re first
offered, the frogs sprang at them eagerly and licked them into their
mouths; no sooner, however, had they done so than they seemed to be
aware of the mistake that they had made, and sat with gaping mouths,
rolling their tongues about until they had got quit of the nauseous
morsels.

With spiders the same thing occurred. These two caterpillars were
repeatedly put into the webs both of the geometrical and hunting spiders
(Epeira diadema and Lycosa sp.), but in the former case they were cut
out and allowed to drop; in the latter, after disappearing in the jaws
of their captor down his dark silken funnel, they invariably reappeared,
either from below or else taking long strides up the funnel again. Mr.
Butler has observed lizards fight with and finally devour humble bees,
and a frog sitting on a bed of stone-crop leap up and catch the bees
which flew over his head, and swallow them, in utter disregard of their
stings. It is evident, therefore, that the possession of a disagreeable
taste or odour is a more effectual protection to certain conspicuous
caterpillars and moths, than would be even the possession of a sting.

The observations of these two gentlemen supply a very remarkable
confirmation of the hypothetical solution of the difficulty which I had
given two years before. And as it is generally acknowledged that the
best test of the truth and completeness of a theory is the power which
it gives us of prevision, we may I think fairly claim this as a case in
which the power of prevision has been successfully exerted, and
therefore as furnishing a very powerful argument in favour of the truth
of the theory of Natural Selection.

_Summary._

I have now completed a brief, and necessarily very imperfect, survey of
the various ways in which the external form and colouring of animals is
adapted to be useful to them, either by concealing them from their
enemies or from the creatures they prey upon. It has, I hope, been shown
that the subject is one of much interest, both as regard a true
comprehension of the place each animal fills in the economy of nature,
and the means by which it is enabled to maintain that place; and also as
teaching us how important a part is played by the minutest details in
the structure of animals, and how complicated and delicate is the
equilibrium of the organic world.

My exposition of the subject having been necessarily somewhat lengthy
and full of details, it will be as well to reca