The Wilmington daily Republican. (Wilmington, Del.) 1890-1902, 1892-11-25
LUMINOUS FISHES.
A SEA ANIMAL THAT CARRIES A
POWERFUL SEARcHLlGHT.

| Endowed by Nature with the Means Of
Finding Their Way About In the Dark.
How They Use Their Ocean Lamps.
Government biological laboratories
at Woods Holl and elsewhere along the
coast have been very busy studying
fishes and other creatures that live in
the sea. Sculpins engaged much of
their attention. One species, known as
the ''sea robin" has pectoral fins re-
sembling hands. They are discovered
to be actually organs of touch, and the
fish walks on them over the bottom,
feeling for its food as 1t goes. The slime
of these "toad fishes" as fishermen call
the family, is secreted by rows of glands.
All fishes have slime secretiug organs.
In those which live in the depths of the
ocean, where is inky darkness, the slime
1 glands are so modified as to be trans
| formed into phosphorescent spots, the
slime being luminous. Thus the finny
dweller in the dark, unfathomed caves
see by.
! Ono species recently discovered is
called the midshipman. 1t has luminous
disks along its sides and belly, on its
head and at the base Of its back fin. In
fact it is as profusely decorated with
lights as a midshipman is with but.
Conscience the name. Each of these
luminous disks is complete bullseye
lantern on small scale, having n lens
for concentrating the rays and reflect
or behind it composed of siliceous spic-
ules. The light comes from a layer Of
phosphorescent cells between the re-
fector and the lens.
No other known fish has such an
| equipment for Illuminating purposes.
There are good many species which
have Feaectors without lenses, while
others have lenses without refectors to
brighten the glow of their luminous
spots, But tho midshipman is the only
marine dweller thus far discovered
which possesses both reflector and lens.
1t is a veritable animated assemblage of
lanterns. There is a wide variation
among deep sea fishes as to their manner
of carrying their lights. One kind has
a barbel hanging to its chin, on the end
of which is suspended what might be
1 fkened to an electric bulb, while an
other sort upholds its light over its
head on the highest point of its back
/ fin. In certain species it is believed that
/ the luminous mucus from the modified
slime glands keeps running continually
/ down the sides OF the fish, rendering the
whole animal brilliant
1t is considered likely that these lam
1 tern bearing fishes of the depths, which
are chiefly head and month and highly
carniverous, are able to turn their lights
on or off at will. This seems probable
on account of the nerves and blood ves-
sells communicating with the slime
glands, which have no other apparent
purpose. Thus the miishipman may
have his power, on approach of an enc
my, to suddenly extiuguish his torches;
whereas, when seeking prey, he can
throw out search lights and brilliantly
illuminate his neighborhood. This phos-
phoreScent light is similar to that of
fireh!es, which Professor Langley, of
the Smithsonian institution, declares to
be the most economical and perfect of
all known lights, giving the greatest
illumination with the least waste and
without perceptble heat. 1t would be
of enormous value to mankind if the
secret Of this light which the fishes use
for their torchhght professions under
the ocean could be discovered. Unfor-
tunately the nature of it is wholly a
mystery, ali efforts to find it out having
thus far proved unavailing. -..
Sharks have lately been affording con
triburions 10 science. The biologist:
have been vivisectiuG them for the pur.
pose of finding out about the functions
Of the ear, which in fishes is made tc
some extent on the same pattern as in
man. The fact has been known fol
some time thai the ear is not merely an
organ Of hearing 1t has TO do with the
sense Of equih brium. Light has been
thrown on this matter by removing por.
tons Of the auditory apparatus of sharks
which are thus rendered unable to main
tam their balance in the water. The
part on which this faculty seems to de
pend is the labyrinth" and the same
. effect is produced by cutting the nerve:
communicating with il,
Science is paying much attention now
70 the observation If marine forms, be
cause the animals that dwell in the
ocean are the oldest in existence. Ac,
cording t. the theory Of evolution human
, beings, as well as all other land animals
i are descended from them. Il is difficult
; to realize that our ancestors in the dis
tant past lived under water, and thai
l they made their first vertebrate appear
! ance as seaworins, but the scientific
I men insist that such is the fact. Shark
are selected for certain experiments be
t cause they are the most ancient of a.
: surviving types Of tishes.-W Washington
Cor. New York World.