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A monograph of the British Spongiadæ online

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development by the necessities of combination with the
adjoining spicula, and their apices are directed in such a
manner that they lap over each other in opposing lines, so
that each two form a spliced joint, giving a much greater
amount of strength than the mere crossing of the radii at
various angles, as in those of Geodia. The inhalant areas



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lOi ANATOMY AND PHYSIOLOaY

thus formed appear to differ very slightly from those of
Halichondria panicea, in each of which several pores are
opened, while those of JDactyhcalyx Prattii seem to be
devoted each to a smaller number (Fig. 806, Plate XXIX).

As the ternate spicula thus united for the support of the
dermal membrane would afford it little or no protection
against the voracity of its smaller enemies, we find the ne-
cessary defence in innumerable short, stout, entirely spined,
cyUndrical spicula, not exceeding g^ inch in length ; thus
minute, there is no conceiving a predaceous creature with a
mouth so small that they would not enter and become a
subject of annoyance so great as to interfere seriously with
its attacks on the membrane ; and they are so numerous,
and so closely packed together, that no portion of it equal
in size to the length of a spiculum could be removed
without one or two of them accompanying it.

A still further advance in this system of dermal support
and defence is exhibited in the beautiful harrow tissue of
Dr. A. Farre's siKceo-fibrous sponge, Farrea occa^ Bower-
bank, MS., to which his specimen of Euplectella cucumery
Owen, is attached. In this case we have a perfect and
regular quadrilateral network of smooth siliceous fibre, from
the angles of which a double set of short, conical, spicular
shafts are projected, each about ^ inch in length and
entirely spined. Each set are at right angles to the plane
of the network, one series pointing inward and serving
the purposes of attachment to the mass of the sponge
beneath, while the other set are directed outward, serving
as defensive weapons ; so that a small piece of this tissue
beneath the microscope closely resembles an agricultural
harrow, with the difference that it has two sets of teeth in
opposite directions instead of one. The dermal membrane
has been nearly all destroyed; but entangled with the
fibres of the skeleton there are some attenuato-stellate
spicula, with which it is probable the dermal membrane was
amply furnished as secondary defences against its minute
enemies.

I beheve the surface presented to the eye in the portion
represented by Fig. 311, Plate XXI, to be the external



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OF THE SPONGIADiB. 105

surface, as the fragments of the dermal membrane which
remain all seem to cover that side of the fibres. Generally
speaking, there is some difficulty in detecting the double
series of spicular organs at the angles of the network, but a
reversal of the object beneath the microscope immediately
removes all doubt on that subject-
In Grantia compressa and ciliata the intermarginal cavities
appear to attain their highest degree of development, and
are multiplied and expanded to such a degree as to almost
supersede every other organ. The whole sponge in these
species is formed of a great accumulation of elongated cells
or cavities, closely adjoining each other and angular by com-
pression. Their conical distal terminations, abounding in
pores, represent the external surface of the sponge, while
their valvular proximal ends form the inner surface, in con-
junction with the shallow cavities, into the distal ends of
which each cell discharges its contents. These shallow
depressions, intervening between the intermarginal cavities
and the cloaca, are all that remains to represent the incur-
rent portion of the interstitial systems so largely developed
in the Halichondroid sponges, the great cloacal cavity
entirely superseding the excurrent spaces and canals (Figs.
312 and 313, Plate XXI).

In these species of Grantia there is no doubt regarding
the existence of cilia, the whole of these great cavities being
completely lined with them.

It is a question whether the intermarginal cavities share,
in common with the interstitial canals, in the function of
the assimilation of nutriment, or whether they are devoted
solely to the aeration of the fluids of the animal ; and this,
if we consider the structure and extent of the interstitial
canals in the Halichondroid sponges, is probably the case.
In Grantia the abundant provision of cilia in those cavities
at once stamp them as breathing organs ; and although
cilia have never yet been satisfactorily proved to exist in
the intermarginal cavities of the Halichondroid sponges,
there can be no reasonable doubt of their being the homo-
logues of the large ciliated cavities in Grantia compressa
and other similarly constructed sponges. Now, in these



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106 ANATOMY AND PHrSIOLOGT

sponges, although the cilia may be readily seen in vivid
action within the open oscula, as I have described at length
in my paper " On the Ciliary Action of the Spongiadae,"
published in the ' Transactions of the Microscopical Society
of London/ vol. iii, p. 137, not the slightest trace of cilia
exists without those organs ; and this seems to indicate that
the aerating functions were strictly confined in these
sponges to the large intermarginal cavities.

