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.
      
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   2. (Zool.) An animal, invisible, or nearly so, to the naked
      eye. See {Infusoria}.
      
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   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
         {Desmidiacae}, and the siliceous {Diatomaceae}.
         
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   {Spermatic animalcules}. See {Spermatozoa}.
      
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