Freshwater Sponges, Hydroids & Polyzoa Part 13

So far as my experience goes, this subspecies has always a bright green colour due to the presence of "green corpuscles," even when it is growing in a pond heavily shaded by trees or under the arch of a small bridge. Probably the more intense light of India enables the corpuscles to flourish in situations in which in Europe they would lose their chlorophyll.

2. Spongilla proliferens*, _Annandale_.

_Spongilla cinerea_, Weber (_nec_ Carter), Zool. Ergeb.

Niederl. Ost-Ind. vol. i, pp. 35, 46 (1890).

_Spongilla proliferens_, Annandale, J. Asiat. Soc. Bengal, 1907, p. 15, fig. 1.

_Spongilla proliferens_, _id._, Rec. Ind. Mus. i, pp. 267, 271 (1907).

_Sponge_ forming soft, shallow cushions rarely more than 10 cm. in diameter on the leaves of water-plants, or small irregular ma.s.ses on their roots and stems. Colour bright green. Oscula moderate, flat, surrounded by deep, cone-shaped collars; radiating furrows and ca.n.a.ls in the parenchyma surrounding them often deep. External pores contained normally in single cells. The surface frequently covered by small rounded buds; true branches if present more or less flattened or conical, always short, as a rule absent.

_Skeleton_ loose, feebly reticulate at the base of the sponge; transverse fibres slender in the upper part of the sponge, often scarcely recognizable at its base. Very little spongin present.

_Spicules._ Skeleton-spicules long, smooth, sharply pointed; the length on an average at least 20 times the greatest breadth, often more.

Flesh-spicules slender, gradually pointed, nearly straight, covered with minute straight or nearly straight spines. Gemmule-spicules very similar, but usually a little stouter and often blunt at the ends; their spines rather longer than those on the flesh-spicules, usually more numerous near the ends than in the middle of the spicule, slightly retroverted, those at the extreme tips often so arranged as to suggest a rudimentary rotule.

[Ill.u.s.tration: Fig. 9.--Gemmule of _Spongilla proliferens_ as seen in optical section (from Calcutta), 140.]

_Gemmules_ usually numerous, lying free near the base of the sponge, very variable in size, spherical, surrounded by a thick granular layer in which the spicules, which are always very numerous, are arranged tangentially, their position being more near the vertical than the horizontal; a few horizontal spicules usually present on the external surface of the gemmule, which frequently has a ragged appearance owing to some of the tangential spicules protruding further than others.

Foraminal tubule stout, cylindrical, usually somewhat contorted; its orifice irregular in outline. Sometimes more than one foramen present.

_S. proliferens_ can be distinguished from all forms of _S. lacustris_ and _S. alba_ by the fact that its gemmules possess a foraminal tubule; from _S. cinerea_ it can be distinguished by its colour and its smooth skeleton-spicules, and from _S. travancorica_ by its free gemmules. I have been enabled by the kindness of Prof. Max Weber to examine specimens from Celebes and Java identified by him as _S. cinerea_, Carter, and have no doubt that they belong to my species.

TYPE in the Indian Museum; a co-type in the British Museum.

GEOGRAPHICAL DISTRIBUTION.--All over Eastern India and Burma; also in Cochin on the west coast; Ceylon; W. China; Java, Flores and Celebes.

_Localities_:--BENGAL, Calcutta and neighbourhood (_Annandale_); Berhampore, Murshidabad district (_R. E. Lloyd_): a.s.sAM, Mangal-dai near the Bhutan frontier (_S. W. Kemp_): MADRAS PRESIDENCY, Madras (town) and neighbourhood (_J. R. Henderson_); Rambha, Ganjam district (_Annandale_); Bangalore, Mysore (alt. _ca._ 3000 ft.) (_Annandale_); Ernakulam and Trichur, Cochin (_G. Mathai_): BURMA, Rangoon (_Annandale_, _J. Coggin Brown_); Prome, Upper Burma (_J. Coggin Brown_); k.a.w.kareik, Amherst district, Tena.s.serim (_Annandale_): CEYLON, between Maradankawela and Galapita-Gala, North Central Province (_Willey_). Mr. J. Coggin Brown has recently brought back specimens from Yunnan.

BIOLOGY.--_S. proliferens_ is usually found in ponds which never dry up; Prof. Max Weber found it in small streams in Malaysia. It is common in India on the leaves of _Vallisneria_ and _Limnanthemum_, on the roots of _Pistia stratiotes_ and on the stems of rushes and gra.s.s. So far as I have been able to discover, the life of the individual sponge is short, only lasting a few weeks.

s.e.xual reproduction occurs seldom or never, but reproduction by means of buds and gemmules continues throughout the year. The former is a rare method of reproduction in most Spongillidae but in this species occurs normally and constantly, the buds being often very numerous on the external surface. They arise a short distance below the surface as thickenings in the strands of cells that accompany the radiating fibres of the skeleton. As they grow they push their way up the fibres, forcing the external membrane outwards. The membrane contracts gradually round their bases, cuts off communication between them and the parent sponge and finally sets them adrift. No hole remains when this takes place, for the membrane closes up both round the base of the bud and over the aperture whence it has emerged.

