166 THE SCIENCE OF LIFE. 



Epistylis differs from Vorticella in having a branching 

 and non-contractile stem. 



Vaginicola possesses a horny, cuticular case, (a cara- 

 pace, or lorica,} into which the animal can retire. 



Stentor is a fresh-water infusorian, shaped like a trum- 

 pet. It may be found either free or attached. 



Paramecium, (Fig. 70,) is a free, fresh-water animal- 



FIG. 70. Paramecium Aurelia, an Infusorian animalcule, magnified 300 times, 



cule, shaped like a slippe~r, the hole for the foot being 

 represented by the mouth. 



Suctorial Infusoria (order Suctoria] may be illustrated 

 by the parasitic Acineta, Chap. I, Sec. 6. They have 

 filaments ending in suctorial disks, which are capable 

 of protrusion and retraction, and are used for pre- 

 hension. 



The Flagellate Infusoria (order Flagellata) perform lo- 

 comotion by means of long filaments, or flagellae, which 

 may be single, double, or multiple. 



The Noctiluca, (Fig. 71,) is the best-known member 

 of this order. It is very minute, about one eightieth of 

 an inch in diameter, and presents little more structure 

 under the microscope than a simple sac of bioplasm, 

 with vacuoles, an oral aperture, and a tail of flagellum, 



