CONTENTS.

1. 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 Remarks 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-Picariæ-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

IV. HUMMING-BIRDS: 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-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

pages 124-157

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 158-220

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

pages 221-218

VII. BY-PATHS IN THE DOMAIN OF BIOLOGY.

BEING AN ADDRESS DELIVERED TO THE BIOLOGICAL SECTION OF 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 OF

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

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 Pale-

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 301-347

TROPICAL NATURE,

AND OTHER ESSAYS.