The Descent of Man

vol. ii. 1840, p. 87.) Classifications may, of course,
be based on any character whatever, as on
size, colour, or the element inhabited; but naturalists
have long felt a profound conviction that
there is a natural system. This system, it is now
generally admitted, must be, as far as possible,
genealogical in arrangement,—that is, the codescendants
of the same form must be kept
together in one group, apart from the codescendants
of any other form; but if the parent-forms
are related, so will be their descendants,
and the two groups together will form a
larger group. The amount of difference between
the several groups—that is the amount of
modification which each has undergone—is
expressed by such terms as genera, families,
orders, and classes. As we have no record of the
lines of descent, the pedigree can be discovered
only by observing the degrees of resemblance
between the beings which are to be classed. For
this object numerous points of resemblance are
of much more importance than the amount of