Thomas County cat. [volume] (Colby, Kan.) 1885-1891, 1889-07-18

depend closely upon temperature and
other external conditions The writer
placed tadpole In an aquarium in
the fall and no growth whatever ap-
peared TO take place until the follow
ing spring. But when growth was
once renewed it proceeded with great
rapidlty. Within period OF ten days
both pairs Of legs budded out and de-
veloped to nearly perfect form. The
hind legs appeared first and attained
a considerable length before the fore
legs showed themselves. The tail
persisted for some time after the de-
velopment oil the legs but its disap-
pearance-bS = process of absorption
= finally took place with great rapid
ity. occupying only two or three days
The gills appear to wither away at
about the time OF the disappearance OF
the tail At any rate at this time the
animal is first soen to come to the
surface for air. Fer limited period
it appears to have the use both OF
gills and lungs. 1t I. curious condi-
ton at this time. when one set OF
breathing organs is shriveling up at
an equal pace with the development
of the other set Not less remarkable
is the fact that at this juncture the
creature changes its d;et-passing
from a herbivOrOus to a cnrnivOrous
animal. Teeth also appear in the
mouth (on the upper jaw only} and the
long. deshy tongue. attached at its front
end and loose behind, attains complete
growth. The opening of the mouth.
too. becomes enormously enlarged. ex-
tending far back at the sides of the
head.
But while these transformations are
truly remarkable it is we'll to keep In
mind that. after all. they are not essen
TALLY different from those through
which other animals pass in their
bodily development Take, for exam
pie. a bird. The changes which take
place within the egg during the early
period OF incubation are quite the same
in their general nature as those which
the frog passes through after it has
completed the period of incubation.
(The frog matches from its egg by the
heat of the SUM-. The chief difference
is that in the bird these changes are
completed during the egg stage. the
animal leaving the egg with all its
class characters in perfection. But in
the frog. at the time the young leaves
the egg it is in the fish stage; that is
to say. it has the characteristics OF a
class at least two grades below its own
proper class. And so it must 60 on in
its development after having passed
the egg stage; and as these final stages
take place before our eyes they attract
our attention. aud are in danger of
leading US to suppose that the develop
mental history of the frog is peculiar
and anomalous.
The frog affords an example of those
animals which secure protection from
the attacks of their enemies by MINI
licking the color of their surroundings.
By some physiological process. the
nature of which is not we'll understood,
they are able to vary the color Of the
pigment of the skin in correspondence
to the color of their surroundings.
Thus. when they sit in the grass on
the bank Of pool or stream, they
change their color to green, and thus
are less likely to be seen by birds and
snakes. which are their chief enemies.
The frogs differ from most animals
in possessing no distinct organs OF de-
tense. But his powerful leaping mus
Giles stand HIM in good stead as
means of escape, both when on the
shore and when in the water, in the
latter case enabling him to swim with
great quickness.
The sense-organs of the frog are
well developed and are quick in their
action. The external part of the ear
is very noticeable, appearing as
round. dark space just behind the eyes.
1t corresponds to the tympanum or
ear-drum of higher animals There
are delicately formed olfactory cells in
the nasal cavities. Indicating that the
sense Of smell is fairly acute. The
eyes are well formed and are provided
with lids. the lower one alone is freely
movable. If the eye be touched it is
drawn inward under the upper lid and
at the same time the lower lid ascends
to close the eye.
The manner in which breathing is
effected in the frog is peculiar. The
lungs are simple sacks, similar to the
swim-bladders of fishes. except that
they are dived internally into minute
chambers or cells. They are not sus-
pended in a chest cavity, but hang
loosely in the general cavity of the
body. Hence they can not be filled
with air by means of movements of the
sides of the body. as is the case with
the higher vertebrated animals. But