Kainogenesis als Ausdruck differenter phylogenetischer Energien

Abstract

IT has become more and more evident, during the past twenty years, that the course of ontogeny may vary in a quite remarkable degree, even within the limits of a genus, and that the individuals of a species may present not unimportant differences in their respective ontogenies. This contradiction of the old-established belief that the type of development was similar for every considerable group of animals, has led to the abandonment of many of the older principles of embryology, and has introduced no small amount of confusion into embryological speculations. The question which confronts the investigator is this: which among the several modes of development which occur in closely allied species is to be regarded as primitive, and which secondary? In other words, what developmental features are palingenetic and what cænogenetic?

Kainogenesis als Ausdruck differenter phylogenetischer Energien.

Von Dr. Ernst Mehnert, Privat-docent an der Universität Strassburg i. Elsass. Pp. 165, and plates. (Jena: Gustav Fischer, 1897.)