James Scott Bowerbank.

A monograph of the British Spongiadæ online

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axial column of this genus differs stnkmgly from that of
the strong, closely packed axis <tf JScumemia, and the peri-
pheral system of spicula are never furnished with ternate
connectu]^ spicula. All the species of this genus I have
hitherto seen are more or less ramous in form. Fig.
366, Plate XXXII, represents part of a small branch of
BictifocyUndrm ruffosua, Bowerbank, exhibiting the radiating
structure of the defensive fasciculi, X 50 linear ; a, part of
the central axis of spicula. Kg. 866, Plate XXXIII,
represents part of a section through the axial column of
Bictyocylindrm ramoms^ showing the elongo-reticulate
structure of the skeleton of the sponge, X 50 linear.



PhakelliAj Bowerbank.

Skeleton. Composed of a multitude of primary cylindrical
axes, radiating from a common base and ramifying
continuously, from which emanate at about right
angles to the axes a secondary series of ramuli, which
ramify continuously as they progress towards the
surface, but never appear to anastomose.

Type, Phakellia ventilahmm^ Bowerbank.

I know of no other species, either British or foreign,
that possesses the peculiar conformation that distinguishes
the sponge that is the type of this genus. The primary
cylindrical axes very closely resemble those of Bictyocylin-^
druSy but in that genus the spicula radiating from the axes
are separate and distinct, each having its proximal end
based on the primary cylinders of the skeleton, and its
distal one reaching nearly to, or passing through the
dermal membrane of the sponge ; or if they be fasciculated,
the fasciculi are simply plumose, and in no case with which
I am acquainted at all ramulous. In PhakeUia the secon-
dary skeleton is formed of distinct slender branches, each



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OF THE SPONGIADiB. 187

composed of numerous spicula ramifying continuously, and
each ramulus increases in size and the number of its
spicula as it approaches the surface of the sponge. Single
spicula are frequently projected from the ramuli in an
ascending direction at an angle of a few degrees, and at
their distal terminations at the surface of the sponge;
the whole of the temuBal spicnla radiate more or less at
angles from their axial line, and passing through the
dermal membrane form the external defences of the
sponge. Although constantly ramifying and freely inter-
mingling, I have never detected them anastomosing. The
term Phakellia is applicable to both the primary and
secondary ramifications of the skeleton. The type of this
genus is Halichondria ventiladrum, Johnston. I have not
yet met with an exotic species of the genus. Fig. 367,
Plate XXXIII, represents a longitudinal section of one of
the primary radial Knes of the skeleton structure, exhibiting
the slender secondary radiations of the skeleton ; a, part of
the primary axial portion of the skeleton ; i, dermal mem-
brane, X 50 linear.

The genera Microciona, Symeraphia, and Hytnedesmia
form a group essentially different in structural character
from the other genera of the Spongiadae ; but they are
closely allied to each other by the peculiar characters of
their basal membranes in conjunction with the other parts
of the skeleton. From the nature of their structures, the
species generally assume a thin coating form and are often
very minute.

In most of the genera of Spongiadae the basal membrane
of the sponge ceases to be of marked importance after the
earliest stages of its development, but in these genera it
continues throughout the whole existence of the sponge to
form an important part of its skeleton structure. It is a
common base whence spring the whole of the other com-
ponent parts of the skeleton ; and its importance is further
indicated by its also being the common base in some
species of the internal as well as the external defensive
spicula of the sponges in which those organs occur.



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188 ANATOMY AND PHYSIOLOGY



MiCROcioNA, Bowerhank.

Skeleton. A common basal membrane, whence spring at
or about right angles to its plane numerous separate
columns of spicula intermixed with keratode, furnished
externally with spicula which radiate from the columns
at various angles towards the dermal surface of the
sponge.

Type, Microciona atrasanguinea^ Bowerbank.

