ae s THE SERVICE OF TAILS 77 
prehenstbility in its tip, similar to that in the toes 
of perching-birds, which close tightly around a 
twig, without any effort on the bird’s part, simply 
as the result of the pressure of its weight. 
Charles Waterton points out that this faculty is 
of manifest advantage to the animal, either when 
sitting in repose on the branch of a tree or during 
its journey onward through the gloomy recesses 
of the wilderness. ‘ You may see this monkey,” 
he writes, “catching hold of the branches with 
its hands, and at the same time twisting its tail 
around one of them, asif in want of additional 
support; and this prehensile tail is sufficiently 
strong to hold the animal in its place, even when 
all its four limbs are detached from the tree, so 
that it can swing to and fro, and amuse itself, 
solely through the instrumentality of its prehen- 
sile tail— which, by the way, would be of no man- 
ner of use to it did accident or misfortune force 
the monkey to take up a temporary abode upon 
the ground. For several inches from its extremity, 
by nature and by constant use, this tail has as- 
sumed somewhat the appearance of the inside of 
a man’s finger, entirely denuded of hair or fur 
underneath, but not so on the upper part.” 
Prehensibility is equally well developed in the 
naked, rat-like tail of the possum of our Northern 
woods, and to a less extent in the manis; in the 
Old World, or true, chameleon ; in the tips of the 
tails of tree-clinging serpents; and among fishes 
