THE CLASSIFICATION OF MICROBES 111 



(2) Microbacteria or bacteria. 



(3) Desmobacteria or bacilli and vibriones. 



(4) Spirobacteria or spirilla. 



(5) Spirochsetae. 



This classification is founded upon the idea that 

 all the various morphologically or physiologically 

 distinct forms belong to different species. Koch's 

 researches with plate-cultivations have given great 

 support to the classification of Cohn, which, in our 

 opinion, is the best, that is, from the bacteriologist's 

 point of view. In such a classification a micro- 

 coccus produces nothing but a micrococcus, a bacil- 

 lus nothing but a bacillus, and so on. 



Zopf (who is the great apostle of the doctrine of 

 pleomorphism) divides microbes into four groups :* 



(1) Coccacese. 



(2) Bacteriaceae. 



(3) Leptothricheae. 



(4) Cladothrichese. 



The first group contains streptococcus, merismopedia, 

 sarcina, micrococcus, and ascococcus forms ; in fact 

 this group only contains cocci. The second group 

 contains the following genera : Bacterium, Spiril- 

 lum, Vibrio, Leuconostoc, Bacillus, and Clostridium. 

 Most of these forms, according to Zopf, pass through 

 a coccus stage. The third group contains four 

 genera : Crenothrix, Beggiatoa, Phragmidiothrix, 

 and Leptothrix. This group (like the second) is 

 believed to possess coccus, rod, and thread forms. 

 The fourth and last group only contains the genus 

 1 Die Spallpilze, 1885. 



