Hadley, Behavior of the American Lobster. 



247 



Case 2. Phototactic reaction — ^August 10, 3:30 p.m. Ten late 

 fourth-stage lobsters were taken from one of the hatching bags and 

 put in box B, which was placed in the dark box so that the end 

 window faced the light, the intensity of light being modified in 

 each case by interposing colored glass plates between the end 

 window and the light. The tests, which were made at three- 

 minute intervals, and which showed a very definite negative reac- 

 tion, were as follows (in the fourth tests of the first and last sets 

 respectively, one lobster was accidently killed, thus making the 

 totals incomplete): 



Conclusions on the reaction of fourth-stage lobsters — The obser- 

 vations thus far made upon the behavior of fourth-stage lobsters 

 appear to demonstrate the following points: (i) Throughout 

 the entire fourth stage-period (with the exceptions noted under 

 Experiment 24, Cases 5 and 6), the lobsters manifest a negative 

 phototactic reaction, which is accentuated in the latter part of this 

 stage. This behavior is quite different from the positive reac- 

 tion which supersedes the negative in the case of second and third- 

 stage larvae just previous to their moult into the third and fourth 

 stages respectively; (2) This type of reaction after the first part 

 of the fourth stage-period, cannot be reversed or modified, as was 



