The curious tumor of which this paper treats, is one that has aroused an immense amount of interest, as weil as some controversy, among the pathologists of the world. In Europe, particularly, has the neoplasm been studied and all its types described. In this country, the paper by A. O. J. Kelly, published in 1896, remains the most important and is the basis of most of the American work on these tumors. To examine the text-books treating of renal tumors is to see the confusion the varieties of hypernephroma have created in the minds of authors. On account of the varying morphology of these growths, pathologists have described them under such different titles as angiosarcoma, perithelioma, papillary adenocarcinoma and cystoma, clear-celled epiithelioma, spheroidal-celled carcinoma, alveolar endothelioma, sarcoma, adenoma and adrenal adenoma. Each observer seems to have excellent ground for his opinion; because, as a rule, the diagnosis is based