.214 EVENINGS AT THE MICROSCOPE. 



joints ; and as the circlet of bristles in the first pair 

 doubtless indicates a short joint, sunken as it were 

 within the preceding, this pair is likewise three-jointed ; 

 the middle pair appears to be but two-jointed. 



The minute horny tubes are themselves composed of 

 two joints, the basal one thick, the terminal one very- 

 slender, and perforated with a very minute orifice, through 

 which the gum oozes at the will of the animal as an 

 equally attenuated thread. On our Clubiona, the number 

 of tubes in all the spinnerets is about three hundred; but 

 in the Garden Spider (Epeird) they exceed a thousand. 



This remarkable multiplicity of the strands with 

 which the apparently simple and certainly slender thread 

 of the Spider is composed, has attracted the attention of 

 those philosophers w r ho seek to discover the reasons of 

 the phenomena they see in nature. The explanation 

 was first suggested, I believe, by Mr. Itennie,* but it 

 has been amplified with much force by Professor Jones, 

 in the following words : — 



" A very obvious reflection will here naturally suggest 

 itself in connexion with this beautiful machinery ; why, 

 in the case of the Spider, it has been found necessary to 

 provide a rope of such complex structure, when in so 

 many Insects a simple, undivided thread, drawn from the 

 orifice of a single tube, like the thread of the silkworm, 

 for instance, was sufficient for all required purposes. And 

 here, as in every other case, it will be found on considera- 

 tion, that a complicated apparatus has been substituted 

 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 

 ©f which it is formed to harden by degrees into a tenacious 

 filament, as it is allowed to issue by instalments from the 

 end of the labial pipe ; but the habits of the Spider re- 

 quire a very different mode of proceeding, as its line must 



* " Insect Architecture," 337. 



