THE LEUCO-THIOBACTERIA loi 



that form, or after they have developed further to the rod form 

 (Fig. Jc). Or the cocci may multiply and enter into the zoo- 

 gloea condition (Fig. Je). The last-named condition may be 

 brought about by inoculating material rich in Beggiatoa into 

 a fluid made up of a mass of Spirogyra and Cladophora in a 

 partial state of putrefaction in water. Also Zopf observed a 

 fragment of a filament being cut off from the end, when it 

 assumed a twisted form and swam away (Fig. 7/). He 

 states that he made a direct observation of this occurrence : 

 " Ich beobachtete diesen Faden zufallig einige Zeit, und sah 

 nun wie das spiralige Stiick in ein Hin- und Her-schwanken- 

 gerieth um schliesslich abzubrechen und als starre Spiralige 

 hinweg zu schwimmen." This fact has been doubted, but 

 the author has observed (Ellis (5)) an intercalary cell being 

 detached from a thread of Cladothrix dichotoma, when it 

 swam away in precisely the same manner as the detached 

 fragment of Beggiatoa^ alba observed by Zopf. Finally, Zopf 

 relates that the elongation of cocci and short rods into short 

 filaments is sometimes followed by the assumption of the 

 spiral shape. 



Beggiatoa alba may therefore exist in the coccus, the bacillus, 

 and the spirillum shapes ; and each one of these may enter the 

 zoogloea condition. Further, each kind may be motile or 

 non-motile. The later development of these different forms 

 is unknown, but there is no reason to doubt that, given the 

 proper conditions, they develop once more into the filamentous 

 condition. 



Other Species of Beggiatoa. 



Our knowledge of other species of this genus is somewhat 

 scanty, and even their title to be included in the genus is 

 doubtful. 



Beggiatoa mirabilis (Cohn), 1865. 



Literature. — Cohn (5), 1865 ; Warming, 1875 ; Engler, 

 1883; Butschli (i), 1890 ; Kolkwitz (i), 1897; Flinze 

 (i), 1901, and (2), 1902 ; Kolkwitz (10) 1918 ; Zuelzer, 

 1924 ; Bavendamm, 1924. 



