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I'll y LI M AWEIJDA 89 



organs it will be necessary to snip with the scissors or cut with a 

 scalpel the septa which hold the body wall close to the alimentary 

 canal. Separate the edges of the cut, spread open the walls of 

 the body, aiul fasten by means of pins inserted diagonrdly near 

 the periphery in segments V, X, and XV. 



At the point where the first incision was made note that the 

 body wall is separated from the intestine by a distinct space, the 

 ca>lom. Do you find any indications of metamerism internally? 

 What is the relation of the scpla to the external rings? Note 

 the glistening, iridescent lining of the body wall. What is the 

 relation of this Hning to the coclom? 



The large cream-colored structures .somewhat obscuring the 

 alimentary canal in segments 10, 11, and 12 are the three pairs of 

 seminal vesicles which are parts of the reproductive system. 

 Laterad of the anterior pair of vesicles in segments 9 and 10 are 

 small white spherical objects, the seminal receptax'les (sperma- 

 thecie), which are also parts of the reproductive system. 



Along the dorsal surface of the intestine can be seen a brown 

 or yellow streak which marks the location of the longitudinal 

 ridge, the typhlosole, which encroaches upon the enteric cavity. 

 Its color is due to the yellow chlorogogen cells of which it is mainly 

 composed. The typhlosole can be more readily distinguished 

 later when a section of the intestine is removed. Note also the 

 dorsal blood vessel visible along this streak. Arising from it are 

 transverse vessels in each segment, best seen in the region of the 

 intestine. One pair of these in each of the seventh to the eleventh 

 segments, inclusive, on either side of the a'sophagus, is specialized 

 as the hearts, which due to their pulsations assist in maintaining 

 a blood current. 



The Digestive Tract. — Identify the following regions in the 

 digestive tract: the mouth or buccal cavity in the first three seg- 

 ments; the longer, thick-walled pharynx extending through about 

 four segments and attached to the body wall by radiating muscle 

 fibers; the narrower asophagus (partly concealed by the five i)airs 

 of hearts and by reproductive structures) extending to segment 

 13 or 14; the large, thin-walled crop or storage reservoir for 

 food, extending through three or four segments; and the white, 

 thick-walled gizzard in which the food is ground into small 

 particles. From the gizzard the intestine stretches to the anus 

 as a long unspecialized tvibe. It is in the intestine that digestion 

 is completed and absorption takes place. 



