isted, 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 stronger case, for these have been exposed
to great changes of climate and have migrated over great distances;
whereas, in Egypt, during the last several thousand years, the
conditions of life, as far as we know, have remained absolutely uniform.
The fact of little or no modification having been effected since the
glacial period, would have been of some avail against those who believe
in an innate and necessary law of development, but is powerless against
the doctrine of natural selection or the survival of the fittest, which
implies that when variations or individual differences of a beneficial
nature happen to arise, these will be preserved; but this will be
effected only under certain favourable circumstances.

The celebrated palaeontologist, Bronn, at the close of his German
translation of this work, asks how, on the principle of natural
selection,