Obviously this aquatic
organisation has no reference to the future life of the animal, nor has it
any adaptation to its embryonic condition; it has solely reference to
ancestral adaptations, it repeats a phase in the development of its
progenitors."
An organ, serving for two purposes, may become rudimentary or utterly
aborted for one, even the more important purpose, and remain perfectly
efficient for the other. Thus, in plants, the office of the pistil is to
allow the pollen-tubes to reach the ovules within the ovarium. The pistil
consists of a stigma supported on the style; but in some Compositae, the
male florets, which of course cannot be fecundated, have a rudimentary
pistil, for it is not crowned with a stigma; but the style remains well
developed and is clothed in the usual manner with hairs, which serve to
brush the pollen out of the surrounding and conjoined anthers. Again, an
organ may become rudimentary for its proper purpose, and be used for a
distinct one: in certain fishes the swim-bladder seems to be rudimentary
for its proper function of giving buoyancy, but has become converted into a
nascent breathing organ or lung. Many similar instances could be given.
Useful organs, however little they may be developed, unless we have reason
to suppose that they were formerly more highly developed, ought not to be
considered as rudimentary. They may be in a nascent condition, and in
progress towards further development.
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