186 



CO-ORDINATION OF BEAT 



since the frequency is the same throughout, the wave velocity 

 must be lower in this region of the row. Measurements of the 

 wave velocity taken in the gullet region and in the main part of 

 the row are shown in Table 14. It is also interesting that the 

 cilia in this region of the row are closer together than in the main 

 part of the row, and it w^as found that the number of cilia in each 



Table 14. The values of vapious parameters of ciliary activity 



IN THE gullet REGION OF THE MEMBRANELLE ROW OF Stentor, COMPARED 

 WITH THOSE IN THE MORE DISTAL REGION OF THE SAME ROW OF CILIA 



Wavelength 



Frequency 



Wave velocity 



Interciliary distance 



Cilia in each wave 



Cilia stimulated per second 



Gullet region 



15-9 /x 



27 -4 beats sec 



436 /Lt/sec 



2-68 )Lt 



5-95 



163 



Distal region 



24-2 /x 



27 -4 beats/sec 



613 fXj'sec 



4-06 IX 



5-97 



163-5 



wave and the number of cilia stimulated per second is constant 

 throughout the row (Table 14). Hence it appears that the 

 conduction depends on the number of cilia involved in the 

 transmission, rather than on the linear distance. These results 

 would not be out of place in a stepwise conduction system where 

 the excitation takes the main part of the total conduction time. 

 Although it is just conceivable that the cilia of the gullet region 

 could give a slower conduction by reduction of mechanical 

 interaction, because they are smaller than the large cilia, the fact 

 that the frequency and wave velocity are independent makes this 

 very unlikely indeed. 



The behaviour of regions of the membranelle row isolated by 

 cuts led to the pacemaker theory (Sleigh, 1957). Cilia which 

 are isolated from all others normally show an autonomous beating 

 activity, and yet, in an epithelium or in a row with others, they 

 may be controlled and made to beat in a co-ordinated rhythm. 

 Such control could be exerted if the co-ordinating impulse was 

 to arrive before the cilium was ready to show a spontaneous beat. 

 If each cilium shows a spontaneous build-up of excitation to a 



