The Microbe as a Whole 9 



posed of a cell wall, cytoplasmic membrane, cytoplasm, and 

 nucleus constitute a sound basis for considering bacterial 

 cells on a par with the cells of higher organisms. Of great 

 promise also are the current investigations on cytological 

 aspects, such as the discovery by WeibuU that Bacillus 

 megaterium, stripped of its cell wall, retains its organiza- 

 tion inside the membrane under appropriate conditions, 

 as well as many of its metabolic properties, although at- 

 tempts to grow such incomplete cells have so far failed. 

 In this connection a comparison with bacteria like the 

 cytophagas, which presumably do not form a cell wall and 

 yet can grow and divide normally, suggests itself as an 

 interesting problem. 



Similarly, the finding that the cytochromes of some bac- 

 terial cells are intimately associated with the cytoplasmic 

 membrane, and that the pigments of the blue-green algae 

 and photosynthetic bacteria are not, as previously believed, 

 uniformly distributed in the cytoplasm but assembled in 

 chromatophore-like structures, gives evidence of enzymatic 

 organization. It may be expected that further studies of 

 this sort will rapidly advance our knowledge. 



The isolation of bacterial flagella, with the subsequent 

 elucidation of their chemical nature as proteins of the 

 myosin group, holds out hope for a better understanding 

 of the mechanism that causes these "monomolecular hairs" 

 to function as organs of locomotion. Besides, the recent 

 work of Clayton shows that phototaxis of purple bacteria 

 displays the typical characteristics of sensory perception, 

 viz., the all-or-none response, accommodation, and refrac- 

 tory period, and that the concepts and equations developed 

 by A. V. Hill and Rashevski to account for sensory stimu- 

 lation are equally satisfactory as formal expressions of 

 phototactic behavior. 



This suggests that flagellar movements are under the 

 control of mechanisms analogous to those operative in 

 sensory perception in general, and that further studies on 



