The Apes which have formed the subject of the previous chapters, and which, from their greater or less resemblance to man, have been called the _Anthropomorpha_, have long arms, short legs, and no tails. The great length of the fore limb distinguishes them not only from man, but also from all the other Quadrumana, and so does the relative shortness of the hinder limbs. The length of limb is thus sufficient to afford data for classifying the Quadrumana of the Old World in two great groups, of which the Anthropomorpha form the first, and the rest of the Monkeys the second. In these the fore limb is invariably the _shortest_, and the hinder one the _longest_; so that there is exactly the reverse condition of that observed in the great Apes. With regard to the tail question, it may be stated that, whilst many species have very long tails, others have them of moderate length, and a few have none. The Monkeys of this second group, or the Cynomorpha, all of which live in the Old World, have a thin division (septum) between the nostrils, whose openings look downwards, or downwards and outwards. They are Catarhine Quadrumana (see page 3), and many have cheek-pouches, but not all, whilst all have the peculiar pads, more or less brightly coloured, which are placed where the animal sits, or on the swelling of the haunch-bone. All these Old World Monkeys have the same number of teeth as the Apes already described, and arranged in the same manner, and most have a laryngeal or air pouch; but there is great diversity in their size, shape, and in the method of progression of the body and shape of the head, and also in the construction of the brain and internal organs. Moreover, the arrangement of the muscles and of the back-bone differs. The presence or absence of the cheek-pouches, the peculiarity in the shape of the teeth, the shape of the body and limbs, and the method of moving along, are all matters of importance to the zoologist, for by them he is enabled to arrange these Monkeys in genera and species, so as to give the naturalist the proper name of the kind whose habits he may be studying. Moreover, the comparative anatomist, in examining the insides of these creatures, and explaining their peculiarities of internal construction, is able to account for many habits and the presence of many structures, as well as to assist the zoologist. For, a classification, to be good for anything, must be more than skin deep, and must depend upon the differences in those parts which are not readily changed by habits or peculiar methods of life.