Like most of the guenons, green monkeys go about in droves, each under the leadership of an old male, who wins and keeps his position by fighting all his rivals. Strange to say, each of these droves seems to have its own district allotted to it; and if by any chance it should cross its boundary, the band into whose territory it has trespassed will at once come and fight it, and do their utmost to drive it back. Wouldn't it be interesting to know how the animals mark out their own domains, and how they let one another know just how far they will be permitted to go? Our second example of the guenons is the diana monkey, which you may at once recognize by its long, pointed, snow-white beard. It seems to be very proud of this beard, and while drinking holds it carefully back with one hand, in order to prevent it from getting wet. Why is it called the "diana" monkey? Because of the curious white mark upon its forehead, which is shaped like the crescent which the ancients used to think was borne by the goddess Diana. It is a very handsome animal, for its back is rich chestnut brown in color, and the lower part of its body is orange yellow, while between the two is a band of pure white. Its face and tail and hands and feet are black. It is a very gentle animal, and is easily tamed. THE MANGABEYS These are very odd-looking monkeys, for they all have white eyelids, which are very conspicuous in their sooty-black faces. Indeed, they always give one a kind of idea that they must spend their whole lives in sweeping chimneys. They are among the most interesting of all monkeys to watch, for they are not only so active and full of life that they scarcely seem able to keep still, but they are always twisting their bodies about into all sorts of strange attitudes. When in captivity they soon find out that visitors are amused by their antics, and are always ready to go through their performances in order to obtain a nut or a piece of cake. Then they have an odd way, when they are walking about their cages, of lifting their upper lips and showing their teeth, so that they look just as if they were grinning at you. And instead of carrying their tails behind them, as monkeys generally do, or holding them straight up in the air, they throw them forward over the back, so that the tip comes just above the head. Only four kinds of mangabey are known, and they are all found in Western Africa. MACAQUES