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. 



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. 