The same mode of reasoning applies equally well to the
intermarginal cavities of Geodia and Pachpnatiama, to
which it is probable that the cilia are in like manner con-
fined. The great valves at the proximal ends of these
cavities in this tribe of sponges appear to strongly indicate
a decided separation of the functions of aeration and di-
gestion ; and if this conclusion be true in regard to the in-
ter-marginal cavities of Geodia and Pachymatisma, it will
probably be so in the homologous organs in Grantia ; and
in this case we must look for the digestive surface in the
shallow cavities intervening between the terminal valve of
the intermarginal cavities and the parietes of the great
cloaca, and of the surfaces of that organ itself. The
structure and functions of the intermarginal cavities, and
especially as displayed in Geodia and Pachymatisma, indi-
cates a closer alliance with the great class Zoophyta than
has hitherto been suspected to exist. In the one case we
have an accumulation of individual animals conjoined in
one mass ; in the other, a similar congregation of organs in
place of individuals.



DERMAL MEMBRANE.

The dermal membrane envelopes the sponge entirely.
When denuded of sarcode by partial decomposition, it has
the appearance of a simple, pellucid, unorganized membrane.
In the living state its inner surface is somewhat thickly
coated with sarcode, and it has the appearance of, com-
paratively speaking, a stout, tough skin, and in many
sponges it requires a considerable amount of violence to



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OF THE SPONGIADiB. 107

tear it. The dermal membrane of the Turkey sponge of
commerce, Spongia offidnalia^ is tkbundantly supplied with
primitive fibrous tissue. It curves round the margins of
the porous areas, thickening and strengthening the whole
of the dermis to a very considerable extent, but it exists to
a very sUght extent in the pellucid membranes of the areas
in which the pores are opened. When ahve, it is replete
with powers of life and action of a very remarkable descrip-
tion. Without the slightest appearance of nerves or
muscles, it has the power of opening pores on any part of
its surface, and of closing them again at pleasure, without
leaving a trace of their existence to indicate the spot they
occupied ; and there is no amount of laceration or destruc-
tion that it does not seem capable of repairing or replacing
in a very short period, reproducing itself over extensively
denuded surfaces in a very few hours. It also shares, in
common with the interstitial membranes, the power of
strongly and quickly adhering to other sponges of the same
species with which it may be brQUght in contact, but never
with those of a different species, however long the two may
remain pressed against each other. In some sponges the
distal extremities of the skeleton pass through and project
beyond the surface of the dermal membrane, while in other
cases the whole of the skeleton is confined within it.

I will not describe at length these remarkable powers of
the dermal membrane, but refer the reader to a series of
observations on the " Vital Powers of the Spongiadae,"
published in the * Reports of the British Association ^ for
1856, p. 438, and for 1857, p. 121, in which I have de-
scribed in detail a series of observations and experiments
on living sponges, which demonstrate in a satisfactory
manner the extent of the vital powers and capabilities of
this highly sensitive membrane.

In some species of sponges the outer surface of the
skeleton is especially modified to strengthen and support
the dermal membrane. Thus, in some of the keratose
sponges of commerce, in parts of the sponge which have
been in contact with other sponges, or with rocks or stones,
we find a fine network of stout fibres immediately beneath



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108 ANATOMY AND PHYSIOLOGY

the dermis, as represented by Fig. 310, Plate XX, and
Isodictya varians, Bowerbank, is always furnished with a
fine network of spicula, the reticulations consisting of a
single series of spicula only, and on this framework the
dermal membrane is firmly cemented. Fig. 309, Plate XX,
represents a small portion of this dermal reticulation, mag-
nified 108 linear.

