But here the point is that, even if any one could
assert the utility of such an elaborate and complicated
development, and suppose it self-caused by accident
or effect of environment, it certainly goes against
the idea that all forms are due to an
accumulation
of small changes. For these curious contrivances
in the case of
Salvia, Coryanthes, and other
plants, would in any case have been no use to the
plant till the whole machinery
was complete.
Now, on the theory of slow changes gradually accumulating
till the complete result was attained, there must
have been generation after generation of plants, in
which the machinery was as yet imperfect and only
partly built up. But in such incomplete stages,
fertilization would have been impossible, and therefore
the plant must have died out. Just the same with
the curious fly-trap in
Dionoea. Whatever
may be its benefit to the plant, till the whole apparatus
as it now is, was
complete, it would have been
of no use. In the animal kingdom also, instances
might be given: the giraffe has a long neck which
is an advantage in getting food that other animals
cannot reach; but what would have been the use of
a neck which was becoming—and had not yet
become—long? here intermediate stages would
not have been useful, and therefore could not have
been preserved.[2] In flat fishes it is curious that,
though they are born with eyes on different sides of
the head, the lower eye gradually grows round to the
upper-side. As remarked by Mr. Mivart, natural
selection could not have produced this change, since
the
first steps towards it could have been
of no possible use, and could not therefore have occurred,
at least not without direction and guidance from without.
Mr. Darwin’s explanation of the case does not
touch this difficulty.
[Footnote 1: This species was instanced because
the lectures which form the basis of the book were
originally delivered at Simla, in the N.W. Himalaya,
where, at certain seasons, the plant is a common wayside
weed. Mr. Darwin notices a similar and, if possible,
more curious structure in a species of Catasetum.]
[Footnote 2: See this fully explained by Mivart,
“Genesis of Species,” pp. 29, 30 (2nd
edition).]
(3) The third point, the occurrence of so much beauty
in organic life, is perhaps one of the most conclusive
arguments for design in nature.
Here, if possible, more clearly than elsewhere, I
see a total failure of “natural causes.”
We are told that the beauty of birds (for instance)
is easily accounted for by the fact, that the ornamented
and beautiful males are preferred by the other sex;
and that this is an advantage, so the beauty has been
perpetuated; and the same with butterflies and beetles.
We are told also that bright-coloured fruits attract
birds, who eat the soft parts of the fruit and swallow
the hard stone or seed which is thus prepared for
germination, and carried about and dispersed over the
earth’s surface. Again, showy coloured flowers
attract insects, which carry away pollen and fertilize
other flowers.