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A monograph of the British Spongiadæ online

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system throughout the whole range of the animal kingdom,
and, as may naturally be expected, may be traced in the
Spongiadee, however they may dijBFer in their structure and
organization. Every cavity in the interior of the animal is
coated with a tBin stratum of sarcode, over which the incur-
rent and excurrent streams of water, continually passing
through the sponge with a greater or less degree of activity,



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OF THE SP0NGIADJ5. 93

are flowing, bearing with them the molecules of animal or
vegetable matter that are floating in the surrounding water,
and in small specimens of SpongUla the molecules, thus
imbibed by the pores, may be seen rapidly traversing the
tortuous canals of the sponge, being frequently suddenly
arrested in their course, and adhering to the sarcodous sur-
face over which they are gliding ; and if, while the rapid
inhalent process is going on, and an infinite number of
extraneous particles of matter are seen entering the pores
in every direction, we turn our attention to the excurrent
streams from the oscula, we shall be at once struck with
the comparatively small number of effete particles that
issue from those orifices. While on the contrary, if we
examine the oscula while the gentle breathing inhalation
only is proceeding — and the nutrient particles are rarely
seen entering the pores — we shall not fail to observe that
the amount of effete particles ejected from the oscula is
still continuing with a regularity that is strikingly indi-
cative of their systematic and gradual liberation from the
sarcodous surfaces of the interior of the animal, and it may
be further observed that the molecules thus ejected are
very much below the average size of those previously
imbibed, and that they are always in an exhausted and
collapsed condition.

If sections of a sponge in a living state be examined by
transmitted light with a power of about 500 or 600 linear,
the vrhole of the sarcodous substance will be seen abound-
ing in the nutrient particles, some simply adhering to the
surface, while others are embedded at different degrees of
depths, exhibiting all the varieties of form and condition
that are so characteristic in the molecules described as
existing in the mucous lining of the intestine of the mouse,
and in many cases, excepting that in the Spongiadae, the
sarcodous surfaces are somewhat more evenly spread over
the membranes on which they repose ; such is their simi-
larity, that the two tissues, so distant from each other in
the scale of created beings, can scarcely be distinguished
from each other under the microscope.

There are other points of similarity existing between the



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94 ANATOMY AND PHYSIOLOGY

sarcode lining the interior of the sponge and the so-termed
mucouB lining of the intestines of the higher animals.
Under natural circumstances the two substances are in-
soluble in water, but under the effects of certain stimuli
they are each discharged from their natural bases with
great facility; and where this discharge prevails to any
great extent, it appears to be speedily fatal to the life of
the animal. Thus in cases of extreme diarrhoea in warm-
blooded animals, immediate prostration of the vital powers
is the inevitable residt ; the final and most important act
in the sustentation of the vital powers is greatly interfered
with or entirely destroyed, and great prostration of strength
or death is speedily the result. The marine Spongiadae,
under ordinary circumstances, may be kept in their natural
element, and death may ensue for want of a supply of fresh
water, without any remarkable amount of viscous dis-
charge. But if we remove a living specimen of Halickon-
dria panicea from salt water and plunge it into fresh water,
the result is frequently an immediate and profuse discharge
of a glairy gelatinoid matter. The same result may be
induced by an addition of a considerable quantity of s«Jt to
the sea water in which the animal was contained, or by the
addition of a small portion of alum ; and when once this
viscous discharge has been induced, the life of the sponge is
inevitably destroyed. In others of the lower marine
animals the same effect is induced by similar causes, and
with many of them the immersion in fresh water is noto-
riously the quickest and most certain mode of destroying
vitality, and in these cases the decease is almost always
accompanied by an abundant flow of viscous matter.
Thus if we have this substance upward from Actynophrys
Sol to man, through the Spongiadae and all its other gra-
dations of animal existence, it is always found to be pre-
sent, and always intimately connected with the digestive
process. Especial organs for respiration, nerves for sensa-
tion, muscles for motion; all these may apparently be
dispensed with in turn, and yet the animal will perform its
accustomed functions ; but this substance, as mucous lining
of intestine, or sarcode, as I have before observed, appears



