E. W. BERGEE ON THE CUBOMEDUS^. 63 



quite in the angle between the proximal complex eye and the group 

 of network cells in the upper part of the club. In this series I 

 could very definitely trace the distal fibers of the retinal cells 

 centrad, past the nucleus and into the subretinal nerve-tissue. 

 These fibers could be so easily followed that no doubt can exist as 

 to the fact noted. It thus appears that the axial fibers just 

 described pass centrad through the cells and are continued as nerve 

 fibers. On the evidence of such sections as Fig. 16 I have indicated 

 these fibers as extending centrad through their cells. The lumen of 

 the simple eyes is filled with a homogeneous vitreous secretion. 

 This is often incomplete in some parts ; occasionally the secretion 

 shows a formation of globules, but all this I believe to be due to 

 the action of reagents. Indeed, I have found simple eyes in which 

 hardly any secretion was present, while others showed an almost 

 completely filled cavity. In that portion of the vitreous secretion 

 just outside the mouth of the distal eyes I occasionally found numbers 

 of very darkly staining granules. I suspect that these are either 

 bacterial or algal organisms. 



As already noted, Glaus and Schewiakoff describe two kinds of 

 cells for the retinas of these eyes which neither Conant nor myself 

 can demonstrate. Further, I believe I have shown that only one kind 

 exists. If any doubt should still exist, a section like Fig. 25 (which 

 is from the epithelium of the club, but similar smaller areas with 

 central dots could often be demonstrated in transverse sections of the 

 retinal cells of the simple eyes) I believe should be convincing. 

 Schewiakoff further describes flagella for the retinal cells (his visual 

 cells) of the simple eyes quite as I have described them for all the 

 cells. The pigmentation that Schewiakoff mentions as occurring in 

 the secretions within the lumina of these eyes I believe to have 

 been dissolved in from the pigmented zones. I find no definite pig- 

 mentation in these vitreous secretions. These secretions are evidently 

 products of the retinal cells and have been so regarded by former 

 observers. 



Lithocyst and Concretion. The cavity filled by the concretion is 

 lined in places by a single layer of cells, two of which are shown in 

 Fig. 7. This fact has been noted by both H. V. Wilson and Conant. 

 Such cells are evidently remnants of the cells that formed the con- 

 cretion. The supporting lamella completely surrounds the cavity of 

 the concretion. 



