1905. | MR. R. I, POCOCK ON A HAINAN GIBBON, 179 
stand third in climbing, third in bipedal and first in quadrupedal 
powers. 
Since, therefore, the action of Monkeys, whether Cercopithecide, 
Cebide, or Hapalide, and of Lemurs is essentially quadrupedal, 
the fore and hind limbs being used to an approximately equal 
extent, both .in terrestrial and arboreal locomotion, it may be 
inferred that the Chimpanzees have departed least in these 
respects from the primitive Primate stock; the Gorillas a little 
more in the line of bipedal erection and, concomitantly, loss of 
climbing power; the Orangs still more in the direction of loss 
of terrestrial activity and increase of arboreal expertness; the 
Gibbons most of all in the line of bipedal activity, dexterity in 
hand-climbing, and loss of quadrupedal power. 
This serial arrangement of the Apes is the exact opposite 
of the one prevalent in text-books, where the order adopted is 
based upon structure with Man placed first as the standard for 
comparison. It suggests that for the origin of Gibbons we must 
look not to forms resembling any known Cercopithecoid type, but 
to forms which had already acquired the Simiine or Authropo- 
morphine characteristics and had either lost or never learnt the 
method and skill in climbing found in the former group. They may 
have started from a type somewhat on a level with the Chimpanzees 
with respect to terrestrial and arboreal activity ; and to swing with 
greater facility from tree to tree and to obviate the risk of injury 
in ease of a fall, it is highly probable that they have become 
dwarfed in stature and grown lighter in build. Their muscularity 
and length of arm, slightness of body and strength of leg, all factors 
of importance in enabling them to traverse the jungle and, in 
case of 2 miss or a breaking branch, to drop lightly to the ground 
and run to the nearest tree for safety, were probably perfected 
concomitantly. That Gibbons are able to drop with safety a 
considerable distance is substantiated by the fact that Mr. de 
St. Croix has seen his specimen come to the ground without 
injury from a height of about 20 feet. When leaping to the 
ground Gibbons swiftly draw up the knees as the feet touch, 
exactly as a man does under similar circumstances, to break the 
shock. 
Another interesting feature connected with the habits of the 
Anthropoid Apes is the size of their ears. T have already suggested 
that the difference in size between the ears of the Orang and 
those of the Chimpanzee may be connected with the difference of 
habits of the two animals. ‘The Orang lives a more arboreal and. 
therefore a safer life than the Chimpanzee, which requires quick 
heaving to enable it to escape to the trees when feeding on the 
ground *, Gibbons also, which have relatively large ears, need 
auditory acuteness for the same purpose as Chimpanzees. This 
explanation, however, is not complete and appears at first sight to 
be contradicted by the case of the Gorillas, which have small ears 
* ‘Nature,’ Oct. 11th, p. 585 (1900). © 
jake 
