This breaking of the egg in a proper manner is as interesting as two well-known facts, one of which may be observed by anybody in the habits of American and other Monkeys. Sometimes a little Monkey has a nut given him, and he is not strong enough to crack it. He will look up into your face with a meaning glimmer of his eyes, and hand you the nut again. Crack it for him, and he receives it as a matter of course. Formerly one of the large Monkeys in the Zoological Gardens had weak teeth, and he used to break open the nuts with a stone, and Mr. Darwin was assured by the keepers that this animal, after using the stone, hid it in the straw, and would not let any other Monkey touch it. Rengger taught one to open palm-nuts by breaking them with a stone, and so satisfied was it with its performance, that it soon began to experiment on other kinds of nuts, and then it began upon boxes. It also crushed off with blows of a stone the soft rind of a fruit that had a disagreeable flavour, in order to get at the luscious food within. Some interesting observations were male by Rengger in Paraguay on the diseases of these Monkeys in their natural state. One kind of Cebus was found liable to what we call “colds,” or, medically speaking, catarrh. It had all the usual symptoms; was uncomfortable evidently for a while, had a stuffiness in the head, and then its nose ran like that of a child. If the colds occurred over and over again the same result took place as happens in man, for symptoms of consumption came on, and death ensued. Moreover, these same Monkeys suffered from apoplexy, inflammation of the bowels, and even from cataract in the eye. Even the tiny ones suffered like human babies in cutting their second set--or rather in shedding their milk, or first set--of teeth. They became feverish, and often died with the symptoms of fever on them. The same author saw a Capuchin Monkey taking great and affectionate care of its infant. The flies were teasing it, and the mother drove them away as sedulously as possible. When in its native woods the Cebus Azaræ utters at least six distinct sounds when it is excited, and these seem to produce corresponding feelings in the Monkeys which are listening. The Capuchins range from Costa Rica to Paraguay. CHAPTER XI. THE CEBIDÆ (_concluded_)--THE SQUIRREL MONKEYS--DOUROUCOULIS--SAKIS.