26 THE OYSTER. 



stage of development, there is a prospect that it may 

 live to complete its growth ; though 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 a thick, massive shell quickly. 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 

 only so fast as the scarce article can be procured. A 

 superfluity of other things is of no value, for it cannot 

 be utilized. 



There are many reasons for believing that the growth 

 of oysters is limited by the supply of lime, and that 

 all the other necessary ingredients of their food are 

 so abundant that an increase in the supply of lime 

 would cause more rapid growth, greater safety from 

 enemies, and an increase in the number of oysters. 



