Internalism and Laws of Form 323
idea under its old Ichthyic vestment, until it became arrayed in the glorious
garb of the Human form (p. 86).Owen drew from his archetype all the standard implications that set the
research program of formalism—the correlations that define the essence (and
continuing relevance) of this pole on the dichotomy: importance of constraint and
mistrust of adaptationism (accompanied by demotion to secondary status).
CONSTRAINT. This term includes two distinct meanings, both in vernacular
English usage (see Gould, 1989a, and Chapter 10, pp. 1025-1061) and in biological
jargon—the negative concept of restriction, and the positive sense of channeling.
Those who belittle the evolutionary importance of the subject do not deny the
phenomenon itself, but rather limit their concept to the negative meaning.
Owen properly depicted constraint as both limitation and channeling. In the
former meaning, for example, he notes that the first digit of the generalized
mammalian hand or foot develops only two phalanges, while the others grow three.
These numbers do not change, even when utility would dictate otherwise—as in
elephants where the first and fifth toes do not differ in length, and all digits are
enclosed in a large pad (1849, p. 37); or in humans, where the first toe becomes
massive and weight-bearing (but cannot gain an additional phalanx), and the little
toe almost vestigial (while still retaining its full complement of three phalanges).
On the positive theme of channels, Owen regards an archetype as a blueprint
of myriad possibilities (made all the more intelligible by limiting their range to
products of common elements in unvarying topological order). All realized
examples on earth therefore include only a small subset of possible forms. Owen
even felt free to speculate about the anatomy of life on other worlds, provided that
the vertebral archetype can lay claim to universal status: "Our thoughts are free to
soar as far as any legitimate analogy may seem to guide them rightly in the
boundless ocean of unknown truth. And if censure be merited for here indulging,
even for a moment, in pure speculation, it may, perhaps, be disarmed by the
reflection that the discovery of the vertebrate archetype could not fail to suggest to
the anatomist many possible modifications of it beyond those that we know to have
been realized in this little orb of ours" (1849, p. 83).
For example, no earthly vertebrate grows more than two pairs of limbs, but
the archetype bears diverging rays (the source of limbs by general homology), on
each vertebra, and additional pairs therefore become possible:
We have been accustomed to regard the vertebrate animals as being
characterized by the limitation of their limbs to two pairs, and it is true that
no more diverging appendages are developed for station, locomotion and
manipulation. But the rudiments of many more pairs are present in many
species. Although they may never be developed as such in this planet, it is
quite conceivable that certain of them may be so developed,