4 AIDS TO BACTERIOLOGY 



organisms. The anthrax bacillus spores when in contact 

 with free oxygen, while the anaerobes generally require 

 absence of oxygen. An organism containing no spore, 

 but ready to divide by fission at maturity, is said to be a 

 vegetative form. 



Arthrospores. Some of the cells formed by fission were 

 formerly thought to possess the characters of spores. The 

 formation was known as ' arthrogenous,' and has only 

 been noticed in the micrococci. The suggestion is based 

 on a misconception. Eyre states that these so-called 

 arthrospores have never been observed to germinate, and 

 they cannot survive a temperature of 80 C. for ten minutes. 

 It is now universally accepted that these individuals are 

 not spores. 



The formation of spores in imperfectly divided sister 

 cells has been interpreted, wrongly, according to most 

 authorities, as ' autogamy.' There is no evidence that 

 either this or other sexual process occurs among bacteria. 



Bacteria cannot arise ab initio, since a living organism 

 can only be derived from a living organism (biogenesis). 

 The supporters of the theory of ' spontaneous generation ' 

 (abiogenesis or archebiosis) believed that organisms could 

 be produced in a sterile medium without the introduction 

 of living organisms. 



Classification. The bacteria possess so few morpho- 

 logical attributes, and so many forms are pleomorphic, 

 that the ingenuity of bacteriologists has hitherto been 

 incapable of formulating either a scientific or a convenient 

 classification. The present nomenclature is more of a 

 hindrance than a help, for so many organisms are crowded 

 together in a single genus, many of them possessing names 

 either unwieldy or unsuitable, that but little assistance 

 can be expected from the classification. We append one 

 scheme, that of Migula, and comment on it where necessary: 



The bacteria are divided into five families: Coccacese, 

 Bacteriacese, Spirillacese, Chlamydo - Bacteriacea3, and 

 Beggiatoacese. These again are subdivided into genera, 

 based partly on the mode of division and partly on the 

 number and arrangement of the flagella. 



I. COCCACE^. Round or oval cells. The division into 

 genera is based on the arrangement of the cocci on division. 



(1) Streptococcus. The cocci form chains. Includes 

 cocci forming pairs (Diplococci). 



