Hadley, Behavior of the American Lobster. ■ 257 



These and other tests were made, but in no case was it apparent 

 that the early fourth-stage lobsters showed any preference for the 

 sanded area. When, in another series of four trials involving 

 ten lobsters each, the window at the sanded end of the box, was 

 opened so as to allow the rays to stream through, every lobster 

 but one was driven to the compartment farthest from the light. 

 When this experiment was tried with late fourth-stage lobsters, 

 it appeared that a greater number remained on the sanded area, 

 even in the presence of the light conditions mentioned above. 

 The results of a typical experiment of this sort involving five trials 

 of ten lobsters showed that, while thirty were driven to the clear 

 space, ten remained on the sanded area. 



Experiment JO. Case i. Fifth-stage lobsters — In this instance 

 ten fifth-stage lobsters were placed in box B as arranged for the 

 previous experiment, no light being admitted at the end of the 

 box. The record of seven trials separated by a period of from 

 five to ten minutes, show^ed a decided preference for the sanded 

 areas; while forty remained on the sanded region, only twenty 

 gathered on the clear area. 



Case 2 — In the next instance the end window at the sanded end 

 of the box was opened to the light, but with a red glass so inter- 

 posed that the intensity of light in this region was not great. A 

 period of from ten to forty-five minutes was allowed for each orien- 

 tation. Although the influence of the light tended to drive the 

 lobsters off^ the sanded area the resultsof six trials (ten lobsterseach) 

 show^ed that thirty-seven fifth-stage lobsters remained in contact 

 with the sand, while twenty-three moved to the clear area. 



Case J — In the next series of six trials (ten lobsters each) the 

 intensity of light was modified by substituting an orange glass 

 before the end window. The results showed twenty-five on the 

 sanded area, thirty-five on the clear. 



Case 4. — In the last series of six trials (ten lobsters in each) the 

 conditions were still further modified by removing the orange glass 

 and thereby greatly increasing the intensity of the light which 

 entered the end window of the box. This demonstrated that a 

 light of great intensity would drive the fifth-stage lobsters off the 

 sanded area. At the end of the experiment only thirteen lobsters 

 remained on the sanded area, while forty-seven remained in the 

 clear region. Finally, the sand was removed from the box, and 

 the reaction of these lobsters was tested with unobstructed light 



