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Planctomyces bekefii Gimesi 1924 was originally described as a planktonic, freshwater fungus. Its spherical bodies on thin stalks were interpreted as sporangia. Colonies of this organism were compared to pine needles whose pointed ends were attached to a common base. Blastocaulis spaerica Henrici and Johnson 1935 is a planktonic, freshwater bacterium of a morphology and size identical to that of the former organism; both organisms occur in the same habitat and at the same time. Because of their rather unique morphology, the organisms are easily recognized. Depositions of ferric hydroxide occasionally thicken the stalks of the two forms. Recent observations on living material have confirmed the original descriptions. As a result of a comparison of the characteristics of the organisms, both are here considered to be identical. Although Planctomyces bekefii has been described as a fungus and its description lacks physiological details, priority must be given to this name, of which B. sphaerica must be considered a later subjective synonym. Because these organisms are the type species of their respective genera, the generic names are also regarded as subjective synonyms, and Planctomyces Gimesi 1924 has priority over Blastocaulis Henrici and Johnson 1935. An amended description of Planctomyces is presented. Besides P. bekefii Gimesi 1924, the following species are currently recognized as belonging to Planctomyces and are described herein: P. gracilis Horrotbágyi 1965, P. condensatus Skuja 1964, and P. kljasmensis comb. nov (basionym: Gallionella kljasmensis Razumov 1949). A key to these species is given. The taxonomic placement of other named organisms which either are or have been associated with the genus Planctomyces is discussed.