CELL-DIVISION 



25 



readily seen that the division of these cells is exactly the same as for 

 Sarcina except that division-walls are in two instead of in three planes. 

 The process is similar vi^hen Streptococci are in process of formation. 

 In this case chains of cells are produced. 



3. Cell-division in the Spirillaceae. In this order the method of 

 cell-division is essentially different from that followed by the Bacteria- 

 ceae and Coccaceae. It has been observed in Spirillum giganteum, 

 which on account of its large size is admirably suited for the 

 purpose. The normal undivided cell is represented in Fig. 39a, the 



Fig, 39.— Mode of division in spiral cells. 



globular contents being reserve materials composed of fat-globules, 

 and volutin. In the first stage of cell-division, the reserve materials 

 are seen to be wanting in a certain area in the middle, which area 

 marks the spot where cell-division is about to take place. 



When stained so that the wall is shown, it is found that in it, as yet, 

 no change has taken place (Fig. 39J). In a slightly more advanced 

 condition, the reserve materials are seen to have so arranged themselves 

 that the separation-area is, roughly, like a broad, double, concave lens 

 in appearance (Fig. 39c), and when this stage is examined after staining, 

 the wall is found to be still unchanged (Fig. SQc^). In the next, and 

 following stages, constriction of the separation-area takes place, with 

 the result that the connection between the two halves gets smaller and 



