human skull on what we may call, figuratively speaking, the ãplaneã of the chimpanzee; and the full diagram in Fig. 406 demonstrates the corôÙreôÙsponôÙdence. In Fig. 407 I have shewn the similar deformation in the case of a baboon, and it is obvious that the transformation is of precisely the same order, and differs only in an increased intensity or degree of deformation.
In both dimensions, as we pass from above downwards and from behind forwards, the corôÙreôÙsponôÙding areas of the network are seen to increase in a gradual and apôÙproxôÙiôÙmateôÙly logarithmic order in the lower as compared with the higher type of skull; and, in short, it becomes at once manifest that the modifications of jaws, braincase, and the regions between are all portions of one continuous and integral process. It is of course easy to draw the {772} inverse diagrams, by which the Cartesian co-ordinates of the ape are transformed into curvilinear and non-equidistant co-ordinates in man.
From this comparison of the gorillaãs or chimpanzeeãs with the human skull we realise that an inherent weakness underlies the anthropologistãs method of comparing skulls by reference to a small number of axes. The most important of these are the ãfacialã and ãbasicranialã axes, which include between them the ãfacial angle.ã But it is, in the first place, evident that these axes are merely the principal axes of a system of co-ordinates, and that their restricted and isolated use neglects all that can be learned from the filling in of the rest of the co-ordinate network. And, in the second place, the ãfacial axis,ã for instance, as ordinarily used in the anthropological comparison of one human skull with another, or of the human skull with the gorillaãs, is in all cases treated as a straight line; but our inôÙvesôÙtiôÙgaôÙtion has shewn that rectilinear axes only meet the case in the simplest and most closely related transôÙforôÙmaôÙtions; and that, for instance, in the anthropoid skull no rectilinear axis is homologous with a rectilinear