54 MICRO-ORGANISMS AND FERMENTATION. 



appear only very faintly coloured. It has not yet been 

 determined with certainty in what part of the organism the 

 colouring-matter is situated. Some species of bacteria are 

 phosphorescent under certain nutritive conditions. 



A remarkable property of many bacteria is their at least 

 apparent free locomotion. This is either quick or slow, the 

 bacteria rotating about their longitudinal axes, assuming the 

 forms of open or contracted spirals. In some of these motile 

 forms we can observe, under high magnifying power, very fine 

 cilia or flagella (Fig. 10 &) ; whether these are to be considered 

 as organs of locomotion is not yet determined, nor has it been 

 decided whether they issue from the membrane or from the 

 cell contents. 



The multiplication of bacteria takes place in different 

 ways. In the main, multiplication by division and by spore- 

 formation in the interior of the cell may be distinguished. 

 The first mode of multiplication has been observed in detail 

 in the larger forms. Fine transverse lines appear, which 

 gradually increase in thickness and become gelatinous ; after 

 this the organism separates at these transverse walls into 

 smaller rods (Fig. 10 <gr). Long before a trace of these 

 transverse walls can be observed, a staining of the organism 

 will show that it consists of a series of segments, each of 

 which corresponds to a subsequently-formed member. The 

 newly-formed segment-cells are all in the same plane. A 

 division in two or three directions of space has only been 

 observed in certain micrococci (Sarcina). 



It was proved by the investigation of the shapes of 

 bacteria in the above-mentioned manner (especially by Zopf), 

 that the same species of bacterium can occur in very different 

 forms, e.g., as spirillum, leptothrix, bacillus, bacterium, 

 and coccus ; and we thus obtained the important addition to 

 our knowledge of the history of these plants that the names 

 quoted very often only express growth forms of the same 

 species, and not distinct species. The following question, 

 however, remains to be answered : Under what conditions 



