VERMES. 35 



3. Is the worm bi-laterally symmetrical ? 



4. How do the somites vary in size ? 



5. How does the most anterior part of the worm 



(prostomium) differ from the somites which 

 follow it ? 



6. Where is the mouth located with reference to the 



prostomium ? 



7. Locate four small eye-spots on the dorsal surface of 



the prostomium. 



B. The Appendages. 



1. What is the general arrangement of the append- 



ages ? 



2. Is any somite without its pair of appendages ? 



3. Why do the appendages vary in size ? 



4. Notice in the make-up of a single appendage, — 

 (a) a tuft of hair-like bristles (setae) ; 



(6) a fleshy part (gill). 



5. Are the setae nearer the dorsal or the ventral side of 



the worm ? 



6. Do you find any tentacles, or " feelers," at either end 



of the body ? 



C. Optical Anatomy. 



In a small mounted specimen trace the alimentary 

 canal through the transparent body wall distin- 

 guishing, — 



(a) the pharynx, an anterior thick-walled enlarge- 

 ment ; 



(6) the crop, a thin-walled enlargement next posterior 

 to pharynx; 



(c) the stomach-intestine, a thin-walled tube extending 

 through the remainder of the body. 



