THE LOWER BACTERIA 15 



form a connecting link between the bacilli and the higher 

 bacteria, e.g., streptothrices. 



Great confusion in nomenclature has arisen in this group in con- 

 sequence of the different artificial meanings assigned to the essentially 

 synonymous terms bacterium and bacillus. Migula, for instance, applies 

 the former term to non-motile species, the latter to the motile. Hueppe, 

 on the other hand, calls those in which endogenous sporulation does 

 not occur, bacteria, and those where it does, bacilli. In the ordinary 

 terminology of systematic bacteriology the word bacterium has been 

 almost dropped, and is reserved, as we have done, as a general term for 

 the whole group. It is usual to call all the rod-shaped varieties bacilli. 



3. /Spirilla. These consist of cylindrical cells more or less 

 spiral or wavy. Of such there are two main types. In one there 

 is a long non-septate, usually slender, wavy or spiral thread 

 (Fig. 1, k, m, n). In the other type the unit is a short curved 

 rod (often referred to as of a "comma" shape). When two 

 or more of the latter occur, as they often do, end to end with 

 their curves alternating, then a wavy or spiral thread results. 

 An example of this is the cholera microbe (Fig. 1, p). This 

 latter type is of much more frequent occurrence. Among 

 the first group motility is often not associated, as far as is 

 known, with the possession of flagella. The cells here apparently 

 move by an undulating or screw-like contraction of the proto- 

 plasm. 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 (Fig. 1, q 4 ). Division takes 

 place as among the bacilli, but in some of the non-septate forms 

 a longitudinal fission may occur. In some species endogenous 

 sporulation has been observed. 



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

 have given different meanings. These terms are spirillum, spirochsete, 

 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 "spirochsete " is reserved for the long unflagellated 

 spiral cells. Hueppe applies the term "spirochsete" to forms without 

 endospores, "vibrio" to those with endospores in which during sporula- 

 tion the organism changes its form, and "spirillum " to the latter when 

 no change of form takes place in sporulation. Flugge, another systematist, 

 applies " spirochaete" and "spirillum" indiscriminately to any wavy or 

 cockscrew 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. 



Within recent years great doubt has arisen as to whether 

 many of the non-septate spirillary forms, e.g., Spirochcete pallida, 



