stands on a very different footing from its substance.

If species have really arisen by the operation of natural conditions, we
ought to be able to find those conditions now at work; we ought to be
able to discover in nature some power adequate to modify any given kind
of animal or plant in such a manner as to give rise to another kind,
which would be admitted by naturalists as a distinct species. Lamarck
imagined that he had discovered this 'vera causa' in the admitted facts
that some organs may be modified by exercise; and that modifications,
once produced, are capable of hereditary transmission. It does not
seem to have occurred to him to inquire whether there is any reason to
believe that there are any limits to the amount of modification
producible, or to ask how long an animal is likely to endeavour to
gratify an impossible desire. The bird, in our example, would surely
have renounced fish dinners long before it had produced the least effect
on leg or neck.

Since Lamarck's time, almost all competent naturalists have left
speculations on the origin of species to such dreamers as the author of
the 'Vestiges', by whose well-intentioned efforts the Lamarckian theory
received its final condemnation in the minds of all sound thinkers.
Notwithstanding this silence, however, the transmutation theory, as it
has been called, has been a "skeleton in the closet" to many an honest
zoologist and botanist who had a soul above the mere naming of dried
plants and skins. Surely, has such an one thought, nature is a mighty
and consistent whole, and the providential order established in the
world of life must, if we could only see it rightly, be consistent with
that dominant over the multiform shapes of brute matter. But what is
the history of astronomy, of all the branches of physics, of chemistry,
of medicine, but a narration of the steps by which the human mind has