James Scott Bowerbank.

A monograph of the British Spongiadæ online

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3. Those having the spicula disposed in fasciculi in
the substance of the gemmule from the centre to the
circumference.

In the first mode of disposition they are sometimes
of the same form as those of the skeleton, but considerably
less both in length and diameter, to adapt them to the
office they have to perform. In other cases they differ
materially in both size and form from those of the
surroimding skeleton; but in every case with which I
am acquainted, their long axes are parallel to the outer
surface of the case of the ovarium, or to the surface of
the ovarium itself

In the second mode of disposition they are immersed in



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58 ANATOMY AND PHYSIOLOGY

the comparatively thick crust of the ovarium, their long
axes being always at right angles to lines radiating from
its centre to its circumference. Their forms become
widely different from those of the skeleton spicula, and
especially adapted to their peculiar oflSce; and their
terminations f^quently expand into broad plates, as in
Spongilla fluviatilis^ Johnston. Their forms vary con-
siderably in shape and structure in different species. In
the ovaries of some sponges, one of these modes of the
disposition of their spicula only can be observed.

In the third mode of arrangement, where the spicula
abound in every part of the gemmule, as in Tethea cranium,
Johnston, they are various in form, but resemble to a
considerable extent those of the skeleton, with an inter-
mixture of forms peculiar to the gemmule.

In Spongilla Carteri, Bowerbank, and S. fluviatilisy
Johnston, our commonest British species, belonging to the
first group, the external series of spicula of the ovaria are of
the same form as those of the skeleton, but frequently
somewhat shorter. They are disposed irregularly over the
surface of the ovarium, and firmly cemented to it by
the middle of the shaft, while each of their apices are
projected in tangental lines. Thus their shafts perform
the office of tension spicula, while their terminations
become efficient weapons of defence, fig. 201, Plate IX,
represents the spiculum of the ovary of 8. Carteri.

In other cases in this group we find these spicula
difiering from those of the skeleton of the parent sponge ;
thus the one represented by Fig. 203, Plate IX, from the
surface of Spongilla lacustris, Johnston, is curved so as
to accommodate it to the rotundity of the ovary (Fig. 320,
Plate XXII), and we do not find its apices projecting
as in those of S. Jluvialilis, but instead of the projecting
apices, the whole spiculum is covered vrith minute spines,
assimilating it in character with the general structure
of those spicula which combine the office of tension and
defensive spicula, but differing considerably in their pro-
portion from the tension spicula of the same sponge,
S. lacmtris, represented by Fig. 90, Plate IV, the one



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OF THE SPONGIADiB. 59

being evidently destined to sustain and protect extended
membranes, while the other is especially adapted for a
small curved surface by its form and small size ; each of
the figures being drawn with the same power, 660
linear.

On the surface of the ovarium of SpongiUa cinerea,
Carter, we find this description of spiculum still more
decidedly produced. It is of a cylindrical form and
entirely spined, and has just the amount of curvature that
is in unison with the surface on which it reposes. The
spines on the middle of the shaft are cylindrical, and
terminated bluntly so as to strengthen its hold on its
imbedment. Those of its apices, on the contrary, are
acutely conical and recurved, and are strongly produced so
as to form very eflBcient weapons of defence. This spiculum
is represented by Fig. 207, Plate IX.

The birotulate and boletiform spicula of the second
group appear to be more purely structural, as regards
the skeleton of the ovarium. The rotulae are very closely
packed at both the external and internal surfaces of that
body, and the crenulation or dentation of each rotula is as
well produced on the internal as on the external ones, and
it appears to be very influential in maintaining each
spiculum in its proper position. In the natural condition
of the ovaria these spicula are entirely imbedded in its
walls, and other spicula of a truly defensive nature are
superimposed for its protection. The large spine in the
shafts of the birotulate spiculum from Spongilla plumom^
Carter (Fig. 208, Plate IX), are also apparently subservient
to strengthening and maintaining the spiculum in its
proper situation, although they are acutely terminated, as
defensive spines usually are ; but in the same relative
position on the birotulate spicula of Spongilla Meyeni,
Carter, we find the spines short, stout, and cylindrical,
spreading or budding at their apices, and evidently more
fitted for assisting to retain the spiculum in its proper
place than for defensive purposes. This spiculum is repre-
sented by Fig. 219, Plate IX.

