^^•^^] Jennings. — Behavior of the Starfish. 79 



described by v. Uexkiill. The pedicellariae of the sea urchin 

 refuse to seize or hold each other, or other parts of their own 

 body, or of other individuals of the same species. If through 

 accident a pedicellaria snaps upon a part of its body it at once 

 opens. Von Uexkiill calls this properly "autodermophilie," and 

 believes that it is due to the presence in the tissues of a substance 

 which paralyzes the closing muscles (1899, p. 376) ; this sub- 

 stance he calls autodennin. 



In this starfish we find nothing of this kind. The pedi- 

 cellariae seize and hold each other apparently as readily as any 

 other object. One often sees cases like the following: Two rays 

 of a starfish were lying side by side, and two pedicellariae of 

 each ray had interlocked jaws with the two of the other ray and 

 were holding on, the stalks stretched far. As the two rays moved, 

 the stalks of the four pedicellariae stretched farther or con- 

 tracted like India rubber, always remaining taut. While under 

 observation these pedicellariae retained their hold on each other 

 for thirteen and one-half minutes. 



Pedicellariae of neighboring rosettes on the same ray fre- 

 quently seize and hold one another. They sometimes hold for a 

 long time, even when there is no tension by either. The pedi- 

 cellariae of one starfish may seize any part of another. I have 

 seen a tube foot of one specimen torn off as a result of being held 

 by a pedicellaria of another. 



In certain experiments the body of a starfish was cut into 

 large and small pieces. When one piece was brought into contact 

 with the surface of another, the pedicellariae of the latter seized 

 any part which they could reach, setting their jaws into the bony 

 framework, the connective tissue, gills, or other tissues, and hold- 

 ing them. I saw pieces thus held for more than five minutes by 

 pedicellariae of the same individual; how much longer I did not 

 observe. 



Independent Reactions and Transmission of Stimuli. — Von 

 Uexkiill has brought forth clearly in the sea urchin the power 

 of independent reaction on the part of the pedicellariae. Each 

 may behave in the usual way when isolated on a small separated 

 piece of the shell of the animal. A somewhat similar condition 

 of affairs is found in the starfish. If a small piece of the body 



