CONCHIFERA. 



379 



anatomy of tlie CONCHIFEROUS MOLLUSCA. In the Oyster, the 

 general disposition of the body resembles that of the Pecten 

 described above ; and the mouth, enclosed between two pairs of 

 delicate lips, occupies a similar position at the termination of the 

 branchial lamellae. In this well-known Mollusk the (esophagus 

 is extremely short, so that the mouth appears to open at once 

 into the stomachal cavity (Jig. 177, a), which is imbedded in the 

 substance of the liver (d), ; the biliary secretion being poured into 

 the stomach itself through several large orifices represented in 

 the figure. A very peculiar arrangement exists in the stomachs 

 of many genera, the digestive cavity being prolonged in one di- 

 rection, so as to form a lengthened caecum, or blind sacculus, 

 wherein is lodged a cartilaginous styliform body, the use of which 

 it is not easy to conjecture, although its office is no doubt con- 

 nected in some way or other with the preparation of the food. 



Fig. 177. 



The liver is propor- 



tionately of large di- 



mensions, and is at 



once recognized by 



its greenish, or, in 



some cases, dark cho- 



colate colour ; it is 



entirely separable in- 



to masses of secern- 



ing follicles loosely 



connected together 



by a delicate cellu- 



losity. The intes- 



tine varies consider- 



ably in extent, and, 



as a necessary con- 



sequence, in the ar- 



rangement and num- 



ber of its convolutions. In the Oyster it is comparatively short, 



bending twice upon itself, and winding around the stomach and 



adductor muscle (6, c, d,f) ; its termination (g) projecting between 



the folds of the mantle upon the opposite side of the body to that 



where the mouth is situated, and so disposed that excrementitious 



matter is cast out beyond the influence of the ciliary currents. In 



Pecten we have already noticed that it performs sundry gyrations 



through the visceral mass, as well as about the muscle that closes 



