foreigners. Nor can organic beings, even if they were at any one time
perfectly adapted to their conditions of life, have remained so, when their
conditions changed, unless they themselves likewise changed; and no one
will dispute that the physical conditions of each country, as well as the
number and kinds of its inhabitants, have undergone many mutations.

A critic has lately insisted, with some parade of mathematical accuracy,
that longevity is a great advantage to all species, so that he who believes
in natural selection "must arrange his genealogical tree" in such a manner
that all the descendants have longer lives than their progenitors! Cannot
our critics conceive that a biennial plant or one of the lower animals
might range into a cold climate and perish there every winter; and yet,
owing to advantages gained through natural selection, survive from year to
year by means of its seeds or ova? Mr. E. Ray Lankester has recently
discussed this subject, and he concludes, as far as its extreme complexity
allows him to form a judgment, that longevity is generally related to the
standard of each species in the scale of organisation, as well as to the
amount of expenditure in reproduction and in general activity. And these
conditions have, it is probable, been largely determined through natural
selection.

It has been argued that, as none of the animals and plants of Egypt, of
which we know anything, have changed during the last three or four thousand
years, so probably have none in any part of the world. But, as Mr. G.H.
Lewes has remarked, this line of argument proves too much, for the ancient
domestic races figured on the Egyptian monuments, or embalmed, are closely
similar or even identical with those now living; yet all naturalists admit
that such races have been produced through the modification of their
original types. The many animals which have remained unchanged since the
commencement of the glacial period, would have been an incomparably