CHAPTER III 

 BIVALVE MOLLUSCS 



PLATE XIII 

 THE OYSTER (i) 



'"PHE " bivalve " molluscs are so called because 

 they live in shells made of two parts, or 

 "valves," which are fastened together by means 

 of a hinge. There are a great many of these, 

 and the Oyster is one of the best known of 

 them all. 



This creature is only found in places where 

 the bottom of the sea is muddy, because in 

 sandy places the sand is very apt to get into 

 the hinges of the shells and to prevent them 

 from being closed; and in that case the animal 

 very soon dies from suffocation. So oysters are 

 generally found in the mouths of rivers, or in 

 land-locked bays where there is no sand at all. 



The history of these creatures is a very curious 

 one indeed. 



In the month of May the mother oyster pro- 

 duces a very large number of eggs sometimes as 

 many as eight or nine hundred thousand ! These 



are called "oyster spat," and for several weeks 



36 



