BIOLOGY.--_P. diffusa_ in Lower Bengal is a cold-weather species. It is remarkable for the enormous number of gemmules it produces and is usually found either on floating objects such as the stems of certain water-plants, or on stones or bricks at the edge of ponds. 33. Plumatella allmani, _Hancock_. (Plate IV, figs. 3, 3 _a_.) _Plumatella allmani_, Hancock, Ann. Nat. Hist. (2) v, p. 200, pl. v, fig. 3-4, pl. iii, fig. 2-3 (1850). _Plumatella allmani_, Allman, Mon. Fresh-Water Polyzoa, p. 106, fig. 16 (1857). _Plumatella elegans_, _id._, _ibid._ p. 107, pl. viii, figs. 6-10. _Plumatella lucifuga_ ("forme rampante") Jullien, Bull. Soc. zool. France, x, p. 114 (1885). This species is closely allied to _P. diffusa_, from which it differs in the following characters:-- (1) The zoarium never covers a large area and as a rule grows sparingly and mainly in two directions. (2) The zooecia are more irregular in shape, not so distinctly elbowed, smaller; they have a much more prominently keeled ridge. The great majority of them are constricted at the base and taper towards the orifice. In young zoaria they are almost colourless but in older ones there is a band of not very dense pigment round the base of the vertical limb. (3) The free statoblasts are comparatively large and usually show a tendency to taper at the extremities, often being almost rhomboidal in form. The swim-ring does not extend so far over the dorsal surface as it does in those of _P. diffusa_; the "cells" of which it is composed are small. TYPE not in existence. I have seen every gradation between this form and Allman's _P. elegans_. GEOGRAPHICAL DISTRIBUTION.--_P. allmani_ is apparently a rare species to which there are few references in literature. It was originally described from England and is stated by Jullien to occur in France. I have found specimens only in the lake Bhim Tal (alt. 4,500 feet) in the W. Himalayas. BIOLOGY.--The original specimens were found by Hancock on stones. My own were growing on the leaves of water-plants, usually on the under side. When the zooecia were forced to stretch across from one leaflet to another they assumed the sinuous form characteristic of Allman's _P. elegans_. 34. Plumatella tanganyikæ, _Rousselet_. _Plumatella tanganyikæ_, Rousselet, Proc. Zool. Soc. London, 1907 (i), p. 252, pl. xiv, figs. 1-4. _Plumatella bombayensis_, Annandale, Rec. Ind. Mus. ii, p. 169, figs. 1, 2 (1908). _Plumatella bombayensis_, _id._, _ibid._ v, p. 51 (1910).