to be in
some necessary manner correlated. Some other correlations are apparently
due to the manner in which natural selection can alone act. For
instance, Alph. De Candolle has remarked that winged seeds are never
found in fruits which do not open; I should explain this rule by
the impossibility of seeds gradually becoming winged through natural
selection, unless the capsules were open; for in this case alone could
the seeds, which were a little better adapted to be wafted by the wind,
gain an advantage over others less well fitted for wide dispersal.

COMPENSATION AND ECONOMY OF GROWTH.

The elder Geoffroy and Goethe propounded, at about the same time, their
law of compensation or balancement of growth; or, as Goethe expressed
it, "in order to spend on one side, nature is forced to economise on
the other side." I think this holds true to a certain extent with our
domestic productions: if nourishment flows to one part or organ in
excess, it rarely flows, at least in excess, to another part; thus it is
difficult to get a cow to give much milk and to fatten readily. The same
varieties of the cabbage do not yield abundant and nutritious foliage
and a copious supply of oil-bearing seeds. When the seeds in our fruits
become atrophied, the fruit itself gains largely in size and quality.
In our poultry, a large tuft of feathers on the head is generally
accompanied by a diminished comb, and a large beard by diminished
wattles. With species in a state of nature it can hardly be maintained
that the law is of universal application; but many good observers, more
especially botanists, believe in its truth. I will not, however, here
give any instances, for I see hardly any way of distinguishing between
the effects, on the one hand, of a part being largely developed through
natural selection and another and adjoining part being reduced by the
same process or by disuse, and, on the other hand, the actual withdrawal
of nutriment from one part owing to the excess of growth in another and
adjoining part.

I suspect, also, that some of the cases of compensation which have been
advanced, and likewise some other facts, may be merged under a more
general principle, namely, that natural selection is continually
trying to economise in every part of the organisation. If under changed
conditions of life a structure, before useful, becomes less useful, its
diminution will be favoured, for it will profit the individual not to
have its nutrimen