BIOLOGY.--Carter writes as regards this species:--"This is the coarsest and most resistant of all the species. As yet I have only found three or four specimens of it, and these only in two tanks. I have never seen it fixed on any solid body, but always floating on the surface of the water, about a month after the first heavy rains of the S.W. monsoon have fallen. Having made its appearance in that position, and having remained there for upwards of a month, it then sinks to the bottom. That it grows like the rest, adherent to the sides of the tank, must be inferred from the first specimen which I found (which exceeds two feet in circumference) having had a free and a fixed surface, the latter coloured by the red gravel on which it had grown. I have noticed it growing, for two successive years in the month of July, on the surface of the water of one of the two tanks in which I have found it, and would account for its temporary appearance in that position, in the following way, viz., that soon after the first rains have fallen, and the tanks have become filled, all the sponges in them appear to undergo a partial state of putrescency, during which gas is generated in them, and accumulates in globules in their structure, through which it must burst, or tear them from their attachments and force them to the surface of the water. Since then the coarse structure of _plumosa_ would appear to offer greater resistance to the escape of this air, than that of any of the other species, it is probable that this is the reason of my having hitherto only found it in the position mentioned." It seems to me more probable that the sponges are actually broken away from their supports by the violence of the rain and retain air mechanically in their cavities. The only specimens of _D. plumosa_ that I have seen alive were attached very loosely to their support. In writing of the "coarse structure" of this species, Carter evidently alludes to the wide interspaces between the component branches of the skeleton. My specimens were attached to the stem of a water-lily growing in a pool of slightly brackish water and were of a brilliant green colour. I mistook them at first for specimens of _S. lacustris_ subsp. _reticulata_ in which the branches had not developed normally. They were taken in March and were full of gemmules. The pool in which they were growing had already begun to dry up. Genus 5. TROCHOSPONGILLA, _Vejdovsky_. _Trochospongilla_, Vejdovsky, Abh. K. Böhm. Ges. Wiss. xii, p. 31 (1883). _Trochospongilla_, Wierzejski, Arch. Slaves de Biologie, i, p. 44 (1886). _Trochospongilla_, Vejdovsky, P. Ac. Philad. 1887, p. 176. _Meyenia_, Potts (_partim_), _ibid._ p. 210. _Tubella_, _id._ (_partim_), _ibid._, p. 248. _Meyenia_, Carter (_partim_), Ann. Nat. Hist. (5) vii, p. 90 (1881). _Trochospongilla_, Weltner, in Zacharias's Tier- und Pflanzenwelt, i, p. 215 (1891).