PERPETUATION OF LIVING BEINGS. 125 



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 Boot, 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 develop the black breed of pigs, and weed out 

 all the white pigs, than the Paint Hoot 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 larvoe and eggs. The field mice are 

 amazingly fond of the honey and larvae ; therefore, 

 wherever there are plenty of field mice, as in the coun- 

 try, the humble bees are kept down ; but in the neigh- 

 bourhood 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 there are to prey upon 

 the larvse of the bees — the cats are therefore the indi- 



