112 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



A considerable number of systems for the classification of the bac- 

 teria have been proposed. One of the most widely used at the present 

 time is that devised by Migula. His system is based on the principle, 

 universally followed by botanists and zoologists, of using morphological 

 characters only to distinguish genera. There has been, however, a 

 growing conviction among bacteriologists that it is necessary to take 

 physiological characters into consideration in determining even the 

 major groups of bacteria in any system of classification. This revolu- 

 tionary doctrine was presented in an extreme form by Orla Jensen who 

 used the metabolic processes of the bacteria as the chief criteria for 

 establishing not only genera but families and orders ' as well. A 

 Committee of the Society of American Bacteriologists have recently 

 reported on the Families and Genera of Bacteria*. This system makes 

 use of both morphological and physiological characters and promises to 

 be an important step towards a natural system of classification. Mi- 

 gula's system and that of the Committee of the Society of American 

 Bacteriologists, in skeleton form, follow: 



MIGULA'S CLASSIFICATION 



ORDERS OF THE SCHIZOMYCETES 

 Cells contain sulphur. Colorless or pigmented rose, 



violet or red by bacteriopurpurin never green.. THIOBACTERIA 

 Cells free from sulphur and bacteriopurpurin, 



colorless or faintly colored EUBACTERIA 



FAMILIES OF EUBACTERIA 

 Cells globose in a free state, not elongating in any 



direction before division into i, 2 or 3 planes.. . . COCCACE^E 

 Cells cylindrical, longer or shorter, and only divid- 

 ing in one plane, and elongating to twice the 

 normal length before division 



1. Cells straight, rod-shaped, without sheath, 



non-motile or motile by means of flagella . . . B ACTERIACE/E 



2. Cells crooked, without sheath SPIRILLACE.E 



3. Cells inclosed in a sheath CHLAMYDOBACTERIACE/E 



GENERA OF THE COCCACE^: 

 Cells without organs of locomotion 



1. Division in one plane Streptococcus 



2. Division in two planes Micrococcus 



3. Division in three planes Sarcina 



Cells with organs of locomotion 



1. Division in two planes Planococcus 



2. Division in three planes Planosarcina 



*Jour. Bact. II, p. 505, 1917. 



