64 FRED W. TANNER 



to the varied character of water bacteria, for the environment 

 of a water determines its bacterial content, and consequently a 

 water flowing from an unpolluted drainage basin will have a 

 different flora from that of a stream which carries the wastes of 

 domestic and industrial life. 



With the exception of some ten bacteria or groups of bacteria, 

 whose presence is supposed to indicate pollution in water, the 

 large number of other bacteria which are present are almost 

 unknown. Information in regard to them would often favor 

 more accurate opinions with regard to quality, and more definite 

 information with regard to the source of water. Certain 

 bacterial standards have been formulated which state that there 

 must not be over 100 bacteria per cubic centimeter in a filter 

 effluent. The character of those bacteria which are present in 

 effluents having a greater number would for instance be impor- 

 tant in making deductions with regard to the efficiency of the 

 filters. 



The group arrangement has been used for some time in treat- 

 ing the flora of a substance like water. Wyatt Johnston (1894) 

 early called attention to this method. He discussed in his paper 

 the tests which should be used to separate bacteria; and thought 

 that a single strongly marked characteristic was more impor- 

 tant for grouping than a number of minor points. The Amer- 

 ican Public Health Association later appointed a committee 

 (1898) to work out uniform methods for the description of bac- 

 teria. This is one of the first instances in which the organized 

 efforts of a society were brought to bear in systematizing meth- 

 ods for the study of bacteria. 



Ward (1897) studied the flora of the Thames River and ar- 

 ranged the forms which he isolated in 21 groups, 2 of which 

 are made up of fluorescent bacteria. The separation was often 

 made on very unimportant characteristics. Ward realized this 

 and stated that his work indicated wider limits of the term spe- 

 cies than are ordinarily assumed. Fuller and Johnson (1899) in 

 studying the flora of river water made an important contribution 

 to water bacteriology. They divided water bacteria into 13 

 groups, and used some prominent character for the separation 



