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 zooglcea, the 

 two first also form swarms. It is characteristic that the 

 longer rods and threads 



are not always cylindrical, ^o°a c.%,<5, oooo«o=a„^oo 

 but often provided with ° '^ 



irregular swellings. Such 

 forms have a rather thick- ^^~^~-^^^;:ri~;XO '--' '^— ' °°°° 

 ened membrane, and a '£\^.^^.-Bacuri^imacei^ {,3.11^ Zo^i). 

 grey colour. (Fig. 74.) 



Has the power of oxidising alcohol into acetic acid. 



96. B. rubescens, Lankester {Quart. Jour. Micr. Set., 

 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 

 Beggiatoa phase in the same journal. Geddes and Ewart describe 

 ("On the Life- History of Spirillum," Proe. Roy. Soe., 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, 



