s standing in
a similar relation to one another. I afterwards found that the offspring
from the union of two plants belonging to the same forms presented a
close and curious analogy with hybrids from the union of two distinct
species.

In the autumn of 1864 I finished a long paper on 'Climbing Plants,' and
sent it to the Linnean Society. The writing of this paper cost me four
months; but I was so unwell when I received the proof-sheets that I was
forced to leave them very badly and often obscurely expressed. The paper
was little noticed, but when in 1875 it was corrected and published as a
separate book it sold well. I was led to take up this subject by reading
a short paper by Asa Gray, published in 1858. He sent me seeds, and
on raising some plants I was so much fascinated and perplexed by the
revolving movements of the tendrils and stems, which movements are
really very simple, though appearing at first sight very complex, that
I procured various other kinds of climbing plants, and studied the
whole subject. I was all the more attracted to it, from not being at all
satisfied with the explanation which Henslow gave us in his lectures,
about twining plants, namely, that they had a natural tendency to grow
up in a spire. This explanation proved quite erroneous. Some of the
adaptations displayed by Climbing Plants are as beautiful as those of
Orchids for ensuring cross-fertilisation.

My 'Variation of Animals and Plants under Domestication' was begun, as
already stated, in the beginning of 1860, but was not published until
the beginning of 1868. It was a big book, and cost me four years and two
months' hard labour. It gives all my observations and an immense number
of facts collected from various sources, about our domestic productions.
In the second volume the causes and laws of variation, inheritance,
etc., are discussed as far as our present state of knowledge permits.
Towards the end of the work I give my well-abused hypothesis of
Pangenesis. An unverified hypothesis is of little or no value; but if
anyone should hereafter be led to make observations by which some such
hypothesis could be established, I shall have done good service, as an
astonishing number of isolated facts can be thus connected together and
rendered intelligible. In 1875 a second and largely corrected edition,
which cost me a good deal of labour, was brought out.

My 'Descent of Man' was published in February, 1871. As soon as I had
become, in t