28 THE OYSTER. 



of the bodies of living animals. Limestone is either 

 old reefs of fossil coral, or beds of extinct shells, or 

 the skeletons of other animals and plants which lived 

 in remote ages and stored up the lime from the ocean 

 at a time when it was more abundant than it is now. 

 The oyster gets the greater part of its lime from these 

 sources in this roundabout way, but a very considera- 

 ble portion is obtained in a much more direct way, by 

 the decomposition of old oyster shells. 



We save up egg shells to feed laying hens, but we 

 recklessly waste our oyster shells, and treat them as if 

 they were of no value. Some are burned for lime ; 

 some are used for making roads and wharves ; some are 

 used for rilling in low land ; some are dumped in great 

 piles at convenient spots in the bay, where they sink 

 far down into the mud and are lost. 



I shall soon show that there is another far more 

 important reason why they should be returned to the 

 beds, but their value as food for the oyster is very 

 great, and should lead us to return them to the beds. 

 On the oyster-beds an old shell is soon honeycombed 

 by boring sponges and other animals, and as soon as 

 the sea-water is thus admitted to its interior, it is 

 rapidly dissolved and diffused. In a few years nothing 

 is left. It has all gone back into a form which makes 

 it available as oyster food, and it soon begins its trans- 

 formation into new oyster shells. In this way the 

 oysters obtain some of their lime directly, without 

 being compelled to draw on the inland beds of ancient 



