SPIRILLA 133 



from a coccus in that two sides are parallel. Some 

 bacilli after fission retain a characteristic arrangement 

 and may be spoken of as Diplobacilli or Streptobacilli. 



(Leptothrix is a term that in the past has been loosely 

 used to signify a long thread, but is now restricted to 

 such forms as belong to the leptothricise (vide infra) . 



3. Spirilla (Fig. 84, 4 to 6). Curved and twisted 

 filaments. Classified, according to shape, into 



Spirillum. 

 Vibrio (comma). 

 Spirochasta. 



Many Spirochaetes appear to belong to the animal 

 kingdom and are grouped under protozoa ; other organ- 

 isms to which this name has been given are undoubt- 

 edly bacteria. 



Higher forms of bacteria are also met with, which 

 possess the following characteristics: They are at- 

 tached, unbranched, filamentous forms, showing 



(a) Differentiation between base and apex; 



(b) Growth apparently apical ; 



(c) Exaggerated pleomorphism ; 



(d) "Pseudo-branching" from apposition of cells; 

 and are classified into 



1. Beggiotoa. 1 Free swimming forms, which 



2. Thiothrix. J contain sulphur granules. 



3. Crenothrix. 



These forms do not contain 



4. Cladothnx. , 



T , . sulphur granules. 



5. Leptothnx. 



6. Streptothrix. A group which exhibits true but 

 not dichotomous branching, and contains some patho- 

 genic species. 



The morphology of the same bacterium may vary 

 greatly under different conditions. 



For example, under one set of conditions the exami- 

 nation of a pure cultivation of a bacillus may show a 

 short oval rod as the predominant form, whilst another 



