ROTIFERS. 203 



glass. In this and similar forms the Rotifer can not 

 only swim, but it can crawl by fixing the front of the 

 body against the slide, drawing in the telescopic joints 

 of the foot and clinging with the toes ; the front is then 

 loosened, the foot extends and carries the whole body 

 forward for a short distance, when the action is re- 

 peated. A Rotifer can do this with surprising rapidity, 

 and so travel over considerable distances in a short time. 

 The mouth is usually placed between the two ciliary 

 disks, when they are present, near the centre of the 

 frontal portion of the body, or, in some forms, it is 

 placed near the front, but on the lower surface of the 

 animal. Those with the mouth in the last - mentioned 

 position usually feed by gliding along with the front of 

 the body in contact with the plant, tearing and biting 

 off small particles as they go. These may be called the 

 nibbling Rotifers. Following the mouth there is often 

 a tubular passage leading to a pair of wonderful jaws 

 inside of the body, which, with a low-power objective, 

 can be seen in action through the transparent tissues of 

 the Rotifer. These jaws are always present in these 

 creatures, and are a great help to the beginner, for as 

 soon as he observes them pounding and crunching away 

 inside of a transparent, legless, microscopic animal, he 

 may be sure that his specimen is a female Rotifer. The 

 ciliary disk may be absent, or replaced by arms, hairs, or 

 some other substitute, but if these internal jaws are 

 present the specimen is a Rotifer, and can be nothing 

 else. By some observers'these curious organs are called 

 10 



