542 



PESCRIPTION OF SPECIES. 



numerous strongly refractive gran- 

 ules consisting of sulphur. They 

 occur as greyish or chalk-white 

 gelatinous threads, 3 to 3 '5 fi 

 "thick, in sulphur springs and 

 marshes. 



Beggiatoa mirabilis (Cohn). — 

 Threads distinguished by their 

 breadth, which may reach 30 /*. 

 They are motile, bent and curled 

 in various ways, and rounded at 

 the ends. Arojund the threads, 

 isolated cells have been observed. 



families, bound together by gela- 

 tinous substance. Later they be- 

 come larger, globular or ovoid in 

 shape, and hollow, containing 

 watery fluid in their interior. The 

 families reach a diameter of 660 fx, 

 in which the cocci form simply a 

 peripheral layer. The hollow fami- 

 lies or vesicles are often perforated, 

 presenting a delicate reticulated ap- 

 pearance, which finally may become 

 broken up into irregular structures. 

 The red colouring-matter can be 



Fig. 214.— Bacterium Zopfii. Successive Changes in the same Thbead, 

 X 740. a, A thread form ; 6, breaking up into rod forms ; c, into cocci (Kurth). 



■macrococci, but spiral forms are as 

 yet unknown. The threads are 

 filled with sulphur granules. They 

 occur in sea-water, forming a white 

 gelatinous scum on decomposing 

 algae. 



Beggiatoa roseo-p ersicina 

 {^Cohnia roseo-persiciiia. Bacterium 

 rubescens, or Peach-coloured bac- 

 terium, Lankester). — Cocci, rods, 

 spirals, and threads (Fig. 216). The 

 cocci, globular or oval,, reach 2'5 /j. 

 in diam. They form at first solid 



distinguished from other red pig- 

 ments, and it is designated by the 

 name hacterio-purpurin. It is quite 

 distinct from the pigment produced 

 by Micrococcus prodigiosus, being 

 peach-blossom red, and insoluble 

 in water, alcohol, etc. Examined 

 spectroscopically, it shows a strong 

 absorption in the yellow, and a 

 weaker band in the green and blue, 

 as well as a darkening in the more 

 refrangible half of the spectrum. 

 In the cocci, especially of the older 



