Seeds of Hierarchy 205
organismal selection for such late stages in the reduction of degenerate organs. "To
use Herbert Spencer's striking illustration, how could the balance between life and
death, in the case of a colossus like the Greenland whale, be turned one way or
another by the difference of a few inches in the length of the hind-leg, as compared
with his fellows, in whom the reduction of the hind-limb may not have gone quite
so far?... Further reduction to their modern state of great degeneration and
absolute concealment within the flesh of the animal cannot be referred even to
negative selection" (Weismann, 1903, vol. 2, p. 114).
This example, and the general phenomenon of degeneration, deeply troubled
Weismann because common sense seemed to demand that his Lamarckian bugbear
and bogeyman—so recently and, as he thought, finally and effectively buried—be
disinterred to explain reduction as inheritance of features shriveled by disuse.
Spencer himself raised this example in order to defend a Lamarckian explanation
prima facie:
Thus, the only reasonable interpretation is the inheritance of acquired
characters. If the effects of use and disuse, which are known causes of
change in each individual, influence succeeding individuals... then this
reduction of the whale's hind limbs to minute rudiments is accounted for.
The cause has been unceasingly operative on all individuals of the species
ever since the transformation began. In one case see all. If this cause has
thus operated on the limbs of the whale, it has thus operated in all creatures
on all parts having active functions (Spencer, 1893b, p. 26).Weismann first attempted to resolve the difficulties posed by degeneration
with his hypothesis of panmixia (not the later Fisherian definition now familiar to
evolutionists). By panmixia, Weismann referred to the effect of recombination in
sexual reproduction (amphimixis in his vocabulary) upon organs no longer subject
to selection. When selection operates, Weismann argued, organs will be actively
maintained, with constant vigilance and no relaxation, at the peak of their potential
size and complexity by elimination of individuals bearing substandard parts. But as
soon as selection ceases to act, formerly "substandard" attributes will no longer be
eliminated; they now mix freely with "good" parts, and the organ slides, by
continuous dilution, down an inclined plane towards total elimination. In a
poignant example (since poor eyesight plagued his own career), Weismann wrote
(1903, pp. 114-115). "If this conservative action of natural selection secures the
maintenance of the parts and organs of a species at their maximum of perfection, it
follows that these will fall below this maximum as soon as the selection ceases to
operate ... Those with inferior organs of vision will, ceteris paribus, produce as
good offspring as those with better eyes, and the consequence of this must be that
there will be a general deterioration of eyes, because the bad ones can be
transmitted as well as the good, and thus the selection of good eyes is made
impossible."
By his own admission and explicit defense (see p. 201), Weismann's
argument