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 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 there are
to prey upon the larvae of the beesthe cats are therefore the INDIRECT
HELPERS of the bees！* Coming back a step farther we may say that the
old maids are also indirect friends of the humble bees； and indirect
enemies of the field mice； as they keep the cats which eat up the
latter！ This is an illustration somewhat beneath the dignity of the
subject； perhaps； but it occurs to me in passing； and with it I will
conclude this lecture。
＇footnote＇ *The humble bees； on the other hand； are direct helpers of
some plants； such as the heartsease and red clover； which are
fertilized by the visits of the bees； and they are indirect helpers of
the numerous insects which are more or less completely supported by the
heartsease and red clover。
End