M. Flourens cannot imagine an unconscious selection--it is for him a
contradiction in terms. Did M. Flourens ever visit one of the
prettiest watering-places of "la belle France," the Baie d'Arcachon? If
so, he will probably have passed through the district of the Landes,
and will have had an opportunity of observing the formation of "dunes"
on a grand scale. What are these "dunes"? The winds and waves of the
Bay of Biscay have not much consciousness, and yet they have with great
care "selected," from among an infinity of masses of silex of all
shapes and sizes, which have been submitted to their action, all the
grains of sand below a certain size, and have heaped them by themselves
over a great area. This sand has been "unconsciously selected" from
amidst the gravel in which it first lay with as much precision as if
man had "consciously selected" it by the aid of a sieve. Physical
Geology is full of such selections--of the picking out of the soft from
the hard, of the soluble from the insoluble, of the fusible from the
infusible, by natural agencies to which we are certainly not in the
habit of ascribing consciousness.

But that which wind and sea are to a sandy beach, the sum of influences,
which we term the "conditions of existence," is to living organisms.
The weak are sifted out from the strong. A frosty night "selects" the
hardy plants in a plantation from among the tender ones as effectually
as if it were the wind, and they, the sand and pebbles, of our
illustration; or, on the other hand, as if the intelligence of a
gardener had been operative in cutting the weaker organisms down. The
thistle, which has spread over the Pampas, to the destruction of native
plants, has been more effectually "selected" by the unconscious
operation of natural conditions than if a thousand agriculturists had
spent their time in sowing it.