Gr. S. GtRAIIAM-SmITII 
37 
been developed from single bacilli (a, c, e, g Fig. 13), and three (B, D, F) 
by the fusion of the products of two or three originally separate bacilli 
(b 1; b 2 ; d lt d 2 ; and f 1( f 2 , f 3 respectively). The right hand colony (F) in 
this figure is the one whose growth has been followed in Figs. 1 to 8. 
Diagram 5 illustrates the development of a colony from a single 
diphtheria bacillus. The tendency to the production of parallelism is 
specially marked in this series. During the course of growth one of 
the newly formed organisms (Fig. 3, No. Ill) apparently degenerates. 
Although it grows large it never divides and later becomes pale and ill 
defined (Fig. 15) and eventually disappears (Fig. 1G). 
Diagram 6 also illustrates the development of a diphtheria colony. 
It differs from the last series in showing a number of giant and 
irregular forms (Fig. 7, No. 31; Fig. 8, No. 32; Fig. 12, No. 21) most of 
which subsequently divide. One curious wedge-shaped organism (Fig. 8, 
No. 313) undergoes no further development. This series also illustrates 
the division of one bacillus (Fig. 7, No. 31) into three (Fig. 8, Nos. 311, 
312 and 313). 
Diagram 6. Illustrating the development of B. diphtheriae on the surface of agar. 
