54 CEYLON PEARL OYSTER REPORT. 



out the hinder or cardiac moiety of the stomach into a right and a left chamber. 

 This postero-ventral fold (P.r.f., Plate VI., fig. 7) dies away before reaching the roof, 

 which, in marked contrast to the rugose floor, is smooth and unbroken, except for a 

 small but well-marked median depression or pit at the junction of the anterior with 

 the median third. The wide bipartite opening into the intestine and intestinal ceecum 

 (Int.ap., Plate VI., fig. 7) marks the hinder end of the floor of the left chamber, which 

 may therefore he named the intestinal or p}doric chamber. In size it slightly exceeds 

 the right or crecal chamber, the former being appreciably deeper, and being as wide as 

 it is deep, whereas the height of the latter is twice as great as its breadth (Plate VI., 

 fig. 4). Anterior to where the postero-ventral fold dies away midway along the floor, 

 a peculiar flattened and obliquely sloping plate (Pl.d., Plate VI., fig. 7), facing back- 

 wards, upwards, and to the right, occupies a sub-central position ; and branching 

 channels radiate forwards on its surface, connected possibly with the distribution of 

 the digestive fluid. To the right of this area, which may be named the dendritic 

 plate, is a ridge with accompanying furrow, running forwards and upwards to the 

 antero-lateral bile-duct, while to the left is a shallow, wide pre-intestinal depression 

 (P.i.dep., Plate VI, fig. 7). A deep, rugose, sub-cesophageal pit (S.ce.p.) is well 

 marked anterior to the dendritic plate, and high up on the right lateral wall the 

 postero-lateral furrow leads from the postero-lateral duct towards the intestinal 

 aperture. On the left side, a stout antero-lateral fold lies between the pre-intestinal 

 depression and the sub-cesophageal pit. 



The digestive gland, or "liver" {D.gl., Plate VI., fig. 1), as already noted, 

 surrounds the stomach except at small areas upon the extreme dorsal and right 

 lateral aspects. Under healthy conditions it is of large size and of a characteristic 

 deep sage-green colour. It is made up of dense clusters of secreting alveoli (Plate IX., 

 fig. 3), which ojien into ductules and thence into the larger ducts, which lead into the 

 stomach. There are eleven of these terminal ducts, namely : 



a. The antero-lateral duct (D.a.l., Plate VI., fig. 6), opening high up on the right 

 side, and posterior to the right of the sub-cesophageal pit. 



b. The postero-later<d duct {D.p.l., fig. 6), opening at the same level and on the 

 same side, within the posterior third of the stomach. Several large ductules open at 

 its very end (as is the case with a and several of the others), and, as the latter is 

 wide, some of these tributary apertures are visible from within the stomach. This 

 duct ramifies within the upper and posterior region of the digestive gland. 



c. The postero-ventral duct (D.p.v., fig. 7) opens in the floor of the posterior third, 

 also upon the right side. It conies from the posterior and ventral parts of the 



gland. 



d. Anterior to the last named are the three sub-central ducts (D.s.c, fig. 7), the 

 inmost one being of large size. 



e. Two pre-intestinal ducts open within the pre-intestinal depression and drain the 

 left ventral portion of the gland. 



