CLASSIFICATION AND DESCKIPTION OF SPECIES. 481 



Zopf, however, does not assert that all the fission-fungi exhibit 

 this pleomorphism, nor does he pretend that his classification will 

 include all the micro-organisms described. Cohn, on the other 

 hand, was ready to admit that all the forms described by him were 

 not truly independent species. De Bary, Hueppe, Baumgarten, and 

 Fliigge have expressed other \iews with regard to the classification 

 of bacteria. 



De Bary divides them into two great groups — bacteria which 

 form endospores, and bacteria which form arthrospores. This 

 affords but little practical assistance, though regarded by 

 botanists, from a scientific standpoint, as a step in the right 

 direction. 



Hueppe, acknowledging that the fructification must eventually 

 be made the basis for classification, suggests an arrangement for 

 provisional use in which this view is introduced (p. 482). 



It has already been mentioned that the production of arthrospores 

 is only established in a very few species. Therefore, we are 

 hardly justified in assuming that all bacteria, the spore-formation 

 of which is quite unknown, are to be included with those in which 

 this kind of fructification has been observed, and consequently to 

 distinguish genera on the same grounds may be considered, to say 

 the least, somewhat premature. In Baumgarten's classification the 

 genus bacterium is dispensed with, and the genera divided into two 

 groups, the monomorphic and the pleomorphic. 



Group I.— Monomorphic. 



Genera. — Coccus. 

 Bacillus. 

 Spirillum. 



Group II.— Pleomorphic. 



Genera. — Spirulina. 

 Leptothrix. 

 Cladothrix. 



Fliigge also, in his revised classification, includes the genus 

 bacterium in the genus bacillus. The new classification differs 

 also from the original one in the grouping together of the different 

 species according to the character and behaviour of the colonies 

 in nutrient gelatine. The abolition, in FlUgge's and Baumgarten's 

 classification, of the genus bacterium is no doubt owing to confusion 

 having arisen from the distinction, between a bacterium and a 

 bacillus, being made to depend upon length. Observers differed 

 as to whether a rod of a certain length ought to be considered a 



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