MORPHOLOGY OF BACTERIA 13 



ful when the lower forms are under consideration. The or- 

 ganisms most important in decomposition processes are 

 morphologically more closely related to the plants than to 

 the animals; physiologically, they are more directly allied 

 to the animals. It is customary, however, to consider the 

 bacteria, yeasts, and molds as members of the plant king- 

 dom. 



Morphology of bacteria. The bacteria may be defined 

 as unicellular plants, devoid of chlorophyl, and reproduc- 

 ing by division of the cell into two daughter cells. This 

 mode of reproduction has given to them the name of schiz- 

 omi/cetes, or splitting fungi. 



The lower or the true bacteria occur in three form types : 

 spheres, rods, and spirals. A spherical organism is termed 

 a coccus (plural, cocci) ; a rod is designated as a bacillus 

 (plural, bacilli) ; a spiral organism is called a spirillum 



Fig. 1. Forms of Bacteria 



A spherical organism is termed a coccus; a rod shaped one a bacillus; a spiral 

 cell is called a spirillum 



(plural, spirilla). The spheres can vary only in size; the 

 rods may vary in the ratio of the two axes, being either 

 long and slender, or short and plump. If the two axes 

 are of almost equal length, the rod will approach a sphere 

 in appearance. Confusion, therefore, may develop in such 

 cases; as, for instance, in the lactic-acid organism, which 

 is so short a rod as to be called a coccus type by some writ- 

 ers. The ends of the rods may vary, being rounded or 

 square cut, or even in a few instances concave. The spiral 

 types may present all the variations of the rods, and may 

 also vary in the extent to which the cell is bent. The cur- 



