The Gibbon shows off to poor advantage in a cage, but in the tree-tops it is a wonderful creature. It is like a long-armed skeleton clothed with skin and hair, animated by the spirit of an Ariel. In its home in the jungles of Borneo and southeastern Asia, it dwells in hilly forests, and never descends to the earth. When attacked, it flees down-hill, if possible, and it seems actually to fly through the tree-tops. It boldly flings itself forward through space, grasps with its hands the first available branch, swings underneath, feet foremost, and after another flight presently catches with its feet, thus actually making revolutions as it goes. Its progress is so swift and so silent that successful pursuit is impossible to any enemy not provided with wings. This animal is naturally very timid, but does not hesitate to expose itself to mortal danger when its young are in distress. In captivity gibbons are shy and nervous, and take life very seriously. [Illustration: HUMBOLDT WOOLLY MONKEY.] Old-World Monkeys. The Baboons have been specially designed by Nature for life upon the ground, surrounded by dangerous enemies. But for their big canine teeth, their fierce tempers and bull-dog courage, backed by a fine combination of strength and agility, the lions, leopards, hyenas and jackals of Africa would have exterminated them all, ages ago. They were not formed to become hand-organ beasts of burden, nor even companions to man, but rather to fight off their enemies, and bluff even the king of beasts when occasion requires. In captivity, their strength and ferocity always inspires respect, and sometimes genuine terror. At all times they require to be treated as dangerous animals. Of the various species of baboons on exhibition in the Primate House, the full-grown Mandrill is the most interesting, and wonderful. It seems like an animal not of this earth, and reminds the visitor of one of the great beasts of the visions of St. John the Divine. The home of this species is in West Africa, and it is found from Senegambia to the Congo. The long shaggy hair, lion-like appearance, the peculiar color markings of the face, and the indescribable grimaces, instantly fix the attention of every visitor. The Hamadryas Baboon, with long side whiskers and cape of long hair, is one of the handsomest animals of this group. Its explosive, ear-racking cry is almost as startling to visitors as a cannon-shot. The Golden Baboon has the liveliest disposition and the best temper possessed by any baboon. Young specimens are full of good-natured mischief, and are much given to hectoring their cage-mates. The Long-Armed Yellow Baboon is quite at home in the Primate House, and has bred here. It is a good species to keep in captivity.