290 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
of balsam and lampblack, and, after allowing the animal to swim in a 
brightly illuminated dish for several hours, it was killed, and both its 
eyes prepared and examined. 
The two sets of experiments yielded essentially the same results, 
namely, the eyes exposed to the light always presented the condition 
normal for the light, and those kept in the dark always showed an ap- 
proach, more or less incomplete, to the condition characteristio for the 
dark. This incompleteness might be taken as evidence of a partial 
sympathetic relation between the two retinas; but I believe it is to be 
explained otherwise. In both sets of experiments the eyes supposed to 
be blinded were in reality only partially cut off from the light. In the 
experiment with the light-proof box, I know by actual observation that 
more or less light made its way through the optic stalk that projected out- 
ward to the exterior, and thus gained access to the interior of the box. 
If this is true of the experiment with the box, it is very probable that in 
the second experiment light passed up through the base of the blinded 
stalk, and thus reached at least the proximal part of the retina. 
These experiments, then, are not wholly conclusive, but, so far as 
they go, indicate considerable independence in the relations of the 
two optie stalks. For reasons to be given later, in connection with the 
experiments on excised stalks, I believe I am justified in concluding that 
the two retinas are, in reality, wholly independent of each other. 
Locauızen PHOTOMECHANICAL CHANGES. 
Another question that naturally presents itself is, whether different 
parts of the same retina are sympathetic toward one another, or whether 
they are entirely independent, i. e. whether or not a retina responds 
locally to stimulus. 
To test this matter, I put minute drops of the mixture of balsam and 
lampblack on the corneal cuticula of the eyes of several shrimps, and 
let them swim for a few hours in well illuminated basins. On examin- 
ing sections of their eyes later, it was found that under each mass of 
applied pigment the retinal cells showed a condition characteristic for the 
dark. This was most pronounced in the distal retinular cells, but was 
also observable in the proximal retinular cells, as well as in the acces- 
sory pigment cells. This experiment shows beyond a doubt that the 
elements of the retina act locally, and respond to differences of light 
and dark independently of one another. "This independence furthermore 
explains what is not infrequently seen in sections of otherwise normal 
