New-York daily tribune. [volume] (New-York [N.Y.]) 1842-1866, 1847-10-28

slug. IL has large foot OF which Il walks and 6
fat shell on its back in which the viscers are con
tanned. From the heart in this animal there
originates large blood-vessel running do~nvsrds
top ard the head and the blood no longer contained
in this vessel - dfiused Into cavity. that the
tongue and posierior apparatus Of the digestive or
sans are actually swimming in the cavity fall Of
blood. From the walls Of this cavity new tubes
srise which unite into other vessels and thus fern
en- artery or a vessel running backward and d.
viding into the body.
In others Of these animals we have the blood
vessels opening into the cavity which contains the
viscera and surrounding the stomach-surrOundng
the intestines-and surrounding the liver and then
again absorbed by vessels 10 be dIfused into the
lower parts Of the animal So that there every
where blood cavities into which the bloodvess
open and from which other vessels arse and diiuse
again the blood into the organs.
The extraordinary structure Of the blood vessels,
and Of the circulation IN the mOllusca hss not been
long known. Ii is the discovery OF one OF our most
eminent naturalists-the present Professor Of Nat
ural History in the J0rdiH des Piaats In Paris. IL
throws most important light the mode Of circuls
ton and OF the organs of circulation in the animal
How are the blOod.vessels and blood formed in
ANIMALS and how does circulation beginl In ex-
aiming the egg Of fish, for example. we first OBJ
serve an accumulation Of red c0rPuscies, which be-
gin 20 move In different directions, but without YES
sells till after certain time. there IL regular
movement Of some Of these blood corpuscles IN a
straight direction and then they will extend over
the surface OF the yolk and form regular streams,
bat always without vessels till the vessels are
formed around the blood when regular channels
for the circulation arise from the fact that vessels be
gin 10 form around the corpuscles, similar 10 what
we see occur after a heavy rain. When the water
runs over the street there Is at first no channel
for the water but after it has for some time in
different directions, channels begin Ia present them
selves, which gradually become deeper and deeper
in the softer parts till the water remains bounded
by them so in living animal the cells, bong
excited by the current OF the blood, are gradually
formed into channels. The young ANIMALS formed
entirely Of cells Some Of these cells become NOV
able and are moved in different directions and form
little streams-litte currents in different ways and
then after these streams have become regular the
vessels are formed around them. In this way you
have foil explanation of those large blood cayl-
ties in the molusca and those unconnected blood YES
sells opening into the larger cavities and a heart
which is central. bat which does not communicate
with the most distant portions OF the body think
the only way ~ understand the circulation
Is 10 consider il and the blood as arising
from the liquefaction as it were Of the cells which
form the animal which then become movable, I'M
dergo a motion in precise and uniform directions
and then are surrounded by cells which form the
vessels and which form the heart. IL is only when
tracing ali these phenomena in the young animal
But could not help advertng to the formation o I
the blood vessels when speaking of aclass IN which
the clrcu alton Is unique as II Is IN the inousca
Let US now turn our attention 10 the molusca
themselves and see what form they show IN the
whole range of the class All the diagrams on the
wall belong 10 that class but you VIII perceive
that they present many different forms Here is an
animal resting on stem. There 10 one very like
a coral Here is one which for a long time has
united with the coral, aud by many naturalists is
ranked as such. You perceive that It has cells
similar 10 those Of the common coral. here You
have animals with two unequal valves. here
others with two equal valves Hers one with one
central valve curved. Others without any protec-
tive valve All these dversities exist IN one and the
same class
The mollusca have bcendividcd into three classes
The first class is the AceDhaie-animss without
head They really have no head. The anterior
and posteriOr extremties hardly differ This class
Of acephalm have the bivalvc shells. You have
here examples of them, two shells united IN Tue
superior margin and movable along the pack. but
many of them unite to form compound masses
Yet the organization Of the individuals thus CON
nected has been ascertsined to show the same
structure as that OF the bvalye class. shall soon
enter upon the details after have explained the
characteristics OF the Acceptable.
The characteristic OF this class is TO have two
symmetrical regions a right and left side, over
which hang the respiratory organs II cut across
au oyster find that the vertical line Is longer than
the longitudinal diameter Here is the anterior re.
gion of the oy ster-here the posteror region and
YOU perceive that the vertical perpendicular d.
ameter Is greater than the longitudinal diameter
Here We have the interior mass OF viscera the sto-
mach aud here both sides, the membranes
covered with bOod-vessels which are the gus two
on each side. That Is the general character oil the
Acceptable 10 have the gills surrounding the ahmen'
tary canal the liver aud other organs which are In
the centre Of the animal and over these sometimes
only one pair OF gills over that again, skin which
lines the shell all over its internal surface winch
has been called the mantle This arrangement
of parts is the general structure OF bivaves or ace
phalous moliusca. This =" mantle Is sometimes
omen the whole length of the animal So It is In
the oyster Perhaps there is no animal among the
molgsca 90 interesting in its structure as the oys
ter Here the learned Professor explained dla-
gram illustrative OF the structure OF the oyster
which with the other diagrams, VIII be given
hereafter
Allow me few minutes beyond the hour which
! see has now expired, IN order 70 hnish the oe'
seription OF the acephels. lApplause.
Tho shells are not always symmetrical some
times that of the right hand side is larger than that
of the ithand aide. and rice rersa- Sometimes
the anterior and pOsterlOr extremitles are equal,
while the two sides are unequal. sometimes on
the other hand, the two sides are equal and the
extremities unequal, and Ia these differences we
have characteristics Oy winch ettas uuui"c' VI
these bivalves may be divided into families rs
important in the beginning 70 give them the same
position when we desire TO compare them For
instance. in some OF them we have one valve con
vex and the other fiat Many natursiists have con.
sidered these cases 70 present instances OF dorsa
valve and ventral valve. But when We examine
the formation properly 1t Is easy to perceive that
this is an error aud that what called the dofsa
valve is nothing more than an exaggeration oil tns
form which we see in the oyster, where one OF the
valves is deeper than the Otherand Is fat. The
only difference between the tcrrabraccula IS that
in them the anterior and posteriof margins are en-
tirely symmetrical. and only the nghthand and
leit-hand sides are unequal Ii Is Dot so IN the
oyster Ii IS important to understand this point
Let US take a symmetrical bvslye shell and be
gin with that Ia that the right aud eit sides are
easily known by the positions OF both, by the
appendices round the mouth and the symmetry OF
the valves There are two equal vslyes-one on
the right the other on the left Here IL the mouth.
Here is the back Here is the foo, BY which the
animal walks protruding between the two valves
Here are the tubes by which the water enters
You see that the anterior end OF the animal 10 broad
er than the pos,erior aud in every respect Il 10 ca
~ to see the proper position OF such shell. In
the oyster these anterior and poseror ends are 50
irregular hat we have no means TO ascertain which
IS the anterior and which the posterior until we
open the animal and discover the position OF the