100 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



recognized; cultivation has been fraught with difficulties which have at 

 times been in some way associated with the change in form or in a sense 

 connected with " involution" alterations; cultural characteristics have 

 likewise been subject to variations which have depended upon the 

 so-called vigor of the organism; and classification of bacteria may be 

 materially affected since some of the cycles approach closely those of 

 protozoa. 



Perhaps the most significant changes upon which the life-cycle of 

 bacteria is based may be those represented by Jones,* and Lohnis and 

 Smith in the life of A zotobacter-types. The polymorphous character of the 



FIG. 78. Change of Azotobacter from the normal cells (I) to arthrospores (II) 

 and involution forms (III) to be lost in symplastic stage (IV) and recovering cell- 

 form in V. Diagrammatic iroptf Lohnis and Smith. 



Azotobacter group has been a matter of intense interest for a long period. 

 Lohnis and Smith have not only endeavored to follow the variations 

 through a consistent historical developmental cycle but have attempted 

 to organize their observations and have them in accord with past 

 observations. 



The organism may be assumed to exist in the form of a distinct cell 

 and at other times in an amorphous condition called by the authors, the 

 symplastic stage. In the usual cell-form the organism may multiply 

 by fission as is. the case with all bacteria, may produce endospores 



*Jones, D. H. : Cent. f. Bact.; Trans. Royal Society of Canada, 1913. 



