o42 



.DESCRIPTION OF SPECIES. 



numerous strongly refractive gran- 

 ules consisting of sulphur. They 

 occur as greyish or chalk- white 

 gelatinous threads, 3 to 3 '5 /* 

 thick, in sulphur springs and 

 marshes. 



Beggiatqa mirabilis (Cohn). 

 Threads distinguished by their 

 breadth, which may reach 30 p. 

 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 



t>Hf Z P1 ?\ S 1 CE88I Y* CHANGES IN THE SAME THREAD, 

 thread form ; b, 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 r oseo-p e r s i c i n a 

 {Co/mm roseo-perttdna. Bacterium 

 rubescens, or Peach-coloured bac- 

 tfirtum, Lankester). Cocci, rods, 

 spirals, and threads (Fig. 216). The 

 occi, globular or oval, reach 2-5 /* 

 an diam. They form at first solid 



distinguished from other red pig- 

 ments, and it is designated by the 

 name bacterio-purpurin. It is quite 

 distinct from the pigment produced 

 by Micrococcus prodigiosus, being 

 peach-blossom red, and insoluble 

 m 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 



