Freshwater Sponges, Hydroids & Polyzoa Part 18

9 _a._ Subsp. calcuttana*, nov.

? _Spongilla decipiens_, Weltner (_partim_), Arch. Naturg.

lxi (i), pp. 117, 134 (1895).

_Spongilla decipiens_, Annandale, Journ. As. Soc. Beng.

1906, p. 57.

_Spongilla fragilis_, _id._, Rec. Ind. Mus. i, p. 390 (1907).

[Ill.u.s.tration: Fig. 15.--_Spongilla fragilis_ subsp. _calcuttana_.

A=group of gemmules, 70; B=spicules, 240. From type specimen.]

This local race, which is common in Calcutta, is distinguished from the typical form mainly by the shape of its skeleton-spicules, most of which are abruptly pointed or almost rounded at the tips, sometimes bearing a minute conical projection at each end. The gemmule-spicules, which are usually numerous, are slender. The foraminal tubules are usually long and bent, but are sometimes very short and quite straight. The colour is usually greyish, occasionally brown.

I have not found this race except in Calcutta, in the ponds of which it grows on bricks or, very commonly, on the stems of bulrushes, often covering a considerable area.

TYPE in the Indian Museum.

9 _b._ Subsp. decipiens*, _Weber_.

_Spongilla decipiens_, Weber, Zool. Ergeb. Niederland.

Ost-Ind. i, p. 40, pl. iv, figs. 1-5 (1890).

This (?) local race is distinguished by the fact that the foraminal tubules are invariably short and straight and thickened at the tips, and that gemmule-spicules do not occur on the external surface of the cellular coat of the gemmules.

I include Weber's _Spongilla decipiens_ in the Indian fauna on the authority of Weltner, who identified specimens from the Museum "tank,"

Calcutta, as belonging to this form. All, however, that I have examined from our "tank" belong to the subspecies _calcuttana_, most of the skeleton-spicules of which are much less sharp than those of _decipiens_. By the kindness of Prof. Max Weber I have been able to examine a co-type of his species, which is probably a local race peculiar to the Malay Archipelago.

TYPE in the Amsterdam Museum; a co-type in Calcutta.

Perhaps the j.a.panese form, which has spindle-shaped gemmule-spicules with comparatively short and regular spines, should be regarded as a third subspecies, and the Siberian form as a fourth.

10. Spongilla gemina*, sp. nov.

_Sponge_ forming small, shallow, slightly dome-shaped patches of a more or less circular or oval outline, minutely hispid on the surface, friable but moderately hard. Oscula numerous but minute and inconspicuous, never star-shaped. Dermal membrane adhering closely to the sponge. Colour grey or brown.

_Skeleton_ forming a close and regular network at the base of the sponge, becoming rather more diffuse towards the external surface; the radiating and the transverse fibres both well developed, of almost equal diameter. Little spongin present.

_Spicules._ Skeleton-spicules slender, smooth, sharply pointed. No flesh-spicules. Gemmule-spicules long, slender, cylindrical, blunt or bluntly pointed, somewhat irregularly covered with minute straight spines.

_Gemmules_ small, bound together in pairs, as a rule free in the parenchyma but sometimes lightly attached at the base of the sponge.

Each gemmule flattened on the surface by which it is attached to its twin, covered with a thin coat of polygonal air-s.p.a.ces which contains two layers of gemmule-spicules crossing one another irregularly in a horizontal plane. One or two foraminal tubules present on the surface opposite the flat one, bending towards the latter, often of considerable length, cylindrical and moderately stout.

TYPE in the Indian Museum.

This species is closely allied to _S. fragilis_, from which it may be distinguished by the curious twinned arrangement of its gemmules. It also differs from _S. fragilis_ in having extremely small and inconspicuous oscula.

_Locality._ I only know this sponge from the neighbourhood of Bangalore, where Dr. Morris Travers and I found it in October, 1910 growing on stones and on the leaves of branches that dipped into the water at the edge of a large tank.

