CHAPTER VII 



FURTHER OBSERVATIONS ON THE GEOMETRICAL SNARE 



Ultimate fate of temporary spiral — Reversal of spiral — Reason of reversal 

 of spiral — Example of plasticity of instinct — Spidei-'s power to esti- 

 mate tension — Delicacy of sense of touch — Industry of Artwcus — 

 Mode of emission of filament — Economy of spider and destruction of 

 snare — Perfection and imperfection in snare. 



In the previous chapter I have endeavoured to make 

 clear the mathematical powers by which I believe the 

 spider works, and I now pass to consider some other 

 features of interest in the geometry of the circular 

 snare. 



I must first mention one incident in the workmanship 

 of the spider, since it serves to illustrate how a certain 

 step in the architecture can serve merely as a temporary 

 support until the next step is complete. I refer to 

 the ultimate disappearance of the temporary spiral. 

 If the viscid spiral was brought to a completion 

 while the temporary spiral still remained in place, 

 then the final workmanship would consist of a 

 mixture of two spirals, one of viscid and the other 

 of non-viscid lines. But so clumsy an architecture 

 will not suit the spider. It works on a more perfect 

 plan. Its edifice must contain only a single spiral 

 composed solely of viscid lines. How does it effect 

 this.'* We watch the spider at its work. In the snare 

 under observation the temporary spiral is complete, 

 and we notice that the spider has just sufficient room 



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