Geoffroy: I said that there was isomorphism but not correspondence. You have to bring "degrees of development or perfection" into the picture. It is not everywhere on a stratum that materials reach the degree at which they form a given aggregate. Anatomical elements may be arrested or inhibited in certain places by molecular clashes, the influence of the milieu, or pressure from neighbours to such an extent that they compose different organs. The same formal relations or connections are then effectuated in entirely different forms and arrangements. It is still the same abstract Animal that is realized throughout the stratum, only to varying degrees, in varying modes. Each time, it is as perfect as its surroundings or milieu allows it to be [TP: 46]