44 
goino’ on. Not every seed that ripens can possibly germinate, 
not all that germinate can grow up, not every one that grows 
up can come to maturity and reproduce itself ; and so m like 
manner with animals. There is a perpetual struggle for 
existence going on, both among rival races and rival indi- 
viduals; this struggle must lead to selection. But selection 
on what principle ? A mere indiscriminate selection would 
have as little tendency to bring about specific differences m 
nature as an indiscriminate isolation of individuals would have 
to produce an improvement in breeds. The selection to be 
effective must be one which lays hold of particular variations, 
and tends to perpetuate them, to the exclusion of others, is 
this the case here ? Again we may say, from the very ttatuie 
of thin o*s it must be so. The selection being mainly ot the 
nature of a competition, it follows that just those races, those 
individuals, will be successful which are most perfectly adapted 
to the conditions under which the struggle is carried on. 
But the variations occurring in individuals cannot but be m 
many cases of considerable moment to such adaptation, either 
beneficially or otherwise. If the former, those individuals 
will be precisely such as natural selection will inevitably tend 
to preserve ; if the latter, they will be such as natural selec- 
tion will inevitably reject. The same will take place with the 
descendants of the favoured few, and so by a continual sitting 
out of those which lack the advantageous variation, or possess 
it in a smaller measure, the predominance of the altered form 
becomes yearly greater and greater, the counteracting influence 
of intercrossing as a consequence less and less, the variation is 
strengthened and rendered constant, and a specific difference 
is the result. Granted that species vary, that their variations 
frequentlv have a bearing on their adaptation to the cncum- 
stances of their life, that they have a tendency to transmit 
variations by inheritance, that there is a continual process ot 
selection among individuals going on, which of necessity favours 
those possessed of advantageous variations to the exclusion ol 
others, and there is no alternative left but to conclude that the 
Darwinian hypothesis is possible. The elements contained in it 
are real elements, their action and reaction exactly that which 
is asserted ; the result is inevitable. The causes assigned by 
Mr. Darwin for the existence of specific differences, are not 
only real causes, such as may account for phenomena similar 
to those sought to be explained; but are, further, causes 
actually at work in the domain where these phenomena occur. 
Not only, therefore, is the hypothesis possible, but it is also 
established as to some extent true. Few, if any, probably 
will deny that there are some races of living beings whose 
