In 1854 he sailed for the Malay Archipelago, where nearly eight years were spent in exploring the region from Sumatra to New Guinea. The large and varied outcome of that labour was embodied in numerous papers communicated to learned societies and scientific journals, and in a series of delightful books from The Malay Archipelago, first published in 1869, to Island Life, published in 1880. Among the minor results of his extensive travels--for all else that Wallace did pales before the great discovery which links his name with Darwin's--was the establishment of a line, known as "Wallace's," which divides the Malay Archipelago into two main groups, "Indo-Malaysia and Austro-Malaysia, marked by distinct species and groups of animals." That line runs through a deep channel separating the islands of Bali and Lombok; the plants and animals on which, although but fifteen miles of water separate them, differ from each other even more than do the islands of Great Britain and Japan. "A similar line, but somewhat farther east, divides on the whole the Malay from the Papuan races of man." Among the more fugitive contributions which mark Mr. Wallace's approach to a solution of the problem in quest of which he and Bates went to the Amazons is a paper On the Law which has Regulated the Introduction of New Species, published in the Annals and Magazine of Natural History, 1855. In this he shows that some form of evolution of one species from another is needed to explain the geological and geographical facts of which examples are given.