14 GENERAL MORPHOLOGY AND BIOLOGY 



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, No. 9). 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, 

 No. 10). This latter type is of much more frequent occurrence, 

 and contains the more important species. 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 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 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 " spirochfete " 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 "spirochsete" and " spirillum " indiscriminately to 

 any wavy or corkscrew form, and "vibrio" to forms where the undula- 

 tions 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. 



Quite recently great doubt has arisen as to whether many of 

 the non-septate spirillary forms are to be looked on as bacteria 

 at all, the view being taken that in, it may be, many cases 

 they represent a stage in the life history of what are really 

 protozoa of the nature of trypanosomes. The ultimate classifica- 

 tion of the spirilla must thus be left an open question. 



II. The Higher Bacteria. These show advance on the lower 

 in consisting of definite filaments branched or unbranched. In 



