CONTENTS xi 
IV. Humine-Birps: As Intusrratine tHe LUXURIANOE OF 
TRopicaL NATURE 
Structure—Colours and Ornaments—Descriptive Names—The Motions and 
Habits of Humming-birds—Display of Ornaments by the Male—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 
: Pages 312-337 
V. Tus Contours or 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—Normal Colours—The 
Nature of Colour—How Animal Colours are produced—Colour a 
Normal Product of Organisation—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 neutralising Sexual Selection—Greater Brilliancy of some Female 
Birds — Colour - development as illustrated by Humming - birds — 
—Theory of Normal Colours—Local causes of Colour-development— 
The influence of Locality on Colour in Butterflies and birds—Sense- 
perception influenced by Colour of the Integuments—Summary on 
Colour-development in Animals. < 7 . 888-394 
VI. Tue Contours of PLANTS AND THE ORIGIN OF THE 
Conour-SENSE 
Source of Colouring Matter in Plants—Protective Coloration and Mimicry 
in 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 Beauti- 
ful—Why Allied Species of Flowers differ in Size and Beauty— 
Absence of Colour in Wind-fertilised Flowers—The same Theory of 
Colour applicable to Animals and Plants—Relation of the Colours 
