[Illustration: BROWN FROGS.]
They have gills, which enable them to breathe in water, to begin with,
and lungs which enable them to breathe in air, later on. They are mostly
without scales, and do not need to drink, because they imbibe moisture from
the air through their soft damp skin. When you see a frog hopping across
your path, you see a creature which has known many a change in its life,
for frogs are among those very interesting animals which undergo what are
called _metamorphoses_. We have met with this word before, and may remember
that it is used to express the change from one form to another which is
wrought in some living creatures in the course of their growth. I daresay
you imagine as I once did, that all young animals are like their parents,
only on a smaller scale; for you see that a young horse, or elephant, or
whale, a pup or a kitten, is at its birth in all respects just what it
will be when full-grown, only smaller. So it is with the reptiles and the
birds--the young ones, when hatched, are like the parents. But in the case
of frogs and newts, and also most insects, the young ones do not merely
increase in size as they grow, but pass from one stage of growth to
another, each different from the former, until like the butterfly when
it emerges from the chrysalis, they reach what is called their perfect
state--and these metamorphoses or changes are very curious and interesting
indeed.
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