters which differentiate it from its continental 
allies and constitute it a new species. We shall in the course of 
our survey meet with cases illustrative of both these processes. 

The best examples of recent continental i.slands are Great 
Britain and Irelanrl, 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 Phydcal Changes in the British Isles. — Great Britain 
is perhaps the most typical example of a large and recent con- 
tinental island now. to be found upon the globe. It is joined to 
the continent by a shallow bank which extends from Denmark 
to the Bay of Biscay, the 100 fathom line from these extreme 
points receding from the coasts so as to include the whole of the 
British Isles and about fifty miles beyond them to the westward. 
{See Map.) Beyond this line the sea deepens rapidly to the 500 
and 1,000 fathom lines, the distance between 100 and 1,000 
fathoms being from twenty to fifty miles, except where there is 
a great outward curve to include the Porcupine Bank 170 miles 
west of Galway, and to tlie north-west of Caithness where a 



314 



ISLAND LIFE. 



[part II- 



narrow ridge less than 500 fathoms below the surface joins the ex- 
tensive bank under 300 fathoms, on which are situated the F;u-oe 
Islands and Iceland, and which stretches across to Greenland. 
In the North Channel between Ireland and Scotland, and in the 




MAP SHOWING THE SHALLOW SANE OONNECTING THE BRITISH I3LKS WITH THE CONIINKNT. 

The light tint indicati's a depth of less than 100 rathums. 

The ligures show the depth in fathoms. 

The narrow channel between Norway and Denmark is 2.5S0 feet deep. 

Minch between the outer Hebrides and Skye, are a series of 
hollows in the sea-bottom from 100 to 150 fathoms deep. 
These con-espond exacth' to the j)oints between the opposing 



rnAP. XVI.] TUB BRITISH ISLES. 315 

highlands where the greatest accumulations of ice wonkl 
necessarily occur during the glacial epoch, and they may well 
be termed submarine lakes, of exactly the same nature as 
those which occur in similar positions on land. 

Proofs of Former Elevation — Svhmerijal Forests. — What renders 
Britain particularly instructive as an example of a recent con- 
tinental island is the amount of direct evidence that exists, of 
several distinct kinds, showing that the land has been sufficiently 
elevated (or the sea depressed) to unite it with the continent, 
— and this at a very recent period. The first class of evidence 
is the existence, all round our coasts, of the remains of sub- 
marine forests often extending far below the present low-water 
mark. Such are the submerged forests near Torquay in Devon- 
shire, and near Falmouth in Cornwall, botli containing stumps 
of trees in their natural position rooted in the soil, with deposits , 
of peat, branches, and nut.s, and often with remains of insects 
and other land animals. These occur in very different conditions 
and situations, and some have been explained by changes in the 
height of the tide, or by pebble banks shutting out the tidal 
waters from estuaries ; but there are numerous examples to 
which such hypotheses cannot apply, and which can only be 
explained by an actual subsidence of tlie 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 Devonsliire, 
at Blackpool near Dartmouth : — 

" We were so fortunate as to reach the beach at spring-tide 
low-water, and to find, admirably exposed, by far the finest 
example of a submerged forest which I have ever seen. It 
occupied a rectangular area, extending from the small river or 
stream at the western end of the inlet, about one furlong east- 
ward ; and from the low-water line thirty yards up the strand. 
The lower or seaward portion of the forest area, occuppng about 
two-thirds of its entire breadth, consisted of a brownish drab- 
coloured clay, whicli was crowded with vegetable debris, such 
as small twigs, leaves, and nuts. There were also numerous 
prostrate tranks and branches of ti-ees, Ij'ing partly imbedded 



316 ISLAND LIFE. [pAUTir. 

in the clay, without anytliing 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 sharj) 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 
horizontahty 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 fore-st area reached the spring-tide low-water 
line ; hence as the greatest tidal range on this coast amounts 
to eighteen feet, we are warranted in inferring that the sub- 
sidence amounted to eighteen feet as a minimum, even if we 
suppose that some of the trees grew in a soil the surface of 
which was not above the level of high water. There is satis- 
factory evidence that in Torbay it was not less than forty feet, 
and that in Falmouth Harbour it amounted to at least sixty- 
seven feet." ^ 

On the coast of the Bristol Channel similar deposits occur, 
as well as along much of the coast of Wales and in Holyhead 
Harbour. It is believed by geologists that the whole Bristol 
Channel was, at a comparatively recent period, an extensive 
plain, through which flowed the River Severn ; for 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 hyenas ; facts which can only be 
explained by the existence of some extent of dry land stretching 
seaward from the present cliffs, but since submerged and washed 
' Geological Magazine, 1870, p. Ifi5. 



niAP. XVI.] THE BRITISH ISLES. 317 

away. This plain may have continued down to very recent times, 
since the whole of the Bristol Channel to beyond Lundy Island 
is under twenty-five fathoms deep. In the east of England 
we b.ave a similar forest-bed at Cromer in Norfolk ; and in the 
north of Holland an old land surface has been found fifty-six 
feet below high-water mark. 

Buried River Channels.— ^t\\\ more remarkable are the buried 
river channels which have been traced on many parts of our 
coasts. In order to facilitate the study of the glacial deposits 
of Scotland, Dr. James Croll obtained tlie 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 tliat there are ancient valleys and river channels 
at depths of from lUU to 200 feet below the present searlevel. 
These old rivers sometimes run in quite different directions from 
the present lines of drainage, connecting what are now distinct 
valleys ; and they are so completely filled up and hidden by 
boulder clay, drift, and sands, that there is no indication of their 
presence on the surface, which often consists of mounds or low 
hills more than 100 feet high. One of these old valleys connects 
the Clyde near Dumbarton with the Forth at Grangemouth, and 
appears to have contained two streams flowing in opposite directions 
from a watershed about midway at Kilsith. At Grangemouth 
the old channel is 2G0 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 j^laces 
the old valley was a ravine with precipitous rocky walls, which 
have been found in mining excavations. Dr. Geikie, who has 
himself discovered many similar buried valleys, is of opinion 
that " they unquestionably belong to the period of the boulder 
clay." 

We have here a clear proof that, when these rivers were 
formed, the land must have stood in relation to the sea at least 
260 feet higher than it does now, and probably much more ; and 
this is sufficient to join England to the continent. Supporting 
this evidence, we have freshwater or littoral shells found at great 
depths off our coasts. Mr. Godwin Au.sten records the dredging 
' Transactions of the Edinburgh Geoloyical Socieli/, Vol. I. p. 330. 



318 ISLAND LIFE. [part ii. 

up of a freshwater shell ( Unio pictorum) off the mouth of the 
English Channel between the fifty fathom and 100 fathom 
lines, while in the same locality gravel banks with littoral shells 
now lie under sixty or seventy fathoms water. ^ More recently 
Mr. Gwyn Jeffreys has recorded the disc■o^'ery 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 tliis great depth is a distinct indication 
of considerable subsidence. - 

.- Time of last Union with the Continent. — The period when 
this last union with the continent took place was comparatively 
recent, as shown by the identity of the shells with living species, 
and the fact that the buried river channels are all covered with 
clays and gravels of the glacial period, of such a character as 
to indicate that most of them were deposited above the sea- 
level. From these and various other indications geologists are 
all agreed that the last continental period, as it is called, was 
subsequent to the greatest development of the ice, but probably 
before the cold epoch had wholly passed away. But if so 
recent, we should naturally expect our land still to show an 
almost perfect community with the adjacent parts of the con- 
tinent in its natural productions ; and such is found to be the 
case. AU 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 pecuhar 
may be accounted for either by an original local distribution, 
by preservation here owing to favourable insular conditions, or 
by shght modifications having been caused by these conditions 
resulting in a local race, sub-species, or species. 

MHiy Britain is2}oor in >S)jfrics. — The former union of our islands 
with the coutineut, is not, however, the only recent change they 
have undergone. There is equally good evidence that a consider- 
able portion, if not the entire area, has been submerged to a depth 
of nearly 2,000 feet (see Chap. IX. p. IGS), at which time only 
what are now the highest mountains would remain as groups 
of rocky islets. This Eubmersion must have destroyed the 

1 Quarterli/ Jmirnal of Geolot/ical Societi/, 1850, p. 96. 
^ British Associalioii Report, Dundee, 1867, p. 431. 



CHAP. XVI.] THE BRITISH ISLES. 319 

greater part of the life of our country ; and as it certainly 
occurred during the latter part of the glacial epoch, the sub- 
sequent elevation and union with the continent cannot have 
been of very long duration, and this fact must have had an 
important bearing on the character of the existing fauna and 
flora of Britain. We know that just before and during the 
glacial period we possessed a fauna almost or (juite identical 
with that of adjacent parts of the continent and equally rich 
in species. The submergence destroyed this fauna ; and the per- 
manent change of climate on the passing away of the glacial 
conditions appears to have led to the extinction or migration 
of many species in the adjacent continental areas, where they 
were succeeded by the assemblage of animals now occupying 
Central Europe. When England became continental, these 
entered our country ; but suiScient time does not seem to have 
elapsed for the migration to have been completed before sub- 
sidence again occurred, cutting off the further influx of purely 
terrestrial animals, and leaving us without the number of species 
which our favourable climate and varied surface entitle us to. 

To this cause we must impute our comparative poverty in 
mammalia and reptiles — more marked in the latter than the 
former, owing to their lower vital activity and smaller powers 
of dispersal. Germany, for example, possesses nearly ninety 
species of land mammalia, and even Scandinavia about sixty, 
while Britain has only forty, and Ireland only twenty-two. The 
depth of the Irish Sea being somewhat greater than that of the 
German Ocean, the connecting land would there probably be 
of small extent and of less duration, thus offering an additional 
barrier to migration, whence has arisen the comparative zoological 
poverty of Ireland. This poverty attains its maximum in the 
reptiles, as shown by the following figures : — 

Belgium lias 22 .species of reptiles and amphibia. 
Britain „ l.S 
Ireland „ 4 „ 

Where the power of flight existed, and thus the period of 
migration was prolonged, the difference is less marked ; .so that 
Ireland has seven bats to twelve in Britain, and about 110 as 
against 130 land-birds. 



320 ISLAND LIFE. [part it. 

Plants, which have considerable facilities for passing over the 
sea, are somewhat intermediate ia proportionate numbers, there 
being about 970 flowering plants and ferns in Ireland to 1425 in 
Great Britain, — or almost exactly two-thirds, a proportion inter- 
mediate between that presented by the birds and the mammalia. 

Peculiar British Birds. — Among our native mammaUa, reptiles, 
and amphibia, it is the opinion of the best authorities that we 
possess neither a distinct species nor distinguishable variety. In 
l)ir(ls, however, the case is different, since some of our species, 
in particular our coal-tit {Panis ater) and long-tailed tit {Parus 
ccncdatus) present well-marked differences of colour as compared 
with continental specimens ; and in Mr. Dresser's work on the 
Birds of Eiiroix they are considered to be distinct species, while 
Professor Newton, in his new edition of Yarrell's British Birds, 
does not consider the difference to be sufficientlj' great or suffi- 
ciently constant to warrant this, and therefore classes them as 
insular races of the continental species. We have, however, 
one undoubted case of a bird peculiar to the British Isles, in the 
red grou.se {Lagopus scoticus), which abounds in Scotland, Ireland, 
the North of England, and Wales, and is very distinct from any 
continental species, although closely allied to the willow gi-ouse 
of Scandinavia. This latter species resembles it considerably in 
its summer plumage, but becomes pure white in winter ; whereas 
our species retains its dark plumage throughout the year, be- 
coming even darker in winter than in summer. We have here 
therefore a most interesting example of an insular form in our 
own country ; but it is difficult to determine how it originated. 
On the one hand, it may be an old continental species which 
during the glacial epoch found a refuge here when driven from 
its native haunts by the advancing ice ; or, on the other hand, it 
may be a descendant of the Northern wiUow grouse, which has 
lost its power of turning white in winter owing to its long re- 
sidence in the lowlands of an island where there is little permanent 
snow, and where assimilation in colour to the heather amons 
which it lurks is at all times its best protection. In either case 
it is equally interesting, as the one large and handsome bird 
which is peculiar to our islands notwithstanding their recent 
separation from the continent. 



CHAP. XVI.] THE BRITISH ISLES. 321 



The following is a list of the birds now held to be peculiar to 
the British Isles : — 

1. Parus britansicus ...Closely allied to P. ater of the continent ; a local 

race or sub-species. 

2. Parus rosea Allied to P. caiidatus of the continent. 

3. Lagopus scoticus Allied to L.albus of Scandinavia, but verj' distinct. 

Freshwater Fishes.— Mthoxigh the productions of fresh waters 
have generally, as Mr. Darwin has shown, a wide range; fishes 
appear to form an exception, many of them being extremely 
limited in distribution. Some are confined to particular river 
valleys or even to single rivers, others inhabit the lakes of a 
limited district only, while some are confined to single lakes, 
often of small area, and these latter offer examples of the most 
restricted distribution of any organisms whatever. Cases of this 
kind are found in our own islands, and deserve our especial atten- 
tion. It has long been known tliat some of our lakes possessed 
peculiar species of trout and charr, but how far these were un- 
known on the continent, and how many of those in different 
parts of our islands were really distinct, had not been ascertained 
till Dr. Giinther, so well known for his extensive knowledge of 
the species of fishes, obtained numerous specimens from every 
part of the country, and by comparison with all known con- 
tinental species determined their specific differences. The 
striking and unexpected result has thus been attained, that 
no less than fifteen well-marked species of freshwater fishes 
are altogether peculiar to the British Islands. The following 
is the list, with their English names and localities : — ^ 

Freshwater Fishes peculiar to the British Isles. 



Latin Name. 

1. Salmo brachtpoma. 

2. „ gallivexsis . 

3. „ orcadensis.. 

4. „ FEROX 



English Xame. 

Short-headed salmon 

Gal way sea-trout .... 
Loch Stennis trout . . 
Great lake-trout 



Locxrlity. 

Firth of Forth, Tweed, 
Ouse. 

Galway, West Ireland. 

Lakes of Orkney. 

Larger lakes of Scot- 
land, the N. of Eng- 
land, and Wales. 



^ The list of names was furnished to me by Dr. Giinther, and I have 
added the localities from the papers containing the original descriptions, 
and from Dr. Haughton's British Freshwater Fishes. 

Y 



322 



ISLAND LIFE. 



[part II. 



Latin Nain^. 

5. Salmo stomachiccs . 

6. „ nigripesxis .. 

7. „ levexeksis ... 



English Name. 

Gillaroo trout 

Black-finned trout . 

Loch Leven trout .. 



8. ., Perish Welsh charr 

9. „ WiLLCGHBii.. I Windermere charr. . . 

10. ,, KiLLiSENSis .. I Lough Killin charr .. 

11. „ CoLii Cole'scharr 

12. „ Grati Gray's charr 

13. CoREGOSUS CLCPE- The gAvyniad, or 

oiDBS Schelly 

14. „ vAKDESlus j The vendace 

15. „ POLLAX.... The poUan 



Locality. 

Lakes of Ireland. 

Mountain lochs of 
Wales and Scotland. 

Loch Leven, Loch 
Lomond, Winder- 
mere. 

Llanberris lakes, N. 
Wales. 

Lake Windermere and 
others in N. of Eng- 
land, and Lake Brui- 
ach in Scotland. 

Eillin lake in Mayo, 
Ireland. 

Lough Eske and Lough 
Dan, Ireland. 

Lough Melvin, Leitrim, 
X. W. Ireland. 

Loch Lomond, Ulles- 
water, Haweswater, 
and Bala lake. 

Loch Maben, Dum- 
friesshire. 

Lough Xeagh and 
Lough Eame, 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 form and size of the 
fins, the number of the fin-rays, and the form or proportions of 
the head, body, or tail. They are in fact, as Dr. Giinther 
assures me, just as good and distinct species as any other re- 
cognised species of fish. It may indeed be objected that, until 
all the small lakes of Scandinavia are explored, and their fishes 
compared with ours, we cannot be sure that we have any pecuhar 
species. But this objection has very little weight if we consider 
how our own species vary from lake to lake and from island to 
island, so that the Orkney species is not found in Scotland, and 
not one of the peculiar British species extends to Ireland, which 
has no less than six species altogether pecuhar to it. If the 
species of our own two islands are thus distinct, what reason have 
we for believing that they will be othem-ise than distinct from 
those of Scandinavia ? At all events, with the amount of evi- 
dence we already possess of the very restricted ranges of many of 



ciiAr. XVI,] THE BRITISH ISLES. 323 



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 tlie two main causes of specific change — 
isolation and altei'cd conditions — ai'e each more powerful than in 
Britain. Whatever difficulty continental fishes may have in 
passing over to Britain, that difficulty will certainly be increased 
by the second sea passage to Ireland ; and the latter country has 
been longer isolated, for the Irish Sea with its northern and 
southern channels is considerably deeper than the German Ocean 
and the eastern half of the English Channel, so that, when the 
last subsidence occurred, Ireland would have been an island for 
some length of time while England and Scotland still formed 
part of the continent. Again, whatever differences have been 
produced by the exceptional climate of our islands will have been 
greater in Ireland, where insular conditions are at a maximum, 
the abundance of moisture and the ecpiability of temperature 
being far more pronounced than in any other part of Europe. 

Among the remarkable instances of limited distribution 
afforded 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 Lough Killm charr, known only from a 
small mountain lake in Ireland, and the vendace, from the 
equally small lakes at Lochmaben in Scotland, are two examples 
of restricted distribution which can hardly be surpassed. 

Cause of Great Speciality in Fishes. — The reason why fishes 
alone should exhibit such remarkable local modifications in lakes 
and islands is sufficiently obvious. It is due to the extreme 
rarity of their transmission from one lake to another. Just as 
we found to be the case in Oceanic Islands, where the means 
of transmission were ample hardly any modification of species 
occurred, while where these means were deficient and individuals 
once transported remained isolated during a long succession of 
awes their forms and characters became so much changed as to 

T 2 



324 ISLAND LTFE. [part ll. 

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 tlie smaller lakes 
contain no fishes, because none have ever been conveyed to them. 
Others contain several ; and some fishes which have pecuUarities 
of constitution or habits which render their transmission somewhat 
less difficult occur in several lakes over a wide area of country, 
though none appear to be common to tlie British and Irish lakes. 
The manner in which fishes are enabled to migrate from lake 
to lake is unknown, but many suggestions have been made. It 
is a fact that whirlwinds and waterspouts sometimes carry living 
fish in considerable numbers and drop them on the land. Here 
is one mode which might certainlj' have acted now and then in 
the course of thousands of yeai-s, and the eggs of fishes may have 
been carried with even greater ease. Again we may well suppose 
that some of these fish have once inhabited the streams that 
enter or flow out of the lakes as well as the lakes themselves ; 
and this opens a wide field for conjecture as to modes of migra- 
tion, because we know that rivers have sometimes changed their 
courses to such an extent as to form a union with distinct 
river basins. This has been effected either by floods connect- 
ing low watersheds, by elevations of the land changing lines of 
drainage, or by ice blocking up valleys and compelling the 
streams to flow over watersheds to find an outlet. This is known 
to have occurred during the glacial epoch, and is especially 
manifest in the case of the Parallel Eoads of Glenroy, and it 
probably affords the true solution of many of the cases in which 
existing species of fish inhabit distinct river basins whether in 
streams or lakes. 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 
diflicult 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 
onlj' in one or two lakes in a single district ; or these last may 
have been originally identical with other forms, but have become 



CHAP. XVI.] THE BRITISH ISLES. 3'25 

modified by the particular conditions of the lake in which they 
have found themselves isolated. 

Peculiar British Insects. — We now come to the class of insects, 
and here we have much more difficulty in determining what are 
the actual facts, because new species are still being yearly dis- 
covered and considerable portions of Europe are but imperfectly 
explored. It often liappens that an insect is discovered in our 
islands, and for some years Britain is its only recorded locality ; 
but at length it is found on some part of the continent, and not 
unfrequently has been all the time known tliere, but disguised 
by another name, or by being classed as a variety of some other 
species. This has occurred so often that our best entomologists 
have come to take it for granted that all our supposed peculiar 
British species are really natives of the continent and will one 
day be found there; and owing to tliis 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 is held by such well-known authorities as 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 Islands, and Ceylon— the insects show an 
equal if not a higher proportion of speciality, and there seems 
no reason whatever why the same law should not apply to us. 
Our climate is undoubtedly very distinct from that of any part 
of the continent, and in Scotland, Ireland, and Wales we possess 
extensive tracts of wild mountainous country where a moist 
uniform climate, an alpine or northern vegetation, and a con- 
siderable amount of isolation, offer all the conditions requisite 
for the preservation of some species which may have become 
extinct elsewhere, and for the slight modification of others 
since our last separation from the continent. I think, therefore, 
tliat it will be very interesting to take stock, as it were, of our 



/ 



326 ISLAND LIFE. [part ir. 

recorded peculiarities in the insect world, for it is only by so 
doing that we can hope to arrive at any correct solution of the 
question on which there is at present so much difference of opinion. 
For the list of Coleoptera with the accompanying notes I am 
indebted to Mr. E. C. Kye; and Dr. SharjD has also given me 
valuable information as to the recent occurrence of some of the 
supposed peculiar species on the continent. For the Lepidoptera 
I first noted all the species and varieties marked as British only 
in Staudinger's Catalogue of European Lepidoptera. This list 
was carefully corrected by Mr. Stainton, who weeded out all the 
species known by liim to have been since discovered, and 
furnished me with valuable information on the distribution and 
habits of the species. This information often has a direct bear- 
ing on the probability of the insect being peculiar to Britain, 
and in some cases may be said to explain why it shoidd be so. 
^For example, the larvse 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 efifect this habit may have on distribution is afforded by one 
of our commonest British species, Elachisia rvfocinerea, the larva 
of which mines in the leaves of Holcvs mollis and other grasses 
IVom December to March. This species, though common every- 
where with us, extending to Scotland and Ireland, is quite 
unknown in similar latitudes on the continent, but appears 
again in Italy, the South of France, and Dalmatia, where the 
mild winters enable it to live in its accustomed manner. 

Such cases as this afford an excellent illustration of those 
changes of distribution, dependent probably on recent changes 
of climate, which may have led to the restriction of certain 
species to our islands. For should any change of climate lead 
to the extinction of the species in South Europe, where it 
is far less abundant than with us, we should have a common 
and wide-spread species entirely restricted to our island.s. 
Other species feed in the larva state on our common gorse, a 
plant found only in limited portions of Western and Southern 
Europe; and the presence of this plant in a mild and insular 
climate such as ours may well be supposed to have led to the 



CHAP, xvi] THE BKITISH ISLES. 327 



preservation of some of the numerous species which are or have 
beeu dependent on it. 

Mr. McLachlan has kindly furnished me with some valuable 
information on certain species of Trichoptera or Caddis flies 
which seem to be pecuUar to our islands; and this completes 
the list of orders which have been studied with sufficient care to 
afford materials for such a comparison. We will now give the 
hst of pecuUar British Insects, beginning with the Lepidoptera, 
and adding such notes as have been kindl}' supplied by the 
gentlemen already referred to. 

Liet of the Species or Varieties of Lepidoptera which, so far as at present 
l-noicn, are confined to the British Islands. {The figures sliow the dates 
when the species was first described.) 

DiURNI. 

1. PoLTOMMATUs DisPAR. " The liipge copper." This fine insect, once 

common in the fens, but now e.\tinct owing to extensive drainage, is 
generally admitted to be peculiar to our island, at all events as a variety 
or local fonu. 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. Lyciena astrarche, var. artaxerxes. This very distinct form is con- 

fined to Scotland and the north of England. The species of which 
it is considered a variety (more generally known to English entomo- 
logists as P. ageslls) is found in the southern half of England, and 
almost everywhere on the continent. 

BOMBVCES. 

.3. Lithosia sericea. North of England (1861). 

4. Hepialus humuli, var. hethlaxdica. Shetland Islands (186S). A 

remarkable form, in which the male is usually yellow and buff instead 
of pure white, as in the common form, but exceedingly variable in 
tint and markings. 

5. Epichnopteryx reticella. Sheemess, Gravesend, and other localities 

along the Thames (1847). 
C. E. pulla, var. radiella. Near London, rare (1830?) ; the species in 
Central and Southern Europe. (Doubtfully peculiar in ]\Ir. Stainton's 
opinion.) 

NOCTU^. 

7. Acroxtcta mtric^. Scotland only (18u2). A distinct species. 

8. AoROTis subrosea. Cambridgeshire and Huntingdonshire fens, perhaps 

extinct (1835). The var. ^ulccrnilea is found in Finland and Livonia. 



328 ISLAND LIFE. [paet ii. 

9. A. ASHWORTHii. South and west (1855). Distinct and not uncommon. 

10. DiANTHEciA BARRETTi. Ireland (1864). Perhaps a fonn of the con- 

tinental D. lutcago, Mr. McLachlan thinks. 

11. Aporophyla australis, var. pascuea. South of Enghmd (1830 ?). This 

is a variety of a species otherwise confined to the South of Europe, 
and Ls thus especially interesting. 

GEOMETR.E. 

12. Boarmia gemmaria, var. perfumabia. Near London (1866). A large 

dark variety of a common species, distinctly marked ; perhaps a good 
species, as the larva feeds on ivy, while the hirva of B. (jfmmaria is 
said to refuse this plant, and to die if it has nothing else to eat ; but 
Mr. McLachlan thinks this wants confirmation. 

13. Cidaria albulata, var. griseata. East of England (1835). A variety of 

a species otherwise confined to Central and Southern Europe. 
1-1. EupiTHEciA coNSTRicTATA. Widely spread, but local (1857). Larva 
on thyme. 

Ptralidisa. 

15. Aglossa pinguinalLs,ror. STREATFiELDi. Mendip Hills, unique ! (1830?) 

A remarkable and distinct variety of the common " tabby." 

16. AsopiA PiCT.\Lis. Unique (1830 ?). Perhaps an imported species. 

17. ScoPAKiA AXPiNA. Scotland (1859). 

TORTRICIXA. 

18. Teras SHEPHErdana. Fens of Cambridgeshire (1852). 

19. CocHTLis DiLuciDAXA. South of England (1829). Scarce, larva in 

stems of the wild parsnip. 

20. Aphelia xigrovittana. Scotland (1852). A local form of the 

generally distributed A. lanceolana. 

21. EuDEMis FULiGANA. South-cast of England (1828). Rire, on fleabane. 

22. Grapholitha n.evana. Generally distributed (1845). Doubtfully 

distinct from continental species in Mr. Stainton's opinion. 

23. G. parvulana. Isle of Wight (1858 ?). Eare. A distinct species. 

24. G. WEiRAXA. South of England ( 1850). A distinct species. 

TiNKINA, 

25. TixEA cocHTLiDELLA. Sanderstcad near Croydon (1 854). LTnique ! 

26. T. PALLESCENTELLA. Near Liverpool (1854). Abimdant ; probably 

imported in wool, Mr. Stainton thinks. 

27. T. FLAVESCENTELLA. Near London (1829). Scarce, perhaps imported. 

28. AcROLEPiA BETULETELLA. Yorkshire and county of Durham (1840). 

Eare. 

29. Arotresthia semifusca. North and West of England (1829). Scarcei 

a distinct species. 

30. Gelechia DivisELLA, A feu insect (1854). Eare. 



CHAP. XVI.] THE BRITISH ISLES. 329 

31. G. CELERELLA. West of England (1854). 

32. Brtophila politella. Moors of N. of England (1854). 

33. LiTA fraterxella. Widely scattered (1834). Larva feeds in shoots 

of Stellaria uliginosa in spring. Mr. Stainton thinks it has been over- 
looked abroad. 

34. AxACAMPSis siRcojiELLA. North and West England (1854). Perhaps 

a melanic variety of the more widely spread A . tteinokUa. 

35. A. IMMACULATELLA. West Wickham (1834). Unique ! A distinct 

species. 

36. Gltphipteryx cladiella. Eastern Counties (1859). Abundant. 

37. G. schcesicolella. In severallocalities (1859). 

38. Gracillaria straminella. North Britain (1850). Perhaps a local 

form of the more southern G. elongella. 

39. Ornix LOGAXELLA. Scotland ( 1848}. Abundant, and a distinct species. 

40. O. DEVOSiELLA. In Devonshire (1854). L^nique! 

41. CoLEOPHORA ALBicosTA. Widely spread (1829). Comniou on furze 

{Ulex etiropccus). May probably be found in the North-west of 
France, where the food-plant abounds. 

42. C. SATDRATELLA. South of Eugland (1850). Abundant on broom. 

43. C. INFLATE South of England (1857). On Silene inflata. 

44. C. SQUAMOSELLA. Surrcy (1856). Very rare, but an obscure species. 

45. C. SALiXELLA. On Sca-coiist (1859). Abundant. 

46. Perittia obscorepunctella. Widely scattered (1848). Larva feeds 

on common honeysuckle in July. Mr. Stainton thinks it must have 
been overlooked on the continent. 

47. Elachista flavicomella. Dublin (1856). Excessively rai-e, two 

specimens only known. 

48. E. coxsortella. Scotland (18.54). A doubtful species. 

49. E. MEGERLELLA. Widely distributed (1854). Common. Larva feeds 

in grass during winter and early spring. 

50. E. obliquella. Near Loudon (1854). Unique! 

51. E. ELEOCHARIELLA. North and East of England (1854). An obscure 

form. 

52. E. suBOCELLEA. Widely distributed (1835). An obscure form. Perhaps 

mixed on the continent with other species. 

53. E. TRiATOMEA. In chalk and limestone districts (1812). Abundant 

and' distinct. 

54. E. TRisERiATELLA. South of England (1854). Very local ; an obscure 

species. 

55. LiTHOCOLLETis xiGREScEXTELLA. Northumberland (1S50). Rare; a 

dark form of i. Breiuielta, which is widely distributed. 

56. L. IRRADIELLA. North Britain (1854). A northern form of the more 

southern and wide-spread L. laulella. 

57. L. TRiGUTTELLA. Sauderstcad, near Croydon (1848). Unique ! very 

peculiiir. 

58. L. ULicicoLELLA. In a few wide-spread localities (1854). A peculiar 

form. 



330 ISLAND LIFE. [part ii. 

59. L. CALEDONiELLA. North Britain (1854). A local variety of the more 

widespread L. corylifoliella. 

60. L. DUNNixGiELLA. North of England (1852). A somewhat doubtful 

species. 
CI. BuccuLATRix DEMARTELLA. Widely distributed (1848). Rather 

common. 
C2. Trifuecula SQr.viiATELLA. South of England (1854). A doubtful 

species. 
C.3. T. atrifro:;tella. South of England, also in Lancashire (1854). Very 

rare and peculiar. 
04. Nepticula igxobiliella. Widely scattered (1854). On hawthorn, 

not common. 
65. N. poterii. South of England (1858). Bred from Larvae in Poterium 

sanguisorba. 
C6. N. QciNQOELLA. South of England (1848). On oak-leaves, very local. 

67. N. APiCELLA. Local (1854). Probably confused with allied species on 

the continent. 

68. N. HEADLEYEI.LA. Local (1S54). A rare specie.''. 

Pterophorisa. 

69. Agdistis bensettii. East coast (1840). Common on Stalk-c limonium. 

We have here a list of sixty-nine species, which, according 
to the best authority, are, in the present state of our know- 
ledge, pecuHar to Britain. It is a curious fact that only five of 
these have been described less than twenty years ago ; and as 
during all that time they have not been recognised on the 
continent, notwithstanding that good coloured figures exist of 
almost all of them, it seems highly probable that many of them 
are really confined to our island. At the same time we must 
not apply this argument too rigidly, for the very day before my 
visit to Mr. Stainton he had received a letter from Professor 
Zeller announcing the discovery on the continent of a species of 
our last family, Pterophorina, which for more than forty years had 
been considered to be exclusively British. This insect, Fiatyptilia 
simUidactyla (PfcrojjhwKS isodadyl us, Stainton's Manual), had 
been taken rarelj' in the extreme north and south of our islands — 
Teignmouth and Orkney, a fact which seemed somewhat indica- 
tive of its being a straggler. Again, seven of the species are 
unique, that is, have only been captured once ; and it may be 
supposed that, as they are so rare as to have been found only 
once in England, the}' may be all equally rare and not yet found 
on the continent. But this is hardiv in accordance with the laws 



CHAP. XVI.] THE BRITISH ISLES. 331 

of distribution. Widely scattered species are generally abun- 
dant in some localities ; while, when a species is on the point of 
extinction, it must for a time be very rare in the single locality 
where it last maintains itself. It is then more probable, that 
some of these unique species represent such as are almost 
extinct, than that they have a wide range and are equally rare 
everywhere ; and the peculiarity of our insular climate, combined 
with our varied soil and vegetation, offer conditions which may 
favour the survival of some species with us after they have 
become extinct on the continent. 

In the list here given nine are recorded as varieties, while 
ten more, in Mr. Stainton's opinion, ought probably to be 
classed as varieties or local forms of other species, making 
nineteen in all. This leaves no less than fifty undoubted species 
not yet found beyond our islands; and thotigli Mr. Stainton 
tliinks that most of these will ultiniatoly be found on the 
continent, we can hardly doubt, botli from general considerations 
dependent on the laws of distribution, and from the peculiar 
habits, conspicuous appearance and restricted range of many of 
our species, that a very considerable number will remain 
permanently as pecuKar British insects. 

