1907] 



Jennings. — Behavior of the Starfisli. 



61 



way, either by t()iicliiii<>' them with a bristle, or by causing some 

 small animal, such as a crustacean, to creep over them. The 

 gills at once collapse and shrink down close against the surface of 

 the starfish, where they are less likely to be injured. And now. 

 after they have received one or two jabs by the bristle, or by 

 the claws of our crustacean, — we suddenly see the ring which 

 surrounds the base of the neighboring spines rise upward to the 

 toj!), so that the spine is completely hidden. At the same time 

 each of the small oval bodies extends outward a distance on a 

 short stalk and opens widely by a cleft down its middle. We now 

 see that each is a pair of broad jaws, with sharp teeth. Under 



A B 



Fig. 1. — Portions of the surface of the starfish, showing the gills {g), 

 the spines (s), and the pedicellariae (/))• -i shows the condition in the un- 

 stimulated animal, in which the rosettes are retracted and the pedicellariae 

 closed. In B the rosettes of pedicellariae have risen to the top of the spines 

 and the jaws are opened. 



a lens the rising ring looks like some hundred-handed or hundred- 

 jawed monster,' each jaw gaping widely and ready to attack 

 (fig. 1, -B) . A half dozen or more of these rings, belonging to the 

 spines immediately surrounding the region where the gills were 

 disturbed, thus rise. 



At the same time the spines all bend over toward the spot 

 where the disturbance is occurring, so as to form a close ring of 

 hundreds of these widely-opened jaws; they almost completely 

 cover the invaded region. A number of them are thus certain 

 to strike against the creature causing the disturbance, so as to 

 find some part of its body between the jaws. These at once snap 