11. Spongilla cra.s.sissima*, _Annandale_.

_Spongilla cra.s.sissima_, Annandale, J. Asiat. Soc. Bengal, 1907, p. 17, figs. 2, 3.

_Spongilla cra.s.sissima_, _id._, _ibid._ p. 88.

_Spongilla cra.s.sissima_, _id._, Rec. Ind. Mus. i. p. 390, pl. xiv, fig. 4 (1907).

_Sponge_ very hard and strong, nearly black in colour, sometimes with a greenish tinge, forming spherical, spindle-shaped or irregular ma.s.ses without branches but often several inches in diameter. Oscula circular or star-shaped, usually surrounded by radiating furrows; pores normally contained in single cells. External membrane closely adherent to the sponge except immediately round the oscula.

_Skeleton_ dense, compact and only to be broken by the exercise of considerable force; radiating and transverse fibres not very stout but firmly bound together by spongin (fig. 6, p. 38), which occasionally extends between them as a delicate film; their network close and almost regular.

_Spicules._ Skeleton-spicules smooth, feebly curved, sausage-shaped but by no means short, as a rule bearing at each end a minute conical projection which contains the extremity of the axial filament. No flesh-spicules. Gemmule-spicules closely resembling those of _S.

fragilis_ subsp. _calcuttana_, but as a rule even more obtuse at the ends.

_Gemmules_ as in _S. fragilis_ subsp. _calcuttana_; a basal layer of gemmules rarely formed.

11 _a._ Var. cra.s.sior*, _Annandale_.

_Spongilla cra.s.sior_, Annandale, Rec. Ind. Mus. i, p. 389, pl. xiv, fig. 3 (1907).

This variety differs from the typical form chiefly in its even stronger skeleton (fig. 3, p. 33) and its stouter skeleton-spicules, which do not so often possess a terminal projection. The sponge is of a brownish colour and forms flat ma.s.ses of little thickness but of considerable area on sticks and on the stems of water-plants.

TYPES.--The types of both forms are in the Indian Museum. Co-types have been sent to London.

GEOGRAPHICAL DISTRIBUTION.--This sponge is only known from Bengal. The variety _cra.s.sior_ was found at Rajshahi (Rampur Bhulia) on the Ganges, about 150 miles N. of Calcutta, while the typical form is fairly common in the "tanks" of Calcutta and very abundant in the Sur Lake near Puri in Orissa.

[Ill.u.s.tration: Fig. 16.--Spicules of _Spongilla cra.s.sissima_ var.

_cra.s.sior_ (from type specimen), 240.]

BIOLOGY.--_S. cra.s.sissima_ is usually found near the surface in shallow water. Attached to the roots of the floating water-plant _Pistia stratiotes_ it a.s.sumes a spherical form, while on sticks or like objects it is spindle-shaped. Sometimes it is found growing on the same stick or reed-stem as _S. carteri_, the two species being in close contact and _S. carteri_ always overlapping _S. cra.s.sissima_. The dark colour is due to minute ma.s.ses of blackish pigment in the cells of the parenchyma. The dense structure of the sponge is not favourable to the presence of _incolae_, but young colonies of the polyzoon _Plumatella fruticosa_ are sometimes overgrown by it. Although they may persist for a time by elongating their tubular zooecia through the substance of the sponge, they do not in these circ.u.mstances reach the same development as when they are overgrown by the much softer _S. carteri_.

_S. cra.s.sissima_ is found during the "rains" and the cold weather. In Calcutta it attains its maximum size towards the end of the latter season. In spite of its hard and compact skeleton, the sponge does not persist from one cold weather to another.

A curious phenomenon has been noticed in this species, but only in the case of sponges living in an aquarium, viz. the cessation during the heat of the day of the currents produced by its flagella.

Subgenus C. STRATOSPONGILLA, _Annandale_.

_Stratospongilla_, Annandale, Zool. Jahrb., Syst. xxvii, p.

561 (1909).

TYPE, _Spongilla bombayensis_, Carter.