the theory
of the distribution of life; nor takes note of the remarkable manner
in which the facts of distribution, in present and past times, accord
with the doctrine of evolution, especially in regard to land animals.

That connection between palaeontology and geology and the present
distribution of terrestrial animals, which so strikingly impressed
Mr. Darwin, thirty years ago, as to lead him to speak of a "law of
succession of types," and of the wonderful relationship on the same
continent between the dead and the living, has recently received much
elucidation from the researches of Gaudry, of Ruetimeyer, of Leidy,
and of Alphonse Milne-Edwards, taken in connection with the
earlier labours of our lamented colleague Falconer; and it has been
instructively discussed in the thoughtful and ingenious work of Mr.
Andrew Murray "On the Geographical Distribution of Mammals."[1]

[Footnote 1: The paper "On the Form and Distribution of the
Land-tracts during the Secondary and Tertiary Periods respectively;
and on the Effect upon Animal Life which great Changes in Geographical
Configuration have probably produced," by Mr. Searles V. Wood, jun.,
which was published in the _Philosophical Magazine_, in 1862, was
unknown to me when this Address was written. It is well worthy of the
most careful study.]

I propose to lay before you, as briefly as I can, the ideas to which a
long consideration of the subject has given rise in my own mind.

If the doctrine of evolution is sound, one of its immediate
consequences clearly is, that the present distribution of life
upon the globe is the product of two factors, the one being the
distribution which obtained in the immediately preceding epoch, and
the other the character and the extent of the changes which have taken
place in physical geography between the one epoch and the other; or,
to put the matter in another way, the Fauna and Flora of any given
area, in any given epoch, can consist only of such forms of life as
are directly descended from those which constituted the Fauna and
Flora of the same area in the immediately preceding epoch, unless the
physical geography (under which I include climatal conditions) of
the area has been so altered as to give rise to immigration of living
forms from some other area.

The evolutionist, therefore, is bound to grapple with the following
problem whenever it is clearly put before him:--Here are the Faunae of
the same area during successive epoc