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Müller, Otto Frederik


(b. Copenhagen, Denmark, 2 March 1730; d. Copenhagen, 26 Decem- ber 1784)

botany, zoology.

The son of a court trumpeter, Müller was educated from the age of ten by his mother’s family at the grammar school of Ribe, Jutland. Five years later he was sent to the University of Copenhagen, where he earned his, living by teaching music while studying theology and law. In 1750 he enrolled in Borch’s College and wrote two short theological theses (1751, 1753) while there. Three years later he was appointed tutor to Sigismund Schulin, the son of an influential noble family; for nearly twenty years he lived with this family on their estate, Frederiksdal (northern Zealand), and traveled with them to Germany, Switzerland, Italy, France, and the Nether- lands. In this way Müller met many outstanding scientists and became a member of the Academia Caesarea Leopoldina (1764), the Royal Swedish Academy of Sciences (1769), and the Norwegian Society of Sciences (1770). In 1771–1773 he was secretary to the Danish Ministry for Norway; but his marriage on 26 May 1773 to a wealthy widow, Anna Carlsen, née Paludan (1735–1787), daughter of a Norwegian bishop, made Müller financially inde- pendent, so that he was able to devote the last thirteen or fourteen years of his life to science. In 1774 he became a corresponding member of the Paris Academy of Sciences and the Berlin Society of Friends of Natural Science, and two years later he became a member of the Royal Danish Academy of Sciences and of the Academy of Sciences of the Institute of Bologna.

During Müller’s years as a tutor, his pupil’s mother interested him in the flora and fauna of the estate, procuring microscopes and other equipment for his growing absorption in biological studies. Because of his theological training Müller examined nature in terms of natural theology, considering it his task to investigate and point out the wisdom of the Creator everywhere in nature. The mainsprings of his scientific research were his love of beauty and his discovery that previous systematise had largely neglected to take microorganisms into account. Even the smallest puddle was full of organisms, and his unique powers of observation enabled Müller to demonstrate their adaptations. Thus he stands as the foremost representative of the Linnaean period in Danish natural history. He established the classification of several groups of animals—including Hydrachnellae, Entomostraca and Infusoria—completely disregarded by Linnaeus. He pursued his zoological studies and became one of the first field naturalists, using surprisingly modern methods long before the development of experimental biology.

At the age of thirty-four Müller published his first zoological work, a systematic study written entirely in the Linnaean spirit, Fauna insectorum Fridrichsdalina (1764). The description of 858 “insects”found at the estate of Frederiksdal—including spiders, wood lice and centipedes—contains several errors. Two years later there appeared Flora Fridrichsdalina (1766), a description of 1,100 species intended to represent most of the Danish flora. But Müller’s main work in systematics consisted of studying animal groups that were very little known before he identified them: the Hydrachnida, the Tardigrada, the Entomostraca, and the Infusoria. Among his works on these groups he lived to see only one published, Hydrachnae, quas in aquis Daniae palustribus detexit (1781). The other fundamental writings “Von dem Bärthierchen”(1785), Entomostraca, seu Insecta testacea (1785), and Animalcula infusoria (1786)—were printed after his death. Müller applied the term “Entomostraca”to the small, often minute crustaceans: many genera belonging to this group—including Daphnia, Cyclops caligus, and Argulus—were first defined by him, and he formulated a systematic classification and created Danish names for the various groups. His classic paper was for many years accepted as the best study of the Infusoria, which he placed near the order Acarina, where it is still placed by most authors. Illustrated with fifty plates, his work on Infusoria describes algae, bacteria, and many other micro-organisms as well as some protozoans.

It was not only on microscopic animals that Müller did significant and fundamental studies. His main work concerning mollusks and worms, Vermium terrestrium et fluviatilium (1773–1774), in which he first described a large number of new species of freshwater and terrestrial mollusks, also presented his primary system on the Infusoria. Neither did Müller limit his interests to invertebrate taxonomy; in Von Würmern des süssen and salzigen Wassers (1771) he clearly demonstrated the propagation of naiads. He wrote on annelids (1771), on the moth (1779), and on helminths (1779). In this field of studies his contem- poraries rightly called him the Danish Linnaeus.

Besides his systematic works Müller wrote several entomological papers in Réaumur’s style, for instance, on the propagation of the daphnids. For the collection of sea animals he invented a special dredge; and with his brother, Christian Frederik Müller (1744–1814), who was responsible for some of the illustrations in Müller’s books, he published an anonymous account of a journey from Norway (1778).

In 1776 Müller published Zoologiae Danicae prodromus, an excellent survey of the fauna of Norway and Denmark. It was the first manual on this topic and was for many years the most compre- hensive. It was planned as the beginning of a large illustrated fauna, but only one volume appeared before his death; the following volumes—the last published in 1806—prepared by Abildgaard, Rathke, and

others, never reached the standard of the Flora Danica begun by Georg Christian Oeder.

Müller also wrote a number of botanical studies dealing especially with fungi and other groups, but they were little known during his lifetime. They presented findings and views pointing far beyond what was known then—for instance, in his “Ueber die Feld-Lilie”(1766).

Besides his systematic and exact studies Müller was also occupied with the philosophy of biology, advancing his “monadic” theory, a view that all living things are composed of minute elements— monads—that are set free by putrefaction and reunited in propagation. This belief indicates that he was an adherent of the preformation hypothesis.


I. Original Works. A full list of Müller’s writings is in H. Ehrencron-Müller, Forfatterlexikon, VI (Copenhagen, 1929), 17–22.

Among his works are Fauna insectorum Fridrichs- dalina … (Copenhagen-Leipzig, 1764); Flora Fridrichs- dalina … (Strasbourg, 1766; 1767); Von Würmern des süssen und salzigen Wassers (Copenhagen, 1771); Vermium terrestrium et fluviatilium…, 2 vols. (Copenhagen Leipzig, 1773–1774); Zoologiae Danicae prodromus (Copen- hagen, 1776); Zoologiae Danicae seu animalium Daniae et Norvegiae rariorum ac minus notorum icones, 2 vols. (Copenhagen, 1777–1780); Rejse igiennem Övre-Tillemarken til Christianssand og tilbage 1775 (Copenhagen, 1778), published anonymously; Hydrachnae, quas in aquis … palustribus detexit … (Leipzig, 1781); Zoologia Danica eller Danmarks og Norges sieldne og ubekiente Dyrs Historie (Copenhagen, 1781), also trans, into German (Leipzig-Dessau, 1782); Entomostraca seu insecta testacea, quae in aquis Daniae et Norvegiae reperit … (Copenhagen, 1785); Animalcula infusoria, fluviatilia et marina … (Copenhagen, 1786); and Zoologia Danica seu animalium Daniae et Norvegiae rariorum ac minus notorum descrip- tiones et historia, 4 vols. (Copenhagen, 1788–1806).

His diary, which remains unpublished, is in the Royal Library, Copenhagen, Add. 4° no. 710.

II. Secondary Literature. See Jean Anker, Otto Friderich Müller (Copenhagen, 1943), of which only the 1st vol., covering 1730–1767, has been published (because of the author’s death); V. Meisen, Prominent Danish Scientists (Copenhagen, 1932), 60–64; and Jens Worm, Lexicon over laerde Maend, II (Copenhagen, 1773), 88–91, and III (Copenhagen, 1784), 548–549.

E. Snorrason

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