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OF THE SPONGIADJE. 95

never to be absent. It even seems to acquire a greater
importance in the animal economy as we descend in the
scale of beings, until the animal in Amcsba and Actifiophrys
Sol becomes entirely composed of it ; and in these creatures
it seems to perform all those varied functions which in
other animals are distributed among a numerous set of
especial organs. It thus appears to be the most constant
and perhaps the most important attribute of animal life.
In its most isolated form it apparently supersedes every
other organ in the animal. In Amceba it appears to exist
in its simplest and most isolated condition, it moves by its
contractile power, and absorbs nutriment. In Actinophrys
it adds another function to its list of capabilities, that of
throwing out pseudo-tentaculae by which it entangles and
conveys its prey to its surface. In the foraminated animals
it develops further powers, it secretes a chambered shell for
the protection of its surface, and throws out pseudo-podia
by which it moves over comparatively a considerable space
in a short period, and anchors itself at its pleasure in any
position or locality it may choose to remain in. As we
proceed higher in the scale of creation its functions become
more limited, but in the act of digestion it always appears
to take a most important part.

The internal vital powers of the Spongiadae seem to be
resident in this substance, which appears to fulfil in these
animals all the functions of the nervous systems in the
higher classes of creation, gifted with elaborately developed
nervous systems, and if we view this extraordinary sub-
stance in reference to nervous matter, it seems to lead us
irresistibly to the hypothesis that they are to a certain
extent identical, or that the latter enters in a diffused state
into the composition of the former. In plants we have
movements resulting from irritation closely resembling
those arising in animals from nervous action ; but who has
ever seen the nerves in plants ?

In the dermal membrane of sponges we have actions
arising from alarm or injury analogous to those induced by
nervous influence, but no nervous filaments can be detected.
We naturally ask, why does alarm immediately cause the



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96 ANATOMY AND PHYSIOLOGY

closing of the pores in Spongilla, and suspend inhalation
and imbibition ? What unknown cause is it that effects
these actions usually dependent on the exertion of nervous
energy ? In the opening and closing of the defensive cones
of spicula in Grantia ciliata we have a resemblance of
muscular action, without the presence of muscles ; but here
we have a sufficient cause for the effect in the active vibra-
tion of the cilia inducing a flow of water which produces
the same results that might otherwise have ensued from
muscular action, but we have no such solution to the
inherent powers of action in the sarcodous membranes of
the Spongiadae, or in sarcode in its purest and most iso-
lated forms. Whence then comes the power that inspires
the action of the cilia in the sponges, if it be not from the
sarcode in which their bases, or the cell whence they ema-
nate, are embedded ? If the cilia be removed from the
animal, enveloped in their surrounding sarcode, their action
is continued vividly for a considerable period, but if a
single cilium be accidentally separated from the mass, its
vibratory motion is almost immediately extinguished ; it
has been separated from the vital influence that endowed it
with action.

But let us return again to the dermal membrane of the
Spongiadae, and its internal lining of sarcode, — what
inherent power then is it that renders this wonderfully
plastic tissue so sensitive and self-acting. Is sarcode
another form of nervous matter? Or is that vital prin-
ciple infused in sarcode? That it contains an inherent
vitaUty independent of its connexion with other parts of the
animal, is distinctly proved by its pure existence in Jcti-
nophrys Sol, and by its independent action and movements
when portions of it are removed from SpongUla^ or from
some of the marine Spongiadae. If this supposition be
true, then the whole of the phenomena of its existence in
Actinophrys Sol, in the Spongiadae and in every other form
is at once explained. Why should we not have nervous
matter without tubular structure surrounding it ? If this
hypothesis, that sarcode is a diffused form of nervous
matter, or that it exists in a diffused form in sarcode, be



