E. W. BERGER ON THE CUBOMEDUS. 5ST 
retinidium. Again, since the rods are usually the shape of truncated 
pyramids or cones the lateral fibrils, which are perpendicular to the 
axial fibers, are of different lengths accordingly as they are situated 
at the larger or smaller end of a rod. Patten assumes similar fibrils 
to exist in the rods and cones (particularly the cones) of the verte- 
brate eye, and he thus makes a general application of his theory. 
He supports himself in this rather sweeping generalization by the 
claim to have demonstrated the twin-cell nature of the cones in 
amphibia and fishes. 
For illustration, Patten supposes that if red light only were 
admitted to the retinophora this would stimulate the fibrils near the 
broader end of the cone (but that all the fibrils of the retinidium 
would be stimulated a little) and that we would thus have the 
sensation of red light. Likewise, if violet light only were admitted, 
the fibrils at the narrower end of the cone would be stimulated, and 
we should have violet light. Similarly, if light including all the 
different wave lengths of the spectrum were admitted, all the lateral 
fibrils would be stimulated and the sensation of white light produced. 
The method of stimulation need not be that of a vibration of the 
fibrils. 
Certain grave objections may be raised against such a theory, 
the most serious, perhaps, being the fact that no such fibrils as 
Patten has described have as yet been demonstrated for the eyes of 
those animals that we know have color vision. Yet, as a whole, the 
objections are perhaps no more serious than any that can be brought 
against other theories of color vision. What Patten’s theory does do, 
—it gives us a definite mechanical basis to work from, and if these 
fibrils should be demonstrated for the rods and cones of vertebrates, 
physiologists would then have a mechanical basis for color vision 
quite as they now have for hearing. As Patten says, the problem 
is primarily a mechanical one. However, the theory cannot well 
pass for more than a suggestion, a stimulus for future work, and in 
this lies its present value. 
It is quite evident that my results for the retinal cells of 
Charybdea are, if any thing, a support to Patten’s theory. While I 
have not been able to demonstrate the fibrils that are the essential 
to Patten’s theory, yet I have demonstrated the axial fibers of the 
rods, and if these fibers should be continued as a nerve fiber to some 
central ganglion (as I believe is reasonable to suppose, see p. 47), I 
