4 
clear that if a natural oyster-bed, for example, be dredged 
constantly and no time left for its reproduction, it will 
amount to the same thing as if one repeatedly dredged 
stones or other inert material—that is the bottom would at 
last be perfectly clear of them. 
Such an obvious argument as this needs no confirmation, 
but if any such confirmation were needed, we might cite 
what has occurred on the north-west coasts of Spain, where, 
until the beginning of the present century, so great was the 
quantity of oysters in the beds that they were sold at four 
cuartos, or a little more than one penny per hundred, while 
the present price averages 12 pesetas or Qs. 7d. for the same 
quantity. Even if we take into account the small con- 
sumption at that time, owing to defective means of 
communication, this circumstance is insufficient to explain 
the enormous difference just mentioned, which points clearly 
to the complete exhaustion of the beds. 
With regard to species which lead a more or less 
migratory existence, there cannot be the least doubt that if 
man had complete control over the area occupied by each, 
the same principle of more fish being caught than could be 
reproduced would lead to exhaustion likewise ; what has to 
be determined is, how far man has such control in a given 
locality. The old fishermen of the Mediterranean relate that 
they remember having seen in their boyhood, species which 
they do not see now, but we need not attach any great 
importance to such a statement, until we have the means 
of ascertaining whether the fish have gone out to deep 
waters, but if there should be no communication between 
two seas, and they were really exhausted under certain 
conditions, this fact would of itself prove the theory of 
exhaustion just propounded. The case is, however, different 
with the ocean, the immensity of which makes extermination 
