2l6 AQUATIC MICROSCOPY TOR BEGINNERS. 



monest of all — Rdtifer vulgaris — the whole foot is ar- 

 ranged with joints that slide on each other like the 

 joints of a spy-glass. In this and in similar forms the 

 Rotifer can not only swim, but it can crawl or creep 

 like a leach, 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 repeated. A 

 Rotifer can do this with surprising rapidity, and so 

 travel over considerable microscopic distances in a 

 short time. 



The mouth is usually placed between the two ciliary 

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

 frontal portion of the body, or, in many forms near 

 the front, but on the lower surface of the animal. 

 Those Rotifera 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, and form 

 by far the greater number of known species. 



Following the mouth is usually 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 animal. 

 These jaws are always present in the creatures, and 

 are agreat help to the beginner, for as soon as he ob- 

 serves 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 or hairs or 

 by some other, substitute, but if these internal jaws 