Pcculiarifies of the Isle of Man Lepidnptcra. — Before quitting 
the Lepidoptera, it will be well to notice some very interest- 
ing examples of local modification, apparently brought about 
by extreme conditions of exposure and insidation, and which 
throw some light on the way in which local forms, varieties, or 
species may be produced. This interesting phenomenon occure 
in the Isle of Man, where Mr. Edwin Birchall has collected 
Lepidoptera assiduously, and has discovered a number of varieties, 
apparently pee^diai- to the island, of which he has been so 
good as to send me specimens accompanied by some valuable 
notes. 

The Isle of Man has no woods, bogs, or heath.s, the moun- 
tains being mostly covered with grass and rocks, so that a very 
abundant insect-fauna cannot be expected. Sixteen .species of 
butterflies have been observed, and of these only one — the 
common tortoise-shell ( Vanessa urticw) presents any peculiarity. 
This, however, is always remarkably small, a .specimen i-arely 



332 ISLA^^D LIFE. [iari ii. 

being found to equal the smallest English specimens ; so that 
we must look upon it as dwarf race developed in the Island and 
confined to it. 

The following moths also present definite peculiarities : 

1. Agrotis lucemea, var. This is of a grayish-black colour, with hardly any 

markings. All are alike, and are very distinct from the common type 
of the species, which is abundant in Wales. 

2. Cirrhtrdia xcrampelina, var. This is much darker and more richly 

coloured than the English form, the yellow band being reduced to a 
narrow line, sometimes a mere thread. This would doubtless be 
regarded as a distinct species if it occurred with equal constancy in 
some more remote island. 

3. Diantluecia capsophila, var. This is an exceedingly dark and richly 

marked form of the Irish D. capsophila, itself a local variety, Mr. 
BirchaU thinks, of D. carpophaga. 

4. Dianthacia ccesia, var. This is another dark form of a rare Irish and 

continental species. 

5. Tephrosia hiundularia, var. This is an exceedingly dark form, and differs 

so much from North of England specimens as to have all the appear- 
ance of another species. Mr. BirchaU has bred it from captured 
parents, and find.'; that the produce is this dark form only. 

We will now pass on io the Coleoptera, or beetles, an order 
wluch has been of late yeai's energetically collected and 
carefully studied by British entomologists. 

List of the Sj>ecies of Beetles lehkh, so far as at prevent known, are confined 
to the British Islands. 

C'arabid.e. 

1. Dromius VECTESsis (Rye). Common in the Isle of Wight, not known 

elsewhere. 

2. *Harpalus btus, var. metallescess (Rye). Unique, but very marked ! 

South coast. 

3. Stesolophus dereuctus (Dawson). Unique ! Nona Kent. 

Helophorid^. 

4. *OcHTHEBirs powERi (Rye). Verj- marked. S. coast. A few specimens 

only. 

Brachtelttra. 

5. *Aleochap.a hiberxica (Rye). Irehuid. Mountain tops. 

6. *OxrpoDA RUPicoLA (Rye). Scotland. Mountain tops; several 

specimens. 



CHAP. XVI ] 



THE BRITISH ISLES. 



333 



7. *OxrpoDA EDiNEXsis (Sharp). Scotland. 

8. „ VEUECUNDA (Sharp). Scotland. 

9. „ WATERHOUSEI (Eye). London district. 

10. HoMALOTA EXIMIA (Sharp). 

11. „ CLAVIPES (Sharp). Scotland on mountains ; not rare. 

12. „ OBLONGiuscuLA (Sharp). [Scotland, perhaps also Swiss. 

13. „ PRiNCEPS (Sharp). A coast insect. 

14. „ cuRTiPEiVNis (Sharp). 

15. „ KXARATA (Sharp). 

16. „ PUBERULA (Sharp). 

17. „ INDISCRETA (Sharp). 

18. „ ATRICOLOR (Sharp). 

19. „ GERMANA (Sharp). 

20. „ SETIOEKA (Sharp). '' 

21. * „ SHARPi (Rye). Very marked, unique ! 

22. *Brtoporus castaneus (Hardy and Bold). Very marked, unique ! 

Northumberland Hills. 

23. *Stenus oscillator (Rye). Unique ! South coast. 

24. *Scop.EUS RYEi (WoUaston). Very distinct; Dorset coast; several 

specimens. 

25. 'Trogopiilteus spimicollis (Rye). Mersey estuary, unique ! Most 

distinguishable, nothing like it in Europe. 

26. Lesteva SHARPI (Rye). Scotch hills. 

27. EuDECTUS wiiitei (Sharp). Scotch hills. Probably a variety of E. 

GiraiuU of Austria (the only European species) yFife Kraatz (Sharp). 

28. *HoMALiUM Rt'ouLipENNE (Rye). Exceedingly marked form. Northern, 

western, and southern coasts ; rare. 



Some continental authors <leny that 
there are good species (Sharp). 



PsELAPIIID-B. 

29. Bry'Axis cotus (Sharji). Coast. 

30. „ WATERHOUSEI i Rye). Coast. 

31. *BTTHiNns GLABRATUS (Rye). Sussex coast ; a few specimens ; very 

distinguishable ; niyrmecophilous (lives in ants' nests). 











TRICHOPTERTGIDiE 


32. 


Ptin 


ELLA 


MAE 


I A 


(Matthews) 


33. 


Trichoptertx sar.e 


V i» 




34. 




)? 


1 . 


POWKRI 


\ )j 




35. 




») 




EDITHIA 


>' 




36. 




J» 




CANTIANA 


. It 




37. 




» 




FUSCULA 


J' 




38. 




» 




KIRHII 


* >' 




39. 




)) 




FRATERCULA 


V )' 




40. 




>j 




WATERHOUSII 


^ i' 




41. 




n 




CHAMPIONIS 


( J) 




42. 




w 




JANSONI 


\ >» 





334 ISLAND LIFE. [part ii. 

43. Tbichopteryx semixitess (Matthews). 

44. „ suFFOc-iTA (Haliday). Ireland. 

45. „ DISPAR (Matthews). 

46. ,, CARBONARIA (Matthews). 

47. Ptilicm halidati (Matthews). 

48. „ CALEDOsicuM (Sharp). Scotland ; very marked form. 

49. „ INSIGXE (Matthews). 

50. AcTiDlCM coscoLoR (Sharp). Scotland ; very marked. 

51. Ptesidiusi kraatzu (Matthews). 

Anisotomid-e. 

52. *AoATHlDHJM RHih'OCEROs (Sharp). Old fir-woods in Perthshire ; 

lociil, many specimens ; a very marked species. 

53. Anisotoma siMiLATA (Rye). Unique ! South of England. 

54. * „ LCNicoLLi.s (Rye). North-east and South of England, a 

very marked form ; several specimens. 

55. * „ CLAvicoRNis (Rye). Unique ! Scotland. 

PHALACRID.E. 

56. *I'halacrus BRisorTi (Rye). A few specimens. South of England. 

CRVPTOrnAGIDJE. 

57. Atomaria wollastosi (Sharp). Unique I Scotland. 

58. ,, DivisA (Rye). Unique! South of England. 

LATHRXDID.E. 

59. Corticaria wollastosi (Waterhouse). South coast. 

BVRRHID.E. 

60. Stncalypta hirscta (Sharp). 

Elaterid.1:. 

61. Elater coccinatus (Rye). Very marked, but possibly a variety of the 

European E. jjrteustus. South of England. 

* TELErH0RID.E. 

62. *TELEPH0Rns DARWixiANUs (Sharp). Scotland, sea-coast. A stunted 

form of abnormal habits. 

CVPHONID.E. 

63. CrPHOK PUNCTlPENSis (Sharp). Scotland. 

ANTHICID.E. 

64. AjtTUicus sALisus (Crotch). South coast. 

65. * „ sconces (Rye). LodiLeven ; very distinct; many specimens. 



CHAP. XVI.] THE BRITISH ISLES. .335 



CURCCLIONID.*;. 

66. *CATHOE5iiocERrs MARiTiMcs (Rve). A few specimens on our south 
coast. A curious genus, only found elsewhere on the coasts of the 
Mediterranean ! 

07. *Ceuthorhynchus contractus, var. pallipes (Crotch). Lundy Island ; 
several specimens. A curious variety only known from this island. 

68. *LiosoMiis TROGLODYTES (Rye). A very queer form. Two or three 

specimens. South of England. 

69. *Apion rtei (Blackburn). Shetland Islands. Several specimens. 

Halticid.e. 
TO. TnYAMis AGiLl.s (Rye). South of England ; many specimens. 

„ DisTiNGUENDA (Rye). South of England ; many specimens. 

71. *PsTLLiODES LURiDiPEHxis (Kutschera). Lundy Island. A vei-y 

curious form, not uncommon in this small island, to which it appcai-s 
to be confined. 

COCCINKLLID.E. 

72. ScYMNUS LiviDus (Bald). Northumberland. A doubtful species. 

Of the seventy-two species of beetles in the preceding list, a 
considerable number no doubt owe their presence there to the 
fact that they have not yet been discovered or recognised on 
the continent. This is almost certainly the case with many of 
those which have been separated from other species by very 
minute and obscure character.'?, and especially with the exces- 
sively minute Trichopterygida; described by Mr. Matthews. 
There are others, however, to which this mode of getting rid of 
them will not apply, as they are so marked as to be at once 
recognised by any competent entomologist, and often so plentiful 
that they can be easily obtained when searched for. Of this 
class are the twenty-three species whose names are marked 
with an asterisk (*), being those which, in ]\Ir. Rye's opinion, 
are most likely to be peculiar to the localities where they are 
found if any are,- — but of this he is still somewhat sceptical. 
Six of these are unique, leaving seventeen which have occurred 
cither rarely or in some abundance. Dividing the probably 
peculiar species according to locality, we find that the South of 
England has produced 9, North of England 2, Scotland 6, 
Ireland 1, Shetland Islands 1, and Lundy Island 2. These 



336 ISLAND LIFE. [i-art h. 

numbers are, generally speaking, proportionate to the richness of 
the district and the amount of work bestowed upon it ; Scotland, 
however, giving more than its due proportion in this respect, 
which must be imputed to its really possessing a greater amount 
of speciality. The single peculiar Irish species stands as a monu- 
ment of our comparative ignorance of the entomology of the 
sister isle. The peculiar species of Apion in the Shetland 
Islands is interesting, and may be connected with the very 
peculiar climatal conditions there prevailing, which have led in 
some cases to a change of habits, so that a species of weevil 
(Otiorhynchits maurus) always found on mountain sides in Scotland 
here occurs on the sea-shore. Still more curious is the occur- 
rence of two distinct forms (a species and a well-marked variety) 
on the small granitic Lundy Island in the Bristol Channel. 
This island is about three miles long and twelve from the coast 
of Devonshire, consisting mainly of granite with a little of the 
Devonian formation, and the presence here of peculiar insects 
can only be due to isolation with special conditions, and im- 
munity from enemies or competing forms. ^\Tien we consider 
the similar islands off the coasts of Scotland and Ireland, with 
the Isle of Man and the Scilly Islands, none of which have 
been yet thoroughly explored for beetles, it is probable that 
many similar examples of peculiar isolated forms remain to be 
discovered. 

Mr. Rye hardly thinks it possible that the Dromnis vectensis 
can really be peculiar to the Isle of Wight, although it is abun- 
dant there, and has never been found el.sewhere ; but the case 
of Lundy Island renders it less improbable ; and when we con- 
sider that the Arum italicum, Calamintha sylvatica, and perhaps 
one or two other plants are found nowhere else in the British Isles, 
we must admit that the same causes which have acted to restrict 
the range of a plant may have had a similar effect with a beetle. 

I must also notice the Cathormiocerus viaritimus, because 
its only near ally inhabits the coasts of the Mediterranean ; and 
it thus offers an analogous case to the small moth, Elachista 
rufocinerca, which is found only in Britain and the extreme 
South of Europe. Looking, then, at what seem to me the proba- 
bilities of the case from the standpoint of evolution and natural 



CHAP, svi.] THE BRITISH ISLES. 337 

selection, and giving due weight to the facts of local distribution 
as they are actually presented to us, I am forced to differ from 
the opinion held by our best entomological authorities, and to 
believe that some considerable proportion of the species which, 
in the present state of our knowledge, appear to be pecuhar to 
our islands, are, not only apparently, but really, so peculiar. 

I am indebted to Mr. Robert McLachlau for the following in- 
formation on certain Trichopterous Neuroptera (or caddis-flies) 
which appear to be confined to our islands. The peculiar 
aquatic habits of the larva; of these insects, some living in 
ponds or rivers, others in lakes, and others again only in clear 
mountain streams, render it not improbable that some of them 
should have became isolated and preserved in the mountain 
districts of our western coasts, or that they should be modified 
owing to such isolation. In these insects the characters depended 
on to separate the species are wholly structural, and the care 
with which Mr. McLachlan has studied them renders it certain 
that the species here refeiTed to are not mere varieties of known 
continental forms, however closely they may resemble them in 
form and coloration. 

Trkhoplera peculiar to the Brittsh Isles. 

1. Setodes abgestipcnctella. — Tliis species is known only from the 
Lakes Windermere and Killarney. It has recently been described by Mr. 
JNIcLachlan, and is quite distinct from any known species though allied to 
S. punctata and S. viridif, which inhabit France and Western Europe. 

2. Rhyacophila munda.— Described by Mr. McLachlan in 1863. A 
very distinct species, found only in mountain streams in Wales and 
Devonshire. 

3. Philopotamus ixsolaris. (? A variety of P. montanus.)— This can 
hardlj' be termed a British species or variety, because, so far as at present 
known, it is peculiar to the island of Guernsey. It agrees structurally 
with P. montanus, a species found both in Britain and on the continent, 
but it differs in its strikingly yellow colour, and less pronounced markings. 
All the specimens from Guernsey are ahke, and resident entomologists 
assured Mr. McLachlan that no other kind is known. Strange to say, 
some examples fiom Jersey differ considerably, resembling the common 
European and British form. Even should this peculiar variety be at some 
future time found on the continent it would still be a remarkable fact that 
the form of insect inhabiting two small islands only twenty miles apart 
should constantly differ ; but as Jersey is between Guernsey and the coast, it 
seems just possible that the more insular conditions, and perhaps some 

z 



338 ISLAND LIFE. [part ii. 

peculiarity of tlie soil auJ water in the former islanii, have really led to 
the prodiictioQ or preservation of a well-marked variety of insect. 

Land and Fresli-water Shells. — As regards the land and 
fresh-water mollusca it seems difficult to obtain accurate infor- 
mation. Several species have been recorded as British only, 
but I am informed by Mr. Gwjti Jeftries that most of these are 
decidedly continental, while a few may be classed as varieties of 
continental species. According to the late Mr. Lovell Reeve 
the following species are peculiar to our islands ; and althougli 
the first two seem extremely doubtful, yet the last two, to which 
alone we accord the dignity of capital t\'pe, may not improbably 

, be peculiar to Ireland, being only found in the remote south- 
western mountain region, where the climate possesses in the 
highest degree the insular characteristics of a mild and uniform 
temperature with almost perpetual moisture, and where several 

"of the peculiar Irish plants alone occur. 

1. Cyclas pisidioides. — A small bivalve shell found in canals. Perhaps 
a variety of C. corneum or C. nvicola according to Mr Gwyn Jeffries. 

2. Assiminia grayana. — A small univalve shell allied to the periwinkles, 
found on the banks of the Thames between Greenwich and Gravesend, on 
the mud at the roots of aquatic plants. 

3. Geojulacus maculosus. — A beautiful slug-, black, spotted with yellow 
or white. It is found on rocks on the shores of Lake Carogh, south of 
Castlemain Bay, in Kerry. It was discovered in 1842, and has never been 
found in any other locality. An allied species is found in Portugal and 
France, which Mr. Gwyn Jeffries thinks may be identical. 

4. LiMN.EA iN'VOLnTA. — A beautiful pond-snail with a small polished 
amber-coloured shell, found only in a small alpine lake and its inflowing 
stream on Cromaghaun mountain near the lakes of Killarney. It appears 
to be a very distinct species, most nearly allied to L. glutinosa which is 
not found in Ireland. It was discovered in 1832, and has frequently been 
obtaiued since in the same locality. 

The facts — that these two last-named species have been known 
for about forty or fifty years respectively, that they have never 
been found in any other locality than the above named very 
restricted stations, and that they have not j-et been clearly iden- 
tified with any continental species, all point to the conclusion 
, that they are the last remains of peculiar forms which have 
everywhere el.se become extinct. 

Peculiarities of (he British Flm-a. — Thinking it probable 



CHAP. XVI.] THE BRITISH ISLES. 339 



that there must also be some peculiar British plants, but 
not finding any enumeration of such in the British Floras of 
Babington, Hooker, or Benthani, I applied to the greatest living 
authority on the distribution of British plants — Mr. H. C. 
Watson, who has very kindly given me all the information I 
required, and I cannot do better than quote his words. He 
says : " It may be stated pretty confidently that there is no 
' species ' (generally accepted among botanists as a good species) 
peculiar to the British Isles. True, during the past hundred 
years, nominally new species have been named and described on 
British specimens only, from time to time. But these have 
gradually come to be identified with species described elsewhere 
under other names— or they have been reduced in rank by suc- 
ceeding botanists, and placed or replaced as varieties of more 
widely distributed species. In his British Ruhi Professor 
Babington includes as good species, some half-dozen which he 
has, apparently, not identified with any foreign species or variety. 
None of these are accepted as ' true species,' nor even as ' sub- 
species ' in the Students' Flora, where the brambles are 
described by Baker, a botanist well acquainted with tlie plants 
of Britain. And as all these nominal species of Rubi are of late 
creation, they have truly never been subjected to real or critical 
tests as ' species.' " 

But besides these obscure forms, about which there is so much 
difference of opinion among botanists, there are a few flowerino- 
plants which, as varieties or sub-species, are apparently peculiar 
to our islands. These are ; — (1) Helianthemum Breweri, an 
annual rock-rose found only in Anglesea and Holyhead 
Island (classed as a sub-species of H. guttntum by Hooker 
and Babington) ; (2) Eosa hihernica, found only in North 
Britain and Ireland (a species long thought jieculiar to the 
Briti.sh Isles, but said to have been recently found in France) ; 
(3) (Eyumthe fluviaiilis, a water-dropwort, found only in the 
south of England and in one locality in Ireland (classed 
as a sub-species of (E. jjhellandHmn by Hooker) ; (4) Hieracium 
iricum, a hawk-weed found in North Britain and Ireland (classed 
by Hooker as a sub-species of E. Lawsoni, and said to be 
" confined to Great Britain)." 

z 2 



340 ISLAND LIFK. [i'ART ii. 

Two other species are, so far as the European Flora is con- 
cerned, peculiar to Britain, being natives of North America, 
and they are very interesting because they are certainly both 
truly indigenous, that is, not introduced by human agency. These 
are, — (1) Spiranthcs romanzoviana, an orchid allied to our 
ladies' tresses, widely distributed in North America, but only 
found elsewhere in the extreme south-west corner of Ireland ; 
and (2) Eriocaidon scjitangulare — the pipewort — a curious 
North American water-plant, found in lakes in the Hebrides and 
the west of Ireland. Along with these we may perhaps class 
the beautiful Irish filmy fern — Trichomanes radicans, which 
inhabits the Azores, Madeira and Canary Islands, the south- 
west of Ireland, Wales, and formerly Yorkshire, but is ntjt 
certainly kno^\^^ to occur in any part of continental Europe 
(except perhaps the south-west of Spain), though found in many 
tropical countries. 

We may here notice the interesting fact that Ireland possesses 
no less than twenty species or sub-species of dowering j)lants not 
f jund 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 lists of these plants, with a 
few remarks on their distribution, will be found interesting : — 

List of Irish Flowering Plants which are not found in Britain. 

1. Helianthemum guttaium. Ireland, near Cork, and on an island off 

the coast of Gahvay (also Channel Islands, Fiance, Italy). 

2. Arenaria ciliata. S. W. Ireland (also Auvergne, Pyrenees, Crete). A 

variety of this species has been recently found in Pembrokeshire. 

3. Saxifraga umhrosa. W. Ireland (also N. Spain, Portugal). 

4. „ geum. S. W. Ireland (also Pjrenees). 

5. ,, hirsuta. S. W. Ireland (also Pyrenees). 

6. Saxi/raga hiria {hypnoides sub. sp.). S. Ireland, apparently unknown 

on the continent. 

7. Inula salicina. W. Ireland (Middle and South Europe). 

8. Erica mediterranea. \V. Ireland (W. France, Spain, Mediterranean). 

9. „ mackiana {ieiralix sub.-sp.) W. Ireland (Spain). 

10. Arbutus unedo. S. W. Ireland (S. of France and Spain). 

11. Dabeocia pol'ifolia. W. Ireland (W. of France and Spain). 

12. Ping'mcttla grandijljra. S. W. Ireland (W. of France, Spain, Alps, &c.). 

13. Xeotinea iittada. W. Ireland (France, S. Europe). 



CHAP. XM.] TlIK BUITISH ISLES. 341 

1 4. Sphantlieg romanxovutna S. W. Iielar.d (North Atiierica). 

15. {Shtjrinchium bermudianum. W. Ireland? introduced; (North America.) 

16. Polamogelon longifolius (luceiis. var.) W. Ireland, nnitjue specimen ! 

17. „ kirlii (natan$ aah.-sp.). W. Ireland (Arctic Europe). 

18. Eriocaulon septangulare. W. Ireland, Skye, Hebrides (North America). 

19. Care.r bujcbaumii. N. E. Ireland, on an island in Lough Neagh (Arctic 

and Alpine Europe, Nortli America). 

20. CalfimaijroKtin strlcta (var. Hoohcri). On the shores and islands of Lough 

Neagh. The species occurs at one locality in Cheshire (Germany, 
Arctic Europe, and North America). 

We find here nine south-west European species which 
probahly had a wider range in mild preghxcial times, and have 
been preserved in the south and west of Ireland owing to its 
niilder climate. It must be remembered that during the height 
of the glacial epoch Ireland was continental, so that these plants 
may have followed the retreating ice to tiieir present stations and 
survived the subsequent depression. This seems more probable 
than that so many species slu)uld have reached Ireland for the 
lirst time during the last union with the continent subsequent 
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 con- 
tinued to exist in Ireland while becoming extinct in the adjacent 
parts of Britain and Western Europe. 

As contrasted with the extreme scarcity of peculiar species 
among the flowering plants, it is the more interesting and un- 
expected to find a considerable number of peculiar mosses and 
Hepaticae, some of which present us with phenomena of distri- 
bution of a very remarkable character. For the following lists 
and the information as to the distribution of the genera and 
species I am indebted to Mr. WiUiam Mitten, one of the first 
authorities on these beautiful little plants. 

List of the Species of Mosses and Hepatice which are peculiar to 

THE British Isles (ou not found in Edkope). 

(Those belonging to iwn-European genera in Italics.) 

Mosses. 

1. Systegium niulticapsul;ire Central and South England. 

2. „ mittenii South of England. 

3. Campylopus shawii North Britain. 

4. ,, setifolius Ireland. 



342 ISLAND LIFE. [part ji. 

5. Seli'Keria calcicola South of England. 

6. Pottia viridifolia Sautli of England. 

7. Leptodontium recun'ifolium ... Ireland and Scotland. 

8. Tortula woodii Ireland. 

9. „ hibemica Ireland. 

10. iStreptopogon gemmascetis Sussex. 

11. Grimmia subsquarrosa North Britain. 

12. ,, stirtoni North Britain. 

13. Glyphomitriura daviesii On basalt generally. 

14. Zygodon nowellii North Britain. 

15. Bryum barnesii North Britain. 

16. Hookeria laetevireiix Ireland and Cornwall (also Madeira). 

17. Daltonia splachnoides .. Ireland. 

Hepatic*. 

1. Gymnomitrium crenulatum ... West England, Ireland. 

2. Kadula voluta Ireland and Wales. 

3. Acrobnlbus vilsoni Ireland. 

4. Lejeunia calyptrifoUa Cornwall, Lake district, Ireland. 

5. „ microscopica Ireland. 

6. Lophocolea spicata Ireland. 

7. Jungemiannia cuneifolia ... Ireland. 

8. ,, doniana Scotland. 

9. Petalophyllum ralfsii West Britain, Ireland. 

Many of the above are minute or obscure plants, and are 
closely allied to other European species with which they may 
have been confounded. We cannot therefore lay any stress on 
these indi^^dualIy as being absent from the continent of Europe 
so much of which is imperfectly explored, though it is probable 
that some of them are really confined to Britain. But there are 
a few — indicated by italics — which are in a very different 
category ; for they belong to genera which are altogether un- 
known in any other part of Europe, and their nearest allies are 
to be found in the tropics or in the southern hemisphere. The 
three non-European genera of mosses to which we refer all have 
their maximum of development in the Andes, while the three 
non-European Hepaticse appear to have their maximum in the 
temperate regions of the southern hemisphere. Mr. Mitten 
has kindly furnished me with the following particulars of the 
distribution of these genera : — 

Streptopogon is a comparatively small genus, with seven species in the 
Andes, one in the Himalayas, and three in the south temperate zone, besides 
our English species. 

Daltonia is a large genus of inconspicuous mosses, having seventeen 
spscies in the Andes, two in Brazil, two in Mexico, one in the Galapsgo^^, 



cH.vr. XVI.] THE BRITISH ISLES. S43 

six in India and Ceylon, five in Java, two in Africa, and three iu the 
Antarctic Islands, and one in Ireland. 

HooKEEl.i (restricting that tenn to the species referable to Cyclodictyon) 
is still a large genus of handsome and remarkable mosses, having twenty- 
six species in the Andes, eleven in Brazil, eight in the Antil'es, one in Mexico, 
two in the Pacific Islands, one in New Zealand, one in Java, one in India, 
and five in Africa — besides our British species, which is found also in 
Madeira and the Azores but in no part of Europe proper. 

These last two are very remarkable cases of distribution, since 
Mr. Mitten assures me that the plants are so markedly different 
from all other mosses that they would scarcely be overlooked in 
Europe. 

The distribution of the non-European genera of Hepaticse is 
as follows : — 

AcROBoLBUS. A small genus found only in New ZcalAud and the adjacent 
islands, besides Ireland. 

Lkjeukia. a very extensive genus abounding in the tropical regions of 
America, Africa, the Indian Archipelago, and the I'acific Islands, reaching 
to New Zealand and Antarctic America, sparingly represented in the Britisli 
and Atlantic Islands, and in North America. 

PETALorHYLLUM. A Small geiuis confined to Australia and New Zealand 
in the southern hemisphere, and Ireland in the northern. 

We have also a moss— .%M)iM«i !iebiiiiantm—ioundon\y in Scotland and 
the Atlantic Islands ; and one of the UepaticK—MastigojyJiara woodsii— 
found in Ireland and (he Himalayas, the genus being most developed in 
New Zealand, and unknown in any part of continental Europe. 

These are certainly very interesting facts, but they are by no 
means so exceptional in this group of plants as to throw any 
doubt upon their accuracy. The Atlantic islands present very 
similar phenomena in the Ehamphiclium in^rpuratum, whose 
nearest allies are in the West Indies and South America ; and 
in three species of Sciaroniium, 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 tlie genus extends over Europe, India, 
and the southern hemisphere, but always represented by a very 
few wide-ranging species except in this one mountain group ! ^ 

' I am indebted to Mr. Mitten for thi^ curious fact. 



344 ISLAND LIFE. [part ii. 

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 that they must be continually carried through the air 
to great distances, and we can hardly doubt that, so far as its 
powers of diffusion are concerned, any species which fruits 
freely might soon spread itself over the whole world. That 
they do not do so must depend on peculiarities of habit and con- 
stitution, which fit the ditferent species for restricted stations 
and special climatic conditions ; and according as the adaptation 
is more general, or the degree of specialisation extreme, species 
will have wide or restricted ranges. Although their fossil 
remains have been rarely detected, we can hardly doubt that 
mosses have as high au antiquity as ferns or Lycopods ; and 
coupUng this antiquity with their great powers of dispersal wc 
may understand how many of the genera have come to occuf)y 
a number of detached areas scattered over the whole earth, but 
always such as afford the peculiar conditions of climate and 
soil best suited to tliem. The repeated changes of temperature 
and other climatic conditions, which, as we have seen, occurred 
through all the later geological epochs, combined with those 
slower changes caused by geographical mutations, must have 
greatly affected the distribution of such ubiquitous yet delicately 
organised plants as mosses. Throughout coimtless 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 
alwaj'S seizing upon every available spot in which they could 
even temporarily maintain themselves. 

Here then we have a group in which there is no question of 
the means of dispersal ; and where the difficulties that present 
themselves are not how the species reached the remote localities 
in which they are now found, but rather why they have not 
estabhshed themselves in many other stations which, so far as 
we can judge, seem equally suitable to them. Yet it is a curious 
fact, that the phenomena of distribution actually presented by 
this group do not essentially differ from those presented by the 
higher flowering plants which have apparently far less diffusive 



CHAP. XVI.] THE BRITISH ISLES. 345 

power, as we shall find when we come to treat of the floras of 
oceanic islands ; and we believe that the explanation of this is, 
that the life of S2)eei€S, and especially of genera, is often so 
prolonged as to extend over whole cycles of such teiTestrial 
mutations as we have just referred to ; and that thus the 
majority of plants are afforded means of dispersal which are 
usually sufficient to carry them into all suitable localities on the 
globe. Hence it follows that their actual existence in such 
localities depends mainly upon vigour of constitution and adap- 
tation to conditions just as it does in the case of the lower and 
more rapidly diffused groups, and only partially on superior 
facilities for diff"usion. This important principle will be used 
further on to afford a solution of some of the most difficult 
problems in the distribution of plant life. 

Concluding remarks on tlie Peculiarities of the British Fauna and 
Flm-a. — The facts, now I believe for the first time, brouglit to- 
gether respecting the peculiarities of the British fauna and flora, 
are sufficient to show that there is considerable scope for the study 
of geographical distribution even in so apparently unpromising 
a field as one of the most recent of continental islands. Looking 
at the general bearing of these facts, they prove, that the idea 
so generally entertained as to the biological identity of the 
British Isles with the adjacent continent is not altogether 
correct. Among birds we have undoubted peculiarities in at 
least three instances ; peculiar fishes are much more numerous, 
and in this case the fact that the Irish species are all different 
from the British, and those of the Orkneys distinct from those 
of Scotland, renders it almost certain that the great majority of 
the fifteen peculiar British fishes are really peculiar and will never 
be found on the European Continent. The mosses and Hepaticse 
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, 
shoiild there not be a proportionate number of peculiar British 
insects ? It is true that numerous species have been first dis- 
covered in Britain, and, subsequently, on the continent ; but we 
have many species which have been known for twenty, thirty, 
or forty years, some of which are not rare with us, and yet have 



346 ISLAND LIFE. [part n. 

never beeu found 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 which has been so very thoroughly worked. Analogy, 
therefore, would lead us to conclude that many other species 
would exist on our islands and not on the continent ; and when 
we find that a \ery large number (150) in three orders only, are 
so recorded, we may I think be sure tliat a considerable portion 
of these (though how many we cannot say) are really endemic 
British species. 

The general laws of distribution also load us to expect such 
phenomena. Very rare and very local species ai'e such as are 
becoming extinct ; and it is among insects, which are so ex- 
cessively varied and abundant, which present so many isolated 
forms, and which, even on continents, afford numerous examples 
of very rare species confined to restricted areas, that we should 
have the best chance of meeting with every degree of rarity 
down to the point of almost complete extinction. But we 
know that in all parts of the world islands are the refuge of 
species or groups which have become extinct elsewhere ; and it 
is therefore in the highest degree probable that some species 
which have ceased to exist on the continent should be preserved 
in some part or other of our islands, especially 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 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 assimiption 
that all our insects do exist on the continent, and will sometime 
or other be found there, as not in accordance with the evidence ; 
and when this is done, and the interesting peculiarities of some 



CHAP. XVI.] THE BRITISH ISLES. 347 

of our smaller islands are remembered, the study of our native 
animals and plants, in relation to those of other countries, 
will acquire a new interest. The British Isles are said to 
consist of more than a thousand islands and islets. How 
many of these have ever been searched for insects ? With 
the case of Lundy Island before us, who shall say that there 
is not yet scope for extensive and interesting investigations 
into the British fauna and flora? 



CHArTEE XVII. 

BOIINEO -iXD J.VV.V. 

Position ni;il pliysical features of Borneo — Zoologic;il features of Borneo : 
llaiuiiialia — Birds — The affinities of the Bornean fauna — Java, its 
position and physical features — General character of the fauna of Java 
— Diiferences between tlie 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 
Pliilippine Islands — Concluding remarks ou the Malay Islands. 

As a representative of recent continental islands situated in 
the tropics, we will take Borneo, since, althongh perhaps not 
much more ancient than Great Britain, it presents a considerable 
amount of speciality ; and, in its relations to the surroimding 
islands and the Asiatic continent, offers us some problems of 
great interest and considerable difficulty. 

The 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 part of it — from the Gulf of Siam to the Java 
Sea — is under fifty fathoms, or about the same depth as the 
sea that separates our own island from the continent. The 
distance from Borneo to the southern extremity of the Malay 
Peninsula is about 350 miles, and it is nearly as far from Sumatra 
and Java, while it is more than 600 miles from the Siamase 
Peninsula, opposite to which its long northern coast extends. 
There is, I believe, nowhere else upon the globe, an island so far 



rnAP. XVII.] 



