he polliwogs have no chance to live
and develop in pools, as is ordinarily the case. So when the eggs are
laid, they are immediately taken by the male frog and placed in these
capacious sacs, which serve as nurseries for them all through their
hatching and growing period of life. Although there is no water in these
chambers, yet their gills grow out and are reabsorbed, just as is the case
in ordinary tadpoles. When their legs are fully developed, they clamber up
to their father's broad mouth and get their first glimpse of the great
world from his lower lip. When fifteen partly developed polliwogs are
found in the pouches of one little frog, he looks as if he had gorged
himself to bursting with tadpoles. To such curious uses may vocal organs
be put.

Turtles are voiceless, except at the period of laying eggs, when they
acquire a voice, which even in the largest is very tiny and piping, like
some very small insect rather than a two-hundred-pound tortoise. Some of
the lizards utter shrill, insect-like squeaks.

A species of gecko, a small, brilliantly coloured lizard, has the back of
its tail armed with plates. These it has a habit of rubbing together, and
by this means it produces a shrill, chirruping sound, which actually
attracts crickets and grasshoppers toward the noise, so that they fall
easy prey to this reptilian trapper. So in colour, sound, motion, and many
other ways, animals act and react upon each other, a useful and necessary
habit being perverted by an enemy, so that the death of the creature
results. Yet it would never be claimed that the lizard thought out this
mimicking. It probably found that certain actions resulted in the approach
of good dinners, and in its offspring this action might be partly
instinctive, and each generation would perpetuate it. If it had been an
intentional act, other nearly related species of lizards would imitate it,
as soon as they perceived the success which attended it.

That many animals have a kind of language is nowadays admitted to be a
truism, but this is more evident among mammals and birds, and, reviewing
the classes of the former, we find a more or less defined ascending
complexity and increased number of varying sounds as we pass from the
lower forms--kangaroos and moles--to the higher herb-and-flesh-eaters, and
particularly monkeys.

Squeaks and grunts constitute the vocabulary, if we dignify it by that
name, of the mammals. The sloths, those curious animals whose