Dictionary.net

• A genus of protozoa parasitic in the digestive tract of vertebrate or invertebrate hosts. Asexual multiplication is accomplished by transverse binary fission. Its organisms are ovoidal in shape and have a ciliated covering over the entire body.

2010 - Medical Dictionary Database
By DataStellar Co., Ltd

• A genus of Protozoa of the phylum Ciliata and the order Heterotricha, having an egg-shaped body, with the ventral and dorsal surfaces almost equally arched.

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe