Ontogeny, Phylogeny, Paleontology, and the Biogenetic Law

Abstract

Nelson, G. (Department of Ichthyology, The American Museum of Natural History, New York, New York 10024) 1978. Ontogeny, Phylogeny, Paleontology, and the Biogenetic Law. Syst. Zool. 27:324–345.—The biogenetic law is restated in a falsifiable form: given an onto-genetic character transformation, from a character observed to be more general to a character observed to be less general, the more general character is primitive and the less general advanced. The law, as restated, may be generally valid. In any case, the ontogenetic argument is a valid direct technique of character phylogeny; the anatomical argument (“outgroup comparison”) is an indirect technique; the paleontological argument is of uncertain status. Falsification of all three types of arguments is explored in an analysis of L. Agassiz's concept of “threefold parallelism.” Neoteny is a falsifier not of the biogenetic law, but of character phylogeny-of all three arguments. Phylogenetic reconstruction in its entirety appears to be an extrapolation of the orderliness of development.