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A monograph of the British Spongiadæ online

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is that of a living, gelatinous flesh, supported by innume-
rable cartilaginous or corneous fibres or spicula, most com-
monly ramified or reticulated, and furnished more or less
with external pores or small mouths which absorb the water,
and which is conveyed by an infinity of minute channels or
capillary tubes through every part of the body, and is there
decomposed and the oxygen absorbed as its principal nou-
rishment, similar to the decomposition of air in the pul-
monary organs of what are called perfect animals/' —
' Wemerian Memoirs,' vol. ii. pp. 74, 75.

Lamouroux's conclusions regarding the nature of sponges
are so thoroughly vague and supposititious as scarcely to
require notice.

Lamarck has placed the Spongiadse in a higher position
than any naturalist who had preceded him, giving them
precedence of the sertularian and celliferous corallines, and
even of the corallidae ; but I cannot concur with him to
the full extent of his conclusions, which, like those of most
previous writers, were derived to a much greater extent
from comparative reasoning than in actual observation of
the animals in a hving and natural condition.

Professor Schweigger's opinions are very much more
those of a practical natinralist, and it is evident that he had
closely observed them in a living condition ; but he too
shares the erroneous opinion of his predecessors, that the
oscula were the organs of imbibition, and that no water
entered through the dermal surface. Professor Bell, in the
* Zoological Journal ' for June, 1824, states that he saw the
action of the streams from the oscula, but, like previous
writers, concluded that they were organs of imbibition as
well as excurrent organs. And it was not until the excel-
lent and accurate " Observations and Experiments on the
Structure and Functions of the Sponge" were published
in the ' Edinburgh Philosophical Journal,' vols, xiii and xiv,
by Professor Grant, that a correct notion was entertained
by naturahsts of the inhalant and exhalant powers of those



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116 ANATOMY AND PHYSIOLOGY

bodies. These details by the learned Professor are so fall
and complete as to leave but little room for the improve-
ment of our knowledge of this portion of their natural
history. And the facts of the imbibition of the surrounding
water by the pores in the dermal membrane, its circulation
through the internal cavities of the sponge, and its final
ejection through the oscula, has been firmly established
and acknowledged by all naturalists who have studied
these animals closely in a living state. Dr. Grant has, in
truth, proved himself to have been, in regard to the aqueous
circulation in the sponge, what Harvey was to that of the
blood of the higher classes of animal life, the first to dis-
cover and to publish the true mode of the circulation of the
water in the animal.

This learned and accurate observer says, *' I first placed
a thin layer from the surface of the S. papiUariSy in a
watch-glass with sea-water under the microscope, and on
looking at its pores I perceived the fioating particles driven
with impetuosity through these openings ; they floated with
a gentle motion to the margin of the pores, rushed through
with a greatly-increased velocity, often striking on the
gelatinous networks, and again relented their course when
they had passed through the openings. The motions were
exactly such as we should expect to be produced by cilia
disposed round the inside of the pores.^* — ' Edinburgh New
Philosophical Journal,' vol. ii. p. 127.

The same author, in describing the excurrent action,
says, " The Spongiapanicea {Halichondria incmstans, John-
ston) presents the strongest current which I have yet seen/'
Two entire round portions of this sponge were placed
together in a glass of sea- water with their orifices opposite
to each other, at the distance of two inches ; they appeared
to the naked eye like two living batteries, and soon covered
each other with feculent matter.

Stimulated by the recital of the observations of Dr.
Grant, I have often sought these currents fiowing from the
oscula, and there is no species in which I have had the
opportunity of examining in a firesh and vigorous condition
in which I have not succeeded in seeing them. In the



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OP THE SPONGIAD^. 117

one observed by Dr. Grant, Hcdichondria incrustans^ John-
ston, the oscula being few in number and very large, the
excurrent streams are more than usually powerful. In the
course of my investigations **0n the Vitality of the
Spongiadae,'' at Tenby, which are published in the ' Reports
of the British Association' for 1856, and in the "Further
Report," published in the same work for 1857, I have
described a long series of observations of the vital actions
of the Spongiadae as displayed in Hymeniacidon carunctda
and Spongilla fiumatiliBy in both of which species there was
a perfect accordance in the habits and modes of exertion of
these vital actions.

