1905.] MK. R. 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 neai- by, and their great stretch of ai-m 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 pui'pose 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 hand-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 terresti-ial progression. Moreovei-, within the limits of 

 the entire order, they ai-e 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 gi'eat pre- 

 cision and strength, and pass with speed from branch to branch in 

 virtue of the great i^ropelling power in their 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 Baboou or Macaque that could catch a Mangabey 

 single-handed, given equal conditions as to health and age, in a large-sized cage. 



Proc. Zool. Soc— 1905, Vol. II. No. XII. 12 