The skeleton of the type of this genus, M. atrasanguinear
is diflFerent from that of any other genus of sponges that I
have hitherto seen. It consists of numerous, nearly equi-
distant, short, straight, separate columns of spicula and
keratode from all parts of the sides of which spring stout,
long, curved, fusiformi-attenuato-subspinulate spicula, the
convex side of each spiculum being outward, and each
column terminates with five or six of these spicula disposed
in the same manner and at the same angle to the axial line
of the column, that is from about twenty to forty-five
degrees. The proportions of the skeleton-columns vary in
different species. In M. atrasanguinea they are short,
stout, and exceedingly well defined. In M. amhigua they
are short and indistinctly produced, and in M. carnosa they
are long, slender, flexuous, and frequently branched ; but
however they may vary in their proportions in different
species, their normal character, both as regards structure
and position in the sponge, is always preserved. Fig. 368,
Plate XXXIII, represents a single column of the skeleton
of Microciona atrasanguinea^ Bowerbank, showing its struc-
ture and the proportions and positions of the external
defensive spicula, X 175 linear. Fig. 369, Plate XXXIV,
represents a section at right angles to the surface of the
sponge exhibiting the columns of the skeleton in situ ; a, the
plane of the dermal membrane with groups of tension
spicula.



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OF THE SPONGIAD^. 189



Genus — Htmbraphia, Bowerbank.

Skeleton. A single basal membrane, whence spring nu-
merous large separate spicula, which pass through the
entire thickness of the sarcodous stratum to, or beyond
the dermal surface of the sponge.

Type, Hymeraphia stelUfera, Bowerbank.

This genus is nearly allied to Microciona, but is more
simple in its structure ; as in place of the columns of the
skeleton compounded of keratode and spicula cemented
together, and emanating from a common basal membrane
as in the latter genus, we find single spicula only, devoid
of keratode and based on a common membrane, whence
they pass through the entire substance of the sponge ; and
in all the species at present known, they penetrate the
dermal membrane and project beyond its surface to a con-
siderable extent, thus combining the two offices of skeleton
and external defensive spicula. These organs are there-
fore, as compared with the skeleton spicula of other mem-
bers of the Spongiadae, and to the entire mass of the
sponges to which they belong, of exceedingly robust pro-
portions ; their length being frequently twice that of the
entire thickness of the sponge.

These peculiarities of structure indicate a common habit
of extreme thinness in the species, and such is in reality
the condition of those with which we are acquainted.
Fig. 370, Plate XXXIV, represents a section of Hymera"
phia stelliferay Bowerbank, showing the large bulbous
skeleton spicula in situ, their apices forming the external
defences ; a, the stelliferous internal defensive spicula ele-
vated by a grain of sand beneath the basal membrane,
X 108 linear. Fig. 34, Plate I, exhibits one of the stel-
liferous defensive spicula, X 260 linear.



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190 ANATOMY AND PHYSIOLOGY



Hymbdesmia, Bowerbank.

Skeleton. A common basal membrane sustaining a thin
stratum of disjoined fasciculi of spicula.

Type, Hymedesmia Zettandicay Bowerbank*

The species on which this genus is founded very closely
resembles in habit and general appearance those of the
genera Microciona and Hymeraphia^ and in regard to the
special offices of the basal membrane, it assimilates with
them completely. But it diflFers from them, inasmuch as
the spicular portions of the skeleton do not emanate imme^
diately from the basal membrane, but are recumbent on it
in the form of disjoined fasciculi of spicula. But although
different from them in this important respect, the close
alliance with them is indicated by the common habit of the
possession by the basal membrane of the whole, or nearly
so, of the defensive spicula of the sponge ; indicating the
common property of extreme thinness of structure which
exists in these genera.

The free condition of the fasciculi of the skeleton con-
nects this genus in some degree with the Halichondroid
genera of sponges, but there are none of the species of those
genera in which the fasciculi of the skeleton are separate
from each other. The nearest allied genus in that direc-
tion appears to be Hymeniaddon. Fig. 371, Plate XXXV,
exhibits the disjoined fasciculi of the skeleton in situ, in
Hymedesmia ZeUandica, X 108 linear; and Kg. 296
Plate XVITI, represents a small portion of the inner surface
of the dermal membrane of the same sponge, showing the
fasciculation of the simple bihamate spicula, the equi-
anchorate ones dispersed singly on the membranes, and the
large attenuato-acuate entirely spined defensive ones in situ,
X 308 linear.



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OF THE SPONGIADiB. 191

Suborder II. Spiculo-membranous skeletons. Composed
of interstitial membranes, having the skeleton spicula
irregularly dispersed on their surfaces.

The prominent character of this Order is that the spicula
of the sponges composing it do not assume either the
radiate, fasciculate, or reticulate structural arrangement.
The distribution of the spicula on the interstitial mem-
branes being without any approximation to order.

