Thus, as I am inclined to
believe, morphological differences, which we consider as important--such as
the arrangement of the leaves, the divisions of the flower or of the
ovarium, the position of the ovules, etc., first appeared in many cases as
fluctuating variations, which sooner or later became constant through the
nature of the organism and of the surrounding conditions, as well as
through the intercrossing of distinct individuals, but not through natural
selection; for as these morphological characters do not affect the welfare
of the species, any slight deviations in them could not have been governed
or accumulated through this latter agency. It is a strange result which we
thus arrive at, namely, that characters of slight vital importance to the
species, are the most important to the systematist; but, as we shall
hereafter see when we treat of the genetic principle of classification,
this is by no means so paradoxical as it may at first appear.
Although we have no good evidence of the existence in organic beings of an
innate tendency towards progressive development, yet this necessarily
follows, as I have attempted to show in the fourth chapter, through the
continued action of natural selection. For the best definition which has
ever been given of a high standard of organisation, is the degree to which
the parts have been specialised or differentiated; and natural selection
tends towards this end, inasmuch as the parts are thus enabled to perform
their functions more efficiently.
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