THE MICROSCOPE IN ZOOLOGY. 163 



A. Intestinal tube absent. 



, Body variable, without cilia. 



Carapace absent, ASTASI.EA. 



Carapace present, DINOBRYINA. 



Cilia or setae present. 



Carapace absent, ..... CYCLIDINA. 



Carapace present, ..... PERIDIN^EA. 



B. Intestinal tube present. 



Orifice single. 



Carapace absent, ..... VORTICELLINA. 

 Carapace present, . . . . OPHRYDINA. 



Two opposite orifices. 



Carapace absent, ENCHELIA. 



Carapace present, ..... COLEPINA. 

 Orifices differently placed. 

 Carapace none. 



No tail, but a proboscis, . . TRACHELINA. 

 Tail present, mouth anterior, . OPHRYOCERCJNA. 



Carapace present, ASPIDISCINA. 



Orifices ventral. 



Carapace absent. 



Motion by cilia, .... COLPODEA. 

 Motion by organs, . . . . OXYTRICHINA. 

 Carapace present, ..... EUPLOTA. 



IV. ROTATOEIA OR WHEEL ANIMALCULES. These are 

 microscopic, aquatic, transparent animals, of a higher 

 organization than the Infusoria, and belonging in all 

 probability to the class Yervn.es. Their chief interest to 

 the microscopist is derived from the possession of a more 

 or less lobed, retractile disk, covered with cilia, which, 

 when in motion, resemble revolving wheels. They have 

 also a complicated dental apparatus, and generally a dis- 

 tinct alimentary canal, and are reproduced by ova. Some 

 are more or lees covered by a carapace, and in most there 

 is a retractile tail-like foot, sometimes terminated by a 

 suctorial disk or a pair of claw-like processes. The ner- 

 vous and vascular systems are not well known, although 

 traces of them are seen. The young of some possess an 

 eye which often disappears in the adult. They are re- 



