RECENT RESEARCHES INTO THE HISTORY OF BACTERIA. 269 



stated in the account of Cohn's earlier paper, has asserted the 

 occurrence of one flagelkim in B. termo^) ; and if this be the 

 case, the Monads here described differ from them merely in 

 their size. But on the other hand, certain Bacteria have very 

 evident relationship with the Oscillarice and Spirulince, which 

 certainly do not move by the aid of ilagella. 



13. The highly refractive granules, already noticed in so 

 many forms, and which are to be found even in the un- 

 coloured Bacteria, are best known and most interesting in 

 the genus Beggiatoa, specimens of which are to be found in 

 every sulphur spring, as well as foul ditches, or other pieces 

 of water containing a large quantity of organic matter. 



14. This last Alga seems, indeed, to be the cause of the 

 production of sulphuretted hydrogen, in the water in which 

 it is found. 



15. The two following sections on the separation of sul- 

 phur are of the very highest interest. On the fertile water 

 received from Dr. Warming, Cohn observed a chalky 

 scum, which was seen, by the aid of the microscope, to con- 

 sist of small highly refracting granules, which did not 

 effervesce on the addition of dilute acids ; thinking, fairly 

 enough, that this was due to the formation of sulphates, he 

 applied other tests, which convinced him that he had to do 

 with pure sulphur. 



The formation of sulphur evidently depends on (1) the 

 presence of a large quantity of sulphates in the water ; and 

 (2) on the absence of iron salts, which would cause the for- 

 mation of ferrous sulphide. Now arises the question, is the 

 formation of free sulphuretted hydrogen due to decaying or 

 to living organisms ? Although unable fully to resolve the 

 question Cohn thinks the living organisms are the chief 

 agents in the matter ; for, in the first place, three species of 

 Beggiatoa, one of which {B. alba) is found in hot sulphur 

 springs, have been observed in such water, and the red- 

 coloured organisms, already spoken of, seem to be not inno- 

 cent ; for they, like Beggiatoa, appear to increase under such 

 conditions of impurity as would be fatal to all other or- 

 ganisms. 



And, further, Morren, Fontan and Joly, and Menighini, 

 have observed red or peach-coloured forms in sulphur springs. 

 If this supposition, that such organisms can sustain life, in 

 water full of free sulphuretted hydrogen, and consequently 

 greatly wanting in free oxygen, be correct, we have to do 



* loc. cit., p. 158. 



^ Meyer : 'Journal fiir Prakt. Chemie,' xci, ], Hedwigia, 1865, No. 6, 

 p. 81, &c. 



