SUBGROUPS AND GENERA OF THE THIOBACTERIALES 463 



Genus 2. Thiophysa Hinze, 1903, p. 310 



Spherical cells laden with sulphur. The protoplasmic layer 

 surrounds a large central vacuole. Cell nucleus not recognized. 

 Flagella lacking. Cells elongate before division, divide to biscuit 

 shaped cells. Cells 7 to ISfx in diameter. 



The type species Thiophysa volutans Hinze was secured from 

 the Bay of Naples. 



Genus 3. Hillhousia West and Griffiths, 1909, p. 398 



Cells very large, 4.2 to 86 by 20 to SS/j.. motile by means of peri- 

 irichous flagella. Cells packed with large globides of oily amorphous 

 sulphur. 



The type species is Hillhousia mirabilis West and Griffiths. 



Family II. Beggiatoaceae Migula, 1895, p. 41 



Filamentous bacteria, usually showing an oscillating motion sim- 

 ilar to Oscillatoria. Cells contain sulphur granules. Spore forma- 

 tion and conidia unknown. 



The genera of the family Beggiatoaceae may be differentiated 

 by means of the following key: 



Key to the genera of Beggiatoaceae 



A. Filament non-motile, with a contrast to base and tip, attached. 



Genus 1. Thiothrix 



B. Filaments motile (oscillating) not attached, no differentiation into tip and 



base. 



1. Filaments not in bundles nor surrounded by a gelatinous sheath. 



Genus 2, Beggiatoa 



2. Filaments in bundles, surrounded by a gelatinous sheath. 



Genus. 3. Thioploca 



Genus 1. Thiothrix Winogradsky, 1888, p. 39 



Filament non-motile, segmented, a definite differentiation into 

 base and lip, attached, usually filled with sulphur granides. The 

 threads produce rod shaped conidia at their ends. These conidia 

 are self motile by means of a slow creeping motion, attach themselves 

 and develop into new threads. The habitat is hot sulphur springs. 



The type species is Thiothrix nivea. (Rabenhorst) Winog- 

 radsky. 



