34 Bacteria 



made use of as an aid in differentiating otherwise similar 

 organisms. 



So soon as the young bacillus escapes it begins to in- 

 crease in size, develops a characteristic capsule, and pres- 

 ently begins the propagation of its species by fission. 



It is believed by Frankel and others that sporulation 

 is not a sign that the food-supply has failed, but a sign that 

 the vital perfection of the organism has been attained. 

 These observers regard spore-formation in the bacteria as 

 analogous to the flowering of higher plants, which takes 

 place only when the conditions of development are best. 



Morphology. Three principal forms of bacteria exist, 

 from which all others seem to be but variations. They are 

 spheres (cocci), rods (bacilli), and screws (spirilla). 



Cocci. The spheric bacteria, from a fancied resemblance 

 to little berries, are called cocci or micrococci (Fig. 2, a). 

 According to peculiarities of multiplication, they are subject 

 to certain subdivisions. When cocci divide, and the result- 

 ing organisms remain attached to one another, a diplococcus 

 (Fig. 2, b) is produced. Diplococci may consist of two at- 



a 

 * 



> 







Fig. 2. Diagram illustrating the morphology of the cocci: a, Coccus 

 or micrococcus ; b, diplococcus; c, d, streptococci; e, f, tetracocci or 

 merismopedia ; g, h, modes of division of cocci ; i, sarcina ; /, coccus 

 with flagella ; k, staphylococci. 



tached spheres, though each half commonly shows flatten- 

 ing of the contiguous surfaces (Fig. 2, g). In a few cases, 

 as the gonococcus, the approximated surfaces may be 

 slightly concave, causing the organism to resemble the 

 German biscuit called a "Semmel" (Fig. 2, h). When 

 a second binary division occurs, and four resulting indi- 

 viduals remain attached to one another, without disturbing 

 the arrangement of the first two, a tetrad, or tetracoccus, is 

 formed. To the entire groups of cocci dividing in two 



