THE WHEEL-ANIMALCULE. 71 



XIII. 



THE ROTIFER VULGARIS, OR COMMON WHEEL- 

 ANIMALCULE. 



Plate XII. 



IN the water first examined may be noticed several 

 elongated leech-like animalcules, swimming about in 

 every direction, now winding their way among the 

 swarms of lesser beings, then fixing themselves by one 

 end, and protruding from the other extremity two cups 

 fringed with cilia, which appear to whirl round and 

 round like a pair of wheels on their axes ; or sud- 

 denly drawing in these organs, shrinking up the entire 

 body into a globular opaque mass, and leaving no 

 part of their internal organisation visible. These crea- 

 tures are the Wheel-animalcules, commonly so called, 

 and were the first species of the Rotifera that attracted 

 the attention of the early observers *. 



* The Rotifer vulgaris was first figured and described by Leeuwen- 

 hoek in 1702; and more fully by Baker in 1744. See " Employment 

 for the Microscope," pi. xi, p. 288, ed. 1785. 



