238 THE BIOLOGY OF STENTOR 



at a rate of about one change per second until the band itself was 

 destroyed. NiS04 in very weak solution is an effective ciliary 

 anaesthetic for protozoa (see Tartar, 1950); body cilia and mem- 

 branelles in Stentor were stopped in weak solutions, but although 

 not beating, the membranelles keep changing their orientation in 

 the two positions shown in Fig. 67B and c. This reorientation in 

 membranelles which were not beating was most striking to 

 observe — like the batting of eyelashes — and it should also be 

 mentioned that the body contractions of the stentor were in no 

 demonstrable way affected by NiS04. Hence the unstriated basal 

 lamellae and associated fibers of the membranelles, homologous 

 with the striated ciliary rootlets described in metazoa by Fawcett 

 and Porter (1954), rnay be contractile (like the unstriated ribbon 

 bundles of the clear stripes) and serve for orienting the membra- 

 nelles in one direction or another, a function which in this case 

 seems to be completely dissociable from ciliary beating. 



2. Coordination of body cilia 



Every part of the ciliated ectoplasm, without endoplasm or 

 nucleus, is a self-contained coordinating system. This was 

 demonstrated for Stentor and Spirostomum by Worley (1934) who 

 found that in isolated patches the ciha could start and stop, reverse 

 their effective stroke, and beat in metachronal rhythm. Treatment 

 with ciliary anaesthetics such as potassium chloride resulted first 

 in loss of the capacity to reverse, then of metachronal rhythm, and 

 finally of ciHary beating itself. These three kinds of ciliary action 

 are hence dissociable. Individual activity of a cilium and the two 

 types of coordinated movement of cilia therefore are probably due 

 to separate processes. Reversal of beating spread instantaneously 

 like a signal passing over the surface, uninterrupted by incisions 

 and therefore probably not mediated by conductile fibers. Meta- 

 chronal waves are much slower. Hence Worley suggested that they 

 are mediated by interciliary fibers, specialized structures whose 

 effectiveness in integrating cilia may, paradoxically, be due to 

 their slowing down interciliary impulses. In Spirostomum^ the 

 kinetics of which closely resemble those of Stentor (Randall, 1956), 

 Worley found that the metachronal beat could circumvent surface 

 cuts, indicating the presence of transverse connections between 

 rows of body cilia. 



