THE OYSTER AND ITS RELATIVES. 



Of all the grand divisions of the Anima-1 The lowest branch of . Mollusca is 

 Kingdom, the subkingdom Mollusca is known as class Pelecypoda, which corn- 

 probably the least known to the ordinary prises all of the different kinds of clams, 

 observer, and if one were asked to enu- mussels, quahaugs, etc., in which the 

 merate as many different kinds of "shell body is protected by two hard, calcareous 

 fish" as he could, it is probable that not shells placed, generally, opposite each 

 over six or eight different varieties would other and connected on the upper mar- 

 be named. The majority of people think gin by a ligament, and the two valves 

 of a clam, oyster, mussel, snail or Nautilus work back and forth in teeth and sockets, 

 and their molluscan vocabulary ends with making a kind of hinge. A set of stout 

 these names. And yet this group of ani- adductor muscles keep the two shells or 

 mals is second only to the insects in num- valves together and allow them to open 

 ber of different species, beauty of colora- and close at the will of the animal. The 

 tion and interest of habitat. They may be majority of clams live in the mud in a 

 found everywhere, in salt and fresh water, horizontal position, the anterior end be- 

 in our forests and fields, our ponds, ing buried and the posterior end, con- 

 brooks and rivers ; in the valleys and on taining the siphons which draw in and ex- 

 the mountain tops, and even in the waters pel the water, being out of the mud, in the 

 of the frozen north, while in the warm water. The clam progresses by pushing 

 waters of the tropics they flourish in un- forward its strong, muscular foot, getting 

 counted millions. In size they range from a firm hold of the mud and then drawing 

 the little sea-snails hidden in the eel grass the shell after it. Some pelecypods, as 

 along the shore, with tiny shells scarcely the oyster, live attached to some object 

 an eighth of an inch in length, to the on the bottom of the water, as a stone, 

 giant squid, which measures forty feet piece of wood or piling of an old wharf, 

 or more from the tip of its tail to the end and are not able to travel from place to 

 of its long arms ; and they range from the place as are the true clams, examples of 

 tide-washed beach to the abyssal depths the latter being fresh water mussels and 

 of the ocean. It is to these lowly crea- the marine quahaug or round clam, 

 tures that I would draw the reader's at- Some bivalves also attach themselves 

 tention. by a byssus composed of a number of 



In nearly all the species of the Mollusca silk-like threads, which anchor their 



the animal is protected by a hard shell, shells to stones, sticks, and other foreign 



made of carbonate of lime, which is cov- objects. In one group (genus Pinna) 



ered with a horny epidermis to protect found in the Mediterranean Sea, this 



the limy shell from being dissolved by byssus is so fine and silky that the Ital- 



the acids in the water. This shell is gen- ians weave it with silk and make caps, 



erally capable of containing the entire gloves and other articles of wearing ap- 



animal, thus affording, in most cases, ad- parel. 



equate protection for the soft body. Another wonderful and interesting ar- 



Those animals not provided with a shell, rangement for the comfort of the animal 



as is the case with the land slugs, are ca- is its breathing organs or branchiae, 



pable of covering themselves with a sort These are two or four in number, and are 



of mucus which encysts and protects made up of numerous small chambers, 



them from both extreme heat and cold. covered with little whip-like organs or 



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