.

■

productive genialities, or
zoophytes, enabling thes
to rise from tJie bottom
place to place during th

On the existence and uses of Cilice in the young of the
Gasteropodous Mollusca, and on the causes of the spiral turn
uf Univalve Shells.* By R. E. Grant, M.D., F.R.S.E.,
Fellow of the Royal College of Physicians of Edinburgh,
and formerly Lecturer on Comparative Anatomy.

C From the Edinburgh Journal of Science, Vol. vii. No. \.)

W hen we examine the surface of the minutest animalcules with
a powerful microscope, we perceive that their quick locomotions
are produced by the rapid vibration of very minute processes
termed cilice, variously disposed on the surface of the body in
the different species. Iu zoophytes, whose fixed and inert
axis prevents them from swimming to and fro in search of
prey like animalcules, we observe incessant currents of water
directed to the mouths of the polypi, caused, not as is gene-
rally supposed by the motions of the tentacula, but by the quick
vibration of cilice disposed either on the tentacula, or around
the mouths of the polypi. I have already shown that the
same minute vibratory organs exist on the surface of the re-
productive gemmules, or so named ova , of a great variety of
zoophytes, enabling these fixed and apparently inert animals
to rise from the bottom of the sea, and swim rapidly from
place to place during the first stage of their existence, sepa-
rate from the body of the parent. Although the cilice , in the
simplest orders of animals, might be considered as organs of
motion destined to supply the place of the muscular system,
a more extended application of the microscope will show that
they are not confined to animals thus low in the scale, but are
likewise of frequent occurrence in such as have the muscular
and nervous systems highly developed, and probably that
they have some influence in the first developement of the em-
bryo of the most perfect animals. While watching the pro-
gress of the embryo of the Buccinum undatum, and of the

• Read before the Wernerian Natural History Society of Edinburgh
on the 24th March 1827.

A

2 Dr Grant on the existence and uses of Cilice

Purpura lapillus, with the view of determining the influence
exerted by the enormous pulsations of the heart of the testa-
ceous gasteropodous mollusca, in causing the oblique spire of
univalve shells to lie always on the side opposite to that or-
gan, I was early struck with the rapid and incessant motion
of the amniotic fluid towards the fore part of the body of
these animals during every stage of their developement within
the ovum, and it was easy to observe by the aid of the micro-
scope that these currents were produced by cilice placed around
the margins of two funnel-shaped projections on the fore part
of the young animal. On examining the cells newly deposited
by the female Buccinum undatum , whether in basons of sea
wrater, or on the sea shore, we find in each cell about a thou-
sand very small yellow opaque spheres, suspended in a trans-
parent gelatinous fluid, which has a saline taste, and leaves
dendritic crystals on evaporation. These yellow bodies do
not effervesce in nitric acid, nor can we perceive any lime se-
creted in the shell of the young animal before it comes in con-
tact with the sea water by the opening of the cell at maturity.
The yellow spheres are observed to assume an arrangement in
curved and convoluted rows, and at length they are found
grouped together into about twenty small separate masses,
where they are united by a gelatinous basis. Soon after the
formation of these twenty round groups, we observe the gela-
tinous connecting matter form a transparent covering on each
group, which is the rudiment of the future shell, and on one
side the gelatinous matter is lengthened outwards, so as to
form the margins of an internal cavity whose entrance is sur-
rounded with vibrating ciliae,axu\ in the interior of which we per-
ceive a constant revolution of the particles of some fluid. The
vibration of the cilice, and the revolving current in the internal
cavity, are perceived long before the pulsations of the heart, or
any appearance of that organ are discernible, and are the first
indications of life in the embryo. The yellow opaque bodies oc-
cupy the shut end of the spire like the testicle and ovarium of
the adult. The heart is formed on the left side of the trans-
parent anterior part, and its motions are so great, that at each
diastole the whole projecting anterior half of the animal is
forced considerably to the right side, causing that part of the

3

in the young of the Gasterupodous Mollusca, fyc.

body, and consequently the shell, to assume a curved form,
with the heart always on the convex side of the curve. The
heart pulsates about twenty times in a minute, and the dias-
tole of its cavities is much more sudden and remarkable than
the systole. If the motions of the heart were the only powers
which turned the body from a straight line, the spire of the
Buccinum would revolve on the same plane round its shut ex-
tremity, like that of a Spirorhis ; but as the animal’s foot re-
quires continually to descend over the columella of the shell,
before it can reach a solid surface to creep upon, the body
and the shell are thus incessantly deflected from the original
plane, and forced to assume the spiral form which we observe
in the adult Buccinum , and in most univalve shells. In the
reverse shells, where the cone lies on the left side of the ani-
mal, we likewise find the heart in a reverse situation, being
then on the right side. The two wide projecting circles of.
cilice at the sides of the mouth continue visible for some time
after the escape of the young Buccinum from the general cell,
and they are of such length and size that their motions can
be easily followed by the eye aided by the microscope. The
young of the Purpura lapillus are also inclosed in a horny
general capsule, like those of the Buccinum. The ovum of the
Purpura is shaped like a grain of corn, while that of the Buc-
cinum is flat like a split pea. When first deposited, the horny
covering in both is white and soft, but soon becomes yellow
and firm, and the transparent gelatinous matter enveloping
the young becomes gradually thinner as the young advance
to maturity. There are about fifty-five young in each cell of
the Purpura, and they exhibit the same mode of develope-
mentas those of the Buccinum ; the same revolution of particles
within the transparent part of the embryo give the first indi-
cation of life, and the same wide ciliated opening is seen on
each side of the head, the cilice continuing to vibrate for some
time after the escape of the young from the cell or ovum, as
in the Buccinum.

