if not the first, to bring the fruits of paleontology to the support of evolution. But Leidy, as far as a hasty search through his writings could reveal, nowhere expressly advocated the doctrine of recapitulation. Indeed, he gave but little attention to the philosophical bearings of paleontology, generally partly because of temperament and partly because in those pioneer days material to serve as a basis for generalization was still scanty.
Gaudry, one of the first European paleontologists to champion the cause of evolution,[1] likewise did not specially advocate the doctrine of recapitulation. An examination of his "Philosophic Paleontologique" fails to reveal any definite belief in this doctrine.
Huxley, as far as I can gather from his papers and essays, believed in this doctrine, though with certain implied reservations as to its general applicability. In his presidential address to the Geological Society of London on "Paleontology and the Doctrine of Evolution" delivered in 1870, we find some interesting comment on the significance of the splints of the living horse, which he regards as indicative of the presence of three complete digits in the horse ancestor. But Huxley was never an out-and-out advocate of the biogenetic law.
Cope and Marsh, as we all know, were staunch upholders of evolution; and Cope, at least, was also a staunch upholder of the doctrine of recapitulation. In his "Primary Factors of Organic Evolution," his last contribution to philosophical paleontology, he devotes considerable space to proving this doctrine. He says:[2]
The representatives of each class passed through the stages which are permanent in the classes below them in the series.
And he backs up this proposition with evidence derived from the ontogeny and phylogeny of batrachia, the antlers of deer and the blood trunks of vertebrates generally. For all that, Cope recognized the justice of certain criticisms which had been brought against the doctrine of recapitulation and urged caution in its application.
An example or two of recapitulation may now be cited from the field of the lower vertebrates.
The mode of development of the teeth in Neoceratodus has sometimes been adduced as an illustration of recapitulation. It is well known that the Devonic dipnoans (e. g., Dipterus) had teeth composed of rows of denticles, those in each row being more or lesls fused at their bases. During the history of the dipnoans since the Devonic period, the separate denticles have merged more and more until in Ceratodus and the living Neoceratodus, the rows of denticles are, in
