CONTENTS 
xi 
IV. Humming-Birds : As Illustrating the Luxuriance op 
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. The Colours op 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 .... 338-394 
VI. The Colours op Plants and the Origin op the 
Colour-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 
