102 Papers from the Marine Biological Laboratory at Tortugas. 



In these 1 5 tests (table 4) it will be seen that the starfish moved to 

 the top of the incline 8 times, to the base 6 times, and to the side once. 

 Although the ratio is slightly in favor of movement up the incline, yet 



we are not justified in considering that a case 

 of "negative geotropism" is demonstrated. 

 Surely the direction of locomotion is not stereo- 

 typed. While it would be desirable to have 

 more data, I think one may draw the conclu- 

 sion that when Echinaster crassispina, which 

 usually reacts positively to bright daylight and 

 which usually crawls to the top in a small aqua- 

 rium exposed to light, is placed on a surface tilted 

 at an angle of 10° {light being excluded), there is 

 no decided tendency for it to move either negatively 

 or positively to the attraction of gravitation. 



In order to test further the behavior of 

 Echinaster on vertical walls, several series of 

 tests were made, using a very large cylindrical 

 glass aquarium filled with sea -water. Inside 

 the aquarium was fixed a flat piece of glass in 

 a vertical position (fig. 4). A specimen which 

 had been tested and found positive in its reac- 

 tion to light was then allowed to attach itself 

 to the vertical plate, with one or two of its rays resting on the bottom. 

 The apparatus was then covered with a thick velvet cloth, so as to be 

 light-tight. The specimen climbed to the top. 10 tests were made with 

 the following results: 



Fig. 4. — Glass cylindrical aqua- 

 rium with vertical glass plate 

 set inside Used for observing 

 the behavior in climbing tests. 



In 9 tests out of the 10 the starfish ascended the vertical wall and 

 in I test descended to the bottom. The results seemed to indicate a 

 strong tendency to ascend, even with light excluded. In these tests, 

 however, the starfish was exposed to light while it was being allowed 

 to attach itself, and it occurred to the writer that during that time the 

 light stimulus might have resulted in the formation of an impulse to move 

 toward the light and that in the attempt to do so it climbed the wall. 

 Accordingly a series of tests was made in a photographic dark room 

 where no light was allowed to reach the starfish except the brief flash 

 from an electric hand-lamp when the creature had completed its test. 

 The results of 20 trials, 8 with the starfish used in table 5 and 12 with 

 another specimen, in which the orientation and handling were varied, 

 show a descent of the vertical wall in 14 tests and an ascent in 6 tests. 

 These trials were made at intervals of 3 minutes. The temperature of 

 the water in the ocean was 29° C. and that in the aquarium 30° C. 



