Wallace Line connected islands on the west (Sumatra, Java, etc.) with the Asian continent and with similar wildlife, and islands on the east such as New Guinea were connected to Australia and were characterised by the presence of marsupials. Wallace used his extensive travel in the region to propose a line to the east of Bali since "all the islands eastward of Borneo and Java formed part of an Australian or Pacific Continent, from which they were separated." The name 'Wallace's Line' was first used by Thomas Huxley in an 1868 paper to the Zoological Society of London, but showed the line
Alfred Russel Wallace the Cambridge University Museum of Zoology. His observations of the marked zoological differences across a narrow strait in the archipelago led to his proposing the zoogeographical boundary now known as the Wallace line. Wallace collected more than 126,000 specimens in the Malay Archipelago (more than 80,000 beetles alone). Several thousand of them represented species new to science. One of his better-known species descriptions during this trip is that of the gliding tree frog "Rhacophorus nigropalmatus", known as Wallace's flying frog. While he was exploring the archipelago, he refined his thoughts about evolution and had his famous insight on natural selection.