ANNULOIDA : ROTIFERA. 



i8i 



are variously disposed over the surface of the body. The 

 Cluetonoti or Hairy-backed Animalcules have no jaws, and have 

 the ventral surface of the body clothed with cilia. They have 

 usually been placed in the Turbellaria, but there seem to be 

 good reasons for regarding them as an aberrant group of Rota- 

 toria. 



The proximal extremity of the body in the free forms ter- 

 minates in a caudal process, or " foot," sometimes telescopic, 

 which ends in a suctorial disc, or in a pair of diverging " toes," 

 which act as a pair of forceps (fig. 53, a). 



Fi& S3' — Rotifera. A Diagrammatic representation of Hydatina. senta (generalised 

 irom Pritchard). a Depression in the ciliated disc leading to the digestive canal ; b 

 Mouth ; c Pharyngeal bulh or mastax, with the masticatory apparatus ; d Stomach ; 

 e Cloaca ; _/" Contractile bladder ; ^^_^espiratory or water-vascular tubes ; h Nerve- 

 ganglion giving iilament to ciliated pit (y&); oQ-vKty. 'Q Melicerta ringetts, (After 

 Gosse.) 



The mouth usually opens into a pharynx, or " buccal fiinnel," 

 which is generally provided with a muscular coat, constituting 

 the " mastax " or " pharyngeal bulb," and which generally con- 

 tains a very complicated masticatory apparatus.* The parts 

 of this apparatus are horny, and are believed by Mr Gosse 

 to be homologous with the parts of the mouth in' Insects. 

 In the females of almost all known speci.es of Rotifera the 

 intestinal canal is a more or less simple tube, extending 



• The lower jaws, or "incus," consist of a fixed portion, the "fulcrum," 

 to which are attached two movable blades — the " rami." The upper jaws, 

 or " mallei," consist each of a handle, or " manubrium," to which is hinged 

 it toothed blade, or " uncus." 



