Vermis contractilis, nudus, ciliis rotatoriis. A naked worm, with rotatory cilia, capable of contracting and extending itself.
281. Vorticella Cincta.
V. trapeziformis, nigro-viridis, opaca. [Plate XXVII.] Fig. 30. This vorticella is in the form of a trapezium, of a blackish green colour, and opake.
It is of an irregular shape, sometimes assuming an oval figure, and appearing as if girt round with a transverse keel, a. It is invisible to the naked eye, ciliated on every side; the hairs all moveable, and longer on one side than the other.
282. Vorticella Sphæroida.
V. cylindrico-globosa, uniformis, opaca. A globous cylinder, uniform and opake.
To the naked eye this appears also little more than a point, but the microscope exhibits it as a globular mass of a dark green colour. It occasions a vehement motion in the surrounding water, which is probably effected by some very short hairs, which are perceptible.
283. Vorticella Viridis.
V. cylindracea, uniformis, viridis opaca. [Plate XXVII.] Fig. 31. Cylindrical, uniform, green, and opake.
This vorticella is visible to the naked eye, appearing like a minute green point; but the microscope discovers it to be nearly cylindrical, of a dark green colour, a little thicker at the fore-part a, than the hinder-part b, and both extremities obtuse. It appears to be totally destitute of limbs; notwithstanding which, it keeps the water in constant motion; so that it has probably some invisible rotatory instrument. It does not change its figure. Its motion is sometimes circular, at others, in a straight line. At c, some short hairs are visible.