James Scott Bowerbank.

A monograph of the British Spongiadæ online

. (page 14 of 25)
Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 14 of 25)
Font size
QR-code for this ebook


various angles, forming, in their imbedment in the envelope,
a strong and very efficient irregular network of spicula. A
portion of one of these prepared ovaria is represented in
Fig. 320, Plate XXII.

In the ovaries of the different species of Spov^illa^ to be
arranged hereafter in accordance vrith these structural
peculiarities, there is a considerable amount of general
resemblance, but accompanied with such permanent
variations in the structure of the spicula, and in other
portions of the development of these organs, as to render a
somewhat detailed description of them necessary. Thus
in the development of the birotulate spicula, the ovaries
oi Sponffillaplumosa, Carter, exceed any other known species.
The thick walls of these organs are filled with them in the
state represented by Fig. 208, Plate IX, and the intervals
between their shafts appear to be filled with indurated
sarcode or keratode. In Spongilla Meyeni, Carter, the
structure of the walls of the ovaria are strikingly similar to
those of S.fluviatiliSy and the form of the spicula the same,
with the exception of the shafts being very much more
spinous, and the size of the spiculum twice that of 8.
fluviatilis. Fig. 219, Plate IX, represents a spiculum from
an ovary of S. Meyeni. The smallest and most simple
development of birotulate spicula exists in Spongilla gregaria^
Bowerbank, from the River Amazon, represented by Figs.
213, 214, 215, and 216, Plate IX.

A gradual transition from the birotulate form to that of
the unirotulate one takes place in the ovaries of S, patdula
(Fig. 221) and S, reticulata (Fig. 223), until we obtain the
perfect and beautiful unirotulate form in the ovaries of
8, recurvata, represented by Figs. 224 and 225 in the
Plate quoted above. In all these species there is a general
accordance in the mode of their structure.

The gradual transition from the birotulate to the uniro-



Digitized by CjOOQ IC



188 ANATOMY AND PHT8IOLOGT

tulate fonn of spiculum in the ovaries of Spanffilla
reticulata is not the only characteristic difference that
exists between it and its congener. The form and structure
of the ovarium also exhibit marked peculiarities of character,
and it is also furnished with a beautiful reticulated spicular
envelope or case. In its natural condition the ovary fills
the reticulated case, and the coriaceous external surface is
pressed into the areas of the network.

It is usually oviform, but it varies to some extent in
its shape. When treated carefully with hot nitric acid, the
outer coriaceous substance of the ovarium is dissolved,
leaving the inner membrane and the boletiform spicula in
situ; their lai^r terminations being applied to the distal
surface of the membrane, while their smaller clavate or
stellate ends are projected outward, reaching, in the natural
condition, to very near the external surface of the ovarium.
The foramen is situated at the small or distal end of the
ovary, and differs from that of any other form of the organ
with which I am acquainted, inasmuch as it exhibite a
tubular elongation outward of the lining membrane equal
in length to about its own diameter, causing the ovarium,
when prepared with nitric acid, to appear like an oil-flask
with a very short neck. Mg. 823, Plate XXIII, represents
one of the ovaria prepared with acid, and Fig. 322 one of
the cases in which they are contained.

In SpongiUa Brownii, Bowerbank, there is a still further
deviation in the structure of the spicula of the ovary. The
shaft entirely disappears, and the spiculum is reduced to
the umbonato-scutulate form. They are situated on the
outer surface of the inner membrane of the ovarium, with
the umbones of the scutellae outwards. This mode of dis-
position obviously renders them inefficient for external
defence, and the ovaries have therefore been further defended
by being inclosed within an elaborately constructed case
of reticulated acerate spicula. The ovary is closely em-
braced by this envelope, and small elongate masses of its
outer surface are projected through some of its interstices,
causing it to be more or less tuberculous ; and, from the
smallness of the interstices, the tubercles of the envelope of



Digitized by CjOOQ IC



OF THE SPOKGIAD^. 189

the ovary are much greater in length than in thickness.
The spicula of the case are disposed in a close and irregular
network, seldom exceeding two spicula in thickness. By a
careful treatment with hot nitric acid, the thick coriaceous
outer portion of the ovarium may be removed, and its thin
hning membrane, with its stratum of umbonato-scutulate
spicula, becomes an exceedingly beautiful object. The same
mode of operation displays the structure of the reticulated
case of the ovary very much more distinctly than when
viewed in its natural condition. Fig. 821, Plate XXII,
represents two of the cases after treatment with acid, one of
them (d) having the ovary very much reduced in size by the
dissolution of the thick coriaceous portion of its structure.

