For detailed descriptions, see pages [87-100].

Figs.1 to 5.—Various kinds of Xanthidia: figs. 2, 3, 4, found in a pond on Clapham Common, and fig. 1. living in a pond near Westpoint, United States.
1.—Xanthidium furcatum: 1/24 of a line in diameter.
2.— ———— hirsutum: 1/36.
3.— ———— aculeatum: 1/24.
4.— ———— fasciculatum: 1/24.
5.— —————————— variety of the above.
2*.—Pyxidicula operculata; Carlsbad, Bohemia: 1/48 of a line in diameter.
6.—Bacillaria vulgaris. 1/36 of a line in diameter. Pond on Clapham Common.
7.—Cocconeis scutellum: from the Baltic: 1/24 of a line.
8.—Navicula viridis: 1/6 of a line. Ponds on Clapham Common.
9.—The same; a side view; showing the currents produced in the water by the animal when in locomotion.
10.—Gallionella lineata: 1/36 of a line. Ponds on Clapham Common.
11.—Gallionella moniliformis: 1/72 of a line.
12.—Synhedra ulna: 1/9 of a line: the point a, marks the pedicle of attachment. Ponds on Clapham and Wandsworth Commons.
13.—Podosphenia gracilis: 1/12 of a line; attached to a thread of Calothria and having by self-division formed a radiating cluster. Common in the ditches communicating with the Thames in Battersea-fields.
14.—Navicula splendida: 1/12 of a line in diameter.
15.—Lateral view of the same.
16.—Eunotia turgida: 1/14 of a line; the empty shell, with sixty-five ribs, viewed laterally.
17.—A living group of the same: 1/20 of a line: a piece of Conferva rivularis, beset with these animalcules. The smaller species are E. Westermanni.

[All the above organisms were figured and described by Ehrenberg as animals (Polygastrica), and are comprised in his family Bacillaria; they are now, however, regarded as unquestionably vegetable structures, belonging to the family of Algæ, termed Diatomaceæ.]

Pl. 5.

J. Dinkel del. G. Scharf lithog.

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