48 MANUAL OF ZOOLOGY SECT, i 



class Infusoria among the Protozoa. But in one section 

 of the class the order Tentaculifera cilia are only pre- 

 sent in the young, their place in the adult being taken by 

 appendages known as tentacles. The form of the body in 

 the Infusoria (Fig. 19) is very varied; it may be globular, 

 ovoid (/), kidney-shaped (2), trumpet-shaped (j), vase- 

 shaped (<?), produced into a long, flexible, neck-like pro- 

 cess (5), or into large paired lappets (6), flattened from 

 above downwards, or elongated and divided into a series 

 of segments. Most are free-swimming, but many are fixed, 

 usually by means of a slender stalk (p). 



The arrangement of the cilia also varies greatly. Some, 

 like Paramoecium, have small cilia of uniform character 

 distributed over the entire surface. Others have different 

 kinds of cilia on different parts of the surface, while in 

 others the cilia are entirely confined to certain regions. 

 An instance of the latter arrangement is the common 

 stalked form Vorticella, with its allies such as Epistylis (<?), 

 in which the cilia are confined to the free extremity. In 

 another group, again, the body, which is of flattened shape, 

 bears on its dorsal surface a small number of very fine, 

 motionless cilia, while on the ventral surface the cilia are 

 very strong, and are modified into the shape of hooks, bristles, 

 or plates with fringed ends. The hooks and plates do not 

 vibrate rhythmically like ordinary cilia, but are moved 

 as a whole at the will of the animal, such Infusoria being 

 able, in addition to swimming freely through the water, 

 to clamber by the aid of these specially modified cilia over 

 the surface of weeds, etc. Tentacles may be present in 

 addition to cilia (14) and a number of other exceptional 

 modifications (10 /j) occur which cannot be specially 

 referred to here. 



In addition to cilia, many genera possess delicate sheets 



