V. 



THE COLOUKS 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 

 Develoi^ment — 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- 



