40 
Growth of Bacilli 
pressure of the proximal ends of the new rods on each other, in com¬ 
position with the restraint exercised by the unruptured strap-hinge-like 
portion of the original membrane.” 
ACTUAL 
MYPOTHETICAL 
Diagram 9. 
Diagram 9 is a reproduction of Hill’s figure illustrating his hypo¬ 
thesis. “Fig. 1 . — Actual. B. diphtheriae, illustrating ‘snapping.’ (A) 
became (B) suddenly, the change occurring under the writer’s eye; 
Fig. 1.— Hypothetical. B. diphtheriae, illustrating the writer’s hypo¬ 
thesis of membrane rupture, devised to account for the snapping and 
subsequently achieved parallelism.” 
Group IV. The “slipping ” group. 
Hill (1901, p. 81) seems to have been the first to accurately describe 
and illustrate by means of a diagram the post-fission movements of 
this group, calling them “ slipping ” movements. 
The writer has found that B. typhosus, B. enteritidis (Gaertner), 
B. coli, B. pneumoniae (Friedlander) and allied organisms, B. pyocyaneus, 
the butter bacillus of Rabinowitch, V. cholerae, S. rubrum and other 
vibrios, B. fluorescens, B. subtilis and allied organisms and many other 
species of non-pathogenic bacilli belong to this group. 
The characteristic mode of development on the surface of agar is 
as follows. The original single rod grows in length and divides, “ the 
fission being always clearly evidenced by a sharp separation of the 
protoplasm of the original rod into two usually equal portions, by a 
translucent segmentation interval. Later a slight curve to one side is 
observed in one of the two new rods still in line with each other ” or 
