CHAPTER VII. 



LEUCO-THIOBACTERIA (COLOURLESS 

 SULPHUR BACTERL\). 



Family 2. AchromatiacecB. Genus i. Achromatium ; Genus 2. Thiophysa : 



Genus 3. ThiosphcBrella ; Genus 4. Thiovulum. 

 Family 3. Thiospirillacecs. Genus i. Thiospirillum. 

 Family 4. Thiobacillacecs. Genus i. Thiobacillus ; Genus 2. Thio- 



pseudonionas. 



Family 2. — Achromatiacem. 



Free, motile, and usually spherical or globoid. In one 

 genus [Thiovuhmi) cilia have been demonstrated. Reproduc- 

 tion by fission ; and in one genus by zoospores. 



Genus i. — Achromatium (Schewiakoff), 1893. 



Literature. — Warming, 1876; Schewiakoff, 1893; Frenzel, 

 1897; Lauterborn (i), 1898, and (6), 1913; Massart, 

 1902 ; Zacharias (2), 1903 ; "West and Griffiths 

 (i), 1912, and (2), 1913 ; Kolkwitz (3), 1909 ; Virieux 

 (i), 1912, and (2), 1913. 



Free, motile, and spherical, or spheroidal or cylindrical- 

 elliptical. Reproduction by fission and by zoospores. 



Achromatium oxaliferum (Schewiakoff), 1893. 

 Literature. — See above. 



Habitat. — Widely distributed in most European countries, 

 and probably outside Europe. 



Description. — The cell is ellipsoidal and normally appears 

 full of dark spherical bodies, as shown in Fig. 14A. The 

 movement is very slow, and consists, usually, of a forward or 



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