Or in what other
way could it have arisen, since scales are also passively useful parts?
It is true that if we are only to call adaptation what has been acquired
by the species we happen to be considering, there would remain a great
deal that could not be referred to selection; but we are postulating an
evolution which has stretched back through aeons, and in the course of
which innumerable adaptations took place, which had not merely ephemeral
persistence in a genus, a family or a class, but which was continued
into whole Phyla of animals, with continual fresh adaptations to
the special conditions of each species, family, or class, yet with
persistence of the fundamental elements. Thus the feather, once
acquired, persisted in all birds, and the vertebral column, once gained
by adaptation in the lowest forms, has persisted in all the Vertebrates,
from Amphioxus upwards, although with constant readaptation to the
conditions of each particular group. Thus everything we can see in
animals is adaptation, whether of to-day, or of yesterday, or of ages
long gone by; every kind of cell, whether glandular, muscular, nervous,
epidermic, or skeletal, is adapted to absolutely definite and specific
functions, and every organ which is composed of these different kinds
of cells contains them in the proper proportions, and in the particular
arrangement which best serves the function of the organ; it is thus
adapted to its function.

All parts of the organism are tuned to one another, that is, THEY ARE
ADAPTED TO ONE ANOTHER, and in the same way THE ORGANISM AS A WHOLE IS
ADAPTED TO THE CONDITIONS OF ITS LIFE, AND IT IS SO AT EVERY STAGE OF
ITS EVOLUTION.

But all adaptations CAN be referred to selection; the only point that
remains doubtful is whether they all MUST be referred to it.

However that may be, whether the LAMARCKIAN PRINCIPLE is a factor that
has cooperated with selection in evolution, or whether it is altogether
fallacious, the fact remains, that selection is the cause of a great
part of the phyletic evolution of organisms on our earth. Those
who agree with me in rejecting the LAMARCKIAN PRINCIPLE will regard
selection as the only GUIDING factor in evolution, which creates what
is new out of the transmissible variations, by ordering and arranging
these, selecting them in relation to their number and size, as the
architect does his building-stones so that a particular style must
result. ("Variation under Domestication"