Spongilla alba, Carter, J. Bombay Asiat. Soc. iii, p. 32, pl. i, fig. 4 & Ann. Nat. Hist. (2) iv, p. 83, pl. iii, fig. 4 (1849)Spongilla alba, Bowerbank, P. Zool. Soc. London, 1863, p. 463 pl. xxxviii, fig. 15.Spongilla alba, Carter, Ann. Nat. Hist. (5) vii, p. 88 (1881).Spongilla alba, Petr, Rozp. Ceske Ak. Praze,Trída, ii, pl. i, figs. 3-6 (1899) (text in Czech).Spongilla alba, Annandale, Rec. Ind. Mus. i, p. 388, pl. xiv, fig. 2 (1907).
Spongeforming masses of considerable area, but never of more than moderate depth or thickness. Surface smooth and undulating or with irregular or conical projections; sponge hard but brittle; colour white or whitish; oscula of moderate or large size, never very conspicuous; radiating furrows absent or very short; external membrane adhering to the substance of the sponge.
Skeletonforming a moderately dense network of slender radiating and transverse fibres feebly held together; little spongin present; the meshes much smaller than inS. lacustrisorS. proliferens.
Spicules.Skeleton-spicules smooth, sharply pointed, slender, feebly curved. Gemmule-spicules (fig. 8, p. 71) slender, cylindrical, blunt or abruptly pointed at the ends, feebly curved, bearing relatively long backwardly directed spines, which are usually more numerous at the ends than near the middle of the shaft. Flesh-spicules very numerous in the parenchyma and especially the external membrane, as a rule considerably more slender and more sharply pointed than the gemmule-spicules, covered with straight spines which are often longer at the middle of the shaft than at the ends.
Gemmulesusually of large size, with a moderately thick granular layer; spicules never very numerous, often lying horizontally on the external surface of the gemmule as well as tangentially in the granular layer; no foraminal tubule; a foraminal cup sometimes present.
3a. Var.cerebellata,Bowerbank.
Spongilla cerebellata, Bowerbank, P. Zool. Soc. London, 1863, p. 465, pl. xxxviii, fig. 16.Spongilla albavar.cerebellata, Carter, Ann. Nat. Hist. (5) vii, p. 88 (1881).Spongilla cerebellata, Weltner, Arch. Naturg. lxi (i), p. 117 (1895).Spongilla cerebellata, Kirkpatrick, Ann. Nat. Hist. (7) xx, p. 523 (1907).
This variety is distinguished from the typical form by the total absence of flesh-spicules. The gemmule-spicules are also more numerous and cross one another more regularly.
3b. Var.bengalensis*,Annandale. (Plate I, figs. 1-3.)
Spongilla lacustrisvar.bengalensis, Annandale, J. Asiat. Soc. Bengal, 1906, p. 56.Spongilla albavar.marina,id., Rec. Ind. Mus. i, p. 389 (1907).
The sponge is either devoid of branches or produces irregular, compressed, and often digitate processes, sometimes of considerable length and delicacy. Flesh-spicules are usually present throughout the sponge, but are sometimes absent from one part of a specimen and present in others. Some of the gemmules are often much smaller than the others. Perhaps this form should be regarded as a phase rather than a true variety (see p. 18).
All forms ofS. albacan be distinguished from all forms ofS. lacustrisby the much closer network of the skeleton and by the consequent hardness of the sponge; also by the complete absence of green corpuscles.
Types.The types of the species and of the var.cerebellataare in the British Museum, with fragments of the former in the Indian Museum; that of var.bengalensisis in the Indian Museum, with a co-type in London.
Geographical Distribution.—India and Egypt.Localities:—Bombay Presidency, island of Bombay (Carter); Igatpuri, W. Ghats (Annandale):Bengal, Calcutta; Port Canning, Ganges delta (var.bengalensis) (Annandale); Garia, Salt Lakes, nr. Calcutta (var.bengalensis) (B. L. Chaudhuri); Chilka Lake, Orissa (var.bengalensis) (Gopal Chunder Chatterjee):Madras Presidency, Rambha, Ganjam district (Annandale):Nizam's Territory, Aurangabad (Bowerbank, var.cerebellata). The var.cerebellatahas also been taken near Cairo.
Biology.—The typical form of the species is usually found growing on rocks or bricks at the edges of ponds, while the varietybengalensisabounds on grass-roots in pools and swamps of brackish water in the Ganges delta and has been found on mussel-shells (Modiola jenkinsi, Preston) in practically salt water in the Chilka Lake. Carter procured the typical form at Bombay on stones which were only covered for six months in the year, and "temporarily on floating objects." In Calcutta this form flourishes in the cold weather on artificial stonework in the "tanks" together withS. carteri,S. fragilis,Ephydatia meyeni, andTrochospongilla latouchiana.
The varietybengalensisis best known to me as it occurs in certain ponds of brackish water at Port Canning on the Mutlah River, which connects the Salt Lakes near Calcutta with the sea.It appears in these ponds in great luxuriance every year at the beginning of the cold weather and often coats the whole edge for a space of several hundred feet, growing in irregular masses which are more or less fused together on the roots and stems of a species of grass that flourishes in such situations. Apparently the tendency for the sponges to form branches is much more marked in some years than in others (see Pl. I, figs. 1-3). The gemmules germinate towards the end of the "rains," and large masses of sponge are not formed much before December. At this season, however, the level of the water in the ponds sinks considerably and many of the sponges become dry. If high winds occur, the dry sponges are broken up and often carried for considerable distances over the flat surrounding country. In January the gemmules floating on the surface of the ponds form a regular scum.S. albavar.bengalensisis the only sponge that occurs in these ponds at Port Canning, butS. lacustris, subsp.reticulata, is occasionally found with it on brickwork in the ditches that drain off the water from the neighbouring fields into the Mutlah estuary. The latter sponge, however, perishes as these ditches dry up, at an earlier period than that at whichS. albareaches its maximum development.
