Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1876-05-08
EVOLUTION.
First an Egg, Then n Tadpale, Next
a Frog, and Lastly n Frog


These animals, in the course of
their development, 60 through a
very singular series Of metamor-
phoses comparable to those bywhich
the grub is converted into a butter
fly. At this season Of the year
every pond is almost certain to con-
tain frog-spawn, masses of trans
parent albuminous matter with
numberless imbedded eggs consist
ing Of yolk, black on one side and
white on the other, A few hours
after these eggs are laid the process
Of development begins by the for
nation of a shallow groove which
appears quickly on the black, more
slowly on the white hemisphere,
and is just such a groove as would
be produced by drawing a blunt in
strument 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, cut
ting it up into smaller and smaller
masses until the whole yolk be-
comes granular, or formed Of micre-
scopic cells. Two ridges then ap-
pear on the surface Of the egg, and,
uniting i'll the middle line, enclosel
cavity, the lining membrane of
which is converted into the brain
and spinal cord. The head gradu-
ally becomes differentiated, and
the mouth appears on its under
side; the tail grows out, and the
little creature getting too long fo1
the egg becomes coiled upon itself,
and, before long, ruptures the egg
membrane and makes its exit from
its mass Of jelly. 1t is now to all
intents and purposes a fish; it has
no limbs, its mouth is provided with
a horny jaw, and it breatheS by
means of a pair Of plumose gills.
1t further differs from the adult
frog in being herbivorous, feeding
on water plants, to which it at,
taches itself by means of two suck
ers near the mouth. The tadpole
grows rapidly, and before long a
fold of skin appears on each side
which gradually closes over the
gills, leaving, however for a con-
siderable time, a small opening on
the left side. In the meantime the
limbs appear, and the lungs are de.
Yeloped, the tadpole breathing for q
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
lis formed, the adult air-breathing
form having thus been attained BY
a wonderful series of changes, ii
(which the fish Lepidosiren, peren'
nibranchiate, and triton are all rep
resented. One would be inclined
Ito infer from these metamorphosel
that, on tracing the amphibia bach
in time, the story of their origiI
should be told, but as a matter o
fact archaeological history tell
la different story altogether
Abundant remains of frogs anC
toads are found in tho Miocen
deposits, some of which are of 81
Ifne a character that even the tad
poles are preserved; but these ter
Hilary frogs and toads do not diffe.
lin any important particular from
those of the present day, and tn
same is true Of the tritons and sal
1amanders. Some Of the latter at
| tanned a great size, and one of then
! a near ally of the great Japanes,
salamander of the present day
has had a very singular fate, having
been described about the middle o
the last century as q fossil man b.
the German naturalist Scheuchzer
| who named it "HOmo diluyii tes
tis," the man who saw the flood. Il
the wealden and Purbeck forma
tions no amphibia have as yet beel
| discovered, but from the lower liza
to the carboniferous they turn vi
Iagain in remarkable numbers an,
Of great size, but differing from ex
listing forms in some important pc
II