The power of inhalation appears to be exerted in the
Spongiadae in perfect accordance with the similar vital
functions in the higher classes of animals, not involuntarily
and continuously as in the vegetable creation, but at inter-
vals, and modified in the degree of its force by the instincts
and necessities of the animal And it may be readily seen
that the faculty of inhalation is exercised in two distinct
modes; one exceedingly vigorous, but of comparatively
short duration, the other very gentle and persistent. In
the exertion of the first mode of inhalation, that is during
the feeding period, a vast number of pores are opened, and
if the water be charged with a small portion of finely-
triturated indigo or carmine, the molecules of pigment are
seen at some distance from the dermal membrane, at first
slowly approaching it, and gradually increasing their pace,
until at last they seem to rush hastily into the open pores
in every direction. In the meanwhile the oscula are widely
open, and pouring out with considerable force each its
stream of the excurrent fiuid ; and if the reflection of one
of the horizontal portions of a window-frame be brought
immediately over an excurrent stream, it will frequently be
seen that the surface of the water is considerably elevated
by its action, even although the osculum be half or three
fourths of an inch beneath its surface, and this vigorous
action will sometimes be continued for several hours, and
then either gently subside or abruptly terminate. Occa-
sionally a cessation of the action may be observed in some



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118 ANATOMY AND PHYSIOLOGY

of the oscula, while in others it is proceeding in its full
vigour, and sometimes it will be suddenly renewed for a
brief period in those in which it had apparently ceased.
These vacillations in the performance of its functions is
always indicative of an approaching cessation of its
vigorous action. When the vivid expulsion of the water
has ceased, the aspect of the oscula undergoes a consider-
able change; some of the smaller ones gradually close
entirely, while in the larger ones their diameters are reduced
to half or one third of what they were while in full action.
Simultaneously with the decline in the force of the excur-
rent action the greater portion of the pores are closed, a
few only dispersed over the surface of the sponge remaining
open to enable the gentle inhalation of the fluid to be
continued, which is necessary for the aeration of the
breathing surfaces of the sponge. The breathing state of
inhalation appears to be very persistent, and I have rarely
failed in detecting it when I have let a drop of water,
charged with molecules of indigo, quietly sink through the
clear fluid immediately above an open osculum. These
alternations of repose and action are not dependent on
mere mechanical causes, and sponges in a state of quiescence
may be readily stimulated to vigorous action by placing
them in fresh cool sea-water, and especially if it be poured
somewhat roughly into the pan, and agitated briskly for a
short period ; and this will take place even in specimens
that have very recently been in powerful action.

No general law seems to guide the animal in the choice
of its periods of action and repose, and no two sponges
appear to coincide entirely in the time or mode of their
actions. In fact each appears to follow the promptings of
its own instinct in the choice of its periods of feeding and
repose.

In the littoral sponges there is a third condition of the
animal, and that is during its exposure to the atmosphere
in the intervals between high and low water, and in some
sponges the pores and oscula are both completely closed.
But this condition does not obtain in all species. Thus,
during the course of my investigations at Tenby, I observed



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OF THE SPONGIADiE. 119

that while amidst the numerous specimens of Hymeniaddon
caruncula and HaJichondriapanicea that covered the rocks in
the neighbourhood of St. Catherine's Cave the former rarely
exhibited an open osculum in the absence of the water,
those of the latter species were frequently more or less
open.

The most beautiful and striking view of the differences
existing between vigorous action and the comparative repose
of the breathing process is exhibited in Grantia ciliata. In
this species the pores are situated on the obtusely conical
distal terminations of the intermarginal cells or cavities, each
of which is furnished with a long fringe of spicula surround-
ing its porous end (Fig. 345, Plate XXVI), their proximal
terminations being cemented, for about a third of their
length, to the slightly curved surface of the base of the cone.
In the state of the comparative repose of aerating inhala-
tion, and when the base of the conical extremity of the
cavity is not distended by the incurrent action, these spicula
all converge to a point at the level of their own apices, and
the water thus gently inhaled passes between the shafts of
the spicula, forming the protective cone to the inhalent pores
and effectually preventing any extraneous matter from
approaching them. But when the vigorous feeding action
commences, the distention of the base'of the conical portion
of the cavity brings it into lines parallel to the axis of the
cell, and thus the conical fringe of spicula assumes a cylin-
drical form, and the molecular food of the animal is freely
admitted to the pores.

