EAKTHWOEM 131 



as fibres, groups of cells, starch-grains, etc., pres- 

 ent in each. 

 Make two sketches of the entire digestive system 

 lying in an outlined body, the first showing the diges- 

 tive organs as seen from above, the second as seen in 

 longitudinal section. 



B. The Circulatory System. 



The student will need to prepare another specimen 

 for the examination of these organs, as some of the 

 most important are destroyed in the examination of 

 the alimentary canal. For this purpose kiU a liv- 

 ing worm by immersion in alcohol and examine at 

 once. Only the more prominent vessels are given be- 

 low. 



a. The dorsal or supra-intestinal blood-vessel. 

 — Where does it begin ? How far back can it 

 be traced ? What is its relation to the septa? 



h. The circum-oesophageal vessels or "hearts." 



— Position? Number? Shape? Color? 



Lying below the alimentary canal, seen by 

 pushing the latter to one side, find 



c. The supra-neural or sub-intestinal vessel. — 



Position ? Eelation to the " hearts " ? 



d. The lateral cesophageal vessel. — Compare 



in size with the dorsal blood-vessel. Note 

 the branches given off to the pharynx and the 

 oesophageal glands. 

 Make a diagram of the portion of the circulatory 



system studied, showing its relation to the digestive 



system. 



e. The blood. — Open the body-cavity of a recently 



drowned worm and with two pairs of fine-pointed 



