LUMBRICUS TERRESTRIS. 47 



f) The intestine leading from the gizzard to the posterior end of the 



body. It is constricted in the intervals between the segments. 



g) The dorsal blood-vessel lying upon the intestine. Some of the 



larger transverse branches of this blood-vessel may show in the 

 region of the oesophagus. These are called the aortic arches. 



h) The reproductive organs, three pairs of large white bodies and 

 two pairs of smaller white sacks, all surrounding the oesophagus. 



i) The oesophageal pouches first pair and cesophageal glands- 

 second and third pairs attached to the oesophagus back of the 

 pharynx. These are dark in color. 



j) The nephridia, slender, much convoluted tubes occurring in pairs 

 in all the segments except the first three and the last. They are 

 organs of excretion. 



k) The cerebral ganglion, a minute, two-lobed, white speck near the 

 anterior end of the pharynx. 



Exercise 2. Make a life-size drawing locating the parts just indicated. 



Technical Note. Sever the intestine at the posterior limit of the slit 

 in the body wall and carefully remove the alimentary tract, picking 

 out with a needle the portion in the region of the cerebral ganglion. 



1) The ventral blood-vessel will be exposed by the above dissection. 

 How does it compare with the dorsal blood-vessel in size ? There 

 are in addition, three smaller blood-vessels in this region, but 

 they are too difficult of demonstration for this exercise. 



m) Beneath the ventral blood-vessel is the ventral nerve cord. 

 Note its branches and the swellings or ganglia. 



n) At the anterior end of the nerve cord a loop, circumcesophageal 

 collar, encircles the oesophagus and connects the cord with the 

 cerebral ganglion. 



Exercise 3. Make a diagram of the nervous tract, showing also the 

 ventral blood-vessel if possible. 



Exercise 4. Cut out a piece of the nerve cord, about a half inch in length, 

 place it in water in a watch glass and study with a dissecting 

 microscope or hand lens. Note the method of branching. Draw. 



