i8 GENERAL MORPHOLOGY AND BIOLOGY. 



type is of much more frequent occurrence, and contains the 

 more important species. Motility among the first group is 

 often not associated, as far as is known, with the possession 

 of flagella. The cells here apparently move by an undu- 

 lating or screw-like contraction of the protoplasm. Most of 

 the motile spirilla, however, possess flagella. Of the latter 

 there may be one or two, or a bunch containing as many 

 as twenty, at one or both poles. Division takes place as 

 among the bacilli, and in some species endogenous sporula- 

 tion has been observed. 



Three terms are used in dividing this group, to which different 

 authors have given different meanings. These terms are spirillum, 

 spirochseta, vibrio. Migula makes "vibrio" synonymous with 

 " microspira," which he applies to members of the group which 

 possess only one or two polar flagella ; " spirillum " he applies to 

 similar species which have bunches of polar flagella, while ' ' spiro- 

 chaeta " is reserved for the long unflagellated spiral cells. Hueppe 

 applies the term " spirochaeta " to forms without endospores, " vibrio " 

 to those with endospores in which during sporulation the organism 

 changes its form, and " spirillum " to the latter when no change of 

 form takes place in sporulation. Fliigge, another systematist, applies 

 " spirochaeta " and "spirillum" indiscriminately to any wavy or 

 corkscrew form, and "vibrio" to forms where the undulations are 

 not so well marked. It is thus necessary, in denominating such a 

 bacterium by a specific name, to give the authority from whom the 

 name is taken. 



II. The Higher Bacteria. These show advance on the 

 lower in consisting of definite filaments branched or un- 

 branched. In most cases the filaments at more or less 

 regular intervals are cut by septa into short rod-shaped or 

 curved elements. Such elements are more or less inter- 

 dependent on one another, and special staining methods are 

 often necessary to demonstrate the septa which demarcate 

 the individuals of a filament. There is further often a 

 definite membrane or sheath common to all the elements 

 in a filament. Not only, however, is there this close organic 

 relationship between the elements of the higher bacteria, 

 but there is also interdependence of function ; for example, 

 one end of a filament is frequently concerned merely in 