In the second group of the ovaries of the Spongillidae
there is also a strong general resemblance in structure to
the type-form of S. lacustris, but each species is distinctly
characterised by peculiarities of form and arrangement of
the spicula.

The normal form is spherical, and the walls of the ovaries,
in six out of the seven species with which I am acquainted,
are comparatively thin. In the seventh species, S. Carteri^
Bowerbank {8. friabilis, Carter), they are very thick and
abundantly furnished with cellular structure, arranged in
lines radiating from the centre to the circumference ; each
Une consists of nine or ten cells, the length of each being
about equal to the diameter. They are very closely packed
together, and are irregularly angular by compression. Their
combined length varies from about one-fifth to one-sixth
the length of the diameter of the ovarium. This is the
only species in which I have detected this description of
cellular structure. Fig. 284, Plate XVI, represents a portion
of the surface and a view of the cells in situ.

Although the spiculated coriaceous form of ovarium pre-
vails so constantly among the freshwater sponges, it is one
of extremely rare occurrence among the marine species ;
and I have met with only one instance of its occurrence, and
that is in a new genus of sponges from Shetland, for which
I am indebted to my late indefatigable friend Mr. Barlee.
The specimen incrusts a portion of the valve of a Peden,



Digitized by CjOOQ IC



140 ANATOMY AND PHTSIOLOGT

covering a space about half an inch in length and the eighth
of an inch in breadth, and it does not exceed lialf a line in
thickness. The ovaries are numerous and closely packed
together, and are distinctly visible to the unassisted eye,
looking like very minute cocoons of some terrestrial insect.
There were nearly thirty in an area equal to about a quarter
of an inch. They are attached by the sides to one or more
branches of the fibrous portion of the skeleton.

The v^^all of the ovary is very thin, and appears to consist
of a single membrane profusely furnished with acerate
spicula, like those of the skeleton. They cross each other in
every possible direction, and occasionally appear to assume
a somewhat fasciculated arrangement. The ovaries are not
uniform in shape, some being regularly oval, while others
are more or less ovoid. I could not detect any trace of a
foramen in those I subjected to examination. I have
designated this interesting species Diplodemia vesicula in
my description of it. Fig. 324, Plate XXIII, represents
two of the ovaries in their natural condition after immersion
in Canada balsam, magnified 83 linear.

In the genera Geodia and Pachymatisma ovaria are pro-
duced in great abundance. They agree in form very closely
with those of Spon^illa, but their structure is widely
difierent, and the soft animal matter that enters so largely
into the structure of those of the freshwater sponges scarcely
makes its appearance in the ovaries of Geodia, their walls
being composed of closely packed spicula, firmly cemented
together by silex. Their situation in the animal is also differ-
ent from those of SpongiUay in which they are dispersed amid
the interstitial tissues, but principally towards the base of the
sponge, while in Geodia and Pachymatisma they are con-
gregated in large quantities immediately beneath the dermal
membrane ; and when they have shed their ova they per-
manently retain their situation, forming a thick crustular
dermis for the protection of the softer portions beneath :
a few only are found dispersed in the interstitial membranes
of the sponge. The progressive development of this kind
of ovarium is very nearly the same in every species of Geodia
or Pachymatisma in which I have had an opportunity of