These circles of long vibrating cilice I have also met with
in the young of other genera of testaceous mollusca, as the
Trochus, Nerita, &c. which are not inclosed in a general horny
cell, but are merely enveloped in a soft gelatinous matter, by

4>

Dr Grant on the existence and uses of cilia

which they adhere to the leaves of fuci till they arrive at ma-
tuiity. In such genera as have the ova enveloped only in a
soft gelatinous matter, we find a delicate membrane surround-
ing each foetus , and inclosing a thin amniotic fluid. In these
the cilice are so long, and so rapid in their motions, that the
young are seen within the ova revolving continually round
their own axis, by striking the cilice against the inside of the
containing membrane; and when they escape from the ova, they
are carried with great velocity through the water by the vibra-
tions of the cilice. I have observed the same appearances in
the young of the naked gasteropoda as in the ova of different
species of Doris , Eolis, &c. which are inclosed in a soft trans-
parent gelatinous matter, and adhere by it to rocks or other
solid marine bodies. The young in these genera are likewise
surrounded, each by a thin membrane and amniotic fluid.
They are seen almost continually revolving round their centre
within the ova, and they swim rapidly forward by the action
of their cilice when they escape from the ova. In those ge-
nera which deposit the young in a general horny cell, as those
first described, we find no membrane or amniotic fluid sur-
rounding each foetus, but the horny covering is lined with a
delicate membrane which incloses the whole of the embryos
and the gelatinous fluid in which they are developed. The
young of the Buccinum, when mature, escape from the cell,
by a part of the horny covering separating on the inner con-
cave side of the cell. The young of the Purpura escape by
the falling off of a firm gelatinous plug from the free extre-
mity of the cell. The portions of the outer covering which
fall off are probably loosened by the motions of the young
within ; and as the young are still safely lodged in their cells
when they first come in contact with the sea water by the for-
mation of the aperture, we find the cilice in such genera much
less developed than in the other genera without a horny co-
vering. Their motions appear destined to bring a constant
supply and renewal of pure sea water in contact with the
young in the cells, in order to perfect the formation of the
shell before their final departure from the now open cavity
of the cell. In the ova which are enveloped in a gelatinous
connecting matter without any horny covering, we observe

in the young of the Gastcropodous Mollusca, fyc. 5

tliat connecting matter become very soft and loose, and se-
parate into long flocculi when the young have arrived at
maturity ; and when the ova separate successively from the
general mass by the action of the waves, the young in each
ovum is so large as nearly to fill the whole of the vesicle which
contains it. The cilice in these species are so long, and move
with such rapidity, while the young gasteropod is incessantly
revolving round its own centre, that probably the continued
pulsations of the ciliae against the sides of the containing ve-
sicle tend to abrade or weaken it, and thus aid the escape of
the young animal. After their escape from the vesicles, the
rapid vibrations of these long cilice cause the young animals
to swim with great velocity to and fro in the water, which will
greatly accelerate their means of procuring food during their
infant state ; and as they have neither a byssus to fix them-
selves to rocks, nor a calcareous shell to protect them from
the violence of the sea, the power of rapid locomotion which
they possess by means of the cilice will add much to their
safety in an element in constant agitation.

There is, a remarkable similarity in the structure of the
ciliated parts in the embryos of all the gasteropodous mollusca
I have yet examined, and even in the general form of these
animals, whether naked or testaceous, in their infant state.
The existence of those singular minute vibrating organs term-
ed cilice , appears not to have been hitherto noticed in animals
so high in the scale ; but from their general occurrence in this
extensive class, it is highly probable that they are much more
frequent and important organs in the economy of the lower
animals than observation has hitherto shown.

^ <*. *BcV

( * '' ■ '

■ • " {

j-'ama;. , <u q»:>, i uuo ^vu, ptyj

: 1 '• '-‘J- ■ v • .... ;

-1' ;,f 1 * - • a i • • L : .. .

‘ • '• ' *‘J ' -• ■■ ■ oM' ' ' . . >

’ ■' !< 1 ... ' ■:= ; V

• . : .

■ . •; ■ .. ....

r?

1 . ! :K‘ <'j . ,

■ \ . Si • .

>< •*•;. •' • .’! . (I ; • . , -;;r ..

.

■ :j j:<J ft, KJ'^IO ; , .,rp;

.

‘

_

. ,