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.