BACTERIA. 



53 



as organisms during propagation by division. They are accord- 

 ingly divided into Macrococci and Micrococd (Fig. 1 3 a). When 

 the spheres occur in pairs, they are called Diplococci (b) ; they 

 also appear in groups consisting of four individuals, Sarcina (&) ; 

 or of a greater number, arranged irregularly, or in chains, 

 Streptococci (c). From the coccus forms there is a gradual 

 transition to the rod forms Bacterium, Bacillus (e), which vary 

 greatly both in length and thickness. When the rods are 



FIG. 13. Growth-forms of Bacteria (in part schematic) : a, Cocci ; b, Diplococci 

 and Sarcina ; c, Streptococci ; d, Zooglcea ; e, Bacteria and Bacilli ; j, Clostridium ; 

 ft, Pseudo-filament, Leptothrix, Cladothrix ; h, Vibrio, Spirillum, Spirochsete, and 

 Spirulina ; i, Involution-forms ; k, Bacilli and Spirilla with cilia or flagella ; 

 I, Spore-forming Bacteria ; m, Germination of the Spore (Bacillus subtilis). 



enlarged in the middle and taper towards the ends, i.e., spindle- 

 shaped, we have the Clostridium form (/). If the rods are 

 elongated so as to become more or less thread-like, they are 

 called Leptothrix (#), which may also occur as pseudo-filaments 

 (g), when several rods are arranged lengthwise, or as Cladothrix, 

 when they lie so close to one another and in such a way that 

 they become seemingly ramified. Eods and filaments fre- 

 quently assume wavy or spiral forms (h) ; when they are 

 only slightly curved, we have the Vibrio form ; when 

 the spirals are more prominent, the Spirillum, and SpirocJicete 



