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them；that every plant has its indirect helpers in the birds that
scatter abroad its seed； and the animals that manure it with their
dung；I say； when these things are considered； it seems impossible
that any variation which may arise in a species in nature should not
tend in some way or other either to be a little better or worse than
the previous stock； if it is a little better it will have an advantage
over and tend to extirpate the latter in this crush and struggle； and if
it is a little worse it will itself be extirpated。
I know nothing that more appropriately expresses this； than the phrase；
〃the struggle for existence〃； because it brings before your minds； in a
vivid sort of way； some of the simplest possible circumstances
connected with it。 When a struggle is intense there must be some who
are sure to be trodden down； crushed； and overpowered by others； and
there will be some who just manage to get through only by the help of
the slightest accident。 I recollect reading an account of the famous
retreat of the French troops； under Napoleon； from Moscow。 Worn out；
tired； and dejected； they at length came to a great river over which
there was but one bridge for the passage of the vast army。 Disorganised
and demoralised as that army was； the struggle must certainly have been
a terrible oneevery one heeding only himself； and crushing through
the ranks and treading down his fellows。 The writer of the narrative；
who was himself one of those who were fortunate enough to succeed in
getting over； and not among the thousands who were left behind or
forced into the river； ascribed his escape to the fact that he saw
striding onward through the mass a great strong fellow；one of the
French Cuirassiers； who had on a large blue cloakand he had enough
presence of mind to catch and retain a hold of this strong man's
cloak。 He says； 〃I caught hold of his cloak； and although he swore at
me and cut at and struck me by turns； and at last； when he found he
could not shake me off； fell to entreating me to leave go or I should
prevent him from escaping； besides not assisting myself； I still kept
tight hold of him； and would not quit my grasp until he had at last
dragged me through。〃 Here you see was a case of selective savingif
we may so term itdepending for its success on the strength of the
cloth of the Cuirassier's cloak。 It is the same in nature； every
species has its bridge of Beresina； it has to fight its way through and
struggle with other species； and when well nigh overpowered； it may be
that the smallest chance； something in its colour； perhapsthe
minutest circumstancewill 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 timeyou 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 descendantssuppose 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 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