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OP THE SPOKGIADiB. 97"

true, we have an intelligible solution to an infinite number
of phenomena among the lower classes of animals that
have hitherto been inscrutable. In the higher classes of
animal existence we know well that nervous energy is the
spring whence every other vital power proceeds, and we
trace the nervous system downward in the scale of animal
existences until from a few simple fibres it becomes obso-
lete ; and yet in those creations in which tubular nerves
are no longer to be detected life and action is as vivid in
proportion to their necessities as in the higher classes,
abounding in complicated nervous ramifications. Again,
then, we may ask, whence, in the a;bsence of nerves, comes
the inspiration of all these vital actions, if it be not that
they are due to the inherent nervous properties of sarcode
— a never-failing material in animal existences. Every other
organ may in turn become obsolete, but sarcode never. It
continues its downward course in the chain of existence
until it at last becomes the sole representative of animal life.
If under all these various conditions we consider its
modes of action, we shall find that its imbibing powers are
not exerted continually. In the Spongiadae, as in all other
animals, it has its intervals of action and of rest,* and this
habit will perhaps afford us a useful mode of distinguishing
between animals and vegetables. Thus in animals the
imbibition of nutriment is voluntary and at intervals, while
in vegetables it is involuntary and continuous.

THE INTERSTITIAL CANALS AND CAVITIES.

These organs exhibit their most complete mode of de-
velopment in the genus Spongia and in the Halichondroid
sponges, occupying nearly the whole of the masses of the
animals. They consist of two distinct systems, an incurrent
and an excurrent one. The incurrent series have their
origin in the intermarginal cavities immediately within the
dermal membrane, and their large open mouths receive
from these organs the water inhaled through the pores,

* " Report on the Vitality of the Spongiadse," • Brit. Assoc. Reports ' for
1856, p. 441, &c.

7



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9B ANATOMY AND PHYSIOLOGY

and convey it to the inmost depths of the sponge, ramifying
continually like arteries as they proceed in their course
downward, until they terminate in numerous minute
branches. The inhaled fluid is then taken up by the
minute commencements of the excurrent series, which
continually unite as they progress towards the surface of
the sponge, in the manner of veins in the higher animals,
until they terminate in one or more large canals which
discharge their contents through the oscula of the
sponge. This system is found to obtain in the whole
of the genus Spongia and in the massive Halichondroid
sponges, which have their oscula dispersed over their
external surfaces. By this mode of organization the
inhaled fluid, laden with nutritive particles, is poured at
pleasure into the internal cavities of the sponge, flowing
over extensive membranous surfaces coated with sarcode ;
so that the aggregated surfaces become a great system of
intestinal action, fully equal in proportional extent to that
of the intestines of the most elaborately organized mammal.

They do not in every genus exhibit the regularity of
structure described above, and in some cases the canalicular
form resolves itself into a series of irregularly formed spaces.
Tn other cases, where a common cloaca exists, there appears
to be but one system of interstitial canals, those which
convey the inhaled fluid from the pores through the sub-
stance of the sponge to the parietes of the great central
cloacal cavity which receives the whole of the faecal streams,
rendering the system of excurrent canals unnecessary.

In the Cyathiform sponges we find a somewhat similar
structure. The outer portion of the cup is essentially the
inhalant surface, and the interior of it the exhalant one, and
there accordingly we generally find a great number of small
oscula dispersed on all parts of it, very often having their
margins slightly elevated, that the faecal matter that issues
may be discharged free of the surrounding membrane.

The large fistular projections which form such striking
and beautiful objects in the genus Alcyoncellum are also
great cloacal organs, their dermal membranes abounding in
pores, and their fnner surfaces furnished with oscular orifices,



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OF THE SPONGIADiB. 99

the intervening space being occupied by the interstitial
cavities, the interior forming one large cloacal cavity,
which discharges its contents through a cribriform mouth
at its distal end. In Grantia both systems, the incivrent
and excurrent interstitial canals, become very nearly obso-
lete, the large intermarginal cavities or cells imbibing the
water through their pores on the distal extremities, and
becoming enlarged and elongated until they reach the
parietes of the great central cloaca, into which they dis-
charge their contents, each through a single osculum, into
a short depression or cavity in the parietes of the great
cloaca, and this shallow cavity represents the nearly obsolete
system of excurrent canals.

