The degrees of their so much vaunted intelligence, which is in general very limited, and rarely capable of being made subservient to the purposes of man, vary almost as much as the ever-changing outline of their form. From the grave and reflective Oran-Otang, whose docility and powers of imitation in his young state have been the theme of so much ridiculous exaggeration and sophistical argumentation, to the stupid and savage Baboon, whose gross brutality is scarcely relieved by a single spark of intelligence, the gradations are regular and easy. A remarkable circumstance connected with the developement of this faculty, or perhaps we should rather say, with its gradual extinction, consists in the fact that it is only in young animals which have not yet attained their full growth, that it is capable of being brought into play; the older individuals, even of the most tractable races, entirely losing the gaiety, and with it the docility, of their youth, and becoming at length as stupid and as savage as the most barbarous of the tribe. The Monkeys of the Old and of the New World differ from each other in several remarkable points, some of which are universally characteristic of all the species of each, while others, although affording good and tangible means of discrimination, are but partially applicable. Thus the nostrils of all the species inhabiting the Old World are anterior like those of man, and divided only by a narrow septum. In those of the New World, on the contrary, they are invariably separated by a broad division, and consequently occupy a position more or less lateral. In the former again the molar teeth are uniformly five in number, crowned with obtuse and flattened tubercles; while in the latter they are either six in number, or in the few anomalous cases in which they are limited to five, and which are peculiar to a group that ought to occupy an intermediate station between the Monkeys and the Insect-eating Carnivora, their crowns are surmounted by sharp and somewhat elevated points. The tails of all the American Monkeys are of great length, but they differ more or less from each other in the power of suspending themselves by means of that organ, a faculty which is nevertheless common to the greater number of them, and of which those of the Old World are entirely destitute. On the other hand the American species never exhibit any traces of the callosities or of the cheek-pouches, which are so common among the Asiatic and African races.