479 
Natural Selection will lead inevitably to the survival of 
the fittest, and that this survival of the fittest will neces 
sarily lead to the transmutation of species, and has led to 
the evolution of all organic forms—then it might be said 
that Organic Evolution by means of Natural Selection is 
a necessary truth. It has been our endeavour to show in 
the First Book of this work that the assumptions of the 
theory do not correspond with the facts of the world in 
which we live; that the fertility of nature does not tend in 
all cases to produce a struggle for existence which is 
selective ; that the struggle for existence is so modified in 
nature that it is not in many cases selective in the sense 
required ; that where selection takes place it does not 
necessarily produce a transmutation of species ; and Mr. 
Wallace himself admits, in a passage just quoted, that if 
the transmutation of species were brought about by the 
action of Natural Selection, we must not therefore infer 
that the same cause, acting in precisely the same way, has 
been the cause of Organic Evolution. Natural Selection 
can only be a necessary truth in so far as it is the logical 
outcome of certain assumptions. But if those assumptions 
are not true, Natural Selection cannot be a necessary law 
of nature. 
Another argument used by Mr. Wallace is based on 
what is known as the law of parsimony. 
“ As the survival of the fittest must inevitably weed out those whose 
colours are prejudicial, and preserve those whose colours are a safe 
guard, we require no other mode of accounting for the protective 
tints of arctic and desert animals.—(Co?üributions. p. 125.) 
Professor Rolleston says of this law :— 
“It was known in the days of the schoolmen as the Razor of Occam, 
and in later days it has been styled the Law of Parsimony or Economy. 
. . . I know that this Régula (of Newton’s) has great influence 
on the minds of many biologists, and I believe that its influence is