Hadley, Behavior of the American Lobster. 213 



the young larvae at once swam backwards toward the source of 

 Hght and grouped themselves closely together at the window side 

 of the glass jar. So perfect was this orientation on the part of the 

 newly hatched larvae that, out of 100 individuals, not one showed 

 a negative reaction. 



Case 2 — ^When the same larvae were put in one of the long 40- 

 centimeter glass tubes so placed in the dark box that the tube was 

 parallel to the direction of the incident rays, the young lobsters 

 in every case swam rapidly to the end of the tube nearest the win- 

 dow and remained there until the tube was reversed, when they 

 again swam toward the window. These reversals might be con- 

 tinued for hours. 



Case J — ^When the same individuals, or other larvae of the same 

 group, were placed in box B, and this was turned with one end 

 toward the window, the reaction of Case 2 occurred. They swam 

 backward toward the window. 



Case </— Another group of fifty first-stage larvae three days old 

 was placed in a glass jar in the dark box and illuminated from the 

 small window. All were definitely positive. Next, the circum- 

 ference of the jar, except a vertical strip three inches wide on the 

 light side, was covered with black paper, and the jar was so placed 

 that direct sunlight had access to the open side. The larvae imme- 

 diately gathered on the darker side of the jar and remained there 

 for one and a half minutes, after which they again returned to 

 the sunlit side and remained there in bright sunlight as long as 

 they were observed. 



Experiment 6. — July 19, 3:30 p.m. Fifty first-stage larvae, 

 two days old, were put in a glass jar and this was placed in the 

 dark box. Though the light was not bright at this time in the 

 afternoon all the larvae gave a positive reaction. The jar now was 

 placed on a black background in the bright sunlight on the west 

 table. Evey lobster moved to the room side of the dish away from 

 the light. Within two minutes, many began to go back to the window 

 side, and this continued until all were again gathered there. After 

 four minutes, however, they again returned to the room side and 

 remained there for ten minutes, at the expiration of which time they 

 were about equally divided between the room side and the window 

 side of the jar. They were now put back in the dark box, and 

 with the slight intensity of light at 7 o'clock in the evening, all 

 were reacting positively. By 8:30 the box was fairly dark and the 



