ON THE NETS OF GEOMETRIC SPIDERS. 287 
radius she walks, drawing out the thread after her, 
and guiding it with one of her hind feet, till she 
reaches its point of union with one of the adjoining 
radii: on this radius she steps, and passing along it 
to the other extremity there makes fast her thread— 
by this simple process connecting with marginal lines 
distant objects between which no direct communica- 
tion previously existed. 
In the formation of their nets, spiders are regu- 
lated chiefly by the sense of touch, which they 
possess in high perfection. This is rendered ex- 
tremely probable by the general tenor of their pro- 
ceedings; for example, they ascertain when they 
have the full complement of radii by approaching 
the centre of the net, which is their common point 
of union, and touching each in succession with the 
feet, supplying deficiences wherever they are per- 
ceived ; and I have already noticed a circumstance 
which greatly tends to confirm this opinion—namely, 
that they frequently construct their snares in the 
night. The fact, however, is established beyond 
dispute by the following experiment. I have re- 
peatedly confined Geometric Spiders in glass jars 
placed in situations absolutely impervious to light, 
and yet, during their captivity, they have produced 
perfect nets of admirable workmanship. 
Spiders were supposed by Dr. Lister * to be able 
to retract their threads within the abdomen; and 
* «De Araneis,’ p. 8. 
