, and thus led them to
leave off using their wings.

Granted, that if there had been nothing to take unmodified beetles away,
there would have been less room and scope for the modified beetles; also
that unmodified beetles would have intermixed with the modified, and
impeded the prevalence of the modification. But anything else than such
removal of unmodified individuals would be contrary to our hypothesis.
The very essence of conditions of existence is that there _shall be_
something to take away those which do not comply with the conditions;
if there is nothing to render such and such a course a _sine qua non_
for life, there is no condition of existence in respect of this course,
and no modification according to Lamarck could follow, as there would be
no changed distribution of use.

I think that if I were to leave this matter here I should have said
enough to make the reader feel that Lamarck's system is direct,
intelligible and sufficient--while Mr. Darwin's is confused and
confusing. I may however quote Mr. Darwin himself as throwing his theory
about the Madeira beetles on one side in a later passage, for he
writes:--

"It is probable that _disuse has been the main agent in rendering organs
rudimentary_," or in other words that Lamarck was quite right--nor does
one see why if disuse is after all the main agent in rendering an organ
rudimentary, use should not have been the main agent in developing
it--but let that pass. "It (disuse) would at first lead," continues Mr.
Darwin, "by slow steps to the more and more complete reduction of a
part, until at last it became rudimentary--as in the case of the eyes of
animals inhabiting dark caverns, and of the wings of birds inhabiting
oceanic islands, which have seldom been forced by beasts of prey to take
flight, and have ultimately lost the power of flying. Again, an organ
useful under certain conditions, might become injurious under others,
_as with the wings of beetles living on small and exposed
islands_;"[372] so that the rudimentary condition of the Madeira
beetles' wings is here set down as mainly due to disuse--while above we
find it mainly due to natural selection--I should say that immediately
after the word "islands" just quoted, Mr. Darwin adds "and in this case
natural selection will have aided in reducing the organ, until it was
rendered harmless and rudimentary," but this is Mr. Darwin's manner, and
must go for what it is worth.

How refreshing to turn