478 Mr. Blackwall on the 



the mean number of globules deposited on seven tenths of an 

 inch of the elastic spiral line ; this product multiplied by 24, 

 the mean number of circumvolutions formed by the elastic 

 spiral line, gives 3,360, the mean number of globules contained 

 between two radii ; which multiplied by 26, the mean number 

 of radii, produces 87,360, the total number of viscid globules in 

 a finished net of average dimensions. A large net, fourteen or 

 sixteen inches in diameter, I have found, by a similar calculation, 

 to contain upward of 120,000 viscid globules, and yet Epeira 

 apoclisa will complete its snare in about forty minutes, on an 

 average, if it meet with no interruption. Astonishingly great 

 as this number of globules is, each is separated from those ad- 

 jacent to it by a sensible space ; indeed the material of which 

 they are composed is so fluid, that they run together the mo- 

 ment they are brought into contact. The globules and the 

 intervals between them may be distinctly seen with the assist- 

 ance of a magnifier of the power of ten ; and it would appear 

 from the following passage extracted from Micrographia, p. 202, 

 that they did not escape the notice of Dr. Hooke. "I observed 

 further," he informs us, " that the radiating chords of the web 

 were much bigger and smoother than those that were woven 

 round, which seemed smaller, and all over knotted or pearled 

 with small transparent globules, not unlike small crystal beads 

 or seed pearls, thin strung on a clew of silk ; which, whether 

 they were so spun by the spider, or by the adventitious mois- 

 ture of a fog (which I have observed to cover all these fila- 

 ments with such crystalline beads), I will not now dispute." 



Messrs. Kirby and Spence, in their Introduction to Ento- 

 mology, vol. i. Letter xiii. state that " the net of the garden 

 spider is composed of two distinct kinds of silk ; that of the 

 radii not adhesive, that of the circles extremely viscid :" and 

 this difference, they remark, " when it is considered that both 



sorts 



