_Plumatella lucifuga_, Jullien, Bull. Soc. zool. France, x, figs. 89, 90, p. 114 (1885). _Plumatella princeps_ var. _emarginata_, Kraepelin (_partim_), Deutsch. Süsswasserbryoz. p. 120, pl. iv, fig. 108, pl. v, fig. 123 (1887). _Plumatella emarginata_, Braem, Unter. ii. Bryoz. süssen Wassers, p. 9, pl. i, figs. 12, 14 (Bibl. Zool. ii) (1890). _Plumatella emarginata_, Annandale (_partim_), J. As. Soc. Bengal, (new series) iii, 1907, p. 89. _Plumatella princeps_, Loppens (_partim_), Ann. Biol. lacustre, iii, p. 162, fig. 7 (1908). _Plumatella emarginata_, Annandale, Rec. Ind. Mus. v, p. 47 (1910). _Zoarium._ The zoarium often covers a considerable area on flat surfaces and is sometimes entirely recumbent. More usually, however, the younger part is vertical. In either case the branching is practically dichotomous, two young zooecia arising almost simultaneously at the tip of a mother-zooecium and diverging from one another at a small angle. When the zoarium becomes vertical, rigid branches of as much as an inch in length are sometimes produced in this way and, arising parallel to one another, are pressed together to form an almost solid mass (=_Alcyonella benedeni_, Allman). In such cases the basal zooecium or at any rate the basal part of each upright branch is considerably elongated. In recumbent zooecia the main branches often radiate outwards from a common centre. _Zooecia._ The zooecia are of almost equal width throughout, slender, and moderately elongate when recumbent. Their ectocyst is stiff; they are emarginate at the tip and more or less distinctly furrowed on the dorsal surface, the keel in which the furrow runs not being prominent. The orifice is often on the dorsal surface even in upright branches. Each zooecium is of a dark brown or almost black colour for the greater part of its length but has a conspicuous white tip which is extended down the dorsal surface in the form of a triangle, its limits being rather more extensive than and parallel to those of the emargination. _Statoblast._ The majority of the free statoblasts are elongate and truncate or subtruncate at the extremities, the sides being as a rule straight and parallel. In every polyparium specimens will be found that are between twice and thrice as long as broad. The capsule is, however, relatively much broader than the swim-ring, often being nearly circular, and there is therefore at either end a considerable extent of free air-cells, while the extent of these cells at the sides of the capsule is small. The air-cells cover a considerable part of the dorsal surface of the capsule. Fixed statoblasts are usually found in old colonies, especially at the approach of the hot weather. They have an oval form and are surrounded by a membranous margin on which traces of reticulation can often be detected. As a rule statoblasts of both types are produced in considerable but not in excessive numbers.