COASTLINES 



millions of eggs in its lifetime. Near the oyster grounds 

 the sea may be literally crowded with myriads of free- 

 swimming larvae, which, when they settle on any hard 

 surface available, may entirely cover it with tiny oysters 

 (each smaller than a pin's head). Observers have counted 

 as many as i ,000 oysters on a single square inch of hard 

 surface : they may be compared with the star-dust of the 

 sky for numbers. One remarkable fact at once emerges — 

 all the tiny creatures lie on their left sides. 



As they spend their lives in their beds they must have 

 their food brought to them. The sea obliges them, taking 

 them microscopic food of all kinds — minute plant life, 

 the bacteria of decaying plants, food in abundance, for 

 oysters' ancestors have chosen their resting-places well: 

 estuaries rich in edible organisms. They have their 

 regular feeding times, and the food is intercepted by the 

 tiny oysters' gills and filtered out as the sea water passes 

 through them, and digested in their gut. 



There are various kinds of oysters, but we will first 

 consider the American variety {Ostrea virginica). The 

 female delivers her eggs — about fifty million at a time — 

 into the sea. They float : the male has already released his 

 sperm, which fertilizes them. He is very casual and un- 

 concerned — only a few of the eggs may be fertilized. The 

 rest die — but more than enough have begun their strange 

 life-cycles. 



We now turn to the European oyster [Ostrea edulis). 

 The female lays only a hundredth of the number of eggs 

 produced by the American oyster — about fifty thousand 

 at a time — but their chances of survival are more than 

 compensated by parental care. For after they have been 

 fertilized within the shell of the mother with sperm collected 

 by her from the water, the little ones swim around, im- 

 prisoned, until she is ready to release them. She literally 

 shoots them out like shots from a blunderbuss when they 

 are about a fortnight old. They now swim freely in the 

 sea and find their own food. After ten days of this free 



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