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TROPICAL NATURE, 

AND OTHER ESSAYS. 



' / 



TEOPICAL NATURE, 



AND 



OTHER ESSAYS. 



ALFEED R. AVALLACE. 

AUTHOR OF "THE MALAY ARCHIPELAGO," "THE GEOGRAPHICAL DISTRIBUTION OF ANIMALS," 
"CONTRIBUTIONS TO THE THEORY OF NATURAL SELECTION," ETC., ETO. 



If 0tT0oit : 
MACMILLAN AND CO. 

1878. 

[Tlie Ilitjlit of Translation and Reproduction is Reserved.] 



LOKDOX ! 
R. CLAY, SONS, AND TAYLOK, 

BREAD STREET HII.I.. 



/ o 



5 L> 5 



THE TKOPICS. 

LAND of the Sun ! where joyous green-robed Spring 

And leaf-crowned Summer deck the Earth for ever ; 

No Winter stern their sweet embrace to sever 

And numb to silence every living thing, 

But bird and insect ever on the wing, 

Flitting 'mid forest glades and tangled bowers, 

While the life-giving orb's effulgent beams 

Through all the circling year call forth the flowers. 

Here graceful palms, here luscious fruits have birth ; 

The fragrant coffee, life-sustaining rice, 

Sweet canes, and wondrous gums, and odorous spice ; 

While Flora's choicest treasures crowd the teeming earth. 

Beside each cot the golden Orange stands, 

And broad-leaved Plantain, pride of Tropic lands. 



ENGLAND. 

SWEET changing Seasons ! Winter cold and stern, 
Fair Spring with budding leaf and opening flower, 
And Summer when the sun's creative power 
Brings leafy groves and glades of feathery fern, 
The glorious blossoms of sweet-scented May, 
The flowery hedgerows and the fragrant hay, 
And the wide landscape's many-tinted sheen. 
Then Autumn's yellow woods and days serene ; 
And when we've gathered in the harvest's treasure, 
The long nights bring us round the blazing hearth, 
The chosen haunt of every social pleasure. 
Land of green fields and flowers ! Thou givest birth 
To shifting scenes of beauty, which outshine 
Th' unvarying splendours of the Tropic's clime. 



PREFACE. 

THE luxuriance and beauty of Tropical Nature is a 
well-worn theme, and there is little new to say about 
it. The traveller and the naturalist have combined 
to praise, and not unfrequently to exaggerate the 
charms of tropical life its heat and light, its superb 
vegetable forms, its brilliant tints of flower and bird 
and insect. Each strange and beautiful object has been 
described in detail ; and both the scenery and the 
natural phenomena of the tropics have been depicted 
by master hands and with glowing colours. But, so far 
as I am aware, no one has yet attempted to give a 
general view of the phenomena which are essentially 
tropical, or to determine the causes and conditions of 
those phenomena. The local has not been separated 
from the general, the accidental from the essential ; 
and, as a natural result, many erroneous ideas have 
become current as to what are really the charac- 
teristics of the tropical as distinguished from the 
temperate zones. 



via PREFACE. 

In the present volume I have attempted to supply 
this want; and for my materials have drawn chiefly 
on my own twelve years' experience of the eastern 
and western tropics of the equatorial zone, where the 
characteristic phenomena of tropical life are fully 
manifested. 

So many of the most remarkable forms of life are 
now restricted to the tropics, and the relations of these 
to extinct types which once inhabited the temperate 
zones open up so many interesting questions as to the 
past history of the earth, that the present inquiry may 
be considered a necessary preliminary to a study of the 
problem how to determine the climates of geologic 
periods from the character of their organic remains. 
This part of the subject is however both complex and 
difficult, and I have only attempted to indicate what 
seem to me the special physical conditions to which 
the existing peculiarities of tropical life are mainly due. 

The three opening chapters treat the subject under 
the headings of climate, vegetation, and animal life. 
The conditions and causes of the equatorial climate 
are discussed in some detail, and the somewhat complex 
principles on which it depends are popularly explained. 
In the chapters on plant and animal life, the general 
aspects and relations of their several component elements 
have been dwelt upon ; all botanical and zoological 
details and nomenclature being excluded, except so far 



PREFACE. ix 

as was absolutely necessary to give precision to the 
descriptions and to enable us to deduce from them 
some conclusions of importance. 

The remaining chapters have all a more or less 
direct connection with the leading subject. The family 
of humming-birds is taken as an illustration of the 
luxuriant development of allied forms in the tropics, 
and as showing the special mode in which natural 
selection has acted to bring about considerable changes 
in a limited period. The discussion on the nature and 
origin of the colours of animals and plants, is intended 
to show how far and in what way these are dependent 
on the climate and physical conditions of the tropics. 
The chapter entitled " By-paths in the Domain of 
Biology " contains an account of certain curious relations 
of colour to locality, which are almost exclusively 
manifested within the tropical zones ; while the essay 
on " Distribution of Animals and Geographical Changes/* 
elucidates the relations of the several continents in 
past time, and the probable origin of many of the 
groups now characteristic of tropical or of temperate 
regions. 

While discussing the general laws and phenomena 
of colour in the organic world, and its special develop- 
ments among certain groups of animals, I have been led 
to a theory of the diverse colours of the sexes and of 
the special ornaments and brilliant hues which dis- 



x PREFACE. 

tinguish certain male birds and insects, which is directly 
opposed to the view held by Mr. Darwin and so well 
explained and illustrated in his great work on " The 
Descent of Man and on Selection in Eelation to Sex." 
Being strongly impressed with the importance and 
fundamental truth of this theory, I published my first 
sketch of the subject in Macmillans Magazine in order 
that it might have the benefit of criticism before making 
it public in a more permanent form. Taking advantage 
of some suggestions from Mr. Darwin and from a 
few other correspondents, I have made considerable 
additions to the original essay and have rearranged, 
and I trust strengthened the argument, which I now 
hope may attract the attention of all who are interested 
in the subject. I may be allowed here to remark, that 
my theory cannot be properly understood without 
reading the whole chapter on " The Colours of 
Animals ; " because the view set forth and illustrated 
in the first part of that chapter that colour in nature 
is normal, and that its presence hardly requires to 
be accounted for so much as its absence is an essential 
part of the theory. 



CROYDON, April, 1878. 



CONTENTS. 



I. THE CLIMATE AND PHYSICAL ASPECTS OF THE EQUATORIAL ZONE. 

The three Climatal Zones of the Earth Temperature of the Equatorial 
Zone Causes of the Uniform High Temperature near the Equator 
Influence of the Heat of the Soil Influence of the Aqueous Vapour of 
the Atmosphere Influence of Winds on the Temperature of the Equator 
Heat due to the Condensation of Atmospheric Vapour General 
Features of the Equatorial Climate Uniformity of the Equatorial Cli- 
mate in all Parts of the Globe Effects of Vegetation on Climate Short 
Twilight of the Equatorial Zone The Aspect of the Equatorial Heavens 
Intensity of Meteorological Phenomena at the Equator Concluding 
Remarks pages 1 26 



II. EQUATORIAL VEGETATION. 

The Equatorial Forest-belt and its Causes General Features of the Equa- 
torial Forests Low-growth Forest-trees Flowery Trunks and their 
Probable Cause Uses of Equatorial Forest-trees The Climbing Plants 
of the Equatorial Forests Palms Uses of Palm-trees and their Pro- 
ducts Ferns Ginger-worts and Wild Bananas Arums Screw-Pines 
Orchids Bamboos Uses of the Bamboo Mangroves Sensitive-plants 
Comparative Scarcity of Flowers Concluding Eemarks on Tropical 
Vegetation pages 27 68 



III. ANIMAL LIFE IN THE TROPICAL FORESTS. 

Difficulties of the Subject General Aspect of the Animal Life of Equatorial 
Forests Diurnal Lepidoptera or Butterflies Peculiar Habits of Tropical 
Butterflies Ants, Wasps, and Bees Ants Special Relations between 
Ants and Vegetation Wasps and Bees Orthoptera and other Insects 
Beetles Wingless Insects General Observations on Tropical Insects 
Birds Parrots Pigeons Picarise Cuckoos Trogons, Barbets, Toucans 
and Hornbills Passeres Reptiles and Amphibia Lizards Snakes 
Frogs and Toads Mammalia Monkeys Bats Summary of the Aspects 
of Animal Life in the Tropics pages 69 123 



xii CONTENTS. 



IV. HuMMING-BlRDS : AS ILLUSTRATING THE LUXURIANCE OF 
TROPICAL NATURE. 

Structure Colours and Ornaments Descriptive Names The Motions and 
Habits of Humming-Birds Display of Ornaments by the Male Food 
Geographical Distribution and Variation Humrning-Birds of Juan 
Fernandez as illustrating Variation and Natural Selection The Relations 
and Affinities of Humming-Birds How to Determine Doubtful Affinities 
Resemblances of Swifts and Humming-Birds Differences between 
Sun-Birds and Humming-Birds pages 124157 

V. THE COLOURS OF ANIMALS AND SEXUAL SELECTION. 

General Phenomena of Colour Theory of Heat and Light as producing 
Colour Changes of Colour in Animals produced by Coloured Light 
Classification of Organic Colours Protective Colours Warning Colours 
Sexual Colours Typical Colours The Nature of Colour How Animal 
Colours are Produced Colour a Normal Product of Organization Theory 
of Protective Colours Theory of Warning Colours Imitative Warning 
Colours The Theory of Mimicry Theory of Sexual Colours Colour 
as a Means of Recognition Colour proportionate to Integumentary 
Development Selection by Females not a Cause of Colour Probable Use 
of the Horns of Beetles Cause of the greater Brilliancy of some Female 
Insects Origin of the Ornamental Plumage of Male Birds Theory of 
the Display of Ornaments by Males Natural Selection as neutralizing 
Sexual Selection Greater Brilliancy of some Female Birds Colour- 
development as illustrated by Humming-Birds Theory of Typical Colours 
Local Causes of Colour-development Summary on Colour-development 
in Animals Concluding Remarks on Causes of Bright Colour in the 
Tropics pages 158220 

VI. THE COLOURS OF PLANTS AND THE ORIGIN OF THE COLOUR-SENSE. 

Source of Colouring-matter in Plants Protective Coloration and Mimicry 
in Plants Attractive Colours of Fruits Protective Colours of Fruits 
Seeds how Protected Attractive Colours of Flowers Attractive Odours 
in Flowers Attractive Grouping in Flowers Why Alpine Flowers are so 
Beautiful Why Allied Species of Flowers differ in Size and Beauty 
Absence of Colours in Wind-fertilized Flowers The same Theory of 
Colour applicable to Animals and Plants Relation of the Colours of 
Flowers and their Geographical Distribution Recent Views as to the 
Direct Action of Light on the Colours of Flowers and Fruits Concluding 
Remarks on the Importance of Colour in the Organic World THE ORIGIN 
OF THE COLOUR-SENSE. Supposed Increase of Colour-perception within 
the Historical Period Concluding Remarks on the Colour-sense 

pzges 221218 



CONTENTS. 



VII. BY-PATHS IN THE DOMAIN OF BIOLOGY. 

BEING AN ADDRESS DELIVERED TO THE BIOLOGICAL SECTION OK THE BRITISH 
ASSOCIATION (GLASGOW, SEPTEMBER GTH, 1876) AS PRESIDENT OF THE 
SECTION. 

Introductory Remarks ON SOME RELATIONS OF LIVING THINGS TO THEIR 
ENVIRONMENT. The Influence of Locality on Colour in Butterflies and 
Birds Sense-perception influenced by Colour of the Integuments 
Relations of Insular Plants and Insects RISE AND PROGRESS OF 
MODERN VIEWS AS TO THE ANTIQUITY AND ORIGIN or- MAN Indica- 
tions of Man's Extreme Antiquity Antiquity of Intellectual Man 
Sculptures on Easter-Island North American Earthworks The Great 
Pyramid Conclusion pages 249 303 



VIII. THE DISTRIBUTION OF ANIMALS AS INDICATING GEOGRAPHICAL 

CHANGES. 

Old Opinions on Continental Changes Theory of Oceanic Islands Present 
and Past Distribution of Land and Sea Zoological Regions The Palse- 
arctic Region The Ethiopian Region The Oriental Region Past changes 
of the Great Eastern Continent Regions of the New World Past His- 
tory of the American Continents The Australian Region Summary 
and Conclusion pages 304 347 



TROPICAL NATURE, 

AND OTHEK ESSAYS. 



TEOPIGAL NATURE, 

AND OTHER ESSAYS. 
L 

THE CLIMATE AND PHYSICAL ASPECTS OF THE 
EQUATORIAL ZONE. 

The three Climatal Zones of the Earth Temperature of the Equatorial Zone 
Causes of the Uniform High Temperature near the Equator Influence 
of the Heat of the Soil Influence of the Aqueous Vapour of the Atmo- 
sphere Influence of Winds on the Temperature of the Equator Heat due 
to the Condensation of Atmospheric Vapour General features of the 
Equatorial Climate Uniformity of the Equatorial Climate in all parts of 
the globe Effects of Vegetation on Climate Short Twilight of the Equa- 
torial Zone The aspect of the Equatorial Heavens Intensity of meteor- 
ological phenomena at the Equator Concluding Remarks. 

IT is difficult for an inhabitant of our temperate land 
to realize either the sudden and violent contrasts of the 
arctic seasons or the wonderful uniformity of the equa- 
torial climate. The lengthening or the shortening days, 
the ever-changing tints of spring, summer, and autumn, 
succeeded by the leafless boughs of winter, are constantly 
recurring phenomena which represent to us the estab" 
lished course of nature. At the equator none of 
these changes occur ; there is a perpetual equinox and 

n. 



U TROPICAL NATURE, AND OTHER ESSAYS. 

a perpetual summer, and were it not for variations in 
the quantity of rain, in the direction and strength of the 
winds, and in the amount of sunshine, accompanied by 
corresponding slight changes in the development of 
vegetable and animal life, the monotony of nature would 
be extreme. 

In the present chapter it is proposed to describe the 
chief peculiarities which distinguish the equatorial from 
the temperate climate, and to explain the causes of the 
difference between them, causes which are by no means 
of so simple a nature as are usually imagined. 

The three great divisions of the earth the tropical, 
the temperate, and the frigid zones, may be briefly 
defined as the regions of uniform, of variable, and of 
extreme physical conditions respectively. They are pri- 
marily determined by the circumstance of the earth's 
axis not being perpendicular to the plane in which it 
moves round the sun ; whence it follows that during 
one half of its revolution the north pole, and during the 
other half the south pole, is turned at a considerable 
angle towards the source of light and heat. This incli- 
nation of the axis on which the earth rotates is usually 
defined by the inclination of the equator to the plane of 
the orbit, termed the obliquity of the ecliptic. The amount 
of this obliquity is 23 J degrees, and this measures the 
extent on each side of the equator of what are called the 
tropics, because within these limits the sun becomes 
vertical at noon twice a year, and at the extreme limit 
once a year, while beyond this distance it is never 
vertical. It will be evident, however, from the nature 
of the case, that the two lines which mark the limits of 
the geographical " tropics " will not define any abrupt 



EQUATORIAL TEMPERATURE. 

change of climate or physical conditions, such as 
characterise the tropical and temperate zones in their 
full development. There will be a gradual transition 
from one to the other, and in order to study them sepa- 
rately and contrast their special features we must only 
take into account the portion of each in which these are 
most fully exhibited. For the temperate zone we may 
take all countries situated between 35 and 60 of lati- 
tude, which in Europe will include every place between 
Christiana and Algiers, the districts further south form- 
ing a transitional belt in which temperate and tropical 
features are combined. In order to study the special 
features of tropical nature, on the other hand, it will be 
Advisable to confine our attention mainly to that portion 
of the globe which extends for about twelve degrees on 
each side of the equator, in which all the chief tropical 
phenomena dependent on astronomical causes are most 
fully manifested, and which we may distinguish as the 
" equatorial zone." In the debateable ground between 
these two well contrasted belts local causes have a pre- 
ponderating influence ; and it would not be difficult to 
point out localities within the temperate zone of our 
maps, which exhibit all the chief characteristics of 
tropical nature to a greater degree than other localities 
which are, as regards geographical position, tropical. 

Temperature of the Equatorial Zone. The most 
characteristic, as it is the most important feature in 
the physical conditions of the great equatorial zone is 
the wonderful uniformity of its temperature, alike 
throughout the changes of day and night, and from one 
part of the year to another. As a general rule, the 
greatest heat of the day does not exceed 90 or 91 

B 2 



4 TROPICAL NATURE, AND OTHER ESSAYS. 

Fahr., while it seldom falls during the night below 74 
Fahr. It has been found by hourly observations car- 
ried on for three years at the meteorological observatory 
established by the Dutch government at Batavia, that 
the extreme range of temperature in that period was 
only 27 Fahr., the maximum being 95 and the mini- 
mum 68. But this is, of course, very much beyond 
the usual daily range of the thermometer, which is, on 
the average, only a little more than 11 Fahr. ; being 
12 '6 in September when it is greatest, and only 8'1 in 
January, when it is least. 

Batavia, being situated between six and seven degrees 
south of the equator, may be taken as affording a fair 
example of the climate of the equatorial zone ; though, 
being in an island, it is somewhat less extreme than 
many continental localities. Observations made at Para, 
which is continental and close to the equator, agree how- 
ever very closely with those at Batavia ; but at the 
latter place all the observations were made with 
extreme care and with the best instruments, and are 
therefore preferred as being thoroughly trustworthy. 1 
The accompanying diagram, showing by curves the 
monthly means of the highest and lowest daily tempera- 
tures at Batavia and London, is very instructive ; more 
especially when we consider that the maximum of 
temperature is by no means remarkably different in the 
two places, 90 Fahr. being sometimes reached with us 
and not being often very much exceeded at Batavia. 

1 " Observations Made at the Magnetical and Meteorological Observatory 
at Batavia. Published by order of the Government of Netherlands India. 
Vol. I. Meteorological, from Jan. 1866 to Dec. 1868 ; and Magnetical, from 
July 1867 to June 1870. By Dr. P. A. Bergsraa. Batavia, 1871." This 
fine work is entirely in English. 



TEMPERATURE AT BATAVIA AND LONDON. 5 



Mordhfy Mean. Temperature cut BaJ^aviw &Iondon. 



90 



85 



80 



70 



Ncanflu* 




00 

56 
50 
45 
<40 
3S 
30 



lowest 



7 



\ 



\ 



2 omion 



7 



85 



C.5 



fit) 



55 



50 



7 



\ 



\ 



40 



6 TROPICAL NATURE, AND OTHER ESSAYS. 

Causes of the Uniform High Temperature near the 
Equator. It is popularly supposed that the uniform 
high temperature of the tropics is sufficiently explained 
by the greater altitude, and therefore greater heating- 
power, of the midday sun ; but a little consideration will 
show that this alone by no means accounts for the 
phenomenon. The island of Java is situated in from 
six and a half to eight and a half degrees of south 
latitude, and in the month of June the sun's altitude 
at noon will not be more than from 58 to 60. In the 
same month at London, which is fifty-two and a half 
degrees of north latitude, the sun's noonday altitude is 62. 
But besides this difference of altitude in favour of London 
there is a still more important difference ; for in Java the 
day is only about eleven and a half hours long in the month 
of June, while at London it is sixteen hours long, so that 
the total amount of sun-heat received by the earth must 
be then very much greater at London than at Batavia. 
Yet at the former place the mean temperature of the 
day and night is under 60 Fahr., while in the latter place 
it is 80 Fahr., the daily maximum being on the average 
in the one case about 68 and in the other about 89. 

Neither does the temperature at the same place depend 
upon the height of the sun at noon ; for at Batavia it 
is nearly vertical during October and February, but 
these are far from being the hottest months, which are 
May, June, and September ; while December, January, 
and February are the coldest months, although then the 
sun attains nearly its greatest altitude. It is evident, 
therefore, that a difference of 30 in the altitude of the 
sun at noon has no apparent influence in raising the 
temperature of a place near the equator, and we must 



CAUSES OF TROPICAL HEAT. 7 

therefore conclude that other agencies are at work 
which often completely neutralise the effect which 
increased altitude must undoubtedly exert. 

There is another important difference between the 
temperate and tropical zones, in the direct heating effect 
of the sun's rays independently of altitude. In England 
the noonday sun in the month of June rarely incon- 
veniences us or produces any burning of the skin ; while 
in the tropics, at almost any hour of the day, and when 
the sun has an elevation of only 40 or 50, exposure to 
to it for a few minutes will scorch a European so that 
the skin turns red, becomes painful, and often blisters 
or peels off. Almost every visitor to the tropics 
suffers from incautious exposure of the neck, the 
leg, or some other part of the body to the sun's 
rays, w T hich there possess a power as new, as it is 
at first sight inexplicable, for it is not accompanied 
by any extraordinary increase in the temperature of 
the air. 

These very different effects, produced by the same 
amount of sun-heat poured upon the earth in different 
latitudes is due to a combination of causes. The most 
important of these are, probably, the constant high 
temperature of the soil and of the surface-waters of the 
ocean, the great amount of aqueous vapour in the 
atmosphere, the great extent of the intertropical 
regions which cause the winds that reach the equatorial 
zone to be always warm, and the latent heat given out 
during the formation of rain and dew. We will briefly 
consider the manner in which each of these causes 
contributes to the degree and the uniformity of the 
equatorial temperature. 



8 TROPICAL NATURE, AND OTHER ESSAYS. 

Influence of the Heat of the Soil. It is well known 
that at a very moderate depth the soil maintains a 
uniform temperature during the twenty-four hours ; 
while at a greater depth even the annual inequalities 
disappear, and a uniform temperature, which is almost 
exactly the mean temperature of the locality, is con- 
stantly maintained throughout the year. The depth at 
which this uniform temperature is reached is greater as 
the annual range of temperature is greater, so that it is 
least near the equator, and greatest in localities near the 
arctic circle where the greatest difference between 
summer and winter temperature prevails. In the 
vicinity of the equator, where the annual range of the 
thermometer is so small as we have seen that it is at 
Batavia, the mean temperature of about 80 Fahr. is 
reached at a depth of four or five feet. The surplus heat 
received during the day is therefore conducted down- 
wards very slowly, the surface soil becomes greatly super- 
heated, and a large portion of this heat is given out at 
night and thus keeps up the high temperature of the air 
when the sun has ceased to warm the earth. In the 
temperate zones, on the other hand, the stratum of 
uniform earth-temperature lies very deep. At Geneva 
it is not less than from thirty to forty feet, and with us 
it is probably fifty or sixty feet, and the temperature 
found there is nearly forty degrees lower than at the 
equator. This great body of cool earth absorbs a large 
portion of the surface heat during the summer, and con- 
ducts it downwards with comparative rapidity, and it 
is only late in the year (in July and August) when the 
upper layers of the soil have accumulated a surplus store 
of solar heat that a sufficient quantity is radiated at 



MOISTURE OF THE ATMOSPHERE. 9 

night to keep up a high temperature in the absence of the 
sun. At the equator, on the other hand, this radiation 
is always going on, and earth-heat is one of the most 
important of the agencies which tend to equalise the 
equatorial climate. 

Influence of the Aqueous Vapour of the Atmosphere. 
The aqueous vapour which is always present in 
considerable quantities in the atmosphere, exhibits 
a singular and very important relation to solar and 
terrestrial heat. The rays of the sun pass through it 
unobstructed to the earth ; but the warmth given off by 
the heated earth is very largely absorbed by it, thus 
raising the temperature of the air ; and as it is the 
lower strata of air which contain most vapour these act 
as a blanket to the earth, preventing it from losing heat 
at night by radiation into space. During a large part 
of the year the air in the equatorial zone is nearly 
saturated with vapour, so that, notwithstanding the heat, 
salt and sugar become liquid, and all articles of iron get 
thickly coated with rust. Complete saturation being 
represented by 100, the daily average of greatest 
humidity at Batavia reaches 96 in January and 92 in 
December. In January, which is the dampest month, 
the range of humidity is small (77 to 96), and at this 
time the range of temperature is also least ; while in 
September, with a greater daily range of humidity (62 
to 92) the range of temperature is the greatest, and the 
lowest temperatures are recorded in this and the pre- 
ceding month. It is a curious fact, that in many parts 
of England the degree of humidity as measured by the 
comparative saturation of the air, is as great as that of 
Batavia or even greater. A register kept at Clifton 



10 TROPICAL NATURE, AND OTHER ESSAYS. 

during the years 1853 1862 shows a mean humidity 
in January of 90, while the highest monthly mean for 
the four years at Batavia was 88 ; and while the lowest 
of the monthly means at Clifton was 79 '1, the lowest at 
Batavia was 78'9. These figures however represent an 
immense difference in the quantity of vapour in every 
cubic foot of air. In January at Clifton, with a tem- 
perature of 35 to 40 Fahr., there would be only about 
4 to 4^ grains of vapour per cubic foot of air, while at 
Batavia, with a temperature from 80 to 90 Fahr., there 
would be about 20 grains in the same quantity of air. 
The most important fact however is, that the capacity 
of air for holding vapour in suspension increases more 
rapidly than temperature increases, so that a fall of ten 
degrees at 50 Fahr. will lead to the condensation of 
about 1^ grains of vapour, while a similar fall at 90 
Fahr. will set free 6|- grains. We can thus understand 
how it is that the very moderate fall of the thermometer 
during a tropical night causes heavier dews and a 
greater amount of sensible moisture than are ever ex- 
perienced during much greater variations of temperature 
in the temperate zone. It is this large quantity of 
vapour in the equatorial atmosphere that keeps up a 
genial warmth throughout the night by preventing the 
radiation into space of the heat absorbed by the surface 
soil during the day. That this is really the case is 
strikingly proved by what occurs in the plains of 
Northern India, where the daily maximum of heat is far 
beyond anything experienced near the equator, yet, owing 
to the extreme dryness of the atmosphere, the clear nights 
are very cold, radiation being sometimes so rapid that 
water placed in shallow pans becomes frozen over. 



INFLUENCE OF WINDS. 11 

As the heated earth, and everything upon its surface, 
does not cool so fast when surrounded by moist as by 
dry air, it follows, that even if the quantity and inten- 
sity of the solar rays falling upon two given portions of 
the earth's surface are exactly equal, yet the sensible and 
effective heat produced in the two localities may be very 
different according as the atmosphere contains much or 
little vapour. In the one case the heat is absorbed 
more rapidly than it can escape by radiation ; in the 
other case it radiates away into space, and is lost, more 
rapidly than it is being absorbed. In both cases an 
equilibrium will be arrived at, but in the one case the 
resulting mean temperature will be much higher than in 
the other. 

Influence of Winds on the Temperature of the 
Equator. The distance from the northern to the 
southern tropics being considerably more than three 
thousand miles, and the area of the intertropical zone 
more than one-third the whole area of the globe, it 
becomes hardly possible for any currents of air to reach 
the equatorial belt without being previously warmed by 
contact with the earth or ocean, or by mixture with the 
heated surface-air which is found in all intertropical and 
sub-tropical lands. This warming of the air is rendered 
more certain and more effective by the circumstance, that 
all currents of air coming from the north or south have 
their direction changed owing to the increasing rapidity 
of the earth's rotational velocity, so that they reach 
the equator as easterly winds, and thus pass obliquely 
over a great extent of the heated surface of the globe. 
The causes that produce the westerly monsoons act in a 
similar manner, so that on the equator direct north or 



12 TROPICAL NATURE, AND OTHER ESSAYS. 

south winds, except as local land and sea breezes, are 
almost unknown. The Batavia observations show, that 
for ten months in the year the average direction of the 
wind varies only between 5 and 30 from due east or 
west, and these are also the strongest winds. In the 
two months March and October when the winds are 
northerly, they are very light, and are probably in great 
part local sea-breezes, which, from the position of 
Batavia, must come from the north. As a rule, therefore, 
every current of air at or near the equator has passed 
obliquely over an immense extent of tropical surface 
and is thus necessarily a warm wind. 

In the north temperate zone, on the other hand, the 
winds are always cool, and often of very low temperature 
even in the height of summer, due probably to their 
coming from colder northern regions as easterly winds, or 
from the upper parts of the atmosphere as westerly winds ; 
and this constant supply of cool air, combined with quick 
radiation through a dryer atmosphere, carries off the 
solar heat so rapidly that an equilibrium is only reached 
at a comparatively low temperature. In the equatorial 
zone, on the contrary, the heat accumulates, on account 
of the absence of any medium of sufficiently low 
temperature to carry it off rapidly, and it thus soon 
reaches a point high enough to produce those scorching 
effects which are so puzzling when the altitude of the 
sun or the indications of the thermometer are alone con- 
sidered. Whenever, as is sometimes the case, exceptional 
cold occurs near the equator, it can almost always be 
traced to the influence of currents of air of unusually 
low temperature. Thus in July near the Aru islands, 
the writer experienced a strong south-east wind which 



SUPPLY AND WASTE OF HEAT. 13 

almost neutralised the usual effects of tropical heat 
although the weather was bright and sunny. But the 
wind, coming direct from the southern ocean during its 
winter without acquiring heat by passing over land, was 
of an unusually low temperature. Again, Mr. Bates 
informs us that in the Upper Amazon in the month of 
May there is a regularly recurring south wind which 
produces a remarkable lowering of the usual equatorial 
temperature. But owing to the increased velocity of the 
earth's surface at the equator a south wind there must 
have been a south-west wind at its origin, and this would 
bring it directly from the high chain of the Peruvian 
Andes during the winter of the southern hemisphere. 
It is therefore probably a cold mountain wind, and blow- 
ing as it does over a continuous forest it has been unable 
to acquire the usual tropical warmth. 

The cause of the striking contrast between the climates 
of equatorial and temperate lands at times when both 
are receiving an approximately equal amount of solar 
heat may perhaps be made clearer by an illustration. 
Let us suppose there to be two reservoirs of water, 
each supplied by a pipe which pours into it a thousand 
gallons a day, but which runs only during the daytime, 
being cut off at night. The reservoirs are both leaky, 
but while the one loses at the rate of nine hundred 
gallons in the twenty-four hours the other loses at the 
rate of eleven hundred gallons in the same time, sup- 
posing that both are kept exactly half full and thus 
subjected to the same uniform water-pressure. If now 
both are left to be supplied by the above-mentioned 
pipes the result will be, that in the one which loses by 
leakage less than it receives the water will rise day by 



14 TROPICAL NATURE, AND OTHER ESSAYS. 

day, till the increased pressure caused the leakage to 
increase so as exactly to balance the supply ; while in 
the other the water will sink till the decreasing pressure 
causes the leakage to decrease so as to balance the 
supply, when both will remain stationary, the one at 
a high the other at a low average level, each rising 
during the day and sinking again at night. Just the 
same thing occurs with that great heat- reservoir the 
earth, whose actual temperature at any spot will depend, 
not alone upon the quantity of heat it receives, but on 
the balance between its constantly varying waste and 
supply. We can thus understand how it is that, although 
in the months of June and July Scotland in latitude 
57 north receives as much sun-heat as Angola or 
Timor in latitude 10 south, and for a much greater 
number of hours daily, yet in the latter the mean 
temperature will be about 80 Fahr., with a daily 
maximum of 90 to 95, while in the former the mean 
will be about 60 Fahr. with a daily maximum of 70 or 
75 ; and, while in Scotland exposure to the full noon- 
day sun produces no unpleasant heat-sensations, a similar 
exposure in Timor at any time between 9 A.M. and 3 
P.M. would blister the skin in a few minutes almost as 
effectually as the application of scalding water. 

Heat Due to the Condensation of Atmospheric 
Vapour. Another cause which tends to keep up a 
uniform high temperature in the equatorial, as compared 
with the variable temperatures of the extra-tropical 
zones, is the large amount of heat liberated during the 
condensation of the aqueous vapour of the atmosphere 
in the form of rain and dew. Owing to the frequent 
near approach of the equatorial atmosphere to the 



RAINFALL AT LONDON AND BATAVIA. 



15 



saturation point, and the great weight of vapour its 
high temperature enables it to hold in suspension, a very 
slight fall of the thermometer is accompanied by the 



Monthfy Rainfall cub London 




condensation of a large absolute quantity of atmospheric 
vapour, so that copious dews and heavy showers of rain 
are produced at comparatively high temperatures and 



16 TROPICAL NATURE, AND OTHER ESSAYS. 

low altitudes. The drops of rain rapidly increase in 
size while falling through the saturated atmosphere ; 
and during this process as well as by the formation of 
dew, the heat which retained the water in the gaseous 
form, and was insensible while doing so, is liberated, and 
thus helps to keep up the high temperature of the air. 
This production of heat is almost always going on, In 
fine weather the nights are always dewy, and the diagram 
on the preceding page showing the mean monthly rain- 
fall at Batavia and Greenwich proves that this source 
of increased temperature is present during every month 
in the year, since the lowest monthly fall at the former 
place is almost equal to the highest monthly fall at the 
latter. 

It may perhaps be objected, that evaporation must 
absorb as much heat as is afterwards liberated by con- 
densation, and this is true ; but as evaporation and 
condensation occur usually at different times and in 
different places, the equalising effect is still very 
important. Evaporation occurs chiefly during the 
hottest sunshine, when it tends to moderate the extreme 
heat, while condensation takes place chiefly at night in 
the form of dew and rain, when the liberated heat helps 
to make up for the loss of the direct rays of the sun. 
Again, the most copious condensation both of dew and 
rain is greatly influenced by vegetation and especially 
by forests, and also by the presence of hills and moun- 
tains, and is therefore greater on land than on the 
ocean ; while evaporation is much greater on the ocean, 
both on account of the less amount of cloudy weather 
and because the air is more constantly in motion. 
This is particularly the case throughout that large 



UNIFORMITY OF CLIMATE. 17 

portion of the tropical and subtropical zones where the 
trade-winds constantly blow, as the evaporation must 
there be enormous while the quantity of rain is very 
small. It follows, then, that on the equatorial land- 
surface there will be a considerable balance of conden- 
sation over evaporation which must tend to the general 
raising of the temperature, and, owing to the conden- 
sation being principally at night, not less powerfully to 
its equalisation. 

General Features of the Equatorial Climate. The 
various causes now enumerated are sufficient to enable 
us to understand how the great characteristic features 
of the climate of the equatorial zone are brought about ; 
how it is that so high a temperature is maintained 
during the absence of the sun at night, and why so 
little effect is produced by the sun's varying altitude 
during its passage from the northern to the southern 
tropic. In this favoured zone the heat is never oppres- 
sive, as it so often becomes on the borders of the 
tropics ; and the large absolute amount of moisture 
always present in the air, is almost as congenial to the 
health of man as it is favourable to the growth and 
development of vegetation. 1 Again, the lowering of 
the temperature at night is so regular and yet so strictly 
limited in amount, that, although never cold enough to 
be unpleasant, the nights are never so oppressively hot 
as to prevent sleep. During the wettest months of 
the year, it is rare to have many days in succession 

1 Where the inhabitants adapt their mode of life to the peculiarities of 
the climate, as is the case with the Dutch in the Malay Archipelago, they 
enjoy as robust health as in Europe, both in the case of persons born in 
Europe and of those who for generations have lived under a vertical sun. 

C 



18 TROPICAL NATURE, AND OTHER ESSAYS. 

without some hours of sunshine, while even in the 
driest months there are occasional showers to cool and 
refresh the overheated earth. As a result of this con- 
dition of the earth and atmosphere, there is no check to 
vegetation, and little if any demarcation of the seasons. 
Plants are all evergreen ; flowers and fruits, although 
more abundant at certain seasons, are never altogether 
absent ; while many annual food-plants as well as some 
fruit-trees produce two crops a year. In other cases, more 
than one complete year is required to mature the large 
and massive fruits, so that it is not uncommon for fruit 
to be ripe at the same time that the tree is covered with 
flowers, in preparation for the succeeding crop. This is 
the case with the Brazil nut tree, in the forests of the 
Amazon, and with many other tropical as with a few 
temperate fruits. 

Uniformity of the Equatorial Climate in all Parts of 
the Globe. The description of the climatal phenomena 
of the equatorial zone here given, has been in great part 
drawn from long personal experience in South America 
and in the Malay Archipelago. Over a large portion of 
these countries the same general features prevail, only 
modified by varying local conditions. Whether we are 
at Singapore or Batavia ; in the Moluccas, or New 
Guinea ; at Para, at the sources of the Rio Negro, or on 
the Upper Amazon, the equatorial climate is essentially 
the same, and we have no reason to believe that it 
materially differs in Guinea or the Congo. In certain 
localities, however, a more contrasted wet and dry 
season prevails, with a somewhat greater range of the 
thermometer. This is generally associated with a sandy 
soil, and a less dense forest, or with an open and more 



CAUSES OF DROUGHT. 19 

cultivated country. The open sandy country with 
scattered trees and shrubs or occasional thickets, which 
is found at Santarem and Monte-Alegre on the lower 
Amazon, are examples, as well as the open cultivated 
plains of Southern Celebes ; but in both cases the forest 
country in adjacent districts has a moister and more 
uniform climate, so that it seems probable that the 
nature of the soil or the artificial clearing away of the 
forests, are important agents in producing the departure 
from the typical equatorial climate observed in such 
districts. The almost rainless district of Ceara on the 
North-East coast of Brazil and only a few degrees south 
of the equator, is a striking example of the need of 
vegetation to react on the rainfall. We have here no 
apparent cause but the sandy soil and bare hills, which 
when heated by the equatorial sun produce ascending 
currents of warm air and thus prevent the condensation 
of the atmospheric vapour, to account for such an 
anomaly ; and there is probably no district where 
judicious planting would produce such striking and 
beneficial effects. In Central India the scanty and 
intermittent rainfall, with its fearful accompaniment of 
famine, is no doubt in great part due to the absence of a 
sufficient proportion of forest-covering to the earth's 
surface ; and it is to a systematic planting of all the 
hill tops, elevated ridges, and higher slopes that we can 
alone look for a radical cure of the evil. This would 
almost certainly induce an increased rainfall ; but even 
more important and more certain, is the action of forests 
in checking evaporation from the soil and causing 
perennial springs to flow, which may be collected in 

c 2 



20 TROPICAL NATURE, AND OTHER ESSAYS. 

vast storage tanks and will serve to fertilise a great 
extent of country ; whereas tanks without regular rain- 
fall or permanent springs to supply them are worthless. 
In the colder parts of the temperate zones, the absence 
of forests is not so much felt, because the hills and 
uplands are naturally clothed with a thick coating of 
turf which absorbs moisture and does not become over- 
heated by the sun's rays, and the rains are seldom 
violent enough to strip this protective covering from the 
surface. In tropical and even in south-temperate 
countries, on the other hand, the rains are periodical 
and often of excessive violence for a short period ; 
and when the forests are cleared away the torrents 
of rain soon strip off the vegetable soil, and thus 
destroy in a few years the fertility which has been the 
growth of many centuries. The bare subsoil becoming 
heated by the sun, every particle of moisture which does 
not flow off is evaporated, and this again reacts on the 
climate, producing long-continued droughts only relieved 
by sudden and violent storms, which add to the 
destruction and render all attempts at cultivation 
unavailing. Wide tracts of fertile land in the south 
of Europe have been devastated in this manner, and 
have become absolutely uninhabitable. Knowingly to 
produce such disastrous results would be a far more 
serious offence than any destruction of property which 
human labour has produced and can replace ; yet we 
ignorantly allow such extensive clearings for coffee 
cultivation in India and Ceylon, as to cause the destruc- 
tion of much fertile soil which generations cannot 
replace, and which will surely, if not checked in time, 



SHORTNESS OF TWILIGHT. 21 

lead to the deterioration of the climate and the 
permanent impoverishment of the country. 1 

Short Twilight of the Equatorial Zone. One of the 
phenomena which markedly distinguish the equatorial 
from the temperate and polar zones, is the shortness 
of the twilight and consequent rapid transition from day 
to night and from night to day. As this depends only 
on the fact of the sun descending vertically instead 
of obliquely below the horizon, the difference is most 
marked when we compare our midsummer twilight with 
that of the tropics. Even with us the duration of 
twilight is very much shorter at the time of the 
equinoxes, and it is probably not much more than a 
third shorter than this at the equator. Travellers usually 
exaggerate the shortness of the tropical twilight, it being 
sometimes said that if we turn a page of the book we 
are reading when the sun disappears, by the time we turn 
over the next page it will be too dark to see to read. 
With an average book and an average reader this is 
certainly not true, and it will be well to describe as 
correctly as we can what really happens. 

In fine weather the air appears to be somewhat more 
transparent near the equator than with us, and the 
intensity of sunlight is usually very great up to the 
moment when the solar orb touches the horizon. As 
soon as it has disappeared the apparent gloom is propor- 
tionally great, but this hardly increases perceptibly during 
the first ten minutes. During the next ten minutes 
however it becomes rapidly darker, and at the end of 

1 For a terrible picture of the irreparable devastation caused by the reckless 
clearing of forests see the third chapter of Mr. Marsh's work The Earth as 
Modified by Human Action. 



22 TROPICAL NATURE, AND OTHER ESSAYS. 

about twenty-five minutes from sunset the complete 
darkness of night is almost reached. In the morning 
the changes are perhaps even more striking. Up to 
about a quarter past five o'clock the darkness is complete ; 
but about that time a few cries of birds begin to break 
the silence of night, perhaps indicating that signs of 
dawn are perceptible in the eastern horizon. A little 
later the melancholy voices of the goatsuckers are heard, 
varied croakings of frogs, the plaintive whistle of moun- 
tain thrushes, and strange cries of birds or mammals 
peculiar to each locality. About half-past five the first 
glimmer of light becomes perceptible ; it slowly becomes 
lighter, and then increases so rapidly that at about a 
quarter to six it seems full daylight. For the next 
quarter of an hour this changes very little in character ; 
when, suddenly, the sun's rim appears above the horizon, 
decking the dew-laden foliage with glittering gems, 
sending gleams of golden light far into the woods, and 
waking up all nature to life and activity. Birds chirp 
and flutter about, parrots scream, monkeys chatter, bees 
hum among the flowers, and gorgeous butterflies flutter 
lazily along or sit with fully expanded wings exposed to 
the warm and invigorating rays. The first hour of 
morning in the equatorial regions possesses a charm and 
a beauty that can never be forgotten. All nature seems 
refreshed and strengthened by the coolness and moisture 
of the past night ; new leaves and buds unfold almost 
before the eye, and fresh shoots may often be observed 
to have grown many inches since the preceding day. 
The temperature is the most delicious conceivable. The 
slight chill of early dawn, whicn was itself agreeable, is 
succeeded by an invigorating warmth ; and the intense 



THE EQUATORIAL HEAVENS. 23 

sunshine lights up the glorious vegetation of the tropics, 
and realises all that the magic art of the painter or the 
glowing words of the poet, have pictured as their ideals 
of terrestrial beauty. 

The Aspect of the Equatorial Heavens. Within the 
limits of the equatorial zone the noonday sun is truly 
vertical twice every year, and for several months it 
passes so near the zenith that the difference can hardly 
be detected without careful observation of the very short 
shadows of vertical objects. The absence of distinct 
horizontal shadows at noon which thus characterises a 
considerable part of the year, is itself a striking pheno- 
menon to an inhabitant of the temperate zones ; and 
equally striking is the changed aspect of the starry 
heavens. The grand constellation Orion, passes verti- 
cally overhead, while the Great Bear is only to be seen 
low down in the northern heavens, and the Pole star 
either appears close to the horizon or has altogether 
disappeared according as we are north or south of the 
equator. Towards the south the Southern Cross, the 
Magellanic clouds, and the jet-black " coal sacks " are the 
most conspicuous objects invisible in our northern lati- 
tudes. The same cause that brings the sun overhead in 
its daily march equally affects the planets, which appear 
high up towards the zenith far more frequently than 
with us, thus affording splendid opportunities for 
telescopic observation. 

Intensity of Meteorological Phenomena at the Equator. 
The excessive violence of meteorological phenomena 
generally supposed to be characteristic of the tropics is 
not by any means remarkable in the equatorial zone. 
Electrical disturbances are much more frequent, but not 



24 TROPICAL NATURE, AND OTHER ESSAYS. 

generally more violent than in the temperate regions. 
The wind-storms are rarely of excessive violence, as 
might in fact be inferred from the extreme steadiness of 
the barometer, whose daily range at Batavia rarely exceeds 
one-eighth of an inch, while the extreme range during 
three years was less than one-third of an inch ! The 
amount of the rainfall is very great, seventy or eighty 
inches in a year being a probable average ; and as the 
larger part of this occurs during three or four month?, 
individual rainfalls are often exceedingly heavy. The 
greatest fall recorded at Batavia during three years 
was three inches and eight-tenths in one hour, 1 but this 
was quite exceptional, and even half this quantity is 
very unusual. The greatest rainfall recorded in twenty- 
four hours is seven inches and a quarter ; but more than 
four inches in one day occurs only on two or three occa- 
sions in a year. The blue colour of the sky is probably 
not so intense as in many parts of the temperate zone, 
while the brilliancy of the moon and stars is not 
perceptibly greater than that of our clearest frosty nights, 
and is undoubtedly much inferior to what is witnessed 
in many desert regions, and even in Southern Europe. 

On the whole, then, we must decide, that uniformity 
and abundance, rather than any excessive manifestations, 
are the prevailing characteristic of all the climatal 
phenomena of the equatorial zone. 

Concluding Remarks. We cannot better conclude 
our account of the equatorial climate than by quoting 
the following vivid description of the physical pheno- 
mena which occur during the early part of the dry 
season at Para. It is taken from Mr. Bates' Naturalist 

1 On January 10th, 1867, from 1 to 2 A.M. 



CLIMATE OF THE AMAZON. 25 

on the Amazons, and clearly exhibits some of the more 
characteristic features of a typical equatorial day. 

" At that early period of the day (the first two hours 
after sunrise) the sky was invariably cloudless, the ther- 
mometer marking 72 or 73 Fahr.; the heavy dew or 
the previous night's rain, which lay on the moist foliage, 
becoming quickly dissipated by the glowing sun, which, 
rising straight out of the east, mounted rapidly towards 
the zenith. All nature was fresh, new leaf and flower- 
buds expanding rapidly. * * * The heat increased hourly, 
and towards two o'clock reached 92 to 93 Fahr., by 
which time every voice of bird and mammal was hushed. 
The leaves, which were so moist and fresh in early 
morning, now became lax and drooping, and flowers shed 
their petals. On most days in June and July a heavy 
shower would fall some time in the afternoon, producing 
a most welcome coolness. The approach of the rain- 
clouds was after a uniform fashion very interesting to 
observe. First, the cool sea-breeze which had commenced 
to blow about ten o'clock, and which had increased in 
force with the increasing power of the sun, would flag, 
and finally die away. The heat and electric tension of 
the atmosphere would then become almost insupportable. 
Languor and uneasiness would seize on every one, even 
the denizens of the forest betraying it by their motions. 
White clouds would appear in the east and gather into 
cumuli, with an increasing blackness along their lower 
portions. The whole eastern horizon would become 
almost suddenly black, and this would spread upwards, 
the sun at length becoming obscured. Then the rush of 
a mighty wind is heard through the forest, swaying the 
tree-tops ; a vivid flash of lightning bursts forth, then a 



26 TROPICAL NATURE, AND OTHER ESSAYS. 

crash of thunder, and down streams the deluging rain. 
Such storms soon cease, leaving bluish-black motionless 
clouds in the sky until night. Meantime all nature is 
refreshed ; but heaps of flower-petals and fallen leaves 
are seen under the trees. Towards evening life revives 
again, and the ringing uproar is resumed from bush and 
tree. The following morning the sun again rises in a 
cloudless sky ; and so the cycle is completed ; spring, 
summer, and autumn, as it were in one tropical day. 
The days are more or less like this throughout the year. 
A little difference exists between the dry and wet seasons; 
but generally, the dry season, which lasts from July to 
December, is varied with showers, and the wet, from 
January to June, with sunny days. It results from this, 
that the periodical phenomena of plants and animals do 
not take place at about the same time in all species, or 
in the individuals of any given species, as they do in 
temperate countries. In Europe, a woodland scene has 
its spring, its summer, its autumnal, and its winter 
aspects. In the equatorial forests the aspect is the same 
or nearly so every day in the year : budding, flowering, 
fruiting, and leaf-shedding are always going on in one 
species or other It is never either spring, summer, or 
autumn, but each day is a combination of all three. 
With the day and night always of equal length, the 
atmospheric disturbances of each day neutralising them- 
selves before each succeeding morn ; with the sun in its 
course proceeding midway across the sky, and the daily 
temperature almost the same throughout the year how 
grand in its perfect equilibrium and simplicity is the 
march of Nature under the equator ! " 



II. 

EQUATORIAL VEGETATION. 

The Equatorial Forest-Belt and its Causes General features of the Equatorial 
Forests- -Low-growth Forest-trees Flowery trunks and their probable 
cause Uses of Equatorial Forest-trees The Climbing Plants of the 
Equatorial Forests Palms Uses of Palm-trees and their Products 
Ferns Ginger-worts and wild Bananas Arums Screw-pines Orchids 
Bamboos Uses of the Bamboo Mangroves Sensitive-plants 
Comparative scarcity of Flowers Concluding Remarks on Tropical 
Vegetation. 

IN the following sketch, of the characteristics of vegetable 
life in the equatorial zone, it is not intended to enter 
into any scientific details or to treat the subject in the 
slightest degree from a botanical point of view ; but 
merely to describe those general features of vegetation 
which are almost or quite peculiar to this region of the 
globe, and which are so general as to be characteristic 
of the greater part of it rather than of any particular 
country or continent within its limits. 

The Equatorial Forest-Belt and its Causes. With 
but few and unimportant exceptions a great forest band 
from a thousand to fifteen hundred miles in width 
girdles the earth at the equator, clothing hill, plain, and 
mountain with an evergreen mantle. Lofty peaks and 
precipitous ridges are sometimes bare, but often the 
woody covering continues to a height of eight or ten 



28 TROPICAL NATURE, AND OTHER ESSAYS. 

thousand feet, as in some of the volcanic mountains 
of Java and on portions of the Eastern Andes. Beyond 
the forests both to the north and south, we meet first 
with woody and then open country, soon changing into 
arid plains or even deserts which form an almost con- 
tinuous band in the vicinity of the two tropics. On 
the line of the tropic of Cancer we have, in America 
the deserts and dry plains of New Mexico ; in Africa the 
Sahara ; and in Asia, the Arabian deserts, those of Beloo- 
chistan and Western India, and further east the dry 
plains of North China and Mongolia. On the tropic of 
Capricorn we have, in America the Grand Chaco desert 
and the Pampas ; in Africa the Kalahari desert and the 
dry plains north of the Limpopo ; while the deserts and 
waterless plains of Central Australia complete the arid zone. 
These great contrasts of verdure and barrenness occurring 
in parallel bands all round the globe, must evidently 
depend on the general laws which determine the distri- 
bution of moisture over the earth, more or less modified 
by local causes. Without going into meteorological 
details, some of which have been given in the preceding 
chapter, the main facts may be explained by the mode 
in which the great aerial currents are distributed. The 
trade winds passing over the ocean from north-east to 
south-west with an oblique tendency towards the equator, 
become saturated with vapour, and are ready to give 
out moisture whenever they are forced upwards or in any 
other way have their temperature lowered. The entire 
equatorial zone becomes thus charged with vapour-laden 
air which is the primary necessity of a luxuriant vege- 
tation. The surplus air (produced by the meeting of the 
two trade \vinds) which is ever rising in the equatorial 



THE GREAT FOREST-BELTS. 29 

belt and giving up its store of vapour, flows off north 
and south as dry, cool air, and descends to the earth in 
the vicinity of the tropics. Here it sucks up whatever 
moisture it meets with and thus tends to keep this zone 
in an arid condition. The trades themselves are believed 
to be supplied by descending currents from the tem- 
perate zones, and these are at first equally dry and 
only become vapour-laden when they have passed over 
some extent of moist surface. At the solstices the sun 
passes vertically over the vicinity of the tropics for 
several weeks, and this further aggravates the aridity ; 
and wherever the soil is sandy and there are no lofty 
mountain-chains to supply ample irrigation the result is 
a more or less perfect desert. Analogous causes, which 
a study of aerial currents will render intelligible, have 
produced other great forest-belts in the northern and 
southern parts of the temperate zones ; but owing to the 
paucity of land in the southern hemisphere these are 
best seen in North America and Northern Euro-Asia, 
where they form the great northern forests of deciduous 
trees and of Coniferse. These being comparatively well- 
known to us, will form the standard by a reference to 
which we shall endeavour to point out and render in- 
telligible the distinctive characteristics of the equatorial 
forest vegetation. 

General Features of the Equatorial Forests. It is not 
easy to fix upon the most distinctive features of these 
virgin forests, which nevertheless impress themselves upon 
the beholder as something quite unlike those of tempe- 
rate lands, and as possessing a grandeur and sublimity 
altogether their own. Amid the countless modifications 
in detail which these forests present, we shall endeavour 



30 TROPICAL NATURE, AND OTHER ESSAYS. 

to point out the chief peculiarities as well as the more 
interesting phenomena which generally characterise them. 

The observer new to the scene would perhaps be first 
struck by the varied yet symmetrical trunks, which rise 
up with perfect straightness to a great height without a 
branch, and which, being placed at a considerable average 
distance apart, give an impression similar to that pro- 
duced by the columns of some enormous building. 
Overhead, at a height, perhaps, of a hundred feet, is an 
almost unbroken canopy of foliage formed by the meeting 
together of these great trees and their interlacing 
branches ; and this canopy is usually so dense that but 
an indistinct glimmer of the sky is to be seen, and even 
the intense tropical sunlight only penetrates to the ground 
subdued and broken up into scattered fragments. There 
is a weird gloom and a solemn silence, which combine 
to produce a sense of the vast the primeval almost 
of the infinite. It is a world in which man seems an 
intruder, and where he feels overwhelmed by the con- 
templation of the ever-acting forces, which, from the 
simple elements of the atmosphere, build up the great 
mass of vegetation which overshadows, and almost seems 
to oppress the earth. 

Characteristics of the Larger Forest-trees. Passing 
from the general impression to the elements of which 
the scene is composed, the observer is struck by the 
great diversity of the details amid the general uniformity. 
Instead of endless repetitions of the same forms of trunk 
such as are to be seen in our pine, or oak, or beech woods, 
the eye wanders from one tree to another and rarely 
detects two of the same species. All are tall and 
upright columns, but they differ from each other more 



FORMS OF TREE-TRUNKS. 31 

than do the columns of Gothic, Greek, and Egyptian 
temples. Some are almost cylindrical, rising up out of 
the ground as if their bases were concealed by accumu- 
lations of the soil ; others get much thicker near the 
ground like our spreading oaks ; others again, and these are 
very characteristic, send out towards the base flat and 
wing-like projections. These projections are thin slabs 
radiating from the main trunk, from which they stand 
out like the buttresses of a Gothic cathedral. They rise 
to various heights on the tree, from five or six, to twenty 
or thirty feet ; they often divide as they approach the 
ground, and sometimes twist and curve along the surface 
for a considerable distance, forming elevated and greatly 
compressed roots. These buttresses are sometimes so 
large that the spaces between them if roofed over would 
form huts capable of containing several persons. Their 
use is evidently to give the tree an extended base, and 
so assist the subterranean roots in maintaining in an 
erect position so lofty a column crowded by a broad and 
massive head of branches and foliage. The buttressed 
trees belong to a variety of distinct groups. Thus, 
many of the Bombacese or silk-cotton trees, several of 
the Leguminosoe, and perhaps many trees belonging to 
other natural orders, possess these appendages. 

There is another form of tree, hardly less curious, in 
which the trunk, though generally straight and cylin- 
drical, is deeply furrowed and indented, appearing as if 
made up of a number of small trees grown together at 
the centre. Sometimes the junction of what seem to be 
the component parts, is so imperfect, that gaps or holes 
are left by which you can see through the trunk in 
various places. At first one is disposed to think this is 



32 TROPICAL NATURE, AND OTHER ESSAYS. 

caused by accident or decay, but repeated examination 
shows it be due to the natural growth of the tree. The 
accompanying outline sections of one of these trees that 
was cut down, exhibits its character. It was a noble 




Sections of trunk of a Bornean Forest-tree. 

1. Section at seven feet from the ground. 

2. 3. Sections much higher up. 

forest-tree, more than 200 feet high, but rather slender 
in proportion, and it was by no means an extreme 
example of its class. This peculiar form is probably 
produced by the downward growth of aerial roots, like 
some New Zealand trees whose growth has been traced, 
and of whose different stages drawings may be seen at 
the Library of the Linnean Society. These commence 
their existence as parasitical climbers which take root in 
the fork of some forest-tree and send down aerial roots 
which clasp round the stem that upholds them. As 
these roots increase in size and grow together laterally 
they cause the death of their foster-parent. The climber 
then grows rapidly, sending out large branches above 
and spreading roots below, and as the supporting tree 
decays away the aerial roots grow together and form a 



TYPES OF FOLIAGE. 33 

new trunk, more or less furrowed and buttressed, but 
exhibiting no other marks of its exceptional origin. 
Aerial-rooted forest-trees like that figured in my 
Malay Archipelago (vol. i. p. 131) and the equally 
remarkable fig-trees of various species, whose trunks are 
formed by a miniature forest of aerial roots, sometimes 
separate, sometimes matted together, are characteristic of 
the Eastern tropics, but appear to be rare or altogether 
unknown in America, and can therefore hardly be in- 
cluded among the general characteristics of the equatorial 
zone. 

Besides the varieties of form, however, the tree-trunks 
of these forests present many peculiarities of colour and 
texture. The majority are rather smooth-barked, and 
many are of peculiar whitish, green, yellowish, or brown 
colours, or occasionally nearly black. Some are perfectly 
smooth, others deeply cracked and furrowed, while in a 
considerable number the bark splits off in flakes or hangs 
down in long fibrous ribands. Spined or prickly trunks 
(except of palms) are rare in the damp equatorial forests. 
Turning our gaze upwards from the stems to the foliage, 
we find two types of leaf not common in the temperate 
zone, although the great mass of the trees offer nothing 
very remarkable in this respect. First, we have many 
. trees with large, thick, and glossy leaves, like those of 
the cherry-laurel or the magnolia, but even larger, 
smoother, and more symmetrical. The leaves of the 
Asiatic caoutchouc-tree (Ficus elastica), so often culti- 
vated in houses, is a type of this class, which has a very 
fine effect among the more ordinary-looking foliage. 
Contrasted with this is the fine pinnate foliage of some 
of the largest forest-trees which, seen far aloft against 

D 



34 TROPICAL NATURE, AND OTHER ESSAYS. 

the sky, looks as delicate as that of the sensitive 
mimosa. 

Forest-trees of Low Growth. The great trees we 
have hitherto been describing form, however, but a 
portion of the forest. Beneath their lofty canopy there 
often exists a second forest of moderate-sized trees, whose 
crowns, perhaps forty or fifty feet high, do not touch 
the lowermost branches of those above them. These are 
of course shade-loving trees, and their presence effectually 
prevents the growth of any young trees of the larger 
kinds, until, overcome by age and storms, some monarch 
of the forest falls down, and, carrying destruction in its 
fall, opens up a considerable space, into which sun and 
air can penetrate. Then comes a race for existence among 
the seedlings of the surrounding trees, in which a few 
ultimately prevail and fill up the space vacated by their 
predecessor. Yet beneath this second set of medium- 
sized forest-trees there is often a third undergrowth of 
small trees, from six to ten feet high, of dwarf palms, of 
tree-ferns, and of gigantic herbaceous ferns. Coming to 
the surface of the ground itself we find much variety. 
Sometimes it is completely bare, a mass of decaying 
leaves and twigs and fallen fruits. More frequently it 
is covered with a dense carpet of selaginella or other 
lycopodiaceae, and these sometimes give place to a 
variety of herbaceous plants, sometimes with pretty, but 
rarely with very conspicuous flowers. 

Flowering Trunks and their Probable Cause. 
Among the minor but not unimportant peculiarities that 
characterise these lofty forests, is the curious way in 
which many of the smaller trees have their flowers 
situated on the main trunk or larger branches instead 



FLOWERING TRUNKS. 35 

of on the upper part of the tree. The cacao-tree is a 
well-known example of this peculiarity, which is not 
uncommon in tropical forests ; and some of the smaller 
trunks are occasionally almost hidden by the quantity 
of fruit produced on them. One of the most beautiful 
examples of this mode of flowering is a small tree of 
the genus Polyaltliea, belonging to the family of the 
custard-apples, not uncommon in the forests of North- 
western Borneo. Its slender trunk, about fifteen or 
twenty feet high, was completely covered with star- 
shaped flowers, three inches across and of a rich orange- 
red colour, making the trees look as if they had been 
artificially decorated with brilliant garlands. The recent 
discoveries as to the important part played by insects 
in the fertilization of flowers offers a very probable 
explanation of this peculiarity. Bees and butterflies 
are the greatest flower-haunters. The former love the 
sun and frequent open grounds or the flowery tops of 
the lofty forest-trees fully exposed to the sun and air. 
The forest shades are frequented by thousands of 
butterflies, but these mostly keep near the ground, 
where they have a free passage among the tree-trunks 
and visit the flowering shrubs and herbaceous plants. 
To attract these it is necessary that flowers should be 
low down and conspicuous. If they grew in the usual 
way on the tops of these smaller trees overshadowed by 
the dense canopy above them they would be out of 
sight of both groups of insects, but being placed openly 
on the stems, and in the greatest profusion, they cannot 
fail to attract the attention of the wandering butterflies. 
Uses of Equatorial Forest-trees. Amid this immense 
variety of trees, the natives have found out such as are 

D 2 



36 TROPICAL NATURE, AND OTHER ESSAYS. 

best adapted to certain purposes. The wood of some is 
light and soft, and is used for floats or for carving out 
rude images, stools, and ornaments for boats and houses. 
The flat slabs of the buttresses are often used to make 
paddles. Some of the trees with furrowed stems are 
exceedingly strong and durable, serving as posts for 
houses or as piles on which the water-villages are built. 
Canoes, formed from a trunk hollowed out and spread 
open under the action of heat, require one kind of wood, 
those built up with planks another ; and, as the species of 
trees in these forests are so much more numerous than 
the wants of a semi-civilized population, there are probably 
a large number of kinds of timber which will some day 
be found to be well adapted to the special requirements 
of the arts and sciences. The products of the trees of 
the equatorial forests, notwithstanding our imperfect 
knowledge of them, are already more useful to civilized 
man than to the indigenous inhabitants. To mention 
only a few of those whose names are tolerably familiar 
to us, we have such valuable woods as mahogany, teak, 
ebony, lignum-vitse, purple-heart, iron- wood, sandal- 
wood, and satin-wood ; such useful gums as india-rubber, 
gutta-percha, tragacanth, copal, lac, and dammar ; such 
dyes as are yielded by log-wood, brazil-wood, and 
sappan-wood ; such drugs as the balsams of Capivi and 
Tolu, camphor, benzoin, catechu or terra-japonica, caju- 
put oil, gamboge, quinine, Angostura bark, quassia, and 
the urari and upas poisons ; of spices we have cloves, 
cinnamon, and nutmegs ; and of fruits, brazil-nuts, 
tamarinds, guavas, and the valuable cacao ; while 
residents in our tropical colonies enjoy the bread-fruit, 
avocado-pear, custard-apple, durian, mango, mangosteen, 



CLIMBING PLANTS. 37 

soursop, papaw, and many others. This list of useful 
products from the exogenous trees alone of the equatorial 
forests, excluding those from the palms, shrubs, herbs, 
and creepers, might have been multiplied many times 
over by the introduction of articles whose names would 
be known only to those interested in special arts or 
sciences ; but imperfect as it is, it will serve to afford a 
notion of the value of this vast treasure-house which is 
as yet but very partially explored. 

The Climbing Plants of the Equatorial Forests. Next 
to the trees themselves the most conspicuous and 
remarkable feature of the tropical forests is the profusion 
of woody creepers and climbers that everywhere meet the 
eye. They twist around the slenderer stems, they drop 
down pendent from the branches, they stretch tightly from 
tree to tree, they hang looped in huge festoons from bough 
to bough, they twist in great serpentine coils or lie in en- 
tangled masses on the ground. Some are slender, smooth, 
and root-like ; others are rugged or knotted ; often they are 
twined together into veritable cables ; some are flat like 
ribands, others are curiously waved and indented. 
Where they spring from or how they grow is at first a 
complete puzzle. They pass overhead from tree to tree, 
they stretch in tight cordage like the rigging of a ship 
from the top of one tree to the base of another, and the 
upper regions of the forest often seem full of them 
without our being able to detect any earth-growing stem 
from which they arise. The conclusion is at length 
forced upon us that these woody climbers must possess 
the two qualities of very long life and almost indefinite 
longitudinal growth, for by these suppositions alone can 
we explain their characteristic features. The growth of 



38 TROPICAL NATURE, AND OTHER ESSAYS. 

climbers, even more than all other plants, is upward 
towards the light. In the shade of the forest they 
rarely or never flower, and seldom even produce foliage ; 
but when they have reached the summit of the tree that 
supports them, they expand under the genial influence 
of light and air, and often cover their foster-parent with 
blossoms not its own. Here, as a rule, the climber's growth 
would cease ; but the time comes when the supporting 
tree rots and falls, and the creeper comes with it in torn 
and tangled masses to the ground. But though its 
foster-parent is dead it has itself received no permanent 
injury, but shoots out again till it finds a fresh support, 
mounts another tree, and again puts forth its leaves and 
flowers. In time the old tree rots entirely away and the 
creeper remains tangled on the ground. Sometimes 
branches only fall and carry a portion of the creeper 
tightly stretched to an adjoining tree ; at other times 
the whole tree is arrested by a neighbour to which the 
creeper soon transfers itself in order to reach the upper 
light. When by the fall of a branch the creepers are 
left hanging in the air, they may be blown about by the 
wind and catch hold of trees growing up beneath them, 
and thus become festooned from one tree to another. 
When these accidents and changes have been again and 
again repeated the climber may have travelled very far 
from its parent stem, and may have mounted to the tree 
tops and descended again to the earth several times over. 
Only in this way does it seem possible to explain the 
wonderfully complex manner in which these climbing 
plants wander up and down the forest as if guided by 
the strangest caprices, or how they become so crossed 
and tangled together in the wildest confusion. 



USES OF CLIMBERS. 39 

The variety in the length, thickness, strength and 
toughness of these climbers, enables the natives of 
tropical countries to put them to various uses. Almost 
every kind of cordage is supplied by them. Some will 
stand in water without rotting, and are used for cables, 
for lines to which are attached fish-traps, and to bind 
and strengthen the wooden anchors used generally in 
the East. Boats and even large sailing vessels are built, 
whose planks are entirely fastened together by this kind 
of cordage skilfully applied to internal ribs. For the 
better kinds of houses, smooth and uniform varieties 
are chosen, so that the beams and rafters can be bound 
together with neatness, strength and uniformity, as is 
especially observable among the indigenes of the Ama- 
zonian forests. When baskets of great strength are 
required special kinds of creepers are used ; and to 
serve almost every purpose for which we should need a 
rope or a chain, the tropical savage adopts some one of the 
numerous forest-ropes which long experience has shown 
to have qualities best adapted for it. Some are smooth 
and supple ; some are tough and will bear twisting or 
tying ; some will last longest in salt water, others in 
fresh ; one is uninjured by the heat and smoke of fires, 
while another is bitter or otherwise prejudicial to insect 
enemies. 

Besides these various kinds of trees and climbers 
which form the great mass of the equatorial forests and 
determine their general aspect, there are a number of 
forms of plants which are always more or less present, 
though in some parts scarce and in others in great pro- 
fusion, and which largely aid in giving a special character 



40 TROPICAL NATURE, AND OTHER ESSAYS. 

to tropical as distinguished from temperate vegetation: 
Such are the various groups of palms, ferns, ginger- worts, 
and wild plantains, arums, orchids, and bamboos ; and 
under these heads we shall give a short account of 
the part they take in giving a distinctive aspect to 
the equatorial forests. 

Palms. Although these are found throughout the 
tropics and a few species even extend into the warmer 
parts of the temperate regions, they are yet so much 
more abundant and varied within the limits of the region 
we are discussing that they may be considered as among 
the most characteristic forms of vegetation of the equa- 
torial zone. They are, however, by no means generally 
present, and we may pass through miles of forest with- 
out even seeing a palm. In other parts they abound ; 
either forming a lower growth in the lofty forest, or in 
swamps and on hill-sides sometimes rising up above the 
other trees. On river-banks they are especially con- 
spicuous and elegant, bending gracefully over the stream, 
their fine foliage waving in the breeze, and their stems 
often draped with hanging creepers. 

