TRANSMISSION OF MODIFICATIONS 171

get secure data, It is uncertain how much of the inequality
in tactile sensitiveness is due to individual exercise and
experience, though it is certain that tactility^in little-used
parts can be greatly increased by use. Nor is it certain how
much of the apparent unlikeness in tactility is due to
unequal distribution of peripheral nerve-endings and how
much to specialised application of the power of central
perception. As Prof. Lloyd Morgan says : " We do not
yet know the limits within which education and practice
may refine the application of central powers of discrimination
within little-used areas. The facts which Mr Spencer
adduces may be in large degree due to individual experience ;
discrimination being continually exercised in the tongue and
finger-tips, but seldom on the back or breast. We need a
broader basis of assured fact." Nor, it may be added, is
the action of selection to be excluded.

(3) Spencer's third set of negative evidences was based on
rudimentary organs which, like the hind limbs of the whale,
have nearly disappeared. Dwindling by natural selection is
here out of the question; and dwindling by panmixia, i.e.
the diminution of a structure when natural selection ceases to
affect its degree of development, " would be incredible, even
were the assumptions of the theory valid." But as a
sequence of disuse the change is clearly explained. Prof.
Lloyd Morgan replies: "Is there any evidence that a
structure really dwindles through disuse in the course of
individual life ? Let us be sure of this before we accept the
argument that vestigial organs afford evidence that this
supposed dwindling is inherited. The assertion may be
hazarded that, in the individual life, what the evidence shows
is that, without due use, an organ does not reach its full
functional or structural development. If this be so, the
question follows: How is the mere absence of full develop-
ment in the individual converted through heredity into a
positive dwindling of the organ in question ?" Moreover,
the convinced Neo-Darwinian is not in the least prepared to
abandon the theory of dwindling in the course of panmixia,
especially in the light which Weisraann's conception of
Germinal Selection has thrown on this process.

The inductive evidence in support of the con-