Definition of "animalculum"

[T]he Eyelids are fortify'd vvith little ſtiffe briſtles as vvith Paliſadoes, againſt the aſſault of Flyes and Gnats, and ſuch like bold Animalcula.

1653, Henry More, “Unavoydable Arguments for Divine Providence Taken from the Accurate Structure of Mans Body, from the Passions of His Mind, and Fitnesse of the Whole Man to be an Inhabiter of the Universe”, in An Antidote against Atheisme, or An Appeal to the Natural Faculties of the Minde of Man, whether There Be Not a God, London: […] Roger Daniel, […], book I, page 94