"A term etymologically applicable to any very small animal, and limited in actual use to those which are microscopical. Animalcules exist in prodigious numbers, and of many different kinds, their size being such that multitudes of them find ample space for all the movements of an active life within a single drop of water; and they abound almost wherever there is moisture, at least wherever organic matter is present." — Chambers' Encyclopedia, 1875

Animalcule

"A term etymologically applicable to any very small animal, and limited in actual use to those which…