GEOMETRICAL SPIDERS 97 



a similar distance away. The line is drawn tight 

 between the radii and secured. So continues the 

 spider on to the next radius and completely round the 

 snare. At every radius the same distance is measured ; 

 the distance being the full expanse of the spider's body 

 from the tip of its fore leg on the hub to the spinnerets 

 applied to the radius. 



The first turn is complete. The spider passes on 

 to the second turn. The same mechanism follows. 

 But the spider measures its distance not from the hub 

 but from the first turn. And as the second turn is 

 measured from the first turn, so also is the third turn 

 measured from the second turn, and the same mechan- 

 ism continues round the snare until all the turns are 

 complete. 



Again we find that the method of construction is a 

 simple geometrical act. The spider is faced with a 

 definite problem and must solve it on mathematical 

 lines. Each turn in the spiral must be parallel, and 

 only by accurate measurement can this parallelism be 

 secured. The spider by its wonderful instinct can 

 meet the problem. It has many organs of measure- 

 ment at its command. In fashioning its temporary 

 spiral it employs the simplest of all — the measurement 

 of its own length. 



The temporary spiral is complete. A solid frame- 

 work is in position to receive the viscid spiral, the 

 deadly element of the snare. No part of the fabric is 

 more beautiful than this, nor displays its mathematical 

 perfection to so remarkable a degree. The question 

 is, how is all this accuracy attained ; how does the 

 spider measure with such precision this most wonderful 

 portion of its architecture ? 



H 



