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 been compelled,
often sorely against its will, to recognise the operation of secondary
causes in events where ignorance beheld an immediate intervention of a
higher power? And when we know that living things are formed of the same
elements as the inorganic world, that they act and react upon it, bound by