50 THE HAUNTS OF LIFE 



linkages of nerve-cells and muscle-cells. So 

 is it in the star-fish when it surrenders an arm. 

 We know that the star-fish does not do this 

 deliberately, for it has a very poorly developed 

 nervous system. There is a strand of nerve- 

 cells up the middle line of the under surface of 

 each arm, and these are united in a pentagon 

 around the mouth ; there are also many 

 scattered nerve-cells ; but there is no brain, 

 not even a single nerve-centre or ganglion. 

 The star-fish does not know what it does, but 

 it has somehow in its constitution learned in 

 the course of time that it is better that one 

 member should perish than that the whole life 

 should be lost. Brittle-stars give off their 

 arms very readily ; sea-cucumbers are less polite, 

 for they discharge their insides in the spasms 

 of capture ; sea-urchins have nothing that they 

 can give away save their spines. We see the 

 same sort of surrender when the lizard gives 

 off its tail, and we find many cases among 

 insects and spiders. It is very marked in the 

 harvest-men, who stalk about in the evening 

 among the stubble, with legs over twenty times 

 the length of their body. The self-mutilation 

 ("autotomy ") is also very common among 

 Crustaceans. 