BORNEO AND JAVA. 



349 




.MAT tT lit'RNEii AM' JAVA. Slli.WIM; IHI: fJllKAT .Sl'BMARlNE BANK OF St'UTU-EASTERS ASIA. 

The light tint shnvis .1 less depth thnn inn fathoms. 
The figures show the depth ol the sen iu fathoms 



350 ISLAND LIFE. [part ii. 

from a continent, yet separated from it by so shallow a sea. 
Recent changes of sea and land must have occurred here on a 
grand scale, and this adds to the interest attaching to the study 
of this large island. 

The internal geography of Borneo is somewhat peculiar. A 
large portion of its surface is lowland, consisting of great alluvial 
valleys which penetrate far into the interior ; while the moun- 
tains except in the north, are of no great elevation, and there 
are no extensive plateaux. A subsidence of 500 feet would allow 
the sea to fill the great valleys of the Pontianak, Banjarmassing, 
and Coti rivers, almost to the centre of the island, greatly reducing 
its extent, and causing it to resemble in form the island of Celebes 
to the east of it. 

In geological structure Borneo is thoroughly continental, 
possessing formations of all ages, with basalt and crystalline 
rocks, but no recent volcanoes. It possesses vast beds of coal of 
Tertiary age ; and these, no less than the great extent of alluvial 
deposits in its valleys, indicate great changes of level in recent 
geological times. 

Having thus briefly indicated those physical features of Borneo 
which are necessary for our inquiry, let us turn to the organic 
world. 

Neither as regards this great island nor those which surround 
it, have we the amount of detailed information in a convenient 
form that is required for a full elucidation of its past history- 
We have, however, a tolerable acquaintance with the two higher 
groups — mammalia and birds, both of Borneo and of all the 
surrounding countries, and to these alone will it be necessary to 
refer in any detail. The most convenient course, and that which 
will make the subject easiest for the reader, will be to give, 
first, a connected sketch of what is knowTi of the zoology of 
Borneo itself, with the main conclusions to which they point ; and 
then to discuss the mutual relations of some of the adjacent 
islands, and the series of geographical changes that seem required 
to explain them. 



17. 


Sciurus 


pluto. 


18. 




macrotis. 


19. 


jj 


sarawakcnsis. 


ao. 


» 


borneonensis. 


21. 




ru('u</ularis. 


22. 
23. 


jj 


atricapillus. 
nifogaster. 


24. 
25. 


Acunthion crassispinis. 
Tricliys lipura. 



CHAP, xvii.] BORNEO AXD JAVA. ,<?51 



Zoological Featuees of Borneo. 

Mammalia. — About ninety-si.K species of mammalia have 
been discovered in Borneo, and of these nearly two-thirds are 
identical with those of the surrounding countries, and nearly 
one half with those of the continent. Among these are two 
lemurs, three civets, three cats, three deer, the tapir, the elephant, 
and several squirrels, an assemblage which could certainly only 
have reached the country by land. The following species of 
mammalia are supposed to be peculiar to Borneo : — 

QUADRUMAN.\. 

1. Simiamorio. A small orang-utan 

with large incisor teeth. 

2. Hj'lobates concolor. 

3. Nasalis larvatus. 

4. Seninopithecus rubicimdns. 

5. „ chrysonielas. 

6. „ frontalus. 

7. Maeacus melanotus. 

Carnivora. Insectivora. 

8. Cynogale hennettii. 2C. Tupaia splendidiila. 

9. Paradoxurus stiginaticiis. 27. „ minor {Giinlher, P. Z. S. 
10. Herpestes semitorquatus. 1876 p. 42G). 

U. „ brachyunis. 2S. Dendrogaie murina. 

12. Fells badia. 29. Ptilocerus lowii. 

13. Lutra lovii [Gunther, P. Z. S. 

1876, p. 736). 

„ ClIIROPTERA. 

UnOULATA. ... T>T, 11 • J • 

14. Sus barbatiis. ^0- Phyllonna dor.iK. 

31. Vesperngo stenopterus. 
Eodentia. 32. „ doriw. 

1.5. Pteromys phteoniela.'^. 33. ., tylopus. 

10. Sciurus ephippium. 34. Taphozous affinis. 

Of the thirty-four peculiar species here enumerated, it is 
probable that when they are more carefully studied some 
will be found to be identical with those of Malacca or Sumatra ; 
but there are also four peculiar genera which are less likely 
to be discovered elsewhere. These are Nasalis, the remarkable 
long-nosed monkey ; Cynogale, a semi-aquatic civet ; Trichys, 
a tailless porcupine ; and Ptilocerus, a feather- tailed arboreal 
insectivore. These peculiar forms do not, however, imply 
that the separation of the island from the continent is of very 
ancient date, for the country is so vast and so much of the 



352 ISLAND LIFE. [pakt ii 

connecting land is covered with water, that the amount of 
speciality is hardly, if at all, greater than occurs in many con- 
tinental areas of equal extent, This will be more evident if we 
consider that Borneo is as large as the Indo-Chinese Peninsula, 
or as the Indian Peninsula south of Bombay, and if either of 
these countries were separated from the continent by the sub- 
mergence of the whole area north of them as far as the Hima- 
layas, they would be found to contain about as many pecuhar 
generj^juid^pecies as Borneo actually does now. A more deci- 
sive( test of the lapse of time -since the separation took place is 
to be found in the presence of a number of representative 
species closely allied to those of the surrounding countries, such 
■ as the taileJ monkeys and the numerous squirrels. These, how- 
ever, are best seen among the birds, wliich have been more 
thoroughly collected and more carefully studied than the 
mammalia. 

Birds. — About 400 species of birds are known to inhabit 
Borneo, of which 3-tO are land birds. There are about seventy 
pecuHar species ; and, according to Count Salvador!, thirty-four 
of these (thirty-nine with later additions) are very distinct forms, 
while no less than thirty-one are slight modifications of species 
found in Sumatra or the Malay Peninsula. The following are 
the species of birds considered by Count Salvadori to be peculiar 
to Borneo, with the addition of a few species since added:— ^ 

Fir.sT Series. Second Series. 

Very distinct Species. Ikpraentatici Sitecies. 

Strigid.« (Owls). 

I 1. Ninox bomeeasis. 

I 2. Ciccaba leptogrammica. 

Meo.\.l.emid.b (Barbets). 

I 3. Chotorea chrysopsis. 

I 4. Calorhamphus fuligiuosus. 

PiciDJ. (Woodpeckers). 

.5. Hemilophus fischeri. 

6. Jungipicus aurantiiventris. 

7. Micropternus badiosus. 

Ci;cuLiD.E (Cuckoos). 

1. Indicator archipelagus. I 8. Rhopodytes bomeensis. 

2. Heterococcy.x ueglectiis. | 



CHAP. XVII. j 



BORNEO AND JAVA. 



353 



FiBST Series. 

Very distinct Speeies. 



Secoks SEBIEa. 
Bepresentatiiv S]>Kies. 



Ceyx sharpei. 
„ dillwynni. 



Alcedinid^ (Kingfishers). 

I 9. Pelargopsis lencocephala. 
I 10. Dacelo melanops. 

PoDARGIDiE. 

1 11. Batrachostomus adspersu3. 
Caprimulgid^ (Goatsuckers). 



5. 


Caprimulgus arundinaceus. 


12. Caprimul 


6. 


„ concrctus. 




7. 


„ salvadorii. 






HiRUNDi.N-iDiE (Swallows). 


8. 


Delichon dasypus. | 




MuscicAPiD-E (Flycatchers). 


9. 


Cyomis rufifrons. 




10. 


„ turcosa. 




11. 


„ beccariai'a. 




12. 


Schwaneria ccerulata. 





13. 



14. 

15. 



16. 



Artamid.*; (Swallow-shrikes). 
Artamus clemencise. I 

Laniid/e (Shrikes). 
Lanius schwaneri. I 13. Volvocivora schierbrandi. 

rityriasis gjmnocephala. | 

NectariniiDjE (Sunbirds). 
Arachnothera crassirostris. | 



17. Zosterops melanura, 



DiCEiDiE (Flower-peckers). 

14. Prionochilus xanthopygius. 

15. Diceum nigrinicntum. 

16. Zosterops parvula. 



Pycnonotidje (Bulbuls). 



18. 
19. 
20. 



21. 
22. 
23. 



24. 
25. 
26. 



Pycnonotus gourdinii. 
Criniger diarili. 
,, tinschii. 



TiMALiiD.E (Babblers). 



Turdinus leucogrammicus. 
Setaria pectoralis. 
„ cinereicapilla. 



17. Pomatorhinus bomeensis. 

18. Mixornis borneeiisis. 

19. Dryuiocataphus capistratioides. 

20. Braehypterj'x unibratilis. 

21. Malacociucla rutiveutris. 



Pitta bertae. 
,, arcuata. 
baudii. 



PlTTID.E (Pittas). 

22. Pitta gi'anatina. 

23. „ sehwaueri. 

24. „ usheri. 

A A 



354 



ISLAND LIFE. [part ii. 



First Series. Secosd Series. 

Very distuKt Species. Bepreseutalive Species. 

Stlviid^ (Warblers). 

27. Abromis schwaneri. 
23. Prinia superciliaris. 

29. Calaniodyta doria?. 

30. Kittacincla stricklandi. 



25. Orthotomus borneonensis. 

26. Kittacincla suavis. 



CoRvlD^ (Crows and Jays). 

j 27. Dendrocitta cinerascens. 
I 28. Platysmurus aterrimus. 

Ai^UDiD.E (Larks). 

31. Mirafra borneensis. | 

Ploceid^ (We.iver Finches). 

32. Miinia fuscans. I 
PHASlAUiDiE (Pheasants). 



29. Argusiauus gray!. 

30. Euplocamus nobilis. 

31. „ pyronotus. 



(33. Polyplectrou eraphanum, I. of 
Palawan.) 

34. P. schleieimacberi. 

35. Lobiophasis bulweri. 

36. „ castaneicauda. 

Eallid^ (Kails). 

37. Eallina rufigenis. | 

Tktraokiu^ (Partridges &c.). 

38. Heraatortyx sanguiniceps. I 

39. Banibusicola hyperj-thra. | 

Representative forms of the same cliaracter as these are 
no doubt found in ail extensive continental areas, but they are 
rarely so numerous. Thus in Mr. Elwes' paper on the " Distri- 
bution of Asiatic Birds," he states that 12-5 per cent, of the land 
birds of Burmah and Tenasserim are peculiar species, whereas we 
find that in Borneo they are about 20 per cent., and the difference 
may fairly be imputed to the greater proportion of slightly 
modified representative species due to a period of complete 
isolation. Of peculiar genera, the Indo-Chinese Peninsula has 
oue — Ampeliceps, a remarkable yellow-crowned starhng, with 
bare pink-coloured orbits; while two others, Temnurus and 
Crypsirhina— singular birds allied to the jays — are found in 
no other part of the Asiatic continent though they-oeeur in 
some of the Malay Islands. Borneo has" three pecuhar genera, 
Schwanoria, a flycatcher ; Hematortyx, a crested partridge ; and 
Lobiophasis, a pheasant hardly distinct from Euplocamus ; while 



cn-ir. svii.] BORNEO AND JAVA. 355 

two others, Pityriasis, an extraordinary bare-headed bird 
between a jay and a shrike, and Carpococcyx, a pheasant-like 
ground cuckoo formerly thought to be peculiar, are said to have 
been discovered also in Sumatra. 

The insects and land-shells of Borneo and of the surrounding 
countries are too imperfectly known to enable us to arrive at 
any accurate results with regard to their distribution. They 
agree, however, with the birds and mammals in their general 
approximation to Malayan forms, but the number of peculiar 
species is perhaps larger. 

The proportion here shown of one-third peculiar species of 
mammaHa to about one-fifth peculiar species of land-birds, 
teaches us that the possession of the power of flight only affects 
the distribution of animals in a Umitcd degree, and gives us 
confidence in the results we may arrive at in those cases where 
we have, from whatever cause, to depend on a knowledge of the 
birds alone. And the difference we here find to exist is almost 
wholly due to thef'wide range of certain groups of powerful flight 
— as the birds of prey, the swallows and swifts, the king-crows, 
and some others ; while the majority of forest-birds appear to 
remain confined,Jiy evemiarrow watery barriers, to almost as 
great an extent as do the mammalia. 

The affinities of the Bornean Fauna.— The. animals of Borneo 
exhibit an almost perfect identity in general character, and a 
close similarity in species, with those of Sumatra and the Malay 
Peninsula. So great is this resemblance that it is a question 
whether it might not be quite as great were the whole united ; 
for the extreme points of Borneo and Sumatra are 1,500 miles 
apart— as far as from Madrid to Constantinople, or from Bombay 
to Rangoon. In this distance we should expect to meet with 
many local species, and even representative forms, so that we 
hardly require a lapse of time sufiicient to have produced specific 
change. So far as the forms of life are concerned, Borneo, as an 
island, may be no older than Great Britain ; for the time that has 
elapsed since the glacial epoch would be amply sufficient to pro- 
duce such a redistribution of the species, consequent on their 
mutual relations being disturbed, as would bring the islands into 
their present zoological condition. There are, however, other 

A A 2 



355 ISLAND LTFE. [rART ii. 



facts to be consilered, 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 
chancres must have been spread over a considerable lapse of time. 
In order to understand what these changes probably were, we 
must give a brief sketch of the fauna of Java, the peculiarities 
of which introduce a new element into the question we have to 
discuss. 

Java. 

The rich and beautiful island of Java, interesting alike to the 

politician, the geographer, and the naturalist, is more especially 

attractive to the student of geographical distribution, because 

it furnishes him with some of the most curious anomalies and 

difficult problems in a place where such would be least expected. 

As Java forms with Sumatra one almost unbroken line of 

volcanoes and volcanic mountains, interrapted only by the 

narrow Straits of Sunda, we should naturally expect a close 

resemblance between the productions of the two islands. But 

in point of fact there is a much greater ditference between them 

than between Sumatra and Borneo, so much further apart, and 

so very unlike in physical features. Java differs from the three 

I great land masses — Borneo, Sumatra, and the Malay Peninsula, 

! far more than either of these do from each other ; and this is 

Uhe first anomaly we encounter. But a more serious difficulty 

than this remains to be stated. Java has certain close resem- 

I blances to the Siamese Penin.sula, and also to the Himalayas, 

I which Borneo and Sumatra do not exhibit, and looking at the 

relative position of these lands respectively, this seems most 

incomprehensible. In order fully to appreciate the singularity 

and difficulty of the problem, it will be necessary to point out 

the exact nature and amount of these peculiarities in the fauna 

of Java. 

General character of tJie Fauna of Java. — If we were only to 
take account of tlie number of peculiar species in Java, and the 
relations of its fauna generally to that of the surrounding lands, 
we might pass it over as a less interesting island than Borneo or 
Sumatra. Its mammalia (ninety species) are nearly as numerous 



CHAT, xvii] BOI;XEO AND JAVA. ?57 

as those of Borneo, but aie apparently less peculiar, noue of 
the genera and only five or six of the species being confined to 
the island. In land-birds it is decidedly less rich, having 
only 270 species, of which forty are peculiar, and only one or two 
belong, to peculiar genera; so that here again the amount of 
/Speciality is less than in Borneo. It is only when we proceed to 
analyse the species of the Javan fauna, and trace their distri- 
bution and affinities, that we discover its interesting nature. 

Difference between the Fauna of Java and that of the other 
great Malay Islands. — Comparing the fauna of Java w^ith that 
which may be called the typical Malayan fauna as exhibited in 
Borneo, Sumatra, and the Malay Peninsula, we find the follow- 
ing differences. No less than thirteen genera of mammalia, 
each of which is known to inhabit at least two, and generally all 
three, of the above-named Malayan countries, are yet totally 
absent from Java ; and they include such important forms as the 
elephant, the tapir, and the Malay bear. It cannot be said that 
this difference depends on imperfect knowledge, for Java is one 
of the oldest European settlements in the East, and has been 
explored by a long succession of Dutch and English naturalists. 
Every part of it is thoroughly well known, and it would be 
almost as difficult to find a new mammal of any size in Europe 
as in Java. Of birds there are twenty-five genera, all typically 
Malayan and occurring at least in two, and for the most part 
in all three of the Malay countries, which are yet absent from 
Java. Most of these arc large and conspicuous forms, such 
as jays, gapers, bee-eaters, woodpeckers, hornbills, cuckoos, 
parrots, pheasants, and partridges, as impossible to have remained 
undiscovered in Java as the large mammalia above referred to. 

Besides these absent ge7iera there are some curious illus- 
trations of Javan isolation in the species; there being several 
cases in which the same species 'occurs in all three of the typical 
Malay countries, while in Java it is represented by an allied 
species. Such appear to be the Malayan monkey, Semno- 
pithecus cristatus, replaced in Java by S. maitrus; and the 
large Malay deer, Iiusa eqidnus, represented in Java by H. 
hippelaphits. Among birds there are more numerous examples, 
no less than seven species which are common to the three great 



,358 ISLAND LIFE. [part ii. 

Malay countries being represented in Java by distinct but 
closely allied species. 

From these facts it is impossible to doubt that Java has 
had a history of its own, quite distinct from that of the other 
portions of the Malayan area. 

Special relatio)U< of the Javan Fauna to that of the Asiatic 
Continent. — These relations are indicated by comparatively 
few examples, but they are very clear and of great im- 
portance. Among mammalia, the genus Helictis is found in 
Java but in no other Malay country, though it inhabits also 
North India ; while two species. Rhinoceros javanicus and Lepvs 
kurgosa, are natives of Indo-Cliinese countries and Java, but not 
of typical Malaya. In birds there are three genera — Zoothera, 
Notodela, and Crypsirhina, which inhabit Java and Indo-China ; 
while four others — Brachypteryx, Allotrius, Cochoa, and Psal- 
tria, inhabit Java and the Himalayas, but no intervening 
country. There are also two species of birds — a trogon {Harpactes 
oreskios), and the Javanese peacock (Pavo muticus), which inhabit 
only Java and the Indo-Chinese Peninsula. 

Here, then, we find a series of remarkable similarities between 
Java and the Asiatic continent, quite independent of the typical 
Malay countries — Borneo, Sumatra, and the Malay Peninsula, 
which latter have evidently formed one connected land, and 
thus appear to preclude any independent union of Java 
and Siam. 

The great difficulty in explaining these facts is, that all the 
required changes of sea and land must have occurred withia 
the period of existing species of mammaha. Sumatra, Borneo, 
and Malacca are, as we have seen, almost precisely ahke 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 speciaUty, since its species, when not Malayan, are 
almost all Indian or Siamese. 

There is, however, one consideration which maj' 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 stabihty of 
the equatorial climate. We have seen, in Chapter X., how 



CHAP, xvn.] BORNEO AND JAVA. 359 

important an agent in producing extinction and modification of 
species must have been the repeated changes from cold to warm, 
and from warm to cold conditions, with the inevitable migrations 
and crowding together that must have been their necessary con- 
sequence. But in the lowlands, near the equator, these changes 
Avould be very little felt, and thus one great cause of specific 
modification would be wanting. Let us now see whether we 
can sketch out a series of not improbable changes which may 
have brought about the existing relations of Java and Borneo to 
the continent. 

Past Geographical Chanr/es of Java and Borneo. — Although 
Java and Sumatra are mainly volcanic, they are by no means 
wholly so. Sumatra possesses in its great mountain masses 
ancient crystalline rocks with much granite, while there are 
extensive Tertiary deposits of Eocene age, overlying which are 
numerous beds of coal now raised up many thousand feet above 
the sea.i The volcanoes appear to have burst through these 
older mountains, and to have partly covered them as well as 
great areas of the lowlands with the product of their erup- 
tions. In Java either the fundamental strata were less extensive 
and less raised above the sea, or the period of volcanic action 
has been of longer duration ; for here no crystalline rocks have 
been found except a few boulders of granite in the western 
part of the island, perhaps a relic of a formation destroyed by 
denudation, or covered up by volcanic dcjjosits. 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 hemi- 
sphere, during the severest part of which a few Himalayan 

1 "On the Geology of Sumatra," by M. R. D. 1[. Veibeck. Geolnr/ical 
Magazine, 1877. 



f 



360 ISLAND LIFE. [part ii. 

species of birds and mammals may have been driven south- 
ward, and ranged over suitable portions of the whole area. 
Java was then separated by subsidence, and these species 
became imprisoned there ; while those in the remaining part of 
the ]Malayan area again migrated northward when the cold had 
passed away from their former home, the equatorial forests of 
Borneo, Sumatra, and the ilalay Peninsula being more especially 
adapted to the typical Malayan fauna which is there developed 
in rich profusion. A little later the subsidence may have 
extended farther north, isolating Borneo and Sumatra, but pro- 
bably leaving the Malay Peninsula as a ridge between them as 
far as the islands of Banca and Biliton. Other slight chansres 
of climate followed, when a further subsidence separated these 
last-named islands from the Malay Peninsula, and left them 
with two or three species which have since become slightly 
modified. We may thus explain how it is that a species is 
sometimes common to Sumatra and Borneo, while the inter- 
vening island (Banca) possesses a distinct form.' 

In my Geographical Distribution of Animals, Yol. I., p. 357, I 
have given a somewhat different hj'pothetical explanation of the 
relations of Java and Borneo to the continent, in which I took 
account of changes of land and sea only ; but a fuller consideration 
of the influence of changes of climate on the migration of animals, 
has led me to the much simpler, and, I think, more probable, 
explanation above given. The amount of the relationship be- 
tween Java and Siam, as well as of that between Java and the 
Himalayas, is too small to be well accounted for by an indepen- 
dent geographical connection in which Borneo and Sumatra did 
not take part. It is, at the same time, too distinct and indisput- 
able to be ignored ; and a change of climate which should drive 
a portion of the Himalayan fauna southward, leaving a few 
species in Java, from which they could not return owing to 
its subsequent isolation by subsidence, seems to be a cause 
exactly adapted to produce the kind and amount of affinity 
between these distant countries that actually exists. 

1 Pitta megarhynchus (Banca) allied to P. brachyunts (Borneo, Suma- 
t:a. Malacca) ; and Pitta bangkanus (Banca) allied to P. sordidus (Borneo 
and Sumatra). 



CEAP. XVII.] THE PHILIPPINES. 301 

Tlie Philippine Islands. — A sufficiently detailed account of the 
fauna of these islands, and their relation to the countries which 
form the subject of this chapter, has been given in my Geo- 
graphical Distrihution of Animals., VoL I. pp. 345-349 ; but since 
that time considerable additions have been made to their fauna, 
and these have had the effect of diminishing their isolation from 
the other islands. Six genera have been added to the terrestrial 
mammalia — Grocidura, Felis, Tragulus, Hystrix, Pteromys, and 
Mus, as well as two additional squirrels ; while the black ape 
(Ci/nojnthecns niger) has been struck out as not inhabiting the 
Philippines. This brings the known mammalia to twenty-one 
species, and no doubt several others remain to be discovered. 
The birds have been increased from 219 to 288 species, and the 
additions include many Malayan genera which were thought to be 
absent. Such are I'hyllornis (green bulbuls) ; Eurylsemus (gaper), 
Malacopteron, one of the babblers ; and Criniger, one of the fruit- 
thrushes; as well as Batrachostomus, the frog-mouthed goat- 
sucker. There still remain, however, a large number of Malayan 
genera absent from the Philippines, while there are a few 
Australian and Indian or Chinese genera which are not Malayan. 
We must also note that about nine-tenths of the mammalia and 
two-thirds of the land-birds are peculiar species, a very much 
larger proportion than is fuuud on any other Malay island. 

The origin of these peculiarities is not difficult to trace. The 
Philippines are almost surrounded by deep sea, but are connected 
with Borneo by means of two narrow submarine banks, on the 
northern of which is situated Palawan, and on the southern the 
Sooloo Islands. Two small groups of islands, the Bashees and 
Babuyanes, have also afforded a partial connection with the 
continent by way of Formosa. It is evident that the Philippines 
once formed part of the great Malayan extension of Asia, but 
that they were separated considerably earlier than Java ; and 
having been since greatly isolated and much broken up by 
volcanic disturbances, their species have for the most part 
become modified into distinct local species. They have also 
received a few Chinese types by the route already indicated, 
and a few Australian forms owing to their proximity to the 
Moluccas. The reason of their comparative poverty in genera 



362 ISLAND LIFE. [part ii. 

and species of the higher animals is, that they have been 
subjected to a great amount of submersion in recent times, 
greatly reducing their area, and causing, no doubt, the ex- 
tinction of a considerable portion of their fauna. This is not 
a mere hypothesis, but is supported by direct evidence ; for I am 
informed by Mr. Everett, who has made extensive explorations 
in the islands, that almost everywhere are found large tracts of 
elevated coral-reefs, containing shells similar to those Hving in 
the adjacent seas ; an indisputable proof of recent elevation. 

Concluding remarks on the Malay Islands. — This completes our 
sketch of the great Malay islands, the seat of the typical 
Malayan fauna. It has been shown that the pecuharities 
presented by the individual islands may be all sufficiently well 
explained by a very simple and comparatively unimportant series 
of geographical changes, combined with a limited amount of 
change of cUmate towards the northern tropic. Beginning in late 
Miocene times when the deposits on the south coast of Java 
were upraised, we suppose a general elevation of the whole of the 
extremely shallow seas uniting what are now Sumatra, Java, 
Borneo, and the Philippines with the Asiatic continent, and 
forming that extended equatorial area in which the typical 
Malayan fauna was developed. After a long period of stability, 
giving ample time for the specialisation of so many peculiar 
types, the Philippines were first separated ; then at a con- 
siderably later period Java ; a httle later Sumatra and Borneo ; 
and finally the islands south of Singapore to Banca and BiUton. 
This one simple series of elevations and subsidences, combined 
with the changes of cUmate 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 puzzUug, relations, of the faunas of Java and the Phihp- 
pines, as compared with those of the larger islands. 

We wiU 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 XVIIT. 

JAPAX AND FOEMOSA. 

Japan, its position and Pliysical features— Zoological features of Japan — 
Mammalia— Bii lis— Birds common to Great Britain and Japan —Birds 
peculiar to Japan — Japan birds recurring in distant areas — Formosa — 
Physical features uf 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 Kecent 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 tlie western, except that they are about 
sixteen degi'ees 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 ; wliile their geological structure is very complex, their 
soil extremely fertile, and their vegetation in the highest degree 
varied and beautiful. Like our own islands, too, they are con- 
nected with the continent by a marine bank less than a hundred 
fathoms below the surface — at all events towards the north and 
south ; but in the intervening space the Sea of Japan opens out 
to a width of six hundred miles, and in its central portion is 
very deep, and this may be an indication that the connection 
between the islands and the continent is of rather ancient 
date. At the Straits of Corea the distance from the main 
land is about 120 miles, while at the northern extremity of 



364 



ISLAND LIFE. 



[pari II. 




MAP OK JAPAN AND FORMOSA (witU dCptllS ill futllOins). 

Light tint, sea under TOO fathoms. Medium tint, under 1.000 fathoms. Dark tint, over 
1,000 fathoms. The figures show the depth in fathoms. 



CHAP, xviii.] JAPAN AXD FORMOSA. 365 



Yesso it is about 200. The island of Saghalien, however, 
separated from Yesso by a strait only twenty- five miles wide, 
forms a connection with Amoorland in about 52° N. Lat. A 
southern warm current flowing a little to the eastward of the 
islands, ameliorates their climate much in the same way as the 
Gulf Stream does ours, and added to their insular position enables 
them to support a more tropical vegetation and more varied 
forms of life than are found at corresponding latitudes in China. 

Zoological features of Japan. — As we might expect from the 
conditions here sketched out, Japan exhibits in all its forms of 
animal life a close general resemblance to the adjacent continent, 
but with a considerable element of specific individuality ; while 
it also possesses some remarkable isolated groups. It also ex- 
hibits indications of there having been two or more lines of 
migration at different epochs. The majority of its animals are I 
related to those of the temperate or cold regions of the continent, 
either as identical or allied species; but a smaller number have a 
tropical character, and these have in several instances no allies 
in China but occur again only in Northern India or the Malay 
Archipelago. There is also a slight American element in the 
fauna of Japan, a relic probably of the period when a land 
communication existed between the two continents over what 
are now the shallow seas of Japan, Ochotsk, and Kamschatka. 
We will now proceed to examine the peculiarities and relations 
of the fauna. 

Mammalia. — The mammalia of Japan at present known are 
forty in number ; not very many when compared with the rich 
fauna of China and Manchuria, but containing monkeys, bears, 
deer, wild goats and wild boars, as well as foxes, badgers, moles, 
squirrels, and hares, so that there can be no doubt whatever 
that they imply a land connection with the continent. No 
complete account of Japan mammals has been given by any 
competent zoologist since the publication of Von Siebold's 
Fauna Jajjonica in 1844, but by collecting together most of the 
scattered observations since that period the following list has 
been drawn up, and will, it is hoped, be of use to naturalists. 
The species believed to be peculiar to Japan are printed in 
italics. These are very numerous, but it must be remembered 



366 ISLAND LIFE. [pabt u. 

that Corea and Manchuria (the portions of the continent 
opposite Japan) are comparatively little kno'vra, 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 Islakds. 

1. Mmocxis speeiosus. A monkey with rudimentary tail and red face, 

allied to the Barbary ape. It inhabits the island of Niphon up to 
41' N. Lat., and has thus the most northern range of any living 
monkey. 

2. Pteropus daxymalhts. 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. Ehinolophus ferrum-equinum. The great horse-shoe bat, ranges from 

Britain across Europe and temperate Asia to Japan. It is the 
R. nippon of the Fauna Japonica according to Mr. Dobson's Mono- 
graph of Asiatic Bats. 

4. R. minor. Found also in Burma, Yiman, 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. 

maerodactylus 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 cf eight in the lower jaw. 

12. Urotrichus talpoides. A peculiar genus of moles confined to Japan 

and the north-west coast of N. America. The American species has 
been named Urotrichtis gibsii, but Mr. Lord after comparing the two 
says that he " can find no difference whatever, either generic or 
specific. In shape, size, and colour, they are exactly alike." 
13r~Sorex myosurus. A shrew, found also in India and Malaya. 

14. Sorex dzi-nezumi. 

15. /S. umhrinus. 

16. S. platycephahis. 

17. Ursus arctos. var. A peculiar variety of the European brown bear 

which inhabits also Amoorland and Kamschatka. It is the Ursus 
ferox of the Fauna Japonica. 

18. Urs^u japonicus. A peculiar species allied to the Himalayan and For- 

uiosan species. Named U. tibetanns in the Fauna Japonica. 



CHAP, xviii.] JAPAN AND FORMOSA. 3fi7 

19. Meles anahuma. Differs from the European and Siberian badgers in 

the form of tlie sl<vilh 

20. Mustcla brachyura. A peculiar marten found also in the Kurilc 

Islands. 

21. Mustela melanopus. The Japanese sable. 

22. M. Ja])onica. A peculiar marten (See Froc. Zool. Soc. 1865, p. lO-l). 

23. M. Sibericus. Also Siberia and China. This is the M. iialsi of the 

Fauna Japonica according to Dr. Gray. 

24. Lutronedes whiideyi. A new genus and species of otter (P. Z. S. 

1867, p. 180). In the Fauna Japonica named Lntra vulgaris. 

25. Enhydris marina. The sea-otter of California and Kamschatka. 

26. Canis hodophylax. According to Dr. Graj- allied to C^^on sumatranus 

of the Malay Islands, and C. alpinus of Siberia, if not identical 
with one of them (P. Z. S. 1868, p. 500). 

27. Vulpes japonica. A peculiar fox. Caiiis ii«/pes of Fauna Japonica. 

28. Nyctcreutes procyonoides. The racoon-dog of N. China and Amoor- 

land. 

29. Lepns Irachyurus. A peculiar hare. 

30. Sciurus lis. A peculiar squirrel. 

31. Fteromys Icucogenys. The white-cheeked flying squirrel. 

32. P. momoga. Perhaps identical with a Cambojan species (P. Z. S. 

1861, p. 137). 

33. Myoxus japonicus. A peculiar dormouse. M. clegans of the Fauna 

Japonica ; M. javaniciis, Schinz {Synopsis Mammalium, ii. p. 530). 
34 Mus argenteus. China. 

35. Mus molossinus. 

36. Mus nezumi. 

37. M. speciosus. 

38. Cervus sika. A peculiar deer allied to C. jjseudaxis of Fonnosa and 

C. mantchuricus of Northern China. 

39. Nemorliechis crispa. A goat-like antelope allied to N. sumatranus of 

Sumatra, and iV. Swivl/oci of Formosa. 

40. Sus leucomystax. A wild boar allied to S. taevaniis of Formosa. 

We thus find that no less than twenty-six out of the forty 
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 closely aUied to 
an American species ; a peculiar genus of otters ; and an antelope 
whose nearest allies are in Formosa and Sumatra. The import- 
ance of these facts will be best understood when we have examined 
the corresponding affinities of the birds of Japan. 



36« ISLAND LIFE. [paut ii. 

