32 THE OYSTER. 



above-named replaces the lungs. The liver (/) is small ; 

 the gall, comparatively speaking, large ; the larger 

 blood vessels Kttle rarefied. The heart {h) consists of 

 two cameras at a tolerable distance from one another, 

 resembling small round bladders. The pulse beats rather 

 slowly (caused by, perhaps, the want of food and sea 

 water). From the stomach the rectum (a) leads directly 

 to the anus. How digestion is effected in this short 

 and simple way, I can scarce venture to assert. But it 

 is a fact well known, that, after the spawning season, the 

 oyster becomes thin, but a very short time enables it to 

 recover its fat and succulence. 



On examining the oyster the mantle (w^), divided into 

 two lobes {?n and w'), the edges of which are fringed, 

 will be perceived filling the greater part of the shell ; 

 also four membranous leaves crossed with stripes, which 

 at their hinder extremities have as many capillary tubes. 

 These leaves, or veins, unequally divided around the 

 edges of the body perform the functions of the lungs, 

 and separate from the water the necessary air for the 

 maintenance of the animal. 



The mouth (b) is a kind of trunk, or long aperture 

 surrounded by four lips nearly resembling those of a gill, 

 but far shorter. 



Behind the muscles is to be seen a large fleshy white 

 and cylindrical substance moving on a central muscle, 

 and containing the stomach and intestines {i). This part 

 resembles the trunk of other conchae, but it has no power 

 of opening or contracting. The canal of the intestines 

 is situated on the top of the muscle {a). 



The oyster has circular vessels, on the bottom of which 



'I 