The chief feature of the palm tribe consists in the 
cylindrical trunk crowned by a mass of large and some- 
what rigid leaves. They vary in height from a few feet 
to that of the loftiest forest-trees. Some are stemless, 
consisting only of a spreading crown of large pinnate 
leaves; but the great majority have a trunk slender in 
proportion to its height. Some of the smaller species 
have stems no thicker than a lead pencil, and four or five 
feet high ; while the great Mauritia of the Amazon has 
a trunk full two feet in diameter, and more than 
100 feet high. Some species probably reach a height 



PALMS. 41 

of 200 feet, for Humboldt states that in South 
America he measured a palm, which was 192 English 
feet high. The leaves of palms are often of immense size. 
Those of the Manicaria saccifera of Para are thirty 
feet long and four or five feet wide, and are not pinnate 
but entire and very rigid. Some of the pinnate leaves 
are much larger, those of the Raphia tcedigera and 
Maximiliana regia being both sometimes more than fifty 
feet long. The fan- shaped leaves of other species are ten 
or twelve feet in diameter. The trunks of palms are some- 
times smooth and more or less regularly ringed, but they 
are frequently armed with dense prickles which are some- 
times eight inches long. In some species, the leaves fall 
to the ground as they decay leaving a clean scar, but in 
most cases they are persistent, rotting slowly away, and 
leaving a mass of fibrous stumps attached to the upper 
part of the stem. This rotting mass forms an excellent 
soil for ferns, orchids, and other semi-parasitical plants, 
which form an attractive feature on what would other- 
wise be an unsightly object. The sheathing margins of 
the leaves often break up into a fibrous material, some- 
times resembling a coarse cloth, and in other cases more 
like horsehair. The flowers are not individually large, 
but form large spikes or racemes, and the fruits are 
often beautifully scaled and hang in huge bunches 
which are sometimes more than a load for a strong man. 
The climbing palms are very remarkable, their tough, 
slender, prickly stems mounting up by means of the 
hooked midribs of the leaves to the tops of the loftiest 
forest- trees, above which they send up an elegant spike 
of foliage and flowers. The most important are the 
American Desmoncus and the Eastern Calamus, the 



42 TKOPICAL NATURE, AND OTHER ESSAYS. 

latter being the well-known rattan or cane of which 
chair-seats are made, from the Malay name "rotang." 
The rattan-palms are the largest and most remarkable 
of the climbing group. They are very abundant in the 
drier equatorial forests, and more than sixty species are 
known from the Malay Archipelago. The stems (when 
cleaned from the sheathing leaves and prickles) vary in 
size from the thickness of a quill to that of the wrist ; 
and where abundant they render the forest almost im- 
passable. They lie about the ground coiled and twisted 
and looped in the most fantastic manner. They hang 
in festoons from trees and branches, they rise suddenly 
through mid air up to the top of the forest, or coil 
loosely over shrubs and in thickets like endless serpents. 
They must attain an immense age, and apparently 
have almost unlimited powers of growth, for some are 
said to have been found which were 600 or even 1000 
feet long, and if so, they are probably the longest of all 
vegetable growths. The mode in which such great 
lengths and tangled convolutions have been attained 
has already been explained in the general account of 
woody climbers. From the immense strength of these 
canes and the facility with which they can be split, they 
are universally used for cordage in the countries where 
they grow in preference to any other climbers, and 
immense quantities are annually exported to all parts of 
the world. 

Uses of Palm-trees and their Products. To the 
natives of the equatorial zone the uses of palms are 
both great and various. The fruits of several species 
more especially the cocoa-nut of the East and the 
peach-nut (Guilielma speciosa] of America furnish 



PRODUCTS OF PALMS. 43 

abundance of wholesome food, and the whole of the trunk 
of the sago-palm is converted into an edible starch 
our sago. Many other palm-fruits yield a thin pulp, too 
small in quantity to be directly eaten, but which when 
rubbed off and mixed with a proper quantity of water 
forms an exceedingly nutritious and agreeable article 
of food. The most celebrated of these is the assai of 
the Amazon, made from the fruit of Euterpe oleracea, 
and which, as a refreshing, nourishing, and slightly 
stimulating beverage for a tropical country, takes the 
place of our chocolate and coffee. A number of other 
palms yield a similar product, and many that are not 
eaten by man are greedily devoured by a variety of 
animals, so that the amount of food produced by this 
tribe of plants is much larger than is generally supposed. 
The sap which pours out of the cut flower-stalk of 
several species of palm when slightly fermented forms 
palm-wine or toddy, a very agreeable drink ; and when 
mixed with various bitter herbs or roots which check 
fermentation, a fair imitation of beer is produced. If 
the same fluid is at once boiled and evaporated it 
produces a quantity of excellent sugar. The Arenga 
saccharifera, or sugar-palm of the Malay countries, is 
perhaps the most productive of sugar. A single tree 
will continue to pour out several quarts of sap daily 
for weeks together, and where the trees are abundant 
this forms the chief drink and most esteemed luxury of 
the natives. A Dutch chemist, Mr. De Vry, who has 
studied the subject in Java, believes that great advan- 
tages would accrue from the cultivation of this tree in 
place of the sugar-cane. According 'to his experiments 
it would produce an equal quantity of sugar of good 



44 TROPICAL NATURE, AND OTHER ESSAYS. 

quality with far less labour and expense, because no 
manure and no cultivation would be required, and the 
land will never be impoverished as it so rapidly becomes 
by the growth of sugar-cane. The reason of this 
difference is, that the whole produce of a cane-field is 
taken off the ground, the crushed canes being burnt ; 
and the soil thus becomes exhausted of the various 
salts and minerals which form part of the woody fibre 
and foliage. These must be restored by the application 
of manure, and this, together with the planting, weeding, 
and necessary cultivation, is very expensive. With the 
sugar-palm, however, nothing whatever is taken away 
but the juice itself ; the foliage falls on -the ground and 
rots, giving back to it what it had taken; and the 
water and sugar in the juice being almost wholly 
derived from the carbonic acid and aqueous vapour 
of the atmosphere, there is no impoverishment ; and a 
plantation of these palms may be kept up on the same 
ground for an indefinite period. Another most impor- 
tant consideration is, that these trees will grow on poor 
rocky soil and on the steep slopes of ravines and hill- 
sides where any ordinary cultivation is impossible, and 
a great extent of fertile land would thus be set free for 
other purposes. Yet further, the labour required for 
such sugar plantations as these would be of a light and 
intermittent kind, exactly suited to a semi-civilized people 
to whom severe and long- continued labour is never 
congenial. This combination of advantages appears to 
be so great, that it seems possible that the sugar of the 
world may in the future be produced from what would 
otherwise be almost waste ground ; and it is to be hoped 
that the experiment will soon be tried in some of our 



USES OF PALMS. 45 

tropical colonies, more especially as an Indian palm, 
Phoenix sylvestris, also produces abundance of sugar, 
and might be tried in its native country. 

Other articles of food produced from palms are, 
cooking-oil from the cocoa-nut and baccaba palm, salt 
from the fruit of a South American palm (Leopoldinia 
major), while the terminal bud or " cabbage " of many 
species is an excellent and nutritious vegetable ; so that 
palms supply bread, oil, sugar, salt, fruit, and vege- 
tables. Oils for various other purposes are made from 
several distinct palms, while wax is secreted from the 
leaves of some South American species ; the resin called 
dragon's-blood is the product of one of the rattan 
palms ; while the fruit of the Areca palm is the " betel- 
nut " so universally chewed by the Malays as a gentle 
stimulant, and which is their substitute for the opium 
of the Chinese, the tobacco of Europeans, and the coca- 
leaf of South America. 

For thatching, the leaves of palms are invaluable, and 
are universally used wherever they are abundant ; and 
the petioles or leaf-stalks, often fifteen or twenty feet 
long, are used as rafters, or when fastened together with 
pegs form doors, shutters, partitions, or even the walls 
of entire houses. They are wonderfully light and strong, 
being formed of a dense pith covered with a hard rind 
or bark, and when split up and pegged together serve 
to make many kinds of boxes, which, when covered 
with the broad leaves of a species of screw-pine and 
painted or stained of various colours, are very strong 
and serviceable as well as very ornamental. Eopes and 
cables are woven from the black fibrous matter that 
fringes the leaves of the sugar-palm and some other 



46 TROPICAL NATURE, AND OTHER ESSAYS. 

species, while fine string of excellent quality used even 
for bow-strings, fishing-lines, and hammocks, is made of 
fibres obtained from the unopened leaves of some American 
species. The fibrous sheath at the base of the leaves of 
the cocoa-nut palm is so compact and cloth-like, that it 
is used for a variety of purposes, as for strainers, for 
wrappers, and to make very good hats. The great 
woody spathes of the larger palms serve as natural 
baskets, as cradles, or even as cooking- vessels in which 
water may be safely boiled. The trunks form excellent 
posts and fencing, and when split make good flooring. 
Some species are used for bows, others for blow-pipes ; 
the smaller species are sometimes used as needles or to 
make fish-hooks, and the larger as arrows. To describe 
in detail all the uses to which palm-trees and their 
products are applied in various parts of the world 
might occupy a volume ; but the preceding sketch will 
serve to give an idea of how important a part is filled 
by this noble family of plants, whether we regard them 
as a portion of the beautiful vegetation of the tropics, or 
in relation to the manners and customs, the lives and 
the well-being of the indigenous inhabitants. 

Ferns. The type of plants which, next to palms, 
most attracts attention in the equatorial zone, is perhaps 
that of the ferns, which here display themselves in vast 
profusion and variety. They grow abundantly on rocks 
and on decaying trees ; they clothe the sides of ravines 
and the margins of streams ; they climb up the trees and 
over bushes ; they form tufts and hanging festoons 
among the highest branches. Some are as small as mosses, 
others have huge fronds eight or ten feet long, while in 
mountainous districts the most elegant of the group, the 



FERNS. 47 

tree-ferns, bear their graceful crowns on slender stems 
twenty to thirty, or even fifty feet high. It is this 
immense variety rather than any special features that 
characterises the fern-vegetation of the tropics. We have 
here almost every conceivable modification of size, form of 
fronds, position of spores, and habit of growth, in plants 
that still remain unmistakably ferns. Many climb over 
shrubs and bushes in a most elegant manner ; others 
cling closely to the bark of trees like ivy. The great 
birds'-nest fern (Platycerium) attaches its shell-like 
fronds high up on the trunks of lofty trees. Many 
small terrestrial species have digitate, or ovate, or ivy- 
shaped, or even whorled fronds, resembling at first sight 
those of some herbaceous flowering-plants. Their 
numbers may be judged from the fact that in the 
vicinity of Tarrapoto, in Peru, Dr. Spruce gathered 
250 species of ferns, while the single volcanic mountains 
of Pangerango in Java (10,000 feet high) is said to 
have produced 300 species. 

Ginger-worts and wild Bananas. These plants, form- 
ing the families Zingiberacese and Musacess of botanists, 
are very conspicuous ornaments of the equatorial forests, 
on account of their large size, fine foliage, and handsome 
flowers. The bananas and plantains are well known as 
among the most luxuriant and beautiful productions of 
the tropics. Many species occur wild in the forests ; 
all have majestic foliage and handsome flowers, while 
some produce edible fruit. Of the ginger-worts (Zingi- 
beracese and Marantacese), the well known cannas of our 
tropical gardens may be taken as representatives, but the 
equatorial species are very numerous and varied, often 
forming dense thickets in damp places, and adorning the 



48 TROPICAL NATURE, AND OTHER ESSAYS. 

forest shades with their elegant and curious or showy 
flowers. The maranths produce " arrow-root," while the 
ginger-worts are highly aromatic, producing ginger, 
cardamums, grains of paradise, turmeric and several 
medicinal drugs. The Musacese produce the most valuable 
of tropical fruits and foods. The banana is the variety 
which is always eaten as a fruit, having a delicate 
aromatic flavour ; the plantain is a larger variety which is 
best cooked. Eoasted in the green state it is an excellent 
vegetable resembling roasted chestnuts ; when ripe it is 
sometimes pulped and boiled with water, making a very 
agreeable sweet soup ; or it is roasted, or cut into slices 
and fried, in either form being a delicious tropical 
substitute for fruit pudding. These plants are annuals, 
producing one immense bunch of fruit. This bunch is 
sometimes four or five feet long containing near 
200 plantains, and often weighs about a hundred- 
weight. They grow very close together, and Humboldt 
calculated that an acre of plantains would supply more 
food than could be obtained from the same extent of 
ground by any other known plant. Well may it be said 
that the plantain is the glory of the tropics, and well 
was the species named by Linnaeus Musa paradisiaca ! 
Arums. Another very characteristic and remarkable 
group of tropical plants are the epiphytal and climbing 
arums. These are known by their large, arrow-shaped, 
dark green and glossy leaves, often curiously lobed or 
incised, and sometimes reticulated with large open 
spaces, as if pieces had been regularly eaten out of 
them by some voracious insects. Sometimes they form 
clusters of foliage on living or dead trees to which they 
cling by their aerial roots. Others climb up the smooth 



SCREW-PINES. 49 

bark of large trees, sending out roots as they ascend 
which clasp around the trunk. Some mount straight 
up, others wind round the supporting trunks, and their 
large, handsome, and often highly-remarkable leaves, 
which spread out profusely all along the stem, render 
them one of the most striking forms of vegetation 
which adorn the damper and more luxuriant parts 
of the tropical forests of both hemispheres. 

Screw-pines. These singular plants, constituting the 
family Pandanacese of botanists, are very abundant in 
many parts of the Eastern tropics, while they are com- 
paratively scarce in America. They somewhat resemble 
Yuccas, but have larger leaves which grow in a close 
spiral screw on the stem. Some are large and palm-like, 
and it is a curious sight to stand under these and look 
up at the huge vegetable screw formed by the bases of 
the long drooping leaves. Some have slender-branched 
trunks, which send out aerial roots ; others are stemless, 
consisting of an immense spiral cluster of stiff leaves ten 
or twelve feet long and only two or three inches wide. 
They abound most in sandy islands, while the larger 
species grow in swampy forests. Their large-clustered 
fruits, something like pineapples, are often of a red 
colour ; and their long stiff leaves are of great use for 
covering boxes and for many other domestic uses. 

Orchids. These interesting plants, so well known 
from the ardour with which they are cultivated on 
account of their beautiful and singular flowers, are pre- 
eminently tropical, and are probably more abundant in 
the mountains of the equatorial zone than in any other 
region. Here they are almost omnipresent in some of 
their countless forms. They grow on the stems, in the 

E 



50 TROPICAL NATURE, AND OTHER ESSAYS. 

forks or on the branches of trees ; they abound on fallen 
trunks ; they spread over rocks, or hang down the face 
of precipices ; while some, like our northern species, 
grow on the ground among grass and herbage. Some 
trees whose bark is especially well adapted for their 
support are crowded with them, and these form natural 
orchid-gardens. Some orchids are particularly fond of 
the decaying leaf-stalks of palms or of tree-ferns. Some 
grow best over water, others must be elevated on lofty 
trees and well exposed to sun and air. The wonderful 
variety in the form, structure, and colour of the flowers 
of orchids is well known ; but even our finest collections 
give an inadequate idea of the numbers of these plants 
that exist in the tropics, because a large proportion of 
them have quite inconspicuous flowers and are not worth 
cultivation. More than thirty years ago the number of 
known orchids was estimated by Dr. Lindley at 3,000 
species, and it is not improbable that they may be now* 
nearly doubled. But whatever may be the numbers of 
the collected and described orchids, those that still remain 
to be discovered must be enormous. Unlike ferns, the 
species have a very limited range, and it would require 
the systematic work of a good botanical collector during 
several years to exhaust any productive district say 
such an island as Java of its orchids. It is not there- 
fore at all improbable that this remarkable group may 
ultimately prove to be the most numerous in species of 
all the families of flowering plants. 

Although there is a peculiarity of habit that enables 
one soon to detect an orchidaceous plant even when 
not in flower, yet they vary greatly in size and aspect. 
Some of the small creeping species are hardly larger 



OKCH1DS. 51 

than mosses, while the large Grammatophyllums of 
Borneo, which grow in the forks of trees, form a mass 
of leafy stems ten feet long, and some of the terrestrial 
species as the American Sobralias grow erect to an 
equal height. The fleshy aerial roots of most species 
gi\ 7 e them a very peculiar aspect, as they often grow 
to a great length in the open air, spread over the surface 
of rocks, or attach themselves loosely to the bark of 
trees, extracting nourishment from the rain and from 
the aqueous vapour of the atmosphere. Yet notwith- 
standing the abundance and variety of orchids in the 
equatorial forests they seldom produce much effect by 
their flowers. This is due partly to the very large pro- 
portion of the species having quite inconspicuous flowers ; 
and partly to the fact that the flowering season for each 
kind lasts but a few weeks, while different species flower 
almost every month in the year. It is also due to the 
manner of growth of orchids, generally in single plants or 
clumps which are seldom large or conspicuous as compared 
with the great mass of vegetation around them. It is only 
at long intervals that the traveller meets with anything 
which recalls the splendour of our orchid-houses and 
flower-shows. The slender-stalked golden Oncidiums of 
the flooded forests of the Upper Amazon ; the grand 
Cattleyas of the drier forests ; the Cselogynes of the 
swamps, and the remarkable Vanda lowii of the hill 
forests of Borneo, are the chief examples of orchid- 
beauty that have impressed themselves on the memory 
of the present writer during twelve years' wandering 
in tropical forests. The last-named plant is unique 
among orchids, its comparatively small cluster of leaves 
sending out numerous flower-stems, which hang down 

E 2 



52 TROPICAL NATURE, AND OTHER ESSAYS. 

like cords to a length of eight feet, and are covered with 
numbers of large star-like crimson-spotted flowers. 

Bamboos. The gigantic grasses called bamboos can 
hardly be classed as typical plants of the tropical zone, 
because they appear to be absent from the entire African 
continent and are comparatively scarce in South 
America. They also extend beyond the geographical 
tropics in China and Japan as well as in Northern India. 
It is however within the tropics and towards the equator 
that they attain their full size and beauty, and it is 
here that the species are most numerous and offer that 
variety of form, size, and quality, which renders them 
so admirable a boon to man. A fine clump of large 
bamboos is perhaps the most graceful of all vegetable 
forms, resembling the light and airy plumes of the bird- 
of-paradise copied on a gigantic scale in living foliage. 
Such clumps are often eighty or a hundred feet high, the 
glossy stems, perhaps six inches thick at the base, spring- 
ing up at first straight as an arrow, tapering gradually to 
a slender point, and bending over in elegant curves with 
the weight of the slender branches and grassy leaves. 
The various species differ greatly in size and proportions ; 
in the comparative length of the joints ; in the thickness 
and strength of the stem- walls ; in their straightness, 
smoothness, hardness, and durability. Some are spiny, 
others are unarmed ; some have simple stems, others are 
thickly set with branches ; while some species even grow 
in such an irregular, zig-zag, branched manner as to form 
veritable climbing bamboos. They generally prefer dry 
and upland stations, though some grow near the banks 
of rivers, and a few in the thick forests and, in South 
America, in flooded tracts. They often form dense 



BAMBOO. 53 

thickets where the forests have been cleared away ; and, 
owing to their great utility, they are cultivated or 
preserved near native houses and villages, and in such 
situations often give a finishing charm to the landscape. 

Uses of the Bamboo. Perhaps more than any other 
single type of vegetation, the bamboo seems specially 
adapted for the use of half- civilized man in a wild 
tropical country ; and the purposes to which it is applied 
are almost endless. It is a natural column or cylinder, 
very straight, uniform in thickness, of a compact and 
solid texture, and with a smooth flinty naturally-polished 
external skin. It is divided into ringed joints at 
regular intervals which correspond to septa or partitions 
within, so that each joint forms a perfectly closed and 
air-tight vessel. Owing to its hollowness, the hardness 
of the external skin, and the existence of the joints 
and partitions, it is wonderfully strong in proportion to 
its weight. It can be found of many distinct sizes and 
proportions ; light or heavy, long or short -jointed, and 
varying from the size of a reed to that of a tall and 
slender palm-tree. It can be split with great facility and 
accuracy ; and, owing to its being hollow, it can be easily 
cut across or notched witji a sharp knife or hatchet. It 
is excessively strong and highly elastic, and whether green 
or dry is almost entirely free from any peculiar taste or 
smell. The way in which these various qualities of 
the bamboo render it so valuable, will be best shown by 
giving a brief account of some of the uses to which it 
is applied in the Malay Archipelago. 

Several effective weapons are easily made from 
bamboo. By cutting off the end very obliquely just 
beyond a joint, a very sharp cutting point is produced 



54 TROPICAL NATURE, AND OTHER ESSAYS. 

suitable for a spear, dagger, or arrow-head, and capable 
of penetrating an animal's body as readily as iron. Such 
spears are constantly used by many of the Malay tribes. 
In the eastern half of the Archipelago, where bows and 
arrows are used, these weapons are often formed entirely 
of bamboo. The harder and thicker sorts, split and 
formed with tapering ends, make a very strong and 
elastic bow, while a narrow strip of the outer skin of the 
same is used for the string, and the slender reed-like 
kinds make excellent arrows. One of the few agricul- 
tural tools used by the Papuans a spud or hoe for 
planting or weeding is made of a stout bamboo cut 
somewhat like the spear. 

For various domestic purposes the uses of bamboo are 
endless. Ladders are rapidly made from two bamboo 
poles of the required length, by cutting small notches 
just above each ring, forming holes to receive the rungs 
or steps formed of a slenderer bamboo. For climbing 
lofty trees to get beeswax, a temporary ladder reaching 
to any height is ingeniously formed of bamboo. One of 
the hardest and thickest sorts is chosen, and from this a 
number of pegs about a foot long are made. These are 
sharpened at one end and then driven into the tree in a 
vertical line about three feet apart. A tall and slender 
bamboo is then placed upright on the ground and 
securely tied with rattan or other cords to the heads of 
these pegs, which thus, with the tree itself, form a ladder. 
A man mounts these steps and builds up the ladder as he 
goes, driving in fresh pegs and splicing on fresh bamboos 
till he reaches the lower branches of the tree, which is 
sometimes eighty or a hundred feet from the ground. As 
the weight of the climber is thrown on several of the 



IJSKS OF I'.AMHOO. 55 

pegs, which arc bound together and supported by the 
upright bamboo, this ladder is much safer that it looks 
at first sight, and it is made with wonderful rapidity. 
When a path goes up a steep hill over smooth ground, 
bamboo steps are often laid down to prevent slipping 
while carrying heavy loads. These are made with 
uniform lengths of stout bamboo in which opposite 
notches are cut at each end just within a joint. These 
notches allow strong bamboo pegs to be driven 
through into the ground, thus keeping the steps securely 
in place. The masts and yards of native vessels are 
almost always formed of bamboo, as it combines light- 
ness, strength, and elasticity in an unequaDed degree. 
Two or three large bamboos also form the best outriggers 
to canoes on account of their great buoyancy. They 
also serve to form rafts ; and in the city of Palembang 
in Sumatra there is a complete street of floating houses 
supported on rafts formed of huge bundles of bamboos. 
Bridges across streams or to carry footpaths along the 
face of precipices are constructed by the Dyaks of 
Borneo wholly of bamboos, and some of these are very 
ingeniously hung from overhanging trees by diagonal 
rods of bamboo, so as to form true suspension bridges. 
The flooring of Malay houses is almost always of 
bamboo, but is constructed in a variety of ways. Gene- 
rally large bamboos are used, split lengthways twice and 
the pieces tied down with rattan. This forms a grated 
floor, slightly elastic, and very pleasant to the barefooted 
natives. A. superior floor is sometimes formed of slabs, 
which are made from very stout bamboos cut into 
lengths of about three or four feet and split down one 
side. The joints are then deeply and closely notched all 



56 TROPICAL NATURE, AND OTHER ESSAYS. 

round with a sharp chopping-knife, so that the piece can 
be unrolled as it were and pressed flat, when it forms a 
hard board with a natural surface which, with a little 
wear, becomes beautifully smooth and polished. Blinds, 
screens, and mats, are formed of bamboos in a variety 
of ways, sometim'es of thin kinds crushed flat and 
plaited, but more frequently of narrow strips connected 
together with cords of bamboo-bark or rattan. Strips 
of bamboo supported on cross-pieces form an excellent 
bed, which from its elasticity supplies the purpose of a 
mattress as well, and only requires a mat laid over it 
to insure a comfortable night's repose. Every kind of 
basket, too, is made of bamboo, from the coarsest heavy 
kinds to such as are fine and ornamental. In such 
countries as Lombock and Macassar, where the land is 
much cultivated and timber scarce, entire houses are 
built of bamboo, posts, walls, floors, and roofs all being 
constructed of this one material ; and perhaps in no 
other way can so elegant and well-finished a house be 
built so quickly and so cheaply. Almost every kind of 
furniture is also made of the same material, excellent 
bamboo chairs, sofas, and bedsteads being made in the 
Moluccas, which, for appearance combined with cheap- 
ness, are probably unsurpassed in the world. A chair 
costs sixpence, and a sofa two shillings. 

Among simpler uses, bamboos are admirably adapted 
for water-vessels. Some of the lighter sorts are cut 
into lengths of about five feet, a small hole being 
knocked through the septa of the joints. This prevents 
the water from running out too quickly, and facilitates 
its being poured out in a regulated stream to the last 
drop. Three or four of these water-vessels are tied 



USES OF BAMBOO. 57 

together and carried on the back, and they stand very 
conveniently in a corner of the hut. Water pipes and 
aqueducts are also readily made from bamboo tubes 
supported at intervals on two smaller pieces tied cross- 
wise. In this way a stream of water is often conveyed 
from some distance to the middle of a village. Measures 
for rice or palm- wine, drinking- vessels, and water- 
dippers, are to be found almost ready-made in a joint of 
bamboo ; and when fitted with a cap or lid they form 
tobacco or tinder-boxes. Perches for parrots with food 
and water vessels are easily made out of a single piece 
of bamboo, while with a little more labour elegant 
bird-cages are constructed. In Timor a musical instru- 
ment is formed from a single joint of a large bamboo, 
by carefully raising seven strips of the hard skin to form 
strings, which remain attached at both ends and are 
elevated by small pegs wedged underneath, the strings 
being prevented from splitting off by a strongly -plaited 
ring of a similar material bound round each end. An 
opening cut on one side allows the bamboo to vibrate in 
musical notes when the harp-like strings are sharply 
pulled with the fingers. In Java strips of bamboo 
supported on stretched strings and struck with a small 
stick produce the higher notes in the "gamelung" or 
native band, which consists mainly of sets of gongs and 
metallic plates of various sizes. Almost all the common 
Chinese paper is made from the foliage and stems of 
some species of bamboo, while the young shoots, as they 
first spring out of the ground, are an excellent vegetable, 
quite equal to artichokes. Single joints of bamboo make 
excellent cooking- vessels while on a journey. Bice can 
be boiled in them to perfection, as well as fish and 



58 TROPICAL NATURE, AND OTHER ESSAYS. 

vegetables. They serve too for jars in which to preserve 
sugar, salt, fruit, molasses, and cooked provisions ; and 
for the smoker, excellent pipes and hookahs can be 
formed in a few minutes out of properly chosen joints 
of bamboo. 

These are only a sample of the endless purposes to 
which the bamboo is applied in the countries of which 
it is a native, its chief characteristic being that in a few 
minutes it can be put to uses which, if ordinary wood 
were used, would require hours or even days of labour. 
There is also a regularity and a finish about it which is 
found in hardly any other woody plant ; and its smooth 
and symmetrically ringed surface gives an appearance 
of fitness and beauty to its varied applications. On 
the whole, we may perhaps consider it as the greatest 
boon which nature gives to the natives of the Eastern 
tropics. 

Mangroves. Among the forms of plants which are 
sure to attract attention in the tropics are the mangroves, 
which grow between tide-marks on coasts and estuaries. 
These are low trees with widely-spreading branches and 
a network of aerial roots a few feet above the ground ; 
but their most remarkable peculiarity is, that their fruits 
germinate on the tree, sending out roots and branches 
before falling into the muddy soil a completely formed 
plant. In some cases the root reaches the ground before 
the seed above falls off. These trees greatly aid the 
formation of new land, as the mass of aerial roots which 
arch out from the stem to a considerable distance collects 
mud and floating refuse, and so raises and consolidates 

O ' 

the shore ; while the young plants often dropping from 
the farthest extremity of the branches, rapidly extend 



SENSITIVE-PLANTS. 59 

the domain of vegetation to the farthest possible limits. 
The branches, too, send down slender roots like those of 
the banyan, and become independent trees. Thus a 
complete woody labyrinth is formed ; and the network 
of tough roots and stems resists the action of the tides, 
and enables the mud brought down by great tropical 
rivers to be converted into solid land far more rapidly 
than it could be without this aid. 

Sensitive- plants. Among the more humble forms of 
vegetation that attract the traveller's notice none are 
more interesting than the sensitive species of Mimosa. 
These are all natives of South America, but one species, 
Mimosa pudica, has spread to Africa and Asia, so that 
sensitive-plants now abound as wayside weeds in many 
parts both of the eastern and western tropics, some- 
times completely carpeting the ground with their 
delicate foliage. Where a large surface of ground is 
thus covered the effect of walking over it is most 
peculiar. At each step the plants for some distance 
round suddenly droop, as if struck with paralysis, 
and a broad track of prostrate herbage, several feet 
wide, is distinctly marked out by the different colour 
of the closed leaflets. The explanation of this pheno- 
menon, given by botanists, is not very satisfactory ; ' 
while the purpose or use of the peculiarity is still 
more mysterious, seeing that out of about two hundred 
species belonging to this same genus Mimosa, only 
some three or four are sensitive, and in the whole 
vegetable kingdom there are no other plants which 
possess more than the rudiments of a similar property. 

1 See Nature, vol. xvi. p. 349, where the German botanist Pf offer's theory 

is given. 



60 TROPICAL NATURE, AND OTHER ESSAYS. 

It is true that, as they are all low-growing herbs or 
shrubs with delicate foliage, they might possibly be liable 
to destruction by herbivorous animals, and might escape 
by their singular power of suddenly collapsing before 
the jaws opened to devour them. The fact that one 
species has been naturalized as a weed over so wide an 
area in the tropics, seems to show that it possesses some 
advantage over the generality of tropical weeds. It is 
however curious that, as most of the species are some- 
what prickly, so easy and common a mode of protection 
as the development of stronger spines should here have 
failed; and that its place should be supplied by so 
singular a power as that of simulating death, in a manner 
which suggests the possession of both sensation and 
voluntary motion. 

Comparative Scarcity of Flowers. It is a very 
general opinion among inhabitants of our temperate 
climes, that amid the luxuriant vegetation of the tropics 
there must be a grand display of floral beauty ; and this 
idea is supported by the number of large and showy 
flowers cultivated, in our hot-houses. The fact is, how- 
ever, that in proportion as the general vegetation 
becomes more luxuriant, flowers form a less and less 
prominent feature ; and this rule applies not only to the 
tropics but to the temperate and frigid zones. It is 
amid the scanty vegetation of the higher mountains and 
towards the limits of perpetual snow, that the alpine 
flowers are most brilliant and conspicuous. Our own 
meadows and pastures and hill-sides produce more gay 
flowers than our woods and forests ; and, in the tropics, 
it is in the parts where vegetation is less dense and 
luxuriant that flowers most abound. In the damp and 



SCARCITY OF FLOWERS. 61 

uniform climate of the equatorial zone the mass of 
vegetation is greater and more varied than in any other 
part of the globe, but in the great virgin forests them- 
selves flowers are rarely seen. After describing the 
forests of the Lower Amazon, Mr. Bates asks : " But 
where were the flowers ? To our great disappointment 
we saw none, or only such as were insignificant in appear- 
ance. Orchids are rare in the dense forests of the 
lowlands, and I believe it is now tolerably well ascer- 
tained that the majority of the forest-trees in equatorial 
Brazil have small and inconspicuous flowers." 1 My 
friend Dr. Richard Spruce assured me that by far the 
greater part of the plants gathered by him in equatorial 
America had inconspicuous green or white flowers. 
My own observations in the Aru Islands for six months, 
and in Borneo for more than a year, while living almost 
wholly in the forests, are quite in accordance with this 
view. Conspicuous masses of showy flowers are so rare, 
that weeks and months may be passed without observing 
a single flowering plant worthy of special admiration. 
Occasionally some tree or shrub will be seen covered 
with magnificent yellow, or crimson, or purple flowers, 
but it is usually an oasis of colour in a desert of 
verdure, and therefore hardly affects the general aspect 
of the vegetation. The equatorial forest is too gloomy 
for flowers, or generally even for much foliage, except of 
ferns and other shade-loving plants ; and were it not 
that the forests are broken up by rivers and streams, 
by mountain ranges, by precipitous rocks and by deep 
ravines, there would be far fewer flowers than there are. 
Some of the great forest-trees have showy blossoms, 

1 The Naturalist on the River Amazon*, 2nd edit. p. 38. 



62 TROPICAL NATURE, AND OTHER ESSAYS. 

and when these are seen from an elevated point looking 
over an expanse of tree-tops the effect is very grand ; 
but nothing is more erroneous than the statement some- 
times made that tropical forest-trees generally have 
showy flowers, for it is doubtful whether the proportion 
is at all greater in tropical than in temperate zones. On 
such natural exposures as steep mountain sides, the 
banks of rivers, or ledges of precipices, and on the 
margins of such artificial openings as roads and forest 
clearings, whatever floral beauty is to be found in the 
more luxuriant parts of the tropics is exhibited. But 
even in such favourable situations it is not the abund- 
ance and beauty of the flowers but the luxuriance 
and the freshness of the foliage, and the grace and 
infinite variety of the forms of vegetation, that will 
most attract the attention and extort the admiration 
of the traveller. Occasionally indeed you will come 
upon shrubs gay w r ith blossoms or trees festooned with 
flowering creepers ; but, on the other hand, you may travel 
for a hundred miles and see nothing but the varied 
greens of the forest foliage and the deep gloom of its 
tangled recesses. In Mr. Belt's Naturalist in Nica- 
ragua, he thus describes the great virgin forests of that 
country which, being in a mountainous region and on 
the margin of the equatorial zone, are among the most 
favourable examples. " On each side of the road great 
trees towered up, carrying their crowns out of sight 
amongst a canopy of foliage, and with lianas hanging 
from nearly every bough, and passing from tree to tree, 
entangling the giants in a great network of coiling 
cables. Sometimes a tree appears covered with beautiful 
flowers which do not belong to it, but to one of the lianas 



SCARCITY OF FLOWERS. 63 

that twines through its branches and sends down great 
rope- like stems to the ground. Climbing ferns and 
vanilla cling to the trunks, and a thousand epiphytes 
perch themselves on the branches. Amongst these are 
large arums that send down long aerial roots, tough and 
strong, and universally used instead of cordage by the 
natives. Amongst the undergrowth several small species 
of palms, varying in height from two to fifteen feet, are 
common ; and now and then magnificent tree ferns 
sending off their feathery crowns twenty feet from the 
ground delight the sight by their graceful elegance. 
Great broad-leaved heliconias, leathery melastomse, and 
succulent-stemmed, lop-sided leaved and flesh-coloured 
begonias are abundant, and typical of tropical American 
forests ; but not less so are the cecropia trees, with their 
white stems and large palmated leaves standing up like 
great candelabra. Sometimes the ground is carpeted 
with large flowers, yellow, pink, or white, that have 
fallen from some invisible tree-top above ; or the air is 
filled with a delicious perfume, the source of which one 
seeks around in vain, for the flowers that cause it are 
far overhead out of sight, lost in the great overshadow- 
ing crown of verdure." 

Although, as has been shown elsewhere, it may be 
doubted whether light directly produces floral colour, 
there can be no doubt that it is essential to the growth 
of vegetation and to the full development of foliage and 
of flowers. In the forests all trees, and shrubs, and 
creepers struggle upwards to the light, there to expand 
their blossoms and ripen their fruit. Hence, perhaps, 
the abundance of climbers which make use of their more 
sturdy companions to reach this necessary of vegetable 



64 TROPICAL NATURE, AND OTHER ESSAYS. 

life. Yet even on the upper surface of the forest, fully 
exposed to the light and heat of the tropical sun, 
there is no special development of coloured flowers. 
When from some elevated point you can gaze down upon 
an unbroken expanse of woody vegetation, it often 
happens that not a single patch of bright colour can be 
discerned. At other times, and especially at the 
beginning of the dry season, you may behold scattered 
at wide intervals over the mottled-green surface a few 
masses of yellow, white, pink, or more rarely of blue 
colour, indicating the position of handsome flowering 
trees. 

The well-established relation between coloured flowers 
and the need of insects to fertilize them, may perhaps be 
connected with the comparative scarcity of the former 
in the equatorial forests. The various forms of life are 
linked together in such mutual dependence that no one 
can inordinately increase without bringing about a 
corresponding increase or diminution of other forms. 
The insects which are best adapted to fertilize flowers 
cannot probably increase much beyond definite limits, 
because in doing so they would lead to a corresponding 
increase of insectivorous birds and other animals which 
would keep them down. The chief fertilizers bees and 
butterflies have enemies at every stage of their growth, 
from the egg to the perfect insect, and their numbers are, 
therefore, limited by causes quite independent of the 
supply of vegetable food. It may, therefore, be the case 
that the numbers of suitable insects are totally inade- 
quate to the fertilization of the countless millions of 
forest-trees over such vast areas as the equatorial zone 
presents, and that, in consequence, a large proportion of 



INSECTS AND FOREST FLOWERS. 65 

the species have become adapted either for self-fertiliza- 
tion or for cross-fertilization by the agency of the wind. 
Were there not some such limitation as this, we should 
expect that the continued struggle for existence among 
the plants of the tropical forests would have led to the 
acquisition, by a much larger proportion of them, of so 
valuable a character as bright-coloured flowers, this being 
almost a necessary preliminary to a participation in the 
benefits which have been proved to arise from cross- 
fertilization by insect agency. 

Concluding Remarks on Tropical Vegetation. In 
concluding this general sketch of the aspect of tropical 
vegetation we will attempt briefly to summarize its main 
features. The primeval forests of the equatorial zone are 
grand and overwhelming by their vastness, and by the 
display of a force of development and vigour of growth 
rarely or never witnessed in temperate climates. Among 
their best distinguishing features are the variety of forms 
and species which everywhere meet and grow side by side, 
and the extent to which parasites, epiphytes, and creepers 
fill up every available station with peculiar modes of life. 
If the traveller notices a particular species and wishes to 
find more like it, he may often turn his eyes in vain in 
every direction. Trees of varied forms, dimensions, and 
colours are around him, but he rarely sees any one of 
them repeated. Time after time he goes towards a tree 
which looks like the one 'he seeks, but a closer exami- 
nation proves it to be distinct. He may at length, 
perhaps, meet with a second specimen half a mile off, or 
may fail altogether, till on another occasion he stumbles 
on one by accident. 

The absence of the gregarious or social habit, so 

F 



G6 TROPICAL NATURE, AND OTHER ESSAYS. 

general in the forests of extra-tropical countries, is 
probably dependent on the extreme equability and per- 
manence of the climate. Atmospheric conditions are 
much more important to the growth of plants than any 
others. Their severest struggle for existence is against 
climate. As we approach towards regions of polar cold 
or desert aridity the variety of groups and species regu- 
larly diminishes ; more and more are unable to sustain 
the extreme climatal conditions, till at last we find only 
a few specially organized forms which are able to 
maintain their existence. In the extreme north, pine or 
birch trees ; in the desert, a few palms and prickly shrubs 
or aromatic herbs alone survive. In the equable equa- 
torial zone there is no such struggle against climate. 
Every form of vegetation has become alike adapted to 
its genial heat and ample moisture, which has probably 
changed little even throughout geological periods ; and 
the never-ceasing struggle for existence between the 
various species in the same area has resulted in a nice 
balance of organic forces, which gives the advantage, 
now to one, now to another, species, and prevents any 
one type of vegetation from monopolising territory to 
the exclusion of the rest. The same general causes have 
led to the filling up of every place in nature with some 
specially adapted form. Thus we find a forest of smaller 
trees adapted to grow in the shade of greater trees. 
Thus we find every tree supporting numerous other forms 
of vegetation, and some so crowded with epiphytes of 
various kinds that their forks and horizontal branches 
are veritable gardens. Creeping ferns and arums run 
up the smoothest trunks ; an immense variety of climbers 
hang in tangled masses from the branches and mount over 



MONOTONY OF TROPICAL VEGETATION. 67 

the highest tree-tops. Orchids, bromelias, arums, and 
ferns grow from every boss and crevice, and cover the 
fallen and decaying trunks with a graceful drapery. 
Even these parasites have their own parasitical growth, 
their leaves often supporting an abundance of minute 
creeping mosses and hepaticae. But the uniformity of 
climate which has led to this rich luxuriance and 
endless variety of vegetation is also the cause of a 
monotony that in time becomes oppressive. To quote 
the words of Mr. Belt : " Unknown are the autumn 
tints, the bright browns and yellows of English woods ; 
much less the crimsons, purples, and yellows of Canada, 
where the dying foliage rivals, nay, excels, the expiring 
dolphin in splendour. Unknown the cold sleep of 
winter ; unknown the lovely awakening of vegetation at 
the first gentle touch of spring. A ceaseless round of 
ever-active life weaves the fairest scenery of the tropics 
into one monotonous whole, of which the component parts 
exhibit in detail untold variety and beauty." 1 

To the student of nature the vegetation of the tropics 
will ever be of surpassing interest, whether for the 
variety of forms and structures which it presents, for 
the boundless energy with which the life of plants is 
therein manifested, or for the help which it gives us in 
our search after the laws which have determined the 
production of such infinitely varied organisms. When, 
for the first time, the traveller wanders in these primeval 
forests, he can scarcely fail to experience sensations of 
awe, akin to those excited by the trackless ocean or the 
alpine snowfields. There is a vastness, a solemnity, a 
gloom, a sense of solitude and of human insignificance 

1 The Naturalist in Nicaragua,, p. 58. 

F 2 



68 TROPICAL NATURE, AND OTHER ESSAYS. 

which for a time overwhelm him ; and it is only when 
the novelty of these feelings have passed away that he 
is able to turn his attention to the separate constituents 
that combine to produce these emotions, and examine 
the varied and beautiful forms of life which, in inex- 
haustible profusion, are spread around him. 



III. 

ANIMAL LIFE IN THE TEOPICAL FORESTS. 

Difficulties of the Subject General Aspect of the Animal life of Equatorial 
Forests Diurnal Lepidoptera or Butterflies Peculiar Habits of Tropical 
Butterflies Ants, Wasps ; and Bees Ants Special Relations between 
Ants and Vegetation Wasps and Bees Orthoptera and other Insects 
Beetles Wingless Insects General Observations on Tropical Insects 
Birds Parrots Pigeons Picariae Cuckoos Trogons, Barbets, Toucans 
and Hornbills Passeres Reptiles and Amphibia Lizards Snakes 
Frogs and Toads Mammalia Monkeys Bats Summary of the 
Aspects of Animal life in the Tropics. 

THE attempt to give some account of the general 
aspects of animal life in the equatorial zone, presents 
far greater difficulties than in the case of plants. On the 
one hand, animals rarely play any important part in 
scenery, and their entire absence may pass quite un- 
noticed ; while the abundance, variety, and character of 
the vegetation are among those essential features that 
attract every eye. On the other hand, so many of the 
more important and characteristic types of animal life 
are restricted to one only out of the three great divisions 
of equatorial land, that they can hardly be claimed as 
characteristically tropical ; while the more extensive 
zoological groups which have a wide range in the tropics 
and do not equally abound in the temperate zones, are 
few in number, and often include such a diversity of 



70 TEOPICAL NATURE, AND OTHER ESSAYS. 

forms, structures, and habits, as to render any typical 
characterisation of them impossible. We must then, in 
the first place, suppose that our traveller is on the look 
out for all signs of animal life ; and that, possessing a 
general acquaintance as an out-door observer with the 
animals of our own country, he carefully notes those 
points in which the forests of the equatorial zone offer 
different phenomena. Here, as in the case of plants, we 
exclude all zoological science, classifications, and nomen- 
clature, except in as far as it is necessary for a clear 
understanding of the several groups of animals referred 
to. We shall therefore follow no systematic order in 
our notes, except that which would naturally arise from 
the abundance or prominence of the objects themselves. 
We further suppose our traveller to have no prepos- 
sessions, and to have no favourite group, in the search 
after which he passes by other objects which, in view 
of their frequent occurrence in the landscape, are really 
more important. 

General Aspect of the Animal Life of Equatorial 
Forests. Perhaps the most general impression produced 
by a first acquaintance with the equatorial forests, is the 
comparative absence of animal life. Beast, bird, and 
insect alike require looking for, and it very often 
happens that we look for them in vain. On this subject 
Mr. Bates, describing one of his early excursions into 
the primeval forests of the Amazon Valley, remarks as 
follows : " We were disappointed in not meeting with 
any of the larger animals of the forest. There was no 
tumultuous movement or sound of life. We did not see 
or hear monkeys, and no tapir or jaguar crossed our 
path. Birds also appeared to be exceedingly scarce." 



ANIMAL LIFE. 71 

Again " I afterwards saw reason to modify my opinion, 
founded on first impressions, with regard to the amount 
and variety of animal life in this and other parts of the 
Amazonian forests. There is in fact a great variety of 
mammals, birds, and rep tiles, but they are widely scattered 
and all excessively shy of man. The region is so exten- 
sive, and uniform in the forest clothing of its surface, 
that it is only at long intervals that animals are seen in 
abundance, where some particular spot is found which 
is more attractive than others. Brazil, moreover, is 
throughout poor in terrestrial mammals, and the species 
are of small size ; they do not, therefore, form a con- 
spicuous feature in the forests. The huntsman would be 
disappointed who expected to find here flocks of animals 
similar to the buffalo-herds of North America, or the 
swarms of antelopes and herds of ponderous pachyderms 
of Southern Africa. We often read in books of travel 
of the silence and gloom of the Brazilian forests. They 
are realities, and the impression deepens on a longer ac- 
quaintance. The few sounds of birds are of that pensive 
and mysterious character which intensifies the feeling of 
solitude rather than imparts a sense of life and cheerful- 
ness. Sometimes in the midst of the stillness, a sudden 
yell or scream will startle one ; this comes from some 
defenceless fruit-eating animal which is pounced upon by 
a tiger-cat or a boa-constrictor. Morning and evening 
the howling monkeys make a most fearful and harrowing 
noise, under which it is difficult to keep up one's buoy- 
ancy of spirit. The feeling of inhospitable wildness 
which the forest is calculated to inspire, is in- 
creased tenfold under this fearful uproar. Often, even 
in the still midday hours, a sudden crash will be heard 



72 TROPICAL NATURE, AND OTHER ESSAYS. 

resounding afar through the wilderness, as some great 
bough or entire tree falls to the ground." With a few 
verbal alterations these remarks will apply equally to 
the primeval forests of the Malay Archipelago ; and it is 
probable that those of West Africa offer no important 
differences in this respect. There is, nevertheless, one 
form of life which is very rarely absent in the more 
luxuriant parts of the tropics, and which is more often 
so abundant as to form a decided feature in the scene. 
It is therefore the group which best characterises the 
equatorial zone, and should form the starting-point for 
our review. This group is that of the diurnal Lepidop- 
tera or butterflies, 

Diurnal Lepidoptera. Wherever in the equatorial 
zone a considerable extent of the primeval forest 
remains, the observer can hardly fail to be struck by the 
abundance and the conspicuous beauty of the butterflies. 
Not only are they abundant in individuals, but their 
large size, their elegant forms, their rich and varied 
colours, and the number of distinct species almost 
everywhere to be met with are equally remarkable. In 
many localities near the northern or southern tropics 
they are perhaps equally abundant, but these spots are 
more or less exceptional ; whereas within the equatorial 
zone, and with the limitations above stated, butterflies 
form one of the most constant and most conspicuous 
displays of animal life. They abound most in old and 
tolerably open roads and pathways through the forest, 
but they are also very plentiful in old settlements in 
which fruit-trees and shrubbery offer suitable haunts. In 
the vicinity of such old towns as Malacca and Amboyna 
in the East, and of Para and Rio de Janeiro in the 



BUTTEKFLIES. 73 

West, they are especially abundant, and comprise some 
of the handsomest and most remarkable species in the 
whole group. Their aspect is altogether different from 
that presented by the butterflies of Europe and of most 
temperate countries. A considerable proportion of the 
species are very large, six to eight inches across the 
wings being not uncommon among the Papilionidge and 
Morphidae, while several species are even larger. This 
great expanse of wings is accompanied by a slow flight ; 
and, as they usually keep near the ground and often 
rest, sometimes with closed and sometimes with ex- 
panded wings, these noble insects really look larger and 
are much more conspicuous objects than the majority of 
our native birds. The first sight of the great blue 
Morphos flapping slowly along in the forest roads near 
Para of the large, white-and-black semi-transparent 
Ideas floating airily about in the woods near Malacca 
and of the golden-green Ornithopteras sailing on bird- 
like wing over the flowering shrubs which adorn the 
beach of the Kd and Aru islands, can never be forgotten 
by any one with a feeling of admiration for the new and 
beautiful in nature. Next to the size, the infinitely 
varied and dazzling hues of these insects most attract 
the observer. Instead of the sober browns, the plain 
yellows, and the occasional patches of red or blue or 
orange that adorn our European species, we meet with 
the most intense metallic blues, the purest satiny greens, 
the most gorgeous crimsons, not in small spots but in 
large masses, relieved by a black border or background. 
In others we have contrasted bands of blue and orange, 
or of crimson and green, or of silky yellow relieved by 
velvety black. In not a few the wings are powdered 



74 TROPICAL NATURE, AND OTHER ESSAYS. 

over with scales and spangles of metallic green, deepen- 
ing occasionally into blue or golden or deep red spots. 
Others again have spots and markings as of molten silver 
or gold, while several have changeable hues, like shot- 
silk or richly-coloured opal. The form of the wings, 
again, often attracts attention. Tailed hind- wings 
occur in almost all the families, but vary much in 
character. In some the tails are broadly spoon-shaped, 
in others long and pointed. Many have double or 
triple tails, and some of the smaller species have them 
immensely elongated and often elegantly curled. In 
some groups the wings are long and narrow, in others 
strongly falcate ; and though many fly with immense 
rapidity, a large number flutter lazily along, as if they 
had no enemies to fear and therefore no occasion to 
hurry. 

The number of species of butterflies inhabiting any 
one locality is very variable, and is, as a rule, far larger 
in America than in the Eastern hemisphere ; but it 
everywhere very much surpasses the numbers in the 
temperate zone. A few months' assiduous collecting in 
any of the Malay islands will produce from 150 to 250 
species of butterflies, and thirty or forty species may be 
obtained any fine day in good localities. In the 
Amazon valley, however, much greater results may be 
achieved. A good day's collecting will produce from 
forty to seventy species, while in one year at Para about 
600 species were obtained. More than 700 species of 
butterflies actually inhabit the district immediately 
around the city of Para, and this, as far as we yet 
know, is the richest spot on the globe for diurnal 
lepidoptera. At Ega, during four years' collecting ; 



ABUNDANCE OF BUTTERFLIES. 75 

Mr. Bates obtained 550 species, and these on the whole 
surpassed those of Para in variety and beauty. Mr. 
Bates thus speaks of a favourite locality on the margin 
of the lake near Ega : " The number and variety of 
gaily-tinted - butterflies, sporting about in this grove 
on sunny days, were so great, that the bright moving 
flakes of colour gave quite a character to the physiog- 
nomy of the place. It was impossible to walk far 
without disturbing flocks of them from the damp sand 
at the edge of the water, where they congregated to 
imbibe the moisture. They were of almost all colours, 
sizes, and shapes ; I noticed here altogether eighty 
species, belonging to twenty -two distinct genera. The 
most abundant, next to the very common sulphur- 
yellow and orange-coloured kinds, were about a dozen 
species of Eunica, which are of large size and conspicuous 
from their liveries of glossy dark blue and purple. A 
superbly adorned creature, the Callithea Markii, having 
wings of a thick texture, coloured sapphire-blue and 
orange, was only an occasional visitor. On certain days, 
when the weather was very calm, two small gilded species 
(Symmachic, Trochilus and Colubris) literally swarmed 
on the sands, their glittering wings lying wide open 
on the flat surface/' 

When we consider that only sixty-four species of butter- 
flies have been found in Britain and about 1 50 in Germany, 
many of whict are very rare and local, so that these 
numbers are the result of the work of hundreds of 
collectors for a long series of years, we see at once the 
immense wealth of the equatorial zone in this form 
of life. 

1 The Naturalist on the Amazons, 2nd edit. p. 331. 



76 TKOPICAL NATURE, AND OTHER ESSAYS. 

Peculiar Habits of Tropical Butterflies. The habits 
of the butterflies of the tropics offer many curious 
points rarely or never observed among those of the 
temperate zone. The majority, as with us, are truly 
diurnal, but there are some Eastern Morphidse and the 
entire American family Brassolidae, which are cre- 
puscular, coming out after sunset and flitting about the 
roads till it is nearly dark. Others, tliough flying in 
the daytime, are only found in the gloomiest recesses of 
the forest, where a constant twilight may be said to 
prevail. The majority of the species fly at a moderate 
height (from five to ten feet above the ground) while a 
few usually keep higher up and are difficult to capture ; 
but a large number, especially the Satyridae, many 
Erycinidae, and some few NymphalidaB, keep always 
close to the ground, and usually settle on or among the 
lowest herbage. As regards the mode of flight, the 
extensive and almost exclusively tropical families of 
Heliconidse and Danaidae, fly very slowly, with a gentle 
undulating or floating motion which is almost peculiar 
to them. Many of the strong-bodied Nymphalidae and 
Hesperidse, on the other hand, have an excessively rapid 
flight, darting by so swiftly that the eye cannot follow 
them, and in some cases producing a deep sound louder 
than that of the humming-birds. 

The places they frequent, and their mode of resting, are 
various and often remarkable. A considerable number 
frequent damp open places, especially river sides and 
the margins of pools, assembling together in flocks of 
hundreds of individuals ; but these are almost entirely 
composed of males, the females remaining in the forests 
where, towards the afternoon, their partners join them. 



HABITS OF BUTTERFLIES. 77 

The majority of butterflies settle upon foliage and on 
flowers, holding their wings erect and folded together, 
though early in the morning, or when newly emerged 
from the chrysalis, they often expand them to the sun. 
Many, however, have special stations and attitudes. 
Some settle always on tree- trunks, usually with the wings 
erect, but the Ageronias expand them and always rest 
with the head downwards. Many Nymphalidse prefer 
resting on the top of a stick ; others choose bushes with 
dead leaves ; others settle on rocks or sand or in dry 
forest paths. Pieces of decaying animal or vegetable 
matter are very attractive to certain species, and if 
disturbed they will sometimes return to the same spot 
day after day. Some Hesperidse, as well as species of 
the genera Cyrestis and Symmachia, and some others, 
rest on the ground with their wings fully expanded and 
pressed closely to the surface, as if exhibiting themselves 
to the greatest advantage. The beautiful little Erycinidae 
of South America vary remarkably in their mode of 
resting. The majority always rest on the under surface 
of leaves with their wings expanded, so that when 
they settle they suddenly disappear from sight. Some, 
however, as the elegant gold-spotted Helicopis cupido, 
rest beneath leaves with closed wings. A few, as the 
genera Charis and Themone, for example, sit on the 
upper side of leaves with their wings expanded ; while 
the gorgeously-coloured Erycinas rest with wings erect 
and exposed as in the majority of butterflies. The 
Hesperidae vary in a somewhat similar manner. All 
rest on the upper side of leaves or on the ground, but 
some close their wings, others expand them, and a third 
group keep the upper pair of wings raised while the 



78 TROPICAL NATURE, AND OTHER ESSAYS. 

hind wings are expanded, a habit found in some of our 
European species. Many of the Lycaenidse, especially 
the Theclas, have the curious habit, while sitting with 
their wings erect, of moving the lower pair over each 
other in opposite directions, giving them the strange 
appearance of excentrically revolving discs. 

The great majority of butterflies disappear at night, 
resting concealed amid foliage, or on sticks or trunks, 
or in such places as harmonise with their colours and 
markings ; but the gaily- coloured Heliconidse and 
Danaidae seek no such concealment, but rest at night 
hanging at the ends of slender twigs or upon fully 
exposed leaves. Being uneatable they have no enemies 
and need no concealment. Day-flying moths of bril- 
liant or conspicuous colours are also comparatively 
abundant in the tropical forests. Most magnificent of 
all are the Uranias, whose long-tailed green-and-gold 
powdered wings resemble those of true swallow-tailed 
butterflies. Many Agaristidae of the East are hardly 
inferior in splendour, while hosts of beautiful clear- 
wings and ^Egeriidaa add greatly to the insect beauty 
of the equatorial zone. 

The wonderful examples afforded by tropical butter- 
flies of the phenomena of sexual and local variation, 
of protective modifications, and of mimicry, have been 
fully discussed elsewhere. For the study of the laws 
of variation in all its forms, these beautiful creatures 
are unsurpassed by any class of animals ; both on 
account of their great abundance, and the assiduity with 
which they have been collected and studied. Perhaps 
no group exhibits the distinctions of species and genera 
with such precision and distinctness, due, as Mr. Bates 



IMPORTANCE OF BUTTERFLIES. 79 

lias well observed, to the fact that all the superficial 
signs of change in the organization are exaggerated, 
by their affecting the size, shape, and colour, of the 
wings, and the distribution of the ribs or veins which 
form their framework. The minute scales or feathers 
with which the wings are clothed are coloured in regular 
patterns, which vary in accordance with the slightest 
change in the conditions to which the species are ex- 
posed. These scales are sometimes absent in spots or 
patches, and sometimes over the greater part of the 
wings, which then become transparent, relieved only 
by the dark veins and by delicate shades or small spots 
of vivid colour, producing a special form of delicate 
beauty characteristic of many South American butter- 
flies. The following remark by Mr. Bates will fitly 
conclude our sketch of these lovely insects : " It may 
be said, therefore, that on these expanded membranes 
Nature writes, as on a tablet, the story of the modifica- 
tions of species, so truly do all the changes of the 
organization register themselves , thereon. And as the 
laws of Nature must be the same for all beings, the 
conclusions furnished by this group of insects must be 
applicable to the whole organic world ; therefore the 
study of butterflies creatures selected as the types 
of airiness and frivolity instead of being despised, will 
some day be valued as one of the most important 
branches of biological science." 

Next after the butterflies in importance, as giving an 
air of life and interest to tropical nature, we must place 
the birds ; but to avoid unnecessary passage, to and fro, 
among unrelated groups, it will be best to follow on 

1 Bates, The Naturalist on the Amazon*, 2nd edit. p. 413. 



80 TROPICAL NATURE, AND OTHER ESSAYS. 

with a sketch of such other groups of insects as from 
their numbers, variety, habits, or other important features, 
attract the attention of the traveller from colder 
climates. We begin then with a group, which owing to 
their small size and obscure colours would attract little 
attention, but which nevertheless, by the universality of 
their presence, their curious habits, and the annoyance 
they often cause to man, are sure to force themselves 
upon the attention of every one who visits the tropics. 

Ants, Wasps, and Bees. The hymenopterous insects 
of the tropics are, next to the butterflies, those which 
come most prominently before the traveller, as they love 
the sunshine, frequent gardens, houses, and roadways as 
well as the forest shades, never seek concealment, and 
are many of them remarkable for their size or form, or 
are adorned with beautiful colours and conspicuous 
markings. Although ants are, perhaps, on the whole 
the smallest and the least attractive in appearance of all 
tropical insects, yet, owing to their being excessively 
abundant and almost omnipresent, as well as on account 
of their curious habits and the necessity of being ever 
on the watch against their destructive powers, they 
deserve our first notice. 

Ants are found everywhere. They abound in houses, 
some living underground, others in the thatched roof on 
the under surface of which they make their nests, while 
covered ways of earth are often constructed upon the 
posts and doors. In the forests they live on the ground, 
under leaves, on the branches of trees, or under rotten 
bark ; while others actually dwell in living plants, which 
seem to be specially modified so as to accommodate them. 
Some sting severely, others only bite ; some are quite 



ANTS. 81 

harmless, others exceedingly destructive. The number 
of different kinds is very great. In India and the 
Malay Archipelago nearly 500 different species have been 
found, and other tropical countries are no doubt equally 
rich. I will first give some account of the various 
species observed in the Malay Islands, and afterwards 
describe some of the more interesting South American 
groups, which have been so carefully observed by Mr. 
Bates on the Amazon and by Mr. Belt in Nicaragua. 

Among the very commonest ants in all parts of the 
world are the species of the family Formicidse, which do 
not sting, and are most of them quite harmless. Some 
make delicate papery nests, others live under stones or 
among grass. Several of them accompany Aphides to 
feed upon the sweet secretions from their bodies. They 
vary in size from the large Formica gigas, more than an 
inch long, to minute species so small as to be hardly 
visible. Those of the genus Polyrachis, which are 
plentiful in all Eastern forests, are remarkable for the 
extraordinary hooks and spines with which their bodies 
are armed, and they are also in many cases beautifully 
sculptured or furrowed. They are not numerous indi- 
vidually, and are almost all arboreal, crawling about 
bark and foliage. One species has processes on its 
back just like fish-hooks, others are armed with long, 
straight spines. They generally form papery nests on 
leaves, and when disturbed they rush out and strike 
their bodies against the nest so as to produce a loud 
rattling noise ; but the nest of every species differs from 
those of all others either in size, shape, or position. As 
they all live in rather small communities in exposed 
situations, are not very active, and are rather large and 

G 



82 TROPICAL NATURE, AND OTHER ESSAYS. 

conspicuous, they must be very much exposed to the 
attacks of insectivorous birds and other creatures ; and, 
having no sting or powerful jaws with which to defend 
themselves, they would be liable to extermination with- 
out some special protection. This protection they no 
doubt obtain by their hard smooth bodies, and by the 
curious hooks, spines, points and bristles with which 
they are armed, which must render them unpalatable 
morsels, very liable to stick in the jaws or throats of 
their captors. 

A curious and very common species in the Malay 
Islands is the green ant (CEcophylla smaragdina), a 
rather large, long-legged, active, and intelligent-looking 
creature, which lives in large nests formed by glueing 
together the edges of leaves, especially of Zingiberaceous 
plants. When the nest is touched a number of the ants 
rush out, apparently in a great rage, stand erect, and 
make a loud rattling noise by tapping against the leaves. 
This no doubt frightens away many enemies, and is 
their only protection ; for though they attempt to bite, 
their jaws are blunt and feeble, and they do not cause 
any pain. 

Coming now to the stinging groups, we have first a 
number of solitary ants of the great genus Odontomachus, 
which are seen wandering about the forest, and are con- 
spicuous by their enormously long and slender hooked 
jaws. These are not powerful, but serve admirably to 
hold on by while they sting, which they do pretty 
severely. The Poneridse are another group of large- 
sized ants which sting acutely. They are very varied in 
species but are not abundant individually. The Ponera 
clavata of Guiana, is one of the worst stinging ants 



ANTS. 83 

known. It is a large species frequenting the forests on 
the ground, and is much dreaded by the natives, as its 
sting produces intense pain and illness. I was myself 
stung by this or an allied species when walking barefoot 
in the forest on the Upper Rio Negro. It caused such 
pain and swelling of the leg that I had some difficulty 
in reaching home, and was confined to my room for two 
days. Sir Robert Schomburgh suffered more ; for he 
fainted with the pain, and had an attack of fever in 
consequence. 

We now come to the Myrmecidse, which may be called 
the destroying ants from their immense abundance and 
destructive propensities. Many of them sting most 
acutely, causing a pain like that of a sudden burn, 
whence they are often called " fire-ants." They often 
swarm in houses and devour everything eatable. Isola- 
tion by water is the only security, and even this does 
not always succeed, as a little dust on the surface will 
enable the smaller species to get across. Oil is, however, 
an effectual protection, and after many losses of valuable 
insect specimens, for which ants have a special affection, 
I always used it. One species of this group, a small 
black Crematogaster, took possession of my house in 
New Guinea, building nests in the roof and making 
covered ways down the posts and across the floor. They 
also occupied the setting boards I used for pinning out 
my butterflies, filling up the grooves with cells and 
storing them with small spiders. They were in constant 
motion, running over my table, in my bed, and all over 
my body. Luckily, they were diurnal, so that on 
sweeping out my bed at night I could get on pretty well ; 
but during the day I could always feel some of them 

G 2 



84 TROPICAL NATURE, AND OTHER ESSAYS. 

running over my body, and every now and then one 
would give me a sting so sharp as to make me jump and 
search instantly for the offender, who was usually found 
holding on tight with his jaws, and thrusting in his sting 
with all his might. Another genus, Pheidole, consists 
of forest ants, living under rotten bark or in the ground, 
and very voracious. They are brown or blackish, and are 
remarkable for their great variety of size and form in the 
same species, the largest having enormous heads many 
times larger than their bodies, and being at least a 
hundred times as bulky as the smallest individuals. 
These great-headed ants are very sluggish and incapable 
of keeping up with the more active small workers, 
which often surround and drag them along as if they 
were wounded soldiers. It is difficult to see what use 
they can be in the colony, unless, as Mr. Bates suggests, 
they are mere baits to be attacked by insect-eating birds, 
and thus save their more useful companions. These ants 
devour grubs, white ants, and other soft and helpless 
insects, and seem to take the place of the foraging ants 
of America and driver-ants of Africa, though they are 
far less numerous and less destructive. An allied genus, 
Solenopsis, consists of red ants, which, in the Moluccas, 
frequent houses, and are a most terrible pest. They form 
colonies underground, and work their way up through 
the floors, devouring everything eatable. Their sting is 
excessively painful, and some of the species are hence 
called fire-ants. When a house is infested by them, all 
the tables and boxes must be supported on blocks of 
wood or stone placed in dishes of water, as even clothes 
not newly washed are attractive to them ; and woe to the 
poor fellow who puts on garments in the folds of which 



ANTS. 85 

a. dozen of these ants are lodged. It is very difficult to 
preserve bird skins or other specimens of natural history 
where these ants abound, as they gnaw away the skin 
round the eyes and the base of the bill ; and if a 
specimen is laid down for even half an hour in an un- 
protected place it will be ruined. I remember once 
entering a native house to rest and eat my lunch ; and 
having a large tin collecting box full of rare butterflies 
and other insects, I laid it down on the bench by my 
side. On leaving the house I noticed some ants on it, 
and on opening the box found only a mass of detached 
wings and bodies, the latter in process of being devoured 
by hundreds of fire-ants. 

The celebrated Saiiba ant of America (CEcodoma 
cephalotes) is allied to the preceding, but is even more 
destructive, though it seems to confine itself to vegetable 
products. It forms extensive underground galleries, and 
the earth brought up is deposited on the surface, forming 
huge mounds sometimes thirty or forty yards in circum- 
ference, and from one to three feet high. On first seeing 
these vast deposits of red or yellow earth in the woods 
near Para, it was hardly possible to believe they were 
not the work of man, or at least of some burrowing 
animal. In these underground caves the ants store 
up large quantities of leaves, which they obtain from 
living trees. They gnaw out circular pieces and carry 
them away along regular paths a few inches wide, form- 
ing a stream of apparently animated leaves. The great 
extent of the subterranean workings of these ants is no 
doubt due in part to their permanence in one spot, so 
that when portions of the galleries fall in or are other- 
wise rendered useless, they are extended in another 



86 TROPICAL NATURE, AND OTHER ESSAYS. 

direction. When in the island of Marajo, near Para, I 
noticed a path along which a stream of Salibas were 
carrying leaves from a neighbouring thicket ; and a 
relation of the proprietor assured me that he had known 
that identical path to be in constant use by the ants for 
tw r enty years. Thus we can account for the fact mentioned 
by Mr. Bates, that the underground galleries were traced 
by smoke for a distance of seventy yards in the Botanic 
Gardens at Para ; and for the still more extraordinary 
fact related by the Rev. Hamlet Clark, that an allied 
species in Rio de Janeiro has excavated a tunnel under 
the bed of the river Parahyba, where it is about a quarter 
of a mile wide ! These ants seem to prefer introduced 
to native trees ; and young plantations of orange, coffee, 
or mango trees are sometimes destroyed by them, so 
that where they abound cultivation of any kind becomes 
almost impossible. Mr. Belt ingeniously accounts for 
this preference, by supposing that for ages there has 
been a kind of struggle going on between the trees and 
the ants ; those varieties of trees which were in any way 
distasteful or unsuitable escaping destruction, while the 
ants were becoming slowly adapted to attack new trees. 
Thus in time the great majority of native trees have 
acquired some protection against the ants, while foreign 
trees, not having been so modified, are more likely to be 
suitable for their purposes. Mr. Belt carried on war 
against them for four years to protect his garden in 
Nicaragua, and found that carbolic acid and corrosive 
sublimate were most effectual in destroying or driving 
them away. 

