LIFE GROWTH;--FROGS

(FROM A SONG OF LIFE.)

BY MARGARET WARNER MORLEY.[1]

[1] Copyright by A. C. McClurg & Co., 1891.


[Illustration]

Somewhat higher than the fish in the scale of life is the frog.
Although he begins life as a fish, and in the tadpole state breathes
by gills, he soon discards the water-diluted air of the pond, and with
perfect lungs boldly inhales the pure air of the upper world. His life
as a tadpole, although so fish-like, is much inferior to true fish
life: for though the fish has not the perfect lung, he has a
modification of it which he fills with air, not for breathing
purposes, but as an air-sac to make him float like a bubble in the
water. Will he rise to the surface? he inflates the air-bladder. Will
he sink to the bottom? he compresses the air-bladder. But in the frog
the air-bladder changes into the lungs, and is never the delicate
balloon which floats the fish in aqueous space. When the frog's lungs
are perfected, his gills close, and he forever abandons fish-life,
though being a cold-blooded creature he needs comparatively little
air, and delights to return to his childhood's home in the bottom of
the pond. But although he can stay under water for a long time, he is
obliged to hold his breath while there, and when he would breathe must