118 ELEMENTABY BIOLOGY. [xi. 



1 inch obj. the auditory sac can readily be seen 

 with a constantly trembling particle, the otolith, 

 in it. 



9. The alimentary canal. 



a. This must be dissected out in another Anodon, as 

 it has been partially removed with the ventricle 

 of the heart. Pass a guarded bristle into the 

 mouth as far as it will readily go, and then lay 

 open the 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 whole canal is opened. 



h. The alimentary canal first runs towards the dorsal 

 side for a short way [ossophagus) , lying on the 

 ventral side of the anterior adductor muscle : it 

 then dilates into a small squarish 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; then curves up 

 in the foot to near its dorsal border ; then bends 

 abruptly down again, towards the ventral part of 

 the foot, where it makes another turn and runs 

 up to the anterior end of the pericardium ; thence 

 it runs back as a straight tube {the rectum), first 

 through the ventricle of the heart, and then 

 (passing on the dorsal side of the posterior ad- 

 ductor 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 glan- 

 dular mass, the liver. 



