34 
Growth of Bacilli 
capsule can be readily demonstrated both in stained and living prepara¬ 
tions (see Plate Y, Fig. 6), in each case distinct, relatively long, intervals 
being seen between the bacilli composing the chain. Its flexibility can 
also be easily demonstrated in young living preparations by running 
successive drops of water between the agar and the cover-glass. The 
currents which are set up cause the chain to bend in various directions, 
with the production of varying angles at the junctions of the bacilli. 
The post-fission folding movements seen in this group can be 
reproduced by replacing the string used to imitate the changes in the 
loop foi’ming group by a chain with long links, or by a series of tubes 
loosely connected by a string run through them. 
B. pestis, which appears to be totally unrelated to the other members 
of this group, also frequently exhibits folding post-fission movements 
in the formation of superficial colonies. Diagram 4, series A and B, 
illustrate early folding movements in short chains developing from 
single bacilli, and series C the folding movements in a long chain of 
seven individuals. 
Group III. The “ snapping ” group. 
The mode of division and the curious post-fission movements 
peculiar to this group were first briefly described by Kurth (1898) and 
later by Nakanishi (1901). Hill (1901, p. 81) however was the first to 
thoroughly investigate the subject in living specimens growing on the 
surface of agar, and to give a detailed description of the process. He 
was also the first to clearly differentiate the “ snapping ” type of post¬ 
fission movement seen in this group from the “ slipping ” type found in 
the next group. Hill and Rickards (1903) continuing these investiga¬ 
tions only found snapping post-fission movements in B. diphtheriae, 
B. pseudo-diplitheriae and B. xerosis. 
The writer, during the course of the present investigations, has made 
observations on a number of diphtheroid organisms obtained from 
various sources. In all these snapping post-fission movements occurred, 
but it was never seen in other types of bacilli. 
The mode of post-fission movement may therefore be regarded as 
characteristic of the diphtheroid group. 
“A gradual enlargement of the bacterial cell in both diameters 
accompanied often by slight changes in outline suggesting some plasti¬ 
city of the bacterial walls” is the first change seen when a single living 
bacillus is carefully examined. “ At times it may be possible to detect 
segmentation of the protoplasm previous to the post-fission movements, 
a hard dark line, not necessarily central, developing across the axis of 
