LOLIGO PEALII LESUEUR 237 



consists of the alimentary canal, three salivary glands, liver and 

 pancreas. The buccal membrane surrounding the mouth has 

 been described above. The mouth leads into the mouth cavity. 

 The walls of this cavity are formed by the buccal bulb, a nearly 

 spherical, muscular body inclosed in the buccal sac and provided 

 with a single retractor. Inside the bulb are two powerful chitinous 

 jaws resembling an inverted beak of a parrot, the upper jaw 

 shutting into the lower one. Their action is dependent upon 

 special muscles. Attached to the base of the lower jaw is an 

 organ called the odontophore, projecting into the mouth cavity. 

 The odontophore consists of two parts. The lower portion of the 

 odontophore is a muscular tongue or ligula. At the tip of the 

 ligula is the opening of the salivary duct of the median or abdom- 

 inal salivary gland which is imbedded in the proximal (ventral) 

 end of the liver. The upper portion of the odontophore is called 

 the radula. The radula bears seven rows of sharp, chitinous 

 teeth and a row of plates on each side. These teeth, as well as 

 the chitinous band connecting and supporting them, are secreted 

 by the cells of the radular sac, into which the radula may be 

 partly withdrawn by the contraction of the retractors of the 

 radula. The opposite movement of the radula is brought about 

 by the protractors of the radula. The exposed portion of the rad- 

 ula is curved. The teeth, which are inclined backward, become 

 more or less erected when the radula is protracted ; the triturating 

 action of the radula is therefore possible only during retraction, 

 and this is the reason why the retractors are stronger than the 

 protractors. Partially imbedded in the muscles between the 

 radula and the oesophagus is a pair of buccal salivary glands with 

 short ducts opening into the mouth cavity on the so-called 

 palatine lobes. 



The oesophagus is a thin and long tube leading from the buccal 

 bulb to the stomach. On leaving the head it passes through a 

 deep groove in the liver to the upper surface of the latter, and 

 continuing in a shallow median groove extends somewhat be- 

 yond the middle of the liver. Here the oesophagus dips down- 



