THE COMMON MUSSELS. 1-3 



edulis. He says that in M. edulis the stomach is composed of two 

 very distinct parts, one dilated and tapering behind, and one narrow 

 and lengthened ont in the form of a tube, which extends back as far 

 as the posterior adductor, where it ends in a small caecum (Figs. 15 

 and 16). The anterior part he calls the utricular stomach (stm. Fig. 

 15), and the second the tubular stomach ; and he states that the latter 

 contains the crystalline style, which he describes as straight and 

 cylindrical, with its anterior extremity blunt, and its posterior 

 extremity pointed near the intestinal orifice (Fig. 15). He continues 

 thus : " Near the posterior extremity of the stomach [tubular] , at the 

 point where the short caecum commences, one sees on the right side 

 an oval opening very plain and sharply cut out. This is the opening 

 of the intestine, which is left clear by the sharp end of the crystalline 

 style [Fig. 15]. . . . The recurrent intestine is of smaller 

 calibre than the tubular stomach. It is cylindrical. After leaving 

 the tubular stomach in an oblique direction it goes forward and places 

 itself outside and below the rectum." Reference to Figs. 15 and 16 

 will explain the above description. 



In describing what he calls the tubular stomach, Sabatier men- 

 tions two parts or semitubes, the upper of which contains the crystal- 

 line style, and tapers slightly from before backwards ; the lower part 

 of the tubular stomach is a deep channel or gutter, almost enclosed by 

 two longitudinal ridges overhanging it. This channel is of nearly 

 equal calibre throughout. 



If, as Sabatier thinks, the crystalline stjde is enclosed in one of 

 the principal divisions of the stomach, and comes between the main 

 part of the stomach and the origin of the intestine, then M. edulis 

 would differ remarkably not alone from M. lotus, but from other 

 Lamellibranchs, as for instance Dreissena, described by Van Beneden 

 (3) in 1835. Van Beneden states that " the intestine [in Dreissena] 

 sets out from the stomach towards the left side of the animal [Fig. 12], 

 while from the right there arises a caeca! appendage of greater 

 diameter than the intestine, but of firmer texture." In a footnote 

 he adds that " M. de Blainville believes this tube [the caecum] is a 

 caecum of the stomach analogous to that which lodges the crystalline 

 style in several bivalves/' His figure also shows an arrangement of 

 parts corresponding to that in M. latus (compare Figs. 12 and 13). 



Gegenbaur (9) states that " in many Lamellibranchs the stomach 

 is remarkable for the possession of a caecal diverticulum, which is 

 often of considerable size, and can be shut off by a valve : this is 

 placed in the pyloric region. In many forms we meet with a peculiar 

 structure in the caeca, or, when they are absent, in the enteric canal 



