324 THE STRUCTURE OF EVOLUTIONARY THEORY
if the Vertebrate type should be that on which any of the inhabitants of
other planets of our system are organized. The conceivable modifications of
the vertebrate archetype are very far from being exhausted by any of the
forms that now inhabit the earth, or that are known to have existed here at
any period (1849, p. 83).ADAPTATION. Neither Owen nor any prominent formalist has ever denied
interest or importance to the manifestly obvious phenomenon of adaptation.
Formalists do not question the high frequency of adaptation, but only dispute the
relative ranking of utility as a causal argument. In the view of functionalists, from
creationists like Paley to evolutionists like Darwin, adaptation embodies the source
and cause of morphological order and change. For formalists, adaptation becomes
a secondary phenomenon, imposed upon primary and underlying laws of form to
fit a particular organism to an immediate environment. Adaptation remains vital;
for without such specific utility, the organic world would feature only abstract
models, but no real creatures in their stunning variety. Yet, adaptation still works
in a sequential and secondary fashion to place an overlay upon the archetype. Thus,
while Owen continually speaks of morphology and teleology, we must not view
him as a mushy pluralist, advocating equality of the two poles. His mode of
blending ranks the poles, with adaptation distinctly subservient to archetype in the
classical mixture of formalist thought.
Owen argued that two great laws build actual organisms from the archetypal
form. The first, called irrelative (or vegetative) repetition, iterates the archetypal
element into a series of similar parts. The second, adaptive or teleological force
then modifies the various segments in different ways demanded by their mode of
life.
Since the adaptive force imposes secondary modifications upon an initial
string of identical archetypal elements, we must penetrate behind this imposed veil
of specific utility and specialization if we wish to apprehend the archetype itself.
Various formalist principles lead us to fruitful strategies for peering behind the
adaptive mask: embryos as more archetypal than adults; early and simple forms as
closer than later and more complex creatures, following "the law that the
Archetype is progressively departed from as the organization is more and more
modified in adaptation to higher and more varied powers and actions" (p. 49).
This secondary and derivative character of adaptation leads to a linguistic
convention of structuralism, where functional fit becomes an impediment to
research upon laws of form. The movement of the tetrapod forelimb away from its
initial position within the last vertebra of the skull, for example, shows "the
antagonizing power of adaptive modification by the removal of that arch from its
proper segment" (p. 59). We focus on embryos and simple anatomies in our study
of the archetype because, in these forms, "the archetype is least obscured by
purposive adaptations" (p. 55).
The derivative nature of adaptation also debars this important phenomenon
from any role as a primary organizing principle of morphology. Owen