Volvox \Vol"vox\, 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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Animalcule \An`i*mal"cule\, n. [As if fr. a L. animalculum, dim. of animal.]

1. A small animal, as a fly, spider, etc. [Obs.]

--Ray.

2. (Zo["o]l.) An animal, invisible, or nearly so, to the naked eye. See Infusoria.

Note: Many of the so-called animalcules have been shown to be plants, having locomotive powers something like those of animals. Among these are Volvox, the Desmidiac[ae], and the siliceous Diatomace[ae].

Spermatic animalcules. See Spermatozoa.

Source: Webster's Revised Unabridged Dictionary (1913)