Digitized by CjOOQ IC



OP THE SPONGIAD^. 141

^examining them. In an early stage they appear as a
globular body of fusiformi-acerate spicula, radiating regu-
larly from a central point in the mass. As the individual
spicula increase in diameter there is a corresponding disten-
sion of the ovarium, and as the spicula do not lengthen
in proportion to their increase of diameter a central cavity
is produced, in which the incipient ova very shortly appear.
The spicula of the wall of the ovary continue to increase
considerably in diameter, but very little in length, and their
distal terminations become gradually less acute as they
approach the period of .the full development of the ovary.
When this organ has attained its greatest diameter, their
distal extremities cease to lengthen, and a gradual change
in the form of the spicula is effected, their apices extending
in diameter and assuming a truncated form, and the whole
of them becoming firmly cemented together, so as to form
a common flat smooth surface to the siliceous skeleton of
the ovarium, each spiculum having now changed from the
acerate to the acuate form, their proximal acute terminations
forming the common inner surface of the cavity of the
ovarium, which is now filled with an opaque mass of ova.
A single conical orifice or foramen -has also been produced
in a portion of the wall, through which the ova are destined
to be ejected. The proximal end of this foramen is very
much the smaller of the two, so that, as soon as an ovum
has fairly entered this conical tube, there is no longer any
impediment to its ejection : and the manner in which this
is effected is very interesting, and appears to be as follows.
When the ova have attained maturity, the proximal termi-
nations of the spicula which have not been cemented
together like their distal ones, are progressively and simul-
taneously lengthened, thereby encroaching on and gradually
lessening the diameter of the cavity within, so that the ova
are compressed and forced through the foramen ; and this
process appears to be continued until the whole of them
have been ejected, and the cavity becomes completely filled
by the continued encroachment of the proximal ends of the
spicula of the walls of the ovarium.

In Fig. 327, Plate XXIII, two ovaries from Geodia



Digitized by CjOOQ IC



142 ANATOMY AND PHYSIOLOGY

McAndremi containing ova are represented : {a) contains
about the greatest quantity of ova that is foimd within
these organs. In this one the distal terminations of the
spicula of the skeleton are still somewhat rounded, and
sUghtly elevated above the common surface ; while in {b\
which has been partially exhausted of the ova, the spicula
have their distal terminations flat and somewhat angular,
and they are level with the general surface, thus indicating
a greater age and a fuller development than obtain in the
one represented by (a), and not a less amount of secretion
of ova, as might possibly be imagined. These circum-
stances are strongly indicative of the fact that the ovaria,
both in an active and effete state, are permanently seated
in the sponge, and that the ova only are discharged from
it. So in like manner the existence of the ovarium in
Spongilla reticulata and JBrownii, Bowerbank, confined
within a strong spicula case firmly incorporated with the
skeleton, is strong presumptive evidence of their also being
permanent organs, and not of the nature of gemmules which
separate from the body of the sponge when they arrive at
maturity and are ejected through the great faecal orifice.

Many other species of Geodia with which f am acquainted
afford these ovaria in great abundance, and with some vari-
ations in size and form from those in G. McAndretoii,
Bowerbank, MS., but in no other sponge are they so large
and so completely developed.

Kg. 325, Plate XXIII, represents an adult ovarium from
Geodia McAndrevni with the conical foramen on its summit,
and the distal ends of the skeleton spicula flat and angular.
Eig. 326 represents a small portion of the surface of the
same specimen as seen with a linear power of 308, ex-
hibiting the flatness and angularity of their distal apices.
Fig. 329, Plate XXIV, represents a portion of a young
ovarium having the distal ends of the skeleton spicula
disunited and acutely conical. Fig. 328, Plate XXIII,
represents a portion of a section of an ovarium of G.
McJndremi, exhibiting the radial arrangement erf its
component spicula.

In Pachymatisma Johmtonia, Bowerbank, a British



Digitized by CjOOQ IC



07 THE SP0K6UDJS. 148

species common on the rocks in the neighbourhood of
Torquay, and which I described in a paper read before the
Microscopical Society of London in 1841, these organs
assume an oval form ; they are also considerably depressed.
In a young specimen of this species of sponge in my pos-
session, the progressive development of the ovaria is very
strikingly illustrated. Fig. 330, Plate XXIV, represents
an adult ovarium. Fig. 331, one in a semideveloped state,
and Fig. 332, one of the same organs in a very early stage
of development. In another species of sponge from the
South Seas we find a singular variety of this class of
ovarium. It is oval in form, the length being to the breadth
as five to three, but it is so much depressed as to appear
rather like a dermal spicular plate than an ovarium ; but the
radiate arrangement of its component spicula is perfectly
visible with a power of 666 linear, and their distal termi-
nations as separate and distinct as those of Geodia or
Fachymatisma. The situation of the foramen is also well
defined in many of them. Fig. 333, Plate XXIV, represents
a mature ovarium ; Fig. 334, a fragment of one to exhibit
its degree of thickness ; and Fig. 335 represents one of the
same species of ovarium in an early stage of development.
I have seen four species of sponge which have this descrip-
tion of ovarium ; in one it is very considerably longer in
its proportions than that represented by Fig. 333, Plate
XXIV, and in another species it is somewhat shorter.