The use to which the ants put the immense quantities 
of leaves they carry away has been a great puzzle, and 



ANTS. 87 

is, perhaps, not yet quite understood. Mr. Bates found 
that the Amazon species used them to thatch the domes 
of earth covering the entrances to their subterranean 
galleries, the pieces of leaf being carefully covered and 
kept in position by a thin layer of grains of earth. In 
Nicaragua Mr. Belt found the underground cells full of 
a brown flocculent matter, which he considers to be the 
gnawed leaves connected by a delicate fungus which 
ramifies through the mass and which serves as food for 
the larvae ; and he believes that the leaves are really 
gathered as manure-heaps to favour the growth of this 
fungus ! 

When they enter houses, which they often do at 
night, the Satibas are very destructive. Once, when 
travelling on the Rio Negro, I had bought about a peck 
of rice, which was tied up in a large cotton handkerchief 
and placed on a bench in a native house where we were 
spending the night. The next morning we found about 
half the rice on the floor, the remainder having been 
carried away by the ants ; and the empty handkerchief 
was still on the bench, but with hundreds of neat cuts in 
it reducing it to a kind of sieve. 1 

The foraging ants of the genus Eciton are another 
remarkable group, especially abundant in the equatorial 
forests of America. They are true hunters, and seem 
to be continually roaming about the forests in great 
bands in search of insect prey. They especially devour 
maggots, caterpillars, white ants, cockroaches, and other 
soft insects ; and their bands are always accompanied by 



1 For a full and most interesting description of the habits and instincts of 
this ant, see Bates' Naturalist on the Amazons, 2nd edit. pp. 11-18; and 
Belt's Naturalist in Nicaragua, pp. 71-84. 



88 TROPICAL NATURE, AND OTHER ESSAYS. 

flocks of insectivorous birds who prey upon the winged 
insects that are continually trying to escape from the 
ants. They even attack wasps' nests, which they cut to 
pieces and then drag out the larvae. They bite and sting 
severely, and the traveller who accidentally steps into a 
horde of them will soon be overrun, and must make his 
escape as quickly as possible. They do not confine 
themselves to the ground, but swarm up bushes and low 
trees, hunting every branch, and clearing them of all 
insect life. Sometimes a band will enter a house, like 
the driver ants in Africa, and clear it of cockroaches, 
spiders, centipedes, and other insects. They seem to 
have no permanent abode and to be ever wandering 
about in search of prey, but they make temporary habi- 
tations in hollow trees or other suitable places. 

Perhaps the most extraordinary of all ants are the 
blind species of Eciton discovered by Mr. Bates, which 
construct a covered way or tunnel as they march along. 
On coming near a rotten log, or any other favourable 
hunting ground, they pour into all its crevices in search 
of booty, their covered way serving as a protection to 
retire to in case of danger. These creatures, of which 
two species are known, are absolutely without eyes ; and 
it seems almost impossible to imagine that the loss of 
so important a sense-organ can be otherwise than in- 
jurious to them. Yet on the theory of natural selection 
the successive variations by which the eyes were reduced 
and ultimately lost must all have been useful. It ia 
true they do manage to exist without eyes ; but that is 
probably because, as sight became more and more imper- 
fect, new instincts or new protective modifications were 
developed to supply its place, and this does not in any 



ANTS AND VEGETATION. 89 

way account for so wide-spread and invaluable a sense 
having become permanently lost, in creatures which still 
roam about and hunt for prey very much as do their 
fellows who can see. 

Special Relations between Ants and Vegetation. 
Attention has recently been called to the very remarkable 
relations existing between some trees and shrubs and 
the ants which dwell upon them. In the Malay Islands 
are several curious shrubs belonging to the Cinchonaceae, 
which grow parasitically on other trees, and whose 
swollen stems are veritable ants' nests. When very 
young the stems are like small, irregular prickly tubers, 
in the hollows of which ants establish themselves ; and 
these in time grow into irregular masses the size of 
large gourds, completely honeycombed with the cells of 
ants. In America there are some analagous cases 
occurring in several families of plants, one of the most 
remarkable being that of certain Melastomas which have 
a kind of pouch formed by an enlargement of the petiole 
of the leaf, and which is inhabited by a colony of small 
ants. The hollow stems of the Cecropias (curious trees 
with pale bark and large palmate leaves which are 
white beneath) are always tenanted by ants, which make 
small entrance holes through the bark ; but here there 
seems no special adaptation to the wants of the insect. 
In a species of Acacia observed by Mr. Belt, the thorns 
are immensely large and hollow, and are always tenanted 
by ants. When young these thorns are soft and full of 
a sweetish pulpy substance, so that when the ants first 
take possession they find a store of food in their house. 
Afterwards they find a special provision of honey-glands 
on the leaf-stalks, and also small yellow fruit-like bodies 



90 TROPICAL NATURE, AND OTHER ESSAYS. 

which are eaten by the ants ; and this supply of food 
permanently attaches them to the plant. Mr. Belt 
believes, after much careful observation, that these ants 
protect the plant they live on from leaf-eating insects, 
especially from the destructive Saiiba ants, that they 
are in fact a standing army kept for the protection of 
the plant ! This view is supported by the fact that 
other plants Passion-flowers, for example have honey- 
secreting glands on the young leaves and on the sepals 
of the flower-buds which constantly attract a small 
black ant. If this view is correct, we see that the need 
of escaping from the destructive attacks of the leaf- 
cutting ants has led to strange modifications in many 
plants. Those in which the foliage was especially 
attractive to these enemies were soon weeded out unless 
variations occurred which tended to preserve them. 
Hence the curious phenomenon of insects specially 
attracted to certain plants to protect them from other 
insects ; and the existence of the destructive leaf-cutting 
ant in America will thus explain why these specially 
modified plants are so much more abundant there than 
in the Old World, where no ants with equally destructive 
habits appear to exist. 

Wasps and Bees. These insects are excessively 
numerous in the tropics, and, from their large size, their 
brilliant colours, and their great activity, they are sure 
to attract attention. Handsomest of all, perhaps, are 
the Scoliadae, whose large and rather broad hairy bodies, 
often two inches long, are richly banded with yellow or 
orange. The Pompilidse comprise an immense number 
of large and handsome insects, with rich blue-black bodies 
and wings and exceedingly long legs. They may often 



WASPS AND BEES. 91 

be seen in the forests dragging along large spiders, 
beetles, or other insects they have captured. Some of 
the smaller species enter houses and build earthen cells 
which they store with small green spiders rendered 
torpid by stinging, to feed the larvae. The Eumenidae 
are beautiful wasps with very long pedunculated bodies, 
which build papery cones covering a few cells in which 
the eggs are deposited. Among the bees the Xylocopas, 
or wood-boring bees, are remarkable. They resemble 
large humble-bees, but have broad, flat, shining bodies, 
either black or banded with blue ; and they often bore 
large cylindrical holes in the posts of houses. True 
honey-bees are chiefly remarkable in the East for then- 
large semi-circular combs suspended from the branches 
of the loftiest trees without any covering. From these 
exposed nests large quantities of wax and honey are 
obtained, while the larvae afford a rich feast to the natives 
of Borneo, Timor, and other islands where bees abound. 
They are very pugnacious, and, when disturbed will 
follow the intruders for miles, stinging severely. 

Ortlioptera and other Insects. Next to the butterflies 
and ants, the insects that are most likely to attract the 
attention of the stranger in the tropics are the various 
forms of Mantidae and Phasmidae, some of which are 
remarkable for their strange attitudes and bright colours ; 
while others are among the most singular of known 
insects, owing to their resemblance to sticks and leaves. 
The Mantidae usually called "praying insects," from 
their habit of sitting with their long fore-feet held up as 
if in prayer are really tigers among insects, lying in 
wait for their prey, which they seize with their powerful 
serrated fore-feet. They are usually so coloured as to 



92 TROPICAL NATURE, AND OTHER ESSAYS. 

resemble the foliage among which they live, and as they 
sit quite motionless, they are not easily perceived. 

The Phasmidae are perfectly inoffensive leaf-eating in- 
sects of very varied forms ; some being broad and leaf-like, 
while others are long and cylindrical so as to resemble 
sticks, whence they are often called walking-stick insects. 
The imitative resemblance of some of these insects to the 
plants on which they live is marvellous. The true leaf- 
insects of the East, forming the genus Phyllium, are the 
size of a moderate leaf, which their large wing-covers 
and the dilated margins of the head, thorax and legs 
cause them exactly to resemble. The veining of the 
wings, and their green tint, exactly corresponds to that of 
the leaves of their food-plant ; and as they rest motion- 
less during the day, only feeding at night, they the more 
easily escape detection. In Java they are often kept 
alive on a branch of the guava tree ; and it is a common 
thing for a stranger, when asked to look at this curious 
insect, to inquire where it is, and on being told that it is 
close under his eyes, to maintain that there is no insect 
at all, but only a branch with green leaves. 

The larger wingless stick-insects are often eight inches 
to a foot long. They are abundant in the Moluccas ; 
hanging on the shrubs that line the forest-paths ; and 
they resemble sticks so exactly, in colour, in the small 
rugosities of the bark, in the knots and small branches, 
imitated by the joints of the legs, which are either pressed 
close to the body, or stuck out at random, that it is 
absolutely impossible, by the eye alone, to distinguish the 
real dead twigs which fall down from the trees overhead 
from the living insects. The writer has often looked at 
them in doubt, and has been obliged to use the sense of 



LEAF AND STICK INSECTS. 93 

touch to determine the point. Some are small and 
slender like the most delicate twigs ; others again have 
wings ; and it is curious that these wings are often beauti- 
fully coloured, generally bright pink, sometimes yellow, 
and sometimes finely banded with black ; but when at 
rest these wings fold up so as to be completely concealed 
under the narrow wing-covers, and the whole insect is then 
green or brown, and almost invisible among the twigs or 
foliage. To increase the resemblance to vegetation, some 
of these Phasmas have small green processes in various 
parts of their bodies looking exactly like moss. These 
inhabit damp forests both in the Malay islands and in 
America, and they are so marvellously like moss-grown 
twigs that the closest examination is needed to satisfy 
oneself that it is really a living insect we are looking at. 

Many of the locusts are equally well- disguised, some 
resembling green leaves, others those that are brown and 
dead ; and the latter often have small transparent spots on 
the wings, looking like holes eaten through them. That 
these disguises deceive their natural enemies is certain, 
for otherwise the Phasmidse would soon be exterminated. 
They are large and sluggish, and very soft and succulent; 
they have no means of defence or of flight, and they are 
eagerly devoured by numbers of birds, especially by the 
numerous cuckoo tribe, whose stomachs are often full of 
them ; yet numbers of them escape destruction, and this 
can only be due to their vegetable disguises. Mr. Belt 
records a curious instance of the actual operation of 
this kind of defence in a leaf-like locust, which 
remained perfectly quiescent in the midst of a host of 
insectivorous ants, which ran over it without finding out 

o 

that it was an insect and not a leaf! It might have 



94 TROPICAL NATURE, AND OTHER ESSAYS. 

flown away from them, but it would then instantly have 
fallen a prey to the numerous birds which always accom- 
pany these roaming hordes of ants to feed upon the 
insects that endeavour to escape. Far more conspicuous 
than any of these imitative species are the large locusts, 
with rich crimson or blue-and-black spotted wings. Some 
of these are nearly a foot in expanse of wings ; they fly 
by day, and their strong spiny legs probably serve as a 
protection against all the smaller birds. They cannot be 
said to be common ; but when met with they fully satisfy 
our notions as to the large size and gorgeous colours of 
tropical insects. 

Beetles. Considering the enormous numbers and 
endless variety of the beetle tribe that are known to 
inhabit the tropics, they form by no means so prominent 
a feature in the animal life of the equatorial zone as we 
might expect. Almost every entomologist is at first 
disappointed with them. He finds that they have to be 
searched for almost as much as at home, while those of 
large size (except one or two very common species) are 
rarely met with. The groups which most attract atten- 
tion from their size and beauty, are the Buprestidae and 
the Longicorns. The former are usually smooth insects 
of an elongate ovate form, with very short legs and 
antennse, and adorned with the most glowing metallic 
tints. They abound on fallen tree-trunks and on foliage, 
in the hottest sunshine, and are among the most brilliant 
ornaments of the tropical forests. Some parts of the 
temperate zone, especially Australia and Chili, abound 
in Buprestidae which are equally beautiful ; but the 
largest species are only found within the tropics, those of 
the Malay islands being the largest of all. 



BEETLES. 95 

The Longicorns are elegantly shaped beetles, usually 
with long antennae and legs, varied in form and structure 
in an endless variety of ways, and adorned with equally 
varied colours, spots and markings. Some are large and 
massive insects three or four inches long, while others 
are no bigger than our smaller ants. The majority have 
sober colours, but often delicately marbled, veined, or 
spotted ; while others are red, or blue, or yellow, or 
adorned with the richest metallic tints. Their antennae 
are sometimes excessively long and graceful, often 
adorned with tufts of hair, and sometimes pectinated. 
They especially abound where timber trees have been 
recently felled in the primeval forests ; and while 
extensive clearings are in progress their variety seems 
endless. In such a locality in the island of Borneo, 
nearly 300 different species were found during one 
dry season, while the number obtained during eight 
years' collecting in the whole Malay Archipelago was 
about a thousand species. 

Among the beetles that always attract attention in 
the tropics are the large, horned, Copridae and Dynastidae, 
corresponding to our dung-beetles. Some of these are 
of great size, and they are occasionally very abundant. 
The immense horn-like protuberances on the head and 
thorax of the males in some of the species are very 
extraordinary, and, combined with their polished or 
rugose metallic colours, render them perhaps the most 
conspicuous of all the beetle tribe. The weevils and 
their allies are also very interesting, from their immense 
numbers, endless variety, and the extreme beauty of 
many of the species. The Anthribidae, which are 
especially abundant in the Malay Archipelago, rival the 



96 TROPICAL NATURE, AND OTHER ESSAYS. 

Longicorns in the immense length of their elegant 
antennae ; while the diamond beetles of Brazil, the 
Eupholi of the Papuan islands, and the Pachyrhynchi of 
the Philippines, are veritable living jewels. 

Where a large extent of virgin forest is cut down in the 
early part of the dry season, and some hot sunny weather 
follows, the abundance and variety of beetles attracted by 
the bark and foliage in various stages of drying is amazing. 
The air is filled with the hum of their wings. Golden and 
green Buprestidae are flying about in every direction, and 
settling on the bark in full sunshine. Green and spotted 
rose-chafers hum along near the ground ; long-horned 
Anthribidae are disturbed at every step ; elegant little 
Longicorns circle about the drying foliage, while larger 
species fly slowly from branch to branch. Every fallen 
trunk is full of life. Strange mottled, and spotted, and 
rugose Longicorns, endless Curculios, queer-shaped 
Brenthidse, velvety brown or steel-blue Cleridae, brown 
or yellow or whitish click beetles, (Elaters), and 
brilliant metallic Carabidae. Close by, in the adjacent 
forest, a whole host of new forms are found. Elegant 
tiger-beetles, leaf-hunting Carabidae, musk-beetles of 
many sorts, scarlet Telephori, and countless Chrysomelas 
Hispas, Coccinellas, with strange Heteromera, and many 
curious species which haunt fungi, rotten bark or decay- 
ing leaves. With such variety and beauty the most 
ardent entomologist must be fully satisfied ; and when, 
every now and then, some of the giants of the tropics 
fall in his way grand Prionidae or Lamiidae several 
inches long, a massive golden Buprestis, or a monster 
horned Dynastes he feels that his most exalted notions 
of the insect-life, of the tropics are at length realized. 



SPIDERS AND SCORPIONS. 97 

Wingless Insects. Passing on to other orders of 
insects, the hemiptera, dragon-flies, and true flies hardly 
call for special remark. Among them are to be found a 
fair proportion of large and handsome species, but they 
require much searching after in their special haunts, and 
seldom attract so much attention as the groups of insects 
already referred to. More prominent are the wingless 
tribes, such as spiders, scorpions, and centipedes. The 
wanderer in the forests often finds the path closed by 
large webs almost as strong as silk, inhabited by gorgeous 
spiders with bodies nearly two inches long and legs 
expanding six inches. Others are remarkable for their 
hard flat bodies, terminating in horned processes which 
are sometimes long, slender, and curved like a pair of 
miniature cow's horns. Hairy terrestrial species of 
large size are often met with, the largest belonging to 
the South American genus Mygale, which sometimes 
actually kill birds, a fact which had been stated by 
Madame Merian and others, but was discredited till Mr. 
Bates succeeded in catching one in the act. The small 
jumping spiders are also noticeable from their immense 
numbers, variety, and beauty. They frequent foliage 
and flowers, running about actively in pursuit of small 
insects; and many of them are so exquisitely coloured 
as to resemble jewels rather than spiders. Scorpions 
and centipedes make their presence known to every 
traveller. In the forests of the Malay islands are huge 
scorpions of a greenish colour and eight or ten inches 
long ; while in huts and houses smaller species lurk under 
boxes and boards, or secrete themselves in almost every 
article not daily examined. Centipedes of immense size 
and deadly venom harbour in the thatch of houses and 

H 



98 TROPICAL NATURE, AND OTHER ESSAYS. 

canoes, and will even ensconce themselves under pillows 
and in beds, rendering a thorough examination necessary 
before retiring to rest. Yet with moderate precautions 
there is little danger from these disgusting insects, as 
may be judged by the fact that during twelve years 
wanderings in American and Malayan forests the author 
was never once bitten or stung by them. 

General Observations on Tropical Insects. The 
characteristics of tropical insects that will most attract 
the ordinary traveller, are, their great numbers, and the 
large size and brilliant colours often met with. But a 
more extended observation leads to the conclusion that 
the average of size is probably no greater in tropical 
than in temperate zones, and that, to make up for a 
certain proportion of very large, there is a corresponding 
increase in the numbers of very small species. The 
much greater size reached by many tropical insects is no 
doubt due to the fact, that the supply of food is always 
in excess of their demands in the larva state, while 
there is no check from the ever-recurring cold of winter ; 
and they are thus able to acquire the dimensions that 
may be on the whole most advantageous to the race, 
unchecked by the annual or periodical scarcities which in 
less favoured climates would continually threaten their 
extinction. The colours of tropical insects are, probably, 
on the average more brilliant than those of temperate 
countries, and some of the causes which may have led 
to this have been discussed in another part of this 
volume. 1 It is in the tropics that we find most largely 
developed, whole groups of insects which are unpalatable 
to almost all insectivorous creatures, and it is among these 

1 Chapters V. and VI. The Colours of Animals and Plants. 



BIRDS. 99 

that some of the most gorgeous colours prevail. Others 
obtain protection in a variety of ways ; and the 
amount of cover or concealment always afforded by the 
luxuriant tropical vegetation is probably a potent agent 
in permitting a full development of colour. 

Birds. Although the number of brilliantly-coloured 
birds in almost every part of the tropics is very great, 
yet they are by no means conspicuous ; and as a rule 
they can hardly be said to add much to the general 
effect of equatorial scenery. The traveller is almost 
always disappointed at first with the birds, as he is with 
the flowers and the beetles ; and it is only when, gun 
in hand, he spends days in the forest, that he finds out 
how many beautiful living things are concealed by its 
dense foliage and gloomy thickets. A considerable number 
of the handsomest tropical birds belong to family groups 
which are confined to one continent with its adjacent 
islands ; and we shall therefore be obliged to deal for the 
most part with such large divisions as tribes and orders, 
by means of which to define the characteristics of tropical 
bird-life. We find that there are three important 
orders of birds which, though by no means exclusively 
tropical, are yet so largely developed there in proportion, 
to their scarcity in extra-tropical regions, that more 
than any others they serve to give a special character 
to equatorial ornithology. These are the Parrots, the 
Pigeons, and the Picariae, to each of which groups we 
will devote some attention. 

Parrots. The parrots, forming the order Psittaci of 
naturalists, are a remarkable group of fruit-eating birds, 
of such high and peculiar organization that they are 
often considered to stand at the head of the entire class. 

IT 2 



100 TROPICAL NATURE, AND OTHER ESSAYS. 

They are pre-eminently characteristic of the intertropical 
zone, being nowhere absent within its limits (except 
from absolutely desert regions), and they are generally 
so abundant and so conspicuous as to occupy among 
birds the place assigned to butterflies among insects. 
A few species range far into the temperate zones. One 
reaches Carolina in North America, another the Magellan 
Straits in South America ; in Africa they only extend 
a few degrees beyond the southern tropic ; in North- 
Western India they reach 35 North Latitude ; but in the 
Australian region they range farthest towards the pole, 
being found not only in New Zealand, but as far as the 
Macquarie Islands in 54 South, where the climate is very 
cold and boisterous, but sufficiently uniform to supply 
vegetable food throughout the year. There is hardly any 
part of the equatorial zone in which the traveller will 
not soon have his attention called to some members of 
the parrot tribe. In Brazil, the great blue and yellow or 
crimson macaws may be seen every evening wending 
their way homeward in pairs, almost as commonly as 
rooks with us ; while innumerable parrots and parraquets 
attract attention by their harsh cries when disturbed 
from some favourite fruit-tree. In the Moluccas and 
New Guinea, white cockatoos and gorgeous lories in 
crimson and blue, are the very commonest of birds. 

No group of birds perhaps no other group of animals 
exhibits within the same limited number of genera 
and species, so wide a range and such an endless variety 
of colour. As a rule parrots may be termed green birds, 
the majority of the species having this colour as the 
basis of their plumage relieved by caps, gorgets, bands 
and wing-spots of other and brighter hues. Yet this 



PARROTS. 101 

general green tint sometimes changes into light or deep 
blue, as in some macaws; into pure yellow or rich orange, 
as in some of the American macaw-parrots (Conurus) ; 
into purple, grey, or dove-colour, as in some American, 
African, and Indian species ; into the purest crimson, as 
in some of the lories ; into rosy-white and pure white, as 
in the cockatoos ; and into a deep purple, ashy or black, 
as in several Papuan, Australian, and Mascarene species. 
There is in fact hardly a single distinct and definable 
colour that cannot be fairly matched among the 390 
species of known parrots. Their habits, too, are such 
as to bring them prominently before the eye. They 
usually feed in flocks ; they are noisy, and so attract 
attention ; they love gardens, orchards, and open sunn} 
places ; they wander about far in search of food, anc 
towards sunset return homewards in noisy flocks, or in 
constant pairs. Their forms and motions are ofteii 
beautiful and attractive. The immensely long tails of 
the macaws, and the more slender tails of the Indian 
parraquets ; the fine crest of the cockatoos ; the swift 
flight of many of the smaller species, and the graceful 
motions of the little love-birds and allied forms ; to- 
gether with their affectionate natures, aptitude for 
domestication, and powers of mimicry combine to 
render them at once the most conspicuous and the 
most attractive of all the specially tropical forms of 
bird-life. 

The number of species of parrots found in the dif- 
ferent divisions of the tropics is very unequal. Africa 
is by far the poorest ; since along with Madagascar 
and the Mascarene islands, which have many peculiar 
forms, it scarcely numbers two dozen species. Asia, along 



102 TKOPICAL NATURE, AND OTHER ESSAYS. 

with the Malay islands as far as Java and Borneo, is 
also very poor, with about thirty species. Tropical Ame- 
rica is very much richer, possessing about 140 species, 
among which are many of the largest and most beautiful 
forms. But of all parts of the globe the tropical islands 
belonging to the Australian region (from Celebes east- 
ward), together with the tropical parts of Australia, are 
richest in the parrot tribe, possessing about 150 species, 
among which are many of the most remarkable and 
beautiful of the entire group. The whole Australian 
region, whose extreme limits may be defined by Celebes, 
the Marquesas, and the New Zealand group, possesses 
about 200 species of parrots. 

Pigeons. These are such common birds in all tem- 
perate countries, that it may surprise many readers to 
learn that they are nevertheless a characteristic tropical 
group. That such is the case, however, will be evident 
from the fact that only sixteen species are known from 
the whole of the temperate parts of Europe, Asia, and 
North America, while about 330 species inhabit the 
tropics. Again, the great majority of the species are 
found congregated in the equatorial zone, whence they 
diminish gradually toward the limits of the tropics, and 
then suddenly fall off in the temperate zones. Yet 
although they are pre-eminently tropical or even equa- 
torial as a group, they are not, from our present point 
of view, of much importance, because they are so shy 
and so generally inconspicuous that in most parts of the 
tropics an ordinary observer might hardly be a ware of 
their existence. The remark applies especially to 
America and Africa, where they are neither very 
abundant nor peculiar ; but in the Eastern hemisphere, 



PIGEONS. 103 

and especially in the Malay Archipelago and Pacific 
islands, they occur in such profusion and present such 
singular forms and brilliant colours, that they are sure 
to attract attention. Here we find the extensive group 
of fruit-pigeons, which, in their general green colours 
adorned with patches and bands of purple, white, blue, 
or orange, almost rival the parrot tribe ; while the 
golden-green Nicobar pigeon, the great crowned pigeons 
of New Guinea as large as turkeys, and the golden- 
yellow fruit-dove of the Fijis, can hardly be surpassed 
for beauty. 

Pigeons are especially abundant and varied in tropi- 
cal archipelagoes; so that if we take the Malay and 
Pacific islands, the Madagascar group, and the Antilles 
or West Indian islands, we find that they possess 
between them more different kinds of pigeons than all 
the continental tropics combined. Yet further, that 
portion of the Malay Archipelago east of Borneo, 
together with the Pacific islands, is exceptionally rich 
in pigeons ; and the reason seems to be that monkeys 
and all other arboreal mammals that devour eggs are 
entirely absent from this region. Even in South Ame- 
rica pigeons are scarce where monkeys are abundant, 
and vice versd ; so that here we seem to get a glimpse 
of one of the curious interactions of animals on each 
other, by which their distribution, their habits, and even 
their colours may have been influenced ; for the most 
conspicuous pigeons, whether by colour or by their crests, 
are all found in countries where they have the fewest 
enemies. 

Picarice. The extensive and heterogeneous series of 
birds now comprised under this term, include most of the 



104 TROPICAL NATURE, AND OTHER ESSAYS. 

fissirostral and scansorial groups of the older naturalists. 
They may be described as, for the most part, arboreal 
birds, of a low grade of organization, with weak or 
abnormally developed feet, and usually less active than 
the true Passeres or perching birds, of which our 
warblers, finches, and crows may be taken as the types. 
The order Picarise comprises twenty-five families, some 
of which are very extensive. All are either wholly or 
mainly tropical, only two of the families the wood- 
peckers and the kingfishers having a few representa- 
tives which are permanent residents in the temperate 
regions ; while our summer visitor, the cuckoo, is the 
sole example in Northern Europe of one of the most 
abundant and widespread tropical families of birds. 
Only four of the families have a general distribution 
over all the warmer countries of the globe the cuckoos, 
the kingfishers, the swifts, and the goatsuckers ; while 
two others the trogons and the woodpeckers are only 
wanting in the Australian region, ceasing suddenly at 
Borneo and Celebes respectively. 

Cuckoos. Whether we consider their wide range, 
their abundance in genera and species, or the pecu- 
liarities of their organization, the cuckoos may be taken 
as the most typical examples of this extensive order of 
birds ; and there is perhaps no part of the tropics where 
they do not form a prominent feature in the ornithology 
of the country. Their chief food consists of soft insects, 
such as caterpillars, grasshoppers, and the defenceless 
stick- and leaf-insects ; and in search after these they 
frequent the bushes and lower parts of the forest, and 
the more open tree-clad plains. They vary greatly in 
size and appearance, from the small and beautifully 



CUCKOOS, TROGONS, TOUCANS. 105 

metallic golden-cuckoos of Africa, Asia, and Australia, 
no larger than sparrows, to the pheasant-like ground 
cuckoo of Borneo, the Scythrops of the Moluccas which 
almost resembles a hornbill, the Khamphococcyx of 
Celebes with its richly-coloured bill, and the Goliath 
cuckoo of Gilolo with its enormously long and ample 
tail. 

Cuckoos, being invariably weak and defenceless birds, 
conceal themselves as much as possible among foliage 
or herbage ; and as a further protection many of them 
have acquired the coloration of rapacious or com- 
bative birds. In several parts of the world cuckoos 
are coloured exactly like hawks, while some of the 
small Malayan cuckoos closely resemble the pugnacious 
drongo-shrikes. 

Trogons, Barbets, and Toucans. Many of the 
families of Picarise are confined to the tropical forests, 
and are remarkable for their varied and beautiful 
colouring. Such are the trogons of America, Africa, 
and Malaya, whose dense puffy plumage exhibits the 
purest tints of rosy-pink, yellow, and white, set off by 
black heads and a golden-green or rich brown upper 
surface. Of more slender forms, but hardly less brilliant 
in colour, are the jacamars and motmots of America, with 
the bee-eaters and rollers of the East, the latter ex- 
hibiting tints of pale blue or verditor-green, which are 
very unusual. The barbets are rather clumsy fruit-eating 
birds, found in all the great tropical regions except 
that of the Austro-Malay islands ; and they exhibit a 
wonderful variety as well as strange combinations of 
colours. Those of Asia and Malaya are mostly green, 
but adorned about the head and neck with patches of 



106 TROPICAL NATURE, AND OTHER ESSAYS. 

the most vivid reds, blues, and yellows, in endless com- 
binations. The African species are usually black or 
greenish-black, with masses of intense crimson, yellow, 
or white, mixed in various proportions and patterns ; 
while the American species combine both styles of 
colouring, but the tints are usually more delicate, and 
are often more varied and more harmoniously inter- 
blended. In the Messrs. Marshall's fine work 1 all the 
species are described and figured ; and few more in- 
structive examples can be found than are exhibited in 
their beautifully-coloured plates, of the endless ways in 
which the most glaring and inharmonious colours are 
often combined in natural objects with a generally 
pleasing result. 

We will next group together three families which, al- 
though quite distinct, may be said to represent each other 
in their respective countries, the toucans of America, the 
plantain-eaters of Africa, and the hornbills of the East 
all being large and remarkable birds which are sure 
to attract the traveller's attention. The toucans are the 
most beautiful, on account of their large and richly- 
coloured bills, their delicate breast-plumage, and the 
varied bands of colour with which they are often adorned. 
Though feeding chiefly on fruits, they also devour birds' 
eggs and young birds ; and they are remarkable for the 
strange habit of sleeping with the tail laid flat upon 
their backs, in what seems a most unnatural and in- 
convenient position. What can be the use of their 
enormous bills has been a great puzzle to naturalists, 
the only tolerably satisfactory solution yet arrived at 

1 A Monograph of the Capitonidce or Scansorial Barbels, by C. F. T. 
Marshall and G. F. L. Marshall. 1871. 



PLANTAIN-EATERS, HORNBILLS. 107 

being that suggested by Mr. Bates, that it simply 
enables them to reach fruit at the ends of slender twigs 
which, owing to their weight and clumsiness, they would 
otherwise be unable to obtain. At first sight it appears 
very improbable that so large and remarkable an organ 
should have been developed for such a purpose ; but 
we have only to suppose that the original toucans had 
rather large and thick bills, not unlike those of the 
barbets (to which group they are undoubtedly allied), 
and that as they increased in size and required more 
food, only those could obtain a sufficiency whose un- 
usually large beaks enabled them to reach furthest. So 
large and broad a bill as they now possess would not 
be required ; but the development of the bill naturally 
went on as it had begun, and, so that it was light and 
handy, the large size was no disadvantage if length 
was obtained. The plantain-eaters of Africa are less 
remarkable birds, though adorned with rich colours and 
elegant crests. The hornbills, though less beautiful 
than the toucans, are more curious, from the strange 
forms of their huge bills, which are often adorned with 
ridges, knobs, or recurved horns. They are bulky and 
heavy birds, and during flight beat the air with pro- 
digious force, producing a rushing sound very like the 
puff of a locomotive, and which can sometimes be 
heard a mile off. They mostly feed on fruits ; and as 
their very short legs render them even less active than 
the toucans, the same explanation may be given of the 
large size of their bills, although it will not account for 
the curious horns and processes from which they derive 
their distinctive name. The largest hornbills are more 
than four feet long, and their laboured noisy flight and 



108 TROPICAL NATURE, AND OTHER ESSAYS. 

huge bills, as well as their habits of perching on the top 
of bare or isolated trees, render them very conspicuous 
objects. 

The Picarise comprise many other interesting families ; 
as, for example, the puff-birds, the todies, and the hum- 
ming-birds ; but as these are all confined to America we 
can hardly claim them as characteristic of the tropics 
generally. Others, though very abundant in the tropics, 
like the kingfishers and the goatsuckers, are too well 
known in temperate lands to allow of their being con- 
sidered as specially characteristic of the equatorial zone. 
We will therefore pass on to consider what are the more 
general characteristics of the tropical as compared with 
the temperate bird-fauna, especially as exemplified 
among the true perchers or Passeres, which constitute 
about three-fourths of all terrestrial birds. 

Passeres. This great order comprises all our most 
familiar birds, such as the thrushes, warblers, tits, shrikes, 
flycatchers, starlings, crows, wagtails, larks, and finches. 
These families are all more or less abundant in the 
tropics ; but there are a number of other families which 
are almost or quite peculiar to tropical lands and give 
a special character to their bird-life. All the peculiarly 
tropical families are, however, confined to some definite 
portion of the tropics, a number of them being American 
only, others Australian, while others again are common 
to all the warm countries of the Old World ; and it is a 
curious fact that there is no single family of this great 
order of birds that is confined to the entire tropics, or 
that is even especially characteristic of the tropical zone, 
like the cuckoos among the Picariae. The tropical 
families of passerine birds being very numerous, and 



PERCHING BIRDS. 109 

their peculiarities not easily understood by any but 
ornithologists, it will be better to consider the series 
of fifty families of Passeres as one compact group, and 
endeavour to point out what external peculiarities are 
most distinctive of those which inhabit tropical countries. 

Owing to the prevalence of forests and the abundance 
of flowers, fruits, and insects, tropical and especially 
equatorial birds have become largely adapted to these 
kinds of food ; while the seed-eaters, which abound in 
temperate lands where grasses cover much of the sur- 
face, are proportionately scarce. Many of the peculiarly 
tropical families are therefore either true insect-eaters or 
true fruit-eaters, whereas in the temperate zones a mixed 
diet is more general. 

One of the features of tropical birds that will first 
strike the observer, is the prevalence of crests and of 
ornamental plumage in various parts of the body, and 
especially of extremely long or curiously shaped feathers 
in the tails, tail-coverts, or wings of a variety of species. 
As examples we may refer to the red paradise-bird, 
whose middle tail-feathers are like long ribands of 
whalebone ; to the wire-like tail-feathers of the king 
bird-of-paradise of New Guinea, and of the wire-tailed 
manakin of the Amazons ; and to the long waving 
tail-plumes of the whydah finch of West Africa and 
paradise-flycatcher of India ; to the varied and elegant 
crests of the cock-of-the-rock, the king-tyrant, the 
umbrella-bird, and the six-plumed bird-of-paradise ; 
and to the wonderful side-plumes of most of the true 
paradise-birds. In other orders of birds we have such 
remarkable examples as the racquet-tailed kingfishers 
of the Moluccas, and the racquet-tailed parrots of 



110 TROPICAL NATURE, AND OTHER ESSAYS. 

Celebes ; the enormously developed tail-coverts of the 
peacock and the Mexican trogon ; and the excessive 
wing-plumes of the argus-pheasant of Malacca and the 
long-shafted goatsucker of West Africa. 

Still more remarkable are the varied styles of colora- 
tion in the birds of tropical forests, which rarely or never 
appear in those of temperate lands. We have intensely 
lustrous metallic plumage in the jacamars, trogons, 
humming-birds, sun-birds, and paradise-birds ; as well as 
in some starlings, pittas or ground thrushes, and drongo- 
shrikes. Pure green tints occur in parrots, pigeons, 
green bulbuls, greenlets, and in some tanagers, finches, 
chatterers, and pittas. These undoubtedly tend to con- 
cealment ; but we have also the strange phenomenon of 
white forest-birds in the tropics, a colour only found 
elsewhere among the aquatic tribes and in the arctic 
regions. Thus, we have the bell-bird of South America, 
the white pigeons and cockatoos of the East, with a few 
starlings, woodpeckers, kingfishers, and goatsuckers, 
which are either very light- coloured or in great part 
pure white. 

But besides these strange, and new, and beautiful 
forms of bird- life, which we have attempted to indicate 
as characterising the tropical regions, the traveller will 
soon find that there are hosts of dull and dingy birds, 
not one whit different, so far as colour is concerned, from 
the sparrows, warblers, and thrushes of our northern 
climes. He will however, if observant, soon note that 
most of these dull colours are protective ; the groups to 
which they belong frequenting low thickets, or the 
ground, or the trunks of trees. He will find groups of 
birds specially adapted to certain modes of tropical life. 



LIZAKDS. Ill 

Some live on ants upon the ground, others peck minute 
insects from the bark of trees ; one group will devour 
bees and wasps, others prefer caterpillars ; while a host 
of small birds seek for insects in the corollas of flowers. 
The air, the earth, the undergrowth, the tree-trunks, the 
flowers, and the fruits, all support their specially adapted 
tribes of birds. Each species fills a place in nature, 
and can only continue to exist so long as that place 
is open to it ; and each has become what it is in every 
detail of form, size, structure, and even of colour, 
because it has inherited through countless ancestral 
forms all those variations which have best adapted it 
among its fellows to fill that place, and to leave behind 
it equally well adapted successors. 

Reptiles and Amphibia. Next to the birds, or 
perhaps to the less observant eye even before them, the 
abundance and variety of reptiles form the chief charac- 
teristic of tropical nature ; and the three groups 
Lizards, Snakes, and Frogs, comprise all that, from our 
present point of view, need be noticed. 

Lizards. Lizards are by far the most abundant in 
individuals and the most conspicuous ; and they con- 
stitute one of the first attractions to the visitor from 
colder lands. They literally swarm everywhere. In 
cities they may be seen runniDg along walls and up 
palings ; sunning themselves on logs of wood, or creeping 
up to the eaves of cottages. In every garden, road, or 
dry sandy path, they scamper aside as you walk along. 
They crawl up trees, keeping at the further side of the 
trunk and watching the passer-by with the caution of 
a squirrel. Some will walk up smooth walls with the 
greatest ease ; while in houses the various kinds of Geckos 



112 TROPICAL NATURE, AND OTHER ESSAYS. 

cling to the ceilings, along which they run back down- 
wards in pursuit of flies, holding on by means of their 
dilated toes with suctorial discs ; though sometimes, 
losing hold, they fall upon the table or on the upturned 
face of the visitor. In the forests large, flat, and marbled 
Geckos cling to the smooth trunks ; small and active 
lizards rest on the foliage ; while occasionally the larger 
kinds, three or four feet long, rustle heavily as they 
move among the fallen leaves. 

Their colours vary much, but are usually in harmony 
with their surroundings and habits. Those that climb 
about walls and rocks are stone-coloured, and sometimes 
nearly black ; the house lizards are grey or pale-ashy, 
and are hardly visible on a palm-leaf thatch, or even on 
a white-washed ceiling. In the forest they are often 
mottled with ashy-green, like lichen- grown bark. Most 
of the ground-lizards are yellowish or brown ; but some 
are of beautiful green colours, with very long and slender 
tails. These are among the most active and lively ; and 
instead of crawling on their bellies like many lizards, 
they stand well upon their feet and scamper about with 
the agility and vivacity of kittens. Their tails are very 
brittle ; a slight blow causing them to snap off, when 
a new one grows, which is, however, not so perfectly 
formed and completely scaled as the original member. 
It is not uncommon, when a tail is half broken, for a 
new one to grow out of the wound, producing the curious 
phenomenon of a forked tail. There are about 1,300 
different kinds of lizards known, the great majority of 
which inhabit the tropics, and they probably increase 
in numbers towards the equator. A rich vegetation and a 
due proportion of moisture and sunshine seem favourable 



LIZARDS. 113 

to them, as shown by their great abundance and their 
varied kinds at Para and in the Aru Islands places 
which are nearly the antipodes of each other, but which 
both enjoy the fine equatorial climate in perfection, and 
are alike pre-eminent in the variety and beauty of their 
insect life. 

Three peculiar forms of lizard may be- mentioned 
as specially characteristic of the American, African, and 
Asiatic tropical zones respectively. The iguanas of 
South America are large arboreal herbivorous lizards 
of a beautiful green colour, which renders them almost 
invisible when resting quietly among foliage. They 
are distinguished by the serrated back, deep dew-lap, 
and enormously long tail, and are one of the few kinds 
of lizards whose flesh is considered a delicacy. The 
chameleons of Africa are also arboreal lizards, and they 
have the prehensile tail which is more usually found 
among American animals. They are excessively slow in 
their motions, and are protected by the wonderful power 
of changing their colour so as to assimilate it with that 
of immediately surrounding objects. Like the majority 
of lizards they are insectivorous, but they are said to be 
able to live for months without taking food. The 
dragons or flying lizards of India and the larger Malay 
islands, are perhaps the most> curious and interesting of 
living reptiles, owing to their power of passing through 
the air by means of wing-like membranes, which stretch 
along each side of the body and are expanded by means 
of slender bony processes from the first six false ribs. 
These membranes are folded up close to the body when 
not in use, and are then almost imperceptible ; but when 
open they form a nearly circular web, the upper surface 

I 



114 TROPICAL NATURE, AND OTHER ESSAYS. 

of which is generally zoned with red or yellow in a 
highly ornamental manner. By means of this parachute 
the animal can easily pass from one tree to another for 
a distance of about thirty feet, descending at first, but as 
it approaches its destination rising a little so as to reach 
the tree with its head erect. They are very small, 
being usually not more than two or three inches long 
exclusive of the slender tail ; and when the wings are 
expanded in the sunshine they more resemble some 
strange insect than one of the reptile tribe. 

Snakes. Snakes are, fortunately, not so abundant or so 
obtrusive as lizards, or the tropics would be scarcely 
habitable. At first, indeed, the traveller is disposed to 
wonder that he does not see more of them, but he will 
soon find out that there are plenty ; and, if he is possessed 
by the usual horror or dislike of them, he may think there 
are too many. In the equatorial zone snakes are less 
troublesome than in the drier parts of the tropics, although 
they are probably more numerous and more varied. 
This is because the country is naturally a vast forest, and 
the snakes being all adapted to a forest life do not as a 
rule frequent gardens and come into houses as in India 
and Australia, where they are accustomed to open and 
rocky places. One cannot traverse the forest, however, 
without soon coming upon them. The slender green 
whip-snakes glide among the bushes, and may often be 
touched before they are seen. The ease and rapidity 
with which these snakes pass through bushes, almost 
without disturbing a leaf, is very curious. More 
dangerous are the green vipers, which lie coiled 
motionless upon foliage, where their colour renders it 
difficult to see them. The writer has often come upon 



LARGE SERPENTS. 115 

them while creeping through the jungle after birds or 
insects, and has sometimes only had time to draw back 
when they were within a few inches of his face. It is 
startling in walking along a forest path to see a long 
snake glide away from just where you were going to set 
down your foot ; but it is perhaps even more alarming 
to hear a long-drawn heavy slur-r-r, and just to catch a 
glimpse of a serpent as thick as your leg and an un- 
known number of feet in length, showing that you 
must have passed unheeding within a short distance of 
where it was lying. The smaller pythons are not how- 
ever dangerous, and they often enter houses to catch 
and feed upon the rats, and are rather liked by the 
natives. You will sometimes be told, when sleeping in 
a native house, that there is a large snake in the roof, 
and that you need not be disturbed in case you should 
hear it hunting after its prey. These serpents no doubt 
sometimes grow to an enormous size, but such monsters 
are rare. In Borneo, Mr. St. John states that he 
measured one twenty-six feet long, probably the largest 
ever measured by a European in the East. The great 
water-boa of South America is believed to reach the 
largest size. Mr. Bates measured skins twenty-one feet 
long, but the largest ever met with by a European 
appears to be that described by the botanist, Dr. Gar- 
diner, in his Travels in Brazil. It had devoured a 
horse, and was found dead, entangled in the branches 
of a tree overhanging a river, into which it had been 
carried by a flood. It was nearly forty feet long. These 
creatures are said to seize and devour full-sized cattle 
on the Kio Branco ; and from what is known of their 
habits this is by no means improbable. 

T 2 



116 TROPICAL NATURE, AND OTHER ESSAYS. 

Frogs and Toads. The only Amphibia that often 
meet the traveller's eye in equatorial countries are the 
various kinds of frogs and toads, and especially the 
elegant tree-frogs. When the rainy season begins, and 
dried-up pools and ditches become filled with water, 
there is a strange nightly concert produced by the frogs, 
some of which croak, others bellow, while many have 
clanging, or chirruping, and not unmusical notes. In 
roads and gardens one occasionally meets huge toads six 
or seven inches long ; but the most abundant and most 
interesting of the tribe are those adapted for an arboreal 
life, and hence called tree-frogs. Their toes terminate 
in discs, by means of which they can cling firmly to 
leaves and stems. The majority of them are green or 
brown, and these usually feed at night, sitting quietly 
during the day so as to be almost invisible, owing to 
their colour and their moist shining skins so closely re- 
sembling vegetable surfaces. Many are beautifully marbled 
and spotted, and when sitting on leaves resemble large 
beetles more than frogs, while others are adorned with 
bright and staring colours ; and these, as Mr. Belt has 
discovered, have nauseous secretions which render them 
uneatable, so that they have no need to conceal them- 
selves. Some of these are bright blue, others are 
adorned with yellow stripes, or have a red body with 
blue legs. Of the smaller tree-frogs of the tropics 
there must be hundreds of species still unknown to 
naturalists. 

Mammals Monkeys. The highest class of animals, 
the Mammalia, although sufficiently abundant in all 
equatorial lands, are those which are least seen by the 
traveller. There is, in fact, only one group the 



MONKEYS. 117 

monkeys which are at the same time pre-eminently 
tropical and which make themselves perceived as one of 
the aspects of tropical nature. They are to be met with 
in all the great continents and larger islands, except 
Australia, New Guinea, and Madagascar, though the 
latter island possesses the lower allied form of Lemurs ; 
and they never fail to impress the observer with a sense 
of the exuberant vitality of the tropics. They are pre- 
eminently arboreal in their mode of life, and are 
consequently most abundant and varied where vegeta- 
tion reaches its maximum development. In the East 
we find that maximum in Borneo, and in the West 
African forests ; while in the West the great forest plain 
of the Amazon stands pre-eminent. It is near the equator 
only that the great Anthropoid apes, the gorilla, chim- 
panzee, and orang-utan are found, and they may be met 
with by any persevering explorer of the jungle. The 
gibbons, or long-armed apes, have a wider range in the 
Asiatic continent and in Malaya, and they are more 
abundant both in species and individuals. Their 
plaintive howling notes may often be heard in the 
forests, and they are constantly to be seen sporting at 
the summits of the loftiest trees, swinging suspended 
by their long arms, or bounding from tree to tree with 
incredible agility. They pass through the forest at a 
height of a hundred feet or more, as rapidly as a deer 
will travel along the ground beneath them. Other 
monkeys of various kinds are more abundant and 
usually less shy ; and in places where fire-arms are not 
much used they will approach the houses and gambol in 
the trees undisturbed by the approach of man. The 
most remarkable of the tailed monkeys of the East is 



120 TROPICAL NATURE, AND OTHER ESSAYS. 

obliged to sleep completely muffled up, in order to avoid 
being made seriously ill or even losing their lives. The 
exact manner in which the attack is made is not posi- 
tively known, as the sufferer never feels the wound. The 
present writer was once bitten on the toe, which was 
found bleeding in the morning from a small round hole 
from which the flow of blood was not easily stopped. 
On another occasion, when his feet were carefully covered 
up, he was bitten on the tip of the nose, only awaking 
to find his face streaming with blood. The motion of 
the wings fans the sleeper into a deeper slumber, and 
renders him insensible to the gentle abrasion of the 
skin either by teeth or tongue. This ultimately forms a 
minute hole, the blood flowing from which is sucked or 
lapped up by the hovering vampyre. The largest South 
American bats, having wings from two to two-and-half 
feet in expanse, are fruit-eaters like the Pteropi of the 
East, the true blood-suckers being small or of medium size 
and varying in colour in different localities. They belong 
to the genus Phyllostoma, and have a tongue with horny 
papillae at the end ; and it is probably by means of this 
that they abrade the skin and produce a small round 
wound. This is the account given by Buffon and Azara, 
and there seems now little doubt that it is correct. 

Beyond these two great types the monkeys and the 
bats we look in vain among the varied forms of mam- 
malian life for any that can be said to be distinctive of 
the tropics as compared with the temperate regions. 
Many peculiar groups are tropical, but they are in almost 
every case confined to limited portions of the tropical 
zones, or are rare in species or individuals. Such are 
the lemurs in Africa, Madagascar, and Southern Asia ; the 



SUMMARY ON ANIMAL LIFE. 121 

tapirs of America and Malaya ; the rhinoceroses and 
elephants, of Africa and Asia ; the cavies and the sloths 
of America ; the scaly ant-eaters of Africa and Asia ; 
but none of these are sufficiently numerous to come 
often before the traveller so as to affect his general ideas 
of the aspects of tropical life, and they are, therefore, 
out of place in such a sketch of those aspects as we are 
here attempting to lay before our readers. 

Summary of the Aspects of Animal Life in the 
Tropics. We will now briefly summarize the general 
aspects of animal life as forming an ingredient in the 
scenery and natural phenomena of the equatorial regions. 
Most prominent are the butterflies, owing to their 
numbers, their size, and their brilliant colours ; as well as 
their peculiarities of form, and the slow and majestic 
flight of many of them. In other insects, the large size, 
and frequency of protective colours and markings are 
prominent features ; together with the inexhaustible 
profusion of the ants and other small insects. Among 
birds the parrots stand forth as the pre-eminent tropical 
group, as do the apes and monkeys among mammals ; 
the two groups having striking analogies, in the pre- 
hensile hand and the power of imitation. Of reptiles, 
the two most prominent groups are the lizards and the 
frogs ; the snakes, though equally abundant, being much 
less obtrusive. 

Animal life is, on the whole, far more abundant and 
more varied within the tropics than in any other part of 
the globe, and a great number of peculiar groups are 
found there which never extend into temperate regions. 
Endless eccentricities of form, and extreme richness of 



122 TROPICAL NATURE, AND OTHER ESSAYS. 

colour are its most prominent features ; and these are 
manifested in the highest degree in those equatorial 
lands where the vegetation acquires its greatest beauty 
and its fullest development. The causes of these 
essentially tropical features are not to be found in the 
comparatively simple influence of solar light and heat, 
but rather in the uniformity and permanence with which 
these and all other terrestrial conditions have acted ; 
neither varying prejudicially throughout the year, nor 
having undergone any important change for countless 
past ages. While successive glacial periods have devas- 
tated the temperate zones, and destroyed most of the 
larger and more specialized forms which during more 
favourable epochs had been developed, the equatorial 
lands must always have remained thronged with life ; 
and have been unintermittingly subject to those complex 
influences of organism upon organism, which seem the 
main agents in developing the greatest variety of forms 
and filling up every vacant place in nature. A constant 
struggle against the vicissitudes and recurring severities 
of climate must always have restricted the range of 
effective animal variation in the temperate and frigid 
zones, and have checked all such developments of form 
and colour as were in the least degree injurious in 
themselves, or which co-existed with any constitutional 
incapacity to resist great changes of temperature or other 
unfavourable conditions. Such disadvantages were not 
experienced in the equatorial zone. The struggle for 
existence as against the forces of nature was there always 
less severe, food was there more abundant and more 
regularly supplied, shelter and concealment were at all 
times more easily obtained ; and almost the only physical 



DEVELOPMENT OF TROPICAL LIFE. 123 

changes experienced, being dependent on cosmical or 
geological changes, were so slow, that variation and 
natural selection were always able to keep the teeming 
mass of organisms in nicely balanced harmony with the 
changing physical conditions. The equatorial zone, in 
short, exhibits to us the result of a comparatively con- 
tinuous and unchecked development of organic forms ; 
while in the temperate regions, there have been a series 
of periodical checks and extinctions of a more or less 
disastrous nature, necessitating the commencement of 
the work of development in certain lines over and over 
again. In the one, evolution has had a fair chance ; in 
the other it has had countless difficulties thrown in its 
way. The equatorial regions are then, as regards their 
past and present life history, a more ancient world 
than that represented by the temperate zones, a world 
in which the laws which have governed the progressive 
development of life have operated with comparatively 
little check for countless ages, and have resulted in those 
infinitely varied and beautiful forms those wonderful 
eccentricities of structure, of function, and of instinct 
that rich variety of colour, and that nicely balanced 
harmony of relations which delight and astonish us in 
the animal productions of all tropical countries. 



IV. 
HUMMING-BIRDS : 

AS ILLUSTRATING THE LUXURIANCE OF TROPICAL 
NATURE. 

Structure Colours and Ornaments Display of Ornaments by the Male 
Descriptive Names The Motions and Habits of Humming-birds Food 
Nests Geographical Distribution and Variation Humming-birds of 
Juan Fernandez as illustrating Variation and Natural Selection The 
relations and affinities of Humming-birds How to determine doubtful 
affinities Resemblances of Swifts and Humming-birds Differences 
between Sun-birds and Humming-birds Conclusion. 

THERE are now about ten thousand different kinds of 
birds known to naturalists, and these are classed in one 
hundred and thirty families which vary greatly in extent, 
some containing a single species only, while others 
comprise many hundreds. The two largest families 
are those of the warblers, with more than six hundred, 
and the finches with more than five hundred species, 
spread over the whole globe ; the hawks and the pigeons, 
also spread over the whole globe, number about three 
hundred and thirty, and three hundred and sixty species 
respectively ; while the diminutive humming-birds, 
confined to one hemisphere, consist of about four 
hundred different species. They are thus, as regards 
the number of distinct kinds collected in a limited area, 



HUMMING-BIRDS. 125 

the most remarkable of all the families of birds. It 
may, however, very reasonably be asked, whether the 
four hundred species of humming-birds above alluded to 
are really all distinct as distinct on the average as 
the ten thousand species of birds are from each other. 
We reply that they certainly are perfectly distinct 
species which never intermingle ; and their differences do 
not consist in colour only, but in peculiarities of form, of 
structure, and of habits ; so that they have to be classed 
in more than a hundred distinct genera or systematic 
groups of species, these genera being really as unlike 
each other as stonechats and nightingales, or as par- 
tridges and blackcocks. The figures we have quoted, 
as showing the proportion of birds in general to hum- 
ming-birds, thus represent real facts ; and they teach 
us that these small and in some respects insignificant 
birds, constitute an important item in the animal life of 
the globe. 

Humming-birds are, in many respects, unusually inter- 
esting and instructive. They are highly peculiar in 
form, in structure, and in habits, and are quite unrivalled 
as regards variety and beauty. Though the name is 
familiar to every one, few but naturalists are acquainted 
with the many curious facts in their history, or know 
how much material they afford for admiration and study. 
It is proposed, therefore, to give a brief and popular 
account of the form, structure, habits, distribution, and 
affinities, of this remarkable family of birds, as illustra- 
tive of the teeming luxuriance of tropical nature, and 
as throwing light on some of the most interesting 
problems of natural history. 

Structure. The humming-birds form one compact 



126 TROPICAL NATURE, AND OTHER ESSAYS. 

family named Trochilidae. They are all small birds, the 
largest known being about the size of a swallow, while 
the smallest are minute creatures whose bodies are hardly 
larger than a humble-bee. Their distinguishing features 
are excessively short legs and feet, very long and pointed 
wings, a long and slender bill, and a long extensible 
tubular tongue ; and these characters are found combined 
in no other birds. The feet are exceedingly small and 
delicate, often beautifully tufted with down, and so short 
as to be hardly visible beyond the plumage. The toes 
are placed as in most birds, three in front and one behind, 
and have very strong and sharply curved claws ; and the 
feet serve probably to cling to a perch rather than to 
give any movement to the body. The wings are long 
and narrow, but strongly formed ; and the first quill is 
the longest, a peculiarity found in hardly any other 
birds but a few of the swifts. The bill varies greatly in 
length, but is always long, slender, and pointed, the 
upper mandible being the widest and lapping over the 
lower at each side, thus affording complete protection to 
the delicate tongue the perfect action of which is 
essential to the bird's existence. The humming-bird's 
tongue is very long, and is capable of being greatly 
extended beyond the beak and rapidly drawn back, by 
means of muscles which are attached to the hyoid or 
tongue-bones, and bend round over the back and top of 
the head to the very forehead, just as in the wood- 
peckers. The two blades or laminae, of which the 
tongues of birds usually seem to be formed, are here 
greatly lengthened, broadened out, and each rolled up ; 
so as to form a complete double tube connected down the 
middle, and with the outer edges in contact but not 



COLOURS OF HUMMING-BIRDS. 127 

united. The extremities of the tubes are, however, flat 
and fibrous. This tubular and retractile tongue enables 
the bird to suck up honey from the nectaries of flowers, 
and also to capture small insects ; but whether the latter 
pass down the tubes, or are entangled in the fibrous tips 
and thus draw back into the gullet, is not known. The only 
other birds with a similar tubular tongue are the sun- 
birds of the East, which however, as we shall presently 
explain, have no affinity whatever with the humming- 
birds. 

Colours and Ornaments. The colours of these small 

birds are exceedingly varied and exquisitely beautiful. 

The basis of the colouring may be said to be green, as in 

parrots ; but whereas in the latter it is a silky green, in 

humming-birds it is always metallic. The majority of 

the species have some green about them, especially on 

the back ; but in a considerable number rich blues, 

purples, and various shades of red are the prevailing 

tints. The greater part of the plumage has more or less 

of a metallic gloss, but there is almost always some part 

which has an intense lustre, as if actually formed of 

scales of burnished metal. A gorget, covering the greater 

part of the neck and breast, most commonly displays this 

vivid colour ; but it also frequently occurs on the head, 

on the back, on the tail-coverts above or below, on the 

upper surface of the tail, on the shoulders or even the 

quills. The hue of every precious stone and the lustre 

of every metal is here represented ; and such terms as 

topaz, amethyst, beryl, emerald, garnet, ruby, sapphire ; 

golden, golden-green, coppery, fiery, glowing, iridescent, 

refulgent, celestial, glittering, shining, are constantly 

used to name or describe the different species. 



128 TROPICAL NATURE, AND OTHER ESSAYS. 

No less remarkable than the colours are the varied de- 
velopments of plumage with which these birds are adorned. 
The head is often crested in a variety of ways ; either a 
simple flat crest, or with radiating feathers, or diverging 
into two horns, or spreading laterally like wings, or erect 
and bushy, or recurved and pointed like that of a plover. 
The throat and breast are usually adorned with broad 
scale-like feathers, or these diverge into a tippet, or send 
out pointed collars, or elegant frills of long and narrow 
plumes tipped with metallic spots of various colours. 
But the tail is even a more varied and beautiful ornament, 
either short and rounded, but pure white or some other 
strongly contrasted tint ; or with short pointed feathers 
forming a star ; or with the three outer feathers on each 
side long and tapering to a point ; or larger, and either 
square, or round, or deeply forked, or acutely pointed ; 
or with the two middle feathers excessively long and 
narrow ; or with the tail very long and deeply forked, 
with broad and richly-coloured feathers ; or with the two 
outer feathers wire-like and having broad spoon-shaped 
tips. All these ornaments, whether of the head, neck, 
breast or tail, are invariably coloured in some effective 
or brilliant manner, and often contrast strikingly with 
the rest of the plumage. Again, these colours often vary 
in tint according to the direction in which they are seen. 
In some species they must be looked at from above, in 
others from below ; in some from the front, in others 
from behind, in order to catch the full glow of the 
metallic lustre ; hence, when the birds are seen in their 
native haunts, the colours come and go and change with 
their motions, so as to produce a startling and beautiful 
effect. 



HUMMING-BIRDS. 129 

The bill differs greatly in length and shape, being 
either straight or gently curved, in some species bent 
like a sickle, in others turned up like the bill of the 
avoset. It is usually long and slender, but in one group 
is so enormously developed that it is nearly the same 
length as the rest of the bird. The legs, usually little 
seen, are in some groups adorned with globular tufts 
of white, brown, or black down, a peculiarity possessed 
by no other birds. The reader will now be in a position 
to understand how the four hundred species of humming- 
birds may be easily distinguished, by the varied combi- 
nations of the characters here briefly enumerated, 
together with many others of less importance. One 
group of birds will have a short round tail, with crest 
and long neck-frill ; another group a deeply -forked broad 
tail, combined with glowing crown and gorget ; one is 
both bearded and crested ; others have a luminous back 
and pendent neck-plumes ; and in each of these groups 
the species will vary in combinations of colour, in size, 
and in the proportions of the ornamental plumes, so as 
to produce an unmistakable distinctness ; while, without 
any new developments of form or structure, there is 
room for the discovery of hundreds more of distinct 
kinds of humming-birds. 

Descriptive Names. The name we usually give to the 
birds of this family is derived from the sound of their 
rapidly-moving wings, a sound which is produced by the 
largest as well as by the smallest member of the group. 
The Creoles of Guiana similarly call them Bourdons or 
hummers. The French term, Oiseau-mouche, refers to 
their small size ; while Colibri is a native name which 
has come down from the Carib inhabitants of the West 

K 



128 TROPICAL NATURE, AND OTHER ESSAYS. 

No less remarkable than the colours are the varied de- 
velopments of plumage with which these birds are adorned. 
The head is often crested in a variety of ways ; either a 
simple flat crest, or with radiating feathers, or diverging 
into two horns, or spreading laterally like wings, or erect 
and bushy, or recurved and pointed like that of a plover. 
The throat and breast are usually adorned with broad 
scale-like feathers, or these diverge into a tippet, or send 
out pointed collars, or elegant frills of long and narrow 
plumes tipped with metallic spots of various colours. 
But the tail is even a more varied and beautiful ornament, 
either short and rounded, but pure white or some other 
strongly contrasted tint ; or with short pointed feathers 
forming a star ; or with the three outer feathers on each 
side long and tapering to a point ; or larger, and either 
square, or round, or deeply forked, or acutely pointed ; 
or with the two middle feathers excessively long and 
narrow ; or with the tail very long and deeply forked, 
with broad and richly-coloured feathers ; or with the two 
outer feathers wire-like and having broad spoon-shaped 
tips. All these ornaments, whether of the head, neck, 
breast or tail, are invariably coloured in some effective 
or brilliant manner, and often contrast strikingly with 
the rest of the plumage. Again, these colours often vary 
in tint according to the direction in which they are seen. 
In some species they must be looked at from above, in 
others from below ; in some from the front, in others 
from behind, in order to catch the full glow of the 
metallic lustre ; hence, when the birds are seen in their 
native haunts, the colours come and go and change with 
their motions, so as to produce a startling and beautiful 
effect. 



HUMMING-BIRDS. 129 

The bill differs greatly in length and shape, being 
either straight or gently curved, in some species bent 
like a sickle, in others turned up like the bill of the 
avoset. It is usually long and slender, but in one group 
is so enormously developed that it is nearly the same 
length as the rest of the bird. The legs, usually little 
seen, are in some groups adorned with globular tufts 
of white, brown, or black down, a peculiarity possessed 
by no other birds. The reader will now be in a position 
to understand how the four hundred species of humming- 
birds may be easily distinguished, by the varied combi- 
nations of the characters here briefly enumerated, 
together with many others of less importance. One 
group of birds will have a short round tail, with crest 
and long neck-frill ; another group a deeply -forked broad 
tail, combined with glowing crown and gorget ; one is 
both bearded and crested ; others have a luminous back 
and pendent neck-plumes ; and in each of these groups 
the species will vary in combinations of colour, in size, 
and in the proportions of the ornamental plumes, so as 
to produce an unmistakable distinctness ; while, without 
any new developments of form or structure, there is 
room for the discovery of hundreds more of distinct 
kinds of humming-birds. 

Descriptive Names. The name w T e usually give to the 
birds of this family is derived from the sound of their 
rapidly-moving wings, a sound which is produced by the 
largest as well as by the smallest member of the group. 
The Creoles of Guiana similarly call them Bourdons or 
hummers. The French term, Oiseau-mouche, refers to 
their small size ; while Colibri is a native name which 
has come down from the Carib inhabitants of the West 

K 



130 TROPICAL NATURE, AND OTHER ESSAYS. 

Indies. The Spaniards and Portuguese call them by 
more poetical names, such as Flower-peckers, Flower- 
kissers, Myrtle-suckers while the Mexican and Peruvian 
names show a still higher appreciation of their beauties, 
their meaning being rays of the sun, tresses of the day- 
star, and other such appellations. Even our modern 
naturalists, while studying the structure and noting the 
peculiarities of these living gems, have been so struck 
by their inimitable beauties that they have endeavoured to 
invent appropriate English names for the more beautiful 
and remarkable genera. Hence we find in common use 
such terms as Sun-gems, Sun-stars, Hill-stars, Wood-stars, 
Sun- angels, Star- throats, Comets, Coquettes, Flame- 
bearers, Sylphs, and Fairies ; together with many others 
derived from the character of the tail or the crests. 

The Motions and Habits of Humming-birds. Let us 
now consider briefly, the peculiarities of flight, the motions, 
the food, the nests, and general habits of the humming- 
birds, quoting the descriptions of those modern naturalists 
who have personally observed them. Their appearance, 
remarks Professor Alfred Newton, is entirely unlike that 
of any other bird : " One is admiring some brilliant and 
beautiful flower, when between the blossom and one's 
eye suddenly appears a small dark object, suspended as 
it were between four short black threads meeting each 
other in a cross. For an instant it shows in front of the 
flower ; again another instant, and emitting a momentary 
flash of emerald and sapphire light, it is vanishing, 
lessening in the distance, as it shoots away, to a speck 
that the eye cannot take note of." Audubon observes 
that the Kuby Humming-birds pass through the air in 
long undulations, but the smallness of their size precludes 



HUMMING-BIRDS. 131 

the possibility of following them with the eye further 
than fifty or sixty yards, without great difficulty. A 
person standing in a garden by the side of a common 
althaea in bloom, will hear the humming of their wings 
and see the little birds themselves within a few feet of 
him one moment, while the next they will be out of 
sight and hearing. Mr. Gould, who visited North 
America in order to see living humming-birds while 
preparing his great work on the family, remarks, that the 
action of the wings reminded him of a piece of machinery 
acted upon by a powerful spring. When poised before 
a flower, the motion is so rapid that a hazy semicircle of 
indistinctness on each side of the bird is all that is 
perceptible. Although many short intermissions of rest 
are taken, the bird may be said to live in the air an 
element in which it performs every kind of evolution 
with the utmost ease, frequently rising perpendicularly, 
flying backward, pirouetting or dancing off, as it were, 
from place to place, or from one part of a tree to another, 
sometimes descending, at others ascending. It often 
mounts up above the towering trees, and then shoots 
off like a little meteor at a right angle. At other times 
it gently buzzes away among the little flowers near 
the ground ; at one moment it is poised over a 
diminutive weed, at the next it is seen at a distance of 
forty yards, whither it has vanished with the quickness 
of thought. 

