DIVISION IN TWO AND IN TIIKKK IMKIXTIONS 43 



direction only, the number of mother- and daughter-cells is always equal ; the 

 total number (e) of cells obtained from the initial cell (a) at the end of the n ih 

 reproduction being : 



e = 2"a. 



A much greater rate of increase is attained in a given time when the sub- 

 division is effected in several directions simultaneously. Examples are known of 

 both possible events, viz., separation in two, and separation in three directions at 

 right angles to one another. 



43. Division in Two Directions. 



In this case the cell contents subdivide into four parts by the formation of 

 two septa intersecting each other at right angles, and each splitting into two 

 lamellae, whereupon the mother-cell becomes four daughter-cells. The latter 

 again undergo subdivision, whereby 4x4=16 cells are formed. At the end 

 of n subdivisions, the total number of cells from a individuals will be 



In this case, where the separation goes on continuously in two directions 

 perpendicular to one another, and so always in the same plane, there results 

 provided the gradually extending cells retain their connection a mosaic-like 

 stratified plate which has been named Merismopedium (divided plate). A coccus 

 exhibiting this method of reproduction is known as a pediococcus. To this 

 group belongs the lactic-acid-producing Pediococcus acidi lactici discovered by 

 Paul Lindner. 



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 for- 

 mation of three flat septa, perpendicular 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. See Fig. 13. 



In the course of reproduction an initial number of 

 cells represented by a will increase by n processes of 

 division to a total of 



e = 8 "a = 



FIG. 13. Sarcina veuiriculi. 



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 classification and accurate characterisation of all 

 known species of the genus /Sarcina has been given by TH. 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 constituted by Sarcina. The behaviour, in this connection, of the 

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



