Evolutionary significance of morphogenetic mechanisms

Different approaches to interpretation of ontogenesis are compared. The importance is emphasized of Ber’s theory of developmental patterns and the law of embryonic similarity. The significance of evolutionary rationalization of morphogenetic mechanisms is discussed (V.N. Beklemishev, V.A. Dogel’ and O.M. Ivanova-Kazas). There are two main pathways of rationalization of morphogenetic mechanisms: by means of epithelial morphogenesis and at the expense of oligocellular primordia (V.N. Beklemishev). When the developmental plans of the taxonomical types are determined, it is important to take into consideration the diversity of morphogenetic mechanisms within a given group in order to reveal morphological spectrums of morphogenetic mechanisms. A comparison of morphogenetic spectrums in different groups provides a wide evolutionary picture and helps us to reconstruct the phylogeny. Influence of morphogenetic mechanisms on the structure of definitive forms is demonstrated: construction technologies determine types of organs, anatomical and histological systems, and even symmetrical features of organisms and their complex parts.