Birds. — Owing to the recent researches of some English resi- 
dents we have prohably a fuller knowledge of the birds than of 
the mammalia ; yet the number of true laud-birds ascertained 
to inhabit the islands either as residents or migrants is only 
165, which is less than might be expected considering the 
highly favourable conditions and the extreme riches of the 
adjacent continent, — Mr. Swinhoe's list of the birds of China 
containing more than 400 land species, after deducting all which 
are peculiar to the adjacent islands. Only sixteen species, or 
about one-tenth of the whole, are now considered to be peculiar 
to Japan ; but even of these, five are classed by ilr. Seebohm as 
sub-species or slightly modified forms of continental birds, so 
that eleven only are well-marked species, undoubtedly distinct 
from those of any other country. 

The great majority of the birds are decidedly temperate forms 
identical with those of Northern Asia and Europe ; while no less 
than forty of the species are also found in Britain, or are such 
slight modifications of British species that the ditference is only 
perceptible to a trained ornithologist. The following list of the 
birds common to Britain and Japan is very interesting, when we 
consider that these countries are separated by the whole extent 
of the European and Asiatic continents, or by almost exactly 
one-foiirth of the circumference of the globe : — 

Birds common to Great BRrriAN and Japan.* 

1. Common Creeper {Certhia /ami- 11. Swallow, sub-sp. {Hirundo gut- 

liaris). iuralh). 

2. Nuthatch (SUta europea). 12. Sand martin {Cotyh riparia). 

3. Coal tit {Panis ater). 13. Brambling (Fringilla montifrin- 

4. Mareh tit, sub-sp. {P.japonicus). gilla). 

b. Long-tailed tit (Acredula cau- 14. Siskin {iChrv/somitris spiniis). 

data). 15. hessei iedpo\e{^Jgiotfius liiiaria). 

6. Great grey shrike {Lanius excu- 16. Tree-sparrow (Passer ?»oHtan!(«..) 

hitor). 17. Pine grosbeak {Fyrrhida emi- 

7. Nutcracker (Nucifraga caryoca- clealor). 

tactes). 18. Reed bunting, sub-sp. {Emheriza 

8. Carrion Crow {Corvus corone). pyrrlndina). 

9. Raven ( Corrus foraa-). 19. Snow bunting {Plectrophanes 
10. Was wing (Ampelis garrula). nivalis). 

1 Extracted from Messrs. Blakiston and Fryer's Catalogue of Birds of 
Japan {Ibis, 1878, p. 209), with Mr. Seebohm's additions and corrections 
[Ibis, 1879, p. 18). 



CHAP, xvin.] JAPAN AND FORMOSA. 369 

20. Grey wagtail, sub-sp. (ITofacfVfa 30. GoUen eag]e{Aquilachri/saefos). 

melanope). 31. White-tailed eagle (Haliaetus 

21. Great spotted woodpecker (P(V«s alhirilla). 

major). 32. Kestrel (Falco timmnculus). 

22. Great black woodpecker {Dry- 33. Hobby (F. suhhuleo). 

ocoptis marlius). 34. Merlin (F. a;salon). 

23. Cuckoo (Cuctdus lanorus). 35. Peregrine falcon (i^.pei-fjnnus). 

24. Hoopoe (Upnpaepops). S6. Greenland falcon (i^. cajirficajis). 

25. Rock-dove (C'o/«mia/ii'm). 37. Ospvey {Pandinn haliaetus). 
2fi. Hen harrier {Circus ci/anevs). 38. Eagle owl {Bubo maxhuus). 

27. Gos-hawk {Astur palumbarius). 39. Short-eared owl {Asia accipitri- 

28. Sparrow-hawk {Accipiler iiisvs). nus). 

29. Rough-legged bnzzard {Buteo 40. Loug-eared owl (^. o/i/«). 

lagopus). 

But these forty species by no means fairly represent the 
amount of resemUance between Britain and Japan as regards 
birds ; for there are also wrens, hedge-spaiTows, gold-crests, sedge- 
warblers, pipits, larks, rock-thrushes, jays, and many others, 
which, though distinct species from our own, have the same 
general appearance, and give a familiar aspect to the ornithology. 
There remains, however, a considerable body of Chinese and 
Siberian species, which link the islands to the neighbouring 
parts of the continent ; and there are also a few which are 
Malayan or Himalayan rather than Chinese, and thus afford us 
an interesting problem in distribution. 

The sixteen species and sub-species which are altogether 
peculiar to Japan are for the most part allied to birds of North 
China and Siberia, but three are decidedly tropical, and one of 
them— a fruit pigeon {Treron sichuldi) — has no close ally nearer 
than Java and the Himalayas. In the following list the affini- 
ties of the species are indicated wherever they have been 
ascertained : — 



List of the Species of Land Birds peculiar to Japan. 

1. Farus Japonicus. A sub-species of P. ^)«/«s()is, very like Siberian 

varieties. 

2. Parusvarius. Very distinct. It nearest ally is in Formosa. 

3. Hypsipetes amaurosis. A tropical genus. Allied to species of S. China 

and India. 

4. Garrxilus japonicus. Allied to our European jay. In Niphon only. 

5. Garrulus lidlhi. A very distinct and handsome species. (See Ibii 

1873,-p. 478.) 

B B 



370 ISLAND LIFE. [paet ii. 

6. Zosterops japonica. Allied to a migratory Chinese species. 

7. Ckelidon hlah'stoni. Allied to C. whiteleyi of N. China. 

8. Chlorospiza laicarahiba. Allied to C. siiiica of China and Japan. 
0. Emheriza ciopsis. A sub-species of the E. chides of X. China. 

10 Emheriza yessoengis. Allied to the Siberian E. passerina. 

11. Euspiza variabilis. A very distinct species. 

12. Picas kisuL-i. Allied to P. pygmteus of Central Asia. 

13. Grcinus awokera. Allied to G. canus (N. Cliina), and G. viridis, Europe. 

14. AluUeripicus richardsi. Allied to J/, craicfurdi of Pegu. In Tzus 

Sinia Island ( P. Z. S. 1879, p. 386). 

15. Treron sieboldi. Allied to T. sphenura (Himalayas), and T. lorthalsi, 

Java. 

16. Accipiter gularis. A sub-species of the Malayan A. virgatus (also in 

Formosa). 

17. Buteo hemilasius. A distinct species. 

18. St/rnium rufescens. A sub-species of S. uraUnse of E. Europe and 

Siberia. 

Japan hirds recurrivg in distant areas. — The most interesting 
feature in the ornithology of Japan is, undoubtecUj, the pre- 
sence of several sjiecies which indicate an alliance with such 
remote districts as the Himalayas, the Malay Islands, and 
Europe. Among the pecuUar species, the most remarkable of 
this class are, — the fruit-pigeon of the genus Treron, entirely un- 
known in China, but reappearing in Formosa and Japan; the 
Hypsipetes, whose nearest ally is in South China at a distance 
of nearly 50U miles ; and the jay {Gamdus jajionicus), whose 
close ally {G. tjlandarius) inhabits Europe only, at a distance of 
3,700 miles. But even more extraordinary are the follo\ving 
non-peculiar species : — Sjnzaetus oricntalis, a crested eagle, in- 
habiting the Himalayas, Formosa, and Japan, but unknown in 
China ; Ceryh guttata, a spotted kingfisher, entirely confined to 
the Himalayas and Japan ; and Halcyon coromanda, a brilliant 
red kingfisher inhabiting Northern India, the Malay Islands to 
Celebes, Formosa, and Japan. We have here an excellent illus- 
tration of the favourable conditions which islands afford both 
for species which elsewhere live further south (Halcyon coro- 
manda), and for the preservation in isolated colonies of species 
which are verging towards extinction ; for such we must consider 
the above-named eagle and kingfisher, both confined to a very 
limited area on the continent, but surviving in remote islands. 



CHAP. XVIII.] JAPAN AND FORMOSA. 371 

The spotted kingfislier, indeed, affords us one of the best ex- 
amples of that rare phenomenon — a species with a discontimious 
range; for although an island is considered, for purposes of 
distribution, to form part of one continuous area with the 
adjacent continent (as when a species is found in France and 
Britain, or in Siam and Borneo, we do not say that the area of 
distribution is discontinuous), yet in this case we have to pass 
over three thousand miles of land after quitting the island, 
before we come to the continental portion of the area occupied 
by the species. Referring to our account of the birth, growth, 
and death of a species (in Chapter IV.) it can hardly be doubted 
that the Ccri/lc cfu/lafa formerly ranged from the Himalayas to 
Japan, and has now died out in the intervening area owing to 
geographical and physical changes, a subject which will be 
better discussed when we have examined the interesting fauna 
of the island of Formosa. 

The other orders of animals are not yet sufficiently known to 
enable us to found any accurate conclusions upon them. The 
main facts of their distribution have already been given in my 
Geographical Distribution of Animals (Vol I., pp. 227-231), and 
they sufficiently agree with the birds and mammalia in showing 
a mixture of temperate and tropical forms with a considerable 
proportion of peculiar species. Owing to the comparatively 
easy passage from the northern extremity of Japan through the 
island of Saghalien to the main land of Asia, a large number of 
temperate forms of insects and birds are still able to enter the 
country, and thus diminish the proportionate number of peculiar 
species. In the case of mammals this is more difficult ; and the 
large proportion of specific difference in their case is a good in- 
dication of the comparatively remote epoch at which Japan was 
finally separated from the continent. How long ago this sepa- 
ration took place we cannot of course tell, but we may be sure 
it was much longer than in the case of our own i.slands, and 
therefore probably in the earlier portion of the Pliocene period. 

Formosa. 
Among recent continental islands there is probably none that 
surpasses in interest and instructiveness the Chinese island 

B B 2 



372 INLAND LIFE. [iartii. 

named by the Portuguese Formosa, or " The Beautiful." Till 
quite recently it was a terra incofjnita to naturalists, and we 
owe all our present knowledge of it to a single man, the late 
Mr. Robert Swinhoe, who, in his official capacity as one of our 
consuls in China, visited it several times between 18.56 and 1866, 
besides residing on it for more than a year. During this jjeriod 
he devoted all his spare time and energy to the study of natural 
history, more especiall}' of the two important groups, birds and 
mammals ; and by employing a large staff" of native collectors 
anl hunters, he obtained a very complete knowledge of its 
fauna. In this case, too, we have the great advantage of a very 
thorough knowledge of the adjacent parts of the continent, in 
great part due to Mr. Swinhoe's own exertions during the twenty 
years of his service in that country. We possess, too, the 
further advantage of having the who!e of the available materials 
in these two classes collected together by Mr. Swinhoe himself 
after full examination and comparison of specimens ; so that 
thei-e is probably no part of the world (if we except Europe, 
North America, and British India) of whose warm-blooded 
vertebrates we poss'^ss fuller or more accurate knowledge than 
we do of those of the coast districts of China and its islands.^ 

Physical fcahtres of Formosa. — The island of Formosa is 
nearly half the size of Ireland, being 220 miles long, and from 
twenty to eij;hty miles wide. It is traversed down its centre by 
a fine mountain range, which reaches an altitude of about 8,000 
feet in the south and 12,000 feet in the northern half of the 
island, and whose higher slopes and valleys are everywhere 
clothed with magnificent forests. It is crossed by the line of the 
Tropic of Cancer a little south of its centre ; and this position, 
combined with its lofty mountains, gives it an unusual variety 
of tropical and temperate climates. These circumstances are 
all highly favourable to the preservation and development of 
animal life, and from what we already know of its productions, 

' Mr. Swinhoe died in October, 1877, at the early age of forty-two. His 
writings on natural liistorj- are chiefly scattered through the volumes of the 
Proceedings of the Zoological Society and The Ibis ; the whole being siiin- 
niariscd in his Catalogue of the 3Ia»tmals 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). 



CHAP. XVIII.] JAPAN AND FORMOSA. 373 

it seems probable that few, if auy islands of appro.NiinntL'ly the 
same size and equally removed from a continent will be found to 
equal it in the number and vai'iety of their higher animals. The 
outline map (at page 'Mji) 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 
contiaent, the submergence of which isolated these islands 
from the mainland. 

Animal Life of Formosa. — We are at present acquainted 
with 35 species of mammalia, and 128 species of land-birds 
from Formosa, fourteen of the former and forty-three of the 
latter being peculiar, while the remainder inhabit also some 
part of the continent or adjacent islands. This proportion of 
peculiar species is perhaps (as regards the birds) the highest to 
be met with in any island which can be classed as both conti- 
nental and recent, and this, in all probabihty, implies that the 
epoch of separation is somewhat remote. It was not, however, 
remote enough to reach back to a time when the continental 
fauna was very different from what it is now, for we find all the 
chief types of living Asiatic mammalia represented in this small 
island. Thus we have monkeys ; insectivora ; numerous ear- 
nivora; pigs, deer, antelopes, and cattle among ungulata; 
numerous rodents, and the edentate Manis, — a very fair repre- 
sentation of Asiatic mammals, all being of known genera, and of 
sjjecies either absolutely identical with some still living else- 
where or very closely allied to them. The birds exhibit analo- 
gous phenomena, with the exception that we have here two 
peculiar and very interesting genera. 

But besides the amount of specific and generic modification 
that has occurred, we have another indication of the lapse 
of time in the peculiar relations of a large proportion of the 
Formosan animals, which show that a great change in the dis- 
tribution of Asiatic species must have taken place since the 
separation of the island from the continent. Before pointing 
these out it will be advantageous to give lists of the mammalia 



374 ISLAND LIFE. [past n. 

and peculiar birds of the island, as we shall have frequent occa- 
sion to refer to them. 



List of thk JlAiiMiLi-i of Foiimosa. (The peculiar species are printed 

in italics.) 

1. Macacus cyclopis. A rock-monkey more allied to 3[. rhesus of India 

tlian to M. saneti-johannis of South China. 

2. Pteropus formosus. A fruit-bat closely allied to the Japanese species. 

None of the genus are foMnd in China. 

3. Vespenigo abranius. China. 

4. Vespertilio formosus. Black and orange Bat. China. 

5. Nyctinomus cestonii. Lirge-eared Bat. China, S. Europe. 

6. Talpa insularin. A blind mole of a peculiar species. 

7. Sorex murinus. Musk Kat. China. 

8. Sorex sp. A shrew, undescribed. 

9. Erinaceus sp. A Hedgehog, undescribed. 

10. UrsHS tibetanus. The Tibetan Bear. Himalayas and North China. 

11. Hclictis subauranliaca. The orange-tinted Tree Civet. Allied to JS. 

nipalensis of the Himalayas more than to //. tnoschafa of Cliina. 

12. Martes fiavigula, 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. Viverricula raalaccensis. Spotted Civet. China, India. 

17. Paguma larvata. Gem-faced Civet. China. 

18. Sus laivanuD. Allied to the wild Pig of Japan. 

19. Cervulus reevesii. Reeve's Muntjac. China. 

20. Cervus pseudaxis. Formosan Spotted Deer. Allied to C. s\ka of 

Japan. 

21. Cervus swinlioii. Swinhoe's Rusa Deer. Allied to Indian and Malayan 

species. 

22. Nemorltadus sicinhoii. Swinhoe's Goat-antelope. Allied to the species 

of Simiatra and Japan. 

23. Bos chincnsis. South China wild Cow. 

24. Mus bandicota. The Bandicoot Rat. Perhaps introduced from India. 

25. Mus indicus. Indian Rat. 

26. J/us coxinga. Spinous Country-rat. 

27. Mus canna. Silken Country-rat. 

28. Mus losea. Brown Country-rat. 

29. Sciurus castaneoventris. Chestnut-bellied Squirrel. China and Hainan 

30. Sciurus m'clellaudi. M'Clelland's S^iuirrel. Himalayas, China. 

31. Sciuroptenis hakensis. Small Formosan Flj-ing Siuirrel. Allied to 

S. alboniijer of Nepal. 

32. Pteromys grandls. Large Red Flying Squirrel. Allied to Himalayan 

and Bomean species. From North Formosa. 



cHAi'. xviii ] JAPAN AND FORMOSA. 375 

33. Piei-omys pectoraUs. 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 {HclidU subaurantiaca), and the small 
flying squirrel {Sciuropterus kaleensis), are both allied to Hima- 
layan species. Swinhoe's deer and goat-antelope are nearest to 
Malayan species, as are the red and white-breasted flying squir- 
rels ; while the fruit-bat, the wild pig, and the spotted deer are 
all allied to peculiar Japanese species. The clouded tiger is a 
Malay species unknown in China, while the Asiatic wild cat is 
a native of the Himalayas and Malacca. It is clear, therefore, 
that before Formosa was separated from the main land the above 
named animals or their ancestral types must have ranged over 
the intervening country as far as the Himalayas on the west, 
Japan on the north,' and Borneo or the Philippines on the south ; 
and that after that event occurred, the conditions were so mate- 
rially changed as to lead to the extinction of these species 
in what are now the coast provinces of China, while they or 
their modified descendants continued to exist in the dense forests 
of the Himalayas and the Malay islands, and in such detached ' 
islands as Formosa and Japan. We will now see what additional 
light is thrown upon this subject by an examination of the 
birds. 

List of the Land Birds peculiar to Formosa. 

TuRDlDiE (Thrushes). 

1. Tiirdus albireps. Allied to Chinese species. 

SvLViDi^ (Warblers). 

2. Cistkola volitans. Allied to C. schu'nicdla of India and Cliina. 

3. Herhivox cantons. Sub-species of H. canlillaus of N. China and 

Japan. 

4. Kotodela montium. Allied to N. leucura of the Himalayas ; no ally in 

China. 



376 ISLAND LIFE. [part ii. 

TlMALiiD^ (Babblers). 

5. Pomatorhinits mtisicus. Allies in S. China and the Himalayas. 

6. P. erythrociiemis. Do. do. 

7. Garrulax riijiceps. Allied to G. aJbogularls of N. India and East 

Thibet, not to the species of S. China ((?. sannio). 

8. Janthocincla pfecilor/n/ncha. Allied to J. ccerulata of the Himalayas. 

Kone cf the genus in China. 

9. Trockalojileron taivanus. Allied to a Chinese species. 

10. Alcipi)e morrisoniaita.\ Near the Hi:nalayan ^. Hi^pa/ensis. None of 
1\. A. hmnnea. f the genus in China. 

12. Sibia auricularis. Allied to the Himalayan S. capistrata. The genus 

not known in China. 

Pasurid* (Bearded Tits, &c). 

13. Sulhora bulomachus. Allied to the Chinese S. sitffusa. 

ClNCLlD-i; (Dippers and Whistling Thrushes). 

14. Myiophoneus tnsularis. Allied to Af. horsfieldi of South India. 

Parid.*; (Tits). 

15. Porus ingperatus. Sub-species of P. monticola of the Himalayas and 

East Thibet. 

16. P. castaneivenlris. Allied to P. rarius of Japan. 

LlOTRICHID* (Hill Tits). 

17. Liocidila steen'i. A peculiar genus of a specially Himalayan family, 

quite unknown in China. 

PycNOXOTiD.i; (Bulbuls). 

18. Pycnonotus {Spizizos) cinereicapillua. Very near P. nemttorques of 

China. 

19. Hypsipetes nigerrimus. Allied to H. coiicolor of Assam, not to H. 

macclellandi of China. 

ORIOLID.E (Orioles). 

20. Analcipvs ardens. Allied to A. traUlii of the Himalayas and Tenas- 

serim. 

Campephagid.e (Caterpillar Shrikes). 

21. Graucalus rex-pineli. Closely allied to the Indian G. macei. No ally 

in China. 

Dicrcrid.t: (King Crows). 

22. Chapfia brauniana. Closely allied to C. wnea of Assim. No ally in 

China. 

Mus:icapid.e (Flycatchers). 

23. Cyornis vlvida. Allied to C. rubeculoides of India. 



CHAP, xviii.] JAPAX AND FORMOSA. 377 

CoRVlD.E (Jays and Crows). 

24. Garrulus taivanus. Allied to G sinensis of S. China. 

25. Urocissa cmrulea. A very distinct species from its Indian and Chinese 

alUes. 

26. DendrocUta formosa:. A s;ih-sp3cie3 of the Chinese D. sinensis. 

PLOCKID.E (Weaver Finches). 

27. Mtima formosana. Allied to M. rubronigra of India and Burniali. 

Alaudid.e (Larks). 

28. Alauda sala.\ .... . „ ,, ^, • 

29. A. wattersi. ] ^I'^es m South China. 

1'iTriD.aE (Pittas). 

30. Pitta oreas. Allied lo P . ci/anoplera oi MilayaandS. China. 

Picin.E (Woodpeckers). 

31. Piciis insularis. Allied to P. leucunotus of Japan and Siheria. 

Megal.emid.e. 

32. Megaltvma nucliali.^. Allied to M. oortii of Sumatra and M. faber of 

Hainan. No allies in China. 

Caprimulgid^ (Goatsuckers). 

33. Caprlmuhjus sticlomiis. A sub-species of C. mnnlicolus of India and 

China. 

CoLUMBiD^ (Pigeons) . 

34. Treron formosa;. Allied to Malayan species. 

35. S^ibenocercus surorius. Allied to Malay species and to S. sieboldi of 

Japan. No allies of these two birds inhabit China. 

36. Chalcopliaps formosana. Allied to the Indian species which extends to 

Tenasseriui and Hainan. 

Tetraonid-e (Grouse and Partridges). 

37. Oreoperdix crudigularis. A peculiar genus of partridges. 

38. Bambusicola sonorivox. Allied to the Chinese B. thoracica. 

39. Areoturnix rosiraia. Allied to the Chinese A. blahistonii. 

Phasianid^ (Pheasants). 

40. Phasianusformosanus. Allied to P. torquatus of China. 

41. Enplocamiis su-inhoil. 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 pardahla. Closely allied to a Chinese species. 

43. Lempiig'im hambroekii. Allied to a Chinese species. 



378 ISLAND LIFE. [part ii. 

This list exhibits to us the marvellous fact that more than 
half the peculiar species of Formosan birds have their nearest 
allies in such remote regions as the Himalayas, South India, the 
Malay Islands, or Japan, rather than in the adjacent parts 
of the Asiatic continent. Fourteen species have Himalayan 
allies, and six of these belong to genera which are unknown in 
China, One has its nearest ally in the Nilgherries, and five in 
the Malay Islands ; and of these sis, four belong to genera which 
are not Chinese. Two have their only near alhes 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. ,Thu3 we have the Formosan babbler 
{Garrulax ruficeps) not allied to the species found in South 
China, but to one inhabiting North India and East Thibet; 
while the black bulbul {Hijpsipctes nigerrimus), is not allied to 
the Chinese species but to an Assamese form. 

In the same category as the above we must place eight 
species not peculiar to Formosa, but which are Indian or 
Malayan instead of Chinese, so that they offer examples of dis- 
continuous distribution somewhat analogous to what we found 
to occur in Japan. These are enumerated in the following 
list. 

Species of Bibds common to Formosa akd I.vdia or Malaya, bdt not 
FOUND IN China. 

1. Siphia siiperciliaris. The Rufous-breasted Flycatcher of the S.F. 

Himalaj-as. 

2. Halcyon coromanda. The Great Red Kingfisher of India, Malaya, and 

Japan. 

3. Palumbus pulchricollis. The Daijeeling Wood-pigeon of the S.E. 

Himalayas. 

4. Turnix dussumieri. The larger Button-quail of India. 

5. Spi::aetus nipalensis. The Spotted Hawk-eagle of Nepal and Assam. 

6. Lo2)hosp\:a trivtrgata. The Crested Gos-hawk of the Malay Islands. 

7. Bulaca newarensis. The Brown Wood-owl of the Himalayas. 

8. Sh-ix 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 for as yet known, strictly con- 
fined to the Himalayan mountains and Formosa, They thus 
afford examples of discontinuous specific distribution exactly 



CHAP, xviii.] JAPAN AND FORMOSA. 379 

parallel to that of the great spotted kingfisher, already referred 
to as found only in the Himalayas and Japan. 

Comparison of the Faunas of Hainan, Formosa, and Japan. — 
The island of Hainan on the extreme south of China, and only 
separated from the mainland by a strait fifteen miles wide, 
appears to have considerable similarity to Formosa, inasmuch as 
it possesses seventeen peculiar land-birds (out of 130 obtained 
by Mr. Swinhoe), two of which are close allies of Formosan 
species, while two others are identical. We also find four 
species whose nearest allies are in the Himalayas. Our know- 
ledge of this island and of the adjacent coast of China is not 
yet sufficient to enable us to form an accurate judgment of its 
relations, but it seems probable that it was separated from the 
continent at, approximately, the same ej)0ch as Formosa and 
Japan, and that the special features of each of these islands 
is mainly due to their geographical position. Formosa, being 
more completely isolated than either of the others, possesses a 
larger proportion of peculiar species of birds, while its tropical 
situation and lofty mountain ranges has enabled it to preserve 
an unusual number of Himalayan and Malayan forms. Japan, 
almost equally isolated towards the south, and having a much 
greater variety of climate as well as a much larger area, pos- 
sesses about an equal number of mammalia with Formosa, and 
an even larger proportion of peculiar species. Its birds, how- 
ever, though more numerous are less peculiar; and this is 
probably due to the large number of species which migrate 
northwards in summer, and find it easy to enter Japan through 
the Kurile Isles or Saghalien. Japan too, is largely peopled by 
those northern types which have an unusually wide range, and 
which, being almost all migratory, are accustomed to cross over 
seas of moderate extent. The regular or occasional influx of 
these species prevents the formation of special insular races, 
such as are almost always produced when a portion of the popu- 
lation of a species remains for a considerable time completely 
isolated. We thus have explained the curious fact, that while 
the mammalia of the two islands are almost equally j)eculiar, 
(those of Japan being most so in the present state of our 



350 ISLAND LIFE. [i-art ii. 

knowledge), the birds of Formosa show a far greater uumber 
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 — m which the jiiocess of formation 
of peculiar species has only just commenced, and terminating 
with Formosa, probably one of the most ancient of the series, 
and which accordingly presents lis with a very large proportion 
of peculiar species, not only in its mammalia, which have no 
means of crossing the wide strait which separates it from the 
mainland, but also in its birds, many of which are quite able to 
cross over. 

Here, too, we obtain a glimpse of the way in which species 
die out and are replaced by others, which quite agrees with 
what the theory of evolution as.sures us must have occurred. 
On a continent, the process of extinction will generally take 
effect on the circumference of the area of distribution, because 
it is there that the species comes into contact with such adverse 
conditions or competing forms as prevent it from advancing 
further. A very slight change will evidently turn the scale and 
cause the species to contract its range, and this usually goes on 
till it is reduced to a very restricted area, and finally becomes 
extinct. It may conceivably happen (and almost certainly has 
sometimes happened) that the process of restriction of range by 
adverse conditions may act in one direction only, and over a 
limited district, so as ultimately to divide the specific area into 
two separated parts, in each of which a portion of the species 
will continue to maintain itself. We have seen that there is 
reason to believe that this has occurred in a very few cases both 
in North America and in Northern Asia. {Sec pp. 64-66.) But 
the same thing has certainly occurred in a considerable number 
of cases, only it has resulted in the divided areas being occupied 
by representative forms instead of by the very same species. The 
cause of this is very easy to understand. We have already 
shown that there is a large amount of local variation in a 



CHAP, xviii.] JAPAN AND FORMOSA. 331 



considerable number of species, aiid we may be sure that were 
it not for the constant intermingling and intercrossing of the 
individuals inhabiting adjacent localities this tendency to local 
variation would soon fcrm distinct races. But as soon as the 
area is divided into two portions the intercrossing is stopped, 
and the usual result is that two closely allied races, classed 
as representative species, become formed. Such pairs of allied 
species on the two sides of a continent, or in two detached areas, 
are very numerous; and their existence is only explicable on the 
supposition that they are descendants of a parent form which 
once occupied an area comprising that of both of them, — that 
this area then became discontinuous, — and, lastly, that, as a 
consequence of the discontinuity, the two sections of the parent 
species became segregated into distinct races or new species. 

Now, when the division of the area leaves one portion of the 
species in an island, a similar modification of the species, either 
in the island or in the continent, occurs, resulting in closely- 
allied but distinct forms ; and such forms are, as we have soon, 
highly characteristic of island-faunas. But islands also fovour 
the occasional preservation of the unchanged species — a pheno- 
menon which very rarely occurs in continents. This is probably 
due to the absence of competition in islands, so that the parent 
species there maintaiiis itself unchanged, while the continental 
portion, by the force of that competition, is driven back to some 
remote mountain area, where it too obtains a comparative free- 
dom from competition. Thus may be explained the curious fact, 
that the species common to Formosa and India are generally 
confined to limited areas in the Himalayas, or in other cases are 
found only in remote islands, as Japan or Hainan. 

The distribution and affinities of the animals of continental 
islands thus throws much light on that obscure subject — the 
decay and extinction of species ; while the numerous and delicate 
gradations in the modification of the continental species, from 
perfect identity, through slight varieties, local forms, and insular 
races, to well-defined species and even distinct genera, afford 
an overwhelming mass of evidence in favour of the theory of 
" descent with modification." 



382 ISLAND LIFE. [part ii. 

We shall now pass on to another class of islands, which, 
though originally forming parts of continents, were separated 
from them at very remote epochs. This antiquity is clearly 
manifested in their existing faunas, which present many pecu- 
liarities, and offer some most curious problems to the student 
of distribution. 



CHAPTER XIX. 

ANCIENT CONTINENTAL ISLANDS : THE MADAGASCAR GROUP. 

Remarks on Ancient Continentiil Islands — Physical features of Madagascar 
—Biological features of Madagascar — Mammalia— Reptiles — Relation 
of Madagascar to Africa — Early history of Africa and Madagascar — 
Anomalies of distribution and how to explain them- — The birds of 
Madagascar as indicating a supposed Lemurian Continent — Submerged 
Islands between Madagascar and India — Concluding remarks on " Lemu- 
ria" — The Mascareno Islands — The Comoro Islands — The Seychelles 
Archipelago — Birds of tlie Seychelles — Reptiles and Amphibia — Fresh- 
water Fishes — Land Shells — Mauritius, Bourbon, and Rodriguez — Birds 
• — Extinct Birds and their probable origin — Reptiles — Flora of Mada- 
gascar and the Mascarcne Islands — Curious relations of Mascarene 
plants — Endemic genera of Mauritius and Seychelles — Fragmentary 
character of the Mascarene Flora — Flora of Madagascar allied to that 
of South Africa — Preponderance of Ferns in the Mascarene Flora — 
Concluding remarks on the Madagascar Group. 

We have now to consider the phenomena presented by a very 
distinct class of islands — those which, although once forming 
part of a continent, have been separated from it at a remote 
epoch when its animal forms were very unlike what they are 
now. Such islands preserve to us the record of a by-gone 
world, — of a period when many of the higher types had not 
yet come into existence and when the distribution of others 
was very different from what prevails at the present day. The 
problem presented by these ancient islands is often complicated 
by the changes they themselves have undergone since the period 
of their separation. A partial subsidence will have led to the 
extinction of some of the types that were originally preserved, 



384 ISLAND LIFE. [part ii. 

and may leave the ancient fauna in a very fragmentary state ; 
while subsequent elevations may have brought it so near to the 
continent that some immigration even of mammalia may have 
taken place. If these elevations and subsidences occurred several 
times over, though never to such an extent as again to unite the 
island with the continent, it is evident that a very complex 
result might be produced ; for besides the relics of the ancient 
fauna, we might have successive immigrations from surrounding 
lands reaching down to the era of existing species. Bearing in 
mind these possible changes, we shall generally be able to arrive 
at a fair conjectural solution of the phenomena of distribution 
presented by these ancient islands. 

Undoubtedly the most interesting of such islands, and that 
which exhibits their chief peculiarities in the greatest perfec- 
tion, is Madagascar, and we shall therefore enter somewhat fully 
into its biological and physical history. 

PJnjxical fcnfurcs of Madagaacar. — This great island is situated 
about 250 miles from the cast coast of Africa, and extends 
from 12° to 25i° S. Lat. It is almost exactly 1,000 miles 
long, with an extreme width of SCO and an average width of 
more than 200 miles. A lofty granitic plateau, from eighty to 
IGO miles wide and from 3,000 to 5,000 feet high, occupies its 
central portion, on which rise peaks and domes of basalt and 
granite to a height of nearly 9,000 feet; and there are also 
numerous extinct volcanic cones and craters. All round the 
. island, but especially developed on the south and west, are 
plains of a few hundred feet elevation, formed of rocks which 
are shown by their fossils to be of Jurassic age, or at all events 
to belong to somewhere near the middle portion of the Secondary 
period. The higher granitic plateau consists of bare undulating 
moors, while the lower Secondary plains are more or less wooded ; 
and there is here also a continuous belt of dense forest, varying 
from six or eight to fifty miles wide, encircling the whole island, 
u.sually at about thirty miles distance from the coast but in the 
north-east coming down to the sea-shore. 

The sea around Madagascar, when the shallow bank on which it 
stands is passed, is generally deep. This 100-fathom bank is only 
from one to three miles wide on the east side, but on the west 



CHAP. XIX.] 



THE MADAGASCAR GEOUP. 



385 




~ Idaurxtiiix 



C G 



386 ISLAND LIFE. [part li. 

it is much broader, and stretches out opposite Mozambique to a 
distance of about eighty miles. The Mozambique Channel varies 
from less than 500 to more than 1,500 fathoms deep, the shal- 
lowest part being where the Comoro Islands and adjacent shoals 
seem to form stepping-stones to the continent of Africa. The 
500-fathom line includes Aldabra and the small Farquhar 
Islands to the north of Madagascar; while to the east the sea 
deepens rapidly to the 1,000-fathom line, and then more slowly, 
a profound channel of 2,400 fathoms separating Madagascar from 
Bourbon and Mauritius. To the north-east of Mauritius are a 
series of extensive shoals, forming four large banks less than 100 
fathoms below the surface, while the 1,000-fathom line includes 
them all, with an area about half that of Madagascar itself. 
A little further north is the Seychelles group, also standing 
on an extensive 1,000-fathom bank, while all around the sea 
is more than 2,000 fathoms deep. 