The membranes hning the incurrent and excurrent canals
are frequently highly organized. In the common honey-
comb sponge of commerce, when in the same condition as
when taken from the sea, these canals are constructed of a
series of compound membranes, each consisting of simple
interstitial membrane with a layer of primitive fibrous tissue
beneath it ; the fibrous portion consisting of a single series
parallel to each other, and so closely adjoining as to touch
each other through nearly their whole- course (Fig. 255,
Plate XII).

When the fibres are clear of the membranous tissue
they appear as simple pellucid threads, but when covered
by the membrane they frequently appear as if moniliform ;
this character seems to be due to minute molecules arranged
in linear series on the membrane immediately above them.
These membranes abound in large, open, oval spaces, so that
the tissue assumes very much the appearance of areolar
tissue, as described by Professor Bowman in his treatise on
mucous membrane in the ' Cyclopaedia of Anatomy and
Physiology.'

The layer of membrane forming the surface of the canal
has its fibres disposed at right angles to the axis of the
canal, while those of the layers beneath it assume various
directions, usually in straight lines, excepting in the vicinity
of the areas of communication, around which they curve to
strengthen their margins.



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100 ANATOMT AND PHYSIOLOGY

In the canals deeply buried in the mass of the sponge
the sides frequently consist of but one layer of membrane
and primitive fibrous tissue, and in this case also the fibres
are always disposed at right angles to the axis of the canal,
but they are neither so numerous nor so closely packed as
in the sides of the great excurrent canals.

The interstitial membranes are also furnished with these
fibres, sometimes in considerable quantity, but rather irre-
gularly disposed, while in other cases a single fibre only
will be observed meandering across the tissue.

The interstitial membranous tissues in a beautiful little
specimen of Alcyoncellum fix)m the North Sea, for which I
am indebted to my friend Captain Thomas, of the Hydro-
graphical Survey, are very similarly constituted to those of
the sponges of commerce. The membranous walls of the
interstitial cavities are each formed of a series of fibro-
membranous layers, the fibres of each layer being disposed
at angles varying from those above and below it.

Figs. 255, 256, 257, and 258, Plate XII, represent
portions of the lining membranes of the incurrent and ex-
current canals, and the mode of the disposition of the
primitive fibrous structure upon them.



INTERMARGINAL CAVITIES.

In the Halichondroid sponges, immediately beneath the
dermal membrane, there are numerous and, comparatively
speaking, large irregularly formed cavities, which receive
the water inhaled by the pores, and convey it to the
mouths of the incurrent canals, which have their origin in
the deepest portions of the spaces. These organs, firom
their 'irregularity in size and form, are not alwaya very
apparent, but if a section be made at right angles to the
surface in a dried specimen of Halichondria panicea or
Chalina aimulans, Bowerbank, they may be readily detected
and distinguished from the interstitial canals and spaces of
the sponge.

Fig. 300, Plate XIX, represents a section of Halichon*



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OP THE SPONGIADJB. 101

-dria panicea, and Fig. 299, Plate XIX, a similar section of
a branch of Chalina simtdanSy Bowerbank, showing that,
however varied the forms of the sponge may be, the inter-
stitial cavities are the same in structure and position.

I have never been able, in the HaUchondroid sponges, to
detect valvular diaphragms separating these spaces from
the interstitial canals and cavities beneath.

In the genera Geodia and Pachymatisma these organs
assume Sk very much greater degree of regularity and a
complexity in their organization that are never apparent in
those of the Halichondroid sponges. In Geodia Barrettiy
Bowerbank, MS., a highly organized species of the genus,
they are found in the crustular dermis in great abundance.
They are in form very like a bell, the top of which has
been truncated. They are situated in the inner portion of
the dermal crust ; the large end of the cavity being the
distal, and the smaller end the proximal one. The open
mouth or distal end of the cavity is not immediately
beneath the dermal membrane. There is an intervening
stratum of membranes and sarcode, of about two-fifths the
entire thickness of the dermal crust, which is permeated by
numerous minute canals which convey the water inhaled
by the pores to the expanded distal extremity of the cavity.
The proximal end is closed by a stout membranous valvular
diaphragm, which the animal has the power of opening and
closing at its pleasure. It is usually entirely destitute of
the characteristic dermal spicula that are found abundantly
in the adjoining membranous tissues.

