r at least a cause which behaves in the same way.
This is to bring in finality again, and a finality this time more than
ever charged with anthropomorphic elements. In a word, if the adaptation
is passive, if it is mere repetition in the relief of what the
conditions give in the mold, it will build up nothing that one tries to
make it build; and if it is active, capable of responding by a
calculated solution to the problem which is set out in the conditions,
that is going further than we do--too far, indeed, in our opinion--in
the direction we indicated in the beginning. But the truth is that there
is a surreptitious passing from one of these two meanings to the other,
a flight for refuge to the first whenever one is about to be caught _in
flagrante delicto_ of finalism by employing the second. It is really
the second which serves the usual practice of science, but it is the
first that generally provides its philosophy. In any _particular_ case
one talks as if the process of adaptation were an effort of the organism
to build up a machine capable of turning external circumstances to the
best possible account: then one speaks of adaptation _in general_ as if
it were the very impress of circumstances, passively received by an
indifferent matter.

But let us come to the examples. It would be interesting first to
institute here a general comparison between plants and animals. One
cannot fail to be struck with the parallel progress which has been
accomplished, on both sides, in the direction of sexuality. Not only is
fecundation itself the same in higher plants and in animals, since it
consists, in both, in the union of two nuclei that differ in their
properties and structure before their union and immediately after become
equivalent to each other; but the preparation of sexual elements goes on
in both under like conditions: it consists essentially in the reduction
of the number of chromosomes and the rejection of a certain quantity of
chromatic substance.[22] Yet vegetables and animals have evolved on
independent lines, favored by unlike circumstances, opposed by unlike
obstacles. Here are two great series which have gone on diverging. On
either line, thousands and thousands of causes have combined to
determine the morphological and functional evolution. Yet these
infinitely complicated causes have been consummated, in each series, in
the same effect. And this effect, could hardly be called a phenomenon of
"adaptation": wher