The Forest Republican. [volume] (Tionesta, Pa.) 1869-1952, 1892-02-03
THEY LIVE In THE DARK,
MANY ANIMALS wHIcH NEVER
SEE DAYLIGHT.

Blind Inhabitants i'm the Mammoth
Cave-How the Sight is Lost
Compensatory Attributes.
There are many animals in the world
which pass all their lives in darkness,
never seeing a ray of light. Every one has
heard of the blind fishes of the Mammoth
Cave. The latter is the biggest of 500
great caverns in the United States. All
Of them are inhabited by numerous other
sorts of creatures that have no eyes for
vision. Literally speaking, there is no
such a thing as a blind fish, since the
most sightless of the fnny tribe possesses
visual, organs in rudimentary condition.
But, through want of use, the optic
ganglia and nerves have broken down
and been absorbed.
Among the animals in these caves
where Egyptian darkness ever dwells are
blind craytish, coloriess, which in the
water by torchlight look like white
phantoms of their outdoor kind. Now
and then in such places one comes across
a common frog, emaciated and seemingly
discouraged, which has found its way,
how no one knows, to the Tartarean
realms. Also one discovers curious cave
rats, of the same color as the domestic
rats, but with longer bodies, like
weasel's, more developed whiskers and
much bigger ears. OF bats there are
multitudes in the caverns, as Que might
expect, inasmuch as they are creatures of
darkness.
Spiders of several kinds are found in
the caves. They are uniformly small,
weak and of sedentary habits. No webs
do they spin, save few irregular threads
sometimes. What they live upon is rather
a puzzle, though it is supposed that they
catch stray mites and other such small
fry. Scavengers constitute large part
of the population of the caverns. Car
nivorous beetles are plentiful, particular
ly In those places where parties take
lunch. The processes of decay seem to
be accomplished chiefly by few fungi.
1t is said that meat hung up at the mouth
OF one of these caverns remains fresh for
long time, and it is surmised that the
bacteria which causes things to become
putrid are probably rare in the under
ground atmosphere.
No animals whatever are found in the
dry parts of the caves. Dampness, or
certain degreed OF moisture, seems to be
essential to their existence. Under the
stones one finds white, eyeless worms,
and in the damp soil around about are to
be discovered blind beetles in little holes
which they excavate and bugs of the
thousand-leg sort. These thousand-leg
bugs, which in the upper world devour
fragments of dead leaves and other veg
table debris, sustain life in the caverns
by feeding upon decayed wood, fungus
growths and bats dung. Kneeling in
beaten path one can see numbers of them
gathered about hardened drps of tallow
from tourists candles. There are plen-
ty of crickets also.
So far as the insects of the cave are
concerned, the loss of sight which they
gradually undergo is sufficiently well
understood. The first step is decrease
in the number of the facets which make
up the compound eyes, with corre-
spending diminishment of the lenses and
retine. After four or five generations
the eyes become useless. 1t would be
most interesting to breed these or other
blind creatures of the caves in the light,
so as to find out if they would get their
sight back. In all animals, including
man, it is found that nature tries to com.
pensate for loss of vision by increasing
the power of the sense of touch. Thus
the antenne of cave insects grow re-
markably long. 1t is very curious to
find that nothing in their behavior sug-
gests the fact that they are blind. They
walk, run, stop, explore the ground and
try to escape from the grasp of the bug
hunter just if they really saw. The
light of candle startles them as much
as if they perceived it visually. 1t is
remarkable fact, proving that the ances-
tors of these creatures could see, that in
the embryo stage of their existence they
have eyes we'll developed.
In the abysses OF the oceans, below
800 fathoms, many animals have either
imperfect eyes or none. Their condition
in this regard affords a suggestive paral-
lei to that of cave life and the causes are
probably the same. Science is of the
opinion that all deep.sea life originally
emigrated from the shadows. The
creatures which dwelt in the darkness of
the depths naturally lost their powers of
vision after a while. 1t is the same way
with the mole, which is doubtless de-
scended from progenitors which could
see. Blindness in the mole is the result
of a degeneration of the optic nerve, the
consequence of which is that images
formed in the eye itself are not trans
mitted to the animals consciousness.
Occasionally mole can see little out
of one eye which has retained its com
munication with the brain. 1t is not
that the mole is born blind, but that it
inherits tendency to atrophy of the
visual organs just as people derive from
their parents an inclination to consump-
tion or other diseases. Some day in the
future there may be no such thing as a
mole shat Is not entirely and hopelessly
blind.