The walls and axis of these nuclei have the structure of a very fine and dense network that stains very dark with iron-hæmatoxylin. It stains quite like the reticulum of any nucleus, but is very dense, as though all the reticulum of the nucleus had been crowded together at the surface. Judging from appearances like p (Fig. 20), the hollowing out, so to speak, of these nuclei, would seem to be a process of vacuolation, the reticulum becoming crowded aside to the surface. But how, on this view, to amount for the formation of the axis, I do not know. Perhaps the axis is formed by a pushing in of two opposite poles of a nucleus, the two invaginations meeting and fusing. On this supposition one might expect the axis to be hollow (cylindrical), but I could not determine that it was. Perhaps the centrosphere (or spheres) (see the next paragraph) has something to do with the formation of the axis (Fig. 20, b, g, e, etc.). In the nuclei of Fig. 20 with the dark outlines, and of Fig. 7 a small reticular body is seen just opposite one end of the axis, or opposite both ends in g. In d (Fig. 20) this body is seen next the axis just below (outside) the hollow cup represented by the hollow ring. In this instance a central granule is seen in the reticular body, as also in c. I take this reticular body to be the centrosphere, and the central granule in c and d the centrosome. In k, l, m, n, and o (Fig. 20), which are from another series, in which the walls of the nuclei did not stain so dark as in the other nuclei of the same figure, a nucleolus could be definitely seen, indeed, sometimes quite perched upon the wall of the nucleus (k, l). In several instances I could see two nuclei, as in o. But besides these nucleoli, I could in several instances see quite definitely a reticular body (centrosphere) opposite the axis (m, n, o) quite as I described for the nuclei with the dark outlines. In a, b, c, d, e and g the nuclei could not be so readily demonstrated, but I could occasionally see a darker stained body as in a, c and g, that I have no doubt is the nucleolus, which here, again, is perched quite upon the surface of the nucleus. This position of the nucleolus is perhaps due to its having been crowded to one side by the nucleus becoming hollow. It is no uncommon thing, either, to find several nuclei in a single cell, sometimes in process of division or just divided as o and e (Fig. 20), also h, i and j. The whole nuclear phenomenon that I have described seems to be one of division. Perhaps it is somehow associated with the giving off of the secretion of the cells, for these nuclei seem to be found in greatest abundance in those cells in which the secretion is most abundant. In Conant’s sections I found but little evidence of these nuclear phenomena as also little secretion, which all goes to show the association of the nuclear phenomenon with the secretion. I have failed to find any descriptions in the literature of nuclei to which I could refer my