118 BRITISH FRESHWATER RHIZOPODA. 
and finally assume its character and habits. These are 
not infrequently met with, fully developed, but distin- 
guished from older individuals by their delicate texture 
and transparency. 
1. Arcella vulgaris Ehrenberg. 
(Plate XV, figs. 1-3 and 13-15, and figs. 17 and 18 
in text.) 
Arcella vulgaris Hurenprra in Abh. K. Akad. Wiss. Berlin, 
1830 (1832), p. 40, t. i, f. vi; op. cit. 1831 (1832), p. 90; 
op. cit. 1871 (1872), p. 234; Infus. (1838), p. 133, t. ix, 
f.v; in Ber. K. Akad. Wiss. Berlin, 1845, p. 307; op. cit., 
1853, pp. 255, 266; and in Monatsh. K. Akad. Wiss. 
Berlin, 1869, p. 260; Buatnvittz Man. d’Actinol. (1834), 
p- 623; Dusarpin Infus. (1841), p. 247, t. u, ff. 3-3; 
Pritcuarp Hist. Infus. (1842), p. 169; new ed. (1852), 
p- 211; and ed. 4 (1861), p. 555, t. xxi, ff. 7-9; Scumarpa 
Kleine Beitr. Naturges. Infus. (1846), p. 30; in Denks. 
K. Akad. Wiss. Wien, VII (1854), 2, pp. 20, 25; and Zool. 
(1871), p. 163, £. 55; Srepotp Anat. Wirb. Thiere (1848), 
p. 20, and (Engl. transl.) Anat. Invert. (1854), p. 30; 
Perry in Mitth. naturf. Ges. Bern, 1849, pp. 124, 163, 
and Kenntn. kleinst. Lebensf. (1852), p. 186, t. ix, ff. 1-3 ; 
Battey in Smithson. Contrib. II (1851), art. 8, passim ; 
Cots in Proc. Essex Inst. I (1858), p. 45; CuararmpE in 
Arch. f£. Anat. 1854, pp. 401, 419; Owzn Anat. Invert. 
Anim. ed. 2 (1855), p. 26; Carrer in Ann. Nat. Hist. (2) 
XVIII (1856), pp. 128, 132, 221, t. vii, f. 79, and op. cit. 
(3) XIII (1864), p. 30, t. ui, f. 14; Limserxunsy in Arch. 
ft. Anat. 1856, p. 33; Craparips & Lacumann Etudes 
Inf. et Rhiz. 2 (1859), p. 444; Gossz Hv. Micr. (1859), 
p. 462; Carpanrer Foram. (1862, Ray Soc.), t.i, f. 19; 
Carus Handb. Zool. II, Prot. (1863), p. 591; ArcHER in 
Q. J. Micr. Sci. VI, n.s. (1866), pp. 185, 186, and in Q. J. 
Micr. Sci. XVII, n.s. (1877), p. 79; Scuocu Mikr. Thiere, 
I (1868), p. 14, t.i, £21; Enextmann in Arch. f. ges. 
Physiol. IT (1869), p. 318, and in Arch. Néerl. IV (1869), 
pp. 424, 438, t. vii, ff. 4,5; Parrirr in Trans. Devon. 
Assoc. III (1869), p. 67; Herrwic & Lasser in Arch. 
f. mikr. Anat. X (1874), Suppl. p. 96; Lerpy in Proc. 
Acad. Nat. Sci. Phil. 1874, p. 14; op. eft. 1876, p. 55; 
op. cit. 1879, p. 162; and Freshw. Rhiz. N. Amer. (1879), 
p. 170, tt. xxvii, xxviii, ff. 1-7; Bivscuii in Arch. f. mikr. 
Anat. XI (1875), p. 459, t. xxv, and in Bronn’s Thier- 
