4. Dorsal or supra-intestinal blood vessel, generally full of blood, 

 and seen on top of the digestive tract, along the dorsal median line. 

 In the 7th to nth somites it gives off laterally 5 large pulsatile ves- 

 sels, or "hearts", which pass around to the ventral side of the di- 

 gestive tract. 



5. Nephridia ; or segmental organs, light-colored fluffy bodies 

 attached to the posterior side of the septum, right and left, in each 

 somite. 



Make a sketch to show the above organs in place. 



II. DIGESTIVE TRACT. 



Make out the following parts in the order named. 



1. Pharynx, thick and muscular, extending back into the 6th 

 somite and attached to the body wall by many radiating muscles. 



2. Oesophagus, the narrow portion from the 6th to the i-].th 

 somites. On its sides in the nth and I2th somites are 3 pairs of 

 light colored swellings, the calciferous glands. Place one of the 

 glands in a watch glass of dilute hydrochloric acid ; explain results. 



3. Crop. A large thin walled expansion in the I5th and i6th 

 somites. 



4. Gizzard, immediately posterior to the crop in the i/th and 

 1 8th somites, and with thick muscular walls. 



5. Stomach-intestine, extending from the gizzard to the anus. 

 It expands in each somite, and is contracted by each septum. Along 

 its dorsal surface is a dark colored body, the liver, or pancreas. Cut 

 open the intestine along one side and note the large ridge on its 

 dorsal internal surface, the typhlosole. Cut open the gizzard and 

 the crop, and note the lining of these structures and the character 

 of the food contained. 



Alake a sketch of the digestive tract, showing the above men- 

 tioned structures. 



III. VASCULAR SYSTEM. 



The dorsal blood vessel and the "hearts" have been mentioned. 

 To observe the other principal vessels, remove the crop, gizzard, and 

 oesophagus. Cut the oesophagus away from the pharynx, pull it 

 gently back while cutting the septa which hold it is position, and 

 leaving all the other organs in place. This will lay bare the white 

 nerve cord on the median ventral line of the body cavity. Upon 

 it the supra-neural blood vessel may be seen. In removing these 

 parts of the digestive tract, the sub-intestinal vessel may be seen on 

 its ventral side. 



41 



