MOVEMENT 



3. Movement. In the first chapter it was noticed 

 that some bacteria are endowed with the power of 

 spontaneous movement ; they can rove from one part of 

 a drop of water to another as readily as fish in a pond. 

 This is brought about by the lashing action of one or more 

 exceedingly delicate hair-like cilia or flagella which are 

 attached to the outer coat or capsule of the bacterium. 

 Some organisms pos- 

 sess only one flagellum 

 at one &M$(monotrichic), 

 others two or more in 

 a tuft at one or both 

 ends (lophotrichic\ while 

 many bacilli have many 

 flagella distributed all 

 over the cell - wall, 

 and are spoken of as 

 peritrichic (Fig. 8). 

 Numbers of species of 

 bacteria are, however, Q 

 devoid of motile cilia, 

 and are incapable of 

 spontaneous movement 

 in liquids. Very 

 frequently non - motile 

 forms exhibit a peculiar oscillatory movement when 

 put in water or other liquids. This motion back- 

 wards and forwards over a very short distance or 

 round and round in a circular or oval path is a purely 

 physical phenomenon known as Brownian movement, 

 and is exhibited by any kind of exceedingly small 

 particles, either living or dead, when they are suspended 

 in water. 



FIG. 8. Arrangement of flagella on bacteria, 

 i, Monotrichic ; 2, lophotrichic ; 3, peritrichic. 