It seems probable, then, that to the north-east of Madagascar 
there was once a series of very large islands, separated from it 
by not very wide straits; while eastward across the Indian 
Ocean we find the Chagos and Maldive coral atolls, marking 
the position of other large islands, which together would form 
a line of communication, by comparatively easy^Btages of 400 
or 500 miles each between Madagascar and India. These sub- 
merged islands, as shown in our map at p. 396, are of great 
importance in explaining some anomalous features in the zoology 
of this great i.sland. 

If the rocks of Secondary age which form a belt around the 
island are held to indicate that Madagascar was once of less 
extent than it is now (though this by no means necessarily 
follows), we have also evidence that it has recently been con- 
siderably larger ; for along the east coast there is an extensive 
barrier coral-reef about 350 miles in length, and varying in 
distance from the land from a quarter of a mile to three or 
four miles. This is good proof of recent subsidence ; while 
•we have no record of raised coral rocks inland which would 
certainly mark any recent elevation, because fringing coral reefs 
surround a considerable portion of the northern, eastern, and 
south-western coasts. We may therefore conclude that during 



CHAP. XIX.] 



THE MADAGASCAR GROUP. 



387 




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C O 

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11 

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C C 2 



388 ISLAND LIFE. [part ii. 

Tertiary times the island was usually as large as, aud often 
probably much larger than, it is now. 

Biological features of Madagascar. — Madagascar possesses an 
exceedingly rich and beautiful fauna and flora, rivalling in 
some groups most tropical countries of equal extent, and even 
when poor in species, of surpassing interest from the singularity, 
the isolation, or the beauty of its forms of life. In order to 
exhibit the full peculiarity of its natural history and the nature 
of the problems it offers to the biological student, we must 
give an outline of its more important animal forms in systematic 
order. 

Mammalia. — Madagascar possesses no less than sixty-six 
species of mammals — a certain proof in itself that the island 
has once formed part of a continent ; but the character of these 
animals is very extraordinary and very different from the as- 
semblage now found in Africa or in any other existing continent. 
Africa is now most prominently characterised by its monkeys, 
apes, and baboons ; by its lions, leopards, and hyaenas ; by its 
zebras, rhinoceroses, elephants, buffaloes, giraffes, and numerous 
species of antelopes. But no one of these animals, nor any 
thing like them, is found in Madagascar, and thus our first 
impression would be that it could never have been united with 
the African continent. But, as the tigers, the bears, the tapirs, 
the deer, and the numerous squirrels of Asia are equally 
absent, there seems no probability of its having been united 
with that continent. Let us then see to what groups the 
mammalia of Madagascar belong, and where we must look for 
their probable allies. 

First and most important are the lemurs, consisting of six 
genera and thirty-three species, thus comprising just half the 
entire mammalian population of the island. This group of 
lowly-organised and very ancient creatures still exists scattered 
over a wide area ; but they are nowhere so abundant as in the 
island of Madagascar. They are found from West Africa to 
India, Ceylon, and the Malay Archipelago, consisting of a 
number of isolated genera and species, which appear to main- 
tain their existence by their nocturnal and arboreal habits, and 
by haunting dense forests. It can hardly be said that the 



CHAP, XIX.] THE MADAGASCAR GROUP. 389 

African forms of lemurs are more nearly allied to those of 
Madagascar tlian are the Asiatic, the whole series appearing to 
be the disconnected fragments of a once more compact and 
extensive group of animals. 

Next, we have about a dozen species of Insectivora, consisting 
of one shrew, a group distributed over all the great continents ; 
and five genera of a peculiar family, Centetidte, which family 
exists nowhere else on the globe except in the two largest West 
Indian Islands, Cuba and Hayti, thus adding still further to 
our embarrassment in seeking for the original home of the 
Madagascar fauna. 

We then come to the Caruivora, which arc represented by a 
peculiar cat-like animal, Cryptoprocta, forming a distinct family, 
and having no allies in any part of the globe ; and eight civets 
belonging to four peculiar genera. Here we first meet with 
some decided indications of an African origin ; for the civet 
family is more abundant in this continent than in Asia, and some 
of the Madagascar genera seem to be decidedly allied to African 
groups — as, for example, Eupleres to Suricata and Crossarchus.^ 

The Rodents consist only of four rats and mice of peculiar 
genera, one of which is said to be allied to an American genus ; 
and lastly we have a river-hog of the African genus Potamo- 
chairus, and a small sub-fossil hippopotamus, both of which being 
semi-aquatic animals might easily have reached the island froni 
Africa, by way of the Comoros, without any actual land-connection. 

Reptiles of Madagascar. — Passing over the biids lor the 
present, as not so clearly demonstrating land-connection, let us 
see what indications are afforded by the reptiles. The large 
and universally distributed family of Colubrine snakes is repre- 
sented in Madagascar, not by African or Asiatic genera, but by 
two American geneva — Pliilodryas and Heterodon, and by Her- 
petodryas, a genus found in America and China. Tlie other 
genera are all peculiar, and belong mostly to widespread tropical 
families ; but two families — Lycodontid» and Viperidw, both 
abundant in Africa and the Eastern tropics — are absent. 
Lizards are mostly rej)resented by peculiar genera of African or 

1 See Dr. .J. E. Gray's "Revision of tlic Viverrida^,'' in Pi-dr. Zoo!. Soc, 
186 1, p. 507. 



390 ISLAND LIFE. [part ii. 

tropical families, but several African genera are represented by 
peculiar species, and there are also some species belonging to 
two American genera of the Iguanid^, a family which is ex- 
clusively 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 Mada- 
gascar. Let us first deal with this fact, of the absence of so 
many of the most dominant African groups. The explanation 
of this deficiency is by no means diflicult, for the rich deposits 
of fossil mammals of Miocene age in France, Germany, Greece, 
and North-west India, have demonstrated the fact that all the 
great African mammals then inhabited Europe and temperate 
Asia. We also know that a little earlier (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 Australia is now, and probably, like it, very poor in the 
higher forms of life. Coupling these two facts, the inference seems 
clear, that all the higher types of mammalia were developed 
in the great Euro-Asiatic continent (which then included 
Northern Africa), and that they only migrated into tropical 
Africa when the two continents became united by the upheaval 
of the sea-bottom, probably in the latter portion of the Miocene 
or early in the Pliocene period.^ 

' This view was, I believe, first advanced by Professor Huxley in his 
'Anniversary Address to the Geological Society,'' in 1870. He says : — '.' In 
fact the iliocene mammalian, fauna of Europe and the Himalayan regions 
contain, associated together, the types which are at present separately 
ocated in the South African and Indian provinces of Arctogfea. Now 
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 North Asia during the Middle and Upper Eocene 
epochs. Hence it becomes highly probable that the well-known similar- 
ities, and no less remarkable differences, between the present faunae of 
India and South Africa have arisen in some such fashion as the following : 



CHAP. XIX.] THE MADAGASCAR GROUP. 391 

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 there- 
fore fairly assume that all the more important groups of birds, 
reptiles, and insects, now abundant in Africa but absent from 
Madagascai", formed no part of the original African fauna, but 
entered the country only after it was joined to Euiope and Asia. 

Early History of Africa mid Madayascnr. — We have seen that 
Madagascar contains an abundance of mammals, and that most 
of them are of types either peculiar to, or existing also in, Africa ; 
it follows that that continent must have had an earlier union 
with Europe, Asia, or America, or it could never have obtained 
any mammals at all. Now these ancient African mammals are 
Lemur.s, Insectivora, and small Carnivora, chiefly Viverridae ; 
and all these groups are known to have inhabited Europe in 
Eocene and Miocene times; and that the union was with 
Europe rather than with America is clearly proved by the fact 
that even the Insectivorous Ccntetida;, now confined to Mada- 
gascar and the West Indies, inhabited France in the Lower 
Miocene period, while the Viverridse, or civets, wliich form so 

Some time during tlie Miocene epoch, tlie bottom of the nnmmiilitic sea 
was upheaved and converted into dry hind in the direction of a line ex- 
tending from Abyssinia to the moutli of tlie Ganges. By tliis means the 
Delilcan on the one hand and South Africa on the other, became connected 
with the Miocene dry land and with one another. The Miocene mammals 
spread gradually over this intermediate dry land ; and if the condition of 
its eastern and western ends offered as wide contrasts as the valleys of the 
Ganges and Arabia do now, many forms which made their way into Africa 
must have been different from those which reached the Uekkan, while 
others might pass into both these sub-provinces." 

This question is fully discussed in my Geographical Distribution of 
Animals (Vol. I., p. 285), where I expressed views somewhat different from 
those of Professor Huxley and made some slight errors which are corrected 
in the present work. As I did not then refer to Professor Huxley's prior 
statement of the theory of Miocene immigration into Africa (which I had 
read but the reference to which I could not recall) I am happy to give 
his views here. 



392 ISLAND LIFE. [rART ii. 

important a part of the fauna of Madagascar as well as of 
Africa, were abundant in Europe throughout the whole Ter- 
tiary period, but are not known to have ever lived in any part 
of the American continent. We here see the application of 
the principle which we have already fully proved and illu-strated 
(Chapter IV., p. G2), that all extensive groups have a wide range 
at the period of their maximum development ; but as they 
decay their area of distribution diminishes or breaks up into 
detached fragments, which one after another disappear till the 
group becomes extinct. Those animal forms which we now 
find isolated in Madagascar and other remote portions of the 
globe all belong to ancient groups which are in a decaying or 
nearly extinct condition, while those which are absent from it 
belong to more recent and more highly-developed types, which 
range over extensive and continuous areas, but have had no 
opportunity of reaching the more ancient continental islands. 

Anomalies of Distribution and hoir to crplfiin 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 In- 
sectivorous Ceutetidae now exist only in these two groups of 
islands ; for we know that the ancestors of this family must 
once have had a much wider range, which almost certainly 
extended over the great northern continents. We might as 
reasonably suppose a land-connection across the Pacific to ac- 
count for the camels of Asia having their nearest existing 
allies in the llamas and alpacas of the Peruvian Andes, and 
another between Sumatra and Brazil, in order that the ances- 
tral tapir of one country might have passed over to the other. 
In both these cases we have ample proof of the former wide 
extension of the group. Extinct camels of numerous species 
abounded in North America in Miocene, Pliocene, and even 
Post-pliocene times, and one has also been found in North- 
western India, but none whatever among all the rich deposits 
of mammalia in Europe. We are thus told, as clearly as pos- 
sible, that from the North American continent as a centre the 
camel tribe spread westward, over now-submerged land at the 
shallow Behring Straits and Kamschatka Sea, into Asia, and 



CHAP. XIX.] THE MADAGASCAE GROUP. 3'J3 



southward along the Andes into South America. Tapirs are 
even more interesting and instructive. Their remotest known 
ancestors appear in Western Europe in the early portion of the 
Eocene period ; in the later Eocene and the Miocene other 
forms occur both in Europe and North America. These seem 
to have become extinct in North America, while in Europe 
they developed largely into many forms of true tapirs, which at 
a mudi later period found their way again to North, and thence 
to South, America, where their remains are found ia caves and 
gi-avel-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, Sumatra, and Borneo only; while in 
the Western continent, where they are comparatively recent 
immigrants, they occupy a much larger area, and are repre- _^ 
sented by three or four distinct species. Who could possibly 
have imagined such migrations, and extinctions, and changes of 
distribution as are demonstrated in the case of the tapirs, if we 
had only the distribution of the existing species to found an 
opinion upon? Such ca.ses 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 fossil remains. When- 
ever we can trace the past history of any group of terrestrial 
animals, we invariably find that its actual distribution can be 
explained by migrations effected by means of comparatively 
sUght 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 chajjter, the testimony of geology itself, if 
fairly interpreted, upholds the same theory of the stability of 
our continents and the permanence of our oceans. Yet so easy 



394 ISLAND LIFE. [part ii. 

and pleasant is it to speculate on former changes of land and 
sea with which to cut the gordian knot offered by anomalies 
of distribution, that we still continually meet with suggestions 
of former continents stretching in every direction across the 
deepest oceans, in order to explain the presence in remote parts 
of the globe of the same genera even of plants or of insects — 
organisms which possess such exceptional facilities both for ter- 
restrial, aerial, and oceanic transport, and of whose distribution 
in past ages we generally know absolutely nothing. 

The Birds of Madagascar, as indicating a supposed Leimirian 
continent. — Having thus shown how the distribution of the land 
mammalia and reptiles of Madagascar may be well explained by 
the supposition of a union with Africa before the greater part of its 
existing fauna had reached it, we have now to consider whether, 
as some ornithologists think, the distribution and affinities of 
the birds present an insuperable objection to this view, and 
require the adoption of a hypothetical continent — Lemuria — 
extending from Madagascar to Ceylon and the Malay Islands. 

There are about one hundred land birds known from the island 
of Madagascar, all but four or five being peculiar ; and about 
half of these peculiar species belong to peculiar genera, many 
of which are extremely isolated, so that it is often difficult to 
class them in any of the recognised families, or to determine 
their affinities to any living birds. Among the other moiety, 
belonging to known genera, we find fifteen which have un- 
doubted African affinities, while five or six are as decidedly 
Oriental, the genera or nearest allied species being found in 
India or the Malay Islands. It is on the presence of these 
peculiar Indian types that Dr. Hartlaub, in his recent work on 
the Birds of Madagascar and the Adjacent Islands, lays great 
stress, as pro^'ing the former existence of " Lemuria ; " while he 
considers the absence of such peculiar African famihes as the 
plantain-eaters, glossy-starlings, ox-peckers, barbets, honey- 
guides, hornbills, and bustards — besides a host of peculiar 
African genera — as sufficiently disproving the statement in my 
Geographical Distribution of Animals that Madagascar is " more 
nearly related to the Ethiopian than to any other region," and 
that its fauna was evidently " mainly derived from Africa." 



CHAP. XIX.] THE MADAGASCAR GROUP. 395 



But the absence of the numerous peculiar groups of African 
birds is so exactly parallel to the same phenomenon among 
mammals, that we are justified in imputing it to the same 
cause, the more especially as some of the very groups that 
are wanting — the plantain-eaters and the trogons, for example, 
— are actually known to have inhabited Europe along with the 
large mammalia which subsequently migrated to Africa. As to 
the peculiarly Eastern genera — such as Copsychus and Hyp- 
sipetes, with a Dicrurns, Ploceus, a Cisticola, and a Scops, all 
closely allied to Indian or Malayan species — although very 
striking to the ornithologist, they certainly do not outweigh 
the fourteen African genera found in Madngascar. Their pre- 
sence may, moreover, be accounted for more satisfactorily than 
by means of an ancient Lemurian continent, which, even if 
granted, would not explain the very facts adduced in its support. 

Let us first prove this latter statement. 

The supposed " Lemuria " must have existed, if at all, at so 
remote a period that the higher animals did not then inhabit 
either Africa or vSouthern Asia, and it must have become par- 
tially or wholly submerged before they reached those countries ; 
otherwise we should find in Madagascar many other animals 
besides Lemurs, Insectivora, and Viverridse, especially such 
active arboreal creatures as monkeys and squirrels, such hardy 
grazers as deer or antelopes, or such wide-ranging carnivores as 
foxes or bears. This obliges us to date the disappearance of the 
hypothetical continent about the earlier part of the Miocene 
epoch at latest, for during the latter part of that period we 
know that such animals existed in abundance in every part of 
the great northern continents wherever we have found organic 
remains. But the Oriental birds in Madagascar, by whose pre- 
sence Dr. Hartlaub upholds the theory of a Lemuria, are slightly 
modified fwms of cristing Indian genera, or sometimes, as Dr. 
Hartlaub himself points out, species hardly distinguisluible 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 different distribution from what they have now. Along 
with so many African and Indian genera of mammals they then 



396 



ISLAND LIFE. 



[part II. 



probably inhabited Europe, wliicb at that epoch enjoyed a sub- 
tropical climate ; and this is rendered almost certain by the 
discovery in the iliocene of France of fossil remains of trogons 
and jungle-fowl. If, then, these Indian birds date back to the 
very period during ■which alone Lemuria could have existed, 
that continent was quite unnecessary for their introduction into 
Madagascar, as they could have followed the same track as the 
mammalia of Miocene Europe and Asia ; while if, as I maintain, 
they are of more recent date, then Lemuria had ceased to 
exist, and could not have been the means of their introduction. 




M\P OF Tne INDIAN OCEAN. 



Showing the position of banks less than 1.0(10 fathoms deep between Africa and the Indian 

Peninsula. 

Submerged Islands between Madagascar and. India. — Looking at 
the accompanying map of the Indian Ocean, we see that betw^een 
Madagascar and India there are now extensive shoals and coral- 
reefs, such as are always held to imlicate subsidence ; and we 
may therefore fairly postulate the former existence here of 
several large islands, some of them not much inferior to Mada- 
gascar itself. These reefs are all sej^arated from each other by 



CHAP. SIX.] THE MADAGASCAR GROUP. 397 



very deep sea — much deeper than that which divides Mada- 
gascar from Africa, and we have therefore no reason to imagine 
their former union. But they would nevertheless greatly facili- 
tate the introduction of Indian birds into the Mascarene Islands 
and Madagascar; and these facilities existing, such an immigra- 
tion would be sure to take place, just as surely as American birds 
have entered the Galapagos and Juan Fernandez, as European 
birds now reach the Azores, and as Australian birds reach such 
a distant island as New Zealand. Tliis 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. 

Mr. Darwin's theory of the formation of atolls is now almost 
universally accepted as the true one, and tliis theory implies 
that the areas in question are still, or have very recently been, 
subsiding. The final disappearance of these now sunken islands 
does not, therefore, in all probability, date back to a very re- 
mote epoch ; and this exactly accords with the fact that some 
of the birds, as well as the fruit-bats of the genus Pteropus, are 
very closely allied to Indian species, if not actually identical, 
others being distinct species of the same genera. The fact that 
not one closely-allied species or even genus of Indian or Malayan 
mammals is found in Madagascar, sufficiently proves that it is 
no land-connection that has brought about this small infusion of 
Indian birds and bats ; while we have sufficiently shown, that, 
when we go back to remote geological times no land-connection 
in this direction was necessary to explain the phenomena of the 
distribution of the Lemurs and Insectivora. A land-connection 
with some continent was undoubtedly necessary, or there would 
have been no mammalia at all in Madagascar ; and the nature 
of its fauna on the whole, no less than the moderate depth of 
the intervening strait and the comparative approximation of the 
opposite shores, clearly indicate that the connection was with 
Africa. 

Concluding remarks on " Lcmuria." — I have gone into this 
question in some detail, because Dr. Hartlaub's criticism on my 



398 ISLAND LIFE. [part ii. 

views has been reproduced in a scientific periodical,^ and the 
supposed Leinurian continent is constantly referred to by quasi- 
scientific writers, as well as by naturalists and geologists, as if its 
existence had been demonstrated by facts, or as if it were abso- 
lutely necessary to postulate such a land in order to account for 
the entire series of phenomena connected with the Madagascar 
fauna, and especially with the distribution of the Lemuridae.^ 
I think I have now shown, on the other hand, that it was 
essentially a provisional hypothesis, very useful in calling atten- 
tion to a remarkable series of problems in geographical distri- 
bution, 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 aflinities 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 

> The Ibis, 1877, p. 334. 

' In a paper read before the Geological Society in 1874, Mr. H. F. Blan- 
ford, from the similarity of the fossil plants and reptiles, 8uppo.sed that 
India and South Africa had been connected by a continent, "and remained 
80 connected with some short intervals from the Permian up to the end of 
the Miocene period," and Mr. Woodward expressed his satisfaction with 
" this further evidence derived from the fossil flora of the Mesozoic series of 
India in corroboration of the former existence of an old submerged conti- 
nent — Lemuria." 

Those who have read the preceding chapters of the present work will 
not need to have pointed out to them how utterly inconclusive is the frag- 
mentary evidence derived from such remote periods (even if there were no 
evidence on the other side) as indicating geographical changes. The notion 
that a similarity in the productions of widely separated continents at any 
past epoch is only to be explained by the existence of a direct land-con- 
nection, is entirely opposed to all that we know of the wide and varying 
distribution of all types at different periods, as well as to the greit powers 
of dispersal over moderate widths of ocean possessed by all animals except 
mammalia. It is no less opposed to what is now known of the general 
permanency of the great continental and oceanic areas ; while in this par- 
ticular case it is totally inconsistent (as has been shown above) with the 
actual facts of the distribution of animals. 



CHAP. XIX.] THE MADAGASCAR GROUP. 399 

what seems an easy solution of a difficult problem, and has 
received an appropriate and easily remembered name, long after 
it has been proved to be untenable. 

It is now more than four years since I first showed, by a 
careful examination of all the facts to be accounted for, that 
the hypothesis of a Lemurian continent was alike unnecessary 
to explain one portion of the facts, and inadequate to explain 
the remaining portion.^ Since that time I have seen no 
attempt even to discuss the question on general grounds in 
opposition to my views, nor on the other hand have those who 
have hitherto supported the hypothesis taken any opportunity 
of acknowledging its weakess and inutility. I have therefore 
here explained my reasons for rejecting it somewhat more fully 
and in a more popular form, in the hope that a check may thus 
be placed on the continued re-statement of this unsound theory 
as if it were one of the accepted conclusions of modern science. 

The Mascarene Islands.'^ — In the Geographical Distribution of 
Animals, a summary is given of all that was known of the 
zoology of the various islands near Madagascar, which to some ex- 
tent partake of its peculiarities, and with it form the Malagasy 
sub-region of the Ethiopian region. As no great additions have 
since been made to our knowledge of the fauna of these islands, 
and my object in this volume being more especially to illustrate 
the mode of solving distributional problems by means of the 
most suitable examples, I shall now confine myself to pointing 
out how far the facts presented by these outlying i.slands 
support the views already enunciated with regard to the origin 
of the Madagascar fauna. 

The Comoro Islands. — This group of islands is situated 
nearly midway between the northern extremity of Madagascar 
and the coast of Africa. The four chief islands vary between 
sixteen and forty miles in length, the largest being 180 miles from 
the coast of Africa, while one or two smaller islets are less than 
100 miles from Madagascar. All are volcanic, Great Comoro being 

• Geographical Disfrlhutifin of Animals, Vol. I., p. 272 — 292. 

2 Tlje term " Mascarene '' is used here in an extended sense, to include 
all the islands near Madagascar which resemble it in their animal and 
vegetable productions. 



400 ISLAND LIFE. [part ii. 

an active volcano 8,500 feet high ; and, as already stated, they 
are situated on a submarine bank with less than 500 fathoms 
soundings, connecting Madagascar with Africa. There is reason 
to believe, however, that these islands are of comparatively 
recent origin, and that the bank has been formed by matter 
ejected by the volcanoes or by upheaval. Any how there is 
no indication whatever of there having been here a land-con- 
nection between Madagascar and Africa ; while the islands 
themselves have been mainly colonised from Madagascar, to 
the 100-fathom bank surrounding which some of them make 
a near approach. 

The Comoros contain two land mammals, a lemur and a civet, 
both of Madagascar genera and the latter an identical species, 
and there is also a peculiar species of fniit-bat {Pteropus 
comorensis), a group which ranges from Australia to Asia and 
Madagascar, but is unknown in Africa. Of land-birds forty-one 
species are known, of which sixteen are peculiar to the islands, 
twenty -one are found also in Madagascar, and three found in 
Africa and not in Madagascar; while of the peculiar species, 
six belong to Madagascar or Mascareue genera. 

These facts point to the conclusion that the Comoro Islands 
have been formerly more nearly connected with Madagascar 
than they are now, probably by means of intervening islets 
and the former extension of the latter island to the westward, 
as indicated by the extensive shallow bank at its northern 
extremity, so as to allow of the easy passage of birds, and 
the occasional transmission of small mammalia by means of 
floating trees.^ 

The Seychelles Archijielago. — 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 continuincf 
the central ridge of that great island. The Seychelles stand 
upon a rather extensive shallow bank, the lOO-fathom line 
around them enclosing an area nearly 200 miles long by 100 
miles wide, while the 500-fathom line shows an extension of 
nearly 100 miles in a southern direction. All the larger islands 

1 For the birds of the Comoro Islands see Froc. Zoul. Soc, 1877, p. 295, 
and 1879, p. 673. 



CHAP. XIX.] THE MADAGASCAR GROUP. 401 

are of granite, with mountains rising to 3,000 feet in Mahe, and 
to from 1,000 to 2,000 feet ia several of tiie 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 favour- 
ably situated as regards the extensive Saya de Malha and 
Cargados banks, which were probably once large islands, and 
may have supported a rich insular flora and fauna of mixed 
Mascarene and Indian type. The existing fauna and flora of 
the Seychelles must therefore be looked upon as the remnants 
which have survived the partial submergence of a very extensive 
island ; and the entire absence of mammalia may be due, either 
to this island having never been actually united to Madagascar, 
or to its having since undergone so much submergence as to 
have led to the extinction of such mammals as may once have 
inhabited it. The birds and reptiles, however, though few in 
number, are very interesting, and throw some further light on 
the past history of the Seychelles. 

Birds of the Seychelles. — Fifteen indigenous land-birds are 
known to inhabit the group, thirteen of which are peculiar 
species,' belonging to genera which occur also in Madagascar or 

1 The following is a list of these peculiar birds. (Sue the Ihis, for 18G7, 
p. 359; and 1879, p. 97.) 

Passeres. Psittaci. 

Ellisia seycheUeims. Coracopsis barklyi. 

Copsijchus seychellarum. Palceornis uardi. 

Jlyj)slpeles crassirostris. CoLUMB.i;. 

Tchitrea cmjina. ^ Alectorcenas pidchemmus. 

Nectarima dmsu m len. y^^^,,^ roslratus. 

Zosteraps modcsla. 

semiflara. Accipitres. 

Foudia seychellarum. Tinnunculus gracilis. 

D D 



402 ISLAND LIFE. [part ii. 

Africa. The genera which are more peculiarly Indian are, — Cop- 
sychus and Hypsipetes, also found in Madagascar ; and Palajornis, 
■which has species in Mauritius and Rodriguez, as well as one 
on the continent of Africa. A black parrot (Coracopsis), con- 
generic with two species that inhabit Madagascar and with one 
that is peculiar to the Comoros ; and a beautiful red-headed 
blue pigeon [Alcctorcenas pulcherrimus) allied to those of Mada- 
gascar and Mauritius, but very distinct, are the most remarkable 
species characteristic of this group of islands. 

Meptiles and Amphibia of the Seychelles. — The reptiles 
and amphibia are rather numerous and very interesting, indicat- 
ing clearly that the islands can hardly be classed as oceanic. 
There are five species of lizards, three being peculiar to the 
islands, while the two others have a rather wide range. The 
first is a chameleon — defenceless slow-moving lizards, especially 
abundant in Madagascar, from which no less than twenty-one 
species are now known, about the same number as on the 
continent of Africa. The Seychelles species {Chatiuleo tvjris) is 
peculiar to the islands. The next is one of the skinks {Euprcpcs 
eyanogastcr) , small ground-lizards with a very wide distribution 
in the Eastern Hemisphere. This species is, however, peculiar 
to the islands. The other peculiar species is one of the geckoes 
{PhiJsuina scychcUensis). An East African species {P. cepedianus) 
is also found in the Seychelles, as well as in the Comoro Islands, 
Bourbon, Mauritius, Madagascar, and Rodriguez ; and there is 
also a third gecko of another genus {Feropus nudilatus) 
which is found also in Mauritius, Bourbon, Rodriguez, and 
Ceylon, and even in Penang and the Philippine Islands. These 
lizards, clinging as they do to trees and timber, are exceedingly 
liable to be carried in ships from one country to another, and I 
am told by Dr. Gunther that some are found almost every year 
in the London Docks. It is therefore probable, that when species 
of this family have a very wide i-ange they have been assisted 
in their migrations by man, though their habit of clinging to 
trees also renders them likely to be floated with large pieces of 
timber to considerable distances. Dr. Percival Wright, to whom 
I am indebted for much information on the productions of the 
Seychelles Archipelago, informs me that the last-named species 



CHAP. XIX.] THE MADAGASCAR GROUr. 403 

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 aualosrous to the curious fact of certain lizards 
on the small islands in the Mediterranean being always very 
different in colour from those of the mainland, usually becoming 
rich blue or black (see Nature, Vol. XIX. p. 97) ; and we thus 
learn how readily in some cases differences of colour are brought 
about by local conditions. 

Snakes, as is usually the case in small or remote islands, are 
far less numerous than lizards, only two species being known. 
One, Dromicus seychellcnsis, is a peculiar species of the family 
Colubridaj, the rest of the genus being found in Madagascar and 
South America. The other, Buodon f/comdricus, one of the 
LycodontidiE, or fanged ground-snakes, inhabits also South and 
West Africa. So far, then, as the reptiles are concerned, there is 
nothing but what is easily explicable by what we know of the 
general means of distribution of these animals. 

We now come to the Amphibia, which are represented in the 
Seychelles by two tailless and two serpent-like forms. The frogs 
are, Hana mascariensis, found also in Mauritius, Bourbon, An- 
gola, and Abyssinia, and probably all over tropical Africa ; and 
Mcgalwmlv.s infmrufv.s, a tree-frog altogether peculiar to the 
islands, and forming a peculiar genus of the widespread tropical 
family Polypedatidse. It is found, Dr. Wright informs me, on 
the Pandani or screw-pines ; and as these form a very character- 
istic portion of the vegetation of the Mascarene Islands, all 
the species being peculiar and confined each to a single island 
or small group, we may perhaps consider it as a relic of the 
indigenous fauna of that more extensive land of which the 
present islands are the remains. 

The serpentine Amphibia are represented by two species of 
Cecilia. These creatures externally resemble large worms, 
except that they have a true head with jaws and rudimentary 
eyes, while internally they have of course a true vertebrate 
skeleton. They live underground, burrowing by means of the 
rinw-like folds of the skin which simulate the jointed segments 
of a worm's body, and when caught they exude a \ascid slime. 
The young have external gills which are afterwards replaced by 

D D 2 



• 404 ISLAND LIFE. [part h. 

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 two 
species have been found, named respectively Ccedlia oxyura 
and C. rostrata. The former also inhabits the Malabar coast of 
India, while the latter has been found in West Africa and also 
South America.' This is certainly one of the most remark- 
able cases of the wide and discontinuous distribution of a species 
known ; and when we consider the habits of life of these animals 
and the extreme slowness with which it is likely they can mi- 
grate into new arciis, we can hardly arrive at any other conclu- 
sion than that this species ouce had an almost world-wide range, 
and that in the process of dying out it has been left stranded, as 
it were, in these three remote portions of the globe. The ex- 
treme stability and long persistence of specific form which this 
implies is extraordinary, but not unprecedented, among the lower 
vertebrates. The crocodiles of the Eocene period dififer but 
slightly from those of the present day, while a small fresh-water 
turtle from the Miocene deposits of the Siwalik Hills is abso- 
lutely identicid with a still living Indian species, Emys techts. 
The mud-fish of Australia, Cerafodns forstcri is a very ancient 
type, and may well have remained S2)ecifically unchanged since 
early Tertiary times. It is not, therefore, incredible that the 
Seychelles Caecilia may be the oldest land vertebrate now living 
on the globe ; dating back to the early part of the Tertiary period, 
when the warm climate of the northern hemisphere in high 
latitudes and the union of the Asiatic and American continents 
allowed of the migration of such types over the whole northern 
hemisphere, from which they subseqiiently passed into the 
southern hemisphere, maintaining themselves only in certain 

' Specimens are recorded from West Africa in the Proceedings of the 
Academy of Natural Science, Philadelphia, 1857, p. 72, while specimens in 
the Paris Museum were brought by D'Orbigny from S. America. Dr. 
Wright's specimens from the Seychelles have, as he informs me, been 
determined to be the same species by Dr. Peters of Berlin. 



CHAI-. XIX.] THE MADAGASCAR GROUP. 405 

limited areas where the physical conditions were especially 
favourable, or where they were saved from the attacks of enemies 
or the competition of higher forms. 

Fresh-imtcr Fishes. — The only other vertebrates in the Sey- 
chelles are two fresh-water fishes abounding in the streams and 
rivulets. One, Haplochilus 2)layfnirii 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 genu.s, as I am informed by Dr. Gtinther, 
often inhabit both sea and fresh water, so that their migration 
from Madagascar to the Seychelles and subsequent modification, 
offers no difliculty. The other species is Fundidus orthonotus, 
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-&hdls. — The only other group of animals inhabiting 
the Seychelles which we know with any approach to complete- 
ness, are the land and fresh-water mollusca, but they do not 
furnish any facts of special interest. About forty species are 
known, and Mr. Geoffrey Nevill, who has studied them, thinks 
their meagre number is chiefly owing to the destruction of so 
much of the forests which once covered the islands. Seven of the 
species — and among them one of the most conspicuous, Achat ina 
fulka — have almost certainly been introduced ; and the remainder 
show a mixture of Madagascar and Indian forms, with a prepon- 
derance of the latter. Five genera — Streptaxis, Cyathoponea, 
Onchidium, Helicina and Paludomus, are mentioned as being 
especially Indian, while only two — Tropidophora and Gibbus, 
are found in Madagascar but not in India.^ About two-thirds 
of the species appear to be peculiar to the islands. 

