198 CO-ORDINATION OF BEAT 



of cilia, and even if the mediator between the nerve and the 

 cilium of Mytiliis is serotonin, the mechanism of its action on the 

 cilium is obscure. Although speculation here is certainly 

 premature, ions may well be concerned in activation as in so many 

 biological phenomena; we badly need to know more about the 

 effects of ions on ciliary activity. 



8. Root-fibre Systems and Co-ordination of Ciliary Beat 



The metachronal waves of the body cilia of organisms like 

 Opalina and Paramecium may be transmitted in directions which 

 do not correspond to the rows of cilia. It is now well known that 

 in both of these organisms there is a system of more or less 

 longitudinal fibres which connect with the basal bodies of the 

 cilia, although the fibres are rather different in the two examples. 

 These fibre systems have often been held to be responsible for 

 the transmission of the metachronal impulses, but in view of the 

 wide variety of wave patterns this seems unlikely (Pitelka, 1956; 

 Parducz, 1958b). In Opalina at least, a reasonable explanation 

 of metachronal co-ordination has been given without reference 

 to such fibril systems. These fibrils seem more likely to be 

 concerned in the '' morphogenetic " relationships between the 

 ciliary bases, and perhaps also serve a physical function in the 

 anchorage of cilia and the preservation of pellicular shape, 

 especially where there are special intuckings of the body surface. 

 In Stentor the fibres connected to the bases of the somatic cilia 

 are believed to be contractile. 



The fibrils which connect more specialized cilia, such as the 

 cirri and membranelles of Euplotes and the membranelles of 

 Stentor, deserve a little more detailed consideration. Severance 

 of the fibres that interconnect the cirri of Euplotes is known to 

 disrupt their normal co-ordination (Taylor, 1920). It is inter- 

 esting that these '' neuromotor " fibres are built up of many 

 tubular fibrils of a similar size to those which compose the 

 connecting fibres between the somatic cilia of Stentor, although 

 they are not lined up in the same way. Kitching (1961) has 

 tentatively suggested that the neuromotor fibrils of Euplotes might 

 function by the conduction of a propagated contraction. It would 

 be interesting if Taylor's very valuable experiments could be 