There is an apparent analogy between the expansions of



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60 ANATOMY AND PHYSIOLOGY

the rotulae and those of the foliato-peltate spicula, but they
do not appear, like the latter, to be derived from the
ternate forms. The radiation of the canaUculi, as repre-
sented by Fig. 222, Plate IX, are not derived from three
primary rays, but each appears to emanate from a central
cavity at the end of the shaft; and their number, 22,
at their proximal termination, is not reconcilable with any
regular number of bifurcations arising from three primary
rays, however short we may imagine them to be.

The progressive decline of the inner rotula in the inequi-
birotulate spiculum of Spongilla patdtday Bowerbank (Fig.
221, Plate IX), and its all but total extinction in Spongilla
reticulata^ and Spongilla recurvata, Bowerbank (Figs. 223
and 224), until the distal rotula merges in the scutulate
form, with an acute external umbo in place of an internal
shaft as in Spongilla JSrottmii, Bowerbank, Figs. 226 and
227, exhibits a very interesting series of gradations of
development in the same description of organ.

I'he whole of this beautiful group of spicula occur in
the thick coriaceous proper coat of the ovaria of the Spon-
gillidae. Sometimes we have but one form thus located, as in
Spongilla JluviatiliSy Johnston, where we find them very close
together in the case of the ovarium, as in Fig. 318, Plate
XXII, the outer rotula supporting the external membrane,
and the inner one performing the same office for the internal
one, as represented by Fig. 319, Plate XXII. At other times
we find two distinct forms in the coat of the ovarium, as in
Spongilla recurvata, Bowerbank, from the River Amazon;
the inner one being slender boletiform (Fig. 224, Plate IX),
and the outer one multihamate birotulate (Fig. 220,
Plate IX). In every case these spicula are so completely
immersed in the thick coriaceous coat of the ovarium, that
they are perfectly invisible under ordinary circumstances ;
and it is only after the ovary has been boiled in nitric acid
for a very short period, that it is rendered sufficiently
transparent to allow of the spicula being seen in situ.

The progressive development of these forms of spicula is
very beautifully exhibited in the spicula from the ovaria of
Spongilla plumosay Carter. We first observe them, with a



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OF THE SPONGIAD^. 61

linear power of 660, in the shape of slender, smooth,
cylindrical spicula, with a slight enlargement at each ter-
mination, and without the slightest indication of spines on
the shaft ; and in this condition the central cavity is large,
occupying about one third of its diameter (Fig. 210,
Plate IX). In the second stage, the only alteration in its
form is an enlargement of the terminations, the edges
assuming an angular shape, and a few slender spines are
observable (Fig. 211). In the third stage of development
the terminations assume the form of distinct circular plates
or incipient rotulae, the margins of which are slightly
crenate ; the shaft exhibits numerous long slender spines,
and the central cavity now does not occupy more than one
fifth of the diameter of the spiculum (Fig. 212). From
this form specimens in every stage of development may be
readily traced, until the strongly spinous margin, the pro-
minent convexity of the rotulse, and this robust shaft with
its long conical spines, indicate the completely adult con-
dition of the spiculum, and in this state the central cavity
can very rarely be seen (Fig. 208).

The growth of these spicula in their early stages is
probably very rapid, as the number of those in the first
and second stages is remarkably small as compared with
those in the third and subsequent stages.

In the inequi-birotulate spicula of Spongilla patdulay
Bowerbank, we find a number of radial canals passing
fi-om each end of the central cavity of the shaft to the
extreme circumference of the rotulae ; and it is therefore
probable that this expanded part of the spiculum is similar
in character to that of the foliato-peltate spiculum which I
have described (Terminology, 102) in treating of the
spicula of the membranes ; and that they are, in fact,
originally composed of a series of terminal radial spicula
expanding and coalescing laterally, and thus forming one
plane circular surface in place of numerous separate
radii (Fig. 222).

The spicula of the third group, those having the spicula
disposed in fasciculi in the substance of the gemmule, differ
less in character from those of the parent sponge than



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62 ANATOMY AND PHYSIOLOGY

those of either of the preceding groups. They are in
reality but modifications of the external defensive spicula of
the parent sponges.

