The Canton mail. [volume] (Canton, Miss.) 18??-1882, 1876-05-06
EVOLUTION.


l FIRST an Eag, Then Tadpole. Merit Fro6
| and Lastly a Frog.
These animals, in the course OF thei
development, go through very singula
series of metamorphoses comparable t.
those by which the grub is converted
into butterfly. At this season of tn
year every pond is almost certain to con
tain frog-spawn, masses of Transparent
albuminous matter with numberless i'm
bedded eggs consisting of yolk, black OF
one side and white on the other. A few
hours after these eggs are laid the pro
cess OF development begins by the forma
ton of shallow groove which appear
quickly on the black, more slowly OF
the white hemisphere, and is just such 6
groove as would be produced by draw
ing blunt instrument along the equator
of a soft globe. The egg is thus divided
into two masses. A second form appears
at right angles to the first, dividing the
whole egg into four, others appear, in
definite order, cutting it up into smaller
and smaller masses until the whole yolk
becomes granular, 'or formed of micro
scopic cells. Two ridges then appear on
the surface of the egg, and, uniting in
the middle line, enclose a cavity the
lining membrane of which is converted
into the brain and spinal cord. The
head gradually becomes differentiated,
and the mouth appears on its under
side; the tail grows out, and the little
creature getting too long for the egg be-
comes coiled upon itself, and, before
Icing, ruptures the egg-membrane and
makes its exit from its mass of jelly. 1t
is now to all intents and purposes fish /;
it has no limbs, its mouth is provided
with a horny jaw, and it breathes by
means of a pair of piumose gills. 1t
further differs from the adult frog in
being herbivorous, feeding on water
plants, to which it attaches itself by
means of two suckers near the mouth.
The tadpole grows rapidly, and before
long fold of skin appears on each side,
which gradually closes over the gills,
leaving, however, for a considerable
time, small opening on the left side.
In the meantime the limbs appear, and
the lungs are developed, the tadople
breathing for a time both by lungs and
gills; the latter eventually disappear,
the tail shortens, the limbs lengthen,
the horny jaws are replaced by teeth,
and an insect-eating, tailless frog is
formed, tine adult air-breathing form
having thus been attained by wonder
full series of changes, in which the fish
Lepidosiren, perennibranchiate, and tri-
ton are all represented. One would be
inclined to infer from these metamor-
phoses that, on tracing the amphibia
back in time, the story of their origin
should be told, but as matter of fact
history tells different
story altogether. Abundant remains of
frogs and toads are found in the Miocene
deposits, some of which are of so fine
character that even the tadpole are pre-
served; but these tertiary frogs and
toads do not differ in any important par
ticulars from those of the present day,
and the same is true It the tritons and
Some of the latter attained
a great size, and one of thenl-a near
ally of the great japanese salamander Of
the present day-has had very singular
fate, having been described about the
middle of the last century as Il fossil
man by the German naturalist Scheu-
cheer, who named it "Homo diluvii les
It's" the man who saw the food. I'm the
wealden and Purbeck formations no am
phibia have as yet been discovered, but
from the lower las to the cafboniferous
they turn up again in remarkable num-
bers and of great size, but differing frem
existing forms in some important pecu-
larities, and ahording no help whatever
to our inquiries as to the origin of the
existing or the tertiary frogs, toads, and
Under the throat these
gigantic amphibia had remarkable
shield OF three bony plates, as well as a
series of plates along the belly. Their
teeth were large and powerful, and pre-
sented an extremely complicated struc-
ture, whence the group has received its
name of LADY rinthodonta