they
can do as much as Mr. Darwin himself said they did, why should they not
do more? Why stop where Mr. Darwin did? And again, where in the name of
all that is reasonable did he really stop? He drew no line, and on what
principle can we say that so much is possible as effect of use and
disuse, but so much more impossible? If, as Mr. Darwin contended, disuse
can so far reduce an organ as to render it rudimentary, and in many cases
get rid of it altogether, why cannot use create as much as disuse can
destroy, provided it has anything, no matter how low in structure, to
begin with? Let us know where we stand. If it is admitted that use and
disuse can do a good deal, what does a good deal mean? And what is the
proportion between the shares attributable to use and disuse and to
natural selection respectively? If we cannot be told with absolute
precision, let us at any rate have something more definite than the
statement that natural selection is "the most important means of
modification."

Mr. Darwin gave us no help in this respect; and worse than this, he
contradicted himself so flatly as to show that he had very little
definite idea upon the subject at all. Thus in respect to the
winglessness of the Madeira beetles he wrote:--

"In some cases we might easily put down to disuse modifications of
structure, which are wholly or mainly due to natural selection. Mr.
Wollaston has discovered the remarkable fact that 200 beetles, out of the
550 species (but more are now known) inhabiting Madeira, are so far
deficient in wings that they cannot fly; and that of the 29 endemic
genera no less than 23 have all their species in this condition! Several
facts,--namely, that beetles in many parts of the world are frequently
blown out to sea and perish; that the beetles in Madeira, as observed by
Mr. Wollaston, lie much concealed until the wind lulls and the sun
shines; that the proportion of wingless beetles is larger on the exposed
Desertas than in Madeira itself; and especially the extraordinary fact,
so strongly insisted on by Mr. Wollaston, that certain large groups of
beetles, elsewhere excessively numerous, which absolutely require the use
of their wings are here almost entirely absent;--these several
considerations make me believe that the wingless condition of so many
Madeira beetles is mainly due to the action of natural selection,
_combined probably with disuse_ [italics mine]. For during many
successive generation