A corresponding action obtains in the exhalant system
of this interesting sponge. The mouth of the great central
cloaca is furnished with a thick fringe of very long and
slender spicula, which by the contraction of its sides near
the mouth are all brought to assume a conical form like
those appended to the inhalant cavities ; but when the in-
halant action is in vigorous operation, and the oscula are all
pouring their streams into the cloaca, the force of the water
thus accumulated distends the mouth of the cloaca to such
an extent as to cause the fringe of long spicula to assume
the form of an open cylinder, or in some cases it is expanded



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120 ANATOMY AND PHYSIOLOGY

to such an extent as to become slightly funnel-shaped, and
in this condition the foecal stream may be seen issuing from
it with considerable force. There are many other interesting
points in the structure of this highly organized and interest-
ing sponge which I will not advert to at length, but refer
my reader to a fuller and more complete history of its
stractme published by me in the * Transactions of the
Microscopical Society of London * for 1859, vol. 7, p. 79,
Plate V.

Thus we find that inhalation is the primary vital opera-
tion induced by ciliary action, and that exhalation is merely
a mechanical efiEect arising from the primary cause. We
find also that these actions are separated into two distinct
modes ; the one exceedingly active and vigorous, exerted
only at intervals and for short periods, and the other gentle
and continuous. If we combine the consideration of these
peculiarities of function with those of the anatomical struc-
ture, we find that the incurrent streams are always received
in intermarginal cavities, and that these organs, however
modified, are always present, and in some cases can be dis-
tinctly and strikingly separated from the great mass of the
interstitial canals and cavities of the sponge. If we trace
the course of the inhaled fluids, we find that on their
entrance through the pores they are first brought into con-
tact with the parietes of the intermarginal cavities, and
passed thence into the complicated system of digestive
surfaces which line the incurrent and excurrent cands and
cavities of the sponge, and that the exhausted fluids charged
with faecal matters are finally discharged without the slight-
est return to or intermixture with the contents of the inter-
marginal cavities. We may therefore, it appears to me,
safely conclude that the respiratory and digestive functions
are separated, and that the latter has its seat in the inter-
marginal cavities, and the former in the interstitial canals
and cavities.

The vital energy of the Spongiadae must be very con-
siderable, and the quantity of oxygen consumed by their
respiration great, if we may judge by the effects of their
presence in the vivarium, where their introduction makes



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OF THE SPONGIAD^. 121

sad havoc among the other inhabitants, few being able to
withstand their deleterious presence, and without a large
supply of water and a frequent change of it they them-
selves quickly expire of exhaustion.



NUTRITION.

In treating on the subjects of inhalation and exhalation,
I have described the energetic period of action in the
sponge during the imbibition of the surrounding fluid as
equivalent to the operation of feeding in the higher classes
of animals. And in my " Further Report on the Vitality
of the Spongiadae," published in the ' Reports of the British
Association' for 1857, p. 121, 1 have described the results of
feeding a small specimen of Spon^iUafluviatilia with finely
comminuted indigo in water, and I have there stated that
*' many of the molecules might be readily followed, as they
meandered through the interior of the sponge, and were
seen flowing in every direction. During the maintenance
of this action in full force, when I directed my observation
to the osculum, it was pouring forth a continuous stream
of water, and along with it masses of flocculent matter, and
many of the larger molecules of the indigo that had entered
by the pores ; but it is remarkable that although the finer
molecules of indigo were being imbibed by the pores in
very considerable numbers, very few indeed of them were
ejected from the osculum ; and if the imbibition of the
molecules continue for half an hour or an hour, and then
cease, the sponge is seen to be very strongly tinted with
the blue colour of the indigo, and it remains so for twelve
or eighteen hours, after which period it resumes its
pellucid appearance, the whole of the imbibed molecules
having undergone digestion in the sarcode lining the
interior of the sponge, and the efiete matter having been
ejected through the osculum." If we kill the sponge im-
mediately after being thus fed, and examine the interstitial
canals and cavities, we find their sarcodous surfaces thickly
dotted with molecules of indigo.



