diatomace[ae]
Webster's Dictionary (GCIDE)
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. [1913 Webster]
2.(Zool.) An animal, invisible, or nearly so, to the naked eye. See Infusoria. [1913 Webster]
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]. [1913 Webster]
Spermatic animalcules. See Spermatozoa. [1913 Webster]