Freshwater Sponges, Hydroids & Polyzoa Part 23

TYPE in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Lower Bengal and Lower Burma.

_Localities_:--BENGAL, Calcutta (_Annandale_): BURMA, jungle pool near k.a.w.kareik, Amherst district, Tena.s.serim (_Annandale_).

BIOLOGY.--This species covers a brick wall at the edge of the Museum tank in Calcutta every year during the "rains." In the cold weather the wall is left dry, but it is usually submerged to a depth of several feet before the middle of July. It is then rapidly covered by a thin layer of the sponge, which dies down as soon as the water begins to sink when the "rains" are over. For some months the gemmules adhere to the wall on account of the cage of spicules in which each of them is enclosed, but long before the water rises again the cages disintegrate and the gemmules are set free. Many of them fall or are carried by the wind into the water, on the surface of which, owing to their thick pneumatic coat, they float buoyantly. Others are lodged in cavities in the wall. On the water the force of gravity attracts them to one another and to the edge of the pond, and as the water rises they are carried against the wall and germinate. In thick jungle at the base of the Dawna Hills near k.a.w.kareik[AI] in the interior of Tena.s.serim, I found the leaves of shrubs which grew round a small pool, covered with little dry patches of the sponge, which had evidently grown upon them when the bushes were submerged. This was in March, during an unusually severe drought.

[Footnote AI: This locality is often referred to in zoological literature as k.a.w.kare_et_ or k.a.w.kari_t_, or even K_o_kari_t_.]

20. Trochospongilla pennsylvanica* (_Potts_).

_Tubella pennsylvanica_, Potts, P. Ac. Philad. 1882, p. 14.

_Tubella pennsylvanica_, _id._, _ibid._ 1887, p. 251, pl.

vi, fig. 2, pl. xii, figs. 1-3.

_Tubella pennsylvanica_, Mackay, Trans. Roy. Soc. Canada, 1889, Sec. iv, p. 95.

_Tubella pennsylvanica_, Hanitsch, Nature, li, p. 511 (1895).

_Tubella pennsylvanica_, Weltner, Arch. Naturg. lxi (i), p.

128 (1895).

_Tubella pennsylvanica_, Hanitsch, Irish Natural. iv, p. 129 (1895).

_Tubella pennsylvanica_, Annandale, J. Linn. Soc., Zool., x.x.x, p. 248 (1908).

_Tubella pennsylvanica_, _id._, Rec. Ind. Mus. iii, p. 102 (1909).

_Tubella_ _pennsylvanica_, _id._, P. U.S. Mus. x.x.xvii, p.

403, fig. 2 (1909).

_Sponge_ soft, fragile, forming small cushion-shaped ma.s.ses, grey or green; oscula few in number, often raised on sloping eminences surrounded by radiating furrows below the external membrane; external membrane adhering to the parenchyma.

_Skeleton_ close, almost structureless. "Surface of mature specimens often found covered with parallel skeleton spicules, not yet arranged to form cell-like inters.p.a.ces" (_Potts_).

_Spicules._ Skeleton-spicules slender, cylindrical, almost straight, sharp or blunt, minutely, uniformly or almost uniformly spined; spines sometimes absent at the tips. No flesh-spicules. Gemmule-spicules with the lower rotula invariably larger than the upper; both rotulae flat or somewhat sinuous in profile, usually circular but sometimes asymmetrical or subquadrate in outline, varying considerably in size.

_Gemmules_ small, numerous or altogether absent, covered with a granular pneumatic coat of variable thickness; the rotulae of the gemmule-spicules overlapping and sometimes projecting out of the granular coat.

The measurements of the spicules and gemmules of an Indian specimen and of one from Lehigh Gap, Pennsylvania, are given for comparison:--

Travancore. Pennsylvania.

Length of skeleton-spicules 0.189-0.242 mm. 0.16-0.21 mm.

(average 0.205 mm.) (average 0.195 mm.) Breadth " " 0.0084-0.0155 mm. 0.0084 mm.

Length of birotulate 0.0126 " 0.0099 "

Diameter of upper rotula 0.0084 " 0.0084 "

" lower " 0.0169 " 0.0168 "

" gemmule 0.243-0.348 mm. 0.174-0.435 mm.

The spicules of the Travancore specimen are, therefore, a trifle larger than those of the American one, but the proportions are closely similar.

