CHAPTER X. 

 THE GENUS MICROCOCCUS. 



THE name Micrococcus, first used by Hallier, was 

 applied by Cohn to all spherical bacteria (Colin, 1872). 

 The genus has since remained a sort of omnium gatherum, 

 into which all cocci could be put which were not sufficiently 

 characterized for a place in other genera. The strepto- 

 cocci and sarcinae gradually came to be recognized as 

 distinguished by their respective chain and packet group- 

 ings. The flagella-bearing forms were separated in the 

 genera Planococcus and Piano sarcina. Morphological 

 characters did not permit of further progress, and Micro- 

 coccus of Migula (1900) and Chester (1901) is a kind of 

 residual genus, including all cocci which do not occur in 

 well-marked chains or packets and which do not exhibit 

 flagella. 



The classification of the genus Micrococcus as defined 

 by Migula and Chester was naturally a difficult task, since 

 it included such widely different forms as the parasitic 

 diplococci and the saprophytic rhodococci. Migula says, 

 "An arrangement of the individual types of this genus 

 according to their natural relationships is even less possible 

 than in the case of the streptococci. Here, too, we are 

 obliged to rely almost exclusively on uncertain and unre- 

 liable biological characteristics" (Migula, 1900). 



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