Transcriber's Notes: Variations in spelling, punctuation and hyphenation have been retained except in obvious cases of typographical error. "Haeckel" and "Hæckel" were used interchangeably and have been standardized to "Haeckel". Image tags interrupting paragraphs have been moved. Footnotes have been moved to end of chapters. End of Project Gutenberg's Colouration in Animals and Plants, by Alfred Tylor