104 University of California Publications in Zoology. [Vol.4 



When the light coming from one side is very weak, there is 

 no reaction. Precise quantitative experiments were not made. 

 But when the starfish was placed in a vessel in a dark room, 

 lighted only by a small hole on one side, they moved without 

 reference to the light. In no case was there evidence of a posi- 

 tive reaction to light. 



2. General Stimulating Effect of Increased Light. — When a 

 starfish that has been in comparative obscurity is subjected to 

 strong light, the animal becomes much roused up and begins to 

 move about and explore actively. If possible it usually goes first 

 away from the source of light; if this is not possible, it follows 

 the walls of the vessel, creeps around it, climbs up to the surface, 

 waves its rays and tube feet in all directions, essays climbing out 

 of the vessel (in the way described later), and in general con- 

 ducts itself in a most perturbed manner. If at the moment when 

 the light is increased it is engaged in any special activity, it 

 usually ceases this to begin its apparent attempts to escape. If 

 it is eating, or is holding prey with its tube feet, it ceases eating 

 or releases its prey. This proved especially troublesome when 

 we were attempting to photograph the starfish while eating or 

 capturing food (figs. 2, 5, 6). As soon as increased light was 

 thrown on the animal in order to give opportunity for a photo- 

 graph, the prey was released*. But after twenty minutes to three- 

 quarters of a hour, the starfish becomes accustomed to a moderate 

 light, such as that coming from a cloudless sky. It may then 

 settle down quietly again and resume its interrupted activities, 

 recapturing its prey and continuing its meal. 



3. Movement toward Darker Regions, and Coming to Best in 

 the Shade. — After exploring the vessel in which it is confined, the 

 starfish usually comes to rest in that part of the vessel that is best 

 protected from the light. In a cylindrical jar it finally stops as 

 a rule on the right or left side, where the curving of the jar serves 

 to refract and reflect the light so as to leave a region less illumin- 

 ated than elsewhere; here the starfish presses itself close against 

 the side and comes to rest. Loeb (1893) has observed that negative 

 flatworms often take a similar position. If the vessel where the 

 starfish is confined contains opaque bodies, the starfish commonly 

 places itself behind one of these. 



* The holding by the pedicellariae is not thus affected by the light. 



