the efforts of
those physiologists who believe in the possibility of it have not
succeeded in showing us a single instance."

Passing over, then, our author's theory of the origination of life from
inorganic matter as utterly untenable, we come to the next point in his
system,--the most chimerical of all,--the gradual development of the
higher orders of being out of those next beneath them in the scale. It
is not pretended, that there is _any known instance_ of the
transmutation of species, or of the evolution, in the ordinary way, of
any being specifically different from its parents. The same animal,
indeed, may pass through different grades of development; but these
changes affect only the individual, not the race. The progeny of this
animal must begin at the same point where its parent did, and run
precisely the same cycle. The tadpole becomes a frog, but the young of
that frog are tadpoles; the worm becomes a winged insect, but the eggs
of that insect are hatched into nothing but worms. These changes in the
life of the individual, like the successive periods of the embryotic
state, of infancy, and manhood in the human being, are perfectly
consistent with persistence of type in the race, and do not indicate
even the possibility that a new species may be developed out of an old
one. On the contrary, the germ must be considered as _potentially_
equivalent to the whole future being, for it is invariably developed
into that being. If there be any one fact unquestionably established by
observation, it is that each species invariably produces its like. "All
the phenomena," says Mueller, "at present observed in the animal kingdom,
seem to prove that the species were originally created distinct, and
independent of each other. There is no remote possibility of one species
being produced from another."

The doctrine of our author, then, is confessedly a pure hypothesis, and,
as such, it might be summarily dismissed into the region of cloud-land
and dreams, where it had its origin. The burden of proof is upon him,
and as he has failed to produce a single instance in which his theory is
exemplified, he may be rightfully debarred the privilege of discussion.
But waiving this point, if we look into the grounds of his conjecture,
we find bold assumptions more than once substituted for the plain
statement of facts, which would destroy every shade of credibility in
his doctrine. True, there is an appearance, both in the animal and