The Rufous Flame-bearer, an exquisite species found 
on the west coast of North America, is thus described 
by Mr. Nuttall : " When engaged in collecting its 
accustomed sweets, in all the energy of life, it seemed 
like a breathing gem, a magic carbuncle of flaming fire, 

K 2 



132 TROPICAL NATURE, AND OTHER ESSAYS. 

stretching out its glorious ruff as if to emulate the sun 
itself in splendour." The Sappho Comet, whose long 
forked tail barred with crimson and black renders it one 
of the most imposing of humming-birds, is abundant 
in many parts of the Andes ; and Mr. Bonelli tells us 
that the difficulty of shooting them is very great from 
the extraordinary turns and evolutions they make when 
on the wing ; at one instant darting headlong into a 
flower, at the next describing a circle in the air with 
such rapidity that the eye, unable to follow the move- 
ment, loses sight of the bird until it again returns to 
the flower which at first attracted its attention. Of the 
little Vervain humming-bird of Jamaica, Mr. Gosse 
writes : " I have sometimes watched with much delight 
the evolutions of this little species at the Moringa- 
tree. 1 When only one is present, he pursues the round of 
the blossoms soberly enough. But if two are at the tree, 
one will fly off, and suspend himself in the air a few 
yards distant ; the other presently starts off to him, and 
then, without touching each other, they mount upwards 
with strong rushing wings, perhaps for five hundred 
feet. They then separate, and each starts diagonally 
towards the ground like a ball from a rifle, and wheeling 
round comes up to the blossoms again as if it had not 
moved away at all. The figure of the smaller humming- 
birds on the wing, their rapidity, their wavering course, 
and their whole manner of flight are entirely those of an 
insect/' Mr. Bates remarks, that on the Amazons 
during the cooler hours of the morning and from four 

1 Sometimes called the horse-radish tree. It is the Moringa pterygosperma, 
a native of the East Indies, but commonly cultivated in Jamaica. It has 
yellow flowers. 



HUMMING-BIRDS. 133 

to six in the afternoon humming-birds are to be seen 
whirring about the trees by scores ; their motions being 
unlike those of any other birds. They dart to and fro 
so swiftly that the eye can scarcely follow them, and 
when they stop before a flower it is only for a few 
moments. They poise themselves in an unsteady manner, 
their wings moving with inconceivable rapidity, probe 
the flower, and then shoot off to another part of the 
tree. They do not proceed in that methodical manner 
which bees follow, taking the flowers seriatim, but skip 
about from one part of the tree to another in the most 
capricious way. Mr. Belt remarks on the excessive 
rapidity of the flight of the humming-bird giving it a 
sense of security from danger, so that it will approach 
a person nearer than any other bird, often hovering 
within two or three yards (or even one or two feet) of 
one's face. He watched them bathing in a small pool 
in the forest, hovering over the water, turning from side 
to side by quick jerks of the tail ; now showing a throat 
of gleaming emerald, now shoulders of glistening 
amethyst ; then darting beneath the water, and rising in- 
stantly, throw off a shower of spray from their quivering 
wings, and again fly up to an overhanging bough and 
commence to preen their feathers. All humming-birds 
bathe on the wing, and generally take three or four dips, 
hovering between times about three or four inches above 
the surface. Mr. Belt also remarks on the immense 
numbers of humming-birds in the forests, and the great 
difficulty of seeing them ; and his conclusion is, that in 
the part of Nicaragua where he was living they equalled 
in number all the rest of the birds together, if they did 
not greatly exceed them. 



134 TROPICAL NATURE, AND OTHER ESSAYS. 

The extreme pugnacity of humming-birds has been 
noticed by all observers. Mr. Gosse describes two 
meeting and chasing each other through the labyrinths 
of twigs and flowers till, an opportunity occurring, the 
one would dart with seeming fury upon the other, and 
then, with a . loud rustling of their wings, they would 
twirl together, round and round, till they nearly came to 
the earth. Then they parted, and after a time another 
tussle took place. Two of the same species can hardly 
meet without an encounter, while in many cases distinct 
species attack each other with equal fury. Mr. Salvin 
describes the splendid Eugenes fulgens attacking two 
other species with as much ferocity as its own fellows. 
One will knock another off its perch, and the two will 
go fighting and screaming away at a pace hardly to be 
followed by the eye. Audubon says they attack any 
other birds that approach them, and think nothing of 
assaulting tyrant-shrikes and even birds of prey that 
come too near their home. 

Display of Ornaments by the Male. It is a well- 
known fact, that when male birds possess any unusual 
ornaments, they take such positions or perform such 
evolutions as to exhibit them to the best advantage while 
endeavouring to attract or charm the females or in 
rivalry with other males. It is therefore probable that 
the wonderfully varied decorations of humming-birds, 
whether burnished breast-shields, resplendent tail, crested 
head, or glittering back, are thus exhibited ; but almost 
the only actual observation of this kind is that of Mr. 
Belt, who describes how two males of the Florisuga 
mellivora displayed their ornaments before a female 
bird. One would shoot up like a rocket, then, suddenly 



HUMMING-BIRDS. 135 

expanding the snow-white tail like an inverted parachute, 
slowly descend in front of her, turning round gradually 
to show off both back and front. The expanded white 
tail covered more space than all the rest of the bird, and 
was evidently the grand feature of the performance. 
Whilst one was descending the other would shoot up 
and come slowly down expanded. 1 

Food. The food of humming-birds has been a matter 
of much controversy. All the early writers down to 
Buffon believed that they lived solely on the nectar of 
flowers ; but since that time every close observer of 
their habits maintains that they feed largely, and in 
some cases wholly, on insects. Azara observed them on 
the La Plata in winter taking insects out of the webs 
of spiders at a time and place where there were no 
flowers. Bullock, in Mexico, declares that he saw them 
catch small butterflies, and that he found many kinds of 
insects in their stomachs. Waterton made a similar 
statement. Hundreds and perhaps thousands of speci- 
mens have since been dissected by collecting naturalists, 
and in almost every instance their stomachs have been 
found full of insects, sometimes, but not generally, 
mixed with a proportion of honey. Many of them in 
fact may be seen catching gnats and other small insects 
just like fly-catchers, sitting on a dead twig over water, 
darting off for a time in the air, and then returning to 
the twig. Others come out just at dusk, and remain on 
the wing, now stationary, now darting about with the 
greatest rapidity, imitating in a limited space the evolu- 
tions of the goatsuckers, and evidently for the same end 
and purpose. Mr. Gosse also remarks : " All the hum- 

1 The Naturalist in Nicaragua, p. 112. 



136 TROPICAL NATURE, AND OTHER ESSAYS. 

ming-birds have more or less the habit, when in flight, 
of pausing in the air and throwing the body and tail 
into rapid and odd contortions. This is most observable 
in the Polytmus, from the effect that such motions have 
on the long feathers of the tail. That the object of these 
quick turns is the capture of insects, I am sure, having 
watched one thus engaged pretty close to me. I observed 
it carefully, and distinctly saw the minute flies in the air 
which it pursued and caught, and heard repeatedly the 
snapping of the beak. My presence scarcely disturbed 
it, if at all." 

There is also an extensive group of small brown hum- 
ming-birds, forming the sub-family Phaethornithinse, 
which rarely or never visit flowers, but frequent the 
shady recesses of the forest, where they hunt for minute 
insects. They dart about among the foliage, and visit 
in rapid succession every leaf upon a branch, balancing 
themselves vertically in the air, passing their beaks 
closely over the under-surface of each leaf, and thus 
capturing, no doubt, any small insects that may lurk 
there. While doing this, the two long feathers of the 
tail have a vibrating motion, serving apparently as a 
rudder, to assist them in performing the delicate opera- 
tion. Others search up and down stems and dead sticks 
in the same manner, every now and then picking off 
something, exactly as a bush-shrike or a tree-creeper 
does, with the difference that the humming-bird is con- 
stantly on the wing ; while the remarkable Sickle-bill is 
said to probe the scale-covered stems of palms and tree- 
ferns to obtain its insect food. 

It is a well-known fact that although humming-birds 
are easily tamed, they cannot be preserved long in 



HUMMING-BIRDS. 137 

captivity, even in their own country, when fed only on 
syrup. Audubon states, that when thus fed they only live 
a month or two and die apparently starved ; while if kept 
in a room whose open windows are covered with a fine 
net, so as to allow small insects to enter, they have been 
kept for a whole year without any ill-effects. Another 
writer, Mr. Webber, captured and tamed a number of 
the Ruby-throat in the United States. He found that 
when fed for three weeks on syrup they drooped, but 
after being let free for a day or two they would return 
to the open cage for more of the syrup. Some which 
had been thus tamed and set free, returned the following 
year, and at once flew straight to the remembered little 
cup of sweets. Mr. Gosse in Jamaica also kept some in 
captivity, and found the necessity of giving them insect 
food; and he remarks that they were very fond of a 
small ant that swarmed on the syrup with which they 
were fed. It is strange that, with all this previous 
experience and information, those who have attempted 
to bring live humming-birds to this country have fed 
them exclusively on syrup ; and the weakness produced 
by this insufficient food has no doubt been the chief 
cause of their death on, or very soon after, arrival. A 
box of ants would not be difficult to bring as food for 
them ; but even finely-chopped meat or yolk of egg 
would probably serve, in the "absence of insects, to supply 
the necessary proportion of animal food. 

Nests. The nests of the humming-birds are, as might 
be expected, beautiful objects, some being no larger inside 
than the half of a walnut-shell. These small cup-shaped 
nests are often placed in the fork of a branch, and the 
outside is sometimes beautifully decorated with pieces of 



138 TROPICAL NATURE, AND OTHER ESSAYS. 

lichen, the body of the nest being formed of cottony 
substances and the inside lined with the finest and most 
silky fibres. Others suspend their nests to creepers 
hanging over water, or even over the sea ; and the 
Pichincha humming-bird once attached its nest to a 
straw-rope hanging from the roof of a shed. Others 
again build nests of a hammock-form attached to the 
face of rocks by spiders' web ; while the little forest- 
haunting species fasten their nests to the points or to 
the under-sides of palm-leaves or other suitable foliage. 
They lay only one or two white eggs. 

Geographical Distribution and Variation. Most 
persons know that humming-birds are found only in 
America ; but it is not so generally known that they are 
almost exclusively tropical birds, and that the few species 
that are found in the temperate (northern and southern) 
parts of the continent are migrants, which retire in the 
winter to the warmer lands near or within the tropics. 
In the extreme north of America two species are regular 
summer visitants, one on the east and the other on the 
west of the Rocky Mountains. On the east the common 
N. American or Ruby-throated humming-bird extends 
through the United States and Canada, and as far as 57 
north latitude, or considerably north of Lake Winnipeg ; 
while the milder climate of the west coast allows the 
Rufous Flame-bearer to extend its range to beyond Sitka 
to the parallel of 61. Here they spend the whole 
summer, and breed, being found on the Columbia River 
in the latter end of April, but retire to Mexico in the 
winter. Supposing that those which go furthest north 
do not return further south than the borders of the 
tropics, these little birds must make a journey of full 



HUMMING-BIRDS. 139 

three thousand miles each spring and autumn. The 
antarctic humming-bird visits the inhospitable shores of 
Tierra-del-Fuego, where it has been seen visiting the 
flowers of fuchsias in a snow-storm, while it spends the 
winter in the warmer parts of Chili and Bolivia. 

In the south of California a,nd in the Central United 
States three or four other species are found in summer ; 
but it is only when we enter the tropics that the number 
of different kinds becomes considerable. In Mexico there 
are more than thirty species, while in the southern parts 
of Central America there are more than double that 
number. As we go on towards the equator they become 
still more numerous, till they reach their maximum in 
the equatorial Andes. They especially abound in the 
mountainous regions ; while the luxuriant forest plains 
of the Amazons, in which so many other forms of life 
reach their maximum, are very poor in humming-birds. 
Brazil, being more hilly and with more variety of vege- 
tation, is richer, but does not equal the Andean valle} T s, 
plateaux, and volcanic peaks. Each separate district of 
the Andes has its peculiar species and often its peculiar 
genera, and many of the great volcanic mountains 
possess kinds which are confined to them. Thus, on the 
great mountain of Pichincha there is a peculiar species 
found at an elevation of about fourteen thousand feet 
only ; while an allied species on Chimborazo ranges 
from fourteen thousand feet to the limits of perpetual 
snow at sixteen thousand feet elevation. It frequents a 
beautiful yellow-flowered alpine shrub belonging to the 
Asteraceae. On the extinct volcano of Chiriqui in 
Veragua a minute humming-bird, called the little Flame- 
bearer, has been only found inside the crater. Its scaled 



140 TROPICAL NATURE, AND OTHER ESSAYS. 

gorget is of such a flaming 'crimson that, as Mr. Goukl 
remarks, it seems to have caught the last spark from 
the volcano before it was extinguished. 

Not only are humming-birds found over the whole 
extent of America, from Sitka to Tierra-del-Fuego, and 
from the level of the sea to the snow-line on the Andes, 
but they inhabit many of the islands at a great distance 
from the mainland. The West Indian islands possess 
fifteen distinct species belonging to eight different genera, 
and these are so unlike any found on the continent that 
five of these genera are peculiar to the Antilles. Even 
the Bahamas, so close to Florida, possess two peculiar 
species. The small group of islands called Tres Marias, 
about sixty miles from the west coast of Mexico, has a 
peculiar species. More remarkable are the two humming- 
birds of Juan Fernandez, situated in the Pacific Ocean, 
four hundred miles west of Valparaiso in Chili, one of 
these being peculiar ; while another species inhabits the 
little island Mas-afuera, ninety miles further west. The 
Galapagos, though very little further from the mainland 
and much more extensive, have no humming-birds ; 
neither have the Falkland islands, and the reason seems 
to be that both these groups are deficient in forest, and 
in fact have hardly any trees or large shrubs, while there 
is a great paucity of flowers and of insect life. 

Humming-birds of Juan Fernandez as illustrating 
Variation and Natural Selection. The three species 
which inhabit Juan Fernandez and Mas-afuera present 
certain peculiarities of great interest. They form a 
distinct genus, Eustephanus, one species of which inhabits 
Chili as well as the island of Juan Fernandez. This, 
which may be termed the Chilian species, is greenish in 



HUMMING-BIRDS. 141 

both sexes, whereas in the two species peculiar to the 
islands the males are red or reddish-brown, and the 
females green. The two red males differ very slightly 
from each other, but the three green females differ con- 
siderably ; and the curious point is, that the female in 
the smaller and more distant island somewhat resembles 
the same sex in Chili, while the female of the Juan 
Fernandez species is very distinct, although the males of 
the two islands are so much alike. As this forms a 
comparatively simple case of the action of the laws of 
variation and natural selection, it will be instructive to 
see if we can picture to ourselves the process by which 
the changes have been brought about. We must first 
go back to an unknown but rather remote period, just 
before any humming-birds had reached these islands. 
At that time a species of this peculiar genus, Eustephanus, 
must have inhabited Chili ; but we must not be sure 
that it was identically the same as that which is now 
found there, because we know that species are always 
undergoing change to a greater or less degree. After 
perhaps many failures, one or more pairs of the Chilian 
bird got blown across to Juan Fernandez, and finding 
the country favourable, with plenty of forests and a fair 
abundance of flowers and insects, they rapidly increased 
and permanently established themselves on the island. 
They soon began to change colour, however, the male 
getting a tinge of reddish-brown, which gradually 
deepened into the fine colour nqw exhibited by the two 
insular species, while the female, more slowly, changed 
to white on the under-surface and on the tail, while the 
breast-spots became more brilliant. When the change 
of colour was completed in the male, but only partially 



142 TROPICAL NATURE, AND OTHER ESSAYS. 

so in the female, a further emigration westward took 
place to the small island Mas-afuera, where they also 
established themselves. Here, however, the change 
begun in the larger island appears to have been checked, 
for the female remains to this day intermediate between 
the Juan Fernandez and the Chilian forms. More re- 
cently, the parent form has again migrated from Chili to 
Juan Fernandez, where it still lives side by side with its 
greatly changed descendant. 1 Let us now see how far 
these facts are in accordance with the general laws of 
variation, and with those other laws which I have en- 
deavoured to show regulate the development of colour. 2 

The amount of variation which is likely to occur in a 
species will be greatly influenced by two factors the 
occurrence of a change in the physical conditions, and 
the average abundance or scarcity of the individuals 
composing the species. When from these or other 
causes variation occurs, it may become fixed as a variety 
or a race, or may go on increasing to a certain extent, 
either from a tendency to vary along certain special lines 
induced by local or physiological causes, or by the con- 
tinued survival and propagation of all such varieties as 
are beneficial to the race. After a certain time a balance 
will be arrived at, either by the limits of useful variation 
in this one direction having been reached, or by the 
species becoming harmoniously adapted to all the sur- 
rounding conditions ; and without some change in these 

1 In the preceding account of the probable course of events in peopling 
these islands with humming-birds, I follow Mr. Sclater's paper on the Land 
Birds of Juan Fernandez, Ibis, 1871, p. 183. In what follows, I give my 
own explanation of the probable causes of the change. 

2 See Macmillan's Magazine, Sept. 1867, " On the Colours of Animals 
and Plants," and Chapters V. and VI. of the present volume. 



HUMMING-BIKDS. 143 

conditions the specific form may then remain unaltered 
for a very long time ; whence arises the common impres- 
sion of the fixity of species. Now in a country like 
Chili, forming part of a great continent very well stocked 
with all forms of organic life, the majority of the species 
would be in a state of stable equilibrium ; the most 
favourable variations would have been long ago selected ; 
and the numbers of individuals in each species would be 
tolerably constant, being limited by the numerous other 
forms whose food and habits were similar, or which in 
any way impinged upon its sphere of existence. We 
may, therefore, assume that the Chilian humming-bird 
which migrated to Juan Fernandez was a stable form, 
hardly if at all different from the existing species which is 
termed Eustephanus galeritus. On the island it met with 
very changed but highly favourable conditions, an abun- 
dant shrubby vegetation and a tolerably rich flora ; less 
extremes of climate than on the mainland ; and, most 
important of all, absolute freedom from the competition 
of rival species. The flowers and their insect inhabitants 
were all its own ; there were no snakes or mammalia to 
plunder its nests ; nothing to prevent the full enjoy- 
ment of existence. The consequence would be, rapid 
increase and a large permanent population, which still 
maintains itself ; for Mr. Moseley, of the Challenger expe- 
dition, has informed the writer that humming-birds are 
extraordinarily abundant in Juan Fernandez, every bush 
or tree having one or two darting about it. Here, then, 
we have one of the special conditions which have always 
been held to favour variation a great increase in the 
number of individuals ; but, as there was no struggle 
with allied creatures, there was no need for any modifi- 



144 TROPICAL NATURE, AND OTHER ESSAYS. 

cation in form or structure, and we accordingly find that 
the only important variations which have become per- 
manent are those of size and of colour. The increased 
size would naturally arise from greater abundance of 
food with a more equable climate throughout the year, 
the healthier, stronger, and larger individuals being pre- 
served. The change of colour would depend on mole- 
cular changes in the plumage accompanying the increase 
of size ; and the superior energy and vitality in the 
male, aided by the favourable change in conditions and 
rapid increase of population, would lead to an increased 
intensity of colour, the special tint being determined 
either by local conditions or by inherited tendencies in 
the race. It is to be noted that the change from green 
to red is in the direction of the less refrangible rays of 
the spectrum, and is in accordance with the law of change 
which has been shown to accompany expansion in 
inorganic, growth and development in organic forms. 1 
The change of colour in the female, not being urged 
on by such intense vital activity as in the case of the 
male, would be much slower, and, owing probably 
to inherited tendencies, in a different direction. The 
under-surface of the Chilian bird is ashy with bronzy- 
green spots on the breast, while the tail is entirely 
bronze-green. In the Juan Fernandez species the under- 
surface has become pure white, the breast-spots larger 
and of a purer golden-green, while the whole inner web 
of the tail-feathers has become pure white, producing a 
most elegant effect when the tail is expanded. 

We may now follow the two sexes to the remoter 

1 See " Colours of Animals," Macmillaris Magazine, Sept. 1877, pp. 
394-398, and Chapter V. in the present volume. 



HUMMING-BIRDS. 115 

island, at a period when the male had acquired his per- 
manent style of colouring, but was not quite so large as 
he subsequently became ; while the change of the female 
bird had not been half completed. In this small and 
comparatively barren island (a mere rock, as it is de- 
scribed by some authors) there would be no such constant 
abundance of food, and therefore no possibility of a large 
permanent population; while the climate would not 
differ materially from that of the larger island. Varia- 
tion would therefore be checked, or might be stopped 
altogether ; and we find the facts exactly correspond to 
this view. The male, which had already acquired his 
colour, remains almost undistinguishable from his imme- 
diate ancestral form ; but he is a little smaller, indicat- 
ing either that the full size of that form had not been 
acquired at the period of migration, or that a slight 
diminution of size has since occurred, owing to a deficiency 
of food. The female shows also a slight diminution of 
size, but in other respects is almost exactly intermediate 
between the Chilian and Juan Fernandez females. The 
colour beneath is light ashy, the breast-spots are inter- 
mediate in size and colour, and the tail-feathers have a 
large ill-defined white spot on the end of the inner web 
which has only to be extended along the whole web to 
produce the exact character which has been acquired in 
Juan Fernandez. It seems probable, therefore, that the 
female bird has remained nearly or quite stationary since 
its migration, while its Juan Fernandez relative has 
gone on steadily changing in the direction already begun ; 
and the more distant species geographically thus appears 
to be more nearly related to its Chilian ancestor. 

Coming down to a more recent period, we find that 

L 



146 TROPICAL NATURE, AND OTHER ESSAYS. 

the comparatively small and dull-coloured Chilian bird 
has again migrated to Juan Fernandez ; but it at once 
came into competition with its red descendant, which 
had firm possession of the soil, and had probably under- 
gone slight constitutional changes exactly fitting it to 
its insular abode. The new-comer, accordingly, only just 
manages to maintain its footing ; for we are told by 
Mr. Reed, of Santiago, that it is by no means common ; 
whereas, as we have seen, the red species is excessively 
abundant. We may further suspect that the Chilian 
birds now pass over pretty frequently to Juan Fernan- 
dez, and thus keep up the stock ; for it must be remem- 
bered that whereas, at a first migration, both a male and 
a female are necessary for colonization, yet, after a colony 
is formed, any stray bird which may come over adds 
to the numbers, and checks permanent variation by 
cross-breeding. 

We find, then, that all the chief peculiarities of the 
three allied species of humming-birds which inhabit 
the Juan Fernandez group of islands, may be fairly 
traced to the action of those general laws which Mr. 
Darwin and others have shown to determine the varia- 
tions of animals and the perpetuation of those varia- 
tions. It is also instructive to note, that where the 
variations of colour and size have been greatest they 
are accompanied by several lesser variations in other 
characters. In the Juan Fernandez bird the bill has 
become a little shorter, the tail feathers somewhat 
broader, and the fiery cap on the head somewhat smaller ; 
all these peculiarities being less developed or absent 
in the birds inhabiting Mas-afuera. These coincident 
changes may be due, either to what Mr. Darwin has 



HUMMING-BIRDS. 147 

termed correlation of growth, or to the partial reap- 
pearance of ancestral characters under more favourable 
conditions, or to the direct action of changes of climate 
and of food ; but they show us how varied and un- 
accountable are the changes in specific forms that may 
be effected in a comparatively short time, and by means 
of very slight changes of locality. 

If now we consider the enormously varied conditions 
presented by the whole continent of America the hot, 
moist, and uniform forest-plains of the Amazon ; the 
open llanos of the Orinoco ; the dry uplands of Brazil ; 
the sheltered valleys and forest slopes of the Eastern 
Andes ; the verdant plateaus, the barren paramos, the 
countless volcanic cones with their peculiar Alpine 
vegetation ; the contrasts of the East and West coasts ; 
the isolation of the West Indian islands, and to a less 
extent of Central America and Mexico which we know 
have been several times separated from South America ; 
and when we further consider that all these characteris- 
tically distinct areas have been subject to cosmical and 
local changes, to elevations and depressions, to diminu- 
tion and increase of size, to greater extremes and greater 
uniformity of temperature, to increase or decrease of 
rainfall ; and that with these changes there have been 
coincident changes of vegetation and of animal life, all 
affecting in countless ways the growth and development, 
the forms and colours, of these wonderful little birds 
if we consider all these varied and complex influences, 
we shall be less surprised at their strange forms, their 
infinite variety, their wondrous beauty. For how many 
ages the causes above enumerated may have acted upon 
them we cannot say ; but their extreme isolation from 

L 2 



148 TROPICAL NATURE, AND OTHER ESSAYS. 

.all other birds, no less than the abundance and variety 
of their generic and specific forms, clearly point to a 
very high antiquity. 

The Relations and Affinities of Humming-birds. The 
question of the position of this family in the class of 
birds and its affinities or resemblances to other groups, 
is so interesting, and affords such good opportunities for 
explaining some of the best-established principles of 
classification in natural history in a popular way, that 
we propose to discuss it at some length, but without 
entering into technical details. 

There is in the Eastern hemisphere, especially in 
tropical Africa and Asia, a family of small birds called 
Sun-birds, which are adorned with brilliant metallic 
colours, and which, in shape and general appearance, 
much resemble humming-birds. They frequent flowers 
in the same way, feeding on honey and insects ; and all 
the older naturalists placed the two families side by side 
as undoubtedly allied. In the year 1850, in a general 
catalogue of birds, Prince Lucien Bonaparte, a learned 
ornithologist, placed the humming-birds next to the 
swifts, and far removed from the Nectarinidse or sun- 
birds ; and this view of their position has gained ground 
with increasing knowledge, so that now all the more 
advanced ornithologists have adopted it. Before pro- 
ceeding to point out the reasons for -this change of 
view, it will be well to discuss a few of the general 
principles which guide naturalists in the solution of 
such problems. 

How to Determine Doubtful Affinities. It is now 
generally admitted that, for the purpose of determining 
obscure and doubtful affinities, we must examine by 



AFFINITIES OF HUMMING-BIRDS. 149 

preference those parts of an animal which have little or 
no direct influence on its habits and general economy. 
The value of an organ, or of any detail of structure, 
for purposes of classification, is generally in inverse 
proportion to its adaptability to special uses. And the 
reason of this is apparent, when we consider that 
similarities of food and habits are often accompanied by 
similarities of external form or of special organs, in 
totally distinct animals. Porpoises, for example, are 
modified externally so as to resemble fishes ; yet they 
are really mammalia. Some marsupials are carnivorous, 
and are so like true carnivora that it is only by minute 
peculiarities of structure that the skeleton of the one 
can be distinguished from that of the other. Many of 
the hornbills and toucans have the same general form, 
and resemble each other in habits, in food, and in their 
enormous bills ; yet peculiarities in the structure of the 
feet, in the form of the breast-bone, in the cranium, and 
in the texture and arrangement of the plumage, show 
that they have no real affinity, the former approaching 
the kingfishers, the latter the cuckoos. Such structural 
peculiarities as these have no direct relation to habits ; 
and they are therefore little liable to change, when from 
any cause a portion of the group may have been driven 
to adopt a new mode of life. Thus all the Old World 
apes, however much they may differ in size or habits, 
and whether we class them as baboons, monkeys, or 
gorillas, have the same number of teeth; while the 
American monkeys all have an additional premolar 
tooth. This difference can have no relation to the 
habits of the two groups, because each group exhibits 
differences of habits greater than often occur between 



150 TROPICAL NATURE, AND OTHER ESSAYS. 

American and Asiatic species ; and it thus becomes a 
valuable character indicating the radical distinctness of 
the two groups, a distinctness confirmed by other 
anatomical characters. 

On the other hand, peculiarities of organization which 
seem specially adapted to certain modes of life, are 
often diminished or altogether lost in a few species of 
the group, showing their essential unimportance to the 
type, as well as their small value for classification. 
Thus, the woodpeckers are most strikingly characterised 
by a very long and highly extensible tongue, with the 
muscles attached to the tongue-bone prolonged backward 
over the head so as to enable the tongue to be suddenly 
darted out ; and also by the rigid and pointed tail which 
is a great help in climbing up the vertical trunks of 
trees. But in one group (the Picumni), the tail becomes 
quite soft, while the tongue remains fully developed ; 
and in another (Meiglyptes) the characteristic tail 
remains, while the prolonged hyoid muscles have almost 
entirely disappeared, and the tongue has consequently 
lost its peculiar extensile power ; yet in both these cases 
the form of the breast-bone and the character of the feet, 
the skeleton, and the plumage, show that the birds are 
really woodpeckers ; while even the habits and the food 
are very little altered. In like manner the bill may 
undergo great changes ; as from the short crow-like bill 
of the true birds-of-paradise to the long slender bills of 
Epimachinse, which latter were on that account long 
classed apart in the tribe of Tenuirostres, or slender- 
billed birds, but whose entire structure shows them to 
be closely allied to the paradise -birds. So, the long 
feathery tongue of the toucans differs from that of every 



AFFINITIES OF HUMMING-BIRDS. 151 

other bird ; yet it is not held to overbalance the weight 
of anatomical peculiarities which show that these birds 
are allied to the barbets and the cuckoos. 

The skeleton, therefore, and especially the sternum or 
breast-bone, affords us an almost infallible guide in 
doubtful cases ; because it appears to change its form 
with extreme slowness, and thus indicates deeper-seated 
affinities than those shown by organs which are in direct 
connection with the outside world, and are readily 
modified in accordance with varying conditions oi 
existence. Another, though less valuable guide is 
afforded, in the case of birds, by the eggs. These often 
have a characteristic form and colour, and a peculiar 
texture of surface, running unchanged through whole 
genera and families which are nearly related to each 
other, however much they may differ in outward form 
and habits. Another detail of structure which has no 
direct connection with habits and economy, is the 
manner in which the plumage is arranged on the body. 
The feathers of birds are by no means set uniformly 
over their skin, but grow in certain definite lines and 
patches, which vary considerably in shape and size in 
the more important orders and tribes, while the mode of 
arrangement agrees in all which are known to be closely 
related to each other ; and thus the form of the feather- 
tracts or the " pterylography " as it is termed, of a bird, 
is a valuable aid in doubtful cases of affinity. 

Now, if we apply these three tests to the humming- 
birds, we find them all pointing in the same direction. 
The sternum or breast-bone is not notched behind ; and 
this agrees with the swifts, and not with the sun-birds, 
whose sternum has two deep notches behind, as in all 



152 TROPICAL NATURE, AND OTHER ESSAYS. 

the families of the vast order of Passeres to which the 
latter belong. The eggs of both swifts and humming- 
birds are white, only two in number, and resembling 
each other in texture. And in the arrangement of the 
feather-tracts the humming-birds approach more nearly 
to the swifts than they do to any other birds ; and 
altogether differ from the sun-birds, which, in this 
respect as in so many others, resemble the honey-suckers 
of Australia and other true passerine birds. 

Resemblances of Swifts and Humming-birds. Having 
this clue to their affinities, we shall find other pecu- 
liarities common to these two groups, the swifts and 
the humming-birds. They have both ten tail-feathers, 
while the sun-birds have twelve. They have both only 
sixteen true quill-feathers, and they are the only birds 
which have so small a number. The humming-birds 
are remarkable for having, in almost all the species, 
the first quill the longest of all, the only other birds 
resembling them in this respect being a few species 
of swifts ; and, lastly, in both groups the plumage 
is remarkably compact and closely pressed to the body. 
Yet, with all these points of agreement, we find an 
extreme diversity in the bills and tongues of the two 
groups. The swifts have a short, broad, flat bill, with 
a flat horny-tipped tongue of the usual character ; while 
the humming-birds have a very long, narrow, almost 
cylindrical bill, containing a tubular and highly ex- 
tensible tongue. The essential point however is, that 
whereas hardly any of the other characters we have 
adduced are adaptive, or strictly correlated with habits 
and economy, this character is pre-eminently so ; for 
the swifts are pure aerial insect-hunters, and their short, 



NESTLING HUMMING-BIRDS. 153 

broad bills, and wide gape, are essential to their mode 
of life. The humming-birds, on the other hand, are 
floral insect-hunters, and for this purpose their peculiarly 
long bills and extensile tongues are especially adapted ; 
while they are at the same time honey-suckers, and 
for this purpose have acquired the tubular tongue. The 
formation of such a tubular tongue out of one of the 
ordinary kind is easily conceivable, as it only requires 
to be lengthened, and the two laminae of which it is 
composed curled in at the sides ; and these changes it 
probably goes through in the young birds. 

When on the Amazon I once had a nest brought me con- 
taining two little unfledged humming-birds, apparently 
not long hatched. Their beaks were not at all like 
those of their parents, but short, triangular, and broad 
at the base ; just the form of the beak of a swallow 
or swift slightly lengthened. Thinking (erroneously) 
that the young birds were fed by their parents on 
honey, I tried to feed them with a syrup made of honey 
and water, but though they kept their mouths constantly 
open as if ravenously hungry, they would not swallow 
the liquid, but threw it out again and sometimes nearly 
choked themselves in the effort. At length I caught 
some minute flies, and on dropping one of these into 
the open mouth it instantly closed, the fly was gulped 
down and the mouth opened again for more ; and each 
took in this way fifteen or twenty little flies in succession 
before it was satisfied. They lived thus three or four 
days, but required more constant care than I could give 
them. These little birds were in the "swift" stage; 
they were pure insect-eaters, with a bill and mouth 
adapted for in sect -eating only. At that time I was not 



154 TROPICAL NATURE, AND OTHER ESSAYS. 

aware of the importance of the observation of the 
tongue ; but as the bill was so short and the tubular 
tongue not required, there can be little doubt that the 
organ was, at that early stage of growth, short and 
flat, as it is in the birds most nearly allied to them. 

Differences between Sun-birds and Humming-birds. 
In respect of all the essential and deep-seated points 
of structure, which have been shown to offer such 
remarkable similarities between the swifts and the 
humming-birds, the sun-birds of the Eastern hemi- 
sphere differ totally from the latter, while they agree 
with the passerine birds generally, or more particularly 
with the creepers and honey-suckers. They have a 
deeply-notched sternum ; they have twelve tail-feathers 
in place of ten ; they have nineteen quills in place of 
sixteen ; and the first quill instead of being the longest 
is the very shortest of all, while the wings are short 
and round, instead of being excessively long and 
pointed ; their plumage is arranged differently ; and 
their feet are long and strong, instead of being exces- 
sively short and weak. There remain only the super- 
ficial characters of small size and brilliant metallic 
colours to assimilate them with the humming-birds, 
and one structural feature a tubular and somewhat 
extensile tongue. This, however, is a strictly adaptive 
character, the sun-birds feeding on small insects and 
the nectar of flowers, just as do the humming-birds ; 
and it is a remarkable instance of a highly peculiar 
modification of an organ occurring independently in 
two widely-separate groups. In the sun-birds the 
hyoid or tongue-muscles do not extend so completely 
over the head as they do in the humming-birds, so 



SUN-BIRDS AND HUMMING-BIRDS, 155 

that the tongue is less extensible ; but it is constructed 
in exactly the same way by the inrolling of the two 
laminae of which it is composed. 

The tubular tongue of the sun-birds is a special 
adaptive modification acquired within the family 
itself, and not inherited from a remote ancestral form. 
This is shown by the amount of variation this organ 
exhibits in different members of the family. It is 
most highly developed in the Arachnotherse, or spider- 
hunters, of Asia, which are sun-birds without any 
metallic or other brilliant colouring. These have the 
longest bills and tongues, and the most developed hyoid 
muscles ; they hunt much about the blossoms of palm- 
trees, and may frequently be seen probing the flowers 
while fluttering clumsily in the air, just as if they had 
seen and attempted to imitate the aerial gambols of 
the American humming-birds. The true metallic sun- 
birds generally cling about the flowers with their strong 
feet ; and they feed chiefly on minute hard insects, as 
do many humming-birds. There is, however, one species 
(Chalcoparia phoenicotis) always classed as a sun-bird, 
which differs entirely from the rest of the species in 
having the tongue flat, horny, and forked at the tip ; 
and its food seems to differ correspondingly, for small 
caterpillars were found in its stomach. More remotely 
allied, but yet belonging to the same family, are the 
little flower-peckers of the genus Diceum, which have 
a short bill and a tongue twice split at the end ; and 
these feed on small fruits, and perhaps on buds and on 
the pollen of flowers. The little white-eyes (Zosterops), 
which are probably allied to the last, eat soft fruits and 
minute insects. 



156 TROPICAL NATURE, AND OTHER ESSAYS. 

Here then we have an extensive group of birds, 
considerably varied in external form, yet undoubtedly 
closely allied to each other, one division of which is 
specially adapted to feed on the juices secreted by 
flowers and the minute insects that harbour in them ; 
and these alone have a lengthened bill and double 
tubular tongue, just as in the humming-birds. We can 
hardly have a more striking example of the necessity 
of discriminating between adaptive and purely structural 
characters. The same adaptive character may coexist 
in two groups which have a similar mode of life, with- 
out indicating any affinity between them, because it 
may have been acquired by each independently, to enable 
it to fill a similar place in nature. In such cases it is 
found to be an almost isolated character, apparently 
connecting two groups which otherwise differ radically. 
Non-adaptive, or purely structural characters, on the 
other hand, are such as have probably been transmitted 
from a remote ancestor ; and thus indicate fundamental 
peculiarities of growth and development. The changes 
of structure rendered necessary by modifications of the 
habits or instincts of the different species, have been 
made, to a great extent, independently of such characters ; 
and as several of these may always be found in the 
same animal their value becomes cumulative. We thus 
arrive at the seeming paradox, that the less of direct 
use is apparent in any peculiarity of structure, the 
greater is its value in indicating true, though perhaps 
remote, afiinities ; while any peculiarity of an organ 
which seems essential to its possessor's well-being is 
often of very little value in indicating its affinity for 
other creatures. 



HUMMING-BIRDS. 157 

This somewhat technical discussion will, it is hoped, 
enable the general reader to understand some of the 
more important principles of the modern or natural 
classification of animals, as distinguished from the 
artificial system which long prevailed. It will also 
afford him an easily remembered example of those 
principles, in the radical distinctness of two families 
of birds often confounded together, the sun-birds of 
the Eastern Hemisphere, and the humming-birds of 
America; and in the interesting fact that the latter 
are essentially swifts profoundly modified, it is true, 
for an aerial and flower-haunting existence, but still 
bearing in many important peculiarities of structure the 
unmistakable evidences of a common origin. 



V. 

THE COLOURS OF ANIMALS AND SEXUAL 
SELECTION. 

General Phenomena of Colour in the Organic World Theory of Heat and 
Light as producing Colour Changes of Colour in Animals produced by 
Coloured Light Classification of Organic Colours Protective Colours 
Warning Colours Sexual Colours Typical Colours The Nature of 
Colour Colour a normal product of Organization Theory of Protective 
Colours Theory of Warning Colours Theory of Sexual Colours Colour 
as a means of Recognition Colour proportionate to Integumentary 
Development Selection by Females not a cause of Colour Probable use 
of the Horns of Beetles Cause of the greater brilliancy of some Female 
Insects Theory of display of Ornaments by Males Natural Selection 
as neutralizing Sexual Selection Theory of Typical Colours Colour- 
development as illustrated by Humming-birds Local causes of Colour- 
development Summary on Colour-development in Animals. 

THERE is probably no one quality of natural objects 
from which we derive so much pure and intellectual 
enjoyment as from their colours. The heavenly blue of 
the firmament, the glowing tints of sunset, the exquisite 
purity of the snowy mountains, and the endless shades 
of green presented by the verdure-clad surface 
of the earth, are a never-failing source of pleasure 
to all who enjoy the inestimable gift of sight. Yet 
these constitute, as it were, but the frame and back- 
ground of a marvellous and ever-changing picture. In 
contrast with these broad and soothing tints, we have 
presented to us in the vegetable and animal worlds, an 
infinite variety of objects adorned with the most beauti- 



THE COLOURS OF ANIMALS. 159 

ful and most varied hues. Flowers, insects and birds, 
are the organisms most generally ornamented in this 
way; and their symmetry of form, their variety of 
structure, and the lavish abundance with which they 
clothe and enliven the earth, cause them to be objects 
of universal admiration. The relation of this wealth of 
colour to our mental and moral nature is indisputable. 
The child and the savage alike admire the gay tints of 
flower, bird, and insect ; while to many of us their con- 
templation brings a solace and enjoyment which is both 
intellectually and morally beneficial. It can then hardly 
excite surprise that this relation was long thought to 
afford a sufficient explanation of the phenomena of 
colour in nature ; and although the fact that 

" Full many a flower is born to blush unseen, 
And waste its sweetness on the desert air " 

might seem to throw some doubt on the sufficiency of 
the explanation, the answer was easy, that in the pro- 
gress of discovery, man would, sooner or later, find out 
and enjoy every beauty that the hidden recesses of the 
earth have in store for him. This theory received great 
support, from the difficulty of conceiving any other use 
or meaning in the colours with which so many natural 
objects are adorned. Why should the homely gorse be 
clothed in golden raiment, and the prickly cactus be 
adorned with crimson bells ? Why should our fields be 
gay with buttercups, and the heather-clad mountains be 
clad in purple robes ? Why should every land produce 
its own peculiar floral gems, and the alpine rocks glow 
with beauty, if not for the contemplation and enjoyment 
of man ? What could be the use to the butterfly of its 



160 TROPICAL NATURE, AND OTHER ESSAYS. 

gaily-painted wings, or to the humming bird of its 
jewelled breast, except to add the final touches to a world- 
picture, calculated at once to please and to refine man- 
kind ? And even now, with all our recently-acquired 
knowledge of this subject, who shall say that these old- 
world views were not intrinsically and fundamentally 
sound ; and that, although we now know that colour has 
" uses " in nature that we little dreamt of, yet the relation 
of those colours or rather of the various rays of light 
to our senses and emotions, may not be another, and 
perhaps more important use which they subserve in the 
great system of the universe ? 

We now propose to lay before our readers a general 
account of the more recent discoveries on this interesting 
subject ; and in doing so, it will be necessary first to 
give an outline of the more important facts as to the 
colours of organised beings ; then to point out the cases 
in which it has been shown that colour is of use ; and 
lastly, to endeavour to throw some light on its nature, 
and on the general laws of its development. 

Among naturalists, colour was long thought to be of 
little import, and to be quite untrustworthy as a specific 
character. The numerous cases of variability of colour led 
to this view. The occurrence of white blackbirds, white 
peacocks, and black leopards ; of white blue-bells, and of 
white, blue, or pink milkworts, led to the belief that colour 
was essentially unstable, that it could therefore be of 
little or no importance, and belonged to quite a different 
class of characters from form or structure. But it now 
begins to be perceived that these cases, though tolerably 
numerous, are, after all, exceptional ; and that colour, as 
a rule, is a constant character. The great majority of 



COLOURS OF ANIMALS. 161 

species, both of animals and plants, are each distinguished 
by peculiar tints which vary very little, while the 
minutest markings are often constant in thousands or 
millions of individuals. All our field buttercups are 
invariably yellow, and our poppies red ; while many of 
our butterflies and birds resemble each other in every 
spot and streak of colour through thousands of indivi- 
duals. We also find that colour is constant in whole 
genera and other groups of species. The Genistas are 
all yellow, the Erythrinas all red ; many genera of Cara- 
bidse are entirely black ; whole families of birds as the 
Dendrocolaptidse are brown ; while among butterflies 
the numerous species of Lycsena are all more or less blue, 
those of Pontia white, and those of Callidryas yellow. 
An extensive survey of the organic world thus leads us 
to the conclusion that colour is by no means so unim- 
portant or inconstant a character as at first sight it 
appears to be ; and the more we examine it the more 
convinced we shall become that it must serve some 
purpose in nature, and that, besides charming us by its 
diversity and beauty, it must be well worthy of our 
attentive study, and have many secrets to unfold 
to us. 

Theory of Heat and Light as producing Colour. In 
commencing our study of the great mass of facts relating 
to the colours of the organic world, it will be necessary 
to consider first, how far the chief theories already 
proposed will account for them. One of the most 
obvious and most popular of these theories, and one 
which is still held, in part at least, by many eminent 
naturalists, is that colour is due to some direct action of 
the heat and light of the sun thus at once accounting 

M 



162 TROPICAL NATURE, AND OTHER ESSAYS. 

for the great number of brilliant birds, insects, and 
flowers, which are found between the tropics. 

But before proceeding to discuss this supposed ex- 
planation of the colours of living things we must ask the 
preliminary question, whether it is really the fact that 
colour is more developed in tropical than in temperate 
climates, in proportion to the whole number of species ; 
and even if we find this to be so, we have to inquire 
whether there are not so many and such striking ex- 
ceptions to the rule, as to indicate some other causes at 
work than the direct influence of solar light and heat. 
As this is a most important branch of the inquiry, we 
must go into it somewhat fully. 

It is undoubtedly the case that there are an immensely 
greater number of richly-coloured birds and insects in 
tropical than in temperate and cold countries, but it is 
by no means so certain that the proportion of coloured 
to obscure species is much or any greater. Naturalists 
and collectors well know that the majority of tropical 
birds are dull-coloured ; and there are whole families, 
comprising hundreds of species, not one of which ex- 
hibits a particle of bright colour. Such are, for example, 
the Timaliidae, or babbling thrushes of the Eastern, 
and the Dendrocolaptidae, or tree-creepers of the Western 
hemispheres. Again, many groups of birds, which are 
universally distributed, are no more adorned with colour 
in the tropical than in the temperate zones ; such are the 
thrushes, wrens, goatsuckers, hawks, grouse, plovers, and 
snipe ; and if tropical light and heat have any direct 
colouring effect, it is certainly most extraordinary that 
in groups so varied in form, structure, and habits as 
those just mentioned, the tropical should be in no wise 



COLOURS OF ANIMALS. 163 

distinguished in this respect, from the temperate 
species. 

It is true that brilliant tropical birds mostly belong to 
groups which are wholly tropical as the chatterers, 
toucans, trogons, and pittas ; but as there are perhaps 
an equal number of groups which are wholly dull- 
coloured, while others contain dull and bright-coloured 
species in nearly equal proportions, the evidence is by 
no means strong that tropical light and heat have any- 
thing to do with the matter. But there are other groups 
in which the cold and temperate zones produce finer- 
coloured species than the tropics. Thus the arctic ducks 
and divers are handsomer than those of the tropical 
zone ; while the king-duck of temperate America and 
the mandarin-duck of North China are the most beau- 
tifully coloured of the whole family. In the pheasant 
family we have the gorgeous gold and silver pheasants 
in North China and Mongolia ; and the superb Impeyan 
pheasant in the temperate North- Western Himalayas, as 
against the peacock and fire-backed pheasants of tropical 
Asia. Then we have the curious fact that most of the 
bright-coloured birds of the tropics are denizens of the 
forests, where they are shaded from the direct light of 
the sun, and that they abound near the equator where 
cloudy skies are very prevalent ; while, on the other 
hand, places where light and heat are at a maximum 
have often dull- coloured birds. Such are the Sahara 
and other deserts, where almost all the living things are 
sand-coloured ; but the most curious case is that of the 
Galapagos islands, situated under the equator, and not 
far from South America where the most gorgeous colours 
abound, but which are yet characterized by prevailing 

M 2 



164 TROPICAL NATURE, AND OTHER ESSAYS. 

dull and sombre tints in birds, insects, and flowers, so 
that they reminded Mr. Darwin of the cold and barren 
plains of Patagonia rather than of any tropical country. 
Insects are wonderfully brilliant in tropical countries 
generally ; and any one looking over a collection of South 
American or Malayan butterflies would scout the idea of 
their being no more gaily-coloured than the average of 
European species, and in this he would be undoubtedly 
right. But on examination we should find that all the 
more brilliantly-coloured groups were exclusively tropical, 
and that, where a genus has a wide range, there is little 
difference in coloration between the species of cold and 
warm countries. Thus the European Vanessides, in- 
cluding the beautiful " peacock," " Camberwell beauty," 
and " red admiral " butterflies, are quite up to the 
average of tropical colour in the same group ; and the 
remark will equally apply to the little "blues" and 
" coppers ; " while the alpine " apollo " butterflies have 
a delicate beauty that can hardly be surpassed. In other 
insects, which are less directly dependent on climate 
and vegetation, we find even greater anomalies. In 
the immense family of the Carabidae or predaceous 
ground-beetles, the northern forms fully equal, if they 
do not surpass, all that the tropics can produce. Every- 
where, too, in hot countries, there are thousands of 
obscure species of insects which, if they were all 
collected, would not improbably bring down the average 
of colour to much about the same level as that of 
temperate zones. 

But it is when we come to the vegetable world that 
the greatest misconception on this subject prevails. In 
abundance and variety of floral colour the tropics are 



COLOURS OF ANIMALS. 165 

almost universally believed to be pre-eminent, not only 
absolutely, but relatively to the whole mass of vegeta- 
tion and the total number of species. Twelve years of 
observation among the vegetation of the eastern and 
western tropics has, however, convinced me that this 
notion is entirely erroneous, and that, in proportion to 
the whole number of species of plants, those having 
gaily-coloured flowers are actually more abundant in 
the temperate zones than between the tropics. This 
will be found to be not so extravagant an assertion as 
it may at first appear, if we consider how many of the 
choicest adornments of our greenhouses and flower- 
shows are really temperate as opposed to tropical plants. 
The masses of colour produced by our Ehododendrons, 
Azaleas, and Camellias, our Pelargoniums, Calceolarias, 
and Cinerarias, all strictly temperate plants can cer- 
tainly not be surpassed, if they can be equalled, by 
any productions of the tropics. 

It may be objected that most of the plants named are 
choice cultivated varieties, far surpassing in colour the 
original stock, while the tropical plants are mostly un- 
varied wild species. But this does not really much affect 
the question at issue. For our florists' gorgeous varieties 
have all been produced under the influence of our 
cloudy skies, and with even a still further deficiency of 
light, owing to the necessity of protecting them under 
glass from our sudden changes of temperature ; so that 
they are themselves an additional proof that tropical 
light and heat are not needed for the production of 
intense and varied colour. Another important con- 
sideration is, that these cultivated varieties in many 
cases displace a number of wild species which are 



166 TROPICAL NATURE, AND OTHER ESSAYS. 

hardly, if at all, cultivated. Thus there- are scores of 
species of wild hollyhocks varying in colour almost as 
much as the cultivated varieties, and the same may be 
said of the pentstemons, rhododendrons, and many 
other flowers; and if these were all brought together 
in well-grown specimens, they would produce a grand 
effect. But it is far easier, and more profitable for our 
nurserymen to grow varieties of one or two species, 
which all require a similar culture, rather than fifty 
distinct species, most of which would require special 
treatment ; the result being that the varied beauty of the 
temperate flora is even now hardly known, except to 
botanists and to a few amateurs. 

But we may go further, and say that the hardy plants 
of our cold temperate zone equal, if they do not surpass, 
the productions of the tropics. Let us only remember 
such gorgeous tribes of flowers as the Roses, Pseonies, 
Hollyhocks, and Antirrhinums ; the Laburnum, Wistaria, 
and Lilac ; the Lilies, Irises, and Tulips ; the Hyacinths, 
Anemones, Gentians, and Poppies ; and even our humble 
Gorse, Broom, and Heather ; and we may defy any 
tropical country to produce masses of floral colour in 
greater abundance and variety. It may be true that 
individual tropical shrubs and flowers do surpass every- 
thing in the rest of the world ; but that is to be expected, 
because the tropical zone comprises a much greater 
land area than the two temperate zones, while, owing 
to its more favourable climate, it produces a still larger 
proportion of species of plants, and a greater number 
of peculiar natural orders. 

Direct observation in tropical forests, plains, and 
mountains, fully supports this view. Occasionally we 



COLOURS OF ANIMALS. 167 

are startled by some gorgeous mass of colour, but as a 
rule we gaze upon an endless expanse of green foliage, 
only here and there enlivened by not very conspicuous 
flowers. Even the orchids, whose superb blossoms 
adorn our stoves, form no exception to this rule. It is 
only in favoured spots that we find them in abundance ; 
the species with small and inconspicuous flowers greatly 
preponderate ; and the flowering season of each kind 
being of short duration, they rarely produce any marked 
effect of colour amid the vast masses of foliage which 
surround them. An experienced collector in the Eastern 
tropics once told me, that although a single mountain in 
Java had produced three hundred species of Orchideae, 
only about two per cent, of the whole were sufficiently 
ornamental or showy to be worth sending home as a 
commercial speculation. The Alpine meadows and rock- 
slopes, the open plains of the Cape of Good Hope or of 
Australia, and the flower-prairies of North America, offer 
an amount and variety of floral colour which can cer- 
tainly not be surpassed, even if it can be equalled, 
between the tropics. 

It appears, therefore, that we may dismiss the theory 
that the development of colour in nature is directly 
dependent on, and in any way proportioned to the 
amount of solar heat and light, as entirely unsupported 
by facts. Strange to say, however, there are some rare 
and little-known phenomena which prove, that in ex- 
ceptional cases, light does directly affect the colours of 
natural objects ; and it will be as well to consider these 
before passing on to other matters. 

Changes of Colour in Animals produced by Coloured 
Light. A few years ago Mr. T. W. Wood called attention 



168 TROPICAL NATURE, AND OTHER ESSAYS. 

to the curious changes in the colour of the chrysalis of 
the small cabbage-butterfly (Pontia rapes) when the 
caterpillars, just before their change, were confined in 
boxes lined with different tints. Thus in black boxes 
they were very dark, in white boxes nearly white ; and 
he further showed that similar changes occurred in a 
state of nature, chrysalises fixed against a white-washed 
wall being nearly white ; against a red brick wall, reddish ; 
against a pitched paling, nearly black. It has also been 
observed that the cocoon of the emperor moth is either 
white or brown, according to the colours surrounding it. 
But the most extraordinary example of this kind of 
change is that furnished by the chrysalis of an African 
butterfly (Papilio Nireus), observed at the Cape by 
Mrs. Barber, and described (with a coloured plate) in 
the Transactions of the Entomological Society, 1874, 
p. 519. 

This caterpillar feeds upon the orange tree, and 
also upon a forest-tree ( Vepris lanceolata) which has a 
lighter green leaf ; and its colour corresponds with that 
of the leaves it feeds upon, being of a darker green 
when it feeds on the orange. The chrysalis is usually 
found suspended among the leafy twigs of its food-plant, 
or of some neighbouring tree, but it is probably often 
attached to larger branches ; and Mrs. Barber has dis- 
covered that it has the property of acquiring the colour, 
more or less accurately, of any natural object it may 
be in contact with. A number of the caterpillars were 
placed in a case with a glass cover, one side of the 
case being formed by a red brick wall, the other sides 
being of yellowish wood. They were fed on orange 
leaves, and a branch of the bottle-brush tree (Banksia, 



COLOURS OF ANIMALS. 169 

sp.) was also placed in the case. When fully fed, some 
attached themselves to the orange twigs, others to the 
bottle-brush branch ; and these all changed to green 
pupse ; but each corresponded exactly in tint to the leaves 
around it, the one being dark, the other a pale faded 
green. Another attached itself to the wood, and the 
pupa became of the same yellowish colour ; while one fixed 
itself just where the wood and brick joined, and became 
one side red, the other side yellow ! These remark- 
able changes would perhaps not have been credited had 
it not been for the previous observations of Mr. Wood ; 
but the two support each other, and oblige us to accept 
them as actual phenomena. It is a kind of natural 
photography, the particular coloured rays to which the 
fresh pupa is exposed in its soft, semi-transparent con- 
dition, effecting such a chemical change in the organic 
juices as to produce the same tint in the hardened skin. 
It is interesting however to note, that the range of 
colour that can be acquired seems to be limited to those 
of natural objects to which the pupa is likely to be 
attached ; for when Mrs. Barber surrounded one of the 
caterpillars with a piece of scarlet cloth no change of 
colour at all was produced, the pupa being of the usual 
green tint, but the small red spots with which it is 
marked were brighter than usual. 

Many other cases are known among insects in which 
the same species acquires a different tint according 
to its surroundings ; this being particularly marked in 
some South African locusts, which correspond with the 
colour of the soil wherever they are found. There are 
also many caterpillars which feed on two or more plants, 
and which vary in colour accordingly. A number of such 



170 TROPICAL NATURE, AND OTHER ESSAYS. 

changes are quoted by Mr. K. Meldola, in a paper on 
Variable Protective Colouring in Insects (Proceedings 
of the Zoological Society of London, 1873, p. 153), and 
some of them may perhaps be due to a photographic 
action of the reflected light. In other cases, however, it 
has been shown that green chlorophyll remains unchanged 
in the tissues of leaf-eating insects, and being discernible 
through the transparent integument, produces the same 
colour as that of the food plant. 

In the case of all these insects, as well as in the great 
majority of cases in which a change of colour occurs in 
animals, the action is quite involuntary ; but among 
some of the higher animals the colour of the integument 
can be modified at the will of the individual, or at all 
events by a reflex action dependent on sensation. The 
most remarkable case of this kind occurs with the 
chameleon, which has the power of changing its colour 
from dull white to a variety of tints. This singular 
power has been traced to two layers of movable pig- 
ment-cells deeply seated in the skin, but capable of being 
brought near to the surface. The pigment-layers are 
bluish and yellowish, and by the pressure of suitable 
muscles these can be forced upwards either together or 
separately. When no pressure is exerted the colour is 
dirty white, which changes to various tints of bluish, 
green, yellow, or brown, as more or less of either pig- 
ment is forced up and rendered visible. The animal is 
excessively sluggish and defenceless, and its power of 
changing its colour so as to harmonise with surround- 
ing objects is essential to its safety. Here too, as 
with the pupa of Papilio Nireus, colours, such as 
scarlet or blue, which do not occur in the immediate 



COLOUKS OF ANIMALS. 171 

environment of the animal, cannot be produced. Some- 
what similar changes of colour occur in some prawns 
and flat-fish, according to the colour of the bottom 
on which they rest. This is very striking in the 
chameleon shrimp (My sis Chamceleon), which is grey 
when on sand, but brown or green when among 
sea-weed of these two colours. Experiment shows, 
however, that when blinded the change does not occur ; 
so that here too we probably have a voluntary or 
reflex sense-action. 

These peculiar powers of change of colour and adap- 
tation are, however, rare and quite exceptional. As a 
rule, there is no direct connection between the colours of 
organisms and the kind of light to which they are 
usually exposed. This is well seen in most fishes and 
in such marine animals as porpoises, whose backs are 
always dark, although this part is exposed to the blue 
and white light of the sky and clouds, while their bellies 
are very generally white, although these are constantly 
subjected to the deep blue or dusky green light from the 
bottom. It is evident, however, that these two tints 
have been acquired for concealment and protection. 
Looking down on the dark back of a fish it is almost 
invisible, while, to an enemy looking up from below, the 
light under-surface would be equally invisible against 
the light of the clouds and sky. Again, the gorgeous 
colours of the butterflies which inhabit the depths of 
tropical forests bear no relation to the kind of light 
that falls upon them, coming as it does almost wholly 
from green foliage, dark brown soil, or blue sky ; and 
the bright underwings of many moths, which are only 
exposed at night, contrast remarkably with the sombre 



172 TROPICAL NATURE, AND OTHER ESSAYS. 

tints of the upper wings, which are more or less exposed 
to the various colours of surrounding nature. 

Classification of Organic Colours. We find, then, 
that neither the general influence of solar light and heat, 
nor the special action of variously tinted rays, are ade- 
quate causes for the wonderful variety, intensity, and 
complexity of the colours that everywhere meet us in 
the animal and vegetable worlds. Let us therefore take 
a wider view of these colours, grouping them into classes 
determined by what we know of their actual uses or 
special relations to the habits of their possessors. This, 
which may be termed the functional and biological clas- 
sification of the colours of living organisms, seems to 
be best expressed by a division into five groups, as 
follows : 

i 1. Protective colours. 

2 Warning colours I " ^ cre atures specially protected. 
Animals J 2 ' \ b. Of defenceless creatures, mimicking a. 

] 3. Sexual colours. 

( 4. Typical colours. 
Plants. 6. Attractive colours. 

It is now proposed, firstly, to point out the nature of 
the phenomena presented under each of these heads ; 
then to explain the general laws of the production of 
colour in nature ; and, lastly, to show how far the varied 
phenomena of animal coloration can be explained by 
means of those laws, acting in conjunction with the laws 
of evolution and natural selection. 

Protective Colours. The nature of the two first 
groups, Protective and Warning colours, has been so 
fully detailed and illustrated in my chapter on " Mimicry 
and other Protective Resemblances among Animals," 
(Contributions to the Theory of Natural Selection, p. 45), 



COLOURS OF ANIMALS. "173 

that very little need be added here except a few words 
of general explanation. Protective colours are exceed- 
ingly prevalent in nature, comprising those of all the 
white arctic animals, the sandy- coloured desert forms, 
and the green birds and insects of tropical forests. It 
also comprises thousands of cases of special resemblance 
of birds to the surroundings of their nests, and 
especially of insects to the bark, leaves, flowers, or soil, 
on or amid which they dwell. Mammalia, fishes, and 
reptiles, as well as mollusca and other marine inverte- 
brates, present similar phenomena ; and the more the 
habits of animals are investigated, the more numerous 
are found to be the cases in which their colours tend to 
conceal them, either from their enemies or from the 
creatures they prey upon. One of the last-observed and 
most curious of these protective resemblances has been 
communicated to me by Sir Charles Dilke. He was 
shown in Java a pink-coloured Mantis which, when at 
rest, exactly resembled a pink orchis-flower. The 
mantis is a carnivorous insect which lies in wait for its 
prey ; and, by its resemblance to a flower, the insects it 
feeds on would be actually attracted towards it. This 
one is said to feed especially on butterflies, so that it 
is really a living trap, and forms its own bait 1 

All who have observed animals, and especially insects, 
in their native haunts and attitudes, can understand how 
it is that an iosect which in a cabinet looks exceedingly 
conspicuous, may yet when alive, in its peculiar attitude 
of repose and with its habitual surroundings, be per- 
fectly well concealed. We can hardly ever tell by the 
mere inspection of an animal, whether its colours are 
protective or not. No one would imagine the exquisitely 



174 TROPICAL NATURE, AND OTHER ESSAYS. 

beautiful caterpillar of the emperor-moth, which is 
green with pink star-like spots, to be protectively 
coloured ; yet, when feeding on the heather, it so har- 
monises with the foliage and flowers as to be almost 
invisible. Every day fresh cases of protective colouring 
are being discovered, even in our own country ; and it is 
becoming more and more evident that the need of pro- 
tection has played a very important part in determining 
the actual coloration of animals. 

Warning Colours. The second class the warning 
colours are exceedingly interesting, because the object 
and effect of these is, not to conceal the object, but to 
make it conspicuous. To these creatures it is useful to 
be seen and recognized ; the reason being that they have 
a means of defence which, if known, will prevent their 
enemies from attacking them, though it is generally 
not sufficient to save their lives if they are actually 
attacked. The best examples of these specially pro- 
tected creatures consist of two extensive families of 
butterflies, the Danaidse and Acrseidse, comprising many 
hundreds of species inhabiting the tropics of all parts of 
the world. These insects are generally large, are all con- 
spicuously and often most gorgeously coloured, present- 
ing almost every conceivable tint and pattern ; they all 
fly slowly, and they never attempt to conceal themselves ; 
yet no bird, spider, lizard, or monkey (all of which eat 
other butterflies) ever touches them. The reason simply 
is that they are not fit to eat, their juices having a 
powerful odour and taste that is absolutely disgusting to 
all these animals. Now we see the reason of their 
showy colours and slow flight. It is good for them to 
be seen and recognised, for then they are never mo- 



COLOURS OF ANIMALS. 175 

lested ; but if they did not differ in form and colouring 
from other butterflies, or if they flew so quickly that their 
peculiarities could not be easily noticed, they would be 
captured, and though not eaten would be maimed or 
killed. 

As soon as the cause of the peculiarities of these butter- 
flies was clearly recognised, it was seen that the same ex- 
planation applied to many other groups of animals. Thus, 
bees and wasps and other stinging insects are showily 
and distinctively coloured ; many soft and apparently 
defenceless beetles, and many gay-coloured moths, were 
found to be as nauseous as the above-named butterflies ; 
other beetles, whose hard and glossy coats of mail render 
them unpalatable to insect-eating birds, are also some- 
times showily coloured ; and the same rule was found to 
apply to caterpillars, all the brown and green (or protec- 
tively coloured species) being greedily eaten by birds, 
while showy kinds which never hide themselves like 
those of the magpie-, mullein-, and burnet-moths were 
utterly refused by insectivorous birds, lizards, frogs, and 
spiders. (Contributions to the Theory of Natural Selec- 
tion, p. 117.) Some few analogous examples are found 
among vertebrate animals. I will only mention here a 
very interesting case not given in my former work. In his 
delightful book entitled, The Naturalist in Nicaragua, 
Mr. Belt tells us that there is in that country a frog 
which is very abundant ; which hops about in the day- 
time; which never hides himself; and which is gorgeously 
coloured with red and blue. Now frogs are usually 
green, brown, or earth-coloured ; feed mostly at night ; 
and are all eaten by snakes and birds. Having full faith 
in the theory of protective and warning colours, to which 



176 TROPICAL NATURE, AND OTHER ESSAYS. 

he had himself contributed some valuable facts and ob- 
servations, Mr. Belt felt convinced that this frog must be 
uneatable. He therefore took one home, and threw it 
to his ducks and fowls ; but all refused to touch it except 
one young duck, which took the frog in its mouth, but 
dropped it directly, and went about jerking its head as 
if trying to get rid of something nasty. Here the un- 
eatableness of the frog was predicted from its colours 
and habits, and we can have no more convincing proof 
of the truth of a theory than such previsions. 

The universal avoidance by carnivorous animals of 
all these specially protected groups, which are thus 
entirely free from the constant persecution suffered by 
other creatures not so protected, would evidently render 
it advantageous for any of these latter which were 
subjected to extreme persecution to be mistaken for the 
former ; and for this purpose it would be necessary that 
they should have the same colours, form, and habits. 
Now, strange to say, wherever there is a large group 
of directly-protected forms (division a of animals with 
warning colours), there are sure to be found a few 
otherwise defenceless creatures which resemble them ex- 
ternally so as to be mistaken for them, and which thus 
gain protection, as it were, on false pretences (division b 
of animals with warning colours). This is what is called 
" mimicry," and it has already been very fully treated 
of by Mr. Bates (its discoverer), by myself, by Mr. 
Trimen, and others. Here it is only necessary to state 
that the uneatable Danaidse and Acrseidae are accom- 
panied by a few species of other groups of butterflies 
(Leptalidae, Papilios, Diademas, and Moths) which are 
all really eatable, but which escape attack by their close 



COLOURS OF ANIMALS. 177 

resemblance to some species of the uneatable groups 
found in the same locality. In like manner there are 
a few eatable beetles which exactly resemble species of 
uneatable groups ; and others, which are soft, imitate those 
which are uneatable through their hardness. For the 
same reason wasps are imitated by moths, and ants by 
beetles ; and even poisonous snakes are mimicked by 
harmless snakes, and dangerous hawks by defenceless 
cuckoos. How these curious imitations have been 
brought about, and the laws which govern them, have 
been discussed in the work already referred to. 

Sexual Colours. The third class comprises all cases 
in which the colours of the two sexes differ. This 
difference is very general, and varies greatly in amount, 
from a slight divergence of tint up to a radical change 
of coloration. Differences of this kind are found among 
all classes of animals in which the sexes are separated, 
but they are much more frequent in some groups than 
in others. In mammalia, reptiles, and fishes, they are 
comparatively rare, and not great in amount, whereas 
among birds they are very frequent and very largely 
developed. So among insects, they are abundant in 
butterflies, while they are comparatively uncommon in 
beetles, wasps, and hemiptera. 

