respect to domesticated productions, by printed enquiries, by
conversation with skilful breeders and gardeners, and by
extensive reading. When I see the list of books of all kinds
which I read and abstracted, including whole series of Journals
and Transactions, I am surprised at my industry. I soon
perceived that selection was the keystone of man's success in
making useful races of animals and plants. But how selection
could be applied to organisms living in a state of nature
remained for some time a mystery to me.

In October 1838, that is, fifteen months after I had begun my
systematic enquiry, I happened to read for amusement 'Malthus on
Population,' and being well prepared to appreciate the struggle
for existence which everywhere goes on from long-continued
observation of the habits of animals and plants, it at once
struck me that under these circumstances favourable variations
would tend to be preserved, and unfavourable ones to be
destroyed. The result of this would be the formation of new
species. Here then I had at last got a theory by which to work;
but I was so anxious to avoid prejudice, that I determined not
for some time to write even the briefest sketch of it. In June
1842 I first allowed myself the satisfaction of writing a very
brief abstract of my theory in pencil in 35 pages; and this was
enlarged during the summer of 1844 into one of 230 pages, which I
had fairly copied out and still possess.

But at that time I overlooked one problem of great importance;
and it is astonishing to me, except on the principle of Columbus
and his egg, how I could have overlooked it and its solution.
This problem is the tendency in organic beings descended from the