ed 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 {148} 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 Proteolepas: for
the car