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 gigantic palate, and serve to strain or
sift the water, and thus to secure the minute prey on which these great
animals subsist. The middle and longest lamina in the Greenland whale is
ten, twelve, or even fifteen feet in length; but in the different species
of Cetaceans there are gradations in length; the middle lamina being in one
species, according to Scoresby, four feet, in another three, in another
eighteen inches, and in the Balaenoptera rostrata only about nine inches in
length. The quality of the whalebone also differs in the different