Kolpodea.] THE INFUSORIA. 309 



Genus CXXI. Paramecium. The long A7iimalcules 

 are ciliated on all sides, possess a (wart-Kke) tongue-like 

 process, but have no visual point. The cilii are disposed 

 in longitudinal series, those near the mouth are sometimes 

 longer than the others, and are alone subservient to loco- 

 motion, except in two doubtful species. In P. chrysalis 

 the long oral cilii are remarkable. The digestive cells are 

 numerous, amounting to more than a hundred ; they are 

 berry- like, and arranged along the alimentary canal, which 

 is curved: in five species they have been demonstrated by 

 artificial means, in a sixth by its usual green food. The 

 ova in two species are seen as a granular mass. In all, 

 except one species, male organs are visible. The curious 

 star-like contractile vesicle in the larger species is highly 

 interesting, when physiologically considered, as are also 

 the little black bodies seen in P. aurelia. In four species 

 complete self-division, transverse and longitudinal, has been 

 observed alternately. 



510. Paramecium aurelia (M.) The slipper Animal- 

 cule has a club-shaped cylindrical body, slightly attenuated 

 anteriorly. An oblique longitudinal fold borders upon the 

 very receding mouth. Ehrenberg states that he has seen 

 small dark crystalline bodies abundant in the frontal 

 region, which he conceives are indications of the presence 

 of nervous matter, as such crystalline bodies often accom- 

 pany it. These creatures appear to have the sense of taste ; 

 and among the same group some individuals prefer one 

 kind of food, and others another. This interesting fact 

 may be observed by mixing blue and red colours together, 

 when some will feed upon the former, others upon the 

 latter, as indicated by the colour of the digestive cells ; in 



