E. W. BERGEE ON THE CUBOMEDUS^E. 77 



SUMMARY. 



The most important results in the histological part of this paper 

 relate to the structure of the retinas of the eyes of the sensory clubs. 



The retina of the distal complex eye is composed of three kinds 

 of cells : two kinds of sensory cells (the prism and pyramid cells), 

 and the long pigment cells (Figs. 1-9). The prism and pyramid cells 

 have each an axial nerve fiber in their prisms and pyramids respect- 

 ively. These fibers I could, however, trace only to the neighborhood 

 of the nuclei. But since I could trace similar fibers in the retinal 

 cells of the simple eyes (Fig. 10) past the nucleus into the subretinal 

 nerve tissue, I believe that the axial fibers in question also extend 

 centrad as nerve fibers into the subretinal nerve tissue. Other observers 

 also figure such fibers as extending centrad as nerve fibers. The axial 

 fibers of the prism cells have each a dumbbell-shaped basal body at 

 their entrance into the pigmented part of a cell. The evidence for a 

 body of such shape in the pyramid cells was not conclusive, though 

 a basal body for. the axial fiber exists. The long pigment cells project 

 or retract their pigment in light or darkness respectively and thus 

 seem to serve to check the diffusion of light in the retina. I have 

 also supposed that these cells may serve for conducting impulses to 

 the lens, and that the latter is adjustable. 



The proximal complex eye (Fig. 13) has only the prism cells 

 present in its retina, and not two kinds of cells as Schewiakoff has 

 described (see text, pp. 53, 60, 63) for all the eyes. 



The simple eyes (Fig. 12), two on each side of a club, four in 

 all, also have only one kind of cells in their retinas, and each cell 

 has a flagellum extending into the vitreous secretion of the lumen. 

 These flagella could be traced centrad as a nerve fiber (Figs. 12, 16). 

 Similarly, a nerve fiber could be traced centrad from the flagella of 

 the epithelial cells of the clubs. Dumbbell-shaped basal bodies for 

 the flagella of the simple eyes could also .be demonstrated, but the 

 evidence for this in the epithelial cells of the clubs was not so 

 satisfactory. 



Other points of interest are: A secretory epithelium lining the 

 ampulla of the clubs, and a somewhat similar epithelium lining 

 the canals of the tentacles (Figs. 7, 27, 31); the partial origin of the 

 "floating bodies" in the canals of the clubs and tentacles and the 

 stomach pockets from these epithelia (Figs. 18, 19) ; two flagella to 



