PRODIGIOUS FERTILITY OF THE CONCHIFERA. 493 



The fertility of this class is prodigious. Leeu- 

 wenhoek reckoned that there were ten millions of 

 embryo young produced by a single oyster. Baster 

 reduces the number to a hundred thousand ; and the 

 reduction might be allowed, had not Poli added his 

 authority for its more abundant fruitfulness. He is 

 more precise : he says, " that an oyster may contain 

 one million two hundred thousand eggs, and may 

 give birth to the contents of twelve thousand barrels." 

 Well might the reverend author of one of the 

 'Bridgewater Treatises' express his opinion, that 

 " Providence has thus taken care that the demands 

 made upon them to gratify the appetite of his creature 

 man shall not annihilate the race." Such, indeed, is 

 the fecundity of the Conchifera, that they would in 

 the course of a short century fill our shallow lakes 

 and rivers, and raise to the sea's surface the banks on 

 its hollow bed, were it not for the numerous checks 

 that oppose their undue multiplication, and retain in 

 equipoise the balance between their prolific increase 

 and the destruction that awaits them. 



