Rotifera
in zoölogy, wheel-animalcules; a group of Metazoa which have been variously classified. Ehrenberg arranged them according to the peculiarities of their trochal disks, trochal disks, and Dujardin according to their methods of locomotion.
They are now often made a class of Vermes, with four families, Philodinidæ, Brachionidæ, Hydatineæ, and Flosculatractile, crowned with vibratile cilia at the anterior part of the body, which, by their motion, often resemble a wheel revolving rapidly. Intestine distinct, terminated at one extremity by a mouth, at the other by an anus; generation oviparous, sometimes viviparous. The nervous system system is represented by a relatively large single ganglion, with one or two eye-spots, on one side of the body, near the mouth, and there are organs which appear to be sensory. They are free or adherent, but never absolutely fixed animals.