xr PHENOMENA OF ORGANIC NATURE 445 
_ 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 ate 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 develop 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. Itis 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 ex- 
planation of the matter is this: the humble bees 
build nests, in which they store their honey and 
deposit the larve and eggs. The field mice are 
amazingly fond of the honey and larvee ; therefore, 
wherever there are plenty of field mice, as in the 
country, the humble bees are kept down; but in 
the neighbourhood of towns, the number of cats 
which prowl about the fields eat up the field mice, 
and of course the more mice they eat up the less 