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122 ANATOMY AND PHYSIOLOGY

The fsBcal matters discharged by the oscula exhibit all
the characteristics of having undergone a complete diges-
tion ; whatever may have been the condition of molecules
of organized matter when they entered the sponge, their
appearance after their ejection is always that of a state of
thorough exhaustion and collapse.

It is diflScult to decide with any degree of certainty what
is really the nature of the nutriment of the Spongiadae,
but in the greater number of species it is probably mole-
cules of both animal and vegetable bodies, either living or
derived from decomposition. This appears to be the case
with the greater number of the Halichondroid sponges; but
even among them, as well as other genera, there are pecu-
liarities of structure that are strongly suggestive of car-
nivorous habits. Thus in the first portion of this paper
published in the ' Philosophical Transactions ' for 1858, p.
293, I have described among the interior defensive spicula
a remarkable form, which has been hitherto found in one
sponge only, the spinulo-recurvo-quaternate spiculum,
which *' occurs in great profusion in the cavities of the
sponge, clusters of them consisting frequently of as many as
twelve or fifteen radiate from the angles of the reticulations
of the skeleton into the interstitial cavities of the animal/'
I have also described, while treating on the internal defensive
spicula, the recurvo-ternate forms, the heads of which are
found projecting their radii, more or less, into the interstitial
cavities beneath the intermarginal ones in Geodia and
Pachymatisma, The spinulo-recurvo-quaternate spicula,
represented in situ in Fig. 292, Plate XVIII, and the re-
curvo-ternate ones figured in situ in Fig. 354, Plate XXVIII,
e, e, are both admirably adapted to destroy the victims
entangled among them.

I have for a long time entertained the idea that these
elaborate and varied forms of defensive spicula, probably
subserved other purposes than that of the protection of the
digestive surface against the incursions of minute annelids
and other predaceous creatures. They are admirably fitted
to retain and make prey of any such intruders. No small
animal could become entangled in the sinuosities of the



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OF THE SPONGIAD^. 123

interstitial cavaties of sponges thus armed without extreme
injury from the numerous points of these spicula, and every
contortion arising from its struggles to escape from its pain-
ful and dangerous entanglement would contribute to its
destruction, and it may then by its death and decomposition
eventually become as instrumental to the sustentation of
the sponge as if actually swallowed by the animal. How
far this mode of nutrimentation may obtain in the physiology
of these creatures it is impossible, in the present imperfect
state of our knowledge of their habits, to say, but from the
complex, varied, and elaborate structure of these organs, and
from their evident adaptation to retain sueh intruders,
as well as to defend the internal surfaces from injury, it is
not improbable that their office extends beyond that of the
mere defensive function, and that they are in fact auxiliary
organs for securing nutriment for the use of the sponge. If
this supposition, that the elaborately formed and ingeniously
disposed recurvo-quatemate spicula combine the office of
securing priey with that of defending the interstitial organs
of the sponge, be correct, it may affi)rd a clue to the organic
purpose of the recurvo-temate spicula with the exceedingly
long and attenuated shafts that so frequently accompany
the stout patento-temate ones in Geodia Barretti. The
apices of these spicula (Fig. 54, Plate II) rarely attain the
height of the plane of the true connecting spicula, and their
recurved radii are most frequently projected into the large
interstitial spaces immediately beneath the plane of the
proximal ends of the cells of the intermarginal cavities, and
may thus form subsidiary defences to those organs. Although
emanating from the fasciculi of the shafts of the true con-
necting spicula, their form, slender proportion and position
evidently indicate a different office from the spicula with
which they are associated, and no other purpose for them
occurs to me so probable as the one I have suggested above.
Or we may carry the supposition further, and believe them
to be not only defensive but aggressive organs ; also, like
the recurvo-quatemate spicula, their office may be to retain
soft annelids that have intruded themselves through the
oscula into the digestive organs, to aid in the nutrimenta-



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124 ANATOMY AND PHYSIOLOGY

tion of the sponge; and this idea appears the more feasible,
as these spicula are never observed in the intermarginal
cavities, where the decomposition of animal matters would be
offensive to their especial function, but always in the spaces
beneath them, which are the commencements of the diges-
tive system.

