Introduction.

The following pages have been written almost entirely from the historical stand-point. Their principal object has been to give some account of the impressions produced on the mind of Darwin and his great compeer Wallace by various difficult problems suggested by the colours of living nature. In order to render the brief summary of Darwin 's thoughts and opinions on the subject in any way complete, it was found necessary to say again much that has often been said before. No attempt has been made to display as a whole the vast contribution of Wallace ; but certain of its features are incidentally revealed in passages quoted from Darwin 's letters. It is assumed that the reader is familiar with the well-known theories of Protective Resemblance, Warning Colours, and Mimicry both Batesian and Müllerian. It would have been superfluous to explain these on the present occasion ; for a far more detailed account than could have been attempted in these pages has recently appeared1. Among the older records I have made a point of bringing together the principal observations scattered through the note-books and collections of W. J. Burchell. These have never hitherto found a place in any memoir dealing with the significance of the colours of animals.

Incidental Colours.

Darwin fully recognised that the colours of living beings are not necessarily of value as colours, but that they may be an incidental result of chemical or physical structure.