66 . LABORATORY DIRECTIONS 



2. The alimentary tract, a straight tube extending through 

 the body, has the following parts arranged in order from anterior 

 to posterior extremities : 



(a) Buccal cavity or mouth cavity, a thin walled sac-shaped 

 structure communicating with the outside through the mouth. 



(b). Pharynx, thick walled region with muscles running to 

 the body wall. 



(c) Esophagus, slender and extending through a number of 

 somites, mostly hidden by the sperm sacs which may now be re- 

 moved by picking away the pieces carefully with a pair of fine 

 pointed forceps. The calciferous glands occur on the sides of the 

 esophagus as small lobular structures. See demonstration dis- 

 section. 



(d) Crop, an enlarged thin-walled sac. With the point of a 

 needle note the difference in resistance of this and the gizzard. 



(e) Gizzard, thick- walled, muscular grinding organ. 



(f) Intestine, a tube of practically uniform diameter ex- 

 tending through the remainder of the body. A layer of brown 

 cells, the chloragogue cells, covers the intestine. These are sup- 

 posed to be associated with the excretory function. 



3. Make a slit in one side of the intestine and fold back the 

 dorsal half for the distance of about 10 mm. or more. If the in- 

 testine is filled with dirt or other matter wash it out and observe 

 the typhlosole, a fold which hangs into the intestine from the dor- 

 sal surface. 



4. Make a full page drawing, dorsal view, of the digestive 

 system found in the anterior part of the body, showing all struc- 

 tures mentioned above. In your drawing number all segments. 



EXCRETORY SYSTEM 



For a distance of several inches behind the clitellum open 

 body wall as before and pin out flat. Remove the intestine care- 

 fully and notice the paired Mctancphridia in each somite. 



