Evening star., 1935-05-05
About Fishes
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Continued From First Pase.)
and correspond to the hind legs Of
an animal. The uppermost nm is
called the dorsal i'm, and oftimes Is
divided into two or even three parts.
appearing to be distinct and not un-
commonly termed "adipose nns." The
remaining vertical member Is known
as the anal fin and, like the dorsal.
may be composed Of spines, rays and
finlets. Great variations occur in
shape, size, division. position and
other features Of the fms Of different
species, thereby offering characters
which serve in . big measure for
classification.
Propulsion Of o fish, for the most
part, is derived from the posterior
part of the body and the caudal m.
due to q series of alternate contrsc-
tions Of the strong muscles on the
side Of the trunk to the tail extremes.
The tail moves to and fro not unlike
an oar blade being used In sculling
Q boat.
Fishes breathe by means OF gills.
which represent the greatest departure
In adaptation of the animals TO an
aquatic environment. Lifting the
opercular, the covering over the sins.
four pairs Of red fringedlike bodies
are exposed. On either side OF the
throat Just behind the mouth cavity
there are four more or less crescent
shaped bones. the gill arches. each
of which bears two gill processes.
Being rightly supplied with blood, the
gills offer surface for gas exchanges.
oxygen, dissolved in water. being taken
in and distributed over the body, while
the blood Is relieved of its carbonic
acid gas charge. passes directly into
the water. Breathing in fishes. rs In
higher forms, must be carried on con-
stantly, the water passing through the
mouth, then On back between the
thin scales OF the gills and out the
opercular opening to the exterior.
An air bladder, internally placed.
regulates the weight displacement fac
tor permitting the fish to remain sta
tionary at varying depths, without
muscular activity. The air bladder is
said to be the remains OF what was
once o lung, or additional arrange
ment for breathing.
The brain Of true fishes represents
o distinct advancement over the other
classes. The sense organs are con-
nected to the brain by cranial nerves
and the spinal cord, encased In the
vertebral column. gives Oh spinal
nerves.
The digestive tract of fishes varies
according to habits. Food In reach
ing the stomach passes over . rather
Ineffective tongue. The stomach In
general Is simple sack-like organ In
which food Is partially digested before
passing into the intestines.
Directly or indirectly, all fishes feed
upon vegetable matter. Some forms
feed upon plants directly. It % the
relation between fishes and aquatic
vegetation that makes Maryland's
fisheries 30 valuable and her Chesa-
peake so highly prized. And, Of course,
fish eat meat, even their own. Mans
most terrific wars against his fellows
have . respite, but the battle Of hsh
against fish Is everlasting. II II al
most impossible for the human mind
to conceive the continuous struggle
for existence that goes on beneath the
surface Of the water.
Chesapeake Bay, the happy hunting
ground for thousands Of Washington
anglers, since the abolition Of the
purse net by the Maryland Legislature
few years ago, is fast becoming q
nsherman's paradise. More and larger
fish and q greater variety are being
landed every year. And the more
fishes entering the bay. needless to
say. the better sport the anglers viii
have In It's tributaries, especially the
Lower Sotomse and Pstuxsnt Rivers.