CHAPTER VIII. 



RHODO-THIOBACTERIA (COLOURED SULPHUR 

 BACTERIA). 



Family i. Lankesteracecs. Genus i. Lankesteron. 



Family 2. Chromatiacece. Genus i. Chromalium; Genus 2. Thioporphyra. 



Family i. — Lankesterace^e. 



Literature. — Lankcster (i), 1873, and (2) 1876; Warming 

 1876 ; Zopf (l), 1882 ; Ellis (ll), 1929. 



A family of highly pleomorphic species which may be 

 filamentous, globular, ellipsoidal-cylindrical, or spiral. The 

 organisms enter the zoogloea condition in any of these phases. 

 May be motile or non-motile. One genus, Lankesteron. 



Proof of the occurrence of pleomorphism in the sulphur 

 bacteria was submitted in Chap. L If the facts there given 

 are accepted, the three organisms, Bacterium ruhescens de- 

 scribed by Ray Lankester, Bacterium sidfuratiim described by 

 Warming, and Beggiatoa roseo-persicina described by Zopf, must 

 be accepted as highly pleomorphic species. Hitherto each has 

 been regarded as a mixture of species, and so has not found a 

 place in existing classifications. The three organisms show a 

 sufficient resemblance to justify their inclusion in the same 

 genus. 



The names Bacterium and Beggiatoa are obviously un- 

 suitable. The former has already two meanings in bacterio- 

 logical literature, and the term Beggiatoa is already in use to 

 indicate a genus in which Beggiatoa roseo-persicina would be 

 unsuitably placed. The term Lankesteron is suggested as a 

 generic name for the inclusion of these species, and from it we 

 derive the family name of Lankester acece. 



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