O.F.Müll.

Otto Friedrich Müller, also Mueller (11 March 1730 – 26 December 1784) was a Danish naturalist.

Müller was born in Copenhagen. He was educated for the church, became tutor to a young nobleman, and after several years' travel with him, settled in Copenhagen in 1767, and married a lady of wealth.

His first important works, Fauna Insectorum Friedrichsdaliana (Leipzig, 1764), and Flora Friedrichsdaliana (Strasbourg, 1767), giving accounts of the insects and flora of the estate of Friedrichsdal, near Copenhagen, recommended him to Frederick V of Denmark, by whom he was employed to continue the Flora Danica a comprehensive atlas of the flora of Denmark. Müller added two volumes to the three published by Georg Christian Oeder since 1761.

The study of microorganisms began to occupy his attention almost exclusively, and in 1771 he produced a work in German on “Certain Worms inhabiting Fresh and Salt Water,” which described many new species of those annulose animals called by Linnaeus aphroditae and nereides, and gave much additional information respecting their habits. He discovered the first diatom ever seen, the colonial diatom Bacillaria paradoxa, though he thought it was an animal because of its movement.

In his Vermium Terrestrium et Fluviatilium, seu Animalium Infusoriorum, Helminthecorum, et Testaceorum non Marinorum, succincta Historia (2 vols. in 4to, Copenhagen and Leipzig, 1773–74), he arranged the Infusoria for the first time into genera and species. His Hydrachnæ in Aquis Daniæ Palustribus detectæ et descriptæ (Leipzig, 1781), and Entomostraca (1785), describe many species of microorganisms previously unknown, amongst other dinoflagellates. To these was added an illustrated work on the infusoria, published in 1786. These three works, according to the contemporary dean of naturalists Baron Cuvier, give the author “a place in the first rank of those naturalists who have enriched science with original observations.”

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