THE GEOMETRICAL SNARE 109 



to fit in four turns of the viscid spiral between the 

 circumference of the snare and the outer turn of the 

 temporary spiral. What I wish to make clear is this : 

 that after the spider commences on its viscid spiral it 

 will have sufficient space to complete the first four 

 turns, but that the fifth turn will happen to meet the 

 outer turn of the temporary spiral and the two will 

 become intermingled. We watch to see what the 

 spider will do. It completes the first three turns in 

 the ordinary way, of course using the outer turn of 

 the temporary spiral as the bridge to pass across from 

 radius to radius. It comes to the fourth turn. It has 

 sufficient room to insert this. It is the next turn 

 that will coincide with the temporary spiral. What 

 does the spider do ? It rises to the emergency. It 

 behaves as though it foresaw its difficulties. It sets 

 about destroying its bridges so as to allow a free space 

 for the fifth turn of its viscid spiral. Each time it 

 completes the fourth turn of the viscid spiral in any 

 segment it at the same moment severs the bridge in 

 that segment. It first crosses the bridge, then divides 

 the line behind it. And this process of division con- 

 tinues until the outer turn of the temporary spiral has 

 been severed all round the snare. The fifth turn of 

 the viscid spiral can then be freely laid down. A 

 similar destruction follows in the case of the inner 

 turns of the temporary spiral. As soon as the spider 

 finds that the next turn of its viscid spiral will get 

 entangled with its bridge it adopts the ingenious 

 method of simply dividing the bridge. Each turn is 

 severed as soon as the viscid spiral reaches it. 



Thus does the temporary spiral disappear. It 

 has served its purpose and has served it well. It has 



