But since the general adoption of the theory of evolution, similarity of descent, that is of p/iylogeny, has come to form an essential part of this conception; in other words, in order that their homology may be established the parts compared must be proved to be homogenetic.
In other words, the Malpighian tubes of the terrestrial Arachnida are homoplastic with those of Hexapoda and Myriapoda, and not homogenetic with them.
His homologous structures are now spoken of as " homogenetic " structures, the idea of community of representation in an archetype giving place to community of derivation from a single representative structure present in a common ancestor.
In accordance with the prevalent antithetic view of the alternation of generations in these plants (see PLANTS, REPRODUCTION or), the forms distinguished as sporophyte and gametophyte are not homogenetic; consequently their leaves are not homologous, but are only functionally similar (homoplastic; see infra).