Since the preceding portion of the account of the ovaria
was written I have received a very remarkable specimen of
these organs, which differs materially in its structure from
any of the forms that I have previously described. The
sponge consists of a small portion of basal membrane, closely
resembling that of a Halichondraceous species. It was
found by my friend Mr. J. Yate Johnson coating rocks
and stones at Madeira. The remains of several exhausted
ovaria are dispersed over the surface of the membrane, a
few only retaining their original form and proportions.
They do not appear to have had a spicular skeleton, but to
have consisted of a coriaceous envelope strengthened and
supported by a reticulated skeleton of apparently keratose



Digitized by CjOOQ IC



144 ANATOMY AND PHYSIOLOGY

structure. They are nearly globular, and are firmly
cemented to the membrane by a broad basal attachment.
Although themselves apparently in an effete state, the
membrane on which they are seated was in a decidedly
living and active condition. It is thickly coated with
sarcode, and abundantly furnished with equi-anchorate
spicula. Numerous slender acuate or subspinulate spicula
are also dispersed over its surface, which are occasionally
fasciculated after the manner of the first indications of the
formation of a Halichondraceous skeleton. But the most
interesting feature of the membrane is, that at intervals
over the whole of its surface, and especially at those parts
most free from the dispersed spicula, there are small de-
tached groups of spicula, each consisting of two or three
irregular fasciculi crossing each other at various angles, re-
sembling in every respect the early stages of development
of the gemmules or ova so graphically described by Dr.
Grant in his account of the gemmules of the sponge he has
designated Halichondria panicea.^ The presence of these
early developments of the ova is precisely in accordance
with the discharged and effete condition of the ovaries, and
is just such an effect as might naturally be expected under
such circumstances. Fig. 336, Plate XXIV, represents
one of these ovaria seen by a microscopic power of 108
linear ; Fig. 337, a small piece of the reticulated wall of
the ovarium with a power of 308 linear ; and Fig. 338 re-
presents the development of one of the ova and the sur-
rounding equi-anchorate spicula with a power of 108
linear.



Gemmules.

If we adopt as a definition that a gemmule is a body not
containing ova, but that it is a vital mass separated fix>m
the parent and capable of being ultimately developed into
a single individucd possessing the same specific characters



• (



Edinburgh New Philosophical Journal,' vol. i, p. 16, plate ii, figs. 24



Digitized by CjOOQ IC



OF THE SPONGIAD^. 145

and capabilities as the parent mass, we must consider the
reproductive bodies so ably and minutely described by
Dr. Grant in his paper " Observations on the Structure and
Functions of the Sponge/^* not under the designation of
ova, but rather under that of gemmules ; and indeed the
learned author seems to have entertained some doubt of
their being correctly designated by the former term, as in
speaking of them in a subsequent portion of his paper in
page 14, he says, " since these germs or so-named ova are,
&c. f I have therefore been induced to arrange them under
the designation of Gemmules.

Dr. Grant describes their first appearance in the sponge
in the months of October and November " as opaque yellow
spots visible to the naked eye, and without any definite
form, size, or distribution, excepting that they are most
abundant in the deeper parts of the sponge and are seldom
observable at the surface ;" he also states that " they have no
cell or capsule, and appear to enlarge by the mere juxta-
position of the monad-like bodies around them. As they
enlarge in size they become oval-shaped, and at length in
their mature state they acquire a regular ovate form."
When they have attained a fully-developed condition, they
separate from their attachment to the parent and pass out
of the fecal orifices. At this period of their existence the
learned author states that they are endowed with sponta-
neous motion, in consequence of their larger extremity being
furnished abundantly with cilia, which the author describes
as "very minute transparent filaments, broadest at their
base, and tapering to invisible points at their free extremi-
ties.'" After floating freely about for a period, they attach
themselves to some fixed body, adhering firmly to it, and
spreading themselves out into " a thin transparent convex
circular film." The author further states that " when two
ova in the course of their spreading on the surface of a
watch-glass come into contact with each other, their clear
homogeneous margins unite without the least interruption,
they thicken, and produce spicula: in a few days we can

* 'Edinbargh New Philosophical Journal,* vol. i, p. 16, plate ii, figs. 24-29.

