At the end of that time the devoted parent, foreseeing developments,
takes to the water once more, so that the tadpoles may be hatched in
their proper element. I may add that this frog is a great musician in
the breeding season, but that as soon as the tadpoles are hatched out
he loses his voice entirely, and does not recover his manly croak till
the succeeding spring. This is also the case with the song of many
birds, the crest of the newt, the plumes of certain highly-decorated
trogons and nightjars, and, roughly speaking, the decorative and
attractive features of the male sex in general. Such features are
given them during the mating period as allurements for their
consorts: they disappear, for the time at least, like a ball-dress
after a ball, as soon as no immediate use can any longer be made of
them.

[Illustration: POUCHED FROG.]

Some American tree-frogs, on the other hand, imitate rather the
motherly Solenostoma than the fatherly instincts of the pipe-fish or
the stickleback. These pretty little creatures have a pouch like the
kangaroo, but in their case (as in the kangaroo's) it is the female
who bears it. Within this safe receptacle the eggs are placed by the
male, who pushes them in with his hind feet; and they not only undergo
their hatching in the pouch, but also pass through their whole tadpole
development in the same place. Owing to the care which is thus
extended to the eggs and young, these advanced tree-frogs are enabled
to lay only about a dozen to fifteen eggs at a time, instead of the
countless hundreds often produced by many of their relations.

Tree-frogs have, of course, in most circumstances much greater
difficulty in getting at water than pond-frogs; and this is especially