The inequi-fusiformi-acerate one (in the Gemmule of
Tethea) diflFers from the fusiformi-acerate one of the
skeleton in no other respect than in the greater propor-
tionate attenuation towards its distal termination, which
gives it a degree of flexibility that allows of its bending
freely under the pressure of any comparatively large body ;
and I have seen them, when two gemmules have been
pressed closely together, bent to the extent of semicircles
without breaking. In the young gemmules these spicula
are usually projected much beyond the other forms of
defensive spicula that accompany them.

In like manner the small attenuato-porrecto-ternate
form in the same gemmule is a modification of the similarly
formed external defensive spicula of the parent sponge.
In the adult gemmule the apices of these spicula rarely
project beyond the dermal membrane, and it is only on
pressure from without that they would be brought into
effective use. The amount of the angle of their radiation
at the apex of the spiculum is therefore greatly increased
beyond those of the external defensive ones of like form in
the parent sponge, so as to accommodate their apices to
the curve of the surface of the gemmule, and to render
each point equally effective ; and as they are not projected
beyond the dermal surface, as in the sponge, their shafts
are shortened proportionally.

The unihamate, bihamate, and recurvo-ternate forms of
the same gemmules are also modified forms of the recurvo-
ternate external defensive spicula of the parent sponges,
Tethea cranium and aimilima*



KERATODE

Is the substance of which the horny elastic fibres of the
skeleton of the officinal sponges of commerce are composed.
It has, correctly speaking, no relationship either chemically



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OF THE SPONGIADiE. 68

or structurally with horn, and Dr. Grant has judiciously
rejected the term4* homy fibre" as applied to the sponges
of commerce, and has substituted that of keratose by way
of distinction ; and in accordance with that term I propose
to designate the substance generally as keratode, whether
it occurs in the elastic fibrous skeleton of true Sponffia,
which are composed almost entirely of this substance, or of
those of the HaUchondraceous tribe of Spongiadae, where
it is subordinate to the spicula in the construction of the
skeleton, and appears more especially in the form of an
elastic cementing medium. In a dried state it is often
extremely rigid and incompressible, but in its natural
condition it is more or less soft, and always flexible and
very elastic. It varies in colour fi'om a very light shade to
an extremely deep tint of amber, and it is always more or
less transparent. In its fully developed condition, in the
form of fibre, it appears always to be deposited in con-
centric layers ; but in the mode of the development of
these layers there are some interesting variations from
the normal course of production. As we find in Aranea
diadema, the common Garden Spider, that the creature has
the power of modifying the deposit of the substance of its
web so that the radiating fibres dry rapidly while the
concentric ones remain viscid for a considerable period, so
we find in the production of the young fibres of the
skeletons of the Spongiadae in some species, as in those of
commerce, there is no adherent power at the apex of the
young fibre, excepting with parts of its own substance ;
while in Byndea^ and in some other genera, the apex of the
newly-produced fibre is remarkably viscid, adhering with
great tenacity to any small extraneous granules that it may
happen to touch in the course of its extension (Fig. 272,
Plate XIV); but this adhesive character appears to be
confined to the earUest stages of its production only, as
exhibited at the apices of the newly-produced fibres, the
external surface immediately below the apex exhibiting no
subsequent adhesive property.

Lehman, in his 'Physiological Chemistry,' Cavendish
Society's edition, vol. i, p. 401, states that Spori^aofficincdia



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64 ANATOMY AND PHYSIOLOGY

of commerce consists of 20 atoms of fibroin, 1 atom of
iodine, and 5 atoms of phosphorus ; and#n treating of the
physiological relations of fibroin as regards sponges, he
observes, " Its chemical constitution affords one of the
arguments why the Spon^ia should be classed among
animals and not among plants, since in the vegetable king-
dom we nowhere meet with a substance in the slightest
degree resembling fibroin."

From the general physiological characters of the skeletons
of the Sertularian and other Zoophytes, I had long suspected
that their component parts were identical, or very nearly
so, with those of the skeletons of the Spongiadae, and
I therefore applied to my friend, Mr. George Bowdler
Buckton, to assist me in determining this point, and he
very kindly undertook to make comparative qualitative
analyses with two species of Zoophytes, Sertularia oper-
ctdata and Flustra foliacea^ with the fibres of Spongia
officinalis and of raw silk, and I cannot do better than
to quote entire the report of the results of his exami-
nation :

"I have examined the Zoophytes you sent me, and
have compared their deportment under chemical agency,
with that shown by white silk and the fibre of ordinary
sponge.

