c. Cothurnia. 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 Parammciwn, 

 Nyctotherus and Balantidium instantly, without destroying the 

 essential features of their organization.") 



