24 



MORPHOLOGY. 



mente, which are curved or spiral. The shorter elements in a pure 

 culture may be simply curved, as in a, Fig. 10, while the spiral form 

 becomes apparent in those which are longer, and we may have one 

 or several turns of the spiral (Fig. 10, b). The spiral form may be 

 but slightly marked (Fig. 10, c), or the turns may be close and deep 

 as in a corkscrew (Fig. 10, d). Again, the curved filaments may be 

 short and rigid, or long and flexible (Fig. 10, e). 



In the genus Cladothrix, which is placed by botanists among 

 the bacteria, the filaments appear to branch ; but this branching is 

 only apparent, and there is no true dichotomous branching in this 

 class of microorganisms. The false branching of Cladothrix 

 <1n'hotoma, Cohn, is shown in Fig. 11. The fact that some of the 

 larger species of bacilli and spirilla are provided with slender, whip- 

 like appendages called flagella has been known for many years, and 

 it has for some time been suspected that all of the motile organisms 



Fio. 10. 



FIG. 11. 



Fio. 12. 



of this class are provided with similar appendages and that these are 

 organs of locomotion. Recently, by improvements in methods of 

 staining, Loftier has demonstrated the presence of flagella in many 

 species in which they had heretofore escaped observation. They are 

 sometimes single, at the ends of the rods (Fig. 12, a); or there may 

 be several at the extremity of a single rod (Fig. 12, &); again, they 

 are seen in considerable numbers around the periphery of the rod 

 (Fig. 12, c). 



The bacilli and spirilla sometimes contain in the interior of the 

 cells granules of different kinds. These may appear like little oil 

 tJ n >ps or they may be more opaque. In the genus Beggiatoa grains 

 of sulphur are found in the interior of the cells. Again, we may 

 find vacuoles in the protoplasm ; or, in stained preparations, deeply 

 M;tin-<I <_rr;mulcs, which are not spores, may be seen at the extremi- 

 ties of the rods end-staining. The morphological characters de- 

 IM ndiiiLC upon the formation of endogenous spores will be referred to 

 hereafter. 