The larvæ ofSisyra indicaare commonly found in the oscula of the typical form ofS. albaas well as in those ofS. lacustrissubsp.reticulata, andS. carteri; but the compact structure of the sponge renders it a less suitable residence for otherincolæthanS. carteri.
In the varietybengalensis, as it grows in the ponds at Port Canning, a large number of arthropods, molluscs and other small animals take shelter. Apart from protozoa and rotifers, which have as yet been little studied, the following are some of the more abundant inhabitants of the sponge:—The sea-anemone,Sagartia schillerianasubsp.exul(see p. 140), which frequently occurs in very large numbers in the broader canals; the free-living nematode,Oncholaimus indicus[W], which makes its way in and out of the oscula; molluscs belonging to several species of the genusCorbula, which conceal themselves in the canals but are sometimes engulfed in the growing sponge and so perish; young individuals of the crabVaruna litterata, which hide among the branches and ramifications of the larger sponges together with several small species of prawns and the schizopodMacropsis orientalis[X]; thepeculiaramphipodQuadrivisio bengalensis[Y], only known from the ponds at Port Canning, which breeds in little communities inside the sponge; a small isopod[Z], allied toSphæroma walkeri, Stebbing; the larva of a may-fly, and those of at least two midges (Chironomidæ).
The peculiarly mixed nature (marine and lacustrine) of the fauna associated withS. albain the ponds at Port Canning is well illustrated by this list, and it only remains to be stated that little fish (Gobius alcockii,Barbus stigma,Haplochilus melanostigma,H. panchax, etc.) are very common and feed readily on injured sponges. They are apparently unable to attack a sponge so long as its external membrane is intact, but if this membrane is broken, they swarm round the sponge and devour the parenchyma greedily. In fresh water one of these fishes (Gobius alcockii, see p. 94) lays its eggs in sponges.
The chief enemy of the sponges at Port Canning is, however, not an animal but a plant, viz., a green filamentous alga which grows inside the sponge, penetrating its substance, blocking up its canals and so causing it to die. Similar algæ have been described as being beneficial to the sponges in which they grow[AA], but my experience is that they are deadly enemies, for the growth of such algæ is one of the difficulties which must be fought in keeping sponges alive in an aquarium. The alga that grows inS. albaoften gives it a dark green colour, which is, however, quite different from the bright green caused by the presence of green corpuscles. The colour of healthy specimens of the varietybengalensisis a rather dark grey, which appears to be due to minute inorganic particles taken into the cells of the parenchyma from the exceedingly muddy water in which this sponge usually grows. If the sponge is found in clean water, to whichever variety of the species it belongs, it is nearly white with a slight yellowish tinge. Even when the typical form is growing in close proximity toS. proliferens, as is often the case, no trace of green corpuscles is found in its cells.
4.Spongilla cinerea*,Carter.
Spongilla cinerea, Carter, J. Bombay Soc. iii, p. 30, pl. i, fig. 5, & Ann. Nat. Hist. (2) iv, p. 82, pl. iii, fig. 5 (1849).Spongilla cinerea, Bowerbank, P. Zool. Soc. London, 1863, p. 468, pl. xxxviii, fig. 19.Spongilla cinerea, Carter, Ann. Nat. Hist. (5) vii, p. 263 (1881).
Spongeforming large, flat sheets, never more than a few millimetres in thickness, without a trace of branches, compact but very friable, of a dark greyish colour; oscula small and inconspicuous or moderately large, never prominent; membrane adhering closely to the sponge.
Skeletonwith well-defined but slender radiating fibres, which contain very little spongin; transverse fibres close together but consisting for the most part of one or two spicules only.
Spicules.Skeleton-spicules short, slender, sharply pointed, minutely serrated or irregular in outline, almost straight. Gemmule-spicules very small, rather stout, cylindrical, pointed, covered with relatively long and stout spines which are either straight or directed towards the ends of the spicule. Flesh-spicules fairly numerous in the external membrane but by no means abundant in the parenchyma, very slender, gradually pointed, covered uniformly with minute but distinct spines.
Gemmulesvery small, only visible to the naked eye as minute specks, as a rule numerous, free in the substance of the sponge, each provided with a slender foraminal tubule and covered with a thick granular coat in which the gemmule-spicules are arranged almost horizontally; a horizontal layer of spicules also present on the external surface of the gemmule; gemmule-spicules very numerous.
Illustration: Fig. 10.—Gemmules and fragment of the skeleton of Spongilla cinerea (from type specimen), × 35.Fig. 10.—Gemmules and fragment of the skeleton ofSpongilla cinerea(from type specimen), × 35.
Fig. 10.—Gemmules and fragment of the skeleton ofSpongilla cinerea(from type specimen), × 35.
