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A monograph of the British Spongiadæ online

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or multigranulate (Figs. 315, 316, Plate XXII).

Imbedded in the sarcodous stratum on the interstitial
membranes in many of the Halichondroid tribes of sponges,
we frequently find numerous compressed circular cells. In
the greater number of cases they are so translucent as to
readily escape observation even with a tolerably high power;
but in other species, as in Ecionemia acervm, Bowerbank,
MS., a new genus of sponges from the South Seas, in the
collection of the Royal College of Surgeons, and in Mali-
chondria nigricans^ Bowerbank, a British species, these
tissues are developed in a more than usually distinct
condition.

In the first-named sponge they are thickly dispersed on
the surfaces of the interstitial membranes, but without any
approach to order or arrangement. They are decidedly
lenticular in form, with a well-defined transparent nucleus,
which varied in size from about one fourth to three fourths
the diameter of the cell in which it was contained. The
cells varied considerably in size : the largest I could find
was 35^ inch in diameter, and one of the smallest ^]^ inch ;
but the greater number were about ^ inch in diameter
(Fig. 281, Plate XVI). In Halichondria niffricans they do
not appear to be quite so convex as in Edonemia acervtis,
nor are they so numerous as in that species, but they are

6



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82 ANATOMY AND PHYSIOLOGY

somewhat larger in size ; one of the largest measured 5^
inch in diameter, and a small one j^ inch : they are repre-
sented in situ in Fig. 282, Plate XVI.

The most complete development of cellular structure
exists in the genus Grantiay where we find them lining the
great interstitial cavities of the sponge, as represented in
Fig. 312, Plate XXI, — each, probably, in a natural and
healthy condition sustaining a cilium. The nucleus in each
cell is constantly present, and strikingly apparent when
viewed i^ith a power of linear, as represented in Fig. 314,
Plate XXI. The only instance with which I am acquainted
of a conjoined arrangement of such cells exists in the enve-
lope of the ovaries of Spongilla Carteri, the species described
by Carter in his ' Account of the Freshwater Sponges in
the Island of Bombay,' which that author believed to be
Spongilla friabilis, Lamarck, but which proves to be a dis-
tinct species, which I have named after its discoverer, as
a slight recognition of the good services he has rendered to
science by his excellent and accurate observations. These
cells may be detected in situ after the envelope of the ovary
has been submitted for a very short time to the action of
hot nitric acid, so as to render the coriaceous envelope
semi-transparent without destroying it. The structure of
its walls is then seen to consist of linear series of cells, six
or eight in length, closely packed together in lines radiating
from the centre of the ovary to its external surface. They
do not appear to be absolutely in contact with each other,
but are usually seen to be separated by a thin stratum of
a transparent substance, probably an indurated membrane
or sarcode. At the surface of the envelope they frequently
appear to be somewhat hexagonal from mutual compres-
sion. I could not detect a nucleus in any of them (Fig. 284,
Plate XVI). Carter and other writers on Spongilla have
designated the granulated forms of the sarcode in those
sponges, " Sponge cells,'' but I cannot coincide with that
opinion. I have frequently tried in vain to detect a proper
coat of cellular tissue on the Amoeba-like granular masses
into which Spongilla fluviatilis resolves itself at certain
periods of its existence, and neither in a healthy and active



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OF THE SPONGIADJB. 83

condition, nor in a state of partial decomposition, have I
ever been able to satisfy myseK of the existence of a sur-
rounding membrane. It appears to me that these bodies
are the result of a natural resolution of the sarcode into
granular masses of various sizes, each of which, on being
liberated from the parent body, becomes an independent
gemmule, which is capable of reproducing the species of
sponge from which it emanates- And I have long suspected
that the Amoebae found in ponds and rivers, and also in
sea-water, are not in reality distinct species of animals, but
that they are free portions of the sarcode of various species
of Spongiadae.



ORGANIZATION AND PHYSIOLOGY.

