1905. | MR. 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 thei 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 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 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 then 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 actsas a balancer, like the pole 
of a tight-rope dancer. Monkeys of this kind leap with great pre- 
cision and strength, and pass with speed from branch to branch in 
virtue of the great propelling power in their hind-quarters. ‘They 
ave 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. 
* T have never yet seen the Baboon or Macaque that could catch a Mangabey 
single-handed, given equal conditions as to health and age, in a large-sized cage. 
Proc. Zoou. Soc.—1905, Vou. Il. No. XII. 12 