This sponge is easily distinguished from its Indian allies by the form of its skeleton-spicules, which are, as Bowerbank expresses it, "subspined"; that it to say, under a high power of the microscope their outline appears to be very minutely serrated, although under a low power they seem to be quite smooth. The spicules also are smaller than those ofS. alba, the only species with whichS. cinereais likely to be confused, and the gemmule has a well-developed foraminal tubule; the skeleton is much closer than inS. proliferens.
Typein the British Museum; a piece in the Indian Museum.
Geographical Distribution.—S. cinereais only known from the Bombay Presidency. Carter obtained the original specimens at Bombay and the only ones I have found were collected at Nasik, which is situated on the eastern slopes of the Western Ghats, about 90 miles to the north-east.
Biology.—Carter's specimens were growing on gravel, rocks and stones at the edge of "tanks," and were seldom covered for more than six months in the year. Mine were on the sides of astone conduit built to facilitate bathing by conveying a part of the water of the Godaveri River under a bridge. They were accompanied bySpongilla indicaandCorvospongilla lapidosa(the only other sponges I have found in running water in India) and in the month of November appeared to be in active growth.
5.Spongilla travancorica*,Annandale.
Spongilla travancorica, Annandale, Rec. Ind. Mus. iii, p. 101, pl. xii, fig. 1 (1909).
Spongesmall, encrusting, without branches, hard but brittle; its structure somewhat loose; colour dirty white. Dermal membrane in close contact with the skeleton; pores and oscula inconspicuous. Surface minutely hispid, smooth and rounded as a whole.
Skeletonconsisting of moderately stout and coherent radiating fibres and well-defined transverse ones; a number of horizontal megascleres present at the base and surface, but not arranged in any definite order. No basal membrane.
Illustration: Fig. 11.—Microscleres of Spongilla travancorica. A=Gemmule-spicules; B=flesh-spicules (from type specimen), × 240.Fig. 11.—Microscleres ofSpongilla travancorica. A=Gemmule-spicules; B=flesh-spicules (from type specimen), × 240.
Fig. 11.—Microscleres ofSpongilla travancorica. A=Gemmule-spicules; B=flesh-spicules (from type specimen), × 240.
Spicules.Skeleton-spicules smooth, pointed at either end, moderately stout, straight or curved, sometimes angularly bent; curvature usually slight. Free microscleres abundant in the dermal membrane, slender, nearly straight, gradually and sharply pointed, profusely ornamented with short straight spines, which are much more numerous and longer at the middle than near the ends. Gemmule-spicules stouter and rather longer, cylindrical, terminating at each end in a sharp spine, ornamented with shorter spines, which are more numerous and longer at the ends than at the middle; at the ends they are sometimes directed backwards, without, however, being curved.
Gemmulesfirmly adherent to the support of the sponge, at the base of which they form a layer one gemmule thick; each provided with at least one foraminal tubule, which is straight and conical: two tubules, one at the top and one at one side, usually present. Granular layer well developed. Spicules arranged irregularly in this layer, as a rule being more nearly vertical than horizontal but pointing in all directions, not confined externally by a membrane; no external layer of horizontal spicules.
Measurements of Spicules and Gemmules.
This species is easily distinguished from its allies of the subgenusEuspongillaby its adherent gemmules with their (usually) multiple apertures and rough external surface.
Typein the collection of the Indian Museum.
Habitat.Backwater near Shasthancottah, Travancore, in slightly brackish water; on the roots of shrubs growing at the edge; November, 1908 (Annandale).
The specimens were dead when found.
6.Spongilla hemephydatia*,Annandale.
Spongilla hemephydatia, Annandale, Rec. Ind. Mus. iii, p. 275 (1909).
Illustration: Fig. 12.—Gemmule and spicules of Spongilla hemephydatia (from type specimen).Fig. 12.—Gemmule and spicules ofSpongilla hemephydatia(from type specimen).
Fig. 12.—Gemmule and spicules ofSpongilla hemephydatia(from type specimen).
Spongesoft, fragile, amorphous, of a dirty yellow colour, with large oscula, which are not conspicuously raised above thesurface but open into very wide horizontal channels in the substance of the sponge. The oscular collars are fairly well developed, but the subepidermal space is not extensive.
Skeletondiffuse, consisting of very fine radiating fibres, which are crossed at wide and irregular intervals by still finer transverse ones; very little chitinoid substance present.
Spicules.Skeleton-spicules smooth, slender, sharply pointed at both ends, nearly straight. No true flesh-spicules. Gemmule-spicules straight or nearly so, cylindrical, or constricted in the middle, obscurely pointed or blunt, clothed with short, sharp, straight spines, which are very numerous but not markedly longer at the two ends; these spicules frequently found free in the parenchyma.
Gemmulesnumerous, small, free, spherical, yellow, with a well-developed granular coat (in which the spicules are arranged almost horizontally) and external to it a fine membrane which in preserved specimens becomes puckered owing to unequal contraction; each gemmule with a single aperture provided with a straight, rather wide, but very delicate foraminal tubule.
Measurements of Spicules and Gemmules.
This sponge in its general structure bears a very close resemblance toSpongilla crateriformis.
Typein the collection of the Indian Museum.
Habitat.Growing on weeds at the edge of the Sur Lake, Orissa, October 1908. Only one specimen was taken, together with many examples ofS. lacustrissubsp.reticulata,S. carteriandS. crassissima.
7.Spongilla crateriformis* (Potts).
