CLASSIFICATION OF BACTERIA IN FAMILIES. f>7 



usually round in form, that are derived 

 from vegetative cells through fission. The 

 cells of the thicker rods divide in three 

 directions of space, those of the thinner 

 threads only at right angles to the long axis 

 of the threads. 



3. Genus: Phragmidiothrix (Engler). Thread 



bacteria with very delicate barely visible 

 sheath, sometimes 100 microns long and 3 

 to 12 microns wide. Cells cylindrical, later 

 flattened. Multiplication through non- 

 motile gonidia, which are derived from 

 vegetative cells through division in three 

 directions of space. Probably similar to 

 crenothrix. 



4. Genus: Sphcerotilus (Kutzing). Cells cylin- 



drical, enclosed in the sheaths, dichoto- 

 mously branched threads, without differen- 

 tiation of base and apex. Multiplication 

 through gonidia, which swarm from the 

 sheaths and attach themselves to objects and 

 develop into new threads. The gonidia have 

 a bunch of flagella attached to one pole. 

 The present tendency is to simplify this morpholog- 

 ical classification, and to distribute the bacteria into 

 three great groups, with their subdivisions, the mem- 

 bers of each group being identified by their individual 

 outline, viz., that of a sphere, a rod, or a spiral. To 

 these three grand divisions are given the names cocci or 

 micrococci, bacilli, and spirilla. 



MODE OF MULTIPLICATION. In 'the group micro- 

 cocci belong all spherical forms /. ^., all those forms 

 the isolated individual members of which are practically 



