29 
requiring to be kept up, either by touching the ground with 
the knuckles, first on one side then on the other, or by up-— 
lifting the arms so as to poise it. As with the Chimpanzee, 
the whole of the narrow, long sole of the foot is placed upon 
the ground at once and raised at once, without any elasticity 
of step.” 
After this mass of concurrent and independent testimony, 
it cannot reasonably be doubted that the Gibbons commonly 
and habitually assume the erect attitude. 
But level ground is not the place where these animals can 
display their very remarkable and peculiar locomotive powers, 
and that prodigious activity which almost tempts one to rank 
them among flying, rather than among ordinary climbing 
mammals. 
Mr. Martin (1. c. p. 430) has given so excellent and graphic 
an account of the movements of a Hylobates agilis, living in 
the Zoological Gardens, in 1840, that I will quote it in full: 
“Tt is almost impossible to convey in words an idea of the 
quickness and graceful address of her movements: they may 
indeed be termed aerial, as she seems merely to touch in her 
progress the branches among which she exhibits her evolu- 
tions. In these feats her hands and arms are the sole organs 
of locomotion; her body hanging as if supended 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 launch is ac- 
quired: 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 un- 
interruptedly, 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 ; so that 
Duvaucel’s assertion that he has seen these animals launch 
