I060 OYSTERS, AND ALL ABOUT THEM. 



community. Any change in any of the relative factors of 

 a bioconose produces changes in other factors of the same. 

 If, at any time, one of the external conditions of life should 

 deviate for a long time from its ordinary mean, the entire 

 bioconose, or community, would be transformed. It would 

 also be transformed if the number of individuals of a parti- 

 cular species increased or diminished through the instru- 

 mentality of man, or if one species entirely disappeared 

 from, or a new species entered into, the community. 

 When the rich beds of Cancale, Rochefort, Marennes, 

 and Oleron were deprived of great masses of oysters, the 

 young broods of the cockles and edible mussels which 

 lived there had more space upon which to settle, and there 

 was more food at their disposal than before, hence a 

 greater number were enabled to arrive at maturity than in 

 former times. The bioconose of those French oyster- 

 banks was thus entirely changed by means of over-fishing, 

 and oysters cannot again cover the ground of these beds 

 with such vast numbers as formerly, until the cockles and 

 edible mussels are again reduced in number to their former 

 restricted limits, because the ground is already occupied 

 and the food all appropriated. The bioconose allows itself 

 to be transformed in favour of the oyster, by taking away 

 the mussels mentioned above, and at the same time pro- 

 tecting the oysters so that the young may become securely 

 established in the place thus made free for them. Space 

 and food are necessary as the first requisites of every social 



community, even in the great seas Even upon 



the best beds the oysters will remain poor if they are 

 allowed to lie too thick upon the bottom ; but if a portion 

 of these poorly nourished oysters are taken away, those 

 which remain as has been found out by experience upon 

 the Huntye Bank, the largest and most fruitful of all the 



