GEOMETRICAL SPIDERS 99 



more wonderful because they are simple. For as the 

 spider paces the distance through its snare, so does man 

 often, in his daily life, pace his distance over the ground. 



The first turn of the viscid spiral being complete, I 

 come now to the construction of the succeeding turns 

 of that spiral, the perfect parallelism of which makes 

 for the beauty and subtlety of the snare. How is this 

 parallelism secured ? How is each filament in the 

 spiral adjusted by the spider at an equal distance from 

 each adjoining filament ? We have seen that the 

 second, third, fourth and succeeding turns of the 

 temporary spiral are measured off each from the pre- 

 ceding turn. We have also seen that the first turn 

 of the viscid spiral is measured off from the last turn 

 of the temporary spiral. In fact the distance of each 

 turn is estimated from the turn immediately internal to 

 it. I therefore first thought that the spider in some 

 way measured all the turns of its viscid spiral from the 

 bridge formed by the temporary spiral. I was unable 

 to understand how it could effect this, until at last a 

 simple experiment convinced me that I was mistaken ; 

 that the temporary spiral was not the guide to measure- 

 ment, but that the architect worked on some different 

 plan. 



I found a spider spinning. The viscid spiral was 

 being laid down. Between every attachment the 

 spider had to cross over its bridge formed by the 

 temporary spiral. With a sharp pair of scissors I 

 divided the bridge in one segment. The spider took 

 no notice and circled on. In every other segment it 

 pursued its normal course, crossing over the customary 

 bridge. But in the experimental segment the bridge 

 was gone and the spider had to continue inwards until 