" All the specimens were treated in a similar manner,
being purified from foreign matter, as far as possible, by
boiling for two hours in water, and subsequently for the
same period in strong acetic acid. With the exception of
Flustra, the substances exhibited by this treatment little
change in their outward appearance. Carbonate of lime
enters so largely into the composition of Flustra, that its
disintegration by acids ought to cause no surprise.

"From the results of the first seven experiments,* I
conclude that all these bodies contain the same, or a very
similar animal principle, which I suppose to be identical
with Mulder's fibroin. The varying colours of the pre-
cipitates from tannic acid and ammonia, I think is probably

* For a table of the results of the analysis of Mr. Buckton, see * Philo-
sophical Transactions * for 1863, page 740.



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OP THE SPONGTADiE. 65

due to the traces of sesquioxide of iron present in the
fibres, and the difference in shade is simply caused by the
greater or less preponderance of that metel.

** Although I have not been able to obtain fibroin in
a state of chemical purity, I would state that, to my
knowledge, there is no vegetable principle which behaves
itself towards reagents in a manner similar to that shown
by the substance of silk, sponge, &c.

" Mulder and Crookewit's analyses show silk and sponge
scarcely to differ in composition.



Fibroin
fromSiOc.



Carbon


. 48-5


Carbon


Hydrogen


6-6


Hydrogen


Nitrogen


. 17-3


Nitrogen


Oxygen
Sulphur • .
&c. &c. .




Oxygen


. 277


Sulphur




PhoBphoms






Iodine



1000



}



Fibroinfrom

Sponges,
46-5 to 48-5
6-3 6-3
. 161 161

. 311 291
1000 1000



Schlossberger has recently expressed his doubts of the
identity of composition of these bodies, from the cir-
cumstance that silk is readily soluble in strong ammonia,
saturated with oxide of copper, whilst sponge is scarcely, or
not at all, affected by long maceration. My own expe-
riments prove the same fact, yet it is not impossible that
the minute quantities of iodine, phosphorus, and sulphur
present in sponge may modify the solubility of the
fibre.

" Under the supposition that a resinous gum might act
as a protection, portions of sponge were boiled in benzol,
ether, and alcohol, but these solvents did not modify the
characters in any noticeable degree.

'*I consider, however, that this difference between
sponge and silk in no wise affects the question of the
former substance being a product of the animal kingdom,
which the other experiments, I think, satisfactorily
prove/'

In considering the results of these analyses with a view

5



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66 ANATOMY AND PHTSIOLOGT

to proving the animal nature of the Spongiadse, the
evidence afforded by the coincidence of its structural
character and its chemical constituents with those of Sertu^
laria operctdata, are still more conclusive than that derived
from the chemical constituents of silk ; and, in truth,
the action of the chemical agents on the zoophyte and the
sponge, as might naturally be expected, are almost in
perfect accordance.



MEMBRANOUS TISSUES.

These structures may be divided into two classes :

1st. Simple membranous tissue.

2nd. Compound membranous tissue.

The first is a simple, apparently unorganized, thin,
pellucid tissue. It is evidently not composed of an exten-
sion of keratode, as it is rapidly decomposed after the
death of the animal. It is found in abundance filling up
the areas of the network of the skeleton in a great variety
of sponges, and it appears to be capable of secreting sarcode
on both its surfaces when thus situated ; on the dermal
membranes the sarcode is found on the internal sur-
face only.

Compound memhranous tissues. — These structures con-
sist of simple membranous tissue combined more or less
with primitive fibrous tissue. Their most simple forms
exist in the membranes lining the interstitial cavities of the
sponge, and in the dermal membranes.

It is difficult in some cases to discriminate between this
class of tissues and simple membranes, unless it be by the
aid of their functional characters, as the compound tissues
are fi-equently quite as pellucid, although not so thin, as
the simple ones.

