26 MORPHOLOGY OF BACTERIA. 



According to the products of their metabolism, bacteria 

 may be classified as : 



AEROGENIC gas-producers. 



Z YMOGENIC -fermentative b acteria. 



SAPROGENIC putrefactive bacteria. 



CHROMOGENIC color-producers. 



PHOTOGENIC phosphorescent bacteria. 

 Migula recently proposed a classification of bacteria which 

 is based on their morphology. Although this classification 

 is technically correct, yet it is hardly wise to adopt it at this 

 time. It is too radical a departure from the classification 

 now in use ; and, furthermore, with the more advanced study 

 of bacteria and our increasing knowledge of the subject it 

 can safely be assumed that still further changes in the classifi- 

 cation will become necessary. For the present, therefore, we 

 would recommend the usual nomenclature. 

 Migula's classification is as follows : 



FAMILIES. 



I. Cells globose in a free state, not elongating in 

 any direction before division into one, two, 



or three planes 1. Coccacece. 



II. Cells cylindrical, longer or shorter, and divid- 

 ing in only 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. 2. Bacteriacece, 



2. Cells crooked, without sheath 3. Spirillacece. 



3. Cells enclosed in a sheath 4. Chlamydobacte- 



riacece. 



4. Cells destitute of a sheath, united into 



threads, motile by means of an undulating 



membrane 5. Beggiatoacece. 



GENERA. 

 1. Coccacece. 

 Cells without organs of motion : 



a. Division in one plane 1 . Streptococcus. 



b. Division in two planes 2. Micrococcus. 



c. Division in three planes 3. Sarcina. 



Cells with organs of motion : 



a. Division in two planes 4. Planococcus. 



b. Division in three planes 5. Planosarcina. 



