VORTICELLA. 



THE BELL ANIMALCULE. 



MOUNT some of the scum from the top of the water in 

 a jar containing Vorticella, and look for tiny bell shaped 

 organisms borne on a stalk. They are much smaller than 

 Paramecium and are usually in groups or colonies. Be 

 sure that there is plenty of water and that the cover does 

 not press on the animals and distort them. It will not be 

 necessary to have a layer of cotton on the slide, since the 

 animals are fastened to a stalk and will not swim away. 



I. Morphology. 



1. The Stalk. What is its shape? Its length as com- 

 pared with its width? Its shape when it is contracted and 

 when expanded? In the stalk there is present cuticle and 

 ectoplasm but no entoplasm. The central axis (ectoplasm) 

 is usually easily seen. Does it run through the exact center 

 of the stalk? With your highest power study the structure 

 of this stalk and make a drawing of it, very much magnified, 

 showing how it is constructed and how it connects with the 

 body of the animal. Can you give any explanation for the 

 coiling of the stalk when it contracts? 



2. The Body. What is the shape when seen from above? 

 from the side? When the animal is contracted? when 

 it is fully expanded? In a fully expanded individual note 

 the peristome or rounded edge of the bell. Does it extend 

 completely around the bell? The top of the animal is 



