_Polypide._ The polypide is shorter and stouter than that of _P. emarginata_ and as a rule has fewer tentacles.
The most characteristic feature of this species is the form of the zooecia, which differ greatly from those of any other Indian species but _P. allmani_. In the latter they are distinctly "keg-shaped" (_i. e._, constricted at the base and swollen in the middle), and the zoarium never spreads out over large surfaces in the way in which that of _P. diffusa_ does.
TYPE--? in the Philadelphia Academy of Sciences.
GEOGRAPHICAL DISTRIBUTION.--This species was originally described from North America (in which it is apparently common) and occurs also in Europe. I have seen Indian specimens from the following localities:--BENGAL, Calcutta and neighbourhood; Rajshahi (Rampur Bhulia): E. HIMALAYAS, Gangtok, Native Sikhim (alt. 6,150 feet) (_Kirkpatrick_, _Stewart_): PUNJAB, Lahore (_Stephenson_).
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.