246 EVENINGS AT THE MICROSCOPE 



consideration, that a complicated apparatus has been sub- 

 stituted for a simple one only to meet the requirements 

 of strict necessity. The slow-moving Caterpillar, as it 

 leisurely produces its silken cord, gives time enough for 

 the fluid of which it is formed to harden by degrees into 

 a tenacious filament, as it is allowed to issue by instal- 

 ments from the end of the labial pipe; but the habits of 

 the Spider require a different mode of proceeding, as its 

 line must be instantly converted from a fluid into a strong 

 rope, or it would be of no use for the purposes it is in- 

 tended to fulfil. Let a fly, for example, become entangled 

 in the meshes of a Spider's web; no time is to be lost; 

 the struggling victim, by every effort to escape, is tearing 

 the meshes that entangle it, and would soon succeed in 

 breaking loose did not its lurking destroyer at once rush 

 out to complete the capture and save its net, spun with 

 so much labor, from ruin. With the rapidity of thought 

 it darts upon its prey; and before the eye of the spectator 

 can comprehend the manoeuvre, the poor fly is swathed 

 in silken bands, until it is as incapable of moving as an 

 Egyptian mummy. To allow the Spider to perform such 

 a feat as this, its thread must evidently be instantaneously 

 placed at its disposal, which would have been impossible 

 had it been a single cord, but being subdivided into nu- 

 merous filaments, so attenuated as we have seen them to 

 be, there is no time lost in the drying; from being fluid 

 they are at once converted into a solid rope, ready for im- 

 mediate service." 1 



No doubt you have often admired the exquisite reg- 

 ularity of those Spiders' webs which are called geometric; 



1 "Nat. Hist, of Anim.," ii. 339. 



