92 A NATURALIST IN HIMALAYA 



radii accurately placed ; legs too widely expanded 

 mean that a radius or more is absent. Thus the first 

 step in the adjustment of the radii takes place at 

 the centre of the snare. It is here that the spider 

 learns in what part of the snare the radii are complete, 

 in what parts more are to be laid down. It is by this 

 mechanism that the spider rests finally satisfied that 

 every radius is in place. 



So much for the process by which the spider locates 

 those parts of the snare not yet supplied with radii. 

 I pass now to a second mechanism, that by which 

 the spider measures the correct distance between the 

 radii. This takes place not at the centre but at 

 the circumference of the snare. It follows in this way. 

 The spider at the centre has discovered an interval 

 not yet supplied with a radius. Its legs, acting 

 as a pair of dividers, have expanded two radial-widths. 

 It therefore knows that a spoke is here absent and 

 it must needs supply it. Out along the nearest radius 

 it hastens, paying out its filament of silk. It reaches 

 the circumference where the radius joins the frame. 

 Now occurs the interesting part of the mechanism. 

 The spider takes four paces along the foundation-line, 

 then halts, draws tight its filament, secures it to 

 the frame, and a new radius is in place. It is the 

 four paces along the foundation-line that makes the 

 measurement exact. In this the spider never errs. 

 Every radius is secured to the frame four paces from 

 an adjoining radius, thus all the radii are equidistant 

 and perfect symmetry is attained. 



It may seem degrading to the exquisite workman- 

 ship of the spider to reduce its methods to mathe- 

 matical terms, To my mind the work appears iriore 



