E. M. DotdCtE 65 



thus formed had divided again by 10.45, the lower became constricted 

 and divided soon after. Subsequently each rod took approximately 

 20 minutes after separation to attain to its maximum size, and then 

 immediately became constricted and fission was complete in another 

 20 minutes. Each individual became slightly curved or bent when 

 it became constricted previous to fission, and when division was com- 

 pleted the resulting rods were not exactly equal. The neAvly formed 

 individuals at once became separated by an appreciable gap, their close 

 contact being prevented by the capsule which could be detected by a 

 careful adjustment of the illumination. 



At 1 p.m. the young colony consisted of IG rods; by 1.30 the 

 number had increased to 22 and it was no longer possible to make 

 accurate drawings as many of the rods had oriented themselves with 

 their long axes parallel to the line of vision and they were overlapping 

 in various directions. 



No further observations were made until 9.15 on the following 

 morning; at that time the surface of the block was covered with highly 

 refractive moruloid masses of bacteria; the capsuled bacteria in each 

 mass were surrounded by a common envelope with a high refractive 

 index, and outside of this were a large number of rods lying free (Plate 

 XII, b). When first examined the free rods round the masses near 

 the edge of the block which were probably better supplied vdih oxygen 

 than the rest were in active motion, and large numbers of them had 

 made their way from the agar to the surface of the cover glass beyond 

 which was covered with a thin film of moisture. After about 15 

 minutes' exposure to brilliant illumination from the Nernst lamp all 

 these rods came to rest. 



Grouping. The rods are most commonly single or in pairs; loose 

 chains are found in the pellicle and also in sediment in some sugar 

 broths, particularly on nutrient broth with 2 per cent, laevulose, 

 but these do not as a rule consist of more than 20 or 30 elements 

 (Plate XIII, a) and they lie amongst large numbers of single rods. 

 There are no chains in the ring above the hquid. 



On solid media the organism almost invariably forms itself to a 

 greater or less extent into the capsuled, moruloid masses described 

 above, they are also found in the pellicle on ordinary nutrient broth. 

 If such masses be mounted in water they do not resolve themselves 

 into chains but isolated rods disentangle themselves and swim away 

 in a state of high activity. 



Mofilifij. The organism is often sluggishly motile when it is taken 



