While discussing the general laws and phenomena of colour in the organic world, and its special developments 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 distinguish 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 Relation to Sex.” Being strongly impressed with the importance and fundamental truth of this theory, I published my first sketch of the subject in Macmillan’s 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 Climate 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
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
III. Animal Life in the Tropical Forests.