James Scott Bowerbank.

A monograph of the British Spongiadæ online

. (page 13 of 25)
Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 13 of 25)
Font size
QR-code for this ebook


Digitized by CjOOQ IC



126 ANATOMY AND PHYSIOLOGY

remarkable, and highly suggestive of a capability of adapta-
tion to circumstances that we should scarcely have expected
to find. By the two instinctive habits, — ^first, that of con-
verting the plant into an artificial skeleton, and then
erecting its spinous spicula on its fibres, — it at once simu-
lates the habits of a kerato-fibrous sponge, and becomes
capable of the carnivorous habits that I have attributed to
those sponges that are so strikingly adapted for preying on
intruding anneUds or other such small creatures. In the
species above described, Hymeniaddon Cliftoni, Bowerbank,
MS., the erection of the spicula on the adopted skeleton is
an estabhshed habit ] and it may be said to be instinctive
in the species, but I have observed the same fact in sponges
not habitually parasitical. I have a specimen of Micro-
dona carnosa, Bowerbank, a British species, in my posses-
sion in which some small fibres of a tubular zoophyte have
been accidentally included during its growth, and which the
sponge has coated with its own tissues, and from these
adopted columns defensive spicula are projected in a similar
manner to those of the columnar skeleton of the sponge.
In this case we have an instinctive adaptation of an
extraneous substance in a sponge in which the introduction
of foreign substances is the exception, and not, as in other
tribes of sponges, the rule.

In Hyalonema mirabilisy Gray, a sponge nearly related
_to the genus Alcyoncellum, we find another extraordinary
series of internal defensive spicula, the structure of which
I have described at length under the head of " Defensive
Organs." These elaborately and wonderfully. formed weapons
are evidently destined for other purposes than that of simple
repulsion. The spiculated cruciform spicula, with their
short stout basal radii planted firmly on the lines of the
skeleton, and projecting from their centre at right angles
to their own plane ; the long spiculated ray finished with
numerous strong sharp recurved spines, it will be at once
seen, is eminently fitted to retain annelids or other such
prey, and to cause every motion of the struggling victim to
contribute to its own laceration and destruction, while the
structure and mode of attachment of the crucifonn base is



Digitized by CjOOQ IC



OF THE SPONGIAD^. 127

admirably calculated to resist the force and motions it has
to sustain in such encounters. But these spicula, although
exceedingly numerous, are not the only organs capable of
retaining intruders into the body of the sponge with which
it is furnished, there is in addition numerous large multi-
hamate birotulate spicula dispersed in various positions on
the sides of the interstitial cavities of the sponge, each of
the rotulae consisting of seven or eight stout recurved
flattened radii, which, if immersed in any struggling
animal, would be capable of sustaining a vastly greater
amount of force than many of the spiculated quadriradiate
ones combined, could endure without injury ; and that their
especial office is that of auxiliary retentive organs, is well
demonstrated by the fact that the trenchant edges of the
flattened radii are all at right angles to the line of force
required to tear away their hold of any body in which they
may have been inserted. Thus they appear destined by
nature to secure the prey while its own struggles among
the lacerating organs contributes to its destruction (Figs.
294, 295, Plate XVIII, and Fig. 60, Plate III).

In the modification of the structure of the contort biha-
mate spicula, and their peculiar adaptation to the retention
and destructiou of intruders within the sponge, which I
have described when treating on the internal defensive spi-
cula, and which is represented in Fig. 293, Plate XVIII, and
Kg. 112, Plate V, we have precisely the same physiological
principle carried out, but by means widely difierent from
those I have previously described.

If we consider the whole of these extraordinary organs to
which I have referred in relation to each other, we cannot
fail to see that, however varied their forms may be, there
is every appearance of perfect harmony of design in the
purposes they are destined to effect in the economy of the
Spongiadae.



Digitized by CjOOQ IC



128 ANATOMY AND PHYSIOLOGY



THE CILIA AND CILIARY ACTION.