The same course of reasoning will apply to their occur-
rence in such considerable quantities amidst the defensive
fasciculi of spicula projected from the surface of Tethea
simiUima, Bowerbank, MS., and also of T, crania, the latter
being represented by Fig. 362, c, c, Plate XXXI, in which it
will be seen that the recurvo-temate heads of the spicula
are always situated beneath the level of the true defensive
spicula. Thus situated they would form an admirable trap
for the entanglement of soft annelids that might attempt to
crawl over the surface of the sponge, and thus they would
be destroyed and retained for the imbibition of their parti-
cles liberated by their gradual decomposition. If this be
not their especial purpose in this situation, I must confess
myself at a loss to imagine their proper function, as the
surface of the sponge is effectually protected by the por-
recto-temate and large acuate spicula that compose the
defensive fasciculi projecting in such abundance from aU
parts of the sponge. If we also consider the structure and
positions of the ordinary forms of internal defensive spicula,
the entirely spined attenuato-acuate ones, in reference to
the idea of their being offensive as well as defensive organs,
we shall not fail to see that, although less striking in their
forms and modes of disposition than the spicula already
described, they are calculated to subserve the office of
retaining prey quite as effectually as the more singular
ones. The abundance in which they occur, the vast
number of spines with which they are covered, the apices
of which are frequently long and recurved, combined with
the mode in which their bases are attached to the fibres of
the skeleton, exhibiting a beautiful combination of strength
and flexibility, are strongly indicative of a purpose beyond
that of mere repulsion.

In the two species of sponges in which are found the



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OP THE SPONGIADiE. 125

acuate entirely and verticillately spined defensive spicula in
situ, represented by Figs. 289, 290, Plate XVII, one
of them has the spicula collected in groups in a manner
very similar to those of the spinulo-recurvo-quatemate
form, and if the latter be considered as organs for the
retention of prey, the physiological purpose of the grouping
together of the former can scarcely be considered in any
other light.

In the isolated positions of these forms of spicula, viewed
in reference to some ideas regarding their physiological pur-
poses, there are circumstances of a very remarkable nature.
These forms of spicula occur in several distinct genera of
sponges, and especially in those having a strong kerato-
fibrous skeleton. Their usual locality is on the fibre of the
skeleton, in which their bases are firmly imbedded, and
from which they are projected at various angles into the
canals and cavities of the sponge, and they are very rarely
seen on the membranes. In Hymeraphia stellifera (Fig.
370, a, Plate XXXIV) and H. clavata, Bowerbank, both
exceedingly thin coating species, they occur in great quan-
tity, but only on the basal membrane ; a portion of them
being erect, the remainder prostrate. But in another
sponge, a remarkably curious parasitical species, Hymenia-
cidon Cliftoni, Bowerbank, MS. (Fig. 291, Plate XVII),
which having no fibrous skeleton of its own, covers and
appropriates a small fibrous Fucus^ and converts its anasto-
mosing vegetable stalks into an artificial skeletpn, closely
coating each stalk of the plant with its membranous struc-
ture, so as to cause them at first sight to be readily mis-
taken for keratose sponge fibfe. The whole of the mem-
branous structure of this sponge abounds with attenuato-
cyUndrical entirely spined defensive spicula, but they are
all prostrate and intermingled with the skeleton spicula of
the sponge when not in contact with any part of the fibres
of the vegetable, but wherever they are in contact with the
plant they instinctively, as it were, assume the erect posi-
tion, and the false skeleton is bristling with them to as
great an extent as if it were truly a kerato-fibrous struc-
ture. This feature in the habit of the sponge is very


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Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 12 of 25)