Mcmritius, Bourbon and Rodriguez. — These three islands 
are somewhat out of place in this chapter, becau.se they 
really belong to the oceanic gi'oup, 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 

1 "Additional Notes on the Land-shells of the Seychelles Islands.' By 
Geoffrey Nevill, C.M.Z.S. Froc. ZooJ. Soc. 1860, p. 61. 



406 ISLAND LIFE. [part ii. 

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 le.ss than 1,000 fathoms deep, while on each 
side it sinks rapidly to depths of 2,400 and 2,600 fathoms. We 
have therefore no reason to believe that they have ever been 
connected with Madagascar, and this view is strongly supported 
by the character of their indigenous fauna. Of this, however, 
we have not a very complete or accurate knowledge, for though 
both islands have long been occupied by Europeans, the study of 
their natural products was for a long time greatly neglected, and 
owing to the rapid spread of sugar cultivation, the virgin forests, 
and with them no doubt many native animals, have been almost 
M'holly 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.^ 

^ In Maillard's Notes sur I'Tsh rie Reunion, a considerable number of 
mammalia are given as "wild," sucli as Lemur mouf/nz and Centetes setosus, 
both Madagascar species, with siicli 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. Tlie latter are both Indian species 
and certainly imported, as are most probably the frogs. Legouat, who 
resided some years in the island nearly two centuries ago, and who was 
a close observer of nature, mentions numerous birds, large bats, land- 
tortoises, and lizard.s, but no other reptiles or venomous animals except 
scorpions. We may be pretty sure, therefore, that the land-mammalia, 
snakes, and frogs, now found wild, have all been introduced. Of lizards, 
on the other hand, there are several species, some peculiar to the island, 
others common to Africa and the other Mascarene Islands. The following 
Ust by Prof. Dumoril is given in Maillard's work : — 

Platydactylus cepedianus. ffemidactylus frenatug. 

„ ocellafus. Gongyhts bojerii. 

Hemidactylus peronil. Ahlepharus peronii. 

,, mutilatus. 

Four species of chameleon are now recorded from Bourbon and one 
from Mauritius (J. Reay Greene, M.D., in Pop. Science Rev. April, 1880), 
but as they are not mentioned by the old writers, it is pretty certain that 
these creatures are recent introductions, and this is the more probable as 
they are favourite domestic pets. 



CHAP. XIX.] THE MADAGASCAR GROUP. 407 

Tbe smaller and more remote Rodriguez is also volcanic; but it 
has, besides, a good deal of coralline rock, an indication of partial 
submergence and helping to account for the poverty of its faunas 
and flora. It stands on a 100-fathom bank of considerable extent, 
but beyond this the sea rapidly deepens to more than 2,000 
fathoms, so that it is truly oceanic like its larger sister isles. 

Birds. — The living birds of these islands are few iu number 
and consist mainly of pecuhar species of Mascarene types, 
together with two peculiar genera — Oxynotus belonging to the 
Campephagidse or caterj^illar-catchers, a family abundant in the 
old-world tropics ; and a dove, Trocazza, forming a peculiar sub- 
genus. The origin of these birds oifers no difficulty, looking at 
the position of the islands and of the surrounding shoals and 
islets. 

E.dind Birds. — These three islands are, however, pre-eminently 
remarkable as being the home of a group of large ground-birds, 
quite incapable of flight, and altogether unlike anything found 
elsewhere on the globe ; and which, though once very abundant, 
have become totally extinct wiiliin the last two hundred years. 
The best known of these birds is the dodo, which inhabited 
Mauritius ; while allied species certainly lived in Bnurbon and 
Eodrigxiez, abundant remains of the sj)ecies of the latter island 
— the "solitaire," having been discovered, corresponding with the 
figure and description given of it by Legouat, who resided in 
Kodriguez in 1C92. These birds constitute a distinct family, 
Dididse, allied to the pigeons but very isolated. They were 
quite helpless, and were rapidly exterminated when man intro- 
duced dogs, pigs, and cats into the islands, and himself sought 
them for food. The fact that such perfectly defenceless creatures 
survived in great abundance to a quite recent period in these 
three islands only, while there is no evidence of their ever 
having inhabited any other countries whatever, is itself almost 
demonstrative that Mauritius, Bourbon, and Rodriguez are very 
ancient but truly oceanic islands. From what we know of the 
general similarity of Miocene birds to living genera and families, 
it seems clear that the origin of so remarkable a type as the 
dodos must date back to early Tertiary times. If we suppose 
some ancestral ground-feeding pigeon of large size to have 



408 ISLAND LIFE. [paet ii. 

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 powerful 
animals, we can well understand that the wings, being useless, 
would in time become almost aborted.^ It is also not im- 
probable that this process would be aided by natural selection, 
because the use of wings might be absolutely prejudicial to the 
birds in their new home. Those that flew up into trees to roost, 
or tried to cross over the mouths of rivers, might be blown out 
to sea and destroyed, especially during the hurricanes which 
have probably always more or less devastated the islands ; while 
on the other hand the more bulky and short-winged individuals, 
wlio took to sleeping on the ground in the forest, would be pre- 
served from such dangers, and perhaps also from the attacks of 
birds of prey which may always have visited the islands. But 
■whether or no this was the mode by which these singular birds 
acquired their actual form and structure, it is perfectly certain 
that their existence and development depended on complete 
isolation and on freedom from the attacks of enemies. We 
have no single example of such defenceless birds having ever 
existed on a continent at any geological period, whereas analogous 

' 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 shown by its 
possessing a keeled sternum, though the keel is exceedingly reduced, being 
only three-quarters of an inch deep in a length of seven inches. The most 
terrestrial pigeon — the Didunculus of the Samoan islands, has a far deeper 
and better developed keel, showing that in the case of the dodo the 
degradation has been extreme. We have also analogous examples in other 
extinct birds of the same group of islands, such as the flightless Rails — 
Aphanapteryx of Mauritius and Erythromachus of Rodriguez, as well as 
the large parrot — Lophopsittacus of Mauritius, and the Night Heron, 
Kycticorax megacephala of Rodriguez, the last two birds probably having 
been able to fl_v a little. The commencement of the same process is to be 
seen in the peculiar dove of the Ssychelles, Turtur rostratus, which, as 
Mr. Edward Newton has shown, has much shorter wings than its close 
ally, T. picturatus, of Madagascar. For a full and interesting account of 
these and other recently extinct birds see Professor Newton's article on 
'■Fossil Birds" in the Encyclopa'dia Britannica, ninth edition, vol. iii., 
}). 7.32; and that on "The Extinct Birds of Rodriguez," by Dr. A. 
Giinther and Mr. E. Newton, in the Royal Society's volume on the Transit 
of Venus Expedition. 



CHAP. XIX.] THE MADAGASCAR GROUP. 409 



though totally distinct forms do exist in New Zealand, where 
enemies are equally wanting. On the other hand, every con- 
tinent has always produced abundance of caruivora adapted to 
prey upon the herbivorous animals inhabiting it at the same 
period ; and we may therefore be sure that these islands have 
never formed part of a continent during any portion of the time 
when the dodos inhabited them. 

It is a remarkable thing that an ornithologist of Dr. Hart- 
laub's reputation, looking at the subject from a purely ornitho- 
logical point of view, should yet entirely ignore the evidence of 
these wonderful and unique birds against his own theory, when 
he so confidently characterises Lemuria as " that .sunken land 
which, containing parts of Africa, must have extended far east- 
ward over Southern India and Ceylon, and the highest points of 
which we recognise in the volcanic peaks of Bourbon and 
Mauritius, and in the central range of Madagascar itself^the 
last resorts of tlie 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 ^Epyornis, which were no 
doubt as well able to protect themselves against the smaller 
carnivora as are the ostriches, emus, and ca.ssowaries 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. 
JReptilcs. — 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 

1 See Ibis, 1877, p. 334. 

2 A common Indian and Malayan toad {Bufo melanostktus) has been 
introduced into Mauritius and also some European toads, as 1 am infonneJ 
bv Dr. Giintber. 



410 ISLAND LIFE. [part ii. 

situated about fourteen miles north-east of Mauritius, possesses 
a snake which is not only unknown in Mauritius, but also in any 
other part of the world, being altogether confined to this minute 
islet ! It belongs to the python family, and forms a peculiar 
and very distinct genus, Casarea, whose nearest allies seem to 
be the Ungalia of Cuba and Bolgeria of Australia. It is hardly 
possible to believe that this serpent has very long maintained 
itself on so small an island ; and though we have no record of 
its existence on Mauritius, it may very well have 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, however, now almost certainly confined to 
the one small islet, and is probably the land-vertebrate of most 
restricted distribution on the globe. 

On the same island there is a small lizard, Thyrus boi/eri, 
also a peculiar species and genus, but this is recorded from 
Mauritius and Bourbon as well, though it appears to be rare in 
both islands. As Round Island is connected with Mauritius by 
a bank under a hundred fathoms below' the surface, it has pro- 
bably been once joined to it, and when first separated would 
have been both much larger and much nearer the main island, 
circumstances which would greatly facihtate the transmission 
of these reptiles to their present dwelling-place. 

Flora of Madagascar and the Mascarcne Islands. — The botany 
of the great island of Madagascar has been perhaps more 
thoroughly explored than that of the opposite coasts of Africa, so 
that its peculiarities may not be really so great as they now 
appear to be. Yet there can be no doubt of its extreme 
richness and grandeur, its remarkable speciality, and its anoma- 
lous external relations. It is characterised by a great abundance 
of forest-trees and shrubs of peculiar genera or species, and 
often adorned with magnificent flowers. Some of these are 
aUied to African forms, others to those of Asia, and it is said 
that of the two affinities the latter preponderates. But there 
are also, as in the animal world, some decided South American 
relations, while others point to Australia, or are altogether 
isolated. 



CHAP. XK.] THE MADAGASCAR GROUP. 411 

Among the most prominent characteristics of tlie Maila- 
gascax flora is the possession of a peculiar and isolated family, 
Chlsenacese, allied somewhat to the balsams, but presenting very 
anomalous characters. It consists of four genera and a number 
of species all entirely confined to the island. They are hand- 
some trees or shrubs, mostly with showy red flowers. One of 
them, Bhodolcena altivola, is a semi-scandent shrub with magni- 
ficent campanulate flowers the size of a camellia and of a 
brilliant purple colour. The genus Chrysopia consists of large 
forest trees with spreading crowns adorned with umbels or co- 
rymbs of large purple flowers. It belongs to the Clusiacese, and 
is most nearly allied to the South American genus Moronobea. 
The Colvillea, a peculiar genus of Legununoste, is a tree with 
splendid scarlet flowers ; and there are a large number of 
other peculiar genera more or less remarkable. CombrctaceaB 
with splendid flowers abound in Madagascar itself, though they 
are rare in the Mascarene islands ; while the Ravenala, or 
" traveller's tree ; " the extraordinary lattice-leaved Ouvirandra ; 
the Poinciana rcgia, one of the most gorgeous of flowering trees ; 
and the long-spurred Angrcccum scsquipedale, one of the most 
elegant and remarkable of orchids, are among its vegetable 
wonders. ' 

Of the flora of the smaller Madagascariau islands we possess 
a much fuller account, owing to tlie recent publication of Mr. 
Baker's Flora of the Mauritius and the Seychelles, including also 
Rodriguez. The total number of species in this flora is 1,058, 
more than half of which (53G) are exclusively Ma.scarene — 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 net 
in Asia, and eighty-six in Asia but not in Africa, showing a similar 
Asiatic preponderance to what is said to occur in Madagascar. 
With the genera, however, the proportions are different, for I 
find by going through the whole of the generic distributions as 
given by Mr. Baker, that out of the 440 genera of wild plants 

1 This sketch of the Flora of Madagascar is taken chieily from a series 
of articles by M. Emile Blanchard in tlie Revue des Deux Moiuks. Vol. 
CI. (1872). 



412 ISLAND LIFE. [part ii. 

fifty are endemic, twenty-two are Asiatic but not African, while 
twenty-eight are African but not Asiatic. This imphes that the 
more ancient connection has been on the side of Africa, while 
a more recent immigration, shown by identity of species, has 
come from the side of Asia; and it is probable that when the 
flora of Madagascar is more thoroughly worked out, the same, or 
a still greater African preponderance, will be found in that island. 

A few Mascarene genera are found elsewhere only in South 
America, Austraha, or Polynesia ; and there are also a con- 
siderable number of genera whose metropolis is South America, 
but which are represented by one or more species in Mada- 
gascar, and by a single often widely distributed species in 
Africa. This fact throws light upon the problem offered by 
those mammals, reptiles, and insects of Madagascar which now 
have their only allies in South America, since the two cases 
would be exactly parallel were the African plants to become 
extinct. Plants, however, are undoubtedly more long-lived 
specifically than animals — especially the more highly organised 
groups, and are less 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 Australia, while such cases are 
numerous among animals, owing to the extinction of the allied 
forms in intervening areas, for which extinction, as we have 
already shown, ample cause can be assigned. 

Curimis Relations of Mascarene Plants. — Among the curious 
affinities of Mascarene plants we have culled the following 
from Mr. Baker's volume. Trochetia, a genus of Stercuhaceae, 
has four species iu Mauritius, one in Madagascar, and one in 
the remote island of St. Helena. Mathurina, a genus of Turner- 
aceae, 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, con- 
sists 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. Neso- 
genes, belonging to the verbena family, has one species in 



CHAP, xix] THE MADAGASCAR GROUP. 413 



Rodriguez and one iu Polynesia. Mespilodaphne, an extensive 
genus of Lauraceie, has six species in the Mascarene islands, 
and all the rest (about fifty species) in South America. Ne- 
penthes, the well-known pitcher plants, are found chiefly in the 
Malay Islands, South China, and Ceylon, with species in the 
Seychelles Islands, and in Madagascar. Milla, a large genus of 
Liliacete, is exclusively American, except one species found in 
Mauritius and Bourbon. Agauria, a genus of Ericaceae, is con- 
fined to the Mascarene islands and the Camaroon Mountains 
in West Africa. An acacia, found in Mauritius and Bourbon 
(A. heterophylla), can hardly be separated specifically fronr 
Acacia kon of the Sandwich Islands. The genus Pandanus, 
or screw-pine, has sixteen species in the three islands — 
Mauritius, Rodriguez, and the Seychelles — all being peculiar, 
and none ranging beyond a single island. Of palms there are 
fifteen species belonging to ten genera, and all these genera are 
peculiar to the islands. We have here' ample evidence that 
jilants exhibit the same anomalies of distribution in these 
islands as do the animals, though in a smaller proportion; while 
they also exhibit some of the transitional stages by which these 
anomalies have, in all probability, been brought about, render- 
ing quite unnecessary any other changes in the distribution of 
sea and land than physical and geological evidence warrants.^ 

' It may be interesting to botanists and to students of geographical 
distribution to give liere an enumeration of tlie endemic genera of tlie 
Flora of the Maun'lius and the Seychelles, as they are nowhere separately 
tabulated in that work. 

Apidoia (BLxaceas) 1 sp., a shrub, Maur., Rod., Sey., also 

Madagascar. 
Medusagyne (Temstromiaceas)..! sp., a shrub, Seychelles. 

Astiria (Sterculiaceie) 1 sp., a shrub, Mauritius. 

Quivisia (Meliacere) 3 ep., shrubs, Mauritius (2 sp.), Rodriguez 

(1 sp. ), also Bourbon. 

Cossignya (Sapindacese) 1 sp., a shrub, Mauritius, also Bourbon. 

Homea „ 1 sp., a shrub, Mauritius. 

Stadtmannia „ 1 sp., a shrub, Mauritius. 

Doratoxylon „ 1 sp., a shnib, Mauritius and Bourbon. 

Gagnebina (LeguminosiE) 1 sp., a shrub, Mauritius, also Madagascar. 

Roussea (Saxifragaceie) 1 sp., a climbing shrub, Mauritius and 

Bourbon. 



414 



ISLAND LIFE. [PAET H. 



Fragmentarij Character of the Mascareiu Flora. — Although thes 
peculiar character and affinities of the vegetation of these islands 
is sufficiently apparent, there can be Uttle 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 

Tetratasis (Lythracew) 1 sp., a shrub, Mauritius. 

Psiloxylon „ 1 sp., a shrub, Mauritius and Bourbon. 

Slathurina (Tumeracea;) ....1 sp., a slu-ub, Rodriguez. 

Foetidia (Myrtaceae) 1 sp., a tree, Mauritius. 

Danais (Kubiaceae) i sp., climbing shrubs, Maur. (1 sp.), Rodr. 

(1 sp.), also Bourbon and Madagascar. 

Femelia (Rubiacese) 1 sp., a shrub, Mauritius and Rodriguez. 

Pyrostria „ 6 sp., shrubs, Mauritius (3 sp.), also Bour- 

bon and Madagascar. 

Scj-phochlamys (Rubiacea;) 1 sp., a shrub, Rodriguez. 

Myonima „ 3 sp, shrubs, Mauridus, also Bourbon. 

Cylindrucline (Compositae) 1 sp., a shrub, Mauritius. 

Monarrhenus „ 2 sp., shrubs, Mauritius, also Bourbon and 

Madagascar. 

Faujasia (Compositae) 3 sp., shrubs, Mauritius, also Bourbon and 

Madagascar. 

Heterochaenia (Campanulaceae)..! sp., a shrub, Mauritius, also Bourbon. 

Tanulepis (Asclepiadacea;) 1 sp., a climber, Rodriguez. 

Decanema „ 1 sp., a climber, Mauritius, also Madagascar. 

Kicodemia (Loganiaceae) 2 sp., shrubs, Slauritius ( 1 sp. ), also Comoro 

Islands and Madagascar. 

Bryodes (Serophulariaceae) 1 sp., herb, Mauritius. 

Kadamsea „ 2 sp., herb, SeycheUes (1 sp.), and Mada- 

gascar. 

Colea (Rignoniaceae) 10 sp., Mauritius' (1 sp.), Seychelles (1 

sp.), also Bourbon and Madagascar. 
(Shrubs, trees, or climbers.) 

Obetia (Urticaceae) 2 sp., shrubs, Mauritius, Seychelles, and 

Madagascar. 

Bosquiea (Mores) 3 sp., trees, Seychelles (1 sp.), also Mada- 
gascar. 

Monimia (Monimiaceoe) 3 sp., trees, Mauritius (2 sp.), also Bourbon. 

Cynorchis (Orchideas) 3 sp., herb, ter., Mauritius. 

Amphorchis , 1 sp., herb, ter., Maiu-itius, also Bourbon. 

Arnottia „ 2 sp., lierb, ter., Mauritius, also Bourbon. 

Aplostellis „ 1 sp., herb, ter., Mauritius. 

Cryptopus „ 1 sp., herb, Epiphyte, Mauritius, also 

Bourbon and Madagascar. 



CHAP. XIX.] THE MADAGASCAR GROUP. 415 

remains of the aboriginal woodlands only linger in the recesses 
of the hills, and numbers of forest-haunting plants must in- 
evitably have been exterminated. The result is, that nearly 
three hundred species of foreign plants have run wild in 
Mauritius, and have in their turn helped to extinguish the native 
species. In the Seychelles, too, the indigenous flora has been 
almost entirely destroyed in most of the islands, although the 
peculiar palms, from their longevity and comparative hardiness, 
have survived. Mr. Geoffrey Nevill tells us, that at 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, especially, grows almost to the tops 
of the mountains. Where the timber and shrubs have been 
destroyed, the water falling on the surface immediately cuts 
chamicls, runs off rapidly, and causes the land to become dry 
and arid ; and the same effect is largely seen both in Mauritius, 

Lomatophyllum (Liliaceie) 3 sji., shrubs (succulent), Mauritius, also 

Bourbon. 

Lodoicea (Pal ma;) 1 sp., tree, Seychelles. 

Latania „ 3 sp., trees, Mauritius (2 sp.), Rodrigue;!, 

also Bourbon. 
Hyophorbe „ 3 up., trees, Mauritius (2 sp.), Rodriguez, 

also Bourbon. 
Dictyosperma ,, 1 sp., tree, Mauritius, Rodriguez, also 

Bourbon. 

Acanthophaenix ,, 2 sp., trees, Mauritius, also Bourbon. 

Deckenia „ 1 sp., tree, Sej'chelles. 

Nephropperma „ 1 sp., tree, Seychelles. 

Roscheria ,, 1 sp., tree, Seychelles. 

Verschaffeltia ,, 1 sp., tree, Seychelles. 

Stevensonia „ 1 sp., tree, Seychelles. 

Ochropteris (Filices) 1 sp., herb, Mauritius, also Bourbon and 

Madagascar. 

Among the curious features in this list are the great number of endemic 
shrubs in Mauritius, and the remarkable assemblage of five endemic genera 
of palms in the Seychelles Islands. We may also notice that one palm 
(Latania loddigesii) is confined to Round Island and two other adjacent 
islets, offering a singular analogy to the peculiar snake also found there. 



416 ISLAND LIFE. [part ii. 

and Bourbon, where, originally, dense forest covered the entire 
surface, and perennial moisture, with its ever-accompanying 
luxuriance of vegetation, prevailed. 

Flora of Madagascar allied to tlmt of South 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 exten- 
sion of the continent at the time when Madagascar was united 
with it. As supporting this view I now quote Mr. Bentham's 
remarks on the Compositse. He says : " The connections of the 
Mascarene endemic Compositse, 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 characteristics in the tendency 
to tall shrubby or aborescent forms in several of the endemic 
or prevailing genera. 

Preponderance of Ferns in the Mascarene Flora. — A striking 
character of the flora of these smaller Mascarene islands is the 
great preponderance of ferns, and next to them of orchidese. The 
following figures are taken from Mr. Baker's Flora for Mauritius 
and the Seychelles, and from an estimate by M. Frappier of the 
flora of Bourbon given in Maillard's volume already quoted : — 

Mauritius, d-c. Bourbon. 

Fems 168 Ferns 240 

Orcliide;e 79 Orchidese 120 

Gramineoe 69 Graminese 60 

Cyperacea 62 Coiupositae 60 

Kubiacefe 57 Leguminosa; 36 

Euphorbiace* 45 Rubiacese 24 

Compositse 43 Cyperacese 24 

Leguminosae 41 Euphorbiaceae 18 

/^ The cause of the great preponderance of ferns in oceanic 
( islands has already been discussed in my book on Trojncal Nature; 

^ and we have seen that Mauritius, Bourbon, and Eodriguez must 
be classed as such, though from their proximity to Madagascar 
they have to be considered as satellites to that great island. 



cnAP. XIX.] TUE MADAGASCAR GROUP. 417 

The abundance of orchids may be in part due to analogous 
causes. Their usually minute and abundant seeds would be as 
easily carried by the wind as the spores of ferns, and their 
frequent epiphytic habit affords them an endless variety of 
stations on which to vegetate, and at the same time removes 
them in a great measure from the competition of other plants. 
When, therefore, the climate is sufliciently moist and equable, 
and there is a luxuriant forest vegetation, we may expect to 
find orchids abundant on such tropical islands as are not too 
far removed from other land-s or continents from which their 
seeds might be conveyed. 

Concluding remarks on Ma dru/ a scar and the Mascarcnc Islands. 
— There is probably no portion of the globe that contains within 
itself so many and such varied features of interest connected with 
geographical distribution, or which so well illustrates the mode 
of solving the problems it presents, as the comparatively small 
iusular region which comprises the great island of Madagascar 
and the smaller islands and island-groups which immediately 
surround it. In Madagascar we have a continental island of 
the first rank, and undoubtedly of immense antiquity; we 
have detached fragments of this island in the Comoros and 
Ahlabra ; in the Seychelles we have the fragments of another 
very ancient island, which may perhaps never have been 
continental ; in Mauritius, Bourbon, and Rodriguez we have 
three undoubtedly oceanic islands ; while in the extensive banks 
and coral reefs of Cargados, Saya de Malha, the Chagos, and the 
Maldive Isles, we have indications of the submergence of many 
large islands which may have aided in the transmission of organ- 
isms from the Indian Peninsula. But between and around all 
these islands we have depths of 2,500 fathoms and upwards, 
which renders it very improbable that there has ever been here 
a continuous land surface, at all events during the Tertiary or 
Secondary periods of geology. 

It is most interesting and satisfactory to find that this conclu- 
sion, arrived at solely by a study of the form of the sea-bottom 
and the general principle of oceanic permanence, is fully sup- 
ported bv the evidence of the organic productions of the several 
islands ; because it gives us confidence in those principles, and 

K E 



418 ISLAND LIFE. [pakt u. 

helps to supply us with a practical demonstration of them. We 
find that the entire group contains just that amount of Indian 
forms which could well have passed from island to island ; that 
many of these forms are slightly modified species, indicating 
that the migration occurred during late Tertiary times, while 
others are distinct genera, indicating a more ancient connec- 
tion ; but in no one case do we find animals which necessitate 
an actual land-connection, while the numerous Indian types of 
mammalia, reptiles, bii'ds, and insects, which must certainly 
have passed over had there been such an actual land-connection, 
\ are totally wanting. The one fact which has been supposed to 
require such a connection — the distribution of the lemurs — 
can be far more naturally explained by a general dispersion of 
the group from Europe, where we know it existed in Eocene 
times ; and such an explanation applies equally to the afiinity 
of the Insectivora of Sladagascar and Cuba ; the snakes (Herpe- 
todryas, &c.) of Madagascar and America ; and the lizards (Cryp- 
toblepharus) of Mauritius and Australia. To suppose, in all these 
cases, and in many others, a direct land-connection, is really 
absurd, because we have the evidence afforded by geology of 
wide diSerences of distribution directly we pass beyond the most 
recent deposits; and when we go back to Mesozoic — and still 
more to Palaeozoic — 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 moUusca ranged from Europe and North 
America to Australia and New Zealand. 

By direct proof (the occurrence of wide areas of marine 
deposits of Eocene age), geologists have established the fact 
that Africa was cut off from Europe and Asia bj' an arm of 
the sea in early Tertiary times, forming a large island-continent. 
By the evidence of abundant organic remains we know that all 
the types of large mammalia now found in Africa (but which are 
absent from Madagascar) inhabited Europe and Asia, and many 
of them also North America, in the Miocene period. At a 
still earlier epoch Africa may have received its low^er types of 



CHAP. XIX.] THE MADAGASCAR GROUP. 419 



mammals— lemurs, insectivora, and small carnivora, together 
with its ancestral struthious birds, and its reptiles and insects 
of American or Australian aflSnity ; and at this period it was 
joined to i\Iadagascar. Before the later continental period of 
Afirica, Madagascar had become an island ; and thus, when the 
large mammalia from the northern continent overran Africa, 
they were prevented from reaching Madagascar, which thence- 
forth was enabled to develop its singular forms of low-type mam- 
malia, its gigantic ostrich-like ^pyornis, its isolated birds, its 
remarkable insects, and its rich and peculiar flora. From it the 
adjacent islands received such organisms as could cross the sea ; 
while they transmitted to Madagascar some of the Indian birds 
and insects which had reached them. ^ 

The method we have followed in these investigations is to \ 
accept the results of geological and palaeontological science, 
and the ascertained facts as to the powers of dispersal of the 1 
various animal groups; to take full account of the laws of 
evolution as affecting distribution, and of the various ocean \ 
depths as implying recent or remote union of islands with i 
their adjacent continents ; and the result is, that wherever \ 
we possess a sufficient knowledge of these various classes of 
evidence, we find it possible to give a connected and intelligible 
explanation of all the most striking peculiarities of the organic 
world. In Madagascar we have undoubtedly one of the most 
difficult of these problems ; but we have, I think, fairly met 
and conquered most of its difficulties. The complexity of the 
organic relations of this island is due, partly to its having 
derived its animal forms from two distinct sources — from one 
continent through a direct land-connection, and from another 
by means of intervening islands now submerged ; but, mainly 
to the fact of its having been separated from a continent 
which is now, zoologically, in a very different condition from 
what it was at the time of the separation ; and to its having 
been thus able to preserve a number of types which may 
date back to the Eocene, or even to the Cretaceous, period. 
Some of these types have become altogether extinct else- 
where ; others have spread far and wide over the globe, and J 
have survived only in a few remote countries — and especially in j 

E E 2 



420 ISL.1KD LIFE. [part. U. 

those which have been more or less secured by their isolated 
position from the incursions of the more highly-developed 
forms of later times. This explains why it is that the nearest 
allies of the Madagascar fauna and flora are now so often to be 
found in South America or Australia — countries in which low 
forms of mammalia and birds still largely prevail ; — it 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 
connecting these remote continents at various geological periods 
been realities, the result would have been that all these interest- 
ing archaic forms, all these helpless insular types, would long 
ago have been exterminated, and one comparatively monotonous 
fauna have reigned over the whole earth. So far from explain- 
ing the anomalous facts, the alleged continental extensions, had 
they existed, would have left no such facts to be explained. 



CHAPTER XX. 

ANO>IALOUS ISLANDS : CELEBES. 

Anomalous relations of Celebes— Physical features of the Island — Zoo- 
logical character of the Islands around Celebes — The Malayan and 
Australian Banks — Zoology of Celebes : Mammalia — Probable derivation 
of the Mammals of Celebes— Birds of Celebes — Bird-types peculiar to 
Celebes — Celebes not strictly a Continental Island — Peculiarities of 
the Insects of Celebes — Himalayan types of Birds and Butterflies in 
Celebes — Peculiarities of shape and colour of Celebcsian Butterflies — 
Concluding Remarks — Appendix on the Birds of Celebes. 

The only other islands of tbo globe which can be clas.sed as 
" ancient continental " are the larger Antilles (Cuba, Haiti, 
Jamaica, and Porto Rico), Iceland, and perhaps Celebes. The 
Antilles have been so fully discussed and illustrated in my 
former work, and there is so little fresh information about 
them, that I do not propose to treat of them here, especially 
as they fall short of Madagascar in all points of biological 
interest, and offer no problems of a different character from 
such as have already been sufficiently explained. 

Iceland, also, must apparently be classed as belonging to the 
" Ancient Continental Islands," for though usually described as 
wholly volcanic, it is, more probably, an island of varied geolo- 
gical structure buried under the lavas of its numerous volcanoes. 
But of late years extensive Tertiary deposits of Miocene age 
have been discovered, showing that it is not a mere congeries of 
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 



4?2 ISL:\ND LIFE. [part ii. 

united with Greenland, and probably with Europe by way of 
Britain, in the early part of the Tertiary period, and thus 
afforded one of the routes by which that intermigration of 
American and European animals and plants was effected which 
we know occurred during some portion of the Eocene and Mio- 
cene periods, and probably also in the Pliocene. The fauna 
and flora of this island are, however, so poor, and offer so few 
peculiarities, that it is unnecessary to devote more time to 
consideration here. 

There remains the great Malay island — Celebes, which, owing 
to its possession of several large and very peculiar mammalia, 
must be classed, zoologicallv, as " ancient continental " ; but 
whose central position and relations both to Asia and to Australia 
render it very difficult to decide in which of the primarj' zoological 
regions it ought to be placed, or whether it has ever been uuitetl 
■with either of the great continents. Although I have pretty 
fully discussed its zoological peculiarities and past history in my 
Geograjjliical Distribution of Animah, 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 re'ations. 

Physiml features of Cclchoi. — This large and still comparatively 
unexplored island is interesting to the geographer on account 
of its remarkable form, but much more so to the zoologist 
for its curious assemblage of animal forms. The geological 
structure of Celebes is almost unknown. The extremity of the 
northern peninsula is volcanic ; while in the southern peninsula 
there are extensive deposits of a crj'stalline limestone, in some 
places overlying basalt. Gold is found in the northern peninsula 
and in the central mass, as well as iron, tin, and copper in small 
quantities ; so that there can be little doubt that the mountain 
ranges of the interior consist of ancient stratified rocks. 

It is not yet known w^hether Celebes is completely separated 
from the surrounding islands by a deep sea, but the facts at our 
command render it probable that it is so. The northern and 
eastern portions of the Celebes Sea have been ascertained to be 
from 2,000 to 2,600 fathoms deep, and such depths may extend 



CHAP. XX.] 



CELEBES. 



423 



over a considerable portion of it, or even be niucii 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 




MAP OF CCLEBE3 AND THE SURROUNDING ISLANDS. 

The depth of sea is shown by three tints: tlie lightest mrlicnting less than ino fatlioms. Ihe 
medium tint less than 1 000 fathoms, and the dark tint more than 1,000 fathoms. The 
figures show depths in fathoms. 



and Banda Seas probably exceed 2,000 fathoms. The southern 
portion of the Straits of Macassar is full of coral reefs, and a 
shallow sea of less than 100 fathoms extends from Borneo to 



424 ISLAND LIFE. [part ii. 

within about forty miles of ttie western promontory of Celebes ; 
but farther north there is deep water close to the shore, and it 
seems probable that a deep channel extends quite through the 
straits, which have no doubt been much shallowed by the deposits 
from the great Bornean rivers as well as by those of Celebes 
itself. Southward again, the chain of volcanic islands from Baly 
to Timor appear to rise out of a deep ocean, the few soundings 
we possess showing depths of from 670 to 1,300 fathoms almost 
close to their northern shores. We seem justified, therefore, in 
concluding that Celebes is entirely surrounded by a deep sea, 
which has, however, become partially filled up by river deposits, 
by volcanic upheaval, or by coral reefs. Such shallows, where 
they exist, may therefore be due to antiquity and isolation, in- 
stead of being indications of a former union with any of the 
surrounding islands. 