The difference between the gemmule-spicules of this species and those of such a form as _T. phillottiana_ is merely one of degree and can hardly be regarded as a sufficient justification for placing the two species in different genera. If, as I have proposed, we confine the generic name _Tubella_ to those species in which the gemmule-spicules are really like "little trumpets," the arrangement is a much more natural one, for these species have much in common apart from the gemmule-spicules. _T.

pennsylvanica_ does not appear to be very closely related to any other known species except _T. phillottiana_.

TYPE in the U.S. National Museum, from which specimens that appear to be co-types have been sent to the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Very wide and apparently discontinuous:--N.

America (widely distributed), Ireland (_Hanitsch_), Hebrides of Scotland (_Annandale_), Travancore, S. India (_Annandale_). The only Indian locality whence I have obtained specimens is Shasthancottah Lake near Quilon in Travancore.

BIOLOGY.--In Shasthancottah Lake _T. pennsylvanica_ is found on the roots of water-plants that are matted together to form floating islands.

It appears to avoid light and can only be obtained from roots that have been pulled out from under the islands. In Scotland I found it on the lower surface of stones near the edge of Loch Baa, Isle of Mull. In such circ.u.mstances the sponge is of a greyish colour, but specimens of the variety _minima_ taken by Potts on rocks and boulders in Bear Lake, Pennsylvania, were of a bright green.

Sponges taken in Travancore in November were full of gemmules; in my Scottish specimens (taken in October) I can find no traces of these bodies, but embryos are numerous.

Genus 6. TUBELLA, _Carter_.

_Tubella_, Carter, Ann. Nat. Hist. (5) vii, p. 96 (1881).

_Tubella_, Potts (_partim_), P. Ac. Philad. 1887, p. 248.

_Tubella_, Weltner (_partim_), Arch. Naturg. lxi (i), p. 128 (1895).

TYPE, _Spongilla paulula_, Bowerbank.

This genus is distinguished from _Ephydatia_ and _Trochospongilla_ by the fact that the two ends of the gemmule-spicules are unlike not only in size but also in form. It sometimes happens that this unlikeness is not so marked in some spicules as in others, but in some if not in all the upper end of the shaft (that is to say the end furthest removed from the inner coat of the gemmule in the natural position) is reduced to a rounded k.n.o.b, while the lower end expands into a flat transverse disk with a smooth or denticulated edge. The spicule thus resembles a little trumpet resting on its mouth. The shaft of the spicule is generally slender and of considerable length. The skeleton of the sponge is as a rule distinctly reticulate and often hard; the skeleton-spicules are either slender or stout and sometimes change considerably in proportions and outline as they approach the gemmules.

GEOGRAPHICAL DISTRIBUTION.--The genus is widely distributed in the tropics of both Hemispheres, its headquarters apparently being in S.

America; but it is nowhere rich in species. Only two are known from the Oriental Region, namely _T. vesparium_* from Borneo, and _T.

vesparioides_* from Burma.

21. Tubella vesparioides*, _Annandale_. (Plate II, fig. 4.)

_Tubella vesparioides_, Annandale, Rec. Ind. Mus. ii, p. 157 (1908).

_Sponge_ forming rather thick sheets of considerable size, hard but brittle, almost black in colour; oscula inconspicuous; external membrane supported on a reticulate horizontal skeleton.

_Skeleton._ The surface covered with a network of stout spicule-fibres, the interstices of which are more or less deeply sunk, with sharp fibres projecting vertically upwards at the nodes; the whole ma.s.s pervaded by a similar network, which is composed of a considerable number of spicules lying parallel to one another, overlapping at the ends and bound together by a profuse secretion of spongin.

[Ill.u.s.tration: Fig. 25.--Spicules of _Tubella vesparioides_ (from type specimen). 240.]

_Spicules._ Skeleton-spicules slender, smooth, amphioxous, bent in a wide arc or, not infrequently, at an angle. No true flesh-spicules.

Gemmule-spicules terminating above in a rounded, k.n.o.b-like structure and below in a relatively broad, flat rotula, which is very deeply and irregularly indented round the edge when mature, the spicules at an earlier stage of development having the form of a sharp pin with a round head; shaft of adult spicules projecting slightly below the rotula, long, slender, generally armed with a few stout conical spines, which stand out at right angles to it.

_Gemmules_ numerous throughout the sponge, spherical, provided with a short, straight foraminal tubule, surrounded by one row of spicules, which are embedded in a rather thin granular coat.

Average length of skeleton-spicule 0.316 mm.