CONTENTS. 



CHAPTER I. 



PAGE 



Introduction .......... i 



Connotation of the term " Sulphur Bacteria " ; geographical 

 distribution ; the sulphur cycle in nature ; methods of investi- 

 gation ; pleomorphism ; evidence of occurrence of pleomor- 

 phism in the sulphur bacteria. 



CHAPTER II. 



The Production of Sulphuretted Hydrogen and its Assimila- 

 tion BY THE Sulphur Bacteria ...... 20 



Natural sources of sulphuretted hydrogen ; the limans ; investiga- 

 tion of the black sand on the Clyde ; the equilibrium of 

 hydrogen sulphide in water. 



CHAPTER III. 

 The Metabolism of the Sulphur Bacteria .... 34 

 Food requirements and sources of energy; metabolism, fermenta- 

 tion and respiration ; sulphuretted hydrogen ; organic matter ; 

 carbon supply ; oxygen ; mineral matters ; hydrogen-ion 

 concentration ; biological explanation of the assimilation of 

 sulphuretted hydrogen ; the denitrifying sulphur bacteria ; 

 physico-chemical speculations. 



CHAPTER IV. 



The Culture of the Sulphur Bacteria . . . . -55 



Methods of culture ; methods of Winogradsky, Molisch, Keil, 

 Jegunow, Skene, Bavendamm, and Ellis. 



CHAPTER V. 



The Principles of Classification and their Application to the 



Sulphur Bacteria . ....... 67 



The principles of a natural classification ; review of attributes 

 used in the subdivision of the sulphur bacteria ; review of 

 previous classifications : by Winogradsky, by Molisch, bv 

 Orla Jensen, by Buchanan ; Ellis's classification. 



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