like the raiders of Vatersay. Darwin argues that the tail-brush may have
materially helped to secure the survival of those species of beasts that
possessed it, and no doubt he is right.

The subject is interminable, but we must give a passing glance to some
quixotic tails. The opossum scampers up a tree, carrying all her
numerous family on her back, and they do not fall off because each
infant is securely moored by its own tail to the uplifted tail of its
mother. The opossum is a very primitive beast, and so early and useful
an invention should, one would think, have been spread widely in after
time; but there appears to be some difficulty in developing muscles at
the thin end of a long tail, for the animals that have turned it into a
grasping organ are few and are widely scattered. Examples are the
chameleon among lizards, our own little harvest mouse, and, pre-eminent
above all, the American monkeys. To a howler, or spider-monkey, its
long tail is a swing and a trapeze in its forest gymnasium. Humboldt saw
(he says it) a cluster of them all hanging from a tree by one tail,
which proceeded from a Sandow in the middle. I should like to see that
too. It is worth noting, by the way, that no old-world monkey has
attained to this application of its tail.

Then there is the beaver, whose tail I am convinced is a trowel. I know
of no naturalist who has mentioned this, but such negative evidence is
of little weight. The beaver, as everybody knows, is a builder, who cuts
down trees and piles log upon log until he has raised a solid, domed
cabin from seven to twenty feet in diameter, which he then plasters over
with clay and straw. If he does not turn round and beat the work smooth
with his tail, then I require to know for what purpose he carries that
broad, heavy, and hard tool behind him.