Meyenia crateriforma, Potts, P. Ac. Philad. 1882, p. 12.Meyenia crateriformis, id., ibid.1887, p. 228, pl. v, fig. 6, pl. x, fig. 5.?Ephydatia crateriformis, Hanitsch, Nature, ii, p. 511 (1895).Ephydatia crateriformis, Weltner, Arch. Naturg. lxi (i), pp. 122, 134 (1895).?Ephydatia crateriformis, Hanitsch, Irish Natural. iv, p. 125, pl. iv, fig. 5 (1895).Ephydatia indica, Annandale, J. Asiat. Soc. Bengal, 1907, p. 20 (figures poor).Ephydatia indica, id., Rec. Ind. Mus. i, pp. 272, 279, 388, 391 (1907).Ephydatia crateriformis, Scharff, European Animals, p. 34 (1907).Ephydatia crateriformis, Annandale, P. U.S. Mus. xxxvii, p. 402, fig. 1 (1909).
Spongevery fragile, forming soft irregular masses on the roots and stems of water-plants, between which it is sometimes stretched as a delicate film, or thin layers or cushions on flat surfaces. Oscula large, flat, circular, or of irregular shape, opening into broad horizontal canals, which at their distal end are superficial and often covered by the external membrane only. Colour white, yellowish, greyish, or blackish.
Skeletonvery delicate; radiating fibres rarely consisting of more than two parallel spicules; transverse fibres far apart, frequently consisting of single spicules; very little spongin present.
Illustration: Fig. 13.—Spicules of Spongilla crateriformis.Fig. 13.—Spicules ofSpongilla crateriformis.
Fig. 13.—Spicules ofSpongilla crateriformis.
A. From specimen taken in July in a tank on the Calcutta maidan. B. From type specimen ofEphydatia indicataken in the Indian Museum tank in winter. Both figures × 240.
Spicules.Skeleton-spicules feebly curved, slender, as a rule irregular in outline, sometimes almost smooth; the ends as a rule sharply pointed, often constricted off and expanded so as to resemble spear-heads, occasionally blunt. No true flesh-spicules. Gemmule-spicules often free in the parenchyma, cylindrical, slender, very variable in length in different sponges, straight or nearly so, as a rule with an irregular circle of strong straight or recurved spines at either end resembling a rudimentary rotule, and with shorter straight spines scattered on the shaft, sometimes without the rudimentary rotule, either truncate at the ends or terminating in a sharp spine.
Gemmulessmall, free, each surrounded by a thick granular layer in which the spicules stand upright or nearly so, and covered externally by a delicate but very distinct chitinous membrane; nohorizontal spicules; foramen situated at the base of a crater-like depression in the granular coat, which is sometimes raised round it so as to form a conspicuous rampart; a short, straight foraminal tubule.
The shape of the spicules is extremely variable, and sponges in which they are very different occur in the same localities and even in the same ponds. It is possible that the differences are directly due to slight changes in the environment, for in one pond in Calcutta a form withSpongilla-like gemmule-spicules appears to replace the typical form, which is common in winter, during the hot weather and "rains." I have not, however, found this to be the case in other ponds. PerhapsS. hemephydatiawill ultimately prove to be a variety of this very variable species, but its smooth and regular skeleton-spicules and short-spined gemmule-spicules afford a ready method of distinguishing it fromS. crateriformis. The two sponges are easily distinguished from all others in the subgenusEuspongillaby the upright and regular arrangement of their gemmule-spicules, for although inS. proliferensandS. travancoricasome of the gemmule-spicules are nearly vertical, their arrangement is always irregular, a large proportion of the spicules make an acute angle with the inner coat of the gemmule and a few as a rule lie parallel to it. The systematic position ofS. crateriformisis almost exactly intermediate betweenEuspongillaandEphydatia, to which genus it has hitherto been assigned. I think, however, that taking into consideration its close relationship toS. hemephydatia, it is best to assign it toSpongilla, as its rudimentary rotules never form distinct disks. I have examined some of Potts's original specimens from different American localities and can detect no constant difference between them and Indian specimens.
Typesin the United States National Museum; co-types in Calcutta.
Geographical Distribution.—This sponge was originally described from North America (in which continent it is widely distributed) and has been recorded from the west of Ireland with some doubt. In India and Burma it is widely distributed.Bengal, Calcutta and neighbourhood (Annandale); Sonarpur, Gangetic delta (Annandale);Bombay Presidency, Igatpuri Lake, W. Ghats (altitudeca.2,000 feet) (Annandale);Madras Presidency, neighbourhood of Madras town (J. R. Henderson); Museum compound, Egmore (Madras town) (Annandale); near Bangalore (alt.ca.3,000 ft.), Mysore State (Annandale); Ernakulam, Cochin (G. Mathai):Burma, Kawkareik, interior of Amherst district, Tenasserim, and the Moulmein waterworks in the same district (Annandale).[AB]
Biology.—S. crateriformisflourishes in Calcutta throughout the year. Here it is usually found adhering to the roots of water-plants, especiallyPistiaandLimnanthemum. In the case of the former it occurs at the surface, in that of the latter at the bottom. When growing near the surface or even if attached to a stone at the bottom in clear water, it is invariably of a pale yellowish or greyish colour. When growing on the roots ofLimnanthemumin the mud of the Gangetic alluvium, however, it is almost black, and when growing in the reddish muddy waters of the tanks round Bangalore of a reddish-brown colour. This appears to be due entirely to the absorption of minute particles of inorganic matter by the cells of the parenchyma. If black sponges of the species are kept alive in clean water, they turn pure white in less than a week, apparently because these particles are eliminated. When growing on stones the sponge, as found in India, often conforms exactly with Potts's description: "a filmy grey sponge, branching off here and there ... yet with a curious lack of continuity...."
