The Animalcules, continued. 123 



Be that as it may, the movement of the cilia gives 

 an air of peculiar liveliness to a group of animalcules. 

 Some possess them around their mouths only, like the 

 vorticellse, but around those mouths the particles dance 

 like sparks from a revolving firework. A vorticella, 

 too, sometimes detaches itself from its stalk, as ob- 

 served at page 112, and it then uses its cilia for pro- 

 pulsion through the water. Others again, as the 

 stentors, and the lively infusoria numbered 6, are 

 nearly covered with them. Their shape and size can 

 only be made out when they chance to move slowly ; 

 it then appears that each filament bends from its root 

 to its point, returning again to its original state, and 

 that there is a sort of " feathering" action, like the 

 stroke of an oar. This being repeated all round a 

 wreath of cilia, conv*eys a strange likeness to a really 

 progressive movement. It is with an effort of the 

 better judgment, based on a recollection of their ap- 

 pearance when detected in slower motion, that the 

 observer manages to rest assured that the object looked 

 -at does not consist of a number of little filaments, 

 chasing each other round a circle, or, in the case of 

 the rotifers, of a little toothed wheel, revolving bodily 

 upon a fixed axle. But the same illusion will take 

 place occasionally with regard to other moving objects, 

 each of which we know experiences no progressive 

 change of place. The appearance of moving waves 

 caused by "the wind that shakes the barley" is a 

 familiar instance ; and one which impressed me 

 forcibly, was the apparently wheel-like movement of 

 some circular devices in gas, when the principal streets 



