Page:Popular Science Monthly Volume 77.djvu/310

304 paper, records very interesting cases of recapitulation in the genus Parasmilia of the Cretaceous. Bernard concludes that the coral colony, like the graptolite colony and the bryozoan colony, behaves as an individual.

In the echinoderms the likeness of the stem ossicles and the development of the anal plate of Antedon, to Paleozoic and Mesozoic forms has become one of the stock illustrations of recapitulation. Jackson has found interesting examples of recapitulation in the development of the ambulacral and inter-ambulacral plates of echinoids. Miss Smith has shown that the young Pentremites is exactly similar in form to the adult Codaster. This is an extremely interesting case, for Bather has independently, and from quite different data, come to the conclusion that Pentremites is derived from Codaster.

The idea of recapitulation has been one of the most fertile in the whole realm of biology, and its usefulness to the paleobiologist has been almost incalculable. But while there can be no doubt that recapitulation is a fact, the paleontologist should observe all due care not to assume too much for it. That there are various sorts of adaptations, arising at all stages of life, and that these may greatly obscure the ancestral record, is a fact too well known to require more than mention. There is also always acceleration, sometimes affecting different characters very unequally; and there may be retardation. All of these factors complicate the record of ontogeny. Nevertheless, after all of these have been taken duly into consideration, the parallel between ontogeny and phylogeny remains a powerful aid to investigation for the paleontologist.



FTER the careful papers of Professors Loomis and Lull in which the doctrine of recapitulation was so fully set forth from the standpoint of vertebrate paleontology, I can perhaps do no better than devote part of the time allotted me to showing how certain leading vertebrate paleontologists have viewed this question. Then I will cite one or two illustrations of this principle drawn from among the lower vertebrates.

Passing over the period of pre-Darwinian paleontology—the paleontology of Cuvier, Owen and Louis Agassiz—we come to the time of Leidy, who, as Professor Osborn has recently shown, was one of the first, 