102 



INTRODUCTION TO ZOOLOGY 



a taiF or " foot " which is often jointed, and is more or less 

 retractile. Sometimes this foot is forked, or divided into 

 three processes or " toes " ; through the tips of these is dis- 



Flosculana Srephan oc cros Melicerta Hydahna 



FIG. 58. Typical Rotifera. (After Hudson and Gosse.) 



charged the secretion from certain cement glands in the tail, 

 by means of which the animal is able to fix itself temporarily 



to any support in the 

 water. Some few Roti- 

 fers are permanently 

 fixed, and in such cases 

 the body is usually sur- 

 rounded by a tube, which 

 may be transparent and 

 is secreted by the skin of 

 the Rotifer (e.g. in Floscu- 

 laria and Stephanoceros), 

 or it may be made of 

 foreign particles which 

 are built up into a case 



D y ^Q creature itself (e (J 

 > 7 . , x , T , -^ ,.. x ^ 

 MdlCerta). Most RotllerS, 



however, can swim freely 

 in the water by the movements of the cilia of the disc (e.g. 

 Hydatina), and some also creep about somewhat like a Looper 

 Caterpillar. A few have stiff, hair -like appendages which 

 can be vigorously moved, causing a skipping movement (e.g. 

 Pedalion, Fig. 59). 



Though these forms are all microscopic, they are compli- 



FIG. 59. The Skipping Rotifer (Pedalion}. 

 (After Hudson and Gosse. ) 



A shows the outer form ; e, eye-spot ; dl, dorsal 

 limit; vl, ventral limit; ll-ll', lateral limbs. 

 B, Diagrammatic to show the muscles, m. 



