VERMES. 29 



C. Segmentation of the Body. 



Segmentation is the repetition of ring-like parts of 

 the body of an animal. 



1. Is the entire body of the earthworm segmented ? 



2. Are all the segments (somites) of the same size ? 



3. Do large earthworms have the same number of 



somites as small ones ? 



D. The Body Reg-ions. 



The forward end of the body of any animal is called 

 the anterior end and the opposite end, the posterior. 

 The upper surface of the body is usually called the 

 dorsal surface and the lower surface, the ventral. 



1. How does the anterior end differ from the posterior 



end in, — 

 (a) shape ; 

 (6) color ; 

 (c) sensitiveness ; 

 (<:?) muscular power ; 

 (e) use ? 



2. How does the dorsal surface differ from the ventral 



surface in, — 

 (a) shape ; 

 (6) color? 



3. Has the earthworm a right and a left side ? How 



do you know ? 



4. How can you always tell the right and the left side 



of an animal ? An animal whose right and left 

 sides are similar is said to be bi-laterally sym- 

 metrical. 



What determines whether there is a " head end " ? 



Why do the dorsal and ventral surfaces differ in 

 shape ? 



