THE EARTHWORM. 133 



5. A swollen region (the clitelluni) between the thirti- 

 eth and fortieth segments (counted from the front), em- 

 bracing several segments. 



Find a pair of small pores on opposite sides of the 

 median ventral line of the fifteenth segment, and another 

 similar but smaller pair on the fourteenth segment. These 

 are the external openings of the reproductive organs. 

 Two other pairs of pores may be made out, sometimes 

 with difficulty, on opposite sides of the median ventral 

 line, a pair on the groove between segments 9 and 10, 

 and another pair on the groove between segments 10 and 

 11. These are the openings of the seminal receptacles, 

 (accessory organs of reproduction). 



A row of pores is present on the median dorsal line, 

 one at the anterior edge of each segment, opening directly 

 into the body cavity. These are not very evident. 



Find two pairs of sette (or locomotor bristles) on each 

 side of each segment, one pair at the edge of the flattened 

 ventral surface ; the other a little higher, on the side of 

 the body. Observe that these are arranged in four longi- 

 tudinal double rows. 



Pin the specimen down for dissection beneath weak 

 alcohol, with one pin through the prostomium only, and 

 another through the last segment, with the body slightly 

 stretched between the pins. Very great care will be 

 necessary to successfully complete the following dissec- 

 tion. Cut no more than directed. 



Dissection. With thin, sharp scissors make a shallow, 

 longitudinal cut through the body wall, along the dorsal 

 surface, the entire length of the body, taking care not to 

 injure the organs which lie beneath. At the middle of 

 the body draw the edges of the cut apart, and observe the 

 septa (or partitions) which extend transversely across the 

 body cavity. Observe that these correspond in position 



