This is one of the most singular of the microscopic animalcula; when viewed sidewise, it is sometimes nearly cylindrical, but somewhat tapering towards the hinder-part, and having a broad pellucid edge; viewed from the top, it has sometimes a broad face or disc furnished with radiating hairs, the under part contracted into a globular shape, of a dark green colour, and filled with small grains. It was found in October with the lesser lemna.
288. Vorticella Nigra.
V. trochiformis nigra. [Plate XXVII.] Fig. 36 and 37. Top-shaped black vorticella.
This may be seen with the naked eye, appearing like a black point swimming on the surface of the water; the microscope exhibits it as a minute conical body, opake, obtuse, and ventricose at one extremity, and acute at the other. When it extends the extremities, two small white hooks become visible; by the assistance of these it moves in the water, and it is probable from some circumstances that they inclose a rotatory organ. It moves continually in a vacillating manner on the top of the water. It is found in August, in meadows that are covered with water. a, the rotatory organ; b, the two small hooks; c, the acute end.
289. Vorticella Multiformis.
V. viridis, opaca, varia, vesiculis sparsis. Green, opake, variable vorticella, with vesicles scattered about the body.
The vesicles of this vorticella are larger; in other respects it so much resembles the preceding one, that a further description is unnecessary. It is found in salt water.
290. Vorticella Polymorpha.
V. multiformis, viridis, opaca. [Plate XXVII.] Fig. 33, 34, 35. Many-shaped vorticella, green, opake.
To the naked eye it appears like a green point, moving with great agility; but, when viewed through a microscope, it assumes such a variety of forms, that they can neither be exhibited to the eye by drawings, nor described by words; it is truly one of the wonders of nature, astonishing the mind, fatiguing the eye, and continually exciting the beholder to ask,