116 GROWTH OF THE OYSTER'S SHELL. 



ous small mollusks. Become large enough for us to find him without 

 the help of lenses, he seems merely a whitish, horny flake on the surface 

 of his support, like the nail on the little finger of a babe. From now 

 until the shells get to be the size of a nickel coin, and begin to look 

 rough, the oysterman calls him a "blister" — an expressive term. 



If the affixture of the infant oyster is made in the midst of a cluster 

 of others, his only opportunity for growth is straight upward by addi- 

 tions around the edges, but most extensively at the " nib," or point of the 

 shell opposite the hinge, while the older part continually hardens and 

 thickens until the maximum is reached. In this situation both halves of 

 the shell will increase at about an equal rate and become very similar, as 

 one sees them in those long, narrow forms of wild oysters from the sur- 

 face of reefs, which are termed by the fishermen " strap " or " stick-up," 

 or (in the South) " coon " oysters. 



When, on the other hand, the bivalve attaches himself (accidentally, 

 of course, for, so far as we can see, this is a matter in which the oyster 

 exercises no choice) where he is not in close contact with others, and has 

 room to grow in any and all directions, then the shells become more and 

 more unequal. That one underneath, as the creature lies on its side, is 

 soon seen to be getting greatly the advantage in size and strength. Con- 

 sequently, by the time adult proportions are reached, the lower valve 

 often broadly overlaps the upper valve, which shuts down into it as com- 

 pletely as the lesser mandible of a duck fits into the concavity of the 

 more capacious opposite half of the beak. When an oyster is opened to 

 be eaten raw, it is this "deep" lower shell that serves as a convenient 

 dish upon which to offer it, while the thinner upper one is thrown away. 



These heavy shells, it is needless to point out, are a provision for the 

 animal's defence. Nature can no longer trust to numbers or minuteness 

 or invisibility to save her oysters. If she cares to preserve any as 

 breeders of future generations, she must take better care of them than 

 heretofore. She does not require them to go abroad in pursuit of food, 

 but undertakes, by a simple apparatus for inducing currents of water, that 

 it shall be brought to them in a never-ceasing supply, without other exer- 

 tion on their part than to open their mouths and sleepily let the nutri- 

 tious streams course their way into and out of the digestive cavity of the 

 body, where an automatic action of the stomach abstracts the food and 

 rejects the superfluous water. 



With this fixed location, and passive method of subsistence, oysters 

 manifestly would have no occasion or opportunity to make use of weap- 

 ons either for active offence or for resistance. Nevertheless, Nature does 



