178 



CO-ORDINATION OF BEAT 



ments that they create may cause some viscous interaction 

 between adjacent cilia. The form of the individual waves was 

 described above and shown in Fig. 45. The beating of each 

 cilium is followed after an interval of about J cycle by the beating 

 of the next distal cilium to give the pattern of waves shown in 



Fig. 49. Diagram of the peristome region of Stentor showing 



the arrangement of membranelles and the direction of meta- 



chronal wave transmission (from Sleigh, 1957). 



Fig. 49. Diaplectic metachronal waves do not seem to show 

 reversal of beat, but this apparent absence of reversal may be 

 because it would have no functional value in the cases observed, 

 and not that it is not possible.* In backward-swimming of 



* Parducz (1961) has published photographs of Didinium fixed during both 

 forward- and backward-swimming; these suggest that the metachronism is 

 always dexioplectic, and that both the beat and the metachronal waves 

 reverse. 



