What is "desmidiacae"

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.