and when well
nigh overpowered, it may be that the smallest chance, something in its
colour, perhaps--the minutest circumstance--will turn the scale one way
or the other.

Suppose that by a variation of the black race it had produced the white
man at any time--you know that the Negroes are said to believe this to
have been the case, and to imagine that Cain was the first white man,
and that we are his descendants--suppose that this had ever happened,
and that the first residence of this human being was on the West Coast
of Africa. There is no great structural difference between the white man
and the Negro, and yet there is something so singularly different in the
constitution of the two, that the malarias of that country, which do not
hurt the black at all, cut off and destroy the white. Then you see there
would have been a selective operation performed; if the white man had
risen in that way, he would have been selected out and removed by means
of the malaria. Now there really is a very curious case of selection of
this sort among pigs, and it is a case of selection of colour too.
In the woods of Florida there are a great many pigs, and it is a very
curious thing that they are all black, every one of them. Professor
Wyman was there some years ago, and on noticing no pigs but these black
ones, he asked some of the people how it was that they had no white
pigs, and the reply was that in the woods of Florida there was a root
which they called the Paint Root, and that if the white pigs were to eat
any of it, it had the effect of making their hoofs crack, and they died,
but if the black pigs eat any of it, it did not hurt them at all. Here
was a very simple case of natural selection. A skilful breeder could not
more carefully develope the black breed of pigs, and weed out all the
white pigs, than the Paint Root does.

To show you how remarkably indirect may be such natural selective
agencies as I have referred to, I will conclude by noticing a case
mentioned by Mr. Darwin, and which is certainly one of the most curious
of its kind. It is that of the Humble Bee. It has been noticed that
there are a great many more humble bees in the neighbourhood of towns,
than out in the open country; and the explanation of the matter is this:
the humble bees build nests, in which they store their honey and deposit
the larvae and eggs. The field mice are amazingly fond of the honey and
larvae; therefore, wherever there are plenty of field