The phenomena of sexual variations of colour, as 
well as of colour generally, are wonderfully similar in 
the two analogous yet totally unrelated groups of birds 
and butterflies ; and as they both offer ample materials, 
we shall confine our study of the subject chiefly to 
them. The most common case of difference of colour 
between the sexes, is for the male to have the same 
general hue as the females, but deeper and more 



178 TROPICAL NATURE, AND OTHER ESSAYS. 

intensified ; as in many thrushes, finches, and hawks ; 
and among butterflies in the majority of our British 
species. In cases where the male is smaller the in- 
tensification of colour is especially well pronounced ; as 
in many of the hawks and falcons, and in most but- 
terflies and moths in which the coloration does not 
materially differ. In another extensive series we have 
spots or patches of vivid colour in the male, which are 
represented in the female by far less brilliant tints or 
are altogether wanting ; as exemplified in the gold-crest 
warbler, the green woodpecker, and most of the orange- 
tip butterflies (Anthocharis). Proceeding with our sur- 
vey, we find greater and greater differences of colour in 
the sexes, till we arrive at such extreme cases as some of 
the pheasants, the chatterers, tanagers, and birds-of- 
paradise, in which the male is adorned with the most 
gorgeous and vivid colours, while the female is usually 
dull brown, or olive green, and often shows no approxi- 
mation whatever to the varied tints of her partner. 
Similar phenomena occur among butterflies ; and in 
both these groups there are also a considerable number 
of cases in which both sexes are highly coloured in a 
different way. Thus many woodpeckers have the head 
in the male red, in the female yellow ; while some 
parrots have red spots in the male, replaced by blue 
in the female, as in Psittacula diopthalma. In many 
South American Papilios, green spots on the male are 
represented by red on the female ; and in several species 
of the genus Epicalia, orange bands in the male are 
replaced by blue in the female, a similar change of 
colour to that in the small parrot above referred to. For 
fuller details of the varieties of sexual coloration we 



COLOURS OF ANIMALS. 179 

refer our readers to Mr. Darwin's Descent of Man, 
chapters x. to xviii., and to chapters iii., iv. and vii. 
of my Contributions to the Theory of Natural Selection. 
Typical Colours. The fourth group of Typically- 
coloured animals includes all species which are bril- 
liantly or conspicuously coloured in both sexes, and for 
whose particular colours we can assign no function or 
use. It comprises an immense number of showy birds, 
such as Kingfishers, Barbets, Toucans, Lories, Tits, and 
Starlings ; among insects most of the largest and hand- 
somest butterflies, innumerable bright-coloured beetles, 
locusts, dragon-flies, and hymenoptera ; a few mammalia, 
as the zebras ; a great number of marine fishes ; thou- 
sands of striped and spotted caterpillars ; and abundance 
of mollusca, star-fish, and other marine animals. Among 
these we have included some which, like the gaudy 
caterpillars, have warning colours ; but as that theory 
does not explain the particular colours or the varied 
patterns with which they are adorned, it is best to 
include them also in this class. It is a suggestive fact, 
that all the brightly-coloured birds mentioned above 
build in holes or form covered nests, so that the females 
do not need that protection during the breeding season 
which I believe to be one of the chief causes of the 
dull colour of female birds when their partners are gaily 
coloured. This subject is fully argued in my Contribu- 
tions, &c., chapter vii. 

As the colours of plants and flowers are very different 
from those of animals both in their distribution and 
functions, it will be well now to consider how the 
general facts of colour here sketched out can be 



180 TROPICAL NATURE, AND OTHER ESSAYS. 

explained. We have first to inquire what is colour, 
and how it is produced ; what is known of the causes 
of change of colour ; and what theory best accords with 
the whole assemblage of facts. 

The Nature of Colour. The sensation of colour is 
caused by vibrations or undulations of the ethereal 
medium of different lengths and velocities. The whole 
body of vibrations caused by the sun is termed radiation, 
or, more commonly, rays ; and consists of sets of waves 
which vary considerably in their dimensions and rate 
of recurrence, but of which the middle portion only is 
capable of exciting in us sensations of light and colour. 
Beginning with the largest waves, which recur at the 
longest intervals, we have first those which produce 
heat-sensations only ; as they get smaller and recur 
quicker, we perceive a dull red colour ; and as the waves 
increase in rapidity and diminish in size, we get succes- 
sively sensations of orange, yellow, green, blue, indigo, 
and violet, all fading imperceptibly into each other. 
Then come more invisible rays, of shorter wave-length 
and quicker recurrence, which produce, solely or chiefly, 
chemical effects. The red rays, which first become 
visible, have been ascertained to recur at the rate of 
458 millions of millions of times in a second, the length 
of each wave being aaaooth of an inch ; while the violet 
rays, which last remain visible, recur 727 millions of 
millions of times per second, and have a wave-length of 
TroTtfth of an inch. Although the waves recur at 
different rates, they are all propagated through the ether 
with the same velocity (192,000 miles per second) ; just 
as different musical sounds, which are produced by 
waves of air of different lengths and rates of recurrence, 



COLOURS OF ANIMALS. 181 

travel at the same speed, so that a tune played several 
hundred yards off reaches the ear in correct time. There 
are, therefore, an almost infinite number of different 
colour-producing undulations, and these may be com- 
bined in an almost infinite variety of ways, so as to 
excite in us the sensation of all the varied colours and 
tints we are capable of perceiving. When all the 
different kinds of rays reach us in the proportion in 
which they exist in the light of the sun, they produce 
the sensation of white. If the rays which excite the 
sensation of any one colour are prevented from reaching 
us, the remaining rays in combination produce a sensa- 
tion of colour often very far removed from white. Thus 
green rays being abstracted leave purple light ; blue, 
orange-red light ; violet, yellowish-green light, and so 
on. These pairs are termed complementary colours. 
And if portions of differently coloured lights are ab- 
stracted in various degrees, we have produced all those 
infinite gradations of colours, and all those varied tints 
and hues which are of such use to us in distinguishing 
external objects, and which form one of the great 
charms of our existence. Primary colours would there- 
fore be as numerous as the different wave-lengths of the 
visible radiations, if we could appreciate all their differ- 
ences ; while secondary or compound colours, caused by 
the simultaneous action of any combination of rays of 
different wave-lengths, must be still more numerous. 

In order to account for the fact that all colours 
appear to us to be produced by combinations of three 
primary colours red, green, and violet it is believed 
that we have three sets of nerve fibres in the retina, 
each of which is capable of being excited by all rays, 



182 TROPICAL NATURE, AND OTHER ESSAYS. 

but that one set is excited most by the larger or 
red waves, another by the medium or green waves, 
and the third set chiefly by the violet or smallest 
waves of light ; and when all three sets are excited 
together in proper proportions we see white. This view 
is supported by the phenomena of colour-blindness, 
which are explicable on the theory that one of these 
sets of nerve-fibres (usually that adapted to perceive 
red) has lost its sensibility, causing all colours to appear 
as if the red rays were abstracted from them. 

It is a property of these various radiations, that they 
are unequally refracted or bent in passing obliquely 
through transparent bodies, the longer waves being least 
refracted, the shorter most. Hence it becomes possible 
to analyse white or any other light into its component 
rays. A small ray of sunlight, for example, which would 
produce a round white spot on a wall, if passed through 
a prism is lengthened out into a band of coloured light, 
exactly corresponding to the colours of the rainbow. 
Any one colour can thus be isolated and separately ex- 
amined ; and by means of reflecting mirrors the separate 
colours can be again compounded in various ways, and 
the resulting colours observed. This band of coloured 
light is called a spectrum, and the instrument by which 
the spectra of various kinds of light are examined is 
called a spectroscope. This branch of the subject has, 
however, no direct bearing on the mode in which the 
colours of living things are produced, and it has only 
been alluded to in order to complete our sketch of the 
nature of colour. 

The colours which we perceive in material substances 
are produced either by the absorption or by the inter- 



COLOURS OF ANIMALS. 183 

ference of some of the rays which form white light. 
Pigmental or absorption- colours are the most frequent, 
comprising all the opaque tints of flowers and insects, 
and all the colours of dyes and pigments. They are 
caused by rays of certain wave-lengths being absorbed, 
while the remaining rays are reflected and give rise to 
the sensation of colour. When all the colour-producing 
rays are reflected in due proportion, the colour of the 
object is white ; when all are absorbed the colour is black. 
If blue rays only are absorbed the resulting colour is 
orange-red ; and generally, whatever colour an object 
appears to us, it is because the complementary colours 
are absorbed by it. The reason why rays of only certain 
refrangibilities are reflected, and the rest of the incident 
light absorbed by each substance, is supposed to depend 
upon the molecular structure of the body. Chemical 
action almost always implies change of molecular 
structure/ hence chemical action is the most potent cause 
of change of colour. Sometimes simple solution in 
water effects a marvellous change, as in the case of the 
well-known aniline dyes ; the magenta and violet 
dyes exhibiting, when in the solid form, various shades 
of golden or bronzy metallic green. 

Heat alone often produces change of colour without 
effecting any chemical change. Mr. Ackroyd has 
recently investigated this subject, 1 and has shown 
that a large number of bodies are changed by heat, 
returning to their normal colour when cooled, and that 
this change is almost always in the direction of the less 
refrangible rays or longer wave-lengths ; and he connects 
the change with the molecular expansion caused by heat. 

1 " Metachromatism, or Colour-Change," Chemical News, August, 1876. 



184 TROPICAL NATURE, AND OTBER ESSAYS. 

As examples may be mentioned mercuric oxide, which is 
orange yellow, but which changes to orange, red, and 
brown when heated ; chromic-oxide, which is green, and 
changes to yellow ; cinnabar, which is scarlet, and changes 
to puce ; and metaborate of copper, which is blue, and 
changes to green and greenish yellow. 

How Animal Colours are Produced. The colouring 
matters of animals are very varied. Copper has been found 
in the red pigment of the wing of the turaco, and Mr. 
Sorby has detected no less than seven distinct colouring 
matters in birds' eggs, several of which are chemically 
related to those of blood and bile. The same colours are 
often produced by quite different substances in different 
groups, as shown by the red of the wing on the burnet- 
moth changing to yellow with muriatic acid, while the red 
of the red-admiral-butterfly undergoes no such change. 

These pigmental colours have a different character in 
animals according to their position in the integument. 
Following Dr. Hagen's classification, epidermal colours 
are those which exist in the external chitinised skin of 
insects, in the hairs of mammals, and, partially, in the 
feathers of birds. They are often very deep and rich, 
and do not fade after death. The hypodermal colours 
are those which are situated in the inferior soft layer of 
the skin. These are often of lighter and more vivid 
tints, and usually fade after death. Many of the reds 
and yellows of butterflies and birds belong to this class, 
as well as the intensely vivid hues of the naked skin 
about the heads of many birds. These colours some- 
times exude through the pores, forming an evanescent 
bloom on the surface. 

Interference colours are less frequent in the organic 



COLOURS OF ANIMALS. 185 

world. They are caused in two ways : either by reflec- 
tion from the two surfaces of transparent films, as seen 
in the soap-bubble and in thin films of oil on water ; or 
by fine strife which produce colours either by reflected or 
transmitted light, as seen in mother-of-pearl and in 
finely-ruled metallic surfaces. In both cases colour is 
produced by light of one wave-length being neutralised, 
owing to one set of such waves being caused to be half 
a wave length behind the other set, as may be found 
explained in any treatise on physical optics. The result 
is, that the complementary colour of that neutralised is 
seen ; and, as the thickness of the film or the fineness of 
the striae undergo slight changes, almost any colour can 
be produced. This is believed to be the origin of many 
of the glossy or metallic tints of insects, as well as those 
of the feathers of some birds. The iridescent colours of 
the wings of dragon-flies are caused by the superposition 
of two or more transparent lamellae ; while the shining 
blue of the Purple-Emperor and other butterflies, and 
the intensely metallic colours of humming-birds, are 
probably due to fine striae. 

Colour a Normal Product of Organization. This 
outline sketch of the nature of colour in the animal 
world, however imperfect, will at least serve to show us 
how numerous and varied are the causes which perpetually 
tend to the production of colour in animal tissues. If 
we consider, that in order to produce white, all the rays 
which fall upon an object must be reflected in the same 
proportions as they exist in solar light whereas, if rays 
of any one or more kinds are absorbed or neutralised, the 
resultant reflected light will be coloured ; and that this 
colour may be infinitely varied according to the propor- 



186 TROPICAL NATURE, AND OTHER ESSAYS. 

tions in which different rays are reflected or absorbed 
we should expect that white would be, as it really is, 
comparatively rare and exceptional in nature. The same 
observation will apply to black, which arises from the 
absorption of all the different rays. Many of the 
complex substances which exist in animals and plants 
are subject to changes of colour under- the influence of 
light, heat, or chemical change, and we know that 
chemical changes are continually occurring during the 
physiological processes of development and growth. 
We also find that every external character is subject to 
minute changes, which are generally perceptible to us 
in closely allied species ; and we can therefore have no 
doubt that the extension and thickness of the transparent 
lamellae, and the fineness of the striae or rugosities of 
the integuments, must be undergoing constant minute 
changes ; and these changes will very frequently pro- 
duce changes of colour. These considerations render 
it probable that colour is a normal and even necessary 
result of the complex structure of animals and plants ; 
and that those parts of an organism which are under- 
going continual development and adaptation to new 
conditions, and are also continually subject to the action 
of light and heat, will be the parts in which changes of 
colour will most frequently appear. Now there is little 
doubt that the external changes of animals and plants in 
adaptation to the environment are much more numerous 
than the internal changes ; as seen in the varied character 
of the integuments and appendages of animals hair, 
horns, scales, feathers, &c. &c. and in plants, the leaves, 
bark, flowers, and fruit, with their various modifications 
as compared with the great uniformity in the texture 



COLOURS OF ANIMALS. 187 

and composition of their internal tissues ; and this 
accords with the uniformity of the tints of blood, 
muscle, nerve, and bone throughout extensive groups, as 
compared with the great diversity of colour of their 
external organs. It seems a fair conclusion that colour 
per se may be considered to be normal, and to need no 
special accounting for ; while the absence of colour (that 
is, either white or black), or the prevalence of certain 
colours to the constant exclusion of others, must be 
traced, like other modifications in the economy of living 
things, to the needs of the species. Or, looking at it in 
another aspect, we may say, that amid the constant 
variations of animals and plants colour is ever tending 
to vary and to appear where it is absent; and that natural 
selection is constantly eliminating such tints as are 
injurious to the species, or preserving and intensifying 
such as are useful. 

This view is in accordance with the well-known fact, of 
colours which rarely or never appear in the species in a 
state of nature, continually occurring among domesticated 
animals and cultivated plants ; showing us that the 
capacity to develop colour is ever present, so that almost 
any required tint can be produced which may, under 
changed conditions, be useful, in however small a degree. 

Let us now see how these principles will enable us to 
understand and explain the varied phenomena of colour 
in nature, taking them in the order of our functional 
classification of colours. 

Theory of Protective Colours. We have seen that 
obscure or protective tints in their infinitely varied 
degrees are present in every part of the animal kingdom, 
whole families or genera being often thus coloured. 



188 TROPICAL NATURE, AND OTHER ESSAYS. 

Now the various brown, earthy, ashy, and other neutral 
tints are those which would be most readily produced, 
because they are due to an irregular mixture of many 
kinds of rays ; while pure tints require either rays of 
one kind only, or definite mixtures in proper proportions 
of two or more kinds of rays. This is well exemplified 
by the comparative difficulty of producing definite pure 
tints by the mixture of two or more pigments ; while a 
haphazard mixture of a number of these will be almost 
sure to produce browns, olives, or other neutral or dingy 
colours. An indefinite or irregular absorption of some 
rays and reflection of others would, therefore, produce 
obscure tints ; while pure and vivid colours would re- 
quire a perfectly definite absorption of one portion of 
the coloured rays, leaving the remainder to produce the 
true complementary colour. This being the case we may 
expect these brown tints to occur when the need of 
protection is very slight or even when it does not exist at 
all ; always supposing that bright colours are not in any 
way useful to the species. But whenever a pure colour is 
protective, as green in tropical forests or white among 
arctic snows, there is no difficulty in producing it, by 
natural selection acting on the innumerable slight 
variations of tint which are ever occurring. Such 
variations may, as we have seen, be produced in a great 
variety of ways ; either by chemical changes in the 
secretions, or by molecular changes in surface structure ; 
and may be brought about by change of food, by the 
photographic action of light, or by the normal process of 
generative variation. Protective colours therefore, how- 
ever curious and complex they may be in certain cases, 
offer no real difficulties. 



COLOURS OF ANIMALS. 189 

Theory of Warning Colours. These differ greatly 
from the last class, inasmuch as they present us with a 
variety of brilliant hues, often of the greatest purity, and 
combined in striking contrasts and conspicuous patterns. 
Their use depends upon their boldness and visibility, not 
on the presence of any one colour ; hence we find among 
these groups some of the most exquisitely-coloured 
objects in nature. Many of the uneatable caterpillars 
are strikingly beautiful ; while the Danaidse, Heliconidae, 
and protected groups of Papilionidse, comprise a series of 
butterflies of the most brilliant and contrasted colours. 
The bright colours of many of the sea-anemones and 
sea-slugs will probably be found to be in this sense 
protective, serving as a warning of their uneatableness. 
On our theory none of these colours offer any difficulty. 
Conspicuousness being useful, every variation tending to 
brighter and purer colours was selected ; the result being 
the beautiful variety and contrast we find. 

Imitative Warning Colours : The Theory of 
Mimicry. We now come to those groups which gain 
protection solely by being mistaken for some of these 
brilliantly coloured but uneatable creatures, and here 
a difficulty really exists, and to many minds is so 
great as to be insuperable. It will be well therefore to 
endeavour to explain how the resemblance in question 
may have been brought about. 

The most difficult case, and the one which may be 
taken as a type of the whole class, is that of the 
genus Leptalis (a group of South American butterflies 
allied to our common white and yellow kinds), many of 
the larger species of which are still white or yellow, and 
which are all eatable by birds and other insectivorous 



190 TROPICAL NATURE, AND OTHER ESSAYS. 

creatures. But there are also a number of species of 
Leptalis, which are brilliantly red, yellow, and black, 
and which, band for band and spot for spot, resemble 
some one of the Danaidse or Heliconidae which inhabit 
the same district and which are nauseous and uneatable. 
Now the usual difficulty is, that a slight approach to 
one of these protected butterflies would be of no use, 
while a greater sudden variation is not admissible on the 
theory of gradual change by indefinite slight variations. 
This objection depends almost wholly on the supposi- 
tion that, when the first steps towards mimicry occurred, 
the South American Danaidae were what they are now ; 
while the ancestors of the Leptalides were like the ordi- 
nary white or yellow Pieridse to which they are allied. 
But the danaioid butterflies of South America are so 
immensely numerous and so greatly varied, not only in 
colour but in structure, that we may be sure they are of 
vast antiquity and have undergone great modification. 
A large number of them, however, are still of compara- 
tively plain colours, often rendered extremely elegant 
by the delicate transparency of the wing membrane, but 
otherwise not at all conspicuous. Many have only 
dusky or purplish bands or spots ; others have patches 
of reddish or yellowish brown perhaps the commonest 
colour among butterflies ; while a considerable number 
are tinged or spotted with yellow, also a very common 
colour, and one especially characteristic of the Pieridae, 
the family to which Leptalis belongs. We may there- 
fore reasonably suppose that in the early stages of the 
development of the Danaidse, when they first began to 
acquire those nauseous secretions which are now their 
protection, their colours were somewhat plain ; either 



COLOURS OF ANIMALS. 191 

dusky with paler bands and spots, or yellowish with 
dark borders, and sometimes with reddish bands or 
spots. At this time they had probably shorter wings 
and a more rapid flight, just like the other unprotected 
families of butterflies. But as soon as they became 
decidedly unpalatable to any of their enemies, it would 
be an advantage to them to be readily distinguished 
from all the eatable kinds ; and as butterflies were no 
doubt already very varied in colour, while all probably 
had wings adapted for rather quick or jerking flight, the 
best distinction might have been found in outline and 
habits ; whence would arise the preservation of those 
varieties whose longer wings, bodies, and antennae, as 
well as their slower flight, rendered them noticeable- 
characters which now distinguish the whole group in 
every part of the world. 

Now it would be at this stage, that some of the 
weaker-flying Pieridee which happened to resemble some 
of the Danaidse around them in their yellow and dusky 
tints and in the general outline of their wings, would be 
sometimes mistaken for them by the common enemy, 
and would thus gain an advantage in the struggle for 
existence. Admitting this one step to be made, and all 
the rest must inevitably follow from simple variation 
and survival of the fittest. So soon as the nauseous 
butterfly varied in form or colour to such an extent that 
the corresponding eatable butterfly no longer closely 
resembled it, the latter would be exposed to attacks, 
and only those variations would be preserved which 
kept up the resemblance. At the same time we may 
well suppose the enemies to become more acute and able 
to detect smaller differences than at first. This would 



192 TROPICAL NATURE, AND OTHER ESSAYS. 

lead to the destruction of all adverse variations, and 
thus keep up in continually increasing complexity the 
outward mimicry which now so amazes us. During 
the long ages in which this process has been going 
on, and the Danaidae have been acquiring those speciali- 
ties of colour which aid in their preservation, many 
a Leptalis may have become extinct from not varying 
sufficiently in the right direction and at the right time 
to keep up a protective resemblance to its neighbour ; 
and this well accords with the comparatively small num- 
ber of cases of true mimicry, as compared with the 
frequency of those protective resemblances to vegetable 
or inorganic objects whose forms are less definite and 
colours less changeable. About a dozen other genera of 
butterflies and moths mimic the Danaidse in various 
parts of the world, and exactly the same explanation 
will apply to all of them. They represent those species 
of each group which, at the time when the Danaidae first 
acquired their protective secretions, happened outwardly 
to resemble some of them, and which have, by concurrent 
variation aided by a rigid selection, been able to keep 
up that resemblance to the present day. 1 

Theory of Sexual Colours. In Mr. Darwin's cele- 
brated work, The Descent of Man and Selection in 
Relation to Sex, he has treated of sexual colour in 
combination with other sexual characters, and has 



1 For fuller information on this subject the reader should consult Mr. 
Bates's original paper, " Contributions to an Insect-fauna of the Amazon 
Valley," in Transactions of the Linnean Society, vol. xxiii. p. 495 ; Mr. 
Trimen's paper in voL xxvi. p. 497 ; the author's essay on "Mimicry," &c., 
already referred to ; and in the absence of collections of butterflies, the plates 
of Heliconidae and Leptalidse, in Hewitson's Exotic Butter/lies, and Felder's 
Voyage of the " Novara" may be examined. 



SEXUAL SELECTION. - 193 

arrived at the conclusion that all or almost all the 
colours of the higher animals (including among these 
insects and all vertebrates) are due to voluntary or 
conscious sexual selection ; and that diversity of colour 
in the sexes is due, primarily, to the transmission of 
colour-variations either to one sex only or to both sexes ; 
the difference depending on some unknown law, and not 
being due to natural selection. 

I have long held this portion of Mr. Darwin's theory 
to be erroneous ; and have argued that the primary cause 
of sexual diversity of colour was the need of protec- 
tion, repressing in the female those bright colours which 
are normally produced in both sexes by general laws ; 
and I have attempted to explain many of the more 
difficult cases on this principle. (" A Theory of Birds' 
Nests," in Contributions, fyc., p. 231.) As I have since 
given much thought to this subject, and have arrived 
at some views which appear to me to be of consider- 
able importance, it will be w T ell to sketch briefly the 
theory I now hold, and afterwards show its application to 
some of the detailed cases adduced in Mr. Darwin's work. 

The very frequent superiority of the male bird or 
insect in brightness or intensity of colour, even when 
the general coloration is the same in both sexes, now 
seems to me to be, primarily, due to the greater vigour 
and activity and the higher vitality of the male. The 
colours of an animal usually fade during disease or 
weakness, while robust health and vigour adds to their 
intensity. This is a most important and suggestive 
fact, and one that appears to hold universally. In all 
quadrupeds a "dull coat" is indicative of ill -health or 
low condition ; while a glossy coat and sparkling eye 





194 TROPICAL NATURE, AND OTHER ESSAYS. 

are the invariable accompaniments of health and energy. 
The same rule applies to the feathers of birds, whose 
colours are only seen in their purity during perfect 
health ; and a similar phenomenon occurs even among 
insects, for the bright hues of caterpillars begin to fade 
as soon as they become inactive preparatory to under- 
going their transformation. Even in the vegetable 
kingdom we see the same thing ; for the tints of foliage 
are deepest, and the colours of flowers and fruits richest, 
on those plants which are in the most healthy and 
vigorous condition. 

This intensity of coloration becomes most developed 
in the male during the breeding season, when the 
vitality is at a maximum. It is also very general in 
those cases in which the male is smaller than the female, 
as in the hawks and in most butterflies and moths. The 
same phenomena occur, though in a less marked degree, 
among mammalia. Whenever there is a difference of 
colour between the sexes the male is the darker or more 
strongly marked, and the difference of intensity is most 
visible during the breeding season (Descent of Man, 
p. 533). Numerous cases among domestic animals also 
prove, that there is an inherent tendency in the male to 
special developments of dermal appendages and colour, 
quite independently of sexual or any other form of 
selection. Thus, "the hump on the male zebu cattle of 
India, the tail of fat-tailed rams, the arched outline of 
the forehead in the males of several breeds of sheep, and 
the mane, the long hairs on the hind legs, and the dew- 
lap of the male of the Berbura goat," are all adduced by 
Mr. Darwin as instances of characters peculiar to the 
male, yet not derived from any parent ancestral form. 



SEXUAL SELECTION. 195 

Among domestic pigeons the character of the different 
breeds is often most strongly manifested in the male 
birds ; the wattles of the carriers and the eye- wattles of 
the barbs are largest in the males, and male pouters dis- 
tend their crops to a much greater extent than do the 
females, while the cock fantails often have a greater num- 
ber of tail-feathers than the females. There are also 
some varieties of pigeons of which the males are striped 
or spotted with black while the females are never so 
spotted (Animals and Plants under Domestication, I. 
161) ; yet in the parent stock of these pigeons there are 
no differences between the sexes either of plumage or 
colour, and artificial selection has not been applied to 
produce them. 

The greater intensity of coloration in the male 
which may be termed the normal sexual difference, 
would be further developed by the combats of the males 
for the possession of the females. The most vigorous 
and energetic usually being able to rear most offspring, 
intensity of colour, if dependent on, or correlated with 
vigour, would tend to increase. But as differences of 
colour depend upon minute chemical or structural dif- 
ferences in the organism, increasing vigour acting un- 
equally on different portions of the integument, and often 
producing at the same time abnormal developments of 
hair, horns, scales, feathers, &c., would almost necessarily 
lead also to variable distribution of colour, and thus to 
the production of new tints and markings. These 
acquired colours would, as Mr. Darwin has shown, be 
transmitted to both sexes or to one only, according as 
they first appeared at an early age, or in adults of one 
sex ; and thus we may account for some of the most 

o 2 



196 TROPICAL NATURE, AND OTHER ESSAYS. 

marked differences in this respect. With the exception 
of butterflies, the sexes are almost alike in the great 
majority of insects. The same is the case in mammals 
and reptiles ; while the chief departure from the rule 
occurs in birds, though even here in very many cases the 
law of sexual likeness prevails. But in all cases where 
the increasing development of colour became disadvan- 
tageous to the female, it would be checked by natural 
selection ; and thus produce those numerous instances of 
protective colouring in the female only, which occur in 
these two groups, birds and butterflies. 

Colour as a Means of Recognition. There is also, I 
believe, a very important purpose and use of the varied 
colours of the higher animals, in the facility it affords 
for recognition by the sexes or by the young of the 
same species ; and it is this use which probably fixes 
and determines the coloration in many cases. When 
differences in size and form are very slight, colour affords 
the only means of recognition at a distance, or while in 
motion ; and such a distinctive character must therefore 
be of especial value to flying insects which are continu- 
ally in motion, and encounter each other, as it were, 
by accident. This view offers us an explanation of the 
curious fact, that among butterflies the females of 
closely-allied species in the same locality sometimes 
differ considerably, while the males are much alike ; 
for, as the males are the swiftest and by far the highest 
fliers, and seek out the females, it would evidently be 
advantageous for them to be able to recognise their true 
partners at some distance off. This peculiarity occurs 
with many species of Papilio, Diadema, Adolias, and 
Colias ; and these are all genera, the males of which are 



SEXUAL SELECTION. 197 

strong on the wing and mount high in the air. In 
birds such marked differences of colour are not required, 
owing to their higher organization and more perfect 
senses, which render recognition easy by means of a 
combination of very slight differential characters. 

This principle may perhaps, however, account for 
some anomalies of coloration among the higher animals. 
Thus, while admitting that the hare and the rabbit are 
coloured protectively, M r. Darwin remarks that the latter 
while running to its burrow, is made conspicuous to the 
sportsman, and no doubt to all beasts of prey, by its 
upturned white tail. But this very conspicuousness 
while running away, may be useful as a signal and guide 
to the young, who are thus enabled to escape danger by 
following the older rabbits, directly and without hesita- 
tion, to the safety of the burrow ; and this may be the 
more important from the semi-nocturnal habits of the 
animal. If this explanation is correct, and it certainly 
seems probable, it may serve as a warning of how impos- 
sible it is, without exact knowledge of the habits of an 
animal and a full consideration of all the circumstances, 
to decide that any particular coloration cannot be pro- 
tective or in any way useful. Mr. Darwin himself is not 
free from such assumptions. Thus, he says : " The 
zebra is conspicuously striped, and stripes cannot afford 
any protection on the open plains of South Africa." 
But the zebra is a very swift animal, and, when in herds, 
by no means void of means of defence. The stripes 
therefore may be of use by enabling stragglers to distin- 
guish their fellows at a distance, and they may be even 
protective when the animal is at rest among herbage 
the only time when it would need protective colouring. 



198 TROPICAL NATURE, AND OTHER ESSAYS. 

Until the habits of the zebra have been observed with 
special reference to these points, it is surely somewhat 
hasty to declare that the stripes " cannot afford any 
protection." 

Colour Proportionate to Integumentary Development. 
The wonderful display and endless variety of colour 
in which butterflies and birds so far exceed all other 
animals, seems primarily due to the excessive develop- 
ment and endless variations of the integumentary struc- 
tures. No insects have such widely-expanded wings in 
proportion to their bodies as butterflies and moths ; in 
none do the wings vary so much in size and form, and 
in none are they clothed with such a beautiful and 
highly-organized coating of scales. According to the 
general principles of the production of colour already 
explained, the.se long-continued expansions of membranes 
and developments of surface structures, must have led 
to numerous colour-changes ; which have been sometimes 
checked, sometimes fixed and utilised, sometimes inten- 
sified, by natural selection, according to the needs of the 
animal. In birds, too, we have the wonderful clothing 
of plumage the most highly organized, the most varied, 
and the most expanded of all dermal appendages. The 
endless processes of growth and change during the deve- 
lopment of feathers, and the enormous extent of this 
delicately- organized surface, must have been highly 
favourable to the production of varied colour-effects ; 
which, when not injurious, have been merely fixed for 
purposes of specific identification, but have often been 
modified or suppressed whenever different tints were 
needed for purposes of protection. 

Selection by Females not a Cause of Colour. To 



SEXUAL SELECTION. 199 

conscious sexual selection, that is, the actual choice by 
the females of the more brilliantly-coloured males, I 
believe very little if any effect is directly due. It is 
undoubtedly proved that in birds the females do some- 
times exert a choice ; but the evidence of this fact 
collected by Mr. Darwin (Descent of Man, chap, xiv.) 
does not prove that colour determines that choice, while 
much of the strongest evidence is directly opposed to 
this view. All the facts appear to be consistent with 
the choice depending on a variety of male characteristics, 
with some of which colour is often correlated. Thus it 
is the opinion of some of the best observers that vigour 
and liveliness are most attractive, and these are no doubt 
usually associated with intensity of colour. Again, the 
display of the various ornamental appendages of the male 
during courtship may be attractive; but these appen- 
dages, with their bright colours or shaded patterns, are 
due probably to general laws of growth, and to that 
superabundant vitality which we have seen to be a 
cause of colour. But there are many considerations 
which seem to show that the possession of these orna- 
mental appendages and bright colours in the male is not 
an important character functionally, and that it has not 
been produced by the action of conscious sexual selection. 
Amid the copious mass of facts and opinions collected by 
Mr. Darwin as to the display of colour and ornaments 
by the male birds, there is a total absence of any evi- 
dence that the females admire or even notice this display. 
The hen, the turkey, and the pea-fowl go on feeding 
while the male is displaying his finery ; and there is 
reason to believe that it is his persistency and energy 
rather than his beauty which wins the day. Again, 



200 TROPICAL NATURE, AND OTHER ESSAYS. 

evidence collected by Mr. Darwin himself proves that 
each bird finds a mate under any circumstances. He 
gives a number of cases of one of a pair of birds being 
shot, and the survivor being always found paired again 
almost immediately. This is sufficiently explained on 
the assumption that the destruction of birds by various 
causes is continually leaving widows and widowers in 
nearly equal proportions, and thus each one finds a fresh 
mate ; and it leads to the conclusion that permanently 
unpaired birds are very scarce ; so that, speaking broadly, 
every bird finds a mate and breeds. But this would 
almost or quite neutralize any effect of sexual selection 
of colour or ornament, since the less highly-coloured birds 
would be at no disadvantage as regards leaving healthy 
offspring. If, however, heightened colour is correlated 
with health and vigour ; and if these healthy and vigorous 
birds provide best for their young, and leave offspring 
which, being equally healthy and vigorous, can best 
provide for themselves which cannot be denied ; then 
natural selection becomes a preserver and intensifier 
of colour. 

Another most important consideration is, that male 
butterflies rival or even excel the most gorgeous male 
birds in bright colours and elegant patterns ; and among 
these there is literally not one particle of evidence that 
the female is influenced by colour, or even that she has 
any power of choice; while there is much direct evidence 
to the contrary (Descent of Man, p. 318). The weak- 
ness of the evidence for conscious sexual selection among 
these insects is so palpable, that Mr. Darwin is obliged 
to supplement it by the singularly inconclusive argument 
that, " Unless the female prefer one male to another, the 



SEXUAL SELECTION. 201 

pairing must be left to mere chance, and this does not 
appear probable " (1. c. p. 317). But he has just said 
" The males sometimes fight together in rivalry, and many 
may be seen pursuing or crowding round the same 
female ;" while in the case of the silk-moths, " the 
females appear not to evince the least choice in regard 
to their partners." Surely the plain inference from all 
this is, that males fight and struggle for the almost 
passive female; and that the most vigorous and energetic, 
the strongest- winged or the most persevering, wins her. 
How can there be chance in this ? Natural selection 
would here act, as in birds, in perpetuating the strongest 
and most vigorous males ; and as these would usually be 
the more highly coloured of their race, the same results 
would be produced as regards the intensification and 
variation of colour in the one case as in the other. 

Let us now see how these principles will apply to 
some of the cases adduced by Mr. Darwin in support 
of his theory of conscious sexual selection. 

In Descent of Man, 2nd ed., pp. 307-316, we find an 
elaborate account of the various modes of colouring of 
butterflies and moths, proving that the coloured parts 
are always more or less displayed, and that they have 
some evident relation to an observer. Mr. Darwin then 
says : " From the several foregoing facts it is impos- 
sible to admit that the brilliant colours of butterflies, 
and of some few moths, have commonly been acquired 
for the sake of protection. We have seen that their 
colours and elegant patterns are arranged and exhibited 
as if for display. Hence I am led to believe that the 
females prefer or are most excited by the more brilliant 
males ; for on any other supposition the males would, as 



202 TROPICAL NATURE, AND OTHER ESSAYS. 

far as we can see, be ornamented to no purpose " (Lc., 
p. 316). I am not aware that any one has ever main- 
tained that the brilliant colours of butterflies have 
" commonly been acquired for the sake of protection/' 
yet Mr. Darwin has himself referred to cases in which 
the brilliant colour is so placed as to serve for protec- 
tion ; as for example, the eye-spots on the hind wings 
of moths, which are pierced by birds and so save the 
vital parts of the insect ; while the bright patch on the 
orange-tip butterflies which Mr. Darwin denies are pro- 
tective, may serve the same purpose. It is in fact 
somewhat remarkable how very generally the black 
spots, ocelli, or bright patches of colour are on the 
tips, margins, or discs of the wings ; and as the insects 
are necessarily visible while flying, and this is the time 
when they are most subject to attacks by insectivorous 
birds, the position of the more conspicuous parts at some 
distance from the body may be a real protection to them. 
Again, Mr. Darwin admits that the white colour of the 
male ghost-moth may render it more easily seen by the 
female while flying about in the dusk ; and if to this we 
add that it will be also more readily distinguished from 
allied species, we have a reason for diverse ornamentation 
in these insects quite sufficient to account for most of the 
facts, without believing in the selection of brilliant males 
by the females, for which there is not a particle of 
evidence. 1 

Probable use of the Horns of Beetles. A somewhat 
analogous case is furnished by the immense horns of 
some beetles of the families Copridse and Dynastidae, 
which Mr. Darwin admits are not used for fighting, and 

1 See M. Fabre's testimony on this point, Descent of Man, p. 291. 



SEXUAL SELECTION. 203 

therefore concludes are ornaments, developed through 
selection of the larger-horned males by the females. 
But it has been overlooked that these horns may be 
protective. The males probably fly about most, as is 
usually the case with male insects ; and as they gene- 
rally fly at dusk they are subject to the attacks of 
large-mouthed goatsuckers and podargi, as well as of 
insect-eating owls. Now the long, pointed or forked 
horns, often divergent, or movable with the head, 
would render it very difficult for these birds to swallow 
such insects, and would therefore be an efficient pro- 
tection ; just as are the hooked spines of some stingless 
ants and the excessively hard integuments of many 
beetles, against the smaller insectivorous birds. 

Cause of the greater Brilliancy of some Female In- 
sects. The facts given by Mr. Darwin to show that 
butterflies and other insects can distinguish colours and 
are attracted by colours similar to their own, are quite 
consistent with the view that colour, which continually 
tends to appear, is utilised for purposes of identifica- 
tion and distinction, when not required to be modified 
or suppressed for the purpose of protection. The 
cases of the females of some species of Thecla, Calli- 
dryas, Colias y and Hipparchia, which have more 
conspicuous markings than the male, may be due to 
several causes : to obtain greater distinction from other 
species ; for protection from birds, as in the case of the 
yellow-under wing moths ; while sometimes as in Hip- 
parchia the lower intensity of colouring in the female 
may lead to more contrasted markings. Mr. Darwin 
thinks that here the males have selected the more 
beautiful females ; although one chief fact in support 



204 TROPICAL NATURE, AND OTHER ESSAYS. 

of his theory of conscious sexual selection is, that 
throughout the whole animal kingdom the males are 
usually so ardent that they will accept any female, 
while the females are coy, and choose the handsomest 
males, whence it is believed the general brilliancy of 
males as compared with females has arisen. 

Perhaps the most curious cases of sexual difference 
of colour are those in which the female is very much 
more gaily coloured than the male. This occurs most 
strikingly in some species of Pieris in South America, 
and of Diadema in the Malay islands ; and in both 
cases the females resemble species of the uneatable 
Danaidse and Heliconidse, and thus gain a protec- 
tion. In the case of Pieris pyrrha, P. malenka, 
and P. lorena, the males are plain white and black, 
while the females are orange, yellow, and black, and so 
banded and spotted as exactly to resemble species of 
Heliconidae. Mr. Darwin admits that these bright 
colours have been acquired for protection ; but as 
there is no apparent cause for the strict limitation of 
the colour to the female, he believes that it has been 
kept down in the male by its being unattractive to her. 
This appears to me to be a supposition opposed to the 
whole theory of sexual selection itself. For this theory 
is, that minute variations of colour in the male are 
attractive to the female, have always been selected, and 
that thus the brilliant male colours have been produced. 
But in this case he thinks that the female butterfly had 
a constant aversion to every trace of colour, even when 
we must suppose it was constantly recurring during 
the successive variations which resulted in such a mar- 
vellous change in herself. But the case admits of a 



SEXUAL SELECTION. 205 

much more simple interpretation. For if we consider the 
fact that the females frequent the forests where the Heli- 
conidse abound, while the males fly much in the open 
and assemble in great numbers with other white and 
yellow butterflies on the banks of rivers ; may it not be 
possible that the appearance of orange stripes or patches 
would be as injurious to the male as it is useful to the 
female, by making him a more easy mark for insecti- 
vorous birds among his white companions ? This seems 
a more probable supposition, than the altogether hypo- 
thetical choice of the female, sometimes exercised in 
favour of and sometimes against every new variety of 
colour in her partner. 

A strictly analogous case is that of the glow-worm, 
whose light, as originally suggested by Mr. Belt, is 
admitted to be a warning of its uneatability to insecti- 
vorous nocturnal animals. The male, having wings, 
does not require this protection. In the tropics the 
number of nocturnal insectivorous birds and bats is 
very much greater, hence winged species possess the 
light, as they would otherwise be eaten by mistake for 
more savoury insects ; and it may be that the luminous 
Elateridse of the tropics really mimic the true fireflies 
(Lampyridse), which are uneatable. This is the more 
probable as the Elateridse, in the great majority of 
species, have brown or protective colours, and are 
therefore certainly palatable to insectivorous animals. 

Origin of the Ornamental Plumage of Male Birds. 
We now come to such wonderful developments of 
plumage and colour as are exhibited by the peacock 
and the Argus-pheasant ; and I may here mention that 
it was the case of the latter bird, as fully discussed by 



206 TROPICAL NATURE, AND OTHER ESSAYS. 

Mr. Darwin, which first shook my belief in " sexual," 
or more properly " female " selection. The long series 
of gradations, by which the beautifully shaded ocelli 
on the secondary wing-feathers of this bird, have been 
produced, are clearly traced out ; the result being a set 
of markings, so exquisitely shaded as to represent 
"balls lying loose within sockets" purely artificial 
objects of which these birds could have no possible 
experience. That this result should have been attained 
through thousands and tens of thousands of female 
birds all preferring those males whose markings varied 
slightly in this one direction, this uniformity of choice 
continuing through thousands and tens of thousands of 
generations, is to me absolutely incredible. And when, 
further, we remember that those which did not so vary, 
would also, according to all the evidence, find mates and 
leave offspring, the actual result seems quite impossible 
of attainment by such means. 

Without pretending to solve completely so difficult a 
problem as that of the origin and uses of the variously 
coloured plumes and ornaments so often possessed by 
male birds, I would point out a few facts which seem 
to afford a clue. And first, the most highly-coloured 
and most richly- varied markings occur on those parts 
of the plumage which have undergone the greatest 
modification, or have acquired the most abnormal de- 
velopment. In the peacock, the tail- coverts are enor- 
mously developed, and the " eyes " are situated on the 
greatly dilated ends. In the birds-of-paradise, breast, 
or neck, or head, or tail-feathers, are greatly developed 
and highly coloured. The hackles of the cock, and the 
scaly breasts of humming-birds are similar developments ; 



SEXUAL SELECTION. 207 

while in the Argus-pheasant the secondary quills are 
so enormously lengthened and broadened as to have 
become almost useless for flight. Now it is easily 
conceivable, that during this process of development, 
inequalities in the distribution of colour may have arisen 
in different parts of the same feather; and that spots and 
bands may thus have become broadened out into shaded 
spots or ocelli, in the way indicated by Mr. Darwin, 
much as the spots and rings on a soap-bubble increase 
with increasing tenuity. This is the more probable, 
because in domestic fowls varieties of colour tend to 
become symmetrical, quite independently of sexual 
selection. (Descent of Man, p. 424.) 

If now we accept the evidence of Mr. Darwin's most 
trustworthy correspondents, that the choice of the female, 
so far as she exerts any, falls upon the " most vigorous, 
defiant, and mettlesome male ; " and if we further 
believe, what is certainly the case, that these are as a 
rule the most brightly coloured and adorned with the 
finest developments of plumage, we have a real and not 
a hypothetical cause at work. For these most healthy, 
vigorous, and beautiful males will have the choice of the 
finest and most healthy females ; will have the most 
numerous and healthy families ; and will be able best to 
protect and rear those families. Natural selection, and 
what may be termed male selection, will tend to give 
them the advantage in the struggle for existence ; and 
thus the fullest plumage and the finest colours will be 
transmitted, and tend to advance in each succeeding 
generation. 

Theory of Display of Ornaments by Males. The full 
and interesting account given by Mr. Darwin of the 



20S TROPICAL NATURE, AND OTHER ESSAYS.- 

colours and habits of male and female birds (Descent of 
Man, Chapters xiii. and xiv.), proves that in most, if 
not in all cases, the male birds fully display their orna- 
mental plumage before the females or in rivalry with 
each other; but on the essential point of whether the 
female's choice is determined by minute differences in 
these ornaments or in their colours, there appears to be 
an entire absence of evidence. In the section on "Pre- 
ference for particular Males by the Females," the facts 
quoted show indifference to colour, except that some 
colour similar to their own seems to be preferred. But 
in the case of the hen canary, who chose a greenfinch in 
preference to either chaffinch or goldfinch, gay colours 
had evidently no preponderating attraction. There is 
some evidence adduced that female birds may, and pro- 
bably do, choose their mates ; but none whatever that 
the choice is determined by difference of colour ; and no 
less than three eminent breeders informed Mr. Darwin 
that they " did not believe that the females prefer cer- 
tain males on account of the beauty of their plumage." 
Again, Mr. Darwin himself says : "As a general rule 
colour appears to have little influence on the pairing 
of pigeons." The oft-quoted case of Sir R. Heron's 
pea-hens which preferred an " old pied cock " to those 
normally coloured, is a very unfortunate one ; because 
pied birds are just those that are not favoured in a state 
of nature, or the breeds of wild animals would become 
as varied and mottled as our domestic varieties. If such 
irregular fancies were not rare exceptions, the produc 
tion of definite colours and patterns by the choice of the 
female birds, or in any other way, would be impossible. 
There remains, however, to be accounted for, the 



SEXUAL SELECTION. 209 

remarkable fact of the display by the male of each 
species of its peculiar beauties of plumage and colour, 
a display which Mr. Darwin evidently considers his 
strongest argument in favour of conscious selection by 
the female. This display is, no doubt, a very interesting 
and important phenomenon ; but it may, 1 believe, be 
satisfactorily explained on the general principles here laid 
down, without calling to our aid a purely hypothetical 
choice exerted by the female bird. 

At pairing-time, the male is in a state of excitement, and 
full of exuberant energy. Even unornamental birds flutter 
their wings or spread them out, erect their tails or crests, 
and thus give vent to the nervous excitability with which 
they are overcharged. It is not improbable that crests 
and other erectile feathers may be primarily of use in 
frightening away enemies, since they are generally 
erected when angry or during combat. Those indi- 
viduals who were most pugnacious and defiant, and who 
brought these erectile plumes most frequently and most 
powerfully into action, would tend to increase them by 
use, and to leave them further developed in some of 
their descendants. If, in the course of this development, 
colour appeared and we have already shown that such 
developments of plumage are a very probable cause 
of colour we have every reason to believe it would 
be most vivid in these most pugnacious and energetic 
individuals ; and as these would always have the advan- 
tage in the rivalry for mates (to which advantage the 
excess of colour and plumage might sometimes conduce), 
there seems nothing to prevent a progressive develop- 
ment of these ornaments in all dominant races ; that is, 
wherever there was such a surplus of vitality, and such 

p 



210 TROPICAL NATURE, AND OTHER ESSAYS. 

complete adaption to conditions, that the inconvenience 
or danger produced by such ornaments was so com- 
paratively small as not to affect the superiority of the 
race over its nearest allies. 

But if those portions of the plumage, which were 
originally erected under the influence of anger or fear, 
became largely developed and brightly coloured, the 
actual display, under the influence of jealousy or sexual 
excitement becomes quite intelligible. The males, in 
their rivalry with each other, would see what plumes 
were most effective ; and each would endeavour to excel 
his enemy as far as voluntary exertion would enable him, 
just as they endeavour to rival each other in song, even 
sometimes to the point of causing their own destruction. 

Natural Selection as Neutralizing Sexual Selection. 
There is also a general argument against Mr. Darwin's 
views on this question, founded on the nature and 
potency of " natural " as opposed to " sexual " selection, 
which appears to me to be of itself almost conclusive 
as to the whole matter at issue. Natural selection, or 
the survival of the fittest, acts perpetually and on an 
enormous scale. Taking the offspring of each pair of 
birds as, on the average, only six annually, one-third 
of these at most will be preserved, while the two- thirds 
which are least fitted will die. At intervals of a few 
years, whenever unfavourable conditions occur, five- 
sixths, nine-tenths, or even a greater proportion of the 
whole yearly production are weeded out, leaving only 
the most perfect and best adapted to survive. Now 
unless these survivors are, on the whole, the most 
ornamental, this rigid natural selection must neutralise 
and destroy any influence that may be exerted by 



SEXUAL SELECTION. 211 

female selection. The utmost that can be claimed for 
the latter is, that a small fraction of the least ornamented 
do not obtain mates, while a few of the most orna- 
mented may leave more than the average number of 
offspring. Unless, therefore, there is the strictest cor- 
relation between ornament and general perfection, the 
more brightly coloured or ornamented varieties can 
obtain no permanent advantage ; and if there is (as I 
maintain) such a correlation, then the sexual selection 
of colour or ornament, for which there is little or no 
evidence, becomes needless, because natural selection 
which is an admitted vera causa, will itself produce all 
the results. 

In the case of butterflies the argument becomes even 
stronger, because the fertility is so much greater than 
in birds, and the weeding-out of the unfit takes place, to 
a great extent, in the egg and larva state. Unless the 
eggs and larvae which escaped to produce the next 
generation were those which would produce the more 
highly -coloured butterflies, it is difficult to perceive how 
the slight preponderance of colour sometimes selected by 
the females, should not be wholly neutralized by the ex- 
tremely rigid selection for other qualities to which the 
offspring in every stage are exposed. The only way in 
which we can account for the observed facts is, by the 
supposition that colour and ornament are strictly corre- 
lated with health, vigour, and general fitness to survive. 
We have shown that there is reason to believe that this 
is the case, and if so, conscious sexual selection becomes 
as unnecessary as it would certainly be ineffective. 

Greater Brilliancy of some Female Birds. There is 
one other very curious case of sexual colouring among 

p 2 



212 TROPICAL NATURE, AND OTHER ESSAYS. 

birds that, namely, in which the female is decidedly 
brighter or more strongly marked than the male ; 
as in the fighting quails (Turnix), painted snipe 
(Rhynchcea) , two species of phalarope (Phalaropus), 
and the common cassowary (Casuarius galeatus). In 
all these cases, it is known that the males take charge 
of and incubate the eggs, while the females are almost 
always larger and more pugnacious. 

In my "Theory of Birds' Nests" (Natural Selection, 
p. 251), I imputed this difference of colour to the 
greater need for protection by the male bird while 
incubating ; to which Mr. Darwin has objected that the 
difference is not sufficient, and is not always so distri- 
buted as to be most effective for this purpose ; and he 
believes that it is due to reversed sexual selection, that 
is, to the female taking the usual rdle of the male, and 
being chosen for her brighter tints. We have already 
seen reason for rejecting this latter theory in every case ; 
and I also admit that Mr. Darwin's criticism is sound, 
and that my theory of protection is, in this case, only 
partially, if at all, applicable. But the theory now 
advanced, of intensity of colour being due to general 
vital energy, is quite applicable ; and the fact that the 
superiority of the female in this respect is quite excep- 
tional, and is therefore probably not in. any case of 
very ancient date, will account for the difference of 
colour thus produced being always very slight. 

Colour-development as Illustrated by Humming-birds. 
Of the mode of action of the general principles of 
colour- development among animals, we have an excellent 
example in the humming-birds. Of all birds these are 
at once the smallest, the most active, and the fullest of 



SEXUAL SELECTION. 213 

vital energy. When poised in the air their wings are 
invisible, owing to the rapidity of their motion, and 
when startled they dart away with the rapidity of a 
flash of light. Such active creatures would not be an 
easy prey to any rapacious bird ; and if one at length 
was captured, the morsel obtained would hardly repay 
the labour. We may be sure, therefore, that they are 
practically unmolested. The immense variety they 
exhibit in structure, plumage, and colour, indicates a 
high antiquity for the race; while their general abundance 
in individuals shows that they are a dominant group, 
well adapted to all the conditions of their existence. 
Here we find everything necessary for the development 
of colour and accessory plumes. The surplus vital 
energy shown in their combats and excessive activity, 
has expended itself in ever-increasing developments of 
plumage, and greater and greater intensity of colour, 
regulated only by the need for specific identification 
which would be especially required in such small and 
mobile creatures. Thus may be explained those remark- 
able differences of colour between closely-allied species, 
one having a crest like the topaz, while in another it 
resembles the sapphire. The more vivid colours and 
more developed plumage of the males, I am now inclined 
to think may be wholly due to their greater vital energy, 
and to those general laws which lead to such superior 
developments even in domestic breeds ; but in some 
cases the need of protection by the female while in- 
cubating, to which I formerly imputed the whole phe- 
nomenon, may have suppressed a portion of the ornament 
which she would otherwise have attained. 

The extreme pugnacity of humming-birds has been 



214: TROPICAL NATURE, AND OTHER ESSAYS. 

noticed by all observers, and it seems to be to some 
extent proportioned to the degree of colour and orna- 
ment in the species. Thus Mr. Salvin observes of Eugenes 
fulgens, that it is "a most pugnacious bird/' and that 
" hardly any species shows itself more brilliantly on the 
wing." Again of Oampylopterus hemileucurus, "the 
pugnacity of this species is remarkable. It is very 
seldom that two males meet without an aerial battle," 
and "the large and showy tail of this humming-bird 
makes it one of the most conspicuous on the wing." 
Again, the elegant frill-necked Lophornis ornatus " is 
very pugnacious, erecting its crest, throwing out its 
whiskers and attacking every humming-bird that may 
pass within its range of vision ; " and of another species 
L. magnificus, it is said that "it is so bold that the 
sight of man creates no alarm." The beautifully- 
coloured Thaumastura Cora " rarely permits any other 
humming-bird to remain in its neighbourhood, but 
wages a continual and terrible war upon them." The 
magnificent bar-tail, Cometes s-parganurus, one of the 
most imposing of all the humming-birds, is extremely 
fierce and pugnacious, "the males chasing each other 
through the air with surprising perseverance and acri- 
mony." These are all the species I find noticed as 
being especially pugnacious, and every one of them is 
exceptionally coloured or ornamented ; while not one of 
the small, plain, and less ornamental species are so 
described, although many of them are common and 
well observed species. It is also to be noticed that 
the remarkable pugnacity of these birds is not confined 
to one season or even to birds of the same species, as 
is usual in sexual combats, but extends to any other 



SEXUAL SELECTION. 215 

species that may be encountered, while they are said 
even to attack birds of prey that approach too closely 
to their nests. It must be admitted that these facts 
agree well with the theory that colour and ornament 
are due to surplus vital energy and a long course of 
unchecked development. We have also direct evidence 
that the males are more active and energetic than the 
females. Mr. Gosse says that the whirring made by 
the male Polytmus humming-bird is shriller than that 
produced by the female ; and he also informs us that 
the male flies higher and frequents mountains while the 
female keeps to the lowlands. 

Theory of Typical Colours. The remaining kinds of 
animal colours, those which can neither be classed as 
protective, warning, or sexual, are for the most part 
readily explained on the general principles of the de- 
velopment of colour which we have now laid down. It 
is a most suggestive fact, that, in cases where colour is 
required only as a warning, as among the uneatable 
caterpillars, we find, not one or two glaring tints only, 
but every kind of colour disposed in elegant patterns, 
and exhibiting almost as much variety and beauty as 
among insects and birds. Yet here, not only is sexual 
selection out of the question, but the need for recognition 
and identification by others of the same species, seems 
equally unnecessary. We can then only impute this 
variety to the normal production of colour in organic 
forms, when fully exposed to light and air and under- 
going great and rapid developmental modification. 
Among more perfect animals, where the need for recog- 
nition has been added, we find intensity and variety of 
colour at its highest pitch among the South American 



216 TROPICAL NATURE, AND OTHER ESSAYS. 

butterflies of the families Heliconidae and Danaidse, as 
well as among the Nymphalidse and Erycinidse, many of 
which obtain the necessary protection in other ways. 
Among birds also, wherever the habits are such that no 
special protection is needed for the females, and where 
the species frequent the depths of tropical forests, and 
are thus naturally protected from the swoop of birds of 
prey, we find almost equally intense coloration ; as in 
the trogons, barbets, and gapers. 

Local Causes of Colour-development. Another real, 
though as yet inexplicable cause of diversity of colour, 
is to be found in the influence of locality. It is 
observed that species of totally distinct groups are 
coloured alike in one district, while in another district 
the allied species all undergo the same change of colour. 
Cases of this kind have been adduced by Mr. Bates, by 
Mr. Darwin, and by myself, and I have collected all the 
more curious and important examples in my Address to 
the Biological Section of the British Association, at 
Glasgow in 1876 (Chap. VII. of this volume). The most 
probable cause for these simultaneous variations would 
seem to be the presence of peculiar elements or chemical 
compounds in the soil, the water, or the atmosphere, 
or of special organic substances in the vegetation ; and 
a wide field is thus offered for chemical investigation 
in connection with this interesting subject. Yet, how- 
ever we may explain it the fact remains, of the same 
vivid colours in definite patterns being produced in quite 
unrelated groups, which only agree, so far as we yet 
know, in inhabiting the same locality. 

Summary on Colour-development in Animals. Let 
us now sum up the conclusion at which we have arrived, 



COLOURS OF ANIMALS. 217 

as to the various modes in which colour is produced or 
modified in the animal kingdom. 

The various causes of colour in the animal world are, 
molecular and chemical change of the substance of their 
integuments, or the action on it of heat, light or mois- 
ture. It is also produced by interference of light in 
superposed transparent lamellae, or by excessively fine 
surface-strise. These elementary conditions for the pro- 
duction of colour are found everywhere in the surface- 
structures of animals, so that its presence must be looked 
upon as normal, its absence as exceptional. 

Colours are fixed or modified in animals by natural 
selection for various purposes ; obscure or imitative 
colours for concealment ; gaudy colours as a warning ; 
and special markings, either for easy recognition by 
strayed individuals, females, or young, or to direct 
attack from a vital part, as in the large brilliantly- 
marked wings of some butterflies and moths. 

Colours are produced or intensified by processes of 
development, either where the integument or its 
appendages undergo great extension or modification, or 
where there is a surplus of vital energy, as in male 
animals generally, and more especially at the breeding- 
season. 

Colours are also more or less influenced by a variety of 
causes, such as the nature of the food, the photographic 
action of light, and also by some unknown local action 
probably dependent on chemical peculiarities in the soil 
or vegetation. 

These various causes have acted and reacted in a 
variety of ways, and have been modified by conditions 
dependent on age or on sex, on competition with new 



218 TROPICAL NATURE, AND OTHER ESSAYS. 

forms, or on geographical or climatic changes. In so 
complex a subject, for which experiment and systematic 
inquiry has done so little, we cannot expect to explain 
every individual case, or solve every difficulty ; but it 
is believed that all the great features of animal colora- 
tion and many of the details become explicable on the 
principles we have endeavoured to lay down. 

It will perhaps be considered presumptuous to put 
forth this sketch of the subject of colour in animals, as 
a substitute for one of Mr. Darwin's most highly elabo- 
rated theories that of voluntary or perceptive sexual 
selection ; yet I venture to think that it is more in ac- 
cordance with the whole of the facts, and with the theory 
of natural selection itself ; and I would ask such of my 
readers as may be sufficiently interested in the sub- 
ject, to read again Chapters XI. to XVI. of the Descent of 
Man, and consider the whole subject from the point of 
view here laid down. The explanation of almost all 
the ornaments and colours of birds and insects as having 
been produced by the perceptions and choice of the 
females, has, I believe, staggered many evolutionists, but 
has been provisionally accepted because it was the only 
theory that even attempted to explain the facts. It 
may perhaps be a relief to some of them, as it has been 
to myself, to find that the phenomena can be shown to 
depend on the general laws of development, and on the 
action of " natural selection/ 5 which theory will, I 
venture to think, be relieved from an abnormal excres- 
cence and gain additional vitality, by the adoption of 
the views here imperfectly set forth. 

Although we have arrived at the conclusion that 



COLOURS OF ANIMALS. 219 

tropical light and heat can in no sense be considered as 
the cause of colour, there remains to be explained the 
undoubted fact that all the more intense and gorgeous 
tints are manifested by the animal life of the tropics ; 
while in some groups, such as butterflies and birds, there 
is a marked preponderance of highly-coloured species. 
This is probably due to a variety of causes, some of which 
we can indicate, while others remain to be discovered. 
The luxuriant vegetation of the tropics throughout the 
entire year affords so much concealment, that colour 
may there be safely developed to a much greater extent 
than in climates where the trees are bare in winter, 
during which season the struggle for existence is most 
severe, and even the slightest disadvantage may prove 
fatal. Equally important, probably, has been the per- 
manence of favourable conditions in the tropics, 
allowing certain groups to continue dominant for long 
periods, and thus to carry out in one unbroken line 
whatever developments of plumage or colour may once 
have acquired an ascendency. Changes of climatal con- 
ditions, and pre-eminently the glacial epoch, probably led 
to the extinction of a host of highly- developed and finely- 
coloured insects and birds intemperate zones ; just as we 
know that it led to the extinction of the larger and more 
powerful mammalia which formerly characterised the 
temperate zone in both hemispheres; and this view is 
supported by the fact that it is amongst those groups 
only which are now exclusively tropical that all the 
more extraordinary developments of ornament and colour 
are found. The obscure local causes of colour to which 
we have referred will also have acted most efficiently 
in regions where the climatal condition remained 



220 TROPICAL NATURE, AND OTHER ESSAYS. 

constant, and where migration was unnecessary ; while 
whatever direct effect may be produced by light or heat, 
will necessarily have acted more powerfully within the 
tropics. And lastly, all these causes have been in action 
over an actually greater area in tropical than in tem- 
perate zones ; while estimated potentially, in proportion 
to its life-sustaining power, the lands which enjoy a 
practically tropical climate (extending as they do con- 
siderably beyond the geographical tropics) are very 
much larger than the temperate regions of the earth. 

Combining the effects of all these various causes we are 
quite able to understand the superiority of the tropical 
parts of the globe, not only in the abundance and 
variety of their forms of life, but also as regards the 
ornamental appendages and vivid coloration which 
these forms present. 



VI. 

THE COLOURS OF PLANTS AND THE ORIGIN 
OF THE COLOUR-SENSE. 

Source of Colouring matter -in Plants Protective Coloration and Mimicry 
among Plants Attractive Colours of Fruits Protective Colours of 
Fruits Attractive Colours of Flowers Attractive Odours in Flowers 
Attractive grouping of Flowers Why Alpine Flowers are so Beautiful 
Why allied species of Flowers differ in Size and Beauty Absence of 
Colours in Wind-fertilized Flowers The same Theory of Colour applicable 
to Animals and Plants Relation of the Colours of Flowers and their 
Geographical Distribution Recent Views as to the Direct Action of Light 
on the Colours of Flowers and Fruits On the Origin of the Colour- 
sense Supposed increase of Colour-perception within the Historical 
Period Concluding Remarks on the Colour-sense. 

THE colouring of plants is neither so varied nor so com- 
plex as that of animals, and its explanation accordingly 
offers fewer difficulties. The colours of foliage are, 
comparatively, little varied, and can be traced in almost 
all cases to a special pigment termed chlorophyll, to 
which is due the general green colour of leaves ; but the 
recent investigations of Mr. Sorby and others have shown 
that chlorophyll is not a simple green pigment, but that 
it really consists of at least seven distinct substances, 
varying in colour from blue to yellow and orange. These 
differ in their proportions in the chlorophyll of different 
plants ; they have different chemical reactions ; they are 



222 TROPICAL NATURE, AND OTHER ESSAYS. 

differently affected by - light ; and they give distinct 
spectra. Mr. Sorby further states that scores of different 
colouring matters are found in the leaves and flowers of 
plants, to some of which appropriate names have been 
given, as erythrophyll which is red, and phaiophyll 
which is brown ; and many of these differ greatly from 
each other in their chemical composition. These in- 
quiries are at present in their infancy, but as the original 
term chlorophyll seems scarcely applicable under the 
present aspect of the subject, it would perhaps be better 
to introduce the analogous word Chromophyll, as a 
general term for the colouring matters of the vegetable 
kingdom. 

Light has a much more decided action on plants than 
on animals. The green colour of leaves is almost wholly 
dependent on it ; and although some flowers will become 
fully coloured in the dark, others are decidedly affected 
by the absence of light, even when the foliage is fully 
exposed to it. Looking therefore at the numerous 
colouring matters which are developed in the tissues 
of plants, the sensitiveness of these pigments to light, 
the changes they undergo during growth and develop- 
ment, and the facility with which new chemical com- 
binations are effected by the physiological processes of 
plants as shown by the endless variety in the chemical 
constitution of vegetable products, we have no difficulty 
in comprehending the general causes which aid in pro- 
ducing the colours of the vegetable world, or the extreme 
variability of those colours. We may therefore here 
confine ourselves to an inquiry into the various uses of 
colour in the economy of plants ; and this will generally 
enable us to understand how it has become fixed and 



COLOURS OF PLANTS. 223 

specialised in the several genera and species of the 
vegetable kingdom. 

Protective Coloration and Mimicry in Plants. In 
animals, as we have seen, colour is greatly influenced by 
the need of protection from, or of warning to, their 
numerous enemies, and by the necessity for identification 
and easy recognition. Plants rarely need to be concealed, 
and obtain protection either by their spines, their hard- 
ness, their hairy covering, or their poisonous secretions. 
A very few cases of what seem to be true protective 
colouring do, however, exist ; the most remarkable being 
that of the " stone mesembryanthemum," of the Cape of 
Good Hope, which, in form and colour closely resembles 
the stones among which it grows ; and Dr. Burchell, who 
first discovered it, believes that the juicy little plant thus 
generally escapes the notice of cattle and wild herbivorous 
animals. Mr. J. P. Mansel Weale also noticed that many 
plants growing in the stony Karoo have their tuberous 
roots above the soil ; and these so perfectly resemble the 
stones among which they grow that, when not in leaf, it 
is almost impossible to distinguish them (Nature, vol. iii. 
p. 507). A few cases of what seems to be protective 
mimicry have also been noted ; the most curious being 
that of three very rare British fungi, found by Mr. 
Worthington Smith, each in company with common 
species which they so closely resembled that only a 
minute examination could detect the difference. One 
of the common species is stated in botanical works to be 
" bitter and nauseous," so that it is not improbable that 
the rare kind may escape being eaten by being mistaken 
for an uneatable species, though itself palatable. Mr. 
Mansel Weale also mentions a labiate plant, the Ajvc/a- 



224 TROPICAL NATURE, AND OTHER ESSAYS. 

ophrydis, of South Africa, as strikingly resembling an 
orchid. This may be a means of attracting insects to 
fertilize the flower in the absence of sufficient nectar or 
other attraction in the flower itself ; and the supposition 
is rendered more probable by this being the only species 
of the genus Ajuga in South Africa. Many other cases 
of resemblances between very distinct plants have been 
noticed as that of some Euphorbias to Cacti ; but these 
very rarely inhabit the same country or locality, and it 
has not been proved that there is in any of these cases 
the amount of inter-relation between the species which is 
the essential feature of the protective "mimicry" that 
occurs in the animal world. 

The different colours exhibited by the foliage of plants 
and the changes it undergoes during growth and decay, 
appear to be due to the general laws already sketched 
out, and to have little if any relation to the special 
requirements of each species. But flowers and fruits 
exhibit definite and well-pronounced tints, often varying 
from species to species, and more or less clearly related 
to the habits and functions of the plant. With the few 
exceptions already pointed out, these may be generally 
classed as attractive colours. 

Attractive Colours of Fruits. The seeds of plants 
require to be dispersed, so as to reach places favourable 
for germination and growth. Some are very minute, 
and are carried abroad by the wind ; or they are violently 
expelled and scattered by the bursting of the containing 
capsules. Others are downy or winged, and are carried 
long distances by the gentlest breeze ; or they are hooked 
and stick to the fur of animals. But there is a large 
class of seeds which cannot be dispersed in either of these 



COLOURS OF PLANTS. 225 

ways, and they are mostly contained in eatable fruits. 
These fruits are devoured by birds or beasts, and the 
hard seeds pass through their stomachs undigested, and, 
owing probably to the gentle heat and moisture to which 
they have been subjected, in a condition highly favourable 
for germination* The dry fruits or capsules containing 
the first two classes of seeds are rarely, if ever, conspicu- 
ously coloured ; whereas the eatable fruits almost in- 
variably acquire a bright colour as they ripen, while at 
the same time they become soft and often full of agreeable 
juices. Our red haws and hips, our black elderberries, 
our blue sloes, and whortleberries, our white mistletoe 
and snowberry, and our orange sea-buckthorn, are 
examples of the colour-sign of edibility ; and in every 
part of the world the same phenomenon is found. Many 
such fruits are poisonous to man and to some animals, 
but they are harmless to others ; and there is probably 
nowhere a brightly-coloured pulpy fruit which does not 
serve as food for some species of bird or mammal. 

