equilibrium, as rope-dancers are assisted by long poles at fairs. Their
progression was not by placing one foot before the other, but by
simultaneously using both, as in jumping." Dr. Salomon Muller also
states that the Gibbons progress along the ground by a short series of
tottering jumps, effected only by the hind limbs, the body being held
altogether upright.

[footnote] *'Boston Journal of Natural History', vol. i., 1834.

But Mr. Martin (l. c. p. 418), who also speaks from direct observation,
says of the Gibbons generally:

"Pre-eminently qualified for arboreal habits, and displaying among the
branches amazing activity, the Gibbons are not so awkward or
embarrassed on a level surface as might be imagined. They walk erect,
with a waddling or unsteady gait, but at a quick pace; the equilibrium
of the body requiring to be kept up, either by touching the ground with
the knuckles, first on one side then on the other, or by uplifting 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."

FIG. 8.--Gibbon ('H. pileatus'), after Wolf.

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