THE FIRST FOOD OF THE COMMON WHITE-FISH. 
(COREGONUS CLUPEIFORMIS, Mitcll.) 
By S. A. FORBES. 
In a very large lake the conditions of life are remarkably uni- 
form. The volume of water remains, of course, nearly constant 
from season 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 exhibit there a regularity and stability which are 
in remarkable contrast 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 ex- 
penditure, of multiplication and destruction, among the inhabit- 
ants of the lake. Here, every species of animal, whether preda- 
ceous or vegetarian, must find, in the surplus products of growth 
and reproduction among the species upon which it depends for 
food, a far more constant and unvarying supply for its needs than 
elsewhere; and the species fed upon must be subject to a far 
more regular drain upon their surplus numbers 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 flexible than one where 
wide and violent fluctuation and continual readjustment are the 
rule; and a species in any way deeply affected will here 
have within itself far less recuperative power than one which has 
been forced again and again — each year, perhaps — to rally 
against the most destructive attacks as the price of its continued 
