THE FROG. 259

When extricated from the gluten they feed on its remains,
and on examination are now found to be furnished with a
pair of branchis, which disappear after a certain time.
These little creatures present an appearance so unlike frogs,
that persons not conversant with natural history would with
difficulty believe in their identity; they appear to consist
simply of a round, black head, and a long, slender tail,
bordered with a very broad, transparent margin. Their
movements are remarkably lively and elegant, and to the
microscopist tadpoles are a great source of interest, from
the extreme beauty of the circulation of the blood, which
can be distinctly seen with a good microscope. When they
have reached the age of five or six weeks the hind legs
appear, and are succeeded in about a fortnight by the fore
legs ; the animal now partakes of the appearance both of
a frog and a lizard, but the tail continuing to decrease,
becoming at length totally obliterated, the frog becomes
perfect, and is seen on the banks of the waters in which, as
a tadpole, it has hitherto existed. It now feeds on animal
food, such as insects, snails, and worms, the structure of
the tongue being particularly well calculated for securing
the former prey, as it is very long, and the tip bifid and
glutinous.