98 ANNELIDA. 



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 ditellum, 

 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? 



4. Leaving the gizzard is the stomach-intestine, which runs 

 through the remainder of the body, giving off lateral diverticula 

 in each somite. Do you know its function? 



Notice the relation of the septa to the alimentary canal. 



Circulatory System. 1. Lying dorsal to the alimentary 

 canal is the blood-vessel that could be seen pulsating in the 

 living specimen. In most cases this vessel is full of blood and 

 appears brown. 



2. Near the anterior end of the body large side branches, 



