Bacterium. 85 



95. B. aceti (Kiitzing), Zopf. 



Possesses (i) coccus forms, (2) short rods, (3) long rods, 

 (4) leptothrix threads; all four can form a zoogloea, the 

 two first also form^ swarms. It is characteristic that the 

 longer rods and threads 

 are not always cylindrical, O Q O 

 but often provided with 

 irregular swellings. Such <==> 

 forms have a rather thick- c;: ^^ :: ^"~!^O c - :i c ' 00 

 ened membrane, and a Fig. 7 ^. Bacterium aceti (after Zopf). 

 grey colour. (Fig. 74.) 



Has the power of oxidising alcohol into acetic acid. 



96. B. rubescens, Lankester (Quart. Jour. Micr. ,/., 



1873, p. 408, pi. 22, 23). 



Includes a series of forms, motile and immotile, which 

 resemble one another in the possession of a common 

 peach-coloured colouring matter, " bacterio-purpurin," which 

 sometimes becomes reddish-brown. The author observed 

 coccus, bacterioid, bacillar, acicular, and spiral forms, in 

 various modes of combination. 



In a fresh-water aquarium in which crayfish (Astacus) 

 were decaying. 



Cohn considers that Monas Okenii (q.v.), which is the form re- 

 presented by Lankester (I.e., pi. 23, figs. 12, 20), does not belong to 

 this life-cycle, and that the other forms belong to Cohnia roseo-persicina ; 

 this is now named by Zopf Beggiatoa roseo-persicina, because it possesses 

 a Beggiatoa phase, which is mentioned by Lankester himself in his 

 second article (I.e., 1876, p. 283). Archer also unwittingly records the 

 Eeggiatoa phase in the same journal. Geddes and Ewart describe 

 ("On the Life-History of Spirillum," Proc. Roy. Soc., xxvii., 1878, p. 

 481) a madder-brown growth, which is evidently identical with Lan- 

 kester's, and in which they have observed and figured the Beggiatoa 

 phase, without perceiving its true significance, and mistaking also the 

 sulphur granules for " spores." Mixed with this was a Spirillum, 



