ELEMENTAR Y BIOLOG Y. [CHAP 



alimentary canal along it, with a pair of scissors. 

 Then push the bristle gently a little farther on, 

 and follow it with the scissors, and so on, until 

 the part where the intestine has already been 

 laid open is reached. 



b. The alimentary canal first runs towards the dorsal 

 side for a short way ((esophagus), lying on the 

 ventral side of the anterior adductor muscle : it 

 then dilates into an irregular sac (the stomach) ; 

 behind the stomach it continues as a long narrow 

 tube, the intestine; this turns abruptly down, be- 

 hind the stomach, into the foot, running at first 

 towards its postero-inferior border; then curves 

 up and forwards in the foot to near its dorsal 

 part ; then bends abruptly down and backwards 

 again, parallel to its previous course, towards the 

 ventral part of the foot, where it makes another 

 turn and after running forwards some way turns 

 upwards and runs to the anterior part of the 

 pericardium, where it turns backwards and runs 

 as a straight tube (the rectum), first through the 

 ventricle of the heart, and then (passing on the 

 dorsal side of the posterior adductor muscle) 

 along the dorsal side of the cloacal chamber, in 

 which it ends in an opening, the anus, placed on 

 a prominent papilla. 



c. On the sides of the stomach lies a brownish 

 glandular mass, the liver. 



a. Tease out a bit of the liver in water, and 

 examine with \ obj. It is composed of 

 branched caecal tubes lined by a layer of 

 brownish epithelial cells. 



