It is very remarkable that an animal so large, so peculiar, and of such a high type of form as the Orang-utan, should be confined to so limited a district--to two islands, and those almost the last inhabited by the higher Mammalia; but in the Mid-Tertiary Period, and just before the formation of the Himalayan Mountains, Orangs lived on the continent of India, and their remains have been found fossilised. With what interest must every naturalist look forward to the time when the caves and Tertiary deposits of the tropics may be thoroughly examined, and the past history and earliest appearance of the great man-like Apes be at length made known! The Orang-utans appear, from what has been written by all competent observers, to be of two kinds, the one larger, and the other smaller in stature; the first is called _Simia satyrus_, and the other _Simia morio_. Simia is translated in old Latin dictionaries as an Ape, or Jackanapes, and the term was used to designate the tribe or genus which should include all the species or kinds of man-shaped Apes. But after a while there was thought to be sufficient reasons for separating the Troglodytes from the genus Simia, and therefore this last-named one, instead of comprising the Gorilla, the Nschiego, the Koolo, the Soko, and the Chimpanzee, has but the Orang-utan. Why this separation should have taken place is of course a very natural question, and the answer is that there are sufficient differences in the construction of the Orangs and the Chimpanzees and the others to warrant it. There is a greater structural difference between the Orang and the Chimpanzee than between this last and any of its congeners, that is to say, species included in the genus Troglodytes. Moreover, on examining several skulls and skeletons of all these kinds, it seems as if, whilst the African Troglodytes may have descended from a common ancestor, probably a Baboon, the Orang-utan could not have come from the same stock. There are some important distinctions in the anatomy of the Orang, some of which are evidently produced by adaptation to a particular habit or mode of life, and others in which the results of cause and effect cannot be traced.