Internalism and Laws of Form 321
and its appendages, down the last phalanx of the little finger, are truly and
essentially bones of the skull" (p. 112).
But all tetrapods separate the shoulder girdle and front appendages from the
skull by a sequence of intercalated vertebrae. Owen argues, as did Geoffroy, that
the haemal portion of the fourth skull vertebra has migrated back in the terrestrial
classes. And why should this degree of transposition be
4 - 15. Owen justifies his bold claim that the entire limb might be derived from a diverging ray by
showing a series of maximally reduced limbs in living vertebrates from Proteus with several
elements but only two digits, to Amphiuma, also with two digits but fewer elements, and finally
to Lepidosiren with a single element maximally similar to the hypothetical diverging ray.
(Author's collection.