Our knowledge of the cilia of the Spongiadae is, compa-
ratively speaking, very small. Dr. Grant is, I believe, the
first author who has seen and described these organs in situ.
This learned and accurate observer, in his paper * Observa-
tions on the Structure and Functions of the Sponge,' has
described the origin and gradual development of the ova or
gemmules of Spongia panicea {Halichondria incrustans,
Johnston), After the liberation of these bodies from the
sponge, he writes, " The most remarkable appearance exhi-
bited by these ova, is their continuing to swim about by
their own spontaneous motions for two or three days after
then* detachment from the parent, when they are placed
separately in vessels of sea-water, at perfect rest. During
their progressive motions they always carry their rounded
broad extremity forward, and when we examine them under
a powerful microscope, we perceive that these motions are
produced by the rapid vibration of cilia, which completely
cover over the anterior two thirds of their surface/' And
he further states that they are '* longest and exhibit the
most distinct motions on the anterior part," and that they
" are very minute transparent filaments, broadest at their
base, and tapering to invisible points at their free extre-
mities; they have no perceptible order of succession in
their motions, nor are they sjrnchronous, but strike the
water by constantly and rapidly extending and infiecting
themselves.'' The author describes the attachment and
spreading out into a thin disk of the ovum or gemmule,
and the cessation of action and gradual disappearance of the
cilia ; and he further observes, ^' although all visible cilia
have ceased to move, we still perceive a clear space round
the ovum, and a halo of accumulated sediment at a little
distance from the margin." This observation is important,
as tending to prove the existence of ciliary action, although
the organs themselves were too minute to be detected.
Dujardin, in his work on the Infusoria, in Plate III, 19, 6,



Digitized by CjOOQ IC



OP THE SPONGIADJE. 129

represents what are apparently the detached cilia and their
hasal cells, and which were probably from Grantia compressa.

If portions of a living sponge of this species be torn into
small pieces, and placed in a cell in sea-water under a
power of about 400 linear, groups of the detached cilia and
their basal cells will be readily seen at the margins of the
specimen ; they are usually thus clustered together, and
have a tremulous and indistinct motion. If a small speci-
men of the sponge be slit open and placed in a cell with
fresh sea- water, with the inner surface of the sponge towards
the eye so as to command a distinct view of the oscula, the
cilia will be seen in the area of that organ in rapid motion,
and the extraneous molecules attached to them exhibit the
extent and nature of their oscillations veiy distinctly (Fig.
313, Plate XXI). If the sponge be carefully torn asunder
in a line at right angles to its long axis, and the torn surface
be placed in a cell with a little fresh sea- water, we occa-
sionally obtain a favorable longitudinal section of some of
the large cells of the sponge, and we then see the cilia in
situ and in motion (Fig. 312, Plate XXI).

The whole length of the cell, from the inner edge of the
diaphragm to its origin near the outer surface of the sponge,
is covered with tessellated nucleated cells, which have each
a long attenuated and very slender cilium at its outer
end. They are oval in form, and have a distinct nucleus.
When in vigorous condition their motions are rapid and
cannot readily be followed, but in some in which the action
was languid, the upper portion of the cilium was thrown
gently backward towards the surface of the sponge, and
then lashed briskly forward towards the osculum, and this
action was steadily and regularly repeated. Their motions
are not synchronous, each evidently acts independently of
the others (Figs. 314, a, b, Plate XXI)-

The numbers, Situation, and peculiarities of their actions
fully account for the continuous and powerful stream that
issues from the great cloacal aperture of this and other
similarly constructed sponges. The natural rate of the
motions of these organs must not be estimated from the
sections last described, but the estimate must be made

9



Digitized by CjOOQ IC



180 ANATOMY AND PHYSIOLOGY

from the appearances manifested at the oscular orifices at
the inner surface of the sponge ; a more detailed account
of these investigations is published in the * Transactions of the
Microscopical Society of London/ vol. iii, p. 1 37 . Fig. 31 2,
Plate XXI, represents a longitudinal section of the inter-
marginal cavities of Grantia compressa vrith the cilia in
situ. Eig. 313, a view of the small portion of the inner
surface of the sponge, exhibiting the oscular orifices and the
appearance of the ciha in motion within them, and detached
cilia and cells from the same sponge.

