15107] Jennings. — Behavior of the Starfish. 85 



Convenient bundles of precisely these necessary chemicals are 

 fonrd in the crabs, niollnsks and other animals that inhabit the 

 rocks of the sea-shore. We find the starfish furnished with an 

 outfit of structures and movements by which such bundles of 

 chemicals are incorporated in its own body and their contained 

 energy is diverted into the channels of its own processes. 



The pcdicellariae, as we have seen, often capture and hold 

 indefinitely the animals which are so unfortunate as to come 

 against the starfish. Sometimes such animals are merely held 

 till they die, and the store of food they might supply is wasted. 

 But usually, if the animal is not too small, the starfish proceeds 

 to devour the captured prey. Indeed, as we shall see, it is clear 

 that one of the main uses of the pcdicellariae is to capture food. 



Let us examine a typical case of the capture of food. Five 

 starfish were placed in a large glass vessel with flat bottom, and 

 into this same vessel were placed nine small crabs. The crabs 

 scuttle quickly to a hiding place on or behind the starfish, but 

 are at once seized by the pcdicellariae of the rosettes. DiscoverT 

 ing their mistake, the crabs struggle to get away, and fight sav- 

 agely, pinching the starfish with their claws and pulling off 

 bunches of pcdicellariae. The largest crab, nearly an inch in 

 diameter, manages to escape, but the others are held on the upper 

 surface of the starfish. 



Now in several of the starfish we see the tube feet with their 

 suckers pushing up from beneath and feeling about toward the 

 captured crabs. They feel about for two or three minutes, and 

 a few of the suckers manage to attach themselves. But by this 

 time the crabs have become quiet, and the tube feet are with- 

 drawn, leaving the crabs attached and immobile on the upper 

 surface of the starfish. Thus they remained for a long time on 

 most of the starfish. 



But after about ten minutes one of the starfish, that had 

 v-aptured, on the sides of two adjacent rays, three small crabs, 

 each about one-half inch across, began to take more active meas- 

 ures toward feeding on them. The three crabs were on the facing 

 sides of the two rays, — thus in one of the interspaces between the 

 rays. The starfish began to bend these two rays toward each 

 other, so as to crowd the crabs together, and at the same time the 



