Note 15 — CEREBRAL DEVELOPMENT OF THE EARLIER VERTEBRATA. ITS APPARENT PRINCIPLE.

Professor Owen, in fixing the homologies of the ichthyic head, differs considerably from Cuvier; but his view seems to be demonstrably the correct one. It will, however, be seen, that in my attempted comparison of the divisions of the ancient ganoid cranium with those of the craniums of existing fishes, the points at issue between the two great naturalists are not involved, otherwise than as mere questions of words. The matter to be determined, for instance, is not whether plate A in the skulls of the cod and Coccosteus be the homologue of a part of the occipital or that of a part of the parietal bones, but whether plate A in the Coccosteus be the homologue of plate A in the cod. The letters employed I have borrowed from Agassiz’s restoration of the Coccosteus; whereas the figures intimate divisions which the imperfect keeping of the specimens on which the ichthyologist founded did not enable him to detect.