down:--"It is a golden rule,
which I try to follow, to put every fact which is opposed to one's
preconceived opinion in the strongest light." ("More Letters", Vol. II.
page 324.)

The result of this method of presentation is that the works mentioned
above represent a collection of most valuable documents even for those
who feel impelled to draw from the data other conclusions than those of
the author. Each investigation is the outcome of a definite question, a
"preconceived opinion," which is either supported by the facts or
must be abandoned. "How odd it is that anyone should not see that all
observation must be for or against some view if it is to be of any
service!" (Ibid. Vol. I. page 195.)

The points of view which Darwin had before him were principally the
following. In the first place the proof that a large number of the
peculiarities in the structure of flowers are not useless, but of the
greatest significance in pollination must be of considerable importance
for the interpretation of adaptations; "The use of each trifling detail
of structure is far from a barren search to those who believe in natural
selection." ("Fertilisation of Orchids" (1st edition), page 351; (2nd
edition 1904) page 286.) Further, if these structural relations are
shown to be useful, they may have been acquired because from the many
variations which have occurred along different lines, those have been
preserved by natural selection "which are beneficial to the organism
under the complex and ever-varying conditions of life." (Ibid. page
351.) But in the case of flowers there is not only the question of
adaptation to fertilisation to be considered. Darwin, indeed,
soon formed the opinion which he has expressed in the following
sentence,--"From my own observations on plants, guided to a certain
extent by the experience of the breeders of animals, I became convinced
many years ago that it is a general law of nature that flowers are
adapted to be crossed, at least occasionally, by pollen from a distinct
plant." ("Cross and Self fertilisation" (1st edition), page 6.)

The experience of animal breeders pointed to the conclusion that
continual in-breeding is injurious. If this is correct, it raises the
question whether the same conclusion holds for plants. As most flowers
are hermaphrodite, plants afford much more favourable material than
animals for an experimental solution of the question, what results
follow from the union of nearly related