VIL] MICROCOCCUS. 39 



Some species are specially characterised by dividing into a 

 dumb-bell, and each of the elements dividing again trans- 

 versely into a dumb-bell ; a group of four (tetrade or sarcina- 

 form) is thereby produced. Some species are occasionally met 

 with, particularly in products of air-contamination, in which 

 the four individuals are closely pressed against one another, 

 and then each assumes more or less the shape of a cube, a true 

 sarcina (see below). But each of these cubes divides into four 

 small micrococci arranged as a small sarcina, so that a sarcina- 

 witlmi-sarcina-form results. 



8 6 





FIG. 11. GIAWT MICROCOCCI, FR^M Fie.12. SARCiNA-MiCRoroccrrs.FROM 

 SAME PUTRID SPUTUM AS IN PRE- AN ARTIFICIAL CULTIVATION. 



vious FIGURES. ,_ The elements of each sarcina-group 



1. Dumb-bells. of four appears single. 



2 Di vision of dnmb-bell s into sarcina. 2 The elements incompletely divided 

 3. Incomplete division into sarcina. into secondary groups. 



3. Each element of the previous 

 groups has divided into four 

 small micrococci. 



In many instances the individual members resulting from 

 division remain closely adherent without any definite arrange- 

 ment, and thus form smaller or larger continuous masses, 

 zooglma or colonies, in which the individuals appear embedded 

 in a hyaline gelatinous matrix ; the amount of this varies in 

 the different species ; in some there is little of the matrix 

 actually visible, the micrococci being in close juxtaposition, 

 in others it is easily recognised, the interstices between the 

 individuals being measurable. 



In some of the pigmented species (see below) the interstitial 

 matrix contains the pigment. Zoogloea masses always present 

 themselves as uniformly granular, the granules or micrococci 

 being of the same size. 



True micrococci never elongate to form rods, although in 

 certain rod-like bacteria the individual elements sometimes 

 assume the shape of spherical elements (see below). 



Some species of micrococci form after some days a pellicle 

 on the surface of the nourishing material, although there is also 

 an abundance of these micrococci in the depth of the nourishing 



