Page:Popular Science Monthly Volume 77.djvu/305

Rh And again:

Hurst is even more emphatic. He says:

It would seem as though two statements could scarcely be more flatly contradictory than those of Bather and Hurst, just quoted. Nevertheless, I venture to make the assertion that both parties to the recapitulation controversy are right, for the simple reason that they are not talking about the same thing. Grabau has called attention to this, by implication, in one of his papers on gastropods. He states that the recapitulation theory has been placed in an evil light by the habit of embryologists of comparing embryonic stages with the adults of existing representatives of primitive types, and that they have commonly neglected to compare the epembryonic stages with the adults of geologically older species. In other words, paleontologists have usually dealt, in their comparisons, with epembryonic stages, and embryologists with embryonic stages.

There arises here a question of definition: does the biogenetic law mean that the ontogeny is a recapitulation of the ph}dogeny, or does it mean that the embryogeny is a recapitulation of the phylogeny? If we take the general consensus of opinion, w T e shall find for the former definition; and if we take the words of Haeckel, whose statement of the law is the one usually quoted, we shall again find for the former definition.

It is certainly true, at any rate, that the epembryonic stages may and do show recapitulation, even when the embryonic stages do not, or when the embryogeny is so obscured by secondary adaptations as to be untrustworthy. There are many reasons why adaptations should occur in infra-uterine or larval life to obscure the ancestral record. These have often been stated and discussed, and I shall pass them with this mere mention. That the record of remote ancestors, contained in the embryogeny, may be lost or obscured, while the record of nearer ancestors, contained in the epembryogeny, is still clear and convincing, is my contention; and I hold that this contention is substantiated by the studies of a host of paleobiologists.

While contrasting the views of biologists and paleobiologists, I do not wish to create the impression that all of the former have turned against the theory of recapitulation. Several recent studies of the development of extant forms seem to afford very satisfactory evidence that the theory is not wholly rejected in the house of its fathers. Of