62 LABORATORY DIRECTIONS 



indrical in form but is slightly flattened on one surface. This 

 flattened surface, which is also usually light in color, is the ven- 

 tral surface of the worm. The anterior region is the more robust 

 of the two body extremities. 



2. The most anterior part, the prostomium, is not a true 

 segment. How far does it extend through the next division, the 

 peristomium, or first true somite? Make a drawing, X5, of the 

 dorsal view to show the relation of these two parts. 



3. The elite Hum consists of several thickened segments 

 forming a partial ring in the anterior region of the body. On 

 which surface of the body is this ring incomplete in this species? 

 Record on the drawing asked for under paragraph 10, the number 

 of segments anterior to the clitellum, in the clitellum, and pos- 

 terior to the clitellum. What part of body has a constant number 

 of segments? Record the results of your counting after your 

 desk number on the table outlined upon the blackboard. 



4. Locate the mouth on the ventral surface just behind the 

 prostomium. 



5. The anus occurs in the last segment. Shape ? Position ? 



6. Find the spermiducal pores on segment XV. Position 

 and appearance? 



7. The oviducal pores occur in similar positions on segment 

 XIV, but are much smaller and visible only upon careful exam- 

 ination with a lens. 



8. Dorsal pores, very small, on dorsal median line at an- 

 terior margin of each segment. Many are indistinct. 



9. Find the setae or short bristle extending beyond the sur- 

 face of the body wall. How many on a somite and how ar- 

 ranged? In what direction do they point? This can be deter- 

 mined by pulling the worm gently between the fingers. 



10. Make an outline drawing X3, of the anterior part of the 

 body as seen from the side, slightly tilted so that part of the ven- 



