WHEEL-BEAEEES. 261 



broad flattish lobes, and in an instant each of the two 

 lateral ones is crowned by a wheel of dark points in 

 rapid horizontal revolution. Is not this a charming 

 sight ? Honnd and round go the wheels, forming two 

 perfect crowns, which rotate with uninterrupted and 

 unceasing course, smooth and regular, which we can 

 compare with nothing else than the crown-wheel of a 

 watch, if allowed to run down. 



IN'ow these are examples of ciliary action. Though 

 at first it is almost impossible to persuade oneself that 

 there is not an actual rotation of parts, yet this is only 

 an illusion, as I have already explained. The waves 

 alone move, the cilia themselves retaining their position 

 unchanged except that they alternately bend and erect 

 themselves. It may assist your idea of this motion to 

 advert to a field of corn, over which a smart breeze is 

 blowing. Ton see that waves chase each other across 

 the field ; but your reason, and indeed your observa- 

 tion, teUs you, that this appearance is produced entirely 

 by the alternate bending and rising of the ears of com, 

 which are of course stationary. 



The beauty and wonderfulness of these ciliary wheels 

 are so striking, especially when one sees them for the 

 first time, that for a while we see nothing else : we can- 

 not take our eye off from them. But when you have a 

 little satisfied your sense of seeing, you may examine 

 other points of interest in this charming little animal. 



The cilia are remarkably stout and long in this 

 genus, but on the middle lobe of the front there are 

 other processes of the same character ; but still stouter. 

 These too are not properly vibratile, at least they 

 do not make circular wheels : ordinarily they project 

 like stiff erect bristles, or converge towards each other. 



