It was then that scholars discovered spermatozoa, bacteria, infusoria and the sheer strangeness and diversity of microscopic life.
From the en.wikipedia.org
More examples
In some recent classifications, coextensive with the Ciliata: minute organisms found in decomposing infusions of organic matter
Infusoria is a collective term for minute aquatic creatures like ciliates, euglenoids, protozoa, and unicellular algae that exist in freshwater ponds. ...
A class of microscopic Animalcules, so called from their having originally been observed in infusions of vegetable matters. ...
Are tiny organisms (protozoa) and algae that are cultured (grown) and fed to fish fry.
Minute organisms that are mainly used for the feeding of fry.
The name given by Biitschli (following O.F. Ledermiiller, 1763) to a group of Protozoa. The name arose 3 FIG. i. Ciliata.
Microscopic organisms, often ciliated protests and rotifers cultured as a food for fish fry.