life; modern writers on evolution for the most part avoid saying
anything expressly; this nevertheless is the conclusion which the
reader naturally draws--and was doubtless intended to draw--from Mr.
Spencer's words. He gathers that these writers put forward an
"utterly inadequate" theory, which cannot for a moment be
entertained in the form in which they left it, but which,
nevertheless, contains contributions to the formation of a just
opinion which of late years have been too much neglected.

This inference would be, as Mr. Spencer ought to know, a mistaken
one. Erasmus Darwin, who was the first to depend mainly on
functionally produced modifications, attributes, if not as much
importance to variations induced either by what we must call chance,
or by causes having no connection with use and disuse, as Mr.
Spencer does, still so nearly as much that there is little to choose
between them. Mr. Spencer's words show that he attributes, if not
half, still not far off half the modification that has actually been
produced, to use and disuse. Erasmus Darwin does not say whether he
considers use and disuse to have brought about more than half or
less than half; he only says that animal and vegetable modification
is "in part produced" by the exertions of the animals and vegetables
themselves; the impression I have derived is, that just as Mr.
Spencer considers rather less than half to be due to use and disuse,
so Erasmus Darwin considers decidedly more than half--so much more,
in fact, than half as to make function unquestionably the factor
most proper to be insisted on if only one can be given. Further
than this he did not go. I will quote enough of Dr. Erasmus
Darwin's own words to put his position beyond doubt. He writes:-

"Thirdly, when we enumerate the great changes produced in the