THE BALANCE OF NATURE. 27 



warmer or colder climate, as the case may be; but, speaking 

 generally, as the salmon returns to its own waters, so do sea 

 fish keep to their own colony. AH they seem to need is a 

 rallying point — thus at any place where there is a wrecked ship 

 in the water, a sand-bank, or a chain of rocks, certain kinds of 

 fish will there be found assembled. Our larger shoals of fish, 

 which form money-yielding industries, are of wonderful extent, 

 and must have been gathering %nd increasing for ages, having a 

 population multiplied almost beyond belief. Century after 

 century must have passed away as these colonies grew in size, 

 and were subjected to all kinds of influences, evil or good : at 

 times decimated by enemies, or perhaps attacked by mysterious 

 diseases, that killed the fish in tens of thousands. Schools or 

 shoals of fish, when they become of an extent that will admit of 

 constant fishing, must have been forming during long periods of 

 time ; for we know that, despite the wonderftd fecundity of aU 

 kinds of sea-fish, the expenditure of both seed and life is some- 

 thing tremendous. We may rest assured that, if a female cod- 

 fish yields its roe by millions, a balancing power exists in the 

 water that prevents the bulk of the eggs from coming to life, or 

 at any rate from reaching maturity. If it were not so, how 

 came it, when there was no fish commerce, and when man only 

 killed the denizens of the sea for the supply of his individual 

 wants, that our waters were not, so to speak, impassable from 

 a superfluity of fish 1 Bufibn has said that if a pair of herrings 

 were left to breed and multiply undisturbed for a period of 

 twenty years, the result would be a bulk of fish equal to that 

 of the globe on which we live ! 



