24 MORPHOLOGY. 
ments, which are curved or spiral. The shorter erements 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 microédrganisms. The false branching of Cladothrix 
dichotoma, 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 
Fie. 10. Fig. 11. Fig. 12. 
of this class are provided with similar appendages and that these are 
organs of locomotion. Recently, by improvements in methods of 
staining, Léffler 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, b); again, they 
are seen in considerable numbers around the periphery of the rod 
(Fig. 12, ¢). 
The bacilli and spirilla sometimes contain in the interior of the 
cells granules of different kinds. These may appear like little oil 
drops 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 
stained granules, which are not spores, may be seen at the extremi- 
ties of the rods—end-staining. The morphological characters de- 
pending upon the formation of endogenous spores will be referred to 
hereafter. 
