observations. The endothelium of the ampulla is flagellated (Figs. 7, 17, 27). It will be seen that there are two slender flagella to a cell. Each pair of flagella has a pair of basal bodies that are longer than thick, and which are continued as a thin fiber towards the nucleus of the cell. That these centrad continuations of the basal bodies extend to or past the nucleus I could not determine. Sometimes the basal bodies with the centrad continuations are pushed quite to one side of the cell (Fig. 27), while in other cells they are applied quite to the distal surface (Figs. 7, 17, 27). Fig. 17, and the part of Fig. 7 that shows these points, are taken just through the tips of the cells. The darker lines within the polygonal areas are the intracellular basal bodies with their centrad continuations, while the thinner lines are the flagella, and are supposed to lie in the plane just below the plane of the figure. In those instances in which the centrad continuations are applied to the distal surface of the cells they could occasionally be seen to bend centrad (Fig. 27b). While these cilia with their basal bodies and centrad continuations are usually separate, as shown in the figures, yet they are at times applied quite closely to each other so that the double nature of the basal bodies and their centrad continuations is not evident. When the intracellular continuations of the cilia become pushed to one side or applied to the distal surface of the cells, I believe this to be due to the turgor of the cells consequent upon the deposition of large masses of secretion within them. But I must add that this explanation is not altogether satisfactory, since in the endoderm cells of the pedalia of both Charybdea and Tripedalia I found like conditions with no evidence of a secreting function. (See below, under tentacles.) No one, to my knowledge, has described the flagellation in detail, although both Claus and Schewiakoff state that the endoderm is ciliated.