In the course of my endeavours to detect the cilia in
Halichondroid sponges, I have frequently observed in slices
of the sponge taken from the surface, that the incurrent
action has continued for a considerable period, while in
sections of the same sponge taken from deep amid the
tissues, no such action of the currents could be detected.
In sections from the surface in which the inhaling process
was in vigorous condition, when the inside of the section
was examined, that pecuhar flickering appearance was often
visible in the cavities immediately beneath the dermal
membrane, which is so characteristic of minute cilia in
very rapid motion; and although many molecules were
rushing inward with considerable velocity, others might be
seen which continually waved from side to side but made
no progress forward ; in fact they presented precisely the
appearance that I have described as taking place in the
oscula of the proximal ends of the great intermarginal cells
of Grantia compressa ; and I have no doubt, in my own
mind, that those of the Halichondroid sponges were also
extraneous particles of matter adhering to the apices of the
minute cilia, rendering their motions apparent, while the
cilia themselves were perfectly invisible.

Carter, in his paper on '' Zoosperms in . Spon^illa/*
published in the ' Annals and Mag. Nat. Hist.,' vol. xiv.
Second series, p. 334, describes ciliated bodies from a
Sponffilla from the water-tanks of Bombay, somewhat
similar to those of Grantia compressa^ but the basal ceU
appears to be larger and the cilium shorter in their pro-
portions than those of G. compressa. The author, in



Digitized by CjOOQ IC



OF THE SPONGIAD4S. 131

describing the detached cells and cilia, says, " At first the
polymorphism of the cell and movements of the tail are so
rapid, that hterally, neither ' head nor tail' can be made out
of the little mass. Presently, however, its power of pro-
gression and motion begins to fail, and if separated from
other fragments it soon becomes stationary, and after a little
polymorphism assumes its natural passive form, which is
that of a spherical cell. During this time the motions of
the tail become more and more languid, and at length
cease altogether." The author continues, " If on the other
hand, there be very large fragments in the immediate
neighbourhood, or an active sponge-cell under polymor-
phism sweeps over the field, it may attach itself to one or
the other of these, when its cell becomes undistinguishable
from the common mass, and the tail floating and undulating
outwards is all that remains visible." This observation is
important, as it accounts in a great measure for our inability
to find the cilia in situ in the living and active condition
of the SpongiUa ; and if the structure and imbedment of the
basal cell in the marine sponges be like those in that genus,
the same results would probably arise in the marine species,
rendering it extremely difiicult, if not impossible, to detect
these organs in situ and in action.

Lieberkuhn, in his paper in Midler's 'Archiv,' 1856,
pp. 1-19, 319-414, gives an account of the cilia and their
cells in siiu. He describes them as forming a single layer
of spherical cells, ^ millim. in diameter, and which, though
touching each other, are not in such contact as to lose their
rounded figure. lieberkuhn's description of the mode of
disposition of these cells in SpongiUa would serve equally
well for those in Grantia compressa. Professor Huxley, in
a paper ** On the Anatomy of the Genus Teihyal' published
in the 'Annals and Mag. Nat. Hist.,' vol vii, p. 370,
describes cells and cilia from an Australian sponge, which
he designates spermatozoa, and which he describes as
having " long pointed, somewhat triangular heads, about
s^th of an inch in diameter, with truncated bases, from
which a very long filiform tail proceeds." These bodies
are figui'ed in Plate XIV, vol. vii, fig. 9.



Digitized by CjOOQ IC



132 ANATOMY AND PHYSIOLOGY

On a careful consideration of the descriptions of the
ciliated cells seen by the authors I have quoted above, it
strikes me forcibly that the so-called zoosperms and sper-
matozoa of Carter and Huxley are identical in origin and
purpose with the similar organs described by Lieberkuhn,
and those found in situ and in action in Grantia compressa,
and in truth that they are the homologues of the breathing
and feeding organs of the zoophytes and more highly
organized animds.



REPEODUCTION.

The ovaria in sponges exhibit considerable variety in
shape and structure. The most familiar form is that of
Spongilla JluviatiliSi represented in Fig. 317, Plate XXII,
in its natural condition.

These bodies have hitherto been usually designated as
gemmules, but this term appears to be inappropriate. Each
of them contains numerous minute vesicular, round or oval
molecules, which are discharged from the foramen in suc-
cession, and each of these appears to be capable of pro-
ducing a sponge. The terms ovarium and ova are there-
fore more in accordance with the rules of modem nomen-
clature, and this alteration in their designation is the more
necessary, as I shall hereafter be enabled to show that in
Tethea lyncurium propagation by true external gemmatian
in that species at least really exists. I propose, therefore,
for the futrae that all such large vesicular organs containing
numerous molecules or ova capable of reproducing the
species, and of being successively ejected from the sponge,
should be designated ovaria and ova, and that the t^rm
gemmule should be restricted to the isolated bodies which
pullulate from the internal or external surfaces of the parent,
and by ultimate separation become each a distinct indi-
vidual.