Hymeniacidon, Bmverbank.

Skeleton without fibre, spicula without order, imbedded in
irregularly disposed membranous structure.

Type, Hymeniacidon caruncvla^ Bowerbank.

In Hymeniaddon the spicula are subordinate to the mem-
branous structure, they follow its course and are imbedded
without order on its surface. The contranr is the case in
Halichondria. The network of spicula m that genus,
although irregular, is decidedly the predominant structure,
and the membranous tissues are secondary to it, and exist
only as interstitial organs. The larger and stouter of the
spicula in Hymeniacidon, although dispersed amid the
slender ones, may be considered as the representative of
the skeleton spicula, while the slender ones are truly those
of the membranes, the tension ones.

In some species the interstitial tissues are constructed
diffusely, as in H caruncvla^ while in other species, as in
H. mberea {Halichondria suberea, Johnston) and a few
other closely allied species, they are more than usually
compact, so that in the dried state the texture of these
sponges are very like that of fine hard cork. From this
peculiarity of their appearance in the dried condition, and
the exceeding compactness of their structure, I was formerly
inclined to believe them to be generically different from the



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192 ANATOMY AND PHYSIOLOGY

great mass of the species of Hymeniacidon, and I accord-
ingly inserted them in the list of British sponges, published
in the " Report of the Dredging Committee" in * the Reports
of the British Association' for 1860, mider the titles of
Halina mberea, ficm^ &c. ; but a closer examination of
their internal structure has convinced me that their only
real difierence from the other species of Hymeniacidon is
in their greater compactness of skeleton structure, and
I have accordingly removed those species to the genus
Hymeniacidon,

In the greater number of the species of this genus the
tension spicula are of the same form as those of the skeleton,
and are only to be distinguished from them by their greater
degree of tenuity, but in a fevr of the known species they
are diflFerent both in size and form.

The mode of propagation in all the species in which I
have found the reproductive organs, appears to be by
internal gemmulation. In H. carnosa and several other
species of the genus they are simple, spherical, aspiculous,
membranous vesicles, filed with round or oval vesicular
molecules. The genus Halisarca, Dujardin, was supposed
by both that author and Dr. Johnston to be entirely des-
titute of spicula ; but I have, since the publication of the
' History of the British Sponges,' found them in H. Du-
jardinii in abundance. They are so minute and so com-
pletely obscured by the surroimding sarcode, that they can
rarely be detected in either the living or the dead specimens
when examined in water ; but if a portion of the sponge be
dried on a slip of glass and covered with Canada balsam,
they may be detected by transmitted light and a power of
400 linear in considerable numbers, dispersed on the inter-
stitial membranes of the sponge. This genus will therefore
merge in that of Hymeniacidon^ with which it agrees in
every structural peculiarity. Fig. 872, Plate XXXV,
exhibits the dispersed condition of the skeleton spicula on
the interstitial membranes of a specimen of Hymeniacidon
caruncula, X 108 linear.



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OF THE SPONGIADiE. 193



Suborder III. Spiculo-reticulate skeletons. Skeletons
continuously reticulate in structure, but not fibrous.

HaUchondria.

Hytdonema.

laodictya.

The sponges of this suborder vary in the different genera
to a great extent in the mode of the construction of the
skeleton, but in all cases the spicula are the dominant
material; their terminations overlap each other, and they
are cemented together by keratode. The reticulations thus
formed sometimes consist of a single series of spicula, at
other times they are very numerous, and are crowded
together in the manner of elongated fasciculi.

The genera Ualichondria and laodictya are exceedingly
rich in species, but the inconvenience attending their dis-
crimination arising from their number may be remedied to
a great extent hereafter by subdivisions of each genus, based
on the characteristic forms of the spicula of their respective
skeletons. The structural distinction between Halichondria
and hodidya is so well marked as to render the recog-
nition of each comparatively certain and easy. The skeletons
of the species of the latter genus, generally speaking, are
very much more slight and fragile than those of the former
one, and the same rule obtains to a great extent as regards
the comparative size of their spicula, and in many species
of Isodictya they are very minute. Hyalonema and Spon-
gilla are readily to be distinguished by the peculiarities of
their structure and localities.

