. page 276 (footnote).) But, he wrote, "the safest conclusion,
as it seems to me, is, that under certain unknown circumstances, and
perhaps at very long intervals of time, one individual of the Bee Ophrys
is crossed by another." ("Fertilisation of Orchids" page 71.)

If, on the one hand, we remember how much more sure self-fertilisation
would be than cross-fertilisation, and, on the other hand, if we call to
mind the numerous contrivances for cross-fertilisation, the
conclusion is naturally reached that "it is an astonishing fact that
self-fertilisation should not have been an habitual occurrence. It
apparently demonstrates to us that there must be something injurious in
the process. Nature thus tells us, in the most emphatic manner, that she
abhors perpetual self-fertilisation... For may we not further infer as
probable, in accordance with the belief of the vast majority of the
breeders of our domestic productions, that marriage between near
relations is likewise in some way injurious, that some unknown great
good is derived from the union of individuals which have been kept
distinct for many generations?" (Ibid., page 359.)

This view was supported by observations on plants of other families,
e.g. Papilionaceae; it could, however, in the absence of experimental
proof, be regarded only as a "working hypothesis."

All adaptations to cross-pollination might also be of use simply because
they made pollination possible when for any reason self-pollination had
become difficult or impossible. Cross-pollination would, therefore, be
of use, not as such, but merely as a means of pollination in general;
it would to some extent serve as a remedy for a method unsuitable in
itself, such as a modification standing in the way of self-pollination,
and on the other hand as a means of increasing the chance of pollination
in the case of flowers in which self-pollination was possible, but which
might, in accidental circumstances, be prevented. It was, therefore,
very important to obtain experimental proof of the conclusion to which
Darwin was led by the belief of the majority of breeders and by the
evidence of the widespread occurrence of cross-pollination and of the
remarkable adaptations thereto.

This was supplied by the researches which are described in the two other
works named above. The researches on which the conclusions rest had, in
part at least, been previously published in separate papers: this is the
case as regards the he