Previously to entering on the subject of the organization
and physiology of the Spongiadae in detail, it will be neces-
sary to take a brief view of the general structure of these
animals. Whatever may be their form, or however they
may diflFer from each other in appearance, there are certain
points in their organization in which they all agree. In
the first place, however variable in its form and mode of
structure, there is always a skeleton present on which the
rest of the organic parts are based and maintained. Amidst
the skeleton, and intimately incorporated with it, are the
interstitial canals, consisting usually of two series ; the first
appropriated to the incurrent streams of the surrounding
water, and the second to the excurrent streams, which they
conduct from the interior of the sponge to the oscula at its
surface, through which they are discharged. In the event
of the absence of the excurrent system of canals, their office
is served by the great cloacal cavities that are found to exist
in some forms of sponges, extending from the base to the
most distant parts of the animal. Beside these large cavi-
ties, there are others of a much more limited character,
the intermarginal cavities, which are situated immediately
below the dermal membrane, and which receive the water



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84 ANATOMY AND PHYSIOLOGY

inhaled by the sponge, and transmit it to the mouths of the
incurrent canals which have their origin in the intermar-
ginal cavities. Enveloping the entire mass of the sponge
we find the dermal membrane, in which are situated the
pores, for inhalation and imbibition of nutriment, and the
supply of the incurrent canals; and the oscula, through
which the excrementitious matter and the exhausted streams
of water are poured from the terminations of the excurrent
canals. These parts are indispensably necessary, and are
always present in a living sponge. The attachment of the
SpongiadsB to the body to which they adhere during life,
is effected by a basal membrane which presents a simple
adhesive surface, following the sinuosities of the body on
which it is based, entering into holes or cracks and filling
them up, thus securing a firm hold of the mass on which
they are fixed. When it so happens that the locality con-
sists of sand or mud, their bases frequently assume the
form of branching roots, which penetrate the mud or sand
to a considerable extent ; but they are never instrumental
to the nutrition of the animal — they are simply the anchors
by which it is fixed to its locality for life.

We will now proceed to consider the structure and func-
tions of these organs in the order indicated at the beginning
of this volume, page 4 ; commencing with



THE SKELETON.

There are two important distinctive characters for con-
sideration in treating of the structure of the skeleton : —
1st, the material of which it is constructed; and, 2nd, the
mode of its arrangement.

By selecting the material substance of the skeleton as
the means of dividing the Spongiadae into Orders, we obtain
three well-defined natural groups, which are again readily
divisible into Families, based on the mode of the arrange-
ment of the substance of which the skeleton is com-
posed.

The first Order Calcarea has the primaiy essential mate-



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OF THE SPONGIADiE. 85

rial composed of calcareous matter, and this division con-
tains but one group : —

Spicula dispersed without order on membranous surfaces,
as in the genus Grantia as defined by Johnston.

The second Order, Silicea, comprises those sponges
in which the primary essential material of the skeleton
consists of siliceous matter. It may be divided into four
sections or groups.

1. Those sponges which have the skeleton composed of
radiating fasciculi of siliceous spicula, as in Tethea Bictyo-
cylindruSy &c.

2. Those in which the skeleton consists of spicula dis-
persed without order on membranous surfaces, as in
Hymeniacidon caruncuta^ Bowerbank.

3. Sponges having the skeleton consisting of spicula
cemented together into a network by keratode, as in
Halichondria panicea, Johnston.

4. Those sponges which have the skeleton composed of
solid siliceous fibres, as in Dactylocalyx pumicea, Stutchbury.

The third order, Keratosa, consists of those sponges in
which the primary essential material of the skeleton is
keratose fibre, and this may be divided into three sections :

1. Those which have the skeletons constructed of
keratose fibre only, as in the best cup-shaped Turkey
sponges of commerce.

2. Those having skeletons of arenated keratose fibre, as
in the genus Dystdea.

3. Those which have the skeleton formed of spiculated
keratose fibre, as in Chalina oculata, Bowerbank,
and some of the common West Indian sponges of com-
merce.

In the first group no earthy material of any kind enters
into the structure of the skeleton.

The sponges of the second group, by a natural transition,
pass into the nearly-allied great division of the Halichon-
droid skeletons ; the inabiUty of the former to secrete silex
in an organized form connecting them closely with the
purely keratose, while the instinctive habit of appropriating
extraneous matters recognises the necessity of other material



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86 ANATOMY AND PHYSIOLOGY

in the skeleton beside pure keratode ; and the secretion of
it by its own inherent power appears to be the next
natural step in the development of the animals.

