s it
contains no reference to the bearings of palaeontology upon 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 Rutimeyer, 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."[5]

[Footnote 5: The paper "On the Form and Distribution of the Landtracts
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 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:--He