DAY: PIGMENT-MIGRATION IN EYE OF CRAYFISH. 319 
animal was exposed to a single color, and a check animal which had 
been confined in the same dark chamber was killed in the dark at 
the end of the experiment. On account of the irregularities in the 
TABLE 1. 
Poe 
Amount of migration shown by sections. 
Values under BV, G, YG, Y and R (blue-violet, green, yellow-green, yellow 
and red, respectively) are estimates of the distance traversed between the 
basement-membrane and the row of nuclei of the retinal cells expressed in 
tenths of that distance. The last column gives similar values for animals 
kept in the same dark chamber and killed in the dark after the others of the 
series had been exposed. In the summary, read horizontally, each color is 
compared with BV and G with Y, showing the number of times one was 
ahead of the other in efficiency. 
Distance Period 
from Cy) 
Series BV G YG Y R Light box | Exposure | Check 
. cm. min. 
Ligne 7 8 7 550 1 5 
2 So 8 6 8 550 1 5 
eco ates 10 8 7 6 550 1 8 
4. 99 10 8 9 7 550 1 2 
De OS) S' 8 8 9 2 950 il 4 
6.7.99 8 6 3 4 550 1 1 
6 Bi9 Z, 8 9 550 i 3 
1 300 1 
B 9 9 6 550 1 2 
8 550 20 
3 550 20 
6 250 1 
8 250 1 
i ak | ri 5 550 I 
6 2 550 1 
Number of times ahead 
Tie Total 
Summary BV G YG Y R Trials 
BV vs. G 4 1 1 6 
sli as 8: 3 1 2 6 
cc cc Y Dy a 3 
dated: inst 3: 9 fk 10 
Genagy 3 3 6 
