This monograph contains the most significant studies of Geoffrey, which contributed to the establishment in science of one of the most fruitful general theoretical generalizations of biology - the doctrine of the unity of structure, animals. This doctrine, materialistically interpreted, has become an integral part of the modern doctrine of the unity of the origin and development of the organic world. Geoffrey's comparative anatomical works are critically considered, including the Philosophy of Anatomy, which essentially laid the foundations of the homological method, the principle of connections, and the dynamic correlation of organs (the "principle of balancing"). Geoffrey's scientific achievements were expressed, as we hope to show, not only in reform based on the doctrine of the unity of the animal world of the taxonomy of vertebrate animals and comparative anatomy.