The wide efferent canals of this sponge afford a convenient shelter to small crustacea, and the isopodTachæa spongillicola, Stebbing (see p. 94), is found in them more abundantly than in those of any other sponge. This is especially the case when the sponge is growing at the bottom. On the surface of the sponge I have found a peculiar protozoon which resembles the EuropeanTrichodina spongillæin general structure but belongs, I think, to a distinct species, if not to a distinct genus.
Subgenus B.EUNAPIUS,J. E. Gray.
Eunapius, J. E. Gray (partim), P. Zool. Soc. London, 1867, p. 552.Spongilla(s. str.), Vejdovsky, in Potts's "Fresh-Water Sponges," P. Ac. Philad. 1887, p. 172.Spongilla(s. str.), Weltner, in Zacharias's Tier- und Pflanzenwelt des Süsswassers, i, p. 214 (1891).Spongilla(s. str.), Annandale, Zool. Jahrb., Syst. xxvii, p. 559 (1909).
Type,Spongilla carteri, Carter.
Spongillæ in which the gemmules are covered with layers of distinct polygonal air-spaces with chitinous walls.
The gemmules are usually fastened together in groups, which may either be free in the sponge or adhere to its support as a "pavement layer"; sometimes, however, they are not arranged in this manner, but are quite independent of one another. The skeleton is usually delicate, sometimes very stout (e. g., inS. nitens, Carter).
The termEunapiushere used is not quite in the original sense, for Gray included under it Bowerbank'sSpongilla pauperculawhich is now regarded as a form ofS. lacustris. His description, nevertheless, fits the group of species here associated except in one particular, viz., the smoothness of the gemmule-spicules to which he refers, for this character, though a feature ofS. carteri, is notfound in certain closely allied forms. The use of "Spongilla" in a double sense may be avoided by the adoption of Gray's name.
The subgenusEunapiusis, likeEuspongilla, cosmopolitan. It is not, however, nearly so prolific in species. Four can be recognized in India, two of which range, in slightly different forms, as far north as Europe, one of them also being found in North America, Northern Asia, and Australia.
8.Spongilla carteri*Carter(Bowerbank, in litt.). (Plate II. fig. 1.)
Spongilla friabilis?, Carter (necLamarck), J. Bombay Asiat. Soc. iii, p. 31, pl. i, fig. 3 (1849), & Ann. Nat. Hist. (2) iv, p. 83, pl. ii. fig. 3 (1849).Spongilla carteri, Carter, Ann. Nat. Hist. (3) iii, p. 334, pl. viii, figs. 1-7 (1859).Spongilla carteri, Bowerbank, P. Zool. Soc. London, 1863, p. 469, pl. xxxviii, fig. 20.Eunapius carteri, J. E. Gray,ibid.1867, p. 552.Spongilla carteri, Carter, Ann. Nat. Hist. (5) vii, p. 86 (1881).Spongilla carteri,id.,ibid.x, p. 369 (1882).Spongilla carteri, Potts, P. Ac. Philad. 1887, p. 194.Spongilla carteri, Weltner, Arch. Naturg. lxi (i), pp. 117, 134 (1895).Spongilla carteri, Kirkpatrick, P. Zool. Soc. London, 1906 (i), p. 219, pl. xv, figs. 3, 4 (? figs. 1, 2).Spongilla carteri, Annandale, J. Asiat. Soc. Bengal, 1906, p. 188, pl. i, fig. 1.Spongilla carteri, Willey, Spolia Zeyl. iv, p. 184 (1907).Spongilla carteri, Annandale,ibid.vii, p. 63, pl. 1, fig. 1 (1910).
Illustration: Fig. 14.—Gemmule of Spongilla carteri (from Calcutta), as seen in optical section, × 140.Fig. 14.—Gemmule ofSpongilla carteri(from Calcutta), as seen in optical section, × 140.
Fig. 14.—Gemmule ofSpongilla carteri(from Calcutta), as seen in optical section, × 140.
Spongemassive, as a rule with the surface smooth and rounded, occasionally bearing irregular ridges, which may even take the form of cockscombs; the oscula large, rounded, conspicuous but not raised above the surface of the sponge, leading into broad verticalcanals; the lateral canals, except in the immediate vicinity of the central vertical ones, not very broad; the oscular collars extending for a considerable distance over the oscula in living or well-preserved specimens, never standing out from the surface; the oscula never surrounded by radiating furrows. The inhalent pores surrounded externally by unmodified cells of the external membrane. Colour greyish, sometimes with a flush of green on the external surface.
The sponge has a peculiarly strong and offensive smell.
Skeletonfairly compact, with well-developed radiating fibres; the transverse fibres splayed out at either end so that they sometimes resemble a pair of fans joined together by the handles (fig. 3, p. 33). A moderate amount of spongin present.
Spicules.Skeleton-spicules smooth, pointed, nearly straight, never very stout but somewhat variable in exact proportions. Gemmule-spicules similar but much smaller. (There are no true flesh-spicules, but immature skeleton-spicules may easily be mistaken for them.)
