CLASSIFICATION OF BACTERIA 103 



chemists, brewers, etc. Until recently no attempt at uni- 

 formity has been made. Obviously, any effort at the cor- 

 relation of the various proposed classifications in a book of 

 this scope would be impossible. Therefore the aim will be 

 to present for due consideration only one classification 

 which will give the clearest idea of the characteristics of the 

 bacteria. As our definite knowledge of the bacteria in- 

 crease these classifications must necessarily be modified. 



It is an established fact that the form, shape, and manner 

 of growth of a definite bacterium may be temporarily modified 

 by the environment which surrounds the organism. The idea 

 that new and well-defined species may be produced by modifi- 

 cations of the environment was held formerly by some bacteri- 

 ologists. This was the theory of pleomorphism. It has since 

 been proved that the organism which has apparently assumed 

 a new form will return to its original shape when placed in the 

 requisite environment. It was also held for some time rather 

 tenaciously that bacteria had the power of assuming new 

 physiological functions. To this power the term pleogeny 

 was applied. It has been found in this case, as in the 

 former, that the bacterial cell will return to normal when a 

 normal environment is provided (see Chap. III). 



There is no doubt but that the last classification of Migula is 

 as accurate and systematic as has been made. This classifica- 

 tion has been adopted by the leading American bacteriologists. 

 It seems advantageous, however, to make a slight rearrange- 

 ment of the classification. A division can be made for suffi- 



