Next come the spider monkeys, so called from their slender bodies and
enormously long limbs and tail. In these monkeys the tail is so long,
strong, and perfect, that it completely takes the place of a fifth hand.
By twisting the end of it round a branch the animal can swing freely in
the air with complete safety; and this gives them a wonderful power of
climbing end passing from tree to tree, because the distance they can
stretch is that of the tail, body, and arm added together, and these are
all unusually long. They can also swing themselves through the air for
great distances, and are thus able to pass rapidly from tree to tree
without ever descending to the ground, just like the gibbons in the
Malayan forests. Although capable of feats of wonderful agility, the
spider monkeys are usually slow and deliberate in their motions, and
have a timid, melancholy expression, very different from that of most
monkeys. Their hands are very long, but have only four fingers, being
adapted for hanging on to branches rather than for getting hold of small
objects. It is said that when they have to cross a river the trees on
the opposite banks of which do not approach near enough for a leap,
several of them form a chain, one hanging by its tail from a lofty
overhanging branch and seizing hold of the tail of the one below it,
then gradually swinging themselves backward and forward till the lower
one is able to seize hold of a branch on the opposite side. He then
climbs up the tree, and, when sufficiently high, the first one lets go,
and the swing either carries him across to a bough on the opposite side
or he climbs up over his companions.

Closely allied to the last are the woolly monkeys, which have an equally
well developed prehensile tail, but better proportioned limbs, and a
thick woolly fur of a uniform gray or brownish color. They have well
formed fingers and thumbs, both on the hands and feet, and are rather
deliberate in their motions, and exceedingly tame and affectionate in