. The biology of cilia and flagella. Cilia and ciliary motion; Flagella (Microbiology). THE FORM OF BEAT OF CILIA 141 cilium returns to the position required to commence a new effective phase. For maximum efficiency of the effective stroke, the cilium should present as large a surface as possible perpendi- cular to, and yet moving parallel with, the required direction of movement of the medium. In the recovery phase the cilium should present the smallest possible surface to the moving medium, and is therefore trailed through the water (see Fig. 37). The beating of the membranelles of Stentor i
. The biology of cilia and flagella. Cilia and ciliary motion; Flagella (Microbiology). THE FORM OF BEAT OF CILIA 141 cilium returns to the position required to commence a new effective phase. For maximum efficiency of the effective stroke, the cilium should present as large a surface as possible perpendi- cular to, and yet moving parallel with, the required direction of movement of the medium. In the recovery phase the cilium should present the smallest possible surface to the moving medium, and is therefore trailed through the water (see Fig. 37). The beating of the membranelles of Stentor is easily observed under stroboscopic illumination, especially at the edge of the peristome where the cilia appear as in Fig. 37. The sequence. Fig. 38. The sequence of movements of a membranelle of Stentor (from Sleigh, 1960). of movements of these cilia in one complete cycle is shown in Fig. 38. The effective phase starts with stage 1, and has nearly ended by stage 3. The wave of flexure which causes the recovery phase has started to move up the cilium before the effective phase has been completed, and, by the time it has reached the tip of the cilium, the cycle of beat is complete. It is interesting that the effective and recovery phases are not separate parts of the beating cycle, but that they overlap, merging together in a single movement that could be caused by a single wave of contraction passing up the cilium from the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Sleigh, Michael A. Oxford, New York, Pergamon Press
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