The Evolution of the Vertebral Column: a Contribution to the Study of Vertebrate Phylogeny

Abstract

IT is now nearly forty years since Dr. Gadow and Miss Abbott published their well-known paper on “The Evolution of the Vertebral Columns” in the Philosophical Transactions of 1895-96, the first attempt at tracing a fundamental plan of structure throughout the Vertebrata. In it they maintained that from fish to man the vertebra is built of four primary paired elements surrounding the notochordal axis. Appearing first as cartilages both in ontogeny and in phylogeny, but later often ossified, these elements give rise to the various types of vertebra characteristic of the different groups, some becoming more important, others dwindling or disappearing. A convenient nomenclature was introduced, since very generally adopted: the four elements or arcualia include the basalia and interbasalia; the former are the basidorsal above (giving rise to neural arch), and the basiventral below (giving rise to haemal arch, rib and chevron); the inter basalia, which alternate with them, are the interdorsal above and interventral below. But, simple and illuminating as this scheme appears to be, it has not met with general acceptance, perhaps because it was to some extent founded on an erroneous interpretation of the development of the arcualia, of their derivation from the sclero-tomes out of which they are formed, and of their relation to the muscle segments with which the vertebrae come to alternate hi the adult. Much work has been done since then by palaeontologists and embryologists on the vertebral column, and there can be little doubt that, on the whole, it has strengthened the main position taken up by Dr. Gadow and Miss Abbott.

The Evolution of the Vertebral Column: a Contribution to the Study of Vertebrate Phylogeny.

By Dr. H. F. Gadow. Edited by J. F. Gaskell and H. L. H. H. Green. Pp.xiv + 356. (Cambridge: At the University Press, 1933.) 25s. net