Animalculism \An`i*mal"cu*lism\, n. [Cf. F. animalculisme.] 1. (Biol.) The theory which seeks to explain certain physiological and pathological phenomena by means of animalcules. [1913 Webster] 2. (Biol.) The theory that the spermatozo["o]n and not the ovum contains the whole of the embryo; spermatism; -- opposed to {ovism}. [Webster 1913 Suppl.]