CHAPTER V. 
PURE DARWINISM. 
(a) VARIATIONS SOMETIMES ASSOCIATED WITH SEXUAL 
REPRODUCTION. 
“ Out of the deep, my child, out of the deep, 
Through all this changing world of changeless law 
And every phase of ever-heightening life, 
And nine long months of ante-natal gloom 
With this last moon, this crescent, her dark orb 
Touched with earth’s light—thou comest, darling boy!” 
—Tennyson. De Profundis. 
THE argument for pure Darwinism, which asserts that 
Natural Selection is the sole cause of the transmutation of 
species, is based upon the belief that no modification of 
“the body” of an individual can be inherited ; that con 
genital or birth variations can be inherited, and that 
Natural Selection will choose out the favourable variations 
which occur. Now in order that this argument should 
have any validity, it must be tacitly assumed that there 
are no birth variations, save those which are necessarily 
and inevitably associated with sexual reproduction ; that 
these variations will not resemble one another through the 
action of a definite cause ; and that there is in nature no 
other way of isolating similar variants for breeding pur 
poses than by Natural Selection. In this and the following 
chapter I shall show that these tacit assumptions are not 
in accordance with the facts of the case.