MORPHOLOGIC VARIATION OF BACTERIA 7 



in its life cycle of development the one-celled stage, the egg, so the 

 bacteria are derived from and return to the elementary unit, the 

 mychit. Each complete life cycle begins with the fusion of two hap- 

 loid mychits, goes through progressive changes in cell complexity, 

 reaches a maximum fixed for the species, and returns again to the 

 haploid mychit. But cycles may be incomplete, shortened, or com- 

 pletely arrested. The progressive development may be completely 

 eliminated and only the multiplicative may occur, and this condition, 

 "mochlosis," is usually the case when bacteria are maintained in a 

 uniform environment as is true when artificially cultivated in the 

 laboratory. 



Space will not permit of a more complete review of this remark- 

 able work, but enough has been given to indicate that, while the 

 whole thing sounds like a strangely complex product of the imagina- 

 tion, the hypothesis is a very orderly and systematic one compared with 

 the rather vague and confused ideas of Almquist, Lohnis, Mellon, 

 and Hort. 



The work of Bergstrand should be noted here, though it should 

 not be considered in the same class with that of the authors pre- 

 viously mentioned, since he does not draw such radical conclusions. 

 From a very extensive and careful study of morphologic variations 

 of a diphtheroid organism (1919), he concludes that morphologic 

 variations of bacteria are much more extensive than is generally be- 

 lieved, and is opposed to the idea that all variations from the normal 

 are to be considered involution or degeneration forms. Bacteria may 

 reproduce by budding or by abstriction. The pleomorphism of 

 bacteria may probably be explained by the fact that they are fungi 

 which may form mycelium. He considers the large globular forms 

 produced by some bacteria, identified as sexual forms by Mellon 

 and Almquist, as resting cells analogous to or identical with the 

 chlamydospores of higher fungi (1923). He finds no evidence of 

 sexual spore formation (1923) or of a nucleus (1921). 



Bergstrand does not go nearly so far as the others, but is satisfied 

 to emphasize the extent of the variation which occurs and the im- 

 portance of the problem. The reader will bear in mind, therefore, 

 that most of the criticism which follows does not apply to his work. 



Notice should also be taken of the papers of Fuhrmann on the 



