The universal belief in the independent creation of living organisms was
revised by Linnaeus and was put upon a new foundation. Before him the
genera were supposed to be created, the species and minor forms having
arisen from them through the agency of external conditions. In his first
book Linnaeus adhered to this belief, but later changed his mind and
maintained the principle of the separate creation of species. The weight
of his authority soon brought this conception to universal acceptance,
and up to the present time the prevailing conception of a species has
been chiefly based on the definition given by Linnaeus. His species
comprised subspecies and varieties, which were in their turn, supposed
to have evolved from species by the common method.

Darwin tried to show that the links which bind species to genera are of
the same nature as those which determine the relationship of [3]
subspecies and varieties. If an origin by natural laws is conceded for
the latter, it must on this ground be granted for the first also. In
this discussion he simply returned to the pre-Linnean attitude. But his
material was such as to allow him to go one step further, and this step
was an important and decisive one. He showed that the relation between
the various genera of a family does not exhibit any features of a nature
other than that between the species of a genus. What has been conceded
for the one must needs be accepted for the other. The same holds good
for the large groups.

The conviction of the common origin of closely allied forms necessarily
leads to the conception of a similar descent even in remote
relationships.

The origin of subspecies and varieties as found in nature was not