DIRECTION OF LOCOMOTION OF THE STARFISH 381 



surface of the starfish causes the branchiae to contract. It will 

 be seen from these experiments and those made by other investi- 

 gators that at least most of the surface of some starfishes is sen- 

 sitive to change in the intensity of light, provided the change is 

 great enough. 



The work of Jennings (1907) and Bohn (1908) seems to show 

 that certain species of starfishes which react negatively to light 

 of ordinary intensity often tend, when placed in the sunlight, to 

 move toward opaque walls when these are not too far away. 

 This occurs even when these walls are arranged so that they cast 

 no shadow. Jennings has found that the reaction is quite 

 variable, fully half of the individuals used moving without 

 any reference to the opaque wall. However, in some cases the 

 reaction was so constant that he considered it not to be accidental 

 and he raises the question " as to whether there exists in the star- 

 fish anything resembling what we speak of as image formation; 

 resulting in the perception of objects, or at least in a reaction 

 toward objects as such." 



The writer has devised a series of experiments in which the 

 object has been to test the behavior of the starfish with reference 

 to white and black walls, keeping other factors which might 

 affect the behavior under control as much as possible. 



The apparatus used consisted of a wooden box, 91.5 cm. high, 

 61 cm. wide and 30.5 cm. deep, set on a cement floor so that 

 the bottom would be level. It was open at the upper end and 

 was painted dull black inside. A rectangular glass dish, 30.5 

 cm. long, 15.3 cm. high and 15.3 cm. wide, covered with dull 

 black paper except on one side where white bristol board was 

 placed, served as an experimenting dish. The open top of the 

 box was provided with a removable cover of thick broadcloth 

 in the center of which was a hole. Into this hole was fixed an 

 acetylene bull's-eye lamp, so that when the latter was lighted 

 the rays were directed downward into the box. The experiment- 

 ing dish was so placed in the bottom of the box that its center 

 came directly below the center of the source of light, thus lighting 

 the bottom of the dish without casting any shadows. This 

 apparatus, which to be sure was rather crude in construction, 

 was the best that could be devised in Montego Bay, Jamaica, 

 where the experiments were performed. The constant results, 

 however, obtained with forty individuals of the starfish Echin- 



