EARTHWORM. IT 



contractile vessels that pass down 

 around the digestive tract in somites 

 7 to 11. 



(b) Smaller circular vessels : some passing 

 into the walls of the intestine, others 

 along the dissepiments into the body- 

 wall. 

 5. The parts of the alimentary canal : 



(a) The buccal pouch : an eversible sac into 



which the mouth-opening leads. (It 

 lies in somites 1 and 2, and should not 

 be dissected out until after the nervous 

 s}-stem has been studied. See C. II. 



7, (/)-) 



(b) The pharynx : an elongated thick-walled 



pouch extending from the 2d to the 7th 

 somite. Numerous small muscles con- 

 nect it to the body-wall. 



(c) The oesophagus : a thin-walled tube much 



smaller in diameter than the pharynx, 

 extending from the 6th to the 15th 

 somite. (More distinctly seen when 

 being taken out ; C. II. 6.) 



(d) The crop : a thin-walled dilatation of the 



alimentary canal at about the 16th 

 somite. 



(e) The gizzard : a thick-walled muscular sac 



at about the 17th somite. 

 (/) The stomach-intestine : a thin-walled tube 



