-— wc ^ 
Structure and Economy of Spiders. 477 
instruments employed by the Geometric Spiders for the purpose 
of suspension, it is obvious why they usually direct their heads 
downwards when they occupy the centre of their nets. 
As several difficulties present themselves in the prosecution 
of these researches, occasioned chiefly by the impracticability 
of comprising all the claws in one distinct view ; and as I have 
not yet succeeded in procuring instruments of sufficient delicacy 
to enable me to accomplish the dissection of exceedingly minute 
objects under the microscope, I cannot completely satisfy myself 
at present whether the number and arrangement of the addi- 
tional claws are uniformly the same on the feet of such spiders 
as I have ascertained to be supplied with them ; though as 
regards the larger species I am thoroughly convinced that this 
is the case, and I have reason to think that it will ultimately 
prove to be so with the rest. In pursuing the inquiry, these 
particulars, of course, will claim my especial attention. 
Itis not at all surprising that the Geometricians, which em- 
ploy their feet in the fabrication of complicated nets, should 
have them more amply provided with claws than those species 
which use theirs principally as instruments of progression. An 
estimate of the number of viscid globules distributed on the 
elastic spiral line in a net of Epeira apoclisa of a medium size, 
will convey some idea of the elaborate operations performed by 
the Geometric Spiders in the construction of their snares*. The 
mean distance between two contiguous 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 glo- 
bules which occur on one tenth of an inch of the elastic spiral 
line at the ordinary degree of tension, the product will be 140, 
* For a circumstantial account of the manner in which the Geometric Spiders con- 
struct their nets, see the Zoological Journal, vol. v. p. 181. et seq. 
the 