In the third division, those having the skeleton formed
of spiculated keratose fibre, the gradual development is
also well marked, as in one group we find spicula only in
the primary or radiating fibres of the skeleton, while in
another group they are found in both the primary and
secondary fibres, and are developed simultaneously with the
keratode of the young fibres of the skeleton.

1 . Calcarea . a, Spicula dispersed on membranes.

2. Silicea . . a. Spiculo-radiate skeletons.

3. Spicula dispersed on membranes.

c, Spicula cemented together by keratode.

d. Solid siliceous fibre.

3. Keratosa . a. Keratose fibre only.

b. Arenated keratose fibre.

c. Spiculated keratose fibre.

These divisions aflbrd a general view only of the principal
types of the skeleton structure. Other well-defined varia-
tions of these divisions, on which the sub-orders will be
based, will be pointed out and described at length when
we arrive at that portion of our subject in which we shall
treat on the classification of the Spongiadae.

The essential parts of the skeleton of the Spongiadae are
keratode, carbonate of lime, silex, and membrane ; and on
the different modes of the combination and arrangement of
these materials their division into orders, sub-orders, and
genera will depend. It will not be necessary to enter here
into a detailed account of the structure of these respective
parts, as each of them are treated on at length under their
respective heads in the portion of this work devoted to
organography and terminology. I shall therefore confine
my observations to a brief general view of the combinations
of the parts essentially necessary to the construction of the
skeleton.

Keratode, in its application to skeleton structure, has an
exceedingly wide range. In the order Keratosa it is the



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OF THE SPONGIAD^. 87

most essential element, and in some genera, as in Spongia,
Spongionellay Vei^ongiuy and Auliskia, the skeleton is entirely
composed of it, in the form of anastomosing fibres. In
other genera the keratose fibres are strengthened either by
siliceous spicula or by grains of extraneous matter, selected
and incorporated in their structure by the fibres. In the
order Silicea it performs a much more subordinate part,
appearing only as a cementing material in the formation of
the various combinations of spicula of which the skeletons
of the sponges of this order are principally composed ; but
although in these cases only appearing as a subordinate
element, it is frequently very abundant. In the order
Calcarea it is less in the ascendant than in either of the
other orders, and in many species we are scarcely able to
distinguish it from the membranous tissues of the sponge.
Carbonate of lime, as an element of the skeleton, always
presents itself in the form of spicula of various forms in
combination with membranous structure.

Silica in the skeletons of the order Silicea, presents itself
in a great variety of forms and combinations of spicula.
Sometimes the skeletons assume the shape of a beautiful
regular or irregular reticulation, composed either of a nearly
single series of elongate forms of spicula cemented firmly
together at their apices by keratode, or by numerous
spicula similarly cemented together, forming a strong and
complicated fasciculated thread of reticulations, as in the
Genera Halichondria and Isodictya. In other cases, as in
Tethea and Geodia, we find no reticulated structure, but
the spicula are arranged in elongated compound fasciculi,
which radiate from either the base or the central axis of the
sponge, and in Bictyocylindrm we find the reticulate and
the radial system both entering into the structure of the
skeleton, a modification of the former prevailing in the
axis, and the latter existing in the peripheral portion of the
sponge. In* Hymeniacidon neither of these modes of
structure exist, the spicula being simply and irregularly
dispersed over the membranous base of the skeleton ; and
finally we find it simulating the form of pure keratose
fibre, and becoming a rigid and solid siliceo-fibrous skeleton.



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88 ANATOMY AND PHYSIOLOGY

as in the genus Bactylocdyx. These are but a few of the
numerous varieties of form that exist in the order Silicea,
but as the whole of them will be described in detail in the
course of the characterisation of the genera, it is unneces-
sary to enter further into a description of them at present.

The membranous structures as applied to the composition
of the skeleton assume generally a much less prominent
position than the previously described part^ yet in some
few genera they are really the principal element. Thus in
Hymeniacidon they are the primary part of the structure,
and the spicula dispersed over their surfaces are the sub-
sidiary portions only ; and in Microciona Hymeraphia and
Hymedesmia the basal membrane is the indispensably
necessary part of the structure.



