G. S. Graham-Smith 
41 
both rods become slightly bent, though one is usually more bent than 
the other. “ This curve tends to straighten afterwards, the straightening 
being achieved by the proximal end of the curved rod slipping slowly 
out of line with the other rod, towards that side on which was the 
convexity of the curved rod. The two rods now free at both ends 
continue to grow, the proximal ends thus passing each other in opposite 
directions, and finally reaching, if nothing prevents, to the distal ends.” 
This process is repeated again and again till a young colony composed 
of a large number of parallel bacilli is produced. 
Plate VII (x 625) illustrates the formation of such a colony in the 
case of an organism of the subtilis group. 
Fig. 1 shows two bacilli end to end, with a clear segmentation 
interval dividing them. The organism to the left is slightly bent with 
the convexity upwards. In Fig. 2 (45 minutes) division has taken 
place in the organism on the left, but all are still in line. In Fig. 3 
(55 minutes) the organism on the right is beginning to slip past the 
Diagram 10. Illustrating the development of B. coli on the surface of agar. 
