256 Description of the Plates. 



a. Cilia, of uniform size all over the body. These organs are 

 supposed to belong- to the parenchyma of the body, and to 

 be protruded through innumerable very fine orifices in the 

 indurated integument. The integument in the ciliated 

 Infusoria is suflSciently resistent to give their bodies the 

 definite outline which distinguishes them from those of the 

 other Protozoa; but it is not ordinarily demonstrable as 

 distinct from the contained parenchyma without the use of 

 reagents. 



h. ' Nucleus ' or ovary, with adherent ' nucleolus ' or testis. 



c. Contractile vesicle, probably representing rudimentarily a 



water- vascular or depuratory system, and opening on the 

 exterior of the body. It is always situated in the cortical 

 layers of the parenchyma, but does not appear to have defi- 

 nite walls of its own, as distinct from the contractile cyto- 

 plasm in which we find it. Tubular ramifications exist in 

 connection with it in some genera. 



d. Particles of alimentary matter, which, together with the struc- 



tures lettered b, c, e, and with pigment granules, oil globules, 

 and very fine cortically-placed granules, make up the mor- 

 phological elements contained in the hyaline ' sarcode' or 

 ' cytoplasm,' 

 €. Oral inlet placed in this species, though not ordinarily ia 

 others, at the apical pole of the body. It is prolonged into 

 an oesophagus lined by a prolongation inwards of the cuticle, 

 and strengthened by the development upon it of longitudinal 

 teeth forming a circlet. The oesophagus opens directly into 

 the central parenchyma of the body, which is less closely 

 compacted together than the cortical layers, and in which 

 the particles of food, together with such water as is swal- 

 lowed with them, can freely circulate. The undigested 

 refuse of the alimentary particles are ultimately extruded 

 by the anus, which has a fixed position in all Infusoria 

 except the aproctous Opalinae and Acinetinae, and which in 

 this species is near the contractile vesicle c, at the aboral 

 pole of the body. It is ordinarily visible only at the moment 

 of the extrusion of the faeces, except in the few cases, of 

 which Prorodon is not one, in which the cuticle is prolonged 

 inwards at that, as it is at the oral orifice. The excess of 



