542 



DESCRIPTION OF SPECIES. 



numerous strongly refractive gran- 

 ules consisting of sulphur. They 

 occur as greyish or chalk-white 

 gelatinous threads, 3 to 3-6 fi 

 thick, in sulphur springs and 

 marshes. 



Beggiatoa miraMlis (Cohn). — 

 Threads distinguished by their 

 breadth, which may reach 30 /i. 

 They are motile, bent and curled 

 in various ways, and rounded at 

 the ends. Around 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 ju, 

 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 



, ':. 





v^^iS 







■.4r. 



Tig. 214. — Bacterium Zopfii. , Successive Changes in the same Thread, 

 : X 740. a, A thread form ; 5, breaking up into rod forms ; c, into cocci (Kurth). 



macrococci, but spiral forms are as 

 yet unknown. The threads are 

 illed with sulphur granules. They 

 occur in sea-water, forming a white 

 gelatinous scum on decomposing 



Beggiatoa roseo-persicina 



(^Cohnia roseo-persiciiia. Bacterium 

 ruhescens, or Peach-coloured hac- 

 ierium, Lankester). — Cocci, rods, 

 spirals, and threads (Fig. 216). The 

 cocci, globular or oval, reach 25 fi 

 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 