In Halicondria panicea the same description of reticula-
tion prevails, but in this sponge the fibres of the network
are always composed of numerous spicula cemented
together, as represented in Fig. 303, Plate XIX, illustrating
the porous system of the above-named species of sponge.
But this regularity of structure is not constant even in the
same individual; thus, in Hal. panicea you wiU often
observe one portion of the dermis beautifully reticulated,
while a closely adjoining spot will be supported by a series
of matted spicula, without any indication of areas for the
pores, and these variations in structure are evidently de-
termined by the presence or absence of those organs at
particular parts of the surface. In other cases, beside a
general attachment of the inner surface of the dermal mem-
brane to the surface of the skeleton, we find it supported
by numerous flat fasciculi of spicula dispersed irregularly on
its inner surface, and diflering materially in size and form
from those of the skeleton, as in our common British
species, Halichondria incrmtanSy Johnston. Great variety
exists in these modes of strengthening and supporting the
dermal membrane; but those which I have described above
will suffice to illustrate the general principles of their appU-
cation. Beside the general systems of external defence, the
dermal membrane is often suppKed with special defences.
Thus, in Tethea muricatay Bowerbank, MS. (Figs. 304 and
305, Plate XIX), we find its outer surface abundantly sup-
plied with elongo-stellate spicula, which project externally
to a considerable extent; and in Bictyocylindrm stuposus,
Bowerbank, beside the numerous defensive spicula pro-
jected through the surface, we find the membrane filled
with minute sphero-stellate spicula, which would effectually
protect it from the assaults of any minute enemies that



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OF THE SPONGIADiB. 109

might attempt to prey upon it. Fig. 298, Plate XVIII,
represents a small portion of the* dermal membrane of this
sponge. This mode of defence is very general in the
genera Geodia^ Tethea, and Pachymatisma^ and it occasion-
ally occurs in other genera of Spongiadae,



THE PORES.

The pores in the Spongiadae are the orifices or mouths
through which the animals breathe and imbibe their nutri*
ment. They are situated in the dermal membrane, and are
exceedingly numerous when the imbibing powers are in
full operation. In PachyinatiBma and Geodia^ and in some
other highly organized genera, there is good reason to
believe that they are permanent organs, opening and closing
repeatedly in the same situations. But in the greater part
of the Halichondroid types of sponges they are certainly
not permanent orifices, like the mouths of higher classes of
animals, and in these sponges, when they are in a state of
complete repose, there is not the slightest indication of
their existence. Their usual form is circular, but they fre-
quently assume the shape of an elongated oval, and within
a limited range they vary to a considerable extent in their
dimensions ; on the whole, they exhibit a very constant and
universal type of form and size ; however different may be
the internal structure of the sponges, or however great may
be the difference in size of the individuals, they always
appear to maintain their normal characters. No definite
law appears to prevail in their distribution over the surface
of the sponge, and they are liable to appear to a greater or
a less extent on every part of its external surface, wherever
there are intermarginal cavities beneath. The situations
where they may be expected to appear may in many in-
stances be readily recognised. Thus, in Halivhondria
paniceay wherever we see on the dermal membrane a well-
defined reticulation of spicula, with clear and distinct areas,
there, when the sponge is inhaling, we may expect to find
the open pores, as represented in Fig. 808, Plate XIX,



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310 ANATOMY AND PHYSIOLOGT

while on spots perhaps immediately adjoining where the
dennal membrane is occupied by a thickly interwoven mass,
a felting of spicula, the probability is that not a single pore
can be detected.

In some of the West India fistulose sponges we find the
large or primary area of the dermal surface composed of
keratose fibre, and within these large areas the dermal
membrane is strengthened and supported by a secondary
reticulation of spicula, in the areas of which the pores are
opened. In these secondary reticulations the spicula are
abundant, while in other parts of the sponge the tension
spicula are rather of rare occurrence. In Graniia, a sponge
of a widely difierent construction to those of the Hali-
chondroid type, they occupy the distal extremities of the
large intermarginal cavities of the sponge, and they appear
to open over the whole of those portions of the cavities not
in contact with the adjoining ones.

