210 HIGH WATER MARK. 



ing themselves, and of so doing this that the move- 

 ments of each individual hair shall be in the most 

 exact harmony with those of its fellows ; not that all 

 bend at the same instant and in the same degree ; 

 but in a rhythmical succession, just as the breeze, 

 supposing it of exactly uniform force, bows down the 

 grass stems in rapid succession. The result is a 

 series of waves : one cilium (or stalk of grass) is at 

 a given moment perfectly erect ; the next, at the 

 same moment, has just begun to bow ; the third is 

 bent still lower ; the fourth has attained its extreme 

 point of flexure ; the fifth has resumed the position of 

 the third, the sixth that of the second, and the seventh 

 is again erect. Thus these seven cilia would limit 

 the extent of one wave ; and the whole line would 

 exhibit a succession of such waves. 



The wave, however, is for no two successive instants 

 in the same spot ; the first cilium iTnTnp.dia.te1y takes 

 the position of the second, the second of the third, the 

 third of the fourth, and so on ; so that while the cilia 

 themselves remain fixed, the waves produced by their 

 alternate flexion and extension perpetually run along. 



If, now, you will take the trouble to draw on paper 

 a number of hairs, equidistant at their bases, but with 

 their extremities in the different states of flexion that 

 I have described, you will see the explanation of the 

 dark running points. Those cilia that are passing 

 from the erect condition to the point of greatest 

 flexure, have their tips more separated than if they 

 were all erect ; whereas those which are passing from 



