THE BATRACHIANS
“I have kept until the last the ugliest and the least esteemed of our
helpers, the toad. With it must be classed the frog and the tree-toad
because of their close resemblance to it in form and, still more,
because of the similar change all three undergo in developing from the
egg to the full-grown animal. Common language gives the name of
reptile, from a Latin word meaning to creep or crawl, to the snake and
the toad, the lizard and the frog, and all similar hairless animals
having either no legs at all or very short ones and crawling on the
stomach. Science, however, makes a difference; it limits the name
reptile to the snake, the lizard, and other animals having a scaly skin
and hatching from the egg in the form they are to keep; and it gives
the name batrachian (from the Greek batrachos, a frog) to the toad,
frog, tree-toad, and some others, which have a naked skin and whose
first shape gives place later to a different one. Reptiles do not
undergo a complete change; batrachians do. Just as the butterfly is
first a caterpillar, quite different in structure, its way of living,
and its diet from what it finally becomes in its perfect state, so the
toad, the frog, and the tree-toad begin their existence as tadpoles
with none of the structure and habits they are finally to have.
“Tadpole or big-head, that is the word to indicate the batrachian in
its transitory state. A very large head merging into a plump stomach
that ends abruptly in a flat tail—such is the animal in the beginning.
It has no limbs, no organs of locomotion unless it be the tail, which
whips the water to push the creature forward and serves as oar and
rudder at the same time. The toad tadpole is small and entirely black;
the frog tadpole is much larger, silvery on the belly and grayish on
the back. All tadpoles inhabit still waters, as ponds or pools warmed
by the sun; but for toad tadpoles even shallow puddles or wagon-ruts
with a few inches of rain will suffice, where they can gather in black
rows or stretch themselves flat on the stomach in the tepid mud at the
water’s edge. Frog tadpoles, however, thrive best in ponds of some
extent, with various water-plants and sufficient depth for diving and
swimming. Like fish, tadpoles breathe the air that is in water; and
like them, also, they die if kept out of water a short time. Thus they
are real fish as far as breathing is concerned. But in their final form
batrachians breathe atmospheric air and die of suffocation in water.
They are land animals in that state, and breathe like other land
animals.
“You have very often seen frogs and toads in the water, and no doubt
you think they could live there indefinitely. Undeceive yourselves:
they go to the water only to lay their eggs or to escape from some
danger or to bathe in hot weather, but they could not remain under
water any length of time without dying. They have to come up at
intervals to breathe, which they do by getting at least the nostrils
out. Here we have a difference between the tadpole and the full-grown
batrachian, between the larva, so to speak, and the creature at its
maturity: the tadpole lives in water and perishes in the air, whereas
the frog that comes from it lives in the air and perishes in water.
“And there is a still further difference: the tadpole lives exclusively
on vegetable matter, its mouth is equipped with a sort of small horny
beak to browse the foliage of water-plants, and in its big belly it has
a very long intestine coiled about several times so as to prolong the
passage of the food through the body and thus make sure that all the
juices it may contain are extracted. The mature batrachian exchanges
this horny beak for real jaws furnished with irregularities that serve
as teeth, it lives solely on an animal diet, especially on insects, and
its intestine is short because the food it eats is easy of digestion
and readily yields what nourishment it contains.
“To turn a tadpole into a frog or a toad it is not enough to change its
respiratory and digestive organs; new organs form, organs of which
there was not the least sign when the creature was hatched, while still
others disappear without leaving any trace. The tadpole is born
absolutely without legs. After a while the hind legs appear, later come
the fore legs, and still later the tail shrinks and vanishes.”
“I remember seeing tadpoles,” said Jules, “some with two legs, some
with four; but every one of them had a tail.”
“When the tail has disappeared the animal is no longer a tadpole, but a
young toad or frog.”
“Does the tail come off itself, or does the animal pull it off?” Emile
inquired with eager interest.
“Neither the one nor the other. The tail is too valuable when the
change takes place to be thrown away in that reckless fashion. It
contains a store of material suitable for making something else in the
bodily organism. When the legs begin to put forth, when the organs of
digestion and those of respiration begin to take a new form, these new
creations, these transformations, require material with which to build.
Fleshy substance is needed for the up-building of the body just as
bricks and mortar are needed for the construction of the house. Of
course the tadpole eats to make flesh and to provide a reserve for the
work of transformation; but this method of accumulation is slow, and
therefore, to save time, the organs useless to the future animal are
destroyed, bit by bit, and their material is used in the construction
of new parts. It is thus that the tail disappears. The blood
circulating through it gradually eats it away, dissolves it, as we
might say, at the proper time and carries elsewhere the fluid
substance, which, turned again into flesh, helps to form the legs or
other parts of the remodeled organism.”
“What a deal of economy in getting rid of a tadpole’s tail!” exclaimed
Emile. “Not a particle of it, even if no bigger than a pin’s head, must
be thrown away, for it might be used to make the little toe on one of
the feet.”
“Yes, my boy, a wonderful economy, an economy careful of every atom of
matter in order that life, the divine worker, may not fail to have at
its disposal, undiminished by waste, the resources committed to its
keeping by the Creator for works that are unceasingly being destroyed
and then restored on a new plan.
“I should add here that certain batrachians keep the tail as long as
they live. To this class belong the salamanders, one species of which,
the terrestrial or land salamander, is extremely ugly. In form it is
half-way between a toad and a lizard, and its color is black with large
bright-yellow spots. It is from one to two decimeters long. It haunts
damp places near springs and eats insects and earthworms. Despite its
repulsive appearance it is perfectly harmless.
“The tadpole of the salamander breathes through fine tuft-like
appendages which spread out in the water on each side of the neck.
These tufts are called gills, and they correspond to the fish’s
breathing organs or gills, which are likewise situated on each side of
the neck under the tiny flap commonly called the ear. Tadpoles of the
frog and the toad have, for the first few days, fringed gills floating
out freely; but in a short time they are drawn in under the skin and
become invisible like the gills of fish.
“Frogs have a slender form not devoid of a certain grace. Their hind
legs are very long and powerful, being especially good at jumping, the
frog’s customary mode of progress. First gathering itself together, the
animal suddenly relaxes like a spring and throws itself forward by a
vigorous thrust of the thighs. The hind toes are very markedly webbed;
in other words, they are united by a membrane as are the toes of
swimming birds, the duck in particular. This arrangement of the toes so
as to form a broad paddle or oar, together with the suppleness of the
hind legs, which are alternately drawn up against the sides and then
forcibly extended, makes the frog an expert swimmer.
“The common or green frog is spotted with black on a green background,
and it has three yellowish stripes on the back, the belly also being
yellow. It abounds on the banks of all still waters, and to it we owe
the noisy croaking that comes from every ditch on a summer evening.
“The red frog is spotted with black on a reddish background, and is
easily recognizable by the black stripe running from the eye over the
ear. It likes cool places such as damp meadows and fields and
underbrush. It is less fond of the water than the one just named, and
it croaks much less.
“Both live on live prey, as for example aquatic larvæ, worms, flies and
other insects, and snails, and they never touch vegetable matter;
therefore they are good helpers in our gardens.
“Tree-toads—or, less correctly, tree-frogs—differ from ordinary frogs
in having viscous cushions at the end of their toes, which enable them
to climb trees, where they hunt insects. They stay all summer in the
foliage and go to the water only to lay their eggs. Their cry, which
gains force from a sort of pocket that shows plainly under the throat,
is very loud and raucous. The tree-toad that we have around here, the
common tree-toad, is of a beautiful delicate green hue on the back and
yellowish-white on the belly.”