1907] Jennings.— Behavior of the Starfish. 63 



undoubtedly their ehief function. Cnenot (1887) describes 

 briefly a similar action of the pedicellariae in Asterias glacialis; 

 he observed that small worms were seized and held immobile by 

 them till they died. 



The protective activities of the pedicellariae are not by any 

 means limited to very small orjianisms. While even eopepods less 

 than a millimeter in length are seized and held, larger sand fleas 

 and other crustaceans, a centimeter or more in length, furnish 

 the commonest examples of their effective activity. And even 

 much larger crabs are dealt with in an equally efifective way. 

 Shore crabs are very numerous on the rocks where the starfish 

 are found, exploring actively in search of garbage or suitable 

 prey. These vary in size from less than a centimeter in width. 

 up to ten or fifteen centimeters. These crabs frequently attempt 

 to run over the surface of the starfish, or to pluck off its gills as 

 tender morsels of food. Any of these crabs, up to perhaps three 

 centimeters in diameter, is held by the pedicellariae in the way 

 we have described. The crab often fights savagely with his large 

 claws, and manages to do considerable damage, pulling off a few 

 score of the pedicellariae before he is rendered immobile. But 

 his limbs are so studded with hairs that his liliputian adversaries 

 are able to seize him in a thousand places, and in a short time 

 he is compelled to succumb. I have often seen crabs two or three 

 centimeters across thus held quiet for days at a time by a starfish 

 upon which they had unluckily ventured. 



Into the large basin where the starfish were kept, a consider- 

 able number of the sand crabs, Hippa anedoga St., were placed. 

 These are two to three centimeters in length. They were quickly 

 captured by the starfish. Fig. 2 is a photograph of a starfish 

 that had thus captured four of these Hippas and one of the shore 

 crabs. The five crabs remain immovable, attached to its dorsal 

 surface. 



As may be judged from these facts, the pedicellariae hold 

 M'ith much strength. This may be easily shown as follows: The 

 back of the hand is pressed against the dorsal sui'face of a star- 

 fish. The pedicellariae seize the hairs of the back of the hand and 

 the starfish may now be lifted completely out of the water by 

 means of them. They are thus able to support the animal 's own 

 weight in the air. 



