preparations; flexible rods in the living state; motile by means of a creeping action on solid surfaces possibly Cytophaga p. 858 (See Manual kej^s for the order Myxobacterales) p. 868 Not as above; cells actively motile in free solution 9 9. Cells relatively rigid; motile by means of polar flagella 10 Cells flexible; motile by means of a helicoid flexing action 12 10. Cells oxidize hydrogen sulfide, depositing sulfur as small globules in the center of the cell with volutin granules towards the ends Thiospira p. 82 Not as above 11 11. Cells consisting of a single complete spiral twist; rather sharply angulated; cells 1.5 to 2.0 microns wide at the center and tapering towards both ends. In the center of the cell is an ovoid to rounded body almost as wide as the cell and clearly visible without staining. It stains deeply with neutral red in killed cells and with Heidenhain's iron- haematoxylin or Giemsa's stain in fixed cells and is considered to be a nucleus; motile by means of polar flagella; when attached to an object at one end, cells are capable of contraction to a more angulated spiral Paraspirilluni p. 257 Note: The author has seen in pond waters several cells very similar morpho- logically to these cells except that the central body appeared pale green and may be a chloroplast. Not as above; spirals quite rigid; movement in liquids of a definite helical type Spirillum p. 253 Note: Several species of vibrios are described as forming spiral chains {V. sputigenus, V. jejuni, V. coli, V. indicus, V. luminosus, V. marinopraesens) . If a vibrio is curved only along one axis, formation of a true spiral is not pos- sible. Cells forming a true spiral when in chains must have the basic helical twist in the axis of the individual cells and should be classified as Spirillum. 12. Cells 20 to 300 microns long and 0.25 to 2.0 microns wide (generally 0.25 to 0.5 micron) with the protoplast wound around a well-defined axial filament; cells very flexible and actively motile; flagella absent; fresh- and salt-water forms Spirochaeta p. 893 Spiral cells, 0.5 to 3.0 microns wide and 10 to 100 microns long, with a spiral amplitude of 6 to 8 microns; flexible cells characterized by a thin membrane or crista on one side of the body which extends the entire length of the cell; cross striations in stained cells are distinct; actively motile without flagella; recorded from the crystalline style sac in the alimentary canal of molluscs Cristispira p. 895 Spiral cells, 0.5 to 1.2 microns wide and 60 to 80 microns long, with a spiral amplitude of 4 to 25 microns; cross striations in stained cells distinct; no axial filament or crista; actively motile but not flagellated; found in oysters and also free living Saprospira p. 894 Not as above 13 13. Not readily stained; stain with Giemsa's stain or by silver impregnation methods; visible unstained under darkground but rarely by ordinary light microscopy 14 Cells stain readily; Gram-negative; cells rarely more than 1 micron wide; spirals fre- quently irregular and of variable amplitude Borrelia p. 897 14. Aerobic; cells 0.1 to 0.2 micron thick; wound in a very fine coil and hooked at one or both ends; can be cultivated in vitro in semi-solid rabbit plasma media Leptospira p. 907 Anaerobic; very fine coiled cells of uniform amplitude; may be pointed at both ends but not hooked Treponema p. 904
