LtJMBRICUS. 101 



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 defer entia open. 



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

 These Hght 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 clitellumj 

 and another view of the posterior end. 



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

 the dorsal wall of the body of a preserved specimen, 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 per- 

 forate 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, 

 the pharynx. Through how many somites does this extend ? It is 

 connected with the body-wall by numerous, radiating muscle 

 fibers. What function do these fibers perform? 



2. Behind the pharynx is the narrow and long esophagus. 

 This runs posteriorly between lobed, light colored organs, the 

 seminal vesicles, that will be studied in connection with the 

 reproductive organs. Press these aside and notice the small 

 calciferous glands. 



3. The esophagus leads to the crop, which lies just anterior 

 to and in contact with the gizzard. In what somites are 

 these organs placed ? What is their shape ? Do you understand 

 the function of each? 



