STRUCTURE AND ECONOMY OF SPIDERS. 299 
of an inch of the elastic spiral line, at the ordinary 
degree of tension, the product will be 140, the mean 
number of globules deposited on seven tenths of an 
inch of the elastic spiral line; this product multi- 
plied 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 
radi, 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 up- 
wards of 120,000 viscid globules; and yet petra 
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 adjacent to it by a sensi- 
ble space: indeed the material of which they are 
composed is so fluid, that they run together the 
moment they are brought into contact. The globules 
and the intervals between them may be distinctly 
seen with the assistance of a magnifier of the power 
of ten; and it would appear from the following pas- 
sage, 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 glo- 