Gemmulesas a rule numerous, spherical or flattened at the base, variable in size, each covered by a thick coat consisting of several layers of relatively large polygonal air-spaces. A single aperture surrounded by a crater-like depression in the cellular coat and provided with a foraminal tubule resembling an inverted bottle in shape. (This tubule, which does not extend beyond the surface of the cellular coat, is liable to be broken off in dried specimens.) The spicules variable in quantity, arranged irregularly among the spaces of the cellular coat and usually forming a sparse horizontal layer on its external surface. Each gemmule contained in a cage of skeleton-spicules, by the pressure of which it is frequently distorted.
8a.Var.mollis*, nov.
This variety is characterized by a paucity of skeleton-spicules. The sponge is therefore soft and so fragile that it usually breaks in pieces if lifted from the water by means of its support. Owing to the paucity of skeleton-spicules, which resemble those of the typical form individually, the radiating and transverse fibres are extremely delicate.
Common in Calcutta.
8b.Var.cava*, nov.
This variety is characterized by the fact that the oscula open into broad horizontal canals, the roof of which is formed by a thin layer of parenchyma and skeleton or, in places, of the external membrane only. The skeleton is loose and fragile, and the living sponge has a peculiar glassy appearance. In spirit the colour is yellowish, during life it is greenish or white.
Taken at Bombay; November, 1907.
8c.Var.lobosa*, nov.
The greater part of the sponge in this variety consists of a number of compressed but pointed vertical lobes, which arise from a relatively shallow, rounded base, in which the oscula occur. The dried sponge has a yellowish colour.
Apparently common in Travancore.
* * * * *
I cannot distinguish these three "varieties"[AC]from the typical form as distinct species; indeed, their status as varieties is a little doubtful in two cases out of the three. Var.cavaappears to be a variety in the strict sense of the word (see p. 18), for it was found on the island of Bombay, the original locality of the species, growing side by side with the typical form. Var.lobosa, however, should perhaps be regarded as a subspecies rather than a variety, for I have received specimens from two localities in the extreme south-west of India and have no evidence that the typical form occurs in that part of the country. Evidence, however, is rather scanty as regards the occurrence of freshwater sponges in S. India. Var.mollis, again, may be a phase directly due to environment. It is the common form in the ponds of certain parts (e. g.in the neighbourhood of the Maidan and at Alipore) of the Calcutta municipal area, but in ponds in other parts (e. g.about Belgatchia) of the same area, only the typical form is found. It is possible that the water in the former ponds may be deficient in silica or may possess some other peculiarity that renders the production of spicules difficult forS. carteri; but this seems hardly probable, forS. crassissima, a species with a rather dense siliceous skeleton, flourishes in the same ponds. I have noticed that in ponds in which the aquatic vegetation is luxuriant and such genera of plants asPistiaandLimnanthemumflourish, there is always a tendency forS. carterito be softer than in ponds in which the vegetation is mostly cryptogamic, and in Calcutta those parts of the town in which sponges of this species produce most spicules are those in which a slight infiltration of brackish water into the ponds may be suspected; but in the interior of India, in places where the water is absolutely fresh, hard specimens seem to be the rule rather than the exception.
S. carteriis closely related toS. nitens, Carter (Africa, and possibly S. America), but differs from that species in its comparatively slender, sharp skeleton-spicules and smooth gemmule-spicules. It may readily be distinguished from all other Indian freshwater sponges by its large, deep, round oscula, but this feature is not so marked in var.lobosaas in the other forms. The typical form andvar.mollisgrow to a larger size than is recorded for any other species of the family. I possess a specimen of the typical form from the neighbourhood of Calcutta which measures 30 × 27 cm. in diameter and 19.5 cm. in depth, and weighs (dry) 24-3/4 oz. The base of this specimen, which is solid throughout, is nearly circular, and the general form is mound-shaped. Another large specimen from Calcutta is in the form of an irregular wreath, the greatest diameter of which is 34 cm. This specimen weighs (dry) 16-1/4 oz. Both these specimens probably represent the growth of several years.
Types.—The types of the varietiesmollis,cavaandlobosaare in the collection of the Indian Museum. I regard as the type of the species the specimen sent by Carter to Bowerbank and by him namedS. carteri, although, owing to some confusion, Carter's description under this name appeared some years before Bowerbank's. This specimen is in the British Museum, with a fragment in the Indian Museum.
