RHODO^THIOBACTERIA 137 



Forster, 1892 ; Beijerinck (i), 1893 ; Mitrophanow, 

 1893 ; Migula (2), 1895 ; Zopf (3), 1895 ; Ewart, 

 1897; Fischer (3), 1897; Butschli (4), 1902; Nadson 

 (2), 1903 ; Russel, 1909 ; Dangeard (i), 1909 ; 

 Strzeszewski (i), and (2), 191 3 ; Issatchenko (2), 

 1914 ; Buder (2), 1915 ; Lauterborn (7), 1915 ; 

 Metzner, 1920; Potthoff (i), 1921, and (2), 1922; 

 Gicklhorn (2), 1921 ; Bergey, 1923 ; Bavendamm, 

 1924 ; Scourfield, 1925-26 ; Buchanan, 1925 ; Elhs 

 (II), 1929. 



Fig. 24. — Lankesleron riibescens (Lankester), Ellis. 

 Syn. Bacterium riibescens (Lankester). 

 Some of the forms of this organism as found on decomposing caddis 



worms (after Lankester) : — 



a. — A " sphaerous combination of cells forming a dark-coloured irregular 

 zoogloea mass." (So described by Lankester.) 



b. — Acicular and sphaerous forms in attachment to another organism. The 

 extremities of the acicular forms showed oscillatory movements. 



c. — Chains of cocci in filamentous formation. (Zopf records a similar forma- 

 tion resulting from the break-up of a filament into cocci.) This 

 " catenular aggregation," as named by Lankester, probably arose in 

 a similar way. 



d. — Biscuit forms. Described as " loose and gloeoginous." 



e. — Biscuit forms. 



,''. — A globose aggregate of spherical units. 



g. — Irregular forms. 



h. — Reticulate aggregation of ellipsoidal cells. These recall the " Amoebo- 

 bacter " of Winogradsky (see p. 170). 



i. — " Multilocular filament." The dense cell contents in such cases were 

 probably disposed so as to give the impression of a cell divided into 

 several compartments. 



The bright colour imparted to the water in which Chroma- 

 Hum Okenii develops, and the interesting organism itself have 

 long made it a favourite object of study. It is the first to be 

 noticed in a group of different microorganisms on account of 

 its comparative largeness, its motility, and its bright colour. 

 The genus was established by Perty in 1852, although the type 

 organism Chromatiiim Okenii was recorded by Ehrenberg as 

 early as 1838, and named Monas Okenii, under the impression 

 that it belonged to the Monas group of Flagellates. Later, 

 other species were added, differences in size being the chief 