The action of the diaphragm of each cavity appears to
be independent of the surrounding ones, the condition or
degree of opening of no two adjacent ones being alike. In
the greater number of cases they were in a closed state,
and in this condition the membrane was filled with con-
centric circles composed of minute rugae or thickened lines,
and at the centre it was closely pressed together, completely
closing the orifice. In some cases the membrane was only
partially closed, and the orifice was either circular or
slightly oval ; in others it was nearly as large as the diameter
of the basal end of the cavity. The pursing of the centre



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102 ANATOMY AND PHYSIOLOOT

of the membrane of the diaphragm was always outward as
regards the cavity, so that when viewed from within it
appeared as a slightly funnel*shaped depression, the bottom
of which was conical. The cavities are lined by a smooth
and tolerably strong membrane, abundantly supplied with
slender fibrous tissue, disposed in nearly parallel lines at
right angles to the long axis of the cavity.

The adaptation of the skeleton to the support of these
elaborately constructed organs is very remarkable. The
sponge is furnished abundantly with large expando-temate
spicula, the radii of which are furcated at their apices.
They occur in a series of bundles; the long attenuated
shafts of each fasciculus approximate at their bases, and
diverge thence until the ternate head of each is about
equally distant from its surrounding neighbours, and the
extremities of the rays touch or slightly cross each other,
thus forming a beautiful and regular network, the meshes
being six- or seven-sided, according to circumstances. The
upper surfaces of the radii are firmly attached to or par-
tially imbedded in the under surface of the crustular stratum,
and the areas thus formed are occupied each with the
proximal valvular terminations of one of the intermarginal
cavities.

The progressive development of these inhalant areas,
formed by combinations of the radii of the ternate forms of
spicula in different species of sponges, is very interesting.
In Fachymatisma they are so indefinite that they can
scarcely be said to exist. The ternate spicula are few in
number, and very irregular in their mode of disposition, and
a faint indication only of their future regular combination to
form the dermal reticulation is apparent. In the more
highly organized genus Geodia we find them in different
species in progressive stages of combination, until, in G,
MAndrewii and Barretti, the apices of the radii of the ter-
nate spicula are interlaced with each other, and a continu-
ous irregular network is formed, each area of which is filled
with the proximal termination of an intermarginal cavity.
In Dactylocaiyx Prattii, Bowerbank, MS., the structure
advances another stage towards perfection.



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OP THE SPONGIADiS. 103

There is the same design as that exhibited in the construc-
tion of the dermal areas in Geodia M'Andrevni and Baretti,
but there is a considerable difference in the application of
the areas produced by the combinations of the ternato
apices. In Geodia these areas are placed beneath the highly
organized and regularly formed intermarginal cavities, and
form the framework and support of their valvular proximal
ends ; while in JDactylocalyx Prattii they are situated above
the distal ends of the intermarginal cavities of the sponge,
which have not the regular structure and valvular appendage
of those of Geodiuy but are similar to the like organs in the
Halichondroid sponges, and in this position they serve only
to support and strengthen the dermal membrane, which
adheres firmly to their distal surfaces. In this situation
they are subject to a greater chance of pressure and dis-
ruption than in the more deeply seated ones of Geodia, and
accordingly we find extra provisions for the safety of the
junctions of their radii. The shafts of these spicula are
short, stout, and conical, and they penetrate but a very short
distance into the substance of the sponge. They do not
appear to be cemented to any part of the rigid siliceo-fibrous
skeleton, but are merely plunged into a somewhat thick
stratum of membranous structure reposing on the surface of
the skeleton. Their radii are compressed considerably and
extended lateraUy, so that their planes are in accordance
with that of the dermal membrane, and they present a
greater amount of adhesive surface than those having
cylindrical radii. The temate rays ramify irregularly.
Sometimes one ramus, after slightly pullulating, remains
nearly obsolete, causing the branch to assume a geniculated
form, like some of the ramifications of a deer's horn, and
no two appear to be exactly alike ; in fact, there is every
appearance that each ray is influenced and modified in its


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Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 10 of 25)