"My own notions of Eozoic structure have been formed on the examination of the Canadian specimens selected by the experienced discrimination of Sir William Logan, as those in which there was _least_ appearance of metamorphism; and having found in these what I regarded as unmistakable evidence of an organic structure conformable to the foraminiferal type, I cannot regard it as any disproof of that conformity, either to show that the true Eozoic structure has been frequently altered by mineral metamorphism, or to adduce the occurrence of Ophites more or less resembling the Eozoon of the Canadian Laurentians at various subsequent geological epochs. The existence of any number or variety of _purely mineral_ Ophites would not disprove the organic origin of the Canadian Eozoon--unless it could be shown that some wonderful process of mineralization is competent to construct not only its multiplied alternating lamellæ of calcite and serpentine, the dendritic extensions of the latter into the former, and the 'acicular layer' of decalcified specimens, but (1) the _pre-existing canalization_ of the calcareous lamellæ, (2) the _unfilled nummuline tubulation_ of the proper wall of the chambers, and (3) the peculiar _calcarine_ relation of the canalization and tubulation, here described and figured from specimens in the highest state of preservation, showing the _least_ evidence of any mineral change. "On the other hand, Professors King and Rowney began their studies of Eozoic structure upon the Galway Ophite--a rock which Sir Roderick Murchison described to me at the time as having been so much 'tumbled about,' that he was not at all sure of its geological position, and which exhibits such obvious evidences of mineralization, with such an entire absence of any vestige of organic structure, that I should never for a moment have thought of crediting it with an organic origin, but for the general resemblance of its serpentine-grains to those of the 'acervuline' portion of the Canadian Eozoon. They pronounced with the most positive certainty upon the mineral origin of the Canadian Eozoon, before they had subjected transparent sections of it to any of that careful comparison with similar sections of recent Foraminifera, which had been the basis of Dr. Dawson's original determination, and of my own subsequent confirmation, of its organic structure. [Illustration: Plate VIII. _Eozoon and Chrysotile Veins, etc._ Fig. 1.--Portion of two laminæ and intervening serpentine, with chrysotile vein. (_a._) Proper wall tubulated. (_b._) Intermediate skeleton, with large canals. (_c._) Openings of small chamberlets filled with serpentine. (_s._) Serpentine filling chamber. (_s^1._) Vein of chrysotile, showing its difference from the proper wall.