The Savannah morning news., 1904-08-07
The Seeing Spot of the AmphiOxus
and the Traces of n Disused Optic
in Many Creatures-The Wonder
full Vision of Birds.
From the New York Post

full Vision of Birds.
From the New York Post.
Look at the eye of a deer and marvel
at it's liquid depth and beauty; the
eye of a dog and see your affection
mirrored in his worshipful gaze This
wonderful organ, though small, is the
principal factor in giving character
and expression to a living being When
a creature is dying, it is the glazing
eye which quickly and most surely be-
trays the passing vitality; and the his
tory of eyes is as wonderful as their
function.
If we recall the saying that, with
no eyes to see color has no existence.
we will realize that at one time the
earth and it's surroundings were per-
haps uniform. But even our minds
eye" refuses to image such state of
affairs; sky, sea, land, crystals, flow
ers, ali dead neutral tint. However,
that may have been, there was certain
ly time long ago when no eyes or
anything like them has appeared.
In creatures now living upon the
earth, we may trace a series of eyes
from the highest and most efficient to
the simplest dot of black pigment. The
eye of the eagle may stand for the
first, and the eye-spot of the amphioxus
or the eight sense-germs of a jelly
fish for the other extreme of the Sc
rieS.
The amphioxus is a little worm, or
fshlike creature which most of the
time lives buried in the sand of our
seashores. He is interesting and i'm
portant out of all proportion to his
size, two inches, for he is one of the
lowliest creatures to honored with a
backbone, the class-mark of all higher
animals. He has no skull and no brain,
but near the front end of the thin
thread of nerve (the foreshadowing of
our spinal chord) is a tiny black dot.
BY means of this, he distinguishes light
from darkness, which is all his simple
life requires. Let us forget the posi-
tion of this single, most primitive of
eyes-in the center of what would be
the brain if the lowly creature had
one.
The eye of a jellyfish is so primitive
that we can hardly say whether it sees
or feels. That is, when floating jelly
fish begins. to sink below the surface
of the water as the shadow of an adj
vancing ship falls upon it, it is proba-
bly, affected by the sensation of dark
ness, but perhaps the pressure of the
onrushing wave has something to do
with it.
How Insects and Fishes See.
Insects have eyes which as a whole
are much more highly developed than
that of the amphioXus, but in a diff
lferent direction from the creatures
which stand higher in the scale of
life. Their compound optical appara
tus consists of many nerves leading
to a honey comb-like mass of lenses,
each cell of which is a very simple
lens, so that the image is reflected like
a mosaic. And yet insects must be
able to perceive colors, as the differ
ing hues of the two sexes are ap-
preciated by many of them and the
various tints of flowers are recogniz-
ed, white blossoms attracting certain
species, yellow blooms being visited
more constantly by others.
That the eye is considered a vul-
nerable and precious organ is shown
in certain fishes. which have a false"
eye outlined upon the long tail-fin,
which, perhaps attracts the atten-
tion of any enemy, which bites at it
supposng it to be the head, thus TAX
ing piece harmlessly out of the tail,
while the fish is given a chance to
escape. This is even more plainly
seen in the wings of certain moths
and butterflies, and the pieces torn out
by birds are very often these con-
spicuous blotches of bright color. But
the strange thing about this is that
the "eyes" in the wings of the in
sects are not like real insects eyes,
but somewhat like those of higher ami
mails about which the insect, of course,
knows nothing. And we, too, know
little as to how these things Came
about, through methods of evolution
more wonderful than fairy tales.
But insects and fishes have two eyes
Cor at any rate most insects have two
clumps of eyes,, and what has be-
come of the central single eye of
amphioxus? If we will examine a.
bottle of water from almost any stag
nant pond or even from the edge of
a pond, we will find many tiny crea-
lures somewhat related to crabs and
Holsters with a single great eye in
the middle of their forehead On
account of this scientists have named
these Cyclops, and at night this eve
occasionally glows with a strange UNI
earthly light, and, indeed, the whole
creature becomes phosphorescent and
our oars may disturb thousands of
them making the water shine as with
a myriad sparks.
The CyclOpean Eye.
If we would see an eye which has
actually been evolved from one like
that of amphioxus, let us examine the
head of a lizard. Disregard for a time
his two bright eyes. one on each side
of his head, and look directly down on
the center of the skull between them
Here we will find an oddly shaped
scale marked with a little depression
and this is, indeed. what is left of our
Cyclopean eye in the tiny sand crea-
ture. Lizards doubtless derive very
little benefit from it, as the nerve lead
ing from it is very small, but in some
of their ancestors II must have been
of great value in detecting the pres
ence of enemies from above. In all
creatures above lizards this third me-
dian eye Called the pineaD is found
although of no use whatever; this per-
sistence, perhaps showing of what
great Importance it once was. In a
chick in the early stages of incuba-
ton this eye is very considerably de-
veloped. while yet the paired eyes are
but small structures. But suddenly
Nature seems to realize that the old
regime has passed-that the little bird
will need other more modern eyes, and
the two side eyes begin to develop with
wonderful rapidity. and soon catch up
with and distance the Cyclops eye,
whose early start ends only in prom
Use.
A horse. a bat. a mole. a monkey, a
seal, all have a trace of this third eye,
and when we put a finger on the soft
spot Of the head of tiny baby, we
realize the wonderful import OF it
that the softness is due TO a near ap-
proach OF this same third eye to the