LUMBRICUS. 75 



Place a living specimen upon moist filter-paper and observe 

 the direction and method of movement. How can it reverse its 

 direction? Gently touch different parts of the body to see 

 which are the most sensitive. 



Observe the movement of the blood in the dorsal vessel. In 

 what direction does it move? Does the vessel change in shape? 



Place a preserved specimen in a dish with a little water and 

 notice : 



1. The difference in shape of the two ends of the body. The 

 mouth is at the anterior end, below the protruding lobe of the 

 prostomium. The anus is a vertical slit at the end of the last 

 somite. 



2. The dorsal and ventral sides. How do they differ? 



3. The right and left sides are symmetrical. Count the somites 

 of the body, compare with others, and record the result. 



4. On the anterior third of the body certain somites are 

 swollen and form the clitellum. What somites are swollen? 

 The clitellum is not present in young individuals. It is used in 

 making egg-cases and providing food for developing embryos. 

 Understand how this is accomplished. 



5. Small swollen areas on the ventral side of the fifteenth 

 somite, where the vasa deferentia open. 



6. Setce project slightly from the surface of each somite. 

 These light colored spines are easily felt with the fingers. See 

 if you can determine the number and position of the rows by 

 stroking gently. How are they used ? 



Draw a ventral view of the anterior end, including the clitellum, 

 and another view of the posterior end. 



Taking care not to cut deep, with fine scissors cut through 

 the dorsal wall of the body, and extend the cut the whole length 

 of the body. Carefully spread and pin the animal open. In 

 doing this you must tear or cut the septa, but be careful not to 

 tear or break the organs that perforate them. 



Alimentary Canal. — This consists of a straight tube that 

 runs the length of the body. 



1. Immediately behind the mouth is a muscular, white organ, 



