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takes place in nature—but it is not Natural Selection, 
for the obvious reason that Natural Selection means the 
transmutation of a species by the selection of favourable 
variations which arise in connection with sexual repro 
duction. 
In those cases in which the displacement of species is 
due to a struggle between race and race, the struggle 
ends in the extermination and possibly the extinction 
of one species and in the survival of the other species, 
unmodified by the struggle through which it has passed. 
The black rat has been exterminated by the brown rat, 
which remains the same as it was before the conflict. 
The willow which exterminates the English watercress 
in New Zealand undergoes no modification. The same 
observation applies to the weeds which take the place 
of cultivated flowers in the abandoned garden. Goldsmith, 
who, in The Deserted Village, has drawn a picture familiar 
to many— 
“ Near yonder copse, where once the garden smiled, 
And still where many a garden flower grows wild”— 
described only the first stage of a strange metamorphosis. 
For not only do weeds soon usurp the ground and destroy 
a number of the flowers, but these weeds in their turn 
give place to other weeds—the very weeds associated with 
human culture giving place in time to weeds of nature’s 
unaided growth. Mr. Wallace would seem to give two 
explanations of this displacement; for, on the one hand, he 
says that “all the plants concerned may be perfectly hardy 
—all may grow freely from seed.” On the other hand, he 
says, “ of the many hundreds of hardy plants which pro 
duce seed freely in our gardens, very few ever run wild, 
and hardly any have become common.” But whichever 
explanation you take makes no difference to the argument.