a theory. Dr. Weismann asserts that we cannot imagine
the process of Natural Selection :—
“ I must say that, in respect of warrant to assume the process of
Natural Selection, it does not seem to matter much whether we can
easily, or with difficulty, or only with great difficulty, imagine it ; and
for this reason, that I do not believe that we are in any case able to
conceive in detail the actual morphological metamorphoses con
cerned.”—(The Contemporary Review, vol. Ixiv., p. 320.)
He asserts that we cannot demonstrate the truth of
Natural Selection :—
“Just as in this instance, so is it in every individual case of Natural
Selection. We cannot demonstrate any of them, and there is no
use attempting to make them seem unanswerable.”—(p. 323.)
“It is true the results of artificial selection are in favour of the
occurrence of Natural Selection, but, as Herbert Spencer justly
observes, the two processes, though they may be analogous, are
certainly not identical. The struggle for existence plays the part of
breeder in the case of Natural Selection ; and how this factor works
we are unable to determine in any single case. Who would say of
any little variation in the form of any existing species that it is
sufficient to give its possessor the victory in the struggle for existence,
and so may become the starting-point of an advantageous metamor
phosis of the part? Even in the simplest of cases that is impossible ;
no one, for instance, could decide how much the colour of a green
insect must vary so as to originate a process of selection dependent
perhaps on adaptation to a new and somewhat differently coloured
fodder-plant. We cannot estimate what Romanes has recently very
well called the ‘selection value’ of variations, which Lloyd Morgan
had previously spoken of as the ‘elimination value’; we can only
say generally with Darwin that selection works by the accumulation
of very slight variations, and conch/de from this that these ‘ slight
variations' must possess selectio?i value. To determine accurately
the degree of this selection value in individual cases is, however, as
yet, impossible.”—(p. 324.)
“As soon as an attempt is made to think out in detail the process
of selection by which perhaps the little bristles or the small baskets
of the worker-bees have arisen, it is seen that all and every one of
the data are wanting. Moreover, in my opinion, we cannot hope
that we shall ever possess them, either in these cases or in any
yet simpler process of Natural Selection. Not only would it be
necessary to form an estimate of the smallest variations so as to know