E. W. BERGER ON THE CUBOMEDUS.E. 49 



which fact is characteristic. In the axis of each pyramid is a 

 darkly-staining fiber quite like the one described for the prism- 

 cells (Figs. 1, 4, 7, 22). That this fiber extends distally beyond the 

 limits of the pyramids I could not determine, but I do not think 

 that it does. Centrad this fiber extends into the pigmented portion 

 of its cell quite to or near the nucleus as was described for the 

 fibers of the prism-cells (Figs. 7, 22). Whether or not these fibers 

 extend past the nucleus and become continued as nerve fibers, the 

 same course of reasoning holds as was given for the fibers of the 

 prism-cells. Each of these fibers possesses a basal body just on its 

 entrance into the pigmented part of the cell (Fig. 7), but I could 

 not determine that it was dumbbell-shape. In form it represents 

 an enlargement of the fiber itself, which gradually tapers again to 

 its normal size. The continuations of these fibers within the pig- 

 mented parts of the pyramid-cells, as also the basal bodies, could 

 only be demonstrated in unpigmented series. 



Patten 5 describes axial fibers extending centrad through the rods 

 (vitreous portions) of retinal cells (" retinophora") into the region 

 of the nucleus and past the nucleus (arthropods and molluscs). My 

 retinal cells (prism and pyramid cells) evidently correspond to Patten's 

 retinophora, but I find no evidence that one of my retinal cells 

 represents more than a single cell, while Patten gives evidence that 

 his retinophora are made up of two cells closely applied to each other 

 as twin cells. If this were also true for the retinal cells that I have 

 described, I believe my macerated preparations would have shown 

 it. Schreiner 12 " and Hesse 13 also figure and describe axial fibers for 

 the rods of the visual cells in polycha3tous annelids, and Schreiner 12a 

 also for molluscs. Neither of these observers finds the fibers to extend 

 distally beyond the rods nor centrad toward the nucleus as Patten 

 and myself show. Neither Schreiner nor Hesse figures these cells as 

 twin cells as Patten does, so that to my knowing Patten stands 

 alone in this respect. Andrews 11 describes and figures rods for the 

 visual cells of polychaste annelids but no axial fibers. He was the 

 first to describe these rods in annelids. 



The pigmented zone of the pyramid cells, in heavily pigmented 

 series, is filled throughout with dark-brown pigment granules, and is 

 quite like that of the prism cells (Figs. 4, 7). In transverse sections, 

 however, through the most distal part of the pigmented zone, of 

 unpigmented series (Fig. 2), lighter areas with central dots could 

 5 



