The ?late-formers??Changing concepts of the opsimorphs (Myxomycetes, Acrasieae, Myxobacteria)

Between Panckow's description of Lycogala and De Bary's exposition of the Myxomycete life cycle, two centuries elapsed in which these forms were considered Gasteromycetes. From De Bary onward they have been recognized as a separate group with probably protozoan affinities. The Acrasieae were first recognized by Brefeld, but an error in interpreting the life cycle has kept them artificially allied with the Myxomycetes as “Slime Moulds”. It appears that the Acrasieae consist of two distinct groups, the Guttulinaceae and Dictyosteliaceae. The Acrasieae differ from the Myxomycetes in the absence of a flagellate swarmer stage, no known sexuality, and in the cellular structure of the fructification, which in the Myxomycetes is secreted. A third group, the minute Protostelida, recently described by Olive appears to be related to the Myxomycetes. The Myxobacteria in their flexuousness to some degree resemble the Cyanophyceae. But the nucleoids resemble more closely those of the Eubacteria. In nucleotide composition the true fruiting Myxobacteria form a very coherent group.