Iowa County democrat. [volume] (Mineral Point, Wis.) 1877-1938, 1884-10-03
ABOUT CRABS

is the head. Notice the position of the
eyes, and that will settle the question
Walking, as they do, forward, back
ward, and even sideways with equal
ease, it seems rs if they, too, might be
slightly puzzled about their formation,
and so, not stopping to decide which
part is intended to go foremost, they
dart off on a venture, and in the oldest
manner possible.
They are so abundant on all our sea-
shores that we rarely lift a bunch of
sea-weed or poke among the rubbish
there without disturbing their hauntS.
yet they scramble off and hide in the
sand so quickly that we are not much
wiser for their discovery. Let us pick
up some cast-otl shell and make n
closer examination.
The bodies of higher animals contain
three principal cavities the head,
thorax and abdomen. In crabs, on the
contrary, the head and thorax are SO
closely united that we can not distn-
euiSh them, and they are covered by
the same shell. The proper name for
head and thoraX thus united is ''ceph-
a-lo-thoraX.
A crab, consequently. has two prin-
cipal parasitic cephalo-thorax and the
abdomen each containing a number of
parts of its own. Tothe cephalo- thorax
are attached five pairs of iointed legs.
The front pair are much larger than
the others, and form the claws. The
abdomen consists of six parts, but it is
small and inconspicuous, being folded
under the cephalo-thorax.
The compound eyes of crabs are on
long stalks, and they may be turned in
different directions or folded back into
little grooves in the shell.
Crabs breathe by gills and by
branchia ellis are leaf-likc plates so
situated as to be readily bathcd with
water. They contain Il great many
blood-vesscls, and the oxygen in the
water, finding its way through their
delicate walls, mixes with the blood to
purify ii. The crabs heart consists of
single contractile sac.
Crabs are often spoken of as crus-
taceans. The name. | think, will
at once suggest to you animals hav-
ing hard crust. As this crust CON
tains number of pieces exactly fitted
to each other, it has been compared to
the armor worn by soldiers in olden
times. The manner in which il is shed
during the growth of the crab is curious
and interesting. This hard shell never
increases in size; therefore aS the crab
grows its shell becomes too small, and
1t is cast of. looking like the perfect ami
nal, with eyes an1 legs attached.
When the proper time for this change
arrives, the body shlinks away from the
shell, separating from il al all points, and
the animal works lis way out. The cX-
hausted creature npv remains quietly
in some secluded place, increasing rap
idly in size, unll tie soft skin again
hardens into new sell.
This IS painful and periIous expert
cnce for the poor crabs. Occurring as
it does several mes in the summer,
their weak and unprotected bodies fall
an easy prey to Their cncm es. and they
are devoured even bE other rrabs which
happen to be in better plight. Now it
j. that they are known - ',oit-shcllcd"
crabs.
Crustaccans. when .uii,; .atrd with
mail, are strong and dcstrae. vc, light
inr amoae thrmsc W. as " ii "s W tn
other ANIMALS Taey eat any small
creatures 1T come in their way.
whether living or lead On the other
hand, tEay t.cin clyes are destroyed by
larger animai>. and crustaccan- form a
large part OF the loo of >tar-iish. sell
urciiinS. mo!luSks, and NAM kinds Of
fish atd birds. consequently great guam
titles Of them are Killed before reaching
their fuil size. 10 protect the race
from dc .truction IN this loss of life, all
cru,taccans produce immense Quantities
OF eggs.
Young crabs are - gn!iae the full
grown ones that naturaiists formerly
thought they belonged 10 a different
class OF animals. 4 soon rs they are
born they rise 10 the surface Of the
water. and swim about freely. After
pass ny through several changes the
body becomes large and heavy toward
the head. and the Young crabs. losing
the power Of swimming. sink To the
bottom, where they hide Tor awhile. As
they gain in size and Strength, and are
ready to begin their new manner of
living, they creep toward the shore,
and most Of them pass the rest of their
DAYS in shallow water among the sea-
weed. In the tropics some species live
IN Tie IffsU-"dItE Ol DloOhs AUo ElbtTs.
Others live in the shades of damp for
ests; still. when breeding-tiIne arrives,
they visit the sea-shore to deposit their
eggs.
The land-crabs Of Jamaica even live
on the mountain-tops, yet every year
they yield to a longing for their
old Eome, and come down to
the shores of the Caribbean Sea
to lay their eggs Tais duty performed.
they return again to the mountains.
The hermit-crab is always an object
Of interest. Unlike other crustaceans,
it has no shell to protect the soft body,
and tempting morsel is thus exposed.
The hermit, conscious of its weak point,
seeks shelter by taking possession OF
some spiral shell in which to place its
soft abdomen. The hard claws and the
first two pairs Of feet generally hang out
over the edge of the shell, which hence
forth moves aboutupon the crab back as
nfhe two belonged together. The shorter
hin6-feet are roughened. enabling the
crab to hold on the inside of the shell,
and Il clings 50 tightly that it win some
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