PATELLA. 219 



coloured tubular glands occupying the front of the 

 visceral hump below the pericardium and rectum. They 

 are usually united practically into one mass, but 

 occasional specimens show, anteriorly, more or less 

 division into four (fig. 16). The two inner ducts run in 

 the grooves formed externally by those inward projections 

 into the gullet cavity, called above the dorsal longitudinal 

 folds. Free at first, they become, towards the front end, 

 involved in the gullet wall (fig. 15), but they run along 

 in it and only open at about the same level as the outer 

 pair. The two outer ducts run freely at the sides of the 

 gullet, and open into slight lateral pouches in the buccal 

 cavity behind the palate ; they often have ampullse placed 

 at irregular intervals along them (tig. 10). Cuvier noticed 

 small patches of yellowish tissue near the openings of the 

 buccal ducts, and named them " salivary glands." It is 

 interesting to note that similar yellowish glandular masses 

 occur in the pharyngeal wall of Fissurella near the open- 

 ing of its (one pair of) buccal ducts ; these Boutan has 

 unhesitatingly called traces of another pair of buccal 

 glands. 



The Digestive gland, or Hepato-pancreas (" liver "), 

 is a large racemose gland, occupying the centre of 

 the visceral mass (figs. 4 and 6). The bilobed condition, 

 which is primitive for Mollusca, may have disappeared 

 long before the differentiation of the Docoglossa, or may 

 be obscured by the consolidation and compression which 

 the viscera have undergone in this group. The ducts of 

 this gland converge into two main ducts, which unite 

 just before they open into the stomach, as described 

 above. The ridge-bounded groove on the internal wall 

 of the stomach is continued on the floor of the main duct 

 and even of its first branches. 



