104 THE OCEAN. 



only to a small extent during the life of the animal. 

 Yet we must not for a moment suppose that these 

 creatures are unhappy, or that the meanest occupant 

 even of a bivalve shell is not supplied with every- 

 thing that could conduce to its welfare. It is sin 

 alone that is the source of unhappiness. I will just 

 point out one or two particulars in which the Divine 

 care for these creatures is manifest. All of them 

 have the vital parts of the body protected by a thick 

 fleshy coat, somewhat projecting at the edges, called 

 the mantle : the surface of this organ has the power 

 of forming the shell, *by depositing stony matter in 

 a sort of glutinous cement, which soon hardens into 

 a thin layer of shell. If a little piece were broken off 

 the edge of the shell of a Whelk, when alive, the 

 animal would press the surface of the mantle against 

 the fracture, and pass it several times over the place ; 

 a very thin transparent film would then be seen to 

 fill up the space, which in the same way it would 

 increase in thickness, until in a few days we could 

 scarcely distinguish the renewed part from the 

 other, or tell that the shell had been broken, except, 

 perhaps, by a slight variation in colour. As the ani- 

 mal grows, it wants a larger shell; and the mantle 

 affords the means of increasing its size: the front 

 edge of this organ is thicker than the rest, and is 

 called the collar; and it is by thrusting this round 

 the edge of the shell, while stony matter is poured 

 out from its surface, that an addition is made to it. 

 In the Bivalves, or those whose shells open and shut 

 like the covers of a book, as the Oyster, the mantle 

 i.* twofold, covering the body on each side, just within 



