14 Biological Relation Between Bacteria and the More 



genus, Cladothrix. These organisms are widely distrib- 

 uted, and are found both in salt and fresh water containing 

 decomposing animal or vegetable material ; in sulphurous 

 waters the beggiatoa are especially abundant and accumu- 

 late upon the muddy bottom, or upon organic substances 

 undergoing decomposition. They cover the bottom of 

 ponds or of small bays, forming different colored layers of 

 an extended and abundant growth. These organisms are 

 found plentifully in the refuse waters of sugar refineries 

 and upon the surface of putrefying vegetable and animal 

 material, in fresh or salt waters. The cladothrix dicho- 

 mata is frequently associated with the beggiatoa and is 

 common in the refuse water of factories, especially sugar 

 factories. It may readily be obtained from the surface of 

 putrefying algae or animal substances immersed in river 

 or swamp water. 



As far as can be determined with the limited experi- 

 mental evidence at hand, it appears evident that the first 

 stage of the reduction and solution of vegetable and animal 

 organic matters in running streams is traceable to the single 

 or combined action of the crenothrix, beggiatoa and cla- 

 dothrix. After these organisms have in part broken up 

 the organic matters, with the assistance of the lower forms 

 of animal life also present in the water, the subsequent 

 stages in the operation are traceable to the action of a 

 species of bacteria of which the nitronomas of Wino- 

 gradsky and the nitrifying bacillus of Winogradsky are, 

 perhaps, the best-known members. These organisms in 

 turn attack the products of decomposition produced by 

 the beggiatoa and cladothrix, and convert them into nitric 

 acid. These nitrifying bacteria, as they are called, are 

 the principal agents concerned in the reduction of organic 

 matter and its conversion back into inorganic matter. 

 They are the active agents upon which the efficiency of 

 sand-filtration in the purification of water supplies and of 

 sewage is dependent. These organisms form a slimy layer 