In Pachymatisma Johnstonia, Bowerbank, a British
sponge closely allied to the genus Geodia, we find the
dermal membrane perforated by innumerable pores, some
as minute as ^-^-^ inch in diameter, while others attained the
size of 535 i"ch. They are nearly equidistant from each
other, but without any order in their arrangement. Imme-
diately beneath the dermal membrane there is a stratum of
membranous structure and sarcode destitute of ovaries, and
about equal in thickness to one third of that of the whole of
the dermal crust, the remaining two thirds of which consists
of a stratum of ovaries closely packed together, but per-
forated at intervals by the intermarginal cavities. Through
the upper stratum, destitute of ovaries, a small canal
passes from each pore to the nearest adjacent intermarginal
cavity, so that there are a series of them at various angles,
all concentrating their streams of inhaled fluid at the distal
end of the cavity, which is gradually expanded in diameter
to receive them. In these sponges, therefore, each mouth
appears to be furnished with a separate oesophagus, if I
may be allowed the term, connecting it with a stomach-
like cavity, common to a group of mouths above it; a
system of organization strikingly in unison with that of the



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OF THE SPONGIADiE. Ill

higher classes of animals. In some cases, as in Geodia
M'Andremi and Barretti, Bowerbank, MS., we find the
pores systematically congregated in groups, as in Fig. 302,
Plate XIX, which represents two groaps from the latter
species, and this congregation is accounted for by the
peculiarities of the form and arrangement of the inter-
marginal cavities of that class of sponges.

In my "Further Report on the Vitality of the Spongiadae,"
published in the ^Reportsof theBritish Association' for 1857,
I have described at length the opening and closing of the
pores in Spongilla jluviatilia ; each operation is commenced
and terminated in less than a minute ; they are perfectly
dependent on the will of the animal, and in neither case are
they simultaneous, but follow in irregular succession, in
accordance with the necessities of the animal ; and when
once closed, they do not appear to ever open again in pre-
cisely the same spot.

In these wonderful opening and closing operations in the
dermal membrane of SpouffiUa^ every movement is accom-
plished as systematically and accurately as if there was a
perfect system of nerves and muscles present, while not a
vestige of fibrous structure can be detected in the thin
translucent membrane and its sarcodous lining. No
cicatrix remains for an instant after closing, no indication
of the spot where the opening is the next moment to be
effected.

In sponges exposed to the action of the atmosphere,
between high- and low-water marks, and in dried speci-
mens, the pores can rarely be detected. In the first case
they are carefully closed on the receding of the tide, that
the water within them may be safely retained during their
exposure to the atmosphere, and in the latter case the
violence offered to it, and the shock of its removal from its
native locality, is sufficient to induce an immediate closing
of those organs, as I have shown in the details of my
observations on these organs in SpongtUa in the volume of
the * Reports of the British Association' for 1857, to which
I have before alluded. But should a specimen of marine
sponge, after a careful removal from its place of growth, be



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112 ANATOMY AND PHYSIOLOGY

placed in a shallow pan of sea-water, and be allowed to die
of inanition, it then frequently expires with the whole or a
considerable portion of the pores open, and in that state it
may be readily preserved for the cabinet.



THE OSCULA.

The oscula are the faecal orifices of the sponge. They
are situated at the distal terminations of the single or con-
centrated excurrent canals of the animal. They vary
considerably in form and size ; sometimes they appear as
single large orifices, while at others they consist of several
small orifices grouped together. When the sponges are
massive and solid, they are usually to be found dispersed
over the dermal surface, but occasionally they are grouped
on the highest portions or on the elevated ridges of the
mass. In Geodia Barretti, Bowerbank, MS., they are
concentrated in deep depressions or pits. In other cases
they are entirely hidden from the view, lining the interior
of elaborately constructed cloacaB, situated in the centre of
the sponge, as in Grantia compreaaa and ciliatay Verongia
Jistulosa, and a numerous series of species of fistulose
sponges from the West Indies.

