CLASSIFICATION. 17 



is scarcely to be considered of practical value, inasmuch as the ques- 

 tion of spore formation is still undetermined for a large number of 

 species. 



In the following table we shall give the characters of the dif- 

 ferent genera which have been described by recent botanists and 

 bacteriologists, arranged under the three headings, MiCROCOCCi, 

 BACILLI, SPIRILLA. Where we doubt the propriety of maintaining 

 a distinct generic name upon the supposed distinguishing characters, 

 the description will be printed in small type. 



MICROCOCCI. 



General Characters. Spherical bacteria which are reproduced 

 by binary division ; usually without spontaneous movements ; do not 

 form endogenous spores. (According to some authors, certain cells, 

 known as arthrospores, may be distinguished by their greater size 

 and refractive power, and these are supposed to have greater resist- 

 ance to desiccation than the ordinary cocci resulting from binary 

 division, and to serve as reproductive bodies. ) Some micrococci are 

 not precisely round, but are somewhat oval in form ; and when in 

 process of division the cocci, necessarily, are more or less elongated 

 in one diameter before a complete separation into two spherical ele- 

 ments has occurred. 



MiCROCOCCUS. Division in one direction ; cocci single, in pairs, 

 or accidentally associated in irregular groups ; sometimes held to- 

 gether in irregular masses by a transparent, glutinous, intercellular 

 substance. (Micrococci belonging to this genus are frequently de- 

 scribed as " staphylococci," and Staphylococcus is used by Rosen- 

 bach as a generic name for the pus cocci described by him, which 

 are solitary or associated in irregular groups, as above described. ) 



Ascococcus. Cocci associated in globular or lobulated, zooglcea 

 masses by a rather firm intercellular substance. 



LEUCOXOSTOC. Cocci, solitary or in chains, surrounded by a 

 thick, gelatinous envelope and forming zoogloea of cartilaginous 

 consistence. 



STREPTOCOCCUS. Division in one direction only ; cocci associ- 

 ated in chains. 



Diplococcus. Division in one direction only ; cocci associated in pairs. 



Association in pairs is common to all of the micrococci, inasmuch as 

 they multiply by binary division. When such association has rather a per- 

 manent character, it is customary to speak of the microorganism as a diplo- 

 coccus, but we doubt the propriety of recognizing- this mode of association 

 as a generic character. 



MERISMOPEDIA. Division in two directions, forming groups of 

 four, which remain associated in a single plane "tetrads." 



SARCINA. Division in three directions, forming packets of eight 

 2 



