86 THE CYTOLOGY AND LIFE-HISTORY OF BACTERIA 



As already indicated (Chapter IV), the lag phase represents the period of 

 germination of the microcyst. The metabolic activity and nucleotide content 

 o( the resting nucleus are both low, but in the young, vegetative cell both 

 are high. 



If the medium is inoculated, not with cells from an aged culture, but with 

 those already in the active condition, the lag does not occur. The nuclear 

 material is already in the reproductive phase and no delay is entailed. 



B: SIMPLE VEGETATIVE REPRODUCTION 



(i, 2, 3, 7, 13. M, 2S) 



The enormously rapid increase in numbers, which occurs in the logarithmic 

 phase of a bacterial culture, attests to the efficiency of simple fission as a 

 method of reproduction. This rapidity of growth is, of course, due mainly 

 to the small size of bacteria, and the consequent high ratio of cell surface to 

 volume. Rapid colonisation of a new medium is, nevertheless, assisted by 

 the means of reproduction employed. 



The epithet " simple," although habitually employed to describe re- 

 production by fission, is less accurate, as a description, than once it was 

 believed to be. 



Many bacteria arc multicellular. Corynebactcria and mycobacteria arc 

 composed of from one to a dozen small cells ; eubacteria of rough morphology 

 are normally four-celled, and even cocci may contain two, three or four cells. 

 In these circumstances mere cell division docs not provide either increased 

 surface area or wider distribution in the medium unless accompanied by 

 fission of the bacterium. In smooth eubacteria multicellularity is mainly 

 associated with active reproduction, in very young cultures, and is seldom 

 evident in older cultures when it might be expected to be disadvantageous, 

 under conditions of more intense competition tor a diminished supply of 

 nutrients. In rough eubacteria the method of septum formation, and 

 filamentous habit of growth (Chapter III) often produces a considerable 

 degree of multicellularity in young cultures although it may also be less, 

 pronounced in older ones. 



