338 Darwin, and after Darwin. 
Take any analogous case. The selective agency 
of specific gravity which is utilised in gold-washing 
does not create the original differences between gold- 
dust and dust of all other kinds. But these differ- 
ences being presented by as many different bodies 
in nature, the gold-washer takes advantage oi the 
selective agency in question, and, by using it as a 
cause of segregation, is enabled to separate the gold 
from all the earths with which it may happen to be 
mixed. So far as the objects of the gold-washer are 
concerned, it is immaterial with what other earths 
the gold-dust may happen to be mixed. For 
although gold-dust may occur in intimate association 
with earths of various kinds in various proportions, 
and although in each case the particular admixture 
which occurs must have been due to definite causes, 
these things, in relation to the selective process of 
the washer, are what is called accidental: that is 
to say, they have nothing to do with the causative 
action of the selective process. Now, in precisely 
the same sense Darwin calls the multitudinous varia- 
tions of plants and animals accidental. By so calling 
them he expressly says he does not suppose them 
to be accidental in the sense of not all being due 
to definite causes. But they are accidental in rela- 
tion to the sifting process of natural selection: all 
that they have to do is to furnish the promiscuous 
material on which this sifting process acts. 
Or let us take an even closer analogy. The power 
of selective breeding by man is so wonderful, that in 
the course of successive generations all kinds of 
peculiarities as to size, shape, colour, special appen- 
dages or abortions, &c., can be produced at pleasure, 
