quite a peculiar manner. In one species of Anaea (A. divina), the resting
butterfly looks exactly like a leaf out of the outer edge of which a large
semicircular piece has been eaten, possibly by a caterpillar; but if we
look more closely it is obvious that there is no part of the wing absent,
and that the semicircular piece is of a clear, pale yellow colour, while
the rest of the wing is of a strongly contrasted dark brown.

But the deceptive resemblance may be caused in quite a different manner. I
have often speculated as to what advantage the brilliant white C could give
to the otherwise dusky-coloured "Comma butterfly" (Grapta C. album).
Poulton's recent observations ("Proc. Ent. Soc"., London, May 6, 1903.)
have shown that this represents the imitation of a crack such as is often
seen in dry leaves, and is very conspicuous because the light shines
through it.

The utility obviously lies in presenting to the bird the very familiar
picture of a broken leaf with a clear shining slit, and we may conclude,
from the imitation of such small details, that the birds are very sharp
observers and that the smallest deviation from the usual arrests their
attention and incites them to closer investigation. It is obvious that
such detailed--we might almost say such subtle--deceptive resemblances
could only have come about in the course of long ages through the
acquirement from time to time of something new which heightened the already
existing resemblance.

In face of facts like these there can be no question of chance, and no one
has succeeded so far in finding any other explanation to replace that by
selection. For the rest, the apparent leaves are by no means perfect
copies of a leaf; many of them only represent the torn or broken piece, or
the half or two-thirds of a leaf, but then the leaves themselves frequently