FAMILY IV. ACHROMATIACEAE 



853 



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. 



