escape, when the bush is roughly shaken, is to drop itself down on the
earth, where it lies simulating death. In falling, it drops just as a
green leaf would drop, that is, not quite so rapidly as a round, solid
body like a beetle or spider. Now in the bushes there is another Epeira,
in size and form like the last, but differing in colour; for instead of
a vivid green, it is of a faded yellowish white--the exact hue of a
dead, dried-up leaf. This spider, when it lets itself drop--for it has
the same protective habit as the other--falls not so rapidly as a green
freshly broken off leaf or as the green spider would fall, but with a
slower motion, precisely like a leaf withered up till it has become
almost light as a feather. It is not difficult to imagine how this comes
about: either a thicker line, or a greater stiffness or tenacity of the
viscid fluid composing the web and attached to the point the spider
drops from, causes one to fall slower than the other. But how many
tentative variations in the stiffness of the web material must there
have been before the precise degree was attained enabling the two
distinct species, differing in colour, to complete their resemblance to
falling leaves--a fresh green leaf in one case and a dead, withered leaf
in the other!

The Tetragnatha--a genus of the Epeira family, and known also in
England--are small spiders found on the margin of streams. Their bodies
are slender, oblong, and resembling a canoe in shape; and when they sit
lengthwise on a stem or blade of grass, their long, hair-like legs
arranged straight before and behind them, it is difficult to detect
them, so closely do they resemble a discoloured stripe on the herbage. A
species of Tetragnatha with a curious modification of structure abounds
on the pampas. The long leg of this spider is no thicker than a bristle
from a pig's back, but at the extremity it is flattened and broad,
giving it a striking resemblance to an oar. These spiders are only found