Plate II, Electron micrographs of sections of Anodonta cilia 

 and their bases. 



{a) Longitudinal section through the basal region of a frontal 

 cilium. The section is perpendicular to the plane of the central 

 fibrils and passes through the basal foot on the left. The 

 structure of the transition region and basal body is illustrated 

 in Fig. 7. Note that the main part of the striated root originates 

 on the right, on the side opposite to the basal foot. >; 47,000. 



{b) Transverse section through ciliary basal bodies of a frontal 

 cell. The basal feet of all the basal bodies project in the 

 same direction (towards the effective stroke of the beat). 

 Tubular fibrils run among the basal bodies and some connect 

 with the basal feet. > 53,000. 



(c) Longitudinal section of a short length of a frontal cilium. 

 The two central fibrils may be seen, and some radial links and 

 spiral striations of the central region are visible in places. 

 X 84,000. 



{d) Transverse section through the double row of cilia on a 



laterofrontal cell. The cilia beat towards the right in the 



effective stroke. Note that all have the same orientation with 



respect to central fibrils, peripheral fibrils and mid-filaments. 



X 34,000. 



All micrographs from Gibbons (1961b). 



