98 



AXIMAL PHYSIOLOGY. 



[LESSON 29. 



FIG. 166. 



FIG. 167. 



Alimentary canal, Vorticella 

 citrina. 



Alimentary canal, Sten- 

 tor polymorphus. 



of the same class, appear to be much more consistent j thus, the 



alimentary canal of Vor- 

 ticella citrina (Fig. 166) 

 is distinctly sacculated, 

 and so, too, in Stentor 

 polymorphus (Fig. 165); 

 in all these figures the 

 ciliated oral (mouth) 

 aperture is marked a. 



In the Vorticella 

 and Stentor (Figs. 166 

 and 167), the circular 

 intestine is perfectly 

 sacculated (c), or alter- 

 nately dilated and con- 

 tracted (b, Cj d) throughout its entire course. 



Two of the figures (166 and 167) are represented as dissected out 

 of the body ; this has been done by the mind's eye, for no earthly 

 power is equal to such a task manually performed. 



ROTIFERA. 



492. The animals of this class have their vibratile 

 cilia placed in circular or semicircular groups, and 

 when in action they appear to revolve hence their 

 name. The so-called wheel animalcule, found in 

 leaden gutters, and in infusions of hay, is a Eotifer^ 

 a view of which is given (Fig. 168). The mouth is 

 seen at a ; eye-spots at b ; antenna (?) at d ; jaws 

 and teeth, ej alimentary canal,/, g (glandular, ?), 

 mass enclosing it ; h, longitudinal muscles ; i, tubes, 

 containing water, or blood ; k, young animals ; and 

 Z, cloaca. 



The body of a Rotifer is more or less elongated ; 

 its posterior extremity is furnished with a pair of 

 forcipated instruments, or claspers, which, when not 

 required for use, can be retracted, and protected 

 within a sheath. 



493. The vibratile cilia are arranged in from 

 two to five groups, placed on lobes, as shown in 

 Notommata clavulata (Fig. 169, a). 



Eotifer vuigaris. This beautiful creature is as transparent as a 