The reproductive powers of the Spongiadae have been
treated on to a considerable extent by preceding authors,
and the amount of our information on this subject is, I



Digitized by CjOOQ IC



OP THE SPONOIADA. 138

believe, both extensive and accurate. I will not attempt a
recapitulation of all that has been written on their repro-
duction, but content myself with a slight sketch of our
knowledge of the various modes of propagation that have
been well ascertained and described. From the researches
of the various authors who have written on the structure
and development of SpongiUa and on the marine Spongiadae,
it appears that there are three well-established modes of
propagation: 1st, by ova; 2nd, by gemmation; and 3rd,
by spontaneous (hvision of the sarcode. The terms ova and
gemmule have been used so indiscriminately by authors,
that it seems to me advisable to endeavour to define and
limit their application in such a manner as to distinctly
separate the one form of reproductive body from the other.
On a careful review of the results of the labours of pre-
vious observers and of my own researches, it appears that
the following may be considered as the varieties that exist
in the modes of the propagation of the Spongiadae : —

1st. By ova without an ovarium.

2nd. By ova generated within ovaria.

3rd. By gemmules secreted within the sponge.

4th. By gemmules produced externally.

5th. By spontaneous division of the sarcode.

On the first mode of propagation by the means of ova
generated in the sponge without the presence of ovaria, very
little seems to be known, and this mode appears to be con-
fined to the true sponges, the genus Spongia. If we ex-
amine microscopically the fibres of the sponges of commerce
in the condition in which they come into the hands of the
dealers, and before they have been soaked, cleaned, and
prepared for sale, we frequently find the fibres covered with
innumerable minute irregularly ovoid vesicular bodies nearly
uniform in size, dispersed evenly over the surface of the
fibres, and imbedded in a thin stratum of sarcode that coats
the membranous sheath that surrounds them. These
bodies Dr. Johnston believes to be " the matured gemmules
or sporules,'' and I feel strongly inclined to agree with him
in the conclusion that they are the reproductive bodies of



Digitized by CjOOQ IC



184 ANATOMY AND PHYSIOLOGT

that tribe of sponges, and no other reproductive bodies
have, I believe, been discovered in the true sponges ; but
in arriving at this conclusion, we must not fail to remember
that our knowledge of these animals in the fleshy and solid
condition in which they are when alive, is so limited and so
few observations have been published regarding them in
that state, that we must not attach too great a value to
these conclusions.

In size and form these ovoid vesicles are very similar to
the ova liberated from the well-characterised ovaria of other
marine species of Spongiadae ; and like them, they present
no appearance of a nucleus. They are somewhat irregular
in their form, and vary to a slight extent in size; an
averaged-sized one measured -nm^^ of an inch in diameter.
Fig. 815, Plate XXII, represents a portion of a fibre from
a Bahama sponge under a power of 400 linear, and
Fig. 316, a part of the same fibre 1250 linear.

Until very recently our knowledge of the vesicular ovaria
of the Spongillidae has been confined to two European
species, but Carter, in his excellent account of the Spongillas
found in the water-tanks of Bombay, has described several
new and interesting varieties of these organs ; and I have
also become acquainted with eight new species from the
River Amazon, through the kindness of Mr. Bate, and of
three undescribed species from North America, through the
kind and liberal assistance of Dr. Asa Gray, Professor
Leidey and Professor Dawson, of McGill College, Montreal,
Canada. The greater portion of these organs resemble each
other very closely in their natural condition, presenting
generally the appearance of a more or less spherical coriaceous
body, but the structure of their walls, when developed by
treating them carefully with hot nitric acid, is so varied
and strikingly characteristic of their organic and specific
differences, as to render it necessary that I should enter
somewhat minutely into their history. Their structual
peculiarities naturally divide them into two great groups.

