and (Economy of the Araneidca. 239 



measures about one-sixteenth of an inch in diameter and usually 

 coniprises two spherical, pink eggs, not agglutinated together. It 

 may he remarked, by way of contrast, tliat Ep'iira qiuidruta fre- 

 <iuently deposits between nine hundred and a thousand spherical 

 eggs of a yellow colour, in a globular cocoon of coarse yellow silk 

 of a loose texture, measuring seven-tenths of an inch in diameter, 

 which is attached to the stems of heath, gorse, and otlier vegetable 

 productions in the vicinity of its haunts. 



Among the silken snares fabricated by spiders for the purpose of 

 rapturing their prey, the most elegant are those constructed with the 

 appearance of geometrical precision in the form of circular nets. 

 They are composed of an elastic spiral line thickly studded with mi- 

 nute globules of lirpiid gum, whose circumvolutions, falling within 

 the same plane, are crossed by radii converging towards a common 

 centre, which is immediately surrounded by several circumvolutions 

 of a short spiral line devoid of viscid globules, forndng a station 

 from which the toils may be superintended by their owner without 

 the inconvenience of being entangled in them. As the radii are 

 unadhesive and possess only a moderate share of elasticity, they must 

 consist of a different material from that of the viscid spiral line, which 

 is elastic in an extraordinary degree. Now the viscidity of this line 

 may be sliown to depend entirely upon the globules with whieli it is 

 studded, for if they be removed by careful applications of the finger, 

 a tine glossy filament remains, which is highly elastic, but perfectly 

 unadhesive. As the globules, therefore, and the line on whicli they 

 are disposed, differ so essentially from each other, and from the radii, 

 it is reasonable to infer that the physical constitution of these several 

 portions of the net must be dissimilar. 



An estimate of the number of viscid globules distributed on the 

 elastic spiral line in a net of Eptira apoclisa of a medium size, will 

 convey some idea of the elaborate operations performed by the 

 Epeirce in the construction of their snares. The mean distance be- 

 tween two adjacent radii, in a net of this species, is about seven- 

 tenths of an inch ; if, therefore, the number 7 be multiplied by 20, 

 the mean number of viscid globules which occur on one-tenth of an 

 inch of the elastic spiral line, at the ordinary degree of tension, the 

 product will be 1-iO, the mean number of globules deposited on 

 seven-tenths of an inch of the elastic spiral line; this product mul- 

 tiplied by 24-, the mean number of circumvolutions described by the 

 elastic spiral line, gives ;}36(), 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, will be found, by a sinular calculation, to contain up- 

 wards of 120,000 viscid globules, and yet Eptira apoclisa will com- 

 plete its snare in about forty minutes if it meet with no interruption. 



In the formation of their snares the EpHirce appear to be regu- 

 lated solely by the sense of touch, as various species when confined 

 in spacious glass jars placed in situations absolutely impervious to 



