strictly natural, as it would connect
together all languages, extinct and modern, by the closest affinities,
and would give the filiation and origin of each tongue.

In confirmation of this view, let us glance at the classification
of varieties, which are believed or known to have descended from one
species. These are grouped under species, with sub-varieties under
varieties; and with our domestic productions, several other grades of
difference are requisite, as we have seen with pigeons. The origin
of the existence of groups subordinate to groups, is the same with
varieties as with species, namely, closeness of descent with various
degrees of modification. Nearly the same rules are followed in
classifying varieties, as with species. Authors have insisted on the
necessity of classing varieties on a natural instead of an artificial
system; we are cautioned, for instance, not to class two varieties of
the pine-apple together, merely because their fruit, though the most
important part, happens to be nearly identical; no one puts the swedish
and common turnips together, though the esculent and thickened stems
are so similar. Whatever part is found to be most constant, is used in
classing varieties: thus the great agriculturist Marshall says the horns
are very useful for this purpose with cattle, because they are less
variable than the shape or colour of the body, etc.; whereas with sheep
the horns are much less serviceable, because less constant. In classing
varieties, I apprehend if we had a real pedigree, a genealogical
classification would be universally preferred; and it has been attempted
by some authors. For we might feel sure, whether there had been more
or less modification, the principle of inheritance would keep the forms
together which were allied in the greatest number of points. In tumbler
pigeons, though some sub-varieties differ from the others in the
important character of having a longer beak, yet all are kept together
from having the common habit of tumbling; but the short-faced breed has
nearly or quite lost this habit; nevertheless, without any reasoning
or thinking on the subject, these tumblers are kept in the same group,
because allied in blood and alike in some other respects. If it could be
proved that the Hottentot had descended from the Negro, I think he would
be classed under the Negro group, however much he might differ in colour
and other important characters from negroes.

With species in a