E. W. BERGER ON THE CUBOMEDUS. Lh 
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. 16) 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 hght 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 
