94 FRED W. TANNER 



Twenty-seven groups are thus secured, many of which are 

 separated by but one characteristic from those closely related 

 to them. With the group number as it now stands, it is possible 

 to obtain 276,480 different types of bacteria. 



Diagram III presents a brief characterization of the action 

 of these cultures on some of the more important substances. 

 Such a diagram was first used by Rogers and Clark (1912). 



Neglecting nitrate reduction and gelatin liquefaction as vari- 

 able characters of little value for classification, the following 

 nine groups are obtained: 



Strains 



22± . 233± 133 49 



22± . 223± 133 15 



22± . 222=fc 133 " 14 



22± . 233± 132^ 7 



22± . 222± 132 5 



12± . 233± 133 4 



22± . 232± 132 3 



22± . 223± 132 1 



22=t . 232± 133 2 



Inspection of the above numbers indicates a very close rela- 

 tionship. Barring the four spore formers, there is an apparent 

 intergrading of characters. Were all of the strains strictly con- 

 sidered as non-fermenters of lactose and sucrose, as might be 

 inferred from Diagram II, the number of groups would be further 

 reduced to five. They might be regarded as falling into two 

 groups with regard to glycerol, and this characteristic might be 

 regarded as a basis for separation. 



DISCUSSION OF RESULTS 



A comparative study of 100 strains of fluorescent bacteria 

 from water by means of the group number system as expressed 

 on the descriptive chart of the Society of American Bacteriolo- 

 gists, 1912, places them in 27 groups. Twelve of these are made 

 up of but one strain and are separated from the adjacent groups 

 by but one characteristic. If gelatin liquefaction and nitrate 

 reduction are excluded as variable characteristics for classifica- 

 tion purposes, as has been suggested by different investigators, 



