day: pigment-migration in eye of crayfish. 



325 



TABLE II. 



Intensity {i. e. distance) varied. 



Time of exposure constant (10 minutes). Evaluations were made with 

 reference to a single arbitrary standard of medium migration. Last two 

 columns give distances corresponding to equivalent migrations for red and 

 blue- violet as deduced from the assigned evaluations. (Evaluations in paren- 

 theses were ignored in making the deductions, because they represented 

 migrations after the eyes had deteriorated in value.) From averages of these 

 distances was computed the relative intensity of BV in terms of R, given in 

 Equation I. Equation II was obtained after rejecting dubious cases. 



= 2.29 in terms of distance. 



Equation I: 

 Equation II; 



BV _ 247 

 R ~ 107.5" 

 BV = (2.29)2 R in terms of intensity, or 

 BV = 5.2 R 



BV = 5.6 R after eliminating G, K, 24, 25, 35 and 36, whose 

 record-s were less easily compared. 



