16 A MANUAL OF ZOOLOGY 



tacles. Draw a ventral view^f_the,aatfirlor half, locating 

 the openmgs jefeiFred to above. The capsulogenous glands 

 wiiFbe seen to vary somewhat on segments 9 to 11 or 8 

 •to 12, on the ventral surface. Does the number of seg- 

 ments containing the glands vary in different specimens? 



Pin a large specimen out straight, dorsal side upper- 

 most. Cover with water. With fine pointed scissors cut 

 through the body wall along the mid-dorsal line. Note the 

 membranous partitions, the septa. Cut these away and 

 pin the specimen out in the tray. The tube extending 

 through the body from the anterior to the posterior end 

 js- the digestive tract. Do the septa referred to above ex- 

 tend entirely across the body? Observe that the general 

 formation of the body is a tube within a tube. The outer 

 tube is known as the body cavity. Study a cross section of 

 the earth worm and find the structure of the body wall. 

 Note the layers of musdie fibers. In what direction do 

 these fibers extend?- Open the body cavity of a live speci- 

 men after giving it chloroform. Note a colorless fluid, the 

 peri-visceral fluid. Examine some of this fluid with the 

 microscope under both the low and the high' power. Cells, 

 coloriess corpuscles, like the amoeba, will be found floating 

 in the colorless fluid. Does the fluid coagulate when ex- 

 posed to the air? What relation do the septa have to 

 the constriction between the segments of the body? The 

 digestive system referred to above is divided into several 

 parts. The first two or three segments are occupied by 

 the buccal cavity. Note the shape and ho-^r It is fastened 

 to the body wall. Following the buccal cavity is the 

 pharynx. How is this cavity separated from the first 

 cavity? Note size, shape, and extent. Find the muscles 

 that hold it In place. Leading from the pharynx is the 

 oesophagus. How far does it extend? Are there any vari- 

 ations in its size? The calciferous glands are located in 

 the 11th and 12th segments. From their position and con- 

 nections what is their probable use? Examihe some of 

 the fluid in them under the microscope.' WJiatjs found? 

 Treat some of the gland in a test tube with HCl. Explain 

 results. In about the 16th segment will be found a thin 

 walled, sac-Uke expansion of the alimentary canal, the 



