crons. Jahn {loc. cit.) notes two varieties of this species, one white, the other cinnabar- red. Gelatin is quickly liquefied, completely in 1 to 2 days, but no fruiting bodies are formed . Kofler secured good growth on Hasting's milk agar and determined digestion of casein. Source: Isolated by Thaxter (Bot. Gaz., 17, 1892, 403) from various decaying sub- stances such as lichens, paper, dung, etc. Found by Smith (Jour. Bot., 39, 1901, 71) on rabbit dung from Wales, by Baur (Arch. f. Protistenkunde, 5, 1905, 95) on cow and dog dungs, by de Kruyff (Cent. f. Bakt., II Abt., 21, 1908, 386) on stable manure in Java, by Jahn {op. cit., 1924, 84) on almost all speci- mens of dung, as well as on bark, decaying wood and lichens, by Krzemieniewski (Acta Soc. Bot. Poloniae, 5, 1927) in Polish soil, and by Kofler (Sitzber. d. kais. Akad. wiss. Wien, math.-nat. Klasse, Abt. I, 122, 1913) on the dung of rabbit, horse, goat, mouse, roe and deer and on the stem of clematis and decaying leaves and in bird nest. Habitat: Found on decaying organic mat- ter in soil and in the dung of various ani- mals. Illustrations: Cohn {op. cit., 1875, PI. 6, Fig. 18), Smith {op. cit., 1901, Fig. 1), Baur {op. cit., 1905, Figs. 1-3 and PI. 4, Figs. 1-13, 16), Jahn {op. cit., 1924, Figs. L-M, page 43; Fig. R, page 47), Krzemieniewski {op. cit., 4, 1926, PI. 1, Figs. 7-8) and Kofler {op. cit., 1913, 845, PI. 2, Figs. 10 and 12). 2. Myxococcus cruentus Thaxter, 1897. (Bot. Gaz., 23, 1897, 395.) cru.en'tus. L. adj. cruentus blood-red. Vegetative cells: Rods 0.8 by 3.0 to 8.0 microns. Not cultivated. Fruiting body: Regularly spherical, 90 to 125 microns, blood-red. Slime forms on the surface a more or less definite membrane in which the microcysts lie. Microcysts el- lipsoidal or irregularly oblong, 0.9 to 1.0 by 1.2 to 1.4 microns. Source: Isolated from cow dung from Ten- nessee. Habitat: Found on decaying organic mat- ter in soil and in the dung of various ani- mals. Krzemieniewski (Acta Soc. Bot. Po- loniae, 5, 1927) states that it is rarely found in Polish soils. Illustrations: Thaxter {op. cit., 1897, PI. 31, Figs. 28-29). 3. Myxococcus virescens Thaxter, 1892. (Bot. Gaz., 17, 1892, 404.) vi.res'cens. L. part. adj. virescens becom- ing green. Vegetative cells: Rod masses greenish yellow. Rods slender, irregularly curved, 0.4 by 3.0 to 7.0 microns. When cultivated on potato agar, they tend to lose their green color and become yellowish. Fruiting body: Spherical, usually less rounded than other species of the genus, 3'ellowish, occasionally greenish, in culture on artificial media, easily becoming white, 150 to 500 microns. The slime deliquesces in continued moisture. Microcysts large, about 2 microns. Source : Isolated from hen and dog dungs from New England. Jahn (Beitrage zur bot. Protistologie. I, Die Polyangiden. Geb. Borntraeger, Leipzig, 1924) states that it is not very abundant on the dungs of rabbit, horse, stag and black cock. Habitat: Found on decaying organic mat- ter in soil and in the dung of various ani- mals. Common in Polish soil, according to Krzemieniewski (Acta Soc. Bot. Poloniae, 5, 1927). Illustrations: Krzemieniewski {op. cit., 4, 1926, PI. 1, Fig. 9) and Badian (Acta Soc. Bot. Poloniae, 7, 1930, 55, PI. 1, 8 Figures). 4. Myxococcus xanthus Beebe, 1941. (Jour. Bact., 4^, 1941, 193.) xan'thus. Gr. adj. xanthus orange, golden. Vegetative cells: Large, flexible, single, Gram-negative rods with rounded ends. Vary in size from 0.5 to 1.0 by 4.0 to 10.0 microns; average, 0.75 by 5.0 microns. Fruiting body: Spherical to subspherical, usually sessile but occasionally constricted at the base giving the appearance of a short stalk or foot. Mature fruiting body up to 300 to 400 microns in diameter, often slightly flattened on top or one side. Color varies from light yellowish orange when young to bright orange when mature; color constant, never tending toward greenish yellow. No outer cyst wall or limiting membrane dis-