Protective Colours of Fruits. The nuts and other 
hard fruits of large forest-trees, though often greedily 
eaten by animals, are not rendered attractive to them 
by colour, because they are not intended to be eaten. 
This is evident ; for the part eaten in these cases is 
the seed itself, the destruction of which must certainly 
be injurious to the species. Mr. Grant Allen, in 
his ingenious work on Physiological ^Esthetics, well 
observes that the colours of all such fruits are protective 
green when on the tree, and thus hardly visible among 
the foliage, but turning brown as they ripen, and fall 
on the ground, as filberts, chestnuts, walnuts, beech- 
nuts, and many others. It is also to be noted that 

Q 



226 TROPICAL NATURE, AND OTHER ESSAYS. 

many of these are specially though imperfectly pro- 
tected ; some by a prickly coat as in the chestnuts, or 
by a nauseous covering as in the walnut ; and the 
reason why the protection is not carried further is 
probably because it is not needed, these trees producing 
such vast quantities of fruit, that however many are 
eaten, more than enough are always left to produce 
young plants. In the case of the attractively coloured 
fruits, it is curious to observe how the seeds are always 
of such a nature as to escape destruction when the 
fruit itself is eaten. They are generally very small 
and comparatively hard, as in the strawberry, goose- 
berry, and fig ; if a little larger, as in the grape, they 
are still harder and less eatable ; in the fruit of the 
rose (or hip) they are disagreeably hairy ; in the orange 
tribe excessively bitter. When the seeds are larger, 
softer, and more eatable, they are protected by an 
excessively hard and stony covering, as in the plum 
and peach tribe ; or they are inclosed in a tough horny 
core, as with crabs and apples. These last are much 
eaten by swine, and are probably crushed and swallowed 
without bruising the core or the seeds, which pass 
through their bodies undigested. These fruits may also 
be swallowed by some of the larger frugivorous birds ; 
just as nutmegs are swallowed by pigeons for the sake 
of the mace which incloses the nut, and which by its 
brilliant red colour is an attraction as soon as the fruit 
has split open, which it does upon the tree. 

There is, however, one curious case of an attractively 
coloured seed which has no soft eatable covering. The 
Abrus precatoria, or "rosary bean/' is a leguminous 
shrub or small tree growing in many tropical countries, 



COLOURS OF PLANTS. 227 

whose pods curl up and split open on the tree, dis- 
playing the brilliant red seeds within. It is very hard 
and glossy, and is said to be, as no doubt it is, " very 
indigestible." It may be that birds, attracted by the 
bright colour of the seeds, swallow them, and that they 
pass through their bodies undigested, and so get dis- 
persed. If so it would be a case among plants analogous 
to mimicry among animals an appearance of edibility 
put on to deceive birds for the plant's benefit. Perhaps 
it succeeds only with young and inexperienced birds, 
and it would have a better chance of success, because 
such deceptive appearances are very rare among plants. 

The smaller plants w r hose seeds simply drop upon the 
ground, as in the grasses, sedges, composites, um- 
belli ferae, &c., always have dry and obscurely- coloured 
capsules and small brown seeds. Others whose seeds 
are ejected by the bursting open of their capsules, as 
with the oxalis and many of the caryophyllacese, scro- 
phulariacese, &c., have their seeds very small and rarely 
or never edible. 

It is to be remarked that most of the plants whose 
large- seeded nuts cannot be eaten without destroying 
their germinating power as the oaks, beeches, and 
chestnuts are trees of large size which bear great 
quantities of fruit, and that they are long lived and 
have a wide geographical range. They belong to what 
are called dominant groups, and are thus able to endure 
having a large proportion of their seeds destroyed with 
impunity. It is a suggestive fact that they are among 
the most ancient of known dicotyledonous plants oaks 
and beeches going back to the Cretaceous period with 
little change of type, so that it is not improbable that 

Q 2 



228 TROPICAL NATURE, AND OTHER ESSAYS. 

they may be older than any fruit-eating mammal 
adapted to feed upon their fruits. The attractive 
coloured fruits on the other hand, having so many 
special adaptations to dispersal by birds and mammals, 
are probably of more recent origin. 1 The apple and 
plum tribes are not known earlier than the Miocene 
period ; and although the record of extinct vegetable life 
is extremely imperfect, and the real antiquity of these 
groups is no doubt very much greater, it is not im- 
probable that the comparative antiquity of the fruit- 
bearing and nut- bearing trees may remain unchanged 
by further discoveries, as has almost always happened as 
regards the comparative antiquity of animal groups. 

Attractive Colours of Flowers. The colours of flowers 
serve to render them visible and recognizable by insects, 
which are attracted by secretions of nectar or pollen. 
During their visits for the purpose of obtaining these 
products, insects involuntarily carry the pollen of one 
flower to the stigma of another, and thus effect cross- 
fertilization ; which, as Mr. Darwin was the first to 
demonstrate, immensely increases the vigour and 
fertility of the next generation of plants. This dis- 
covery has led to the careful examination of great 
numbers of flowers ; and the result has been that the 
most wonderful and complex arrangements have been 
found to exist, all having for their object to secure that 
flowers shall not be self-fertilized perpetually, but that 
pollen shall be carried, either constantly or occasionally, 
from the flowers of one plant to those of another. 
Mr. Darwin himself first worked out the details in 
orchids, primulas, and some other groups ; and hardly 

1 I owe this remark to Mr. Grant Allen, author of Physiological ^Esthetics. 



COLOURS OF PLANTS. 229 

less curious phenomena have since been found to occur 
even among some of the most regularly-formed flowers. 
The arrangement, length, and position of all the parts 
of the flower is now found to have a purpose, and not 
the least remarkable portion of the phenomenon is the 
great variety of ways in which the same result is 
obtained. After the discoveries with regard to orchids, 
it was to be expected that the irregular, tubular, and 
spurred flowers should present various curious adapta- 
tions for fertilization by insect-agency. But even 
among the open, cup-shaped, and quite regular flowers, 
in which it seemed inevitable that the pollen must fall 
on the stigma and produce constant self-fertilization, it 
has been found that this is often prevented by a phy- 
siological variation the anthers constantly emitting 
their pollen either a little earlier or a little later than 
the stigmas of the same flower, or of other flowers on 
the same plant, were in the best state to receive it ; and 
as individual plants in different stations, soils, and 
aspects, differ somewhat in the time of flowering, the 
pollen of one plant would often be conveyed by insects 
to the stigmas of some other plant in a condition to be 
fertilized by it. This mode of securing cross-fertilization 
seems so simple and easy, that we can hardly help 
wondering why it did not always come into action, and 
so obviate the necessity for those elaborate, varied, and 
highly complex contrivances found perhaps in the 
majority of coloured flowers. The answer to this of 
course is, that variation sometimes occurred most freely 
in one part of a plant's organization, and sometimes 
in another ; and that the benefit of cross-fertilization 
was so great that any variation that favoured it was 



230 TROPICAL NATURE, AND OTHER ESSAYS. 

preserved, and then formed the starting-point of a whole 
series of further variations, resulting in those marvellous 
adaptations for insect fertilization, which have given 
much of their variety, elegance, and beauty, to the floral 
world. For details of these adaptations we must refer 
the reader to the works of Darwin, Lubbock, Herman 
Miiller, and others. We have here only to deal with 
the part played by colour, and by those floral structures 
in which colour is most displayed. 

Attractive Odours in Flowers. The sweet odours of 
flowers, like their colours, seem often to have been 
developed as an attraction or guide to insect fertilizers, 
and the two phenomena are often complementary to 
each other. Thus, many inconspicuous flowers like the 
mignonette and the sweet-violet, can be distinguished 
by their odours before they attract the eye, and this 
may often prevent their being passed unnoticed ; while 
very showy flowers, and especially those with varie- 
gated or spotted petals, are seldom sweet. White, or 
very pale flowers, on the other hand, are often exces- 
sively sweet, as exemplified by the jasmine and clematis ; 
and many of these are only scented at night, as is 
strikingly the case with the night-smelling stock, our 
butterfly orchids (Habenaria chlorantha), the greenish- 
yellow Daphne pontica, and many others. These white 
flowers are mostly fertilized by night-flying moths ; and 
those which reserve their odours for the evening pro- 
bably escape the visits of diurnal insects, which would 
consume their nectar without effecting fertilization. The 
absence of odour in showy flowers, and its preponderance 
among those that are white, may be shown to be a fact 
by an examination of the lists in Mr. Mongredien's work 



COLOURS OF PLANTS. 231 

on hardy trees and shrubs. 1 He gives a list of about 
160 species with showy flowers, and another list of sixty 
species with fragrant flowers : but only twenty of these 
latter are included among the showy species, and these 
are almost all white flowered. Of the sixty species with 
fragrant flowers, more than forty are white, and a 
number of others have greenish, yellowish, or dusky and 
inconspicuous flowers. The relation of white flowers to 
nocturnal insects is also well shown by those which, 
like the evening primroses, only open their large white 
blossoms after sunset. The red Martagon lily has been 
observed by Mr. Herman Miiller to be fertilized by the 
humming-bird hawk moth, which flies in the morning 
and afternoon when the colours of this flower, exposed 
to the nearly horizontal rays of the sun, glow 
with brilliancy, and when it also becomes very sweet- 
scented. 

Attractive grouping of Flowers. To the same need of 
conspicuousness the combination of so many individually 
small flowers into heads and bunches is probably due, 
producing such broad masses as those of the elder, the 
guelder-rose, and most of the Umbelliferse, or such 
elegant bunches as those of the lilac, laburnum, horse 
chestnut, and wistaria. In other cases minute flowers 
are gathered into dense heads, as with Globularia, 
Jasione, clover, and all the Compositae ; and among the 
latter the outer flowers are often developed into a ray, as 
in the sunflowers, the daisies, and the asters, forming a 
starlike compound flower, which is itself often produced 
in immense profusion. 

1 Trees and Shrubs for English Plantations, by Augustus Mongredien. 
Murray, 1870. 



232 TROPICAL NATURE, AND OTHER ESSAYS. 

Why Alpine Flowers are so Beautiful. The beauty 
of alpine flowers is almost proverbial. It consists either 
in the increased size of the individual flowers as com- 
pared with the whole plant, in increased intensity of 
colour, or in the massing of small flowers into dense 
cushions of bright colour ; and it is only in the higher 
Alps, above the limit of forests and upwards towards the 
perpetual snow-line that these characteristics are fully 
exhibited. This effort at conspicuousness under adverse 
circumstances may be traced to the comparative scarcity 
of winged insects in the higher regions, and to the 
necessity for attracting them from a distance. Amid 
the vast slopes of debris and the huge masses of rock so 
prevalent in higher mountain regions, patches of intense 
colour can alone make themselves visible and serve to 
attract the wandering butterfly from the valleys. Mr. 
Herman Muller's careful observations have shown, that in 
the higher Alps bees and most other groups of winged 
insects are almost wanting, while butterflies are tolerably 
abundant ; and he has discovered, that in a number of 
cases where a lowland flower is adapted to be fertilized by 
bees, its alpine ally has had its structure so modified as 
to be adapted for fertilization only by butterflies. 1 But 
bees are always (in the temperate zone) far more abun- 
dant than butterflies, and this will be another reason why 
flowers specially adapted to be fertilized by the latter 
should be rendered unusually conspicuous. We find, 
accordingly, the yellow primrose of the plains replaced by 
pink and magenta-coloured alpine species ; the straggling 
wild pinks of the lowlands by the masses of large flowers 
in such mountain species as Dianthus alpinus and D. 

1 Nature, vol. xi. pp. 32, 110. 



COLOURS OF PLANTS. 233 

glacialis; the saxifrages of the high. Alps with bunches of 
flowers a foot long as in Saxifraga longifolia and S. coty- 
ledon, or forming spreading masses of flowers as in S. oppo- 
sitifolia; while the soapworts, silenes, and louseworts 
are equally superior to the allied species of the plains. 

Why Allied Species of Flowers Differ in Size and 
Beauty. Again, Dr. Miiller has discovered that when 
there are showy and inconspicuous species in the same 
genus of plants, there is often a corresponding difference 
of structure, those with large and showy flowers being 
quite incapable of self-fertilization, and thus depending 
for their very existence on the visits of insects ; while 
the others are able to fertilize themselves should insects 
fail to visit them. We have examples of this difference 
in Malva sylvestris, Epilobium augustifolium, Poly- 
gonum bistorta, and Geranium pratense which have 
all large or showy flowers, and must be fertilized by 
insects as compared with Malva rotundifolia, Epilo- 
bium parviflorum, Polygonum aviculare, and Geranium 
pusillum, which have small or inconspicuous flowers, 
and are so constructed that if insects should not visit 
them they are able to fertilize themselves ?* 

Absence of Colour in Wind-fertilized Flowers. As 
supplementing these curious facts showing the relation 
of colour in flowers to the need of the visits of insects 
to fertilize them, we have the remarkable, and on any 
other theory, utterly inexplicable circumstance, that in 
all the numerous cases in which plants are fertilized 
by the agency of the wind they never have specially 
coloured floral envelopes. Such are our pines, oaks, 
poplars, willows, beeches, and hazel ; our nettles, grasses, 

1 Nature, vol. ix. p. 164. 



234 TROPICAL NATURE, AND OTHER ESSAYS. 

sedges, and many others. In some of these the male 
flowers are, it is true, conspicuous, as in the catkins of 
the willows and the hazel, but this arises incidentally 
from the masses of pollen necessary to secure fertiliza- 
tion, as shown by the entire absence of a corolla or of 
those coloured bracts which so often add to the beauty 
and conspicuousness of true flowers. 

The Same Theory of Colour Applicable to Animals 
and Plants. It may be thought that this absence of 
colour where it is not wanted is opposed to the view 
maintained in the earlier part of the preceding chapter, 
that colour is normal and is constantly tending to appear 
in natural objects. It must be remembered, however, 
that the green colour of foliage, due to chlorophyll, 
prevails throughout the greater part of the vegetable 
kingdom, and has, almost certainly, persisted through 
long geological periods. It has thus acquired a fixity 
of character which cannot be readily disturbed ; and, as 
a matter of fact, we find that colour rarely appears in 
plants except in association with a considerable modifica- 
tion of leaf-texture, such as occurs in the petals and 
coloured sepals of flowers. Wind-fertilized plants never 
have such specially organized floral envelopes and, in most 
cases, are entirely without a calyx or corolla. The con- 
nection between modification of leaf-structure and colour 
is further seen in the greater amount and variety of 
colour in irregular than in regular flowers. The latter, 
which are least modified, have generally uniform or but 
slightly varied colours ; while the former which have 
undergone great modification, present an immense range 
of colour and marking, culminating in the spotted and 
variegated flowers of such groups as the Scrophularineae 



COLOURS OF PLANTS. 235 

and Orchideoe. The same laws as to the conditions of a 
maximum production of colour are thus found to obtain 
both in plants and animals. 

Relation of the Colours of Flowers and their Geo- 
graphical Distribution, The adaptation of flowers to be 
fertilized by insects often to such an extent that the 
very existence of the species depends upon it has had 
wide-spread influence on the distribution of plants and 
the general aspects of vegetation. The seeds of a 
particular species may be carried to another country, 
may find there a suitable soil and climate, may grow 
and produce flowers ; but if the insect which alone can 
fertilize it should not inhabit that country, the plant 
cannot maintain itself, however frequently it" may be 
introduced or however vigorously it may grow. Thus 
may probably be explained the poverty in flowering- 
plants and the great preponderance of ferns that distin- 
guishes many oceanic islands, as well as the deficiency 
of gaily-coloured flowers in others. This branch of the 
subject is discussed at some length in my Address to the 
Biological Section of the British Association, 1 but I may 
here just allude to two of the most striking cases. New 
Zealand is, in proportion to its total number of flowering- 
plants, exceedingly poof in handsome flowers, and it is 
correspondingly poor in insects, especially in bees and 
butterflies, the two groups which so greatly aid in 
fertilization. In both these aspects it contrasts strongly 
with Southern Australia and Tasmania in the same 
latitudes, where there is a profusion of gaily -coloured 
flowers and an exceeding rich insect-fauna. The other 
case is presented by the Galapagos islands, which, though 

1 See Chapter VII. of this volume. 



236 TROPICAL NATURE, AND OTHER ESSAYS. 

situated on the equator off the west coast of South 
America, and with a tolerably luxuriant vegetation in 
the damp mountain zone, yet produce hardly a single 
conspicuously-coloured flower ; and this is correlated 
with, and no doubt dependent on, an extreme poverty of 
insect life, not one bee and only a single butterfly having 
been found there. 

Again, there is reason to believe that some portion of 
the large size and corresponding showiness of tropical 
flowers is due to their being fertilized by very large 
insects and even by birds. Tropical sphinx-moths often 
have their probosces nine or ten inches long, and 
we find flowers whose tubes or spurs reach about the 
same length ; while the giant bees, and the numerous 
flower-sucking birds, aid in the fertilization of flowers 
whose corollas or stamens are proportionately large. 

Recent Views as to Direct Action of Light on the 
Colours of Flowers and Fruits. The theory that the 
brilliant colours of flowers and fruits is due to the 
direct action of light, has been supported by a recent 
writer by examples taken from the arctic instead of from 
the tropical flora. In the arctic regions vegetation is 
excessively rapid during the short summer, and this is 
held to be due to the continuous action of light through- 
out the long summer days. " The further we advance 
towards the north the more the leaves of plants increase 
in size as if to absorb a greater proportion of the solar 
rays. M. Grisebach says, that during a journey in 
Norway he observed that the majority of deciduous trees 
had already, at the 60th degree of latitude, larger leaves 
than in Germany, while M. Ch. Martins has made a 
similar observation as regards the leguminous plants 



COLOUKS OF PLANTS. 237 

cultivated in Lapland." 1 The same writer goes on to 
say that all the seeds of cultivated plants acquire a 
deeper colour the further north they are grown, white 
haricots becoming brown or black, and white wheat 
becoming brown, while the green colour of all vegetation 
becomes more intense. The flowers also are similarly 
changed : those which are white or yellow in central 
Europe becoming red or orange in Norway. This is 
what occurs in the Alpine flora, and the cause is said 
to be the same in both the greater intensity of the 
sunlight. In the one the light is more persistent, in 
the other more intense because it traverses a less thick- 
ness of atmosphere. 

Admitting the facts as above stated to be in them- 
selves correct, they do not by any means establish the 
theory founded on them ; and it is curious that Grisebach, 
who has been quoted by this writer for the fact of the 
increased size of the foliage, gives a totally different ex- 
planation of the more vivid colours of Arctic flowers. 
He says " We see flowers become larger and more 
richly coloured in proportion as, by the increasing length 
of winter, insects become rarer, and their co-operation 
in the act of fecundation is exposed to more uncertain 
chances." (Vegetation du Globe, vol. i. p. 61 
French translation.) This is the theory here adopted to 
explain the colours of Alpine plants, and we believe 
there are many facts that will show it to be the pre- 
ferable one. The statement that the white and yellow 
flowers of temperate Europe become red or golden in the 
Arctic regions must we think be incorrect. By roughly 

1 Revue des Deux Mondes, 1877. " La Vegetation dans les hautes Lati- 
tudes," par M. Tisserand. 



240 TROPICAL NATURE, AND OTHER ESSAYS. 

delicate contrasts and subtle harmonies of colour, which 
are possessed by the more intellectual races of mankind, 
since even the lower human races do not possess it. All 
that seems required in the case of animals, is a per- 
ception of distinctness or contrast of colours ; and the 
dislike of so many creatures to scarlet may perhaps be 
due to the rarity of that colour in nature, and to the 
glaring contrast it offers to the sober greens and browns 
which form the general clothing of the earth's surface, 
though it may also have a direct irritating effect on 
the retina. 

The general view of the subject now given must 
convince us that, so far from colour being as it has 
sometimes been thought to be unimportant, it is in- 
timately connected with the very existence of a large 
proportion of the species of the animal and vegetable 
worlds. The gay colours of the butterfly and of the 
alpine flower which it unconsciously fertilizes while 
seeking for its secreted honey, are each beneficial to its 
possessor, and have been shown to be dependent on the 
same class of general laws as those which have deter- 
mined the form, the structure, and the habits of every 
living thing. The complex laws and unexpected 
relations which we have seen to be involved in the 
production of the special colours of flower, bird, and 
insect, must give them an additional interest for every 
thoughtful mind ; while the knowledge that, in all 
probability, each style of coloration, and sometimes 
the smallest details, have a meaning and a use, must 
add a new charm to the study of nature. 



ON THE ORIGIN OF THE COLOUR-SENSE. 

Throughout the preceding discussion we have accepted 
the subjective phenomena of colour that is, our perception 
of varied hues and the mental emotions excited by them, 
as ultimate facts needing no explanation. Yet they 
present certain features well worthy of attention, a brief 
consideration of which will form a fitting sequel to the 
present essay. 

The perception of colour seems, to the present writer, 
the most wonderful and the most mysterious of our 
sensations. Its extreme diversities and exquisite beauties 
seem out of proportion to the causes that are supposed 
to have produced them, or the physical needs to which 
they minister. If we look at pure tints of red, green, 
blue, and yellow, they appear so absolutely contrasted 
and unlike each other, that it is almost impossible to 
believe (what we nevertheless know to be the fact) that 
the rays of light producing these very distinct sensations 
differ only in wave-length and rate of vibration ; and 
that there is from one to the other a continuous series 
and gradation of such vibrating waves. The positive 
diversity we see in them must then depend upon special 
adaptations in ourselves ; and the question arises for 
what purpose have our visual organs and mental per- 
ceptions become so highly specialised in this respect ? 

When the sense of sight was first developed in the 
animal kingdom, we can hardly doubt that what was 
perceived was light only, and its more or less complete 
withdrawal. As the sense became perfected, more deli- 
cate gradations of light and shade would be perceived ; 

R 



242 TROPICAL NATURE, AND OTHER ESSAYS. 

and there seems no reason why a visual capacity might 
not have been developed as perfect as our own, or even 
more so in respect of light and shade, but entirely 
insensible to differences of colour except in so far as 
these implied a difference in the quantity of light. The 
world would in that case appear somewhat as we see it 
in good stereoscopic photographs ; and we all know how 
exquisitely beautiful such pictures are, and how com- 
pletely they give us all requisite information as to form, 
surface-texture, solidity, and distance, and even to some 
extent as to colour ; for almost all colours are dis- 
tinguishable in a photograph by some differences of tint, 
and it is quite conceivable that visual organs might exist 
which would differentiate what we term colour by deli- 
cate gradations of some one characteristic neutral tint. 
Now such a capacity of vision would be simple as 
compared with that which we actually possess ; which, 
besides distinguishing infinite gradations of the quantity 
of light, distinguishes also, by a totally distinct set of 
sensations, gradations of quality, as determined by 
differences of wave-lengths or rate of vibration. At 
what grade in animal development this new and more 
complex sense first began to appear we have no means 
of determining. The fact that the higher vertebrates, 
and even some insects, distinguish what are to us 
diversities of colour, by no means proves that their 
sensations of colour bear any resemblance whatever to 
ours. An insect's capacity to distinguish red from blue 
or yellow may be (and probably is) due to perceptions 
of a totally distinct nature, and quite unaccompanied by 
any of that sense of enjoyment or even of radical dis- 
tinctness which pure colours excite in us. Mammalia 



ORIGIN -OF THE COLOUR-SENSE. 243 

and birds, whose structure and emotions are so similar 
to our own, do probably receive somewhat similar im- 
pressions of colour ; but we have no evidence to show 
that they experience pleasurable emotions from colour 
itself, when not associated with the satisfaction of their 
wants or the gratification of their passions. 

The primary necessity which led to the development 
of the sense of colour, was probably the need of dis- 
tinguishing objects much alike in form and size, but 
differing in important properties; such as ripe and 
unripe, or eatabls and poisonous fruits ; flowers with 
honey or without ; the sexes of the same or of closely 
allied species. In most cases the strongest contrast 
would be the most useful, especially as the colours of the 
objects to be distinguished would form but minute spots 
or points when compared with the broad masses of tint 
of sky, earth, or foliage against which they would be set. 

Throughout the long epochs in which the sense of 
sight was being gradually developed in the higher 
animals, their visual organs would be mainly subjected to 
two groups of rays the green from vegetation, and the 
blue from the sky. The immense preponderance of these 
over all other groups of rays would naturally lead the 
eye to become specially adapted for their perception ; and 
it is quite possible that at first these were the only kinds 
of light-vibrations which could be perceived at all. 
When the need for differentiation of colour arose, rays 
of greater and of smaller wave-lengths would necessarily 
be made use of to excite the new sensations required ; 
and we can thus understand why green and blue form 
the central portion of the visible spectrum, and are the 
colours which are most agreeable to us in large surfaces ; 

K 2 



244 TROPICAL NATURE, AND OTHER ESSAYS. 

while at its two extremities we find yellow, red, and 
violet colours which we best appreciate in smaller 
masses, and when contrasted with the other two, or with 
light neutral tints. We have here probably the founda- 
tions of a natural theory of harmonious colouring, derived 
from, the order in which our colour-sensations have arisen 
and the nature of the emotions with which the several 
tints have been always associated. The agreeable and 
soothing influence of green light may be in part due to 
the green rays having little heating power ; but this can 
hardly be the chief cause, for the blue and violet, 
though they contain less heat, are not generally felt 
to be so cool and sedative. But when we consider how 
dependent are all the higher animals on vegetation, and 
that man himself has been developed in the closest 
relation to it, we shall find, probably, a sufficient ex- 
planation. The green mantle with which the earth is 
overspread caused this one colour to predominate over 
all others that meet our sight, and to be almost always 
associated with the satisfaction of human wants. Where 
the grass is greenest, and vegetation most abundant and 
varied, there has man always found his most suitable 
dwelling-place. In such spots hunger and thirst are 
unknown, and the choicest productions of nature gratify 
the appetite and please the eye. In the greatest heats 
of summer, coolness, shade, and moisture are found in 
the green forest glades ; and we can thus understand how 
our visual apparatus has become especially adapted to 
receive pleasurable and soothing sensations from this 
class of rays. 

Supposed increase of Colour-perception within the 
Historical Period. Some writers believe that our 



ORIGIN OF THE COLOUR-SENSE. 245 

power of distinguishing colours has increased even 
in historical times. The subject has attracted the 
attention of German philologists, and I have been 
furnished by a friend with some notes from a work of 
the late Lazarus Geiger, entitled, Zur EntwicJcelungs- 
geschichte der Menscliheit (Stuttgart, 1871). Accord- 
ing to this writer it appears that the colour of grass and 
foliage is never alluded to as a beauty in the Vedas 
or the Zendavesta, though these productions are con- 
tinually extolled for other properties. Blue is described 
by terms denoting sometimes green, sometimes black, 
showing that it was hardly recognised as a distinct 
colour. The colour of the sky is never mentioned in 
the Bible, the Vedas, the Homeric poems, or even in the 
Koran. The first distinct allusion to it known to Geiger 
is in an Arabic work of the ninth century. " Hyacin- 
thine locks" are black locks, and Homer calls iron 
" violet-coloured." Yellow was often confounded with 
green ; but, along with red, it was one of the earliest 
colours to receive a distinct name. Aristotle names 
three colours in the rainbow red, yellow, and green. 
Two centuries earlier Xenophanes had described the 
rainbow as purple, reddish, and yellow. The Pytha- 
goreans admitted four primary colours white, black, 
red, and yellow ; the Chinese the same, with the addi- 
tion of green. 

Simultaneously with the first publication of this 
essay in Macmillan's Magazine, there appeared in the 
Nineteenth Century an article by Mr. Gladstone on 
the Colour-sense, chiefly as exhibited in the poems of 
Homer. He shows that the few colour-terms used by 
Homer are applied to such different objects that they 



246 TROPICAL NATURE, AND OTHER ESSAYS 

cannot denote colours only, as we perceive and differentiate 
them ; but seem more applicable to different intensities 
of light and shade. Thus, to give one example, the 
word porphureos is applied to clothing, to the rainbow, 
to blood, to a cloud, to the sea, and to death ; and no 
one meaning will suit all these applications except com- 
parative darkness. In other cases the same thing has 
many different epithets applied to it according to its 
different aspects or conditions ; and as the colours of 
objects are generally indicated in ancient writings by 
comparative rather than by abstract terms, as wine- 
colour, fire-colour, bronze-colour, &c. it becomes still 
more difficult to determine in any particular case what 
colour was really meant. Mr. Gladstone's general con- 
clusion is, that the archaic man had a positive perception 
only of degrees of light and darkness, and that in 
Homer's time he had advanced to the imperfect dis- 
crimination of red and yellow, but no further ; the 
green of grass and foliage or the blue of the sky being 
never once referred to. 

These curious facts cannot, however, be held to 
prove so recent an origin for colour-sensations as 
they would at first sight appear to do, because we 
have seen that both flowers and fruits have become 
diversely coloured in adaptation to the visual powers of 
insects, birds, and mammals. Red, being a very common 
colour of ripe fruits which attract birds to devour them 
and thus distribute their seeds, we may be sure that the 
contrast of red and green is to them very well marked. 
It is indeed just possible that birds may have a more 
advanced development of the colour- sense than mammals, 
because the teeth of the latter commonly grind up and 



ORIGIN OF THE COLOUR-SENSE. 247 

destroy the seeds of the larger fruits and nuts which 
they devour, and which are not usually coloured ; but the 
irritating effect of bright colours on some of them does 
not support this view. It seems most probable there- 
fore that man's perception of colour in the time of 
Homer was little if any inferior to what it is now, but 
that, owing to a variety of causes, no precise nomencla- 
ture of colours had become established. One of these 
causes probably was, that the colours of the objects of 
most importance, and those which were most frequently 
referred to in songs and poems, were uncertain and 
subject to variation. Blood was light or dark red, or 
when dry, blackish ; iron was grey or dark or rusty ; 
bronze was shining or dull ; foliage was of all shades of 
yellow, green, or brown ; and horses or cattle had no 
one distinctive colour. Other objects, as the sea, the 
sky, and wine, changed in tint according to the light, 
the time of day, and the mode of viewing them ; and 
thus colour, indicated at first by reference to certain 
coloured objects, had no fixity. Things which had more 
definite and purer colours as certain species of flowers, 
birds, and insects were probably too insignificant or 
too much despised to serve as colour-terms ; and even 
these often vary, either in the same or in allied species, 
in a manner which would render their use unsuitable. 
Colour-names, being abstractions, must always have 
been a late development in language, and their com- 
parative unimportance in an early state of society and 
of the arts would still further retard their appearance ; 
and this seems quite in accordance with the various 
facts set forth by Mr. Gladstone and the other writers 
referred to. The fact that colour-blindness is so pre- 



248 TROPICAL NATURE, AND OTHER ESSAYS. 

valent even now, is however an indication that the fully 
developed colour-sense is not of primary importance to 
man. If it had been so, natural selection would long 
ago have eliminated the disease itself, and its tendency 
to recur would hardly be so strong as it appears to be. 

Concluding Remarks on the Colour-sense. The pre- 
ceding considerations enable us to comprehend, both why 
a perception of difference of colour has become developed 
in the higher animals, and also why colours require to 
be presented or combined in varying proportions in order 
to be agreeable to us. But they hardly seem to afford a 
sufficient explanation, either of the wonderful contrasts 
and total unlikeness of the sensations produced in us 
by the chief primary colours, or of the exquisite charm 
and pleasure we derive from colour itself, as distinguished 
from variously-coloured objects, in the case of which 
association of ideas comes into play. It is hardly con- 
ceivable that the material uses of colour to animals and 
to ourselves, required such very distinct and powerfully- 
contrasted sensations ; and it is still less conceivable 
that a sense of delight in colour per se should have been 
necessary for our utilization of it. 

The emotions excited by colour and by music, alike, 
seem to rise above the level of a world developed on 
purely utilitarian principles. 



VJI. 
BY-PATHS IN THE DOMAIN OF BIOLOGY : 

BEING AN ADDRESS DELIVERED TO THE BIOLOGICAL 
SECTION OP THE BRITISH ASSOCIATION, (GLASGOW, 
SEPTEMBER 6TH, 1876,) AS PRESIDENT OF THE 
SECTION. 

Introductory Remarks ON SOME RELATIONS OF LIVING THINGS TO THEIR 
ENVIRONMENT The Influence of Locality on Colour in Butterflies and 
Birds Sense-perception influenced by Colour of the Integuments 
Relations of Insular Plants and Insects RISE AND PROGRESS or 
MODERN VIEWS AS TO THE ANTIQUITY AND ORIGIN OF MAN Indica- 
tions of Man's extreme Antiquity Antiquity of Intellectual Man 
Sculptures on Easter-Island North American Earthworks The Great 
Pyramid Conclusion. 

THE range of subjects comprehended within the domain 
of Biology is so wide, and my own acquaintance with 
them so imperfect, that it is not in my power to lay 
before you any general outline of the recent progress "of 
the biological sciences. Neither do I feel competent to 
give you a summary of the present status of any one of 
the great divisions of our science, such as Anatomy, 
Physiology, Embryology, Histology, Classification, or 
Evolution Philology, Ethnology, or Prehistoric Archaeo- 
logy ; but there are fortunately several outlying and 
more or less neglected subjects to which I have for some 
time had my attention directed, and which I hope will 



250 TROPICAL NATURE, AND OTHER ESSAYS. 

furnish matter for a few observations, of some interest 
to biologists and at the same time not unintelligible to 
the less scientific members of the Association who may 
honour us with their presence. 

The subjects I first propose to consider have no general 
name, and are not easily grouped under a single descrip- 
tive heading; but they may be compared with that 
recent development of a sister science which has been 
termed surface-geology or Earth-sculpture. In the older 
geological works we learnt much about strata, and rocks, 
and fossils, their superposition, contortions, chemical con- 
stitution, and affinities, with some general notions of 
how they were formed in the remote past ; but we often 
came to the end of the volume no whit the wiser as to 
how and why the surface of the earth came to be so 
wonderfully and beautifully diversified ; we were not 
told why some mountains are rounded and others pre- 
cipitous ; why some valleys are wide and open, others 
narrow and rocky ; why rivers so often pierce through 
mountain-chains ; why mountain-lakes are often so 
enormously deep ; whence came the gravel, and drift, 
and erratic blocks so strangely spread over wide areas 
while totally absent from other areas equally extensive. 
So long as these questions were almost ignored, geology 
could hardly claim to be a complete science, because, 
while professing to explain how the crust of the earth 
came to be what it is, it gave no intelligible account of 
many phenomena presented by its surface. But of late 
years these surface-phenomena have been assiduously 
studied ; the marvellous effects of denudation and glacial 
action in giving the final touches to the actual contour 
of the earth's surface, and their relation to climatic 



BY-PATHS OF BIOLOGY. 251 

changes and the antiquity of man, have been clearly 
traced, thus investing geology with a new and popular 
interest, and at the same time elucidating many of the 
phenomena presented in the older formations. 

Now just as a surface-geology was required to com- 
plete that science, so a surface-biology was wanted to 
make the science of living things more complete and 
more generally interesting, by applying the results 
arrived at by special workers to the interpretation of 
those external and prominent features whose endless 
variety and beauty constitute the charm which attracts 
us to the contemplation or to the study of nature. We 
have the descriptive zoologist, for example, who gives us 
the external characters of animals ; the anatomist studies 
their internal structure ; the histologist makes known 
the nature of their component tissues ; the embryologist 
patiently watches the progress of their development ; the 
systematist groups them into classes and orders, families, 
genera, and species ; while the field-naturalist studies for 
us their food and habits and general economy. But, till 
quite recently, none of these earnest students nor all of 
them combined, could answer satisfactorily, or even 
attempted to answer, many of the simplest questions 
concerning the external characters and general relations 
of animals and plants. Why are flowers so wonderfully 
varied in form and colour 1 what causes the Arctic fox 
and the ptarmigan to turn white in winter ? why are 
there no elephants in America and no deer in Australia ? 
why are closely allied species rarely found together ? 
why are male animals so frequently bright-coloured ? 
why are extinct animals so often larger than those which 
are now living ? what has led to the production of the 



252 TROPICAL NATURE, AND OTHER ESSAYS. 

gorgeous train of the peacock and of the two kinds of 
flower in the primrose ? The solution of these and a 
hundred other problems of like nature was rarely ap- 
proached by the old method of study, or if approached 
was only the subject of vague speculation. It is to the 
illustrious author of the Origin of Species that we 
are indebted for teaching us how to study nature as one 
great, compact, and beautifully-adjusted system. Under 
the touch of his magic wand the countless isolated facts 
of internal and external structure of living things 
their habits, their colours, their development, their distri- 
bution, their geological history, all fell into their ap- 
proximate places ; and although, from the intricacy of 
the subject and our very imperfect knowledge of the 
facts themselves, much still remains uncertain, yet we 
can no longer doubt that even the minutest and most 
superficial peculiarities of animals and plants either, on 
the one hand, are or have been useful to them, or, on 
the other hand, have been developed under the influence 
of general laws, which we may one day understand to a 
much greater extent than we do at present. So great is 
the alteration effected in our comprehension of nature 
by the study of variation, inheritance, cross-breeding, 
competition, distribution, protection, and selection 
showing, as they often do, the meaning of the most 
obscure phenomena and the mutual dependence of the 
most widely-separated organisms that it can only be 
fitly compared with the analogous alteration produced 
in our conception of the universe by Newton's grand 
discovery of the law of gravitation. 

I know it will be said (and is said), that Darwin is 
too highly rated, that some of his theories are wholly 



BY-PATHS OF BIOLOGY. 253 

and others partially erroneous, and that he often builds 
a vast superstructure on a very uncertain basis of 
doubtfully interpreted facts. Now, even admitting this 
criticism to be well founded and I myself believe that 
to a limited extent it is so I nevertheless maintain that 
Darwin is not and cannot be too highly rated ; for his 
greatness does not at all depend upon his being in- 
fallible, but on his having developed, with rare patience 
and judgment, a new system of observation and study, 
guided by certain general principles which are almost as 
simple as gravitation and as wide-reaching in their 
effects. And if other principles should hereafter be 
discovered, or if it be proved that some of his subsidiary 
theories are wholly or partially erroneous, this very 
discovery can only be made by following in Darwin's 
steps, by adopting the method of research which he has 
taught us, and by largely using the rich stores of 
material which he has collected. The Origin of Species, 
and the grand series of works which have succeeded it, 
have revolutionized the study of biology ; they have 
given us new ideas and fertile principles ; they have 
infused life and vigour into our science, and have opened 
up hitherto unthought-of lines of research on which 
hundreds of eager students are now labouring. What- 
ever modifications some of his theories may require, 
Darwin must none the less be looked up to as the 
founder of philosophical biology. 

As a small contribution to this great subject, I propose 
now to call your attention to some curious relations of 
organisms to their environment, which seem to me 
worthy of more systematic study than has hitherto been 
given them. The points I shall more especially deal 



254 TROPICAL NATURE, AND OTHER ESSAYS. 

with are the influence of locality, or of some unknown 
local causes, in determining the colours of insects, and, 
to a less extent, of birds ; and the way in which certain 
peculiarities in the distribution of plants may have been 
brought about by their dependence on insects. The 
latter part of my address will deal with the present state 
of our knowledge as to the antiquity and early history 
of mankind. 



ON SOME RELATIONS OF LIVING THINGS TO THEIR 
ENVIRONMENT. 

Of all the external characters of animals, the most 
beautiful, the most varied, and the most generally 
attractive are the brilliant colours and strange yet often 
elegant markings with which so many of them are 
adorned. Yet of all characters this is the most difficult 
to bring under the laws of utility or of physical con- 
nection. Mr. Darwin as you are well aware has 
shown how wide is the influence of sex on the intensity 
of coloration ; and he has been led to the conclusion 
that active or voluntary sexual selection is one of the 
chief causes, if not the chief cause, of all the variety 
and beauty of colour we see among the higher animals. 
This is one of the points on which there is much di- 
vergence of opinion even among the supporters of Mr. 
Darwin, and one as to which I myself differ from him. 
I have argued, and still believe, that the need of protec- 
tion is a far more efficient cause of variation of colour 
than is generally suspected ; but there are evidently 
other causes at work, and one of these seems to be an 
influence depending strictly on locality, whose nature 



EFFECTS OF LOCALITY ON COLOUR. 255 

we cannot yet understand, but whose effects are every- 
where to be seen when carefully searched for. 

Although the careful experiments of Sir John Lubbock 
have shown that insects can distinguish colours as 
might have been inferred from the brilliant colours of 
the flowers which are such an attraction to them yet 
we can hardly believe that their appreciation and love 
of distinctive colours is so refined as to guide and regu- 
late their most powerful instinct that of reproduction. 
We are therefore led to seek some other cause for the 
varied colours that prevail among insects ; and as this 
variety is most conspicuous among butterflies a group 
perhaps better known than any other it offers the best 
means of studying the subject. The variety of colour 
and marking among these insects is something marvellous. 
There are probably about ten thousand different kinds of 
butterflies now known, and about half of these are so 
distinct in colour and marking that they can be readily 
distinguished by this means alone. Almost every con- 
ceivable tint and pattern is represented, and the hues 
are often of such intense brilliance and purity as can be 
equalled by neither birds nor flowers. 

Any help to a comprehension of the causes which 
may have concurred in bringing about so much diversity 
and beauty must be of value ; and this is my excuse 
for laying before you the more important cases I have 
met with of a connection between colour and locality. 

The influence of Locality on Colour in Butterflies 
and Birds. Our first example is from tropical Africa, 
where we find two unrelated groups of butterflies 
belonging to two very distinct families (Nymphalidae 
and Papilionidse) characterized by a prevailing blue- 



256 TROPICAL NATURE, AND OTHER ESSAYS. 

green colour not found in any other continent. 1 Again, 
we have a group of African Pieridse which are white 
or pale yellow with a marginal row of bead-like black 
spots ; and in the same country one of the Lycaenidse 
(Leptena erastus) is coloured so exactly like these that 
it was at first described as a species of Pieris. None of 
these four groups are known to be in any way specially 
protected, so that the resemblance cannot be due to 
protective mimicry. 

In South America we have far more striking cases ; 
for in the three subfamilies Danainse, Acraeinse, and 
Heliconiinse, all of which are specially protected, we 
find identical tints and patterns reproduced, often in the 
greatest detail, each peculiar type of coloration being 
characteristic of separate geographical subdivisions of 
the continent. Nine very distinct genera are implicated 
in these parallel changes Lycorea, Ceratinia, Mecha- 
nitis, Ithomia, Melinsea, Tithorea, Acrsea, Heliconius, 
and Eueides, groups of three or four (or even five) of 
them appearing together in the same livery in one 
district, while in an adjoining district most or all of 
them undergo a simultaneous change of coloration or of 
marking. Thus in the genera Ithoinia, Mechanitis, 
and Heliconius we have species with yellow apical spots 
in Guiana, all represented by allied species with white 
apical spots in South Brazil. In Mechanitis, Melinsea, 
and Heliconius, and sometimes in Tithorea, the species 
of the Southern Andes (Bolivia and Peru) are charac- 
terized by an orange and black livery, while those of 
the Northern Andes (New Granada) are almost always 

1 Romaleosoma and Euryphene (Nyrnphalida-), Papilio zalmoxis and 
several species of the Nireus-group (Papilionidae). 



EFFECTS OF LOCALITY ON COLOUR. 257 

orange-yellow and black. Other changes of a like 
nature, which it would be tedious to enumerate but 
which are very striking when specimens are examined, 
occur in species of the same groups inhabiting these 
same localities, as well as Central America and the 
Antilles. The resemblance thus produced between widely 
different insects is sometimes general, but often so close 
and minute that only a critical examination of structure 
can detect the difference between them. Yet this can 
hardly be true mimicry, because all are alike protected 
by the nauseous secretion which renders them unpalat- 
able to birds. 

In another series of genera (Catagramma, Callithea, 
and Agrias) all belonging to the Nymphalidse, we have 
the most vivid blue ground, with broad bands of orange, 
crimson or a different tint of blue or purple, exactly 
reproduced in corresponding, yet unrelated species, 
occurring in the same locality ; yet, as none of these 
groups are known to be specially protected, this can 
hardly be true mimicry. A few species of two other 
genera in the same country (Eunica and Siderone) also 
reproduce the same colours, but with only a general 
resemblance in the markings. Yet again, in tropical 
America we have species of Apatura which, sometimes 
in both sexes, sometimes in the female only, exactly 
imitate the peculiar markings of another genus (Hetero- 
chroa) confined to America : here, again, neither genus 
is protected, and the similarity must be due to unknown 
local causes. 

But it is among islands that we find some of the most 
striking examples of the influence of locality on colour, 
generally in the direction of paler, but sometimes of 



256 TROPICAL NATURE, AND OTHER ESSAYS. 

green colour not found in any other continent. 1 Again, 
we have a group of African Pieridse which are white 
or pale yellow with a marginal row of bead-like black 
spots ; and in the same country one of the Lycaenidse 
(Leptena erastus) is coloured so exactly like these that 
it was at first described as a species of Pieris. None of 
these four groups are known to be in any way specially 
protected, so that the resemblance cannot be due to 
protective mimicry. 

In South America we have far more striking cases ; 
for in the three subfamilies Danainse, Acrseinse, and 
Heliconiinse, all of which are specially protected, we 
find identical tints and patterns reproduced, often in the 
greatest detail, each peculiar type of coloration being 
characteristic of separate geographical subdivisions of 
the continent. Nine very distinct genera are implicated 
in these parallel changes Lycorea, Ceratinia, Mecha- 
nitis, Ithomia, Melinsea, Tithorea, Acraea, Heliconius, 
and Eueides, groups of three or four (or even five) of 
them appearing together in the same livery in one 
district, while in an adjoining district most or all of 
them undergo a simultaneous change of coloration or of 
marking. Thus in the genera Ithornia, Mechanitis, 
and Heliconius we have species with yellow apical spots 
in Guiana, all represented by allied species with white 
apical spots in South Brazil. In Mechanitis, Melinsea, 
and Heliconius, and sometimes in Tithorea, the species 
of the Southern Andes (Bolivia and Peru) are charac- 
terized by an orange and black livery, while those of 
the Northern Andes (New Granada) are almost always 

1 Romaleosoma and Euryphene (Nyinphaliche), Papilio salmoxis and 
several species of the Nireus-group (Papilionidae). 



EFFECTS OF LOCALITY ON COLOUR. 257 

orange-yellow and black. Other changes of a like 
nature, which it would be tedious to enumerate but 
which are very striking when specimens are examined, 
occur in species of the same groups inhabiting these 
same localities, as well as Central America and the 
Antilles. The resemblance thus produced between widely 
different insects is sometimes general, but often so close 
and minute that only a critical examination of structure 
can detect the difference between them. Yet this can 
hardly be true mimicry, because all are alike protected 
by the nauseous secretion which renders them unpalat- 
able to birds. 

In another series of genera (Catagramma, Callithea, 
and Agrias) all belonging to the Nyrnphalidse, we have 
the most vivid blue ground, with broad bands of orange, 
crimson or a different tint of blue or purple, exactly 
reproduced in corresponding, yet unrelated species, 
occurring in the same locality ; yet, as none of these 
groups are known to be specially protected, this can 
hardly be true mimicry. A few species of two other 
genera in the same country (Eunica and Siderone) also 
reproduce the same colours, but with only a general 
resemblance in the markings. Yet again, in tropical 
America we have species of Apatura which, sometimes 
in both sexes, sometimes in the female only, exactly 
imitate the peculiar markings of another genus (Hetero- 
chroa) confined to America : here, again, neither genus 
is protected, and the similarity must be due to unknown 
local causes. 

But it is among islands that we find some of the most 
striking examples of the influence of locality on colour, 
generally in the direction of paler, but sometimes of 

s 



258 TROPICAL NATURE, AND OTHER ESSAYS. 

darker and more brilliant hues, and often accompanied 
by an unusual increase of size. Thus in the Moluccas 
and New Guinea we have several Papilios (P. euchenor, 
P. ormenus, and P. tydeus) distinguished from their allies 
by a much paler colour, especially in the females which 
are almost white. Many species of Danais (forming 
the subgenus Ideopsis) are also very pale. But the 
most curious are the Euploeas, which in the larger 
islands are usually of rich dark colours, while in the 
small islands of Banda, Ke', and Matabello at least three 
species not nearly related to each otlier (E. hoppferi, 
E. euripon, and E. assimilata) are all broadly banded 
or suffused with white, their allies in the larger islands 
being all very much darker. Again, in the genus 
Diadema, belonging to a distinct family, three species 
from the small Aru and Kd islands (D. deois, D. hewit- 
so?rii, and D. polymena) are all more conspicuously 
white-marked than their representatives in the larger 
islands. In the beautiful genus Cethosia, a species from 
the small island of Waigiou (C. cyrene) is the whitest 
of the genus. Prothoe is represented by a blue species 
in the continental island of Java, while those inhabiting 
the ancient insular groups of the Moluccas and New 
Guinea are all pale yellow or white. The genus Drusilla, 
almost confined to these islands, comprises many species 
which are all very pale ; while in the small island of 
Waigiou is found a very distinct genus, Hyantis, which, 
though differing completely in the neuration of the 
wings, has exactly the same pale colours and large 
ocellated spots as Drusilla. 

Equally remarkable is the increase of size in some 
islands. The small island of Amboina produces larger 



EFFECTS OF LOCALITY ON COLOUR. 259 

butterflies than any of the much larger islands which 
surround it. This is the case with at least a dozen 
butterflies belonging to many distinct genera, 1 so that it 
is impossible to attribute the fact to other than some local 
influence. In Celebes, as I have elsewhere pointed out, 2 
we have a peculiar form of wing and much larger size 
running through a whole series of distinct butterflies ; 
and this seems to take the place of any speciality in 
colour. 

In a very small collection of insects recently brought 
from Duke-of-York Island (situated between New 
Britain and New Ireland) are several of remarkably 
white or pale coloration. A species of Euplsea is the 
whitest of all known species of that extensive genus ; 
while a beautiful diurnal moth is much whiter than its 
ally in the larger island of New Guinea. There is also 
a magnificent longicorn beetle almost entirely of an ashy 
white colour. 3 

From the Fiji Islands we have comparatively few 
butterflies ; but there are several species of Diadema of 
unusually pale colours, some almost white. 

The Philippine Islands seem to have the peculiarity of 
developing metallic colours. We find there at least three 
species of Euplsea 4 not closely related, and all of more 
intense metallic lustre than their allies in other islands. 

1 Ornithoptera priamus, 0. helena, Papilio deiphobus, P. ulysses, P. gam- 
brisius, P. codrus, Iphias leucippe, Euplcea prothoe, Hestia idea, A thyma 
jocaste, Diadema pandarus, Nymphalis pyrrhus, N. euryalus, Drusilla 
jairus. 

a "Contributions to the Theory of Natural Selection," pp. 168-173. 

3 These insects are described and figured in the " Proceedings of the 
Zoological Society," for 1877, p. 139. Their names are Euplcea browni, 
Alcides aurora, and Batocera browni. 

4 Euplcea hewiteonii, E. diocletiana, E. leetijica. 

s 2 



2 GO TROPICAL NATURE, AND OTHER ESSAYS. 

Here also we have one of the large yellow Ornithopterae 
(0. magellanus), whose hind wings glow with an intense 
opaline lustre not found in any other species of the 
entire group ; and an Adolias 1 is larger and of more 
brilliant metallic colouring than any other species in the 
archipelago. In these islands also we find the extensive 
and wonderful genus of weevils (Pachyrhynchus), which 
in their brilliant metallic colouring surpass anything 
found in the whole eastern hemisphere, if not in the 
whole world. 

In the Andaman Islands in the Bay of Bengal there 
are a considerable number of peculiar species of butter- 
flies differing slightly from those on the continent, and 
generally in the direction of paler or more conspicuous 
colouring. Thus two species of Papilio which on the 
continent have the tails black, in their Andaman re- 
presentatives have them either red or white-tipped. 2 
Another species 3 is richly blue-banded where its allies 
are black ; while three species of distinct genera of 
Nymph alidse 4 all differ from their allies on the continent 
in being of excessively pale colours as w r ell as of some- 
what larger size. 

In Madagascar we have the very large and singularly 
white-spotted Papilio anterior; while species of three 
other genera 5 are very white or conspicuous as compared 
with their continental allies. 

Passing to the West-Indian Islands and Central 
America (which latter country has formed a group of 

1 Adolias calliphorus. 

9 Papilio rhodifer (near P. doubledayi), and Papilio charicles (near P, 
memnori). 3 Papilio mayo. 

4 Euplcea andamanensis, Cethosia biblis, Cyrcstis codes. 

5 Danais nossima, Melanitis mas^oura, Diadema dexithea. 



EFFECTS OF LOCALITY ON COLOUR. 261 

islands in very recent times) we have similar indications. 
One of the largest of the Papilios inhabits Jamaica, 1 
while another, the largest of its group, is found in 
Mexico. 2 Cuba has two of the same genus whose 
colours are of surpassing brilliancy; 3 while the fine 
genus Clothilda confined to the Antilles and Central 
America is remarkable for its rich and showy 
colouring. 

Persons who are not acquainted with the important 
structural differences that distinguish these various 
genera of butterflies can hardly realize the importance 
and the significance of such facts as I have now de- 
tailed. It may be well, therefore, to illustrate them by 
supposing parallel cases to occur among the Mammalia. 
We might have, for example, in Africa, the gnus, the 
elands, and the buffaloes, all coloured and marked like 
zebras, stripe for stripe over the whole body exactly 
corresponding. So the hares, marmots, and squirrels of 
Europe might be all red with black feet, while the 
corresponding species of Central Asia were all yellow 
with black heads. In North America we might have 
raccoons, squirrels, and opossums, in particoloured 
livery of white and black, so as exactly to resemble the 
skunk of the same country ; while in South America 
they might be black with a yellow throat-patch, so as 
to resemble with equal closeness the tayra of the Bra- 
zilian forests. "Were such resemblances to occur in 
anything like the number and with the wonderful 
accuracy of imitation met with among the Lepidop- 
tera, they would certainly attract universal attention 
among naturalists, and would lead to the exhaustive 

1 Papilio homerus. 2 P. daunus. * P. gundlachianus, P. villiersi. 



262 TROPICAL NATURE, AND OTHER ESSAYS. 

study of the influence of local causes in producing such 
startling results. 

One somewhat similar case does indeed occur among 
the Mammalia, two singular African animals, the Aard- 
wolf (Proteles) and the hyaena-dog (Lycaon), both strik- 
ingly resembling hyaenas in their general form as well 
as in their spotted markings. Belonging as they all 
do to the Carnivora, though to three distinct families, 
it seems quite an analogous case to those we have 
imagined ; but as the Aard-wolf and the hyaena-dog 
are both weak animals compared with the hyaena, the 
resemblance may be useful, and in that case would come 
under the head of mimicry. This seems the more pro- 
bable because, as a rule, the colours of the Mammalia 
are protective, and are too little varied to allow of the 
influence of local causes producing any well-marked 
effects. 

When we come to birds, however, the case is differ- 
ent ; for although they do not exhibit such distinct 
marks of the influence of locality as do butterflies 
probably because the causes which determine colour are 
in their case more complex yet there are distinct indi- 
cations of some effect of the kind, and we must devote 
some little time to their consideration. 

One of the most curious cases is that of the parrots 
of the West-Indian Islands and Central America, several 
of which have white heads or foreheads, occurring in 
two distinct genera, 1 while none of the more numerous 
parrots of South America are so coloured. In the small 
island of Dominica we have a very large and richly- 

1 Pionua albifrons and Chryeotis senilis (C. America), Chrysotis sallcei 
(Hajti), 



EFFECTS OF LOCALITY ON COLOUR. 263 

coloured parrot (Chrysotis augusta) corresponding to 
the large and richly- coloured butterfly (Papilio 
homerus) of Jamaica. 

The Andaman Islands are equally remarkable, at least 
six of the peculiar birds differing from their continental 
allies in being much lighter, and sometimes with a large 
quantity of pure white in the plumage, 1 exactly corre- 
sponding to what occurs among the butterflies. 

In the Philippines this is not so marked a feature ; 
yet we have here the only known white-breasted king- 
crow (Dicrurus mirabilis) ; the newly discovered Eury- 
Icemus steerii, wholly white beneath ; three species of 
Diceum, all white beneath ; several species of Parus, 
largely white-spotted ; while many of the pigeons have 
light ashy tints. The birds generally, however, have 
rich dark colours, similar to those which prevail among 
the butterflies. 

In Celebes we have a swallow-shrike and a peculiar 
small crow allied to the jackdaw, 2 whiter than any of 
their allies in the surrounding islands ; but otherwise 
the colours of the birds call for no special remark. 

In Timor and Flores we have white-headed pigeons, 3 
and a long- tailed flycatcher almost entirely white. 4 

In Duke-of-York Island east of New Guinea we find 
that the four new species figured in the " Proceedings of 
the Zoological Society," for 1877, are all remarkable for 
the unusual quantity of white in their plumage. They 
consist of a flycatcher, a diceum, a wood-swallow, and 



1 Kittacincla albiventris, Geocichla albigularis, Sturnia andamanensis, 
Hyloterpe grisola var., lanthcenas palumboides, Osrnotreron chloroptera. 

2 Artamus monachus, Corvus advena. 

3 Plilopus cinctus, P. albocinctus. * Tchitrea affinin, var. 



261 TROPICAL NATURE, AND OTHER ESSAYS. 

a ground pigeon ; l all equalling if not surpassing their 
nearest allies in whiteness, although some of these, from 
the Philippines Moluccas and Celebes, are sufficiently 
remarkable in this respect. 

In the small Lord Howe's Island we have the recently 
extinct white rail (Notornis alba), remarkably contrasting 
with its allies in the larger islands of New Zealand. 

We cannot, however, lay any stress on isolated ex- 
amples of white colour, since these occur in most of 
the great continents ; but where we find a series of 
species of distinct genera all differing from their con- 
tinental allies in a whiter coloration, as in the Andaman 
Islands, Duke-of-York Island, and the West Indies, 
and, among butterflies, in the smaller Moluccas, the 
Andamans, and Madagascar, we cannot avoid the con- 
clusion that in these insular localities some general cause 
is at work. 

There are other cases, however, in which local influ- 
ences seem to favour the production or preservation of 
intense crimson or a very dark coloration. Thus in the 
Moluccas and New Guinea alone we have bright red 
parrots belonging to two distinct families, 2 and which 
therefore most probably have been independently pro- 
duced or preserved by some common cause. Here, too, 
and in Australia we have black parrots and pigeons ; 3 
and it is a most curious and suggestive fact that in 
another insular subregion that of Madagascar and the 
Mascarene Islands these same colours reappear in the 
same two groups. 4 

1 Monarcha verticalis, Diceum eximium, Artamus instgnis, Pldogainas 
johannce. 

Lorius, Eos (Tricboglossidae), Echctus (Palseomithidae). 
3 Microglossus, Calyptorlynchus, Turaccena. * Coracopsis, Alectramas. 



SENSE-PERCEPTION AND COLOUR. 2G5 

Sense-perception influenced by Colour of the Integu- 
ments. Some very curious physiological facts bearing 
upon the presence or absence of white colours in the 
higher animals have lately been adduced by Dr. Ogle. 1 
It has been found that a coloured or dark pigment in 
the olfactory region of the nostrils is essential to perfect 
smell, and this pigment is rarely deficient except when 
the whole animal is pure white. In these cases the 
creature is almost without smell or taste. This, Dr. 
Ogle believes, explains the curious case of the pigs in 
Virginia adduced by Mr. Darwin, white pigs being killed 
by a poisonous root which does not affect black pigs. 
Mr. Darwin imputed this to a constitutional difference 
accompanying the dark colour, which rendered what was 
poisonous to the white-coloured animals quite innocuous 
to the black. Dr. Ogle, however, observes that there 
is no proof that the black pigs eat the root, and he 
believes the more probable explanation to be that it is 
distasteful to them ; while the white pigs, being deficient 
in smell and taste, eat it and are killed. Analogous facts 
occur in several distinct families. White sheep are 
killed in the Tarentino by eating Hypericum crispum, 
while black sheep escape ; white rhinoceroses are said to 
perish from eating Euphorbia candelabrum ; and white 
horses are said to suffer from poisonous food where 
coloured ones escape. Now it is very improbable that a 
constitutional immunity from poisoning by so many dis- 
tinct plants should, in the case of such widely different 
animals, be always correlated with the same difference 
of colour ; but the facts are readily understood if the 
senses of smell and taste are dependent on the presence 

1 " Medico-Chirurgical Transactions," vol. liii. (1870). 



266 TROPICAL NATURE, AND OTHER ESSAYS. 

of a pigment which is deficient in wholly white animals. 
The explanation has, however, been carried a step further, 
by experiments showing that the absorption of odours 
by dead matter, such as clothing, is greatly affected by 
colour ; black being the most powerful absorbent ; then 
blue, red, yellow, and lastly white. We have here a 
physical cause for the sense-inferiority of totally white 
animals which may account for their rarity in nature ; 
for few, if any, wild animals are wholly white. The head, 
the face, or at least the muzzle or the nose, are generally 
black ; the ears and eyes are also often black ; and there 
is reason to believe that dark pigment is essential to 
good hearing, as it certainly is to perfect vision. We 
can therefore understand why white cats with blue eyes 
are so often deaf, a peculiarity we notice more readily 
than their deficiency of smell or taste. 

If, then, the prevalence of white coloration is generally 
associated with some deficiency in .the acuteness of the 
most important senses, this colour becomes doubly 
dangerous ; for it not only renders its possessor more 
conspicuous to its enemies, but at the same time makes 
it less ready in detecting the presence of danger. Hence, 
perhaps, the reason why white appears more frequently 
in islands, where competition is less severe and enemies 
less numerous and varied. Hence, also, a reason why 
albinoism, although freely occurring in captivity, never 
maintains itself in a wild state, while melanism does. 
The peculiarity of some islands in having all their 
inhabitants of dusky colours (as the Galapagos) may 
also perhaps be explained on the same principles ; for 
poisonous fruits may there abound which weed out 
all white- or light-coloured varieties, owing to their 



INSULAR PLANTS AND INSECTS. 267 

deficiency of smell and taste. We can hardly believe, 
however, that this would apply to white-coloured butter- 
flies ; and this may be a reason why the effect of an 
insular habitat is more marked in these insects than in 
birds or mammals. 

It is even possible that this relation of sense-acuteness 
with colour may have had some influence on the 
development of the higher human races. If light tints 
of the skin were generally accompanied by some de- 
ficiency in the senses of smell, hearing, and vision, the 
white could never compete with the darker races so long 
as man was in a very low or savage condition, and 
wholly dependent for existence on the acuteness of his 
senses. But as the mental faculties became more fully 
developed and more important to his welfare than mere 
sense-acuteness, the lighter tints of skin and hair and 
eyes would cease to be disadvantageous whenever they 
were accompanied by superior brain-power. Such varia- 
tions would then be preserved ; and thus may have 
arisen the Xanthochroic race of mankind, in which we 
find a high development of intellect accompanied by a 
slight deficiency in the acuteness of the senses as com- 
pared with the darker forms. 

Relations of Insular Plants and Insects. I have 
now to ask your attention to a few remarks on the 
peculiar relations of plants and insects as exhibited 
in islands. 

Ever since Mr. Darwin showed the immense import- 
ance of insects in the fertilization of flowers, great 
attention has been paid to the subject, and the relation 
of these two very different classes of natural objects 



268 TROPICAL NATURE, AND OTHER ESSAYS. 

has been found to be more universal and more complex 
than could have been anticipated. Whole genera and 
families of plants have been so modified as, first to attract 
and then to be fertilized by, certain groups of insects ; 
and this special adaptation seems in many cases to have 
determined the more or less wide range of the plants in 
question. It is also known that some species of plants 
can be fertilized only by particular species of insects ; 
and the absence of these from any locality would 
necessarily prevent the continued existence of the plant 
in that area. 

In this direction, I believe, will be found the clue to 
much of the peculiarity of the floras of oceanic islands ; 
since the methods by .which these have been stocked 
with plants and with insects will be often quite different. 
Many seeds are, no doubt, carried by oceanic currents, 
others probably by aquatic birds. Mr. H. N. Moseley 
informs me that the albatrosses, gulls, puffins, tropic 
birds and many others, nest inland, often amidst dense 
vegetation ; and he believes they often carry seeds, 
attached to their feathers, from island to island for 
great distances. In the tropics they often nest on 
the mountains far inland, and may thus aid in the 
distribution even of mountain-plants. Insects, on the other 
hand, are mostly conveyed by aerial currents, especially 
by violent gales ; and it may thus often happen that 
totally unrelated plants and insects may be brought 
together, in which case the former must often perish for 
want of suitable insects to fertilize them. This will, I 
think, account for the strangely fragmentary nature of 
these insular floras, and the great differences that often 
exist between those which are situated in the same 



INSULAR PLANTS AND INSECTS. 269 

ocean ; as well as for the preponderance of certain orders 
and genera. 

In Mr. Pickering's valuable work on the "Geographical 
Distribution of Animals and Plants " (founded on his 
researches during the United States exploring expedition), 
he gives a list of no less than sixty-six natural orders 
of plants unexpectedly absent from Tahiti, or which 
occur in many of the surrounding lands ; some being 
abundant in other islands as the Labiatse at the 
Sandwich Islands. In these latter islands the flora is 
much richer, yet a large number of families which 
abound in other parts of Polynesia are totally wanting. 
Now much of the poverty and exceptional distribution 
of the plants of these islands is probably due to the 
great scarcity of flower-frequenting insects. Lepidoptera 
and Hymenoptera are exceedingly scarce in the eastern 
islands of the Pacific, and it is almost certain that many 
plants which require these insects for their fertilization 
have been thereby prevented from establishing them- 
selves. In the western islands, such as the Fijis, several 
species of butterflies occur in tolerable abundance, and 
no doubt some flower-haunting Hymenoptera accompany 
them ; and in these islands the flora appears to be much 
more varied, and especially to be characterized by a 
much greater variety of showy flowers, as may be seen 
by examining the plates of Dr. Seeman's " Flora 
Vitiensis." 

Darwin and Pickering both speak of the great pre- 
ponderance of ferns at Tahiti ; and Mr. Moseley, who 
spent several days in the interior of the island, informs 
me that "at an elevation of from 2,000 to 3,000 feet 
the dense vegetation is composed almost entirely of 



270 TROPICAL NATURE, AND OTHER ESSAYS. 

ferns. A tree fern (Alsophila tahitensis) forms a sort of 
forest to the exclusion of almost every other tree, and, 
with huge plants of two other ferns (Angiopteris evecta 
and Aspelenium nidus), forms the main mass of the 
vegetation." And he adds, " I have nowhere seen ferns 
in so great proportionate abundance." This unusual 
proportion of ferns is a general feature of insular as 
compared with continental floras ; but it has, I believe, 
been generally attributed to favourable conditions, 
especially to equable climate and perennial moisture. 
In this respect, however, Tahiti can hardly differ greatly 
from many other islands, which yet have no such vast 
preponderance of ferns. This is a question that cannot 
be decided by mere lists of species, since it is probable 
that in Tahiti they are less numerous than in some other 
islands where they form a far less conspicuous feature in 
the vegetation. The island most comparable with Tahiti 
in this respect is Juan Fernandez. Mr. Moseley writes 
to me : " In a general view of any wide stretch of the 
densely clothed mountainous surface of the island, the 
ferns, both tree ferns and the unstemmed forms, are 
seen at once to compose a very large proportion of the 
mass of foliage." As to the insects of Juan Fernandez, 
Mr. Edwyn C. Reed, who made two visits and spent 
several weeks there, has kindly furnished me with some 
exact information. Of butterflies there is only one 
(Pyrameis carie), and that rare a Chilian species and 
probably an accidental straggler. Four species of moths 
of moderate size were observed (all Chilian), and a few 
larvae and pupae. Of bees there were none, except one 
very minute species (allied to Chilicola), and of other 
Hymenoptera a single specimen 'of Ophion luteus a 



INSULAR PLANTS AND INSECTS. 271 

cosmopolitan ichneumon. About twenty species of 
flies were observed, and these formed the most prominent 
feature of the entomology of the island. 

o^ 

Now, as far as we know, this extreme entomological 
poverty agrees closely with that of Tahiti ; and there 
are probably no other portions of the globe equally 
favoured in soil and climate, and with an equally 
luxuriant vegetation, where insect-life is so scantily 
developed. It is curious, therefore, to find that these 
two islands also agree in the wonderful predominance 
of ferns over the flowering plants in individuals even 
more than in species ; and there is no difficulty in con- 
necting the two facts. The excessive minuteness and 
great abundance of fern-spores causes them to be far 
more easily distributed by winds than the seeds of 
flowering plants ; and they are thus always ready to 
occupy any vacant places in suitable localities, and to 
compete with the less vigorous flowering plants. But 
where insects are so scarce, all plants which require 
insect-fertilization, whether constantly to enable them 
to produce seed at all or occasionally to keep up their 
constitutional vigour by crossing, must be at a great 
disadvantage ; and thus the scanty flora which oceanic 
islands must always possess, peopled as they usually are 
by waifs and strays from other lands, is rendered still 
more scanty by the weeding out of all such as depend 
largely on insect-fertilization for their full development. 
It seems probable, therefore, that the preponderance of 
ferns in islands (considered in mass of individuals rather 
than in number of species) is largely due to the absence 
of competing phaenogamous plants, and that this is in 
great part due to the scarcity of insects. In other 



272 TROPICAL NATURE, AND OTHER ESSAYS. 

oceanic islands, such as New Zealand and the Galapagos, 
where ferns, although tolerably abundant, form no such 
predominant feature in the vegetation, but where the 
scarcity of flower-haunting insects is almost equally 
marked, we find a great preponderance of small, green, 
or otherwise inconspicuous flowers, indicating that only 
such plants have been enabled to flourish there as are 
independent of insect-fertilization. In the Galapagos 
(which are perhaps even more deficient in flying insects 
than Juan Fernandez) this is so striking a feature that 
Mr. Darwin speaks of the vegetation as consisting in 
great part of " wretched-looking weeds," and states that 
" it was some time before he discovered that almost 
every plant was in flower at the time of his visit." He 
also says that he " did not see one beautiful flower " 
in the islands. It appeal's, however, that Composite, 
Leguminosse, Rubiaceae, and Solan acese form a large 
proportion of the flowering plants ; and as these are 
orders which usually require insect-fertilization, we must 
suppose, either that they have become modified so as to 
be self-fertilized, or that they are fertilized by the visits 
of the minute Diptera and Hymenoptera which are the 
only insects recorded from these islands. 

