DIVISION IX THREE DIRECTIONS. 



57 



44. Division in Three Directions. 



Cocci, wherein the reproduction of the cell is effected by 

 division in all the three directions of space, are designated 

 Sarcina. In this case the contents of the mother-cell divide 

 into eight equal parts by the formation of three flat septa, per- 

 pendicular to each other, which subsequently split up into two 

 layers, whereby each of the eight daughter-cells is surrounded on 

 all sides with cell-membrane. 



When these, as they generally do, remain attached together, 

 their appearance resembles a corded 

 bale of goods, or a cubical packet. ffsf* 



C1 T7' VteltS 



See .big. 13. (g 



In the course of reproduction an c 

 initial number of cells represented by 



a will increase by n processes of divi- 



sion to a total of 5 



e = 8"o. = 2 3n a. 



a 



FIG. 13. Sarcina ventriculi. 



From the contents of a diseased 

 stomach, a. individual cell ; 

 b. the same divided in one 

 direction only ; c. the same 

 divided in three directions; 

 d. packet colony of cells. 



The Sarcina maxima, frequently 

 met with in malt mashes, may be 

 cited as an example of this form of 

 growth. A comprehensive classifica- 

 tion and accurate characterisation of 

 all known species of the genus Sarcina 

 has been given by.Tn. GRUBER (I.). 



Subdivision in more than one direction, and therefore the 

 formation of sheet-like or packet-shaped aggregations of daughter - 

 cells, has hitherto been observed solely among iso-diametric and a 

 few thread bacteria. The first group (of coccus form) is consti- 

 tuted by Sarcina. The behaviour, in this connection, of the 

 second group (e.g. Crenothrix) will be subsequently discussed. 



45. Form of the Daughter-Cells. 



Cocci, when observed immediately after their production by 

 subdivision, exhibit a more or less angular outline, since the 

 surface of separation between the mother- and daughter-cell is 

 flat, appearing to the eye as a straight line. This shape, how- 

 ever, very soon undergoes alteration, the cell-membrane being 

 caused to bulge outward by the pressure of the plasma, whereby 

 the plane surfaces are rounded and the cell assumes the customary 

 appearance of the non-facetted coccus. By the same cause the 

 initially plane circular outline of the smaller side of a cylindrical 

 bacillus, newly formed by fission, becomes dome-shaped. 



