84 ANNELIDA. 



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, 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, 

 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 

 cakiferous glands. 



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

 to and hi 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, 

 the aortic arches, are given off on either side and pass down 

 around the esophagus. How many aortic arches do you find? 

 In what somites are they placed? 



3. Examine with a lens and see whether you find other vessels 



