368 ELEMENTARY BIOLOGY. [CHAP. VII. 



a. Epistylis. Bell-shaped animals growing on 

 h'a?tched no7i-contractile stalk. 



b. Carchesium. A form very like Vortkella but 

 borne on a branched contractile stalk. 



c. Cothumia. An almost sessile form, provided 

 with a cup or envelope into which the bell can 

 be retracted. 



[The activity of the movements of the free Infusoria interferes 

 with the complete examination of the living animal. It is well 

 therefore to add a little osmic acid solution to the drop of water 

 under examination. This kills such Infusoria as P ara7ncBciuni^ 

 Nyctotherus and Balaiitidiuin instantly, without destroying the 

 essential features of their organization.] 



