EARTHWORM 73 



poinled forceps. The ralciferous glands occur on the sides of the 

 esophagus as small lobular structures. See demonstration 

 dissection. 



(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) Intestrnf, a tube of practically uniform diameter ex- 

 tending through the remainder of the bodv. A laver of brown 

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

 posed to be associated with the excretory function. 



2. 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 w^ash it out and observe 

 the fyphlosole, a fold which hangs into the intestine from the 

 dorsal surface. 



3. 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 

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

 carefully. Observe the paired structures lying loosely in each. 

 somite, flat against the ventral body wall. These are the 

 metanephridia. 



Each metanephridium is composed of two distinct parts lo- 

 cated in different somites. The conspicuous white masses, one 

 on each side of the nerve cord in each somite, are the nephridial 

 tubes. Under the hand lens only a part of each mass shows its 

 tubular nature. The tube leads forward to a transverse septum 

 through which it passes and extends as a minute knob-shaped 

 nephrostome into the segment next ahead. The other extremity 

 of the tube is attached to the body wall through which it opens 



