20 THE BIOLOGY OF THE CELL 



expanded condition ? "What causes it ? "What 

 part is the first to resume the expanded state ? 

 Compare the rate of contraction with that of 

 expansion. ISTote that the body sometimes sep- 

 arates from the stallc. How does the body- 

 move after separation ? What becomes of it ? 

 What position does the stalk assume? What 

 reasons can you give for such behavior of body 

 and stalk ? 



2. Ciliary movement. — What differences between 



the bell animal and the slipper animal in this 

 respect? What use does Vorticella make of 

 its cilia ? What is the significance of the ani- 

 mal's scientific name ? 



Under Ee-production insert : — 



3. Encystalion. — Look for bell animals which have 



become encysted. How do they diflier from 

 the others? Of what use is this process ? What 

 seems to be the cause of it ? 

 Make drawings of specimens undergoing fission ; con- 

 jugating; encysted. 



General Questions. — To what different uses do you 

 find in general the various parts of the beU animal's 

 body adapted ; in other words, to what extent do you 

 find the principle of the "physiological division of la- 

 bor " carried out in this simple animal? From your 

 study of the Protozoa, as exemplified by Amoeba, Para- 

 mecium, and Vorticella, what do you consider to be 

 some of their principal characteristics and differences ? 



