must use it, otherwise I should incessantly have
to expand it into some such (here miserably expressed) formula as
the following: "The tendency to the preservation (owing to the severe
struggle for life to which all organic beings at some time or generation
are exposed) of any, the slightest, variation in any part, which is of
the slightest use or favourable to the life of the individual which
has thus varied; together with the tendency to its inheritance." Any
variation, which was of no use whatever to the individual, would not be
preserved by this process of "natural selection." But I will not weary
you by going on, as I do not suppose I could make my meaning clearer
without large expansion. I will only add one other sentence: several
varieties of sheep have been turned out together on the Cumberland
mountains, and one particular breed is found to succeed so much better
than all the others that it fairly starves the others to death. I should
here say that natural selection picks out this breed, and would tend to
improve it, or aboriginally to have formed it...

You speak of species not having any material base to rest on, but is
this any greater hardship than deciding what deserves to be called a
variety, and be designated by a Greek letter? When I was at systematic
work, I know I longed to have no other difficulty (great enough) than
deciding whether the form was distinct enough to deserve a name, and not
to be haunted with undefined and unanswerable questions whether it was a
true species. What a jump it is from a well-marked variety, produced by
natural cause, to a species produced by the separate act of the hand
of God! But I am running on foolishly. By the way, I met the other day
Phillips, the palaeontologist, and he asked me, "How do you define a
species?" I answered, "I cannot." Whereupon he said, "at last I have
found out the only true definition,--any form which has ever had a
specific name!"...

LETTER 80. TO C. LYELL. Ilkley, October 31st [1859].

That you may not misunderstand how far I go with Pallas and his many
disciples I should like to add that, though I believe that our domestic
dogs have descended from several wild forms, and though I must think
that the sterility, which they would probably have evinced, if crossed
before being domesticated, has been eliminated, yet I go but a very
little way with Pallas & Co. in their belief in the importance of
the crossing and blending of the aboriginal sto