[41] THE OYSTER AND OYSTER-CULTURE. 128 
which serve as nourishment to the oysters. If the dredge is thrown out 
and dragged over the sea-flats between the oyster-beds, fewer and also 
different animals will be found upon this muddy bottom than upon thesand. 
Every oyster-bed is thus, to a certain degree, acommunity of living beings, 
a collection of species, and a massing of individuals, which find here 
everything necessary for their growtlhand continuarce, such as suitable 
soil, sufficient food, the requisite percentage of salt, and a temperature 
favorable to their development. Each species which lives here is repre- 
sented by the greatest number of individuals which can grow to matur- 
ity subject to the conditions which surround them, for among all species 
the number of individuals which arrive at maturity at each breeding 
period is much smaller than the number of germs produced at that 
time. The total number of mature individuals of all the species living 
together in any region is the sum of the survivors of all the germs 
which have been produced at all past breeding or brood periods; and 
this sum of matured germs represents a ceriain quantum of life which 
enters into a certain number of individuals, and which, as does all life, 
gains permanence by meaas of transmission. Science possesses, as yet, 
no word by which such a community of living beings may be designated ; 
no word for a community where the sum of species and individuals, 
being mutually limited and selected under the average external condi- 
tions of life, have, by means of transmission, continued in possession of 
a certain definite territory. I propose the word Biocenosis* for such a 
community. Any change in any of the relative factors of a biocénose 
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 biocénose, or community, would be trans- 
formed. It would also be transformed, if the number of individuals 
of a particular species increased or diminished through the instrumen- 
tality of man, or if one species entirely disappeared from, or a new spe- 
cies entered into, thecommunity. When the rich bedsof Cancale, Roche- 
fort, Marennes, and Oléron 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 biocdnose 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 biocdnose allows itself to 
be transformed in favor of the oyster, by taking away the mussels men- 
tioned above, and at the same time protecting 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 so- 
* From Bioc, life, and xoivéew, to have something in common, 
Ss) ? ? 8 