SARCODE

Is a pellucid, semi-transparent gelatinoid substance,
variable in colour and insoluble in water. It dries readily,
and its physical characters are restored by immersion in
water with little or no apparent alteration. It is usually
spread thinly and rather evenly over the interna] tissues,
but the surface is rarely perfectly smooth ; sometimes it
abounds in obtuse elevations, and occasionally separates
naturally into innumerable irregularly round or oval masses
which are exceedingly variable in size. When examined
by transmitted light with a microscopic power of 400 or
500 linear, it is always found to contain innumerable
minute molecules of apparently extraneous animal or
vegetable matter, the molecules being always more or less
in a shrivelled or collapsed condition, and very variable in
size. Occasionally it is found abundantly furnished with
lenticular nucleated cells, nearly uniform in size, and often
highly coloured. Fig. 285, Plate XVI, represents a portion
of the interstitial membrane of the honeycomb sponge of
commerce, with the sarcode in its natural condition, filled
with the remains of the nutrient molecules in a collapsed
state. Figs. 281 and 282, Plate XVI, exhibit the same



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OF THE SPONGIAD^. 89

tissues with the addition of nucleated cells immersed in the
sarcx>de. In the sponges of commerce it is exceedingly
largely developed, and nothing can be more diflPerent in
character than their soft and flexible skeletons and the
animal in its natural condition. Specimens of it in this
state, which have been preserved in spirit immediately on
being taken from the sea, have the whole of their interior
nearly as solid and firm as a piece of animal liver; the
colour being a very Ught grey, or nearly white. While the
sponge, as a whole, is sensitive and amenable to disturbing
causes, the sarcode does not appear to be especially so, as I
have frequently observed a minute parasitical anneUd which
infests the interior of Spongilla Jluviatilis, passing rapidly
over the sarcodous surfaces, and biting pieces out of its
substance without apparently creating the slightest sensa-
tion to the sarcode, or at all interfering with the general
action of the internal organs of the sponge ; and in many
cases we find foraminiferous and other minute creatures
permanently located in its large cavities without appearing
to cause it the slightest inconvenience.

When separated from the Uving sponge, it has at certain
periods an inherent power of locomotion ; small detached
masses of it may be observed slowly but continuously
changing their form, and occasionally progressing in dififerent
directions ; and Carter, in his valuable ^ History of the
Freshwater Sponges of Bombay,' describes such detached
masses of sarcode, when progressing and encountering a
fixed point, as dividing longitudinally to avoid the impedi-
ment, and again uniting when it has been passed. This
gliding motion appears to be dependent on an inherent
contractile power, as no cilia appear to have been detected
on the surface of such locomotive masses. Dujardin has
recorded similar movements in portions of the sarcodous
substance from specimens of his genus Halisarca {Hymenia-
cidon Dujardinii,) Bowerbank ; and similar observations
have been recorded by Lieberkuhn and other writers during
their observations of the Spongiadae. 1 have frequently,
at dificrent seasons of the year, taken portions of the sarcode
from living and healthy specimens of Spongilla, in which I



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90 ANATOMY AND PHYSIQXiOGT

could not by the clo8^ observation detect these motions,
which are so readily to be seen at other periods of their
existence; and even at the same period of the year the
sarcode of some specimens exhibit these motions, while in
others they could not be detected. I have often sought for
these phenomena in portions of the sarcode of Halichondria
panicea^ Hymeniaddon carunculay and other marine species,
but I have never yet been fortunate enough to detect them.
It is highly probable that the capability of such notions
exists in the sarcode of these and other marine species for a
limited period, but it does not appear that such powers of
motion are a constant condition of this substance.



THE SARCODOUS SYSTEM.

