CILIAKY MOVEMENTS 



301 



Sometimes the cilia are replaced by a single long pro- 

 jection which performs movements of a whip-lash char- 

 acter. Such modifications are called flagella, and are found 



Fig. 133 — A 



lated protozoan ; Ft 

 flagellum ; N, nu- 

 oleus ; B, body of 

 cell. 



Fig. 134— Colony of flag- 

 ellated protozoans with 

 two flagella. 



in many one-celled plant and animal forms. (See Figs. 

 133 and 134.) 



In many of the higher animals, including man, are 

 found cells provided with similar, ciliary projections, but 

 here the action of the cilia is not to produce movement 

 of the cells themselves. On the contrary, their function 

 here is to produce currents in the liquid that bathes them 

 or to remove obstacles from the surface of the cells. Their 

 action may be compared to the motion of the oars when 



