Psammonemata
Creators: name: Gunther, Albert C. L. G.
name: Dallas, William S.
name: Carruthers, William
name: Francis, William
Publisher: name: TAYLOR AND FRANCIS
Year: 1885
Subjects: Biodiversity
Taxonomy
Animalia
Psammonemata

description: Order III. PSAMMONEMATA.
As an examination of Mr. Wilson’ s specimens has suggested to me much that indicates a necessary revision of this order, and I find that it can be done best by beginning with the lowest forms and building upwards, instead of following the arrangement given in my classification, which is the re ­ verse, I shall pursue this course after having premised the following introductory remarks:—
It is desirable, when about to introduce anything new, to state such generalities as may not only facilitate its under ­ standing, but, if possible, curtail length of description, in order that the student may of himself be able to supply the former, which otherwise might become tedious repetition in the latter.
Tw ’enty-six years have passed since my observations on the growth of the young Spongilla from the statoblast were pub ­ lished, and although much has been done since in structural description, yet a key to a great part of this might be found in my illustration of a minute but entire specimen of Spongilla, whose component parts were then drawn to the same scale, “ in order that their relative proportions might be preserved as much as possible” for diagrammatic purposes in teaching; but I question if such use was ever made of it (l Annals,’ 1857, vol. xx. pl. i. fig. 1).
In this figure, it may be observed that the parenchyma, of ■which the body of the sponge is composed, is surrounded by a dermal membrane, which is kept at a certain distance off by the projection of conical bundles of spicules issuing from the parenchyma, thus leaving a hollow between the two, subsequently termed by Dr. Bowerbank the “ subdermal cavity.”
This “ dermal membrane,” or cuticle, I named at the time “ investing membrane,” and the interval between it and the parenchyma the “cavity” of the “investing membrane.” I also then stated that the “ investing membrane ” was pierced by “apertures” or pores (ib. p. 22), and that the parenchyma was traversed throughout by the branches of the excretory canal-system, which ended in a single tubular vent that passed directly through the cavity of the investing mem ­ brane (l. c. pl. i. fig. 1, g), to terminate a little distance beyond the latter, with which it was intimately connected at the point of its passage, so that the contents of the excretory canal ­ system could not get into the cavity of the investing mem ­ brane. Thus all the main features of sponge-structure were foreshadowed.
Now it is evident, as shown in the figure to which I have alluded, that if the “ investing membrane ” should sink in towards the parenchyma by collapse or otherwise, the points of the bundles of spicules which support it would become conical, and hence the features thus produced have been termed the “conuli,” while the space between the conuli would be more or less occupied by the Cl apertures ” or pores. Still the conuli are by no means present on all sponges, and they are especially absent on the slippery surfaces of the Carnosa, while they arc perhaps most typically developed on some of the Psammonemata; but the former is the exception.
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Again, they are of course subject to variety in composition, being spiculiferous in the spiculiferous sponges, simply keratosc in the Ceratina, and areniferous in the Psammonemata. Also subject to variety in form, since they may consist of a simple point, and this may be single or grouped; or obtusely pointed singly or cn groupe, or by extension in line and uniting with one another form a reticulation which may be more or less general; but in all cases the points are origi ­ nally covered by the dermal sarcode, that is, tn their natural state, although often naked and protruding afterwards.
It is necessary to be prepared for all these modifications, or the same thing may be described indefinitely under different names.
The same may be said of the “ investing ” or dermal mem ­ brane itself, which in the spiculiferous sponges may or may not be charged with spicules (chiefly the minute or flesh ­ spicules) which are more or less arranged in a reticulated form, so that the pores may be in the interstices; or it may be travel sed by a soft fleshy fibrous reticulation, as in the Cera ­ tina; or charged with foreign microscopic bodies (sand, fragments of sponge-spicules, Ac.), as is often the case in the Psammonemata, where they may assume a similar form; but in all instances the reticulation may become so thickened as to obliterate the interstices and so pass into a simple incrus ­ tation, wherein, however, holes for the pores are always preserved, because these are essential to the existence of the sponge.
As regards the mineral element, this may be produced by the sponge itself or borrowed from the exterior; the former is the case with the spiculiferous sponges and the latter with the psammiferous ones. Of course in the spiculiferous sponges the spicules, which have been termed “ proper,” are all of one or more forms and all entire-, whereas in the borrowed material, which has been termed “ foreign,” they are gene ­ rally of many kinds and mostly fragmentary, more or less mixed up with other microscopic objects, such as grains of sand Ac.; but the predominance of one more than the other will depend upon the prevailing element in the locality where the sponge may be growing. At the same time it cannot be denied that, in some instances, the sponge itself appears to manifest a power of selection or preference in this respect.
With reference to the development of the keratose fibre in the dermal membrane, it may be observed that this originates chiefly in the conuli which are the growing terminations of the main or vertical fibre of the sponge, from each of which it extends outwards and downwards radiatingly, like the ropes of a tent, so that, as the fibre diminishes in size by branching and subdividing, the subdivisions not only become united between themselves, but meet and become continuous with the like from the neighbouring conuli, whereby an inter ­ uniting fibrous reticulation is formed in the dermal sarcode between the conuli, in whose interstices the pores are situated and protected; while the keratose fibre may be cored or not with mineral elements, as already noticed.
