f adaptative characters, which _in
their own opinion_ are subservient merely to comfort or convenience, as
having been produced by such means. Clearly this is illogical; for it
belongs to the essence of Darwin's theory to suppose, that natural
selection can have no jurisdiction beyond the line where structures or
instincts already present a sufficient degree of adaptational value to
increase, in some measure, the expectation of life on the part of their
possessors. We cannot speak of adaptations as due to natural selection,
without thereby affirming that they present what I have elsewhere termed
a "selection value."

* * * * *

Lastly, as a mere matter of logical definition, it is well-nigh
self-evident that the theory of natural selection is a theory of the
origin, and cumulative development, of _adaptations_, whether these be
distinctive of species, or of genera, orders, families, classes, and
sub-kingdoms. It is only when the adaptations happen to be distinctive
of the first (or lowest) of these taxonomic divisions, that the theory
which accounts for _these_ adaptations accounts also for the forms which
present them,--i. e. becomes _also_ a theory of the origin of species.
This, however, is clearly but an accident of particular cases; and,
therefore, even in them the theory is _primarily_ a theory of
adaptations, while it is but secondarily a theory of the species which
present them. Or, otherwise stated, the theory is no more a theory of
the origin of species than it is of the origin of genera, families, and
the rest; while, on the other hand, it is _everywhere_ a theory of the
adaptive modifications whereby each of these taxonomic divisions has
been differentiated as such. Yet, sufficiently obvious as the accuracy
of this definition must appear to any one who dispassionately considers
it, several naturalists of high standing have denounced it in violent
terms. I shall therefore have to recur to the subject at somewhat
greater length hereafter. At present it is enough merely to mention the
matter, as furnishing another and a curious illustration of the not
infrequent weakness of logical perception on the part of minds well
gifted with the faculty of observation. It may be added, however, that
the definition in question is in no way hostile to the one which is
virtually given by Darwin in the title of his great work. _The Origin of
Species by means of Natural Selection_ is beyond doubt