THEIR MORPHOLOGY. 



'45 



This unproved pleoinorphism we declined to recognise at the time, 

 but must now revert to it in order to append the remark that, 

 though we are not indebted to the last-named worker for any 

 revelations regarding the morphology of these 

 organisms, we have to thank him for an ex- 

 haustive study of their colouring matter, which 

 he termed bacterio-purpurin. A form similar 

 to Chromatium Okenii was discovered by E. 

 WARMING (I.) on the coast of Seeland and 

 afterwards examined by Cohn, and by him 

 entitled Monas Warmingii (Fig. 35), so that 

 Perty's proposition with respect to the generic 

 name Chromatium seems not to have been 

 accepted by the Breslau bacteriologist. Whilst 

 the species hitherto mentioned differ among Magn> 6oo . (AfterCohn.) 

 themselves in point of size, but not appreci- 

 ably in form, and all more or less correspond with the plump, short 

 rods shown in the drawing, a second group of similar species exhibits 

 the spirillum form of growth. One example of this is afforded by 



FIG. 35- 

 Monas Warmingii. 



FIG. 36. 



Spirillum volutans. 

 Magn. 600. (After F. Cohn.) 



FIG. 37. 



Ophidomonas sanguinea. 

 Magn. 600. (After F. Cohn.) 



FIG. 38. 



Rhabdomonas rosea. 

 Magn. 600. (After F. Cohn.) 



Spirillum rubrum (Fig. VI. Plate I.), a second being the Spirillum 

 volutans, shown in Fig. 36, and a third the Ophidomonas (Fig. 37), 

 described by Ehrenberg. A third sub-group finally comprises 

 organisms of elongated spindle form, and therefore resembling a 

 whetstone in outline ; e.g. Rhabdomonas rosea (Fig. 38) 4-5 ft 

 wide and 20-30 /A long first observed and described by Cohn. 

 These organisms are not infrequently to be found in ponds and 

 lakes ; sometimes being so abundant as to colour the water red. 

 A series of observations respecting such occurrences was made by 

 CHARLES MORREN (I.). 



VOL. I. 



