CONTKIBUTIOXS TO THE CYTOLOGY OF THE BACTERIA. 421 



characteristic dranb-beil shape (fig-. 40). The long axis of the 

 dumb-bell coincides frequently with the long axis of the cell 

 but it is also often seen to be slightly displaced from this axis 

 — occupying a somewhat oblique position in the cell. The 

 ends of the dumb-bell separate from one another, but remain 

 attached by the slender intermediate strand foi- some time. 

 When the central body has reached this stage, a constriction 

 appears in the middle of the cell in a plane at right angles to 

 the long axis of the dumb-bell figure. The cell now presents 

 the appearance shown in fig. 47 (PI. 17) . A little later the ends 

 of the dumb-bell lose their connection with one another, 

 through the disappearance of the connecting strand. The 

 constriction of the cell wall is now more marked (fig. 48). 

 After the two new central bodies have been formed in this 

 way from the original body, the cytoplasmic constriction 

 becomes complete, and two daughter-cells are formed which 

 lie at first in close contact with one another (fig. 49). In this 

 Diploco ecus-condition the daughter-cells may remain; or 

 they may separate forming two free Micrococci; or they 

 may divide again, and so give rise to a chain of coccus forms. 

 Division always takes place in the manner just described — the 

 central body dividing with the formation of a characteristic 

 dumb-bell figure, and being followed by the fission of the 

 cytoplasm. 



Now I think there can be little cause for complaint if I call 

 the central deepl}" staining body a nucleus. This body is a 

 constant morphological feature of every cell : it divides with 

 the formation of figtires which are closely comparable with 

 those of a vei-y simple amitosis — on a very small scale : and 

 is takes up the nuclear stain strongly. I shall discuss this 

 more fully in a later part of the paper, and will henceforward 

 call the central body the nucleus. 



As I have pointed out above, the dividing nucleus not 

 uncommonly occupies a slightly oblique position in the cell. 

 It also shows occasionally another modification, which is of 

 the greatest interest — a modification which is characterised 

 by the dividing nucleus assuming the form of a zig-zag 



