nature from the beginning of their existence. To determine which of
these two opinions is the best entitled to assent, or at least to
set before my readers a clear and distinct notion of the evidence
that can be brought to bear upon the question, will be my principal
object in the following work."

Now, as they are here stated, the two opinions are not necessarily
contradictory; differences in external condition may effect remarkable
changes in tribes of human beings, and yet the collective body may be
made up of different races: and to set before the reader a clear and
distinct notion, is to prove nothing, although indeed, as we shall see
in the sequel, the author has a very strong conviction, and believes
that he succeeds in proving, as far as a matter incapable of
mathematical demonstration can be proved, the negative of the latter
proposition. What the author seems to intend, or rather what the whole
tenor of his book imports, though his expressions at times go much
further, is, not that community of origin is proved inductively by the
researches which have been made into the existing and past state of man,
but that the natural history of man presents nothing inconsistent with
such a view.

The researches of Cuvier and others have negatived the theory of
Lamarcke as to the transmutation of species. The "_nisus formativus_" is
admitted, but admitted with limits, "_quos ultra citraque nequit
consistere rectum_".

The extreme rarity of hybrids, their inability of continuous
procreation, the absence of any well-authenticated cases of a permanent
species formed by the union of two distinct ones, the return to the
original type when the disturbing causes are removed, with various other
arguments tending the same way, have been considered, by the most
competent and impartial judges, as conclusive evidence of the real and
permanent existence in nature of distinct species. These arguments are
stated in detail in the second volume of Lyell's _Principles of
Geology_, to which we refer those of our readers who wish for further
information.

Having briefly stated these and similar arguments, Dr Prichard expresses
his conclusion as follows:--

"It seems to be the well-established result of enquiries into the
various tribes of organized beings, that the perpetuation of
hybrids, whether of plants or animals, so as to produce new and
intermediate tribes, is impossible.

"Now