ve expected, if the real meaning of classification be that of
tracing lines of pedigree; but on the theory of special creation no
reason can be assigned why single characters are not such sure tokens of
a natural arrangement as are aggregates of characters, however trivial
the latter may be. For it is obvious that unity of ideal might have been
even better displayed by everywhere maintaining the pattern of some one
important structure, than by doing so in the case of several unimportant
structures. Take an analogous instance from human contrivances. Unity of
ideal in the case of gun-making would be shown by the same principles of
mechanism running through all the different sizes and shapes of
gun-locks, rather than by the ornamental patterns engraved upon the
outside. Yet it must be supposed that in the mechanisms assumed to have
been constructed by special creation, it was the trivial details rather
than the fundamental principles of these mechanisms which were chosen by
the Divinity to display his ideals.

And this leads us to the next consideration--namely, that when in two
different lines of descent animals happen to adopt similar habits of
life, the modifications which they undergo in order to fit them for
these habits often induces striking resemblances of structure between
the two animals, as in the case of whales and fish. But in all such
instances it is invariably found that the resemblance is only
superficial and apparent: not anatomical or real. In other words, the
resemblance does not extend further than it is necessary that it
should, if both sets of organs are to be adapted to perform the same
functions. Now this, again, is just what one would expect to find as the
universal rule on the theory of descent, with modification of ancestral
characters. But, on the opposite theory of special creation, I know not
how it is to be explained that among so many instances of close
superficial resemblance between creatures belonging to different
branches of the tree of life, there are no instances of any real or
anatomical resemblance. So far as their structures are adapted to
perform a common function, there is in all such cases what may be termed
a deceptive appearance of some unity of ideal; but, when carefully
examined, it is always found that two apparently identical structures
occurring on different branches of the classificatory tree are in fact
fundamentally different in respect of their structural plan.

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