a rather faint
chirping noise which comes mysteriously from overhead. On looking up
in search of the source of this peculiar sound, we may see a small,
dark, shadow-like creature sweeping to and fro with great rapidity. It
is one of the curious groups of animals called Bats, representatives
of which are to be met with in in all countries, always active at
night or in the twilight, and presenting a remarkable general
similarity of structure, although in some respects they may differ
considerably in habits. In the British Islands some fourteen species
have been distinguished.

Like the owls, with which they share the dominion of the evening air,
the Bats have a perfectly noiseless flight; their activity is chiefly
during the twilight, although some species are later, and in fact seem
to keep up throughout the whole night. As they rest during the day,
concealed usually in the most inaccessible places they can find, and
are seen only upon the wing, their power of flight is their most
striking peculiarity in the popular mind, and it is perhaps no great
wonder that by many people, both in ancient and modern times they have
been regarded as birds. Nevertheless, their hairy bodies and leathery
wings are so unlike anything that we ordinarily understand as
pertaining to a bird, that opinion was apparently always divided, as
to the true nature of these creatures--"a mouse with wings," as
Goldsmith called it once, according to James Boswell, is certainly a
curious animal, and very difficult to classify so long as the would-be
systematist has no particularly definite ideas to guide him. The
likeness of the Bat to a winged mouse has made itself felt in the name
given to the creature in many languages, such as the "Chauvesouris" of
the French and the "Flitter-mouse" of some parts of England, the
latter being reproduced almost literally in German, Dutch, and
Swedish, while the Danes called the Bat a "Flogenmues," which has
about the same meaning, and the Swedes have a second name, "Laedermus,"
evidently referring to the texture of the wings, as well as to the
mouse-like character of the body.

But so soon as we have definite characters to appeal to in
classification, we find no difficulty in assigning these puzzling
creatures to their proper place in the system. Bats produce their
young alive, and suckle them; the milk being produced by special
glands. Now, these are characters which are peculiar among all animals
to the vertebrate