Again, what has been stated of the external parts of the sponge applies act. par. to the internal ones or parenchyma; for as the sponge grows by the addition of layers to its circumference, that is radiatingly, so the surface of to-day becomes part of the internal structure of to-morrow, and thus somewhat modified it passes into a cancellated form, which is the parenchyma; that is to say, the fibrous skeleton, cored by mineral material or not, becomes a solid mass of reticulation, in which the interstices arc tympanized by the still poriferous sarcode (as may be seen in a dried specimen), and the cancel ­ lated chambers thus completed. Lastly, the whole is traversed by the blanches of the excretory canal-systems. I use the latter in the plural number, because generally every vent indicates a system.
Still another condition arises from the amount of keratine developed, which may be entirely absent in the lowest forms of the Psammonemata (for I must confine myself henceforth to this order, as we are now more immediately concerned with it), where the sarcode retains its delicate pristine nature; or it may be diffused throughout the sarcode generally, so as to give it a horny consistence, as if the sarcode itself had passed into this state, which is better seen in the dry than in the wet specimen, when it presents a light amber colour, while it is all grey together in the wet one; so in the pro ­ duction of fibre the mineral element, that is the foreign objects, may be held together by a mere film of keratine, while on other occasions the investiture of keratine may not only exceed the core of foreign objects in thickness, but assume the con ­ sistence and toughness of horn; then as regards colour, the keratine, which is generally yellow and transparent like amber, may in some species be as transparent and colourless as glass. Lastly the keratose fibre may be generally or partially cored with foreign objects, in which case the vertical fibre is gene ­ rally the most, and the lateral the least so; but it is a remarkable fact that, throughout the Psammonemata, the arenaceous fibre is frequently so thinly clad with keratine as in many instances to appear to be nothing more than a simple chain of foreign objects. The terms “ vertical ” and “ lateral ” are synonymous with Dr. Bowerbank ’s “ primary ” and “ secon ­ dary” fibre.
With these preliminary remarks let us now enter upon the revision of the order Psammonemata after the manner to ■which I have above alluded, that is beginning with the lowest forms first and working upwards, in which it should be remembered that I am chiefly limited in this respect here to what Mr. Wilson ’s specimens indicate, as I tvant to point out, by them too, what is to be found on the south coast of Australia.
After noticing that which I considered to be the Dysidea Kirkii of Dr. Bowerbank (‘ Annals,’ 1881, vol. vii. p. 374), a summary was given of wliat had been stated of thisas well as the British species Dysidea fragilis, in which was quoted the following passage from Dr. Bowerbank’s ‘ Monograph of the British Spongiadm ’ (vol. i. p. 212), viz.:—“In our British species, Dysidea fragUis, Johnston, the primary fibres are often as abundantly arcuated as those of the Australian species {DysideaKirkii), while the secondary ones are only partially filled with extraneous matter.” Thus both species weYQ fibrous, and both the “ primary ” and “ secondary” fibres were arcuated, that is contained foreign objects. In short both species werefibrous and all the fibres arenated, although not equally so, which is what I want to insist upon here. Hence 1 was wrong in stating that Dysidea fragilis and Spongelia pallescens, Sdt., were the same; for by consulting Schulze’s representation (Zeitschrift f. wiss. Zoologie, Bd. xxxii. Taf. vi. fig. 5), which I am ableto confirm by having a type specimen of Schmidt’s N. pallescens, it will be observed that “ all ” the fibre here is not “ arenated,” but that the lateral or secondary fibre is mostly keratose and homogeneous, i. e. clear or not cored with foreign bodies, while the vertical or primary fibre is completely cored or arenaceous. Aly mistake arose from the conulated surface of Dysidea fragilis when dried in its natural state being precisely like that of Spongeliapallescens. Thus Hyatt was right in separating Dysidea from Spongelia, i. e. S. pallescens (Mem. Boston Soc. Nat. Hist. 1877, vol. ii. pt. 4, p. 539). Both Dgsideafragilis and Dysidea Kirkii therefore arefibrous, and all the fibre arenated; while on microscopically examining the fibre itself it will be found to represent the lowest degree of it above mentioned, viz. that in which the fibre is composed of foreign objects held together by the merest minimum or film of keratine, and hence its delicate and fragile nature, from which Johnston’ s designation 11 fragilis ” was derived; but still it is fibre.
However, leaving this subject for the present, Mr. Wilson ’s specimens from the neighbourhood of Port Phillip Heads, South Australia, have brought me acquainted with a still lower form, viz. that in which there is absolutely no fibre, but where the foreign material is diffused, and so far held together by being imbedded in the delicate flakes of the parenchymatous sarcode generally; where, traversed by branches of the excretory canal-systems, it thus forms the skeletal or supporting structure of the sponge, and under this condition may assume many different sponge-like forms, which may distinctly vary according to the species or variety, but at the same time are all developed out of the same kind of structure and composition through the specific agency of the (l sponge-sarcode" in which the whole originates and which in all cases throughout the class of Spongida determines both the form and the composition of the sponge.
For this group 1 would propose the term “ Ilolopsamma," under the following diagnosis, viz.:—
description: Published as part of Gunther, Albert C. L. G., Dallas, William S., Carruthers, William & Francis, William, 1885, The Annals and Magazine of Natural History, Including Zoology, Botany, and Geology, pp. 1-96 in Reptiles and Batrachians from Brazil, LONGMANS, GREEN, AND CO.; SIMPKIN, MARSHALL, AND CO.; KENT AND CO.,; WHITT AKER AND CO.: BAILLIERE, PARIS: MACLACHLAN AND STEWART, EDINBURGH: HODGES, FOSTER, AND CO., DUBLIN: AND ASHER, BERLIN :TAYLOR AND FRANCIS on pages 206-211, DOI: 10.5281/zenodo.14926803