volvox

‖n. (Bot.) A genus of minute, pale-green, globular, organisms, about one fiftieth of an inch in diameter, found rolling through water, the motion being produced by minute colorless cilia. It has been considered as belonging to the flagellate Infusoria, but is now referred to the vegetable kingdom, and each globule is considered a colony of many individuals. The commonest species is Volvox globator, often called globe animalcule. [ 1913 Webster ]