168 



H. C. STEVENS 



from the colored aquaria. The procedure of these experiments 

 was exactly the same as that already described. The general 

 type of orientation, the effects of thigmotropism and habitua- 

 tion, the length of the reaction times were about the same as 

 those described above. The results of these experiments are 

 shown in Tables IV, V, VI and VII ; and their corresponding 

 Figures, 4, 5, 6 and 7. Each centimeter of the cross-section 

 paper indicates one reaction. 



TABLE IV 



Shows the Reactions of Individuals which Had Been Exposed to 



Red Light 



7 

 6 

 5 

 4 

 3 

 2 



1 



FIG 



R Y G B W 

 Figure 4. Shows the curve of distribution of the reactions of Table IV 



It appears to be very certain, judging from the results of 

 these experiments, at least, that the color reactions of Oregonia 

 gracilis are influenced in a dominant degree by the color of the 

 light to which the crab is exposed. The curves show clearly 

 that the maximum number of reactions invariably falls to the 

 colored light of the same quality as that to which the animal 

 has been previously exposed. Of the ten specimens used in 

 this series only two, Specimens 18 and 21 failed to react maxi- 

 mally to the light to which they had previously been exposed. 



