THE NATURAL HISTORY OF THE OYSTER. 15 



not be done simply by the weight of the lid, as before. Now, if 

 we unlock the desk, up springs the lid, raised by the expansive force 

 of the rubber at the hinges. This is precisely one of the functions of 

 the hino-e-ligament of the oyster. When the animal desires to shut up 

 the valves, it contracts the great adductor muscle. When it needs to 

 open them, it relaxes that muscle, and the valves open of themselves. 

 Patrick's mishap was not merely amusing, regarded as a blunder, but 

 even more so when viewed in this physiological light. He was told 

 to go into the cellar and bring up some oysters in the shell ; and his 

 mistress gave him a strict charge not to bring any that were dead. 



Mouth. Tentacles. 



Heart. 



Hinge. ^ v 



Liver. -- 



Lower valve. - 



Intestine. 



Anus. - 



Eight mantle 



/ \ 



Left mantle. Lower valve. 



Fig. 7. Organism of an Oyster. 



Muscle. 



Left mantle. 



Gills. 



Patrick brought up a tray full, and every bivalve upon it was gaping 

 wide ! In reply to the astonished look of his mistress he said : " Sure, 

 mam, they must be alive, or how could they keep their mouths open ? " 

 " But, Patrick," urged the lady, " could you not tell the difference by 

 the smell ?" " And sure, mam, I was remarking that same to meself. 

 But mightn't the others have bad breaths too, if they'd only open their 

 mouths a bit ? " Had the matter been pressed to an explanation, 

 perhaps the mistress would have been as severely taxed as the servant 

 to render a reason. 



The growth of an oyster-shell is always at the edge. It is effected 

 by the rim of the mantle, as a series of delicate tips assorting the lime 

 which is held in solution in the sea-water, and most daintily laying in 



