back, at least for the above purposes, into the less efficient power of
gliding through the air. Bats, might, indeed, like many birds, have had
their wings greatly reduced in size, or completely lost, through disuse;
but in this case it would be necessary that they should first have acquired
the power of running quickly on the ground, by the aid of their hind legs
alone, so as to compete with birds or other ground animals; and for such a
change a bat seems singularly ill-fitted. These conjectural remarks have
been made merely to show that a transition of structure, with each step
beneficial, is a highly complex affair; and that there is nothing strange
in a transition not having occurred in any particular case.

Lastly, more than one writer has asked why have some animals had their
mental powers more highly developed than others, as such development would
be advantageous to all? Why have not apes acquired the intellectual powers
of man? Various causes could be assigned; but as they are conjectural, and
their relative probability cannot be weighed, it would be useless to give
them. A definite answer to the latter question ought not to be expected,
seeing that no one can solve the simpler problem, why, of two races of
savages, one has risen higher in the scale of civilisation than the other;
and this apparently implies increased brain power.

We will return to Mr. Mivart's other objections. Insects often resemble
for the sake of protection various objects, such as green or decayed
leaves, dead twigs, bits of lichen, flowers, spines, excrement of birds,
and living insects; but to this latter point I shall hereafter recur. The
resemblance is often wonderfully close, and is not confined to colour, but
extends to form, and even to the manner in which the insects hold
themselves. The caterpillars which project motionless like dead twigs from
the bushes on which they feed, offer an excellent instance of a resemblance
of this kind. The cases of the imitation of such objects as the excrement