DISTRIBUTION.--This species is confined to Sumatra and to Siam. In the former country it is known by the name of "Ongka" by the Malays, who, with the keen powers of observation they possess in regard to all natural objects, recognise two varieties, the white or yellow variety--"Ongka putih," and the black one--"Ongka itam" (_H. rafflesi_). The capped variety (_H. pileatus_) with its variously coloured forms inhabits Siam. HABITS.--The habits of the "Ongka" are very similar to those of the Wau-wau, or the Siamang (_H. syndactylus_). The natives, however, aver that it is much more silent, rarely howling as either of these other two species do. They are also seen generally in quite small troops, and often in pairs only. "It is almost impossible," writes Mr. Martin of a specimen that lived formerly in the Zoological Gardens, "to convey in words an idea of the quickness and graceful address of her movements: they may, indeed, be termed aërial, as she seems merely to touch, in her progress, the branches among which she exhibits her evolutions. In these feats her hands and arms are the sole organs of locomotion; her body hanging as if suspended by a rope, sustained by one hand (the right, for example), she launches herself by an energetic movement to a distant branch, which she catches with the left hand. But her hold is less than momentary; the impulse for the next {154}launch is acquired; the branch then aimed at is attained by the right hand again, and quitted instantaneously, and so on, in alternate succession. In this manner spaces of twelve and eighteen feet are cleared with the greatest ease, and uninterruptedly for hours together, without the slightest appearance of fatigue being manifested; and it is evident that if more space could be allowed, distances very greatly exceeding eighteen feet would be as easily cleared.... Sometimes on seizing a branch in her progress, she will throw herself, by one arm only, completely round it, making a revolution with such rapidity as almost to deceive the eye, and continue her progress with undiminished velocity. It is singular to observe how suddenly this Gibbon can stop, when the impetus given by the rapidity and distance of her swinging leaps would seem to require a gradual abatement of her movements. In the very midst of her flight a branch is seized, the body raised, and she is seen, as if by magic, quietly seated on it, grasping it with her feet.... A live bird was let loose in her apartment; she marked its flight, made a long swing to a distant branch, caught the bird with one hand in her passage, and attained the branch with her other hand; her aim, both at the bird and the branch, being as successful as if one object only had engaged her attention. It may be added, that she instantly bit off the head of the bird, picked its feathers, and then threw it down, without attempting to eat it." II. THE WAU-WAU GIBBON. HYLOBATES LEUCISCUS. A. _Javan Race_ (_H. leuciscus_).