200 MICROSCOPY FOR BEGES'NERS. 



CHAPTER VIII. 



KOTIFEKS. 



WHEN these transparent microscopic animals are 

 swimming or taking food, there is usually an appear- 

 ance of two, small, rapidly rotating wheels on the front 

 border of the body, an appearance that suggested the 

 name of Rotifera, or Wheel -bearers, for the group. 

 The two organs certainly do seem like rapidly revolv- 

 ing wheels when viewed under a low power, but they 

 are in reality two disks or lobes surrounded by wreaths 

 of fine cilia, which vibrate so quickly that the eye can 

 perceive the effect only. It is by the action of these 

 cilia that the Rotifer swims and captures food, the cur- 

 rents produced by them when the animal is at rest set- 

 ting in towards the mouth, usually situated between the 

 ciliary (or cilia-bearing) disks, and carrying particles of 

 food which the Rotifer accepts or rejects. As a rule 

 the ciliary disks are two separate organs, but they may 

 be united into one, or the Rotifer may have the front 

 margin of the body bordered by a single line of cilia, or 

 the disks may be entirely absent, and replaced by long 

 arms, as in Stephanoceros, or by clusters of long, fine 

 hairs, as in Flvsculdria, both of which are Rotifers. 



Most of these animals have eyes at some period of 

 their life, or little red specks supposed to be imperfect 



