Savannah courier. (Savannah, Tenn.) 1885-1979, 1889-07-18

depend closely upon temperature and
other external conditions. The writer
placed a tadpole in an aquarium in
the fall and no growth whatever APP
peared TO take place until the follow
ing spring. But when growth was
once renewed it proceeded with great
rapidity. 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
considerable length before the fore
legs showed themselves. The tail
persisted for some time after the de-
velopment of the legs but its disap-
pearance-by 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 seen to come to the
surface for air. For limited period
it appears to have the use both of
gills and lungs. 1t is 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 passing
from herbivorous to carnivorous
animal. Teeth also appear in the
mouth (on the upper jaw only and the
long, heshy tongue, attached az 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 well 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, 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 ii must go on in
it's development after having passed
the egg stage; and as these final stages
take place before our eyes they attract
our attention, and 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 well 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 q
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 theil
action. The external part of the cal
is very noticeable, appearing as ,
round, dark space just behind the eyes,
1t corresponds to the tympanum OF
ear-drum of higher animals There
are dclicately formed olfactory cells il
the nasal cavities. indicating that tn,
sense of smell is fairly acute. Thu
eyes are well formed and are provided
with lids, the lower one alone is freely
movable. If the eye be touched it i:
drawn inward under the upper lid and
at the same time the lower lid ascend
to close the eye.
The manner in which breathing il
effected in the frog is peculiar. Thu
lungs are simple sacks, similar to the
swim-bladders of fishes, except tina
they are dived internally into minut
chambers or cells. They are not sus
pended in chest cavity, but han!
loosely in the general cavity of tn
body. Hence they can not be fillet
with air by means of movements of tn
sides of the body, as is the case will
the higher vertebrated animals. Blu
mechanism of similar principle o
operation is found in the floor of tn
mouth. This is capable of beini
lowered by the muscular action, thu
greatly charging the mouth cavity
The vacuum thus formed is filled b
air passing in through the nostrils
These passages are then closed, an
the floor of the mouth raised, the al
thus being forced into the lungs Tn
action is therefore not dissimilar +
that of a force-pump. The lung
having been filed, expiration take
place by the mere reaction OF thei
elastic tissue, as in the higher animals
The skin appears to be a necessar
accessory organ in breathing. AT an
rate frog soon dies when kept in
dry place, the explanation seeming
be that the pores Of the skin are close
= 49, Al