ZOOLOGY: S. O. MAST 
217 
end on black become uniformly maximum white over the entire pig- 
mented surface, with the anterior end on black and the posterior end on 
white or on a glass plate with intense light reflected through it from 
below they become uniformly maximum black; with one eye on white 
and the other on black they assume an intermediate shade (uniform 
gray) over the entire surface. Specimens, with one eye on a background 
having a given pattern and the other eye on a background having a 
different one, assume uniformly over the entire pigmented surface of 
the body, a pattern intermediate between those assumed when entirely 
on either background. Careful observation shows that this pattern 
really consists of a sort of superimposition of a coarser and a finer pat- 
tern; for large areas similar to those ordinarily produced when the fish 
is entirely on the coarser grained of the two backgrounds can still be 
faintly seen, as well as small areas similar to those ordinarily produced 
when the fish is entirely on the finer grained background. Thus the 
configuration in the skin when one eye is on a background having a 
given pattern and the other on one having a different pattern consists 
of a superimposition of the configuration produced by each of the two 
different backgrounds acting alone. The influence of the light received 
by each of the two eyes is evidently distributed over the entire body and 
the resulting pattern in the skin is due to a combination of the specific 
effect of stimuli received from the two eyes. 
On a background consisting of any combination of black and white, 
only black and white is seen in the skin, no color whatever. But if a 
yellow card is placed within 3 cm. of the anterior end of the fish it be- 
comes strikingly yellow. All of these results indicate that if light has 
any direct effect on the chromatophores it is insignificant in the process 
of adjustment to the background. This conclusion is further supported 
by results obtained with blind specimens. 
The removal of either eye interferes but little with the activities of 
flounders. If the operation is carefully performed the wound heals in 
a few days and the animals respond normally. They move about and 
feed apparently with the same degree of freedom as they do with both 
eyes functional and there is no difference in the extent or the rate of 
adaptation to the background, neither in color nor in shade nor in pattern. 
Specimens with both eyes removed also learn to get around in the 
aquarium without serious difficulty; but they do not simulate the back- 
groimd, either in shade, color, or pattern. 
c. Direction of the light: Specimens on a white background, if they 
respond at all, become maximum white even if the intensity of the light 
is so low that they can scarcely be seen and the background appears 