The physical characters and the peculiarities of the
sarcodous matter of SpongUla has engaged the attention of
naturalists of late years to a considerable extent, and its
inherent vitality and mobile powers have long been known
and treated on by many eminent observers ; but its general
functional powers in the marine Spongiadae have scarcely
received that amount of attention that their importance in
the system of the animal demanded. With a view of
assisting in the elucidation of these phenomena, I com-
menced a series of experimental researches on the ' Vitality
of the Spongiadae' in the spring and summer of 1856, at
Tenby, where I had every facility for continually observing
them in a living and healthy state ; and the results of these
observations are pubKshed in detail in the reports of the
British Association for the years 1856 and 1857, at the
special request of the Natural History Section. It is
unnecessary, therefore, to repeat these observations here,
and I shall confine myself accordingly to a few general
conclusions arising from the facts developed by previous
observations and by my own experiences as detailed in
these reports. In thus considering the subject, and on
comparing the sarcodous system as it appears in the Spon-
giadae with its structure and functions in other and higher,



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OP THE SPONGIAD^. 91

classes of animals, we must bear in mind that the tenn
sarcode is apphed in the sense in which it is employed by
Kolliker in his observations on Actinophrys Sol, and in
accordance with its appearance and functions in the Amoebae,
and not in the more extended sense and general application
of the word as applied to moscnlar masses of flesh.
Dujardin has also employed the same term in the same
sense many years before Kolliker wrote on these subjects.

As we descend in the organic scale of life, we find the
great systems of animal functions,, the osseous, the muscular,
the nervous, the sanguineous, all becoming simplified, until
at last one or more of them is found entirely wanting.
But the sarcodous digestive system appears never to be
absent. We find it from the highest organized mammals
in the form of the mucous lining of the alimentary organs,
passing through animals of every degree of development,
until the animal itself becomes simplified to the degree of
appearing as a mass of gelatinoid sarcode only, or with
possibly a central nucleus of membrane, as in Actinopkrt/8
Soly &c.

The presence of the stomach has been insisted upon by
some naturalists as the organ absolutely necessary to con-
stitute an animal. On the contrary, it would appear, from
its functions in the higher animals, that it is at best but a
preparatory organ for the less striking but more important
one of the sarcodous system which appears invariably to
cover the digestive surfaces of animals. In mammals it
has hitherto been considered by many physiologists as a
subordinate portion of the digestive system, a merely
lubricating material to assist the passage of the faecal
matters in its course downwards. On the contrary, if we
view it in the light in which it exhibits itself as sarcode,
and not as mere mucous effusion, it becomes the ultimate
and most important part of the digestive system ; the final
receptacle, through its wonderful inherent powers of imbi-
bition of the fully elaborated pabulum presented to it, and
the ultimate refiner and digester of all the nutriment that is
destined to pass into the sanguineous system.

If we examine the digestive surface of the sacular polypi,



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92 ANATOMY AND PHYSIOLOGY

of Actinia, or of the common StarfiaheSy we find this
substance presenting the same unmistakable and peculiar
characters, th6 pellucid, semi-transparent gelatinoid appear-
ance, abounding in molecules and minute vesicles always
more or less in a state of collapse. The mucous membranes
of the intestines of a mouse which was drowned in warm
water to preserve the tissues during examination as nearly
as possible in a natural condition, when examined by
transmitted light with a microscopical power of 666 linear,
presented the same chtiracteristic appearances. Some por-
tions of the mucous lining of the intestine abounded more
in the particles than others ; they also varied considerably
in size, and were all more or less in a state of collapse, and
none had the appearance of living and fully distended
vesicles. These molecules were not confined to the surface
of the mucous or sarcodous matter, but were also embedded
at various depths in its substance. They varied consider-
ably in size and character within a small distance. At
one place I observed a group of them, each being of, com-
paratively, a considerable size, while, at a very little
distance, there was but very rarely a large particle to be
observed, and when they appeared to be of more than
average number and size, they were observed to be at the
surface of the mucous or sarcodous structure, as if they
had not yet been absorbed and lessened in size by the pro-
cess of digestion. All these circumstances are indicative of
the molecules being extraneous to the sarcodous structure
itself, and tend to induce us to believe them to be the
nutritive matters in course of preparation for final assimila-
tion with the blood after the previous preparatory portions
of the process of digestion in the stomach.

These are the general characteristics of the sarcodous



Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 9 of 25)