94 ELEMENTARY BIOLOGY. [iX. 



B. Other forms closely allied to Vorticella which may he 

 met with, and which will do nearly as well for exami- 

 nation, are ; — i 



a. Epistylis. Bell-shaped animals growing on a 

 Iranched non-contractile stalk. 



b. Carchesiilin. A form very like Vorticella hut home 

 on a iranched contractile stalk. 



C. Cothumia. An almost sessile form, provided with 

 a cup or envelope into which the bell can be re- 

 tracted. 



[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 Parammcimn, 

 Ryototherus and Balantidium instantly, without destroying the 

 essential features of their organization.] 



