Most of Haeckel's Monera, described as non-nucleate, belong here. Several have been proved to be nucleate, and to be rightly placed here; and all require renewed study.
Even the Acystosporidiae have sickle-germs (blasts) in the insect host.
See Zopf, Beitr. Nied. Org. ii. 1892, p. 36, iv. 1894, p. 60, for the doubtful genus Chlamydomyxa; Hieronymus, abstracted by Jenkinson, in Quart. J. Micr. Sci. xiii. 1899; Penard, Arch. Protist. iv. 1904, p. 296.
The name "aethalium" is now always used in this sense.
The group was monographed by Schröter in Engler and Prantl's Pflanzenfamilien, I. Teil, Abt. 1, 1897. See also A. Lister's Monograph of the Mycetozoa, 1894; Massee, Monog. of the Myxogastres, 1893; Sir Edward and Agnes Fry, The Mycetozoa, 1899; and Massee MacBride, The North American Slime Moulds, 1899.