1907] Jennings. — Behavior of the Starfish. 109 



Tlie two rays on that side of the body next to the light are curvecl, 

 to right and left, as shown in the figures, so as to leave a wide gap 

 between them; while the distal ray either extends straight out 

 (fig. 9B) or is brought near or against one of the other rays 

 (fig. 9A). An important feature of the orientation, that cannot 

 be brought ont in the outline figures, is the following: the rays 

 are so twisted that the ventral surface is very completely pro- 

 tected from the light. The two rays on the lighted side are 

 slightly inclined on their long axes so as to make the dorsal sur- 

 face face the light, while the ventral surface is completely cov- 

 ered. The other rays are either similarly tilted, or are so placed 

 that their lower surfaces are well sheltered by the rays next the 

 light (fig. 9 A). The entire position looks like an attempt on the 

 part of the animal to protect the ventral surface and the tips of 

 the rays from the light. That this is indeed the case is indicated 

 by the following facts: (1) If when the starfish is oriented as 

 shown in fig 9, light is reflected from beneath, either from a 

 mirror or a sheet of white paper, so as to strike the ventral sur- 

 face, the starfish soon moves away. (2) If while in the position 

 of orientation the starfish is turned so that the light strikes the 

 tips of the rays and the partly exposed ventral surface (though 

 the animal is still synnnetrical to the rays) it after a time moves 

 away from the lighted side, and in time reverses its position, 

 again inclining ventral surface and tips of the rays away from 

 the light. (3) Commonly, when exposed to the light from one 

 side, the starfish creeps to that side of the vessel farthest away 

 from the light, then places itself in the angle between that side 

 and the bottom of the vessel, with the ventral surface completely 

 hidden from the light, while the dorsal surface is fully exposed. 

 If now we turn the vessel around, so that the light shines on the 

 ventral surface, the starfish is roused and begins to move about 

 until it again gets into a position with the ventral surface di- 

 rected away from the light. 



It is worth while to notice that in this position of orientation 

 the starfish receives the same amount of light as when it is turned 

 around with ventral surface to the light. The efforts of the ani- 

 mal seem directed toward protecting the ventral surface, and. 

 to a less degree, the tips of the rays. The ventral surface is of 



