CanÌƒon City record. [volume] (CanÌƒon City, Colo.) 1883-192?, 1897-10-14
NEED NO EYES.
Creatures That SEQ Through Their
Skins
Some C.rious Facts Concerning the
Lower orders of Animal Life
-snails, slugs and b.
valves.

Eyes are popularity considered to be
an error, if we are to believe DIR. Nagel,
recent German experimenter. Many
creatures without eyes can see, at last
they can distinguish perfectly well be-
tween light and darkness, and even be-
tween different degrees OF light. This
is the lowest degree of seeing, to be
sure, but still it is really sight, and diff
fers scarcely more from the visions of
some insects that possess eyes than
this does from our own clear sight.
Creatures that see without eyes see
by means of their skins. All skins,
says DR.. Nagel. are potential eyes; that
is, they are sensitive to light. In an
imals that have eyes the sensitiveness
has been highly localized and greatly
insreased-so that man, for instance,
has q retina very sensitive to light,
and an expanse Of ordinary skin which
possesses sensitiveness to light SO
slight that il is hardly conscious of it.
Yet the 50 is sensitive in some de-
gree, as is proved by the fact that it
sunburns-that is, light may cause a
disturbance in the pigment of the skin
Just as it does in that of the eye. In
the eye the disturbance is accompanied
by nervous change which sends a
telegraphic message along the optic
nerve to the BRAIN In the skin, too,
there are nerves, and there are mes
sages, also, but their tidings imprint
no image on the mind; they simply
express discomfort cry out sun.
burn"
But in many eyeless creatures the
lack OF eyes il in part made up by in-
creased sensitiveness of the whole
skin surface to light Darwin long ago
noticed that the earthworms, although
they have no eyes, will suddenly with
draw into their holes on the approach oi
lighted candle. Some creatures seem
more sensitive to suddenly increased
light, others to sudden diminution. II
a number of oysters, kept in vesse!
together, are found to be open, they
will shut all at once If q dark object
comes between them and the light.
Another bivalve called PsamD.odia
has long, whitish, transparent tube
which protrude from the sand in which
it lies buried. If they are suddenly il.
Illuminated, they contract, and the
brighter the light the greater the con.
traction. If number of them be car
ried into direct sunlight, they hasten tt
bury themselves in the sand; or.
there is no sand, they move rcstlessl,
to and fro in the water until they ar,
exhausted.
yt general, DIR. Nagel finds thai
shadows are those that live in strong
H..
den increase of light live in sand oi
mud, from which they emerge occasion
ally. In both cases the sensitiyeness OF
the skin to changes Of light serves u
protect-the animal.
How does the skin acquire this pc
culiar sensitiveness? 1t will be bes'
for the non-expert to suspend judg
ment, since even the scientists do no,
agree on this point. 1t may be that il
ir universal and rudimentary prop
erty of all skin. and that animals witt,
eyes have lost il in a greater or less de
gree, because they have no further need
for it. This is one view. Or it may
be that this property has been devei.
eped in eyeless creatures just because
they are eyeless and need it. That i
another view. Those who favor the lat
ter opinion point to the fact that some
of the creatures which now have skins
sensitive TO the light are probably de-
scendants OF creatures with skins NOT
so sensitive; in these instances the
sensitiveness must have been recently
developed. Snails are sensitive, but
their relatives, the slugs, are not; this
looks as IL the former had acquired the
faculty, However this may be, DR..
Nagels study Of these curious and out
of-the-way facts is certainly interest
ing, and may lead in the future to an nd.
vance in our knowledge Of the mechan-
ism of sight.--Boston Journal.