CHAPTER VI. 



MORPHOLOGY OF BACTERIA. 



BACTERIA are minute organisms not containing chlorophyll, 

 and multiplying by fission hence the term schizomycetes (v. 

 Nageli).' They are composed of a kind of protoplasm, the 

 mycoprotein of Nencki, and are invested with a membrane, 

 which is composed chiefly of cellulose and a certain amount 

 of mycoprotein (Nencki). 



Their contents are transparent and clear, but sometimes con- 

 tain minute bright granules of sulphur (Beggiatoa). Owing to 

 the cellulose membrane they resist the action of acids _ and 

 alkalies. Many species of bacteria micrococcus, bacterium, 

 spirillum are able by rapid multiplication to form colonies ; 

 the individuals are then embedded in a hyaline gelatinous 

 matrix produced by them, this is also mycoprotein. Some 

 species are possessed of one or two straight or slightly spiral 

 cilia or flagella, and thereby they are capable of locomotion, 

 darting through, or spinning round, in the fluid in which they 

 are suspended. Such is the case with many kinds of bacteria, 

 bacilli, and spirilla. 



Bacteria grow best when left undisturbed ; movement of the 

 vessel in which they grow is not advantageous. Light and 

 electricity do not appear to have a decided influence, since 

 most of them grow well in the light. "According to Cohn and 

 Mendelssohn, 1 strong electric currents have a noxious influence 

 on the growth of micrococci. 



Some bacteria require free access of oxygen, and are called 

 aerobic (Pasteur) ; others grow without free oxygen, and are 

 anaerobic (Pasteur). All require for their growth certain 

 nourishing materials containing carbon and nitrogen. Water 



1 Colm's Beitr. z. Biol. d. Pfl. Bil. iii. 1. 



