228 



LESLIE B. AREY AND W. J. CROZIER 



side was in comparative darkness, the other side in the light. 

 Diffused sunlight, employed with chitons of medium to large 

 size, induced responses of a variable kind. 



Experiment 1. Two chitons introduced. One moved partly toward 

 the dark side, and subsequently, in the course of 45 min., moved back 

 into the center of the light compartment. The other one rotated 

 through 180°, its anterior end passing through the dark side and then 

 orienting into the light. 



Experiment^ 6. Two chitons used. One began to move at once; 

 oriented 90° into the dark, and moved so that almost the whole of 

 its body was in the dark compartment; after 5 min., it turned through 

 180° and moved straight out into the light. The other one within a. 



Fig. 13 Sectional view of apparatus for the partial illumination of a Chiton: 

 a shallow pan fitting the bottom of a box with blackened walls; one half of box 

 open to receive light, as indicated by the arrows, the other half covered and 

 separated from first half by a blackened vertical partition extending into the 

 sea-water, that nearly fills the pan; horizontal overhang from the lip of the pan 

 exposed to light reduces reflection. 



few minutes oriented weakly into the Ught, halted 1 min., and then 

 oriented anterior end back into the dark, so that haK of its body was 

 on either side of the partition. 



In 15 individual tests of this nature, 



4 chitons turned and moved directly into the light, where they 

 remained. 



chiton turned and moved directly into the dark. 



4 chitons turned and moved into the dark, then into the light. 



chiton turned and moved into the light, then into the dark. 



4 chitons turned directly into the light, but did not creep. 



chiton turned directly into the dark, but did not creep. 



1 chiton oriented into the light, then into the dark. 



2 chitons gave no response during the time allowed for the ex- 



periment. 



