188 Mr. Blackwall on the Construction, &c. 
doing extensive injury to the frame-work of the snare. How this viscid 
line is fabricated is at present unknown. An examination of its struc- 
ture, and of the apparatus by which it is produced would furnish interest- 
ing employment for the microscope. 
In order to determine whether objects entangled in their toils are ani- 
mate or inanimate, the geometric Spiders pull with their feet the radii 
immediately in connection with that part of the snare in which they are 
suspended, and suddenly letting go their hold, produce by this means a 
vibratory motion in the net which seldom fails to excite to action such 
insects as are ensnared. Guided by the struggles of her prey, the Spider 
runs along the most contiguous radius to seize her victim, avoiding any 
contact with the viscid line as much as possible, and drawing out after her 
a thread attached to one of the lines near the centre of her net, which 
serves to facilitate her return. 
I regret that fam unable to particularize those species of Spiders which 
have been more especially the objects of the preceding observations and 
experiments; but so little has been accomplished in this interesting 
branch of zoology by British faunists since the time of Lister, that hitherto 
all my attempts to determine some of them have proved ineffectual. 
Previously to giving my remarks publicity, I would gladly have availed 
myself of the labours of our continental neighbours in this department of 
natural history, but this would have been attended with considerable in- 
convenience and much delay, and I am well informed that the works of 
M. Walckenaer, who is regarded as the highest authority on this subject, 
are out of print, and cannot be procured either in London or Paris.* A 
book descriptive of British Spiders, if ably conducted, and accompanied 
with accurately coloured engravings illustrative of species, would, I do 
not doubt, be very favourably received by the naturalists of this kingdom. 
That such a publication should still be a desideratum in the country which 
has produced a Ray, a Lister and a Willughby is a humiliating reflection. 
* M. Walckenaer has commenced, in the Faune Frangaise, (a work now in 
progress,) a history of the spiders which inhabit France, This will probably 
include the greater number of the British species. —Eb. 
