As to the structure of the vitreous body, apart from the fibres and pigment streaks already mentioned, I find it to be made up of prisms extending from retina to capsule of lens, each containing a central axis or fibre. Fig. 64 shows that the space around the pigment areas and “visual fibres,” instead of being homogeneous, is wholly filled with the polygonal cross-sections of these prisms. In Charybdea they are generally more difficult to perceive than in my best material of Tripedalia which was killed in acetic acid. In this the polygonal areas stood apart from each other more plainly. Curiously enough I have been unable to demonstrate in Tripedalia the “visual fibres” of Schewiakoff. Here and there were found spaces that at first sight reminded of them (Fig. 69, _sh_), but they contained no central fibre, and were probably due to shrinkage. The polygonal areas themselves, however, often contained a clear spot in the centre, at one side of which would be found the cross-section of the fibre, as is shown in many cases in Fig. 68. The clear spot is here undoubtedly due to shrinkage of the gelatinous substance of the prism. I think that these prisms and fibres are the direct continuations of retinal cells. In a section such as that drawn in Fig. 63, which takes just the very tops of the cells of a slightly pigmented retina, in the centre of the section just grazing the space that lies between the retina and the shrunken vitreous body, most of the cells toward the middle (where especially the extreme tips are taken) show in their centres a dot exactly corresponding to the dots in the polygonal areas of the vitreous body. In the exact middle of the section, where only the cell walls appear, slightly indicated, a dot is seen in each case. The size and shape of the ends of the cells correspond with those of the polygonal areas in the vitreous body, and I do not doubt that the latter are continuations of the former. The vitreous body, then, instead of being homogeneous, is composed of the clear highly refracting outer ends of retinal cells. The assumption lies near that these are the true visual rods, but of course it is assumption only. To give a brief review, the points in which my conclusions differ from those of Schewiakoff are as follows: I find (1) that the long pigment streaks are parts of retinal cells continued into processes like his visual rods; (2) that the vitreous body is composed of prisms with central fibres proceeding from retinal cells; (3) that I am unable to get satisfactory evidence of two types of cell distinguishable within the retina, and at any rate find considerable evidence against the two types he distinguishes.