E. M. DoiDGE 11) 



Each rod as soon as it divided, pushed away and became completely 

 separated from its neighbour. By a careful adjustment of the illumina- 

 tion, a delicate capsule could be detected surrounding each and pre- 

 venting close contact. 



The small colony which was being formed from the two rods originally 

 selected was kept under observation until 4.30 p.m., when it consisted 

 of 28 rods. At this time other colonies on the agar hanging block 

 numbered 2—24 individuals. In most cases these were the result of 

 the division of a single rod. 



At 9 a.m. on the following morning the colonies were easily visible 

 to the naked eye. Under the low magnification their structure was 

 grumose. 



Development in the agar hanging block was comparatively slow, 

 doubtless owing to the fact that growth was anaerobic and that for part 

 of the time took place under very strong illumination. After 24 hours 

 the colonies appeared to the naked eye as small white pin spots, whereas 

 a poured plate kept in the incubator at 30° C. for the same length of 

 time developed surface colonies 5 — 7 mm. in diameter. The submerged 

 colonies, however, were very little larger than those developed on the 

 hanging block. 



Grouping. 



In young cultures on agar and gelatine, the rods are usually single, 

 but in liquid cultures they frequently occur in pairs. 



In the pellicle on the surface of beef broth cultures, chains are 

 formed; these are composed of elements similar to the single rods 

 and may comprise from 2 — 40 individuals. The chains are straight or 

 curved (Plate XIV, figs, a and 6) and very easily fall apart. There 

 are no chains in the sediment which forms when the tube is in any way 

 disturbed and the pellicle sinks to the bottom. 



The chains are not disposed in any particular way, but the orien- 

 tation is irregular. 



Internal structure. 



Young, actively dividing rods stain very evenly, but in the older 

 cultures some changes of structure can be observed. 



Rods from a ten days' old culture in 2 % dextrose broth when 

 examined with the paraboloid condenser frequently show one or several 

 highly refractive granules (Plate XIV, fig. c). In preparations made 

 from very old agar cultures to test for the presence of spores, some of 



2—2 



