12 THE BIOLOGY OF THE CELL 



pare with Amoeba. What determines the shape ? 

 Is there any variation in shape as the animal as- 

 sumes different positions ? Is the body symmet- 

 rical? Has the animal an anterior and a poste- 

 rior end ? How are they distinguished ? What 

 is the significance of the animal's common name ? 

 Make drawings to show the shape of the animal 

 as seen in different positions. 



h. Size. — How does Paramecium compare in size with 

 Amoeba ? Examine several specimens to see if 

 there are any variations in size. Is the animal 

 large enough to be seen without a microscope? 

 Compare length with breadth. Make a camera 

 drawing of a specimen and find its actual size. 



0. Structure. 



1. The cuticle or cell-wall. — Note its extreme 



transparence and flexibility. Is it present over 

 the entire surface ? Is it a complete film — i. e., 

 is it entirely without openings? Place some 

 specimens in a drop of water on a slide, but 

 do not put on the cover-glass. Note the ap- 

 pearance of the cuticle as the water evaporates 

 and the body of the animal becomes dry. Can 

 you discover any variations in thickness ? Any 

 markings on the surface ? 



2. The ectosarc. — Is it similar to that of Amoeba ? 



Account for any differences that you may find. 



3. The endosarc. — Compare with that of Amoeba. 



Look carefully for food- vacuoles — i. e., drops 

 of fluid containing particles of ingested sub- 

 stances. 



4. The contractile vacuoles. — How many do you 



find? Where are they situated? Examine sev- 



