cal with hemispherical extremities. Division by constriction in the middle. Cells vary in size from spheres of about 7 microns or even less in diameter to giant forms, 35 by 100 microns; the extremes are connected by a continuous series of intermediate sizes. May show motility of a jerky and rotating kind, always very slow and dependent upon a substrate. Typical organs of locomotion are absent. Normally contain small sulfur glob- ules accompanied by much larger calcium carbonate crystals, the latter in the form of large, highly refract ile spherules; under favorable environmental conditions, these may disappear before the sulfur globules. Cells with calcium carbonate inclusions have a very high specific gravity and there- fore are found only in the bottom of pools, streams, etc., usually in the mud. Strictly microaerophilic; apparentlj^ re- quire hydrogen sulfide. Source: Described from fresh-water and brackish mud containing hydrogen sulfide and calcium salts. According to Nadson and Wislouch (Bull, princip. Jard. bot., Republ. Russe, 22, 1923, Suppl. 1, 33), found also in marine mud. 2. .chroinaliiini volutans (Hinze, 1903) van Niel, 1948. {Thiophysa volutans Hinze, Ber. d. deut. bot. Gcs., 21, 1903, 309; Thio- physa macrophysa Nadson, Bull. Jard. Imp. Bot., St. Petersb., 13, 1913, 106; and Jour. Microb., St. P6tersb., 1, 1914, 54; Thio- sphaerella amylifera Nadson, Bull. Jard. Imp. Bot., St. Petersb., 13, 1913, 106; and Jour. Microb., St. Petersb., 1, 1914, 54; van Niel, in Manual, 6th ed., 1948, 999.) vo'lu.tans. L. part. adj. volutans rolling. Unicellular organisms which are spherical to ovoid in shape. Division by constriction in the middle. Size variable, ranging from spheres about 5 microns in diameter to ovals up to 40 microns in length. May show motil- ity of a jerky and rotating kind, always very slow and dependent upon a substrate. Typ- ical organs of locomotion are absent. Nor- mally contain sulfur globules but lack large, internal, calcium carbonate deposits. Microaerophilic; apparently require hy- drogen sulfide. Source: Described from marine mud con- taining hydrogen sulfide ; also from decaying seaweeds.
