Geographical Distribution.—India and Sumatra. Localities:—Bengal, Calcutta and neighbourhood (Annandale); Madras Presidency, Cape Comorin, Travancore (Trivandrum Mus.): Bombay Presidency, Island of Bombay (Carter): Himalayas, Bhim Tal, Kumaon (alt. 4,500 feet) (Annandale).
Biology.—My experience agrees with Carter's, that this species is never found on floating objects but always on stones or brickwork. It grows in the Calcutta "tanks" on artificial stonework at the edge of the water, together with Spongilla carteri, S. alba, S. fragilis subsp. calcuttana, and Trochospongilla latouchiana. It flourishes during the cold weather and often occupies the same position in succeeding years. In this event the sponge usually consists of a dead base, which is of a dark brownish colour and contains no cells, and a living upper layer of a whitish colour.
The larva of Sisyra indica is sometimes found in the canals, but the close texture of the sponge does not encourage the visits of other incolæ.
Genus 4. DOSILIA, Gray.
Dosilia, J. E. Gray, P. Zool. Soc. London, 1867, p. 550.
Type, Spongilla plumosa, Carter.
This genus is distinguished from Ephydatia by the nature of the free microscleres, the microscleres of the gemmule being similar in the two genera. The free microscleres consist as a rule of several or many shafts meeting together in several or many planes at a common centre, which is usually nodular. The free ends of these shafts often possess rudimentary rotulæ. Occasionally a free microsclere may be found that is a true monaxon and sometimes such spicules are more or less distinctly birotulate. The skeleton is also characteristic. It consists mainly of radiating fibres which bifurcate frequently in such a way that a bush-like structure is produced. Transverse fibres are very feebly developed and are invisible to the naked eye. Owing to the structure of the skeleton the sponge has a feathery appearance.
Gray originally applied the name Dosilia to this species and to "Spongilla" baileyi, Bowerbank. It is doubtful how far his generic description applies to the latter, which I have not seen; but although the position of "Spongilla" baileyi need not be discussed here, I may say that I do not regard it as a congener of Dosilia plumosa, the free microscleres of which are of a nature rare but not unique in the family. With Dosilia plumosa we must, in any case, associate in one genus the two forms that have been described as varieties, viz., palmeri*, Potts from Texas and Mexico, and brouini*, Kirkpatrick from the White Nile. By the kindness of the authorities of the Smithsonian Institution and the British Museum I have been able to examine specimens of all three forms, in each case identified by the author of the name, and I am inclined to regard them as three very closely allied but distinct species. Species with free microscleres similar to those of these three forms but with heterogeneous or tubelliform gemmule-spicules will probably need the creation of a new genus or new genera for their reception.
Geographical Distribution.—The typical species occurs in Bombay and Madras; D. palmeri has probably an extensive range in the drier parts of Mexico and the neighbouring States, while D. brouini has only been found on the banks of the White Nile above Khartoum, in Tropical Africa.
17. Dosilia plumosa* (Carter).