XI 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 Ptoot 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 ex- 

 planation 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 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 



