218 THE STRUCTURE OF EVOLUTIONARY THEORY
highway for new variation, and any positive natural selection can automatically
engender, by germinal selection, a wave of increasing variation ahead of the
advancing mean.
- Spencer (1893a and b) had invested his major defense of Lamarck in the
phenomenon of co-adaptation. How could natural selection, working separately on
each trait, produce an intricate coordination of numerous parts, all changing in the
same direction? But Weismann now argued that any positive organismal selection
will strengthen the determinants of all traits involved, thereby triggering a
coordinated trend in germinal selection. Co-adaptation becomes less puzzling if all
positively selected traits achieve such a strong boost from germinal selection: "As
soon as utility itself is supposed to exercise a determinative influence on the
direction of variation, we get an insight into the entire process and into much else
besides that has hitherto been regarded as a stumbling block to the theory of
selection ... as, for example, the like directed variation of a large number of already
existing similar parts, seen in the origin of feathers from the scales of reptiles"
(1896, p. 39). - In his furthest extension—a remarkable claim given his previous faith in
the Allmacht of purely organismal selection—Weismann now argued that any
intricately precise adaptation probably requires a boost from germinal selection to
reach a pinnacle of exquisite design. Writing of mimicry in Lepidoptera, he
argued:
It would have been impossible for such a minute similarity in the design,
and particularly in the shades of the coloration, ever to have arisen, if the
process of adaptation rested entirely on personal selection ... In such cases
there can be no question of accident, but the variations presented to
personal selection must themselves have been produced by the principle of
the survival of the fit! And this is effected, as I am inclined to believe,
through such profound processes of selection in the interior of the germ
plasm as I have endeavored to sketch ... under the title of germinal selection
(1896, p. 32).This list, while granting broad scope and power to the newly formulated
domain of suborganismal struggle, also illustrates the strictly limited conceptual
role that Weismann envisaged for germinal selection when he first formulated the
concept in 1895 and 1896. The action of germinal selection must always be
synergistic with conventional organismal selection. In degeneration, the "type"
example if you will, germinal selection "finishes off" what natural selection began
but could not complete. In all other cases of evolutionary construction
(maintenance of variation, co-adaptation, and "extreme perfection"), germinal
selection works hand in hand with organismal selection, either to supply positive
variation, or to accelerate change by supplying an impetus in the same direction
from another level.
Over and over again, Weismann emphasizes the purely synergistic action of
germinal with organismal selection. Thus, for example, ordinary natural selection
can initiate the decline of an organ rendered useless by environmental change. In