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Term used by believers in the preformation theory to designate the supposed miniature body contained in a gamete. See: homunculus.
[Mod. L. animalculum, dim. of L. animal, a living being]


(ăn′ə-măl′kyo͞ol) also


n. pl. animal·cules also animal·cula (-kyə-lə)
A microscopic or minute organism, such as an amoeba or paramecium, usually considered to be an animal.


An obsolete, nonspecific term for:
(1) Any microscopic organism; 
(2) Any “core” organism of the now-discarded preformation theory.
References in periodicals archive ?
A medical student, Johan Ham, was the first to see animalcules (spermatozoa) in human semen, and he drew this to Leeuwenhoek's attention.
Leeuwenhoek tried ingenious ways to estimate the size of his animalcules.
Louis Pasteur was studying what these little animalcules were running around under his microscope.
He called them animalcules, but we call them microorganisms.
I examined it, and perceived some of the Animalcules lying closely heaped together.
The preceding kinds of experiments I have many times repeated with the same success, and in particular with some of this sediment, which had been kept in my study for above five months, and upon pouring on it rain water, which had been boiled, and afterwards cooled, I saw in a few hours time many of the Animalcules before described.
His Majesty, founder and patron of the Royal Society, has not issued a direct comment but, according to Hooke, is desirous of observing the animalcules for himself.