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THE FIRST FOOD OF THE COMMON WHITE-FISH. 



(COREGONUS CLUPEIFORMIS, Mitcll.) 

 By S. a. Forbes.' 



lu a very large lake the conditions of life are remarkably uniform. 

 The volume of water remains, of coarse, nearly constant Jrom treason 

 to season and from year to year, and the extremes of summer heat 

 and winter cold have but a moderate effect upon the temperature of 

 the lake as a whole. Consequently both plant and animal life ex- 

 hibit there a regularity and stability which are in remarkable con- 

 trast to their fluctuations in smaller bodies of water and on the 

 surrounding land. Not only do the relative numbers of individuals 

 in the various species remain about the same, but the absolute 

 number of each must necessarily change but little, as a rule. 



Such a state of affairs is eminently favorable to an exact and 

 economical balance of supply and demand, of income and expenditure, 

 of multiplication and destruction, among the inhabitants of the lake. 

 Here, every species of animal, whether predaceous or vegetarian, 

 must find, in the surplus products of growth and reproduction among 

 the species upon which it depends tor food, a far more constant and 

 unvarying supply for its needs than elsewhere; and the species fed 

 upon mubt be subject to a far more regular drain upon their sur- 

 plus numl)ers or unessential structures. Where there is little 

 fluctuation there is little waste, 



A system of life like this, running on with relatively even tenor 

 for centuries, must of course be much less JicxtUle than one where 

 wide and violent fluctuation and continual readjustment are the 

 rule; and a species in any way deeply afl'ected will here have within 

 itself far less recuperative power than one which has been forced 

 again and again — each year, perhaps— lo rally agamst the most de- 

 structive attacks as the price of its continued existence. Disturbances 

 of the natural balance of life, of the primitive and spontaneous sys- 

 tem of reaction by which the different groups of organisms are re- 

 lated, will therefore be unusually serious and lasting; and where 

 such disturbances result from human interference, as bv the yearly 

 capture of large numbers of any important flsh, it is especially 

 desirable that artificial means of compensation be taken to restore 

 the disturbed balance as nearly as ])o-!Sil»le. Excessive loss will be 

 made good by natural reactions far more slowly than if it occurred 

 to a pond or river species, accustomed, as most of the latter are, to 

 till up rapidly enormous gaps in their numbers. 