The genus Halichondria, as constituted by Dr. Fleming
in his * History of British Animals,' and adopted by Dr.
Johnston in his * History of British Sponges/ contains
species which differ exceedingly in their mode of organiza-
tion. Thus, if we take H. panicea of Johnston, which is
imdoubtedly the " sponge-like crumb of bread " of Ellis,

13



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194 ANATOMY AND PHYSIOLOGY

and the older authors, and therefore the proper type of the
genus, we find the skeleton destitute of fibre, but composed
of an irregular network of spicula cemented together at their
apices by keratode. If we examine the well-known branching
sponge so common on all our coasts, Hcdichondria octdata
of the same author, we find an abundance of keratose fibre
containing spicula deeply imbedded in its substance, but
not necessarily uniting at their apices, and the network of
the skeleton is not irregular as in the first instance, but on
the contrary is more or less symmetrically disposed in all
parts of the sponge. If we take Haliehondria suberea of
the same authors we find neither network of spicula nor a
keratose fibrous structure, but apparently an amorphous
sarcoid mass containing spicula and membranes, on which
the former are dispersed without any order or connection.
As we extend our researches among the other British
species of Fleming's genus Halichondriaj other striking
, and permanent variations in the arrangement of their
skeleton tissues present themselves. Their great difierences
in structure therefore afibrd ample grounds for the division
of the species comprehended under Haliehondria as consti-
tuted by Fleming into a series of genera, having each for
its base a separate type of organization ; and as the vari-
ations in structural character, some of which are mentioned
above, are both numerous and strikingly characteristic, I
propose to limit the genus Haliehondria to those species
only, which agree in their organization with H, panicea of
Johnston, and to distribute the remaining species in other
genera, the distinctive characters being in all cases based
primarily on the diflferent modes of the organization of the
skeleton of the animal, and when necessary taking in aid
such other organic characters as may be found available for
the purpose of accurate discrimination. I therefore propose
to limit the genus Haliehondria to those sponges only, that
exhibit the following characters.



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OF TH£ SPONGIADJB. 195



Halichondria, Fleming,

Sponge. Skeleton without fibre ; composed of an irregular
polyserial network of spicula cemented together by
keratode.

Type, Halichondria panicea, Johnston.

The anatomical structure of the group included under
this genus is distinct and unmistakeable. There is no fibre
whatever, the -skeleton being formed of spicula collected
into bundles of a greater or less number cemented together
by keratode, but which substance does not extend beyond
the space occupied by the respective bundles ; and when
parts of the reticulated skeleton are formed of single series
of spicula only, they are simply cemented together at their
points, and the reticulated skeleton thus formed has no
definite arrangement.

In some species of the genus the reticular character of
the skeleton is much more distinct than in others. IT.
oanicea, although the type of the genus is by no means the
best specimen of its character. Fig. 300, Plate XIX, repre-
sents a section of If. panicea at right angles to its surface,
md Fig. 303, the reticulations supporting the dermal mem-
brane, X 108 linear. Fig. 373, Plate XXXV, represents
i section at right angles to the surface of a specimen of
Halichondria incrmtans^ Johnston, X 50 Unear, a better
type of the structural character of the genus than H.
panicea.



Hyalonbma, Gray,

Dr. Gray has characterised this genus in his descriptions
of genera of Axiform Zoophites, or Barked Corals, as
" coral subcylindrical, rather attenuated, and immersed in
a fixed sponge. Axis in the form of numerous elongated,
slender, filiform, siliceous fibres, extending from end to end



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196 ANATOMY AND PHYSIOLOGY

of the coral, and slightly twisted together like a rope.
Bark fleshy, granular, strengthened with short cylindrical
spicula. Polypiferous cells scattered, rather produced,
wart-like, with a flat radiated tip/' (* Proceedings of the
Zoological Society of London * for 1857, page 279.) This
description apphes only to the singular cloacal appendage
to the sponge from amidst which it springs, the structure
of the body of the animal being evidently considered by the
author as an extraneous mass. The basal sponge is un-
doubtedly a portion of the animal to which the part de-
scribed by Dr. Gray belongs, the spicula of the elongated
cloacal portion being also abundant in the basal mass of
sponge ; and the basal mass of the specimen described by
Dr. Gray is identical in its structural character with that of
the specimen of Hydonema mirabilis in the Bristol Museum.
It becomes necessary therefore to remodel the generic cha-
racters so as to embrace the leading distinctive structures
of the skeleton of the animal, and I propose the following
form of description :

Skeleton an indefinite network of siliceous spicula, composed
of separated elongated fasciculi, reposing on continuous
membranes, having the middle of the sponge perforated
vertically by an extended spiral fasciculus of single,
elongated, and very large spicula, forming the axial
skeleton of a columnar cloacal system.

