WHEEL-ANIMALC ULFS. 1 7 3 



means of curious appendages resembling distorted limbs or moveable claws. 

 As an example, we mention the Lcmea monilaris, which attaches itself to the 

 eye of the sprat, plunging its whole head into the coats of that organ, where 

 it is retained by means of barbed projections. It is luminous in the dark, and 

 the fishermen are accustomed to call the unfortunate fishes thus infested 

 " lantern sprats.'' 



WHEEL-ANIMALCULES. ORDER ROTIFERA.* 



Our stagnant waters everywhere abound with innumerable 

 tribes of microscopic animalcules, some of which have been de- 

 scribed in an early chapter. Returning to this spectacle, suppose 

 we take from any pool a leaf of duck-weed, with a few drops 

 adhering to it, and placing this beneath our microscope, carefully 

 inspect the little world exhibited within. The crowds of Infusoria 

 are recognized at once, as they go gliding past or sporting in a 

 mazy dance ; but ever and anon there comes rushing among their 

 swarms, like a fierce tiger through a flock of sheep, some monster 

 of a different kind, having on its head what appear to be great 

 wheels, that spin continually round and round, and, like the 

 paddles of a steamboat, serve to move it through the water. The 

 animals in question have been named Rotifcra or " Wheel-bearers." 

 In their size they much exceed the humbler Infusoria, over which 

 they tyrannize. Their length may be roughly estimated at about 

 one-fiftieth to one-hundredth of an inch terrific giants when 

 compared with the small fry around them, although themselves 

 scarcely perceptible by unassisted vision. 



The distinguishing character from which these minute but 

 highly-organized beings have derived their name, is the remark- 

 able appearance of their so-called wheels. This exactly resembles 

 the movement of the crown-wheel of a watch in swift rotation, 

 and the early microscopic observers supposed such to be actually 

 the kind of movement with which the organs in question were 

 endowed, though by what kind of mechanism living wheels could 

 really spin round, and yet preserve their connexion with the 

 animal, they could not conceive. Better instruments, however, 

 and closer observation, have solved the difficulty. Instead .of 

 being real revolutions of wheels, it is now clearly established that 

 the apparent rotations are merely an optical illusion, similar to 

 that by which, when the tide is rolling in upon the beach, the 

 waves appear to the eye to move rapidly forward, while, as is 

 well known, they merely rise and fall in constant succession. The 



* Rota, clicked; fero, I carry. 



