the similarity of organ structures that are located symmetrically on the sides of a body (for example, right and left hands). Sometimes homotypy is masked by secondary changes, for example in the lungs, the ovaries, and the oviducts in birds. This is the meaning of the term “homotypy” according to the German biologists E. Haeckel and C. Gegenbaur. The English biologist R. Owen calls serial homology “homotypy.” Homotypic organs are called antimeres.