a smooth or downy, a yellow or purple fleshed fruit,
should succeed.

In looking at many small points of difference between species, which, as
far as our ignorance permits us to judge, seem to be quite unimportant,
we must not forget that climate, food, etc., probably produce some
slight and direct effect. It is, however, far more necessary to bear in
mind that there are many unknown laws of correlation of growth, which,
when one part of the organisation is modified through variation, and the
modifications are accumulated by natural selection for the good of the
being, will cause other modifications, often of the most unexpected
nature.

As we see that those variations which under domestication appear at any
particular period of life, tend to reappear in the offspring at the
same period;--for instance, in the seeds of the many varieties of our
culinary and agricultural plants; in the caterpillar and cocoon stages
of the varieties of the silkworm; in the eggs of poultry, and in the
colour of the down of their chickens; in the horns of our sheep and
cattle when nearly adult;--so in a state of nature, natural selection
will be enabled to act on and modify organic beings at any age, by
the accumulation of profitable variations at that age, and by their
inheritance at a corresponding age. If it profit a plant to have its
seeds more and more widely disseminated by the wind, I can see no
greater difficulty in this being effected through natural selection,
than in the cotton-planter increasing and improving by selection the
down in the pods on his cotton-trees. Natural selection may modify
and adapt the larva of an insect to a score of contingencies,
wholly different from those which concern the mature insect. These
modifications will no doubt affect, through the laws of correlation, the
structure of the adult; and probably in the case of those insects which
live only for a few hours, and which never feed, a large part of their
structure is merely the correlated result of successive changes in the
structure of their larvae. So, conversely, modifications in the adult
will probably often affect the structure of the larva; but in all cases
natural selection will ensure that modifications consequent on other
modifications at a different period of life, shall not be in the least
degree injurious: for if they became so, they would cause the extinction
of the species.

Natural selection will modify the structure of the young in re