ctions; that they should be infinitely better adapted to the
most complex conditions of life, and should plainly bear the stamp of
far higher workmanship?

It may metaphorically be said that natural selection is daily and hourly
scrutinising, throughout the world, the slightest variations; rejecting
those that are bad, preserving and adding up all that are good; silently
and insensibly working, whenever and wherever opportunity offers, at the
improvement of each organic being in relation to its organic and
inorganic conditions of life. We see nothing of these slow changes in
progress until the hand of time has marked the lapse of ages, and then
so imperfect is our view into long-past geological ages that we see only
that the forms of life are now different from what they formerly were.

Although natural selection can act only through and for the good of
each being, yet characters and structures, which we are apt to consider
as of very trifling importance, may thus be acted on.

Natural selection will modify the structure of the young in relation to
the parent, and of the parent in relation to the young. In social
animals it will adapt the structure of each individual for the benefit
of the whole community, if the community profits by the selected change.
What natural selection cannot do is to modify the structure of one
species, without giving it any advantage, for the good of another
species; and though statements to this effect may be found in works of
natural history, I cannot find one case which will bear investigation.

A structure used only once in an animal's life, if of high importance to
it, might be modified to any extent by natural selection; for instance,
the great jaws possessed by certain insects, used exclusively for
opening the cocoon, or the hard tip to the beak of unhatched birds, used
for breaking the egg. It has been asserted that of the best short-beaked
tumbler pigeons a greater number perish in the egg than are able to get
out of it; so that fanciers assist in the act of hatching. Now, if
Nature had to make the beak of a full-grown pigeon very short for the
bird's own advantage, the process of modification would be very slow,
and there would be simultaneously the most rigorous selection of all the
young birds within the egg, for all with weak beaks would inevitably
perish; or more easily broken shells might be selected, the thickness of
the shell being known to vary like every other structure.