r those producing seed less fitted for dispersal; and
this process could not possibly go on in fruit which did not open.

The elder Geoffroy and Goethe propounded, at about the same period,
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 this 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, any
diminution, however slight, in its development, will be seized on by
natural selection, for it will profit the individual not to have its
nutriment wasted in building up an useless structure. I can thus
only understand a fact with which I was much struck when examining
cirripedes, and of which many other instances could be given: namely,
that when a cirripede is parasitic within another and is thus protected,
it loses more or less completely its own shell or carapace. This is the
case with the male Ibla, and in a truly extraordinary manner with the
Proteolep