Geographical Distribution.—The range of the species extends westwards to Hungary, southwards to Mauritius and eastwards to the island of Madura in the Malay Archipelago; a specimen from Lake Victoria Nyanza in Central Africa has been referred to it by Kirkpatrick (P. Zool. Soc. London, 1906 (i), p. 219), but I doubt whether the identification is correct. In IndiaS. carteriis by far the most universally distributed and usually much the commonest freshwater sponge; it is one of the only two species as yet found in Ceylon. Specimens are known from the following localities:—Punjab, Lahore (J. Stephenson):Bombay Presidency, island of Bombay (Carter,Kirkpatrick,Annandale); Igatpuri, W. Ghats (alt.ca.2,000 ft.) (Annandale):United Provinces(plains), Agra (Kirkpatrick); Lucknow:Himalayas, Bhim Tal, Kumaon (alt. 4,500 ft.) (Annandale); Tribeni, Nepal (Hodgart):Bengal, Calcutta and neighbourhood; Rajshahi (Rampur Bhulia) on the R. Ganges about 150 miles N. of Calcutta (Annandale); Berhampur, Murshidabad district (R. E. Lloyd); Pusa, Darbbhanga district (Bainbrigge Fletcher); Siripur, Saran district, Tirhut (M. Mackenzie); Puri and the Sur Lake, Orissa (Annandale):Madras Presidency, near Madras town (J. R. Henderson); Madura district (R. Bruce Foote); Bangalore (Annandale) and Worgaum, Mysore State (2,500-3,000 ft.); Ernakulam and Trichur, Cochin (G. Mathai); Trivandrum and the neighbourhood of C. Comorin, Travancore (var.lobosa) (R. S. N. Pillay):Burma, Kawkareik, interior of Amherst district, Tenasserim (Annandale); Rangoon (Annandale); Bhamo, Upper Burma (J. Coggin Brown):Ceylon, Peradeniya (E. E. Green); outlet of the Maha Rambaikulam between Vavuniya and Mamadu, Northern Province (Willey); Horowapotanana, between Trincomalee and Anuradihapura, North-Central Province (Willey).
Biology.—S. carteriusually grows in ponds and lakes; I have never seen it in running water. Mr. Mackenzie found it on the walls of old indigo wells in Tirhut.
The exact form of the sponge depends to some extent on theforces acting on it during life. At Igatpuri, for instance, I found that specimens attached to the stems of shrubs growing in the lake and constantly swayed by the wind had their surface irregularly reticulated with high undulating ridges, while those growing on stones at the bottom of a neighbouring pond were smooth and rounded.
Sponges of this species do not shun the light.
In CalcuttaS. carteriflourishes during the cold weather (November to March). By the end of March many specimens that have attached themselves to delicate stems such as those of the leaves ofLimnanthemum, or to the roots ofPistia stratiotes, have grown too heavy for their support and have sunk down into the mud at the bottom of the ponds, in which they are quickly smothered. Others fixed to the end of branches overhanging the water or to bricks at the edge have completely dried up. A large proportion, however, still remain under water; but even these begin to show signs of decay at this period. Their cells migrate to the extremities of the sponge, leaving a mass of gemmules in the centre, and finally perish.
Few sponges exist in an active condition throughout the hot weather. The majority of those that do so exhibit a curious phenomenon. Their surface becomes smoothly rounded and they have a slightly pinkish colour; the majority of the cells of their parenchyma, if viewed under a high power of the microscope, can be seen to be gorged with very minute drops of liquid. This liquid is colourless in its natural condition, but if the sponge is plunged into alcohol the liquid turns of a dark brown colour which stains both the alcohol and the sponge almost instantaneously. Probably the liquid represents some kind of reserve food-material. Even in the hot weather a few living sponges of the species may be found that have not this peculiarity, but, in some ponds at any rate, the majority that survive assume the peculiar summer form, which I have also found at Lucknow.
Reproduction takes place inS. carteriin three distinct ways, two of which may be regarded as normal, while the third is apparently the result of accident. If a healthy sponge is torn into small pieces and these pieces are kept in a bowl of water, little masses of cells congregate at the tips of the radiating fibres of the skeleton and assume a globular form. At first these cells are homogeneous, having clear protoplasm full of minute globules of liquid. The masses differ considerably in size but never exceed a few millimetres in diameter. In about two days differentiation commences among the cells; then spicules are secreted, a central cavity and an external membrane formed, and an aperture, the first osculum, appears in the membrane. In about ten days a complete young sponge is produced, but the details of development have not been worked out.
The most common normal form of reproduction is by means of gemmules, which are produced in great numbers towards the end of the cold weather. If small sponges are kept alive in an aquarium even at the beginning of the cold weather, they beginto produce gemmules almost immediately, but these gemmules although otherwise perfect, possess few or no gemmule-spicules. If the sponge becomes desiccated at the end of the cold weather and is protected in a sheltered place, some or all of the gemmules contained in the meshes of its skeleton germinatein situas soon as the water reaches it again during the "rains." It is by a continuous or rather periodical growth of this kind, reassumed season after season, that large masses of sponge are formed. In such masses it is often possible to distinguish the growth of the several years, but as a rule the layers become more or less intimately fused together, for no limiting membrane separates them. A large proportion of the gemmules are, however, set free and either float on the surface of the water that remains in the ponds or are dried up and carried about by the wind. In these circumstances they do not germinate until the succeeding cold weather, even if circumstances other than temperature are favourable; but as soon as the cold weather commences they begin to produce new sponges with great energy.
Sexual reproduction, the second normal form, takes place inS. carterimainly if not only at the approach of a change of season, that is to say about March, just before the hot weather commences, and about November, just as the average temperature begins to sink to a temperate level. At these seasons healthy sponges may often be found full of eggs and embryos, which lie in the natural cavities of the sponge without protecting membrane.
In the ponds of Calcutta a large number of animals are found associated in a more or less definite manner withSpongilla carteri. Only one, however, can be described with any degree of certainty as being in normal circumstances an enemy, namely the larva ofSisyra indica,[AD]and even in the case of this little insect it is doubtful how far its attacks are actually injurious to the sponge. The larva is often found in considerable numbers clinging to the oscula and wide efferent canals ofS. carteri, its proboscis inserted into the substance of the sponge. If the sponge dies and the water becomes foul the larvæ swim or crawl away. If the sponge dries up, they leave its interior (in which, however, they sometimes remain for some days after it has become dry) and pupate in a silken cocoon on its surface. Hence they emerge as perfect insects after about a week.
