io5 
those with which it comes into competition ; and the 
consequent extinction of the less favoured forms almost 
inevitably follows.”* 
Mr. Wallace asserts that “this daily and hourly struggle, 
this incessant warfare . . . affords one of the most 
important elements in bringing about the origin (? trans 
mutation) of species.” He then proceeds to illustrate this 
struggle by the displacement of one species by another ; 
by the weeds which take the place of flowers in the 
neglected garden ; by the disappearance of native weeds 
in the presence of imported ones ; by the failure to 
naturalise suitable plants ; by the victory of the beech 
over the birch ; by the survival of one set of plants and 
the extinction of others in the Pampas ; by the exter 
mination of the English watercress in New Zealand by 
the willows which are planted on the banks of the streams; 
by the expulsion of the black rat by the brown rat ; by 
the victory of the European horse-fly over a fly native 
to New Zealand ; and by the survival of the small Asiatic 
cockroach and the extermination of a larger Russian 
species. He does not say that these phenomena prove 
the transmutation of species by Natural Selection ; but 
one does not see the force of the argument in a work 
on Darwinism unless he meant us to infer this. It is 
true that he might have argued that this struggle between 
race and race is a proof of a struggle for existence, and 
that it prepares the mind for admitting the probability of 
the struggle for existence which produces a transmutation 
of species by means of Natural Selection. But he does 
not say this distinctly ; and we may presume that he 
intended us to infer what Mr. Romanes and Mr. Darwin 
assert so emphatically. 
Origin of Species, pp. 2ÇJ-6.