THE KINSHIP OF LIFE. 23 
increase is actually impossible; for more than a hundred 
other species of similar birds are disputing the same ter- 
ritory, and there can not be place or food for all. With 
such conditions, the struggle for exist- 
ence between sparrow and sparrow, and 
between sparrows and other birds, grows 
yearly more severe. Each year now the sparrow gains a 
little and other birds lose correspondingly, but sooner or 
later with each species a point will be reached when the 
loss exactly balances the increase. This produces a 
condition of apparent equiliibrum—the equilibrium of 
Nature; a sort of armed neutrality which a superficial 
observer mistakes for real peace and permanence. But 
this equilibrium is broken as soon as any individual or 
group of individuals appears that can do something 
more than merely hold its own ina struggle for existence. 
It is thus evident that throughout all Nature the 
number of organisms born into life is far in excess of 
the number of those which can come to 
maturity. In every species the majority 
never reach their full growth, and this 
is because, for one reason or another, 
they can not do so. All live who can. Nature asks 
each organism, Why should you live? And those who 
can not give an answer pass away. “So careful of the 
type she seems; so careless of the single life.” It is 
also evident, to use the language of Professor Bergen, 
that “the killing will not be indiscriminate, but it will 
first and mainly comprise those individuals which are 
least able to resist the attack.” It is this “ weeding- 
out” process in Nature, this “natural selection,” which 
in Darwin’s view constitutes the essential cause of 
change and progress. Of the many possible illustra- 
tions of the action of “natural selection,” one may serve 
our purpose at present. ; 
The equilibrium 
of Nature, 
More organisms 
born than can 
mature. 