An animal that may be an enemy ofS. carteriis a flat-worm (an undescribed species ofPlanaria) common in its larger canals and remarkable for the small size of its pharynx. The same worm, however, is also found at the base of the leaves of bulrushes and in other like situations, and there is no evidence that it actually feeds on the sponge. Injured sponges are eaten by the prawnPalæmon lamarrei, which, however, only attacks them when the dermal membrane is broken. ATanypuslarva (ChironomidDiptera) that makes its way though the substance of the sponge may also be an enemy; it is commoner in decaying than in vigorous sponges.
The presence of another Chironomid larva (Chironomus, sp.) appears to be actually beneficial. In many cases it is clear that this larva and the sponge grow up together, and the larva is commoner in vigorous than in decayed sponges. Unlike theTanypuslarva, it builds parchment-like tubes, in which it lives, on the surface of the sponge. The sponge, however, often grows very rapidly and the larva is soon in danger of being engulfed in its substance. The tube is therefore lengthened in a vertical direction to prevent this catastrophe and to maintain communication with the exterior. The process may continue until it is over an inch in length, the older part becoming closed up owing to the pressure of the growing sponge that surrounds it. Should the sponge die, the larva lives on in its tubes without suffering, and the ends of tubes containing larvæ may sometimes be found projecting from the worn surface of dead sponges. The larva does not eat the sponge but captures small insects by means of a pair of legs on the first segment of its thorax. In so doing it thrusts the anterior part of its body out of the tube, to the inner surface of which it adheres by means of the pair of false legs at the tip of the abdomen. This insect, which is usually found in the varietymollis, appears to do good to the sponge in two ways—by capturing other insects that might injure it and by giving support to its very feeble skeleton.
A precisely similar function, so far as the support of the sponge is concerned, is fulfilled by the tubular zoœcia of a phase of the polyzoonPlumatella fruticosa(see p. 218) which in India is more commonly found embedded in the substance ofS. carterithan in that of any other species, although in Great Britain it is generally found in that ofS. lacustris, which is there the commonest species of freshwater sponge.
Another animal that appears to play an active part in the œconomy of the sponge is a peculiar little worm (Chætogaster spongillæ) also found among the zoœcia ofPlumatellaand belonging to a widely distributed genus of which several species are found in association with pond-snails.Chætogaster spongillæoften occurs in enormous numbers in dead or dying sponges ofS. carteri, apparently feeding on the decaying organic matter of the sponge and assisting by its movements in releasing numerous gemmules. In so doing it undoubtedly assists in the dissemination of the species.
Major J. Stephenson (Rec. Ind. Mus. v, p. 233) has recently found two other species of oligochætes inhabitingS. carterivar.lobosafrom Travancore. Both these species, unlikeChætogaster spongillæ, belong to a genus that is vegetarian in habits. One of them,Nais pectinata, has not yet been found elsewhere, while the other,Nais communis, has a very wide distribution. The latter, however, occurs in the sponge in two forms—one with eyes, the other totally blind. The blind form (N. communisvar.cæca) hasonly been found in this situation, but the other (var.punjabensis) lives free as well as in association with the sponge, in which the blind form was the commoner of the two.
The majority of the animals found in association withS. carterigain shelter without evident assistance to the sponge. This is the case as regards the little fish (Gobius alcockii), one of the smallest of the vertebrates (length about 1/2 inch), which lays its eggs in the patent oscula, thus securing for them a situation peculiarly favourable to their development owing to the constant current of water that passes over them. In the absence of sponges, however, this fish attaches its eggs to the floating roots of the water-plantPistia stratiotes. Numerous small crustacea[AE]also take temporary or permanent refuge in the cavities ofS. carteri, the most noteworthy among them being the IsopodTachæa spongillicola[AF], the adults of which are found in the canal of this and other sponges, while the young cling to the external surface of the carapace ofPalæmon lamarreiand other small prawns. Many worms and insects of different kinds also enter the canals ofS. carteri, especially when the sponge is becoming desiccated; from half-dry sponges numerous beetles and flies may be bred, notably the moth-flyPsychoda nigripennis[AG]of which enormous numbers sometimes hatch out from such sponges.
As the sponge grows it frequently attaches itself to small molluscs such as the young ofVivipara bengalensis, which finally become buried in its substance and thus perish. Possibly their decaying bodies may afford it nourishment, but of the natural food of sponges we know little.S. carteriflourishes best and reaches its largest size in ponds used for domestic purposes by natives of India, and thrives in water thick with soap-suds. It is possible, though direct proof is lacking, that the sponge does good in purifying water used for washing the clothes, utensils, and persons of those who drink the same water, by absorbing decaying animal and vegetable matter from it.
Various minute algæ are found associated withS. carteri, but of these little is yet known. The green flush sometimes seen on the surface of the typical form is due to the fact that the superficial cells of the parenchyma contain green corpuscles. These, however, are never very numerous and are not found in the inner parts of the sponge, perhaps owing to its massive form. It is noteworthy that these green bodies flourish in large numbers throughout the substance of sponges ofS. proliferens, a species always far from massive, growing in the same ponds asS. carteri.
9.Spongilla fragilis,Leidy.