220 ZOOLOGY 



readily responds to direct stimuli, of course, but is it 

 capable of utilizing its past experiences ? When a star- 

 fish is turned on its back, it feels uncomfortable, or acts 

 as if it felt so. With its arms it tries to take hold of 

 some neighboring object and turn over. Obviously if 

 all five arms acted at once, they would counteract one 

 another, and the animal would remain in the reversed 

 position. Hence as soon as one arm has a good hold, 

 the others cease to oppose it, and success results. When 

 the surface is flat, it is a matter of chance which arm 

 initiates the work. Now Professor Jennings conceived 

 the idea of holding down four of the five arms, and caus- 

 ing a given starfish repeatedly to use a particular mem- 

 ber in the act of righting itself. After repeated lessons, 

 he found that the animals would continue for a time to 

 use this arm in preference to the others, even when not 

 interfered with. Thus it seemed to have memory, 

 though the education of starfishes is an expensive busi- 

 ness, requiring a separate tutor for each individual and 

 the repetition of the whole course about once a week. 

 Critics suggested that after all there was perhaps no true 

 educational process, but that the impeded arms were 

 slightly injured or stiffened, or suffered from lack of 

 exercise, giving the active one a better chance. Whether 

 the starfish remembers or not, it is a persevering animal. 

 It can open clamshells by sheer persistence, although in 

 a single pull the mollusk is the stronger. The starfish 

 envelops the shell, and the poor mollusk, striving to save 

 its life, exerts its adductor muscles to the utmost, shut- 

 ting the valves "as tight as a clam." It has been cal- 

 culated that the starfish can exert a pull equivalent to 

 I 3S grams, but the mollusk can resist one of 4000 

 grams. However, the starfish has more " staying power," 

 and tires out its prey, which finally has to succumb. 