In Juan Fernandez, on the other hand, there is no 
such total deficiency of showy flowers. I am informed 
by Mr. Moseley that a variety of the Magnoliaceous 
winter-bark abounds and has showy white flowers, and 
that a Bignoniaceous shrub with abundance of dark blue 
flowers was also plentiful ; while a white-flowered Lili- 
aceous plant formed large patches on the hill- sides. 
Besides these, there were two species of woody Com- 
positse with conspicuous heads of yellow blossoms, and 



INSULAR PLANTS AND INSECTS. 273 

a species of white-flowered myrtle also abundant ; so 
that, on the whole, flowers formed a rather conspi- 
cuous feature in the aspect of the vegetation of Juan 
Fernandez. 

But this fact which at first sight seems entirely at 
variance with the view we are upholding of the im- 
portant relation between the distribution of insects 
and plants is well explained by the existence of two 
species of humming-birds in Juan Fernandez, which, in 
their visits to these large and showy flowers, fertilize 
them as effectually as bees, moths, or butterflies. Mr. 
Moseley informs me that " these humming-birds are 
extraordinarily abundant, every tree or bush having 
one or two darting about it." He also observed that 
" nearly all the specimens killed had the feathers round 
the base of the bill and front of the head clogged and 
coloured yellow with pollen." Here, then, we have the 
clue to the perpetuation of large and showy flowers in 
Juan Fernandez ; while the total absence of humming- 
birds in the Galapagos may explain why no such large- 
flowered plants have. been able to establish themselves 
in those equatorial islands. 

This leads to the observation that many other groups 
of birds also, no doubt, aid in the fertilization of 
flowers. I have often observed the beaks and faces of 
the brush -tongued lories of the Moluccas covered with 
pollen ; and Mr. Moseley noted the same fact in a species of 
Artamus, or swallow-shrike, shot at Cape York, showing 
that this genus also frequents flowers and aids in their fer- 
tilization. In the Australian region we have the immense 
group of the Meliphagidae, which all frequent flowers ; 
and as these range over all the islands of the Pacific, 

T 



274 TROPICAL NATURE, AND OTHER ESSAYS. 

their presence will account for a certain proportion of 
showy flowers being found there, such as the scarlet 
Metrosideros, one of the few conspicuous flowers in 
Tahiti. In the Sandwich Islands, too, there are forests 
of Metrosideros ; and Mr. Charles Pickering writes me, 
that they are visited by honey-sucking birds, one of 
which is captured by sweetened bird-lime, against which 
it thrusts its extensile tongue. I am also informed that 
a considerable number of flowers are occasionally fertil- 
ized by humming-birds in North America ; so that there 
can, I think, be little doubt that birds play a much 
more important part in this respect than has hitherto 
been imagined. It is riot improbable that in Tropical 
America, where the humming-bird family is so enor- 
mously developed, many flowers will be found to be 
expressly adapted to fertilization by them, just as so 
many in our own country are specially adapted to the 
visits of certain families or genera of insects. 1 

It must also be remembered, as Mr. Moseley has 
suggested to me, that a flower which has acquired a 
brilliant colour to attract insects might, on transference 
to another country and becoming so modified as to be 
capable of self-fertilization, retain the coloured petals for 

1 The probable influence of fertilization by birds on the flowers of the 
Auckland Isles has been referred to at p. 238. Mr. Darwin, in his book on 
Cross and Self-Fertilisation of Plants (p. 371), gives in a note numerous 
cases in which birds are known to fertilise flowers, the most important being 
that of several species of Abutilon in South Brazil, which, according to Fritz 
Muller, are sterile unless fertilised by humming-birds. This proves, not 
only that birds fertilise flowers in the same manner as insects, but that the 
two classes of organisms have become so correlated as to be mutually neces- 
sary to each other ; and it completely justifies us in imputing the fertilization 
of flowers to flower-frequenting birds wherever these are present and suitable 
insects are notoriously scarce, as is the case in so many of the islands here 
referred to. 



INSULAR PLANTS AND INSECTS. 275 

an indefinite period. Such is probably the explanation 
of the Pelargonium of Tristan d'Acunha, which forms 
masses of bright colour near the shore during the 
flowering season ; while most of the other plants of the 
island have colourless flowers in accordance with the 
almost total absence of winged insects. The presence 
of many large and showy flowers among the indigenous 
flora of St. Helena must be an example of a similar 
persistence. Mr. Melliss indeed states it to be " a 
remarkable peculiarity that the indigenous flowers are, 
with very slight exceptions, all perfectly colourless ; " 
but although this may apply to the general aspect of 
the remains of the indigenous flora, it is evidently not 
the case as regards the species, since the interesting 
plates of Mr. Melliss's volume show that about one 
third of the indigenous flowering plants have more or 
less coloured or conspicuous flowers, while several of 
them are exceedingly showy and beautiful. Among 
these are a Lobelia, three Wahlenbergias, several Com- 
positse, and especially the handsome red flowers of the 
now almost extinct forest-trees, the ebony and redwood 
(species of Melhania, Byttneriaceae). We have every 
reason to believe, however, that when St. Helena was 
covered with luxuriant forests, and especially at that 
remote period when it was much more extensive than 
it is now, it must have supported a certain number of 
indigenous birds and insects, which would have aided in 
the fertilization of these gaily- coloured flowers. The 
researches of Dr. Hermann Mtiller have shown us by 
what minute modifications of structure or of function, 
many flowers are adapted for partial insect and self- 

1 Melliss's St. Hel&w, p. 226, note. 

T 2 



276 TROPICAL NATURE, AND OTHER ESSAYS. 

fertilization in various degrees; so that we have no 
difficulty in understanding how, as the insects dimin- 
ished and finally disappeared, self- fertilization may have 
become the rule, while the large and showy corollas 
remain to tell us plainly of a once different state of things. 

Another interesting fact in connexion with this sub- 
ject is the presence of arborescent forms of Composite 
in so many of the remotest oceanic islands. They occur 
in the Galapagos, in Juan Fernandez, in St. Helena, in 
the Sandwich Islands, and in New Zealand ; but they 
are not directly related to each other ; representatives 
of totally different tribes of this extensive order be- 
coming arborescent in each group of islands. The 
immense range and almost universal distribution of the 
Composite is due to the combination of a great facility 
of distribution (by their seeds) with a great attractive- 
ness to insects ; and to the capacity of being fertilized by 
a variety of species of all orders, and especially by flies 
and small beetles. Thus they would be among the 
earliest of flowering plants to establish themselves on 
oceanic islands ; but where insects of all kinds were 
very scarce, it would be an advantage to gain increased 
size and longevity, so that fertilization at an interval of 
several years might suffice for the continuance of the 
species. The arborescent form would combine with in- 
creased longevity the advantage of increased size in 
the struggle for existence with ferns and other early 
colonists ; and these advantages have led to its being 
independently produced in so many distant localities, 
whose chief feature in common is their remoteness from 
continents and the extreme poverty of their insect life. 

As the sweet odours of flowers are known to act in 



INSULAR PLANTS AND INSECTS. 277 

combination with their colours, as an attraction to insects, 
it might be anticipated that where colour was deficient 
scent would be so also. On applying to my friend Sir 
Joseph Hooker for information as to the odoriferous 
qualities of New-Zealand plants, he informed me, that 
the New-Zealand flora is, speaking generally, as strik- 
ingly deficient in sweet odours as it is in conspicuous 
colours. Whether this peculiarity occurs in other islands 
I have not been able to obtain information ; but we may 
certainly expect to find it where colour is so strikingly 
deficient as in the flora of the Galapagos Islands. 

Another question which here comes before us, is the 
origin and meaning of the odoriferous glands of leaves. 
Sir Joseph Hooker informed me that not only are New- 
Zealand plants deficient in bright coloured and sweet- 
smelling flowers, but equally so in scented leaves. This 
led me to think that perhaps such leaves were in some 
way an additional attraction to insects though it is not 
easy to understand how this could be, except by adding 
a general attraction to the special attraction of the 
flowers, or by supporting the larvae which, as perfect in- 
sects, aid in fertilization. Mr. Darwin, however, informs 
me that he considers that leaf-glands bearing essential oils 
are a protection against the attacks of insects where these 
abound, and would thus not be required in countries 
where insects were very scarce. But it seems opposed 
to this view that highly aromatic plants are charac- 
teristic of deserts all over the world, and in such places 
insects are not abundant. Mr. Stainton informs me that 
the aromatic Labiatse enjoy no immunity from insect 
attacks. The bitter leaves of the cherry-laurel are often 
eaten by the larvre of moths that abound on our fruit- 



278 TROPICAL NATURE, AND OTHER ESSAYS. 

trees ; while in the Tropics the leaves of the orange tribe 
are favourites with a large number of lepidopterous 
larvee ; and our northern firs and pines, although abound- 
ing in a highly aromatic resin, are very subject to the 
attacks of beetles. My friend Dr. Richard Spruce who 
while travelling in South America allowed nothing con- 
nected with plant-life to escape his observation informs 
me that trees whose leaves have aromatic and often 
resinous secretions in immersed glands abound in the 
plains of tropical America, and that such are in great 
part, if not wholly, free from the attacks of leaf-eating 
ants, except where the secretion is only slightly bitter, 
as in the orange tribe, oraDge-trees being sometimes 
entirely denuded of their leaves in a single night. Aro- 
matic plants abound in the Andes up to about 13,000 
feet, as well as in the plains, but hardly more so than in 
Central and Southern Europe. They are perhaps more 
plentiful in the dry mountainous parts of Southern 
Europe ; and as neither here nor in the Andes do leaf- 
eating ants exist, Dr. Spruce infers that, although in the 
hot American forests where such ants swarm the oil- 
bearing glands serve as a protection, yet they were not 
originally acquired for that purpose. Near the limits of 
perpetual snow on the Andes such plants as occur are 
not, so far as Dr. Spruce has observed, aromatic ; and 
as plants in such situations can hardly depend on insect 
visits for their fertilization, the fact is comparable with 
that of the flora of New Zealand, and would seem to 
imply some relation between the two phenomena, though 
what it exactly is cannot yet be determined. 

I trust I have now been able to show you that there 



BY-PATHS OF BIOLOGY. 279 

are a number of curious problems lying as it were on the 
outskirts of biological inquiry which well merit attention, 
and which may lead to valuable results. But these 
problems are, as you see, for the most part connected 
with questions of locality, and require full and accurate 
knowledge of the productions of a number of small 
islands and other limited areas, and the means of 
comparing them one with the other. To make such 
comparisons, however, is now quite impossible. No 
museum contains any fair representation of the pro- 
ductions of these localities ; and such specimens as do 
exist, being scattered through the general collection, are 
almost useless for this special purpose. If, then, we are 
to make any progress in this inquiry it is absolutely essen- 
tial that some collectors should begin to arrange their 
cabinets primarily on a geographical basis, keeping to- 
gether the productions of every island or group of islands, 
and of such divisions of each continent as are found to 
possess any special or characteristic fauna or flora. We shall 
then be sure to detect many unsuspected relations between 
the animals and plants of certain localities, and we shall 
become much better acquainted with those complex reac- 
tions between the vegetable and animal kingdoms, and 
between the organic world and the inorganic, which have 
almost certainly played an important part in determining 
many of the most conspicuous features of living things. 



280 TROPICAL NATURE, AND OTHER ESSAYS. 



RISE AND PROGRESS OF MODERN VIEWS AS TO THE 
ANTIQUITY AND ORIGIN OF MAN. 

I now come to a branch of our subject which I would 
gladly have avoided touching on ; but as the higher 
powers of the British Association have decreed that I 
should preside over the Anthropological Department, it 
seems proper that I should devote some portion of my 
address to matters more immediately connected with the 
special study to which that Department is devoted. 

As my own knowledge of and interest in Anthropology 
is confined to the great outlines rather than to the special 
details of the science, I propose to give a very brief and 
general sketch of the modern doctrine as to the Antiquity 
and Origin of Man, and to suggest certain points of diffi- 
culty which have not, I think, yet received sufficient 
attention. 

Many now living remember the time (for it is little 
more than twenty years ago) when the antiquity of man, 
as now understood, was universally discredited. Not 
only theologians, but even geologists then taught us, that 
man belonged altogether to the existing state of things ; 
that the extinct animals of the Tertiary period had finally 
disappeared, and that the earth's surface had assumed 
its present condition before the human race first came 
into existence. So prepossessed were even scientific men 
with this idea which yet rested on purely negative 
evidence, and could not be supported by any arguments 
of scientific value that numerous facts which had been 
presented at intervals for half a century, all tending to 
prove the existence of man at very remote epochs, were 



ANTIQUITY OF MAN. 281 

silently ignored ; and, more than this, the detailed 
statements of three distinct and careful observers con- 
firming each other, were rejected by a great scientific 
Society as too improbable for publication, only because 
they proved (if they were true) the coexistence of man 
with extinct animals. l 

But this state of belief in opposition to facts, could 
not long continue. In 1859 a few of our most eminent 
geologists examined for themselves into the alleged 
occurrence of flint implements in the gravels of the 
north of France, which had been made public fourteen 
years before, and found them strictly correct. The 
caverns of Devonshire were about the same time care- 
fully examined by equally eminent observers, and were 
found fully to bear out the statements of those who 
had published their results eighteen .years before. Flint 
implements began to be found in all suitable localities 
in the south of England, when carefully searched for, 
often in gravels of equal antiquity with those of France. 
Caverns giving evidence of human occupation at various 
remote periods were explored in Belgium and the south 
of France lake-dwellings were examined in Switzerland 
refuse-heaps in Denmark and thus a whole series of 
remains have been discovered carrying back the history 
of mankind from the earliest historic periods to a long 
distant past. 

The antiquity of the races thus discovered cannot be 
measured in years ; but it may be approximately deter- 

1 In 1854 (?) a communication from the Torquay Natural-History Society 
confirming previous accounts by Mr. Godwin- Austen, Mr. Vivian, and the 
Eev. Mr. M'Enery, that worked flints occurred in Kent's Hole with remains 
of extinct species, was rejected as too improbable for publication. 



282 TROPICAL NATURE, AND OTHER ESSAYS. 

mined by the successively earlier and earlier stages of 
civilization through which we can trace them, and by the 
changes in physical geography and of animal and vege- 
table life that have since occurred. As we go back 
metals soon disappear, and we find only tools and 
weapons of stone and of bone. The stone weapons get 
ruder and ruder ; pottery, and then the bone imple- 
ments, cease to occur ; and in the earliest stage we 
find only chipped flints of rude design, though still of 
unmistakably human workmanship. In like manner 
domestic animals disappear as we go backward ; and 
though the dog seems to have been the earliest, it is 
doubtful whether the makers of the ruder flint imple- 
ments of the gravels possessed even this. Still more 
important as a measure of time are the changes in 
the distribution of animals, indicating changes of 
climate, which have occurred during the human period. 
At a comparatively recent epoch in the record of pre- 
historic times we find that the Baltic was far salter than 
it is now and produced abundance of oysters, and that 
Denmark was covered with pine forests inhabited by Caper- 
cailzies, such as now only occur further north in Norway. 
A little earlier we find that reindeer were common even 
in the south of France ; and still earlier this animal was 
accompanied by Ihe mammoth and woolly rhinoceros, 
by the arctic glutton, and by huge bears and lions of 
extinct species. The presence of such animals implies 
a change of climate ; and both in the caves and gravels 
we find proofs of a much colder climate than now 
prevails in Western Europe. Even more remarkable are 
the changes of the earth's surface which have been 
effected during man's occupation of it. Many extensive 



ANTIQUITY OF MAN. 283 

valleys in England and France are believed by the best 
observers to have been deepened at least a hundred feet ; 
caverns now far out of the reach of any stream must for 
a long succession of years have had streams flowing 
through them, at least in times of floods ; and this often 
implies that vast masses of solid rock have since been 
worn away. In Sardinia land has risen at least 300 feet 
since men lived there who made pottery and probably 
used fishing-nets j 1 while in Kent's Cavern remains of 
man are found buried beneath two separate beds of 
stalagmite, each having a distinct texture, and each 
covering a deposit of cave-earth having well-marked 
differential characters, while each contains a distinct 
assemblage of extinct animals. 

Such, briefly, are the results of the evidence that has 
been rapidly accumulating for about fifteen years, as to 
the antiquity of man ; and it has been confirmed by so 
many discoveries of a like nature in all parts of the globe, 
and especially by the comparison of the tools and weapons 
of prehistoric man with those of modern savages (so that 
the use of even the rudest flint implements has become 
quite intelligible), that we can hardly wonder at the vast 
revolution effected in public opinion. Not only is the 
belief in man's vast and still unknown antiquity uni- 
versal among men of science, but it is hardly disputed 
by any well-informed theologian ; and the present gene- 
ration of science-students must, we should think, be 
somewhat puzzled to understand what there was in the 
earliest discoveries that should have aroused such general 
opposition, and been met with such universal incredulity. 

But the question of the mere " Antiquity of Man " 

1 Lyell's Antiquity of Man, fourth edition, p. 115. 



284 TROPICAL NATURE, AND OTHER ESSAYS. 

almost sank into insignificance at a very early period of 
the inquiry, in comparison with the far more momentous 
and more exciting problem of the development of man 
from some lower animal form, which the theories of Mr. 
Darwin and of Mr. Herbert Spencer soon showed to be 
inseparably bound up with it. This has been, and to 
some extent still is, the subject of fierce conflict; but 
the controversy as to the fact of such development is 
now almost at an end, since one of the most talented 
representatives of Catholic theology, and an anatomist 
of high standing Professor Mivart fully adopts it as 
regards physical structure, reserving his opposition for 
those parts of the theory which would deduce man's 
whole intellectual and moral nature from the same 
source and by a similar mode of development. 

Never, perhaps, in the whole history of science or phi- 
losophy has so great .a revolution in thought and opinion 
been effected as in the twelve years from 1859 to 1871, the 
respective dates of publication of Mr. Darwin's Origin of 
Species and Descent of Man. Up to the commencement 
of this period the belief in the independent creation or 
origin of the species of animals and plants, and the very 
recent appearance of man upon the earth, were, prac- 
tically, universal. Long before the end of it these two 
beliefs had utterly disappeared, not only in the scientific 
world, but almost equally so among the literary and 
educated classes generally. The belief in the inde- 
pendent origin of man held its ground somewhat longer; 
but the publication of Mr. Darwin's great work gave 
even that its death-blow, for hardly any one capable of 
judging of the evidence now doubts the derivative nature 
of man's bodily structure as a whole, although many be- 



ANTIQUITY OF MAN. 285 

lieve that his mind, and even some of his physical 
characteristics, may be due to the action of other forces 
than have acted in the case of the lower animals. 

We need hardly be surprised, under these circum- 
stances, if there has been a tendency among men of 
science to pass from one extreme to the other ; from a 
profession (so few years ago) of total ignorance as to the 
mode of origin of all living things, to a claim to almost 
complete knowledge of the whole progress of the uni- 
verse, from the first speck of living protoplasm up to 
the highest development of the human intellect. Yet 
this is really what we have seen in the last sixteen 
years. Formerly difficulties were exaggerated, and it 
was asserted that we had not sufficient knowledge to 
venture on any generalizations on the subject. Now 
difficulties are set aside, and it is held that our theories 
are so well established and so far-reaching, that they 
explain and comprehend all nature. It is not long ago 
(as I have already reminded you) since facts were con- 
temptuously ignored, because they favoured our now 
popular views ; at the present day it seems to me that 
facts which oppose them hardly receive due consideration. 
And as opposition is the best incentive to progress, and 
it is not well even for the best theories to have it all 
their own way, I propose to direct your attention to a 
few such facts, and to the conclusions that seem fairly 
deducible from them. 

Indications of Man's Extreme Antiquity. It is a 
curious circumstance that, notwithstanding the attention 
that has been directed to the subject in every part of the 
world, and the numerous excavations connected with 
railways and mines which have offered such facilities 



286 TROPICAL NATURE, AND OTHER ESSAYS. 

for geological discovery, no advance whatever has been 
made for a considerable number of years in detecting 
the time or mode of man's origin. The Palaeolithic 
flint weapons first discovered in the North of France 
more than thirty years ago, are still the oldest undisputed 
proofs of man's existence ; and amid the countless relics 
of a former world that have been brought to light, no 
evidence of any one of the links that must have con- 
nected man with the lower animals has yet appeared. 

It is, indeed, well known that negative evidence in 
geology is of very slender value ; and this is, no doubt, 
generally the case. The circumstances here are, how- 
ever, peculiar, for many converging lines of evidence 
show that, on the theory of development by the same 
laws which have determined the development of the 
lower animals, man must be immensely older than any 
traces of him yet discovered. As this is a point of 
great interest we must devote a few moments to its 
consideration. 

1. The most important difference between man and 
such of the lower animals as most nearly approach him 
is undoubtedly in the bulk and development of his brain, 
as indicated by the form and capacity of the cranium. 
We should therefore anticipate that these earliest races, 
who were contemporary with the extinct animals and 
used rude stone weapons, would show a marked de- 
ficiency in this respect. Yet the oldest known crania 
(those of the Engis and Cro-Magnon caves) show no 
marks of degradation. The former does not present so 
low a type as that of most existing savages, but is (to 
use the words of Prof. Huxley) " a fair average human 
skull, which might have belonged to a philosopher, or 



ANTIQUITY OF MAN. 287 

might have contained the thoughtless brains of a savage." 
The latter are still more remarkable, being unusually 
large and well formed. Dr. Pruner-Bey states that they 
surpass the average of modern European skulls in 
capacity, while their symmetrical form without any trace 
of prognathism, compares favourably not only with those 
of the foremost savage races, but with many civilised 
nations of modern times. 

One or two other crania of much lower type, but of less 
antiquity than this, have been discovered ; but they in 
no way invalidate the conclusion which so highly de- 
veloped a form at so early a period implies, viz., that we 
have as yet made a hardly perceptible step towards 
the discovery of any earlier stage in the development 
of man. 

2. This conclusion is supported and enforced by the 
nature of many of the works of art found even in the 
oldest cave-dwellings. The flints are of the old chipped 
type, but they are formed into a large variety of tools 
and weapons such as scrapers, awls, hammers, saws, 
lances, &c., implying a variety of purposes for which 
these were used, and a corresponding degree of mental 
activity and civilization. Numerous articles of bone 
have also been found, including well-formed needles ; 
implying that skins were sewn together, and perhaps 
even textile materials woven into cloth. Still more 
important are the numerous carvings and drawings re- 
presenting a variety of animals, including horses, rein- 
deer, and even a mammoth, executed with considerable 
skill on bone, reindeer-horns, and mammoth- tusks. 
These, taken together, indicate a state of civilization 
much higher than that of the lowest of our modern 



288 TROPICAL NATURE, AND OTHER ESSAYS. 

savages, while they are quite compatible with a consider- 
able degree of mental advancement, and lead us to be- 
lieve that the crania of Engis and Cro-Magnon are not 
exceptional, but fairly represent the characters of the 
race. If we further remember that these people lived 
in Europe under the unfavourable conditions of a sub- 
Arctic climate, we shall be inclined to agree with Dr. 
Daniel Wilson, that it is far easier to produce evidences 
of deterioration than of progress, in instituting a com- 
parison between the contemporaries of the mammoth 
and later prehistoric races of Europe or savage nations 
of modern times. 1 

3. Yet another important line of evidence as to the 
extreme antiquity of the human type has been brought 
prominently forward by Prof. Mivart. 2 He shows, by a 
careful comparison of all parts of the structure of the 
body, that man is related not to any one, but almost 
equally to many of the existing apes to the orang, the 
chimpanzee, the gorilla, and even to the gibbons in a 
variety of ways ; and these relations and differences are 
so numerous and so diverse that, on the theory of evolu- 
tion, the ancestral form which ultimately developed into 
man must have diverged from the common stock whence 
all these various forms and their extinct allies originated. 
But so far back as the Miocene deposits of Europe we 
find the remains of apes allied to these various forms, 
and especially to the gibbons ; so that in all probability 
the special line of variation which led up to man 
branched off at a still earlier period. And these early 
forms, being the initiation of -a far higher type, and 

1 Prehistoric Man, 3rd edit. vol. i. p. 117. 
Man and Ape, pp. 171-193, 



ANTIQUITY OF MAN. 289 

having to develop by natural selection into so specialized 
and altogether distinct a creature as man, must have 
risen at a very early period into the position of a 
dominant race, and spread in dense waves of popula- 
tion over all suitable portions of the great continent 
for this, on Mr. Darwin's hypothesis, is essential to 
developmental progress through the agency of natural 
selection. 

Under these circumstances we might certainly expect 
to find some relics of these earlier forms of man along 
with those of animals, which were presumably less 
abundant. Negative evidence of this kind is not very 
weighty, but still it has some value. It has been sug- 
gested that as apes are mostly tropical, and anthropoid 
apes are now confined almost exclusively to the vicinity 
of the equator, we should expect the ancestral forms of 
man to have inhabited these same localities West Africa 
and the Malay Islands. But this objection is hardly 
valid, because existing anthropoid apes are wholly de- 
pendent on a perennial supply of easily accessible fruits, 
which is only found near the equator ; while not only 
had the south of Europe an almost tropical climate in 
Miocene times, but we must suppose even the earliest 
ancestors of man to have been terrestrial and omnivorous, 
since it must have taken ages of slow modification to 
have produced the perfectly erect form, the short arms, 
and the wholly non-prehensile foot, 1 which so strongly 
differentiate man from the arboreal apes. 

1 The common statement of travellers as to savages having great prehensile 
power in the toes, has been adopted by some naturalists as indicating an ap- 
proach to the apes. But this notion is founded on a complete misconception. 
Savages pick up objects with their feet, it is true, but always by a lateral 
motion of the toes, which we should equally possess if we never wore shoes or 

U 



290 TROPICAL NATURE, AND OTHER ESSAYS. 

The conclusion which I think we must arrive at is, 
that if man has been developed from a common ancestor 
with all existing apes, and by no other agencies than 
such as have affected their development, then he must 
have existed, in something approaching his present form, 
during the tertiary period and not merely existed, but 
predominated in numbers, wherever suitable conditions 
prevailed. If then, continued researches in all parts of 
Europe and Asia fail to bring to light any proofs of his 
presence, it will be at least a presumption that he came 
into existence at a much later date, and by a much more 
rapid process of development. In that case it will be a 
fair argument that, just as he is in his mental and moral 
nature, his capacities and aspirations, so infinitely raised 
above the brutes, so his origin is due, in part, to distinct 
and higher agencies than such as have affected their 
development. 

Antiquity of Intellectual Man. There is yet another 
line of inquiry bearing upon this subject to which I 
wish to call your attention. It is a somewhat curious 
fact that, while all modern writers admit the great 
antiquity of man, most of them maintain the very 
recent development of his intellect, and will hardly 
contemplate the possibility of men equal in mental 
capacity to ourselves having existed in prehistoric times. 
This question is generally assumed to be settled by such 
relics as have been preserved of the manufactures of the 
older races, showing a lower and lower state of the arts ; 
by the successive disappearance in early times of iron, 

stockings. In no savage have I ever seen the slightest approach to opposa- 
bility of the great toe, which is the essential distinguishing feature of apes ; 
nor have I ever seen it stated that any variation in this direction has been 
detected in the anatomical structure of the foot of the lower races. 



ANTIQUITY OF MAN. 291 

bronze, and pottery ; and by the ruder forms of the older 
flint implements. The weakness of this argument has 
been well shown by Mr. Albert Mott in his very original 
but little known presidential address to the Literary and 
Philosophical Society of Liverpool in 1873. He main- 
tains that " our most distant glimpses of the past are 
still of a world peopled as now with men both civilised 
and savage," and " that we have often entirely misread 
the past by supposing that the outward signs of civilisa- 
tion must always be the same, and must be such as are 
found among ourselves." In support of this view he 
adduces a variety of striking facts and ingenious argu- 
ments, a few of which I will briefly summarize. 

Sculptures on Easter Island. On one of the most 
remote islands of the Pacific Easter Island, 2,000 
miles from South America, 2,000 from the Marquesas, 
and more than 1,000 from the Gambier Islands, are 
found hundreds of gigantic stone images, now mostly 
in ruins. They are often forty feet high, while some seem 
to have been much larger, the crowns on their heads, 
cut out of a red stone, being sometimes ten feet in 
diameter, while even the head and neck of one is said 
to have been twenty feet high. 1 These images once all 
stood erect on extensive stone platforms. 

The island containing these remarkable works of art has 
only an area of about thirty square miles, or considerably 
less than Jersey. Now as one of the smallest images 
(eight feet high) weighs four tons, the largest must weigh 
over a hundred tons, if not much more ; and the exist- 
ence of such vast works implies a large population, 
abundance of food, and an established government. Yet 

1 Journ. of Roy. Geog. Soc. 1870, pp. 177, 178. 

u 2 



292 TROPICAL NATURE, AND OTHER ESSAYS. 

how could these coexist on a mere speck of land wholly 
cut off from the rest of the world ? Mr. Mott maintains 
that these facts necessarily imply the power of regular 
communication with larger islands or a continent, the arts 
of navigation, and a civilisation much higher than now 
exists in any part of the Pacific. Very similar remains 
in other islands scattered widely over the Pacific add 
weight to this argument. 

North American Earthworks. The next example is 
that of the ancient mounds and earthworks of the North 
American continent, the bearing of which is even more 
significant. Over the greater part of the extensive Missis- 
sippi valley, four well-marked classes of these earthworks 
occur. Some are camps, or works of defence, situated on 
bluffs, promontories, or isolated hills ; others are vast 
inclosures in the plains and lowlands, often of geo- 
metric forms, and having attached to them roadways 
or avenues often miles in length ; a third are mounds 
corresponding to our tumuli, often seventy to ninety 
feet high, and some of them covering acres of ground ; 
while a fourth group consists of representations of 
various animals modelled in relief on a gigantic scale, 
and occurring chiefly in an area somewhat to the north- 
west of the other classes, in the plains of Wisconsin. 

The first class the camps or fortified inclosures 
resemble in general features the ancient camps of our 
own islands, but far surpass them in extent. Fort Hill, 
in Ohio, is surrounded by a wall and ditch a mile and a 
half in length, part of the way cut through solid rock. 
Artificial reservoirs for water were made within it, while 
at one extremity, on a more elevated point, a keep is 
constructed with its separate defences and water- 



ANTIQUITY OF MAN. 293 

reservoirs. Another, called Clark's Work, in the 
Scioto valley, which seems to have been a fortified 
town, incloses an area of 127 acres, the embankments 
' measuring three miles in length, and containing not 
less than three million cubic feet of earth. This area 
incloses numerous sacrificial mounds and symmetrical 
earthworks, in which many interesting relics and works 
of art have been found. 

The second class the sacred inclosures, may be 
compared for extent and arrangement with Avebury 
or Carnak, but are in some respects even more re- 
markable. One of these at Newark, Ohio, covers an 
area of several miles, with its connected groups of circles, 
octagons, squares, ellipses, and avenues on a grand scale, 
and formed by embankments from twenty to thirty feet 
in height. Other similar works occur in different parts 
of Ohio ; and by accurate survey it is found, not only 
that the circles are true, though some of them are one- 
third of a mile in diameter, but that other figures are 
truly square, each side being over 1,000 feet long ; and, 
what is still more important, the dimensions of some of 
these geometrical figures in different parts of the 
country and seventy miles apart, are identical. Now 
this proves the use, by the builders of these works, of 
some standard measures of length ; while the accuracy 
of the squares, circles, and, in a less degree, of the 
octagonal figures, shows a considerable knowledge of 
rudimentary geometry and some means of measuring 
angles. The difficulty of drawing such figures on a 
large scale is much greater than any one would imagine 
who has not tried it ; and the accuracy of these is far 
beyond what is necessary to satisfy the eye. We must 



294 TROPICAL NATURE, AND OTHER ESSAYS. 

therefore impute to the builders the wish to make these 
figures as accurate as possible ; and this wish is a greater 
proof of habitual skill and intellectual advancement than 
even the ability to draw such figures. If, then, we take 
into account this ability and this love of geometric 
truth, and further consider the dense population and 
civil organisation implied by the construction of such 
extensive systematic works, we must allow that these 
ancient people had reached the earlier stages of a civil- 
isation of which no traces existed among the savage 
tribes who alone occupied the country when first visited 
by Europeans. 

The animal mounds are of comparatively less import- 
ance for our present purpose, as they imply a somewhat 
lower grade of advancement ; but the sepulchral and 
sacrificial mounds exist in vast numbers, and their 
partial exploration has yielded a quantity of articles and 
works of art which throw some further light on the 
peculiarities of this mysterious people. Most of these 
mounds contain a large concave hearth or basin of burnt 
clay, of perfectly symmetrical form, on which are found 
deposited more or less abundant relics, all bearing traces 
of the action of fire. We are therefore only acquainted 
with such articles as are practically fire-proof, or have 
accidentally escaped combustion. These consist of bone 
and copper implements and ornaments, disks, and tubes ; 
pearl, shell, and silver beads, more or less injured by 
the fire ; ornaments cut in mica ; ornamental pottery ; 
and numbers of elaborate carvings in stone, mostly 
forming pipes for smoking. 1 The metallic articles are 

1 Woven cloth, apparently of flax or henip, as well as gauges supposed to 
have been used to regulate the thickness of the thread, have also been found 



ANTIQUITY OF MAN. 295 

all formed by hammering, but the execution is very 
good ; plates of mica are found cut into scrolls and 
circles ; the pottery, of which very few remains have 
been found, is far superior to that of any of the Indian 
tribes, since Dr. Wilson is of opinion that it must have 
been formed on a wheel, as it is often of uniform thick- 
ness throughout (sometimes not more than one-sixth of 
an inch), polished, and ornamented with scrolls and 
figures of birds and flowers in delicate relief. But the 
most instructive objects are the sculptured stone pipes, 
representing not only various easily recognizable ani- 
mals, but also human heads, so well executed that they 
appear to be portraits. Among the animals, not only 
are such native forms as the panther, bear, otter, wolf, 
beaver, raccoon, heron, crow, turtle, frog, rattlesnake, 
and many others well represented, but also the manatee, 
which perhaps then ascended the Mississippi as it now 
does the Amazon, and the toucan, which could hardly 
have been obtained nearer than Mexico. The sculptured 
heads are especially remarkable, because they present to 
us the features of an intellectual and civilised people. 
The nose in some is perfectly straight, and neither 
prominent nor dilated ; the mouth is small, and the 
lips thin ; the chin and upper lip are short, contrasting 
with the ponderous jaw of the modern Indian, while 
the cheek-bones present no marked prominence. Other 
examples have the nose somewhat projecting at the apex 
in a manner quite unlike the features of any American 
indigenes ; and although there are some which show a 
much coarser face, it is very difficult to see in any of 

in several of the mounds of Ohio. (Foster's Prehistoric Races of the United 
States, 1873, pp. 225-229.) 



296 TROPICAL NATURE, AND OTHER ESSAYS. 

them that close resemblance to the Indian type which 
these sculptures have been said to exhibit. The few 
authentic crania from the mounds present corresponding 
features, being far more symmetrical and better de- 
veloped in the frontal region than those of any 
American tribes, although somewhat resembling them 
in the occipital outline ; l while one was described by 
its discoverer (Mr. W. Marshall Anderson) as a "beau- 
tiful skull, worthy of a Greek." 

The antiquity of this remarkable race may perhaps 
not be very great as compared with the prehistoric man 
of Europe, although the opinion of some writers on the 
subject seems affected by that " parsimony of time " on 
which the late Sir Charles Lyell so often dilated. The 
mounds are all overgrown with dense forest, and one of 
the large trees was estimated to be 800 years old, while 
other observers consider the forest growth to indicate an 
age of at least 1,000 years. But it is well known that it 
requires several generations of trees to pass away before 
the growth on a deserted clearing comes to correspond 
with that of the surrounding virgin forest, while this 
forest, once established, may go on growing for an 
unknown number of thousands of years. The 800 or 
1,000 years estimate from the growth of existing vege- 
tation is a minimum which has no bearing whatever on 
the actual age of these mounds ; and we might almost 
as well attempt to determine the time of the glacial 
epoch from the age of the pines or oaks which now 
grow on the moraines. 

The important thing for us, however, is that when 
North America was first settled by Europeans, the Indian 
1 Wilson's Prehistoric Man, 3rd edit. voL ii. pp. 123-130. 



ANTIQUITY OF MAN. 297 

tribes inhabiting it had no knowledge or tradition of 
any preceding race of higher civilisation than them- 
selves. Yet we find that such a race existed ; that they 
must have been populous and have lived under some 
established government ; while there are signs that they 
practised agriculture largely, as, indeed, they must have 
done to have supported a population capable of execut- 
ing such gigantic works in such vast profusion ; for it 
is stated that the mounds and earthworks of various 
kinds in the state of Ohio alone, amount to between 
eleven and twelve thousand. In their habits, customs, 
religion, and arts, they differed strikingly from all the 
Indian tribes ; while their love of art and of geometric 
forms, and their capacity for executing the latter upon so 1 
gigantic a scale, render it probable that they were a 
really civilised people, although the form their civilisation 
took may have been very different from that of later 
peoples, subject to very different influences and the 
inheritors of a longer series of ancestral civilisations. 
We have here, at all events, a striking example of the 
transition, over an extensive country, from comparative 
civilisation to comparative barbarism, the former leaving 
no tradition and hardly any trace of its influence on 
the latter. 

As Mr. Mott well remarks : Nothing can be more 
striking than the fact that Easter Island and North 
America both give the same testimony as to the origin 
of the savage life found in them, although in all circum- 
stances and surroundings the two cases are so different. 
If no stone monuments had been constructed in Easter 
Island, or mounds containing a few relics saved from 
fire, in the United States, we might never have suspected 



298 TROPICAL NATURE, AND OTHER ESSAYS. 

the existence of these ancient peoples. He argues, 
therefore, that it is very easy for the records of an ancient 
nation's life entirely to perish or to be hidden from 
observation. Even the arts of Nineveh and Babylon 
were unknown only a generation ago, and we have only 
just discovered the facts about the mound-builders of 
North America. 

But other parts of the American continent exhibit 
parallel phenomena. Eecent investigations show that in 
Mexico, Central America, and Peru the existing race of 
Indians has been preceded by a distinct and more 
civilised race. This is proved by the sculptures of the 
ruined cities of Central America, by the more ancient 
terra- cot tas and paintings of Mexico, and by the oldest 
portrait-pottery of Peru. All alike show markedly 
non-Indian features, while they often closely resemble 
modern European types. Ancient crania, too, have 
been found in all these countries, presenting very different 
characters from those of any of the existing indigenous 
races of America. 1 

The Great Pyramid. There is one other striking 
example of a higher being succeeded by a lower degree 
of knowledge, which is in danger of being forgotten 
because it has been made the foundation of theories 
which seem wild and fantastic, and are probably in great 
part erroneous. I allude to the Great Pyramid of 
Egypt, whose form, dimensions, structure, and uses have 
recently been the subject of elaborate works by Prof. 
Piazzi Smyth. Now the admitted facts about the 
pyramid are so interesting and so apposite to the subject 

1 Wilson's Prehistoric Man, 3rd edit. vol. ii. pp. 125, 144. 



ANTIQUITY OF MAN. 299 

we are considering, that I beg to recall them to your 
attention. Most of you are aware that this pyramid 
has been carefully explored and measured by successive 
Egyptologists, and that the dimensions have lately 
become capable of more accurate determination, owing 
to the discovery of some of the original casing-stones, 
and the clearing away of the earth from the corners of 
the foundation showing the sockets in which the corner- 
stones fitted. Prof. Smyth devoted many months of 
work with the best instruments, in order to fix the 
dimensions and angles of all accessible parts of the 
structure ; and he has carefully determined these by a 
comparison of his own and all previous measures, the 
best of which agree pretty closely with each other. The 
results arrived at are : 

1. That the pyramid is truly square, the sides being 
equal and the angles right angles. 

2. That the four sockets on which the four first stones 
of the corners rested, are truly on the same level. 

3. That the directions of the sides are accurately to 
the four cardinal points. 

4. That the vertical height of the pyramid bears the 
same proportion to its circumference at the base, as the 
radius of a circle does to its circumference. 

Now all these measures, angles, and levels are accurate, 
not as an ordinary surveyor or builder could make them, 
but to such a degree as requires the very best modern 
instruments and all the refinements of geodetical science 
to discover any error at all. In addition to this we 
have the wonderful perfection of the workmanship in 
the interior of the pyramid, the passages and chambers 
being lined with huge blocks of stones fitted with the 



300 TROPICAL NATURE, AND OTHER ESSAYS. 

utmost accuracy, while every part of the building 
exhibits the highest structural science. 

In all these respects this largest pyramid surpasses 
every other in Egypt. Yet it is universally admitted 
to be the oldest, and also the oldest historical building 
in the world. 

Now these admitted facts about the Great Pyramid 
are surely remarkable, and worthy of the deepest con- 
sideration. They are facts which, in the pregnant words 
of the late Sir John Herschel, "according to received 
theories ought not to happen," and which, he tells us, 
should therefore be kept ever present to our minds, 
since " they belong to the class of facts which serve 
as the clue -to new discoveries." According to modern 
theories, the higher civilisation is ever a growth and an 
outcome from a preceding lower state ; and it is inferred 
that this progress is visible to us throughout all history 
and in all material records of human intellect. But 
here we have a building which marks the very dawn of 
history, which is the oldest authentic monument of 
man's genius and skill, and which, instead of being far 
inferior, is very much superior to all which followed it. 
Great men are the products of their age and country, 
and the designer and constructors of this wonderful 
monument could never have arisen among an unintellec- 
tual and half-barbarous people. So perfect a work 
implies many preceding less perfect works which have 
disappeared. It marks the culminating point of an 
ancient civilisation, - of the early stages of which we 
have no trace or record whatever. 

The three cases to which I have now adverted (and 
there are many others) seem to require for their satis- 



ANTIQUITY OF MAN. 301 

factory interpretation a somewhat different view of 
human progress from that which is now generally 
accepted. Taken in connection with the great intellec- 
tual power of the ancient Greeks which Mr. Galton 
believes to have been far above that of the average of 
any modern nation and the elevation, at once intellec- 
tual and moral, displayed in the writings of Confucius, 
Zoroaster, and the Vedas, they point to the conclusion 
that, while in material progress there has been a tolerably 
steady advance, man's intellectual and moral develop- 
ment reached almost its highest level in a very remote 
past. The lower, the more animal, but often the more 
energetic types have, however, always been far the more 
numerous ; hence such established societies as have here 
and there arisen under the guidance of higher minds 
have always been liable to be swept away by the incursions 
of barbarians. Thus in almost every part of the globe 
there may have been a long succession of partial civilisa- 
tions, each in turn succeeded by a period of barbarism ; 
and this view seems supported by the occurrence of 
degraded types of skull along with such " as might have 
belonged to a philosopher," at a time when the mammoth 
and the reindeer inhabited southern France. 

Nor need we fear that there is not time enough for 
the rise and decay of so many successive civilisations as 
this view would imply ; for the opinion is now gaining 
ground among geologists that palaeolithic man was 
really preglacial, and that the great gap (marked alike 
by a change of physical conditions and of animal life) 
which in Europe always separates him from his neolithic 
successor, was caused by the coming on and passing 
away of the great ice age. 



302 TROPICAL NATURE, AND OTHER ESSAYS. 

If the views now advanced are correct, many, 
perhaps most, of our existing savages are the successors 
of higher races ; and their arts, often showing a wonder- 
ful similarity in distant continents, may have been 
derived from a common source among more civilised 
peoples. 

Conclusion. I must now conclude this very imperfect 
sketch of a few of the offshoots from the great tree of 
Biological study. It will, perhaps, be thought by some 
that my remarks have tended to the depreciation of our 
science, by hinting at imperfections in our knowledge 
and errors in our theories where more enthusiastic students 
see nothing but established truths. But I trust that I 
may have conveyed to many of my hearers a different 
impression. I have endeavoured to show that, even in 
what are usually considered the more trivial and super- 
ficial characters presented by natural objects, a whole 
field of new inquiry is opened up to us by the study of 
distribution and local conditions. And as regards man, 
I have endeavoured to fix your attention on a class of 
facts which indicate that the course of his development 
has been far less direct and simple than has hitherto 
been supposed ; and that, instead of resembling a single 
tide with its advancing and receding ripples, it must 
rather be compared to the progress from neap to spring 
tides, both the rise and the depression being comparatively 
greater as the waters of true civilisation slowly advance 
towards the highest level they can reach. 

And if we are thus led to believe that our present 
knowledge of nature is somewhat less complete than we 
have been accustomed to consider it, this is only what 



BY-PATHS OF BIOLOGY. 303 

we might expect ; for however great may have been the 
intellectual triumphs of the nineteenth century, we can 
hardly think so highly of its achievements as to imagine 
that, in somewhat less than twenty years, we have passed 
from complete ignorance to almost perfect knowledge on 
two such vast and complex subjects as the Origin of 
Species and the Antiquity of Man. 



VIII. 

THE DISTRIBUTION OF ANIMALS 
AS INDICATING GEOGRAPHICAL CHANGES. 1 

Old Opinions on Continental Changes Theory of Oceanic Islands Present 
and Past Distribution of Land and Sea Zoological Regions The 
Palaearctic Region The Ethiopian Region The Oriental Region Past 
Changes of the Great Eastern Continent Regions of the New World 
Past History of the American Continents The Australian Region 
Summary and Conclusion. 

THERE is a curious old book entitled Restitution of De- 
cayed Intelligence in Antiquities Concerning the Most 
Noble and Renowned English Nation, written in 1605, 
by R. Verstegen. The fourth chapter treats "Of the 
Isles of Albion, and how it is showed to have been con- 
tinent or firm land with Gallia, now named France, since 
the Flood of Noe ; " and after referring to several ancient 
writers wljo had held this opinion but without giving any 
reasons for it, the author proceeds to argue the point, 
referring to the narrowness of the straits, their extreme 
shallowness, the similarity of the opposite coasts both in 
height and character, the meaning of the word "cliff" 

1 This is one of the Lectures on Scientific Geography delivered before the 
Royal Geographical Society, but the introductory portion has been rewritten. 
The original Lecture appeared in the Proceedings of the Society for September, 
1877, under the title : " On the Comparative Antiquity of Continents, as 
indicated by the Distribution of Living and Extinct Animals." 



DISTRIBUTION AND GEOGRAPHY. 305 

as being that which is cleft asunder, and other matters ; 
after which comes this quaint and interesting passage : 

" Another reason there is that this separation hath 
been made since the flood, which is also very consider- 
able, and that is the patriarch Noe, having had with 
him in the Ark all sorts of beasts, these then, after the 
flood, being put forth of the ark to increase and mul- 
tiply, did afterward in time disperse themselves over 
all parts of the continent or main land ; but long after 
it could not be before the ravenous wolf had made his 
kind nature known to man, and therefore no man unless 
he were mad, would ever transport of that race out of 
the continent into the isles, no more than men will 
ever carry foxes (though they be less damageable) out 
of our continent into the Isle of Wight. But our Isle, 
as is aforesaid, continuing since the flood fastened by 
nature unto the Great Continent, those wicked beasts 
did of themselves pass over. And if any should object 
that England hath no wolves on it they may be answered 
that Scotland, being therewith conjoined, hath very 
many, and so England itself sometime also had, until 
such time as King Edgar took order for the destroying 
of these throughout the whole realm." 

The preservation of foxes for sporting purposes was 
evidently quite out of the range of thought at this not 
very distant epoch, and our author, in consequence, 
made a little mistake as to what men " ever" would do 
in the case of these noxious animals ; but his general 
argument is sound, and it becomes much strengthened 
when we 'take into consideration the smaller vermin, such 
as stoats, weasels, moles, hedgehogs, fieldmice, vipers, 
toads, and newts, which would certainly not all have been 

x 



306 TROPICAL NATURE, AND OTHER ESSAYS. 

brought over by uncivilised man, even if any one of them 
might have been. But there is another reason why they 
were not so brought over. For on that supposition we 
should discover remains of fewer and fewer species as we 
go back into past times till at last when we reached the 
time of the first occupation of the country by man we 
should find none at all. But the actual facts are the 
very reverse of this. For the further we go back the 
more species of noxious and dangerous animals we dis- 
cover, till in the time of the palaeolithic (or oldest) 
prehistoric men, we find remains not only of almost 
every animal now living, but of many others still less 
likely to have been introduced by man's agency. Such 
are the mammoths, rhinoceroses, lions, horses, bears, 
gluttons, and many others ; and it is equally impossible 
that these could all have swum across an arm of the sea, 
which although only about twenty miles wide in its 
narrowest past, is yet so influenced by strong tides and 
currents that it becomes as effective a barrier as many 
straits of double the width. 

Owing, however, to the want of all definite ideas as 
to the mode by which the earth became stocked with 
animals and plants, the existence of identical species in 
countries separated by arms of the sea attracted very 
little attention till quite recent times. It is probable 
that Mr. Darwin was really the first person to see the 
full importance of the principle, for in his Naturalist's 
Voyage Round the World, he remarks, that " the South 
American character of the "West Indian mammals seems 
to indicate that this archipelago was formerly united to 
the southern continent." Some years later, in 1845, 
Mr. George Windsor Earl called special attention to the 



OCEANIC ISLANDS. 307 

subject by pointing out that the great Malay Archipelago 
may be divided in two portions, all the islands in the 
western half being united to each other and to the 
continent of Asia by a very shallow sea, and all having 
very similar productions, while many large animals, such 
as the elephant, rhinoceros, wild cattle, and tigers, range 
over most of them. We then come to a profoundly 
deep sea, and the islands of the eastern half of the archi- 
pelago are either surrounded by a deep sea or are con- 
nected by a shallow sea to Australia; and in this half 
the productions resemble those of Australia, marsupials 
being found in all the islands while the large quadrupeds 
of Asia are almost wholly unknown. 

Theory of Oceanic Islands. In 1859 the Origin of 
S$>ecies was published, and in the thirteenth chapter 
of this celebrated work Mr. Darwin put forth his views 
on oceanic islands or such as are situated far away from 
any continent and are surrounded by deep oceans. It 
had been up to this time believed that in most cases 
these islands were fragments of ancient continents ; as 
an example of which we may refer to the Azores, Madeira, 
and the other Atlantic islands, which were thought to 
support the notion of an Atlantic or western extension of 
the European continent. In order to ascertain what was 
the condition of these islands when first discovered, Mr. 
Darwin searched through all the oldest voyages, and 
found that in none of them was a single native mammal 
known to exist, while in almost all of them frogs and 
toads were also absent. All the Atlantic isles from the 
Azores to St. Helena ; Mauritius, Bourbon, and the 
other isles of the Indian Ocean ; and the Pacific islands, 
east of the Fijis, as far as the Galapagos and Juan 

X 2 



308 TROPICAL NATURE, AND OTHER ESSAYS. 

Fernandez are thus deficient. They all of them, however, 
possess birds, and most of them bats ; and whenever 
small mammalia, such as goats, pigs, rabbits, and mice 
have been introduced they have run wild and often in- 
creased enormously, proving that the only reason why 
such animals were not originally found there was the 
impossibility of them crossing the sea ; while such as 
could fly over birds, bats, and insects existed in 
greater or less abundance. If, on the other hand, they 
had once formed part of the continent, it is impossible 
to believe that some of the smaller mammalia, as well 
as frogs, would not have continued to exist in the 
islands to the present day. 

If we compare the productions of different islands, we 
meet with peculiarities which throw much light on the 
subject of distribution. In the Galapagos islands, 
between 500 and 600 miles from the west coast of South 
America, there are thirty-two species of land-birds, all 
but two or three being peculiar to the group. In 
Madeira, about 400 miles from the coast of Morocco, 
there are nearly twice as many land-birds as in the 
Galapagos, but only two of these are peculiar to the 
island, the rest being South European or N. African 
species. The Azores are 1,000 miles west of Portugal, 
and they contain twenty-two species of land-birds, every 
one of which is European except one bullfinch which is 
slightly different and forms a peculiar species. This 
remarkable difference in the proportion of peculiar 
species between the Galapagos and the Atlantic islands, 
is well explained by the theory that land-birds rarely 
fly directly out to sea, except when carried against 
their will by storms and gales of wind. Now the 



OCEANIC ISLANDS. 309 

Azores are situated in an especially stormy zone, and 
it is an observed fact that after every severe gale of 
wind some new bird or insect is seen on the islands. 
The Galapagos, on the contrary, are in a very calm 
sea where violent storms are almost unknown, and 
thus new birds from the mainland very rarely visit these 
islands. Madeira is less stormy than the Azores, but 
its comparative nearness makes up for this difference in 
the case of birds. In insects, however, the species of 
Madeira are much more peculiar (and more numerous) 
than those of the more distant Azores ; while those of 
the Galapagos are few, but all peculiar, and belonging 
to groups many of which are widely spread over the 
globe. All these facts are entirely in accordance with 
the view that oceanic islands have been peopled from 
the nearest continents by various accidental causes; 
while they are entirely opposed to the theory that such 
islands are remnants of old continents and have 
preserved some portion of their inhabitants. 

It is a curious fact, that land reptiles, such as snakes 
and lizards, are found in many islands where there are 
no mammalia or frogs ; and we therefore conclude that 
there must be some means by which their ova can be 
safely carried across great widths of sea. A single 
peculiar frog inhabits New Zealand, and some species are 
found in the Pacific islands as far eastward as the Fijis, 
but they are absent from all other oceanic islands. 
Snakes also extend to the Fijis, and there are two species 
in the Galapagos, but none in the other oceanic islands. 
Lizards, however, are found in Mauritius and Bourbon ; 
in New Zealand ; in all the Pacific islands, and in the 
Galapagos. It is clear then that next to Mammals, 



310 TROPICAL NATURE, AND OTHER ESSAYS. 

frogs and toads are most completely shut out by an 
ocean barrier ; then follow snakes, but as these are only 
found in the Galapagos and are very like South American 
species, they may possibly have been conveyed in boats 
or by floating trees. Lizards, however, are so wide- 
spread over almost all the warmer islands of the great 
oceans, that they must have some natural way of passing 
over, but the exact mode in which this is effected has 
not yet been discovered. Birds, as we have seen, are 
liable to be carried by winds and storms over great 
widths of sea, but this only applies to certain groups ; 
and large numbers which feed on the ground or which 
inhabit the depths of the forests, are almost as strictly 
confined to their respective countries by even a narrow 
arm of the sea as are the majority of the mammalia. 

This sketch of the mode in which the various kinds 
of islands have been stocked with their animal inhabitants 
forms the best introduction to the study of those changes 
in our continents which have led to the existing distri- 
bution of animals. It demonstrates the importance of 
the sea as a barrier to the spread of all the higher 
animals ; and we are thus naturally led on to inquire, 
how far and to what extent such barriers have in past 
time existed between lands which are now united, and 
on the other hand what existing oceanic barriers are of 
comparatively recent origin. In pursuing this inquiry 
we shall have to take account of those grand views of 
the course of nature associated with the names of Lyell 
and Darwin of the slow but never-ceasing changes in 
the physical conditions, the outlines and the mutual 
relations of the land-surfaces of the globe ; and of the 
equally slow and equally unceasing changes in the 



LAND AND SEA. 311 

forms and structures of all organisms, to a great extent 
correlated with, and perhaps dependent on, the former 
set of changes. Combining these two great principles 
with other ascertained causes of distribution, we shall 
be enabled to deal adequately with the problem before 
us, and give a rational, though often only an approxi- 
mative and conjectural, solution of the many strange 
anomalies we meet with in studying the distribution of 
living things. 

Past and Present Distribution of Land and Sea. 
Before proceeding to give details as to the distribution 
of animals, it is necessary to point out certain geo- 
graphical features which have had great influence hi 
bringing about the existing state of things. 

The extreme inequality with which land and water is 
distributed has often been remarked, but what is less 
frequently noted is the singular way in which all the 
great masses of land are linked together. Notwith- 
standing the small proportion of land to water, the vast 
difference in the quantity of land in the northern and 
southern hemispheres, and the apparently hap-hazard 
manner in which it is spread over the globe, we yet find 
that no important area is completely isolated from the 
rest. We may even travel from the extreme north of 
Asia to the three great southern promontories Cape 
Horn, the Cape of Good Hope, and Tasmania without 
ever going out of sight of land ; and, if we examine a 
terrestrial globe, we find that the continents in their 
totality may be likened to a huge creeping plant, whose 
roots are at or around the North Pole, whose matted 
stems and branches cover a large part of the northern 
hemisphere, while it sends out in three directions great 



312 TROPICAL NATURE, AND OTHER ESSAYS. 

offshoots towards the South Pole. This singular arrange- 
ment of the land surface into what is practically one 
huge mass with diverging arms, offers great facilities for 
the transmission of the varied forms of animal life over 
the whole earth, and is no doubt one of the chief causes 
of the essential unity of type which everywhere charac- 
terises the existing animal and vegetable productions of 
the globe. 

There is, moreover, good reason to believe that the 
general features of this arrangement are of vast 
antiquity ; and that throughout much of the Tertiary 
period, at all events, the relative positions of our con- 
tinents and oceans have remained the same, although 
they have certainly undergone some changes in their 
extent, and in the degree of their connection with each 
other. This is proved by two kinds of evidence. In 
the first place, it is now ascertained by actual measure- 
ment that the depths of the great oceans are so vast 
over wide areas, while the highest elevations of the land 
are limited to comparatively narrow ridges, that the 
mass of land (above the sea-level) is not more than ^Vth 
part of the mass of the ocean. Now we have reason to 
believe that subsidence and elevation bear some kind of 
proportion to each other, whence it follows that although 
several mountain ranges have risen to great heights 
during the Tertiary period, this amount of elevation 
bears no proportion to the amount of subsidence required 
to have changed any considerable area of what was 
once land into such profound depths as those of the 
Atlantic or Pacific Oceans. In the second place, we find 
over a considerable area of all the great continents fresh- 
water deposits containing the remains of land animals 



ANCIENT LANDS AND SEAS. 313 

and plants ; which deposits must have been formed in 
lakes or estuaries, and which therefore, speaking generally, 
imply the existence in their immediate vicinity of land 
areas comparable to those which still exist. The Miocene 
deposits of Central and Western Europe, of Greece, of 
India, and of China, as well as those of various parts of 
North America, strikingly prove this ; while the Eocene 
deposits of London and Paris, of Belgium, and of 
various parts of North and South America, though often 
marine, yet by their abundant remains of land-animals 
and plants, equally indicate the vicinity of extensive 
continents. For our purpose it is not necessary to go 
further back than this, but there is much evidence to 
show that throughout the Secondary, and even some 
portion of the Palaeozoic periods, the land-areas coincide^ 
to a considerable extent with our existing continents. 
Professor Eamsay has shown 1 that not only the Wealden 
formation, and considerable portions of the Upper and 
Lower Oolite, but also much of the Trias, and the larger 
part of the Permian, Carboniferous, and Old Red Sand- 
stone formations, were almost certainly deposited either 
in lakes, inland seas, or extensive estuaries. This would 
prove that, throughout the whole of the vast epochs 
extending back to the time of the Devonian formation, 
our present continents have been substantially in ex- 
istence, subject, no doubt, to vast fluctuations by ex- 
tension or contraction, and by various degrees of union 
or separation, but never so completely submerged as to 
be replaced by oceans comparable in depth with our 
Atlantic or Pacific. 

1 Nature, 1873, p. 333 ; Quarterly Journal of the Geological Society, 1871, 
pp. 189 and 241. 



314 TROPICAL NATURE, AND OTHER ESSAYS. 

This general conclusion is of great importance in the 
study of the geographical distribution of animals, be- 
cause it bids us avoid the too hasty assumption that the 
countless anomalies we meet with are to be explained 
by great changes in the distribution of land and sea, 
and leads us to rely more on the inherent powers of 
dispersal which all organisms possess, and on the union 
or disruption, extension or diminution, of existing lands 
but always in such directions and to such a limited 
extent as not to involve the elevation of what are now 
the profoundest depths of the great oceans. 

Zoological Regions. We will now proceed to sketch 
out the zoological features of the six great biological 
regions ; and will afterwards discuss their probable 
changes during the more recent geographical periods, in 
accordance with the principles here laid down. 

The Palcearctic Region. 

The Palaearctic, or North Temperate region of the 
Old World, is not only by far the most extensive of the 
zoological regions, but is the one which agrees least 
with our ordinary geographical divisions. It includes 
the whole of Europe, by far the largest part of Asia, 
and a considerable tract of North Africa ; yet over the 
whole of this vast area there prevails a unity of the 
forms of animal life which renders any primary sub- 
division of it impossible, and even secondary divisions 
difficult. But besides being the largest of the great 
zoological regions, there are good reasons for believing 
this to represent the most ancient, and therefore the 
most important centre of the development of the higher 



THE PAL^EAECTIC KEGIOK 315 

forms of animal life, and it is therefore well to con- 
sider it first in order. 

In enumerating the most important animal groups 
characteristic of this and other regions, it must be 
clearly understood that such groups are not always 
absolutely confined to one region. Here and there 
they will often overlap the boundaries, while in other 
cases single species may have a wide distribution in one 
or more of the adjacent regions ; but this does not at all 
affect the main fact, that the group as a whole is very 
abundant and very widely spread over the region in 
question, while it is very rare, or confined to a very 
limited area in adjacent regions, and is therefore spe- 
cially characteristic of the one as compared with other 
parts of the world. Bearing this in mind, we shall find 
that the Palsearctic region is well characterized by a 
considerable number of typical groups, although, as we 
shall presently see, it has in recent geological times 
lost much of its ancient richness and variety of animal 
life. 

Among Mammalia the groups most characteristic of 
this region are the moles (Talpidse), a family consisting 
of eight distinct genera which range over the whole 
region, but beyond it barely enter the Oriental region 
in North India, and the Nearctic region in North- West 
America ; camels, confined to the deserts of North 
Africa and Asia ; sheep and goats (Capra), only found 
beyond the region in the Nilgherries and Rocky Moun- 
tains ; several groups of antelopes, and many peculiar 
forms of deer ; hamsters (Cricetus), sand rats (Psam- 
momys), mole rats (Spalax), and pikas (Lagomys), with 
several other forms of rodents. Wolves, foxes, and 



316 TROPICAL NATURE, AND OTHER ESSAYS. 

bears, are also very characteristic, though by no means 
confined to the region. 

Among birds the most important group is certainly 
the small-sized, but highly-organized warblers (Sylviidee), 
which, although almost universally distributed, are more 
numerous, and have more peculiar and characteristic 
genera here than in any other region. Most of our 
song-birds, and many of the commonest tenants of our 
fields, woods, and gardens, belong to this family ; and 
identical or representative species are often found rang- 
ing from Spain to China, and from Ireland to Japan. 
The reedlings (Panuridse), the tits (Paridae), and the 
magpies (Pica), are also very characteristic ; while 
among the finches (Fringillidae), a considerable number 
of genera are peculiar. A large number of peculiar 
groups of grouse (Tetraonidse), and pheasants (Pha- 
sianidse) are also characteristic of this region. Although 
the reptiles and fresh-water fishes are comparatively 
few, yet many of them are peculiar. Thus, no less than 
2 genera of snakes, 7 of lizards, and 16 of batrachia, 
are confined to the Palaearctic region, as well as 20 
genera of fresh-water fishes. 

The insects and land- shells offer their full proportion 
of peculiar types; but it would lead us beyond our 
special object to enter into details with regard to these 
less known groups of animals. 1 



1 Details will be found in the Author's work on The Geographical Dis- 
tribution of Animals. 



THE ETHIOPIAN REGION. 317 



The Ethiopian Region. 

The Ethiopian region, consisting of Africa south of 
the Tropic of Cancer with Madagascar, is of very 
small area compared with the Palaearctic region ; yet 
owing to the absence of extreme climates, and the 
tropical luxuriance of a considerable portion of its 
surface, it supports a greater number and variety of 
large animals than any other part of the globe of equal 
extent. Much of the speciality of the region is, how- 
ever, due to the rich and isolated fauna of Madagascar, 
the peculiarities of which may be set aside till we come 
to discuss the past history of the Ethiopian region. 

Considering then, first, the zoological features of 
tropical and southern Africa alone, we find a number 
of very peculiar forms of mammalia. Such are the 
golden moles, the Potamogale, and the elephant-shrews 
among Insectivora ; the hippopotami and the giraffes, 
among Ungulata ; the hyaena-like Proteles (Aard-wolf), 
and Lycaon (hysena-dog), among Carnivora ; and the 
Aard-varks (Orycteropus) among Edentata. These are 
all peculiar ; but among highly characteristic forms are 
the baboons, and several genera of monkeys and apes ; 
several peculiar Lemurs ; a great variety of the civet- 
family (Viverridae), and of rodents ; peculiar genera of 
swine (Potamochserus and Phacochserus), and a greater 
abundance and variety of antelopes than are to be found 
in all the other regions combined. But the Ethiopian 
region is strikingly distinguished from all others, not 
only by possessing many peculiar forms, but by the 
absence of a number of common and widely distributed 



318 TROPICAL NATURE, AND OTHER ESSAYS. 

groups of mammalia. Such are the bears, which 
range over the whole northern hemisphere, and as far 
south as Sumatra in the eastern and Chili in the western 
hemisphere, yet they are totally wanting in Tropical 
and South Africa ; the deer, which are still more 
widely distributed, ranging all over North and South 
America, and over all Asia to Celebes and the Moluccas, 
yet they are totally absent from the Ethiopian region ; 
goats and sheep, true oxen (Bos), and true pigs (Sus), 
are also absent ; though as to the last there is some 
doubt, certain wild pigs having been observed, though 
rarely, in various parts of Tropical Africa, but it is not 
yet determined whether they are indigenous, or escaped 
from domestication. The absence of such wide-spread 
families as the bears and deer is, however, most im- 
portant, and must be taken into account when we 
come to consider the geographical changes needed to 
explain the actual state of the Ethiopian fauna. 

The birds are not proportionately so peculiar, yet 
there are many remarkable forms. Most important are 
the plantain-eaters, the ground-hornbills, the colies, and 
the anomalous secretary-bird ; while among character- 
istic families there are numbers of peculiar genera of 
flycatchers, shrikes, crows, sun-birds, weaver-birds, 
starlings, larks, francolins, and the remarkable sub- 
family of the Guinea-fowls. There are not such 
striking deficiencies among birds as among mammals, 
yet there are some of importance. Thus, there are no 
wrens, creepers, or nut-hatches, and none of the wide- 
spread group comprising the true pheasants and jungle 
fowl a deficiency almost comparable with that of the 
bears or the deer. Among the lower vertebrates there 



THE ORIENTAL REGION. 319 

are 3 peculiar families of snakes and 1 of lizards, as 
well as 1 of toads and 3 of fresh-water fishes. 



The Oriental Region. 

