34 Structure and Classification of Micro-organisms 



Germination of Spores.— When a spore is about to germinate, the 

 contents, which have been clear and transparent, become granular, 

 the body increases slightly in size, the capsule becomes less distinct, 

 and in the course of time splits open to allow the escape of a young 

 organism. The direction in which the capsule ruptures varies m 

 different species. Bacillus subtilis escapes from the side of the 

 spore; Bacillus anthracis from the end. This difference can be 

 made use of as an aid in differentiating otherwise similar organisms. 



So soon as the young bacillus escapes it begins to increase in size, 

 develops a characteristic capsule, and presently begins the propaga- 

 tion of its species by fission. 



Morphology. — The three principal forms of bacteria are spheres 

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



Cocci.— The spheric bacteria, from a fancied resemblance to 

 little berries, are called cocci or micrococci. When they divide, 

 and the resulting organisms remain attached to one another, a 



O<9®^0 







^ 



Q 



»9 



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

 micrococcus; 6, diplococcus ; c, d, streptococci; e, f, tetracocci or merismopedia.; 

 g, h, modes of division of cocci; i, sarcina; j, coccus with flagella; k, staphylococci. 



diplococcus is produced. Diplococci may consist of two attached 

 spheres, though each half commonly shows flattening of the con- 

 tiguous surfaces. In a few cases, as the gonococcus, the approxi- 

 mated surfaces may be slightly concave, causing the organism to 

 resemble the German biscuit called a "Semmel." When a second 

 binary division occurs, and four resulting individuals remain at- 

 tached 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 directions of space so as to produce fours, 

 eights, twelves, etc., on the same plane, the name merismopedia has 

 been given. Migula uses the term micrococcus for the unflagellated 

 tetrads, and planococcus for the flagellated forms. 



If division takes place in three directions of space, so as to pro- 

 duce a cubic "package" of cocci, the resulting aggregation is 

 described as a sarcina. This form resembles a dice or a miniature 

 bale of cotton. Few sarcinas have flagella, similar flagellated 

 organisms being called by Migula planosarcina. 



If division always take place in the same direction, so that the 



