The probable origin and true histologic character of the meningioma, a tumor best known as dural endothelioma, are fairly old problems. A century ago, Cruveilhier1(1835) intimated the meningeal origin of such tumors by naming them "cancerous growths of the meninges." He substituted this name for the older term "fungus growth of the dura," used by earlier writers. Since then, almost each decade has brought to the foreground important contributions on this subject, embodying observations and conclusions of some outstanding anatomist, pathologist or neurosurgeon. At first sight it would seem that these studies have resulted in little more than the creation of a large assortment of names, which include such terms as cylindroma, of Billroth;2psammoma and dural sarcoma, of Virchow;3epithelial cancer, of Bennett;4fibroplastic tumor, of Lebert;5epithelioma, of Bouchard6and Robin;7endothelioma, of Golgi;8cancer of the arachnoid, of