CHAPTER 5 



THE CO-ORDINATION OF BEAT 



OF CILIA 



1. Introduction 



Where many ciliary organelles occur together, an economical 

 use of their activity can only be achieved if the movements are 

 organized in some way. Organelles with a typical flagellar beat 

 are usually found singly or in pairs on single-celled bodies like 

 spermatozoa or the simpler flagellates, while, in those organisms 

 where many flagella are present, the arrangement and attachment 

 of these flagella is such that they all work together in that they 

 cause movements of water in the same direction relative to the 

 body. In sponges, for example, the arrangement of the flagellated 

 cells is such that flagellar beating causes a current of water to pass 

 through the sponge in one direction only, and there is no 

 possibility of change in beat direction or direction of water 

 current, only stoppage. Similarly, in the trichonymphid flagel- 

 lates, the flagella are inserted on the body in such a way that 

 their free ends are directly posteriorly. In Pseudotrichonympha 

 the basal regions of the flagella are even attached to the walls of 

 grooves on the body surface to keep them in position, and Gibbons 

 and Grimstone (1960) noticed that, although the basal bodies are 

 nearly perpendicular to the body surface, the flagella may bend 

 fairly sharply at the body surface; they also found that in 

 Holomastigotoides the basal 0*8 /x of the flagellum " appears to be 

 closely applied to the body surface ". The beating of these 

 flagella always moves the water posteriorly over the surface of 

 the animal, and all the flagella work together in the sense that 

 all are similarly orientated and all move the water in the direction 

 from flagellar base to tip. Groups of flagella like this may still 

 be subject to control by inhibition, but it is doubtful whether 



170 