The Oriental region comprises all tropical Asia east 
of the Indus, with the Malay Islands as far as Java, 
Borneo, and the Philippines. In its actual land-area it 
is the smallest region except the Australian ; but if we 
take into account the wide extent of shallow sea con- 
necting Indo-China with the Malay Islands, and which 
has, doubtless, at no distant epoch, formed an extension 
of the Asiatic Continent, it will not be much smaller 
than the Ethiopian region. Here we find all the 
conditions favourable to the development of a rich 
and varied fauna. The land is broken up into great 
peninsulas and extensive islands ; lofty mountains and 
large rivers everywhere intersect it ; while along its 
northern boundary stretches the highest mountain- 
range upon the globe. Much of this region lies within 
the equatorial belt, where the equability of temperature 
and abundance of moisture produce a tropical vegetation 
of unsurpassed luxuriance. We find here, as might be 
expected, that the variety and beauty of the birds and 
insects is somewhat greater than in the Ethiopian 
region ; although, as regards mammalia, the latter is 
the most prolific, both in genera, species, and indi- 
viduals. 

The families of Mammalia actually peculiar to this 
region are few in number, and of limited extent. 
They are, the Galeopithecidae, or flying lemurs ; the 
Tarsiidee, consisting of the curious little tarsier, allied 



320 TROPICAL NATURE, AND OTHER ESSAYS. 

to the lemurs ; and the Tupaiidae, a remarkable group 
of squirrel-like Insectivora. There are, however, a con- 
siderable number of peculiar genera, forming highly 
characteristic groups of animals such as the various 
apes, monkeys, and lemurs, almost all the genera of 
which are peculiar ; a large number of civets and 
weasels; the beautiful deer- like Chevrotains, often 
called mouse-deer ; and a few peculiar antelopes and 
rodents. It must be remarked that we find here none 
of those deficiencies of wide-spread families which were 
so conspicuous a feature of the Ethiopian region the 
only one worth notice being the dormice (Myoxidae), a 
small family spread over the Palsearctic and Ethiopian 
regions, but not found in the Oriental. 

The birds of the Oriental region are exceedingly 
numerous and varied, there being representatives of 
about 350 genera of land-birds, of which nearly half 
are peculiar. Three families are confined to the region 
the hill-tits (Liotrichidae), the green bulbuls (Phyl- 
lornithidae), and the gapers (Eurylaeinidae) ; while four 
other families are more abundant here than elsewhere, 
and are so widely distributed throughout the region as 
to be especially characteristic of it. These are the 
elegant pittas, or ground-thrushes (Pittidae), the trogons 
(Trogonidae), the hornbills (Bucerotidse), and the phea- 
sants (Phasianidae) ; represented by such magnificent 
birds as the fire-backed pheasants, the ocellated phea- 
sants, the Argus-pheasant, the pea-fowl, and the 
jungle-fowl. 

Reptiles are very abundant, but only 3 small families 
of snakes are peculiar. There are also 3 peculiar 
families of fresh -water fishes. 



MIOCENE CONTINENTS. 321 

Past Changes of the Great Eastern Continent. 
Having thus briefly sketched the main features of the 
existing faunas of Europe, Asia, and Africa, it will be 
well, while their resemblances and differences are fresh 
in our memory, to consider what evidence we have of 
the changes which may have resulted in their present 
condition. All these countries are so intimately con- 
nected, that their past history is greatly elucidated by 
the knowledge we possess of the tertiary fauna of 
Europe and India ; and we shall find that when we 
once obtain clear ideas of their mutual relations, we 
shall be in a better position to study the history of 
the remaining continents. 

Let us therefore go back to the Miocene or middle 
tertiary epoch, and see what was then the distribution 
of the higher animals in these countries. Extensive 
deposits, rich in animal remains of the Miocene age, occur 
in France, Switzerland, Germany, Hungary, Greece; and 
also in North- Western India at the Siwalik Hills, in 
Central India in the Nerbudda Valley, in Burmah, and 
in North China ; and over the whole of this immense 
area we find a general agreement in the fossil mammalia, 
indicating that this great continent was probably then, 
as now, one continuous land. The next important geo- 
graphical fact that meets us, is, that many of the largest 
and most characteristic animals, now confined to the 
tropics of the Oriental and Ethiopian regions, were then 
abundant over much of the Palaearctic region. Elephants, 
rhinoceroses, tapirs, horses, giraffes, antelopes, hyaenas, 
lions, as well as numerous apes and monkeys, ranged all 
over Central Europe, and were often represented by a 
greater variety of species than exist now. Antelopes 



322 TROPICAL NATURE, AND OTHER ESSAYS. 

were abundant in Greece, and several of these appear 
to have been the ancestors of those now living in Africa ; 
while two species of giraffes also inhabited Greece and 
North- West India. Equally suggestive is the occurrence 
in Europe of such birds as trogons and jungle-fowl 
characteristic of tropical Asia, along with parrots and 
plaintain-eaters allied to forms now living in West 
Africa. 

Let us now inquire what information Geology affords 
us of changes in land and sea at this period. From the 
prevalence of early tertiary deposits over the Sahara 
and over parts of Arabia, Persia, and Northern India, 
geologists are of opinion that a continuous sea or strait 
extended from the Bay of Bengal to the Atlantic 
Ocean, thus cutting off the Peninsula of India with 
Ceylon, as well as all tropical and South Africa from the 
great northern continent. 1 At the same time, and down 
to a comparatively recent period, it is almost certain 
that Northern Africa was united to Spain and to Italy, 
while Asia Minor was united to Greece, thus reducing 
the Mediterranean to the condition of two inland seas. 
We also know that the north-western Himalayas and 
some of the high lands of Central Asia were at such a 
moderate elevation as to enjoy a climate as mild as that 
which prevailed in Central Europe during the Miocene 
epoch, 2 and was therefore perhaps equally productive in 
animal and vegetable life. 

1 Mr. Searles V. Wood, " On the Form and Distribution of the Land-tracts 
during the Secondary and Tertiary Periods respectively," Philosophical 
Magazine, 1862. 

2 This part of the Himalayas was elevated during the Eocene period, and 
remains of a fossil Rhinoceros have been found at 16,000 feet elevation in 
Thibet. 



EARLY CONDITION OF AFRICA. 323 

We have, therefore, good evidence that the great 
Euro-Asiatic continent of Miocene times exhibited in its 
fauna a combination of all the main features which now 
characterise the Paleearctic, Oriental, and Ethiopian 
regions ; while tropical Africa, and such other tropical 
lands as were then, like the peninsula of India, detached 
and isolated from the continent, possessed a much more 
limited fauna, consisting for the most part of animals of a 
lower type, and which were more characteristic of Eocene 
or Secondary times. Many of these have no doubt 
become extinct, but they are probably represented by 
the remarkable and isolated lemurs of West Africa and 
Southern Asia, by the peculiar Insectivora of South 
Africa and Malaya, and by the Edentata of Africa and 
India. These are all low and ancient types, which were 
represented in Europe in the Eocene and early Miocene 
periods, at a time when the more highly specialised 
horses, giraffes, antelopes, deer, buffaloes, hippopotami, 
elephants, and anthropoid apes had not come into 
existence. And if these large herbivorous animals were 
all wanting in tropical Africa in Miocene times, we may 
be quite sure that the large felines and other carnivora 
which prey upon them were absent also. Lions, leopards, 
and hyaenas can only exist where antelopes, deer, or 
some similar creatures abound ; while smaller forms 
allied to the weasels and civets would be adapted to a 
country where small rodents or defenceless Edentata 
were the chief vegetable-feeding mammalia. 

If this view is correct (and it is supported by a con- 
siderable amount of evidence which it is not possible 
here to adduce), all the great mammalia which now 
seem so specially characteristic of Africa the lions, 

Y 2 



324 TROPICAL NATURE, AND OTHER ESSAYS. 

leopards, and hyaenas, the zebras, giraffes, buffaloes, 
and antelopes, the elephants, rhinoceroses, and hippo- 
potami, and perhaps even the numerous monkeys, 
baboons, and anthropoid apes, are every one of them 
comparatively recent immigrants, who took possession of 
the country as soon as an elevation of the old Eocene 
and Miocene sea-bed afforded a passage from the southern 
borders of the Palsearctic region. This event probably 
occurred about the middle of the Miocene period, and 
it must have effected a vast change in the fauna of 
Africa. A number of the smaller and more defenceless 
of the ancient inhabitants must have been soon exter- 
minated, as surely as our introduced pigs, dogs, and 
goats, exterminate so many of the inhabitants of 
oceanic islands ; while the new comers finding a country 
of immense extent, with a tropical climate, and not too 
much encumbered with forest vegetation, spread rapidly 
over it, and thenceforth, greatly multiplying, became 
more or less modified in accordance with the new condi- 
tions. We shall find that this theory not only accounts 
for the chief specialities, but also explains many of the 
remarkable deficiencies of the Ethiopian fauna. Thus, 
bears and deer are absent, because they are compara- 
tively late developments, and were either unknown or 
rare in Europe till late Miocene or Pliocene times ; 
while, on the other hand, the immense area of open 
tropical country in Africa has favoured the preservation 
of numerous types of large mammalia which have 
perished in the deteriorated climate and diminished area 
of Europe. 

Our knowledge of the geology of Africa is not suffi- 
ciently detailed to enable us to determine its earlier 



EARLY CONDITION OF ASIA. 325 

history with any approach to accuracy. It is clear, 
however, that Madagascar was once united with the 
southern portion of the Continent, but it is no less clear 
that its separation took place before the great irruption 
of large animals just described ; for all these are 
wanting, while lemurs, insectivora, and civets abound, 
the same low types which were once the only inhabitants 
of the mainland. It is worthy of note, that south 
temperate Africa still exhibits a remarkable assemblage 
of peculiar forms of mammalia, birds, and insects, the 
two former groups mostly of a low grade of organisa- 
tion ; and these, taken in connection with the wonder- 
fully rich and highly specialised flora of the Cape of Good 
Hope, point to the former existence of an extensive 
south-temperate land in which so many peculiar types 
could have been developed. Whether this land was 
separated or not from Equatorial Africa, or formed with 
it one great southern continent, there is no sufficient 
evidence to determine. 

Turning now to tropical Asia, we find a somewhat 
analogous series of events, but on a smaller scale and with 
less strongly-marked results. At the time when tropical 
and South Africa were so completely cut off from the 
great northern continent, the peninsula of India with 
Ceylon was also isolated ; and it seems probable that 
their union with the continent took place at a somewhat 
later period. The ancient fauna of this south- Asiatic island 
may be represented by the slow Loris a peculiar type 
of lemurs, some peculiar rats (Murida3), and perhaps by 
the Edentate scaly ant-eater ; by its Uropeltidse a 
peculiar family of snakes, and by many peculiar genera 
of snakes and lizards, and a few peculiar amphibia. On 



326 TROPICAL NATURE, AND OTHER ESSAYS. 

the other hand, we must look upon the monkeys, the 
large carnivora, the deer, the antelopes, the wild pigs, 
and the elephants, as having overrun the country from 
the north; and their entrance must, no doubt, have 
led to the extermination of many of the lower types. 

But there is another remarkable series of changes 
which have undoubtedly taken place in Eastern Asia in 
Tertiary times. There is such a close affinity between 
the animals of the Sunda Islands and those of the 
Malay Peninsula and Siam ; and between those of Japan 
and of Northern Asia, that there can be little doubt that 
these islands once formed a southern and eastern exten- 
sion of the Asiatic continent. The Philippines and 
Celebes perhaps also formed a part of this continent ; 
but if so, the peculiarity and poverty of their mammalian 
fauna shows that they must have been separated at a 
much earlier period. 1 The other islands probably 
remained united to the continent till the Pliocene 
period. The result is seen in the similarity of the 
flora of Japan to that which prevailed in Europe in Mio- 
cene times ; while in the larger Malay Islands we find, 
along with a rich flora developed under long-continued 
equatorial conditions of uniform heat and moisture, a 
remnant of the fauna which accompanied it, of which 
the Malay tapir, the anthropoid apes, the tupaias, the 
galeopitheci or flying lemurs, and the sun-bears, may be 
representatives. 

There is another very curious set of relations worthy 
of our notice, because they imply some former com- 

1 For a full account of the evidence and conclusions as to these islands see 
the author's Geographical Distribution of Animals, vol. i. pp. 345, 359, 
426, 436. 



EARLY CONDITION OF ASIA. 327 

munication between the Malay Islands, on the one hand, 
and South India with Ceylon, on the other. We find, 
for example, such typical Malay forms as the Tupaia, 
some Malay genera of cuckoos and Timaliidse, some 
Malayan snakes and amphibia. The remarkable genus 
Hestia among butterflies, and no less than seven genera 
of beetles of purely Malay type, 1 all occurring either 
in Ceylon only or in the adjacent parts of the Peninsula, 
but in no other part of India. These cases are so 
numerous and so important, that they compel us to 
assume some special geographical change to account for 
them. But directly between Ceylon and Malaya there in- 
tervenes an ocean-depth of more than 15,000 feet; and 
besides the improbability of so great a subsidence, of 
which we have no direct evidence, a land communication 
of this kind would almost certainly have left more 
general proofs of its existence in the faunas of the two 
countries. But, when in Miocene times a sub-tropical 
climate extended into Central Europe, it seems probable 
that the equatorial belt of vegetation accompanied by 
its peculiar fauna, would have been wider than at present 
extending perhaps as far as Burma. If then the shallow 
northern part of the Bay of Bengal had been tempo- 
rarily elevated during the late Miocene or Pliocene 
epochs, a few Malayan types may have migrated to the 
Peninsula of India ; and have been preserved only in 
Ceylon and the Nilgherries, where the climate still retains 
somewhat of its equatorial character and the struggle 
for existence is somewhat less severe than in the northern 
part of the region, which is so much more productive 
in varied forms of life. 

1 For details see Geographical Distribution of Animals, vol. i. p. 327. 



328 TROPICAL NATURE, AND OTHER ESSAYS. 

There are also indications hardly less clear, of some 
communication between India and Malaya on the one 
hand, and Madagascar on the other ; but as these indi- 
cations depend chiefly on resemblances in the birds and 
insects, they do not imply that any land connection has 
occurred. If, as seems probable, the Laccadive and 
Maldive Islands are the remains of a large island or 
indicate a western extension of India, while the Sey- 
chelles, with the shallow banks to the south-east and the 
Chagos group are the remains of other extensive lands 
in the Indian Ocean, we should have a sufficient approxi- 
mation of these outlying portions of the two continents 
to allow a certain amount of interchange of such winged 
groups as birds and insects, while preventing any inter- 
mixture of the mammalia. 

The presence of some African types (and even some 
African species) of mammals in Hindostan appears to 
be due to more recent changes, and may perhaps be 
explained by a temporary elevation of the comparatively 
shallow borders of the Arabian Sea, admitting of a land 
passage from North-East Africa to Western India. 

There remains to be considered the supposed indi- 
cations of a very ancient communication between Africa, 
Madagascar, Ceylon, Malaya, and Celebes, furnished by 
the occurrence over this extensive area of isolated forms 
of the Lemur tribe. The anomalous range of this group 
of animals has been thought to require for its explanation 
the existence of an ancient southern continent which has 
been called Lemuria, but a consideration of all the facts 
does not seem to warrant such a theory. Had such a 
continent ever existed we are sure that it must have 
disappeared long before the Miocene period, or it would 



THE NEARCTIC REGION. 329 

assuredly have left more numerous and widespread 
indications of the former connections of these distant 
lands than actually exist. And when we go back to 
the Eocene period we are met by the interesting dis- 
covery of an undoubtedly Lemurine animal in France, 
and what are supposed to be allied forms in North 
America. This proof of the great antiquity and wide 
range of lemurs is quite in accordance with their low 
grade of development ; while the extreme isolation and 
specialization of many of the existing types (of which 
the Aye-aye of Madagascar is a wonderful example), 
and their scattered distribution over a wide tropical 
area, all suggest the idea that these are but the rem- 
nants of a once extensive and widely distributed group 
of animals, which, in competition with higher forms, 
have preserved themselves either by their solitary and 
nocturnal habits, or by restriction to ancient islands, 
like Madagascar, where the struggle for existence has 
been less severe. Lemuria, therefore, may be discarded 
as one of those temporary hypotheses which are useful 
for drawing attention to a group of anomalous facts, 
but which fuller knowledge shows to be unnecessary. 

Regions of the New World. We will now pass across 
the Atlantic to the "Western Hemisphere, and consider 
first the Nearctic region, or temperate North America, 
whose present and past zoological relations with the rest 
of the world are of exceeding interest. 

If we omit such animals as the musk-sheep (Ovibos), 
which is purely Arctic, and the peccaries (Dicotyles), 
which are hardly less distinctly tropical, the land- 



330 TROPICAL NATURE, AND OTHER ESSAYS. 

mammalia of North America are not very numerous ; 
and they can be for the most part divided into two 
groups, the one allied to the Palsearctic, and the other 
to the Neotropical fauna. The bears, the wolves, the 
cats, the bison, sheep and antelope, the hares, the mar- 
mots, and the pikas, resemble Palaearctic forms ; while 
the racoons, skunks, opossum, and vesper-mice are now 
more peculiarly Neotropical. There are also many 
genera which are altogether peculiar and characteristic 
of the region, as the prong-horn antelope (Antilocapra), 
the jumping-mouse (Jaculus), five genera of pouched 
rats (Saccomyidae), the prairie dogs (Cynomys), the tree 
porcupines (Erethizon), and some others. 

Birds present the same mixture of the two types ; but 
the wild turkeys (Meleagris), the passenger pigeon (Ec- 
topistes), the crested quails (Lophortyx, &c.), the ruffed 
grouse (Cupidonia), and some other groups of less 
importance, are peculiar ; while the family of the wood 
warblers (Mniotiltidse) is so largely developed that it 
may claim to be more characteristic of North than of 
South America. 

Reptiles and Amphibia present a number of peculiar 
types ; while no less than five peculiar families of fresh- 
water fishes would alone serve to mark out this as 
distinct from every other part of the world. 

Considering the evident affinity between the Nearctic 
and Palsearctic regions, there are here some curious 
deficiencies of groups which are common and widely- 
spread in the latter. Thus hedgehogs, wild horses and 
asses, swine, true oxen, goats, dormice, and true mice 
are absent ; while sheep and antelopes are only repre- 
sented by solitary species in the Rocky Mountains. 



THE NEOTROPICAL REGION. 331 

Among birds, too, we have such striking deficiencies as 
the extensive families of flycatchers, starlings, and 
pheasants. 

Turning now to the Neotropical region, comprising 
all South America and the tropical parts of the northern 
continent, we find that the Old World types have still 
further diminished, while a number of new and alto- 
gether peculiar forms have taken their place. Insec- 
tivora have wholly disappeared with the exception of 
one anomalous form in the greater Antilles ; bears are 
represented by one Chilian species ; swine are replaced 
by peccaries ; the great Bovine family are entirely un- 
known ; the camel tribe are confined to the Southern 
Andes and the south temperate plains ; deer are not 
numerous ; and all the varied Ungulata of the Old 
World are represented only by a few species of tapirs. 
These great gaps are, however, to some extent filled up 
by a variety of interesting and peculiar types. Two 
families of monkeys (Cebidse and Hapalidae) differ in 
many points of structure from all the Quadrumana of 
the eastern hemisphere. There is a peculiar family of 
bats the vampyres ; many peculiar weasels and Pro- 
cyonidae ; a host of peculiar rodents, comprising five 
distinct families, among which are the largest living 
forms of the order ; and a great number of Edentata, 
comprising the families of the sloths, armadillos, and 
ant-eaters ; and lastly, a considerable number of the 
marsupial family of opossums. As compared with the 
Old World, we find here a great abundance and variety 
of the lower types, with a corresponding scarcity of 
such higher forms as characterise the tropics of Africa 
and Asia. 



332 TROPICAL NATURE, AND OTHER ESSAYS. 

In birds we meet with corresponding phenomena. 
The most abundant and characteristic families of the 
Old World tropics are replaced here by a series of 
families of a lower grade of organisation, among which 
are such remarkable groups as the chatterers (Cotingidse), 
the manakins (Pipridse), the ant-thrushes (Formica- 
riidse), the toucans (Rhamphastidse), the motmots 
(Momotidae), and the humming-birds (Trochilidae), the 
last perhaps the most remarkable and beautiful of all 
developments of the bird-type. Parrots are numerous, 
but these, too, are mostly of peculiar families ; while 
pheasants and grouse are replaced by curassows and 
tinamous, and there are an unusual number of remark- 
able and isolated forms of waders. 

Reptiles, amphibia, fresh-water fishes, insects, and 
land-shells, are all equally peculiar and abundant ; so that 
South America presents, on the whole, an assemblage of 
curious and beautiful natural objects, unsurpassed 
perhaps even unequalled in any other part of the 
globe. 

Past History of the American Continents. We will 
now proceed to examine what is known of the past 
history of the two American continents, and endeavour 
to determine what have been their former relations to 
each other and to the Old World, and how their existing 
zoological and geographical features have been brought 
about. And first let us see what knowledge we possess 
of the past relations of North America with the Eastern 
continents. 

If we go back to that recent period termed the Post- 
Pliocene corresponding nearly to the Post-Glacial 
period and to that of pre -historic man in Europe we 



ANCIENT AMERICA. 333 

find at once a nearer approximation than now exists 
between the Nearctic and Palsearctic faunas. North 
America then possessed several large cats, six distinct 
species of the horse family, a camel, two bisons, and four 
species of elephants and mastodons. A little earlier, in 
the Pliocene period (although fossil remains of this age 
are scanty), we have in addition the genus Rhinoceros 
several distinct camels, some new forms of ruminants 
and an Old- World form of porcupine. Further back, in 
the Miocene period, we find a Lemuroid animal, 
numerous insectivora, a host of carnivora, chiefly feline 
and canine, a variety of equine and tapirine forms, 
rhinoceroses, camels, deer, and an extensive extinct 
family the Oreodontidse allied to deer, camels, and 
swine. There are, however, no elephants. In the still 
earlier Eocene period most of the animals were peculiar, 
and unlike anything now living, but some were identical 
with European types of the same age, as Lophotherium 
and the family Anchitheridse. 

These facts compel us to believe that at distinct 
epochs during the Tertiary period the interchange of 
large mammalia between North America and the Old 
World has been far more easy than it is now. In the 
Post-Pliocene period, for example, the horses, elephants, 
and camels of North America and Europe were so closely 
allied that their common ancestors must have passed 
from one continent to the other, just as we feel assured 
that the common ancestors of the American and 
European bison, elk, and beaver, must have so migrated. 
We have further evidence in the curious fact that certain 
groups appear to come into existence in the one continent 
much later than in the other. Thus cats, deer, masto- 



334 TROPICAL NATURE, AND OTHER ESSAYS. 

dons, true horses, porcupines, and beavers, existed in 
Europe long before they appeared in America ; and as 
the theory of evolution does not admit the independent 
development of the same group in two disconnected 
regions to be possible, we are forced to conclude that 
these animals have migrated from one continent to the 
other. Camels, and perhaps ancestral horses, on the 
other hand, were more abundant and more ancient in 
America, and may have migrated thence into Northern 
Asia. 

There are two probable routes for such migrations. 
From Norway to Greenland by way of Iceland and 
across Baffin Bay to Arctic America, there is everywhere 
a comparatively shallow sea, and it is not improbable 
that during the Miocene period, or subsequently, a land 
communication may have existed here. On the other 
side of the continent, at Behring Straits, the probability 
is greater. For here we have a considerable extent of 
far shallower sea, which a very slight elevation would 
convert into a broad isthmus connecting North America 
and North-East Asia. It is true that elephants, horses, 
deer, and camels would, under existing climatal condi- 
tions, hardly range as far north as Greenland and 
Alaska ; but we must remember that most mysterious 
yet indisputable fact of the luxuriant vegetation, 
including even magnolias and other large-leaved ever- 
greens, which flourished in these latitudes during the 
Miocene period ; so that we have all the conditions of 
favourable climate and abundant food, which would 
render such interchange of the animals of the two con- 
tinents not only possible, but inevitable, whenever a 
land communication was effected ; and there is reason 



ANCIENT AMERICA. 335 

to believe that this favourable condition of things con- 
tinued in a diminished degree during a portion of the 
succeeding Pliocene period. 

We must not forget, however, that the faunas of the 
two continents were always to a great extent distinct 
and contrasted such important Old- World groups as 
the civets, hyaenas, giraffes, and hippopotami, never 
passing to America, while the extinct Oreodontidae, 
Brontotheridae, and many others are equally unknown 
in the Old World. This renders it probable that the 
communication even in the north was never of long 
continuance ; while it wholly negatives the theory of an 
Atlantis bridging over the Atlantic Ocean in the Tem- 
perate Zone at any time during the whole Tertiary 
period. 

But the past history of the North-American fauna is 
complicated by another set of migrations from South 
America, which, like those from the Old World, appear 
to have occurred at distant intervals, and to have con- 
tinued for limited periods. In the Post-Pliocene epoch, 
along with elephants and horses from Europe or Asia we, 
find a host of huge sloths and other Edentata, as well as 
llamas, capybaras, tapirs, and peccaries, all characteristic 
of South America. Some of these were identical with 
living species, while others are closely allied to those 
found fossil in Brazilian caves and other deposits of 
about the same age, while nothing like them inhabited 
the Old World at the same period. We are therefore 
quite sure that they came from some part of the Neo- 
tropical region ; but the singular fact is, that in the 
preceding Pliocene epoch none of them are found in 
North America. We conclude, therefore, that their 



336 TROPICAL NATURE, AND OTHER ESSAYS. 

migration took place at the end of the Pliocene or 
beginning of the Post-Pliocene epoch, owing to some 
specially favourable conditions, but that they rapidly 
disappeared, having left no survivors. We must, how- 
ever, study the past history of South America in order 
to ascertain how far it has been isolated from or con- 
nected with the northern continent. 

Abundant remains of the Post-Pliocene epoch from 
Brazilian caves show us that the fauna of South America 
which immediately preceded that now existing had the 
same general characteristics, but was much richer in 
large mammalia and probably in many other forms of 
life. Edentata formed the most prominent feature ; but 
instead of the existing sloths, armadillos, and ant-eaters, 
there were an immense variety of these animals, some of 
living genera, others altogether different, and many of 
them of enormous size. There were armadillos as large 
as the rhinoceros, while the megatherium and several 
other genera of extinct sloths were of elephantine 
bulk. The peculiar families of South American rodents 
cavies, spiny-rats, and chinchillas were represented by 
other species and genera, some of large size ; and the 
same may be said of the monkeys, bats, and carnivora. 
Among Ungulata, however, we find, in addition to the 
living tapirs, llamas, peccaries, and deer, several species 
of horse and antelope, as well as a mastodon, all three 
forms due probably to recent immigration from the 
northern continent. 

Further south, in Bolivia, the Pampas, and Patagonia, 
we also find abundant fossil remains, probably a little 
older than the cave fauna of Brazil, and usually referred 
to the newer part of the Pliocene period. The same 



ANCIENT AMERICA. 337 

families of rodents and Edentata are here abundant, 
many of the genera being the same but several new ones 
also appearing. There are also horses, peccaries, a mas- 
todon, llamas, and deer ; but besides these there are a 
number of altogether peculiar forms, such as the 
Macrauchenia, allied to the Tapir 'and Palseotherium ; 
the Homalodontotherium, allied to the miocene Hyraco- 
don of North America ; and the Toxodontidae, a group 
of very large animals having affinities to Ungulates, 
rodents, Edentata, and Sirenia, and therefore probably 
the representative of a very ancient type. 

Here then we meet with a mixture of highly developed 
and recent, with low and ancient types, but the latter 
largely predominate ; and the most probable explana- 
tion seems to be that the same concurrence of favourable 
conditions which allowed the megatherium and mega- 
lonyx to enter North America also led to an immigration 
of horses, deer, mastodons, and many of the Felidae into 
South America. These inter-migrations appear to have 
taken place at several remote intervals, the northern and 
southern continents being for the most part quite sepa- 
rated, and each developing its own peculiar forms of life. 
This view is supported by the curious fact of a large 
number of the marine fishes of the two sides of Central 
America being absolutely identical implying a recent 
union of the two oceans and separation of the continents 
while the mollusca of the Pacific coast of America 
bear so close a relation to those of the Caribbean Sea and 
the Atlantic coasts, as to indicate a somewhat more 
remote but longer continued sea-passage. The straits 
connecting the two oceans were probably situated in 
Nicaragua and to the south of Panama, leaving the 

z 



338 TROPICAL NATURE, AND OTHER ESSAYS. 

highlands of Mexico and Guatemala united to North 
America. 

Around the Gulf of Mexico and the Caribbean Sea 
there is a wide belt of rather shallow water, and during 
the alternate elevations and subsidences to which this 
region has been subjected, the newly raised land would 
afford a route for the passage of immigrants between 
North and South America. The great depression of the 
ocean, believed to have occurred during the Glacial 
period (caused by the locking-up of the water in the two 
polar masses of ice), may perhaps have afforded the 
opportunity for those latest immigrations which gave so 
striking a character to the North American fauna in 
Post- Pliocene times. 

Among the changes which South America itself has 
undergone, perhaps the most important has been its 
separation into a group of large islands. Such a change 
is clearly indicated by the immense area and low eleva- 
tion of the great alluvial plains of the Orinoko, Amazon, 
and La Plata, as well as by certain features in the dis- 
tribution of the existing Neotropical fauna. A subsi- 
dence of less than 2,000 feet would convert the highlands 
of Guiana and Brazil into islands separated by a shallow 
strait from the chain of the Andes. When this occurred 
the balance of the land was probably restored by an 
elevation of the extensive submerged banks on the east 
coast of South America, which in South Brazil and 
Patagonia are several hundred miles wide, embracing 
the Falkland Islands, and reaching far to the south of 
Cape Horn. 

Looking, then, at the whole of the evidence at our 
command, we seem justified in concluding that the past 



ANCIENT AMERICA. 339 

histories of North and South America have been different, 
and in some respects strongly contrasted. North America 
was evidently in very early times so far connected with 
Europe and Asia as to interchange with those continents 
the higher types of animal life as they were successively 
developed in either hemisphere. These more perfectly 
organised beings rapidly gained the ascendency, and led 
to the extinction of most of the lower forms which had 
preceded them. The Nearctic has thus run a course 
parallel to that of the Palsearctic region, although its 
fauna is, and perhaps always has been, less diversified 
and more subject to incursions of lower types from 
adjacent lands in the southern hemisphere. 

South America, on the other hand, has had a history 
in many respects parallel to that of Africa. Both have 
long existed either as continents or groups of large 
islands in the southern hemisphere, and for the most 
part completely separated from the northern continents ; 
and each accordingly developed its peculiar types from 
those ancestral and lowly- organised forms which first 
entered it. South America, however, seems to have had 
a larger area and more favourable conditions, and it 
remained almost completely isolated till a later period. 
It was therefore able to develop a more-varied and 
extensive fauna of its own peculiar types, and its union 
with the northern continent has been so recent, and is 
even now maintained by so' narrow an isthmus, that it 
has never been overrun with the more perfect mammalia 
to anything like the extent that has occurred in Africa. 
South America, therefore, almost as completely as Aus- 
tralia, has preserved for us examples of a number of low 
and early types of mammalian life, which, had not the 

z 2 



340 TROPICAL NATURE, AND OTHER ESSAYS. 

entire country been isolated from the northern continent 
during middle and late Tertiary times, would long since 
have become extinct. 

The Australian Region. There only remains for us 
now to consider the relation of the island-continent 
of Australia to Asia and South America, with both 
which countries it has a certain amount of zoological 
connection. 

Australia, including New Guinea (which has in recent 
times been united with it), differs from all the other 
continents by the extreme uniformity and lowly organ- 
isation of its mammalia which almost all belong to one 
of the lowest orders the marsupials. Monkeys, carni- 
vora, insectivora, and the great and almost ubiquitous 
class of hoofed-animals, are all alike wanting ; the only 
mammals besides, marsupials being a few species of a 
still lower type the monotremes, and a few of the very 
smallest forms of rodents the mice. The marsupials, 
however, are very numerous and varied, constituting 
G families and 33 genera, of which there are about 120 
known species. None of these families is represented 
in any other continent ; and this fact alone is sufficient 
to prove that Australia must have remained almost or 
quite isolated during the whole of the Tertiary period. 

In birds there is, as we might expect, less complete 
isolation ; yet there are a number of very peculiar types. 
About 15 families are confined to the Australian region, 
among which are the paradise-birds, the honey-suckers, 
the lyre-birds, the brush-tongued lories, the mound- 
makers, and the cassowaries. 

Our knowledge of the former mammalian inhabitants 



THE AUSTRALIAN REGION. 341 

of Australia is imperfect, as all yet discovered are from 
Post-Tertiary or very late Tertiary desposits. It is 
interesting to find, however, that all belong to the 
marsupial type, although several are quite unlike any 
living animals, and some are of enormous size, almost 
rivalling the mastodons and megatheriums of the northern 
continents. In the earliest Tertiary formation of Europe 
remains of marsupials have been found, but they all 
belong to the opossum type, which is unknown in 
Australia ; and this supports the view that no commu- 
nication existed between the Paleearctic and Australian 
regions even at this early period. Much farther back, 
however, in the Oolite and Trias formations, remains of 
a number of small mammalia have been found which 
are almost certainly marsupial, and bear a very close 
resemblance to the Myrmecobius, a small and very rare 
mammal still living in Australia. An animal of some- 
what similar type has been discovered in rocks of the 
same age in North America ; and we have, therefore, 
every reason to believe, that it was at or near this 
remote epoch when Australia, or some land which has 
been since in connection with it, received a stock of 
mammalian immigrants from the great northern conti- 
nent ; since which time it has almost certainly remained 
completely isolated. 

The occurrence of the marsupial opossums in America 
has been thought by some writers to imply an early 
connection between that continent and Australia ; but 
the fact that opossums existed in Europe in Eocene and 
Miocene times, and that no trace of them has been found in 
North or South America before the Post-Pliocene period, 
renders it almost certain that they entered America 



342 TROPICAL NATURE, AND OTHER ESSAYS. 

from Europe or North Asia in middle or late Tertiary 
times, and have flourished there in consequence of a 
less severe competition with highly-developed forms 
of life. 

The birds of Australia and South America only exhibit 
a few cases of very remote and general affinity, which are 
best explained by the preservation in each country of 
once wide-spread types, but is quite inconsistent with 
the theory of a direct union between the two countries 
during Tertiary times. 

Keptiles are even more destitute of proofs of any 
such connection than even mammalia or birds ; but 'in 
amphibia, fresh-water fishes, and insects the case is 
different, all these classes furnishing examples of the 
same families or genera inhabiting the temperate parts 
of both continents. But the fact that such cases are 
confined to these three groups and to plants, is the 
strongest possible proof that they are not due to land- 
connection ; for all these organisms may be transmitted 
across the ocean in various ways. Violent storms of 
wind, floating ice, drift-wood, and aquatic birds, are all 
known to be effective means for the distribution of 
these animals or their ova, and the seeds of plants. All 
of them too, it must be noted, are to a considerable 
degree patient of cold ; the reverse being the case with 
true reptiles and land-birds, which are essentially heat- 
loving ; so that the whole body of facts seems to point 
rather to an extension of the Antarctic lands and islands 
reducing the width of open sea, than to any former 
union, or even close approximation of the Australian 
and South American continents. 



ANCIENT CONTINENTS. 343 



Summary and Conclusion. 

Let us now briefly review the conclusions at which we 
have arrived. If we look back to remote Tertiary times, 
we shall probably find that all our great continents and 
oceans were then in existence, and even bore a general 
resemblance to the forms and outlines now so familiar 
to us. But in many details, and especially in their 
amount of communication with each other, we should 
observe important changes. The first thing we should 
notice would be a more complete separation of the 
northern and the southern continents. Now, there is 
only one completely detached southern land Australia ; 
but at that period Africa and South America were also 
vast islands or archipelagos, completely separated from 
their sister continents. Examining them more closely, 
we should observe that the great Euro- Asiatic continent 
had a considerable extension to the south-east, over what 
are now the shallow seas of Japan, China, and Java. In 
the south-west it would include Northern Africa, the 
Mediterranean then forming two inland seas ; while to 
the west and north-w r est it would include the British 
Isles, and perhaps extend even to Iceland and Greenland. 
As a balance to these extensions, much of Northern Siberia 
and North -Western Asia may have been under water ; 
the peninsula of India would be an island with a con- 
siderable south-west extension over what are now the 
Laccadive and Maldive coral-reefs. The Himalayas 
would be a moderate range of hills ; the great desert 
plateau of Central Asia a fertile plain ; the greater 
part of the continent would enjoy a tropical or sub- 



344 TROPICAL NATURE, AND OTHER ESSAYS. 

tropical climate, while even tlie extreme north would 
support a luxuriant vegetation. This great continent 
would abound in animal life, and would be especially 
remarkable for its mammalia, which would comprise 
ancestral forms of all our existing higher types, along 
with a number of those lower grades of organisation 
(such as lemurs and opossums) now found chiefly in the 
southern hemisphere. 

Connected with this continent by what is now 
Behring Straits and the Sea of Kamschatka, we should 
find North America, perhaps somewhat diminished in 
the east, but more extensive in the south and north, and 
abounding as now with great inland lakes which were 
situated to the west of the present lake district. This 
continent seems to have had a less tropical climate and 
vegetation than prevailed in the eastern hemisphere, but 
it supported an almost equally varied though very 
distinct fauna. Ancestral horses no larger than dogs ; 
huge tapir-like and pig-like animals ; strange forms allied 
to rhinoceroses ; the Dinocerata huge horned animals 
allied to elephants and to generalised Ungulata; and 
the Tillodontia, still more unlike anything now living, 
since they combined characters now found separated in 
the carnivora, the Ungulata, and the rodents. Ancestral 
Primates, allied to both the lemurs and the South 
American monkeys, also inhabited this continent. 

The great land masses of the northern hemisphere 
thus appear to have possessed between them all the 
higher types of animal life ; and these seem to have 
been developed for a time in one continent and then to 
have been in part transferred by migration to the other, 
where alone they have sometimes maintained themselves. 



ANCIENT CONTINENTS. 345 

Thus, the elephants and the camels appear to have 
descended from what were once exclusively American 
types, while the opossums were as certainly European. 
Many groups, however, never passed out of the continent 
in which they originated the civets, hyaenas, and the 
giraffes being -wholly eastern, while the Oreodontidse 
and Brontotheridse were no less exclusively western. 

South America seems to have been united to the 
northern continent once at least in Secondary or early 
Tertiary times, since it was inhabited in the Eocene 
period by many forms of mammalia, such as rodents, 
felines, and some ancient forms of Ungulata. It must 
also have possessed the ancestors of the Edentata 
(though they have not yet been discovered), or we 
should not find such a variety of strange and gigantic 
forms of this order in later Tertiary deposits in this 
part of the world only. During the greater part of 
the Tertiary period, therefore, South America must 
have been separated from the North and protected from 
incursions of the higher forms of mammalia which 
were there so abundant. Thus only does it seem pos- 
sible to understand the unchecked development of so 
many large but comparatively helpless animals as the 
Edentata of the Pampas and the Brazilian caves a 
development only comparable with that of the Australian 
marsupials, still more completely shut off from all 
competition with higher forms of life. 

In Africa the evidence of a long period of insulation 
is somewhat more complex and less easily apparent, but, 
it seems to me, equally conclusive. We have first, the 
remarkable fauna of Madagascar, in which lemurs and 
insectivora predominate, with a few low forms of 



346 TROPICAL NATURE, AND OTHER ESSAYS. 

carnivora ; but none of the higher animals, such as 
apes, antelopes, buffaloes, rhinoceroses, elephants, lions, 
leopards, and hyaenas, which swarm on the continent. 
The separation of Madagascar from Africa must therefore 
have occurred before these important groups existed there. 
Now, we know that all these large animals lived in 
Europe and Asia during late Miocene times, while 
lemurs are only known there during the Eocene period, 
and were probably more abundant in late Mesozoic times. 
It is almost certain, therefore, that Southern Africa 
must have been cut off from Europe and Asia during 
the whole intervening period, or the same development 
of high forms and extinction of low would have gone 
on in the one country as in the other. The persistence 
of a number of low and isolated types in South and 
West Africa, which are probably a remnant of the 
ancient fauna of the country, is also favourable to this 
view. At the time we are considering, therefore, we 
look upon tropical and South Africa, with Madagascar, 
as forming a completely isolated land or archipelago ; 
while the Seychelles and Chagos banks, with Bourbon 
and Mauritius, perhaps, formed another island or group 
permanently separated from the larger masses. The 
extra- tropical portion of South Africa was also probably 
more extensive, affording an area in which its remarkable 
flora was being developed. ... 

Turning to Australia, we should probably find it, at 
this remote period, more extensive than it is now, 
including in its area New Guinea and some of the 
adjacent islands, as well as Tasmania ; while another 
extensive land probably occupied the site of the New 
Zealand group. It may be considered certain that, 



GEOGRAPHICAL REVOLUTIONS. 347 

whatever elevations and subsidences these countries may 
have undergone, they have not been connected either with 
Asia, Africa, or South America during the whole 
Tertiary period. 

In conclusion, I would especially remark that the 
various changes in the outlines and mutual relations 
of our continents, which I have now endeavoured to 
establish, must not be supposed to have been all strictly 
contemporaneous. Some may have been a little earlier 
or a little later than others ; some changes may have 
been slower, others more rapid ; some may have had but 
a short duration, while others may have persisted through 
considerable geological periods. But, notwithstanding 
this uncertainty as to details, the great features of the 
geographical revolutions which I have indicated, appear 
to be established by a mass of concurring evidence ; and 
the lesson they teach us is, that although almost the 
whole of what is now dry land has undoubtedly once 
lain deep beneath the waters of the ocean, yet such 
changes on a great scale are excessively slow and gradual ; 
so that, when compared with the highest estimates of 
the antiquity of the human race, or even with that of 
most of the higher animals, our existing continents and 
oceans may be looked upon as permanent features of 
the earth's surface. 



ERRATUM. 

AT page 59 I have said that there are only three or four species of Mimosa 
which are sensitive. This is a mistake, as the greater portion of the species in the 
extensive genus Mimosa, as well as some species of several other genera of 
Leguminosae, and also of Oxalidacese, possess this curious property. I cannot find, 
however, that any one has suggested in what way the sensitiveness may have been 
useful to the species which first acquired it. My guess at an explanation may 
therefore induce botanists who are acquainted with the various species in a state 
of nature, to suggest some better solution of the problem. 



INDEX. 



A. 



Abrus precatoria, perhaps a case of 

mimicry, 226 

Absorption-colours or pigments, 183 
Acraeidse, warning colours of, 174 
Adaptive characters, 150, 155 
Affinities, how to determine doubtful, 

148 

African large mammalia, recent immi- 
grants, 323 
Allen, Mr. Grant, on protective colours 

of fruits, 225 

Alpine flowers, why so beautiful, 232 
Amboyna, large sized butterflies of, 258 
American monkeys, 118 
American Continents, past history of, 

332 
Ancient races of North and South 

America, 298 

Andaman Islands, pale butterflies of, 
260 

white-marked birds of, 263 
Anderson, Mr. W. Marshall, on cranium 

from N. American mound, 296 
Andes, very rich in humming-birds, 139 
Animal colours, how produced, 184 

life in tropical forests, 70 
Anthribidfe, 95 
Ants, wasps, and bees, 80 

numbers of, in India and Malaya, 

8188 

destructive to insect-specimens, 85 
and vegetation, special relation 

between, 89 
Apatura and Heterochroa, resemblance 

of species of, 257 
Apes, 116 

Aqueous vapour of atmosphere, its 
influence on temperature, 9 

quantity at Batavia and Clifton, 10 
Arctic plants, large leaves of, 236 

flowers and fruits brightly coloured, 

237 

Areca palm, 45 
Arenga saccharifera, 43 



Argus-pheasant, wonderful plumage of, 

205 

Arums, 48 

Assai of the Amazon, 43 
Auckland Isles, handsome flowers of, 

238 
Audubon, on the ruby hummine-birds, 

130, 137 

Australian Region, mammalia of, 340 
birds of, 340 
extinct fauna of, 341 
its supposed union with S. America, 

341 
Azara, on food of humming-birds, 135 



B. 

BAMBOOS, 52 

uses of, 5358 
Bananas, wild, 47 
Banana, 48 
Barber, Mrs. on colour changes of pupa 

of Papilio nireus, 168 
Barbets, 105 

Bark, varieties of in tropical forests, 33 
Barometer, range of, at Batavia, 24 
Batavia, Meteorology of, 4 

and London, diagram of mean 

temperatures, 5 
greatest rainfall at, 24 
range of barometer at, 24 
Bates, Mr. on climate at the Equator, 24 
on scarcity of forest-flowers on 

Amazon, 6] 

on animal life in Amazon valley, 70 
on abundance of butterflies at Ega, 

75 

on importance of study of butter- 
flies, 78 

on leaf-cutting ants, 86 
on blind ants, 88 
on bird-catching spider, 97 
on use of toucan's bill, 106 
on large serpents, 115 
on the habits of humming-bird?, 
132 



350 



INDEX. 



Bats, 118 
Beetles, 94 

abundance of, in New Forest-clear- 
ings, 96 

probable use of horns of, 202 
Belt, Mr. on virgin forests of Nicaragua, 
62 

on aspects of tropical vegetation, 67 
on leaf-cutting ants, 86 
on an Acacia inhabited by ants, 89 
on uses of ants to the trees they 

live on, 90 

on a leaf-like locust, 93 
on tree-frogs, 116 
on the habits of humming-birds, 

133, 134 
on uneatable bright-coloured frog, 

175 

on use of light of glow-worm, 205 
Betel-nut, 45 

Bill of humming-birds, 129 
Biology, by-paths of, illustrated, 251 
Birds, 99 

how many known, 124 

cases of local variation of colour 

among, 262 
influence of locality on colours of, 

255 

which fertilize flowers, 273, 274 
and insects blown to oceanic islands, 

308 

of Palsearctic Region, 316 
of Ethiopian Region, 318 
of Oriental Region, 320 
Bonelli, Mr., on the Sappho comet 

humming-bird, 132 

Bullock on food of humming-birds, 153 
Buprestidae, 94 
Burchell, Dr., on the "stone mes- 

embryanthemum, " 223 
Butterflies, abundance of, in tropical 
forests, 72 
conspicuousness of in tropical 

forests, 73 

colours and form of, 74 
peculiar habits of tropical, 76 
tropical and temperate compared as 

to colour, 164 

females do not choose their part- 
ners, 200 

with gaily-coloured females, 204 
numbers and variety of, 255 
influence of locality on colours of, 

255 
Buttressed trees, 31 



C. 

CALAMUS, 41 

Callithea, imitated by species of Cata- 

gramma and Agrias, 257 
Callithea markii, 75 



Campyloptcrus hemileucurus, pugna- 
cious and ornamental, 214 
Cattleyas, 51 

Cecropias, trees inhabited by ants, 89 
Celebes, large and peculiarly formed 
butterflies of, 259 

white-marked birds of, 263 
Centipedes, 97 
Ceylon and Malaya, resemblances of 

fauna of, 327 
Chameleons, 113 
Chameleon, cause of changes of its 

colour, 170 

Chemical action changes colours, 183 
Chili, humming-birds of, 141 
Chiroptera, 119 
Chrysobactron Jlossii, 238 
Clark, Rev. Hamlet on leaf-cutting 

ants, 86 
Climate of Equator, general features of, 

17 

Climates of Timor, Angola, and Scot- 
land compared, 14 
Climbing plants of tropical forests, 37 

uses of, 39 
Cockatoos, 100 
Coelogynes, 51 

Coloration of tropical birds, 110 
Colour, cause of change of, in humming- 
birds, 144 

Colour in nature, problems of, 159 
how far constant, 161 
as affected by heat and light, 161 
of tropical birds, 163 
of tropical butterflies, 164 
of temperate and tropical flowers, 

165 
changes of, in animals produced by 

coloured light, 167 
voluntary change of, in animals, 

170 
not usually influenced by coloured 

light, 171 

Colour, the nature of, 180 
how produced, 183 
changed by heat, 183 
a normal product of organization, 

185 

as a means of recognition, 196 
proportionate to integumentary de- 
velopment, 198 

not caused by female selection, 198 
Colour absent in wind-fertilized flowers, 
233 
same theory of, in animals and 

plants, 234 
of flowers and their distribution, 

235 

Colour, nomenclature of, formerly im- 
perfect, 247 

Colour-development as illustrated by 
humming-birds, 212 



INDEX. 



351 



Colour-development, local causes of, 
216 

in animals, summary, 216 
Colour-perception, supposed recent 

growth of, 244 

Colour-sense, origin of the, 241 
need for, 243 
not of recent origin, 246 
not wholly explicable, 248 
Colours, classification of organic, 172 
protective, 172 
warning, 174 
sexual, ]77 
typical, 179 

of animals, how produced, 184 
theory of protective, 187 
theory of warning, 189 
theory of sexual, 192 
theory of typical, 215 
Colours and ornaments of humming- 
birds, 127 
Colours of fruits, attractive, 224 

protective, 225 

Colours, which first perceived, 243 
Cometcs sparganurus, very pugnacious, 

214 
Composite, arborescent in oceanic 

islands, 276 
Continent, past changes of the great 

Eastern, 321 
Continents of Tertiary period, probable 

aspect of, 343 
Copridse, 95 

probable use of horns of, 202 
Crematogaster, genus of ants, 83 
Cross-fertilization of flowers, use of, 
228 

complex arrangements for, 229 
Cuckoos, 104 



D. 



DA.XAID.E, warning colours of, 174 
Danainse, Acneinse and Heliconiinre, 

local resemblances of, 256 
Daphne pontica, 230 
Darwin, Mr. , on mode of cross-fertiliza- 
tion and its use, 228 

not too highly rated, 252 

on vegetation of Galapagos, 272 

on use of scented leaves, 277 

on former union of West Indian 

islands and S. America, 306 
on oceanic islands, 307 
revolution in thought effected by, 

284 

Deserts on line of tropics, 28 
Desmoncus, 41 

De Vry, Mr., on the sugar-palm, 43 
Dews, cause of heavy tropical, 10 



Diagram of mam temperature at Batavia 
and London, 5 

of rainfall at Batavia and London, 

15 

Dianthus alpinus, D. glacialis, 232 
Distribution of humming-birds, 138 
Dragons or flying-lizards, 113 
Drugs from equatorial forest-trees, 36 
Duke-of-York - Island, pale-coloured 
insects of, 259 

Islands, remarkable white plum- 
aged birds of, 263 

Dyes from equatorial forest-trees, 36 
Dynastidre, 95 

probable use of horns of, 202 



E. 



EARL, MR. GEORGE WINDSOR, on divi- 
sion of Malay Archipelago, 307 

Earth-sculpture or surface-geology, 250 

EarUi-works, North American, 292 

Easter Island, sculptures on, 291 

Eciton, genus of foraging ants, 87 

Elateridse, luminous species perhaps 
mimetic, 205 

Emperor-moth, protective coloration of, 
174 

Environment, relation of living things 
to, 254 

Epicalia, sexes of, differently coloured, 
178 

Epilobium angitstifolium, E. parvi- 
florum, 233 

Epimachhue, 150 

Equator, cause of uniform high tempera- 
ture near, 6 

short twilight at, 21 

Equatorial climate, general features of, 
17 
uniformity of in all parts of the 

world, 18 
local diversities of, 19 

Equatorial forests, general features of, 
29 

Eqxiatorial forest-belt, cause of, 27 

Equatorial heavens, aspect of, 23 

Equatorial zone, temperature of, 3 

Ethiopian Region, 317 

Eugenes fulgens, 134 

Eunica and Siderone, resemblance of 
species of, 257 

Euplcea, pale species of, in Moluccas 
and New Guinea, 258 

Euro- Asiatic continent, miocene fauna 
of, 323 

Eustephanus, 141 

Eustephanus galeritus, 143 

Euterpe olcracea, 43 

Evaporation and condensation, equa- 
lising effects of, 16 



352 



INDEX. 



F. 



FEMALE birds, greater brilliancy of 

some, 211 
Female insects, greater brilliancy of 

some, 208 
Ferns, 46 
Ferns, preponderance of in Tahiti and 

Juan Fernandez, 269, 270 
Fiji Islands, pale butterflies of, 259 
Fire-ants, 83 
Fishes, causes of general coloration of, 

171 

Flowering-trunks, probable cause of, 34 
Flowers, comparative scarcity of in 

equatorial forests, 60 
Flowers and insects, 64 
Flowers of temperate zones brilliantly 
coloured, 165 

comparatively scarce in tropical 

forests, 167 

Flowers, attractive colours of, 228 
fertilized by insects, 228 
attractive odours of, 230 
when sweet-scented not conspi- 
cuously coloured, 230 
attractive grouping of, 231 
alpine, why so beautiful, 232 
why allied species differ in beauty, 

233 
when wind-fertilized not coloured, 

233 

relation of colours of, to distribu- 
tion, 235 
and fruits, recent views as to action 

of light on, 236 
Flowers of Auckland and Campbell's 

Isles, bright coloured, 238 
Flying-lizards, 113 

Foliage, two chief types of, in tropical 
forests, 33 . 

colours of, 221 
Foot of savages does not approach 

that of apes, 289 (note) 
Forest-belt, cause of equatorial, 27 
Forest-belts, temperate, 29 
Forest-tree, section of a Bornean, 32 

formed from climbers, 32 
Forest-trees, characteristics of, 30 
Forest-trees of low growth, 34 
Forest-trees, uses of equatorial, 35 
Forests, eflectof on rainfall and drought, 
19 
devastation caused by destruction 

of, 20 

equatorial, 29 

undergrowth of tropical, 34 
Formica gigas, 81 
Foxes, none in Isle of Wight in 1605, 

305 

Frogs and toads, 116 
Frog, with bright colours uneatable, 175 



Frogs of oceanic islands, 309 

Fruit-bats, 119 

Fruits of equatorial forest-trees, 36 

Fruits, attractive colours of, 224 
protective colours of, 225 
greater antiquity of protected than 
attractive, 227 



G. 



GALAPAGOS, colours of productions of, 
163 

poor in flowers and insects, 235 
weedy vegetation of, 272 

Gardener, Dr., on a large water-boa, 115 

Geckos, 112 

Geiger, on ancient perception of colour, 
245 

Geranium pratense, G. pusillum, 233 

Gibbons, 116 

Ginger-worts, 47 

Gladstone, Mr., on the colour-sense, 245 

Glow-worm, use of its light, 205 

Goliath cuckoo, 105 

Gosse, Mr. on Jamaica humming-birds, 
132, 135 
on the pugnacity of humming-birds, 

134 
on food of humming-birds, 137 

Gould, Mr. on the motions of humming- 
birds, 131 

Grammatophyllums, 51 

Green, why the most agreeable colour, 
244 

Grisebach, on cause of vivid colours of 
arctic flowers, 237 

Guilielma speciosa, 42 

Gums from equatorial forest-trees, 36 



H. 

ffabenaria chlorantha, 230 
Habits of humming-birds, 130 
Heat due to condensation of atmo- 
spheric vapour, 14 

changes colours, 183 
Heliconiiuae and Acraeinae, local re- 
semblances of, 256 
Hindostan and Africa, resemblances of 

fauna o:, 328 

Hooker, Sir J. on flowers of Auckland 
Isles,. 238 
on deficient odour of New Zealand 

flowers, 277 
Hornbills, 107 

Horns of beetles, probable use of, 202 
Howling-monkeys, 118 
Humming-birds, number of, 124, 133 
distinctness of, 125, 129 
structure of, 125 



INDEX. 



353 



Humming-birds, colours and ornaments 
of, 127 

descriptive names of, 129 

motions and habits of, 130 

display of ornaments by males, 134 

food of, 136 

nests of, 137 

geographical distribution and varia- 
tion of, 138 

of Juan Fernandez, 140 

influenced by varied conditions in 
South America, 147 

relations and affinities of, 148 

sternum of, 151 

eggs of, 152 

feather-tracts of, 152 

resemblance of swifts to, 152 

nestlings of, 153 

differences from sun-birds, 164 



IGUANAS, 113 

Indian peninsula once an island, 325 

ancient fauna of, 325 
Insects, wingless, 97 

general observations on tropical, 98 
Insular plants and insects, relations of, 

267 

Interference-colours in animals, 184 
Islands, influence of locality on colour 

in, 257 



J. 



JACAMARS, 105 

Juan Fernandez, humming-birds of, 140 

insects of, 270 

abundance of humming-birds in, 
273 



L. 



LAND and sea, peculiar distribution of, 
311 
existing distribution of, very 

ancient, 312 
Leaf-insects, 92 

Leaves, supposed use of odours of, 277 
Lemuria, an hypothetical 'continent, 

not required, 328 
Leopoldinia major, 45 
Lepidoptera, diurnal, 72 
Leptalis, a good case of mimicry, 189 _ 
Leptena erastus, 256 
Light, theory of, as producing colours, 
161 

action of, on plants, 222 
supposed direct action of, on colours 

of flowers and fruits, 236 
Lizards, 111 



Local causes of colour-development, 216 
Locusts, richly coloured tropical, 94 
Longicorns, 95 
Lophornis ornatus, veiy pugnacious, 

214 

Lord Howe's Island, white rail in, 264 
Lubbock, Sir John, on colour percep- 
tion in insects, 255 



1L 

MACAWS, 100 

Madagascar, white-marked butterflies 

of, 260 

Madagascar once united to Africa, 325 
Madagascar and Malaya, resemblances 

of fauna of, 328 

Male birds, origin of ornamental plum- 
age of, 205 

Male birds which incubate, 212 
Male humming-birds produce a shriller 

sound, 215 
Males, theory of display of ornaments 

by, 207 

Malva sylvestris, M. rotundifolia, 233 
Mammals, 116 

Mammalia, supposed variations of, com- 
parable to those of butterflies, 261 

localresemblances of, in Africa, 262 
Mammalia of Palaearctic Region, 315 
of Ethiopian Region, 317 
of Oriental Kegion, 319 
of miocene period in Euro-Asia, 

321 
Man, antiquity and origin of, 280 

indications of extreme antiquity 

of, 285 
highly developed at very early 

period, 286 

antiquity of intellectual, 290 
Mangroves, 58 
Manicaria saccifera, 41 
Mantidae, 91 

Mantis resembling an orchis-flower, 173 
Marantaceae, 47 
Marmosets, 118 

Marshall, Messrs, on barbets, 106 
Martins, M. Charles, on increased size 

of leaves of arctic plants, 236 
Mates readily found by birds, 200 
MaUritia, palm, 40 
Maximiliana regia, 41 
Meiglyptea, 150 
Meldola, Mr. R. on variable colouring 

in insects, 170 

Meliphagidse in Auckland Isles pro- 
bably flower-fertilizers, 239 
Melliss, Mr. on flora of St. Helena, 275 
Migrations between N. America and 
Euro-Asia, 334 

between N. America and South 
America, 335 

A A 



354 



INDEX. 



Mescmbryanthemnm, stone, 223 
Meteorological phenomena, intensity of, 

at the equator, 23 
Mimicry, theory of, 189 
Mimosa pudica, 59 

Mivart, Professor, on animal origin of 
man, 284 

on the divergent affinities of man 

and apes, 288 
Mungredien, Mr. on showy and fragrant 

flowers, 230 
Monkeys, 116 
Monkeys and pigeons, 102 
Moseley, Mr. on humming-birds of Juan 

Fernandez, 143 
Moseley, Mr. H. N. on birds conveying 

seeds to islands, 268 
Moths, conspicuously coloured cater- 
pillars of, uneatable, 175 
Motmots, 105 

Mott, Mr. Albert, on antiquity of in- 
tellectual man, 291 
Mounds of N. America, antiquity of, 

296 
Mound-builders, a semi-civilized race, 

297 

Miiller, Dr. Hermann, on fertilization 
of alpine flowers, 232 
on fertilization of Martagon lily, 

231 
on variations of insect-fertilized 

flowers, 275 
on differences of allied species of 

flowers, 233 
M usa paradisiaca, 48 
Musaceae, 48 

Mygale, a bird-catching spider, 97 
Mysis chameleon, changes of colour of, 
171 

N. 

NEARCTIC REGION, mammalia of, 329 
birds of, 330 

Neotropical region, mammalia of, 331 
birds of, 332 

Nests of humming-birds, 137 

Newton, Professor, on appearance of 
living humming-birds, 130 

New Zealand, poor in flowers and in- 
sects, 235 

New World, regions of the, 329 

North American earth-works, 292 

Nuttall, Mr. on the rufous flame-bearer, 
131 

Nymphalidse, local resemblances of 
species of distinct genera of, 257 



0. 



OCEANIC ISLANDS, peculiar floras of, 269 
theory of, 307 



Odontomaclms, genus of ants, 82 

Odour deficient in New Zealand flowers, 
277 

Odours absorbed unequally by dif- 
ferently coloured stuffs, 266 
of flowers attractive, 230 

(Ecodoma cepluilotes, 85 

(Ecophylla smaragdina, 82 

Ogle, Dr. on colour and sense-percep- 
tion, 265 

Oil from palms, 45 

Oncidiums, 51 

Optical theory of colour, 180 

Orchids, 49 

Oriental Region, 319 

Ornamental humming-birds, the most 
pugnacious, 214 

Ornaments, display of, by male hum- 
ming-birds, 134 

Orthoptera, 91 



P. 



PAL^ARCTIC Region, 314 
Palms, 40 

height of, 41 
climbing, 41 
Palm-wine, 43 
Palm-trees, uses and products of, 42 

46 

Pandanaceae, 49 
Papilio, pale varieties of, in Moluccas 

and New Guinea, 258 
Papilionidae and Nymphalidae, local 

resemblances of, 255 
Papilio nireus, changes of colour of 

pupa of, 168 
Parrots, 99 

red in. Moluccas and New Guinea, 

264 

black in New Guinea and Mada- 
gascar, 264 
Passeres, 108 
Phyllostoma, 120 
Phasmidse, 9193 
Phoenix sylvcstr is, 45 
Phaethornithinae, 136 
Pheasants, brilliant plumage of, in cold 

countries, 163 
Pheidole, genus of ants, 84 
Philippine Islands, metallic colours of 
butterflies of, 259 

white-marked birds of, 263 
Picariae, 103 
Pickering, Mr. on plants of Pacific 

Islands, 269 

Pieridae and Lyceenidae, local resem- 
blances of, 256 
Pigeons, 102 

black in Australia and Madagascar, 
264 



INDEX. 



355 



Pigs, white poisoned in Virginia, black 

not, 265 

Pipes from N. American mounds, 295 
Plantain, 48 
Plantain-eaters, 197 
Plants, protective coloration in, 223 
Platyccrium, 47 
Plumage of tropical 1>irds, 109 

of humming-birds, 128 
Polyrachis, genus of ants, 81 
Polyalthea, tree with flowers on trunk, 

35 

Polygonum bistorta, P. aviculare, 233 
Pontia rapce, changes of colour of 

chrysalis of, 168 

Ponera clavala, terrible sting of, 82 
Portraits on sculptured pipes from 

mounds, 295 
Prosthemadera in the Auckland Isles, 

239 

Protective colours, theory of, 187 
Psittacula dio-pthalma, sexual difference 

of colour of, 178 
Pterylography, 151 
Pyramid, the Great, 298 

the Great, indicates an earlier 

civilization, 300 
Pythons. 115 



R. 



RABBITS, why white-tailed, 197 

Rainbow, how described by ancient 
writers, 245 

Rainfall at London and Batavia, dia- 
gram of, 15 

Rainfall, greatest recorded at Batavia, 
24 

Ramsay, Prof, on ancient fresh-water 
deposits, 313 

Raphia tcedigera, 41 

Rattan-palms, 42 

Recognition aided by colour, 196 

Reed, Mr., on humming-birds in Juan 
Fernandez, 146 

Mr. Edwyn C., on insects of Juan 
Fernandez, 270 

Reptiles, 111 

Reptiles of oceanic islands, 309 

Rhamphococcyx, 105 



SALVIN, MR. on the pugnacity of 

humming-birds, 134, 214 
Sauba ant, 85 
Saxifraga longifolia, 233 
S. cotyledon, 233 
S. oppositi/olia, 233 



Scorpions, 97 

Screw-pines, 49 

Scythrops, 105 

Seeds, how protected, 226 

Sensitive-plants, 59 

Sexes of butterflies differently coloured 

for recognition, 196 
Sexual colours, 177 
theory of, 192 

Sexual selection not a cause of colour, 
198 
neutralized by natural selection, 

210 

Sickle-bill humming-bird, 136 
Size, correspondence of, in tropical 

flowers and insects, 236 
Sky, colour of not mentioned in old 

books, 245 
Smith, Mr. Worthington, on mimicry 

in fungi, 223 
Smyth, Professor Piazzi, on the Great 

Pyramid, 298 
Snakes, 114 
Sobralias, 51 
Soil, heat of, 8 

influence of temperature on climate, 

8 

Solenopsis, genus of ants, 84 
Sorby, Mr., on composition of chloro- 
phyll, 221 

South America, extinct fauna of, 336 
geographical changes of, 338 
its parallelism with Africa, 339 
an area of preservation of ancient 

types, 339 

Spices from equatorial forest-trees, 36 
Spiders, 97 

Spruce, Dr. Richard, on number of 
ferns at Tarapoto, 47 

on inconspicuousness of tropical 

flowers, 61 
on use of aromatic secretions of 

leaves, 278 
Stainton, Mr., on insects attacking 

scented leaves, 277 
Stick-insects, 92 

St. Helena, indigenous flowers of, 275 
St. John, Mr., on large python, 115 
Structure of humming-birds, 125 
Sugar from palm-trees, 44 
Sunda Islands and Japan once joined to 

Asia, 326 

Sun-birds, differences from humming- 
birds, 154 
Sun's noonday altitude in Java and 

London compared, 6 
Sun's rays, heating effect of, 7 
Sunrise in the equatorial zone, 22 
Swifts, resemblances of to humming- 
birds, 152 

Symmachia trochilus, 75 
colubris, 75 



356 



INDEX. 



T. 



TAHITI, preponderance of ferns in, 269 
Temperature of London and Batavia 
compared, 6 

of different latitudes, various causes 

of, 7 

Temperature, influenced by heat of soil, 
8 

influenced by aqueous vapour of 

atmosphere, 9 
Temperature of tropical and temperate 

zones, cause of, illustrated, 12 
Tertiary faunas and their relations, 344, 

347 

Tkaumastura cora, veiy pugnacious, 214 
Timor and Scotland, climates com- 
pared, 14 
Timor and Flores, white-marked birds 

of, 263 
Toucans, 106 
Tree-frogs, 116 
Tristan d'Acunha, bright - coloured 

Pelargonium of, 275 
Trochilidae, 125 
Trogons, 105 

Tropical vegetation, concluding re- 
marks on, 65 
probable causes of its luxuriance 

and variety, 66 
Mr. Belt on, 67 

Tropical birds, dull-coloured, 110 
coloration of, 110 
green, 110 
Tropics, limitation of, 3 

aspects of animal life in, 121 
Trunks, variety of, 31, 33 

probable cause of flowering, 34 
Twilight, short at equator, 21 
Typical colours, 179 



V. 

Vanda lowii, 51 
Vampyre-bats, 119 



Variation, how influenced, 142 

Vegetation, equatorial, 27 

Vipers, green, 114 

Vitality a cause of bright colour, 193 



w. 

WARNING COLOURS, theory of, 189 
Wasps and bees, 90 
Wave-lengths of coloured rays, 180 
Weale, Mr. J. P. Mansel, on plants of 

Karoo, 223 

on Ajuga ophrydLs, 223 
Webber Mr. on food of humming-birds, 

137 
West-Indian Islands, large and brilliant 

butterflies of, 261 

peculiarly coloured birds of, 262 
Whip-snakes, 114 
White animals poisoned where black 

escape, 265 

White colours influencing sense-percep- 
tion, 265 
White colour doubly prejudicial to 

animals, 266 

White tropical birds, 110 
Wilson, Dr. on potteiy from N. American 

mounds, 295 

Winds, influence of on temperature, 11 
direction of near equator, 11, 12 
cause of cold near equator, 12, 13 
Wolves in England show its union with 

continent, 305 
Woods from equatorial forest-trees, 36 



ZEBRA, possible use of its stripes, 197 
Zingiberaceae, 47 
Zoological regions, 314 
Zoological regions of the New World 
329 



LONDON I P.. CLAY, SONS, .VXD TAYLOR, bR::.U' SiKEET HILL 



WORKS 



ALFRED RUSSEL WALLACE. 



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dently of Mr. Darwin, the theories which he so ably defends." 



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