EOTIFERA. 229 



the eye of the sprat, plunging its whole head into the coats of tliat 

 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. 



Ninth Order of Crustaceans. 

 Wheel-bearers (Rotifera)* 



Our stagnant waters everywhere abound with in- 

 numerable tribes of microscopic animalcules, some of 

 which have been described in an early chapter. Re- 

 turning 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, care- 

 fully inspect the little w^orld exhibited within. The 

 crowds of Infusoria are recognized at once, as they go 

 gliding past, or sporting in mazy dance, but ever and 

 anon there comes rushing among their swarms, like 

 a fierce tiger tlirough 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 tln-ough the water. The animals in ques- 

 tion have been named Rotifera or " Wheel-bearers." 

 In their size they much exceed the humbler Infu- 

 soria, 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 fi-y around them, although them- 

 selves scarcely perceptible by unassisted vision. 



The distinguishing character from which these 

 minute but highly-organized beings have derived 

 their name, is the remarkable appearance of their 

 so-called wheels. This exactly resembles the move- 

 ment of the crown-wheel of a watch in swift rota- 

 tion, and the early microscopic observers suppose<:l 

 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 



t Rota, a wheel ; fero, I carry. 