The newly liberated bud already possesses numerous minute pores, but as yet no osculum; its shape exhibits considerable variation, but the end that was farthest from the parent-sponge before liberation is always more or less rounded, while the other end is flat. The size also varies considerably. Some of the buds float, others sink. Those that float do so either owing to their shape, which depends on the degree of development they have reached before liberation, or to the fact that a bubble of gas is produced in their interior. The latter phenomenon only occurs when the sun is shining on the sponge at the moment they are set free, and is due to the action of the chlorophyll of the green bodies so abundant in certain of the parenchyma cells of this species. If the liberation of the bud is delayed rather longer than usual, numbers of flesh-spicules are produced towards the ends of the primary skeleton-fibres and spread out in one plane so as to have a fan-like outline; in such buds the form is more flattened and the distal end less rounded than in others, and the superficial area is relatively great, so that they float more readily. Those buds that sink usually fall in such a way that their proximal, flattened end comes in contact with the bottom or some suspended object, to which it adheres. Sometimes, however, owing to irregularity of outline in the distal end, the proximal end is uppermost. In this case it is the distal end that adheres. Whichever end is uppermost, it is in the uppermost end, or as it may now be called, the upper surface, that the osculum is formed.

Water is drawn into the young sponge through the pores and, finding no outlet, acc.u.mulates under the external membrane, the subdermal cavity being at this stage even larger than it is in the adult sponge.

Immediately after adhesion the young sponge flattens itself out. This process apparently presses together the water in the subdermal cavity and causes a large part of it to acc.u.mulate at one point, which is usually situated near the centre of the upper surface. A transparent conical projection formed of the external membrane arises at this point, and at the tip of the cone a white spot appears. What is the exact cause of this spot I have not yet been able to ascertain, but it marks the point at which the imprisoned water breaks through the expanded membrane, thus forming the first osculum. Before the aperture is formed, it is already possible to distinguish on the surface of the parenchyma numerous channels radiating from the point at which the osculum will be formed to the periphery of the young sponge. These channels as a rule persist in the adult organism and result from the fact that the inhalent apertures are situated at the periphery, being absent from both the proximal and the distal ends of the bud. In the case of floating buds the course of development is the same, except that the osculum, as in the case of development from the gemmule in other species (see Zykoff, Biol. Centrbl. xii, p. 713, 1892), is usually formed before adhesion takes place.

The sponge of _S. proliferens_ is usually too small to afford shelter to other animals, and I have not found in it any of those commonly a.s.sociated with _S. carteri_ and _S. alba_.

Owing to its small size _S. proliferens_ is more easily kept alive in an aquarium than most species, and its production of buds can be studied in captivity. In captivity a curious phenomenon is manifested, viz. the production of extra oscula, often in large numbers. This is due either to a feebleness in the currents of the sponge which makes it difficult to get rid of waste substances or to the fact that the ca.n.a.ls get blocked. The effluent water collects in patches under the external membrane instead of making its way out of the existing oscula, and new oscula are formed over these patches in much the same way as the first osculum is formed in the bud.

3. Spongilla alba*, _Carter_.

_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. x.x.xviii, fig. 15.

_Spongilla alba_, Carter, Ann. Nat. Hist. (5) vii, p. 88 (1881).

_Spongilla alba_, Petr, Rozp. Ceske Ak. Praze, Trida, ii, pl. i, figs. 3-6 (1899) (text in Czech).

_Spongilla alba_, Annandale, Rec. Ind. Mus. i, p. 388, pl.

xiv, fig. 2 (1907).

_Sponge_ forming ma.s.ses 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.

_Skeleton_ forming a moderately dense network of slender radiating and transverse fibres feebly held together; little spongin present; the meshes much smaller than in _S. lacustris_ or _S. 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.

_Gemmules_ usually 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.

3_a_. Var. cerebellata, _Bowerbank_.

_Spongilla cerebellata_, Bowerbank, P. Zool. Soc. London, 1863, p. 465, pl. x.x.xviii, fig. 16.

_Spongilla alba_ var. _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.

3_b_. Var. bengalensis*, _Annandale_. (Plate I, figs. 1-3.)

_Spongilla lacustris_ var. _bengalensis_, Annandale, J.

Asiat. Soc. Bengal, 1906, p. 56.

_Spongilla alba_ var. _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 of _S. alba_ can be distinguished from all forms of _S.

lacustris_ by 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. _cerebellata_ are in the British Museum, with fragments of the former in the Indian Museum; that of var. _bengalensis_ is in the Indian Museum, with a co-type in London.