EARTHWORM. 93 



is a glandular structure to secrete the cases or cocoons in 

 which the eggs are laid. 



Hold a living worm near the anterior end. Does it pro- 

 ject a proboscis from the mouth? Look on the back and 

 see the red dorsal blood-vessel showing through the skin. 

 Study the somites in front of the clitellum, looking for 

 openings of the reproductive organs on the ventral surface. 

 How many pairs of these do you find, and on what seg- 

 ments are they? Leave a dead worm in water for several 

 hours; can you separate from it an external transparent 

 cuticle? 



Draw a worm from the side, being careful to get in the 

 right number of segments, back to the posterior end of 

 the clitellum, and bringing out as many of the points dis- 

 covered as possible. 



Pin a worm which has been in alcohol with pins pass- 

 ing through the preoral lobe and the hinder end of the 

 body in a dissecting-pan. With the scissors open the 

 dorsal wall of the body from just behind the clitellum to 

 the anterior end, taking care to cut through only the dor- 

 sal wall. It is best to make this cut just a little to one 

 side of the median line. As you start to lay open the body, 

 notice the partitions (septa or dissepiments) running in from 

 the body-wall and holding the parts together. Do the 

 septa correspond in position to the external rings or to 

 the spaces between them? Do they divide up the body 

 into a series of body-cavities? Do the cavities of the right 

 side correspond in position with those of the left? Is 

 there a partition (mesentery) separating the cavities of 

 the two sides? 



Cut the septa with the scissors and pin out the body- 

 wall. This exposes the digestive tract lying in the axis 

 of the body. In it make out the following regions: (1) A 



