52 THOUGHTS ON ANIMALCULES. 



X. 



THE ROTIFERA, OR ROTATING ANIMALCULES. 



THE term ROTIFERA, or Wheel-bearing Animalcules, 

 by which this class is distinguished, refers to the ap- 

 pearance assumed by the zones, or circular rows of cilia, 

 around the upper part of the body, when rapidly vibrat- 

 ing; and which so closely resembles that presented by the 

 rotation of a wheel, that every one who sees the pheno- 

 menon is struck with the similitude. The resemblance 

 is heightened by the wavy or undulating motion by 

 which one cilium is carried out of sight, while the next 

 is visible ; for this alternate presence and disappearance 

 of the image contributes to the optical illusion. The 

 cilia do not occur on any other part of the body, as in 

 the Polygastria; the semblance of such processes on 

 some of the larger Rotifera is produced by parasitic 

 plants*. 



The ROTIFERA possess a definite form, and rotators 

 formed of cilia ; many species have a false foot, or pedi- 



* Ehrenberg. 



