22 
Growth of Bacilli 
As has already been stated growth in the long axis of the original 
organism first occurs and then division, followed by post-fission move¬ 
ments. By repeated divisions and movements colonies are produced. 
In every species hitherto investigated a decided tendency towards the 
adoption of a parallel arrangement by the newly formed rods has been 
noted. This parallel arrangement, which may be of short duration or 
which may persist indefinitely, is brought about by the post-fission 
movements. Four different well marked varieties of post-fission 
movement have been observed, and according to their post-fission 
movements the organisms investigated have been divided into four 
groups. 
I. The “ loop forming ” group. 
II. The “ folding ” group. 
III. The “ snapping ” group. 
IV. The “ slipping ” group. 
The differences in post-fission movement appear to be explicable on 
the hypothesis that the variations are mainly due to differences in the 
strength and behaviour of the capsule. 
Up to the present however it has been found impossible to make 
direct observations on the behaviour of the capsule during division in 
the living state, either with the ultramicroscope or by any other means. 
That a capsule or membrane exists may be clearly demonstrated for 
even in crowded preparations individuals lying side by side are rarely 
or ever in visible contact, an interval always remaining between them. 
Very little information has been gained by the study of stained 
specimens. 
It was early clearly recognised that the behaviour of an organism 
growing in a confined space between agar and glass might be totally 
different from its behaviour when growing freely on the surface of an 
agar plate. Parallel observations were therefore frequently made by 
simultaneously watching a specimen prepared by the method described 
and the growth occuning on the surface of an agar plate made from the 
same emulsion. While the former was under almost constant observation 
the latter was taken out of the incubator at frequent intervals and 
examined. The growth taking place in the two cultures could thus be 
easily compared. These experiments showed that bacilli growing under 
ordinary conditions on the surface of agar plates behave for many hours 
in exactly the same manner as those growing between agar and glass. 
