50 THE HAUNTS OF LIFE 



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 delib- 

 erately, 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 pen- 

 tagon 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 po- 

 lite, 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. 



