ng its typical character! How are we to explain this? By
design manifested in special creation, or by descent with adaptive
modification? If it is said by design manifested in special creation, we
must suppose that the Deity formed an archetypal plan of certain
structures, and that He determined to adhere to this plan through all
the modifications which those structures exhibit. Now the difficulties
in the way of this supposition are prodigious, if not quite
insurmountable. In the first place, why is it that some structures are
selected as typical and not others? Why should the vertebral skeleton,
for instance, be tortured into every conceivable variety of modification
in order to make it serviceable for as 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? Will any one have the
hardihood to assert that in the case of the skeleton the Deity has
endeavoured to show His _ingenuity_ by the manifold functions to which
He has made the same structure subservient; while in the case of the
eye He has endeavoured to show his _resources_ by the manifold
structures which He has to subserve the same function? If so, it appears
to me a most unfortunate circumstance, that throughout both the
vegetable and animal kingdoms, all cases which can be pointed to as
showing ingenious adaptation of the same typical structure to the
performance of widely different functions, are cases which come within
the limits of the same natural group of plants and animals, and
therefore admit of being equally well explained by descent from a common
ancestry; while all cases of widely different structures performing the
same function are to be found in different groups of plants or animals,
and are therefore suggestive of independent variations arising in the
different lines of hereditary descent.

To take a specific illustration. The octopus or devil-fish belongs to a
widely different class of animals from a true fish, and yet its eye, in
general appearance, looks wonderfully like the eye of a true fish. Now,
Mr. Mivart pointed to this fact as a great difficulty in the way of the
theory of evolution by natural selection, because it must clearly be a
most improbable thing that so complicated a structure as the eye of a
fish should happen to be arrived at through each of two totally
different lines of