parts, and disuse diminished
them; and that such modifications are inherited."

Now on turning to the first edition, p. 134, it will be found that
instead of the words--"I think there can be no doubt," the words
originally used were--"I think there can be _little_ doubt." That this
deliberate erasure of a qualifying word and substitution of a word
implying unqualified belief, was due to a more decided recognition of a
factor originally under-estimated, is clearly implied by the wording of
the above-quoted passage from the preface to the _Descent of Man_; where
he says that "_even_ in the first edition of the 'Origin of Species,'"
&c.: the implication being that much more in subsequent editions, and
subsequent works, had he insisted on this factor. The change thus
indicated is especially significant as having occurred at a time of life
when the natural tendency is towards fixity of opinion.

During that earlier period when he was discovering the multitudinous
cases in which his own hypothesis afforded solutions, and simultaneously
observing how utterly futile in these multitudinous cases was the
hypothesis propounded by his grandfather and Lamarck, Mr. Darwin was,
not unnaturally, almost betrayed into the belief that the one is
all-sufficient and the other inoperative. But in the mind of one so
candid and ever open to more evidence, there naturally came a reaction.
The inheritance of functionally-produced modifications, which, judging
by the passage quoted above concerning the views of these earlier
enquirers, would seem to have been at one time denied, but which as we
have seen was always to some extent recognized, came to be recognized
more and more, and deliberately included as a factor of importance.

* * * * *

Of this reaction displayed in the later writings of Mr. Darwin, let us
now ask--Has it not to be carried further? Was the share in organic
evolution which Mr. Darwin latterly assigned to the transmission of
modifications caused by use and disuse, its due share? Consideration of
the groups of evidences given above, will, I think, lead us to believe
that its share has been much larger than he supposed even in his later
days.

There is first the implication yielded by extensive classes of phenomena
which remain inexplicable in the absence of this factor. If, as we see,
co-operative parts do not vary together, even when few and close
together, and may not therefore be assu