The opening of Preface
The present work is an attempt to collect and summarize the existing information on the Distribution of Land Animals; and to explain the more remarkable and interesting of the facts, by means of established laws of physical and organic change.
The main idea, which is here worked out in some detail for the whole earth, was stated sixteen years ago in the concluding pages of a paper on the "Zoological Geography of the Malay Archipelago," which appeared in the Journal of Proceedings of the Linnean Society for 1860; and again, in a paper read before the Royal Geographical Society in 1863, it was briefly summarized in the following passage:--
"My object has been to show the important bearing of researches into the natural history of every part of the world, upon the study of its past history. An accurate knowledge of any groups of birds or of insects and of their geographical distribution, may enable us to map out the islands and continents of a former epoch,--the amount of difference that exists between the animals of adjacent districts being closely related to preceding geological changes.