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Show 1 9 0 5 . ] MR. K. I. POCOCK ON A HAINAN GIBBON. 177 abandoned the habit of employing the hand at the time when an injury deprived her of the use of her right arm. And since the left is frequently occupied in supporting herself upon the bars or perches in the cage, she has no hand available for the purpose of drinking without quitting her hold. This method of hand-drinking, probably common to all Gibbons, may have arisen in connection with their arboreal life. To avoid descending to the ground, they would naturally lick the rain-drops off the leaves near by, and their great stretch of arm would enable them to wipe the water off foliage hanging beyond reach of the mouth, the hairy back of the hand being clearly more fitted for the purpose than the smooth palm. In connection with this habit, it is interesting to recall the story told by Duvaucel of female Gibbons carrying their young to the waterside and washing their faces with their hands. This alleged proceeding, presumably witnessed in the jungle, can hardly, I think, be accepted without confirmation, on account of the absence of any obvious reason for the ablutions. If the young Gibbons of which the tale is told were hanging, as is their wont, to the breasts of the mothers, the action of lxand-drinking by the latter might very easily be mistaken at a distance for the face-washing. Amongst " quadrumanous " Primates the Gibbons have no equals in proficiency in the use of the arms for arboreal and the legs for terrestrial progression. Moreover, within the limits of the entire order, they are only surpassed in bipedal activity by the specialised biped Man. Although able to stand and walk to a very limited extent, Monkeys are essentially quadrupedal and employ their arms and legs to an approximately equal extent in traversing the level ground, scaling rocks, or climbing trees. Generally speaking, the most active climbers are long non-prehensile tailed species, such as the Mangabeys*, in which the tail acts as a balancer, like the pole of a tight-rope dancer. Monkeys of this kind leap with great precision and strength, and pass with speed from branch to branch in virtue of the great propelling power in then hind-quarters. They are specialised for that manner of progression, which only differs in degree of perfection from that of other Monkeys and Lemurs as a whole. The method, however, is entirely distinct from that practised by the Gibbons, which swing from branch to branch, with the legs tucked up out of harm's way against the body, the motor power lying exclusively in the arms. Both groups have been specialised for arboreal progression, but along totally different lines; and it is as difficult to believe that the Gibbons, expert gymnasts though they be, have been derived from active long-tailed climbers, like the Mangabeys or Langurs for instance, as it is to believe that the tail-swimming Cetaceans have been derived from forms like the flipper-swimming Seals. * I have never yet seen the Baboon or Macaque that could catch a Mangabey single-hatided, given equal conditions as to health and age, in a large-sized cage. P roc. Z o o l. S oc.-1905, V o l . II. No. XII. 12 |