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that all species are bound together by the ties of genetic relationship.
If all species were separately created, it is almost incredible that we
should everywhere observe this progressive shading off of characters
common to larger groups.”—(ftp. 23-4.)
But this argument had been anticipated by Mr. Chambers.
After speaking of the obvious gradation amongst the
families of both the vegetable and animal kingdoms, he
confines himself to the animal kingdom, and says :—
“ It is to be observed that the gradation is much less simple and
direct than is generally supposed. It certainly does not proceed on
all parts of its course at least, upon one line. . '. . It even
appears that there are intimations of more than two lines at various
parts of the animal scale. (Fourth edition. ftp. 193.) These facts
clearly show how all the various organic forms of our world are
bound up in one—how a fundamental unity pervades and embraces
them all After what we have seen, the idea of a separate
exertion for each must appear totally inadmissible.”—(A 201-2.)
In “The Argument from Morphology or Structure,” Mr.
Romanes points to the evidence which there is of adaptive
modification of structure in cases where the need for such
adaptation is apparent,* and instances the various modi
fications of the arm in mammals, f
“ Why should the vertebral skeleton, for instance, be tortured into
every conceivable variety of modification in order to make it service
able for âs great a variety of functions ; while another structure, such
as the eye, is made in different sub-kingdoms on fundamentally
different plans, notwithstanding that it has throughout to perform the
same function ? ”—(ft. 31.)
Mr. Chambers calls attention to the “unity of structure,”
which “ becomes the more remarkable when we observe that
the organs, while preserving a resemblance, are often put
to different uses.” And he goes on to observe that
analogous purposes are served in different animals by
organs essentially different. +
* p. 26. t pp. 29-30. I pp. 196-7.
