GENERAL MORPHOLOGY AND PHYSIOLOGY. 1 2 I 



occur as a continuous sheath around a chain 

 of bacteria, which by its disappearance sets the 

 individual links free. The capsule is soluble in 

 water, and under some circumstances is difficult to 

 demonstrate. In the pneumo-coccus of Friedlander 

 the capsule disappears on cultivation, but reappears 

 in preparations made from an inoculated animal. 

 In the pleuritic fluid of a mouse these cocci are 

 often found with a strikingly well-marked capsule, 

 and in other capsuled cocci the extent of the 

 envelope has been observed to vary considerably 

 in the same species of bacterium. 



When this gelatinous material forms a matrix, in 

 which numbers of bacteria are congregated in an 

 irregular mass, we have what is termed a zoogloea. 

 Thezooglcean stage is a resting stage, often preceded 

 or followed by a motile stage. Thus bacteria may 

 be present in a solution in an active state, and after 

 a time a scum or pellicle forms on the surface of the 

 liquid, which consists of zooglcea. At the edges of 

 the zooglcea individuals may be seen again to 

 become motile, detaching themselves from the 

 edges of the mass, and swimming off in the 

 surrounding fluid. 



The same may be observed sometimes in culti- 

 vations started in nutrient gelatine. The inoculated 

 bacteria grow and multiply, and liquefy the gelatine, 

 and after a time a zooglcean film appears on the 

 surface of the liquefied layer. On potatoes the 

 appearances are very varied. In a bacillus which 