Type, Hydonema mirabUis, Gray.

The construction of the skeleton of the mass of the
sponge is intermediate between that of Hdichondria pa-
nicea and Hymeniacidcm carunctda^ the respective types of
those genera. The network of fasciculated spicula appears
never to be definite and continuous as in the former, nor
are the skeleton spicula in a dispersed condition on the con-
tinuous membranes as in the latter, but are gathered into
elongated fasciculi which cross each other in the same plane
in every imaginable direction, but without ever appearing
to anastomose. The fasciculi vary exceedingly in the



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OF THE SPONGIAD^. 197

number of spicula of which their diameter is formed, some-
times consisting of two or three spicula only, and at oth^
times of more than it is possible to count. They often
divide, the branches passing in different directions, but they
never reunite or anastomose with other fasciculi. A portion
of this network of spicula is represented by Fig. 375, Plate
XXXV. The columnar axis of the cloacal system consists
of one large spiral fasciculus of spicula, each of which
extends &om the base or very near that part of the sponge,
to near or quite to the apex of the column, the direction of
the spiral being from right to left. Fig. 374, Plate
XXXV, represents a portion of the great cloacal column,
exhibiting part of the spiral axial fasciculus surrounded by
the remains of its dermal coat, with numerous oscula pro-
jecting from its surface, copied from ^ Zoological Proceed-
ings ' for 1857.

There is a close approximate alliance to this form of the
cloacal appendage of Hyalonema in the corresponding organs
of the British genus Ciocalypta^ Bowerbank.



IsoDiCTYA, Bowerbank.

Spovoia, M<mt€tgu,
Halichondbia, Fiemng.
Halichondbu, Johnston,

Skeleton vrithout fibre ; composed of a symmetrical network
of spicula ; the primary lines of the skeleton passing
from the base or centre to the surface, and the
secondary lines disposed at about right angles to the
primary ones. Propagation by internal, membra-
naceous, aspiculous gemmules.

Types, Isodietya palmata and Normani, Bowerbank.

This genus, in the structure and arrangement of its
skeleton, is intermediate between Halichondria and Chalina,
as defined in the present work. Like the former, the
spicula of the network composing the skeleton are merely
cemented together, not inclosed within a regular horny



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198 ANATOMY AND PHYSIOLOGY

fibre ; but the disposition of the network is not entirely
irregolar, but like that of the latter genus, more or less
composed of a primary series of lines radiating from the
axis or base of the sponge, and of secondary series connect-
ing the primary ones at about right angles to them ; in fact
simulating very closely the arrangement of the skeleton of
CAalina oculata, but without the keratose fibre surrounding
the spicula of the skeleton in that sponge.

In some of the species of this genus the symmetrical
arrangement of the lines of the skeleton is distinct only near
the surface of the sponge, while in the more deeply seated
parts, the irregular characters of a Halichondria is simu-
lated. In determining the species of this genus, the
sponge requires to be carefully examined by sections at
right angles to the surface, where the distinctive character
rarely fails to be readily detected. On the contrary, in
Halichondria panicea, the type of that genus, I have never
succeeded in finding such a linear arrangement of the
skeleton as marks that of Isodictya. In a hasty examina-
tion a single linear series of spicula will therefore often
prove an excellent guide to the discrimination of this
genus.

In most of the species with which I am acquainted there
is a generally prevailing character of fragility ; the primary
lines being composed of very few spicula, while the secon-
dary ones, are most frequently unispicular. Most of the
species are thin, coating or encrusting sponges, and rarely
appear to rise in tuberous masses, as the numerous species
of Halichondria are in the habit of doing.

laodictya infundibuliforrnis is perhaps the most perfect
type of the genus, as in it we have the primary and secondary
lines of the skeleton distinctly separated by the difierence
in the form of their spicula. In some species of the genus,
as in /. simulo, the cementing keratode of the skeleton is


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Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 18 of 25)