Zoological character of the Islands around Celebes. — In order to 
have a clear conception of the peculiar character of the Cele- 
besian fauna, we must take into account that of the surrounding 
countries from which we may suppose it to have received immi- 
grants. These we may divide broadly into two groups, those 
on the west belonging to the Oriental region of our zoological 
geography, and those on the east belonging to the Australian 
region. Of the first group Borneo is a tj'pical representative ; and 
from its proximity and the extent of its ojjposiug coasts it is 
the island which we should expect to show most resemblance to 
Celebes. We have already seen that the fauna of Borneo is essen- 
tially the same as that of Southern Asia, and that it is excessively 
rich in all the Malayan types of mammalia and birds. Java and 
Baly closely resemble Borneo in general character, though some- 
what less rich and with several peculiar forms ; while the 
Philippine Island-s, 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. 



o 



\ 



CHAP. XX.] ' CELKBES. 425 

lu tlie islands east and south of Celebes — the Moluccas, New 
Guinea, and the Timor group from Lombok eastward — we find, 
on the other hand, the most wonderful contrast in the forms of 
life. Of twenty-seven families of terrestrial mammals found in 
the great Malay islands, all have disappeared but four, and of 
these it is doubtful whether two have not been introduced by 
man. We also find here four families of Marsupials, all totally 
unknown in the western island.s. 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 A.sia, the other to Australia. The Asiatic or 
Malayan group is found to be bounded strictly by the eastward 
limits of the great bank (for the most part less than fifty 
fathoms below the surface) which stretches out from the Siamese 
and Malayan peninsulas as far as Java, Sumatra, Borneo, and 
the Philippines. To the east another bank unites New Guinea 
and the Papuan Islands as far as Aru, Mysol, and Waigiou, with 
Australia ; while the Moluccas and Timor groups are surrounded 
by much deeper water, which forms, in the Banda and Celebes 
Seas and perhaps in other parts of this area, great basins of 
enormous depths (2,000 to 3,000 fathoms or even more) enclosed 
by tracts under a thousand fathoms, which separate the basins 

1 Families of Malayan Birds not Families of Moluccan Birds not 
found in islands East of found in islands West of 

Celebes. Celebes. 

Troglodytidse. Paradiseidao. 

SittidsB. Meliphagidaa. 

Parida. Cacatuida\ 

Liotrichidaj. Platycerciduj. 

PhyllornithidsB. Trichoglossidas. 

Eurylsmida;. Nestoridse. 

Picidaj. 

Indicatoridaj. 

Megciliemidie. 

Trogonidse. 

PliasiiUiid.'P. 



426 ISLAND LIFE. [part ii. 

from each otber and from tlie adjacent Pacific and Indian 
Oceans (see map). This peculiar formation of the sea -bottom 
probably indicates that this area has been the seat of great local 
upheavals and subsidences ; and it is quite in accordance with 
this view that we find the Moluccas, while closely agreeing with 
New Guinea in their forms of life, yet strikingly deficient in 
many important groups, and exhibiting an altogether poverty- 
striken appearance as regards the higher animals. It is a 
suggestive fact that the Philippine Islands bear an exactly 
parallel relation to Borneo, being equally deficient in many of 
the higher groups ; and here too, in the Sooloo Sea, we find a 
similar enclosed basin of great depth. Hence we may in both 
cases connect, on the one hand, the extensive area of land-surface 
and of adjacent shallow sea with a long period of stability and a 
consequent rich development of the forms of life ; and, on the 
other hand, a highly broken land-surface with the adjacent seas 
of great but very unequal depths, with a period of disturbance, 
probably involving extensive submersions of the land, resulting 
in a scanty and fragmentary vertebrate fauna. 

Zoology of Celebes. — The zoology of Celebes differs so remark- 
ably from that of both the great divisions of the Archipelago 
above indicated, that it is very difficult to decide in which 
to place it. It possesses only about sixteen species of terrestrial 
mammalia, so that it is at once distinguished from Borneo and 
Java by its extreme poverty in this class. Of this small number 
four belong to the Moluccan and Australian fauna — there being 
two marsupials of the genus Cuscus, and two forest rats said 
to be allied to Australian types. 

The remaining twelve species are, generally speaking, of 
Malayan or Asiatic types, but some of them are so peculiar 
that they have no near allies in any pait 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 Ccrrus hipixlaphus of 
Borneo that it may well have been introduced by man hot 



CHAP. XX.] CELEBES. 427 

here and in the Moluccas ; a civet, Viverra tangalunga, common 
in all the Malay Islands, and also perhaps introduced; the 
curious Malayan tarsier (Tarsius spectrum) said to be only 
found in a small island off the coast ; — and besides these, three 
remarkable animals, all of large size and all quite unlike any- 
thing found in the Malay Islands or even in Asia. These are 
a black and almost tailless baboon-like ape (Cynopithems 
nigrescens) ; an antelopean buffalo {Anoa dcpressicomis), and 
the strange babirusa (Babirusn alfurus). 

Neither of these three animals last mentioned have any close 
allies elsewhere, and their presence in Celebes may be considered 
the crucial fact which must give us the clue to the past history 
of the island. Let us then see what they teach us. The ape 
is apparently somewhat intermediate between the great baboons 
of Africa and the short-tailed macaques of Asia, but its cranium 
shows a nearer approach to the former group, in its flat project- 
ing muzzle, large superciliary crests, and maxillary ridges. The 
anoa, though anatomically allied to the buffaloes, externally 
more resembles the bovine antelopes of Africa ; while the 
babirusa is altogether unlike any other living member of the 
swine family, the canines of the upper jaws growing directly 
upwards like horns, forming a spiral curve over the eyes, instead 
of downwards, as in all other mammalia. An approach to 
this peculiarity is made by the African wart-hogs, in which 
the upper tusk grows out laterally and then curves up; but 
these animals are not otherwise closely allied to the babirusa. 

Probable derivation of the Mammals of Celebes. — It is clear 
that we have here a gi^oup of extremely peculiar, and, in all 
probability, very ancient forms, which have been preserved to 
us by isolation in Celebes, just as the monotremes and mar- 
supials have been preserved in Australia and so many of the 
lemurs and Insectivora in Madagascar. And this compels us 
to look upon the existing island as a fragment of some ancient 
land, once perhaps forming part of the great northern continent, 
but separated from it far earlier than Borneo, Sumatra, and 
Java. The exceeding scantiness of the mammalian fauna, how- 
ever, remains to be accounted for. We have seen that Formosa, 
a much smaller island, contains more than twice as many 



428 ISLAND LIFE. [part ii. 

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 are entirely unrepresented in Celebes by any 
peculiar and ancient forms except the squirrels. 

The question at issue can only be finally determined by 
geological investigations. If Celebes has once formed part of 
Asia, and participated in its rich mammalian fauna which has 
been since destroyed by submergence, then some remains of 
this fauna must certainly be preserved in caves or late Tertiary 
deposits, and proofs of the submergence itself will be found 
when sought for. If, on the other hand, the existing animals 
fairly represent those which have ever reached the island, then 
no such remains will be discovered, and there need be no 
evidence of any great and extensive subsidence in late Tertiary 
times. 

JBmJs of Celebes. — Having thus clearly placed before us the 
problem presented by the mammalian fauna of Celebes, we 
may proceed to see what additional evidence is afforded by 
the birds, and any other groups of which we have sufficient 
information. About 164 species of true land-birds are now 



CHAP. XX.] CELEBES. 429 

known to inhabit the island of Celebes itself. Considerably 
more than half of these (ninety-four species) are peculiar to it ; 
twenty-nine are found also in Borneo and the other Malay 
Islands, to which Chey specially belong j while sixteen are common 
to the Moluccas or other islands of the Australian region ; the 
remainder being species of wide range and not characteristic 
of either division of the Archipelago. "We have here a large pre- 
ponderance of western over eastern species of birds inhabiting 
Celebes, though not to quite so great an extent as in the mam- 
malia ; and the inference to be drawn from this fact is, simply, 
that more birds have migrated from Borneo than from the 
Moluccas — which is exactly what we might expect both from 
the greater extent of the coast of Borneo opposite that of 
Celebes, and also from the much greater richness in species of J 
the Bornean than the Moluccan bird-fauna. 

It is, however, to the relations of the peculiar species of 
Celebesiau birds that we must turn, in order to ascertain the 
origin of the fauna in past times ; and we must look to the 
source of the generic types which they represent to give us this 
information. The ninety-four peculiar species above noted 
belong to about sixty-six genera, of which about twenty-three 
are common to the whole Archipelago, and have therefore little 
significance. Of the remainder, twelve are altogether peculiar 
to Celebes; twenty-one are Malayan, but not Moluccan or 
Australian ; while ten are Moluccan or Australian, but not 
Malayan. This proportion does not differ much from that 
afforded by the non-peculiar species ; and it teaches us that, for 
a considerable period, Celebes has been receiving immigrants 
from all sides, many of which have had time to become modified ; 
into distinct representative species. These evidently belong to 
the period during which Borneo on the one side, and the Moluc- 
cas on the other, have occupied very much the same relative 
position as now. There remains the twelve peculiar Celebesian 
genera, to which we must look for some further clue as to the 
origin of the older portion of the fauna; and as these are 
especially interesting we must examine them somewhat closely. 

Bird-types peculiar to Celebes. — First we have Ai-tamides, one 
of the Campephaginas or caterpillar-shrikes — a not very well- 



430 ISLAND LIFE. [past ii. 

marked geuus, and which may have been derived, either from 
the Malayan or the Moluccan side of the Archipelago. Two 
peculiar genera of kingfishers — Monachalcyon and Cittura — seem 
allied, the former to the widespread Todiramphus and to the 
Caridonax of Lombok, the latter to the Australian Melidora. 
Another kingfisher, Ceycopsis, combines the characters of the 
Malayan Ceyx and the African Ispidina, and thus forms an 
example of an ancient generalised form analogous to what 
occurs among the mammalia. Streptocitta is a peculiar form 
allied to the magpies ; while Basilornis (found also in Ceram), 
Enodes, and Scissirostrum, are very peculiar starlings, the latter 
altogether unlike any other bird, and perhaps forming a distinct 
sub-family. Meropogon is a peculiar bee-eater, allied to the 
Malayan Nyctiornis ; Rhamphococyx is a modification of 
Phajuicophaes, a Malayan genus of cuckoos ; Prioniturus (found 
also iu the Philippines) is a genus of parrots distinguished by 
raquet-formed tail feathers, altogether unique in the order; 
while Megacephalon is a remarkable and very isolated form of 
the Austndian Megapodiidai, or mound-buUders. 

Omitting those whose affinity may be pretty clearly traced to 
groups still inhabiting the islands of the western or the eastern 
half of the Archipelago, we find four birds which have no near 
allies at all, but appear to be either ancestral forms, or extreme 
modifications, of Asiatic or African birds — Basilornis, Enodes, 
Scissirostrum, Ceycopsis. These may fairly be associated with 
the baboon-ape, anoa, and babirusa, as indicating extreme 
antiquity and some communication with the Asiatic continent 
at a period when the forms of life and their geographical dis- 
tribution differed considerably from what they are at the 
present time. 

But here again we meet with exactly the same difficulty as 
in the mammalia, in the comparative poverty of the types of 
birds now inhabiting Celebes. Although the preponderance of 
affinity, especially in the case of its more ancient and peculiar 
forms, is undoubtedly with Asia rather than with Australia; 
yet, still more decidedly than in the case of the mammalia, are 
we forbidden to suppose that it ever formed a part of the old 
Asiatic continent, on account of the total absence of so manv 



CHAP. XX.] CELEBES. 431 

important and extensive groups of Asiatic birds. It is not 
single species or even genera, but whole families that are thus 
absent, and among them families which are ])re-eminently 
characteristic of all tropical Asia. Such are the Tiniahidae, or 
babblers, of which there are twelve genera in Borneo, and 
nearly thirty genera in tlie Oriental Region, but of which one 
species only, hardly distinguishable from a Malayan form, in- 
habits Celebes ; the Phylloruithidae, or green bulbuls, and the 
PycnonotidsB, or bulbuls, both absolutely ubiquitous in tropical 
Asia and Malaya, but unknown in Celebes ; the Eurylajmida;, 
or gapers, found everywhere in the great Malay Islands ; the 
Megaltemidffi, or barbcts ; the Trogouidaj, or trogons ; and the 
Phasianidae, or pheapants, all pre-eminently Asiatic and Malayan 
but all absent from Celebes, with the exception of the common 
jungle-fowl, which, owing to the passion of Malays for cock- 
fighting, may have been introduced. To these important 
families may be added Asiatic and Malayan genera by the score ; 
but, confining ourselves to these seven ubiquitous families, 
we must ask, — is it possible, that, at the period when the 
ancestors of the peculiar Celebes mammals entered the island, 
and when the forms of life, though distinct, could not have been 
quite unlike those now living, it could have actually formed a 
part of the continent without possessing representatives of the 
greater part of these extensive and important families of birds ? 
To get rid altogether of such varied and dominant types of 
bird-life by any subsequent process of submersion is more 
difficult than to exterminate mammalia ; and we are therefore 
ao'ain driven to our former conclusion — that the present land of 
Celebes has never (in Tertiary times) been united to the Asiatic 
continent, but has received its population of Asiatic forms by 
migration across narrow straits and intervening islands. Taking 
into consideration the amount of affinity on the one hand, and 
the isolation on the other, of the Celebesian fauna, we may 
probably place the period of this earlier migration in the early 
part of the latter half of the Tertiary period, that is, in middle 
or late Miocene times. 

Celebes not strictli/ a Continental Island. — A study of the 
mammalian and of the bird-fauna of Celebes thus leads us in 



43-2 ISLAND LIFE. [r art ir. 

both cases to the same conclusion, and forbids us to rank it as 
a strictly continental island on the Asiatic side. But facts of 
a very similar character are equally opposed to the idea of 
a former land-connection with Australia or New Guinea, or 
even with the Moluccas. The numerous marsupials of those 
countries are all wanting in Celebes, except the phalangers of 
the genus Cuscus, and these arboreal creatures are very hable 
to be carried across narrow seas on trees uprooted by earth- 
quakes or floods. The teiTcstrial cassowaries are equally absent ; 
and thus we can account for the presence of all the Moluccan 
or Australian types actually found in Celebes without supi^osing 
any land-connection on this side during the Tertiary period. 
The presence of the Celebes ape in the island of Batchian, 
and of the babirusa in Bouru, can be sufficiently explained by 
a somewhat closer approximation of the respective lands, or by 
a few intervening islands which have since disappeared, or it 
may even be due to human agency. 

If the explanation now given of the peculiar features presented 
by the fauna of Celebes be the correct one, we are fully justified 
in classing it as an "anomalous island," since it possesses a 
small but very remarkable maminahan fauna, without ever 
having been directly united with any continent or extensive 
land ; and, both by what it has and what it wants, occupies 
such an exactly intermediate position between the Oriental and 
Australian regions that it will perhaps ever remain a mere 
matter of opinion with which it should properly be associated. 
Forming, as it does, the western limit of such typical Aus- 
tralian groups as the Marsupials among mammalia, and the 
Trichoglossidfe and Meliphagid* among birds, and being so 
strikingly deficient in all the more characteristic Oriental 
families and genera of both classes, I have always placed it in 
the Australian Region ; but it may perhaps witli equal propriety 
be left out of both till a further knowledge of its geology enables 
us to determine its early history with more precision. 

Peculiarities of the Insects of Celebes. — The only other class of 
animals in Celebes, of which we have a tolerable knowledge, is 
that of insects, among which we meet with peculiarities of a 
very remarkable kind, and such as are found in no other island 



CHAF. XX.] CELEBES. 433 



on the globe. Having already given a full account of some 
of these peculiarities in a paper read before the Linnean 
Society — republished in my Con/ribuiions to the Theory of 
Natural Selection, — while others have been discussed in my 
Gcograj}h,ical Distrihution of Animals (Vol. I. p. 434j — I will 
only here briefly refer to them in order to see whether they 
accord with, or receive any explanation from, the somewhat 
novel view of the ptist history of the island here advanced. 

The general distribution of the two best known groups of 
insects — the buttcitiics and the beetles— agrees very closely 
with that of the birds and mammalia, inasmuch as Celebes 
forms the eastern limit of a number of Asiatic and Malayan 
senera. and at the same time the western limit of several 
Moluccan and Australian genera, the former perhaps pre- 
ponderating as in the higher animals. 

Himalayan Types of Birds and Butterflies in Celebes. — A 
curious fact of distribution exhibited both among butterflies 
and birds, is the occurrence in Celebes of species and genera 
unknown to the adjacent islands, but only found again when 
we reach the Himalayan mountains or the Indian Peninsula. 
Among birds we have a small yellow flycatcher {Myialestes 
helianthea), a flower-pecker {Pachyglossa aureolimbata), a finch 
{Munia brunneieeps), and a roller {Coracias temminckii), all 
closely allied to Indian (not Malayan) species, — all the genera, 
except Munia, being, in fact, unknown in any Malay island. 
Exactly parallel cases are two butterflies of the genera Dichor- 
rhagia and Euripus, which have very close allies in the Hima- 
layas, but nothing like them in any intervening country. These 
facts call to mind the similar case of Formosa, where some of 
its birds and mammals occurred again, under identical or closely 
allied forms, in the Himalayas ; and in both instances they can 
only be explained by going back to a period when the distribu- 
tion of these forms was very different from what it is now. 

Peculiarities of Shape and Colour in Cclebesian Butterflies. — 
Even more remarkable are the peculiarities of shape and colour 
in a number of Celebesian butterflies of different genera. These 
are found to vary all in the same manner, indicating some 
general cause of variation able to act upon totally distinct 

F F 



434 ISLAND LIFE. [part ii. 

groups, and produce upon them all a common result. Nearly 
thirty species of butterflies, belonging to thi'ee different families, 
have a common modification in the shape of their wings, by 
which they can be distinguished at a glance from their allies 
in any other island or country whatever ; and all these are 
larger than the representative forms inhabiting most of the 
adjacent islands.^ No such remarkable local modification as 
this is known to occur in any other part of the globe ; and 
whatever may have been its cause, that cause must certainly 
have been long in action, and have been confined to a limited 
area. We have here, therefore, another argument in favour of 
the long-continued isolation of Celebes from all the surrounding 
islands and continents — a hypothesis which we have seen to 
afford the best, if not the only, explanation of its peculiar 
vertebrate fauna. 

Concluding Remarks. — If the view here given of the origin 
of the remarkable Celebesian fauna is correct, we have in this 
island a fragment of the great eastern continent which has pre- 
served to us, perhaps from Miocene times, some remnants of its 
ancient animal forms. There is no other example on the globe 
of an island so closely surrounded by other islands on every 
side, yet preserving such a marked individuality in its forms of 
life ; while, as regards the special features which characterise its 
insects, it is, so far as yet known, absolutely unique. Unfortu- 
nately very little is known of the botany of Celebes, but it 
seems probable that its plants will to some extent partake of 
the speciality which so markedly distinguishes its animals ; 
and there is here a rich field for any botanist who is able to 
penetrate to the forest-clad mountains of its interior. 

> For outline figures of the chief types of these butterflies, see my 
Malay Archipelago, Vol. I. p. 441, or p. 281 of the second edition. 



ArPENDIX TO CHAPTER XX. 



The following list of the Land Birds of Celebes and the adjacent 
islands which partake of its zoological peculiarities, in which are incor- 
porated all the species discovered up to the present year, has been drawn 
up from the following sources : — 

1. A List of the Birds known to inhabit the Island of Celebes. By Arthur, 

Viscount Walden, F.R.S. (Trans. Zool. Soc. 1872. Vol. viii. pt. ii.) 

2. Intomo al Genere Hermotimia. (Rclib.) Nota di Tommaso Salvadori. 

(Atti della Reale Accademia delle Scienze di Torino. Vol. x. 1874.) 

3. Intomo a due Collezioni di Ucelli di Celebes — Note di Tommaso 

Salvadori. (Annali del Mus. Civ. di St. Xat. di Genova. Vol. vii. 
1875.) 

4. Beitrage zur Omithologie von Celebes und Sangir. Von Dr. Friedrich 

Briiggemann. Bremen, 1876. 

5. Intorno a due piccole Collezioni di Ucelli di Tsole Sanghir e di Tifore. 

Nota di Tommaso Salvadori. (Annali del Mus. Civ. di St. Nat. di 
Genova. Vol ix. 1876-77.) 

6. Intorno alle Specie di Nettarinie delle Molucche e del Gruppo di 

Celebes. Note di Tommaso Salvadori. (Atti della Beale Accad. 
delle Scienze di Torino. Vol. xii. 1877.) 

7. Descrizione di tre Nuove Specie di Ucelli, e note intomo ad altre poco 

conosciute delle Isole Sanghir. Per Tommaso Salvadori. (L. c. 
Vol. xiii. 1878.) 

8. Field Notes on the Birds of Celebes. By A. B. Meyer, M.D., &c. 

(Ibis, 1879.) 

9. On the Collection of Birds made by Dr. Meyer during his Expedition 

to New Guinea and some neighbouring Islands. By R. Boulder 
Sharpe. (Mitth. d. kgl. Zool. Mus. Dresden, 1878. Heft 3.) 
New species from the Sula and Sanghir Islands are described. 
10. List of Birds from the Sula Islands (East of Celebes) with Descrip- 
tions of the New Species. By Alfred Bussel Wallace, F.Z.S. 
{Proc. Zool. Soc. 1862, p. 333.) 



F F 2 



LIST OF LAND BIRDS OF CELEBES. 

-V. /?. The Species marked with an * are not included in Viscount Waldtn's list. For 
these only, an authorily is usually given. 





Celebca. , Sula Is. 


SangUir Is 


Range and Remarks. 


TuBDIDiE. 








1. Geocichia er}"throuota 

2. Monticola solitaria 


X 
X 


X 


Phil., China, Japan 


Svi.viiDj;.' 








3. CUticola curaitaus 


>: 




Assam 


*• ., grayi 

5. Acrocepbalus orientalis ... 

*6. ,, insiilaris .. 

7. Pratincola caprata 


X 
X 

X 


X iSalv.) 


China, Japan 

Slolaccas 

Asia, Java, Timor 

[ 


*S. Gcrygone flaveola (Cab.).. 


X (Meyer) 




(Near O. sulphiirea, Timor) 



TlMALIID/E. 

9. Triehostoma celebense 

PvCXOXOTIDi. 

*10. Crinigerlongiro3tri3(WaH.) ' 



11. 



aureus (WalJ.)... 



Oriolid.e. 

12. Oriolus celebcDsis 

13. ,, formosus (Cab.) .. 

14. „ frootalis (Wall.) . 

CxyiVEVH-kOWM. 

15. Graucalus atriceps 

16. ,, leucopygius 

17. ,, temminckii 

18. Campephaga morio 

*19. „ melanotis 

•20. ,, salTadorii (Sharpe) 

21. Lalage leucopygialis... 
*22. ,, dominica 

23. Artamides bicolor ... 
*24. „ schistaccus (Sharpe) 

DicRunrDJS. 

25. Diorurus leucops 

*2o. „ axillaris (Salv.)... 
*i7- pectoralis 'Wall ) 



— 




x(Brugg.) 


X 
X 






X 


X 




X 






— 


X (Wall ) 




X 






x(iIe;eT) 


— 


— 


X 






— 


X 




X 








X 





[ Oriental genus (near Bourn 
sp.) 



(Var. of 0. coronatus, Java) 
(Var. of Philijip. sp.) 



Coram, Flores 

Moluccas 
Java 



CHAP. XX.] 



LIST OF LAND BIRDS OF CELEBES. 



437 





Celebes. 


SuJa Is. Sanghir Is. 


Range and Remarks. 


MUSCICAPID-E. 










28. Cyornis rufigiila 


X 








29. „ banyumas 


X 






Java and Boineo 


30. Myialestes heliaiithea 


X 






(Indian ally) 


31. Hypothymis puellii 


X 


X 






32. „ mcnadensis ?.. 


X 








*33. llonarcha commutata 










(Brugg.) 


X 








*34. ,, cinerascens 


— 


x(WaU.) 




Moluccas 


Paciiycf.fhalid.?;. 










35. Hylocharis sulfuriventra ... 


X 








*36. rachycepliala lineolata 










(Wall.) 


— 


X 


— 


Bouiu 


*37. Pachyrephala rufesceiis 










(Wall.) 


— 


X 


— 


Bourn 


*38. Pachyci-phala clio (Wall.) 


— 


X 


— 


Bouru 


Laxiid.k. 










*39. Laniusmagnirostris(Mcyer) 


X 


— 


— 


Java 


CollVIDJE. 










40. Corvus enca 


X 


X var. 




Java 


•41. ,, annectens (Bnigg.) 


X 








42. ,, (Gazzola) typica ... 


X 








43. Stfeptocitta caleilonica ... 


X 








44. „ torcpiata 


X 








*45. (Charitornis)albertiii' (Sihl. ) 


— 


X 






MKLIPHAGIDJ3. 










46. Myzomela chloroptera ... 


X 






(Nearest M. sanguinolenta 
of Australia) 


Nectarixiid.e. 










47. Anthrcptcs nialaccensis 










(celebensis, Shelley) ... 






X 


Siam, Jlalaya 


48. ChalcostethiaporphyolKma 










»49. „ auriceps 


— 


X(WalI.) 


— 


Ternatc 


*50. „ sangiren.sis (Jlej'cr) 


— 


— 


X 




51. Arachnecthia frcnata 






— 


Moluccas and N. Guinea. 


52. Is'ectarophila gi-ayi 










53. .Etliopyga flavostriata ... 








(An Oriental geim.s) 


*54. ,, beccarii (Sal v.) ... 


X 








*55. ., duyvenbodei(Sclil.) 




— 


X 




DiCXID.E. 


■ 








56. Zosterops iuteiinedia 


X 


1 




Loinbock 


57. ,, atrifrons 


X 








58. Dicsenm celebicum 


X 


X 






*59. ,, sanghirense(Saly.) 


— 


— 


X 




60. Pachyglossa aureolinibata . 




— 


X 




HlHlTNPINlP.E. 


i 








6!. Hirimdo giitturali.? 


1 X 




X 


Indian region 


(>2. ,, javanica 




•■ 




Indo-Malaya 



448 



ISLAND LIFE. 



[part : 



Ploceid,e. 

63. lluuia oryzivora 

64. „ nisoria 

65. „ molucca 

66. „ brunneiceps .. 
*67. „ .iagori 

Stuenim;. 
68. Basilornis celebenfis 



Celebes. | Bula Is. Sarghir Is. Range and Remarks 



69. 

70. 

71. 

•72, 



X (Meyer) 



Acridotheres cinerc-us 
Starnia pyrrhogeuys 

Caloniis ueglecta 

,, luetallica 

73. Enodes crythroptirys 

74. Scissirostrum pagei 

Aktamidj;. 

75. Artamus monachus 

76. „ leucorhynchus ... 

HoTACILLIDf. 

77. Corydalla gustavi 

78. Budyte.s viridis 

*79. Calobates melanope 

( = iIotac. sulfurea, Brugg. ) 

PlTTIDJE. 

80. Pitta forsteni 

•81. „ sanghii-ana (Schl.) ... 

82. „ celfbensis 

•83. „ palliccps (Brugg.) ... 
•84. „ cceruleitorques (Salv.) 
•85. ,, irena( = crassirostris) 

PiCID.E. 

86. Mulleripicus fulviis 

87. Yungipicus temuiinckii ... 

CVCVLTDJE. 

88. Rhami>hocoecyx calorbyn- 

cluis 

89. Ceiitropus celebensis ...| 
HO. ,, affiois 

91. „ javauensis 

92. Cueulus cauoras 

93. Caconiautes lanceolatus ... 

94. ,, sepulcbralis ... 
96. Hierococcyx crassirostris... 
96. Eudvnamis melanorhTncha 

•97. ,', facialis (Wall.) 

•98. ,, orieutalis 

99. Scythrops novfehoUandiffi. . 

C0KACIID.E. 

100. Coracias temminckii 

101. Eiirystomiis orieutalis ... 



X (Bragg.) x(WaU.) 



X 

X 



Java 

Java 

Moluccas 

(Near M. nibronigra, India) 

Philippines 



Malaya 
Moluccas 



Malay Archipcl. 

Java, Moluccas 
China, Philipp. 



X (Wall.) — 



Timor, Ternate ? 



xiBrugg.) 



Java 

Java, Borneo 

Java 



Moluccas ? 
Moluccas, &3 



X , Asia 



CHAP. XX.] 



LIST or LAND BIKDS OF CELEBES. 



4.S9 





Celebes. 


Bula Is. 


Sanghir Is. 


Bange and Remarks. 


Meropidx. 












102. Meropogon forsteni 


X 










103. Merops philippinus 


X 


« 




Oriental region 




lOi. „ ornatus 


X 


X 




Java, Australia 




ALCEDISIlliE. 












105. Alcedo moluccensis 


X 




X 


Moluccas 




106. „ asiatica 


X 






ludo-Malaya 




107. Pelars;opsismelanorliyncha 


X 


X 








*108. Ceyx'wallacei (Shurpe) ... 


— 


X 




(Allied to Mol. sp.) 




109. Ceycopsis fallax 


X 










110. Halcyon chloris 


X 


X 


X 


All Archipel. 




111. „ sancta 


X 


X 




All AiclxiptL 




112. „ forsteni 


X 










113. „ rufa 


X 


X 








114. Monaclialcyon princeps... 


X 










•115. ,, cyanocephala (IJrugg.) 


X 










116. C'ittura cyanotis 


X 










*117. ,, sanghirensis (SchL) 


— 


— 


X 






BUCEROTID-E. 












lis. Hydrocissa exarata 


X 










119. Cranorhiuus ca-ssidix 


X 










CAPP.IMULGIDiE. 












120. Caprimulgus affinis 


X 










121. „ sp 


X 










122. Lyucomis macroptenis ... 


X 










Ctpsklid^. 












123. Dcndrochelidoii waUucei. 


X 


X 








124. Collocalia escuk-iita 


X 






Mol. to Aru Is. 




125. „ fuoipliaga 


X 




I India, Java 




126. Clicetura gigantea 


X 






India, Java 




PSITTACI. 












127. Cacatua sulphurea 


X 






Lombok, Flores 




128. Priouituriis platurus 


X 










129. ,, flavicans 


X 










*130. Platycercus dorsalis, var. 





x(WalI.) 




N. Guinea ? 




131. Tanygnathus mulleri ... 


X 


X 








*132. „ megalorhynchus 


X 


— 


X 


Moluccas. An island 
Menado (Meyer) 


near 


*133. „ hizoniensis 


__ 





xCBrugg.) 




134. Lorieulus stigmatus 


X 










*135. ,, quadricolor (Wald.) 


X 






Togian Is., Gulf of Tomiui. 


136. ,, sclateri 


? 


X 








137. ,, exilis 


X 










*138. ,, catamene (Sclil.) ... 








X 






139. Trichoglossus ornatus ... 


X 










»140. „ flavoTiridi3(Wall.) 


— 


X 








141. ,, nieyeri 


X 










•142. Eos histrio — E. coecinea 


— 


— 


X 







440 


ISLAND LIFE. 


[iWRT II. 


i 


Celebes. 


Sulals. 


Sangbir Is.' 


K.nnge end Remarks. 


COLUMRS. 


1 








1 4-3. Treron vemans 




. 


Malacca, Java, Philipp. 


144. ,, griseicanda 


X X 


X Tar. 

Sanghi- 

rensis. 




145. Ptilopus formosus 


X 






146. :, melanocephalus... 


X :< 


X var. 

Xanthor- 

rhoa. 


Java, Lombock 




, Salv. 




147. ,, gnlaris 


X 






*148. „ fischeri (Bingg.) 


X 




> 


149. Carpophaga paulina 


X X 






»150. ,, pnlchella (Wald.) 


X 




Togian Is. {Jnn. and Mag. 
Kat. Hist., 1874.) 


151. „ concinna ... 


— 


X (Salv.) 


Ke Coram 


152. ,, rosacea 


X ( 




GUolo, Tin:or 


*153. , , {wcilorrhoa ( Bragg. ) 


X 1 






154. ,, luctiiosa ... 


X 


X 






*155. „ bicolor 


X (Meyer) 




X 


Kew Gaines, Moluccas 


156. „ mdiata 


X 




X 




157. „ forsteni 


X 








158. Maciopygia albicajjilla ... 


X 


X 






159. „ macassariensis ... 


X 








•160. „ sanghirciisis(Salv.) 


. — 


— 


X 




161. Turacotna menadensis ... 


X 


X 






*162. Reinwai-dtoenas reinwardti 


X Meyer 






Moluccas and New Guinea 


163. Turtur tigrina 


X 






Jlalaya, ilolnccas 


164. Chalcopliaps stephaiii ... 


X 






New Guinea 


165. ,, indica 


X 


X var. 


X 


India and Archipelago 


166. PUogsenas tristigmata ... 


X ' 






167. Geopelia striata 


X 


China, Java, Lombock 


168. Cahenas nicobaiica 


■■' 


M.ilacca and New Guinea 


GAllIXiK. 






