It may be well, in the first place, to point out that the terms “ape,” “baboon,” and “monkey” are no longer used as they were by the older naturalists. Formerly the term “ape” was limited to tailless simians having no cheek-pouches, and the same number of teeth as man; the term “baboon” to short-tailed simians with dog-shaped heads; and the term “monkey,” unless used generically, to the long-tailed species. This was the usage suggested by Ray, and adopted systematically thirty or forty years ago. But it is no longer followed, though no uniform classification has been substituted for the old arrangement. Thus Mivart divides the apes into two classes—calling the first the _Simiadæ_, or Old World apes; and the second the _Cebidæ_, or New World apes. He subdivides the _Simiadæ_ into (1) the _Siminæ_, including the gorilla, chimpanzee, orang, and gibbon; (2) the _Semnopithecinæ_; and (3) the _Cynopithecinæ_; neither of which subdivisions will occupy much of our attention here, save as respects the third subdivision of the _Cynopithecinæ_, viz., the _Cynocephali_, which includes the baboons. The other great division, the _Cebidæ_, or New World apes, are for the most part very unlike the Old World apes. None of them approach the gorilla or orang-outang in size; most of them are long-tailed; and the number and arrangement of the teeth is different. The feature, however, which most naturalists have selected as the characteristic distinction between the apes of the Old World and of the New World is the position of the nostrils. The former are called Catarhine, a word signifying that the nostrils are directed downwards; the latter are called Platyrhine, or broad-nosed. The nostrils of all the Old World apes are separated by a narrow cartilaginous plate or septum, whereas the septum of the New World apes is broad. After the apes come, according to Mivart’s classification, the half-apes or lemuroids. I ought, perhaps, to have mentioned that Mivart, in describing the lemuroids as the second sub-order of a great order of animals, the Primates, speaks of a man as (zoologically speaking) belonging to the first sub-order. So that, in point of fact, the two sub-orders are the Anthropoids, including the Anthropos (man) and the Lemuroids, including the lemur. The classification here indicated will serve our present purpose very well. But the reader is reminded that, as already mentioned, naturalists do not adopt at present any uniform system of classification. Moreover, the term _Simiadæ_ is usually employed—and will be employed here—to represent the entire simian race, _i.e._, both the Simiadæ and the Cebidæ of Mivart’s classification.