n growth of the required modification; nor would these efforts
be made with any far-sighted perception of what next and next and after,
but only of what next; while many of the happiest thoughts would come
like all other happy thoughts--thoughtlessly; by a chain of reasoning
too swift and subtle for conscious analysis by the individual, as will
be more fully insisted on hereafter. Some of these modifications would
be noticeable, but the majority would involve no more noticeable
difference than can be detected between the length of the shortest day,
and that of the shortest but one.

Thus a bird whose toes were not webbed, but who had under force of
circumstances little by little in the course of many generations learned
to swim, either from having lived near a lake, and having learnt the art
owing to its fishing habits, or from wading about in shallow pools by
the sea-side at low water, and finding itself sometimes a little out of
its depth and just managing to scramble over the intermediate yard or so
between it and safety--such a bird did not probably conceive the idea of
swimming on the water and set itself to learn to do so, and then
conceive the idea of webbed feet and set itself to get webbed feet. The
bird found itself in some small difficulty, out of which it either saw,
or at any rate found that it could extricate itself by striking out
vigorously with its feet and extending its toes as far as ever it could;
it thus began to learn the art of swimming and conceived the idea of
swimming synchronously, or nearly so; or perhaps wishing to get over a
yard or two of deep water, and trying to do so without being at the
trouble of rising to fly, it would splash and struggle its way over the
water, and thus practically swim, though without much perception of what
it had been doing. Finding that no harm had come to it, the bird would
do the same again, and again; it would thus presently lose fear, and
would be able to act more calmly; then it would begin to find out that
it could swim a little, and if its food lay much in the water so that it
would be of great advantage to it to be able to alight and rest without
being forced to return to land, it would begin to make a practice of
swimming. It would now discover that it could swim the more easily
according as its feet presented a more extended surface to the water; it
would therefore keep its toes extended whenever it swam, and as far as
in it lay, would make the most of