Optimum temperature, between 20° and 25° C. Habitat: Found free-living in fresh or salt water. Optimum temperature, 20° C. Habitat: Found in swamp water and in grossly polluted water containing hydrogen sulfide. 2. Spirochaeta marina Zuelzer, 1912. (Spirochaeta plicatilis marina Zuelzer, Arch, f. Protistenk., 24, 1912, 17; Zuelzer, ibid., 51.) ma.ri'na. L. adj. marirms of the sea. Probably a subspecies or variant of Spiro- chaeta plicatilis. Cylindrical, spiral-shaped rods, 0.5 by 100 to 200 microns, with blunt ends. A flex- ible, elastic, axial filament is present. Mul- tiplication is by transverse fission. The cy- toplasmic spirals take stain. Contain smaller and more irregularly distributed volutin granules than those found in Spiro- chaeta plicatilis. Grows best at low oxygen tension. Optimum temperature, 20° C. Habitat : Sea water. 3. Spirochaeta eurystrepta Zuelzer, 1912. {Spirochaeta plicatilis eurystrepta Zuel- zer, Arch. f. Protistenk., 24, 1912, 17; Zuel- zer, ibid., 51.) eu.ry.strep'ta. Gr. adj. eurys broad; Gr. adj. streptus easily twisted, pliant; M.L. adj. eurystreptus loosely coiled. Probably a subspecies or variant of Spiro- chaeta plicatilis. Cj^lindrical, spiral-shaped rods, 0.5 by 300 microns, with blunt ends. A flexible, elastic, axial filament is present. Spiral am- plitude: more shallow than that of S. plica- tilis. Multiplication is by transverse fission. The cytoplasmic spirals take stain. Cells contain fewer volutin granules than do those of S. plicatilis. 4. Spirochaeta stenostrepla Zuelzer, 1912. (Arch. f. Protistenk., 24, 1912, 16.) ste.no. strep 'ta. Gr. adj. stenus narrow; Gr. adj. streptus easily twisted, pliant; M.L. adj. stenostreptus tightly coiled. Cylindrical, spiral-shaped rods, 0.25 by 20 to 60, occasionally up to 200, microns, with pointed ends. A flexible, elastic, axial filament is present. Spiral amplitude: very narrow with steep windings. Multiplication is by transverse fission. The cytoplasmic spirals take stain. Cells contain fewer gran- ules than do those of Spirochaeta plicatilis. Optimum temperature, 20° C. Habitat: Found in water containing hy- drogen sulfide. 5. Spirochaeta daxensis Cantacuzene, 1910. (Compt. rend. Soc. Biol., Paris, 68, 1910, 75.) dax.en'sis. M.L. adj. daxensis pertaining to Dax; named for Dax, a watering place in France. Large, spiral -shaped cells, 0.5 b}^ 2.5 by 30 to 100 microns, possessing a longitudinal chromatin filament and tapering at the ends. The cells are flattened and exhibit a double series of curls, smaller waves being super- imposed on larger undulations. Optimum temperature, between 44° and 52° C. Source: From water from a hot spring at Dax (52° to 56° C). Habitat: Found in hot springs. Genus II. Saprospira Gross, 1911. (Mittheil. Zool. Stat, zu Neapel, 20, 1911, 190.) Sap.ro.spi'ra. Gr. adj. saprus rotten, putrid; Gr. noun spira a spiral; M.L. fem.n. Sapro- spira rot -spiral. Cells contain spiral protoplasm without an evident axial filament; transverse markings or septa (?) are observed in stained and unstained specimens. Possess a distinct periplast membrane. The spirals are rather shallow. Motility is active and rotating. Found free-living in marine ooze. The type species is Saprospira grandis Gross.