In dermal membrane, and the membranous linings of
the internal cavities of the sponge, they are thin and
very translucent ; but by a careful examination with high
microscopic powers and transmitted light, with the aid of
polarization, we frequently detect the elastic primary



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OF THE 8PONGIADJ5. 67

fibrous tissues incorporated with the structure. In the
contractile membranes forming the oscular diaphragms in
Grantia, and in those at the base of the intermarginal
cavities in Geodia and Pachymatiama, they attain a greater
degree of thickness, and especially in the two latter genera
of sponges. In Jlcyoncellum, Quoy et Gaimard, the orga-
nization of their tissue is still more complex, and we there
find them constructed of repeated layers of membranous
structure^ abounding in primitive fibrous tissue disposed
in parallel lines in each layer, the fibres disposed so closely
together as to completely cover the membrane beneath, and
the direction of the fibres being at various angles to the
axis of the great cloacal appendages of the sponge^ so as
most efiectually to aid in the contraction or expansion
of that organ. They are so closely packed together and so
intermingled, that I could not ascertain their length but
from the gradual attenuation of some of their terminations ;
they would seem not to be continuous for any considerable
distance. On some of the layers of this compound
membrane the fibres were disposed in an even and con-
tinuous stratum, while in others they were gathered
into broad, flat, parallel fasciculi. When the compound
structure consists of several layers of fibro-membranous
structure, the disposition of the fibres on the different
layers are not coincident. In some cases they cross each
other at right angles, while in others the angle does not
exceed 45 degrees. The latter mode of arrangement
appears to prevail in the membranes connecting the great
longitudmal fasciculi of spicula, forming to a great extent
the skeleton of the cloacal appendages of the sponge;
while the arrangement at right angles appears also in
the tissues immediately surrounding the great skeleton
fasciculi.

This fibro-membranous tissue abounds in the dermal
and interstitial structures of the sponges of commerce^
but the greatest development of this structure is exhibited
in the genus Stematumenia.

Fig. 255, Plate XII, represents a small portion of the
lining membrane of one of the great excurrent canals of



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68 ANATOMY AND PHYSIOLOGY

the common honeycomb sponge of commerce, in the con-
dition in which it came from the sea. The primitive
fibrous tissue is seen arranged in a single layer in parallel
hues at right angles to the long axis of the canal, but
partially obscured by the stratum of sarcode on the
membrane.

Fig. 2B6, Plate XII, represents a small portion of
the dermal membrane of a Sternatumenia, in which the
primitive fibres are seen wandering in every direction over
the surface of the membrane.

Figs. 257 and 258 in the same plate represent portions
of a stouter and a more compound membranous structure,
from the walls of one of the great cloacal projections from
the surface of Alcyoncellum robusta, Bowerbank. In this
case the membrane is strengthened by two or more layers
of primitive fibrous structure, the parallel fibres of each
crossing the others at various angles.



FIBROUS STRUCTURES.

There are two well-characterised classes of fibrous
structure :

1st. Primitive fibrous tissue.
2nd. The fibres of the skeleton.

1. Primitive Fibrom lisaue.

The first of these tissues is exceedingly minute. The
fibres are cylindrical in form, and are usually of considerable
length ; but where they are fully developed, they occur in
such numbers, and in such a matted condition, that I have
been unable to separate an unbroken one from the mass.
They continue through the whole of their length as nearly
as possible of the same diameter, and there rarely appears
to be any attenuation towards their terminations, which are
usually obtuse. They are evidently very elastic and
contractile. When partially separated from their attach-
ments to the membranes, the free ends seldom remain



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OF THE SPONGIAD^. 69

straight, and most frequently they curl considerably in
different directions. They appear to be perfectly soUd ; I
could not by the aid of polarization discover the slightest
indication of a central cavity. They vary in diameter
in different species of sponge, and frequently so even
in the same individual. In a species of Stematumenia from
the Mediterranean, I measured an average-sized fibre which
was ^ inch in diameter, while a smaller one, closely
adjoining, measured 5^ inch. In this genus these fibres
are more fully developed and larger in size than in any
other sponges with which I am acquainted. In the
sponges of commerce, in the membranes of which they are
exceedingly numerous, they are much more slender. In one
of the excurrent canals of the common honeycomb sponge,
one of the largest measured yg^ooo iiich in diameter, and one of
the smallest ty,W i^^h. In the dermal membrane of the
best Turkey sponge they were still less, not exceeding



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