ich is common to
many allied forms, is ranked by us as of high systematic importance,
and consequently is often assumed to be of high vital importance to the
species. 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.

A distinguished zoologist, Mr. St. George Mivart, has recently collected
all the objections which have ever been advanced by myself and others
against the theory of natural selection, as propounded by Mr. Wallace
and myself, and has illustrated them with admirable art and force. When
thus marshalled, they make a formidable array; and as it forms no
part of Mr. Mivart's plan to give the various facts and considerations
opposed to his conclusions, no slight effort of reason and memory is
left to the reader, who may wish to weigh the evidence on both sides.
When discussing special cases, Mr. Mivart passes over the effects of the
increased use and disuse of parts, which I have always maintained to be
highly important, and have treated in my "Variation under Domestication"
at