204 THE SCIENTIFIC RESULTS OF V 



of some other organism, may lead to tlie destruction 

 of the proper food of the carp, and the yield of the 

 pond may be endangered. The whole of these circum- 

 stances can, in the case of the carp-pond, be studied 

 and controlled. 



If we now pass to the consideration of any given 

 area of the sea-bottom, we find that, though the area 

 is not definitely limited, the same interaction of the 

 various organisms inhabiting it holds good. One 

 form is preying upon another, and determining by its 

 presence the numbers and the interaction of all the 

 others. Physical conditions which aff'ect one form, 

 may in the same way, as in the carp-pond, afi'ect the 

 prosperity and abundance of another form. Currents, 

 varying seasons, and such-like conditions, must obvi- 

 ously produce their efi"ect. But still more influential 

 must be the operations of man in removing a large 

 number of edible fish from such an area. It is a mis- 

 take to suppose that the whole ocean is practically 

 one vast storehouse, and that the place of the fish 

 removed on a particular fishing-ground is immediately 

 taken by some of the grand total of fish, which are so 

 numerous in comparison with man's depredations as 

 to make his operations in this respect insignificant. 

 Even were it proved that there is this sort of cosmo- 

 politan solidarity about such fish as the Cod, which 

 live in deep water, there is, on the contrary, evidence 

 that shoal fish, like Herrings, Mackerel, and Pilchard, 

 and ground-fish, such as Soles and other flat-fishes, 

 are really localised. If man removes a large propor- 

 tion of these fish from the areas which they inhabit 



