t, and then collect seed from the few survivors, with care
to prevent accidental crosses, and then again get seed from these
seedlings, with the same precautions, the experiment cannot be said to
have been even tried. Nor let it be supposed that differences in the
constitution of seedling kidney-beans never appear, for an account has
been published how much more hardy some seedlings are than others; and
of this fact I have myself observed striking instances.

On the whole, we may conclude that habit, or use and disuse, have,
in some cases, played a considerable part in the modification of the
constitution and structure; but that the effects have often been largely
combined with, and sometimes overmastered by, the natural selection of
innate variations.

CORRELATED VARIATION.

I mean by this expression that the whole organisation is so tied
together, during its growth and development, that when slight variations
in any one part occur and are accumulated through natural selection,
other parts become modified. This is a very important subject, most
imperfectly understood, and no doubt wholly different classes of facts
may be here easily confounded together. We shall presently see that
simple inheritance often gives the false appearance of correlation. One
of the most obvious real cases is, that variations of structure arising
in the young or larvae naturally tend to affect the structure of the
mature animal. The several parts which are homologous, and which, at
an early embryonic period, are identical in structure, and which are
necessarily exposed to similar conditions, seem eminently liable to vary
in a like manner: we see this in the right and left sides of the body
varying in the same manner; in the front and hind legs, and even in the
jaws and limbs, varying together, for the lower jaw is believed by some
anatomists to be homologous with the limbs. These tendencies, I do not
doubt, may be mastered more or less completely by natural selection:
thus a family of stags once existed with an antler only on one side; and
if this had been of any great use to the breed, it might probably have
been rendered permanent by natural selection.

Homologous parts, as has been remarked by some authors, tend to cohere;
this is often seen in monstrous plants: and nothing is more common than
the union of homologous parts in normal structures, as in the union of
the petals into a tube. Hard parts seem to affect the form of adjoining
so