GENERAL SYSTEMATIC BACTERIOLOGY 235 



Trichomati simplicia, tenuissima, hyalina, muco involuta (non-vaginata), 

 libera, solitaria vel aggregata, rigida, oscillantia cytioplasma pallidissime albi- 

 dum (subachromaticum), punctis asterisciformibus, primum in fascias dispositis, 

 deinde inordinates, notatum. 



Seven species are listed. 



Cohn (1875, p. 173) included this genus in the tribe Nematogenae 

 with the description: "Zellen in Faden geordnet, ZelKaden stets un- 

 verzweigt, frei oder verfilzt, faden cylindrisch,farblos,undeutlich geglie- 

 dert, starker, lang." Cohn also noted the presence of sulphur granules 

 in the cells. 



Luerssen (1879, p. 24) differentiates this genus from Bacillus b}^ the 

 relatively large, long, more or less definitely jointed filaments, more or 

 less filled with dark granules, resembling in many ways Oscillaria among 

 the Cyanophyceae, and showing a similar oscillating movement, forming 

 slimy masses in sulphur springs, etc. 



Trevisan (1879, p. 138) includes this in his subtribe Euvibrionieae, 

 with the following description: "Somatia cylindrica, plus minus dis- 

 tincte articulata valida, elongata, filiformia, recta, laxe aggregate." 

 Six species are described. 



The genus is included among the bacteria by several writers before 

 1888, including Magnin (1879), Winter (1880, p. 57), Van Tieghem (1884, 

 p. 1114), Grove (1884, p. 36), Zopf (1885, p. 95), and Fliigge (1886, p. 

 396). Hansgirg (1888, p. 263) included this as the only genus of his 

 subfamily Beggiatoeae. He divided the genus into two subgenera 

 Eubeggiatoa and Chromobeggiatoa. 



Winogradsky (1888, p. 17) as a result of his study of the sulphur bac- 

 teria made the generic diagnosis somewhat clearer. Previous descrip- 

 tions were not all in harmony. He described the genus as made up of 

 exclusively colorless, sheathless, always freely motile filaments never 

 attached to a substratum. The filaments are quite variable in thick- 

 ness, they show a uniform intercalary growth, and have no differentia- 

 tion between base and tip. Under normal growing conditions they 

 always contain sulphur granules in quantities varying with the condi- 

 tions. These granules appear in the form of round oily drops, which 

 consist of a semi-fluid or soft sulphur; crystals of sulphur are never ob- 

 served in the living filament. The definite jointing of the filaments 

 can be seen in cells full of sulphur only after the sulphur has been dis- 

 solved out. The differentiation of good species on the basis of siza 

 Winogradsky considers to be difficult. 



