EAETHWORM 69 



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

 prostomium. 



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



6. Find the supermiducal pores on segment XV. Position 

 and appearance? 



7. The ovichical 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 all segments except a few at the anterior ex- 

 tremity. 



9. Find the setae or short bristles 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 forty 

 segments as seen in lateral view. Label all of the parts. 



11. Make a diagram of a cross section showing locations of 

 the setae. 



II. Internal Anatomy 



The method of opening the body wall will be demonstrated 

 to small groups in the laboratory. In dissecting the earthworm it 

 is necessary to split open the body wall so it may be pinned out 

 flat, thus revealing the internal organs. In the region just be- 

 hind the clitellum insert one point of the dissecting scissors and 

 cut forward along the mid-dorsal line of the body to about the 

 second segment. While making this cut hold the one point of the 

 scissors just inside the body wall stationary, moving only the 

 free blade of the scissors. This will avoid injury to the in- 

 ternal organs. 



Note that the space inside the body wall is divided into small 

 chambers by partitions called septa. With what do these septa 



