INFUSORIA. 



55 



2. Example of the group : Yorticella. 



— A good example of the true Infusoria is fur- 

 nished by Vorticella, a large and well-known 

 form, found plentifully on the roots of duckweed 

 and other similar situations. A group of these 

 elegant organisms, when placed under the micro- 

 scope, presents the appearance of a number of 

 bell-shaped vases, each of which surmounts the 

 extremity of a slender pedicle or stalk {fig. 12, a). 



F'u. 



12. 



Structure of Yorticella, &c. : — a, group of Vorticella ne- 

 hulifera, showing at a, a Vorticella spirally contracted on its 

 stalk ; /3, another form, with its cilia retracted ; 7, a third form, 

 undergoing fissiparous division ; 5, a detached Vorticella bud, 

 furnished with a posterior circlet of cilia ; — h, upper portion of 

 Vorticella campanula (very much magnified) ; (p, commence- 

 ment of ciliary spiral ; tt, peristome , A, lumen of CESophagus ; 

 /3, bent bristle situated in the vestibulum ; 0, one of the stronger 

 cilia which arise in front of the mouth ; k, contractile vesicle ; 

 V, band-like nucleus ; j, cuticle ; ,u, contractile filament of stem 

 forming apical prolongation of contractile layer ; — c, diagram- 

 matic section of Paramecium, showing t, cuticle bearing the 

 cilia ; K, K, contractile vesicles contained in the parenchyma of 

 the body, |. 



E 4 



