The family Ophrydinidee presents us again with very remarkable forms of Polygastric ani malcules, allied in structure to the Vorticellx, but having their bodies inclosed in cases of different kinds, of which it will be necessary to give one or two examples.
The genus 0 phrydium, (jelly-bell-animal cules,) of which the Oplirydium versatile (fig. 10) is an example, was regarded by the older naturalists as being a mass of vegetable matter, and had the names of ulva, fucus, conferva, &c. conferred upon it by different authors, until Muller, in 1786, first announced its real nature and relationship to the vorticelline animalcules. It is found under the shape of a gelatinous mass of a lively or dull green colour, which in consistence may be compared to frog's spawn, some specimens attaining the size of four or five inches in diameter ; the whole forming an irregularly shaped but smooth mass, which is composed of many millions of distinct animal cules, each about Ath of a line in thickness, and about the liuth of a line in length. The space of a square line would therefore contain 9216 of these diminutive beings; a cubic line six times as many, or 55,296; and a cubic inch nearly eight millions, namely, 7,962,624. In the water all these congregated animalcules are disposed in close rows, something in the same manner as in Volvox. On shaking the mass many others show themselves within be tween the former, so as to form from three to five different ranks. At first all the gelatinous cells appear to be connected with the centre of the mass by filamentary prolongations, but these disappear as they proceed internally, so that the middle seems to be hollow and full of water; the whole, indeed, might be compared to 'the gelatinous polyp masses ( e) found upon the sea-shore, only the structure of the animalcules is polygastric and not that of polyps.
In the other genera belonging to the family Ophrydinid, namely, Tintinnus, Vaginicola (9, fig. 11,) and Cothurnia, although living in gelatinous transparent sheaths, and resembling Vorticellw in their structure, are not associated in masses, but remain permanently detached and solitary.
The family Encheliadm contains various forms of animalcules, having the oral and anal orifices distinct and situated at the opposite extremities of the body. The different genera of which it is coinposed may be distinguished as follows :— Enchelis, ( revolving animaleule,) has its body flask-shaped, (1, jig. 11,) without any cilia externally, but with a circlet around the mouth, which is suddenly truncated and desti tute of any dental armature.
Disoma, ( double-bodied animakule,) crea tures nearly resembling Enchelis in form and structure, but with a double body (6, 7,fig. 11).
Actinophrys, (sun animalcule,) ha,ving the exterior of the body unprovided with loco motive cilia, but stuck over with setaceous ten tacula which radiate in all directions.
Trichodiscus, (radiated disc animalcule,) re sembling Actinophrys, only the body is here compressed, and only furnished with a single row of setaceous tentacula, situated around its margin.
Podophyra, (radiated foot animalcule,) is an Actinophrys with a spherical body, from which projects a long straight pedicle, which, however, is not attached to any foreign body.
Trichoda, ( hair animalcule,) an Enchelis having its mouth obliquely truncated and fur nished with a lip; its body is unprovided with a neck-like prolongation.
Lachrymaria, ( lachrymator!' animakule,) (8, jig. 11,) an Enchelis having its body destitute of cilia externally, but terminated by a long thin neck, which is clavate at the extre mity, and ends with a mouth provided with a lip and ciliated margin.
Leucophrys, (ciliated animalcule,) an En chelis, with its body entirely covered with vibratile cilia—its mouth is obliquely terminal and provided with a kind of lip, but without dental organs. (1, fig. 12.) Holophrya, (woolly anintalcule,) an En chelis having the exterior of its body entirely ciliated.
Prorodon (toothed rolling animakule). In this genus, like the last, the body is covered all over with vibratile cilia, and the mouth truncated, but the latter is remarkable for being armed with a circlet of teeth of a very peculiar structure situated within its margin. (2, fig. 12.) The family Colepinidm consists of but one genus, Coleps (1, 2, fig. 13) the animalcules belonginu to which have all the characters of Enchelis, except that they are loricated. These animalcules are found among confervm, more especially in summer time. As long as they are swimming it is difficult to perceive the transparent case in which they are enclosed ; but if they are allowed to get dry or are crushed between two plates of glass, its presence be comes manifest as well as its brittleness. In shape this external covering resembles a little barrel made up of rows of plates or rings, be tween which the cilia seem to be exserted ( testulct multipartita). Anteriorly it is trun cated, its margin being either smooth or toothed, and posteriorly terminates in three or five little sharp points.