5o 



the continuous development and growth of new rows at 

 the hinder extremity. 



As is natural the thin valves of young oysters are much 

 more readily pierced than the thick, dense, and harder 

 shells of adult individuals ; indeed at Arcachon it has been 

 proved that whereas a Murex is able to bore a hole 

 through a valve of a month-old oyster within half an hour, 

 it takes eight hours for the same sized enemy to pierce the 

 shell of one three years old. These little gastropod vermin 

 show a very great preference for brood oysters and have 

 been responsible tor the destruction of great quantities 

 in some years. So numerous were they at one time at 

 Arcachon and so extensive the losses they caused that both 

 the Dutch oyster-rearers and the Whitstable oyster com- 

 panies which till then had been in the habit of taking- 

 some of their supplies from Arcachon, alarmed lest they 

 should import the scourge, decided in 1883 to buy no 

 further quantities of young oysters from Arcachon ; great 

 difficulty was experienced in persuading these buyers to 

 remove the embargo. 



As an instance of the dimensions assumed by this 

 plague in former years, we may note that one season men 

 of the guard boat then stationed to protect the Imperial 

 oyster parks collected in a single tide from one park 

 having an area of 4 hectares, nearly 15,000 Cormaillots, 

 as this little Murex is named locally ; the next day almost 

 as many were gathered from the same ground. We may 

 be certain that if 30,000 were taken in two days on these 4 

 hectares, the original Murex population of this area must 

 have approached 100,000, if indeed it did not exceed this 

 number. It requires no abstruse calculation to realize 

 how rapidly a bed of brood oysters will diminish before 

 the inroads of such a host. F'ortunately the war which 

 the parkers have waged incessantly on this most danger- 

 ous enemy have been eminently successful ; its numbers 

 have so diminished that the parkers no longer dread it, 

 confident that the exercise of ordinary care in destroying 

 adults and ego cases whenever seen, will prevent the 

 reappearance of the scourge in dangerous numbers. 



