24 THE OYSTER. 



I have leaned over a wharf and watched the sheeps- 

 head moving up and down with their noses close to 

 the piles, crushing the shells of the young oysters 

 between their strong jaws and sucking out the soft 

 bodies. As I watched them I have seen the juices 

 from the bodies of the little oysters streaming down 

 from the corners of their mouths, to be swept away by 

 the tide. 



The sooner a young oyster can make a shell thick 

 enough to resist such attacks the better, not only for 

 the oyster but for us also; for once past this dangerous 

 stage of development, there is a prospect that it may 

 live to complete its growth ; although it is true that 

 the fully grown oyster has many enemies which either 

 crush the shell or pull it apart, or else bore holes 

 through it in order to reach the delicate flesh within. 

 At all times in its life its chance of survival is greatest 

 when the supply of lime is so abundant that it is able 

 to construct rapidly a thick, massive shell. The rate of 

 growth of any animal must be regulated by the supply 

 of that necessary ingredient of its food which is least 

 abundant, as may be illustrated in many ways. To 

 run a locomotive the engineer must have fuel and 

 water and oil. He needs very little oil, but that little 

 he must have. After this is gone, an unlimited supply 

 of fuel and water will not help him. He must have 

 oil or stop. So, too, if he have plenty of oil and fuel, 

 but only a little water, he must stop as soon as the 

 water fails. In general, the amount of work he can 

 do is determined by his supply of that of which he has 

 least. If food in general is abundant while there is a 

 scarcity of one necessary article, growth can take place 



