THE FORM OF BEAT OF FLAGELLA 



133 



Total 

 thrusc 



Fig. 33. Diagram of the forces exerted by the water on three 

 elements of the tail of a bull sperm. The waves of bending 

 are moving posteriorly and elements A and C are moving to 

 the right while element B is moving to the left (as indicated by 

 small arrows). The reactions to the movements of these three 

 elements are shown by Ta, Rb and Re. The components Fb 

 and Fc act together in moving th^ sperm forwards, and are 

 opposed by drag acting in the whole sperm, while the 

 transverse components Ta, Tb and Tc more or less cancel out. 

 Compare this with Fig. 30 and note that here the increased 

 angle of inclination of element C gives an increased forward 

 component Fc (from Gray, 1958). 



