284 SYSTEMATIC BIOLOGY VOL. 63

evidence for mass migration of species, and drastic and repeated climatic changes throughout the earth’s history. The book has two parts. The first is The Dispersal of Organisms: its Phenomena, Laws, and Causes (10 chapters), in which the biogeography of plants and animals across the planet is explored in relation to the effects of climate and dispersal. Wallace particularly emphasizes changes of climate involving glacial epochs, which is something that he also covered in several of his research papers, producing thefirst theoryof continental glaciationbased on a combination of geographical and astronomical causes. He also covers the estimated age of the earth, and the relative permanence of continents compared with many of the islands. Ultimately, of course, he considers evolution to be “the key to distribution ” of all living things; and conversely, geographical distribution was always his strongest evidence in favor of biological evolution. The second part of the book is Insular Faunas and Floras (14 chapters), where case studies are examined for most of the major and/or biogeographically significant islands around the world. These include: (i) oceanic islands, such as the Azores, Bermuda