and higher animals do not
(with the exception, as far as I know, of one fish) resemble for the
sake of protection special objects, but only the surface which commonly
surrounds them, and this chiefly in colour. Assuming that an insect
originally happened to resemble in some degree a dead twig or a decayed
leaf, and that it varied slightly in many ways, then all the variations
which rendered the insect at all more like any such object, and thus
favoured its escape, would be preserved, while other variations would
be neglected and ultimately lost; or, if they rendered the insect at
all less like the imitated object, they would be eliminated. There would
indeed be force in Mr. Mivart's objection, if we were to attempt to
account for the above resemblances, independently of natural selection,
through mere fluctuating variability; but as the case stands there is
none.

Nor can I see any force in Mr. Mivart's difficulty with respect to "the
last touches of perfection in the mimicry;" as in the case given by
Mr. Wallace, of a walking-stick insect (Ceroxylus laceratus), which
resembles "a stick grown over by a creeping moss or jungermannia."
So close was this resemblance, that a native Dyak maintained that the
foliaceous excrescences were really moss. Insects are preyed on by birds
and other enemies whose sight is probably sharper than ours, and
every grade in resemblance which aided an insect to escape notice or
detection, would tend towards its preservation; and the more perfect the
resemblance so much the better for the insect. Considering the nature
of the differences between the species in the group which includes
the above Ceroxylus, there is nothing improbable in this insect having
varied in the irregularities on its surface, and in these having become
more or less green-coloured; for in every group the characters which
differ in the several species are the most apt to vary, while the
generic characters, or those common to all the species, are the most
constant.

The Greenland whale is one of the most wonderful animals in the world,
and the baleen, or whalebone, one of its greatest peculiarities. The
baleen consists of a row, on each side of the upper jaw, of about 300
plates or laminae, which stand close together transversely to the longer
axis of the mouth. Within the main row there are some subsidiary rows.
The extremities and inner margins of all the plates are frayed into
stiff bristles, which clothe the whole gi