_Plumatella fruticosa_, Johnston, Brit. Zooph. (ed. 2), p. 404 (1847). _Plumatella coralloides_, Allman, Rep. Brit. Assoc. 1850, p. 335. _Plumatella stricta_, _id._, Mon. Fresh-Water Polyzoa, p. 99, fig. 14 (1857). _Plumatella fruticosa_, _id._, _ibid._ p. 102, pl. vi, figs. 3-5. _Plumatella coralloides_, _id._, _ibid._ p. 103, pl. vii, figs. 1-4. _Plumatella repens_ and _P. stricta_, Carter, Ann. Nat. Hist. (3) iii, p. 341 (1859). _Plumatella lucifuga_, Jullien (_partim_), Bull. Soc. zool. France, x, p. 114 (1885). _Plumatella princeps_ var. _fruticosa_, Kraepelin, Deutsch. Süsswasserbryozoen, i, p. 120, pl. vii, fig. 148 (1887). _Plumatella fruticosa_, Braem, Unter. ii. Bryozoen des süssen Wassers, p. 9, pl. i, fig. 15 (Bibl. Zool. ii) (1890). _Plumatella repens_, Annandale, J. As. Soc. Bengal (new series) iii, 1907, p. 88. _Plumatella emarginata_, Loppens (_partim_), Ann. Biol. lacustre, iii, p. 161 (1908). _Plumatella fruticosa_, Annandale, Rec. Ind. Mus. v, p. 45 (1910). _Zoarium._ The zoarium in the typical form has a loose appearance due to the fact that the branches are far apart and the ectocyst by no means rigid. When young the zoarium is adherent, but in well-grown polyparia vertical branches, often an inch or more in length, are freely produced. As a rule they have not the strength to stand upright if removed from the water. Branching is ordinarily lateral and as a rule occurs chiefly on one side of a main branch or trunk. In certain circumstances upright zooecia are pressed together and reach a great length without branching, and in this form (_P. coralloides_, Allman) daughter-zooecia are often produced at the tip of an elongated mother-zooecium in fan-like formation. A depauperated form (_P. stricta_, Allman), occurs in which the vertical branches are absent or very short. In all forms internal partitions are numerous and stout. _Zooecia._ The zooecia are cylindrical and bear a simple keel on their dorsal surface. They are never emarginate or furrowed. In the typical form their diameter is more than half a millimetre, and they are always of considerable length. The ectocyst is thin and never very rigid or deeply pigmented, the colour usually being an almost uniform pale pinkish brown and fading little towards the tip of the zooecium.