would
result in 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. Some of these
modifications would be noticeable, but the majority would involve no more
noticeable difference that 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 wherever it swam, and as far as in it lay, would
make the most of whatever skin was already at