n that
we have an idea of in such a case is a genealogical one. And the
supposition of a genealogical connection is surely not unnatural in such
cases,--is demonstrably the natural one as respects all those tertiary
species which experienced naturalists have pronounced to be identical
with existing ones, but which others now deem distinct. For to identify
the two is the same thing as to conclude the one to be the ancestors of
the other. No doubt there are differences between the tertiary and
the present individuals, differences equally noted by both classes of
naturalists, but differently estimated. By the one these are deemed
quite compatible, by the other incompatible, with community of origin.
But who can tell us what amount of difference is compatible with
community of origin? This is the very question at issue, and one to be
settled by observation alone. Who would have thought that the peach and
the nectarine came from one stock? But, this being proved, is it now
very improbable that both were derived from the almond, or from some
common amygdaline progenitor? Who would have thought that the cabbage,
cauliflower, broccoli, kale, and kohlrabi are derivatives of one
species, and rape or colza, turnip, and probably rutabaga, of another
species? And who that is convinced of this can long undoubtingly hold
the original distinctness of turnips from cabbages as an article of
faith? On scientific grounds may not a primordial cabbage or rape be
assumed as the ancestor of all the cabbage races, on much the same
ground that we assume a common ancestry for the diversified human races?
If all our breeds of cattle came from one stock, why not this stock from
the auroch, which has had all the time between the diluvial and the
historic periods in which to set off a variation perhaps no greater than
the difference between some sorts of cattle?

That considerable differences are often discernible between tertiary
individuals and their supposed descendants of the present day affords
no argument against Darwin's theory, as has been rashly thought, but is
decidedly in its favor. If the identification were so perfect that no
more differences were observable between the tertiary and the recent
shells than between various individuals of either, then Darwin's
opponents, who argue the immutability of species from the ibises and
cats preserved by the ancient Egyptians being just like those of the
present day, could triumphantly add a few hun