10



Digitized by CjOOQ iC



146 AXATOMY AND PHYSIOLOGY

detect no line of distinction between them, and they con-
tinue to grow as one ovum."

I have never had the good fortune to see the living
gemmnle with its cilia in action, as described by Dr. Grant;
but I have frequently found Halichondraceous sponges with
an abundance of these gemmules attached to their tissues ;
and I have in my possession a beautiful Uttle specimen,
dredged off Shetland, for which I am indebted to my kind
friend Mr. Barlee, which is very illustrative of Dr. Grant's
description of the mode of the development of the young
sponge after the ovum or gemmule has attached itself. On
a fragment of a bivalve shell there are more than twenty or
thirty of Dr. Grant's ova or gemmules, which are all in the
same early stage of development, each forming a small
group of extremely slender spicula. The groups are sepa-
rate from each other, but very closely adjoining. The
diameter of one of the largest does not exceed gJoth of an
inch, and their distance from each other is about half or
once the diameter of one of them. In their present state,
as represented by six of them in Fig. 339, Plate XXIV, it
is evident that they are separate developments ; and it is
equally evident that a slightly further amoimt of extension
would have caused them to merge in one comparatively
large flat surface of sponge. We see by this instance that
a sponge is not always developed from a single ovum or
gemmule, but, on the contrary, that many ova or gemmules
are often concerned in the production of one large indivi-
dual ; and this fact may probably account for the compara-
tively very few small sponges that are to be found, — a few
days probably serving by this mode of simultaneous deve-
lopment to form the basal membrane of the sponge, of con-
siderable magnitude, as compared with the individual ovum
or gemmule, or with a sponge developed from a single
ovum only. This mode of reproduction appears to have
a very wide range. It is common to several distinct genera
of Hahchondraceous sponges ; and I have observed it also
in a siliceo-fibrous sponge, Iphiteon panicea of the Museum
of the Jardin des Plantes, Paris. Fig. 340, Plate XXV,
represents a small piece from the interior of the skeleton of



Digitized by CjOOQ IC



OF THE SPONGIADiE. , 147

Iphiteon panicea. Although the latter sponge is so widely
different in structure from the Halichondraceous tribes of
sponges, its mode of propagation by gemmation seems to
be in perfect accordance with them. In Tethea cranivm
the same mode of reproduction by gemmules obtains, but
the form of the organ is different, and there are other pecu-
liarities in its growth and development that are extremely
interesting.

The form of the gemmules is regularly lenticular ; and
there are two distinct sorts of them, which are always
grouped together. The first is rather the smaller of the
two, and has a nucleus of slender curved fusiformi-acerate
spicula only. The bases of the spicula cross each other at
the centre of the gemmule, and the apices radiate in all
directions towards the external surface, but do not, in the
fully developed state of the gemmule, project beyond it.
The second sort of gemmule is furnished with three distinct
forms of spiculum. The first are like those of the gemmule
described above, slender fusiformi-acerate ; the second are
attenuato-p*recto4ernate, the radii being given off from
the apex at about an angle of 46 degrees ; and the third
form is attenuato-bihamate or unihamate, and the hooked
apices of this form are projected further than either of the
other two forms, but do not pass beyond the inner surface
of the tough dermal envelope of the gemmule when in the
adult state. I have examined a great number of these
gemmules, and could never find in the form first described
any indication of either temate or hamate spicula, and I am
therefore satisfied that they are separate descriptions of
gemmule, and that the first form is not a transition state
from the young and undeveloped to the fully developed
one. In like manner I have closely observed the second
form, and have always found it uniform in character, and
furnished with the whole three forms of spicula that charac-
terise it. It is highly probable that this marked difference
in structure is sexual, and, from the more highly developed
condition of the second or large form, that it is the female
or prolific gemmule ; but on this point we must at present
be satisfied with conjecture only, as although I have searched



Digitized by CjOOQ IC



148 ANATOMY AND PHYSIOLOGY

diligently for spermatozoa in both forms of gemmule and
in the surrounding sarcode, I have not been able to detect


1 2 3 4 5 6 7 8 9 10 11 12 14 16 17 18 19 20 21 22 23 24 25

Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 14 of 25)