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surface of a coccus may well have been the starting-point for the devel- 

 opment of motile rods with peritrichous flagella. As a result of this the 

 representatives of the Gram-negative colon group (in its widest sense) 

 and of the Gram-positive genus Kurthia would have arisen. It lies at 

 hand that the endospore forming rods with peritrichous flagella rep- 

 resent a higher stage of development of these groups. 

 d. The fourth line of morphological evolution of the spherical cells 

 seems to lead via the streptococci to the short Gram-positive rods in 

 the group of lactic acid bacteria and corynebacteria. The further 

 development of these universally immotile bacteria can have given 

 rise to the mycobacteria which apparently form the connecting link 

 with the simpler actinomycetes. 



The various stages of these four independent evolutionary trends are 

 represented in the following diagram (Fig. i, see p. 307). 



It appears appropriate to assign the rank of a family to each one of 

 the four domains described and the names Aiicrococcaceae, Pseudo- 

 monadaceae, Bacteriaceae and Mycobacteriaceae are indicated. 



The various morphological groups distinguished in each family will 

 be designated as tribes. In accordance herewith the following tribes will 

 be recognized: 



Family Tribes 



, Micrococceae 



Micrococcaceae 



Streptococceae 

 Sarcineae 

 Sporosarcineae 

 Pseudomonadeae 

 Pseudomonadaceae { Vibrioneae 



Bacteriact 



Spirilleae 

 Bacterieae 



Bacilleae 



I Corynebacterieae 

 Mycobacteriaceae \ , , , , . 



^ l Mycobacterieae 



Next we have listed the known, well distinguishable types of kata- 

 bolism and so classified the bacteria answering the morphological re- 

 quirements of the tribe according to their characteristic type of kata- 

 bolism. As has already been argued organisms which on the basis 

 of this procedure are collected in one and the same group should 

 together constitute a genus. 



308 



