11 



The transversely elongated mouth M. of the oyster lies 

 between the upper bends of the palps, it is followed by 

 a very short gullet or oesophagus oe^ which opens into 

 tne stomach 8t^ the walls of which are very much folded 

 and wrinkled, the folds often dip into the substance of 

 the massive brownish green liver L. and give entrance to 

 the numerous and spacious bile ducts of the latter. At 

 the hinder end of the stomach one of the deep folds ap- 

 pears to be continued backwards in the form of a blind, 

 cylindrical pouch to or beyond and between the openings 

 of the oviducts of either side ; this pouch contains a 

 transparent, but at the same time oyjalescent rod, the 

 so-called crystalline style C st^ the function of which is 

 not known. The intestine as it first leaves the stomach 

 proper is somewhat wider than at other points, but I do 

 not know why Prof. H. J. Clark considered this por- 

 tion, as far back as the first bend, part of the stomach. 

 It seems to me that the irregular digestive cavity enclosed 

 in the liver-mass should be regarded as the stomach, 

 because the first portion of the intestine already contains 

 the commencement of a peculiar pair of folds running 

 lengthwise, which will be spoken of later. Returning to 

 the course of the intestine Int^ after passing backwards 

 beneath the adductor muscle, into the mesosomal or 

 middle part of the body, when it suddenly bends and is 

 prolonged toward the head, passing a little to the right 

 of the stomach and along the back of the animal, when 

 it again suddenly turns to the left and crossing the gullet 

 oe, descends in a gentle curve along the left, lower side 

 of the body, passing obliquely upwards over the pericar- 

 dial space Per, which contains the heart, to end in the 

 anal opening at V. A peculiar double fold, /. flds^ 

 which projects into the intestinal cavity, extends from 

 the pyloric end of the intestine to the vent ; its function 

 is probably to afford a greater amount of surface for the 

 absorption of nutriment, or it may be valvular in charac- 

 ter. The greater portion of the inner intestinal surfaces 



