Infusoria

Infusoria was the term used by early naturalists to describe microscopic organisms because most of their observations were based on ‘infusions’ of water and other substances. Scientific circles used this term until the second half of the 19th century, when the development of cell theory and the simultaneous diffusion of evolutionary theory brought about different nomenclatures and understandings of microbial worlds. Dismissing the early views of microorganisms as miniature animals defended by naturalists like Christian Gottfried Ehrenberg in the origins of micropaleontology, cellularity and the extensive microscopic observations of early scientists provided other terms, like Protozoa and Protista.¹ Today, the term infusoria is still in use among hobbyists to describe microorganisms cultivated to feed fish and other aquarium animals.