169. Gallns hankiva 


X ; 


Java, Timor 


170. Coturnix minima 


X 




(Var. of C. Cliinensis) 


171. Tumix nifilatus 


X 


. 




*J72. ,, beecarii (Salv.) ... 


X 






173. Megapodius gilberti 


X 






174. Megacpphalon malleo ... 


X 


X 




' ACCIPITKES. 






175. Hrcus assimilis 


i 


Australia 


176. Astur griseiceps 


X 




»177. ■• „ tenuiiostris( Bragg.) 


X 




178. ,, rhodogastra 


X 






179. „ trinotata 


X 






180. Accipiter sulaensis (Schl. ) 








181. „ soloensis 


X 




Slalacca and New Guinea 


182. Neopus malayensis 


X 




Nepaul,Suui. , Java, Molucc.is 


183. Spizaetus laneeolatus ... 


X ^ 






184. Haliaetus leucogastcr : ... 


X 




Oriental region 


85. Spilomis rafipectn? 




x 







.HAP. XX.] 



LIST OF LAND BIRDS OF CELEB KS. 



441 



1 Celebes. 

1 


£ula Is. iSnngliir Is, 


Range and Remarks. 


186. Butastur liyenter 


X 


1 


Java, Timor 


187. ,, indicus 


X 


X 


India, Java 


188. Haliastur leucostemus ... 


X 




Moluccas, New Guinea 


189. Milvusaffinis 


X 




Australia 


190. Elanus hypoleucus 


X 




? Java, liorneo 


191. Pernis ptilorhyncUa (var. 








celcbensis) 


X 






(Var. Java, &c.) 


192. Baza erythrothorax 


X 


X 






193. Falco sevenis 


X 






All Aicliipel. 


194. Cerchueis moluecensis ... 


X 






Java, Moluccas 


19.'). Polioactus Inimilis 


X 






India, Malaya 


Stiugid.e. 










196. Athene puutluliita 


X 








197. ,, ocliracca 


X 








198. Scops magicus 


X 






Aniboyna, &c. ? 


199. ,, iiieii,ideni-i.s 


X 






Floics, Madagascar 


•200. Nino.^ japoiiicus 


X 






China, Japan 


*201. „ scutulata 


_ 


— 


X (Salv.) JIalacca 


202. Stri.x rosenbergi 


X 









CHAPTER XXI. 

ANOMALOUS ISLANDS : NEW ZEALAND. 

Position and Physical Features of New Zealand — Zoological character of 
New Zealand — Mammalia — Wingless Birds living and extinct — Recent 
Existence of the Moa — Past Changes of New Zealand deduced from 
its Wingless Birds — Birds and Reptiles of New Zealand — Conclusions 
from the Peculiarities of the New Zealand Fauna. 

The fauna of New Zealand has been so recently described, and 
its bearing on the past history of the islands so fully discussed 
in my large work already referred to, that it would not be neces- 
sary to introduce the subject again, were it not that we now 
approach it from a somewhat different point of view, and with 
some important fresh material, which will enable us to arrive 
at more definite conclusions as to the nature and origin of this 
remarkable fauna and flora. The present work is, besides, 
addressed to a wider class of readers than my former volumes, 
and it would be manifestly incomplete if all reference to one of 
the most remarkable and interesting of insular faunas was 
omitted. 

The two great islands which mainly constitute New Zealand 
are together about as large as the kingdom of Italy. They 
stretch over thirteen degrees of latitude in the warmer portion 
of the south-temperate zone, their extreme points correspond- 
ing to the latitudes of Vienna and Cyprus. Their climate 
throughout is mild and equable, their vegetation is luxuriant, 
and deserts or uninhabitable regions are as completely unknown 
as in our own islands. 



CHAP. XXI.] 



NEW ZEALAND. 



443 



The geological structure of these islands has a decidedly 
contineutal character. Ancient sedimentary rocks, granite, 
and modern volcanic formations abound ; gold, silver, copper, 
tin, iron, and coal are plentiful ; and there are also some con- 
siderable deposits of early or late Tertiary age. The Secondary 
rocks alone are very scantily developed, and such fragments as 
exist are chiefly of Cretaceous age, often not clearly separated 
from the succeeding Eocene beds. 




MAP SUOWINO DEPTHS OF SEA AROlTs'D AUSTRALIA AND SEW ZEALAND. 

The light tint indicfttos a depth of less than l.ono fathoms. 
The dark tint ,, „ more than 1,000 fathoms. 



The position of New Zealand, in the great Southern Ocean, 
about 1,200 miles distant from the Australian continent, is very 
isolated. It is surrounded by a moderately deep ocean ; but 
the form of the sea-bottom is peculiar, and may help us in the 
solution of some of the anomalies presented by its living pro- 
ductions. The line of 200 fathoms encloses the two islands 
and extends their area considerably ; but the 1,000-fathom 
line, which indicates the land-area that would be produced if 



444 ISLAND LIFE. [paet ii. 

the sea-bottom were elevated 6,000 feet, has a very remarkable 
conformation, extending in a broad mass westward, and then 
sending out two great arms, one reaching to beyond Lord Howe's 
Island, while the other stretches over Norfolk Island to the 
great barrier reef, thus forming a connection with tropical 
Australia and New Guinea. Temperate Australia, on the other 
hand, is divided from New Zealand by an oceanic gulf about 
700 miles wide and between 2,000 and 3,000 fathoms deep. 
The 2,000-fathom line embraces all the islands immediately 
round New Zealand ; and a submarine plateau at a depth 
somewhere between one and two thousand fathoms stretches 
southward to the Antarctic continent. Judging from these indi- 
cations, we should say that the most probable ancient connections 
of New Zealand were with tropical Australia and New Guinea, 
and perhaps, at a still more remote epoch, with the great 
Southern continent b}' means of intervening lands and islands ; 
and we shall find that a land-connection or near approximation 
in these two directions, at remote periods, will serve to ex- 
plain many of the remarkable anomalies which these islands 
present. 

Zoological Character of Neiv Zealand. — We see, then, that 
both geologically and geographically New Zealand has more 
of the character of a " continental " than of an " oceanic " i.sland, 
yet its zoological characteristics are such as almost to bring it 
within the latter category — and it is this which gives it its 
anomalous character. It is usually considered to possess no 
indigenous mammalia ; it has no snakes, and only one frog ; 
it possesses (living or quite recently extinct) an extensive group 
of birds incapable of flight ; and its productions generally are 
wonderfully isolated, and seem to bear no predominant or close 
relation to those of Australia or any other continent. Tliese 
are the characteristics of an oceanic island ; and thus we find 
that the inferences from its physical structure and those from 
its forms of life directly contradict each other. Let ns see 
how far a closer examination of the latter will enable us to 
account for this apparent contradiction. 

Mammalia of Nev Zealand. — The only undoubtedly indi- 
genous mammalia appear to be two species of bats, one of which 



Ciur. XXI.] J«KW ZEALAND. 445 

{Scotojihilus tuberculatus) is, according to Mr. Dobson, identical 
with an Australian form, while the other {Mystacina tuhcrculata) 
forms a very remarkable and isolated genus of Emballonurida^, 
a family which extends throughout all the tropical regions of 
the globe. The genus I\Iystaciua was formerly considered to 
belong to the American Phyllostomidse, but this has been 
shown to be an error. ^ The poverty of New Zealand in bats 
is very remarkable when compared with our own islands where 
there are at least twelve distinct species, though having a far 
less favourable climate. 

Of the existence of truly indigenous land mammals in New 
Zealand there is at present no positive evidence, but there is 
some reason to believe that one if not two species may be found 
there. The Maoris say that before Europeans came to thoir 
country a forest-rat abounded and was largely used for food. 
They believe that their ancestors brovight it with them when 
they first came to the country ; but it has now become almost, if 
not quite, exterminated by the European brown rat. What 
this native animal was is still somewhat doubtful. Several 
specimens have been caught at different times which have been 
declared by the natives to be the true Kiorc Maori — as they term 
it, but these have usually proved on examination to be either 
the European black rat or some of the native Australian rats 
which now often find their way on board ships. But within 
the last few years many skulls of a rat have been obtained from 
the old Maori cooking-places, and from a cave associated with 
raoa bones ; and Captain Hutton, who has examined them, states 
that they belong to a true Mus, but differ from the Mus rattus. 
This animal might have been on the islands when the Maoris 
first arrived, and in that case would be truly indigenous ; while 
the Maori legend of their " ancestors " bringing the rat from their 
Polynesian home may be altogether a myth invented to account 
for its presence in the islands, because the only other land 
mammal which they knew — the dog — was certainly so brought. 
The question can only be settled by the discovery of remains 

' Dubson oft the Classification of Chiroptera (^Arni. and Mag. of Kat, 
TT!s>. Nov. 1875). 



446 ISLAND LIFE. [part ii. 



of a rat in some deposit of an age decidedly anterior to the 
first arrival of the Maori race in New Zealand.' 

Much more interesting is the reported existence in the moun- 
tains of the South Island of a small otter-like animal. Dr. 
Haast has seen its tracks, resembling those of our Euroi^ean otter, 
at a height of 3.000 feet above the sea in a region never before 
trodden by man ; and the animal itself was seen by two 
gentlemen near Lake Heron, about seventy miles due west of 
Christchurch. It was described as being dark bro%\'n and the 
size of a large rabbit. On being struck at with a whip, it uttered 
a shrill yelping sound and disappeared in the water.- An animal 
seen so closely as to be struck at with a whip could hardly have 
been mistaken for a dog — the only other animal that it could 
possibly be supposed to have been, and a dog would certainly not 
have "disappeared in the water." This account, as well as the 
footsteps, point to an aquatic animal; and if it now frequents 
only the high alpine lakes and streams, this might explain 
why it has never yet been captured. Hochstetter also states 
that it has a native name — Waitoteke — a striking evidence 
of its actual existence, while a gentleman who lived many years 
in the district assures me that it is universally believed in by 
residents in that part of New Zealand. The actual capture of 
this animal and the determination of its characters and affinities 
could not fail to aid us greatly in our speculations as to the 
nature and origin of the New Zealand fauna.^ 

1 See BuUer, " On the New Zealand Rat," Trans, of the N. Z. Institute 
(1870), Vol. III. p. 1, and Vol. IX. p. 348 ; and Button, " On the Geogra- 
phical Relations of the New Zealand Fanna," Trans. N. Z. Instit. 1872, 
p. 229. 

- Hochstetter's Neti: Zealand, p. 161, note. 

^ The animal described by Captain Cook as having been seen at Piok. 
ersg^ll Harbour in Dusky Bay (Cook's 2nd Voyage, Vol. I. p. 98) may have 
been the same creature. He says, " A four-footed animal was seen by three 
or four of our people, but as no two gave the same description of it, I can- 
not say what kind it is. All, however, agreed that it was about the size of 
a cat, with short legs, and of a mouse colour. One of the seamen, and he 
who had the best view of it, said it had a bushy tail, and was the most like 
a jackal of any animal he knew." It is suggestive that, so far as the 
points on which "all agreed '' — the size and the dark colour — this description 
would answer well to the animal so recently seen, while the " short legs " 



CHAP. XXI.] XEW ZEALAND. 417 

Wingless Birds, living and extinct. — Almost equally valuable 
with mammalia in affording indications of geographical changes 
are the wingless birds for which New Zealand is so remarkable. 
These consist of four species of Apterj-s, called by the natives 
"kiwis," — creatures which hardly look like birds owing to the 
apparent absence (externally) of tail or wings and the dense 
covering of hair-like feathers. They vary in size from that of 
a small fowl up to that of a turkey, and have a long slightly 
cur%'ed bill, somewhat resembling that of the snipe or ibis. 
Two species appear to be confined to the South Island, and one 
to the North Island, but all are becoming scarce, and they will 
no doubt gradually become extinct. These birds are generally 
classed with the Struthiones or ostrich tribe, but they form a 
distinct family, and in many respects differ greatly from all 
other known birds. 

But besides these, a number of other wingless birds, called 
" moas," inhabited New Zealand during the period of human 
occupation, and have only recently become extinct. These were 
much larger birds than the kiwis, and some of them were even 
larger than the ostrich, a specimen of Dinornis maximus 
mounted in the British Museum in its natural attitude being 
eleven feet high. They agreed, however, with the living 
Apteryx in having four toes, and in the character of the pelvis 
and some other parts of the skeleton, while in their short bill 
and in some important structural features they resembled 
the emu of Australia and the cassowaries of New Guinea.' 
No less than eleven distinct species of these birds have 
now been discovered ; and their remains exist in such 

correspond to the otter-like tracks, and the thick tail of an otter-like animal 
may well have appeared " bushy " when the fur was dry. It has been 
suggested that it was only one of the native dogs ; but 88 none of those 
who saw it took it for a dog, and the points on which they all agreed are 
not dog-like, we can hardly accept this explanation ; while the actual exist- 
ence of an unknown animal in New Zealand of corresponding size and 
colour is confirmed by this account of a similar animal having been seen 
about a century ago. 

1 Owen, " On the Genus Dinornis," Trans. Zool. Soc. Vol. X. p. 181. 
Mivart, " On the Axial Skeleton of the Struthionidfe," Trans. Zool. Soc. 
Vol. X. p. 51. 



448 ISLAND LIFE. [iaet ii. 



abundance — in recent fluviatile deposits, in old native cooking 
places, and even scattered on the surface of the ground — that 
complete skeletons of several of them have been put together, 
illustrating various periods of growth from the chick up to the 
adult bird. Feathers have also been found attached to portions 
of tlie skin, as well as the stones swallowed by the birds to 
assist digestion, and eggs, some containing portions of the 
embryo bird ; so that everything confirms the statements of the 
Maoris — that their ancestors found these birds in abundance on 
the islands, that they hunted them for food, and that they 
finally e.xterminated them only a short time before the arrival of 
Europeans.^ Bones of Apteryx are also found fossil, but appar- 
ently of the same species as the living birds. How far back in 
geological time these creatures or their ancestral types lived in 
New Zealand we have as yet no evidence to show. Some 
specimens have been found under a considerable depth of 
fluviatile deposits which may be of Quaternary or even of 
Pliocene age ; but this evidently affords us no approximation to 
the time required for the origin and development of such highly 
peculiar insular forms. 

Past Chan^fcs of New Zealand deduced from its Wingless Birds. 

1 Tlie recent existence of the Mosi and its having been extenniniitcd by 
the Maoris appears to be at lengtli sot at rest by tlie statement of Mr. 
John White, a gentleman who lias been collecting materials for a history of 
the natives forthirty-iive years, who has been initiated by their priests into 
all their mysteries, and is said to " Icnow more about the history, habits, 
and customs of the Maoris tlian they do themselves." His information on 
this subject was obtained from old natives long before the controversy on 
the subject arose. He says that the histories and songs of the Maoris 
abound iu allusions to the Moa, and that they were able to give full 
accounts of "its habits, food, the season of the year it was killed, it~< 
appearance, strength, and all the numerous ceremonies which were enacted 
by the natives before they began the hunt, the mode of hunting, how cut 
up, how cooked, and what wood was used in the cooking, with an account 
of its nest, and liow the nest was made, where it usually lived, &c." Two 
pages are occupied by these details, but they are only- given from memory, 
and Mr. White promises a full account from his MSS. Many of the details 
given correspond with facts ascertained from the discovery of native cook- 
ing places with Moa's bones; and it seems quite incredible that such an 
elaborate and detailed account should be all invention. (See Transactions 
of the New Zealaml Institute, Vol. VIIL p. 79.) 



CHAP, xxi.] NEW ZEALAND. 449 



— It has been well observed by Captam Huttou, iu his inter- 
esting paper ah^eady referred to, that the occurrence of such a 
number of species of Struthious birds living together in so 
small a country as New Zealand is altogether unparalleled else- 
where on the globe. This is even more remarkable when we 
consider that the species are not equally divided between the 
two islands, for remains of no less than ten out of the eleven 
known species of Dinornis have been found iu a single swam^i 
in the South Island, where also three of the species of Apteryx 
occur. The New Zealand Strutbiones, in fact, very nearly equal 
in number those of all the rest of the world, and nowhere else 
do more than three species occur in any one continent or island, 
while no more than two ever occur in the same district. Thus, 
there appear to be two closely allied species of ostriches inhabiting 
Africa and South-western Asia respectively. South America 
has three species of Rhea, each in a separate district. Australia 
has an eastern and a western variety of emu, and a cassowary 
in the north ; wliile eight other cassowaries are known from the 
islands north of Australia — one from Cerani, two from the Aru 
Islands, one from Jobie, one from New Britain, and three from 
New Guinea — but of these last one is confined to the uorthei'n 
and another to the southern part of the island. 

This law, of the distribution of allied species in separate areas 
— which is found to apply more or less accurately to all classes 
of animals — is so entirely opposed to the crowding together of 
no less than fifteen species of wingless birds in the small area of 
New Zealand, that the idea is at once suggested of great geogra- 
phical changes. Captain Hutton points out that if the islands 
from Ceram to New Britain were to become joined together, we 
should have a large number of species of cassowary (perhaps 
several more than are yet discovered) in one land area. If now 
this land were gradually to be submerged, leaving a central 
elevated region, the diilerent species would become crowded 
together in this portion just as the moas and kiwis were in 
New Zealand. But we also require, at some remote epoch, a more 
or less complete union of the islands now inhabited by the 
.separate species of cassowaries, in order that the common 
ancestral form which afterwards became luodLfied into these 

G G 



450 ISLAND LIFE. [part ii. 

species, coukl have reached the places where they are now 
found ; and tliis gives us an idea of the complete series of 
changes through which New ^^ealand is believed to have passed 
in order to bring about its abnormally dense population of wing- 
less birds. First, we must suppose a land connection with some 
country inhabited by struthious birds, from which the ancestral 
forms might be derived ; secondly, a separation into many con- 
siderable islands, in which the various distinct species might 
become diflfercntiated ; thirdly, an elevation bringing about the 
union of these islands to unite the distinct species in one 
area ; and fourtlily, a subsidence of a large part of the area, 
leaving the present islands with the various species crowded 
together.. 

If New Zealand has really gone through such a series of 
changes as here suggested, some proofs of it might perhaps be 
obtained in the outlying islands which were once, presumably, 
joined with it. And this gives great importance to the state- 
ment of the aborigines of the Chatham Islands, that the 
Aptei-yx formerly lived there but was exterminated about 183-5. 
It is to be hoped that some search will be made here and also in 
Norfolk Island, in both of which it is not improbable remains 
either of Apteryx or Dinornis might be discovered. 

So far we find nothing to object to in the speculations of 
Captain Hutton, with which, on the contrary, we almost whoUj- 
concur ; but we cannot follow hira when he goes on to suggest an 
Antarctic continent uniting New Zealand and Australia with 
South America, and probably also with South Africa, in 
order to explain the existiag distribiition of struthious birds. 
Our best anatomists, as we have seen, agree that both Dinornis 
and Apteiyx are more nearly allied to the cassowaries and emus 
than to the ostriches and rheas ; and we see that the form of 
the sea-bottom suggests a former connection with North Aus- 
tralia and New Guinea — the very region where these type.s 
most abound, and where in all probability they originated. The 
suggestion that all the struthious birds of the world sprang 
from a common ancestor at no very remote period, and that 
their existing distribution is due to direct land communication 
between the countries they 7ioiu inhabit, is one utterly opposed 



CHAP. XXI.] NEW ZEALAND. 451 

to all sound principles of reasoning in questions of geogiaphical 
distribution. For it depends upon two assumptions, both of 
which are at least doubtful, if not certainly false — the first, 
that their distribution over the globe has never in past ages 
been very different from what it is now ; and the second, that 
the ancestral forms of these birds never had the power of flight. 
As to the first assumption, %ve have found in almost every case 
that groups now scattered over two or more continents formerly 
lived in intervening areas of existing land. Thus the marsupials 
of South America and Australia are connected by forms which 
lived in North America and Europe ; the camels of Asia and 
the llamas of the Andes had many extinct common ancestors 
in North America ; the lemurs of Africa and Asia had their 
ancestors in Europe, as did the trogons of South America, 
Africa, and tropical Asia. But besides this general evidence we 
have direct proof that the struthious birds had a witler range 
m past times than now. Remains of extinct rheas have been 
found in Central Brazil, and those of ostriches in North India ; 
while remains, believed to bo of struthious birds, are found in 
the Eocene deposits of England ; and the Cretaceous rocks of 
North America have yielded the extraordinary toothed bird, 
Hesperomis, which Professor O. Marsh declares to have been 
" a carnivorous swimmiog ostrich." 

As to the second point, we have the remarkable fact that all 
known birds of this group have not only the rudiments of wing- 
bones, but also the rudiments of wings, that is, an external 
limb bearing rigid quills or largely-developed plumes. In the 
cassowary these 'wing-feathers are reduced to long spines like 
porcupine-quills, while even in" the Apteryx, the minute 
external wing bears a series of nearly twenty stiff quill-like 
feathers.^ These facts render it probable that the struthious 
birds do not owe their imperfect wings to a direct evolution 
from a reptilian type, but to a retrograde development from 
some low form of winged birds, analogous to that which has pro- 
duced the dodo and the solitaire from the more highly-developed 
pigeon-type. Professor Marsh has proved, that so far back as 

I See fig. in Trans. ofN. Z. Institute, Vol. III., plate 126, fi?. 2. 

G G 2 



452 ISLAND LIFE. [part ii. 

the Cretaceous period, the two great forms of birds — those with 
a keeled sternum and fairly-developed wings, and those with a 
convex keel-less sternum and rudimentary wings — already 
existed side by side ; while in the still earlier Archseopteryx of 
the Jurassic period we have a bird with well-developed wings, 
and therefore probably with a keeled sternum. We are evidently, 
therefore, very far from a knowledge of the earher stages of 
bird life, and our acquaintance with the various forms that have 
existed is scanty in the extreme ; but we may be sure that birds 
acquired wings, and feathers, and some power of flight, before 
they developed a keeled sternum, since we see that bats with no 
such keel fly very well. Since, therefore, the struthious birds 
all have perfect feathers, and all have rudimentary wings, which 
are anatomically those of true birds, not the rudimentary fore- 
legs of reptiles, and since we know that in many higher groups 
of birds — as the pigeons and the rails — the wings have become 
more or less aborted, and the keel of the sternum greatly 
reduced in size by disuse, it seems probable that the very 
remote ancestors of the rhea, the cassowary, and the apteryx, 
were true flying birds, although not perhaps provided with a 
keeled sternum, or possessing very great powers of flight. But 
in addition to the possible ancestral power of flight, we have 
the undoubted fact that the rhea and the emu both swim 
freely, the former having been seen swimming from island to 
island ofl' the coast of Patagonia. This, taken in connection 
with the wonderful aquatic ostrich of the Cretaceous period 
discovered by Professor Marsh, opens up fresh possibilities of 
migration; while the immense antiquity thus given to the 
group and their universal distribution in past time, renders 
all suggestions of special modes of communication between the 
parts of the globe in which their scattered remnants novj 
happen to exist, altogether superfluous and misleading. 

The bearing of this argument on our present subject is, that 
so far as accounting for the presence of wingless birds in New 
Zealand is concerned, we have nothing whatever to do with 
any possible connection, by way of a southern continent or 
antarctic islands, with South America and South Africa, 
because the nearest allies of its moas and kiwis are the 



CHAr. rv5i.] NEW ZEALAND. 453 

cassowaries and emus, and we have distinct indications of a 
former land extension towards North Australia and New Guinea, 
which is exactly what wo require for the original entrance of 
the struthious type into the New Zealand area. 

Winged Birds and- lower Vertebrates of Nciu Zealand. — Having 
given a pretty full account of the New Zealand fauna else- 
where ' I need only here point out its hearing on the hypo- 
thesis now advanced, of the former land-connection having been 
with North Australia, New Guinea, and the Western Pacific 
Islands, rather than with the temperate regions of Australia. 

Of the Australian genera of birds, which are found also in 
New Zealand, almost every one ranges also into New Guinea 
or the Pacific Islands, while the few that do not extend beyond 
Australia are found in its northern districts. As regards the 
peculiar New Zealand genera, all whose affinities can be traced 
are allied to birds which belong to the tropical parts of the 
Australian region ; while the starling family, to which four of 
the most remarkable New Zealand birds belong (the genera 
Creadion, Heterolocha, and Calla\as), is totally wanting in 
temperate Australia and is comparatively scarce in the entire 
Australian region, but is abundant in the Oriental region, with 
which New Guinea and the ^loluccas are in easy communication. 
It is certainly a most suggestive fact that there are more than 
sixty genera of birds peculiar to the Australian continent (with 
Tasmania), many of them almost or quite confined to its tempe- 
rate portions, and that no single one of these should be repre- 
sented in temperate New Zealand." The affinities of the Kving 
and more highly organised, no less than those of the extinct and 
wingless birds, strikingly accord with the line of commmiication 
indicated by the deep submarine bank connecting these temperate 
islands with the tropical parts of the Australian region. 

The reptiles, so far as they go, are quite in accordance with 

1 Geograpliical Distrihution of Animah, Vol. I., p. 450. 

2 In my Geograpliical Disiribution of Animah (I. p. 541) I have given 
two peculiar Australian genera {Orlltomjx and Trihonyx) as occurring in 
New Zealand. But the former has been found in New Guinea, while the 
New Zealand bird is considered to fonn a distinct genus, CliUmyx; and 
the latter inhabits Tasmania, and was recorded from New Zealand through 
an error. (Seo Ibis, 1873, p. 427.) 



454 ISLAXD LIFE. [pakt u. 

the birds. The lizards belong to three genera, — Hinulia and 
Mocoa, which have a wide range in the Eastern tropics and the 
Pacific and Malayan regions, as weU as Australia ; and Naultinus, 
a genus peculiar to New Zealand, but belonging to a family — 
Geckotidae, spread over the whole of the warmer parts of the 
world. AustraUa, on the other hand, has three small "bxit 
pecuhar famihes, and no less than thirty-sis peculiar genera of 
lizards, many of which are confined to its temperate regions, 
but no one of them extends to temperate New Zealand. The 
extraordinary Uzard-like Hattcria 2mnctata of New Zealand 
forms of itself a distinct order of reptOes, in some respects 
intermediate between lizards and crocodiles, and having therefore 
no affinity with any hving animal. 

The only representative of the Amphibia in New Zealand is 
a soHtaiy frog of a pecuhar genus {Liopelma Jioehstettei-i) ; but 
it has no affinity for any of the Australian frogs, which are 
Qumerous, and belong to eleven different fivmiHes; while the 
Liopelma belongs to a very distinct family (Bombinatoridae), 
confined to Europe and temperate South America. 

Of the fresh-water fishes we need only say here, that none 
belong to pecuhar Anstrahan types, but are related to those of 
temperate South America or of Asia. 

The Invertebrate classes are comparatively little known, and 
their modes of dispersal are so varied and exceptional that the 
facts presented by their distribution can add little weight to 
those already adduced. We will, therefore, now proceed to the 
conclusions which can fairly be drawn from the general facts of 
New Zealand natural history already known to us. 

Deductions from the ]3cculiarities of the Keiv Zealand Fauna. — 
The total absence (or extreme scarcity) of mammals in New 
Zealand obhges us to place its union with North Austraha and 
New Guinea at a very remote epoch. We must either go back 
to a time when Australia itself had not yet received the ancestral 
forms of its present marsupials and monotremes, or we must 
suppose that the portion of Australia with which New Zealand 
was connected was then itself isolated £rom the mainland, and 
was thus without a mammalian population. We shall see in 
our next chapter that there are certain facts in the distribution 



CHAP. XXI.] NEW ZEALAND. 455 



of plants, no less than in the geological structure of the country, 
which favour the latter view. But we must on any supposition 
place the union veiy far back, to account for the total want of 
identity between the winged birds of New Zealand and those 
peculiar to Australia, and a similar want of accordance in the 
lizards, the fresh-water fishes, and the more important insect- 
groups of the two countries. From what we know of the long 
geological duration of the generic types of these groups we 
must certainly go back to the earlier portion of the Tertiary 
period at least, in order that there should be such a complete 
disseverance as exists between the characteristic animals of the 
two countries; and we must further suppose that, since their 
separation, there has been no subsequent union or sufficiently 
near approach to allow of any important iutermigration, even 
of winged birds, between them. It seems probable, therefore, 
that the Bampton shoal west of New Caledonia, and Lord 
Howe's Island further south, formed the western limits of that 
extensive land in which the great wingless birds and other 
isolated members of the New Zealand f;iuna were developed. 
Whether this early land extended eastward to the Chatham 
Islands and southward to the Macquaries we have no means of 
ascertaining, but as the intervening sea appears to be not more 
than about 1,500 fathoms deep it is quite possible that such an 
amount of subsidence may have occurred. It is possible, too, 
that there may have been an extension northward to the 
Kemiadec Islands, and even further to the Tonga and Fiji 
Islands, though this is hardly probable, or we should find more 
community between their productions and those of New 
Zealand. 

A southern extension towards the Antarctic continent at a 
somewhat later period seems more probable, as affording an 
easy passage for the numerous species of South American and 
Antarctic plants, and also for the identical and closely alHed 
fresh-water fishes of these countries. 

The subsequent breaking up of this extensive land into a 
number of separate islands in which the distinct si^ecies of moa 
and kiwi were developed — their union at a later period, and 
the final submergence of all but the existing islands, is a pure 



456 ISLAND LIFE. [pakt n. 



hypothesis, wliich st ems necessaiy to explain the occiurence of 
so many species of these birds in a small area but of which we 
have no independent proof. There are, however, some other 
facts which would be explained by it, as the presence of three 
peculiar but allied genera of starlings, the three species of 
parrots of the genus Nestor, and the six distinct rails of the 
genus Ocydromus, as well as the numerous species in some of 
the peculiar New Zealand genera of plants, which seem less 
Ukely to have been developed in a single area than when 
isolated, and thus jjreserved from the counteracting influence 
of intercrossing. 

In the present state of our knowledge these seem all the 
conclusions we can arrive at from a study of the New Zealand 
fauna; but as we fortunately possess a very full and accurate 
knowledge of the flora of New Zealand, as well as of that of 
Australia and the south temperate lands generally, it will be 
well to see how far these conclusions are supported by the facts 
of plant distribution, and what further indications they afford us 
of the early history of these most interesting countries. This 
inquiry is of sufficient importance to occupy a sepai'ate chapter. 



CHAPTER XXII. 

THE FLOKA OF NEW ZEALAND : ITS AFFINITIES 
AND PROBABLE OEIGIN. 

Relations of the New Zealand Flora to that of Australia— General features 
of tlie Australian Flora— The Floras of South-eastern and South-westem 
Australia— Geological explanation of the differences of these two 
Floras — The origin of the Australian element in the New Zealand Flora 

Tropical character of the New Zealand Flora explained— Species 

common to New Zealand and Australia mostly temperate forms—Why 
easily dispersed plants have often restricted ranges— Summary and 
Conclusion on the New Zealand Flora. 

Although plants have means of dispersal far exceeding those 
possessed by animals, yet as a matter of fact comparatively few 
species are can-icd for very great distances, and the flora of a 
country taken as a whole usually affords trustworthy indications 
of its past history. Plants, too, are more numerous in species 
than the higher animals, and arc almost always tetter hnown ; 
their affinities have been more systematically studied ; and it may 
be safely affirmed that no explanation of the origin of the fauna 
of a country can be sound, which does not also explain, or at 
least harmonise with, the distribution and relations of its flora. 

The relations of the flora of New Zealand to that of Aus- 
tralia have long formed an insoluble enigma for botanists. Sir 
Joseph Hooker, in his most instructive and masterly essay on 
the flora of Australia, says :—" Under whatever aspect I 
regard the flora of Australia and of New Zealand, I find all 
attempts to theorise on the possible causes of their community 
of feature frustrated by anomalies in distribution, such as I 



458 ISLAND LIFE. [part ii. 

believe no two other similarly situated countries in tlie globe 
present. Everywhere else I recognise a parallelism or harmony 
in the main common features of contiguous floras, which 
conveys the impression of their generic affinitj-, at least, being 
affected by migration from centres of dispersion in one of them, 
or in some adjacent country. In this case it is widely different. 
Regarding the question from the Australian point of view, it is 
impossible in the present state of science to reconcile the fact 
of Acacia, Eucalyptus, Ccisiuirina, Callitris, &c., being absent in 
New Zealand, with any theory of trans-oceanic migration that 
may be adopted to explain the presence of other Australian 
plants in New Zealand ; and it is very difficult to conceive of a 
time or of conditions that could explain these anomalies, except 
by going back to epochs when the prevalent botanical as well 
as geographical features of each were widely different from what 
they are now. On the other hand, if I regard the question from 
the New Zealand point of view, I find such broad features of 
resemblance, and so many connecting links that afford irre- 
sistible evidence of a close botanical connection, that I cannot 
abandon the conviction that these great differences ■\vill present 
the least difficulties to whatever theory may explain the whole 
case." I will now state, as briefly as possible, what are the 
facts above referred to as being of so anomalous a character, 
and there is little difficulty in doing so, as we have them fully 
set forth, with admirable clearness, in the essay above alluded 
to, and in the same writer's Introduction to the Flora of Keiv 
Zealand, only requiring some slight modifications, owing to 
the later discoveries v.-hich are given in the Haiulhook of the 
New Zealand Flora. 

Confining ourselves always to flowering plants, we find that 
the flora of New Zealand is a very poor one, consideri