They are permanent organs, and are capable of being
opened or closed at the will of the animal, and are subject
to a considerable amount of variation in size and form, in
accordance with the variations in the actions of the sponge.
Thus in littoral sponges they are frequently entirely closed,
and their situation even quite indeterminable during the
period of their exposure to the air ; but when immersed in
water, and the sponge is in the energetic action of the imbi-
bition of nutriment, they are expanded to their full extent ;
but when this action ceases and that of gentle respiration
only exists, many of them close entirely, and others exhibit
apertures not exceeding half their former diameters, while
the imbibition of nutriment was in vivid action. Their
expansion or contraction is not rhythmical ; each can be
opened or closed at the will of the sponge without any



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OP THE SPONGIADiE. 118

apparent effect on the others. Nor is the habit of opening
and closing the oscula the same in every species. Thus in
the course of my observations on Halichondria panicea and
Hymeniaddon caruncida in their natural and undisturbed
localities, I have frequently observed during their exposure
to the air at low tide, that while no oscula in an open
condition could be found in Hymeniaddon caruncula^ the
greater portion of those on the specimens of Halichondria
panicea were more or less in an open state.

They appear also to be subject to a considerable amount
of modification as regards situation, even in the same
sponge. Thus in our common British species, Halichondria
panicea^ when of small size, they are situated on the surface
of the sponge, and are scarcely, if at all, elevated above the
dermal surface ; while in large specimens of the same
species we find them collected in the insidesof large elongated
tubular projections or common cloacae, and these organs
vary from a few lines only in height and diameter to
tubular projections several inches in height, with an
internal diameter of half or three fourths of an inch. When
they attain such dimensions their parietes are often of con-
siderable thickness, and their external surface becomes an
inhalant one, like that of the body of the sponge.

In many species the oscula are always elevated above
the dermal surface, and these thin pellucid elevations are
permanent, while in others, as in Spongilla fluviatilis, the
tube exists only during the course of the energetic excur-
rent action ; and in such cases it appears to be subject to
great variation in size and form, as I have shown in the
description of SpongiUa in my " Further Report on the
Vitality of the Spongiadae," ' Reports of the British Asso-
ciation ' for 1867.



INHALATION AND EXHALATION.

The works of the old writers on Natural History are full
of vague opinions on the nature of sponges, but none of
them seem to have seriously studied their anatomy, or to

8



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114 ANATOMY AND PHYSIOLOGY

have kept them alive in sea-water and examined their daily
habits. They appear to have excited abundant attention
in the closet, and but very little in their natural localities.
Their ideas are so loose and indefinite that it would really
be a loss of time to seriously examine and attempt to
refute them; and as Dr. Johnston, in his 'History of
British Sponges/ has given in his Introduction, Chapter II,
an excellent digest of the various opinions of the previous
writers on the subject, I shall content myself with referring
my readers to the work of that eminent author for further
information on these subjects, and of briefly referring to
the few actual observations that appear to have been made
by naturalists.

Marsigli, at the beginning of the eighteenth century, has
stated that he had seen contraction and dilatation in the
oscula of several sponges just removed from the sea.

After Marsigli, Ellis (Ellis and Solander), pp. 184, 186,
and 187, (see also ' Zool. Joum./ pp. 375, 376,) enunciated
similar opinions founded on his own observations on the
action of the oscula and their currents ; but neither of those
authors was aware of the true mode of the entrance of the
water into the sponge — a much more difficult problem to
solve than its exit through the oscula.

Cavolini, in his researches, although made on sponges
recently taken from the sea, failed in seeing the action of
the oscula as Ellis had done, and he accordingly disputed
their truth. At a later period, Colonel Montagu, although
actually examining them in the places of their growth,
arrived at similar conclusions to those of Cavolini, and, like
that author, he believed them to be animals of a very torpid
nature, Montagus reasoning to prove the animality of
sponges is for the most part sound and excellent ; he says :
" Whether motion has ever been discovered or not in any
species of sponge, is not, I conceive, of so much importance
as some naturalists would appear to consider. Those who
are solicitous in their inquiries after the animals which they
have supposed to construct the vesicular fabric of sponges,
have expressed their surprise that in this age of cultivated
science no one should have discovered them, must have



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OF THE SPONGIADiE. 115

taken a very limited view of matter possessing vitality, and
have grounded their hypothesis only upon supposed ana-
logy/' He also observes, " The true character of Spongia


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Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 11 of 25)