CLASSIFICATION OF BACTERIA IN FAMILIES. 59 



The bacilli comprise all oval or rod-formed bacteria. 

 (See Fig. 3.) 



To the spirilla belong all organisms that are curved 

 when seen in short segments, or when in longer threads 

 are twisted in the form of a corkscrew. (See Fig. 4.) 



The micrococci are subdivided according to their pre- 

 vailing mode of grouping, as seen in growing cultures, 

 into staphylococci those growing in masses like clusters 

 of grapes (see Fig. 2, a) ; streptococci those growing in 

 chains consisting of a number of individuals strung 

 together like beads upon a string (see Fig. 2, 6) ; diplo- 

 cocci those growing in pairs (Fig. 2, c) ; tetrads those 

 developing as fours (Fig. 2, d) ; and sarcince those 

 dividing into fours, eights, etc., as cubes that is, in 

 contradistinction to all other forms, the segmentation, 

 which is rarely complete, takes place regularly in three 

 directions of space, so that when growing the bundle of 

 segmenting cells presents somewhat the appearance of a 

 bale of cotton (Fig. 2, e). 



To the bacilli belong all straight, rod-shaped bacteria 

 *. e., those in which one diameter is always greater 

 than the other. 



In this group are found those organisms the life- 

 cycle of many of which presents deviations from the 

 simple rod-shape. Many of them in the course of 

 development increase in length into long threads, 

 along which traces of segmentation may usually be 

 found the anthrax bacillus and bacillus cereus are 

 conspicuous examples of this. Again, under certain 

 conditions, many of them possess the property of form- 

 ing within the body of the rods oval, glistening spores 

 (see Fig. 6), and, if the conditions are not altered, the 

 rods may entirely disappear and nothing be left in 



