BACTERIAL CLASSIFICATION 23 



of characters, the whole forming a more or less 

 linear series from such strict parasites as the diplococci 

 and certain streptococci to the vigorous saprophytic rho- 

 dococci. Within each genus several distinct species can 

 be denned by separate type centers of variation in single 

 properties. If our conclusions are justified, the arrange- 

 ment approaches a natural phylogenetic one. 



It is interesting to notice that particular tendencies 

 seem to lie latent in cocci of all the main groups. Thus 

 the property of liquefying gelatin appears to some extent 

 in each of the six genera mentioned, altho it is rare 

 in Streptococcus and very feeble in Rhodococcus. The 

 power of reducing nitrates is lacking in most strains of 

 each genus (except Rhodococcus)] but in each genus 

 except Streptococcus some cultures show reduction. 

 Zooglea and capsule formation too, altho appearing most 

 markedly in the genus Diplococcus and among the 

 Ascococcus forms of the sugar refineries, crop out in one 

 species of Albococcus and in rare strains of Sarcina. 

 Many of these properties are apparently latent in bac- 

 teria of widely separated groups outside the Coccaceae. 

 Thus Molisch (1907) finds zooglea formation and the 

 sarcina grouping, as well as the fundamental bacterial 

 forms of cocci, bacilli, and spirilla, among the purple 

 bacteria, whose peculiar pigment and characteristic 

 physiology and distribution mark them off as a sepa- 

 rate order. 



It was the success of biometrical methods as applied 