1st. Those in which the walls of the ovaria are strength-
ened and supported by birotulate or unirotulate spicula
radiating in lines from the centre to the circumference of



Digitized by CjOOQ IC



OF THE SPONGIADiE. 185

the ovarium ; and 2nd, those having the walls of the ovaria
supported by elongate forms of spicula, disposed on or
near its' surface at right angles to Unes radiating from the
centre to the circumference of the ovarium; and fortu-
nately the types of these two forms of spicular arrange-
ment on the cortex of the ovarium are admirably illus-
trated in the two European species of Spongilla ; the first
mode existing in SponyUla flumatUiSy and the second
one in 8. lacustris. After having described the ovaria
of these two species as types of their respective groups,
I shall in my future descriptions of these organs confine
my observations rather to their anatomical structure
than to their external characters, excepting when the latter
are of an unusual description. These bodies occur in great
profusion in the basal portions of S. Jluviatilis ; they are
spherical and of an average diameter of ^th of an inch, and
they are furnished with a circular foramen at their distal
extremity of about ^rd of an inch in diameter. In their
natural condition they exhibit very slight indications of the
birotulate spicula imbedded in their coriaceous-looking
envelope. In the dried state they become cup-shaped by
the contraction of the upper half inward during the process
of desiccation, and in this condition the foramen appears at
the bottom of the cup. The edges of the cup being thick
and round in consequence of the presence of the birotulate
spicula beneath the fold of the membrane, and the surface
becomes pitted with numerous minute lacunae, which are
produced by the adhesion of the inner surface of the
envelope to the distal extremities of the birotulate spicula.
Immersion in water for an hour restores them to their
spherical form, but does not obliterate th6 lacunae produced
by desiccation; and I have several times observed that,
under these circumstances, the expansion of the ova within
has forced one or more of them through the foramen.

If we take several of the ovaria, either in the living con-
dition or in the expanded state I have described above, and
place them in a test-tube with a little nitric acid, and raise
the temperature of the whole until the ovaria becomes of a
bright yellow colour and semi-transparent, and then arrest



Digitized by CjOOQ IC



136 ANATOMY AND PHYSIOLOGY

the operation of the acid by immediately pouring in a
quantity of cold water, we shall have preserved their form
and have retained the spicula in their natural positions, and
have rendered the whole so transparent, as to exhibit their
form and arrangement in the walls of the ovarium, either
in water or mounted in Canada balsam, in a very beautiful
and satisfactory manner. They are packed very closely
together, their shafts being in lines radiating from the centre
of the ovarium to the circumference ; their distal rotulae
supporting the outer surface of its wall, while the proximal
rotulae sustain the inner one. Fig. 319, Plate XXII, re-
presents a portion of one of these prepared ovaria, and
Fig. 319, «, one of the detached spicula. Two views of this
form of spiculum are also represented in Figs. 217, 218,
Plate IX, and a perfect ovarium prepared by acid by
Fig. 318, Plate XXII.

Carter, in his paper '* On the Freshwater Sponges in the
Island of Bombay," in describing the birotulate spicula of
the ovaria of Spongilla Meyeni and plumosa^ species vrith
ovaries of very similar structure to those of 8. fluviatUis,
states that the spaces between the rotulae are " filled up
with a white siliceous amorphous matter which keeps them
in position." I am indebted to the kindness and liberality
of the author for specimens of these species, and I have
frequently subjected their ovaries to the action of hot nitric
acid, but I have never succeeded in finding any intervening
siliceous matter, nor have I ever found any such siliceous
cementing material in any other similarly constructed ovary
of a Spongilla.

In the second group of ovaries of the Spongillidae, re-
presented by those of S. lacustris, in which the walls of the
ovaria are supported by elongate forms of spicula disposed
at right angles to lines radiating from its centre, the ovaria,
in their natural condition, exhibit but very sHght traces of
the spicula imbedded in their walls. When dried they cup
inward like those of S. lacmtris ; but the margin of the
cup is thin and sharp compared with that formed in a
similar manner by those of S. fluviatiliSy and they expand
also in like manner when immersed in water. When



Digitized by CjOOQ IC



OP THE SPONGIAD^. 187

treated with hot nitric acid they display an abundance of
short, stout, entirely spined subarcuate acerate spicula, one
of which is represented in Fig. 203, Plate IX. These
spicula are in many instances exceedingly numerous ; they
are disposed without order, and overlie each other at


1 2 3 4 5 6 7 8 9 10 11 13 15 16 17 18 19 20 21 22 23 24 25

Online LibraryJames Scott BowerbankA monograph of the British Spongiadæ → online text (page 13 of 25)